High pressure discharge lamp lighting device and illumination instrument

The present invention relates to a high pressure discharge lamp lighting device that lights a high pressure discharge lamp, and to an illumination instrument including the high pressure discharge lamp lighting device.

Heretofore, a lighting device as described in Patent Literature 1 has been proposed as a high pressure discharge lamp lighting device that lights a high pressure discharge lamp such as a high-intensity discharge lamp (HID lamp). In a conventional example described in Patent Literature 1, instead of applying a high-voltage pulse to the high pressure discharge lamp from an igniter (starting circuit) at a starting time, an output voltage of a boost chopper circuit at the starting time is increased more than an output voltage at a time of steady lighting, whereby the high pressure discharge lamp is started.

Moreover, in the above-described conventional example, a power supply of a control circuit (control power supply) for adjusting the output voltage of the boost chopper circuit is obtained from an induced voltage that is induced in a winding magnetically coupled to an inductor that composes the boost chopper circuit.

Patent Literature

Patent Literature 1: Japanese Patent No. 3846619

Technical Problem

Incidentally, in the case of increasing and reducing the output voltage of the boost chopper circuit before and after the start of the high pressure discharge lamp as in the above-described conventional example, power consumed in the high pressure discharge lamp immediately after the start is small. Accordingly, a both-end voltage of a smoothing capacitor provided on an output stage of the boost chopper circuit is not lowered soon. Therefore, in some case, controlling means that is performing feedback control so as to allow the output voltage to coincide with a target value has temporarily stopped the boost chopper circuit. Then, when the boost chopper circuit is stopped, the induced voltage ceases to be induced in the winding magnetically coupled to the inductor of the boost chopper circuit, and accordingly, it has been apprehended that supply of the control power to the controlling means may also be stopped. For this matter, capacitance of the capacitor for smoothing the induced voltage is increased, thus making it possible to supply the control power also while the boost chopper circuit is stopped. However, there is a problem that such an increase of the capacitance of the capacitor brings about size and cost increases of a power supply circuit that supplies the control power.

The present invention has been made in consideration of the above-described circumstances. It is an object of the present invention to provide a high pressure discharge lamp lighting device and an illumination instrument, which are capable of supplying the control power also when a DC output voltage of the boost chopper circuit is switched at the starting time of the high pressure discharge lamp while avoiding the size and cost increases of the power supply circuit that supplies the control power.

Solution to Problem

In order to achieve the foregoing object, an invention of claim 1 is a high pressure discharge lamp lighting device including: a boost chopper circuit that boosts a DC input voltage to a desired DC output voltage; a boost chopper control circuit that controls the boost chopper circuit to allow a DC output voltage of the boost chopper circuit to coincide with the desired DC output voltage; a power conversion circuit that converts a DC output of the boost chopper circuit into power necessary to start and light a high pressure discharge lamp; a power conversion control circuit that controls the power conversion circuit to adjust the power to be supplied to the high pressure discharge lamp; and a control power supply circuit that supplies a control power for an operation to at least the boost chopper control circuit, wherein the boost chopper circuit includes: an inductor; a switching element that connects and disconnects a current flowing through the inductor; a rectifier that rectifies the current flowing out of the inductor; and a smoothing capacitor that smoothes the current rectified by the rectifier, the control power supply circuit includes a winding magnetically coupled to the inductor provided in the boost chopper circuit, and obtains the control power by rectifying and smoothing an induced voltage induced in the winding, and the boost chopper control circuit controls the DC output voltage of the boost chopper circuit to coincide with a first DC output voltage at a starting time of the high pressure discharge lamp, allows the output voltage of the boost chopper circuit to coincide with a second DC output voltage lower than the first DC output voltage after the high pressure discharge lamp is started, and operates the boost chopper circuit intermittently in an event of switching the DC output voltage of the boost chopper circuit from the first DC output voltage to the second DC output voltage.

