JP2001118693A - Lighting apparatus of discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting apparatus of discharge lamp which reduces higher harmonics of power source at low cost. SOLUTION: The lighting apparatus is constructed by rectifying circuit which full-wave rectifies the alternating current of commercial power source, and a means of first and second switchings which are serially connected with each other and convert the voltage of alternating current from rectifying circuit to high frequency voltage by mutual on-off action, and driver which drives the means of switching, and the discharge lamp, and first capacitor which is serially connected to above discharge lamp, and serial circuit of second and third capacitors which is connected in parallel to serial circuit of the means of first and second switchings, and transformer which is constructed by two windings, of which one end and magnetic circuit are owned in common, and the common end of winding is connected to the connecting point of the means of first and second switchings, and a means of control which make the driving frequency of above means of first and second switchings alter synchronously with the voltage of alternating current.

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 converting a commercial AC power supply into a DC voltage and switching the DC voltage by turning ON / OFF a switching means to supply a high frequency power to the discharge lamp. Input current distortion,
That is, the present invention relates to a discharge lamp lighting device that reduces power supply harmonics.

[0002]

2. Description of the Related Art FIG. 13 is a circuit diagram of a conventional discharge lamp lighting device disclosed in Japanese Patent Application Laid-Open No. 2-75200. In the figure, a DC voltage obtained by rectification by a rectifier circuit 3 from a commercial power supply 1 via a noise filter 2 is applied to first and second switching means 4 and 5 connected in series. The switching means 4 and 5 are composed of transistors 6 and 7 and regenerative diodes 8 and 9, respectively. The diodes 8 and 9 are connected in anti-parallel to the transistors 6 and 7, respectively. The switching means 4 and 5 convert a DC voltage into a high-frequency AC voltage. Transistors 6, 7
A driver 10 is connected to and drives the transistors 6 and 7 so as to be turned ON / OFF alternately. A load circuit 11 is connected from a connection point between the switching means 4 and 5.
The load circuit 11 has a configuration in which a discharge lamp (hereinafter, referred to as a lamp 13) is connected in series to a coil 12, and a capacitor 14 is connected to the lamp 13 in parallel. The capacitor 14 is provided for preheating the electrodes of the lamp 13, and the coil 12 is provided for limiting the current flowing through the lamp 13. The other end of the load circuit 11 is a capacitor 15,
It is connected to the connection points of 16 series circuits. A diode 17 is connected in parallel to the capacitor 16, and both ends of a series circuit of the capacitors 15 and 16 are connected to switching means 4, 5
Is connected to the rectifier circuit 3 as in the series circuit of FIG. The capacitor 15 operates to smooth the AC voltage from the commercial power supply 1 by making the capacity relatively large as compared with the capacitor 16. The capacitor 16 is connected to the switching means 4,
5 is selected so that complete charging and discharging can be performed in synchronization with the switching frequency of 5.

The operation of the conventional circuit will be described with reference to FIG. First, the transistor 6 is turned on. During the ON period, a current flows through the coil 12 and the lamp 13 via the transistor 6 by the output from the rectifier circuit 3 and the capacitor 15 is charged. Next, the transistor 6 is turned off.
When the transistor 7 is turned on, the charge of the capacitor 15 is discharged through the lamp 13, the coil 12, and the transistor 7. Thereafter, when the transistor 7 is turned off and the transistor 6 is turned on again, the coil 12
The energy stored in the capacitor 16 charges the capacitor 16.

Accordingly, the coil 12 and the capacitor 16 form a voltage resonance circuit. This allows the capacitor 16
Even when the potential of the capacitor 15 and the potential of the capacitor 15 are lower than the output voltage of the rectifier circuit 3, the current continues to flow over the entire phase of the commercial power supply 1. The resulting input current and lamp current waveforms are as shown in FIGS. 14 (a) and (b), respectively.

[0005]

However, in the prior art, the resonance circuit composed of the coil 12 and the capacitor 16 is damped by the discharge resistance of the lamp 13, and as a result, the resonance voltage cannot be increased. An input current waveform close to a wave cannot be obtained, and particularly, a current cannot flow near the zero voltage phase of the commercial power supply 1, and there is a problem that the harmonic reduction performance is not good. Further, the distortion of the input current waveform causes a problem that the lamp current waveform also has a large ripple and the luminous efficiency decreases.

