JP2000068082A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of the cataphoresis phenomenon in a discharge lamp lighting device using a voltage resonance type inverter circuit by mounting a DC voltage component control means for reducing the DC voltage component superposed on both ends of a discharge lamp to a degree which is substantially free of the cataphotoresis phenomenon. SOLUTION: A no-load detecting circuit composed of the resistances R1, R2, R3 and a voltage detecting part 2, is added to a one transistor-type inverter. By applying this structure, the DC voltage determined by the resistance values of the resistances R1, R2, R3 are superposed in the direction from a point (b) to a point (a), on both ends of a discharge lamp La. Meanwhile, when the on time of a switching element Q1 of which the on/off control is performed by an oscillation circuit 1 is longer than the off time, since the DC voltage component is superposed in the direction from a point (a) to a point (b) by the unbalance in the lamp voltage, the DC voltage component by a no-load detecting circuit is canceled, and the cataphoresis phenomenon can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting apparatus for lighting a discharge lamp at a high frequency using an inverter circuit.

[0002]

2. Description of the Related Art Various types of discharge lamp lighting devices for applying a high-frequency voltage to a discharge lamp have been known.
The circuit configuration shown in FIG. This discharge lamp lighting device performs full-wave rectification of an AC power supply Vs via a filter circuit FT with a rectifier DB composed of a diode bridge, and performs DC-AC conversion with an inverter circuit INV. Is applied to the discharge lamp La. Here, the inverter circuit I
The NV includes a switching element Q1 connected to a capacitor C1 serving as a power supply thereof via a parallel circuit of an inductor Lo and a capacitor Co. Then, a one-piece type in which a series circuit of a load circuit and a DC cut capacitor C3 is connected between both ends of a parallel circuit of an inductor Lo and a capacitor Co is adopted. The load circuit is inductor L1
And a series resonance circuit of a capacitor C2, and the resonance voltage is applied to the discharge lamp La. When the switching element Q1 is a bipolar transistor or the like, an antiparallel regenerative diode D is required. The switching element Q <b> 1 is set in an ON period and an OFF period by a drive signal of the oscillation circuit 1 and driven. Switching element Q1 is MOS-
FET may be used, in which case, an antiparallel regenerative diode D
Is unnecessary because it is built into the element.

Here, the switching element Q1 is switched on and off, but there has been no particular limitation on its duty in the past. Rather, when it is used for adjusting the output in the manufacturing process by changing the ON width, or after detecting the rectified voltage or the smoothed voltage which is the output of the rectifier DB, it is fed back or fed forward. If the on-duty control is used to change the on-duty to compensate for the power supply voltage fluctuation, or if the dimming is performed by changing the on-duty, etc. The method of obtaining the effect has been often used conventionally.

[0004] As described above, since the single-type inverter circuit can be provided as a ballast for a discharge lamp with a small number of circuit components and at low cost, the inverter circuit INV having the structure shown in FIG. I have.

[0005]

It is generally known that when a direct current voltage is applied between both electrodes of a discharge lamp such as a fluorescent lamp and the lamp is turned on, the brightness decreases near the anode. This phenomenon is caused by mercury ions in the discharge lamp gathering on the cathode side, and is called an electrophoresis phenomenon or a cataphoresis phenomenon.

In order to prevent the occurrence of the cataphoresis phenomenon,
It has been considered effective to apply an AC voltage between both electrodes of the discharge lamp. However, when the technology for lighting a discharge lamp at a high frequency using an inverter circuit as in recent years has become widespread, it has been found that even when a high-frequency AC voltage is applied to the discharge lamp, a cataphoresis phenomenon may occur. Have been. Such a cataphoresis phenomenon becomes more remarkable as the environmental temperature at which the discharge lamp is turned on is lower.

Hitherto, it has been estimated that there is a factor that causes a cataphoresis phenomenon in an inverter ballast used for a discharge lamp load, but the factor has not been elucidated.
It is an object of the present invention to clarify the factors and suppress the cataphoresis phenomenon with high accuracy and reproducibility based on the factors.