In accordance with the invention of claim 1 , in the event of switching the DC output voltage of the boost chopper circuit from the first DC output voltage to the second DC output voltage, the boost chopper control circuit operates the boost chopper circuit intermittently. Therefore, a stop period of the boost chopper circuit is shortened as compared with the case where the boost chopper control circuit does not operate the boost chopper circuit intermittently. As a result, it becomes possible to supply a control power also when the DC output voltage of the boost chopper circuit is switched at the starting time of the high pressure discharge lamp while avoiding the size and cost increases of the power supply circuit that supplies the control power.

In an invention of claim 2 according to the invention of claim 1 , the boost chopper control circuit detects the DC output voltage of the boost chopper circuit, and performs feedback control so as to allow a detected value of the DC output voltage to coincide with a target value thereof, in which, in the event of switching the DC output voltage of the boost chopper circuit from the first DC output voltage to the second DC output voltage, a first target value corresponding to the first DC output voltage and a second target value corresponding to the second DC output voltage or a first detected value corresponding to the first DC output voltage and a second detected value corresponding to the second DC output voltage are alternately switched.

In an invention of claim 3 according to the invention of claim 1 , the boost chopper control circuit detects the DC output voltage of the boost chopper circuit, and performs feedback control so as to allow a detected value of the DC output voltage to coincide with a target value thereof, in which, in the event of switching the DC output voltage of the boost chopper circuit from the first DC output voltage to the second DC output voltage, the DC output voltage of the boost chopper circuit is switched to a third target value corresponding to a third DC output voltage lower than the first DC output voltage and higher than the second DC output voltage or to a third detected value corresponding to the third DC output voltage, and thereafter, is switched to a second target value corresponding to the second DC output voltage or a second detected value corresponding to the second DC output voltage.

In an invention of claim 4 according to any one of the inventions of claims 1 to 3 , a voltage difference between the first DC output voltage and the second DC output voltage is 30 volts or more.

In order to achieve the foregoing object, an invention of claim 5 is an illumination instrument including: the high pressure discharge lamp lighting device according to any one of the inventions of claims 1 to 4 ; and an instrument main body that holds the high pressure discharge lamp lighting device and a high pressure discharge lamp.

Advantageous Effects of Invention

In accordance with the present invention, it becomes possible to supply the control power also when the DC output voltage of the boost chopper circuit is switched at the starting time of the high pressure discharge lamp while avoiding the size and cost increases of the power supply circuit that supplies the control power.

FIG. 1 is a circuit diagram illustrating Embodiment 1 of a high pressure discharge lamp lighting device according to the present invention.

FIGS. 2( a ) and 2 ( b ) are operation explanatory diagrams of Embodiment 1.

FIGS. 3( a ) and 3 ( b ) are other operation explanatory diagrams of Embodiment 1.

FIG. 4 is a circuit diagram illustrating Embodiment 2 of a high pressure discharge lamp lighting device according to the present invention.

FIGS. 5( a ) to 5 ( d ) are operation explanatory diagrams of Embodiment 2.

FIGS. 6( a ) to 6 ( c ) are other operation explanatory diagrams of Embodiment 2.

FIG. 7 is an exterior appearance perspective view illustrating an embodiment of an illumination instrument according to the present invention.

A description is made below in detail of embodiments of the present invention.

As illustrated in FIG. 1 , a high pressure discharge lamp lighting device of this embodiment includes: a boost chopper circuit 1 that boosts a DC input voltage, which is formed by performing full-wave rectification for an AC power source AC by a rectifier circuit DB, to a desired DC output voltage Vbus; a boost chopper control circuit 2 that performs switching control for a switching element Q 1 that composes the boost chopper circuit 1 ; a power conversion circuit 3 that converts such a DC output of the boost chopper circuit 1 into a desired AC output; a power conversion control circuit 4 that controls the power conversion circuit 3 to adjust power to be supplied to a high pressure discharge lamp LA; and a control power supply circuit 5 that supplies an operation power supply (control power Vcc) to a boost chopper control unit IC 1 that composes the boost chopper control circuit 2 , and to a power conversion control unit IC 2 that composes the power conversion control circuit 4 .

