Lighting device, luminaire, vehicle with same, and lighting method

This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2016-168429, filed on Aug. 30, 2016, the entire content of which is incorporated herein by reference.

This disclosure relates to lighting devices, luminaires, vehicles with the same and lighting methods and, more particularly, to a lighting device causing a semiconductor light source to emit light, a luminaire, a vehicle with the same, and a lighting method.

Conventionally, there has been a vehicle luminaire that includes a power converter for converting DC power, which is inputted thereto, and supplying its output current to a Light Emitting Diode (LED) (refer to a Document 1: JP 2013-203273). Regarding the LED which is a load for the power converter, there is a variation in a light output characteristic (luminous characteristic) with respect to a drive current among products. For this reason, the luminous characteristic of the LED is previously ranked, and the LED is provided with an output current setting device that includes a resistor having a resistance value which is made associated with a rank thereof. The vehicle luminaire divides a voltage supplied from a constant voltage source, using a voltage dividing resistor and the output current setting device, and an output controller controls an output of the power converter in accordance with a divided voltage.

In the above-mentioned vehicle luminaire, the voltage from the constant voltage source is continuously applied to a series circuit formed by the voltage dividing resistor and the output current setting device. Accordingly, there is a problem that current consumption is increased, depending on a current flowing through the series circuit.

The present disclosure is directed to a lighting device, a luminaire, a vehicle with the same, and a lighting method, which can reduce power consumption.

A lighting device according to an aspect of the present disclosure is to cause at least one light source unit to emit light. Each of the at least one light source unit includes a light source and a corresponding load information outputter for outputting load information when electric power is supplied thereto. The load information represents a luminous characteristic of the light source. The lighting device includes at least one current outputter, a load characteristic obtainer and a controller. The at least one current outputter is configured to supply a current to the light source of the at least one light source unit. The load characteristic obtainer is configured to obtain the load information from the corresponding load information outputter of the at least one light source unit, by supplying the electric power to the load information outputter. The controller is configured to control the current of the at least one current outputter, which is supplied to the light source of the at least one light source unit, based on the load information obtained by the load characteristic obtainer. The load characteristic obtainer is configured to supply the electric power to the corresponding load information outputter only during a time period of obtaining the load information, but stop supply of the electric power to the corresponding load information outputter during a time period other than the time period of obtaining the load information.

A luminaire according to an aspect of the present disclosure includes the lighting device and a luminaire body holding the lighting device.

A vehicle according to an aspect of the present disclosure includes the luminaire and a vehicle body to which the luminaire is attached.

A lighting method according to an aspect of the present disclosure is to cause at least one light source unit to emit light. Each of the at least one light source unit includes a light source and a corresponding load information outputter for outputting load information when electric power is supplied thereto. The load information represents a luminous characteristic of the light source. The lighting method includes: supplying a current to the light source of the at least one light source unit; obtaining the load information from the corresponding load information outputter of the at least one light source unit, by supplying the electric power to the load information outputter; controlling the current of the at least one current outputter, which is supplied to the light source of the at least one light source unit, based on the load information obtained; and supplying the electric power to the corresponding load information outputter only during a time period of obtaining the load information, but stopping supply of the electric power to the corresponding load information outputter during a time period other than the time period of obtaining the load information.

A lighting device according to an aspect of the present invention is to cause at least one light source unit to emit light. Each of the at least one light source unit includes a light source and a corresponding temperature probe. The lighting device includes at least one current outputter, a temperature obtainer and a controller. The at least one current outputter is configured to supply a current to the light source of the at least one light source unit. The temperature obtainer is configured to obtain a measuring value of a temperature from the corresponding temperature probe, by supplying power to the temperature probe. The controller is configured to control the current of the at least one current outputter, which is supplied to the light source of the at least one light source unit, based on the measuring value of the temperature obtained by the temperature obtainer. The temperature obtainer is configured to supply the power to the corresponding temperature probe only during a time period of obtaining the measuring value of the temperature, but stop supply of the power to the corresponding temperature probe during a time period other than the time period of obtaining the measuring value of the temperature.

The figures depict one or more implementations in accordance with the present disclosure, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.

FIG. 1 is a circuit diagram of a lighting device according to a First Embodiment of the present disclosure.

FIG. 2 is a flowchart for explaining operation of the lighting device according to the First Embodiment.

FIG. 3 is a circuit diagram of a First Variation of the lighting device according to the First Embodiment.

FIG. 4 is a circuit diagram of a Second Variation of the lighting device according to the First Embodiment.

FIG. 5 is a circuit diagram of a lighting device according to a Second Embodiment of the present disclosure.

FIG. 6 is a circuit diagram of a First Variation of the lighting device according to the Second Embodiment.

FIG. 7 is a circuit diagram of a Second Variation of the lighting device according to the Second Embodiment.

FIG. 8 is a circuit diagram of a Third Variation of the lighting device according to the Second Embodiment.

FIG. 9 is a flowchart for explaining operation of the lighting device according to the Second Embodiment.

FIG. 10 is a circuit diagram of a Fourth Variation of the lighting device according to the Second Embodiment.

FIG. 11 is a cross-sectional view of a luminaire according to a Third Embodiment of the present disclosure.

FIG. 12 is a perspective view of a vehicle according to a Fourth Embodiment of the present disclosure.

Embodiments explained below are merely examples. The present disclosure is not limited to the following embodiments, but may include embodiments other than the following embodiments. In the following embodiments, numerous modifications and variations can be made according to designs and the like without departing from the technical ideas according to the present disclosure.

First Embodiment

(1. 1) Configuration

As shown in FIG. 1 , a lighting device 1 according to a First Embodiment is used for causing a light source unit 100 to emit light. The lighting device 1 of this embodiment is used for causing the light source unit 100 , installed to a vehicle such as an automobile, to emit light.

First, the light source unit 100 , which is a load for the lighting device 1 , will be described.

The light source unit 100 includes a light source 110 and a load information outputter 120 . The light source 110 includes a semiconductor light-emitting element(s) such as a Light Emitting Diode(s) (LED). The load information outputter 120 outputs load information representing a luminous characteristic of the light source 110 , when electric power is supplied to the load information outputter 120 .

The light source 110 includes e.g., LEDs, which are connected in series or in parallel.

The load information outputter 120 includes e.g., a resistor R 10 . The light source 110 is previously classified into one of a plurality of levels (e.g., five levels), based on its luminous characteristic (luminous flux rank), and the resistor R 10 of the load information outputter 120 has a resistance value, which is previously determined based on the classified level. For example, in manufacturing of light source units 100 or the like, the luminous characteristic of each light source 110 is determined, and the resistor R 10 with the resistance value corresponding to the luminous characteristic is installed in the load information outputter 120 of each light source unit 100 .

When a constant DC voltage is applied to a series circuit formed by the load information outputter 120 and a voltage dividing resistor (resistor R 2 ), namely, electric power is supplied to the load information outputter 120 , a voltage is generated across the resistor R 10 , depending on the resistance value thereof. The voltage has a value corresponding to the luminous characteristic of the light source 110 , namely, the value of the voltage is the load information. The “load information” mentioned herein means information corresponding to the luminous characteristic of the light source 110 . The luminous characteristic of the light source 110 can be therefore specified, using the load information. The luminous characteristic of the light source 110 is information that represents, for example, input specification of the light source 110 . The input specification of the light source 110 preferably includes information on any one or more of an input current, an input voltage and input power. In this embodiment, the luminous characteristic (load information) of the light source 110 includes information on the input current of the light source 110 . An output current of a current outputter 10 described later can be set, using the information on the input current of the light source 110 .

The following Table 1 shows a relation between five levels of luminous characteristics (luminous flux ranks), resistance values of resistors R 10 , and target values of output currents flowing through light sources 110 respectively corresponding to the luminous flux ranks.

Next, the lighting device 1 of this embodiment will be described.

As shown in FIG. 1 , the lighting device 1 includes a current outputter 10 , a load characteristic obtainer 20 and a controller 30 . The lighting device 1 of this embodiment further includes an output current detector 40 . The lighting device 1 and the light source unit 100 are electrically connected to each other with electric wires and the like.

The current outputter 10 is formed as, for example, a step-up DC-DC converter that includes an inductor L 1 , a switching element Q 1 , a diode D 1 and a smoothing capacitor C 1 .

The inductor L 1 has a first end connected to a positive electrode of a DC power supply E 1 so that a power supply switch SW 1 is interposed between the inductor L 1 and the DC power supply E 1 . The DC power supply E 1 is, for example, a battery of an automobile, or a power supply circuit using the battery of the automobile as a power source. Alternatively, the DC power supply E 1 may be an AC-DC conversion circuit of rectifying and smoothing AC power supplied from an AC power supply and then converting it into DC power.

The switching element Q 1 is, for example, a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The switching element Q 1 has: a drain electrode connected to a second end of the inductor L 1 ; a source electrode connected to a negative electrode of the DC power supply E 1 ; and a gate electrode for receiving a drive signal VS 1 from the controller 30 .

The diode D 1 has an anode connected to a connecting point between the inductor L 1 and the switching element Q 1 .

The smoothing capacitor C 1 is connected between a cathode of the diode D 1 and the source electrode of the switching element Q 1 . A series circuit formed by the light source 110 and a resistor R 1 (output current detector 40 ) is connected across the smoothing capacitor C 1 .

The load characteristic obtainer 20 is constituted by the resistor R 2 , a switch element Q 2 and a microcomputer 31 . The resistor R 2 has a first end to which a DC voltage Vcc is applied, and a second end connected to a first end of the resistor R 10 . The switch element Q 2 is, for example, a MOSFET. The switch element Q 2 has: a drain electrode connected to a second end of the resistor R 10 ; a source electrode connected to the ground of circuit; and a gate electrode connected to an output port PO 1 of the microcomputer 31 , described later.

As one example, the following Table 2 shows a relation between values of a divided voltage VL 1 and values of a current I 1 flowing through a series circuit formed by the resistors R 2 and R 10 in the luminous flux ranks, where the resistor R 2 has a resistance value of 1 kΩ and the DC voltage Vcc with a voltage value of 5V is applied to the series circuit formed by the resistors R 2 and R 10 .

In this embodiment, a range of values which the divided voltage VL 1 can obtain each luminous flux rank (hereinafter referred to as a “determination range”) is previously set based on the values of the divided voltage VL 1 respectively corresponding to the luminous flux ranks. The following Table 3 shows a relation between determination ranges of the divided voltage VL 1 and target values of the output current in the luminous flux ranks. The microcomputer 31 of the controller 30 has a memory previously storing information (data) on that the determination ranges of the divided voltage VL 1 are respectively made associated with the target values of the output current in the luminous flux ranks (refer to Table 3). The memory of the microcomputer 31 may previously store the data as shown in the Tables 1 and 2.

The output current detector 40 includes the resistor R 1 connected in series to the light source 110 .

The controller 30 includes the microcomputer 31 and a drive signal generating circuit (DSGC) 32 .

The microcomputer 31 includes a Central Processing Unit (CPU) and the memory. The CPU executes a program(s) stored in the memory, thereby the following functions and the like being realized: a function of obtaining the load information from the load information outputter 120 ; a function of determining the luminous characteristic of the light source 110 , using the load information; and a function of controlling the output of the current outputter 10 in accordance with the luminous characteristic of the light source 110 . The microcomputer 31 has: the output port PO 1 connected to the gate electrode of the switch element Q 2 ; an analog input port AD 1 to which a voltage at a connecting point between the resistors R 2 and R 10 is input; an analog input port AD 2 to which a voltage V 6 is input; and an analog output port DA 1 . The voltage V 6 is a voltage obtained by an input voltage V 1 being divided by resistors R 3 and R 4 .

