JP2920957B2 - Discharge lamp lighting device - Google Patents

Description

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

[Conventional technology]

FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device disclosed in Japanese Patent Application Laid-Open No. 64-34178, for example.

In FIG. 1, reference numeral 1 denotes an AC power supply. An AC current from the AC power supply 1 is supplied to full-wave rectifier circuits 3 and 4 via a filter circuit 2, where it is converted into a DC current. A polarity inversion type chopper circuit 5 is connected to an output terminal of the rectifier circuit 3.
Is connected to an output terminal of the transistor 6 via a collector and an emitter of a transistor 6 serving as a switching element. A smoothing capacitor 9 is connected to both ends of the inductance element 7 via a diode 8, and an input terminal of a single-type inverter circuit 11 is connected to both ends of the capacitor 9 via a diode 10.
The input terminal of the inverter circuit 11 is connected to a series circuit of the output terminal of the full-wave rectifier circuit 4 and the capacitor 9. Reference numeral 12 denotes a high-frequency bypass capacitor, which is connected to an input terminal of the inverter circuit 11. A switching control circuit 13 has one output terminal connected to the base of the transistor 14 which is a switching element in the inverter circuit 1 and the other output terminal connected to the base of the transistor 6 in the chopper circuit 5. A parallel resonance circuit of an inductance element 15 and a capacitor 16 is connected to the input terminal of the inverter circuit 11 via the collector and the emitter of the transistor 14, and a diode 17 is connected in anti-parallel between the collector and the emitter of the transistor 14. Have been. A discharge lamp 20 is connected to both ends of the parallel resonance circuit of the inverter circuit 11 via a series circuit of a current limiting inductance element 18 and a coupling capacitor 19. Also discharge lamp
Capacitors 21 are connected in parallel to both ends of 20.

6 is an operation waveform diagram of the circuit of FIG. 1, (a) is an input current waveform of the inverter circuit 11, (b) is an input current waveform of the chopper circuit 5, and (c) is the above (a), ( (b) shows the combined current waveform of each input current, and (d) shows the ON (ON) and OFF (OFF) control signal waveforms for the transistor 14 of the switching control circuit 13, respectively.

Next, the operation of the discharge lamp lighting device of FIG. 5 will be described with reference to the waveform diagram of FIG. First, the case where the switching control circuit 13 outputs an ON signal to the base of the transistor 6 in the chopper circuit 5 and outputs an OFF signal to the base of the transistor 14 in the inverter circuit 11 will be described. In this case, only the transistor 6 is turned on, and a current flows from the AC power supply 1 to the inductance element 7 via the filter circuit 2, the full-wave rectifier circuit 3, and the collector and emitter of the transistor 6.

This current increases with a gradient proportional to the output voltage of the full-wave rectifier circuit 3 as shown in FIG. Next, the output of the switching control circuit 13 is inverted and the transistor 6
The case where an off signal is output to the base of the transistor 14 and an on signal is output to the base of the transistor 14 will be described. In this case, the transistor 6 is turned off, and the chopper circuit 5
No current flows into the inductance element 7 inside, but since the inductance element 7 has energy accumulated up to that time, a voltage is generated at both ends of the inductance element 7 via the diode 8. Current flows through the capacitor 9 to charge the capacitor 9. On the other hand, when the transistor 14 is turned on,
A parallel resonance circuit including an inductance element 15 and a capacitor 16 in the inverter circuit 11 and a discharge lamp are generated by a voltage obtained by adding the voltage of the capacitor 9 to the output voltage of the full-wave rectifier circuit 4.
A current flows through 20 and its attached circuit (see FIG. 5 (a)). This input current flows from the AC power supply 1 to the inverter circuit 11 via the filter circuit 2 and the full-wave rectifier circuit 4. Here, the capacitor 12 is a high-frequency bypass capacitor for bypassing a high-frequency feedback current flowing from the parallel resonance circuit via the diode 17 when the transistor 14 is turned off. Next, the transistor 14
, The current stops flowing from the full-wave rectifier circuit 4 to the inverter circuit 11. Thereafter, the same operation as described above is repeated, and a current flows from the AC power supply 1 to the chopper circuit 5 and the inverter circuit 11 alternately. Then, the oscillating current from the parallel resonance circuit flows to the discharge lamp 20 via the series circuit of the inductance element 18 and the capacitor 19, and the discharge lamp 20 is turned on.