[0008]

The mechanism of the occurrence of the cataphoresis phenomenon, which is the basis of the technology of the present invention and is now clarified, will be described below. <Explanation of the cause of cataphoresis in high frequency lighting>
First, a case where the drive duty is 50:50 (basically, no cataphoresis phenomenon occurs) will be described. To simplify the description, consider a basic half-bridge type inverter lighting circuit as shown in FIG. In the figure, C1
Is a smoothing capacitor, C2 is a resonance capacitor, C3 is a DC cut capacitor, L1 is a resonance inductor, Q1,
Q2 is a semiconductor switching element such as a MOS-FET or a transistor, which is turned on / off alternately. D1, D2
Is a regenerative diode.

FIG. 12 shows waveforms of a drive input signal of the switching elements Q1 and Q2, a lamp current Ila of the discharge lamp La, and a lamp voltage Vla. In the figure, T1 'is an ON (High level) section of the drive input signal of the switching element Q1, and T2' is an ON (High level) section of the drive input signal of the switching element Q2. DT1 is a dead time from the fall of the drive input signal of the switching element Q1 to the rise of the drive input signal of the switching element Q2, and DT2 is the dead time of the drive input signal of the switching element Q1 from the fall of the drive input signal of the switching element Q2. It is the dead time until the start. further,
T1 is a section of a positive half cycle of the lamp voltage Vla and the lamp current Ila, and T2 is a section of the lamp voltage Vla and the lamp current Ila.
This is a section of a negative half cycle of la. T is a driving cycle, and T = T1 + T2 = T1 '+ DT1 + T2' + DT2
It is.

Here, if the switching elements Q1 and Q2 are driven at a drive duty of 50:50, T1 '=
T2 '. In the lamp current Ia, the positive half cycle T1 and the negative half cycle T2 are the same (T1 = T
2), the peak value becomes the same value. Lamp current Ila
Has a symmetrical waveform like this, and the waveform of the lamp voltage Vla is also the same. There is no problem in this respect, and the cataphoresis phenomenon does not basically occur.

Next, consider a case where switching elements Q1 and Q2 are driven with an unbalanced duty. FIG.
3 shows waveforms of the drive input signals of the switching elements Q1 and Q2, the lamp current Ila of the discharge lamp La, and the lamp voltage Vla. Here, if the switching elements Q1 and Q2 are driven with an unbalanced duty, T1 ′ <T2 ′ as shown in FIG. Then, the lamp current I
In (a), the positive half cycle T1 and the negative half cycle T2 are different (T1 <T2), and the peak value thereof is higher in the section T1. However, since the DC cut capacitor C3 is provided, the area of the lamp current Ila is the same even if the waveform is asymmetric. (That is, the total amount of charge exchanged in the positive and negative directions is the same.)

Next, consider the waveform of the lamp voltage Vla. Here, the resistance value changes in the sections T1 and T2 due to the characteristics of the discharge lamp. Therefore, regarding the lamp voltage Vla, not only the peak value but also the area differs between the positive half cycle T1 and the negative half cycle T2. The fact that the areas are different means that the average value does not become zero. Here, the average value is a DC voltage.

When the switching elements Q1 and Q2 are driven with an unbalanced duty by the inverter ballast, a DC voltage is superimposed on the lamp voltage due to the characteristics of the discharge lamp. The above is the basic part of the present invention, which is the explanation of the cause of the occurrence of the cataphoresis phenomenon which we have elucidated this time.

<Verification on Actual Device> Next, a description will be given based on waveforms verified by the actual device. As described above, the generation of the DC voltage component in the lamp voltage is caused by the characteristics of the discharge lamp. Therefore, in order to exchange only AC power, a cataphoresis phenomenon occurs according to the same principle even when the resonance circuit and the load are connected via the insulating transformer Tf as shown in FIG.

FIG. 14 is a circuit diagram of a prototype used for verification by an actual machine. In the figure, C1 is a smoothing capacitor, C2 is a resonance capacitor, C3 is a DC cut capacitor, L1
Is a resonant inductor, L2 is a chopper inductor, Q
Reference numerals 1 and Q2 denote semiconductor switching elements such as MOS-FETs and transistors, which are turned on / off alternately.

