JP2003217881A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of stably lighting a discharge lamp without generating the unpleasant flash in the moment when a condition is transferred to a deep-dimming lighting condition of a dimming ratio of approximately 0.5 or less or under a condition of the deep-dimming lighting in a constitution of a simple control circuit. <P>SOLUTION: In this discharge lamp lighting device comprising a DC power source circuit, a voltage converting circuit, an inverter circuit, a load circuit, a control means 1, and a pulse voltage superimposing means for controlling a switching element of the inverter circuit, and superimposing the pulse voltage to a discharge lamp LA, a period by the time when the discharge lamp LA is lit, is composed of a preheating period for preheating the discharge lamp and a starting period for starting the discharge lamp, the output voltage Vdc of the voltage converting circuit is gradually increased by the control means 1 in the starting period, and the pulse voltage is superimposed to the discharge lamp by the pulse voltage superimposing means 3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device capable of dimming a discharge lamp.

2. Description of the Related Art In recent years, a discharge lamp lighting device for dimming has come to be used in various scenes for the purpose of production and energy saving. As a discharge lamp lighting device for dimming, conventionally, a chopper circuit that rectifies a voltage from a commercial power source and converts the voltage into a desired DC voltage and outputs the DC voltage, and an inverter that converts the DC voltage of the chopper circuit into an AC rectangular wave voltage. Generally, a circuit and a load circuit connected to the inverter circuit and having a discharge lamp and an LC resonance circuit are provided. Recently, for such a discharge lamp lighting device for dimming,
A function that allows dimming to a lower dimming ratio, such as a dimming ratio of a few percent, and that does not cause unpleasant flashes when the discharge lamp in the dimming state at the dimming ratio is turned off and then turned on again. Is becoming required to have. As a conventional example of this type, for example, the one disclosed in JP-A-7-6889 can be cited. As shown in FIG. 1, this is a load circuit including a chopper circuit for converting AC power into DC power, an inverter circuit for converting DC power into high frequency power, and a discharge lamp connected to an output end of the inverter circuit. In the discharge lamp lighting device configured to operate the inverter circuit first and drive the chopper circuit later, a means for intermittently applying a pulsed voltage sufficient for starting the discharge lamp is added. It was done. In the discharge lamp lighting device for dimming, as shown in FIG. 2, the operation of the chopper circuit is stopped during the preheating period of the discharge lamp, and the peak value of the AC power supply voltage is input to the input of the chopper circuit. Then, when the preheating period ends and the starting period starts, the operation of the chopper circuit starts, and the output voltage of the chopper circuit becomes constant during the starting period. During this starting period, the pulsed voltage is superimposed on the discharge lamp, and the superposition mode of this pulsed voltage gradually increases the peak value of the pulsed voltage with the elapse of the starting time. This can be realized by gradually increasing the change width of the drive frequency. By performing such control, it is possible to prevent unpleasant flashing of the discharge lamp even at the moment when the discharge lamp is changed from the starting state to the deep dimming state. Furthermore, JP-A-7-6
In Japanese Patent No. 889, in order to prevent a flash light from being generated even when the discharge lamp is deeply dimming with a dimming ratio of 0.5% or less, FIG.
The drive frequency of the inverter circuit is controlled as shown in FIG. That is, by turning on the transistor Q5 while the transistor Q3 is on, the transistor Q3 is forcibly turned off and the on period of the transistor Q3 is changed. As a result, the transistors Q2 and Q
Since the ON period of 3 becomes unbalanced and the oscillation frequency changes, the output of the inverter circuit 12 is changed in a wide range. As a result, even if the dimming ratio is 0.5% or less during deep dimming, it is possible to start dimming without flashing.