[Problems to be solved by the invention]

However, in the above-described conventional discharge lamp lighting device, when the driving (operating) frequency of the inverter circuit is increased, the driving frequency of the chopper circuit is also increased. Therefore, switching loss in the chopper circuit is increased, and dimming is performed. For example, there is a problem that it is not preferable to increase the operating frequency of the inverter circuit. Further, this problem can be avoided by providing separate control circuits for the chopper circuit and the inverter circuit and using different signal generation means. However, there is a problem that two sets of control circuits are required and the circuit becomes large and complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. Even if the driving frequency of the inverter circuit is increased by dimming or the like, the loss in the chopper circuit is small, and the control circuit is minimized. It is an object of the present invention to obtain a discharge lamp lighting device that can be simplified.

[Means for solving the problem]

The discharge lamp lighting device according to the present invention is a discharge lamp lighting device comprising: a chopper circuit connected to a DC power supply; and an inverter circuit that converts an output of the chopper circuit into high-frequency power and supplies the high-frequency power to the discharge lamp. A control circuit having a common oscillating circuit for generating a signal for driving each switching element of the circuit and the inverter circuit, and a frequency dividing circuit for dividing the output frequency of the oscillating circuit in the control circuit; The control of lowering the driving frequency of the chopper circuit from the driving frequency of the inverter circuit is performed by a peripheral circuit.

[Action]

The control means in the present invention lowers the drive frequency of the chopper circuit from the drive frequency when the drive frequency of the inverter circuit is increased, and suppresses the loss in the chopper circuit due to the increase in the drive frequency. Further, since the control circuit shares the oscillation circuit, there is no need to provide a separate circuit, and the control circuit can be simplified.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and the same reference numerals are given to the same components as those in the conventional example of FIG. In the figure, reference numeral 22 denotes a DC power supply, and 5 denotes a step-up chopper circuit connected to the DC power supply 22. The chopper circuit 5 includes a coil 23, a diode 24, and a switching element 25 such as a transistor. 9 is a smoothing capacitor, 11 is an inverter circuit that converts the DC output of the chopper circuit 5 to high-frequency power and outputs the high-frequency power.
A switching element 26, a switching element 26, a diode 17 connected in anti-parallel to the switching element 26, and a current-limiting inductance element 18 are provided. Reference numeral 20 denotes a discharge lamp to which the high frequency power of the inverter circuit 11 is supplied, 21 a capacitor connected in parallel to the discharge lamp 20, 27 a drive circuit for driving the switching element 26, and 28 a drive frequency of the inverter circuit 11 An oscillator (oscillation circuit) 29 is a frequency dividing circuit for dividing the frequency of the signal from the oscillator 28, and is composed of a flip-flop or the like. Reference numeral 30 denotes a drive circuit for driving the switching element 25, which has a function of controlling the conduction period of the switching element 25 so that the output voltage of the chopper circuit 5 becomes constant. A control circuit 31 controls the drive of the inverter circuit 11 and the chopper circuit 5, and includes a drive circuit 27, 30 and a common oscillator 28.
And a frequency dividing circuit 29. The frequency dividing circuit 29 is provided as control means for lowering the driving frequency of the chopper circuit 5 from the driving frequency of the inverter circuit 11 at the time of dimming or the like.

Next, the operation of the circuit of FIG. 1 will be described with reference to the operation waveform diagrams of FIG. 2 and FIG.

First, a normal operation when the discharge lamp 20 is turned on with all light will be described. FIG. 2 is an operation waveform diagram at the time of all light. The value of the capacitor 9 is set such that the voltage applied to both ends of the capacitor 9 is always higher than the instantaneous value of the input power supply. Then, the switching element 25 is connected to (a) of FIG.
Is applied, the switching element 25 is turned on, a current flows from the DC power supply 22 to the coil 23, and the input current of the chopper circuit 5 gradually increases as shown in FIG. 2 (b). Then, when the switching element 25 is turned off,
The coil 23 tries to keep the current flowing, and generates a voltage at both ends thereof. The current flows through the diode 24 to the contesan 9 to charge the capacitor 9. When the capacitor 9 is charged, the inverter circuit 11 operates using the terminal voltage of the capacitor 9 as an input. Next, the inverter circuit 11
Will be described. When the switching element 26 is turned on by a signal as shown in FIG.
The electric charge stored in the discharge lamp 20 is discharged by the parallel resonance circuit formed by the inductance element 15 and the capacitor 16.
In addition, a current flows through the current limiting inductor element 18 and the capacitor 21. Next, when the switching element 26 is turned off,
The current from the parallel resonance circuit flows to the discharge lamp 20 through the current limiting inductance element 18 (see (c) in the figure). The discharge lamp 20 is a current-limiting inductance element.
A high voltage is applied by a series resonance circuit constituted by the capacitor 18 and the capacitor 21 to light the lamp. Next, when the switching element 25 is turned on again, the capacitor 9 is charged as described above, the inverter circuit 11 operates, and thereafter the discharge lamp 20 is kept lit by repeating this operation.

