Light source module and lighting apparatus, and illumination apparatus using same

Referring to FIG. 1 , the LED module 21 includes a light source unit 1 in which a plurality of light emitting diodes (LEDs) are connected in series; and a characteristic setting unit (CSU) 2 for setting characteristic information of the LEDs, e.g., information corresponding to a targeted current value. A positive terminal of the light source unit is coupled to a connecting terminal A which can be electrically connected to or disconnected from a lighting apparatus disposed outside the LED module 21 . A negative connecting terminal of the light source unit 1 is coupled to a connecting terminal B 2 . The characteristic setting unit 2 is connected between the low potential terminal (i.e., the negative connecting terminal) of the light source unit 1 and a connecting terminal B 1 .

FIG. 3 shows an exemplified configuration of the LED module 21 . As shown in FIG. 3 , one or more substrates having multiple light emitting diodes (LEDs) mounted thereon which form the light source unit 1 are coupled such that, if there are multiple substrates, surfaces of substrates are coplanar and a surface shape of the coupled substrates is rectangular and are received in a light-transmitting housing 22 . The connecting terminal A is provided at one end of the housing 22 , and the connecting terminals B 1 and B 2 are provided at the other end.

Although the characteristic setting unit 2 is not described in FIG. 3 , it is mounted on the substrate close to the connecting terminal B 1 . The characteristic setting unit 2 is formed of electronic components which will be described below. The light source unit 1 and the characteristic setting unit 2 included in the LED module 21 are connected to a lighting apparatus via the connecting terminals A, B 1 and B 2 , and a block diagram of the lighting apparatus is shown in FIG. 2 .

Referring to FIG. 2 , the lighting apparatus includes a voltage conversion unit 8 having at least one switching element (not shown) for turning on/off the LED module 21 to supply current to the LED module 21 . The lighting apparatus also includes an output control unit 6 for outputting a driving signal so that the voltage conversion unit 8 can provide a desired output; a first power supply unit 7 for supplying control power to circuits for controlling the output control unit 6 and the like; and a second power supply unit 3 for receiving the control power from the first power supply unit 7 and for supplying control power to the characteristic setting unit 2 . Furthermore, the lighting apparatus further includes a characteristic detection unit 4 for detecting a waveform on a wire for supplying the control power to the characteristic setting unit 2 from the second power supply unit 3 and controlling the output control unit based on the detected result, and a connection determination unit 5 for determining the connection of the LED module 21 based on the waveform on the wire.

For example, each LED included in the light source unit 1 of the LED module 21 , as shown in FIG. 1 , has electrical characteristics: 0.3 A and 3.5 V. When 50 LEDs are connected in series, a current of 0.3 A is supplied to the light source unit 1 from the voltage conversion unit 8 , the voltage between two terminals of the light source unit 1 becomes 175 (=3.5×50) V and power consumption of the light source unit 1 is 52.5 (=3.5×0.3×50) W.

The voltage conversion unit 8 may have any configuration only if it can provide direct-current power sufficient to turn the LED module 21 on and, for example, it may include, e.g., a voltage reduction chopper or a voltage reduction/boosting chopper.

The characteristic setting unit 2 stores current setting information. The voltage conversion unit 8 supplies a current to the LED module 21 at a desired value ranging, e.g., from 0.35 A to 0.10 A, based on the current setting information. In the example described above, since an output current of each LED included in the light source unit 1 is 0.3 A and, accordingly, the characteristic setting unit 2 stores 0.3 A of current setting information for the LED module 21 having the light source unit 1 .

FIG. 4 shows a detailed configuration of the characteristic setting unit 2 . In this example, the second power supply unit 3 is constituted by a current source and supplies control power to the characteristic setting unit 2 via the connecting terminal B 1 as described above. Furthermore, the characteristic detection unit 4 and the connection determination unit 5 control the output control unit 6 based on the detected result from a waveform on the wire from the second power supply unit 3 to the connecting terminal B 1 .

The control power supplied from the second power supply unit 3 is applied between the connecting terminals B 1 and B 2 and thus it is applied to a parallel circuit of a Zener diode ZD 1 and a capacitor C 2 through a diode D 1 . The control power is clamped to Zener voltage Vz 1 of the Zener diode ZD 1 and at the same time it is smoothed by the capacitor C 2 . As shown in FIG. 4 , Zener current flowing through the Zener diode ZD 1 can be controlled to a desired value by adopting a constant current source as the second power supply unit 3 . The Zener voltage Vz 1 to which the control power supplied from the second power supply unit 3 is clamped is mainly applied to mirror circuits M 1 and M 2 , a comparator CP 1 , a transfer gate circuit G, a series circuit of resistors R 2 and R 3 and a series circuit of resistors R 4 and R 5 .

The reference voltage Vref 1 is obtained by dividing the Zener voltage Vz 1 by a resistive divider formed of the series circuit of the resistors R 2 and R 3 . The reference voltage Vref 2 is produced by dividing the Zener voltage Vz 1 by a resistive divider formed of the series circuit of the resistors R 4 and R 5 . The reference voltages Vref 1 and Vref 2 are fed to the positive input terminal of the comparator CP 1 via the transfer gate circuit G. The mirror circuit M 1 supplies current i 1 determined by a resistor R 1 to a capacitor C 1 and the mirror circuit M 2 . Current i 2 flowing through the mirror circuit M 2 is set to be greater than the current i 1 by changing a mirror ratio.

If a switching element Q 1 , which is turned on or off by an output signal of the comparator CP 1 , is on, the current i 2 becomes zero and thus the current i 1 flows to the capacitor C 1 . If the switching element Q 1 is off, current i 1 -i 2 becomes negative and thus current i 2 -i 1 is drawn from the capacitor C 1 .

The voltage waveform of the capacitor C 1 is determined by switching between the reference voltages Vref 1 and Vref 2 in the transfer gate circuit G based on the output voltage of the comparator CP 1 shown in FIG. 5B and thus it becomes a triangular waveform with charging time T 1 as shown in (a) of FIG. 5 .

The output of the comparator CP 1 is fed into the gate of a switching element Q 3 , and a switching element Q 2 is turned on and off by turning the switching element Q 3 on and off. Since the drain of the switching element Q 2 is connected to the connecting terminal B 1 , both having same potential, the drain voltage of the switching element Q 2 , i.e., the voltage of the connecting terminal B 1 , has a waveform which has a high voltage level, i.e., an H level during a period of time approximately identical to the charging time T 1 of the capacitor C 1 as shown in (c) of FIG. 5 .

If the switching element Q 2 is turned off, the voltage of the connecting terminal B 1 is Vout, the sum of the turn-on voltage of the diode D 1 and the Zener voltage Vz 1 of the Zener diode ZD 1 . If the switching element Q 2 is turned on, the control current inputted from the second power supply unit 3 flows through the switching element Q 2 . Therefore, while the switching element Q 2 is turned on, the circuit continues to operate by using the voltage charged in the smoothing capacitor C 2 .

If the reference voltage Vref 1 produced by the series circuit of the resistors R 2 and R 3 is reduced to Vref 1 ′ by changing a voltage-dividing ratio between the resistors R 2 and R 3 , the charging time of the capacitor C 1 decreases from T 1 to T 1 ′ as shown in (a) of FIG. 6 . Further, the time period during which the drain voltage of the switching element Q 2 , i.e., the voltage of the connecting terminal B 1 , is at an H level, becomes almost identical to the reduced charging time T 1 ′ as shown in (c) of FIG. 6 .

The characteristic detection unit 4 is constituted by, e.g., a microcomputer and performs a process for measuring a time period during which the voltage at the connecting terminal B 1 is at an H level. Then, the set current is calculated from the measured time period based on the relation as shown in FIG. 7 . The set current may be read from a data table prepared in advance. The characteristic detection unit 4 sends an operation signal to the output control unit 6 , thereby adjusting a supply current to the set current derived above.

For example, if an LED module 21 including 50 LEDs connected in series, each with electrical characteristics: 0.3 A and 3.5 V, is connected to the illuminating device, the set current is controlled such that the time period during which the voltage at the connecting terminal B 1 is at an H level is set to be T 1 , as shown in (c) of FIG. 5 , in the characteristic setting unit 2 . On the other hand, if an LED module 21 including 40 LEDs connected in series, each with electrical characteristics: 0.25 A and 3.5 V, is connected to the illuminating device, the set current is controlled such that the time period during which the voltage of the connecting terminal B 1 is at an H level is set to be T 1 ′, as shown in (c) of FIG. 6 , in the characteristic setting unit 2 .

Thus, the time period during which the voltage at the connecting terminal B 1 is at an H level set in the characteristic setting unit 2 serves as information corresponding to the set current supplied to the LED module 21 .

Like the characteristic detection unit 4 , the waveform inputted to the connecting terminal B 1 is fed to the connection determination unit 5 , and operation of the connection determination unit 5 will be described. The connection determination unit 5 is constituted by, e.g., a comparator or a microcomputer' like in the characteristic detection unit 4 and detects the voltage of the connecting terminal B 1 . When the LED module 21 is connected to the illuminating device, the voltage of the connecting terminal B 1 is the sum voltage Vout of the turn-on voltage of the diode D 1 and the Zener voltage Vz 1 of the Zener diode ZD 1 as described above.

When the LED module 21 is not connected, the voltage of the connecting terminal B 1 is not clamped by the Zener voltage Vz 1 of the Zener diode ZD 1 and is higher than the voltage Vout. By using this relationship, the connection determination unit 5 determines that the LED module 21 is disconnected if the voltage of the connecting terminal B 1 is higher than the predetermined voltage Vref 3 .

If the connection determination unit 5 determines that the LED module 21 is not connected, then it sends a stop signal to the output control unit 6 to stop current supplied from the voltage conversion unit 8 to the LED module 1 . At the same time, although not shown, it is desirable that the stop signal is sent to the characteristic detection unit 4 and, accordingly, the characteristic detection unit 4 stops detection of characteristic information or adjustment of the set current based on the information from the characteristic setting unit 2 . If so, the characteristic detection unit 4 and the connection determination unit 5 may be constituted by a common microcomputer.

Timing charts shown in (a) to (c) of FIG. 8 describe the operation sequence when the LED module 21 is connected to the illuminating device. The LED module 21 is not connected until t 0 . At this time, the output voltage of the second power supply unit 3 is higher than the predetermined voltage Vref 3 used to determine connection/non-connection of the LED module 21 as shown in (a) of FIG. 8 . Thus, as shown in (c) of FIG. 8 , a driving signal is not sent to the voltage conversion unit 8 from the output control unit 6 .

When the LED module 21 is connected at t 0 , constant current for control power is supplied from the second power supply unit 3 to the characteristic setting unit 2 of the LED module 21 and the potential of the smoothing capacitor C 2 gradually increases as shown in (b) of FIG. 8 . At t 1 , the potential reaches the Zener voltage Vz 1 of the Zener diode ZD 1 .

Meanwhile, during the time period from t 0 to t 1 , the characteristic detection unit 4 might detect incorrect information due to the unstable operation of the characteristic setting unit 2 . Therefore, from t 0 when the LED module 21 is determined to be connected by the connection determination unit 5 to t 1 when the operation of the characteristic setting unit 2 becomes stable, a timer is provided to stop information detection of the characteristic detection unit 4 . After t 1 , the characteristic detection unit 4 starts information detection. Then, the output control unit 6 generates a driving signal at t 2 when the information detection or the control of the set current is completed.

With this configuration, information corresponding to the characteristics of LEDs for use in the LED module 21 is prepared in advance and thus the lighting apparatus can supply the appropriate set current based on the information, thereby preventing a breakdown or lifetime reduction due to an over current flowing through the LEDs in use. Since the connection of the LED module 21 can be detected through the wire used to detect the characteristic information of the LED, wiring can be reduced. Furthermore, the operation of the lighting apparatus is stopped when the LED module 21 is not connected, resulting in no extra power consumption.

In this example, although the set current flowing through the LED module 21 has been described as the characteristic information of the characteristic setting unit 2 , the characteristic information may include a voltage applied to the LED module 21 .