Accordingly, an object of the present invention is to provide a discharge lamp lighting device in which input current distortion, that is, power supply harmonics is reduced by a simple method and ripples in a lamp current waveform are suppressed.

[0007]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device comprising: a rectifier circuit for full-wave rectifying an AC voltage from a commercial power supply;
First and second switching means for turning off the DC voltage from the rectifier circuit to a high-frequency voltage, a driver for driving the switching means, a discharge lamp, a first capacitor connected in series to the discharge lamp, Second and third parallel-connected series circuits of the first and second switching means;
, And a winding having two ends sharing a magnetic circuit with one end. The common end of the winding is connected to the connection point of the first and second switching means, and the first other end is open. A second end is connected in series to an electric lamp, and a second end is connected to a connection point of the second and third capacitor series circuits, and a drive frequency of the first and second switching means is synchronized with the AC voltage. Control means for changing the temperature.

According to a second aspect of the present invention, in the discharge lamp lighting device according to the first aspect, a relatively high frequency is used in a period near the peak or zero point of the output of the rectifier circuit, and a relatively high frequency is used in other periods. Very low frequency,
A control means for driving the first and second switching means is provided.

According to a third aspect of the present invention, in the discharge lamp lighting device according to the first or second aspect, the output of the rectifier circuit is subjected to arithmetic processing such as addition and subtraction with a DC voltage, discrimination, and amplification. A circuit that forms a voltage signal that synchronizes near the peak and zero point of the output of the rectifier circuit and changes the voltage only when synchronized, and uses the voltage signal as an input signal to respond to an increase or decrease in the amount of change in the input signal And a conversion circuit having a frequency output for monotonically increasing and decreasing the frequency.

According to a fourth aspect of the present invention, in the discharge lamp lighting device according to the first aspect of the present invention, there is provided a feedback circuit for detecting a load current of the first or second switching means and feeding it back to the control means. In addition, a synchronous signal synchronized near the peak or zero point of the output of the rectifier circuit is superimposed on the feedback signal from the feedback circuit.

According to a fifth aspect of the present invention, in the discharge lamp lighting device according to the first aspect, a feedback circuit for detecting a load current of the first or second switching means and feeding back the load current to the control means is provided. The target value of the feedback circuit is a synchronization signal that is synchronized near the peak or zero point of the output of the rectifier circuit.

According to a seventh aspect of the present invention, in the discharge lamp lighting apparatus according to the fourth aspect, the synchronous signal is subjected to arithmetic processing such as addition and subtraction with a DC voltage to the output of the rectifier circuit, discrimination, amplification, and the like. It has a frequency output that forms such that the voltage changes only when synchronized and superimposes the synchronization signal on the feedback signal, and monotonically increases or decreases the frequency in response to an increase or decrease in the amount of change in the input signal. Input to the conversion circuit
The output signal of the conversion circuit is used as the input signal of the driver.

The discharge lamp lighting device according to claim 8 of the present invention is the discharge lamp lighting device according to claims 5 and 6, wherein
The output of the rectifier circuit is subjected to arithmetic processing such as addition and subtraction with DC voltage, discrimination, amplification, etc., so that the voltage changes only when synchronized, and the feedback signal of the feedback circuit with the synchronization signal as the target value is input signal. Is input to a conversion circuit having a frequency output that monotonically increases or decreases the frequency in response to an increase or decrease in the amount of change of the input signal, and an output signal of the conversion circuit is used as an input signal of the driver.

[0014]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention. The circuit related to high voltage generation (hereinafter referred to as a high voltage section 19). ) And other circuits. The same or corresponding parts as in the conventional example are denoted by the same reference numerals, description thereof will be omitted, and different configurations will be described.

First, the high pressure section 19 will be described. 2 in the figure
Reference numeral 0 denotes a transformer composed of a primary coil 20a and a secondary coil 20b that are electrically and magnetically coupled, 21 denotes a DC cut capacitor connected in series with the secondary coil 20b of the transformer 20, and 22 denotes a rectifier circuit 3. Is a high-speed rectifier connected to the output. In the transformer 20, the primary coil 20a has one end connected to the output point of the switching means 4 and 5, and the other end connected to the connection point between the first capacitor 15 and the second capacitor 16. The secondary coil 20b has one end connected to the lamp 13 via the DC cut capacitor 21 and the other end connected to the output points of the first and second switching means 4, 5. In order to smooth the output of the rectifier element 22, the capacity of the first capacitor 15 is selected to be relatively larger than the capacity of the second capacitor 16. In addition, the second capacitor 16 is selected so that complete charging / discharging can be performed in synchronization with the driving frequency of the first and second switching means 4, 5.

