JP2000058286A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device whereby a stable output free of flicker, etc., can be emitted till a low light flux dimmer condition within the ambient temp. range in service of a piezo transformer in an illumination field. SOLUTION: An intermittent oscillation control circuit 7 is to operate a driver circuit 1 when the dimmer mode is selected and is equipped with a duty adjusting circuit 9 to change the dimmer quantity and a control circuit 8 for the frequency of intermittent oscillation depending upon the temperature. The frequency control circuit 8 has a function to change the frequency of intermittent oscillation in compliance with varying ambient temp. and lowers the frequency of intermittent oscillation if the ambient temp. sinks.

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 device using a piezoelectric transformer.

[0002]

2. Description of the Related Art Conventionally, in a power supply circuit using a piezoelectric transformer, when the output voltage (output current) is controlled to a desired value, a method utilizing the dependence of the driving frequency on the step-up ratio of the piezoelectric transformer is used. I was

For example, Japanese Patent Application Laid-Open No. Hei 8-107678 discloses an output voltage control means for controlling an output current to a desired value in a state of high efficiency, preventing a breakdown of a piezoelectric transformer, and adjusting brightness. In this case, there is disclosed a configuration in which the duty is changed by time-division driving for switching on and off to increase or decrease the average tube current. (See FIG. 12)
Circuit, the piezoelectric transformer 20 and the piezoelectric transformer 2
0, a high voltage side terminal of the discharge lamp load 21 and a voltage input terminal of the output voltage comparison circuit 22 are connected to the secondary electrode of the piezoelectric transformer 20, and the low voltage side terminal of the discharge lamp load 21 is connected to the load. The current input terminal of the current comparison circuit 23 is connected, and the load current comparison circuit 23 converts the load current flowing through the discharge lamp load 21 into a voltage level, and compares the voltage level with the reference voltage Vrefa. The output voltage comparison circuit 22 detects whether the current exceeds a predetermined value, and outputs the output voltage of the piezoelectric transformer 20 and the reference voltage Vr.
By comparing with efb, it is detected whether or not the output voltage of the piezoelectric transformer 20 exceeds a predetermined value, and each detected output is transmitted to the frequency sweeping oscillator 25. The frequency sweeping oscillator 25 supplies an oscillating frequency signal to the driving circuit 26 and drives the piezoelectric transformer 20 at the frequency of the oscillating frequency signal.
The output current is controlled to a desired value based on the outputs of the output terminals 3 and 22, and output voltage suppressing means for preventing breakage of the piezoelectric transformer is provided.

A time-division driving control circuit 24 controls the frequency sweep oscillator 25 and the driving circuit 26 in order to time-divisionally drive the piezoelectric transformer 20 by the driving circuit 26 based on the duty control signal _Vduty. Transformer 2
0 is an intermittent oscillation drive, so that the discharge lamp load 2
A brightness adjustment (light control) means for controlling the output to the light control unit 1 to control the light is configured.

[0005] The method of performing luminance adjustment (dimming) is time-division driving because, when the luminance is adjusted by reducing the lamp current, the shunting of the lamp current through the stray capacitance parasitic to the discharge lamp load is performed. This is to prevent the brightness of the lamp from becoming uneven.

[0006]

By the way, the present inventors have actually measured that, in the above-mentioned conventional example, the operation at the time of low light flux dimming of about 10% in the operating ambient temperature range of the piezoelectric transformer is insufficient. It revealed that. In the field of lighting, the ambient temperature condition ranges from -30 ° C to 80 ° C, and the operating ambient temperature range of the piezoelectric transformer 20 also ranges from -30 ° C to 80 ° C.

FIGS. 13 and 14 show that the resonance frequency is 120 kHz.
The duty control signal V _duty (each diagram (a)) and the output voltage V _out (each diagram (b)) when the discharge lamp load 21 composed of a cold cathode lamp is time-divisionally driven (intermittent oscillation drive) by the piezoelectric transformer inverter z. ) And the lamp current (I _la ). However, the intermittent oscillation frequency is 500Hz (2ms)
FIG. 13 shows a case where the ambient temperature Ta is 25 ° C., and FIG. 14 shows a case where the ambient temperature Ta is −30 ° C., where the on-duty is 10% <200 μs> (dimming ratio is about 10%). Show.

