JPH01186790A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To make it possible to reduce the loss of a main transistor and to lower the rated collector current by employing a frequency switching circuit for controlling the oscillation frequency of an inverter in a partial smoothing zone so that the impedance of a ballast element of a discharge lamp is lowered relative to the other zone. CONSTITUTION:When a DC power source 1 is turned on, an oscillation start current flows via an oscillation start resistance 10, a transistor inverter 2 is oscillated, and a discharge lamp 3 is lit. At this time, the oscillation frequency of the inverter circuit 2 is controlled by a frequency switching circuit 25 in synchronism with the input voltage of the inverter circuit 2 so that the impedance of a ballast element 4 becomes low in a zone (zone B) other than a partially smoothed zone (zone A) of each cycle of the oscillation frequency. As a result, the difference in the lamp current values of the high frequency between the zones A and B becomes small. This makes it possible to restrict the loss of a transistor 6 as well as to lower its rated collector current.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for lighting a discharge lamp at high frequency using an inverter circuit, and particularly to a device that uses a DC power source in which the input voltage of the inverter circuit is partially smoothed. This invention relates to a lighting device for a discharge lamp.

[Conventional technology]

FIG. 3 shows a circuit diagram of a discharge lamp lighting device previously proposed by the present inventor in Japanese Patent Application No. 127808/1982.

In the figure, (1) is a DC power supply, and a commercial AC power supply (16
) between the output terminals of the rectifier (17), and the capacitors (20), (2
A diode (22) in the charging direction is connected in series to 1), and diodes (23) and (24) in the discharging direction are connected to both ends of each capacitor (20) and (21), respectively. (2) is a load current feedback type automatic transistor inverter that converts the power supply voltage of DC power supply (1) into high frequency voltage, (3) is the electrode (3a), (3b)
(4) is a parasitic choke that limits the lamp current of the discharge lamp (3), and (5) is a starting capacitor connected across the discharge lamp (3).

Next, the circuit configuration of the transistor inverter (2) will be explained. (6) is the main transistor that performs switching operation, and its emitter is connected to the DC power supply (11 (7) negative m), and between the positive terminal of the DC power supply (1) and the collector, there is an output transformer (7) and a resonant capacitor (8 ) are connected in parallel. (9) is the primary winding (9) inserted in the load circuit.
a) and a current transformer N (hereinafter referred to as CT) having a secondary winding (9b), the head (11) and (12) are an oscillation starting resistor, a resistor and a diode connected in series, and the DC power supply (
An oscillation starting resistor QO) is connected between the positive terminal of 1) and the base of the main transistor (6).
A resistor (11) and a diode (12) are connected between the emitters. Further, a frequency switching circuit (25) is connected to the input section of the main transistor (6), and is configured as follows.

CT (91 secondary winding t! (9b), an auxiliary capacitor (27) connected in parallel with a capacitor (26) connected in series, and a changeover switch connected in series with this auxiliary capacitor (27). , (28), and this changeover switch (28) is made up of a transistor (29) and a diode (30) connected in antiparallel to each other.The resistor (31) and the resistor (32) A constant voltage diode (34) is connected in series between the input terminals of the inverter (2), and between the midpoint of these and the base of the transistor (33).Resistors (35) and (3B) are connected in series. Transistor inverter (2
), and the other ends are connected to the base and collector of the transistor (37), respectively. Further, resistors (38), (39) and a capacitor (40) are connected between the base of the transistor (29) and the collector of the transistor (37).

Next, the operation of the discharge lamp lighting device having such a configuration will be explained. Figure 4 is a waveform diagram of each part of Figure 3 for this purpose, (a) is the voltage waveform of the commercial AC power supply (16), (b)
is the voltage waveform of the DC power supply (1), (e) is the terminal voltage waveform of the resistor (32), v2 is the Zener voltage level of the constant voltage diode (34), and (d) is the voltage waveform of the transistor (29).
), (e) is a discharge lamp (3)
The dotted line in the lamp current waveform shows the envelope of this high frequency lamp current.