However, in order to gradually increase the variation range of the drive frequency in order to gradually increase the peak value of the pulsed voltage, a complicated control circuit is required, and the discharge lamp lighting device has a This will increase the cost. Further, in the case where the control of the above-mentioned conventional example is performed after the discharge lamp shifts to the deep dimming lighting state, the difference between the oscillation frequency in the deep dimming lighting state and the oscillation frequency when generating the pulsed voltage is large. Therefore, it may be difficult to generate a pulsed voltage having a sufficient peak value for preventing flash light from being generated in the discharge lamp, especially in the deep dimming lighting state where the dimming ratio is 0.5% or less. The present invention has been made in view of the above problems, and an object thereof is to shift to a deep dimming lighting state with a dimming ratio of about 0.5% or less with a simple control circuit configuration. An object of the present invention is to provide a discharge lamp lighting device capable of performing stable lighting without an unpleasant flash of light in the discharge lamp in an instantaneous or deep dimming lighting state.

A discharge lamp lighting device according to claim 1; a DC power supply circuit; a voltage conversion circuit for converting a voltage from the DC power supply circuit into another voltage and outputting the voltage; and at least one switching element. And a load circuit including a discharge lamp and an LC resonance circuit, the load circuit performing resonance operation by the high frequency voltage from the inverter circuit; Discharge lamp lighting device comprising: control means for controlling output voltage of circuit; drive means for driving switching element of inverter circuit; pulse voltage superposition means for controlling drive means and superposing pulse voltage on discharge lamp In, the period until the discharge lamp is lit consists of a preheating period for preheating the discharge lamp and a starting period for starting the discharge lamp, and the voltage is controlled by the control means during the starting period. Gradually with increasing output voltage of the circuit, the pulse voltage superimposing unit, is characterized in that for superimposing a pulse voltage to the discharge lamp. In such a discharge lamp lighting device, since the pulse voltage is superimposed on the discharge lamp during the period in which the output voltage of the voltage conversion circuit is gradually increased by the control means, the pulse voltage The peak value rises. A discharge lamp lighting device according to a second aspect is the discharge lamp lighting device according to the first aspect, characterized in that a pulse voltage is superimposed on the discharge lamp during a preheating period and a starting period. The discharge lamp lighting device according to claim 3 is the discharge lamp lighting device according to claim 1 or 2, wherein:
It is characterized by periodically superposing a pulse voltage on the discharge lamp. The discharge lamp lighting device according to claim 4 is the discharge lamp lighting device according to any one of claims 1 to 3, wherein the output voltage of the voltage conversion circuit is gradually increased from a value smaller than the peak value of the commercial power supply. It is characterized by that. The discharge lamp lighting device according to claim 5 is the discharge lamp lighting device according to any one of claims 1 to 3, wherein the pulse voltage superposing means changes a driving frequency or a duty of the driving means. It is a feature. When the drive frequency of the switching element is changed, the operating point on the resonance curve of the LC resonance circuit changes, and the voltage superimposed on the discharge lamp increases or decreases. When the duty of the switching element is changed, the entire resonance curve of the LC resonance circuit goes up and down, and the voltage superimposed on the discharge lamp increases or decreases. A discharge lamp lighting device according to a sixth aspect of the present invention is the discharge lamp lighting device according to the fifth aspect, characterized in that the variation range of the drive frequency or the duty is substantially constant. A discharge lamp lighting device according to a seventh aspect of the present invention is the discharge lamp lighting device according to the fifth aspect, characterized in that the variation range of the drive frequency is gradually increased. The discharge lamp lighting device according to an eighth aspect of the present invention is the discharge lamp lighting device according to the fifth aspect, wherein the change width of the drive frequency is gradually reduced. The discharge lamp lighting device according to claim 9,
In the discharge lamp lighting device according to any one of claims 5 to 8, the lower limit of the change of the drive frequency is substantially the resonance frequency of the LC resonance circuit. A discharge lamp lighting device according to a tenth aspect of the present invention is characterized in that, in the discharge lamp lighting device according to any one of the fifth to ninth aspects, the driving frequency at the start of the starting period is different. The discharge lamp lighting device according to claim 11 is the discharge lamp lighting device according to claim 10, wherein the drive frequency at the end of the preheating period is lower than the drive frequency at the start of the starting period. The discharge lamp lighting device according to claim 12 is the discharge lamp lighting device according to claim 5,
The starting period is 100 msec or more. The discharge lamp lighting device according to claim 13 is the discharge lamp lighting device according to any one of claims 5 to 12, wherein a drive frequency of a predetermined period from the start of the preheating period is set to a preheating period after a predetermined period has elapsed. It is characterized in that it is higher than the driving frequency. A discharge lamp lighting device according to a fourteenth aspect is the discharge lamp lighting device according to the first aspect, wherein the discharge lamp is dimmed by controlling the output voltage of the voltage conversion circuit after a start period has elapsed. It is a thing. A discharge lamp lighting device according to a fifteenth aspect is the discharge lamp lighting device according to the fourteenth aspect, wherein the dimming lower limit is a dimming ratio of approximately 1% or less.