When the ambient temperature is 25 ° C., when an ON signal is input, a high output voltage V _out is generated and the start time tx
(6 μs ≦ tx ≦ 20 μs) After that, the lamp is turned on and the lamp current I
_la flows. At this time, the intermittent oscillation drive operated normally, and a luminous flux having a dimming ratio of about 10% was stably obtained. This is because the ratio of the start time tx to the on-duty time width of 200 μs is 1/10 or less, and the time during which the lamp current flows (lighting time) is stable.

However, when the ambient temperature Ta is -30.degree.
With respect to the on-duty time width of 200 μs, the start time tx from when an ON signal is input to the occurrence of a high output voltage V _out and lighting is increased to 60 μs ≦ tx ≦ 200 μs, and as shown in FIG. As the ratio of the starting time tx to the duty time width increases, the flowing lamp current _Ila decreases, and a light flux with a dimming ratio of about 10% cannot be obtained. Further, it has been found that the light beam output becomes unstable due to the variation in the start time tx, and the lighting state flickers.

[0010] This is considered to be because the ambient temperature Ta becomes low and the discharge lamp load becomes difficult to start and turn on, so that the start time tx becomes long. The reason why the starting time tx becomes longer is as follows. That is, in the case of the cold cathode lamp, unlike the hot cathode lamp, the starting operation is performed by the voltage energy (
(The magnitude of the output voltage and the time of application of the output voltage). This is because energy insufficient for lighting is compensated for by increasing the application time. FIG. 1 shows the result of actually measuring the relationship between the starting time tx and the ambient temperature Ta.
It is shown in FIG. As shown in the figure, there is a variation X in the start time at the same temperature, but the start time tx is inversely proportional to the ambient temperature Ta, that is, the start time tx tends to increase as the ambient temperature Ta decreases.

As described above, in the case where low light flux dimming is performed by the conventional method, the starting time tx becomes longer as the ambient temperature decreases, and the lighting time becomes shorter or fluctuates. As a result, a desired light flux cannot be obtained. And the lighting state of the discharge lamp load is unstable and flickers.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a stable output without flickering and low light flux dimming in an ambient temperature range of use of a piezoelectric transformer in the field of lighting. It is an object of the present invention to provide a discharge lamp lighting device that can perform the above.

[0013]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device including a piezoelectric transformer, a driving circuit for driving the piezoelectric transformer, and a discharge lamp load. The driving circuit is operated intermittently at the time of dimming, and the frequency of the intermittent driving is reduced according to a decrease in ambient temperature.

According to a second aspect of the present invention, in a discharge lamp lighting device including a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, the drive circuit is operated intermittently at the time of dimming and the ambient temperature is controlled. The dimming ratio is increased according to the decrease of

According to a third aspect of the present invention, in a discharge lamp lighting device including a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, the drive circuit is operated intermittently at the time of dimming. The driving frequency is reduced in accordance with a decrease in the ambient temperature.
It is characterized by increasing from 0 Hz and increasing the dimming ratio.

According to a fourth aspect of the present invention, in a discharge lamp lighting device including a piezoelectric transformer, a driving circuit for driving the piezoelectric transformer, and a discharge lamp load, the output voltage of the piezoelectric transformer starts the discharge lamp load during dimming. A driving circuit that alternately repeats a period in which the piezoelectric transformer is driven so that the voltage can be turned on, and a period in which the piezoelectric transformer is driven so that the output voltage of the piezoelectric transformer is lower than the lighting voltage of the discharge lamp load. Is operated intermittently.

According to a fifth aspect of the present invention, in a discharge lamp lighting device including a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, the drive circuit is operated intermittently at the time of dimming, and the discharge lamp load is reduced. Is characterized in that the on-duty period during which the drive circuit operates is changed so that the lighting-on time of is constant.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the piezoelectric transformer has an output voltage limiting function.