The boost chopper circuit 1 is a circuit heretofore well known, and includes: an inductor L 1 in which one end is connected to a high potential-side output end of the rectifier circuit DB; the switching element Q 1 composed of a field-effect transistor inserted between the other end of the inductor L 1 and a low potential-side output end of the rectifier circuit DB together with a resistor R 7 ; a diode D 1 in which an anode is connected to a node between the inductor L 1 and the switching element Q 1 ; and a smoothing capacitor C 4 inserted between a cathode of the diode D 1 and the low potential-side output end of the rectifier circuit DB. Note that a secondary winding N 2 is magnetically coupled to the inductor L 2 .

The boost chopper control circuit 2 includes: the boost chopper control unit IC 1 that performs switching control (PWM control) for the switching element Q 1 ; voltage dividing resistors R 1 , R 2 and R 3 which divide the DC input voltage inputted from the rectifier circuit DB to the boost chopper circuit 1 ; a series circuit of resistors R 4 and R 5 and a capacitor C 1 , which are connected between the output ends of the rectifier circuit DB for supplying the operation power supply to the boost chopper control unit IC 1 at the time when the power supply is turned on; and a voltage detection circuit 2 a for detecting the DC output voltage Vbus of the boost chopper circuit 1 . The boost chopper control unit IC 1 is composed of, for example, a power factor improving control IC (model number: MC33262) made by ON Semiconductor Corporation, and performs feedback control (PWM control) for adjusting an ON-duty ratio of the switching element Q 1 so as to allow a detected value (voltage value corresponding to the DC output voltage Vbus of the boost chopper circuit 1 ) of the voltage detection circuit 2 a to coincide with a desired target value. Moreover, the boost chopper control circuit IC 1 detects the DC input voltage, which is inputted to the boost chopper circuit 1 , by a series circuit of the resistors R 1 , R 2 and R 3 , and detects an input current, which flows through the inductor L 1 , by an induced voltage induced in the secondary winding N 2 , thereby performs power factor improving control for imparting resistivity to the circuit so that phases of the input current and the DC input voltage cannot be shifted from each other.

The voltage detection circuit 2 a is composed of: a series circuit of four voltage dividing resistors R 8 , R 9 , R 10 , and R 11 connected in parallel to the smoothing capacitor C 4 that composes the boost chopper circuit 1 ; and a switching element Q 2 that is connected in parallel to the voltage dividing resistor R 11 in which one end is connected to the ground, and short-circuits both ends of the voltage dividing resistor R 11 so as to be freely openable and closable. Note that, as will be described later, the switching element Q 2 is turned on/off by a control signal Vten outputted from the power conversion control circuit 4 .

The power conversion circuit 3 is a so-called full-bridge circuit, and is composed in such a manner that a series circuit of two switching elements Q 3 and Q 4 formed of field-effect transistors and a series circuit of two switching elements Q 5 and Q 6 also formed of field-effect transistors are connected in parallel to each other between output ends of the boost chopper circuit 1 , and that a load circuit 6 including a high pressure discharge lamp LA is connected between midpoints (node between the switching elements Q 3 and Q 4 and node between the switching elements Q 5 and Q 6 ) of both of the series circuits. The load circuit 6 includes: a series circuit of two inductors L 2 and L 3 and the high pressure discharge lamp LA; and a capacitor C 6 connected in parallel to the inductor L 3 and the high pressure discharge lamp LA, in which the inductor L 2 and the capacitor C 6 compose a resonant circuit.

The power conversion control unit IC 2 is composed of, for example, a microcomputer, detects a voltage applied to the high pressure discharge lamp LA (lamp voltage), and detects, in response to a result of such detection, a state of the high pressure discharge lamp LA (being lighted, being tuned out, and so on). Moreover, from the power conversion control unit IC 2 , drive signals a to d are outputted, which drive the switching elements Q 3 to Q 6 of the power conversion circuit 3 .

