JP3760476B2 - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE: To cause rectangular-wave lighting of a discharge lamp without extinction even at the end of its life. CONSTITUTION: Energy supplied from a voltage converting part 2 is stored in a capacitor C0 , and the voltages Vc at both ends of the capacitor C0 are polarity-inverted by means of an inverter part 3 to cause rectangular-wave lighting of a discharge lamp LP. A drive circuit 7 which performs switching control of the switching elements Q1 to Q4 of the inverter part 3 is provided with a low-frequency oscillating circuit 14. An output of the low-frequency oscillating circuit 14 is given to a control circuit 6 controlling the switching element Q0 of the voltage converting part 2. When the output of the low-frequency oscillating circuit 14 is at L level (dead time), the switch SW1 of the control circuit 6 is switched to the side of a reference power supply 13. As a result, the duty ratio of the switching element Q0 is increased during dead time, and the voltage needed to re-ignite the discharge lamp LP can be obtained.

Description

[0001]
[Industrial application fields]
The present invention relates to a discharge lamp lighting device that converts a voltage of a direct current power source into a predetermined voltage and supplies it to a discharge lamp with alternating polarity, thereby lighting the discharge lamp in a rectangular wave.
[0002]
[Prior art]
Conventionally, there has been a discharge lamp lighting device that converts the voltage of a DC power source into a predetermined voltage and supplies the discharge lamp with alternating polarities to light the discharge lamp in a rectangular wave. FIG. 8 shows an example of such a discharge lamp lighting device, and a high-intensity discharge lamp (so-called HID lamp) is used as the discharge lamp. Such a discharge lamp lighting device for a high-intensity discharge lamp may be used for a vehicle headlamp.
[0003]
This discharge lamp lighting device includes a voltage converter 2 that converts the voltage of the DC power supply 1 into a predetermined voltage, a capacitor C ₀ that is connected between the output terminals of the voltage converter 2 via a diode D ₁ , and a voltage converter. An inverter unit 3 that alternates the polarity of the voltage Vc across the capacitor C ₀ by an output from the unit 2, and a load circuit unit 4 that includes a discharge lamp LP as a load and an igniter circuit 5 for starting the discharge lamp. ing.
[0004]
The voltage conversion unit 2 includes a switching element Q ₀ composed of a MOSFET and a transformer T, and connects a series circuit of the primary winding n ₁ of the transformer T and the switching element Q ₀ between both ends of the DC power source 1. A capacitor C ₀ is connected to both ends of the secondary winding n ₂ of the transformer T via a diode D ₁ which is a rectifying element, so that a so-called flyback type DC-DC converter is formed. The switching element Q ₀ is switching-controlled by a drive signal from the control circuit 6.
[0005]
Next, a specific operation of this conventional apparatus will be described.
First, the operation of the voltage conversion unit 2 will be described. When the switching element Q ₀ is turned on by a drive signal from the control circuit 6, a current flows from the DC power source 1 to the primary winding n ₁ of the transformer T and energy is transferred to the transformer T. Is accumulated. The energy stored in the transformer T, switching element Q ₀ is discharged to the capacitor C ₀ through the diode D ₁ from the secondary winding n ₂ of the transformer T is turned off, the capacitor by turning on and off the switching element Q ₀ Energy supplied from the DC power source 1 is transmitted to C ₀ . Then, by adjusting the duty ratio or the switching frequency of the switching element Q ₀ by the control circuit 6, is the desired voltage Vc as possible flat across the capacitor C ₀ is obtained as shown in Figure 9 (a).