According to a seventh aspect of the present invention, in any one of the first to fifth aspects, the discharge lamp load is a cold cathode lamp.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. (Embodiment 1) FIG. 4 shows a circuit of this embodiment. In the present embodiment, as shown, a drive circuit 1 for driving the piezoelectric transformer 2 is connected to an input terminal of the piezoelectric transformer 2, and a discharge lamp load 3 is connected to an output terminal of the piezoelectric transformer 2. The discharge lamp load 3 is further connected to a load current detection circuit 6. The load current detection circuit 6 detects the load current and outputs a voltage signal corresponding to the load current value. The load signal is used to change the drive frequency of the drive circuit 1 so that the load current has a predetermined value. To the frequency control circuit 4.
The output terminal of the piezoelectric transformer 2 has an output voltage detection circuit 5.
Is connected. The output voltage detection circuit 5 is for detecting the output voltage of the piezoelectric transformer 2,
Is transmitted to the frequency control circuit 4. The frequency control circuit 4 controls the driving circuit based on the voltage signals of the load current detection circuit 6 and the output voltage detection circuit 5 so that the output voltage of the piezoelectric transformer 2 does not exceed a predetermined voltage and the load current becomes a predetermined value. 1 is adjusted.

The drive circuit 1 further includes an intermittent oscillation control circuit 7
Is connected. This intermittent oscillation control circuit 7 is for intermittently driving the drive circuit 1 when the dimming mode is selected, and is provided with a duty adjustment circuit 9 for changing the dimming light amount and a temperature-dependent intermittent oscillation frequency control circuit 8. The temperature-dependent intermittent oscillation frequency control circuit 8 controls the ambient temperature T as shown in FIG.
a function of changing the intermittent frequency with respect to the change of a,
When the ambient temperature Ta decreases, the intermittent frequency decreases.

The drive circuit 1 receives the duty control signal V _duty of the intermittent oscillation control circuit 7 and drives the piezoelectric transformer 2 during the on-duty period, and stops driving the piezoelectric transformer 2 during the off-duty period. That is, during the on-duty period, the piezoelectric transformer 2 generates and applies the output voltage _Vout to the discharge lamp load 3, and does not apply the output voltage _Vout to the discharge lamp load 6 during the off-duty period.

If the intermittent frequency has the ambient temperature dependency as shown in FIG. 2, for example, when the ambient temperature is 25 ° C., the intermittent frequency is 1 kHz (one cycle time 1 s, on-duty 100 μs when the dimming ratio is 10%, average start-up). (Time tx = 10 μs)
, 100 Hz at -30 ° C (10 m for one cycle)
s, the on-duty is 1 ms when the dimming ratio is 10%, and the average starting time tx = 100 μs).
The ratio occupied by x can be made substantially constant, and a stable output can be obtained by preventing the lighting time from being shortened or varied.

That is, in the present embodiment, with the configuration shown in FIG. 1, the operating ambient temperature range of the piezoelectric transformer 2 shown in FIG.
By adjusting the intermittent frequency in the range of 30 ° C. to 80 ° C. in accordance with the change of the ambient temperature Ta, a stable output free from flickering or the like can be obtained up to the time of low light flux dimming.

(Embodiment 2) FIG. 3 shows a circuit of this embodiment. As shown, in the present embodiment, a drive circuit 1 for driving the piezoelectric transformer 2 is connected to an input terminal of the piezoelectric transformer 2 and a discharge lamp load 3 is connected to an output terminal of the piezoelectric transformer 2 as in the first embodiment. You. The discharge lamp load 3 is further connected to a load current detection circuit 6. The load current detection circuit 6 detects the load current and outputs a voltage signal corresponding to the load current value in the same manner as in the first embodiment, and drives the drive circuit 1 so that the load signal has a predetermined value. This is for changing the frequency, and is transmitted to the frequency control circuit 4. An output voltage detection circuit 5 is connected to the output terminal of the piezoelectric transformer 2 as in the first embodiment. The output voltage detection circuit 5 is for detecting the output voltage of the piezoelectric transformer 2 and transmits a voltage signal corresponding to the output voltage of the piezoelectric transformer 2 to the frequency control circuit 4. The frequency control circuit 4 includes a load current detection circuit 6 and an output voltage detection circuit 5 as in the first embodiment.
The drive frequency of the drive circuit 1 is adjusted based on the voltage signal so that the output voltage of the piezoelectric transformer 2 does not exceed a predetermined voltage and the load current becomes a predetermined value.

The intermittent oscillation control circuit 7 connected to the drive circuit 1 is for driving the drive circuit 1 intermittently by the duty control signal V _duty when the dimming mode is selected as in the first embodiment. An intermittent oscillation frequency generating circuit 11 for oscillating the clock and a temperature-dependent duty control circuit 10 are additionally provided. The temperature-dependent duty control circuit 10 has a function of changing the dimming ratio in response to a change in the ambient temperature Ta as shown in FIG. 4, for example, and increases the dimming ratio when the ambient temperature Ta decreases.