The LED module 21 is not limited to the shape similar to a straight-tube fluorescent lamp as shown in FIG. 3 and may have any shape. For example, LEDs may be mounted on a circular substrate and this substrate may be received in a cylindrical module.

Although the circuit configuration of the first power supply unit 7 serving as control power supply has not been described, circuit of the control power supply circuit can be made by a well known technique. For example, if the voltage conversion unit 8 includes an inductor, power fed from a second coil of the inductor can serve as the control power supply.

As shown in FIG. 9 , the light source unit 1 of the LED module 21 may be constituted by two series circuits connected in anti-parallel, each series circuit having LEDs connected in series. In this case, the light source unit 1 is turned on if current is supplied to either the connecting terminal A or the connecting terminal B 2 . In the configuration of FIG. 9 , the voltage conversion unit 8 may supply current to the LED module 21 by using an inverter circuit which is generally used in a lighting apparatus for a fluorescent lamp.

FIG. 10 illustrates a configuration of a lighting apparatus in accordance with Example 2. The lighting apparatus in this example is prepared to turn on two LED modules 21 a and 21 b connected in parallel, each LED module being the same as that in Example 1.

A second power supply unit 3 of the lighting apparatus includes second power supply units 3 a and 3 b for supplying power to the LED modules 21 a and 21 b , respectively. Each second power supply unit 3 a or 3 b is preferably formed of a constant current source as described above in Example 1.

A characteristic detection unit 4 may be constituted by a microcomputer as described in Example 1 and thus the basic operation is the same. It can use any configuration if information of the LED modules 21 a and 21 b can be detected by using a voltage waveform at a connecting terminal B 1 of the LED module 21 a and a voltage waveform at the connecting terminal B 1 of the LED module 21 b.

If multiple LED modules such as the LED modules 21 a and 21 b are connected as in this example, users might mistakenly connect LED modules having electrical characteristics different between each other. In order to determine if there is a wrong connection, the characteristic detection unit 4 determines if two informations inputted from the connecting terminals B 1 of the LED modules 21 a and 21 b are identical to each other. If they are identical, the characteristic detection unit 4 sends an operation signal to the output control unit 6 to adjust to the set current based on the information. If not, the characteristic detection unit 4 is controlled to perform a more stable operation as will be described later.

The operation of a connection determination unit 5 may be basically the same as that in Example 1. That is, the connection determination unit 5 detects a voltage of the connecting terminal B 1 and determines whether or not the LED module is connected by comparing the voltage of the connecting terminal B 1 with a reference value. In this example where the two LED modules 21 a and 21 b are connected in parallel, a stop signal is sent to the output control unit 6 only if both the LED modules 21 a and 21 b are determined not to be connected.

It will now be described on operation when the users mistakenly connect LED modules with different electrical characteristics. For example, if an LED module 21 a includes LEDs connected in series, each with electrical characteristics: 0.3 A and 3.5 V, and an LED module 21 b includes 40 LEDs connected in series, each with electrical characteristics: 0.25 A and 3.5 V, the characteristic detection unit 4 determines that LED modules with different electrical characteristics are connected based on the two different informations inputted from the LED modules 21 a and 21 b.

Then, the characteristic detection unit 4 prioritizes the information of the LED module 21 b having a lower characteristic current and outputs an operation signal for controlling the output control unit 6 to supply a current of 0.25 A from the voltage conversion unit 8 . Alternatively, the characteristic detection unit 4 may output a stop signal for preventing the output control unit 6 from generating a driving signal, resulting in no current supplied to the LED modules.

If the voltage conversion unit 8 supplies the current of 0.25 A, the actual current flowing through the LED module 21 b is smaller than 0.25 A, because the current is divided to flow to the LED module 21 a as well as the LED module 21 b.

In this example, the same effect as in Example 1 can be achieved and furthermore multiple LED modules can be turned on at once. Besides, when different types of LED modules are connected, the voltage conversion unit 8 is controlled to supply a current based on the set current of the LED module having a lower characteristic current or to stop supplying current. Accordingly, even when different types of LED modules remain connected by mistake, there does not occur broken-down or lifetime reduction of the LED module.

FIG. 11 shows a configuration of a lighting apparatus in accordance with Example 3. The lighting apparatus in this example is also prepared to turn on two LED modules connected in parallel. The two LED modules 21 a and 21 b have the same configuration as that in Examples 1 and 2 except for the detailed configuration of a characteristic setting unit 2 shown in FIG. 12 .

In the lighting apparatus of FIG. 11 , a single second power supply unit 3 supplies control power to each characteristic setting unit 2 of the LED modules 21 a and 21 b unlike in Example 2. The second power supply unit 3 in this example includes a resistor and a switching element as shown in FIG. 12 . The switching element of the second power supply unit 3 is turned on and off responding to a timing signal outputted from a characteristic detection unit 4 as shown in (a) of FIG. 13 .

The characteristic setting unit 2 has connecting terminals B 1 and B 2 between which control power is applied from the second power supply unit 3 . The control power is inputted to a parallel circuit of a Zener diode ZD 1 and a capacitor C 2 via a diode D 1 . Further, the control power is clamped to the Zener voltage Vz 1 of the Zener diode ZD 1 and at the same time smoothed by the capacitor C 2 . The resistor of the second power supply unit 3 limits the Zener current flowing through the Zener diode ZD 1 to a predetermined value.

The control power is supplied from the second power supply unit 3 , clamped by Zener voltage Vz 1 and then applied to a mirror circuit M 3 , a comparator CP 2 and a series circuit of resistors R 6 and R 7 . The reference voltage Vref 4 is obtained by dividing the Zener voltage Vz 1 by a voltage divider circuit formed of the resistors R 6 and R 7 connected in series. The reference voltage Vref 4 is applied to the positive input terminal of the comparator CP 2 .

The mirror circuit M 3 supplies current to a capacitor C 3 , the current being determined by a resistor R 8 . That is, current flows into the mirror circuit M 3 and the resistor R 8 based on the voltage Vz 1 of the capacitor C 2 , and current in proportion to the current flowing in the resistor R 8 flows through the capacitor C 3 . The voltage between two ends of the capacitor C 3 is applied to the negative input terminal of the comparator CP 2 and compared to the reference voltage Vref 4 . The output of the comparator CP 2 is applied into the gate of a switching element Q 3 and a switching element Q 2 is turned on or off by turning the switching element Q 3 on or off.

FIG. 13 shows a timing chart for describing operation of the characteristic setting unit 2 . The operation will be described in detail with reference to FIG. 13 .

The output voltage of the second power supply unit 3 is determined by a timing signal outputted from the characteristic detection unit 4 as shown in (a) of FIG. 13 . During T 2 , the timing signal is at an H level and power is supplied from the second power supply unit 3 to the characteristic setting unit 2 . The voltage of the capacitor C 2 in the characteristic setting unit 2 has a waveform shown in (b) of FIG. 13 according to the output voltage of the second power supply unit 3 . The voltage across the capacitor C 3 linearly increases as shown in (c) of FIG. 13 by the current supplied from the mirror circuit M 3 .

By the comparator CP 2 , the voltage of the capacitor C 3 is compared to the reference voltage Vref 4 , the output voltage of the comparator CP 2 is at an H level during T 3 when the voltage of the capacitor C 3 is greater than the reference voltage Vref 4 , as shown in FIG. 13D . When the output voltage of the comparator CP 2 becomes an L level after T 3 , the switching element Q 3 is turned off and, accordingly, the switching element Q 2 is turned on. Since the drain of the switching element Q 2 is connected to the connecting terminal B 1 via the resistor R 9 , the voltage of the connecting terminal B 1 when the switching element Q 2 is on is determined by dividing the voltage supplied from the first power supply unit 7 by resistive ratio of the resistor of the second power supply unit 3 and the resistor R 9 .

The characteristic detection unit 4 detects characteristic information by a time period where the voltage of the connecting terminal B 1 is greater than a reference voltage Vref 5 when the switching element Q 2 is turned on. As shown in (e) of FIG. 13 , the set current is determined based on the time period where the voltage of the connecting terminal B 1 is higher than the reference voltage Vref 5 . Information on characteristics of LED is set by adjusting the resistive values of the resistors R 6 and R 7 included in the characteristic setting unit 2 to change the reference voltage Vref 4 and thereby controlling the time period T 3 where the voltage of the connecting terminal B 1 is higher than the reference voltage Vref 5 .

Here, it is considered that an LED module 21 a having T 3 where the voltage of the connecting terminal B 1 is higher than the reference voltage Vref 5 and an LED module 21 b having T 3 ′ shorter than T 3 are connected. The capacitor C 3 of each characteristic setting unit 2 of the LED modules 21 a and 21 b is charged based on the timing signal fed to the second power supply unit 3 from the characteristic detection unit 4 . However, as described above, the voltage of the connecting terminal B 1 decreases based on time period T 3 ′ set in the LED module 21 b.

That is, the characteristic detection unit 4 detects characteristic information by prioritizing the LED module 21 b having a lower characteristic current, i.e., a shorter time period T 3 ′. Accordingly, the characteristic detection unit 4 sends an operation signal to the output control unit 6 so that the supply current from the voltage conversion unit 8 can be set based on the information of the LED module 21 b.

Meanwhile, the connection determination unit 5 may operate like that in Example 1. Normally, because a voltage of the connecting terminal B 1 is higher when the LED modules 21 a and 21 b are not connected than when the LED modules 21 a and 21 b are connected, the connection determination unit 5 may determine by detecting the voltage of the connecting terminal B 1 .

With this example, the same effects as in Examples 1 and 2 can be obtained. Further, since only a single wire is used to supply power from the second power supply unit 3 to each connecting terminal B 1 of the multiple LED modules 21 a and 21 b , wiring can be reduced compared to Example 2. Furthermore, the circuit configuration of the characteristic setting unit 2 can be simplified.

FIG. 14 is a circuit diagram of an LED module 21 in accordance with Example 4. As shown in FIG. 14 , a voltage applied between a connecting terminal A 2 and a connecting terminal B 2 is rectified by a rectifier DB 1 . The positive output terminal of the rectifier DB 1 is coupled to the positive terminal of a light source unit 1 , whereas the negative output terminal of the rectifier DB 1 is coupled to the negative connecting terminal of the light source unit 1 . A characteristic setting unit 2 a is disposed between the connecting terminals A 1 and A 2 , whereas a characteristic setting unit 2 b is disposed between the connecting terminals B 1 and B 2 .

FIG. 15 shows an exemplified configuration of the LED module 21 . As shown in FIG. 15 , one or more substrate having multiple LEDs forming the light source unit 1 mounted thereon are received in a light-transmitting housing 22 like in Example 1. The connecting terminals A 1 and A 2 are located at one end of the housing 22 , and the connecting terminals B 1 and B 2 are located to diagonally face the connecting terminals A 1 and A 2 at the other end.

Although the specific circuit configurations of the characteristic setting units 2 a and 2 b are not illustrated, the configuration described in Example 1 or 3 may be employed. The two characteristic setting units 2 a and 2 b are set to have the same characteristic information, i.e., circuit constant, and are mounted on the same substrate as that where the light source units 1 is mounted. More specifically, the characteristic setting unit 2 a is disposed close to the connecting terminals A 1 and A 2 , whereas the characteristic setting unit 2 b is disposed close to the connecting terminals B 1 and B 2 .

One of the illuminating devices described in Examples 1 to 3 can be used to supply current to the LED module 21 in this example. However, unlike Examples 1 to 3 where the current is supplied to the connecting terminal A of the LED module 21 , the current is supplied to the connecting terminal A 2 or the connecting terminal B 2 of the LED module 21 in this example.

FIG. 16 illustrates an example of an illumination apparatus 20 which an LED module 21 can be connected to. The above-described illuminating devices are provided in a main body 25 of the illumination apparatus shown in FIG. 16 . The lighting apparatus and the LED module 21 are electrically connected via sockets 23 and 24 . For example, the connecting terminals A 1 and A 2 are inserted into the socket 23 , and the connecting terminals B 1 and B 2 are inserted into the socket 24 . When current is supplied to the LED module 21 from the lighting apparatus and flows in through the connecting terminal A 2 , for example, the characteristic setting unit 2 b provided at a side of the connecting terminals B 1 and B 2 is connected to the lighting apparatus and detects information of the LED module 21 .