[0006]
On the other hand, the polarity of the DC voltage Vc obtained across the capacitor C ₀ as described above is alternated by the inverter unit 3 at the next stage. In other words, the inverter unit 3 is a so-called full bridge type having a bridge circuit of _four switching elements Q _{1 to} Q ₄ made of MOSFETs, and these four switching elements Q _{1 to} Q ₄ are basically connected to a pair of bridges. A period for alternately turning on and off each pair of switching elements Q ₁ and Q ₄ and Q ₂ and Q _{3 at} the corner is provided, and each period is provided by a drive circuit 7 including an oscillator and a drive circuit (not shown). By switching at a low frequency, the polarity of the voltage across the capacitor C ₀ is alternated. Usually, in order to prevent a short circuit of the bridge, there is provided an idle period (hereinafter referred to as “dead time”) in which all the switching elements Q _{1 to} Q ₄ are turned off at the time of polarity reversal.
[0007]
Further, by supplying a low-frequency rectangular wave voltage (current) whose polarity is changed by the inverter unit 3 to the load circuit unit 4, the discharge lamp LP as a load is lit in a rectangular wave via the starting igniter circuit 5. is doing. The igniter circuit 5 connects, for example, the secondary side of a high-pressure pulse transformer (not shown) to the discharge lamp LP, and superimposes the high-pressure pulse on the low-frequency rectangular wave voltage supplied from the inverter unit 3, thereby The discharge lamp LP is started by obtaining a high voltage necessary for starting.
[0008]
Further, between the capacitor C ₀ and the inverter unit 3, resistors R _{1 to} R ₃ for detecting a voltage Vc and current (a discharge lamp current flowing through the discharge lamp LP) of the capacitor C ₀ are connected. The respective detection outputs are given to the control circuit 6, and the control circuit 6 performs switching control of the switching element Q ₀ of the voltage conversion unit 2 to light the discharge lamp LP with desired characteristics based on these detection outputs. Each detection output is input to a voltage detection circuit 8 and a current detection circuit 9 each having a filter function and an amplification function. The output of the voltage detection circuit 8 is given to the current target value setting circuit 10, and the target current value necessary for the discharge lamp LP is output according to the current discharge lamp voltage. Then, the target current value and the output value from the current detection circuit 9 are input to the error amplifier 11, and both error signals are given from the error amplifier 11 to the pulse width modulator 12. In the pulse width modulator 12, the drive signal is adjusted based on the error signal given from the error amplifier 11, and the duty ratio of the switching element Q ₀ of the voltage converter 2 is varied. The current target value setting circuit 10 may be constituted by a microcomputer. In that case, the target power value is set by the output of the voltage detection circuit 8, and the set target power value is used as the output of the voltage detection circuit 8. To obtain the target current value.
[0009]
[Problems to be solved by the invention]
However, when a high-intensity discharge lamp (HID lamp) is used as the discharge lamp LP in the above-described conventional apparatus, it tends to disappear once the discharge lamp current becomes zero due to the nature of the high-intensity discharge lamp. When the high-intensity discharge lamp is turned on in a rectangular wave, there has been a problem that the extinction occurs at the time of polarity reversal. There are two main causes for such extinction, and one is that a voltage sufficient to re-ignite the discharge lamp LP at the time of polarity reversal (re-ignition voltage) cannot be obtained. In other words, in the above conventional example, the voltage Vc across the capacitor C ₀ and the discharge lamp voltage are almost equal, and therefore, a re-ignition voltage that is sufficiently higher than the discharge lamp voltage at the time of lighting cannot be immediately supplied during polarity reversal. It is.
[0010]
The second cause is that the secondary side of the high-pressure pulse transformer included in the igniter circuit 5 for starting the discharge lamp LP is inserted and connected in series with the discharge lamp LP. The inversion time of the discharge lamp current at the time of polarity reversal becomes longer due to the inductance component. In particular, it was difficult to stably light a discharge lamp at the end of its life. FIG. 9 shows operating waveforms of the voltage Vc across the capacitor C ₀ and the discharge lamp current in the above conventional example . FIG. 9A shows a case where the polarity reversal is smoothly performed, and FIG. This is the case. That is, as shown in FIG. 5B, if the re-ignition voltage is insufficient at the time of polarity reversal, the discharge lamp current has a pause period and falls off and cannot be lit stably.