The control power supply circuit 5 is composed of a diode D 2 in which an anode is connected to a node between the secondary winding N 2 and a resistor R 6 ; a resistor R 12 in which one end is connected to a cathode of the diode D 2 ; a smoothing capacitor C 5 inserted between the other end of the resistor R 12 and the ground; and a Zener diode D 4 connected in parallel to the smoothing capacitor C 5 . The control power supply circuit 5 rectifies the induced voltage, which is induced in the secondary winding N 2 , by the diode D 2 , smoothes the induced voltage by the smoothing capacitor C 5 , and clamps the induced voltage by the Zener diode D 4 , thereby generates a substantially constant control power Vcc. Note that the control power Vcc generated by the control power supply circuit 5 is supplied to the boost chopper control unit IC 1 through a diode D 3 , and is supplied to the power conversion control unit IC 2 .

A description is made below of basic operations of the high pressure discharge lamp lighting device of this embodiment. However, the following basic operations are merely an example, and the high pressure discharge lamp lighting device is also capable of performing other operations within the scope without departing from the spirit of the present invention.

(Starting Mode)

First, in order to start the high pressure discharge lamp LA, it is necessary to break down insulation between electrodes thereof by applying a high voltage between the electrodes. In this embodiment, the power conversion control unit IC 2 alternately switches between two pairs in the power conversion circuit 3 , which are a pair of the switching elements Q 3 and Q 6 and a pair of the switching elements Q 4 and Q 5 , at a frequency close to a resonant frequency of the resonant circuit composed of the inductor L 2 and the capacitor C 6 . In such a way, the power conversion control unit IC 2 applies, between the electrodes of the high pressure discharge lamp LA, a high voltage (resonant voltage) sufficiently higher (for example, several kilovolts) than the DC output voltage Vbus of the boost chopper circuit 1 , and thereby starts the high pressure discharge lamp LA. However, another configuration may be adopted, in which a resonant circuit composed of a capacitor having one end connected to a part of a winding of the inductor L 2 and a resistor connected in series to the other end of the capacitor concerned is provided, and such a high voltage for starting the high pressure discharge lamp LA is generated by the resonant circuit concerned. Note that, in this starting mode, the high-level control signal Vten is outputted from the power conversion control unit IC 2 , the switching element Q 2 of the voltage detection circuit 2 a is turned on, and both ends of the voltage dividing resistor R 11 are short-circuited by the switching element Q 2 , whereby the detected value becomes a relatively small value (hereinafter, referred to as a first detected value). At this time, with respect to the target value of the boost chopper circuit 1 , the first detected value inputted from the voltage detection circuit 2 a to the boost chopper control unit IC 1 becomes lower than when the switching element Q 2 is turned off. Accordingly, in order to approximate the first detected value to the target value, the boost chopper control unit IC 1 raises the DC output voltage of the boost chopper circuit 1 . The DC output voltage Vbus at this time is a first DC output voltage V 1 , and for example, is approximately 300 volts.

(Low Lamp Voltage Mode)

After the high pressure discharge lamp LA is started, the power conversion control unit IC 2 switches a switching mode of the switching elements Q 3 to Q 6 . In a low lamp voltage range approximately from 0 to 60 volts before the lamp voltage reaches 90 to 110 volts as an approximate rated lighting voltage, the power conversion control unit IC 2 performs control to flow a larger lamp current through the high pressure discharge lamp LA so that the high pressure discharge lamp LA can be prevented from being faded and can be warmed rapidly. Note that, when an operation mode of the high pressure discharge lamp lighting device is switched from the starting mode to the low lamp voltage mode, the control signal Vten outputted from the power conversion control unit IC 2 is switched from such a high-level to a low-level, and the switching element Q 2 of the voltage detection circuit 2 a is turned off, whereby the detected value becomes a relatively large value (hereinafter, referred to as a second detected value). At this time, with respect to the target value of the boost chopper circuit 1 , the second detected value inputted from the voltage detection circuit 2 a to the boost chopper control unit IC 1 becomes higher than the first detected value. Accordingly, in order to approximate the second detected value to the target value, the boost chopper control unit IC 1 stops the boost chopper circuit 1 . Note that the DC output voltage Vbus corresponding to the second detected value is defined as a second DC output voltage V 2 .