The drive signal generating circuit 32 includes an amplifier 321 , an error arithmetic part 322 , a comparator 323 and an oscillation circuit 324 .

The amplifier 321 is, for example, an operational amplifier and to amplify a voltage V 2 generated across the resistor R 1 .

The error arithmetic part 322 is, for example, an operational amplifier and to output an error voltage between an output voltage V 3 of the amplifier 321 and a target voltage V 4 output from the analog output port DA 1 of the microcomputer 31 .

The oscillation circuit 324 is configured to generate a triangular wave with a prescribed frequency.

The comparator 323 has a positive input terminal connected to an output terminal of the error arithmetic part 322 . The comparator 323 further has a negative input terminal connected to an output terminal of the oscillation circuit 324 . The comparator 323 further has an output terminal connected to the gate electrode of the switching element Q 1 .

(1. 2) Explanation of Operation

Operation of the lighting device 1 of this embodiment will be explained below with reference to FIG. 2 .

When the power supply switch SW 1 is turned on in response to an operation of a driver who drives a vehicle or an on-command from an Electronic Control Unit (ECU) of the vehicle, the DC power supply E 1 starts supply of electric power to the lighting device 1 . Accordingly, the microcomputer 31 starts an initialization process (refer to a Step S 1 ). After the initialization process, the microcomputer 31 performs operation for reading the load information from the load information outputter 120 of the light source unit 100 (refer to a Step S 2 ).

Until starting the operation for reading the load information, the microcomputer 31 keeps a voltage level of the output port PO 1 at a Low-level, so that the switch element Q 2 is in an off state. In this state, no electric power is supplied into the load information outputter 120 . Then upon the operation for reading the load information, the microcomputer 31 switches the voltage level of the output port PO 1 to a High-level to make the switch element Q 2 in an on state. At this time, the DC voltage Vcc is applied to the series circuit formed by the resistors R 2 and R 10 , and thus the analog input port AD 1 of the microcomputer 31 receives the divided voltage VL 1 obtained by the DC voltage Vcc being divided by the resistors R 2 and R 10 .

In the on state of the switch element Q 2 , the microcomputer 31 subjects the divided voltage VL 1 , input to the analog input port AD 1 , to an Analog/Digital conversion (A/D conversion) to obtain the divided voltage VL 1 . After obtaining the divided voltage VL 1 , the microcomputer 31 switches the voltage level of the output port PO 1 to the Low-level to make the switch element Q 2 in the off state. Supplying of the electric power to the resistor R 10 is accordingly cut off. In this way, the microcomputer 31 supplies the electric power to the load information outputter 120 only during a time period of obtaining the load information, but stops supply of the electric power to the load information outputter 120 during a time period other than the time period of obtaining the load information.

After obtaining the divided voltage VL 1 , the microcomputer 31 compares a measured value of the divided voltage VL 1 with the determination range of the divided voltage VL 1 in each luminous flux rank in order to determine a luminous flux rank of the light source 110 , namely, load specification of the light source 110 (refer to a Step S 3 ). When succeeding in determination of the luminous flux rank of the light source 110 , the microcomputer 31 obtains a setting value of an output current corresponding to the determined luminous flux rank from the memory (refer to a Step S 4 ). If the measured value of the divided voltage VL 1 fails to meet any of the determination ranges corresponding to the luminous flux ranks 1 to 5, the microcomputer 31 determines that abnormality occurs in a circuit obtaining the load information from the load information outputter 120 , or the like, and cancels a process for setting the target value of the output current.

When succeeding in determination of the luminous flux rank of the light source 110 , the microcomputer 31 subjects the voltage V 6 , input to the analog input port AD 2 , to an A/D conversion, and then detects the input voltage V 1 , using a measured value of the voltage V 6 (refer to a Step S 5 ). The microcomputer 31 then determines whether or not a detected value of the input voltage V 1 is within an operational range (refer to a Step S 6 ). Since the DC power supply E 1 uses a battery of the vehicle as a power source, a power supply voltage of the DC power supply E 1 may be changed. The microcomputer 31 starts a process for lighting the light source 110 , if the detected value of the input voltage V 1 is within the operational range.

If the detected value of the input voltage V 1 is determined to be within the operational range (the Step S 6 : Yes), the microcomputer 31 outputs the target voltage V 4 corresponding to the setting value of the output current to the positive input terminal of the comparator 323 through the analog output port DA 1 (refer to a Step S 7 ).

At this time, in the drive signal generating circuit 32 , the amplifier 321 amplifies the voltage V 2 generated across the resistor R 1 , and the error arithmetic part 322 amplifies the error voltage between the output voltage V 3 of the amplifier 321 and the target voltage V 4 received from the microcomputer 31 .

If a voltage value of the triangular wave from the oscillation circuit 324 is equal to or less than the output voltage of the error arithmetic part 322 , a voltage level of the output voltage of the comparator 323 is switched to a High-level. On the other hand, if the voltage value of the triangular wave from the oscillation circuit 324 exceeds the output voltage of the error arithmetic part 322 , the voltage level of the output voltage of the comparator 323 is switched to a Low-level. Accordingly, the comparator 323 generates the drive signal VS 1 that is a Pulse Width Modulation (PWM) signal which of a duty ratio (an on-duty) is increased, as the output voltage V 5 of the error arithmetic part 322 is increased, that is, as the error voltage between the voltage V 3 and the target voltage V 4 is increased. The drive signal generating circuit 32 then outputs the drive signal VS 1 to the gate electrode of the switching element Q 1 . Accordingly, the duty ratio of the switching element Q 1 in the current outputter 10 is adjusted, and a current to be supplied to the light source 110 from the current outputter 10 is therefore controlled into the target value of the output current corresponding to the luminous flux rank of the light source 110 .

On the other hand, if the detected value of the input voltage V 1 is determined to be out of the operational range (the Step S 6 : No), the microcomputer 31 does not output the target voltage V 4 to the drive signal generating circuit 32 so that the output of the current outputter 10 is at a standstill (refer to a Step S 8 ), thereby causing the light source 110 to emit no light.

In this embodiment, the load characteristic obtainer 20 supplies the electric power to the load information outputter 120 only during a time period of obtaining the load information from the light source unit 100 , but stops supply of the electric power to the load information outputter 120 during a time period other than the time period of obtaining the load information. It is therefore possible to reduce power consumption. Furthermore, the load characteristic obtainer 20 obtains the load information from the light source unit 100 , while the current outputter 10 as a step-up chopper is in non-operation. The load characteristic obtainer 20 can therefore obtain the load information, while influence of noise is reduced. If power consumption in the load characteristic obtainer 20 is increased, it leads to an increase in a power loss or heat generation in a power supply circuit supplying an operational voltage to the load characteristic obtainer 20 . However, since the power consumption in the load characteristic obtainer 20 can be reduced in this embodiment, it is possible to suppress the increase in the power loss or the heat generation in the power supply circuit.

During the time period of obtaining the load information, the load characteristic obtainer 20 makes the current I 1 of 100 μA or more (in this embodiment, 1 mA or more) flow through the resistor R 10 of the load information outputter 120 . The load characteristic obtainer 20 and the load information outputter 120 are connected to each other with electric wires, and provided with connectors for connecting the electric wires. If a slight current with a value less than 100 μA flows through contact parts of the connectors or the like, oxide films may be formed on the contact parts, and a contact failure or the like may therefore occur. In this embodiment, since the load characteristic obtainer 20 makes the current I 1 of at least 100 μA flow through the resistor R 10 , the oxide films are hardly formed on the contact parts, even when the lighting device 1 and the light source unit 100 are connected, using the connectors. Accordingly, even when the electric wires connecting the lighting device 1 and the light source unit 100 are connected with the connectors, the contact parts of the connectors do not need to be plated with gold or the like. Reliability of electrical connection between the lighting device 1 and the light source unit 100 can be therefore improved, and noise resistance performance can be also enhanced. Note that, in consideration of suppression of the power consumption and adverse influence due to the slight current, the current supplied to the resistor R 10 is preferably in a range from 100 μA to 10 mA, more preferably from 1 mA to 10 mA, while the load characteristic obtainer 20 obtains the load information.

(1. 3) Variations

Hereinafter, variations of the above embodiment will be listed. Note that the variations explained below can be applied in appropriately combination with the above embodiments.

(1. 3. 1) First Variation

FIG. 3 is a circuit diagram of a lighting device 1 according to a First Variation.

In the above embodiment one lighting device 1 causes one light source unit 100 to emit light, but in this First Variation one lighting device 1 causes two light source units 100 A and 100 B to emit light. Hereinafter, components similar to those of the above Embodiment are denoted by same reference signs and explanations thereof are omitted.

The light source units 100 A and 100 B respectively include light sources 110 A and 110 B, each of which includes a semiconductor light-emitting element(s) such as an LED(s). The light source units 100 A and 100 B further include load information outputters 120 A and 120 B which are to output load information representing luminous characteristics of the light sources 110 A and 110 B, when electric power is supplied to the load information outputters 120 A and 120 B, respectively. The light source 110 A includes e.g., LEDs, which are connected in series or in parallel. Also, the light source 110 B includes e.g., LEDs, which are connected in series or in parallel. The load information outputter 120 A includes a resistor R 11 having a resistance value according to a luminous flux rank of the light source 110 A. The load information outputter 120 B includes a resistor R 12 having a resistance value according to a luminous flux rank of the light source 110 B.

The lighting device 1 includes current outputters 10 A and 10 B, a load characteristic obtainer 20 , a controller 30 , and output current detectors 40 A and 40 B.

The current outputters 10 A and 10 B are configured to supply currents to the light source units 100 A and 100 B, respectively.

The load characteristic obtainer 20 is constituted by a resistor R 2 , switch elements Q 2 and Q 3 , and a microcomputer 31 . The resistor R 2 has a first end to which a DC voltage Vcc is applied, and a second end connected to a first end of the resistor R 11 and a first end of the resistor R 12 . The switch element Q 2 has a first end connected to a second end of the resistor R 11 , and a second end connected to the ground of circuit. Also, the switch element Q 3 has a first end connected to a second end of the resistor R 12 , and a second end connected to the ground of circuit. FIG. 3 illustrates the switch elements Q 2 and Q 3 by schematic symbols, but the switch elements Q 2 and Q 3 are, for example, MOSFETs.

The output current detectors 40 A and 40 B are to detect output currents of the current outputters 10 A and 10 B, respectively.

The controller 30 includes the microcomputer 31 and drive signal generating circuits (DSGCs) 32 A and 32 B.

The microcomputer 31 has: an analog input port AD 1 to which a voltage at a connecting point between the resistors R 2 , R 11 and R 12 is input; an analog input port AD 2 to which a voltage is input, obtained by an input voltage V 1 A of the current outputter 10 A being divided by resistors R 3 and R 4 ; and an analog input port AD 3 to which a voltage is input, obtained by an input voltage V 1 B of the current outputter 10 B being divided by resistors R 5 and R 6 . Note that, in this embodiment, the input voltage V 1 A is equal to the input voltage V 1 B. The microcomputer 31 further has output ports PO 1 and PO 2 respectively connected to control terminals of the switch elements Q 2 and Q 3 . The microcomputer 31 further has: an analog output port DA 1 from which a target voltage is output to the drive signal generating circuit 32 A; and an analog output port DA 2 from which a target voltage is output to the drive signal generating circuit 32 B.

The drive signal generating circuit 32 A is configured to control the output of the current outputter 10 A so that the output current matches a target current according to the luminous flux rank of the light source unit 100 A, based on a detection voltage received from the output current detector 40 A and the target voltage received from the microcomputer 31 .