Circuits other than the high voltage section 19 include a voltage dividing circuit 23 connected to the output of the rectifier circuit 3 and a voltage dividing circuit 23.
And a VCO circuit 25 that drives the driver 10 based on the output of the modulation signal generation circuit 24. The modulation signal generation circuit 24 includes three operational amplifiers 24a, 24b, and 24c. The VCO circuit 25 converts an input voltage into an output having a frequency, and has a characteristic that the output frequency monotonically increases or decreases with an increase or decrease of the input voltage.

The operation of the discharge lamp lighting device according to the first embodiment of the present invention will be described with reference to FIGS. First, FIG.
Will be described. FIG. 2A shows an output waveform of the rectifier circuit 3 or a voltage divider circuit 23 obtained by dividing the rectifier circuit 3. FIGS. 2B and 2C respectively show first and second operational amplifiers 24a,
24B shows the output voltage waveform from 24b. The former clips the vicinity of the peak of the output voltage waveform of the voltage dividing circuit 23, and the latter clips the vicinity of the zero point of the output voltage waveform of the voltage dividing circuit 23 and inverts it. It has a wavy shape. FIG.
(D) shows an output voltage waveform of the operational amplifier 24c obtained by adding the DC voltage and the output voltages of the first and second operational amplifiers 24a and 24b. FIG. 2E shows the driving frequency of the switching means 4 and 5 obtained through the driver 10 by frequency-converting the output voltage of the operational amplifier 24c by the VCO circuit 25.
(F) and (g) show the input current waveform and the lamp current waveform, respectively.

Next, the operation of the discharge lamp lighting device according to the first embodiment of the present invention will be described with reference to FIG. First, when the first switching means 4 is turned on, the first capacitor 1
5 is discharged, and a current flows through the loop of the first capacitor 15, the first switching means 4, and the primary coil 20a.

Next, when the first switching means 4 is turned off, series resonance occurs in the primary coil 20a and the second capacitor 16, and a resonance current flows. Then, when the second switching means 5 is turned on and the resonance current is reversed, 1
A current flows through a loop of the next coil 20a, the second switching means 5, and the second capacitor 16.

Thereafter, when the resonance voltage decreases and the voltages of the second and first capacitors 16 and 15 both decrease, the rectifying element 22 is turned on to supply a pulsating flow, and the rectifying circuit 3, the rectifying element 22, 1 capacitor 15, primary coil 20
a, A current flows in the loop of the second switching means 5.

When this series of operations is completed, the first switching means 4 is turned on again, and the same operation is repeated. On the other hand, in this series of operations, the primary coil 20a
The energy obtained by transmitting the energy stored in the secondary coil 20b and the energy obtained directly from the first and second switching means 4, 5 are extracted.
Resonance is caused by the secondary coil 20b and the DC cut capacitor 21, and the lamp 13 is discharged.

At this time, when the switching means 4 and 5 are driven at a fixed frequency, the input current waveform and the lamp current waveform are as shown in FIGS. 3A and 3B, respectively. It is considerably improved. However,
In this case, since the switching means is driven at a constant frequency while a current flows through the lamp 13 at a predetermined crest factor, the rectifying circuit 3 and the rectifying element 22 are turned on while the first switching means 4 is ON. A large current flows through the path of the first switching means 4, the primary coil 20a, and the second capacitor 16, and the input current tends to have a spire waveform near the peak. There is a problem in that the input current distortion does not reduce the power supply harmonics, especially the third-order component. For the same reason, too much current flows in the same path near the zero point of the input current, and the input current sharply changes the polarity near the zero point.
There is a problem that the next component is deteriorated.