[0011]
An object of the present invention is to provide a discharge lamp lighting device capable of lighting a discharge lamp in a rectangular wave without causing extinction even in a discharge lamp at the end of its life. is there.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is directed to a DC power supply, a voltage conversion unit that converts the voltage of the DC power supply into a predetermined voltage using a switching operation of the switching element, and an output of the voltage conversion unit. a capacitor connected via a rectifier element between the ends, and said rectifying element connected between the output terminal and the capacitor of the voltage converter in a direction to charge the capacitor at the oFF time of the switching elements is supplied from the capacitor A discharge lamp lighting device comprising: an inverter unit that alternates voltage polarity; and a load circuit unit that has at least a discharge lamp as a load and is connected between output terminals of the inverter unit, and that ignites the discharge lamp with an alternating output of the inverter unit a is, polarity more power than when other than the polarity reversed to the polarity inversion time of the alternating output by controlling the switching operation of the switching element Boosting be greater than the reignition voltage required an alternating output voltage of the inverter unit to re-ignition of the discharge lamp greater than the voltage and the discharge lamp during at least steady lighting by supplying the voltage converter to the capacitor during rolling Means is provided.
[0013]
According to a second aspect of the invention, in the invention of claim 1, the polarity inversion at the time of the discharge lamp current increases the voltage to supply power to the capacitor from between the voltage converter for changing the predetermined value in one polarity to a predetermined value of the opposite polarity Means is provided .
[0014]
[Action]
In the configuration of the first aspect of the present invention, a DC power supply, a voltage conversion unit that converts the voltage of the DC power supply to a predetermined voltage using the switching operation of the switching element, and a rectifying element between the output terminals of the voltage conversion unit a capacitor connected through, said rectifying element connected between the output terminal and the capacitor of the voltage converter in a direction to charge the capacitor at the oFF time of the switching element, alternating the polarity of the voltage supplied from the capacitor A discharge lamp lighting device comprising: an inverter unit; and a load circuit unit having at least a discharge lamp as a load and connected between output terminals of the inverter unit, wherein the discharge lamp is lit by an alternating output of the inverter unit. voltage converter high power when polarity reversal than when other than the polarity reversal when the polarity reversal of the alternating output by controlling the switching operation of the It is provided with the voltage increasing means to be larger than the re-ignition voltage required to restrike the larger and the discharge lamp than the discharge lamp voltage during at least steady lighting an alternating output voltage of the inverter section by supplying Luo capacitor This can compensate for the shortage of the re-ignition voltage of the discharge lamp at the time of polarity reversal, prevents the discharge lamp from extinguishing, enables stable rectangular wave lighting, and reliably re-ignites the discharge lamp at the time of polarity reversal. Can be made.
[0015]
In the configuration of the invention of claim 2, the discharge lamp current when the polarity reversal is provided a voltage increasing means for supplying power to the capacitor from between the voltage converter for changing the predetermined value in one polarity to a predetermined value of the opposite polarity When the polarity is reversed, a large amount of power can be supplied from the inverter unit to the discharge lamp, and the discharge lamp can be reliably re-ignited when the polarity is reversed .
[0016]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
Example 1
FIG. 1 shows the circuit configuration of the present embodiment. The basic configuration is the same as that of the conventional example shown in FIG. 8 , and common portions are denoted by the same reference numerals and description thereof is omitted. Only the characteristic part of the example will be described. That is, in this embodiment, there is provided voltage increasing means for increasing the alternating output voltage supplied to the discharge lamp LP when the polarity of the alternating output of the inverter unit 3 is reversed to a level sufficient for the re-ignition voltage of the discharge lamp LP. There is a feature in the point.