The drive signal generating circuit 32 B is configured to control the output of the current outputter 10 B so that the output current matches a target current according to the luminous flux rank of the light source unit 100 B, based on a detection voltage received from the output current detector 40 B and the target voltage received from the microcomputer 31 .

Hereinafter, operation of the lighting device 1 according to the First Variation will be described.

In the case of the lighting device 1 according to the First Variation, when any one of switches SW 1 and SW 2 is turned on, a DC power supply E 1 starts supply of electric power to the lighting device 1 . Accordingly, the microcomputer 31 starts an initialization process. After the initialization process, the microcomputer 31 performs operation for reading the load information from the load information outputters 120 A and 120 B of the light source units 100 A and 100 B.

Until starting the operation for reading the load information, the microcomputer 31 keeps voltage levels of the output ports PO 1 and PO 2 at Low-levels, so that the switch elements Q 2 and Q 3 are in off states, respectively. In this state, no electric power is supplied into the load information outputters 120 A and 120 B.

Then upon the operation for reading the load information, first, the microcomputer 31 switches: the voltage level of the output port PO 1 to a High-level to make the switch element Q 2 in an on state; and the voltage level of the output port PO 2 to the Low-level to make the switch element Q 3 in the off state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistors R 2 and R 11 , and thus the analog input port AD 1 of the microcomputer 31 receives a divided voltage V 11 obtained by the DC voltage Vcc being divided by the resistors R 2 and R 11 .

In the on state of the switch element Q 2 and the off state of the switch element Q 3 , the microcomputer 31 subjects the divided voltage V 11 , input to the analog input port AD 1 , to the A/D conversion to obtain the divided voltage V 11 . The microcomputer 31 compares a measured value of the divided voltage V 11 with a determination range of a divided voltage in each luminous flux rank in order to determine load specification of the light source 110 A, namely, a luminous flux rank of the light source 110 A.

When succeeding in determination of the luminous flux rank of the light source 110 A, the microcomputer 31 switches: the voltage level of the output port PO 1 to the Low-level to make the switch element Q 2 in the off state; and the voltage level of the output port PO 2 to a High-level to make the switch element Q 3 in an on state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistors R 2 and R 12 , and thus the analog input port AD 1 of the microcomputer 31 receives a divided voltage V 12 obtained by the DC voltage Vcc being divided by the resistors R 2 and R 12 .

In the off state of the switch element Q 2 and the on state of the switch element Q 3 , the microcomputer 31 subjects the divided voltage V 12 , input to the analog input port AD 1 , to the A/D conversion to obtain the divided voltage V 12 . The microcomputer 31 compares a measured value of the divided voltage V 12 with a determination range of a divided voltage in each luminous flux rank in order to determine load specification of the light source 110 B, namely, a luminous flux rank of the light source 110 B.

When succeeding in determination of the luminous flux ranks of the light sources 110 A and 110 B, the microcomputer 31 switches the voltage levels of the output ports PO 1 and PO 2 to the Low-levels to make the switch elements Q 2 and Q 3 in the off states. The microcomputer 31 performs the A/D conversion to voltages respectively input to the analog input ports AD 2 and AD 3 , and calculates input voltages V 1 A and V 1 B of the current outputters 10 A and 10 B based on converted voltages.

While the switch SW 1 is in an on state and further if the power supply voltage of the DC power supply E 1 is within an operational range, the microcomputer 31 outputs the target voltage obtained based on the luminous flux rank of the light source 110 A to the drive signal generating circuit 32 A. The drive signal generating circuit 32 A controls the output of the current outputter 10 A so that the current according to the luminous flux rank is supplied to the light source 110 A, based on the detection voltage received from the output current detector 40 A and the target voltage received from the microcomputer 31 .

While the switch SW 1 is in an off state, or while the switch SW 1 is in the on state but if the power supply voltage of the DC power supply E 1 is out of the operational range, the microcomputer 31 does not output the target voltage to the drive signal generating circuit 32 A, thereby causing the light source 110 A to emit no light.

Similarly, while the switch SW 2 is in an on state and further if the power supply voltage of the DC power supply E 1 is within the operational range, the microcomputer 31 outputs the target voltage obtained based on the luminous flux rank of the light source 110 B to the drive signal generating circuit 32 B. The drive signal generating circuit 32 B controls the output of the current outputter 10 B so that the current according to the luminous flux rank is supplied to the light source 110 B, based on the detection voltage received from the output current detector 40 B and the target voltage received from the microcomputer 31 .

While the switch SW 2 is in an off state, or while the switch SW 2 is in the on state but if the power supply voltage of the DC power supply E 1 is out of the operational range, the microcomputer 31 does not output the target voltage to the drive signal generating circuit 32 B, thereby causing the light source 110 B to emit no light.

As described above, in this First Variation, the one lighting device 1 causes the two light source units 100 A and 100 B to emit light, and the load characteristic obtainer 20 of the lighting device 1 obtains the load information of the light source units 100 A and 100 B, before causing them to emit light. The load characteristic obtainer 20 supplies the electric power to the load information outputter 120 A of the light source unit 100 A only during a time period of obtaining the load information from the load information outputter 120 A, but stops supply of the electric power to the load information outputter 120 A during a time period other than the time period of obtaining the load information. Also, the load characteristic obtainer 20 supplies the electric power to the load information outputter 120 B of the light source unit 100 B only during a time period of obtaining the load information from the load information outputter 120 B, but stops supply of the electric power to the load information outputter 120 B during a time period other than the time period of obtaining the load information. It is therefore possible to suppress the power consumption of the load characteristic obtainer 20 , compared with a case of continuously supplying the electric power to the load information outputters 120 A and 120 B even during the time period other than the time period of obtaining the load information.

Furthermore, the load characteristic obtainer 20 supplies the electric power to the load information outputters 120 A and 120 B at timings different from each other, respectively. It is therefore possible to reduce the power consumption, compared with a case of supplying the electric power to the load information outputters 120 A and 120 B at the same timing.

In this First Variation, the resistor R 2 , the switch element Q 2 and the microcomputer 31 constitute a circuit obtaining the load information from the load information outputter 120 A, and the resistor R 2 , the switch element Q 3 and the microcomputer 31 constitute a circuit obtaining the load information from the load information outputter 120 B. That is, in the load characteristic obtainer 20 , the circuits obtaining the load information from the load information outputters 120 A and 120 B include a common circuit element(s) (resistor R 2 ) so as to share the common circuit element. Thus, it is possible to reduce the number of circuit components, and downsize the whole circuit of the lighting device 1 .

In the load characteristic obtainer 20 of this First Variation, the switch element Q 2 is connected between the resistor R 11 of the load information outputter 120 A and the ground of circuit, but it may be connected between the resistors R 2 and R 11 . In this case, the resistor R 11 has a first end connected to the switch element Q 2 and a second end connected to the ground of circuit.

Also in the load characteristic obtainer 20 of this First Variation, the switch element Q 3 is connected between the resistor R 12 of the load information outputter 120 B and the ground of circuit, but it may be connected between the resistors R 2 and R 12 . In this case, the resistor R 12 has a first end connected to the switch element Q 3 and a second end connected to the ground of circuit.

In this way, since the switch elements Q 2 and Q 3 are connected between the resistors R 2 and R 11 and between the resistors R 2 and R 12 , respectively, it is possible to prevent currents from continuously flowing through the resistors R 2 , R 11 and R 12 , even when a failure occurs, such that the electric wires connecting the lighting device 1 and the light source units 100 A and 100 B are in a ground fault.

The load characteristic obtainer 20 obtains the load information from the light source unit 100 A and then from the light source unit 100 B, but the order obtaining the load information is not limited to this. The load characteristic obtainer 20 may supply the electric power to the load information outputter 120 B to obtain the load information from the light source unit 100 B, and then supply the electric power to the load information outputter 120 A to obtain the load information from the light source unit 100 A. That is, the load characteristic obtainer 20 may supply the electric power to the corresponding load information outputters 120 of the plurality of light source units 100 in sequence so as to obtain the load information from the load information outputters 120 in sequence.

In this First Variation, the one lighting device 1 causes the two light source units 100 A and 100 B to emit light, but it may cause three or more light source units 100 to emit light. Also in this case, the load characteristic obtainer 20 may supply electric power to a load information outputter 120 of each light source unit 100 individually, only during a time period of obtaining the load information from the load information outputter 120 .

(1. 3. 2) Second Variation

FIG. 4 is a circuit diagram of a lighting device 1 according to a Second Variation.

In the First Variation the lighting device 1 includes the two current outputters 10 A and 10 B configured to respectively supply currents to the two light source units 100 A and 100 B, but in this Second Variation the lighting device 1 includes a single current outputter 10 configured to supply a current to two light source units 100 A and 100 B.

Hereinafter, components similar to those of the First Embodiment (including the First Variation) are denoted by same reference signs and explanations thereof are omitted. In particular, since a current outputter 10 , a drive signal generating circuit (DSGC) 32 and an output current detector 40 of this Second Variation are similar to those of the First Embodiment, explanations thereof are omitted. Also since a load characteristic obtainer 20 of this Second Variation is similar to that of the First Variation, an explanation thereof is omitted.

Light sources 110 A and 110 B of the light source units 100 A and 100 B are connected in series to each other between output terminals of the current outputter 10 . A switch element Q 4 is connected in parallel to the light source 110 B, which is one of the light sources 110 A and 110 B. As a result, a current output from the current outputter 10 continuously flows through the light source 110 A, regardless of on/off of the switch element Q 4 . On the other hand, regarding the light source 110 B the current output from the current outputter 10 flows through it only while the switch element Q 4 is in an off state. It is herein assumed that the light source units 100 A and 100 B are used for headlights, and in particular, for example, the light source 110 A of the light source unit 100 A is a headlight for passing beam (so-called low-beam) and the light source 110 B of the light source unit 100 B is a headlight for travelling beam (so-called high-beam). The light source 110 B is accordingly configured to emit light only while the switch element Q 4 is in the off state.

A microcomputer 31 of this Second Variation has: an input port PI 1 connected to a positive electrode of a DC power supply E 1 so that a switch SW 2 is interposed between the input port PI 1 and the positive electrode; and an output port PO 3 connected to a control terminal of the switch element Q 4 .

Hereinafter, operation of the lighting device 1 according to the Second Variation will be described.

When a switch SW 1 is turned on, the DC power supply E 1 starts supply of the electric power to the lighting device 1 . Accordingly, the microcomputer 31 starts an initialization process. After the initialization process, the microcomputer 31 performs operation for reading the load information from load information outputters 120 A and 120 B of the light source units 100 A and 100 B. After reading the load information from the load information outputters 120 A and 120 B, the microcomputer 31 determines luminous flux ranks of the light sources 110 A and 110 B, and sets respective target values of the output currents according to the luminous flux ranks. Since in the Second variation, a series of processes from a step of the load characteristic obtainer 20 obtaining the load information to a step of setting the target values of the output currents are similar to those in the First Variation, explanations thereof are omitted.

The microcomputer 31 monitors a voltage level at the input port PI 1 to determine, based on the voltage level, whether both of the light source units 100 A and 100 B or only the light source unit 100 A should be turned on.

For example, when the switch SW 2 is in an off state and the voltage level at the input port PI 1 is accordingly made to a Low-level, the microcomputer 31 outputs a High-level signal via the output port PO 3 to make the switch element Q 4 in an on state, thereby causing only the light source unit 100 A to emit light. The microcomputer 31 further sets a value in a case of causing only the light source unit 100 A to emit light, as a setting value of an output current of the current outputter 10 . The microcomputer 31 determines whether or not an input voltage of the current outputter 10 is within an operational range, and outputs a target voltage according to the setting value of the output current to the drive signal generating circuit 32 if the input voltage is determined to be within the operational range. The drive signal generating circuit 32 controls an output of the current outputter 10 , based on a detection voltage received from the output current detector 40 and the target voltage received from the microcomputer 31 . Thus, the current outputter 10 can supply, to the light source unit 100 A, a current required to cause only the light source unit 100 A to emit light.