If the dimming ratio has the ambient temperature dependence as shown in FIG. 7, for example, the intermittent frequency is constant at 200 Hz, and the dimming ratio is 5% when the ambient temperature is 25 ° C. (one cycle time 5 ms,
When the dimming ratio is 5%, the on-duty is 100 μs, the average starting time tx = 100 μs), and when the dimming ratio is -30 ° C., the dimming ratio is 20.
% (Time of one cycle: 5 ms, on-duty: 1 ms when the dimming ratio is 20%, average starting time tx = 100 μs), the ratio of the average starting time tx to the dimming on-duty time even when the ambient temperature changes is calculated. Can be almost constant,
Therefore, a stable output can be obtained by preventing the lighting time from being shortened or varied.

That is, in the present embodiment, the operating temperature range of the piezoelectric transformer 2 shown in FIG.
At 30 ° C. to 80 ° C., a stable output without flickering or the like can be obtained until low light flux dimming.

(Embodiment 3) FIG. 5 shows a circuit of this embodiment. In this embodiment, a drive circuit 1 for driving the piezoelectric transformer 2 is connected to the input terminal of the piezoelectric transformer 2 as in the first and second embodiments, and a discharge lamp load 3 is connected to the output terminal of the piezoelectric transformer 2 as shown in the figure. Connected. The discharge lamp load 3 is further connected to a load current detection circuit 6. The load current detection circuit 6 detects the member load current and outputs a voltage signal corresponding to the load current value as in the first and second embodiments, and converts the voltage signal to the drive circuit 1 so that the load current becomes a predetermined value. And to the frequency control circuit 4. The output terminal of the piezoelectric transformer 2 is connected to an output voltage detection circuit 5. The output voltage detection circuit 5 detects the output voltage of the piezoelectric transformer 2 as in the first and second embodiments, and transmits a voltage signal corresponding to the output voltage of the piezoelectric transformer 2 to the frequency control circuit 4. Frequency control circuit 4
Is based on the voltage signals of the load current detection circuit 6 and the output voltage detection circuit 5, so that the output voltage of the piezoelectric transformer 2 does not exceed a predetermined voltage and the drive frequency of the drive circuit 1 is controlled so that the load current becomes a predetermined value. To adjust.

The intermittent oscillation control circuit 7 connected to the drive circuit 1 is for intermittently driving the drive circuit 1 by the duty control signal V _duty when the dimming mode is selected, as in the first and second embodiments. A temperature-dependent intermittent frequency control circuit 8 provided in the first embodiment and a temperature-dependent duty control circuit 10 provided in the second embodiment are additionally provided.

In particular, the temperature-dependent intermittent frequency control circuit 8 of the present embodiment has an ambient temperature T as shown in FIG.
Although the intermittent frequency is changed in accordance with the change of a, when the ambient temperature Ta reaches a temperature at which the intermittent frequency decreases to 100 Hz, a function of maintaining the intermittent frequency at 100 Hz even when the ambient temperature Ta lowers is provided, On the other hand, the temperature-dependent duty control circuit 10 sets the ambient temperature Ta to a temperature at which the intermittent frequency is set to 100 Hz as shown in (b) of FIG.
The dimming ratio is kept constant until the temperature decreases, and when the ambient temperature Ta further decreases, the dimming ratio is increased.

In an ambient temperature range lower than the ambient temperature Ta at which the intermittent frequency is 100 Hz as shown in FIG. 6B, temperature dependency which functions to increase the intermittent frequency when the ambient temperature Ta decreases. In addition to the intermittent frequency control circuit 8, when the ambient temperature Ta decreases in an ambient temperature range lower than the ambient temperature Ta at which the intermittent frequency is 100 Hz as shown in (b) of FIG. May be provided with a degree-dependent duty control circuit 10 which functions.