[0017]
That is, in the conventional example, the duty ratio of the switching element Q ₀ of the voltage converter 2 is adjusted by the control circuit 6 so that the voltage Vc across the capacitor C ₀ is as flat as possible in the steady lighting state of the discharge lamp LP. but when the polarity inversion in this embodiment, that is, by all the switching elements Q ₁ to Q ₄ of the inverter unit 3 is increased forcibly temporarily duty ratio of the switching element Q ₀ in the dead time to be off The voltage Vc across the capacitor C ₀ is increased.
[0018]
Specifically, based on a signal from the drive circuit 7 that controls the switching operation of the switching elements Q _{1 to} Q ₄ of the inverter unit 3, the current target value setting circuit 10 and the error amplifier 11 of the control circuit 6 by switching control the switch SW ₁ which is provided between, switches the switch SW ₁ to the current target value setting circuit 10 side and in the other cases when the polarity reversal is to switch the switch SW ₁ to the reference power supply 13 side at the time of polarity reversal . As a result, during polarity reversal, an output larger than the output from the normal current target value setting circuit 10 is given from the reference power supply 13 to the error amplifier 11, so that the error signal output from the error amplifier 11 also increases, and the switching element Q The duty ratio of ₀ is forcibly increased regardless of the discharge lamp voltage.
[0019]
Here, the drive circuit 7 is composed of a low-frequency oscillation circuit 14, a flip-flop 15, and two AND circuits 16 ₁ and 16 ₂ , and each of the switching elements Q ₁ and 16 ₂ uses the outputs of the AND circuits 16 ₁ and 16 ₂ as drive signals. ₁ and Q ₄ and Q ₂ and Q ₃ are given. The length of the dead time during which all the switching elements Q _{1 to} Q ₄ are turned off is determined by the period during which the output of the low-frequency oscillation circuit 14 is at the L level. In this embodiment, switching the low frequency oscillation circuit has the output of 14 to switch the switch SW _1, the switch SW ₁ to the current target value setting circuit 10 side when the output of the low frequency oscillation circuit 14 is at H level , The reference power supply 13 is switched to the L level.
[0020]
Next, the operation of this embodiment will be described with reference to the waveform diagram of FIG. As shown in FIG. 6C, the output of the low frequency oscillation circuit 14 is at the H level, and _one set (Q ₁ and Q ₄ or Q ₂ and Q ₃ of the switching elements Q _{1 to} Q ₄ of the inverter unit _3). ) Is on and the other set is off, that is, other than the dead time, the control circuit 6 converts the voltage so that the voltage Vc across the capacitor C ₀ is substantially flat as shown in FIG. Part 2 is controlled. When the output of the low frequency oscillation circuit 14 changes to L level, the switching elements Q _{1 to} Q _{4 of the} inverter unit 3 are all turned off, and the on / off state of the switching elements Q _{1 to} Q _{4 is} switched through a dead time. The polarity of the output of the inverter unit 3 is inverted.
[0021]
On the other hand, as shown in FIG. 5B, the discharge lamp current flowing in the discharge lamp LP starts to gradually decrease from the start of the dead time, and eventually the polarity is reversed and starts flowing in the opposite direction. Here, when the output of the low frequency oscillation circuit 14 of the drive circuit 7 is at L level, the switch SW ₁ of the control circuit 6 is switched to the reference power source 13 side as described above, and the switching element Q ₀ of the voltage converter 2 is switched. Since the duty ratio increases, the capacitor C ₀ is supplied with larger energy from the DC power source 1 via the voltage converter 2 than when the polarity is not reversed. As a result, the voltage Vc across the capacitor C ₀ increases during the dead time as shown in FIG. 5A, and exceeds the re-ignition voltage necessary for re-ignition of the discharge lamp LP. Then, when the switching elements Q _{1 to} Q ₄ are turned on after the dead time, a voltage large enough to re-ignite the discharge lamp LP is applied from the inverter unit 3. Even when the resting state occurs, the discharge lamp LP can be promptly re-ignited.
