JPH03250600A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To lower loss and widen the control range by controlling a variable capacitance circuit connected to secondary coiled wire in series between a control terminals of a switching device and one main terminal by pulse width signal through an insulating means. CONSTITUTION:A capacitor 53 is charged with d.c. of a d.c. power source 21, a SSS55 is broken-over to turn a transistor 24 on, saturate a variable saturation transformer 27, and after that, transistors 23, 24 are turned on reciprocally to induce high frequency a.c. and light a discharge lamp 64. At the time of output control of a half-bridge-type inverter 40, the pulse width of the electric power source 71 is changed variably to change the light emitting time of light- emitting diodes of insulating means 38, 51 so as to pot out pulse width signals, on-time of photo-transistors 38s, 51a is changed to control the capacitance of variable capacitance circuits 31, 44, and the output of the inverter 40 is changed to change the lamp current flowing in the discharge lamp 64.

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, for example, a first
The structure shown in FIG. 0 is known.

In the device shown in FIG. 10, a rectifier circuit 2 is connected to a commercial AC power source 1, and a partial smoothing circuit 3 is connected to the rectifier circuit 2. A series-connected transistor 5.6 of a half-bridge inverter 4 is 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. In addition, a saturable current transformer 9 is connected to the transistor 5.6.
The primary winding of this saturable current transformer 9 is connected to the bases of the transistors 5 and 6, and
The saturable current transformer 9 is provided with a control winding 10 and connected to a variable resistor 11.

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 half-bridge 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 Problems) A discharge lamp lighting device of the present invention includes two switching elements that are connected to a DC power source and constitute a half-bridge inverter, and a device that is energized by the output of the /1-two-bridge inverter. a discharge lamp, a secondary winding is connected so as to be able to detect the output current of the half-bridge inverter, and a secondary winding is inserted between the control terminal and one main terminal of each of the switching elements, a saturable current transformer that causes the half-bridge inverter to self-oscillate; 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; and control means for controlling the capacitance of the capacitor circuit using a pulse width signal via an insulating means.

(Function) According to the present invention, according to the saturation of the saturable current transformer, the switching element is controlled to convert the direct current of the direct current power source into high-frequency alternating current using the half-bridge inverter, thereby lighting the discharge lamp. When controlling the output of the half-bridge inverter, the control means changes the capacitance of the variable capacitance circuit using a pulse width signal via the insulating means to turn on and control the switching elements.

(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 DC power supply, and this DC power supply 21
A half-bridge inverter 22 is connected to. This half-bridge inverter 22 has transistors 23 and 24 as two switching elements connected in series between the output terminals of a DC power supply 21, and these transistors 23 and 24 each have a feedback diode 2.
5.26, and one end of the primary winding 271 of the saturable current transformer 27 is connected to the connection point between the emitter of the transistor 23 and the collector of the transistor 24. Also,
A series circuit of a diode 28 and a resistor 29 is connected between the base and emitter, which are the control terminals of the transistor 23, and the first secondary winding 27b and the first secondary winding of the saturable current transformer 27 are connected in parallel to this series circuit. A series circuit of a diode 30 is connected, and a variable capacitance circuit 3 is connected in parallel to the diode 30.
1 is connected. In this variable capacitance circuit 31, a capacitor 32 is connected in parallel to a diode 30, and a capacitor 32 is connected in parallel to this capacitor 32.
A series circuit of the drain and source of 3 and a field effect transistor 34 is connected, and a parallel circuit of an electrolytic capacitor 35 and a resistor 36 is connected between the gate and source, and an insulating means is connected to the gate via a resistor 37. is connected to the emitter of the phototransistor 381 of the photocoupler 38 as the phototransistor 38! The collector of is connected to a DC power supply 21. Furthermore, a series circuit of a diode 41 and a resistor 42 is connected between the base and emitter of the transistor 24, and the second secondary winding 27c of the saturable current transformer 27 is connected in parallel to this series circuit. A series circuit of diodes 43 is connected, and a variable capacitance circuit 44 is connected in parallel to this series circuit. This variable capacitance circuit 44 has a capacitor 45 connected in parallel to the guide 43, a drain-source series circuit of a capacitor 46 and a field effect transistor 47 connected in parallel to the capacitor 45, and a gate - A parallel circuit of an electrolytic capacitor 48 and a resistor 49 is connected between the sources, and a gate is connected to the
A photocoupler 51 as an insulating means is connected via a resistor 50.
is connected to the emitter of the phototransistor 51M of -phototransistor 51! The collector of is DC power supply 2
Connected to 1. Further, a series circuit of a resistor 52 and a capacitor 53 is connected between the terminals of the DC power supply 21, and a connection point between the resistor 52 and the capacitor 53 and the emitter of the transistor 23 and the collector of the transistor 24 is connected between the terminals of the DC power supply 21. , a diode 54 is connected to the connection point between the resistor 52 and the capacitor 53 and the transistor 2.
5SS55 is connected between the base of 4 and the base of 4.