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. The discharge lamp lighting device shown in FIG. 1 includes a DC power supply circuit (AC power supply AC; an input filter circuit having a capacitor C1, a filter LF1 and a capacitor C2; a rectifier circuit DB);
Voltage conversion circuit (switching elements Q1, Q2, diodes D1, D2 and inductor L1); smoothing circuit (capacitor C3); inverter circuit (switching element Q
3 and Q4); a load circuit (a resonance inductor L2, a resonance capacitor C6 and a discharge lamp LA); a DC blocking capacitor C4; a control means 1 for controlling the output voltage Vdc of the voltage conversion circuit; and an inverter circuit. Drive means 2 for driving the switching element which it has; pulse voltage superposition means 3 for controlling the drive means 2 and superposing a pulse voltage on the discharge lamp LA
And a dimmer 4 for sending a dimming signal to the control means 1. Hereinafter, the configuration of each unit will be described in detail. AC power supply AC is
It is a commercial AC power supply, and the voltage is, for example, 100V,
It is 200V or 240V. The input filter circuit prevents noise from the AC power supply AC from entering the inverter circuit, or conversely prevents noise from the inverter circuit from leaking to the power supply side. Rectifier circuit D
B rectifies the AC voltage from the AC power supply AC into a pulsating voltage, and is composed of, for example, a diode bridge. The voltage conversion circuit converts the voltage from the rectifier circuit DB into another voltage, and in this embodiment, a step-up / down chopper circuit is adopted. Since the operation of this circuit is well known, its explanation is omitted. Here, the voltage conversion circuit includes a step-up chopper, step-down chopper,
Alternatively, a polarity reversal chopper circuit may be used. In short, any circuit configuration may be used as long as it converts one DC voltage into another DC voltage. The capacitor C3, which is a smoothing circuit, smoothes the output voltage of the voltage conversion circuit and is composed of, for example, an electrolytic capacitor. The inverter circuit converts the DC voltage from the capacitor C3 into a rectangular wave voltage by turning on / off the switching elements Q3 and Q4, and is composed of, for example, a field effect transistor. In this embodiment, a so-called two-stone half-bridge type inverter circuit having switching elements Q3 and Q4 is adopted as the inverter circuit, but of course, the circuit system of the inverter circuit is not limited to this. It may be a full-bridge type, one-stone type, or push-pull type inverter circuit. Since the operation of this half-bridge type inverter circuit is well known, its operation description is omitted. The load circuit starts / lights the discharge lamp LA by the resonance operation of the series resonance circuit of the inductor L2 and the capacitor C6. The discharge lamp LA is, for example, a fluorescent lamp having filaments at both ends. Here, when the discharge lamp voltage of the discharge lamp LA at the time of normal lighting is high, an insulating transformer or a leakage transformer having the discharge lamp LA as the secondary side may be separately provided. The DC cutoff capacitor C4 cuts off the DC component flowing through the inverter circuit, whereby the inverter circuit operates only with an AC voltage. Capacitor C
The capacitance of No. 4 is usually set larger than that of the capacitor C6. The control means 1 is a switching element Q1.
And the switching frequency of Q2 is controlled to change the output voltage Vdc of the voltage conversion circuit. This allows
The dimming of the discharge lamp LA becomes possible. As a specific circuit configuration, for example, an integrated circuit MC342 manufactured by Motorola, Inc.
61 may be used. The drive unit 2 controls the drive frequency or duty of the switching elements Q3 and Q4 that form the inverter circuit. As a specific circuit configuration, for example, a high voltage integrated circuit IR2110 manufactured by International Rectifier may be used. The pulse voltage superimposing means 3 transmits to the driving means 2 a control signal for controlling the driving frequency or duty of the switching elements Q3 and Q4. As a specific circuit configuration, for example, the one disclosed in FIG. 7 of JP-A-7-45386 may be used. Dimmer 4
Is for generating a dimming signal and transmitting the dimming signal to the control means 1. For example, a dimmer NQ21 manufactured by Matsushita Electric Works, Ltd.