(Stable Lighting Mode)

When the high pressure discharge lamp LA is warmed and a tube voltage of the high pressure discharge lamp LA reaches the approximate rated lamp voltage, the power conversion control unit IC 2 further switches the switching mode of the switching elements Q 3 to Q 6 , and flows a lamp current with a triangular wave shape through the high pressure discharge lamp LA. Note that, in such a stable lighting mode, the DC output voltage Vbus that is approximately 2 to 2.5 times the rated lamp voltage (for example, approximately 160 to 270 volts) is supplied from the boost chopper circuit 1 to the power conversion circuit 3 . Hence, a voltage difference between the first DC output voltage V 1 and the second DC output voltage V 2 becomes 30 volts (=300−270) or more.

Next, a description is made of, as the spirit of the present invention, operations when the operation mode is switched from the starting mode to the low lamp voltage mode.

As illustrated in FIG. 2( b ), in the event where the power conversion control unit IC 2 shifts from the starting mode to the low lamp voltage mode, when an extremely short time (for example, several hundred microseconds) elapses after the control signal Vten is switched from the high-level to the low-level at an ending time point t 1 of the starting mode, the control signal Vten is switched from the low-level to the high-level one more time, and thereafter, until a time point t 2 when a predetermined time elapses from the ending time point t 1 of the starting mode, the control signal Vten is alternately switched between the low-level and the high-level in an extremely short cycle (for example, several hundred microseconds). When the control signal Vten is switched between the high-level and the low-level in the short cycle as described above, the boost chopper control unit IC 1 controls the boost chopper circuit 1 to alternately switch the DC output voltage Vbus between the first DC output voltage V 1 and the second DC output voltage V 2 . Therefore, the DC output voltage Vbus of the boost chopper circuit 1 during such a period from the ending time point t 1 of the starting mode to the time point t 2 when the predetermined time elapses therefrom (for example, several hundred milliseconds) becomes a voltage V 3 to the eye, which is located between the first DC output voltage V 1 and the second DC output voltage V 2 (refer to FIG. 2( a )). Then, at the elapsed time point t 2 of the predetermined time, the power conversion control unit IC 2 fixes the control signal Vten to the low-level. When the control signal Vten is fixed to the low-level, the boost chopper control unit IC 1 temporarily stops the boost chopper circuit 1 in order to control the boost chopper circuit 1 so that the DC output voltage Vbus can be the second DC output voltage V 2 . However, at this time point, the DC output voltage Vbus of the boost chopper circuit 1 is lowered to the voltage V 3 lower than the first DC output voltage V 1 . Accordingly, at a time point t 3 when an extremely short time elapses from the elapsed time point t 2 of the predetermined time, the DC output voltage Vbus drops to the second DC output voltage V 2 (refer to FIG. 2( a )).

Incidentally, if the control signal Vten is switched from the high-level to the low-level and is fixed to the low-level at the ending time point t 1 of the starting mode, then the boost chopper circuit 1 is stopped during a period while the DC output voltage Vbus is dropping from the first DC output voltage V 1 to the second DC output voltage V 2 (period from t 1 to t 3 ), and the induced voltage ceases to be induced in the secondary winding N 2 magnetically coupled to the inductor L 1 of the boost chopper circuit 1 , and therefore, it becomes impossible for the control power supply circuit 5 to generate the control power Vcc. As opposed to this, in this embodiment, the control signal Vten is alternately switched between the low-level and the high-level during the period from the ending time point t 1 to the elapsed time point t 2 , whereby the boost chopper circuit 1 is operated intermittently. Accordingly, during the period from t 1 to t 2 , the induced voltage is induced intermittently in the secondary winding N 2 as mentioned above, and therefore, it becomes possible for the control power supply circuit 5 to generate the control power Vcc. In addition, the period while the boost chopper circuit 1 is temporarily stopped (period from t 2 to t 3 ) can be shortened.