As described above, the intermittent frequency and the dimming ratio are shown in FIG.
(A) By giving the ambient temperature dependency as in (b), the ratio of the average starting time tx to the dimming on-duty time is almost constant even when the ambient temperature changes, as in the first and second embodiments. Thus, a stable output can be obtained by preventing the lighting time from being shortened or varied. In the present embodiment, the switching is performed so that the intermittent frequency does not become 100 Hz or less, because the lighting of the discharge lamp load 3 appears to be flickering at a low frequency of 100 Hz or less.

In the present embodiment, the configuration shown in FIG.
FIG. 6A or FIG. 6B shows the intermittent frequency and the dimming ratio in the use ambient temperature range of -30 ° C. to 80 ° C.
By controlling as shown in (1), a stable output without flickering or the like can be obtained until the low light flux dimming. Also, the intermittent frequency should not be lower than 100 Hz, and the discharge lamp load 3
It can be avoided that the lighting state of the LED flashes.

(Embodiment 4) FIG. 7 shows a circuit of this embodiment. As shown in FIG.
A drive circuit 1 for driving the piezoelectric transformer 2 is connected to an input terminal of the piezoelectric transformer 2 and a discharge lamp load 3 is connected to an output terminal of the piezoelectric transformer 2 as in the cases 2 and 3. The discharge lamp load 3 is further connected to a load current detection circuit 6. The load current detection circuit 6 detects the load current and outputs a voltage signal corresponding to the load current value in the same manner as in the first to third embodiments, and converts the voltage signal into a drive signal such that the load current becomes a predetermined value. And to the frequency control circuit 4. The output terminal of the piezoelectric transformer 2 is connected to an output voltage detection circuit 5. The output voltage detection circuit 5 is also for detecting the output voltage of the piezoelectric transformer 2 as in the first to third embodiments, and transmits a voltage signal corresponding to the output voltage of the piezoelectric transformer 2 to the frequency control circuit 4. I have. The frequency control circuit 4 controls the driving circuit based on the voltage signals of the load current detection circuit 6 and the output voltage detection circuit 5 so that the output voltage of the piezoelectric transformer 2 does not exceed a predetermined voltage and the load current becomes a predetermined value. 1 is adjusted.

The frequency control circuit 4 includes an intermittent light control circuit 1
2 is attached. The intermittent light control circuit 12 is provided with a duty adjustment circuit 9 used in the first embodiment and an intermittent oscillation frequency generation circuit 11 used in the second embodiment, and is a diagram generated by receiving signals from these circuits 9 and 11. The duty control signal V _duty shown in FIG. _8A is _supplied to the frequency control circuit 4. The frequency control circuit 4 outputs the duty control signal V
_In response to the duty, the drive frequency of the drive circuit 1 is adjusted so that the output voltage _Vout of the piezoelectric transformer 2 shown in FIG. 8B becomes a voltage capable of lighting the discharge lamp load 3 during the on-duty period. During the off-duty period, the output voltage V _out of the piezoelectric transformer 2 is the voltage V at which the discharge lamp load 3 is not turned on.
The drive frequency of the drive circuit 1 is adjusted so as to be a.

That is, in the present embodiment, the above-mentioned first to first embodiments
3, the lighting of the discharge lamp load 3 is turned off without turning off the output voltage V _out (lighting power source) from the piezoelectric transformer 2 during the off duty. In other words, even when the lighting is off (the lamp current _Ila shown in FIG. 8C is 0), the output voltage _Vout is applied to the discharge lamp load 3 as the bias voltage Va at which the discharge lamp load 3 does not light. is there.

Since the energy required for starting and lighting the discharge lamp load 3 can be assisted by applying the bias voltage when the lighting is turned off, the starting time tx can be shortened.

FIG. 9 shows the dependency of the starting time tx on the ambient temperature Ta at this time. The ambient temperature dependency of the start time tx is relatively small as compared with the conventional case of FIG. 15, and the change X of the start time tx is very small with respect to the temperature change.

That is, in the present embodiment, the ratio of the average starting time tx to the dimming on-duty time can be made substantially constant even if the ambient temperature Ta changes as shown in FIG. A stable output is obtained by preventing the output from becoming short or fluctuating, and a stable output free from flickering or the like is obtained in the ambient temperature range of -30 ° C. to 80 ° C. of the piezoelectric transformer 2 until low light flux dimming. .