On the other hand, when the switch SW 2 is in an on state and the voltage level at the input port PI 1 is accordingly made to a High-level, the microcomputer 31 outputs a Low-level signal via the output port PO 3 to make the switch element Q 4 in an off state, thereby causing both of the light source units 100 A and 100 B to emit light. The microcomputer 31 sets a smaller value of values in cases of causing the light source units 100 A and 100 B to emit light, as the setting value of the output current of the current outputter 10 . The microcomputer 31 determines whether or not the input voltage of the current outputter 10 is within the operational range, and outputs the target voltage according to the setting value of the output current to the drive signal generating circuit 32 if the input voltage is determined to be within the operational range. The drive signal generating circuit 32 controls the output of the current outputter 10 , based on the detection voltage received from the output current detector 40 and the target voltage received from the microcomputer 31 . Thus, the current outputter 10 can supply, to both of the light source units 100 A and 100 B, a current required to cause them to emit light.

Note that, in a case of causing a plurality of light source units 100 connected in parallel to each other to emit light, using a single current outputter 10 , a controller 30 may control the output current of the single current outputter 10 so as to match a total value of rated currents of the plurality of light source units 100 , based on the load information received from the plurality of light source units 100 .

(1. 3. 3) Other Variations

In the First Embodiment, the number of ranks in luminous characteristics of light sources 110 is five, but may be two or more.

The light source 110 is not limited to an LED(s), but may be, for example, an organic light-emitting diode(s), as long as the light source 110 is a semiconductor light source.

The load information outputter 120 includes a resistor, and outputs a voltage value previously determined for a luminous characteristic of the lights source 110 when electric power is supplied thereto. However, instead of the voltage value, the load information outputter 120 may output a current value previously determined for the luminous characteristic.

Instead of the resistor, the load information outputter 120 may include a memory storing the load information, or the like. In this case, the load characteristic obtainer 20 may have an interface for obtaining the load information from the memory of the load information outputter 120 , and supply electric power to the memory (load information outputter 120 ) only during a time period of reading the load information.

Second Embodiment

A lighting device 1 according to a Second Embodiment will be described with reference to FIG. 5 . A configuration in the Second Embodiment (including variations) described below can be applied in appropriately combination with configurations in the other embodiments (including variations).

(2. 1) Configuration

The lighting device 1 of this embodiment includes a current outputter 10 , a load characteristic obtainer 20 , a temperature obtainer 50 and a controller 30 . The lighting device 1 of this embodiment further includes an output current detector 40 . Since the current outputter 10 , the load characteristic obtainer 20 and the output current detector 40 are similar to those in the First Embodiment, explanations thereof are omitted.

The lighting device 1 of this embodiment is used for causing a light source unit 100 , installed to a vehicle such as an automobile, to emit light. The light source unit 100 includes a light source 110 , a load information outputter 120 and a temperature probe 130 for measuring a temperature of the light source unit 100 . Note that since the light source 110 and the load information outputter 120 are similar to those in the First Embodiment, explanations thereof are omitted.

The temperature probe 130 is used for measuring a temperature around the light source 110 . The temperature probe 130 includes, for example, a thermistor Rt 1 disposed inside a casing of the light source unit 100 . A resistance value of the thermistor Rt 1 is changed, depending on the temperature around the light source 110 . The temperature probe 130 may be disposed so as to measure directly a temperature of the light source 110 .

The temperature obtainer 50 of the lighting device 1 is constituted by a resistor R 21 , a switch element Q 5 and a microcomputer 31 . The resistor R 21 has a first end to which a DC voltage Vcc is applied, and a second end connected to a first end of the thermistor Rt 1 . The switch element Q 5 is connected between a second end of the thermistor Rt 1 and the ground of circuit.

The controller 30 includes the microcomputer 31 and a drive signal generating circuit 32 . Since the drive signal generating circuit 32 in this embodiment has a configuration similar to that in the First Embodiment, an explanation thereof is omitted.

The microcomputer 31 includes a CPU and a memory. The CPU executes a program(s) stored in the memory, thereby the following functions and the like being realized: a function of obtaining the load information from the load information outputter 120 ; a function of determining the luminous characteristic, using the load information; a function of obtaining a measuring value of the temperature from the temperature probe 130 ; and a function of controlling an output of the current outputter 10 in accordance with the luminous characteristic and the measuring value of the temperature. The microcomputer 31 has output ports PO 1 and PO 4 connected to control electrodes of the switch elements Q 2 and Q 5 , respectively. The microcomputer 31 further has: an analog input port AD 1 to which a voltage at a connecting point between resistors R 2 and R 10 is input; an analog input port AD 4 to which a voltage at a connecting point between the resistor R 21 and the thermistor Rt 1 is input; and an analog output port DA 1 connected to the drive signal generating circuit 32 . The program(s) to be executed by the CPU of the microcomputer 31 may be previously stored in the memory in time of factory shipment of the lighting device 1 , or may be recorded and provided in a storage medium such as a memory card. Alternatively, the program(s) may be provided through an electric telecommunication line.

(2. 2) Explanation of Operation

Operation of the lighting device 1 of this embodiment will be explained below.

When a power supply switch SW 1 is turned on in response to an operation of a driver who drives a vehicle or an on-command from an ECU of the vehicle, electric power is supplied from a DC power supply E 1 to the lighting device 1 . Accordingly, the microcomputer 31 starts an initialization process. After the initialization process, the microcomputer 31 performs operation for reading the load information from the load information outputter 120 of the light source unit 100 . After the operation for reading the load information, the microcomputer 31 performs operation for determining the luminous flux rank based on the load information. Note that since this operation for determining the luminous flux rank is similar to that in the First Embodiment, an explanation thereof is omitted.

Next, the microcomputer 31 performs operation for reading the measuring value of the temperature from the temperature probe 130 of the light source unit 100 . Until starting the operation for reading the measuring value of the temperature, the microcomputer 31 keeps a voltage level of the output port PO 4 at a Low-level, so that the switch element Q 5 is in an off state. In this state, no electric power is supplied into the temperature probe 130 . Then upon the operation for reading the measuring value of the temperature, the microcomputer 31 switches the voltage level of the output port PO 4 to a High-level to make the switch element Q 5 in an on state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistor R 21 and the thermistor Rt 1 , and thus the analog input port AD 4 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistor R 21 and the thermistor Rt 1 .

In the on state of the switch element Q 5 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 4 , to the A/D conversion to obtain the divided voltage. The microcomputer 31 calculates a resistance value of the thermistor Rt 1 , using the divided voltage, input to the analog input port AD 4 , and then obtains the temperature around the light source 110 from the resistance value of the thermistor Rt 1 . After obtaining a measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 4 to the Low-level to make the switch element Q 5 in the off state. Supplying of the electric power to the thermistor Rt 1 is accordingly cut off. In this way, the microcomputer 31 supplies the electric power to the temperature probe 130 only during a time period of obtaining the measuring value of the temperature, but stops supply of the electric power to the temperature probe 130 during a time period other than the time period of obtaining the measuring value of the temperature.

When succeeding in determination of the luminous flux rank of the light source 110 , the microcomputer 31 obtains a setting value of an output current corresponding to the luminous flux rank from the memory. Furthermore, the microcomputer 31 corrects the setting value of the output current determined based on the luminous flux rank, using the measuring value of the temperature obtained from the temperature probe 130 . The memory of the microcomputer 31 previously stores, for example, a temperature threshold and a correction amount to be used when the measuring value of the temperature exceeds the temperature threshold.

If the measuring value of the temperature obtained from the temperature probe 130 is less than the temperature threshold, the microcomputer 31 determines a target voltage, using the setting value of the output current determined based on the luminous flux rank, and then outputs the target voltage to the drive signal generating circuit 32 through the analog output port DA 1 . On the other hand, if the measuring value of the temperature obtained from the temperature probe 130 is equal to or more than the temperature threshold, the microcomputer 31 subtracts the correction amount from the setting value of the output current determined based on the luminous flux rank, in order to obtain a corrected setting value of the output current. The microcomputer 31 then determines the target voltage based on the corrected setting value of the output current, and outputs the target voltage to the drive signal generating circuit 32 through the analog output port DA 1 .

The drive signal generating circuit 32 adjusts a duty ratio (an on-duty) of a drive signal VS 1 so that a detection voltage obtained from the output current detector 40 matches the target voltage received from the microcomputer 31 , and the output current of the current outputter 10 is accordingly controlled so as to have a desired current value.

In this embodiment, the microcomputer 31 periodically obtains the measuring value of the temperature from the temperature probe 130 while the light source unit 100 is in lighting, and further periodically performs a processing for correcting the setting value of the output current, using the measuring value of the temperature. In this embodiment, the microcomputer 31 performs operation for reducing the output current when the temperature is relatively high, using the measuring value of the temperature.

Incidentally, in the light source unit 100 , the LED of the light source 110 is attached to a heat radiation board, a heat sink or the like. For this reason, it is expected that a change in the temperature of the light source 110 is slower than a control period for the feedback control of the drive signal generating circuit 32 . Therefore, the microcomputer 31 obtains the measuring value of the temperature from the temperature probe 130 , at a period longer than the control period for the feedback control of the drive signal generating circuit 32 . For example, when the control period is set to almost 100 μsec, the microcomputer 31 may obtain the measuring value of the temperature from the temperature probe 130 , at a period from almost 10 msec to almost 1 sec.

It is herein assumed that, in the temperature obtainer 50 of the lighting device 1 , the DC voltage Vcc and the resistance value of the resistor R 21 are 5V and 1 kΩ, respectively. It is also assumed that the thermistor Rt 1 has specification where a resistance value at 25° C. agrees with 10 kΩ, and a B constant between 25° C. and 50° C. is 3380K.

The resistance value of the thermistor Rt 1 is changed into 10 kΩ at 25° C., 0.9760 kΩ at 100° C., and 0.5324 kΩ at 125° C., that is, it is reduced depending on an increase in the temperature. Accordingly, the divided voltage, input to the analog input port AD 4 of the microcomputer 31 , is reduced, as the temperature is increased. Specifically, the divided voltage becomes, for example, 4.545V at 25° C., 2.470V at 100° C., and 1.737V at 125° C. The microcomputer 31 can therefore obtain the temperature around the light source 110 , using the divided voltage, input to the analog input port AD 4 .

While the temperature obtainer 50 obtains the measuring value of the temperature from the temperature probe 130 , the current flowing through the thermistor Rt 1 becomes, for example, 0.455 mA at 25° C., 2.530 mA at 100° C., and 3.263 mA at 125° C. Since the resistance value of the thermistor Rt 1 is reduced depending on the increase in the temperature as described above, the current flowing through the thermistor Rt 1 is increased as the temperature is increased, while the temperature obtainer 50 obtains the measuring value of the temperature from the temperature probe 130 . In this embodiment, even when the temperature is relatively high, the temperature obtainer 50 supplies the power to the temperature probe 130 only during a time period of obtaining the temperature. It is therefore possible to suppress power consumption of the temperature probe 130 , compared with a case where the power is continuously supplied to the temperature probe 130 .

(2. 3) Variations

Hereinafter, variations of the above embodiment will be listed. Note that the variations explained below can be applied in appropriately combination with the First and Second Embodiments.

