JPH03127496A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To keep the loss in a chopper circuit low with a simple structure even when the operation frequency of an inverter circuit is elevated by suitably controlling respective frequencies of a chopper circuit and an inverter circuit constructing a lighting device with a control circuit. CONSTITUTION:Switching elements 26, 25 in respective inverter circuit 11 and chopper circuit 5 are operated with an oscillator 28 in a control circuit 31 and a driving circuit 27, and a frequency divider circuit 29 dividing the frequency of the output of the oscillator 28 and a driving circuit 30 respectively, to make the driving frequency of the circuit 5 lower than that of the circuit 11. Therefore with a simple structure using only one control circuit 31, driving frequencies of the circuit 11, 5 are controlled separately to keep the driving frequency of the circuit 5 low even when the driving frequency of the circuit 11 is elevated for dimming or the like, and the loss in the circuit 5 can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device that lights a discharge lamp at high frequency using a chopper circuit and an inverter circuit.

(Prior Art) FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device disclosed in, for example, Japanese Unexamined Patent Publication No. 64-34178.

In the figure, 1 is an AC power supply, and AC current from this AC power supply 1 is supplied to a full-wave rectifier circuit 3.4 via a filter circuit 2, where it is converted into a DC current. A chopper circuit 5 of polarity inversion type is connected to the output terminal of the rectifier circuit 3, and within this chopper circuit 5, the rectifier circuit 3
An inductance element 7 is connected to the output end of the transistor 6, which is a switching element, between its collector and emitter. Further, a smoothing capacitor 9 is connected to both ends of the inductance element 7 via a diode 8, and an input terminal of a one-way inverter circuit IT is connected to both ends of the capacitor 9 via a diode 0. . A series circuit consisting of the output terminal of the full-wave rectifier circuit 4 and the capacitor 9 is connected to the input terminal of the inverter circuit 11. No. 2 is a capacitor for high frequency bypass,
It is connected to the input end of the inverter circuit 11. 13 is a switching control circuit, one output terminal "f" is connected to the base of a transistor 14 which is a switching element -L in the inverter circuit 11, and the other output terminal is connected to the base of a transistor 6 in the chopper circuit 5. In addition, a transistor 1 is connected to the input terminal of the inverter circuit 11.
A parallel resonant circuit of an inductance element 15 and a capacitor 16 is connected between the collector and emitter of transistor 14, and a diode is connected between the collector and emitter of transistor 14. 7 are connected in antiparallel. A current-limiting inductance element 18 and a coupling capacitor 19 are connected in series [!] to both ends of the parallel resonant circuit of the inverter circuit 11. l! A discharge lamp 20 is connected through one path. In addition, discharge lamp 20
A capacitor 21 is connected in parallel to both ends of the capacitor 21 .

6 is an operating waveform diagram of the circuit shown in FIG. 1, in which (a) is the input terminal waveform of the inverter circuit 11, (b) is the input current waveform of the chopper circuit 5, and (c) is , (b) shows the composite current waveform of each input current, and (d) shows the on (ON) and off (off) of the transistor 14 of the switching control circuit 13.
OFF) control signal waveforms are shown.

Next, the operation of the discharge lamp lighting device shown in Fig. 7jrJ5 will be explained with reference to the waveform diagram shown in Fig. 6. First, a case will be described in which the switching control circuit 13 outputs an off signal to the base of the transistor 6 in the chopper circuit 5 and also outputs an off signal to the base of the transistor 14 in the inverter circuit 11. In this case, only the transistor 6 is turned on, and the AC power supply 1 connects the filter circuit 2, the full-wave rectifier circuit 3, and the collector of the transistor 6.
A current flows through the inductance bulb 7 between the emitters.

This current increases with a slope proportional to the output voltage of the full-wave rectifier circuit 3, as shown in FIG. 5(b). Next, the output of the switching control circuit I3 is inverted, and the transistor 6
A 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 explained. In this case, the transistor 6 is turned off and the chopper circuit 5
Current no longer flows into the inductance element 7, but since the inductance element 7 still contains the energy accumulated during that period, a voltage is generated across it.
A current flows from the inductance element 7 to the capacitor 9 via the diode 8, and the capacitor 9 is charged. On the other hand, since the transistor 14 is turned on, the voltage obtained by adding the voltage of the capacitor 9 to the output voltage of the full-wave rectifier circuit 4 causes the parallel resonant circuit consisting of the inductance element 15 and the capacitor 16 in the inverter circuit 11 to Current flows through the lamp 20 and its attached circuit ((a) in Figure 5).
reference). This input current flows from the AC current [1] to the inverter circuit 11 via the filter circuit 2 and the full-wave rectifier circuit 4. Here, the capacitor 12 is a transistor! 4 is turned off, it serves as a high frequency bypass capacitor for bypassing the high frequency feedback current flowing from the parallel resonant circuit through the diode 17. Next, when an off signal is manually applied to the transistor 14, no current flows from the full-wave rectifier circuit 4 to the inverter circuit 11. below,
- By repeating the same operation as in section h, current flows alternately from the AC voltage [1 to the chopper circuit 5 and the inverter circuit 11.

