JPH03250598A - Discharge lamp lighting apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a discharge lamp lighting device using a half-bridge inverter.

(Prior art) As a conventional discharge lamp lighting device of this type, the third
The structure shown in the figure is known.

The device shown in FIG. 3 includes a commercial AC power supply 1 and a rectifier circuit 2.
is connected to the rectifier circuit 2, and a partial smoothing circuit 3 is connected to the rectifier circuit 2. Transistors 5 and 6 connected in series of a half-bridge inverter 4 are connected to the partial smoothing circuit 3, and an output transformer 7 is provided at the output end of the half-bridge inverter 4. The filaments of the discharge lamps 8 are respectively connected to the wires. Further, the primary winding of a saturable current transformer 9 is connected to the transistors 5 and 6, and the secondary winding of the saturable current transformer 9 is connected to the bases of the transistors 5 and 6. The current transformer 9 is provided with a control winding 10 and a variable resistor 1
1 is connected.

Then, the alternating current from the commercial alternating current power supply 1 is rectified by a rectifier circuit 2, smoothed by a partial smoothing circuit 3, and supplied to a Hartsbridge type inverter 4. In this half-bridge type inverter 4, the transistors 5 and 6 are turned on alternately to generate a high frequency alternating current in the output transformer 7, thereby lighting the discharge lamp 8.

By changing the resistance value of the variable resistor 11, the impedance of the saturable current transformer 9 is changed, and the output of the half-bridge inverter 4 is varied.

(Problem to be Solved by the Invention) However, if the output of the half-bridge inverter 4 is varied by the variable resistor 11 connected to the control winding 10 of the saturable current transformer 9, as in the conventional configuration described above, , the problem is that the output control range of the half-bridge inverter 4 is small, although the loss caused by the variable resistor 11 and the like is large.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a discharge lamp lighting device that has less loss and can widen the control range.

[Structure of the invention]

(Means for Solving the Problem) Two switching elements constituting a half-bridge inverter, a discharge lamp energized by the output of the inverter, and a second winding can detect the output current of the inverter. and a secondary winding is inserted between the control terminal of each switching element and one main terminal,
a saturable current transformer that causes the half-bridge inverter to self-oscillate; and a variable capacitance circuit connected in series with the secondary winding between a control terminal and one main terminal of each of the switching elements. It is equipped with.

(Function) The present invention is a half-bridge inverter that controls switching elements and self-oscillates according to the saturation of a saturable current transformer, converting direct current from a direct current power source into high-frequency alternating current. and,
When controlling the output of the half-bridge inverter, the capacitance of the variable capacitance circuit is changed to control the time during which the switching elements are turned on.

(Example) Hereinafter, an example of the discharge lamp lighting device of the present invention will be described with reference to the drawings.

In FIG. 1, 21 is a commercial AC power supply, and this commercial AC power supply 21 includes a rectifier circuit 22 such as a diode bridge.
are connected, and these commercial AC power supply 21 and rectifier circuit 2
2 constitutes a DC power supply 23.

A partial smoothing circuit 24 is connected to this DC power supply 23,
This partial smoothing circuit 24 includes an electrolytic capacitor 25 and a diode 2 connected in series between the output terminals of the rectifier circuit 22.
6 and an electrolytic capacitor 27, a diode 28 connected in parallel to the electrolytic capacitor 25 and the diode 26, and a diode 29 connected in parallel to the diode 26 and the electrolytic capacitor 27.

A half-bridge inverter 31 is connected to this partial smoothing circuit 24 . This half-bridge inverter 31 has transistors 3, 2, and 33 as two switching elements connected in series between the output terminals of the partial smoothing circuit 24, and these transistors 32, 33 each have a feedback diode 34°. It has 35. Further, capacitors 36 and 37 for voltage division are connected in parallel to the two transistors 32 and 33, and between the connection point of the emitter of the transistor 32 and the collector of the transistor 33, and the connection point of the capacitor 36 and the capacitor 37. is connected to the primary winding 38a1 of the saturable current transformer 38, the inductor 39, and the input winding 40a of the output transformer 40, and a resonant capacitor 41 is connected in parallel to the input winding 4h. Furthermore, the transistor 32
A series circuit of a diode 42 and a resistor 43 is connected between the base and emitter of the control terminal, and the first secondary winding 3 of the saturable current transformer 38 is connected in parallel to this series circuit.
8b and a diode 44 are connected in series, and a capacitor 45 is connected in parallel to the diode 44. Furthermore, a series circuit of a diode 46 and a resistor 47 is connected between the base and emitter of the transistor 33, and a second secondary winding 38c of a saturable current transformer 38 and a diode are connected in parallel to this series circuit. 48 series circuits are connected, and a variable capacitance circuit 49 is connected in parallel to the series circuits.