(2. 3. 1) First Variation

FIG. 6 is a circuit diagram of a lighting device 1 according to a First Variation. Hereinafter, components similar to those of the Second Embodiment are denoted by same reference signs and explanations thereof are omitted.

In the above Second Embodiment, the switch element Q 2 is connected between the resistor R 10 and the ground of circuit, and the switch element Q 5 is connected between the thermistor Rt 1 and the ground of circuit, so that the switch elements Q 2 and Q 5 are individually turned on/off by the microcomputer 31 . On the other hand, in this First Variation, a switch element Q 6 is connected between a resistor R 10 and the ground of circuit and further between a thermistor Rt 1 and the ground of circuit. The switch element Q 6 has a control terminal connected to an output port PO 5 of a microcomputer 31 .

The microcomputer 31 keeps a voltage level of the output port PO 5 at a Low-level, so that the switch element Q 6 is in an off state, during a time period other than a time period of obtaining the load information and the measuring value of the temperature. Accordingly, no electric power is supplied to a load information outputter 120 and a temperature probe 130 .

On the other hand, the microcomputer 31 switches the voltage level at the output port PO 5 to a High-level, so that the switch element Q 6 is in an on state, only during the time period of obtaining the load information and the measuring value of the temperature. In the on state of the switch element Q 6 , the electric power is supplied to the load information outputter 120 and the temperature probe 130 . While keeping the voltage level of the output port PO 5 at the High-level, the microcomputer 31 subjects input voltages of the analog input ports AD 1 and AD 4 to an A/D conversion to obtain the load information of a light source 110 and the measuring value of the temperature.

The microcomputer 31 determines a luminous flux rank based on the load information of the light source 110 , and controls an output current of a current outputter 10 based on the luminous flux rank and the measuring value of the temperature. In the microcomputer 31 , since the process controlling the output current of the current outputter 10 based on the luminous flux rank of the light source 110 and the measuring value of the temperature is similar to that in the Second Embodiment, an explanation thereof is omitted.

In this First Variation, a load characteristic obtainer 20 is constituted by a resistor R 2 , the switch element Q 6 and the microcomputer 31 , and a temperature obtainer 50 is constituted by a resistor R 21 , the switch element Q 6 and the microcomputer 31 . In other words, circuits of the load characteristic obtainer 20 and the temperature obtainer 50 include a common circuit element (switch element Q 6 ) so as to share the common circuit element. It is therefore possible to downsize the whole circuit of the lighting device 1 , compared with a case where the load characteristic obtainer 20 and the temperature obtainer 50 respectively include switch elements different from each other.

(2. 3. 2) Second Variation

FIG. 7 is a circuit diagram of a lighting device 1 according to a Second Variation. Hereinafter, components similar to those of the Second Embodiment are denoted by same reference signs and explanations thereof are omitted.

In the Second Embodiment, the power supply circuit generating the DC voltage Vcc applies voltages to the load information outputter 120 and the temperature probe 130 . In contrast, in this Second Variation, a microcomputer 31 applies, through output ports PO 6 and PO 7 thereof, voltages to a load information outputter 120 and a temperature probe 130 , respectively.

In other words, resistors R 2 and R 10 are connected in series to each other between the output port PO 6 of the microcomputer 31 and the ground of circuit, so that a voltage at a connecting point between the resistors R 2 and R 10 is input to an analog input port AD 1 of the microcomputer 31 .

Furthermore, a resistor R 21 and a thermistor Rt 1 are connected in series to each other between the output port PO 7 of the microcomputer 31 and the ground of circuit, so that a voltage at a connecting point between the resistor R 21 and the thermistor Rt 1 is input to an analog input port AD 4 of the microcomputer 31 .

In this Second Variation, the microcomputer 31 keeps a voltage level of the output port PO 6 at a Low-level, so that no electric power is supplied to the load information outputter 120 , during a time period other than a time period of obtaining the load information. The microcomputer 31 switches the voltage level of the output port PO 6 to a High-level, so that a constant voltage is applied through the output port PO 6 to the series circuit formed by the resistors R 2 and R 10 , during the time period of obtaining the load information. At this time, the microcomputer 31 subjects a divided voltage, input to the analog input port AD 1 , to an A/D conversion to obtain a voltage across the resistor R 10 , and then determines a luminous flux rank of a light source 110 , using the voltage across the resistor R 10 .

Also the microcomputer 31 keeps a voltage level of the output port PO 7 at a Low-level, so that no electric power is supplied to the temperature probe 130 , during a time period other than a time period of obtaining the measuring value of the temperature. The microcomputer 31 switches the voltage level of the output port PO 7 to a High-level, so that a constant voltage is applied through the output port PO 7 to the series circuit formed by the resistor R 21 and the thermistor Rt 1 , during the time period of obtaining the measuring value of the temperature from the temperature probe 130 . At this time, the microcomputer 31 subjects a divided voltage, input to the analog input port AD 4 , to an A/D conversion to obtain a voltage across the thermistor Rt 1 , and then obtains the measuring value of the temperature from the voltage across the thermistor Rt 1 .

In this Second Variation, since the microcomputer 31 applies, through the output ports PO 6 and PO 7 , the voltages to the load information outputter 120 and the temperature probe 130 , respectively, the switch elements Q 2 and Q 5 in the Second Embodiment are not required. It is therefore possible to downsize the whole circuit of the lighting device 1 , compared with the Second Embodiment.

(2. 3. 3) Third Variation

FIG. 8 is a circuit diagram of a lighting device 1 according to a Third Variation. Hereinafter, components similar to those of the Second Embodiment are denoted by same reference signs and explanations thereof are omitted.

In the Second Embodiment one lighting device 1 causes one light source unit 100 to emit light, but in this Third Variation one lighting device 1 causes two light source units 100 A and 100 B to emit light. Note that components similar to those of the Second Embodiment or the First Variation of the First Embodiment are denoted by same reference signs and explanations thereof are omitted.

The light source units 100 A and 100 B respectively include light sources 110 A and 110 B, each of which includes a semiconductor light-emitting element(s) such as an LED(s). The light source units 100 A and 100 B further include load information outputters 120 A and 120 B which are to output load information representing luminous characteristics of the light sources 110 A and 110 B, when electric power is supplied to the load information outputters 120 A and 120 B, respectively. The light source units 100 A and 100 B further include temperature probes 130 A and 130 B which are used for measuring temperatures of the light sources 110 A and 110 B, respectively.

The lighting device 1 includes current outputters 10 A and 10 B, a load characteristic obtainer 20 , a temperature obtainer 50 , a controller 30 , and output current detectors 40 A and 40 B. Since configurations of the current outputters 10 A and 10 B and the output current detectors 40 A and 40 B are similar to those in the First Variation of the First Embodiment, explanations thereof are omitted.

The load characteristic obtainer 20 is constituted by a resistor R 2 , switch elements Q 2 and Q 3 , and a microcomputer 31 . The resistor R 2 has a first end to which a DC voltage Vcc is applied, and a second end connected to first ends of the switch elements Q 2 and Q 3 . A first end and a second end of a resistor R 11 are connected to a second end of the switch element Q 2 and the ground of circuit, respectively. A first end and a second end of a resistor R 12 are connected to a second end of the switch element Q 3 and the ground of circuit, respectively.

The temperature obtainer 50 is constituted by a resistor R 21 , switch elements Q 5 and Q 7 , and the microcomputer 31 . The resistor R 21 has a first end to which the DC voltage Vcc is applied, and a second end connected to first ends of the switch elements Q 5 and Q 7 . A first end and a second end of a thermistor Rt 1 are connected to a second end of the switch element Q 5 and the ground of circuit, respectively. A first end and a second end of a thermistor Rt 2 are connected to a second end of the switch element Q 7 and the ground of circuit, respectively.

The controller 30 includes the microcomputer 31 and drive signal generating circuits 32 A and 32 B. Since configurations of the drive signal generating circuits 32 A and 32 B are similar to those in the First Variation of the First Embodiment, explanations thereof are omitted.

The microcomputer 31 has: an analog input port AD 1 to which a voltage at a connecting point between the resistor R 2 and the switch elements Q 2 and Q 3 is input; an analog input port AD 2 to which a voltage is input, obtained by an input voltage V 1 A of the current outputter 10 A being divided by resistors R 3 and R 4 ; an analog input port AD 3 to which a voltage is input, obtained by an input voltage V 1 B of the current outputter 10 B being divided by resistors R 5 and R 6 ; and an analog input port AD 4 to which a voltage at a connecting point between the resistor R 21 and the switch elements Q 5 and Q 7 is input. The microcomputer 31 further has output ports PO 1 , PO 2 , PO 8 and PO 9 connected to control terminals of the switch elements Q 2 , Q 3 , Q 5 and Q 7 , respectively. The microcomputer 31 further has: an analog output port DA 1 from which a target voltage is output to the drive signal generating circuit 32 A; and an analog output port DA 2 from which a target voltage is output to the drive signal generating circuit 32 B.

Hereinafter, operation of the lighting device 1 according to the Third Variation will be described with reference to a flowchart of FIG. 9 .

In the case of the lighting device 1 according to the Third Variation, when any one of switches SW 1 and SW 2 is turned on, electric power is supplied from a DC power supply E 1 to the lighting device 1 . Accordingly, the microcomputer 31 starts an initialization process (refer to a Step S 11 ). After the initialization process, the microcomputer 31 performs operation for reading the load information from the load information outputters 120 A and 120 B of the light source units 100 A and 100 B (refer to a Step S 12 ).

Until starting the operation for reading the load information, the microcomputer 31 keeps voltage levels of the output ports PO 1 and PO 2 at Low-levels, so that the switch elements Q 2 and Q 3 are in off states, respectively. In this state, no electric power is supplied into the load information outputters 120 A and 120 B. Then upon the operation for reading the load information, first, the microcomputer 31 switches the voltage level of the output port PO 1 to a High-level to make the switch element Q 2 in an on state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistors R 2 and R 11 , and thus the analog input port AD 1 of the microcomputer 31 receives a divided voltage VL 1 obtained by the DC voltage Vcc being divided by the resistors R 2 and R 11 . In the on state of the switch element Q 2 , the microcomputer 31 subjects the divided voltage VL 1 , input to the analog input port AD 1 , to an A/D conversion to obtain a value of the divided voltage VL 1 . After obtaining the divided voltage VL 1 , the microcomputer 31 switches the voltage level of the output port PO 1 to the Low-level to make the switch element Q 2 in the off state. Supplying of the electric power to the resistor R 11 is accordingly cut off.

Next, the microcomputer 31 switches the voltage level of the output port PO 2 to a High-level to make the switch element Q 3 in an on state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistors R 2 and R 12 , and thus the analog input port AD 1 of the microcomputer 31 receives a divided voltage VL 2 obtained by the DC voltage Vcc being divided by the resistors R 2 and R 12 . In the on state of the switch element Q 3 , the microcomputer 31 subjects the divided voltage VL 2 , input to the analog input port AD 1 , to an A/D conversion to obtain a value of the divided voltage VL 2 . After obtaining a measured value of the divided voltage VL 2 , the microcomputer 31 switches the voltage level of the output port PO 2 to the Low-level to make the switch element Q 3 in the off state. Supplying of the electric power to the resistor R 12 is accordingly cut off.