Although the connecting terminals A 1 and A 2 and the connecting terminals B 1 and B 2 are disposed as shown in FIG. 15 , it is considerable that a user mistakenly connects the connecting terminals A 1 and A 2 and the connecting terminals B 1 and B 2 of the LED module in reverse to the illuminating device. In this case, current supplied to the LED module 21 from the lighting apparatus flows in through the connecting terminal B 2 , and the characteristic setting unit 2 a disposed at a side of the connecting terminals A 1 and A 2 is connected to the lighting apparatus and detects information of the LED module 21 .

As described above, the same effect as in Example 1 can be obtained in this example. Furthermore, the connecting terminals, e.g., A 2 and B 2 for supplying current to the light source unit of the LED module and the connecting terminals, e.g., A 1 and B 1 for detecting information of the LED module are arranged to diagonally face when viewed on plane coplanar or parallel to the substrate surface of the LED module as described above in this example. Therefore, when the LED module is connected to the illumination apparatus, the connection of the light emitting diodes with the wrong polarity or the wrong connection between the power supply line and the signal supply line does not occur. Further, a user can easily remove the LED module from the illumination apparatus or reinstall it.

FIG. 17 is a circuit diagram of a lighting apparatus in accordance with Example 5. A voltage conversion unit 8 may be constituted by a well-known voltage reduction chopper circuit. The voltage conversion unit 8 has a direct-current power supply DC obtained by rectifying and smoothing alternating-current power or by raising direct-current power with a voltage boosting chopper circuit. The voltage conversion unit 8 further includes a switching element Q 4 whose drain is coupled to the positive output terminal of the direct-current power supply DC; an inductor L 1 whose one is coupled to a source of the switching element Q 4 and the other end connected to a connecting terminal A of an LED module 21 ; a diode D 4 connected to a connection point between the source of the switching element Q 4 and the inductor L 1 ; and a smoothing capacitor C 7 connected to the other end of the inductor L 1 .

The on/off operation of the switching element Q 4 is controlled by a driving signal outputted from a terminal Hout of a driver circuit 9 included in an output control unit 6 . When the switching element Q 4 is turned on, current flows through the inductor L 1 and thereby electromagnetic energy is stored in the inductor L 1 . When the switching element Q 4 is turned off, the electromagnetic energy stored in the inductor L 1 is discharged through a diode D 4 connected between the source of the switching element Q 4 and the ground.

The basic configuration of the LED module 21 is the same as that in Example 1 except for a characteristic setting unit 2 constituted by a resistor R 10 . A second power supply unit 3 for supplying control power to the characteristic setting unit 2 is constituted by a constant current source as shown in FIG. 17 . This constant current source supplies current to resistors R 11 and R 10 . The resistor R 11 in the lighting apparatus is connected between a connecting terminal B 1 and the ground. Both the resistor R 11 of the lighting apparatus and the resistor R 10 of the characteristic setting unit 2 are connected to the connecting terminal B 1 .

A resistor Rs is located between a connecting terminal B 2 and the ground of the illuminating device, the connecting terminal B 2 being connected to a negative connecting terminal of a light source unit 1 included in the LED module 21 . Current supplied from the connecting terminal A flows in through the light source unit 1 and flows out through the connecting terminal B 2 . Then, it flows to the ground via the resistor Rs. The smoothing capacitor C 7 is connected to the resistor Rs and, accordingly, the smoothing capacitor C 7 is charged and discharged by the current flowing through the resistor Rs. Therefore, the sum current of the current flowing through the LED module 21 and the current flowing through the reservoir capacitor C 7 is detected through the resistor Rs.

The voltage across the resistor Rs is obtained by multiplying a resistive value of the resistor Rs to a current flowing through the resistor Rs, and is fed to a feedback operational circuit 10 of the output control unit 6 . The feedback operational circuit 10 may be constituted by an operational amplifier OP 1 . The detected voltage is fed into the negative input terminal of the operational amplifier OP 1 via a resistor R 12 . A capacitor C 4 is coupled between the negative input terminal and the output terminal of the operational amplifier OP 1 , which forms a well-known integrator circuit.

On the other hand, a setting signal from the characteristic detection unit 4 is fed to the positive input terminal of the operational amplifier OP 1 , the setting signal being based on information set of the LED module 21 . Then, the setting signal and the detected signal are integrated and the integrated result is outputted from the output terminal of the operational amplifier OP 1 . The output terminal of the operational amplifier OP 1 is connected to a terminal Pls of the driver circuit 9 via a diode D 3 and a resistor R 14 . The terminal Pls is a terminal for controlling an ON-pulse width of the switching element Q 4 driven by the driver circuit 9 .

Next, operation of the terminal Pls of the driver circuit 9 will be briefly described. In the driver circuit 9 , connected to the terminal Pls is a constant voltage buffer circuit, a mirror circuit and a driving signal setting capacitor. Specifically, a resistor R 13 is connected between the ground and the terminal Pls serving as an output terminal of the constant voltage buffer circuit. Current flowing through the resistor R 13 is mirrored by the mirror circuit and thereby the driving signal setting capacitor is charged and discharged, as is well known.

If the time period until the driving signal setting capacitor is charged to a predetermined level is set to be the same as a time period Ton where the driving signal fed to the switching element Q 4 is at an H level, the relation between current Ipls flowing through the resistor R 13 from the terminal Pls and the time period Ton can be represented as shown in FIG. 18 . That is, as the current Ipls flowing through the resistor Rs from the terminal Pls increases, the time period Ton decreases.

Here, the operation of the feedback operational circuit 10 will be described again. For example, if the current flowing through the inductor L 1 increases, the level of the signal detected from the resistor Rs increases. At this point, the output voltage of the operational amplifier OP 1 of the feedback amplifier circuit 10 is reduced, and the current drawn by the operational amplifier OP 1 from the terminal Pls increases. Because of this, the current Ipls flowing out through the terminal Pls increases. As the current Ipls flowing out through the terminal Pls increases, the driver circuit 9 is controlled to decrease the time period Ton where the driving signal outputted from the terminal Hout is at an H level and to suppress an increase of the current flowing through the inductor L 1 , i.e., to reduce the current supplied to the LED module 21 .

In the driver circuit 9 , control power for control circuits used to feed the driving signal to the switching element Q 4 from the terminal Hout can be obtained by charging a capacitor C 5 via a diode D 2 . Since this can be easily implemented by a half bridge driver circuit generally used as an inverter circuit for fluorescent lamps, detailed description thereof will be omitted.

Next, the operations of the characteristic setting unit 2 , the characteristic detection unit 4 and the connection determination unit 5 in this example will be described.

For example, if the resistor Rs has a resistive value less than a few ohms and the resistor R 10 of the characteristic setting unit 2 included in the LED module 21 has a resistive value more than several tens kilo-ohms, a value of the resistor Rs can fall within an error range of the resistor R 10 .

When the LED module 21 is connected to the lighting apparatus but the switching element Q 4 is not operating, a voltage of the connecting terminal B 1 is determined by the current supplied to the resistor R 10 from the second power supply unit 3 and the resistive value of the resistor R 10 . The set current is determined by this voltage based on relationship as shown in FIG. 19 .

Next, description will be made on a case where the LED module 21 is connected to the lighting apparatus and the switching element Q 4 is operating. For example, if a current of 0.35 A is supplied to the LED module 21 , a peak current flowing through the inductor L 1 is about 0.70 A. The voltage across the resistor Rs having a resistive value of, e.g., 1 ohm varies in the range from 0 V to 0.7 V. Thus, the voltage of the connecting terminal B 1 varies depending on the switching operation.

Accordingly, in order to prevent misreading characteristic information of the LED module 21 , the information detection operation of the characteristic detection unit 4 is not performed while the switching element Q 4 is operating.

When the LED module 21 is not connected, the resistor R 10 in the LED module 21 is disconnected and thus all the constant current outputted from the second power supply unit 3 flows through the resistor R 11 of the illuminating device, resulting in an increase of the voltage of the resistor R 11 . The connection determination unit 5 compares the voltage of the connecting terminal B 1 with a reference voltage Vref 6 and determines the connection/non-connection of the LED module 21 as described in Example 1. When the connection determination unit 5 determines that the LED module 21 is removed, it outputs a stop signal to a terminal Reset of the driver circuit 9 . Upon receiving the stop signal at the terminal Reset, the driver circuit 9 stops generating a driving signal.

Next, description will be made on the operation sequence after the direct-current power DC is supplied and control power is outputted by the control power supply unit 7 with reference to FIG. 20 .

When the direct-current power supply DC is supplied as shown in (a) of FIG. 20 , the first power supply unit 7 starts supplying control power as shown in (b) of FIG. 20 . At time t 0 , when the voltage of the control power reaches a predetermined voltage level, the second power supply unit 3 starts supplying control power by constant current as shown in (c) of FIG. 20 . The characteristic detection unit 4 and the connection determination unit 5 also start operating at t 0 .

Regardless of the connection of the LED module 21 , the connection determination unit 5 provided with a timer unit outputs a stop signal to the terminal Reset to prevent the driver circuit 9 from supplying a driving signal until a predetermined time t 2 as shown in (d) of FIG. 20 .

Meanwhile, the characteristic detection unit 4 detects the characteristic information preset in the characteristic setting unit 2 until the time point t 1 and then outputs a setting signal corresponding to a set current to the feedback operational circuit 10 as shown in (e) of FIG. 20 .

When the LED module 21 is connected at t 2 , the connection determination unit 5 clears the stop signal and, accordingly, the driver circuit 9 outputs a driving signal for the switching element Q 4 as shown in (f) of FIG. 20 .

On the other hand, when the LED module 21 is not connected at t 2 , the connection determination unit 5 does not count any longer and keeps a state at t 0 until the LED module 21 is connected. In the meantime, the characteristic detection unit 4 repeats detection of the characteristic information.

The LED module and the lighting apparatus as described in this example can be also installed in the illumination apparatus shown in FIG. 16 as described in Example 4. When they are installed in the illumination apparatus, the lighting apparatus can be wrongly connected to the sockets in electrical wiring. In particular, it is considered the connecting terminals B 1 and B 2 are reversely connected. Since the characteristic setting unit 2 in this example is constituted by the resistor R 10 , the current flowing through the light source unit 1 flows to the resistor Rs and the ground via the characteristic setting unit 2 .

Furthermore, the characteristic detection unit 4 detects the information of the LED module 21 and the output control unit 6 outputs the driving signal based on the detected information. However, since the voltage of the connecting, terminal B 1 increases, the connection determination unit 5 detects the voltage of the connecting terminal B 1 higher than the predetermined reference voltage Vref 6 and outputs the stop signal to the output control unit 6 . Thus, when the connecting terminals B 1 and B 2 is reversely connected, a power supply to the LED module 21 can be safely stopped by the connection determination unit 5 .

For example, the connection determination unit 5 may compare the voltage of the connecting terminal B 1 with reference voltage Vref 7 lower than the reference voltage Vref 6 and continue to output a stop signal to the terminal Reset of the driver circuit while the voltage of the connecting terminal B 1 is lower than the reference voltage Vref 7 . With this configuration, even when the characteristic setting unit 2 of the LED module 21 or wiring for connecting the connecting terminals B 1 and B 2 to the lighting apparatus is short-circuited for any reason, the lighting apparatus can remain stopped by the stop signal from the connection determination unit 5 . Accordingly, the lighting apparatus and the LED module can be used more safely.

Although the driving signal is outputted from the output control unit 6 and then the characteristic detection unit 4 stops the characteristic detection operation in this example, the characteristic detection unit 4 may stop the characteristic detection operation based on the stop signal inputted to the terminal Reset from the connection determination unit 5 . Alternatively, the characteristic detection unit 4 may stop the characteristic measurement operation based on the stop signal fed to the terminal Reset of the driver circuit 9 from the connection determination unit 5 . Further, the second power supply unit 3 supplies power during the predetermined time right after control power has been outputted and the characteristic measurement operation may be performed during this time.