FIG. 15 shows waveforms (ambient temperature: -10 ° C.) of the lamp voltage Vla and the lamp current Ila in the actual machine of this prototype. When the vicinity of the top on the positive side is point A and the vicinity of the top on the negative side is point B, the discharge lamp equivalent resistance Rla at these two points is calculated. At point A, Vla = 98 V, Ila = 200 × 26.0. / 10 =
520 mA 点 Rla = 98 / 0.52 ≒ 188Ω At point B, Vla = 148 V, Ila = 200 × 32.0 / 10 =
640 mA ∴Rla = 148 / 0.64 ≒ 231 Ω, and there is a difference in the discharge lamp equivalent resistance Rla between the points A and B. This is consistent with the description of the phenomenon occurrence described above.

Next, the DC superimposed voltage at a low temperature (ambient temperature: -10 ° C.) was measured. 15 and 16 show the lamp voltage and lamp current of the prototype, FIG. 15 shows the case of DC coupling, and FIG. 16 shows the case of AC coupling. Here, a difference between the DC coupling and the AC coupling is a DC component (= DC superimposed component). In this example, attention is paid to the maximum value and the minimum value of the lamp voltage and the lamp current. Several volts for maximum and minimum lamp voltage
However, the lamp current has exactly the same value. From this, it is confirmed that a DC component (= DC superimposed voltage) rides on the lamp voltage, but a DC component hardly appears on the lamp current.

In the drawing, there is a difference of 8 V in the positive direction (maximum value) and 6 V in the negative direction (minimum value). AC coupling and DC
FIG. 17 is a waveform diagram in which the waveforms in the case of the combination are superimposed. As described above, when the DC voltage of about 6 to 8 V is applied, the waveform of the lamp voltage has a waveform as if translated downward in the drawing.

In the above description, only a part is viewed (only the maximum value and the minimum value are focused) for the sake of simplicity. More precisely, however, the whole shape including the half cycle of the power supply is used. It should be measured, and since the DC component is an average value, it should be measured by observing the average value of each waveform and taking the difference. FIG. 18 shows the waveform measured in consideration of the above. In the figure, (a) shows the case of DC coupling and (b) shows the case of AC coupling. In this example, the DC superimposed voltage is 6.2V.

Next, a technique for suppressing the cataphoresis phenomenon clarified as described above will be described. <Description of specific technology to solve the problem> If the DC voltage is superimposed on the high-frequency AC voltage by the inverter circuit as described above, the mechanism of the cataphoresis phenomenon generation is as follows. Due to the unbalanced driving and the characteristics of the discharge lamp, the DC voltage is superimposed on the lamp voltage, and the temperature of the discharge lamp becomes low, causing the mercury vapor pressure to drop. Mercury atoms contributing to the emission of light)
It can be said that the cataphoresis phenomenon occurs due to the combination of the two factors that the cataphoresis phenomenon occurs.

Therefore, as a countermeasure, it is only necessary to make the above two factors not uniform. It is possible that the inverter luminaire is used in a low-temperature environment, and in that case, it is considered that a decrease in mercury vapor pressure is basically unavoidable. Therefore, as a countermeasure against this problem, it is sufficient that the high-frequency AC generated in the inverter circuit and applied to the discharge lamp is not unbalanced and the DC voltage is not superimposed.

In the voltage resonance type inverter ballast described in the present invention, in which the voltage waveform of the main switching element is a sine wave, such as the one-push type or the L push-pull type, the voltage waveform becomes 0 V during the OFF period of the main switching element. Do not enter the next ON cycle until it comes down. Also, the setting of the ON period is similarly restricted. This is because the voltage waveform in the OFF period attenuates in a sine wave shape if there is no next ON signal, so that energy to be sent from the main switching element during the ON period is required to some extent. Therefore, the ON period of the main switching element is also limited to a certain width.