Further, voltage dividing capacitors 61 and 62 are connected in parallel to the two transistors 23 and 24, and connect the other end of the primary winding 271 of the saturable current transformer 27 and the connection point between the capacitors 61 and 62. Inductor 6 is inserted between
3 through the filaments 641, 64b of the discharge lamp 64
A starting capacitor 65 is connected between the filaments 64M and 64b.

Furthermore, the light emitting diode 38b of the photocoupler 38 and the light emitting diode 51b of the photocoupler 51 are connected via a resistor 72 to a power source 71 which outputs a pulse width signal with a variable duty ratio and serves as a control means.

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

First, the capacitor 53 is charged with DC from the DC power supply 21,
5SS55 is caused to break over, and transistor 24
A base current is passed through the base of the transistor 24 to turn on the saturable current transformer 27, and then the transistor 23 and the transistor 24 are turned on alternately.
A high frequency alternating current is induced and the discharge lamp 64 is turned on.

Furthermore, when controlling the output of the half-bridge type inverter 22, the pulse width of the power source 71 is varied as shown in FIG. 2, FIG. 4, or FIG. By changing the on-time of the phototransistors 521 and 59b, the charges charged in the capacitor 32 and the capacitor 33, and the capacitor 45 and the capacitor 46 are changed. control the on time of the , change the frequency,
Varying the output of the half-bridge inverter 22,
For example, the lamp current flowing through the discharge lamp 64 is set to 100% as shown in FIG. 3, and 50% as shown in FIG.
, or to 20% as shown in FIG.

According to the embodiment shown in FIG. 1, the capacitance of the capacitor connected to the base of each transistor 23, 24 can be varied by a single power supply 71, allowing for more efficient and easy control over a wide range. can be done.

Further, another embodiment will be described with reference to FIG. The circuit shown in FIG. 8 is different from the circuit shown in FIG. 1 in that the DC power supply 21 is connected to a commercial AC power supply 81 and
For example, a rectifier circuit 82 such as a diode bridge is connected, and a partial smoothing circuit 83 is connected to the rectifier circuit 82 . This partial smoothing circuit 83 has a series circuit of an electrolytic capacitor 84, a diode 85, and an electrolytic capacitor 86 connected between the output terminals of the rectifier circuit 82, and a diode 87 connected in parallel to the electrolytic capacitor 84 and diode 85. , a diode 88 is connected to the diode 85 and the electrolytic capacitor 86. Furthermore, in the half-bridge type inverter 22, a resistor 89 is connected between the capacitor 53 and the negative output terminal of the DC power supply 21, and a resistor 89 is connected between the emitter of the transistor 23 and the collector of the transistor 24, and the junction between the capacitor 61 and the capacitor 62. The input winding 90& of the output transformer 90 is connected between the output windings 90b, and two cascade-connected discharge lamps 64 are connected between the output windings 90b. A capacitor 91 for resonance is connected between both ends of the filaments 641 and 64b of the two discharge lamps 64, and a capacitor 92 for lighting is connected between both ends of the filaments 64t and 64b of one of the discharge lamps 64. An output transformer 90 is connected between the filaments 641 and 64b of the two discharge lamps 64.
A preheating winding 90c provided at is connected to the preheating winding 90c. The output transformer 90 is further provided with a power winding 90d and a power winding 90e, and the power winding 90d is connected to the phototransistor 38! through a rectifying and smoothing diode 93 and an electrolytic capacitor 94. The power supply winding 90e is connected to the emitter and the collector via the resistor 36 and the resistor 37, and the power supply winding 90e is connected to the rectifying and smoothing diode 9 like the power supply winding 90d.
5 and an electrolytic capacitor 96 to the emitter of a phototransistor 511 and to a collector via a resistor 49 and a resistor 50.