In this example, the same effects as in Examples 1 to 3 can be achieved. Furthermore, since a feedback control has been done by detecting the current supplied to the LED module, more stable current can be supplied to the LED module, thereby preventing over current from flowing to the LED module. Additionally, the operation of the lighting apparatus can be stopped when breakdown of electronic components or wiring error occurs, thereby significantly improving reliability.

By adapting to this example the basic circuit configuration of the LED module as described in Example 4, the same effect as in Example 4 can be achieved. Further, a user can easily remove the LED module from the illumination apparatus or reinstall it.

FIGS. 21 and 22 illustrate circuit diagrams of a lighting apparatus of Example 6. In this example, the lighting apparatus capable of turning on both direct-current driven light sources such as the LEDs described in Examples 1 to 5 and alternating-current driven fluorescent lamps will be described. FIG. 21 shows a basic configuration of the lighting apparatus with an LED module 21 connected thereto, and FIG. 22 presents a basic configuration of the lighting apparatus with a fluorescent lamp La connected thereto.

In FIG. 21 , the configuration of the LED module 21 is basically the same as that described in Example 4 as shown in FIG. 14 . The difference is that there are provided connecting terminals A 1 , A 2 and A 3 , connecting terminals B 1 , B 2 and B 3 , and characteristic setting units 2 a and 2 b having the same circuit and the same circuit constant, characteristic setting units 2 a and 2 b being located between the connecting terminals A 1 and A 2 and between the connecting terminals the B 1 and B 2 , respectively. The characteristic setting units 2 a and 2 b in this example are constituted by a resistor as described in Example 5.

As shown in FIG. 23 , the connecting terminals A 1 , A 2 and A 3 of the LED module 21 are located on one end of a light-transmitting housing 22 , and connecting terminals B 1 , B 2 and B 3 are located on the other end of the housing 22 . The connecting terminals A 1 , A 2 and A 3 and the connecting terminals B 1 , B 2 and B 3 are arranged to face each other. For example, the connecting terminals A 1 and A 3 are disposed to diagonally face the connecting terminals B 1 and B 3 , and the connecting terminals A 2 and B 2 are disposed to face each other.

Further, the arrangement and the shape of the connecting terminals A 1 , A 3 and the connecting terminals B 1 and B 3 may be the same as those in the conventional fluorescent lamps, and the connecting terminals A 2 and B 2 may be located at an arbitrary point on the dashed-dotted line c-d in FIG. 24 .

If the LED module 21 is connected to the lighting apparatus as shown in FIG. 21 , it is turned on by direct-current power outputted from a voltage conversion unit 8 a . The voltage conversion unit 8 a is constituted by a voltage reduction chopper circuit as in Example 5, wherein like reference numerals will be assigned to like parts having the same operations and redundant description thereof will be omitted.

In this example, there is provided a voltage conversion unit 8 b for supplying high-frequency power to turn on the fluorescent lamp La when the fluorescent lamp La is connected thereto. The circuit operation of the voltage conversion unit 8 b and an inverter driver circuit 11 for outputting a driving signal to the voltage conversion unit 8 b will be described later.

An output control unit 6 includes a driver circuit 9 , the inverter driver circuit 11 and a feedback operational circuit 10 . A setting signal is inputted to the feedback operational circuit 10 from a characteristic detection unit 4 , and changes a driving signal outputted from the driver circuit 9 or the inverter driver circuit 11 based on an output signal from the feedback operational circuit 10 .

Unlike the other examples, a second power supply unit 3 is constituted by a resistor R 15 and thus forms a voltage divider together with the characteristic setting unit 2 a or 2 b connected thereto, thereby supplying a voltage divided by the voltage divider.

The characteristic detection unit 4 , like in Example 5, outputs a setting signal based on the divided voltage, and thus the feedback operational circuit 10 controls the driver circuit 9 based on the setting signal and a signal detected from a resistor Rs.

As shown in FIG. 25 , the set current of the characteristic detection unit 4 increases in stepwise as the voltage of the connecting terminal B 1 varies from V 1 to V 2 .

If the LED module 21 is not connected, the voltage at the connecting terminal B 1 increases. If the voltage is higher than the voltage V 2 of FIG. 25 , the connection determination unit 5 determines that the LED module 21 is disconnected like in Example 5. Then, the connection determination unit 5 sends a stop signal to the driver circuit 9 to stop the operation of the voltage conversion unit 8 a . When the LED module 21 is connected, the connection determination unit 5 clears the stop signal inputted to the driver circuit 9 and resumes the operation of the voltage conversion unit 8 a.

If the fluorescent lamp La is connected as shown in FIG. 22 , a capacitor C 0 is charged through the route from the second power supply unit 3 , via the connecting terminal B 1 , a filament of the fluorescent lamp La, and the connecting terminal B 3 , to the capacitor C 0 . The voltage of the capacitor C 0 is fed to a filament detection unit 12 and thereby the connection of the fluorescent lamp La is determined. If the filament detection unit 12 determines that the fluorescent lamp La is connected, it stops generating a stop signal to the terminal Reset of the inverter driver circuit 11 , thereby resuming the operation of the inverter driver circuit 11 and the voltage conversion unit 8 b.

As shown in FIG. 22 , a high-frequency power is supplied to the capacitor C 0 via the connecting terminal A 1 , the fluorescent lamp La and the connecting terminal B 3 from the voltage conversion unit 8 b.

The filament of the fluorescent lamp La is connected between the connecting terminals A 1 and A 3 and the connecting terminals B 1 and B 3 . Preheating current is supplied to the filament from a preheating circuit (not shown) after the operation of the voltage conversion unit 8 b is resumed.

The voltage conversion unit 8 b includes a series circuit having two switching elements Q 5 and Q 6 connected in series which is connected to the output terminal of a direct-current power supply DC; and a resonant circuit mainly including a resonant inductor L 2 and a resonant capacitor C 9 , the resonant circuit being connected in parallel to the switching element Q 6 . One end of the resonant capacitor C 9 is coupled to the connecting terminal A 1 , and the other end of the resonant capacitor C 9 is connected to the connecting terminal B 3 via the capacitor C 0 .

The switching elements Q 5 and Q 6 are alternately turned on and off by driving signals from terminals Hout and Lout of the inverter driver circuit 11 , respectively. The frequency of the driving signals outputted from the inverter driver circuit 11 is controlled by the current flowing out through a terminal Osc of the inverter driver circuit 11 into an operational amplifier of the feedback operational circuit 10 (see FIG. 17 ).

For example, the inverter driver circuit 11 includes a constant voltage buffer circuit, a mirror circuit and a driving signal setting capacitor connected to the terminal Osc, and a resistor R 16 connected between the terminal Osc serving as the output terminal of the constant voltage buffer circuit and the ground. The inverter driver circuit 11 can charge or discharge the driving signal setting capacitor by converting current flowing through a resistor R 16 by the mirror circuit. As the current flowing through the fluorescent lamp La increases, the level of the signal detected from the resistor Rs increases by the operation of the feedback operational circuit 10 as described above.

If the feedback operational circuit 10 is constituted by, e.g., that of Example 5 adapted to both of the alternating current and direct current, the output voltage of the operational amplifier OP 1 of the feedback amplifier circuit 10 is reduced as the level of the detected signal increases. Thus, since the current drawn by the operational amplifier OP 1 of the feedback operational circuit 10 from the terminal Osc of the inverter driver circuit 11 increases, current Iosc flowing out through the terminal Osc increases. As the current Iosc flowing out through the terminal Osc of the inverter driver circuit 11 increases, the inverter driver circuit 11 is controlled such that the frequency of the driving signals from terminals Lout and Hout increases, thereby suppressing an increase of the current flowing through the fluorescent lamp La.

In the inverter driver circuit 11 , control power for control circuits used to feed the driving signal into the switching element Q 5 at a high potential level through the terminal Hout can be obtained by charging a capacitor C 6 via a diode D 5 . Since this can be easily implemented by a general technique, detailed description thereof will be omitted.

Although not described in this example, the connection determination unit 5 determines the connection of the LED module 21 after the direct-current power supply DC is supplied and the control power is outputted from the second power supply unit 7 , like in Example 5. The filament detection unit 12 may also determine the connection of the fluorescent lamp La at the same timing.

As described above, if the LED module is used, information may be prepared in advance based on characteristics information of LEDs for use in the LED module. Accordingly, the lighting apparatus can supply a set current based on the prepared information, thereby preventing a breakdown or lifetime reduction due to over current flowing through the LEDs in LED module. Furthermore, since the connection/non-connection of the LED module can be detected through the wire used for detecting the characteristics of the LEDs, wiring can be reduced.

Moreover, when the LED module is connected to the illumination apparatus, the connection of the LEDs with the wrong polarity or the wrong connection between the power supply line and the signal supply line does not occur. Further, a user can easily remove the LED module from the illumination apparatus or reinstall it. If there is provided an illumination apparatus with sockets capable of receiving both the fluorescent lamp and the LED module, a user can choose which to install between the fluorescent lamp and the LED module.

Second Preferred Embodiment

Next, examples of a second preferred embodiment in accordance with the present invention will be described. Throughout the drawings, like reference numerals will be given to same parts as that in the above described examples.

Referring to FIG. 26 , an LED module 21 in this example includes a first light source unit 1 a , a second light source unit 1 b , an characteristic setting unit 2 a , a positive connecting terminal A, a negative connecting terminal B 1 and a connecting terminal B 2 . The first light source unit 1 a includes a plurality of LEDs, e.g., 5 LEDs 1001 a in FIG. 26 , connected in series in the forward direction, the LEDs having identical electrical characteristics. Alternatively, the first light source unit 1 a may include multiple series circuits connected in parallel, each series circuit including multiple LEDs connected in series in the forward direction.

The second light source unit 1 b includes multiple LEDs, e.g., 2 LEDs 1002 a in FIG. 26 , connected in parallel, the anode of each LED of the second light source unit 1 b being coupled to the negative connecting terminal of the LEDs of the first light source unit 1 a . The LEDs 1002 a included in the second light source unit 1 b have also identical electrical characteristics. Further, it is preferable that the LEDs 1001 a of the first light source unit 1 a and the LEDs 1002 a of the second light source unit 1 b have identical or similar electrical and optical characteristics to prevent uneven illumination. The number of the LEDs in the first and second source units 1 a and 1 b is not limited to the above number.

The characteristic setting unit 2 a carries information on electrical characteristics such as a forward voltage or a forward current of the LEDs included in the first and second source units 1 a and 1 b and its circuit configuration is illustrated in FIG. 29 . The circuit configuration of the characteristic setting unit 2 a will be described later in detail.

As shown in FIG. 27 , the first and second light source units 1 a and 1 b are mounted on one side, e.g., the top surface in FIG. 27 , of a printed circuit board 1007 made of a long rectangular flat plate. Some of the LEDs 1001 a are not shown. Furthermore, although not shown, the characteristic setting unit 2 a is mounted at either lengthwise end on the other side, e.g., the bottom surface in FIG. 27 ) of the printed circuit board 1007 . The printed circuit board 1007 is inserted into a light-transmitting cylindrical housing 1008 . Each end of the housing 1008 is blocked by metal caps 1009 , while each end of the printed circuit board 1007 is supported by each metal cap 1009 . The connecting terminal A made of a round pin protrudes out from one metal cap 1009 , whereas the connecting terminals B 1 and B 2 protrude out from the other metal cap 1009 .

The connecting terminal A is electrically coupled to the anode of the tail LED 1001 a of the first light source unit 1 a . On the other hand, the negative connecting terminal B 1 is electrically connected to the cathode of one of the multiple LEDs 1002 a of the second light source unit 1 b . Furthermore, the second negative connecting terminal B 2 is electrically connected to the cathode of the LED 1002 a which is not connected to the first negative connecting terminal B 1 among the multiple LEDs 1002 a of the second light source unit 1 b.