On the other hand, in the first embodiment of the present invention, the frequency for driving the switching means 4 and 5 is not fixed, but is based on the output from the modulation signal generating circuit 24. That is, in the drawing, the full-wave rectified voltage divided by the voltage dividing circuit 23 is inputted to the modulation signal generating circuit 24 and inputted to the operational amplifiers 24a and 24b, respectively. Operational amplifier 24
In FIG. 2A, a direct current is input to a negative input, a full-wave rectified voltage divided by a voltage dividing circuit 23 is input to a positive input, and an appropriate gain is selected to obtain a waveform near a peak as shown in FIG. Can be obtained. On the other hand, in the operational amplifier 24b, DC is input to the + input, and the voltage dividing circuit 2 is applied to the-input.
By inputting the full-wave rectified voltage divided in step 3, the waveform near the zero point as shown in FIG.
An inverted output waveform can be obtained. In the operational amplifier 24c, an output of the operational amplifier 24a, an output of the operational amplifier 24b, and a DC voltage adding circuit are formed, and an output waveform as shown in FIG. 2D can be obtained. This waveform is a waveform in which the voltage peak appears at the timing near the peak of the full-wave rectified voltage and the zero point, and when this is input to the VCO circuit 25, the modulation frequency shown in FIG.

Therefore, when the switching means 4 and 5 are driven by this modulation frequency, the driving frequency becomes high near the peak of the input current due to the modulation signal generated by the operational amplifier 24a, and the lamp 1 is transmitted through the transformer 20.
3 can be suppressed. This makes it possible to suppress spikes near the peak of the input current and greatly reduce the third-order component of power supply harmonics. In addition, the frequency near the zero point of the input current increases due to the modulation signal generated by the operational amplifier 24b, and the current flowing into the lamp 13 via the transformer 20 can be suppressed. Therefore, a sharp change in the input current near the zero point can be suppressed, and higher-order components of power supply harmonics can be reduced. As described above, the spike at the peak and the steepness at the zero point can be suppressed, and the input current waveform and the lamp current are as shown in FIGS. 2F and 2G, respectively.

Further, by changing the voltages V1, V2 and V3 and the gains of the operational amplifiers 24a and 24b, the amplitude and the period of the modulation waveform can be freely created. If necessary, the gain of the operational amplifier 24a or 24b can be reduced to zero. As a result, the effect can be eliminated.

Second Embodiment FIG. 4 shows a second embodiment of the present invention. In the figure, the same parts as in the first embodiment are omitted, and different modulation signal generation circuit parts are extracted and described. FIG. 5 shows a waveform diagram of the second embodiment, and FIG. 5A shows an output waveform of the rectifier circuit 3. The modulation signal generation circuit 26 includes two operational amplifiers 26a and 26b each operating as a comparator for discriminating the magnitude of an input signal with respect to a reference voltage, and an OR circuit 26c including three diodes.

In the operational amplifier 26a, by inputting a predetermined voltage to the-input and a full-wave rectified voltage divided by the voltage dividing circuit 23 to the + input, a full-wave rectified voltage as shown in FIG. Thus, an output waveform of a rectangular pulse train rising at a timing near the peak is obtained. In the operational amplifier 26b,
By inputting a predetermined voltage to the + input and a full-wave rectified voltage divided by the voltage dividing circuit 23 to the-input, at a timing near the zero point of the full-wave rectified voltage as shown in FIG. An output waveform of a rising rectangular pulse train is obtained. The output terminals are pulled up with appropriate voltages V6 and V7 so that the outputs of the operational amplifiers 26a and 26b become appropriate voltages, respectively, and are used as the outputs of the comparators.

The outputs of the operational amplifiers 26a and 26b and the DC voltage V7 are input to the OR circuit 26c, and the output of the OR circuit 26c shown in FIG. 5D is output from the modulation signal generation circuit 26 and input to the VCO circuit 25. Therefore, the output of the VCO circuit 25 becomes a signal in which the frequency peak appears at the timing near the peak of the full-wave rectified voltage and the zero point, and the switching means 4 and 5 are driven by the modulation frequency as shown in FIG. Will be.

Since the frequency increases near the peak of the input current due to the modulation signal generated by the operational amplifier 26a, the current flowing into the lamp 13 via the transformer 20 can be suppressed, and the spike near the peak is suppressed. That is, the third order component of the power supply harmonic can be greatly reduced. In addition, since the frequency increases near the zero point of the input current due to the modulation signal generated by the operational amplifier 26b, the current flowing into the lamp 13 via the transformer 20 can be suppressed, and the input current near the zero point sharply increases. Such changes can be suppressed, and higher-order components of power supply harmonics can be reduced. Therefore, the input current waveform and the lamp current are as shown in FIGS. 5 (f) and 5 (g), respectively.

Further, the voltage V4, V5, V6, V7 or V
8, the amplitude and the period of the modulation waveform can be freely created. If necessary, V6 or V7 can be set to 0.
As a result, the effect can be eliminated.