In this variable capacitance circuit 49, a capacitor 50 is connected in parallel to the diode 48, a capacitor 51 and the drain source of a field effect transistor 52 are connected in parallel to the capacitor 50, and the gate and gate of the field effect transistor 52 are connected in parallel. - A series circuit of a resistor 53 and a variable voltage source 54 is connected between the sources. Further, a series circuit of a resistor 55 and a capacitor 56 is connected between the output terminals of the partial smoothing circuit 24, and a connection point between the resistor 55 and the capacitor 56 and the connection point between the emitter of the transistor 32 and the collector of the transistor 33. for,
A series circuit of a resistor 57 and a diode 58 is connected,
An SSS 59 is connected between the connection point of the resistor 55 and the capacitor 56 and the base of the transistor 33.

Furthermore, filaments 60a and 60b of a discharge lamp 60 are connected to the output winding 40b of the output transformer 40, which serves as the output terminal of the half-bridge inverter 31, respectively.

Next, the operation of the above embodiment will be explained.

First, the AC from the commercial AC power source 21 is rectified by the rectifier circuit 22 and smoothed by the partial smoothing circuit 24 . And when starting,
The capacitor 56 is charged, the SSS 59 is caused to break over, a base current is passed to the base of the transistor 33, the transistor 33 is turned on, and the saturable current transformer 38 is turned on.
is saturated, and then the transistors 32 and 33 are turned on alternately to induce high frequency alternating current in the output winding 40b of the output transformer 40, and the discharge lamp 60 is lit.

Furthermore, when controlling the output of the half-bridge inverter 31, the voltage of the variable voltage source 54 is varied to change the gate voltage of the field effect transistor 52, thereby changing the charges charged in the capacitor 51 and the capacitor 50. The on-time of the transistor 33 is controlled, and the on-time of the transistor 32 is controlled accordingly to change the frequency and the output of the half-bridge inverter 31 is varied.

Further, another embodiment will be described with reference to FIG.

The discharge lamp lighting device shown in FIG. 2 also includes a variable capacitance circuit 61 on the transistor 32 side of the discharge lamp lighting device shown in FIG.
At the same time, remove the output transformer 40, and
Two discharge lamps 60 are connected. That is, a variable capacitance circuit 61 is connected to the diode 44. In this variable capacitance circuit 61, a capacitor 62 is connected in parallel to the diode 44, and a capacitor 63 and a field effect circuit are connected in parallel to the capacitor 62. A series circuit of transistors 64 is connected, and a field effect transistor 6
A resistor 65 and a variable voltage source 6 are connected between the gate and source of 4.
6 is connected. Furthermore, two discharge lamps 60 are connected between the saturable current transformer 38 and the capacitors 36 and 37 via reactors 67, respectively, and a starting capacitor 68 is connected between the filaments 601 and 60b of these discharge lamps 6G. It is connected.

According to the embodiment shown in FIG. 2, since the base capacitance of each transistor 32, 33 can be varied, control over a wide range can be performed more efficiently.

In the discharge lamp lighting device shown in FIG. 1 or 2, the DC power source 23 is not limited to a rectified alternating current, but may also be a battery or the like, and the partial smoothing circuit 24 may simply be a capacitor or other smoothing circuit. Alternatively, it may not be provided.

〔Effect of the invention〕

According to the present invention, by connecting a variable capacitance circuit to the control terminal of the switching element of the half-bridge inverter, it is possible to change the frequency of the half-bridge inverter by changing the on-time of the switching element. It is possible to reduce the amount of noise and widen the control range.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the discharge lamp lighting device of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the same, and FIG. 3 is a circuit diagram showing a conventional discharge lamp lighting device. be. 23... DC power supply, 31... Half bridge type inverter, 32. 33...Transistor as a switching element, 38...Saturable current transformer, 38! ...-Secondary winding, 38b, 38C secondary winding, 49.61--Variable capacitance circuit, 6G@discharge lamp. February 2, 1990 Inventor Tsutomu Kakitani Megumi Shimizu

Claims (1)

[Claims] (1) Two switching elements connected to a DC power source and forming a half-bridge inverter, a discharge lamp energized by the output of the inverter, and a primary winding connected so as to be able to detect the output current of the inverter. a saturable current transformer in which a secondary winding is inserted between the control terminal of each of the switching elements and one main terminal to cause the half-bridge inverter to self-oscillate; and a control terminal of each of the switching elements. and a variable capacitance circuit connected in series with the secondary winding between one main terminal.