The oscillating current from the parallel resonant circuit is transmitted to the discharge lamp 2 through the series circuit of the inductance element 18 and the capacitor 19.
0, thereby lighting up the discharge lamp 20.

[Problem to be solved by the invention]

However, in the conventional discharge lamp lighting device as described above, when the driving (operating) frequency of the inverter circuit is increased, the driving frequency of the chopper circuit is also increased, which increases the switching loss in the chopper circuit and makes dimming difficult. There is a problem that it is not preferable to increase the operating frequency of the inverter circuit. Additionally, this problem can be avoided by providing separate control circuits for the chopper circuit and the inverter circuit and using different signal generation means;
There is a problem that the circuit is large and complicated.

This invention was made to solve the above-mentioned problems. Even if the drive frequency of the inverter circuit is increased for dimming only, the loss in the chopper circuit is small, and the control circuit can be reduced to the minimum necessary. The purpose of the present invention is to obtain a discharge lamp lighting device that can be simplified.

[Means to solve the problem]

A discharge lamp lighting device according to the present invention includes a chopper circuit connected to a DC power source, and an inverter circuit that converts the output of the chopper circuit into high-frequency power and supplies it to the discharge lamp. The present invention includes a control circuit having a common oscillation circuit for controlling the driving of each switching element of the circuit and the inverter circuit, and a control means for lowering the driving frequency of the chopper circuit below the driving frequency of the inverter circuit.

(Function) When the drive frequency of the inverter circuit is increased, the control means in the present invention lowers the drive frequency of the chopper circuit from the drive frequency of the inverter circuit, thereby suppressing loss in the chopper circuit due to the increase in the drive frequency. In addition, since the control circuit shares the oscillation circuit, there is no need to provide separate control circuits, and the control circuit can be simplified.

(Embodiment) Figure 1 is a circuit diagram showing an embodiment of the present invention.
The same components as those in the conventional example shown in the figure are given the same reference numerals.

In the figure, 22 is a DC power supply, 5 is this DC 'fL current 2
The chopper circuit 5 is a step-up type chopper circuit connected to the power source 2, and the chopper circuit 5 is composed of 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 into high frequency power and outputs it, a parallel resonant circuit consisting of an inductance element 15 and a capacitor 16, a switching element 26, and this switching element %26.
It consists of a diode 17 and a current-limiting inductance element 18 connected in antiparallel to each other. 20 is a discharge lamp to which the high-frequency power of the inverter circuit 11 is supplied, 21 is a capacitor connected in parallel to the discharge lamp 20, 27 is a drive circuit that drives the switching element 26, and 28 determines the drive frequency of the inverter circuit 11. oscillator (oscillation circuit),
A frequency dividing circuit 29 divides the frequency of the signal from the oscillator 28, and is composed of flip-flops and the like. 30 is a drive circuit for driving the switching element 25, and has a function of controlling the conduction period of the switching element 25 so that the output voltage of the chopper circuit 5 is constant. 31 is the inverter circuit! ! and a control circuit for controlling the drive of the chopper circuit 5, which is composed of the drive circuit 27, 30, a shared oscillator 28, and a frequency divider circuit z9, and the frequency divider circuit 29.
is provided as a control means for lowering the drive frequency of the chopper circuit 5 below the drive frequency of the inverter circuit 11 during dimming or the like.

Next, the operation of the circuit shown in FIG. 1 will be explained using the operation waveform diagrams shown in FIGS. 2 and 3.

First, the normal operation when the discharge lamp 20 is fully lit will be described. FIG. 2 is an operational waveform diagram during full light. The value of capacitor 9 is set such that the voltage applied across capacitor 9 is always higher than the instantaneous value of the input power supply. Then, the switching element 25 is
), the switching element 25
is turned on, current flows from the DC power supply 22 to the coil 23, and the input terminal of the chopper circuit 5 gradually increases as shown in FIG. tries to keep the current flowing and generates a voltage across it, current flows into the capacitor 9 through the diode 24, and the capacitor 9 is charged. When this capacitor 9 is charged, the inverter circuit 11 operates using the terminal voltage of this capacitor 9 as human power. next,
The operation of the inverter circuit 11 will be explained. When the switching element 26 is turned on by a signal as shown in FIG. Current flows through the diverted inductor 18 and capacitor 21. Next, when the switching element 26 is turned off, TltIL from the parallel resonant circuit flows into the discharge lamp 20 through the current-limiting inductance element 18 (see (c) in the figure). Further, the discharge lamp 20 is lit by applying a high voltage through a series resonant circuit constituted by a current-limiting inductance element 18 and a capacitor 21. Next, the switching element 25
When turned on, capacitor 9 is charged as described above,
The inverter circuit if operates, and the discharge lamp 20 continues to be lit by repeating this operation.