As mentioned above, in accordance with this embodiment, in the event of switching the DC output voltage Vbus of the boost chopper circuit 1 from the first DC output voltage V 1 to the second DC output voltage V 2 , the boost chopper control circuit 2 operates the boost chopper circuit 1 intermittently. Accordingly, the stop period of the boost chopper circuit 1 is shortened as compared with the case where the boost chopper circuit 1 is not operated intermittently. As a result, it becomes possible to supply the control power Vcc also when the DC output voltage Vbus of the boost chopper circuit 1 is switched at the starting time of the high pressure discharge lamp LA while avoiding size and cost increases of the control power supply circuit 5 that supplies the control power Vcc. Note that, in this embodiment, the detected value of the voltage detection circuit 2 a is switched by the power conversion control unit IC 2 in order to operate the boost chopper circuit 1 intermittently; however, it is possible to operate the boost chopper circuit 1 intermittently also in such a manner that the target value of the DC output voltage Vbus in the boost chopper control circuit 2 is switched instead of switching the detected value.

Incidentally, as illustrated in FIG. 3( b ), with regard to the control signal Vten outputted from the power conversion control unit IC 2 during the period from the ending time point t 1 of the starting mode to the elapsed time point t 2 , if a ratio H/L of a high-level time (H) to a low-level time (L) is made gradually smaller, then as illustrated in FIG. 3( a ), the voltage V 3 at which the DC output voltage Vbus of the boost chopper circuit 1 is temporarily stabilized can be approximated to the second DC output voltage V 2 . As a result, it becomes possible to further shorten the stop period of the boost chopper circuit 1 , which corresponds to the period from t 2 to t 3 .

As illustrated in FIG. 4 , the high pressure discharge lamp lighting device of this embodiment has a feature in the configuration of the voltage detection circuit 2 a , in which other configurations are common to those of Embodiment 1. Hence, the same reference numerals are assigned to constituents common to those of Embodiment 1, and a description thereof is omitted.

The voltage detection circuit 2 a in this embodiment is different from that in Embodiment 1 in that there are added: a voltage dividing resistor R 20 inserted between the voltage dividing resistor R 11 and the ground; a switching element Q 20 composed of a field-effect transistor connected in parallel to the voltage dividing resistor R 20 ; and a delay circuit, which is composed of a capacitor C 20 and a resistor R 21 , and delays the control signal Vten in the low-level inputted from the power conversion control unit IC 2 to a gate of the switching element Q 20 .

Next, a description is made of, as the spirit of the present invention, operations when the operation mode is switched from the starting mode to the low lamp voltage mode.

As illustrated in FIG. 5( b ), in the event of shifting from the starting mode to the low lamp voltage mode, the power conversion control unit IC 2 switches the control signal Vten from the high-level to the low-level at the ending time point t 1 of the starting mode. At this time, as illustrated in FIG. 5( c ), the gate voltage Vgs at the switching element Q 2 of the voltage detection circuit 2 a is rapidly turning to the low-level, and the switching element Q 2 is immediately turned off. Meanwhile, as illustrated in FIG. 5( d ), the gate voltage Vgs at the switching element Q 20 is gradually shifted to the lower-level by a function of the delay circuit (capacitor C 20 and resistor R 21 ), and as a result, the switching element Q 20 is not turned off until the time point t 3 when a predetermined time elapses from the ending time point t 1 . During a period while the switching element Q 2 is turned off and the switching element Q 20 is turned on (period from t 1 to t 3 ), a detected value smaller than the first detected value and larger than the second detected value (third detected value) is outputted from the voltage detection circuit 2 a to the boost chopper control unit IC 1 . Accordingly, the boost chopper circuit 1 is stopped until the time point t 2 (<t 3 ) when the predetermined time elapses from the ending time point t 1 of the starting mode. However, as illustrated in FIG. 5( a ), during the period from the time point t 2 to the time point t 3 , while the DC output voltage Vbus of the boost chopper circuit 1 is lowered to the third DC output voltage V 3 corresponding to the third detected value, the boost chopper circuit 1 operates continuously.