In FIG. 3, when the DC power supply (1) is turned on, a base current is supplied to the main transistor (6) via the oscillation starting resistor α, and the main transistor (6) is turned on. As a result, a current flows through the main transistor (6) to the output transformer (7) or the load current line (the series circuit of the parasitic chain (4), the electrodes (3a) and (3b), and the starting capacitor (5)), This load current is C
Positive feedback is provided to the input of the output transistor (6) via T (9), and the main transistor (6) remains on while the capacitor (13) is charged. This oscillatory base current then begins to flow in the opposite direction, and the main transistor (6) is rapidly turned off. That is, CT
The ON (conduction) period of the main transistor (6) is determined by the inductance of the secondary winding M (9b) and the LC resonance of the capacitor (26) (or may include the capacitor (27)). The electrical energy stored in the tank circuit consisting of the output transformer (7) and the resonant capacitor (8) resonates, and a resonant current flows through the load circuit.This load current flows through the CT (91) and the diode (12 ), and the main transistor (6) remains off.Then, the resonant load current causes c to flow again.
A transistor (
A positive feedback current starts to flow to the main transistor (6), and the main transistor (6) turns on and repeats the above operation.
6) performs switching. At this time, since the capacitance of the starting capacitor (5) is set to a value that causes LC resonance with the ballast capacitor (4), the current of the discharge lamp (3) (3a
), (3b), and at the same time a high voltage is generated across the starting capacitor (5), and this voltage lights up the discharge lamp (3). After the discharge lamp (3) is lit, the impedance of the discharge lamp (3) is connected in parallel with the starting capacitor (5), and the transistor inverter (2) operates using this as a load circuit in the same way as described above. The oscillation operation continues and the discharge lamp (3)
A high frequency current limited by the ballast choke (4) flows through the ballast.

The operation of the frequency switching circuit (25) at this time will be explained next.

The A section and the B section in each cycle of the partially smoothed DC voltage waveform shown in FIG. 4(b) are respectively shown in FIG. 4(e).
), the terminal voltage of the resistor (32) is set to be smaller and larger than the Zener voltage (2) of the constant voltage diode (34). Therefore, first in section B, transistor (33) is ON1.
7), the 0FF1 transistor (29) is ON, that is, the changeover switch (28) is ON, and the capacitor (26) is connected in series with the secondary winding (9b).
A parallel circuit of an auxiliary capacitor (27) and an auxiliary capacitor (27) are connected, and the transistor inverter (2) oscillates at an oscillation frequency f determined by this resonance condition.

On the other hand, in section A, the transistor (33) is OF.

Transistor (37) is ONl Transistor (29)
is OFF, that is, the changeover switch (28) is OFF.
It is in the FF state. Therefore, compared to section B, secondary volume 1! ! (9b), the capacitor capacity becomes smaller, so the conduction period of the above-mentioned main transistor becomes short, and the oscillation frequency f of the transistor inverter (2) becomes f a > f b.

By the way, transistor (29) and transistor (37)
) The circuit of resistors (38), (39) and capacitor (40) inserted between them is a transistor inverter (2).
It is designed so that the oscillation frequency of is gradually switched from f1 to f1 or from f to f, and as a result,
Can you prevent the noise generated by this device?

[Problem to be solved by the invention]

In the above-mentioned discharge lamp lighting device, the ON period of the main transistor (6) which performs switching operation at high frequency is mainly as follows: DC power supply (1) → discharge lamp (3) → ballast check (4) → CT ( Volume 91 of 91! (91)
The lamp current flows in the loop from the main transistor (6) to the DC power supply (1), and the high-frequency collector current I0 is approximately the fifth
The waveform has a peak value Ice as shown in the figure,
The larger the lamp current, the larger the IOl.

By the way, in section A and section B in Fig. 4, this 1. , firstly, the input current voltage of transistor inverter (2) is lower in section A than in section B, and secondly, the input current voltage of transistor inverter (2) is lower than that in section B.
], the oscillation frequency in section A is higher than that in section B, and therefore the oscillation frequency of the ballast choke (4
) is larger than that in section B, compared to section A, the impedance of section I6. becomes about twice as large. In addition, when the DC power source (1) is a DC power source that is almost completely smoothed, Iop has approximately the same value over the entire section (this value is assumed to be ■., f).

For the above reasons, in the above device, when the effective lamp current values of the discharge lamps are set to the same value, the voltage waveform of the DC power supply (1) shown in FIG.
. , is the above ■. 9. Therefore, the loss of the main transistor (16) becomes large, and there is a problem that an expensive transistor with a large collector current rating must be used as the main transistor (6).

[Means to solve the problem]

In the discharge lamp lighting device of the present invention, in each cycle of the partially smoothed input DC voltage waveform of the inverter circuit, the oscillation frequency of the inverter in section A, which includes the entire partially smoothed section, is changed to the oscillation frequency of the inverter in section B, which is the other section. It is equipped with a frequency switching circuit that controls the ballast element of the discharge lamp to have a low impedance for each section.

[Effect]

In the discharge lamp lighting device of the present invention, the oscillation frequency of the inverter circuit is synchronized with the input voltage of the inverter circuit by the frequency switching circuit in a section (B section) other than the partially smoothed section (A section) of each cycle. In this case, the ballast element is printed so as to have a low impedance. Therefore, the difference in high-frequency lamp current values between section A and section B can be reduced, which reduces the difference in the peak value of the high-frequency collector current of the main transistor, suppresses loss in the main transistor, and enables a reduction in the collector current rating. do.