Although it can be said that these voltage resonance type inverters have low controllability as described above, on the other hand, cataphoresis is basically unlikely to occur. This is because, in these methods, in determining the operation cycle of the inverter, the factors determined by the resonance conditions are strong, so that the duty is unlikely to be unbalanced.

For example, in a single inverter, the OFF time of the main switching element is determined by the resonance condition of a collector voltage (a drain voltage in the case of an FET) that rises in a sine wave shape. This is because it is not possible to shift to the next ON cycle until the sinusoidal voltage waveform falls to 0V. As described above, since the operation of the single-stone inverter at the time of OFF is determined by the resonance condition of the main circuit, the energy supplied to the resonance circuit at the time of ON is also limited to a certain range. Therefore, O
There is also a restriction on N time, and the duty of the voltage / current waveform in the discharge lamp is basically close to 50%. Thus, from the viewpoint of basically preventing the occurrence of the cataphoresis phenomenon, it can be said that the single-stone inverter is a system that is unlikely to cause the phenomenon.

Similarly, the L-push-pull type inverter operates in a range close to 50% because the duty of the lamp voltage and current is determined by the condition of the resonance circuit. It can be said that it is a system that is unlikely to occur.

Inverter systems in which the operating cycle and duty are limited depending on the conditions of the resonance circuit, such as the single type and L push-pull type, are systems in which the cataphoresis phenomenon is unlikely to occur, but the duty is always 50%. is not. Further, the DC superimposed voltage does not always become 0 V, and a slight imbalance can occur.

By adding a technology based on elucidation of the above-described cataphoresis phenomenon generating mechanism to these inverter systems, it is possible to realize an inverter ballast that is less likely to generate a cataphoresis phenomenon. As a result, a ballast that can cope with a lower temperature environment can be provided.

As a specific means and concept, the DC superimposed voltage is set to a level lower than a certain level at which the cataphoresis phenomenon hardly occurs, or the DC voltage is superimposed in a reverse direction by some additional circuit, and the DC voltage due to imbalance is set. There is a way of thinking that cancels out. A more specific description will be given in the following examples.

[0029]

(Embodiment 1) FIG. 1 shows a circuit diagram of Embodiment 1 of the present invention. This is an example in which a no-load detection circuit including resistors R1, R2, and R3 and a voltage detection unit 2 is added to a conventional single-type inverter. With this configuration, a DC voltage determined by the resistance values of the resistors R1, R2, and R3 is superimposed on both ends of the discharge lamp La in the direction from the point b to the point a. On the other hand, if the ON time of the switching element Q1 that is turned on and off by the oscillation circuit 1 is longer than the OFF time, a DC voltage component is superimposed in the direction from the point a to the point b due to the imbalance of the lamp voltage.
The DC voltage component by the no-load detection circuit is canceled, and the cataphoresis phenomenon is suppressed.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention. The difference from the first embodiment shown in FIG. 1 is that instead of the no-load detection circuit, a battery E having a voltage value equivalent to the direction of generation of the DC voltage component generated at both ends of the discharge lamp La by the operation of the inverter is opposite. Is connected in parallel with the discharge lamp La. With such a configuration, even if the duty of the output voltage of the oscillation circuit is slightly unbalanced and the DC voltage component is superimposed, by applying the DC voltage in the opposite direction by the battery E, Since no DC voltage component is applied to both ends of the discharge lamp La, the occurrence of the cataphoresis phenomenon can be suppressed.

(Embodiment 3) The circuit configuration of Embodiment 3 of the present invention is the same as that of FIG. 10 (conventional example). The present embodiment is characterized in that the duty of the output voltage waveform of the oscillation circuit 1 is set so that the DC voltage component generated at both ends of the discharge lamp La is 5 V or less. With this setting, the duty of the output voltage waveform of the oscillation circuit is 5
In a one-stone inverter that operates in a range close to 0%,
The cataphoresis phenomenon can be almost completely suppressed.