560-321 may be used. Next, the operation of this embodiment will be described with reference to FIGS. 2 and 3. The horizontal axis of FIG. 2 indicates the elapsed time after the AC power supply AC is turned on at t = 0, a period T1 is a preheating period for preheating the filament of the discharge lamp LA, and a period T2 is started at both ends of the discharge lamp LA. A starting period for applying a voltage and a period T3 respectively indicate a lighting period in which the discharge lamp LA is lit. Here, in the lighting period T3, the discharge lamp LA may be dimmed and may be normally lit. The vertical axis of FIG. 2A shows the change over time in the output voltage Vdc of the voltage conversion circuit, and that of FIG. 2B is the voltage Vla applied across the discharge lamp LA (hereinafter referred to as the discharge lamp voltage Vla). 2C, that of FIG. 2C shows the change over time of the driving frequency of the switching elements Q3 and Q4 by the driving means 2. Further, the horizontal axis of FIG. 3 shows the drive frequency of the switching elements Q3 and Q4, and the vertical axis shows the discharge lamp voltage Vla. Now, at t = 0, AC power supply A
When C is turned on, the voltage conversion circuit starts operation, and the voltage conversion circuit outputs the output voltage Vdc to the inverter circuit side. At the same time, preheating of the filament of the discharge lamp is started. At this time, since the drive frequency f is controlled to be constant by the drive unit 2, the output voltage Vdc and the discharge lamp voltage Vla are constant during the preheating period T1. Then, the discharge lamp voltage Vla is a voltage of such a magnitude that the discharge lamp LA does not start discharging. Next, t =
At t1, the starting period T2 for applying the starting voltage across the discharge lamp LA starts. Then, at this time, the control means 1 gradually increases the output voltage Vdc.
At the same time, the pulse voltage superposing means 3 detects the start of the starting period T2 and transmits a control signal to the driving means 2,
The drive frequency f is changed to f1 → f2 or f2 → f1. When the drive frequency f is f = f1, the inverter circuit operates in a portion where resonance is strong as shown in FIG.
The pulse voltage Vp having a high peak value can be superimposed on the discharge lamp LA. Here, the change time of the drive frequency f is
Several msec to several tens mse depending on the type of discharge lamp and discharge mode
It may be set appropriately between about c. Also, the peak value Vp of the pulse voltage is several hundreds V depending on the type of discharge lamp and the discharge mode.
It may be appropriately set within a range from to several kV. In the present embodiment, the frequency f1 which is the lower limit of modulation of the drive frequency is set to LC
Although the resonance frequency of the resonance circuit is set near f0, of course, even if the peak value of the pulse voltage is small, if the flash of the discharge lamp can be prevented, the lower limit of modulation of the drive frequency is set to the resonance frequency f.
The frequency may be set higher than 0 as appropriate. As described above, when the output voltage Vdc of the voltage conversion circuit is gradually increased by the control means 1 and the pulse voltage is superimposed on the discharge lamp LA by the pulse voltage superimposing means 3 in the starting period T2, the starting period T2 of the discharge lamp LA. In the vicinity of t = t2 when the lighting period T3, which is the dimming lighting, starts,
It is possible to prevent an unpleasant flash of light from occurring in the discharge lamp LA.
When such control is performed, the dimming ratio is approximately 1% or less,
Even at about 0.1%, the flash light can be suppressed.
In the present embodiment, the drive frequency f is periodically changed and the pulse voltage is periodically superimposed on the discharge lamp LA.
In the control method in which the drive frequency f is changed periodically, the circuit configuration of the pulse voltage superposing means 3 can be simplified as compared with the control method in which the drive frequency f is changed irregularly, but, of course, the type of discharge lamp and the discharge mode. Depending on the situation, when the pulse voltage is irregularly superimposed on the discharge lamp, the flash of the discharge lamp at the time of starting may be more effectively suppressed. In such a case, the cycle of pulse voltage superposition may be set appropriately. According to the present embodiment, the peak value of the pulse voltage can be gradually increased with the elapse of the starting time without performing complicated control such as changing the change width of the drive frequency, and the discharge lamp LA flashes. It is possible to obtain good starting characteristics without causing
Further, according to the experiment by the applicant of the present application, the starting period T2 is 10