After obtaining the divided voltages VL 1 and VL 2 , the microcomputer 31 compares a measured value of each of the divided voltages VL 1 and VL 2 with a determination range of a divided voltage in each luminous flux rank in order to determine luminous flux ranks (load specification) of the light sources 110 A and 110 B (refer to a Step S 13 ). When succeeding in determination of the luminous flux ranks of the light sources 110 A and 110 B, the microcomputer 31 obtains setting values of output currents corresponding to the determined luminous flux ranks from the memory (refer to a Step S 14 ). If at least any one of the measured values of the divided voltages VL 1 and VL 2 fails to meet any of the determination ranges corresponding to the luminous flux ranks 1 to 5, the microcomputer 31 determines that abnormality occurs in a circuit obtaining the load information from the load information outputter 120 , or the like, and cancels a process for setting the target values of the output currents.

When succeeding in determination of the luminous flux ranks of the light sources 110 A and 110 B, the microcomputer 31 subjects a voltage V 6 , input to the analog input port AD 2 , to an A/D conversion, and then obtains an input voltage V 1 A input to the current outputter 10 A from a measured value of the voltage V 6 . Also the microcomputer 31 subjects a voltage V 7 , input to the analog input port AD 3 , to an A/D conversion, and then obtains an input voltage V 1 B input to the current outputter 10 B from a measured value of the voltage V 7 (refer to a Step S 15 ).

After obtaining measured values of the input voltages V 1 A and V 1 B, the microcomputer 31 determines whether or not each of the measured values of the input voltages V 1 A and V 1 B is within an operational range (refer to Steps S 16 , S 17 and S 18 ). Since the DC power supply E 1 uses a battery of a vehicle as a power source, a power supply voltage of the DC power supply E 1 may be changed. If the measured values of the input voltages V 1 A and V 1 B each are within the operational range, the microcomputer 31 starts a process for lighting the light sources 110 A and 110 B, otherwise cancels the process.

If the measured values of the input voltages V 1 A and V 1 B each are within the operational range in determination processes of the Steps S 16 and S 17 (i.e., the Step S 16 : Yes, the Step S 17 : Yes), the microcomputer 31 starts a process for lighting both of the light sources 110 A and 110 B. The microcomputer 31 outputs a target voltage V 41 according to the luminous flux rank of the light source 110 A to the drive signal generating circuit 32 A (refer to a Step S 19 ), and further a target voltage V 42 according to the luminous flux rank of the light source 110 B to the drive signal generating circuit 32 B (refer to a Step S 20 ). The respective outputs of the current outputters 10 A and 10 B are controlled by the drive signal generating circuits 32 A and 32 B so that currents are supplied from the current outputters 10 A and 10 B to the light source units 100 A and 100 B, and the light sources 110 A and 110 B accordingly emit light.

After that, the microcomputer 31 performs a process for obtaining the measuring values of the temperatures from the temperature probes 130 A and 130 B, for example, every 10 msec (refer to a Step S 21 ). Until starting the operation for reading the measuring values of the temperatures, the microcomputer 31 keeps voltage levels of the output ports PO 8 and PO 9 at Low-levels, so that the switch elements Q 5 and Q 7 are in off states, respectively. In this state, no electric power is supplied into the temperature probes 130 A and 130 B. Then upon the operation for reading the measuring values of the temperatures, first, the microcomputer 31 switches the voltage level of the output port PO 8 to a High-level to make the switch element Q 5 in an on state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistor R 21 and the thermistor Rt 1 , and thus the analog input port AD 4 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistor R 21 and the thermistor Rt 1 . In the on state of the switch element Q 5 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 4 , to an A/D conversion to obtain the temperature of the light source 110 A from a value of the divided voltage. After obtaining the measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 8 to the Low-level to make the switch element Q 5 in the off state. Supplying of the electric power to the thermistor Rt 1 is accordingly cut off.

Next, the microcomputer 31 switches the voltage level of the output port PO 9 to a High-level to make the switch element Q 7 in an on state. At this time, the DC voltage Vcc is applied to a series circuit formed by the resistor R 21 and the thermistor Rt 2 , and thus the analog input port AD 4 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistor R 21 and the thermistor Rt 2 . In the on state of the switch element Q 7 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 4 , to an A/D conversion to obtain the temperature of the light source 110 B from a value of the divided voltage. After obtaining the measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 9 to the Low-level to make the switch element Q 7 in the off state. Supplying of the electric power to the thermistor Rt 2 is accordingly cut off.

After obtaining the measuring values of the temperatures from the temperature probes 130 A and 130 B, the microcomputer 31 performs a process for correcting the target voltages V 41 and V 42 , using the measuring values of the temperatures of the light sources 110 A and 110 B. The microcomputer 31 outputs the corrected target voltages V 41 and V 42 to the drive signal generating circuits 32 A and 32 B, so that the output currents of the current outputters 10 A and 10 B are corrected in accordance with the measuring values of the temperatures (refer to a Step S 22 ).

In this way, for example, whenever 10 msec pass, the microcomputer 31 obtains the measuring values of the temperatures from the temperature probes 130 A and 130 B, and corrects the values of the currents to be supplied from the lighting device 1 to the light source units 100 A and 100 B in accordance with changes in the temperatures of the light source units 100 A and 100 B.

In the determination processes of the Steps S 16 and S 17 , if the detected value of the input voltage V 1 A is within the operational range, but the measured value of the input voltage V 1 B is out of the operational range (the Step S 16 : Yes, the Step S 17 : No), the microcomputer 31 starts a process for lighting only the light source 110 A.

The microcomputer 31 outputs the target voltage V 41 according to the luminous flux rank of the light source 110 A to the drive signal generating circuit 32 A (refer to a Step S 23 ). The output of the current outputter 10 A is controlled by the drive signal generating circuit 32 A so that a current is supplied from the current outputter 10 A to the light source unit 100 A, and the light source 110 A accordingly emits light.

After that, the microcomputer 31 performs a process for obtaining the measuring value of the temperature from the temperature probe 130 A, for example, every 10 msec (refer to a Step S 24 ).

After obtaining the measuring value of the temperature from the temperature probe 130 A, the microcomputer 31 performs a process for correcting the target voltage V 41 , using the measuring value of the temperature of the light source 110 A. The microcomputer 31 then outputs the corrected target voltage V 41 to the drive signal generating circuit 32 A, so that the output current of the current outputter 10 A is corrected in accordance with the measuring value of the temperature (refer to a Step S 25 ). The value of the current to be supplied from the lighting device 1 to the light source unit 100 A can be therefore corrected in accordance with a change in the temperature of the light source unit 100 A.

In the determination processes of the Steps S 16 and S 18 , if the measured value of the input voltage V 1 B is within the operational range, but the detected value of the input voltage V 1 A is out of the operational range (the Step S 16 : No, the Step S 18 : Yes), the microcomputer 31 starts a process for lighting only the light source 110 B.

The microcomputer 31 outputs the target voltage V 42 according to the luminous flux rank of the light source 110 B to the drive signal generating circuit 32 B (refer to a Step S 26 ). The output of the current outputter 10 B is controlled by the drive signal generating circuit 32 B so that a current is supplied from the current outputter 10 B to the light source unit 100 B, and the light source 110 B accordingly emits light.

After that, the microcomputer 31 performs a process for obtaining the measuring value of the temperature from the temperature probe 130 B, for example, every 10 msec (refer to a Step S 27 ).

After obtaining the measuring value of the temperature from the temperature probe 130 B, the microcomputer 31 performs a process for correcting the target voltage V 42 , using the measuring value of the temperature of the light source 110 B. The microcomputer 31 then outputs the corrected target voltage V 42 to the drive signal generating circuit 32 B, so that the output current of the current outputter 10 B is corrected in accordance with the measuring value of the temperature (refer to a Step S 28 ).

After that, for example, whenever 10 msec pass, the microcomputer 31 obtains the measuring value of the temperature from the temperature probe 130 B, and corrects the value of the current to be supplied from the lighting device 1 to the light source unit 100 B in accordance with a change in the temperature of the light source unit 100 B.

In the determination processes of the Steps S 16 and S 18 , if both of the measured values of the input voltages V 1 A and V 1 B are out of the operational range (the Step S 16 : No, the Step S 18 : No), the microcomputer 31 cancels a process for lighting the light sources 110 A and 110 B and keeps them in non-lighting states.

The microcomputer 31 does not output the target voltages V 41 and V 42 to the drive signal generating circuits 32 A and 32 B (refer to a Step S 29 ), so that the light sources 110 A and 110 B are kept in the non-lighting states.

Incidentally in this Third Variation, the switch element Q 2 of the load characteristic obtainer 20 is connected between the resistors R 2 and R 11 , but it may be connected between the resistor 11 and the ground of circuit. Similarly, the switch element Q 3 of the load characteristic obtainer 20 is connected between the resistors R 2 and R 12 , but it may be connected between the resistor R 12 and the ground of circuit.

In this Third Variation, the switch element Q 5 of the temperature obtainer 50 is connected between the resistor R 21 and the thermistor Rt 1 , but it may be connected between the thermistor Rt 1 and the ground of circuit. Similarly, the switch element Q 7 of the temperature obtainer 50 is connected between the resistor R 21 and the thermistor Rt 2 , but it may be connected between the thermistor Rt 2 and the ground of circuit.

In this Third Variation, the one lighting device 1 causes the two light source units 100 to emit light, but it may cause three or more light source units 100 to emit light. Also in this case, the load characteristic obtainer 20 may supply electric power to load information outputters 120 of the three or more light source units 100 individually, only during time periods of obtaining the load information from the load information outputters 120 . The temperature obtainer 50 may also supply electric power to temperature probes 130 of the three or more light source units 100 in sequence only during time periods of obtaining the measuring values of the temperatures from the temperature probes 130 .

(2. 3. 4) Fourth Variation

FIG. 10 is a circuit diagram of a lighting device 1 according to a Fourth Variation.

In this Fourth Variation, circuits of the load characteristic obtainer 20 and the temperature obtainer 50 , of the lighting device 1 explained in the Third Variation of the Second Embodiment, include a common circuit element so as to share the common circuit element. Note that since components other than the load characteristic obtainer 20 and the temperature obtainer 50 are similar to those in the Third Variation, such components are denoted by same reference signs and explanations thereof are omitted.

The load characteristic obtainer 20 is constituted by a resistor R 2 , switch elements Q 2 and Q 3 , and a microcomputer 31 . The resistor R 2 has a first end to which a DC voltage Vcc is applied, and a second end connected to first ends of the switch elements Q 2 and Q 3 . A resistor R 11 is connected between a second end of the switch element Q 2 and the ground of circuit. A resistor R 12 is connected between a second end of the switch element Q 3 and the ground of circuit.

The temperature obtainer 50 is constituted by the resistor R 2 , switch elements Q 5 and Q 7 , and the microcomputer 31 . To the first end of the resistor R 2 , the DC voltage Vcc is applied. To the second end of the resistor R 2 , first ends of the switch elements Q 5 and Q 7 are connected. A thermistor Rt 1 is connected between a second end of the switch element Q 5 and the ground of circuit. A thermistor Rt 2 is connected between a second end of the switch element Q 7 and the ground of circuit.

The microcomputer 31 has an analog input port AD 1 to which a voltage at a connecting point between the switch elements Q 2 , Q 3 , Q 5 and Q 7 and the resistor R 2 is input.

Hereinafter, operation of the load characteristic obtainer 20 and the temperature obtainer 50 will be described.

Until starting operation for reading the load information and the temperature, the microcomputer 31 keeps voltage levels of the output ports PO 1 , PO 2 , PO 8 and PO 9 at Low-levels, so that the switch elements Q 2 , Q 3 , Q 5 and Q 7 are in off states, respectively. In this state, no electric power is supplied into the load information outputters 120 A and 120 B and the thermistors Rt 1 and Rt 2 .