(Embodiment 4) FIG. 3 shows Embodiment 4 of the present invention. In the present embodiment, detecting means 3a and 3b for detecting the voltage in each of the positive and negative cycles of the lamp voltage and a differential amplifier for obtaining a difference between the detected voltages are provided in a conventional single-type inverter. And a control circuit for controlling the duty of the output voltage waveform of the oscillation circuit 1 so that the DC voltage component generated at both ends of the discharge lamp La becomes zero based on the DC voltage detected as described above. 5 is added. With such a configuration, the occurrence of the cataphoresis phenomenon can be completely suppressed even if there is a load change or a change in the ambient temperature.

(Embodiment 5) The circuit configuration of Embodiment 5 of the present invention is the same as that of FIG. 10 (conventional example). In the present embodiment, the switching element Q
Paying attention to the fact that the duty of the oscillation circuit 1 fluctuates due to the temperature characteristic 1, the duty fluctuating according to the temperature characteristic is set to be 50% between -10 ° C and 0 ° C. With such a setting, it is possible to suppress the occurrence of the cataphoresis phenomenon at a low temperature (−10 ° C. to 0 ° C.).

(Embodiment 6) FIG. 4 shows Embodiment 6 of the present invention. The present embodiment is characterized in that a control circuit 6 having a function of exchanging a High level and a Low level of the output signal of the oscillation circuit 1 every time the power is turned ON / OFF is added. With such a configuration, the direction of the DC voltage component generated at both ends of the discharge lamp La is inverted each time the power is turned ON / OFF, so that it is possible to increase the time until the occurrence of the cataphoresis phenomenon.

(Embodiment 7) FIG. 5 shows Embodiment 7 of the present invention. The present embodiment is characterized in that the oscillation circuit 1 includes a parallel circuit of a capacitor Ct and a thermistor Rt and a drive circuit 10. The parallel circuit of the capacitor Ct and the thermistor Rt determines the pulse width of the output voltage waveform of the oscillation circuit 1. As shown in FIG. 6, the duty of the output voltage waveform of the oscillation circuit 1 is controlled to be smaller at low temperatures than at room temperature, and the duty d at −10 ° C. is controlled by a change in resistance due to the temperature characteristics of the thermistor Rt, as shown in FIG. By limiting the range to 45 ≦ d ≦ 55, the DC voltage component generated at both ends of the discharge lamp La at −10 ° C. can be reduced to some extent. Therefore, the degree of occurrence of the cataphoresis phenomenon can be reduced.

(Eighth Embodiment) FIG. 7 shows an eighth embodiment of the present invention. In this embodiment, a feedforward circuit including diodes D8 and D9, resistors R4 and R5, a capacitor C7 and a duty control circuit 7 is added to the conventional single-type inverter, and the duty d of the output voltage of the It is characterized in that control is performed so as to have both an area where d> 50 and an area where d <50 within one cycle of the cycle. More specifically, since the detection voltage of the duty control circuit 7 is a full-wave rectified voltage waveform and is not constant, the output voltage waveform of the oscillation circuit 1 does not become constant within one cycle of the power supply, and d> 50. And d <50. By performing such control, the DC voltage components generated at both ends of the discharge lamp La in one cycle of the power supply are offset to some extent, and the occurrence of the cataphoresis phenomenon can be suppressed.

(Embodiment 9) The circuit configuration of Embodiment 9 of the present invention is the same as that of FIG. 10 (conventional example). In this embodiment, the duty d of the output voltage waveform of the oscillation circuit 1 during the rated operation is
By setting d ≦ 55, the DC voltage component generated at both ends of the discharge lamp is reduced, and the occurrence of the cataphoresis phenomenon is suppressed.

(Embodiment 10) FIG. 8 shows Embodiment 10 of the present invention.
It is. The circuit shown here is a one-piece inverter circuit. C1 is a smoothing capacitor, C2 is a resonance capacitor, C
Reference numeral 3 denotes a DC cut capacitor, L1 denotes a resonance inductor, and Q1 denotes a semiconductor switching element such as a MOS-FET or a transistor, which is driven by the oscillation circuit 1 and turned on / off alternately. D is a regenerative diode. A parallel circuit of an inductor Lo and a capacitor Co is connected to a smoothing capacitor C1 serving as a power supply via a switching element Q1. La is a discharge lamp.