It was confirmed that a smooth start could be achieved visually by setting it to 0 msec or more. Here, in order to perform a smooth start visually, the rate of temporal change of the output voltage Vdc may be appropriately set. Next, an application form of this embodiment will be described with reference to FIG. The circuit configuration of this embodiment is similar to that shown in FIG. In the present embodiment, the drive frequency at the end of the preheating period T1 is set lower than the drive frequency at the start of the starting period T2, that is, the discharge lamp voltage at the end of the preheating period T1 is set at the start of the starting period T2. It is set higher than the discharge lamp voltage. Depending on the type of discharge lamp, the circuit configuration of the control means 1, the driving means 2 and the pulse voltage superposition means 3, the instant t = t1 at which the preheating period T1 ends and the starting time T2 starts, that is, from preheating to starting. Flash light may be generated in the discharge lamp LA when the mode is switched. Even in such a case, if the above control is performed, it is possible to suppress the generation of flash light when the mode is changed. The operations, effects, and the like not specifically mentioned in the above description are the same as those in the first embodiment. Next,
Another application of this embodiment will be described with reference to FIG. In addition,
The circuit configuration of this embodiment is similar to that shown in FIG. In the present embodiment, as shown in FIG. 5, the preheating period T1
Also in the above, the drive frequency f is changed to f1 → f2 or f2 → f1 by the pulse voltage superposing means 3 and the driving means 2, and the pulse voltage is superposed on the discharge lamp LA. When such control is performed, at the end of the preheating period T1 or the starting period T
A circuit for detecting the start time of 2 is unnecessary, and the circuit configurations of the pulse voltage superposing means 3 and the driving means 2 can be simplified. The operations, effects, and the like not specifically mentioned in the above description are the same as those in the first embodiment. Next, another application mode of this embodiment will be described with reference to FIGS. 6 and 7. The circuit configuration of this embodiment is similar to that shown in FIG. In the present embodiment, as shown in FIG. 6 or 7, in the starting period T2, the pulse voltage superposing means 3 and the driving means 2 gradually increase or decrease the change width of the driving frequency. Depending on the type and discharge mode of the discharge lamp, when a high voltage is superposed on the discharge lamp LA at the start of the starting period T2, the discharge becomes unstable and flicker or moving stripes may occur in the discharge lamp LA. Therefore, as shown in FIG. 6, by using the pulse voltage superposing means 3 and the driving means 2, the variation width of the driving frequency is gradually increased, so that the flicker and the moving fringes can be suppressed. Alternatively, conversely, depending on the type of discharge lamp and the discharge mode, it may be possible to suppress the occurrence of flickering and moving stripes of the discharge lamp LA by superimposing the pulse voltage immediately after the start of the starting period T2. In such a discharge lamp, as shown in FIG. 7, the pulse voltage superposing means 3 and the driving means 2 may be controlled so as to gradually reduce the change width of the driving frequency. Also in the present embodiment, the cycle of pulse voltage superposition and the peak value of the pulse voltage may be appropriately set depending on the type of discharge lamp and the discharge mode. The operations, effects, and the like not specifically mentioned in the above description are the same as those in the first embodiment. Next, another application mode of this embodiment will be described with reference to FIG. The circuit configuration of this embodiment is similar to that shown in FIG. In the present embodiment, as shown in FIG. 8, the driving frequency in the predetermined period immediately after the start of the preheating period T1 is set higher than the driving frequency in the preheating period T1 after the lapse of the predetermined period. At the moment when the AC power supply AC is turned on at t = 0 and the voltage conversion circuit starts operating, a so-called overshoot voltage may be superimposed on the output voltage Vdc. Even when such an overshoot voltage is superimposed on the output voltage Vdc, the drive frequency is increased for a certain period longer than the period in which the overshoot voltage is generated in order to prevent the discharge lamp LA from flashing. , That is, discharge lamp voltage Vl
It is controlled so that a becomes low. When controlled in this way,
Even when the overshoot voltage is superimposed on the output voltage Vdc, the discharge lamp voltage Vla is low, so that flashing can be prevented. The operations, effects, and the like not specifically mentioned in the above description are the same as those in the first embodiment.