A lighting apparatus in this example is provided with a voltage conversion unit 8 for supplying a direct-current power to the LED module 21 A 1 by converting alternating-current power fed from an alternating-current power supply unit AC as shown in FIG. 28 . The voltage conversion unit 8 , which is formed of a well-known voltage reduction chopper circuit or a voltage reduction/boosting chopper circuit, controls switching frequency or an on-duty ratio of switching elements. Its output voltage and output current are variable. The positive output terminal of the voltage conversion unit 8 is connected to the positive connecting terminal A of the LED module 21 A 1 , whereas the negative output terminal of the voltage conversion unit 8 is connected to either the first negative connecting terminal B 1 or the second negative connecting terminal B 2 of the LED module 21 A 1 .

The lighting apparatus in this example further includes a first power supply unit 7 , a second power supply unit 3 , a characteristic detection unit 4 , a connection determination unit 5 and an output control unit 6 . The first power supply unit 7 generates control power such as direct-current power of 3.3 V or 5 V from the alternating-current power fed from the alternating-current power supply unit AC and supplies the control power to the second control power unit 3 , the characteristic detection unit 4 , the connection determination unit 5 and the output control unit 6 . The second power supply unit 3 , which is formed of a current source for converting the direct current fed from the control power supply unit 7 to constant current, supplies the constant current to the first negative connecting terminal B 1 or the second negative connecting terminal B 2 of the LED module 21 A 1 .

The characteristic detection unit 4 includes a microcomputer and it measures the electrical characteristics, e.g., the forward current, of the LEDs 1001 a and 1002 a carried by the characteristic setting unit 2 a of the LED module 21 A 1 based on a voltage waveform between the first and second negative connecting terminals B 1 and B 2 of the LED module 21 A 1 as will be described later. The connection determination unit 5 determines the connection of the LED module 21 A 1 to the lighting apparatus based on the voltage waveform between the first and second negative connecting terminals B 1 and B 2 of the LED module 21 A 1 as will be described later.

If the connection determination unit 5 determines that the LED module 21 A 1 is not connected, the output control unit 6 stops the operation of the voltage conversion unit 8 . If the connection determination unit 5 determines that the LED module 21 A 1 is connected, the output control unit 6 adjusts either or both the output voltage and the output current of the voltage conversion unit 8 based on the electrical characteristics detected by the characteristic detection unit 4 .

As shown in FIG. 29 , the characteristic setting unit 2 a of the LED module 21 A 1 includes a full-wave rectifier, i.e., a diode bridge, DB whose alternating-current input terminals are coupled to the first and second negative connecting terminals B 1 and B 2 , a diode D 1 whose anode is coupled to the high potential direct-current output terminal of the full-wave rectifier DB, and a parallel circuit of a smoothing capacitor C 2 and a Zener diode ZD, the parallel circuit being connected between the cathode of the diode D 1 and the low potential direct-current output terminal of the full-wave rectifier DB. The voltage between the direct-current output terminals of the full-wave rectifier DB is clamped to Zener voltage Vz of the Zener diode ZD and at the same time it is smoothed by the capacitor C 2 .

Zener current flowing through the Zener diode ZD can be controlled to a desired value by adopting a constant current source serving as the second power supply unit 3 . In FIG. 29 , although the second power supply unit 3 is connected to the first negative connecting terminal B 1 , it may be connected to the second negative connecting terminal B 2 . In either case, the Zener voltage Vz is generated between two ends of the smoothing capacitor C 2 by the rectifying operation of the full-wave rectifier DB.

Two resistor voltage dividers are connected in parallel to the smoothing capacitor C 2 . One of the resistor voltage dividers is constituted by a series circuit of resistors R 2 and R 3 , thereby creating the first reference voltage Vref 1 . The other resistor voltage divider is constituted by a series circuit of resistors R 4 and R 5 , thereby creating the second reference voltage Vref 2 lower than the first reference voltage Vref 1 . The first reference voltage Vref 1 or the second reference voltage Vref 2 is selectively fed to the non-inverting input terminal of a comparator CP via a transfer gate circuit TG. The comparator CP compares the voltage Vc 1 of two ends of a capacitor C 1 to the first reference voltage Vref 1 or the second reference voltage Vref 2 . The capacitor C 1 is charged by first mirror current I 1 generated from a first mirror circuit M 1 . The value of the first mirror current I 1 is determined by the resistive value of a resistor R 1 provided outside the first mirror circuit M 1 .

The capacitor C 1 is discharged through a second mirror circuit M 2 . Specifically, a switching element Q 1 is coupled to the second mirror circuit M 2 and, if the switching element Q 1 is turned off, second mirror current I 2 greater than the first mirror current I 1 flows out from the capacitor C 1 to thereby discharge the capacitor C 1 . However, if the switching element Q 1 is turned on, the second mirror current I 2 becomes zero and thus the capacitor C 1 is charged by the first mirror current I 1 . On the other hand, the output terminal of the comparator CP is connected to the gate of the switching element Q 1 and thus, if the output of the comparator CP is at an H level, the switching element Q 1 is turned on. If the output of the comparator CP is at an L level, the switching element Q 1 is turned off.

A switching element Q 2 and a series circuit of a resistor R 0 and a switching element Q 3 are connected between the high potential output terminal of the full-wave rectifier DB and the anode of the diode D 1 . The gate of the switching element Q 2 is connected to the connection point between the resistor R 0 and the switching element Q 3 , i.e., to the drain of the switching element Q 3 . Since the gate of the switching element Q 3 is connected to the output terminal of the comparator CP, if the output of the comparator CP is at an H level, the switching element Q 3 is turned on and thereby the switching element Q 2 is turned off. If the output of the comparator CP is at an L level, the switching element Q 3 is turned off and thereby the switching element Q 2 is turned on.

Next, the operation of the characteristic setting unit 2 a will be described with reference to timing charts shown in FIG. 5 . As shown in (a) of FIG. 5 , if constant current from the second power supply unit 3 of the lighting apparatus is supplied as will be described later, the first mirror current I 1 is supplied from the first mirror circuit M 1 to the capacitor C 1 and thereby the capacitor C 1 is charged and the voltage Vc 1 of the capacitor C 1 linearly increases.

Meanwhile, since the first reference voltage Vref 1 is fed to the non-inverting input terminal of the comparator CP through the transfer gate circuit TG and the voltage Vc 1 of the capacitor C 1 is lower than the first reference voltage Vref 1 , the output of the comparator CP is at an H level as shown in (b) of FIG. 5 and the second mirror current I 2 becomes zero, thereby the switching element Q 3 being turned on and the switching element Q 2 being turned off. In (c) of FIG. 5 , the potential of the first negative connecting terminal B 1 , which the drain of the switching element Q 2 is connected to, relative to the second negative connecting terminal B 2 (hereinafter, referred to as the “information carrying voltage”) Vout becomes the sum voltage of the turn-on voltage of diodes forming the full-wave rectifier DB, the turn-on voltage of the diode D 1 and the Zener voltage Vz.

If the voltage Vc 1 of the capacitor C 1 increases and reaches the first reference voltage Vref 1 as shown in (a) of FIG. 5 , the output of the comparator CP turns to the L level as shown in (b) of FIG. 5 . Then, since the second mirror circuit M 2 starts its operation and, accordingly, the capacitor C 1 is discharged, the voltage Vc 1 of the capacitor C 1 gradually decreases as shown in (a) of FIG. 5 .

The transfer gate circuit TG switches the voltage fed to the non-inverting input terminal of the comparator CP from the first reference voltage Vref 1 to the second reference voltage Vref 2 when the output of the comparator CP is switched from the H level to the L level in (b) of FIG. 5 . Since the voltage Vc 1 of the capacitor C 1 is higher than the second reference voltage Vref 2 , the output of the comparator CP is maintained at an L level in (b) of FIG. 5 . Furthermore, since the output of the comparator CP is at an L level, the switching element Q 3 is turned off and the switching element Q 2 is turned on. Accordingly, the information carrying voltage Vout approaches almost zero as shown in (c) of FIG. 5 .

If the voltage Vc 1 across the capacitor C 1 reaches the second reference voltage Vref 2 as shown in (a) of FIG. 5 , the output of the comparator CP is switched to the H level as shown in (b) of FIG. 5 and the second mirror circuit M 2 stops its operation. Thus, the capacitor C 1 starts to be charged, thereby gradually increasing the voltage Vc 1 of the capacitor C 1 as shown in (a) of FIG. 5 . The transfer gate circuit TG switches the voltage fed to the non-inverting input terminal of the comparator CP from the second reference voltage Vref 2 to the first reference voltage Vref 1 when the output of the comparator CP is switched from the L level to the H level in (b) of FIG. 5 . Since the voltage Vc 1 across the capacitor C 1 is lower than the first reference voltage Vref 1 , the output of the comparator CP is maintained at an H level in (b) of FIG. 5 .

Furthermore, since the output of the comparator CP is at an H level, the switching element Q 3 is turned on and thus the switching element Q 2 is turned off. Therefore, as shown in (c) of FIG. 5 , the information carrying voltage Vout becomes the sum voltage of the turn-on voltage of diodes forming the full-wave rectifier DB, the turn-on voltage of the diode D 1 and the Zener voltage Vz. On the other hand, while the output of the comparator CP becomes an L level and, accordingly, the switching element Q 2 is being on, power discharged from the capacitor C 2 is supplied to circuits including the comparator CP.

As apparent from FIG. 5 , the information carrying voltage Vout, i.e., the voltage of the connecting terminal B 1 has a relatively higher voltage during time T 1 where the voltage Vc 1 of the capacitor C 1 increases and has a relatively lower voltage during time where the voltage Vc 1 of the capacitor C 1 decreases. T 1 can be adjusted by varying the first reference voltage Vref 1 and the second reference voltage Vref 2 . For example, if the first reference voltage is reduced to Vref 1 ′ by varying a resistance ratio, i.e., a voltage-dividing ratio, between the resistors R 2 and R 3 , the time while the information carrying voltage Vout is at a higher voltage level is reduced to T 1 ′ as shown in FIG. 6 .

Thus, the characteristic setting unit 2 a of the LED module 21 A 1 in this example sets information about electrical characteristics of the LEDs 1001 a and 1002 a by changing at least one of the resistance ratio between the resistors R 2 and R 3 and the resistance ratio between the resistors R 4 and R 5 . Further, in this example, the characteristic setting unit 2 a is provided with the full-wave rectifier DB connected between the first and second negative connecting terminals B 1 and B 2 . Therefore, even if the second power supply unit 3 is connected to the second negative connecting terminal B 2 , the characteristic setting unit 2 a can operate in the same way as it does when the second power supply unit 3 is connected to the first negative connecting terminal B 1 .

The LED module 21 A 1 includes a first light source unit 1 a and a second light source unit 1 b , the first light source unit 1 a being formed of 49 LEDs 1001 a connected in series in the forward direction, each with electrical characteristics: a forward voltage of, e.g., 3.5 V and a forward current of, e.g., 0.3 A, and the second light source unit 1 b being formed of two LEDs 1002 a connected in parallel, each having same electrical characteristics as that of the first light source unit 1 a . Here, a time period where the information carrying voltage Vout of the characteristic setting unit 2 a is at a higher voltage level is set to be T 1 .

On the other hand, an LED module 21 A 1 ′ includes a first light source unit 1 a ′ and a second light source unit 1 b ′, the first light source unit 1 a ′ being formed of 49 LEDs 1001 a connected in series in the forward direction, each with electrical characteristics: a forward voltage of 3.5 V and a forward current of 0.25 A, and the second light source unit 1 b ′ being formed of two LEDs 1002 a connected in parallel, each having same electrical characteristics as that of the first light source unit 1 a ′. In this case, a time period where the information carrying voltage Vout of the characteristic setting unit 2 a is at a higher voltage level is set to be T 1 ′.

When the LED module 21 A 1 or 21 A 1 ′ is connected, the characteristic detection unit 4 detects the time period where the information carrying voltage Vout applied between the first and second negative connecting terminals B 1 and B 2 of the connected LED module is at a high level. Based on whether the detected time period is T 1 or T 1 ′, it determines the electrical characteristics of the LED module 21 A 1 or 21 A 1 ′, i.e., the electrical characteristics of the LEDs 1001 a and 1002 a.