The generation of the drive signal for the switching element Q1 of the inverter circuit may be a separately excited system or a self-excited another system.
In the oscillation circuit 1 that supplies a drive signal for the switching element Q1, Ct is an external timer capacitor, R is an external timer resistor, and NTC is a thermistor having a negative temperature characteristic. The drive frequency generated by the oscillation circuit 1 is determined by a timer circuit including a capacitor Ct, a resistor R, and a thermistor NTC. Here, at low temperatures, the resistance value of the thermistor NTC increases, so that the time constant of the circuit increases, and the driving frequency decreases as the temperature decreases. Due to the temperature characteristics of the discharge lamp La, the output is lower at low temperatures than at room temperature, but the power supplied to the load circuit according to the present embodiment is higher at low temperatures than when the present invention is not added. Thereby, even if the DC voltage component is superimposed to some extent on the discharge lamp, the temperature of the discharge lamp can be increased to such an extent that the cataphoresis phenomenon generated by the voltage can be suppressed.

The cause of the cataphoresis phenomenon is that both the reduction of the mercury vapor pressure and the superposition of the DC voltage on the discharge lamp are the same. The present embodiment acts in the direction of removing the former factor (drop of mercury vapor pressure), and prevents the occurrence of the cataphoresis phenomenon. According to the present invention, if the temperature change that increases is large, the occurrence of the cataphoresis phenomenon can be suppressed even when a larger DC voltage is superimposed.

(Embodiment 11) FIG. 9 shows Embodiment 11 of the present invention.
It is. The circuit shown here is a one-piece inverter circuit. C1 is a smoothing capacitor, C2 is a resonance capacitor, C
Reference numeral 3 denotes a DC cut capacitor, L1 denotes a resonance inductor, and Q1 denotes a semiconductor switching element such as a MOS-FET or a transistor. The semiconductor switching element is driven by an inverter control circuit 9 and is turned ON / OFF alternately. D is a regenerative diode, and La is a discharge lamp. The control method of the switching element Q1 may be a separately excited method or a self-excited another control method. Th is a thermistor for detecting an ambient temperature, and is connected to the inverter control circuit 9.

In the circuit shown in FIG. 9, the dimming signal receiving section 8 receives a dimming signal from the outside and changes the drive signal from the inverter control circuit 9 to the switching element Q1. The duty of the drive signal is controlled to be unbalanced in order to increase the degree of dimming and reduce the luminous flux output from the discharge lamp La. In the inverter control circuit 9, a constant voltage is applied to a series circuit of the thermistor Th and the resistor, and the voltage between both ends of the thermistor Th is compared with a certain threshold value, thereby detecting a decrease in the ambient temperature. At low temperatures, the dimming signal from the outside is cut or limited to a certain limit to reduce the mercury vapor pressure due to low temperatures,
In addition, the unbalance operation due to dimming acts on both of the factors of the superposition of the DC voltage on the discharge lamp, which is the cause of the cataphoresis phenomenon, in such a direction that the cataphoresis phenomenon can be prevented. That is, under the strictest conditions relating to the cataphoresis phenomenon of deep dimming due to unbalanced duty in a low-temperature environment, the luminous flux from the discharge lamp is extremely reduced. The control is performed so as to maintain the light output from the light source.

[0043]

According to the present invention, a one-stone inverter,
In a discharge lamp lighting device using a voltage resonance type inverter circuit in which a sinusoidal resonance voltage is applied to a main switching element such as an L push-pull inverter, a DC voltage component superimposed on both ends of the discharge lamp is substantially reduced. DC voltage component suppressing means for reducing the cataphoresis phenomenon to the extent that cataphoresis does not occur, or discharge lamp temperature increasing means for increasing the temperature of the discharge lamp to such an extent that the cataphoresis phenomenon does not substantially occur due to the DC voltage component occurring in the discharge lamp Has the effect that the occurrence of the cataphoresis phenomenon can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 4 is a circuit diagram of a sixth embodiment of the present invention.