Upon the operation for reading the load information of the light source unit 100 A, the microcomputer 31 switches the voltage level of the output port PO 1 to a High-level, while keeping the voltage levels of the output ports PO 2 , PO 8 and PO 9 at the Low-levels. At this time, only the switch element Q 2 is turned on, but the remaining switch elements Q 3 , Q 5 and Q 7 are kept in off, and the DC voltage Vcc is therefore applied to a series circuit formed by the resistors R 2 and R 11 . Thus, the analog input port AD 1 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistors R 2 and R 11 . In the on state of only the switch element Q 2 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 1 , to an A/D conversion to obtain the load information (luminous flux rank) of the light source 110 A from a value of the divided voltage. After obtaining the measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 1 to the Low-level to make the switch element Q 2 in the off state. Supplying of the electric power to the resistor R 11 is accordingly cut off.

Upon the operation for reading the load information of the light source unit 100 B, the microcomputer 31 switches the voltage level of the output port PO 2 to a High-level, while keeping the voltage levels of the output ports PO 1 , PO 8 and PO 9 at the Low-levels. At this time, only the switch element Q 3 is turned on, but the remaining switch elements Q 2 , Q 5 and Q 7 are kept in off, and the DC voltage Vcc is therefore applied to a series circuit formed by the resistors R 2 and R 12 . Thus, the analog input port AD 1 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistors R 2 and R 12 . In the on state of only the switch element Q 3 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 1 , to an A/D conversion to obtain the load information (luminous flux rank) of the light source 110 B from a value of the divided voltage. After obtaining the measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 2 to the Low-level to make the switch element Q 3 in the off state. Supplying of the electric power to the resistor R 12 is accordingly cut off.

Upon the operation for reading the temperature of the light source unit 100 A, the microcomputer 31 switches the voltage level of the output port PO 8 to a High-level, while keeping the voltage levels of the output ports PO 1 , PO 2 and PO 9 at the Low-levels. At this time, only the switch element Q 5 is turned on, but the remaining switch elements Q 2 , Q 3 and Q 7 are kept in off, and the DC voltage Vcc is therefore applied to a series circuit formed by the resistor R 2 and the thermistor Rt 1 . Thus, the analog input port AD 1 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistor R 2 and the thermistor Rt 1 . In the on state of only the switch element Q 5 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 1 , to an A/D conversion to obtain the temperature of the light source 110 A from a value of the divided voltage. After obtaining the measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 8 to the Low-level to make the switch element Q 5 in the off state. Supplying of the electric power to the thermistor Rt 1 is accordingly cut off.

Upon the operation for reading the temperature of the light source unit 100 B, the microcomputer 31 switches the voltage level of the output port PO 9 to a High-level, while keeping the voltage levels of the output ports PO 1 , PO 2 and PO 8 at the Low-levels. At this time, only the switch element Q 7 is turned on, but the remaining switch elements Q 2 , Q 3 and Q 5 are kept in off, and the DC voltage Vcc is therefore applied to a series circuit formed by the resistor R 2 and the thermistor Rt 2 . Thus, the analog input port AD 1 of the microcomputer 31 receives a divided voltage obtained by the DC voltage Vcc being divided by the resistor R 2 and the thermistor Rt 2 . In the on state of only the switch element Q 7 , the microcomputer 31 subjects the divided voltage, input to the analog input port AD 1 , to an A/D conversion to obtain the temperature of the light source 110 B from a value of the divided voltage. After obtaining the measured value of the divided voltage, the microcomputer 31 switches the voltage level of the output port PO 9 to the Low-level to make the switch element Q 7 in the off state. Supplying of the electric power to the thermistor Rt 2 is accordingly cut off.

As above, the microcomputer 31 can obtain the load information or the measuring value of the temperature, of the light source unit 100 A or 100 B, by turning on any one of the switch elements Q 2 , Q 3 , Q 5 and Q 7 .

In this Fourth Variation, particularly, the circuits of the load characteristic obtainer 20 and the temperature obtainer 50 include a common circuit element (resistor R 2 ) so as to share the common circuit element. It is therefore possible to downsize the whole circuit of the lighting device 1 . Furthermore, the number of the analog input ports of the microcomputer 31 can be reduced.

Third Embodiment

FIG. 11 is a cross-sectional view of a luminaire 200 according to this embodiment.

The luminaire 200 according to this embodiment is, for example, a vehicle headlight device.

The luminaire 200 includes a luminaire body 201 for housing the lighting device 1 and the light source unit 100 , described in the Second Embodiment.

The luminaire body 201 is constituted by a body 202 and a cover 203 .

The body 202 is made of synthetic resin or metal so as to have a box-shape, which of front face has an opening.

The cover 203 is made of material, such as glass or acrylic resin, which allows light to pass through, and is to be attached to the opening of the body 202 .

The light source unit 100 includes a substrate 101 on which the light source 110 is mounted. On the substrate 101 , the load information outputter 120 including the resistor R 10 and the temperature probe 130 including the thermistor Rt 1 are also mounted.

The substrate 101 is attached to a heat radiation member 102 . The heat radiation member 102 is secured to the body 202 with a support member 103 , such as a screw.

The light source unit 100 further includes a lens 105 for controlling light distribution. The lens 105 is attached to the heat radiation member 102 with a support member 104 . To the heat radiation member 102 , a reflection member 106 is attached. The reflection member 106 reflects light emitted by the light source 110 so as to cause reflected light to enter the lens 105 .

Also the body 202 houses therein the lighting device 1 . The lighting device 1 and the substrate 101 of the light source unit 100 are electrically connected to each other with electric wires 61 . The lighting device 1 is further connected to the DC power supply E 1 with electric wires 62 .

The luminaire 200 is not limited to a configuration with the lighting device 1 and the light source unit 100 described in the Second Embodiment, but may include the lighting device 1 described in any one of the First and the Second Embodiments (including variations) and the light source unit 100 .

Since the luminaire 200 of this embodiment includes the lighting device 1 described in any one of the First and the Second Embodiments (including variations), it is possible to provide the luminaire 200 including the lighting device 1 which can reduce power consumption.

Note that the luminaire 200 is not limited to the vehicle headlight device, but may be a facility luminaire to be applied for a facility, such as a home, an office building or a commercial facility, or a luminaire such as a downlight.

Fourth Embodiment

FIG. 12 is a perspective view of a vehicle 300 according to this embodiment.

The vehicle 300 is, for example, a sedan type of general automobile.

The luminaire 200 described in the Third Embodiment is disposed on each of a front right side and a front left side of a vehicle body 301 of the vehicle 300 . Since the luminaire 200 includes the lighting device 1 described in any one of the First and the Second Embodiments (including variations), it is possible to provide the vehicle 300 including the lighting device 1 which can reduce power consumption.

As apparent from the above-mentioned embodiments, a lighting device ( 1 ) of a first aspect is to cause at least one light source unit ( 100 , 100 A, 100 B) to emit light. Each of the at least one light source unit ( 100 , 100 A, 100 B) includes a light source ( 110 , 110 A, 110 B) and a corresponding load information outputter ( 120 , 120 A, 120 B) for outputting load information when electric power is supplied thereto, the load information representing a luminous characteristic of the light source ( 110 , 110 A, 110 B). The lighting device ( 1 ) includes at least one current outputter ( 10 , 10 A, 10 B), a load characteristic obtainer ( 20 ) and a controller ( 30 ). The at least one current outputter ( 10 , 10 A, 10 B) is configured to supply a current to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B). The load characteristic obtainer ( 20 ) is configured to obtain the load information from the corresponding load information outputter ( 120 , 120 A, 120 B) of the at least one light source unit ( 100 , 100 A, 100 B), by supplying the electric power to the load information outputter ( 120 ). The controller ( 30 ) is configured to control the current (output current) of the at least one current outputter ( 10 , 10 A, 10 B), which is supplied to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B), based on the load information obtained by the load characteristic obtainer ( 20 ). The load characteristic obtainer ( 20 ) is configured to supply the electric power to the corresponding load information outputter ( 120 , 120 A, 120 B) only during a time period of obtaining the load information, but stop supply of the electric power to the corresponding load information outputter ( 120 , 120 A, 120 B) during a time period other than the time period of obtaining the load information.

According to the lighting device ( 1 ) of the first aspect, since the load characteristic obtainer ( 20 ) stops supply of the electric power to the corresponding load information outputter ( 120 , 120 A, 120 B) during a time period other than the time period of obtaining the load information, the lighting device ( 1 ) can reduce power consumption, compared with a case where the electric power is continuously supplied to the corresponding load information outputter ( 120 , 120 A, 120 B).

Regarding a lighting device ( 1 ) of a second aspect, in the first aspect, the at least one current outputter ( 10 ) is configured to supply the current to the light sources ( 110 , 110 A, 110 B) included in a plurality of the light source units ( 100 , 100 A, 100 B). The load characteristic obtainer ( 20 ) is configured to supply the electric power to the corresponding load information outputters ( 120 , 120 A, 120 B) included in the plurality of the light source units ( 100 , 100 A, 100 B) so as to obtain the load information from the load information outputters ( 120 , 120 A, 120 B).

According to the lighting device ( 1 ) of the second aspect, even when the at least one current outputter ( 10 ) supplies the current to the light sources ( 110 , 110 A, 110 B) of the plurality of the light source units ( 100 , 100 A, 100 B), the controller ( 30 ) can control the current to be supplied to each of the light sources ( 110 , 110 A, 110 B), based on the load information of the light source unit ( 100 , 100 A, 100 B).

Regarding a lighting device ( 1 ) of a third aspect, in the second aspect, the load characteristic obtainer ( 20 ) includes a plurality of circuits configured to respectively supply the electric power to the load information outputters ( 120 , 120 A, 120 B) so as to obtain the load information from the load information outputters ( 120 , 120 A, 120 B). The plurality of circuits include a common circuit element so as to share the common circuit element.

According to the lighting device ( 1 ) of the third aspect, since the plurality of circuits include the common circuit element, it is possible to downsize the whole circuit of the lighting device ( 1 ).

Regarding a lighting device ( 1 ) of a fourth aspect, in the second aspect or the third aspect, the load characteristic obtainer ( 20 ) is configured to supply the electric power to the load information outputters ( 120 , 120 A, 120 B) in sequence so as to obtain the load information from the load information outputters ( 120 , 120 A, 120 B) in sequence.

According to the lighting device ( 1 ) of the fourth aspect, since the load characteristic obtainer ( 20 ) supplies the electric power to the load information outputters ( 120 , 120 A, 120 B) in sequence, the lighting device ( 1 ) can reduce power consumption, compared with a case where the electric power is supplied to the load information outputters ( 120 , 120 A, 120 B) at the same timing.

Regarding a lighting device ( 1 ) of a fifth aspect, in any one of the second to the fourth aspects, the at least one current outputter ( 10 ) includes a single current outputter ( 10 ) configured to supply the current to the light sources ( 110 , 110 A, 110 B) included in the plurality of the light source units ( 100 , 100 A, 100 B). The controller ( 30 ) is configured to control the current to be supplied to the light sources ( 110 , 110 A, 110 B) by the single current outputter ( 10 ) to have a current value set based on the load information of the plurality of the light source units ( 100 , 100 A, 100 B).

According to the lighting device ( 1 ) of the fifth aspect, when the single current outputter ( 10 ) supplies the current to the light sources ( 110 , 110 A, 110 B) of the plurality of the light source units ( 100 , 100 A, 100 B), the controller ( 30 ) can control the current to be supplied to the light sources ( 110 , 110 A, 110 B) by the single current outputter ( 10 ), based on the load information of the plurality of the light source units ( 100 , 100 A, 100 B).