Here, the characteristic detection unit 4 has a memory (not shown) storing a data table showing the relation between the time T 1 or T 1 ′ and the electrical characteristics of the LEDs 1001 a and 1002 a such as set current. Thus, the characteristic detection unit 4 reads the set current corresponding to the detected time T 1 and T 1 ′ from the data table and at the same time it instructs the output control unit 6 to set the output current of the voltage conversion unit 8 to be equal to the read set current.

Instead of the data table showing the relation between the time T 1 and T 1 ′, and the electrical characteristics of the LEDs 1001 a and 1002 a , a linear function shown in FIG. 7 may be stored in the memory. By using the linear function, the electrical characteristics of the LEDs 1001 a and 1002 a can be derived based on the time T 1 and T 1 ′. Although the set current is used as the information about the electrical characteristics set by the characteristic setting unit 2 a , the present invention is not limited thereto and set voltage or both the set current and the set voltage may also be carried as the information about the electrical characteristics.

On the other hand, the voltage between the terminals (not shown) of the lighting apparatus connected to the first and second negative connecting terminals B 1 and B 2 of the LED module 21 A 1 or 21 A 1 ′ is equal to the control voltage Vcc of the second power supply unit 7 if the LED module 21 A 1 or 21 A 1 ′ is not connected. If the LED module 21 A 1 or 21 A 1 ′ is connected, the voltage is clamped to the Zener voltage Vz and thereby it becomes the information carrying voltage Vout lower than the control voltage Vcc. Accordingly, the connection determination unit 5 compares the third reference voltage Vref 3 , which is lower than the control voltage Vcc but higher than the information carrying voltage Vout, to the voltage between the terminals connected to the first and second negative connecting terminals B 1 and B 2 of the LED module 21 A 1 or 21 A 1 ′ (hereinafter, referred to as the “detected voltage”).

If the detected voltage is above the reference voltage Vref 3 , the LED module 21 A 1 or 21 A 1 ′ is determined not to be connected (non-connection), and the LED module 21 A 1 or 21 A 1 ′ is determined to be connected (connection) if the detected voltage is below the critical voltage Vref 3 , as shown in (a) of FIG. 8 . In case of non-connection, the connection determination unit 5 sends a stop signal to both the output control unit 6 to stop the operation of the voltage conversion unit 8 and to the characteristic detection unit 4 to stop the characteristic detection operation.

Next, the operation of the connection determination unit 5 of the lighting apparatus will be described in detail with reference to timing charts shown in FIG. 8 . Until t 0 when the LED module 21 A 1 or 21 A 1 ′ is not connected to the lighting apparatus as shown in (a) to (c) of FIG. 8 , the operation of the voltage conversion unit 8 is stopped because a stop signal is generated from the connection determination unit 5 to the output control unit 6 . If the LED module 21 A 1 or 21 A 1 ′ is connected to the lighting apparatus at t 0 , constant current from the second power supply unit 3 of the lighting apparatus is supplied to the LED module 21 A 1 or 21 A 1 ′ via either the first negative connecting terminal B 1 or the second negative connecting terminal B 2 , thereby the smoothing capacitor C 2 being charged.

Since the characteristic setting unit 2 a is in a transition state until the voltage Vc 2 of the smoothing capacitor C 2 reaches the Zener voltage Vz, i.e., until t 1 , the characteristic detection unit 4 might misread the information about the electrical characteristics carried by the characteristic setting unit 2 a . Therefore, the connection determination unit 5 continues sending the stop signal to both the output control unit 6 and the characteristic detection unit 4 during a predetermined time period after the connection is determined, i.e., during t 0 to t 1 . After the operation of the characteristic setting unit 2 a is stable, i.e., after t 1 , the connection determination unit 5 stops generating the stop signal to both the output control unit 6 and the characteristic detection unit 4 . Accordingly, an over direct-current flow from the voltage conversion unit 8 to the LED module 21 A 1 or 21 A 1 ′ due to the misreading of the characteristic detection unit 4 can be prevented.

Since the characteristic setting unit 2 a operates normally when the stop signal is not generated from the connection determination unit 5 after the predetermined time period, the characteristic detection unit 4 can correctly detect information about electrical characteristics set by the characteristic setting unit 2 a . If the information about the electrical characteristics is detected by the characteristic detection unit 4 at t 2 , a driving signal for driving a switching element of the chopper circuit included in the voltage conversion unit 8 is generated from the output control unit 6 to the voltage conversion unit 8 . Accordingly, a direct-current output corresponding to the electrical characteristics of the LED module 21 A 1 or 21 A 1 ′ is supplied from the voltage conversion unit 8 .

As described above, since the LED module 21 A 1 or 21 A 1 ′ in this example has the characteristic setting unit 2 a carrying the information about the electrical characteristics of the diodes 1001 a of the first light source unit 1 a and the diodes 1002 a of the second light source unit 1002 , the lighting apparatus can supply an appropriate direct current based on the information, thereby preventing an over current flow not matching the electrical characteristics of the diodes 1001 a or the diodes 1002 a . Further, since the characteristic setting unit 2 a is provided with the full-wave rectifier DB connected between the first and second negative connecting terminals B 1 and B 2 , the second power supply unit 3 of the lighting apparatus can be connected to either the first negative connecting terminal B 1 or the second negative connecting terminal B 2 , thereby avoiding complicated wiring of the lighting apparatus and the LED module 21 A 1 or 21 A 1 ′.

Furthermore, by increasing or decreasing the time period while the information carrying voltage Vout applied between the first and second negative connecting terminals B 1 and B 2 is at a higher voltage level, e.g., T 1 or T 1 ′, the characteristic setting unit 2 a can control the voltage waveform fed in through the full-wave rectifier DB based on the information of the electrical characteristics. Therefore, an electrically programmable non-volatile semiconductor memory such as flash memory is not necessary, thereby reducing the manufacturing cost of the LED module 21 A 1 or 21 A 1 ′. Since the characteristic detection unit 13 detects the information for the electrical characteristics of the characteristic setting unit 2 a by using the terminals for supplying power from the second power supply unit 3 , e.g., the first negative connecting terminal B 1 or the second negative connecting terminal B 2 , wiring can be reduced.

In this example, the connection determination unit 5 of the lighting apparatus determines the connection of the LED module 1000 A or 1000 A′ based on the voltage applied between the first and second negative connecting terminals B 1 and B 2 and it stops the operation of the voltage conversion unit 8 in case of non-connection. Accordingly, wiring can be reduced since no additional wiring is required to determine the connection, whereas power can be saved since the voltage conversion unit 8 stops operation if the LED module 1000 A or 1000 A′ is not connected.

Although the LED module 21 A 1 in this example has the shape similar to a straight-tube fluorescent lamp, it is not limited thereto. For example, the first and second light source units 1 a and 1 b and the characteristic setting unit 2 a mounted on a circular printed circuit board can be inserted into a cylindrical housing.

Next, description will be made on Example 2 of the second embodiment in accordance with the present invention. A lighting apparatus in Example 2 can be connected to multiple LED modules, e.g., two LED modules 21 A 1 in FIG. 30 , and it can simultaneously turn them on. Since the basic configuration of the lighting apparatus in this example is the same as that in Example 1, like reference numerals will be assigned to like parts and description thereof will be omitted. The LED module 21 A 1 in this example is the same as that in Example 1.

Unlike the lighting apparatus in Example 1 of the second preferred embodiment of the present invention, the lighting apparatus in this example includes multiple second power supply units, e.g., two second power supply units 3 in FIG. 30 , each supplying direct current to a first negative connecting terminal B 1 or a second negative connecting terminal B 2 of each LED module 21 A 1 . Furthermore, a characteristic detection unit 4 individually detects information about electrical characteristics set in a characteristic setting unit 2 a of the two LED modules 21 A 1 , and a connection determination unit 5 individually determines the connection of the LED modules 21 A 1 .

Since direct current is supplied to the two LED modules 21 A 1 from a single voltage conversion unit 8 of the lighting apparatus in this example, it is preferable that the LED modules 21 A 1 connected thereto have identical electrical characteristics. Next, the operation of the lighting apparatus if LED modules 21 A 1 and 21 A 1 ′ with different electrical characteristics as described in Example 1 are connected will be described.

If the electrical characteristics of the LED modules 21 A 1 and 21 A 1 ′ are different from each other, the characteristic detection unit 4 sends a stop signal to the output control unit 6 to stop the operation of the voltage conversion unit 8 . In this case, both the LED modules 21 A 1 and 21 A 1 ′ are not turned on. Alternatively, since the set current of the LED module 21 A 1 ′, i.e., 0.25 A is smaller than that of the LED module 21 A 1 , i.e., 0.3 A, the characteristic detection unit 4 may instruct the output control unit 6 so that the voltage conversion unit 8 can generate output current equal to the lower set current, i.e., 0.25 A. In this case, the output current of the voltage conversion unit 8 is divided into the LED modules 21 A 1 and 21 A 1 ′, the current flowing through the LED module 21 A 1 ′ is smaller than the set current 0.25 A but both the LED modules 21 A 1 and 21 A 1 ′ can be turned on. The operation of the connection determination unit 5 is the same as that in Example 1, and thus description thereof will be omitted.

As described above, the lighting apparatus in this example can turn on the multiple LED modules, e.g., the LED modules 21 A 1 or the LED modules 21 A 1 ′. Even when the LED modules 21 A 1 and 21 A 1 ′ with different electrical characteristics are mistakenly connected, over current does not flow through the LED modules 21 A 1 and 21 A 1 ′, thereby preventing a breakdown of the LED modules 21 A 1 and 21 A 1 ′.

Next, description will be made on Example 3 of the second embodiment in accordance with the present invention. Like the lighting apparatus in Example 2, a lighting apparatus in this example can be connected to multiple LED modules, e.g., two LED modules 21 A 2 in FIG. 31 , and it can simultaneously turn them on. However, unlike the lighting apparatus in Example 2, the lighting apparatus in this example has only one second power supply unit 3 and first and second negative connecting terminals B 1 and B 2 of the LED modules 21 A 2 are connected in parallel to a characteristic detection unit 4 and a connection determination unit 5 . Furthermore, the configuration of the second power supply unit 3 is different from that of the lighting apparatus in Example 2. Since the basic configuration of the lighting apparatus in this example is the same as that in Example 2, like reference numerals will be assigned to like parts and description thereof will be omitted. The LED module 21 A 2 in this example is the same as the LED module 21 A 1 in Example 1 except for the circuit configuration of a characteristic setting unit 2 a.

Referring to FIG. 32 , the second power supply unit 3 of the lighting apparatus in this example includes a series circuit of a resistor 3 a and a switching element 3 b . Switching of the switching element 3 b is controlled by the characteristic detection unit 4 . That is, only while the switching element 3 b is being turned on by the characteristic detection unit 4 , direct current is supplied from the second power supply unit 3 to the LED modules 21 A 2 .

In the characteristic setting unit 2 a of the LED module 21 A 2 , the drain of a switching element Q 2 is connected to both the anode of a diode D 1 and the high potential direct-current output terminal of a full-wave rectifier DB via a resistor R 9 as shown in FIG. 32 . Zener current flowing through a Zener diode ZD is limited to a predetermined value by the resistor 3 a of the second power supply unit 3 . Although the second power supply unit 3 is connected to the first negative connecting terminal B 1 in FIG. 32 , it may also be connected to the second negative connecting terminal B 2 . Even in this case, Zener voltage Vz is applied between two ends of a smoothing capacitor C 2 by the rectifying operation of the full-wave rectifier DB.

A series circuit of a mirror circuit M 3 and a capacitor C 3 is connected to both ends of the smoothing capacitor C 2 . The capacitor C 3 is charged by mirror current, i.e., constant current, generated from the mirror circuit M 3 . This mirror current is determined by the resistive value of a resistor R 8 provided outside the mirror circuit M 3 .