FIG. 5 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 6 is an operation explanatory view of Embodiment 7 of the present invention.

FIG. 7 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 8 is a circuit diagram according to a tenth embodiment of the present invention.

FIG. 9 is a circuit diagram of an eleventh embodiment of the present invention.

FIG. 10 is a circuit diagram of a conventional example.

FIG. 11 is a circuit diagram for explaining a problem of the conventional example.

FIG. 12 is an operation waveform diagram of the conventional circuit shown in FIG. 11 at the time of positive / negative symmetric drive.

13 is an operation waveform diagram of the conventional circuit shown in FIG. 11 at the time of positive / negative asymmetric drive.

FIG. 14 is a circuit diagram of an actual device used to verify a problem of the conventional example.

FIG. 15 is a waveform diagram of an operation waveform of the conventional circuit shown in FIG. 14 measured by DC coupling.

FIG. 16 is a waveform chart of an operation waveform of the conventional circuit shown in FIG. 14 measured by AC coupling.

17 is a waveform diagram in which the waveform diagram of FIG. 15 and the waveform diagram of FIG. 16 are superimposed.

18 is a waveform chart for calculating an average value of operation waveforms of the conventional circuit shown in FIG.

[Explanation of symbols]

 Q1 Switching element La Discharge lamp L1 Resonant inductor C1 Smoothing capacitor C2 Resonant capacitor C3 Coupling capacitor (DC cut capacitor) DB Rectifier

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K072 AA02 BA03 BB01 BC01 CA01 DB03 DC02 DD04 EA02 EB01 EB04 EB05 GA01 GA03 GB04 GC01 GC04 HA10 HB03

Claims (10)

[Claims] In a discharge lamp lighting device using a voltage resonance type inverter circuit in which a sinusoidal resonance voltage is applied to a main switching element, a DC voltage component superimposed on both ends of the discharge lamp substantially causes a cataphoresis phenomenon. A discharge lamp lighting device characterized by adding DC voltage component suppressing means for reducing the voltage to a level that does not occur. 2. A discharge lamp lighting device using a voltage resonance type inverter circuit in which a sinusoidal resonance voltage is applied to a main switching element, a cataphoresis phenomenon substantially occurs due to a DC voltage component generated in the discharge lamp. A discharge lamp lighting device characterized by adding a discharge lamp temperature increasing means for increasing the temperature of the discharge lamp to such an extent that the temperature does not increase. 3. The discharge lamp lighting device according to claim 1, wherein the duty of the main switching element is controlled to be 55% or less. 4. The power supply according to claim 1, wherein the duty of the main switching element is 5 within one cycle of the power supply cycle.
A discharge lamp lighting device characterized in that there are 0% or more places and 50% or less places. 5. The discharge lamp lighting device according to claim 1, wherein the polarity of the DC voltage component superimposed on both ends of the discharge lamp is switched every time the main power supply is turned on and off. 6. The operating point according to claim 1, wherein the operating point at which the duty of the main switching element is approximately 50% is 0 ° C. to −10 ° C.
A discharge lamp lighting device characterized in that the temperature is set between ℃. 7. The discharge lamp lighting device according to claim 1, wherein the duty of the main switching element is −45% to 55% at −10 ° C., and the duty has a positive temperature characteristic. 8. The discharge lamp lighting device according to claim 1, further comprising a circuit for superimposing a DC voltage in a direction opposite to a DC voltage component superimposed on both ends of the discharge lamp by an inverter circuit. 9. The discharge lamp lighting device according to claim 1, wherein a DC voltage component superimposed on both ends of the discharge lamp by the inverter circuit is set to 5 V or less. 10. A means for detecting a temperature decrease or an increase in a DC voltage component superimposed on both ends of a discharge lamp, which causes a cataphoresis phenomenon, and a detected temperature decrease or an increase in the DC voltage component. Discharge lamp lighting device, characterized in that a means for compensating for the cataphoresis phenomenon is provided.