[0022]
Accordingly, the lighting of the discharge lamp LP is maintained without going through a resting state where the discharge lamp current does not flow, and the discharge lamp LP can be lit stably. That is, in this embodiment, the low frequency oscillation circuit 14 of the drive circuit 7, the switch SW ₁ of the control circuit 6 and the reference power supply 13 constitute voltage increasing means, and the switch SW ₁ is switched at the time of polarity inversion to switch the voltage converter 2. By increasing the duty ratio of the switching element Q ₀ and increasing the voltage Vc across the capacitor C ₀ , the alternating output of the inverter unit 3 is increased and the discharge lamp LP can be re-ignited.
[0023]
(Example 2)
In this embodiment, as shown in FIG. 3, instead of the switch SW ₁ and the reference power supply 13 in the embodiment 1 shown in FIG. 1, a current target value setting circuit provided in the control circuit 6 at the output of the low frequency oscillation circuit 14. 10, the output of the current target value setting circuit 10 is forcibly increased when the output of the low frequency oscillation circuit 14 becomes L level, and the same effect as in the first embodiment can be obtained. . Further, when the current target value setting circuit 10 is constituted by a microcomputer, there is an advantage that the same effect can be obtained at a low cost without providing the switch SW ₁ or the reference power source 13 as compared with the first embodiment.
[0024]
Example 3
In this embodiment, as shown in FIG. 4, the switch SW ₁ in the embodiment 1 shown in FIG. 1 is provided between the pulse width modulator 12 and the error amplifier 11, and the output of the low-frequency oscillation circuit 14 is other than polarity inversion. (When the output of the low-frequency oscillation circuit 14 is at the H level), the switch SW ₁ is switched to the error amplifier 11 side, and at the time of polarity reversal (when the output of the low-frequency oscillation circuit 14 is at the L level) SW ₁ is switched to the reference power supply 13 side, and the duty ratio of the switching element Q ₀ at the time of polarity reversal is increased to a value defined by the reference voltage of the reference power supply 13 to be the same as in the first embodiment. An effect is obtained.
[0025]
In the configuration of this embodiment, the error amplifier 11 and the output and the reference voltage of the reference power supply 13 are switched by the switch SW ₁ and input to the pulse width modulator 12. Even when the polarity is poor, there is an advantage that the duty ratio of the switching element Q ₀ can be increased quickly and reliably at the time of polarity reversal.
[0026]
(Example 4)
In this embodiment, as shown in FIG. 5, instead of the switch SW ₁ and the reference power supply 13 in the embodiment 3 shown in FIG. 4, the output of the low frequency oscillation circuit 14 is provided between the output terminal of the error amplifier 11 and the control power supply. a series circuit of a transistor Q ₆ is turned on and off and a resistor R _4, the low-frequency control power voltage V of the transistor Q ₆ from on to control power supply when the output of the oscillation circuit 14 is at the L level is obtained by so as to enter the _DD to the pulse width modulator 12, the polarity inversion time simply example 1 and that it increases to a value defined by the control power supply voltage V _DD duty ratio of the switching element Q ₀ in The same effect as in Example 3 can be obtained.
[0027]
In the first to fourth embodiments, the duty ratio of the switching element Q ₀ of the voltage conversion unit 2 is increased when the output of the low-frequency oscillation circuit 14 of the drive circuit 7 is at the L level. The duty ratio may be increased at other timings and periods. For example, with the timing of polarity reversal by the signal from the drive circuit 7, it may be to increase the duty ratio of the switching element Q ₀ from after the start before or the start of the dead time. Further, the period during which the duty ratio of the switching element Q ₀ is increased as described above need not be the same as the dead time of the inverter unit 3.