Connection point between the mirror circuit M 3 and the capacitor C 3 is connected to the inverting input terminal of the comparator CP. The comparator CP compares the voltage Vc 3 of the capacitor C 3 to a reference voltage Vref 4 created by dividing the Zener voltage Vz by a voltage divider formed of resistors R 6 and R 7 . Since the output terminal of the comparator CP is connected to the gate of the switching element Q 3 , if the output of the comparator CP is at H level, i.e., Vref 4 is higher than the Vc 3 , the switching element Q 3 is turned on and thereby the switching element Q 2 is turned off. If the output of the comparator CP is at an L level, i.e., Vref 4 is equal to or lower than Vc 3 , the switching element Q 3 is turned off and thereby the switching element Q 2 is turned on.

Next, the operation of the characteristic setting unit 2 a will be described with reference to timing charts shown in FIG. 33 . Direct current from the second power supply unit 3 is supplied to the characteristic setting unit 2 a of the LED modules 21 A 2 during a predetermined time period T 2 where the switching element 3 b is being turned on by the characteristic detection unit 4 of the illuminating device, as shown in (a) of FIG. 33 . Accordingly, in the characteristic setting unit 2 a , the Zener voltage Vz is generated for the predetermined time period and thereby the mirror circuit M 3 starts operating. The capacitor C 3 is charged by the mirror current, and the voltage Vc 3 across the capacitor C 3 linearly increases as shown in (c) of FIG. 33 .

While the voltage Vc 3 of the capacitor C 3 is below the reference voltage Vref 4 , the output of the comparator CP is at an H level as shown in (d) of FIG. 33 , thereby the switching element Q 3 being turned on and the switching element Q 2 being turned off. As shown in (e) of FIG. 33 , the potential of the first negative connecting terminal B 1 connected to the drain of the switching element Q 2 relative to the second negative connecting terminal B 2 , i.e., the information carrying voltage Vout becomes the sum voltage of the turn-on voltages of diodes forming the full-wave rectifier DB, the turn-on voltage of the diode D 1 and the Zener voltage Vz.

If the voltage Vc 3 across the capacitor C 3 increases and reaches the reference voltage Vref 4 in (c) of FIG. 33 , the output of the comparator CP turns to the L level as shown in (d) of FIG. 33 , thereby the switching element Q 3 being turned off and the switching element Q 2 being turned on. At this time, the information carrying voltage Vout is reduced to the voltage obtained by dividing control voltage fed from the first power supply unit 7 by a voltage divider constituted by the resistor 3 a of the second power supply unit 3 and the resistor R 9 connected to the drain of the switching element Q 2 , as shown in (e) of FIG. 33 .

Here, a time period where the information carrying voltage Vout is at a relatively higher voltage level within predetermined time period T 2 , i.e., a high voltage time period T 3 , varies depending on the reference voltage Vref 4 . By reducing the reference voltage Vref 4 by changing a resistance ratio, i.e., a voltage-dividing ratio between the resistors R 6 and R 7 , the high voltage time period T 3 can be reduced. Accordingly, the characteristic setting unit 2 a of the LED module 21 A 2 in this example carries information about electrical characteristics of the LEDs 1001 a and 1002 a by the resistance ratio between the resistors R 6 and R 7 .

Further, since the characteristic setting unit 2 a is provided with the full-wave rectifier DB connected between the first and second negative connecting terminals B 1 and B 2 , it is apparent that, although the second power supply unit 3 is connected to the second negative connecting terminal B 2 , the characteristic setting unit 2 a operates in the same way as it does when the second power supply unit 3 is connected to the first negative connecting terminal B 1 .

On the other hand, the characteristic detection unit 4 detects the high voltage time period T 3 by comparing the information carrying voltage Vout with a predetermined reference voltage Vref 5 as shown in (e) of FIG. 33 , and determining the electrical characteristics of the LED module 21 A 2 based on the detected high voltage time period T 3 .

As described in Example 2, it is considered that two types of LED modules 21 A 2 and 21 A 2 ′ having different electrical characteristics are mistakenly connected to the illuminating device. For example, the LED module 21 A 2 has electrical characteristics: a set voltage of 3.5 V and a set current of 0.3 A, and the LED module 21 A 2 ′ has electrical characteristics: a set voltage of 3.5 V and a set current of 0.25 A. Furthermore, the high voltage time period T 3 in direct proportion to the set current is prepared as the information about the electrical characteristics.

In this case, the first and second negative connecting terminals B 1 and B 2 of the two types of the LED modules 21 A 2 and 21 A 2 ′ are connected in parallel to the characteristic detection unit 4 , and the characteristic detection unit 4 detects first the electrical characteristics of the LED module 21 A 2 ′ with relatively shorter high voltage time period T 3 . Accordingly, the characteristic detection unit 4 can instruct the output control unit 6 so that the voltage conversion unit 8 can generate output current equal to the lower set current, i.e., 0.25 A, which turns on both the LED modules 21 A 2 and 21 A 2 ′. Since the determination operation of the connection determination unit 5 is the same as that in Example 1, description thereof will be omitted.

As described above, the lighting apparatus of this example can turn on the multiple LED modules, e.g., the LED modules 21 A or the LED modules 21 A 2 ′. Even when the LED modules 21 A 2 and 21 A 2 ′ having the different electrical characteristics are mistakenly connected, over current does not flow through the LED modules 21 A 2 and 21 A 2 ′, thereby preventing a breakdown of the LED modules 21 A 2 and 21 A 2 ′. Furthermore, wiring for connecting the lighting apparatus with the LED modules 21 A 2 as well as the circuit configuration of the characteristic setting unit 2 a of the LED modules 21 A 2 and 21 A 2 ′ can be simplified compared to Example 1 or 2.

FIG. 34 is a circuit diagram of an LED module 21 A 3 of Example 4. The LED module 21 A 3 includes a third light source unit 1 b ′ formed of multiple LEDs, e.g., 4 LEDs 1002 a 1 ′ to 1002 a 4 ′ in FIG. 34 , connected in parallel. In the third light source unit 1 b ′, the cathode of each LED is coupled to the anode of a tail LED 1001 a of a first light source unit 1 a . The LED module 21 A 3 further includes a first positive terminal Aa connected to the anode of the LED 1002 a 1 ′ of the third light source unit 1 b ′, a second positive terminal Ab connected to the anode of the LED 1002 a 2 ′ which is not connected to the first positive terminal Aa, and a second characteristic setting unit 2 a ′ for carrying the same information as that in the characteristic setting unit 2 a , the second characteristic setting unit 2 a ′ being connected between the first and second positive terminals Aa and Ab.

Among the multiple LEDs 1002 a 1 ′ to 1002 a 4 ′ of the third light source unit 1 b ′, each anode of the LEDs 1002 a 3 ′ and 1002 a 4 ′, which are not connected to either the first positive connecting terminal Aa or the second positive connecting terminal Ab, is connected to first and second negative connecting terminals B 1 and B 2 , respectively. Further, among multiple LEDs, e.g., 4 LEDs 1002 a 1 to 1002 a 4 in FIG. 34 , of a second light source unit 1 b , each cathode of the LEDs 1002 a 3 and 1002 a 4 , which are not connected to either the first negative connecting terminal B 1 or the second negative connecting terminal B 2 , is connected to the first and second positive connecting terminals Aa and Ab, respectively.

Here, it is preferable that the LEDs 1001 a of the first light source unit 1 a , the LEDs 1002 a 1 to 1002 a 4 of the second light source unit 1 b , and the LEDs 1002 a 1 ′ to 1002 a 4 ′ of the third light source unit 1 b ′ have identical or similar electrical and optical characteristics to each other to prevent uneven illumination. The number of the LEDs 1001 a , 1002 a 1 to 1002 a 4 , and 1002 a 1 ′ to 1002 a 4 ′ is not limited to the above number. Since the circuit configuration of the characteristic setting unit 2 a and the second characteristic setting unit 2 a ′ is the same as that of the LED module 21 A 1 or 21 A 2 in Example 1, 2 or 3, description thereof will be omitted.

On the route from the first positive connecting terminal Aa to the second negative connecting terminal B 2 , the LED 1002 a 1 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 1 of the second light source unit 1 b are connected in the forward direction. Furthermore, on the route from the first positive connecting terminal Aa to the first negative connecting terminal B 1 , the LED 1002 a 1 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 2 of the second light source unit 1 b are connected in the forward direction.

If the positive output terminal of the lighting apparatus is connected to the first positive connecting terminal Aa and, at the same time, its negative output terminal and the output terminal of the second power supply unit 3 are connected to the first and second negative connecting terminals B 1 and B 2 , respectively, or vice versa, the characteristic detection unit 4 of the lighting apparatus can detect electrical characteristics of the characteristic setting unit 2 a connected between the first and the second negative connecting terminals B 1 and B 2 , and the LED module 21 A 3 can be turned on by appropriate direct current supplied thereto.

Likewise, on the route from the second positive connecting terminal Ab to the second negative connecting terminal B 2 , the LED 1002 a 2 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 1 of the second light source unit 1 b are connected in the forward direction. Furthermore, on the route from the second positive connecting terminal Ab to the first negative connecting terminal B 1 , the LED 1002 a 2 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 2 of the second light source unit 1 b are connected in the forward direction.

Thus, although the positive output terminal of the lighting apparatus is connected to the second positive connecting terminal Ab and, at the same time, its negative output terminal and the output terminal of the second power supply unit 3 are connected to the first and second negative connecting terminals B 1 and B 2 , respectively, or vice versa, the characteristic detection unit 4 of the lighting apparatus can detect electrical characteristics of the characteristic setting unit 2 a connected between the first and the second negative connecting terminals B 1 and B 2 , and the LED module 21 A 3 can be turned on by appropriate direct current supplied thereto.

On the other hand, on the route from the first negative connecting terminal B 1 to the second positive connecting terminal Ab, the LED 1002 a 3 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 3 of the second light source unit 1 b are connected in the forward direction. Furthermore, on the route from the first negative connecting terminal B 1 to the first positive connecting terminal Aa, the LED 1002 a 3 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 4 of the second light source unit 1 b are connected in the forward direction.

If the positive output terminal of the lighting apparatus is connected to the first negative connecting terminal B 1 and, at the same time, its negative output terminal and the output terminal of the second power supply unit 3 are connected to the first and second positive connecting terminals Aa and Ab, respectively, or vice versa, the characteristic detection unit 4 of the lighting apparatus can detect electrical characteristics of the second characteristic setting unit 2 a ′ connected between the first and the second positive connecting terminals Aa and Ab, and the LED module 21 A 3 can be turned on by appropriate direct current supplied thereto.

Likewise, on the route from the second negative connecting terminal B 2 to the second positive connecting terminal Ab, the LED 1002 a 4 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 3 of the second light source unit 1 b are connected in the forward, direction. Furthermore, on the route from the second negative connecting terminal B 2 to the first positive connecting terminal Aa, the LED 1002 a 4 ′ of the third light source unit 1 b ′, the LEDs 1001 a of the first light source unit 1 a and the LED 1002 a 4 of the second light source unit 1 b are connected in the forward direction.

Thus, although the positive output terminal of the lighting apparatus is connected to the second negative connecting terminal B 2 and, at the same time, its negative output terminal and the output terminal of the second power supply unit 3 are connected to the first and second positive connecting terminals Aa and Ab, respectively, or vice versa, the characteristic detection unit 4 of the lighting apparatus can detect electrical characteristics of the second characteristic setting unit 2 a ′ connected between the first and the second positive connecting terminals Aa and Ab, and the LED module 21 A 3 can be turned on by appropriate direct current supplied thereto.

Since the LED module 21 A 3 in this example has no restriction on the connection of the output terminal of the lighting apparatus to the first and second positive connecting terminals Aa and Ab and the first and second negative connecting terminals B 1 and B 2 as described above, there cannot occur wrong connection of the LED module to the illuminating device.