Third Embodiment FIG. 6 shows a third embodiment of the present invention. In the figure,
The description of the same parts as in the first embodiment will be omitted, and different parts will be described. 27 is a load current detecting resistor connecting the switching means 5 to the ground (ground), 28 is a low-pass filter for cutting the high frequency component of the signal from the load current detecting resistor, and 29 is an inverting amplifier using the output of the low-pass filter 28 as a negative input. The circuit 30 is an error amplifier which receives the output of the inverting amplifier circuit 29 as a negative input. Reference numeral 31 denotes a modulation signal generation circuit according to the third embodiment.
a, 31b and 31c, and 31a and 31b are operational amplifiers 24a and 24b according to the first embodiment, respectively.
Works the same as b.

In the figure, the output of the error amplifier 30 is used as the + input of the operational amplifier 31c in the modulation signal generating circuit 31, and the output obtained by adding the output of the operational amplifiers 31a and 31b is used as the input of the VCO circuit 25. This is a modulation signal based on a full-wave rectified voltage in a load current feedback path system for returning a current signal flowing through the switching means 5 to the operational amplifier 31 for driving the driver 10 again through the low-pass filter 28, the inverting amplifier circuit 29, and the error amplifier 30. Is superimposed on the feedback signal.

Therefore, the driving is performed while the driving frequency determined by the load current feedback and the driving frequency determined by the modulation interact with each other. The strong relationship between the influence of the feedback and the modulation is determined by the error amplifier 30
By selecting an appropriate gain, it is possible to control to reduce power supply harmonics while keeping the load current constant.

As a specific example of the modulation signal generation circuit,
If the same one as described in the first embodiment is adopted,
FIG. 7A shows the output waveform of the rectifier circuit 3.
7 (b), and the input of the VCO circuit 25 becomes as shown in FIG. 7 (c). Thereby, the frequency increases near the peak of the input current due to the modulation signal generated by the operational amplifier 31a, so that the current flowing into the lamp 13 via the transformer 20 can be suppressed.
Therefore, the spike near the peak of the input current can be suppressed, and the third-order component of the power supply harmonic can be greatly reduced. Further, since the frequency increases near the zero point of the input current due to the modulation signal generated by the operational amplifier 31b, the current flowing into the lamp 13 via the transformer 20 is suppressed, and the input current near the zero point sharply increases. Such changes can be suppressed, and higher-order components of power supply harmonics can be reduced. Accordingly, the input current waveform and the lamp current output waveform have shapes substantially matching those of FIGS. 2 (f) and 2 (g) of the first embodiment.

As described in the first embodiment, by changing the voltage V1, V2 or V3 or the gain of the operational amplifiers 31a, 31b and 31c, the amplitude and period of the modulation waveform can be freely created.

Fourth Embodiment FIG. 8 shows a fourth embodiment of the present invention. In the figure,
The same parts as in the third embodiment will be omitted, and different parts will be described. 8, the output of the modulation signal generation circuit 31 is input as the + input of the error amplifier 30, that is, the target value, and the output of the error amplifier 30 is not input to the operational amplifier 31c but is input to the VCO circuit 25.

Therefore, the driving is performed while the driving frequency determined by the load current feedback and the driving frequency determined by the modulation affect each other. The strength of the influence of feedback and modulation is determined by the magnitude of the gain of the error amplifier 30. By selecting an appropriate gain, it is possible to control to reduce power supply harmonics while keeping the load current constant. Is the same as in the third embodiment.

As a specific example of the modulation signal generation circuit,
When the same configuration as that described in the first embodiment is employed, the waveform diagram thereof substantially matches FIG. 7 of the third embodiment. Since the frequency increases near the peak of the input current due to the modulation signal generated by the operational amplifier 31a, the current flowing into the lamp 13 via the transformer 20 is suppressed, and the spike near the peak of the input current is suppressed. And the modulation signal generated by the operational amplifier 31b increases the frequency near the zero point of the input current, thereby suppressing the current flowing into the lamp 13 via the transformer 20 and suppressing the sharp change in the input current near the zero point. What can be done is the same as the embodiment described so far. Therefore, the input current waveform and the lamp current output waveform are the same as those in FIG.
(F) and (g) substantially coincide with each other.

Further, by changing the voltage V1, V2 or V3 or the gain of the operational amplifiers 31a, 31b and 31c, the amplitude and the period of the modulation waveform can be freely created. If necessary, the gain of the operational amplifier 31a or 31b can be changed. Can be set to 0 to eliminate that effect.