In the discharge lamp lighting device according to any one of claims 1 to 4, the output voltage of the voltage conversion circuit is gradually increased by the control means during the starting period, and the discharge lamp lighting device is discharged during the preheating period or the starting period. Since the pulse voltage is superposed on the electric lamp, the peak value of the pulse voltage can be increased as the starting time advances without adding a complicated control circuit. As a result, for example, even at the time of deep dimming with the dimming ratio of 0.1% or less, no flash light is generated,
The discharge lamp can be started. Further, in the discharge lamp lighting device according to claim 2, a circuit for detecting the start of the starting period and superimposing a pulse voltage on the discharge lamp is unnecessary, and in addition to the effect of the discharge lamp lighting device according to claim 1, The discharge lamp lighting device can be simplified. The discharge lamp lighting device according to any one of claims 5 to 9,
In the discharge lamp lighting device according to any one of claims 1 to 3, since the pulse frequency is generated by changing the drive frequency or duty of the switching element included in the inverter circuit, it is complicated to generate the pulse voltage. The control circuit becomes unnecessary. The discharge lamp lighting device according to claim 10 or 11, wherein the drive frequency at the end of the preheating period is lower than the drive frequency at the start of the starting period, that is, the peak value of the pulse voltage at the end of the preheating period is at the start of the starting period. Since it is smaller than the peak value of the pulse voltage of, the flash of the discharge lamp can be surely prevented even when the pulse voltage is superimposed immediately after the start of the starting period. A discharge lamp lighting device according to a twelfth aspect of the present invention is the discharge lamp lighting device according to the fifth aspect, in which the starting period is set to 100 msec or more, so that the discharge lamp can be turned on without causing any discomfort. The discharge lamp lighting device according to claim 13 is the discharge lamp lighting device according to any one of claims 5 to 12, wherein a drive frequency of a predetermined period from the start of the preheating period is set to a preheating period after a predetermined period has elapsed. Since the driving frequency is higher than the driving frequency, it is possible to prevent flashing of the discharge lamp by preventing overvoltage from being applied to the discharge lamp due to overshoot occurring immediately after the operation of the chopper circuit. Claim 14
Alternatively, the discharge lamp lighting device according to claim 15 is the discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimmed by controlling the output voltage of the voltage conversion circuit after the start period elapses. Even in the discharge lamp lighting device for dimming,
The same effect as that of the discharge lamp lighting device according to the first aspect can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 shows the output voltage Vdc in the first embodiment,
It is a wave form diagram which shows the waveform of discharge lamp voltage Vla and a drive frequency.