Regarding a lighting device ( 1 ) of a sixth aspect, in any one of the second to the fourth aspects, the at least one current outputter ( 10 ) includes a plurality of current outputters ( 10 , 10 A, 10 B) configured to supply currents to the light sources ( 110 , 110 A, 110 B) included in the plurality of the light source units ( 100 , 100 A, 100 B), respectively. The controller ( 30 ) is configured to control the currents to be supplied to the light sources ( 110 , 110 A, 110 B) by the plurality of current outputters ( 10 , 10 A, 10 B) to have current values set based on the load information of the plurality of the light source units ( 100 , 100 A, 100 B), respectively.

According to the lighting device ( 1 ) of the sixth aspect, since the plurality of current outputters ( 10 , 10 A, 10 B) are provided to supply the currents to the light sources ( 110 , 110 A, 110 B) included in the plurality of the light source units ( 100 , 100 A, 100 B), respectively, the controller ( 30 ) can control the currents to be supplied to the light sources ( 110 , 110 A, 110 B) by the plurality of current outputters ( 10 , 10 A, 10 B), based on the load information of the plurality of the light source units ( 100 , 100 A, 100 B), respectively.

Regarding a lighting device ( 1 ) of a seventh aspect, in any one of the first to the sixth aspects, the load characteristic obtainer ( 20 ) is configured to supply, before the at least one current outputter ( 10 ) supplies the current to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B), the electric power to the load information outputter ( 120 , 120 A, 120 B) so as to obtain the load information from the corresponding load information outputter ( 120 , 120 A, 120 B).

According to the lighting device ( 1 ) of the seventh aspect, since the output current controlled based on the load information of the at least one light source unit ( 100 , 100 A, 100 B) is supplied from the current outputter ( 10 ) to the light source ( 110 , 110 A, 110 B), it is possible to supply a current appropriate for the light source ( 110 , 110 A, 110 B) to cause the at least one light source unit ( 100 , 100 A, 100 B) to emit light.

A lighting device ( 1 ) of an eighth aspect, in any one of the first to the seventh aspects, further includes a temperature obtainer ( 50 ) configured to obtain a measuring value of a temperature from a corresponding temperature probe ( 130 , 130 A, 130 B) included in the at least one light source unit ( 100 , 100 A, 100 B), by supplying power to the temperature probe ( 130 , 130 A, 130 B). The controller ( 30 ) is configured to control the current of the at least one current outputter ( 10 ), which is supplied to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B), based on the load information and the measuring value of the temperature obtained by the temperature obtainer ( 50 ). The temperature obtainer ( 50 ) is configured to supply the power to the corresponding temperature probe ( 130 , 130 A, 130 B) only during a time period of obtaining the measuring value of the temperature, but stop supply of the power to the corresponding temperature probe ( 130 , 130 A, 130 B) during a time period other than the time period of obtaining the measuring value of the temperature.

According to the lighting device ( 1 ) of the eighth aspect, since the temperature obtainer ( 50 ) is configured to stop supply of the power to the corresponding temperature probe ( 130 , 130 A, 130 B) during a time period other than the time period of obtaining the measuring value of the temperature, the lighting device ( 1 ) can reduce power consumption, compared with a case where the electric power is continuously supplied to the corresponding temperature probe ( 130 , 130 A, 130 B).

Regarding a lighting device ( 1 ) of a ninth aspect, in the eighth aspect, the at least one current outputter ( 10 ) is configured to supply the current to the light sources ( 110 , 110 A, 110 B) included in a plurality of the light source units ( 100 , 100 A, 100 B). The temperature obtainer ( 50 ) is configured to supply the power to the corresponding temperature probes ( 130 , 130 A, 130 B) included in the plurality of the light source units ( 100 , 100 A, 100 B) so as to obtain measuring values of a plurality of the temperatures from the temperature probes ( 130 , 130 A, 130 B).

According to the lighting device ( 1 ) of the ninth aspect, even when the at least one current outputter ( 10 ) supplies the current to the light sources ( 110 , 110 A, 110 B) of the plurality of the light source units ( 100 , 100 A, 100 B), the controller ( 30 ) can control the current to be supplied to each of the light sources ( 110 , 110 A, 110 B), based on the measuring values of the plurality of the temperatures obtained from the corresponding temperature probes ( 130 , 130 A, 130 B) of the plurality of the light source units ( 100 , 100 A, 100 B).

Regarding a lighting device ( 1 ) of a tenth aspect, in the ninth aspect, the temperature obtainer ( 50 ) includes a plurality of circuits configured to respectively supply the power to the temperature probes ( 130 , 130 A, 130 B) so as to obtain the measuring values of the plurality of the temperatures from the temperature probes ( 130 , 130 A, 130 B). The plurality of circuits include a common circuit element so as to share the common circuit element.

According to the lighting device ( 1 ) of the tenth aspect, since the plurality of circuits, which obtain the measuring values of the plurality of the temperatures from the temperature probes ( 130 , 130 A, 130 B), include the common circuit element, it is possible to downsize the whole circuit of the lighting device ( 1 ).

Regarding a lighting device ( 1 ) of an eleventh aspect, in the ninth aspect or the tenth aspect, the temperature obtainer ( 50 ) is configured to supply the power to the temperature probes ( 130 , 130 A, 130 B) in sequence so as to obtain the measuring value of the temperature from the temperature probes ( 130 , 130 A, 130 B) in sequence.

According to the lighting device ( 1 ) of the eleventh aspect, since the temperature obtainer ( 50 ) supplies the power to the temperature probes ( 130 , 130 A, 130 B) in sequence, the lighting device ( 1 ) can reduce power consumption, compared with a case where the electric power is supplied to the temperature probes ( 130 , 130 A, 130 B) at the same timing.

Regarding a lighting device ( 1 ) of a twelfth aspect, in any one of the eighth to the eleventh aspects, the temperature obtainer ( 50 ) is configured to periodically supply, while the light source ( 110 , 110 A, 110 B) included in the at least one light source unit ( 100 , 100 A, 100 B) is in lighting, the power to the corresponding temperature probe ( 130 , 130 A, 130 B) so as to periodically obtain the measuring value of the temperature from the temperature probe ( 130 , 130 A, 130 B).

According to the lighting device ( 1 ) of the twelfth aspect, even when the temperature of the light source ( 110 , 110 A, 110 B) included in the at least one light source unit ( 100 , 100 A, 100 B) is changed while it is in lighting, the controller ( 30 ) can control the current to be supplied to the light source ( 110 , 110 A, 110 B) based on the measuring value of the temperature, periodically obtained by the temperature obtainer ( 50 ).

Regarding a lighting device ( 1 ) of a thirteenth aspect, in the twelfth aspect, the controller ( 30 ) is configured to measure the current (output current) of the at least one current outputter ( 10 ) at a prescribed control period to perform a feedback control. A period at which the temperature obtainer ( 50 ) obtains the measuring value of the temperature is longer than the prescribed control period.

According to the lighting device ( 1 ) of the thirteenth aspect, the period of obtaining the measuring value of the temperature is set to be longer than the prescribed control period, based on an expectation that a change in the temperature of the light source ( 110 , 110 A, 110 B) is slower than the control period for the feedback control. The power consumption can be therefore reduced without deteriorating responsiveness.

Regarding a lighting device ( 1 ) of a fourteenth aspect, in any one of the eighth to the thirteenth aspects, circuits respectively constituting the temperature obtainer ( 50 ) and the load characteristic obtainer ( 20 ) include a common circuit element so as to share the common circuit element.

According to the lighting device ( 1 ) of the fourteenth aspect, since the circuits respectively constituting the temperature obtainer ( 50 ) and the load characteristic obtainer ( 20 ) include the common circuit element, it is possible to downsize the whole circuit of the lighting device ( 1 ).

A luminaire ( 200 ) of a fifteenth aspect includes the lighting device ( 1 ) according to any one of the first to the fourteenth aspects and a luminaire body ( 201 ) holding the lighting device ( 1 ).

According to this, it is possible to provide the luminaire ( 200 ) including the lighting device ( 1 ), which can reduce power consumption.

A vehicle ( 300 ) of a sixteenth aspect includes the luminaire ( 200 ) according to the fifteenth aspect and a vehicle body ( 301 ) to which the luminaire ( 200 ) is attached.

According to this, it is possible to provide the vehicle ( 300 ) including the lighting device ( 1 ), which can reduce power consumption.

A lighting method for a lighting device ( 1 ), of a seventeenth aspect, is to cause at least one light source unit ( 100 , 100 A, 100 B) to emit light. Each of the at least one light source unit ( 100 , 100 A, 100 B) includes a light source ( 110 , 110 A, 110 B) and a corresponding load information outputter ( 120 , 120 A, 120 B) for outputting load information when electric power is supplied thereto. The load information represents a luminous characteristic of the light source ( 110 , 110 A, 110 B). The lighting method includes: supplying a current to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B); obtaining the load information from the corresponding load information outputter ( 120 , 120 A, 120 B) of the at least one light source unit ( 100 , 100 A, 100 B), by supplying the electric power to the load information outputter ( 120 , 120 A, 120 B); controlling the current of at least one current outputter ( 10 , 10 A, 10 B), which is supplied to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B), based on the load information obtained; and supplying the electric power to the corresponding load information outputter ( 120 , 120 A, 120 B) only during a time period of obtaining the load information, but stopping supply of the electric power to the corresponding load information outputter ( 120 , 120 A, 120 B) during a time period other than the time period of obtaining the load information.

According to the lighting method of the seventeenth aspect, it is possible to reduce power consumption.

A lighting device ( 1 ) of an eighteenth aspect is to cause at least one light source unit ( 100 , 100 A, 100 B) to emit light. Each of the at least one light source unit ( 100 , 100 A, 100 B) includes a light source ( 110 , 110 A, 110 B) and a corresponding temperature probe ( 130 , 130 A, 130 B). The lighting device ( 1 ) includes at least one current outputter ( 10 , 10 A, 10 B), a temperature obtainer ( 50 ) and a controller ( 30 ). The at least one current outputter ( 10 , 10 A, 10 B) is configured to supply a current to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B). The temperature obtainer ( 50 ) is configured to obtain a measuring value of a temperature from the corresponding temperature probe ( 130 , 130 A, 130 B), by supplying power to the temperature probe ( 130 , 130 A, 130 B). The controller ( 30 ) is configured to control the current of the at least one current outputter ( 10 ), which is supplied to the light source ( 110 , 110 A, 110 B) of the at least one light source unit ( 100 , 100 A, 100 B), based on the measuring value of the temperature obtained by the temperature obtainer ( 50 ). The temperature obtainer ( 50 ) is configured to supply the power to the corresponding temperature probe ( 130 , 130 A, 130 B) only during a time period of obtaining the measuring value of the temperature, but stop supply of the power to the corresponding temperature probe ( 130 , 130 A, 130 B) during a time period other than the time period of obtaining the measuring value of the temperature.

According to the lighting device ( 1 ) of the eighteenth aspect, it is possible to reduce power consumption.

Regarding a lighting device ( 1 ) of a nineteenth aspect, in any one of the first to the fourteenth aspects, the electric power supplied to the corresponding load information outputter ( 120 ) by the load characteristic obtainer ( 20 ) is a current in a range from 100 μA to 10 mA.

Regarding a lighting device ( 1 ) of a twentieth aspect, in the nineteenth aspect, the current is in a range from 1 mA to 10 mA.

Regarding a lighting device ( 1 ) of a twenty-first aspect, in any one of the first to the fourteenth aspects, the corresponding load information outputter ( 120 ) includes a resistor (R 10 , R 11 , R 12 ).

Regarding a lighting device ( 1 ) of a twenty-second aspect, in any one of the first to the fourteenth aspects, the corresponding load information outputter ( 120 ) includes a memory.

While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present teachings.