Next, an inverter circuit 11 is used to perform output control such as dimming.
The case in which the driving frequency of the above is changed to a higher one will be described. FIG. 3 is an operation waveform diagram showing this operation. As shown in FIG. 3B, the signal from the oscillator 28 (see FIG. 3A) is frequency-divided by the frequency dividing circuit 29 so that the driving circuit 30
Is input to The drive circuit 30 includes a switching element 25
Is turned on and off, and the capacitor 9 is charged. The chopper circuit 5 is a switching element when the driving frequency is lowered.
Since the output voltage increases when the conduction ratios of the switching elements 25 are equal (see FIG. 3C), the drive circuit 30 controls the conduction period of the switching element 25 so that the output voltage of the chopper circuit 5 becomes constant ( (See (d) and (e) in the figure).
Then, similarly to the above-described all-light operation, the terminal voltage of the capacitor 9 is input to operate the inverter circuit.

In this way, the frequency at which the chopper circuit 5 operates can be made lower than the frequency at which the inverter circuit 11 operates at the time of dimming or the like, and an increase in loss due to an increase in operating frequency in the chopper circuit 5 can be prevented. Can be. Further, since separate control circuits are not required for the chopper circuit 5 and the inverter circuit 11, the circuit does not become large and can be simplified.

FIG. 4 shows an example in which the control circuit 31 is embodied. In the figure, the same reference numerals as those in FIG. 1 denote the same (corresponding) components. The oscillator 28 is an oscillator using a gate IC, and outputs an output frequency f1 by an external resistor 28a and an output frequency f2 (f1 <f2) by a resistor 28b. S is a dimming switch. The dividing circuit 29 uses a Johnson counter.
This is an N frequency dividing circuit, and inputs the output of the oscillator 28 as a clock. Then, at the time of Q1, a frequency of 1/2 frequency is outputted, and furthermore, the frequency is reduced to 1/3 by connecting Q2. Further, the drive circuit 30 is configured by a timer IC 30a and the like.

R1 and R2 are resistors for voltage division. The terminal voltage of the capacitor 9 is extracted and input to the modulation input terminal 30b. When the input voltage to the modulation input terminal 30b rises, the switching element 2
The ON period of 5 is reduced to prevent the voltage from rising. The drive circuit 27 may be similar to the drive circuit 30. However, if the ON period of the switching element 26 is constant, a configuration like a monostable multivibrator may be used.

Although not shown in the above description, the DC power supply 22 is obtained by rectifying and smoothing a commercial AC power supply. Further, the chopper circuit 5 and the inverter circuit 11 are not the same as those described in the above embodiment, but can be similarly implemented with other chopper circuits and inverter circuits. Further, the driving frequency of the chopper circuit 5 may be divided from the time when the power is turned on. Although the drive frequency of the inverter circuit 11 and the drive frequency of the chopper circuit 5 are synchronized in the present embodiment, they need not be synchronized. The frequency change during dimming may be a continuous change,
Frequency division other than 1/3 frequency division is also possible.

〔The invention's effect〕

As described above, according to the present invention, the means for lowering the driving frequency of the chopper circuit from the driving frequency of the inverter circuit is provided. Therefore, even when output control such as dimming is performed by increasing the driving frequency of the inverter, Since the driving frequency is low, the loss in the chopper circuit due to the high driving frequency can be reduced, and two control circuits are required by using different driving frequencies. However, since only one control circuit is required, there is an effect that the control circuit can be simplified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the circuit of FIG. 1 at the time of all light, and FIG. 3 is an operation waveform diagram of the circuit of FIG. 1 at the time of dimming. 4, FIG. 4 is a circuit diagram showing an example of the control circuit of FIG. 1, and FIG. 5 is a diagram showing a conventional device, and FIG. 6 is an operation waveform diagram of the circuit of FIG. 5 Chopper circuit 11 Inverter circuit 22 DC power supply 25, 26 Switching element 27 Drive circuit 28 Oscillator (oscillation circuit) 29 Frequency divider circuit (control means) 30 Drive circuit 31 Control circuit In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 41/38-41/42 H02M 7/48 H05B 41/29

Claims (1)

(57) [Claims] 1. A discharge lamp lighting device comprising: a chopper circuit connected to a DC power supply; and an inverter circuit for converting an output of the chopper circuit into high-frequency power and supplying the high-frequency power to a discharge lamp. A control circuit having a common oscillation circuit for generating a signal for driving each switching element is provided, and the control circuit is provided with a frequency dividing circuit for dividing the output frequency of the oscillation circuit, and the chopper circuit is provided by the frequency dividing circuit. A discharge lamp lighting device characterized by performing control to lower the driving frequency of the inverter from the driving frequency of the inverter circuit.