FIG. 3 is a resonance curve showing a resonance mode of the LC resonance circuit in the first embodiment.

FIG. 4 is a waveform diagram showing waveforms of an output voltage Vdc, a discharge lamp voltage Vla, and a driving frequency in another embodiment.

FIG. 5 shows the output voltage Vd in still another embodiment.
It is a waveform diagram which shows the waveform of c, the discharge lamp voltage Vla, and a drive frequency.

FIG. 6 shows the output voltage Vd in still another embodiment.
It is a waveform diagram which shows the waveform of c, the discharge lamp voltage Vla, and a drive frequency.

FIG. 7 shows the output voltage Vd in still another embodiment.
It is a waveform diagram which shows the waveform of c, the discharge lamp voltage Vla, and a drive frequency.

FIG. 8 shows the output voltage Vd in still another embodiment.
It is a waveform diagram which shows the waveform of c, the discharge lamp voltage Vla, and a drive frequency.

[Explanation of symbols]

AC AC power supply (part of DC power supply circuit) C1, C2 capacitor (part of DC power supply circuit) LF1 filter (part of DC power supply circuit) DB rectifier circuit (part of DC power supply circuit) Q1, Q2 switching element ( Part of voltage conversion circuit D1, D2 Diode (part of voltage conversion circuit) L1 Inductor (part of voltage conversion circuit) Q3, Q4 Switching element (part of inverter circuit) LA Discharge lamp (part of load circuit) ) C6 capacitor (part of load circuit) L2 inductor (part of load circuit) 1 control means 3 pulse voltage superposition means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshinori Murakami             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company (72) Inventor Shigeru Ido             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F term (reference) 3K072 AA02 AC02 AC04 AC11 BA05                       BB10 CA16 CB02 DA02 DB03                       DC02 DC07 DC08 DD03 DD05                       DD06 DE02 DE04 GB03 GB12                       HA05 HA06 HA10                 3K098 CC16 CC24 CC41 DD22 DD35                       DD37 DD46 EE03 EE11 EE12                       EE14 EE31 EE32 EE40

Claims (15)

[Claims] 1. A DC power supply circuit; a voltage conversion circuit that converts a voltage from the DC power supply circuit into another voltage and outputs the voltage; and a voltage conversion circuit having at least one switching element, and converting the voltage from the voltage conversion circuit into a high-frequency voltage. An inverter circuit that converts and outputs; a load circuit that includes a discharge lamp and an LC resonance circuit and that performs resonance operation by a high-frequency voltage from the inverter circuit; control means that controls the output voltage of the voltage conversion circuit; and the inverter circuit has In a discharge lamp lighting device comprising: a driving unit that drives a switching element; a pulse voltage superposing unit that controls the driving unit and superimposes a pulse voltage on a discharge lamp, the discharge lamp is turned on until the discharge lamp is lit. It consists of a preheating period for preheating and a starting period for starting the discharge lamp.In the starting period, the control means gradually increases the output voltage of the voltage conversion circuit and A discharge lamp lighting device, wherein a pulse voltage is superimposed on a discharge lamp by a loose voltage superimposing means. 2. The discharge lamp lighting device according to claim 1, wherein a pulse voltage is superimposed on the discharge lamp during the preheating period and the starting period. 3. The pulse voltage superimposing means periodically superimposes the pulse voltage on the discharge lamp.
Or the discharge lamp lighting device according to 2. 4. The discharge lamp lighting device according to claim 1, wherein the output voltage of the voltage conversion circuit is gradually increased from a value smaller than the peak value of the commercial power source. 5. The discharge lamp lighting device according to claim 1, wherein the pulse voltage superposing means changes a driving frequency or a duty of the driving means. 6. The discharge lamp lighting device according to claim 5, wherein the variation width of the driving frequency or the duty is substantially constant. 7. The discharge lamp lighting device according to claim 5, wherein the range of variation of the driving frequency is gradually increased. 8. The discharge lamp lighting device according to claim 5, wherein the variation width of the driving frequency is gradually reduced. 9. The discharge lamp lighting device according to claim 5, wherein the lower limit of the change of the driving frequency is substantially the resonant frequency of the LC resonant circuit. 10. The discharge lamp lighting device according to claim 5, wherein the drive frequency at the end of the preheating period and the drive frequency at the start of the starting period are different from each other. 11. The discharge lamp lighting device according to claim 10, wherein the drive frequency at the end of the preheating period is lower than the drive frequency at the start of the starting period. 12. The discharge lamp lighting device according to claim 5, wherein the starting period is 100 msec or more. 13. The driving frequency for a predetermined period from the start of the preheating period is set higher than the driving frequency for the preheating period after the lapse of the predetermined period. Discharge lamp lighting device. 14. The discharge lamp lighting device according to claim 1, wherein dimming of the discharge lamp is performed by controlling the output voltage of the voltage conversion circuit after the start period has elapsed. 15. The discharge lamp lighting device according to claim 14, wherein the lower limit of dimming is a dimming ratio of about 1% or less.