Fifth Embodiment FIG. 9 is a diagram showing a fifth embodiment of the present invention.
FIG. 10 is a waveform diagram. The modulation waveform generation circuit 32 includes three operational amplifiers 32a, 32b, and 32c. The operational amplifiers 32a and 32c have the same function as the operational amplifiers 24a and 24c in the first embodiment, and the operational amplifier 32b has a comparator 26a in the second embodiment.
Works the same as b. Thereby, the modulation signal generation circuit 3
2 is different from the output of the rectifier circuit 3 in FIG.
As shown in FIG. 10B, the switching means 4 and 5 are driven accordingly. Further, as in the third or fourth embodiment, it may be used in combination with the feedback of the load current.

Sixth Embodiment FIG. 11 is a diagram showing a sixth embodiment of the present invention, and FIG. 12 is a waveform diagram thereof. Modulation waveform generation circuit 33
Is composed of three operational amplifiers 33a, 33b and 33c. The operational amplifiers 33b and 33c operate in the same manner as the operational amplifiers 24b and 24c in the first embodiment.
The operational amplifier 33a has the same function as the comparator 26a in the second embodiment. Thus, the output of the modulation signal generating circuit 33 becomes as shown in FIG. 12B with respect to the output of the rectifying circuit 3 shown in FIG. 12A, and the switching means 4 and 5 are driven accordingly. Further, as in the third or fourth embodiment, it may be used in combination with the feedback of the load current.

Seventh Embodiment In the third and fourth embodiments, the modulation waveform may be a waveform as employed in the second, fifth or sixth embodiment.

[0043]

According to the first aspect of the present invention, the drive frequency of the switching means can be changed in synchronization with the AC voltage from the commercial power supply, so that each harmonic of the power supply can be reduced.

According to the second aspect of the present invention, the drive frequency of the switching means is increased in a period near the peak and zero point of the input current. Wave components can be reduced, and a sharp change in polarity near the zero point can be suppressed, and higher-order harmonic components can be reduced.

According to the third aspect of the present invention, since the signal of the drive frequency change is generated by performing a simple arithmetic processing on the output of the rectifier circuit, the power supply harmonics can be reduced with a simple circuit.

According to the fourth and fifth aspects of the present invention, the power supply harmonics are suppressed and the balance of the entire input current waveform is maintained while maintaining a constant load current by combining the signals of the load current feedback circuit and the modulation signal generation circuit. Can be.

According to the sixth and seventh aspects of the present invention, the drive frequency change signal is generated by performing a simple arithmetic processing on the output of the rectifier circuit. The balance of the entire input current waveform can be maintained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a waveform chart showing voltage, current, and frequency signals at each part of the discharge lamp lighting device.

FIG. 3 is a waveform diagram showing an input current and a lamp current when the switching means is driven at a fixed frequency in the discharge lamp lighting device.

FIG. 4 is a circuit diagram of a modulation signal generation circuit of the discharge lamp lighting device according to the second embodiment of the present invention.

FIG. 5 is a waveform diagram showing a voltage, a current, and a frequency signal in each part of the discharge lamp lighting device.

FIG. 6 is a circuit diagram of a discharge lamp lighting device according to Embodiment 3 of the present invention.

FIG. 7 is a waveform diagram showing a voltage signal at each part of the discharge lamp lighting device.

FIG. 8 is a circuit diagram showing a load current feedback path and a modulation signal generation circuit of a discharge lamp lighting device according to Embodiment 4 of the present invention.

FIG. 9 is a circuit diagram of a modulation signal generation circuit of a discharge lamp lighting device according to Embodiment 5 of the present invention.

FIG. 10 is a waveform chart showing voltage signals at respective parts of the discharge lamp lighting device.

FIG. 11 is a circuit diagram of a modulation signal generation circuit of a discharge lamp lighting device according to Embodiment 6 of the present invention.

FIG. 12 is a waveform chart showing voltage signals at each part of the discharge lamp lighting device.

FIG. 13 is a circuit diagram of a conventional discharge lamp lighting device.

FIG. 14 shows an input current in a conventional example of the discharge lamp lighting device,
FIG. 4 is a waveform diagram showing a lamp current.