Next, the inverter circuit 11 is used to perform output control such as dimming.
The case where the driving frequency is changed to a higher one will be explained. FIG. 3 is an operational waveform diagram showing this operation. As shown in FIG. 3(b), the frequency dividing circuit 29 causes the oscillator 2 to
The signal from 8 (see <a) in the figure) is frequency-divided and input to the drive circuit 30. This drive circuit 30 turns on and off the switching element 25 and charges the capacitor 9. In addition, when the drive frequency of the chopper circuit 5 decreases, the output voltage increases when the conduction ratio of the switching element 25 is the same (see (C) in the same figure). Control the conduction period of the switching element "/-25" so that ((in the same figure)
d), (e)).

Then, the inverter circuit is operated using the terminal voltage of the capacitor 9 as human power, similar to the operation during full light described above.

In this way, the frequency at which the chopper circuit 5 is operated can be lower than the frequency at which the inverter circuit 11 is operated during dimming, etc., thereby preventing an increase in loss due to an increase in the operating frequency in the chopper circuit 5. Can be done. Further, since separate control circuits are not required for the chopper circuit 5 and the inverter circuit 11, the circuits do not become large and can be simplified.

FIG. 4 shows an example of the control circuit 31 described above. In the figure, the same reference numerals as in FIG. 1 indicate the same (corresponding) components. The oscillator 28 is an oscillator using a gate IC, and the output frequency fl is controlled by an external resistor 28a.
The resistor 28b outputs an output frequency f2 (fl<f2). S is a dimmer switch. The frequency dividing circuit 29 is a 17N frequency dividing circuit using a Johnson Gaunt filter, and inputs the output of the oscillator 28 as a clock. And Ql
When , it outputs the frequency divided by 1/2, and further outputs the frequency divided by 1/2 by connecting Q2.
The frequency will be divided into 3. The drive circuit 30 also includes a timer IC 30.
It consists of a, etc.

R1 and R2 are voltage dividing resistors, which take out the terminal voltage of the capacitor 9 and input it to the modulation input terminal 30b. When the input voltage to the modulation input terminal 30b increases, the on period of the switching element 25 decreases, thereby preventing the voltage from increasing. 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 structure such as a monostable multivibrator may be used.

Although not shown in the above explanation, it is a DC type! I22
is obtained by rectifying and smoothing a commercial AC power source. Further, the chopper circuit 5 and the inverter circuit 11 are not those shown in the above embodiments, and other chopper circuits and inverter circuits can be used in the same manner. Furthermore, the drive frequency of the chopper circuit 5 may be divided from the time the power is turned on. Also,
Although the drive frequency of the inverter circuit 11 and the drive frequency of the chopper circuit 5 are synchronized in this embodiment, they may not be synchronized. The frequency change during dimming may be a continuous change, and frequency division other than 1/3 frequency division is also possible.

(Effects of the Invention) As described above, according to the present invention, since a means is provided to lower the drive frequency of the chopper circuit than the drive frequency of the inverter circuit, output control such as dimming is performed by increasing the drive frequency of the inverter. Even in the case of
By making the drive frequencies different, there is no need for two control circuits, but only one, so the control circuit is ti! ! It has the effect of being able to be refined.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an operational waveform diagram of the circuit shown in Fig. 1 at full light, and Fig. 3 is an operation of the circuit shown in Fig. 1 during dimming. FIG. 4 is a circuit diagram showing an example of the control circuit shown in FIG. 1, FIG. 5 is a diagram showing a conventional device, and FIG. 6 is an operational waveform chart of the circuit shown in FIG. 5...Chopper circuit 11-...Inverter circuit 22...DC power supply 25.26...Switching element z7...
...Drive circuit 28...Oscillator (oscillation circuit) 29...
. . . Frequency dividing circuit (control means) 30 . . . Drive circuit 31 - . . . Control circuit Note that the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] In a discharge lamp lighting device comprising a chopper circuit connected to a DC power source and an inverter circuit that converts the output of the chopper circuit into high-frequency power and supplies it to the discharge lamp, driving each switching element of the chopper circuit and the inverter circuit. What is claimed is: 1. A discharge lamp lighting device comprising: a control circuit having a shared oscillation circuit for controlling the inverter circuit;