As shown in FIG. 35 , LEDs 1001 a of the first light source unit 1 a , a LED 1002 a of the second light source unit 1 b and a LED 1002 a ′ of the third light source unit 1 b ′ are mounted on one side, e.g., the top surface in FIG. 35 , of a printed circuit board 1007 made of a long rectangular flat plate. Some of the LEDs 1001 a are not shown. Although not shown, the characteristic setting unit 2 a is mounted on the other side, e.g., the bottom surface in FIG. 35 ) of the printed circuit board 1007 and it is mounted at one lengthwise end, i.e., where the first and second negative connecting terminals B 1 and B 2 are disposed, whereas the second characteristic setting unit 2 a ′ is mounted at the other end.

The printed circuit board 1007 is received in a light-transmitting cylindrical housing 1008 . The first and second positive connecting terminals Aa and Ab formed of a round pin protrude out from one metal cap 1009 blocking both ends of the housing 1008 , and the first and second negative connecting terminals B 1 and B 2 formed of a round pin protrude out from the other metal cap 1009 . Furthermore, the first and second positive connecting terminals Aa and Ab and the first and second negative connecting terminals B 1 and B 2 have the same shape, size and are spaced equally.

The LED module 21 A 3 of this example is installed in an illumination apparatus as shown in FIG. 16 . This illumination apparatus includes a apparatus main body 20 directly attached to a ceiling and a pair of sockets 23 and which the LED module 21 A 3 can be connected to or disconnected from, the sockets 23 and 24 being disposed at the apparatus main boy 20 .

A lighting apparatus is installed inside the apparatus main body 20 of a long prism shape whose shape viewed in the lengthwise direction is trapezoidal. The sockets 23 and 24 are installed at both lengthwise ends on the bottom surface of the apparatus main body 20 . These sockets 23 and 24 have the same configuration as those of conventional cylindrical fluorescent lamps. The first and second positive connecting terminals Aa and Ab and the first and second negative connecting terminals B 1 and B 2 of the LED module 21 A 3 are connected to the lighting apparatus via the sockets 23 and 23 .

The LED module 21 A 3 in this example has no restriction on the connection of the output terminal of the lighting apparatus to the first and second positive connecting terminals Aa and Ab and the first and second negative connecting terminals B 1 and B 2 , and furthermore, the first and second positive connecting terminals Aa and Ab and the first and second negative connecting terminals B 1 and B 2 have the same shape, size and are spaced equally as described above. Because of this, there is no restriction on the connection of the sockets 23 and 24 of the illumination apparatus. Accordingly, installation of the LED module 21 A 3 or wiring between the lighting apparatus installed in the apparatus main body 20 and the sockets 23 and 24 can be much easier.

FIG. 37 is a circuit diagram of a lighting apparatus of Example 5. Like reference numerals will be assigned to like parts from the lighting apparatus in Examples 1 to 4 and description thereof will be omitted. An LED module 21 A 4 in this example is the same as the LED module 21 A in Example except that a characteristic setting unit 2 a is constituted by a resistor R 10 .

A voltage conversion unit 8 of the lighting apparatus is constituted by a well-known voltage reduction chopper circuit. Specifically, the voltage conversion unit 8 includes a switching element Q 4 whose drain is connected to the positive terminal of a direct-current power supply unit DC, and an inductor L 1 whose one end is connected to the source of the switching element Q 4 . Further, the voltage conversion unit 8 includes a diode D 4 whose cathode is connected to the source of the switching element Q 4 and whose anode is grounded and a capacitor C 7 whose high potential terminal is connected to the other end of the inductor L 1 and whose low potential terminal is connected to the anode of the diode D 4 via a detection resistor Rs. The direct-current power supply DC can be obtained either by rectifying and smoothing alternating-current power or by using a voltage boosting chopper circuit.

The output control unit 6 includes a driver circuit 9 for generating a driving signal to the gate of the switching element Q 4 of the voltage conversion unit 8 and a feedback control circuit 10 for controlling ON-time Ton of the driving signal generated from the driver circuit 9 . The feedback control circuit 10 is constituted by an operational amplifier OP 1 , a resistor R 11 connected to the inverting input terminal of the operational amplifier OP 1 , a capacitor C 4 connected between the inverting input terminal and the output terminal of the operational amplifier OP 1 , a diode D 3 whose cathode is connected to the output terminal of the operational amplifier OP 1 , and a resistor R 14 connected to the anode of the diode D 3 .

Voltage detected at the detection resistor Rs, which is in proportion to output current of the voltage conversion unit 8 , is fed to the inverting input terminal of the operational amplifier OP 1 via the resistor R 12 , and a current setting signal outputted from the characteristic detection unit 4 is fed to the non-inverting input terminal of the operational amplifier OP 1 . A well-known integrator circuit is constituted by the operational amplifier OP 1 , the resistor R 12 and the capacitor C 4 .

The non-inverting input terminal of the operational amplifier OP 1 , which is usually grounded, is connected to the output terminal of the characteristic detection unit 4 . Thus, the operational amplifier OP 1 integrates a voltage obtained by adding the detected voltage to the voltage (i.e., offset voltage) of the current setting signal, and outputs the integrated result from the output terminal thereof. For that reason, as the voltage of the current setting signal increases based on the set current carried in the characteristic setting unit 2 a of the LED module 21 A 4 , the output voltage of the operational amplifier OP 1 decreases.

The driver circuit 9 , which may be constituted by a general purpose integrated circuit, includes an output terminal Hout generating a driving signal, an ON-pulse width control terminal Pls for controlling ON-time Ton, a control power terminal Vcc through which control power from a first power supply unit 7 is supplied and a reset terminal Reset for stopping the generation of the driving signal. In the driver circuit 9 , connected to the ON-pulse width control terminal Pls is a circuit including, e.g., a constant voltage buffer circuit, a current mirror circuit and a driving signal setting capacitor.

The ON-pulse width control terminal Pls connected to the output terminal of the constant voltage buffer circuit is grounded via a resistor R 13 connected outside the ON-pulse width control terminal Pls, and current Ipls flowing from the ON-pulse width control terminal Pls to the resistor R 13 is equal to the current generated by the current mirror circuit. A time period until the voltage of the driving signal setting capacitor charged by output current of the current mirror circuit reaches a predetermined voltage becomes ON-time Ton. The connection point between the ON-pulse width control terminal Pls and the resistor R 13 is connected to the output terminal of the operational amplifier OP 1 via the resistor R 14 and the diode D 3 . Thus, as the output voltage of the operational amplifier OP 1 decreases, the current Ipls from the ON-pulse width control terminal Pls increases, resulting in a reduction of ON-time Ton as shown in FIG. 18 .

Thus, if the output current of the voltage conversion unit 8 increases, the voltage detected at the detection resistor Rs increases and thereby the output voltage of the operational amplifier OP 1 of the feedback control circuit 10 is reduced. Accordingly, ON-time Ton of the driving signal generated from the output terminal Hout of the driver circuit 9 is reduced and thereby the output current of the voltage conversion unit 8 is reduced.

Between a control power terminal Vcc and a control power boosting terminal HVcc of the driver circuit 9 , a rectification diode D 12 is connected, while a capacitor C 5 is connected between a control power boosting ground terminal Hgnd and the cathode of the diode D 12 , the terminal Hgnd being connected to the source of the switching element Q 4 of the voltage conversion unit 8 . Power for the driving signal generated from the output terminal Hout is produced by the voltage charged in the capacitor C 5 provided outside the driver circuit 9 .

Next, the operations of the characteristic setting unit 2 a , the characteristic detection unit 4 and the connection determination unit 5 in this example will be described.

If the LED module 21 A 4 is connected to the lighting apparatus but the voltage conversion unit 8 is not operating, by using the detection resistor Rs having a resistive value less than a few ohms and the resistor R 10 having a resistive value greater than a few tens of kilohms, effect of the detection resistor Rs on the information carrying voltage Vout applied between the first and second negative connecting terminals B 1 and B 2 can be ignored. Namely, the information carrying voltage Vout can be regarded as determined only by the current value of the direct current supplied from the second power supply unit 3 and the resistive value of the resistor R 10 of the characteristic setting unit 2 a . Accordingly, if the information carrying voltage Vout varies in proportion to the resistive value of the resistor R 10 , information about electrical characteristics such as the set current Iout can be represented by the resistive value of the resistor R 10 in the characteristic setting unit 2 a as shown in FIG. 19 .

On the other hand, if the LED module 21 A 4 is connected to the lighting apparatus and the voltage conversion unit 8 is operating, and if the set current Iout of the LED module 21 A 4 is, e.g., 0.35 A, a peak current flowing through the inductor L 1 of the voltage conversion unit 8 is about 0.70 A. The voltage across the detection resistor Rs having a resistive value of 1 ohm varies in the range from 0 V to 0.7 V, while the information carrying voltage Vout varies depending on the switching operation of the switching element Q 4 . In order to correctly detect the electrical characteristic of the LED module 21 A 4 based on the information carrying voltage Vout, it is preferred that the characteristic detection unit 4 performs the detection when the voltage conversion unit 8 is not operating.

If the LED module 21 A 4 is not connected, the direct current from the second power supply unit 3 flows through the resistor R 11 connected between the output terminal of the second power supply unit 3 and the ground, thereby increasing the voltage between two ends of the resistor R 11 , i.e., the information carrying voltage Vout. If the information carrying voltage Vout is above a reference voltage Vref 6 , the connection determination unit 5 determines that the LED module 21 A 4 is not connected and then generates a stop signal. However, if the information carrying voltage Vout is below the reference voltage Vref 6 , the connection determination unit 5 determines that the LED module 21 A 4 is connected and thus does not generate a stop signal. While the stop signal is fed to the reset terminal Reset of the driver circuit 9 of the output control unit 6 , no driving signal is generated from the output terminal Hout of the driver circuit 9 and thereby the voltage converting unit 8 stops.

Next, the operation until the LED module 21 A 4 turns on after the direct-current power DC is supplied will be described in detail with reference to timing charts shown in FIG. 20 .

After the direct-current power DC is supplied, the control voltage of the first power supply unit 7 gradually increases as shown in (a) and (b) of FIG. 20 . If the control power reaches a predetermined level at to, constant direct current is generated from the second power supply unit 3 as shown in (c) of FIG. 20 . Although both the characteristic detection unit 4 and the connection determination unit 5 start operating at t 0 , the connection determination unit 5 keeps generating a stop signal during a predetermined time period after t 0 , i.e., during a time period from t 0 to t 2 , regardless of the connection of the LED module 21 A 4 as shown in (d) of FIG. 20 .

In the meantime, the characteristic detection unit 4 detects information about electrical characteristics such as set current based on the information carrying voltage Vout during a time period from t 0 to t 1 , t 1 being shorter than t 2 , and then generates a current setting signal corresponding to the detected set current as shown in (e) of FIG. 20 .

At t 2 , if the LED module 21 A 4 is connected to the illuminating device, the connection determination unit 5 determines there is a connection and thus stops generating a stop signal as shown in (d) of FIG. 20 . Therefore, a driving signal is generated from the output control unit 6 to thereby start the operation of the voltage conversion unit 8 as shown in (f) of FIG. 20 .

If the LED module 21 A 4 is not connected to the lighting apparatus at t 2 , the connection determination unit 5 determines there is no connection and keeps generating a stop signal. Thus, no driving signal is generated from the output control unit 6 and thereby the voltage converting unit 8 does not start operating. Meanwhile, the characteristic detection unit 4 repeats the characteristic detection.

If the first and second negative connecting terminals B 1 and B 2 of the LED module 21 A 4 are short-circuited by a breakdown or the like of the characteristic setting unit 2 a , the information carrying voltage Vout approaches almost zero. To this end, it is preferable that the connection determination unit 5 compares the information carrying voltage Vout with a reference voltage Vref 7 set to be lower than the reference voltage Vref 6 , and generates a stop signal to stop the operation of the voltage conversion unit 8 when the information carrying voltage Vout is below the reference voltage Vref 7 .

The characteristic detection unit 4 may stop detecting the characteristics after a driving signal is generated from the output control unit 6 . Further, the set current Iout as the information about the electrical characteristics may increase in stepwise for the information carrying voltage Vout as shown in FIG. 25 .

With the lighting apparatus as described above in this example, the output current of the voltage conversion unit 8 is feedback controlled by the output control unit 6 , thereby supplying more stable direct current to the LED module 21 A 4 .

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.