(Embodiment 5) FIG. 10 shows a circuit of this embodiment. In this embodiment, a drive circuit for driving the piezoelectric transformer 2 is provided at the input terminal of the piezoelectric transformer 2 as in the first to fourth embodiments. The discharge lamp load 3 is connected to the output terminal of the piezoelectric transformer 2. The discharge lamp load 3 is further connected to a load current detection circuit 6, and the load current detection circuit 6 transmits a voltage signal for changing the frequency of the load current to a predetermined value to the frequency control circuit 4. The output voltage detection circuit 5 detects the output voltage of the piezoelectric transformer 2 as in the first and second embodiments, and transmits a voltage signal corresponding to the output voltage of the piezoelectric transformer 2 to the frequency control circuit 4. The frequency control circuit 4 controls the driving circuit based on the voltage signals of the load current detection circuit 6 and the output voltage detection circuit 5 so that the output voltage of the piezoelectric transformer 2 does not exceed a predetermined voltage and the load current becomes a predetermined value. 1 is adjusted.

The intermittent oscillation control circuit 7 is similar to the first and second embodiments.
When the dimming mode is selected, the duty control signal V_duty
To drive the drive circuit 1 intermittently by
Intermittent frequency control circuit 11 provided in Embodiment 2 and Embodiment 1
And a duty control circuit 9 provided in the above. this
The duty control circuit 9 calculates the voltage from the load current detection circuit 6
This embodiment is different from the first embodiment in receiving signals.
As shown in FIG._laIs a predetermined time T
Until the duty control signal V shown in FIG. _dutyof
It has a function to extend the on-duty period. That is, start
Even if the time tx changes due to the ambient temperature Ta and increases.
A lamp with a desired dimming amount by extending the on-duty period
The lighting time T is kept constant. FIG. 11B shows a piezoelectric transformer.
Output voltage V_outIs shown.

In this embodiment, the configuration shown in FIG.
Even if the ambient temperature Ta changes, the lighting-on time T can be made substantially constant as shown in FIG. 11, and a stable output can be obtained by preventing the lighting time from being shortened or varied. In the temperature range of −30 ° C. to 80 ° C., a stable output free from flickering or the like is obtained until low light flux control.

[0044]

According to a first aspect of the present invention, in a discharge lamp lighting device including a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, the drive circuit intermittently operates during dimming, Since the frequency of the intermittent drive is reduced in accordance with a decrease in the ambient temperature, the invention according to claim 2 is directed to a discharge lamp lighting device including a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load. And intermittently operating the drive circuit during dimming,
Since the dimming ratio increases as the ambient temperature decreases, even if the ambient temperature changes, the ratio of the average starting time to the dimming on-duty time can be made almost constant, so that the lighting time becomes shorter or fluctuates. , A stable output is obtained, and a stable output free from flickering or the like can be obtained up to the time of low light flux dimming in the operating ambient temperature range of the piezoelectric transformer.

According to a third aspect of the present invention, in a discharge lamp lighting device including a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, the drive circuit is operated intermittently at the time of dimming. The driving frequency is reduced in accordance with a decrease in the ambient temperature, and if the frequency is to be reduced to less than 100 Hz, the frequency is maintained at 100 Hz or 100 Hz.
Hz, and the dimming ratio is increased, so that even if the ambient temperature changes, the ratio of the average starting time to the dimming on-duty time can be made almost constant, so that the lighting time is shortened or varied. A stable output can be obtained by preventing this, and a stable output without flickering etc. can be obtained until the low luminous flux dimming in the operating ambient temperature range of the piezoelectric transformer. There is an effect that the lighting does not flicker.

According to a fourth aspect of the present invention, in a discharge lamp lighting device comprising a piezoelectric transformer, a driving circuit for driving the piezoelectric transformer, and a discharge lamp load, the output voltage of the piezoelectric transformer starts the discharge lamp load during dimming. A driving circuit that alternately repeats a period in which the piezoelectric transformer is driven so that the voltage can be turned on, and a period in which the piezoelectric transformer is driven so that the output voltage of the piezoelectric transformer is lower than the lighting voltage of the discharge lamp load. Intermittently operates, so that a bias voltage can be applied to the discharge lamp load when the lamp is turned off to assist the energy required for starting the lamp, so that the starting time can be shortened.
As a result, even if the ambient temperature changes, the ratio of the average starting time to the dimming on-duty time can be made almost constant,
As a result, a stable output can be obtained by preventing the lighting time from becoming short or fluctuating, and a stable output without flickering can be obtained until low light flux dimming in the operating temperature range of the piezoelectric transformer. There is.