〔Example〕

FIG. 1 is a circuit diagram showing one embodiment of the present invention;
When compared with the device previously proposed by the inventor in the figure, the resistance (
35) and the transistor (33) connected in series with this resistor (35) is missing 9, and the constant voltage diode (34) 1
The difference is that the node terminal is connected to the base of the transistor (37), and the other circuit configuration is the same as that of the device shown in FIG. 3, so a description thereof will be omitted.

Next, the operation of the discharge lamp lighting device having such a configuration will be explained. Figure 2 is a waveform diagram of each part of Figure 1 for this purpose, and as in Figure 4, (&) is the voltage waveform of the commercial AC power supply (16), (b) is the voltage waveform of the DC power supply (19), and (c ) is the terminal voltage waveform of the resistor (32), v shows the Zener voltage level of the constant voltage diode (34), (d) is a diagram showing ON and OFF of the transistor (29), (e) is the discharge lamp In the lamp current waveform (3), the dotted line indicates the envelope of this high frequency lamp current.

In Fig. 1, when the DC power supply (1) is turned on, an oscillating starting current flows through the oscillating starting current, and the transistor inverter (2) oscillates in the same manner as the conventional device described above, causing the discharge lamp ( 3) lights up. The operation of the frequency switching circuit at this time will be explained next.

The A section and B section in each cycle of the partially smoothed DC voltage waveform shown in FIG. 2(b) are respectively shown in FIG.
), the terminal voltage of the resistor (32) is set to be smaller and larger than the Zener voltage v2 of the constant voltage diode (34). Therefore, first, in section B, transistor (37) is turned on, and transistor (29) is turned on.
) is OFF, that is, the selector switch (2
8) is in the OFF state, a parallel circuit of a capacitor (26) and an auxiliary capacitor (27) is connected in series with the secondary winding (9b), and the transistor inverter (2)
oscillates at an oscillation frequency fb determined by this resonance condition.

On the other hand, in section A, the transistor (37) is OFF.

The transistor (29) is turned on, that is, the changeover switch (28) is turned on. therefore,
Since the capacitance of the capacitor connected in series with the secondary winding (9b) is larger than in section B, the conduction period of the main transistor mentioned above becomes longer, and the oscillation frequency f of the transistor inverter (2) becomes fl<f b. It has become.

Comparing the lamp current waveforms in Fig. 2(e) and Fig. 4(e), the difference in high-frequency lamp current values between section A and section B is smaller in Fig. 2(e). I understand.

By the way, as in this embodiment, the high voltage generated in the starting capacitor (5) due to the resonance phenomenon between the starting capacitor (5) and the palast choke (4) causes the discharge lamp (3) to
In the case of the starting method that starts the discharge lamp (3), if it becomes difficult to maintain the discharge of the discharge lamp (3) in the A section by controlling the oscillation frequency so that f<fb' as described above, the output voltage ( 7) becomes effective.

Furthermore, by setting the oscillation frequency f in section A where the lamp current value of the discharge lamp (3) is small, for example, at or near the upper limit of the modulation frequency of the infrared remote controller, the oscillation frequency f −< f b can be obtained. Therefore, the probability of causing trouble to infrared remote controller application equipment is low.

In the above embodiment, the transistor inverter is of the load current feedback type, but it may be of the output voltage feedback type, for example, and the frequency switching circuit (25) and the changeover switch (28)
The configuration of is not limited to these.

〔Effect of the invention〕

As explained above, according to the present invention, the input power factor of the commercial AC power supply is high due to partial smoothing of the input current voltage of the transistor inverter, and the transistor By providing a frequency switching circuit that changes the oscillation frequency of the inverter, the difference in high frequency lamp current values between section A and section B is reduced, thereby reducing the high frequency collector current of the main transistor.

The peak value of■. By reducing the difference between , the loss of the main transistor can be reduced, and an inexpensive transistor with a relatively low collector current rating can be used.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, FIG. 3 is a circuit diagram of a discharge lamp lighting device previously proposed by the inventor, and FIG. This figure is a waveform diagram of each part of FIG. 3 corresponding to FIG. 2, and FIG. 5 is a collector current waveform diagram of the main transistor shown in FIG. 3. In the figure, (1) is a DC power supply, (2) is a transistor inverter, (3) is a discharge lamp, (4) is a palast choke, (5) is a starting capacitor, and (251 is a frequency switching circuit. The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A DC power source is made by rectifying an AC power source and partially smoothing the resulting pulsating DC voltage, an inverter circuit that converts this partially smoothed DC voltage into a high-frequency voltage, and lighting is generated by this high-frequency voltage. In a discharge lamp lighting device consisting of a discharge lamp and a reactance component ballast element that limits the lamp current of the discharge lamp, in each cycle of the voltage waveform of the partially smoothed DC power supply, the partially smoothed The invention is characterized by comprising a frequency switching circuit that controls the oscillation frequency of the inverter circuit in section A, which includes all of the sections, so that the ballast element has a low impedance for section B, which is the section other than section A. A lighting device for discharge lamps.