Then, in the DC power supply 21 , the AC from the commercial AC power supply 81 is rectified by a rectifier circuit 82 and smoothed by a partial smoothing circuit 83 .

Furthermore, power is supplied to the phototransistor 381 and the phototransistor 511 by voltages induced in the power supply winding 90d and the power supply winding 9[1e of the output transformer 90, respectively.

Furthermore, another embodiment will be described with reference to FIG. In the circuit shown in FIG. 9, in FIG. 8, the rectifier circuit 82 is formed by one electrolytic capacitor 84, and the phototransistor 38 of the half-bridge inverter 22! The collector of the phototransistor 511 is connected to the positive output terminal of the DC power supply 21 via the resistor 101 and the resistor 102, and is also connected to the emitter of the transistor 23 and the collector of the transistor 24 via the electrolytic capacitor 103. Resistor 104 and Resistor 105
It is connected to the positive output terminal of the DC power supply 21 via the electrolytic capacitor 106 and to the negative output terminal of the DC power supply 21 via the electrolytic capacitor 106 . Furthermore, a reactor! The input winding 90a of the output transformer 90 is connected through the input winding 90s, and the resonance capacitor 10g is connected in parallel to the input winding 90s. Moreover, the filament 64 of the discharge lamp 64 is connected to the output winding 90b! , 64b are connected.

〔Effect of the invention〕

According to the present invention, a variable capacitance circuit is connected to the control terminal of a switching element of a half-bridge inverter, and the on-time of the switching element is changed by controlling the variable capacitance circuit with a pulse width signal by the control means via the insulation means. Since the frequency of the half-bridge inverter can be changed, loss can be reduced and the control range can be widened. Furthermore, since control is performed using a pulse width signal, variations in brightness can be reduced.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an embodiment of the discharge lamp lighting device of the present invention, Figure 2 is a diagram showing a pulse width signal in the case of 100% of the same as above, and Figure 3 is a diagram showing the lamp current in the case of Figure 2. Figure shown, 4th
The figure shows the pulse width signal in the case of 50% of the same as above, Figure 5 shows the lamp current in the case of Figure 4, and Figure 6 shows the pulse width signal in the case of 50% of the same as above.
Fig. 7 is a diagram showing the lamp current in the case of Fig. 6, Fig. 8 is a circuit diagram showing another discharge lamp lighting device, and Fig. 9 is a diagram showing the pulse width signal in the case of 0%. FIG. 10 is a circuit diagram showing a conventional discharge lamp lighting device. 21...DC power supply, 22...11-bridge type inverter, 23.24...Transistor as a switching element, 27...Saturable current transformer, 271...-Secondary winding, 27b, 27c...Secondary Winding wire, 31.44・
- Variable capacitance circuit, 38; 51... Photocoupler as a control means, 64... Discharge lamp, 71. Power supply as a control means. Thought 2 Farming

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 half-bridge inverter, and a primary winding connected to the output current of the half-bridge inverter. a saturable current transformer, which is connected to enable detection of the inverter, and has a secondary winding inserted between the control terminal and one main terminal of each of the switching elements, and causes the half-bridge inverter to self-oscillate; A variable capacitance circuit connected in series with the secondary winding between the control terminal and one main terminal of each switching element, and control means for controlling the capacitance of the variable capacitance circuit by a pulse width signal via an insulating means. A discharge lamp lighting device comprising: and.