[0028]
(Example 5)
In this embodiment, as shown in FIG. 6, the control circuit 6 in the embodiment 4 shown in FIG. 5 includes a voltage determination circuit 19 including a comparator 17 and a reference power supply 18, and an inversion timing signal (for example, given from the drive circuit 7). The one-shot multivibrator 20 triggered by the rising (or falling) of the low-frequency oscillation circuit 14, the inverter 21 for inverting the output of the one-shot multivibrator 20, the inverter 21 output, and the voltage discrimination circuit 19 output OR circuit 22 that takes the logical sum of the above and is additionally provided.
[0029]
Voltage discrimination circuit 19, when the reference voltage of the detection voltage and the reference power supply 19 in response to the voltage Vc across the capacitor C ₀ compared in comparator 17, the detection voltage is lower than the reference voltage, i.e., across the capacitor C ₀ When the voltage Vc is lower than the predetermined voltage, the comparator 17 outputs an L level signal.
In addition, the one-shot multivibrator 20 receives a signal indicating the start timing of the dead time (falling output of the low-frequency oscillation circuit 14) and outputs an H level signal for a predetermined period. An L level signal is output from the inverter 21 connected to the output terminal.
[0030]
Accordingly, in the predetermined period from the start of the dead time, the inputs of the OR circuit 22 are all at L level, so that the output of the OR circuit 22 becomes L level, the transistor Q ₆ is turned on, and the pulse width modulator 12 is turned on. The control power supply voltage V _DD is input, the duty ratio of the switching element Q ₀ is forcibly increased, and the output of the one-shot multivibrator 20 becomes L level or the output of the voltage determination circuit 19 becomes H level. Continue until.
[0031]
According to the configuration of the present embodiment, not only the same effects as in the fourth embodiment are obtained, but also the voltage discrimination circuit 19 prevents the voltage Vc across the capacitor C _{0 from} rising above a predetermined value. The voltage Vc across the capacitor C ₀ can be increased to a desired voltage without excessively increasing regardless of the power supply voltage of the DC power supply 1, etc., and as a result, the discharge lamp LP can be more stably lit with a rectangular wave. Can be made.
Further, since the period during which the output of the one-shot multivibrator 20 is set to the H level can be arbitrarily set, for example, from when the discharge lamp current starts to invert during steady lighting of the discharge lamp LP until zero crossing occurs. If the period is the same as that required, the voltage Vc across the capacitor C ₀ is increased from the start of the inversion operation, and the voltage Vc increased at the time when the discharge lamp current crosses zero is passed through the inverter unit 3 via the inverter unit 3. It can be applied to LP, and the discharge lamp LP can be more effectively prevented from extinguishing.
[0032]
(Example 6)
In this embodiment, as shown in FIG. 7, the power supply voltage of the DC power supply 1 and the reference voltage of the reference power supply 23 are input to the operational amplifier 24 in the configuration of the fourth embodiment shown in FIG. The signal is input to the maximum duty ratio setting terminal of the modulator 12. Here, the pulse width modulator 12 is the maximum value of the duty ratio of the switching element Q ₀ in response to an input of the maximum duty ratio setting terminal is adapted to be regulated.
[0033]
In the configuration of this embodiment, the maximum duty ratio of the pulse width modulator 12 decreases when the power supply voltage of the DC power supply 1 is higher than the reference voltage of the reference power supply 23, and conversely when the power supply voltage is lower than the reference voltage. Since the ratio increases, fluctuations in the supply energy to the capacitor C ₀ that occur according to the power supply voltage of the DC power supply 1 can be suppressed, and the discharge lamp LP can be lit with a rectangular wave more stably regardless of the power supply voltage. . Needless to say, the configuration of the control circuit 6 may be any of the configurations of the first to third embodiments other than the configuration of the present embodiment.
[0034]
By the way, in the said Examples 1-6, although the current control system is employ | adopted for the control in the control circuit 6, other control systems, such as the power control system which makes the electric power supplied to the discharge lamp LP a desired value, are used. The technical idea of the present invention is also applicable. In addition, the present invention can be applied to peak value control in which the peak value of the current flowing through the switching element Q ₀ of the voltage conversion unit 2 is a controlled variable. Is obtained .