[Explanation of symbols]

1 commercial power supply, 2 noise filter, 3 rectifier circuit, 4 first switching device, 5 second switching device, 6,7 transistor, 8,9 diode, 10 driver, 11 load circuit,
12 coils, 13 lamps (discharge lamps), 14, 15,
16 capacitor, 17 diode, 18 capacitor, 19 high voltage section, 20 transformer, 20a 1
Secondary coil, 20b secondary coil, 21 DC cut capacitor, 22 rectifier, 23 voltage divider,
24 Modulation signal generation circuit, 24a, 24b, 24c
Operational amplifier, 25 VCO circuit, 26 modulation signal generation circuit, 26a, 26b operational amplifier (comparator), 26c OR circuit, 27 load current detection resistor, 28 low-pass filter, 29 inverting amplifier circuit, 30 error amplifier, 31 modulation signal generation circuit,
31a, 31b, 31c operational amplifier, 32 modulation signal generation circuit, 32a, 32b, 32c operational amplifier,
33 modulation signal generation circuit, 33a, 33b, 33c
Operational amplifier

Continued on the front page (72) Inventor Kenichiro Nishi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Kentaro Eguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. Company F term (reference) 3K072 AA02 BA03 BB01 BC01 BC03 BC07 CA14 DB03 DD04 EB06 GA02 GB12 GC04 HB03

Claims (7)

[Claims] 1. A rectifier circuit for full-wave rectification of an AC voltage from a commercial power supply, and first and second switching means connected in series and alternately turned ON / OFF to convert a DC voltage from the rectifier circuit to a high-frequency voltage. A driver for driving the switching means, a discharge lamp, a first capacitor connected in series to the discharge lamp, and a second and a second capacitor connected in parallel to a series circuit of the first and second switching means. And a series circuit of three capacitors and two windings sharing one end and a magnetic circuit, and a common end of the winding is connected to a connection point of the first and second switching means.
Is connected in series to the discharge lamp, and the second other end is connected to the second
And a transformer connected to a connection point of the third capacitor series circuit, and control means for changing a drive frequency of the first and second switching means in synchronization with the AC voltage. Lighting device. 2. The method according to claim 1, wherein the first and second frequencies are relatively high in a period near the peak or zero point of the output of the rectifier circuit, and relatively low in other periods.
2. The discharge lamp lighting device according to claim 1, further comprising control means for driving said switching means. 3. An output from the rectifier circuit is subjected to arithmetic processing such as addition and subtraction with a DC voltage, discrimination, amplification, etc., so that the output of the rectifier circuit is synchronized near a peak or near a zero point,
It has a circuit that forms a voltage signal whose voltage changes only when synchronized, and a frequency output that takes the voltage signal as an input signal and monotonically increases or decreases the frequency in response to an increase or decrease in the amount of change in the input signal. 3. The discharge lamp lighting device according to claim 1, wherein said control means comprises a conversion circuit. 4. A feedback circuit for detecting a load current of said first or second switching means and feeding it back to said control means, wherein a feedback signal from said feedback circuit outputs a peak or zero of the output of said rectifier circuit. 3. The discharge lamp lighting device according to claim 1, wherein a synchronization signal synchronized near the point is superimposed. 5. A feedback circuit for detecting a load current of said first or second switching means and feeding it back to said control means, wherein a target value of said feedback circuit is set near a peak or a zero point of an output of said rectifier circuit. The discharge lamp lighting device according to claim 1 or 2, wherein the synchronization signal is a synchronized signal. 6. The synchronizing signal is subjected to arithmetic processing such as addition and subtraction with a DC voltage, discrimination, and amplification with respect to an output of the rectifier circuit, so that the voltage is changed only when synchronized, and the synchronizing signal is generated. The signal superimposed on the feedback signal monotonically increases in frequency in response to the
5. The discharge lamp lighting device according to claim 4, wherein the signal is input to a conversion circuit having a frequency output to be reduced, and an output signal of the conversion circuit is used as an input signal of the driver. 7. The synchronizing signal is formed such that the voltage is changed only when the synchronizing signal is synchronized by performing arithmetic processing such as addition and subtraction, discrimination, and amplification with respect to a DC voltage to the output of the rectifier circuit. The feedback signal of the feedback circuit having a value is input to a conversion circuit having a frequency output for monotonically increasing / decreasing the frequency in response to an increase / decrease in the amount of change in the input signal,
6. The discharge lamp lighting device according to claim 5, wherein an output signal of the conversion circuit is used as an input signal of the driver.