Then, when the switching element Q 20 is turned off at the time point t 3 , the detected value outputted from the voltage detection circuit 2 a to the boost chopper control unit IC 1 is switched from the third detected value to the second detected value. Accordingly, the boost chopper circuit 1 is stopped one more time. Then, the boost chopper circuit 1 operates continuously one more time from a time point t 4 when the DC output voltage Vbus of the boost chopper circuit 1 is lowered to the second DC output voltage V 2 (refer to FIG. 5( a )).

As mentioned above, also in this embodiment, in the event of switching the DC output voltage Vbus of the boost chopper circuit 1 from the first DC output voltage V 1 to the second DC output voltage V 2 , the boost chopper circuit 1 is operated intermittently by providing the periods (t 1 to t 2 , t 3 to t 4 ) while the boost chopper circuit 1 is stopped and the period (t 2 to t 3 ) while the boost chopper circuit 1 is operated. Accordingly, similarly as in Embodiment 1, the stop period of the boost chopper circuit 1 is shortened as compared with the case where the boost chopper circuit 1 is not operated intermittently. As a result, it becomes possible to supply the control power Vcc also when the DC output voltage Vbus of the boost chopper circuit 1 is switched at the starting time of the high pressure discharge lamp LA while avoiding the size and cost increases of the control power supply circuit 5 that supplies the control power Vcc.

Note that, in Embodiments 1 and 2, it is possible to adjust the power (lamp current), which is supplied from the power conversion circuit 3 to the high pressure discharge lamp LA, by the power conversion control circuit 4 . Accordingly, as illustrated in FIG. 6( c ), at the same time when the control signal Vten is switched from the high-level to the low-level at the ending time point t 1 of the starting mode, the power conversion control unit IC 2 controls the switching elements Q 3 to Q 6 to temporarily increase the lamp current supplied from the power conversion circuit 3 to the high pressure discharge lamp LA. Then in this case, power consumption by the high pressure discharge lamp LA is increased, whereby the DC output voltage Vbus of the boost chopper circuit 1 is lowered rapidly (refer to a solid line of FIG. 6( a )). As a result, the stop period of the boost chopper circuit 1 can be shortened. However, when the lamp current (lamp power) is temporarily increased, a light output of the high pressure discharge lamp LA is also increased, resulting in an occurrence of flickering. Therefore, it is desired that the lamp current be increased to an extent where the flickering is not felt, for example, to an extent where an increase ratio of the light output becomes 50% or less with respect to the case where the lamp current is not increased.

FIG. 7 is an exterior appearance perspective view of an illumination instrument including: the high pressure discharge lamp lighting device of Embodiment 1 or 2; and an instrument main body 12 that holds the high pressure discharge lamp LA. This illumination instrument is a down light in which the instrument main body 12 is embedded and arranged in an embedding hole provided on a ceiling. In the illumination instrument, the high pressure discharge lamp lighting device is housed in a case 11 with a box shape, and the high pressure discharge lamp lighting device in the case 11 and the high pressure discharge lamp LA are electrically connected to each other by a cable 13 .

The present invention can be used as a technology for making it possible to supply the control power also when the DC output voltage of the boost chopper circuit is switched at the starting time of the high pressure discharge lamp while avoiding the size and cost increases of the power supply circuit that supplies the control power.

1 boost chopper circuit

2 boost chopper control circuit

2 a voltage detection circuit

3 power conversion circuit

4 power conversion control circuit

IC 1 boost chopper control unit

IC 2 power conversion control unit