[0035]
【The invention's effect】
According to the first aspect of the present invention, a DC power supply, a voltage conversion unit that converts the voltage of the DC power supply to a predetermined voltage using the switching operation of the switching element, and a rectifier element between the output terminals of the voltage conversion unit are provided. a capacitor connected, and the rectifying element connected between the output terminal and the capacitor of the voltage converter in a direction to charge the capacitor at the oFF time of the switching element, an inverter unit for alternating the polarity of the voltage supplied from the capacitor A discharge lamp lighting device for lighting a discharge lamp with an alternating output of an inverter unit, comprising at least a discharge lamp as a load and connected between output terminals of the inverter unit, and switching of a switching element Con from the voltage conversion unit large power during polarity reversal than when other than the polarity reversal when the polarity reversal of the alternating output by controlling the operation Since the voltage increasing means to be larger than the re-ignition voltage required to restrike the larger and the discharge lamp than the discharge lamp voltage during at least steady lighting an alternating output voltage of the inverter is provided by supplying to the capacitors, The shortage of re-ignition voltage of the discharge lamp during polarity reversal can be compensated, the discharge lamp can be prevented from extinguishing and stable rectangular wave lighting is possible, and the discharge lamp is reliably re-ignited during polarity reversal. There is an effect that can be.
[0036]
According to a second aspect of the invention, the discharge lamp current when the polarity reversal is provided a voltage increasing means for supplying power to the capacitor from between the voltage converter for changing the predetermined value in one polarity to a predetermined value of the opposite polarity, the polarity Large power can be supplied from the inverter unit to the discharge lamp at the time of inversion, and the discharge lamp can be reliably re-ignited at the time of polarity inversion .
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram showing a first embodiment.
FIG. 2 is a waveform diagram for explaining the operation described above.
FIG. 3 is a schematic circuit diagram showing a main part of a second embodiment.
FIG. 4 is a schematic circuit diagram showing a main part of a third embodiment.
FIG. 5 is a schematic circuit diagram showing a main part of a fourth embodiment.
6 is a schematic circuit diagram showing Example 5. FIG.
7 is a schematic circuit diagram showing Example 6. FIG.
FIG. 8 is a schematic circuit diagram showing a conventional example .
FIG. 9 is a waveform diagram for explaining the operation described above .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 DC power supply 2 Voltage conversion part 3 Inverter part 5 Igniter circuit 6 Control circuit 7 Drive circuit Q ₀ Switching element C ₀ Capacitor

Claims (2)

A DC power supply, a voltage converter that converts the voltage of the DC power supply to a predetermined voltage using the switching operation of the switching element, a capacitor connected via an rectifier element between the output terminals of the voltage converter, and switching load and the rectifying element connected between the output terminal and the capacitor of the voltage converter in a direction to charge the capacitor at the oFF time of the element, and an inverter unit for alternating the polarity of the voltage supplied from the capacitor, at least the discharge lamp A discharge lamp lighting device having a load circuit unit connected between output terminals of the inverter unit and lighting the discharge lamp by an alternating output of the inverter unit, wherein the alternating operation is performed by controlling a switching operation of the switching element. this is supplied to the capacitor from the voltage conversion unit large power during polarity reversal than when other than the polarity reversal when the polarity inversion of the output Discharge lamp, characterized in that an alternating output voltage of the inverter section provided with voltage increasing means to be larger than the re-ignition voltage required to restrike at least greater than the discharge lamp voltage during steady-state lighting and the discharge lamp by Lighting device. From between the voltage conversion unit discharge lamp current polarity inversion time is changed from a predetermined value of one polarity to a predetermined value of the opposite polarity according to claim 1, characterized in that a voltage increasing means for supplying power to the capacitor Discharge lamp lighting device .

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