According to a fifth aspect of the present invention, in a discharge lamp lighting device comprising a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, the drive circuit is operated intermittently at the time of dimming, and the discharge lamp load is reduced. The on-duty period during which the drive circuit operates so that the lighting-on time of the lamp is constant is changed, so that the ratio of the average start-up time to the dimming on-duty time can be made almost constant, so that the lighting time is shortened or varies. Thus, there is an effect that a stable output without flickering can be obtained in the ambient temperature range of the piezoelectric transformer until the low light flux dimming.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the piezoelectric transformer has an output voltage limiting function, so that the piezoelectric transformer does not output an excessive voltage, and It can be prevented from being damaged by an excessive voltage output.

According to a seventh aspect of the present invention, in any one of the first to fifth aspects of the present invention, since the discharge lamp load is a cold cathode lamp, a lighting device for a cold cathode lamp having each of the above effects can be realized.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a relationship between an intermittent frequency and an ambient temperature.

FIG. 3 is a circuit configuration diagram according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a dimming ratio and an ambient temperature according to the first embodiment.

FIG. 5 is a circuit configuration diagram according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between an intermittent frequency and an ambient temperature.

FIG. 7 is a circuit configuration diagram according to a fourth embodiment of the present invention.

FIG. 8 is a waveform diagram for explaining the operation of the above.

FIG. 9 is an explanatory diagram showing a relationship between a starting time and an ambient temperature according to the first embodiment.

FIG. 10 is a circuit configuration diagram according to a fourth embodiment of the present invention.

FIG. 11 is a waveform chart for explaining the operation of the above.

FIG. 12 is a circuit configuration diagram of a conventional example.

FIG. 13 is a waveform diagram for explaining the operation of the above.

FIG. 14 is a waveform chart for explaining the operation of the above.

FIG. 15 is an explanatory diagram showing a relationship between a starting time and an ambient temperature according to the first embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drive circuit 2 piezoelectric transformer 3 discharge lamp load 4 frequency control circuit 5 output voltage detection circuit 6 load current detection circuit 7 intermittent oscillation control circuit 8 temperature-dependent intermittent oscillation frequency control circuit 9 duty adjustment circuit

Claims (7)

[Claims] 1. A discharge lamp lighting device comprising a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, wherein the drive circuit is operated intermittently at the time of dimming, and the frequency of the intermittent drive is set to A discharge lamp lighting device characterized in that the temperature is decreased in accordance with a decrease in temperature. 2. A discharge lamp lighting device comprising a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, wherein the drive circuit is operated intermittently at the time of dimming, and in response to a decrease in ambient temperature. A discharge lamp lighting device characterized by increasing a dimming ratio. 3. A discharge lamp lighting device comprising a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, wherein the drive circuit is operated intermittently at the time of dimming, and the frequency of the intermittent drive is set to If the frequency is to be reduced to less than 100 Hz, the frequency is decreased in accordance with the decrease in temperature.
A discharge lamp lighting device characterized by maintaining 0 Hz or increasing it above 100 Hz and increasing the dimming ratio. 4. A discharge lamp lighting device comprising a piezoelectric transformer, a driving circuit for driving the piezoelectric transformer, and a discharge lamp load, wherein the output voltage of the piezoelectric transformer starts the discharge lamp load during dimming.
The drive circuit is configured to alternately repeat a period during which the piezoelectric transformer is driven to achieve a lighting voltage and a period during which the piezoelectric transformer is driven such that the output voltage of the piezoelectric transformer is lower than the lighting voltage of the discharge lamp load. A discharge lamp lighting device characterized by intermittent operation. 5. A discharge lamp lighting device comprising a piezoelectric transformer, a drive circuit for driving the piezoelectric transformer, and a discharge lamp load, wherein the drive circuit is operated intermittently at the time of dimming, and the lighting ON time of the discharge lamp load. A discharge lamp lighting device characterized by changing an on-duty period during which a drive circuit operates so as to be constant. 6. The discharge lamp lighting device according to claim 1, further comprising an output voltage limiting function of the piezoelectric transformer. 7. The discharge lamp lighting device according to claim 1, wherein the discharge lamp load is a cold cathode lamp.