JPH03250597A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To lower loss and widen the control range by changing the capacitance of a variable capacitance circuit with a controlling means through an insulating means and controlling the time for turning a switching device on so as to control the output of an inverter. CONSTITUTION:An alternating current (a.c.) of commercial a.c. electric power source 21 is rectified by a rectifying circuit 26 and filtered by a filter circuit 30. At the starting time, a capacitor 62 is charged and SSS65 is broken-over so as to turn a transistor 42 on, saturate a variable saturation transformer 45, and after that, transistors 41, 42 are reciprocally turned on the induce high frequency a.c. and light a discharge lamp 70. At the time of output control of a half-bridge-type inverter 40, the voltage of a variable voltage source 81 is changed variably to change luminance of light emitting diodes 52b, 59b, the current amount of the transistors 52a, 59a is changed to change the capacitance of a variable capacitance circuits 49, 56, and on-time of the transistors 41, 42 are controlled to change the output of the inverter 40 variably.

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,
The structure shown in the figure is known.

The device shown in FIG. 6 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. 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. 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 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 IO of the saturable current transformer 9, as in the above conventional configuration, , the problem is that the output control range of the half-bridge inverter 4 is small, although the impedance loss due to 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 connected to a DC power source and forming a half-bridge inverter, and a discharge lamp energized by the output of the inverter.
- A secondary winding is connected so as to be able to 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, and the half-bridge inverter is self-excited. a saturable current transformer for oscillation; 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 means for insulating the capacitance of the variable capacitance circuit. and a control means for controlling through the.

(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 control means changes the capacitance of the variable capacitance circuit via the insulating means 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 a constant voltage element 23, a capacitor 24, and a primary winding 251 of an inductor transformer 25 and a secondary winding 25b are connected to both ends of the commercial AC power supply 21 via a fuse 22. Furthermore, a rectifier circuit 26 such as a diode bridge is connected to this inductor transformer 25 to constitute a DC power supply 27.

A partial smoothing circuit 30 is connected to this DC power supply 27,
This partial smoothing circuit 30 includes an electrolytic capacitor 31 and a diode 3 connected in series between the output terminals of the rectifier circuit 26.
2 and an electrolytic capacitor 33, a diode 34 connected in parallel to the electrolytic capacitor 31 and the diode 32, and a diode 35 connected in parallel to the diode 32 and the electrolytic capacitor 33.

A half bridge type inverter 40 is also connected to this partial smoothing circuit 30. This half-bridge inverter 40 has two transistors 4 and 42 as switching elements connected in series between the output terminals of the partial smoothing circuit 30, and these transistors 41 and 42 are connected to feedback diodes 43 and 44, respectively. One end of a primary winding 45a of a saturable current transformer 45 is connected to a connection point between the emitter of the transistor 41 and the collector of the transistor 42. Further, a series circuit of a diode 46 and a resistor 47 is connected between the base and emitter, which are the control terminals of the transistor 41, and a first secondary winding of a saturable current transformer 45 is connected in parallel to this series circuit. A series circuit of diode 45b and diode 48 is connected, and diode 4
8 is connected in parallel with a variable capacitance circuit 49. In this variable capacitance circuit 49, a capacitor 50 is connected in parallel to the diode 48.
A series circuit of a capacitor 51 and a phototransistor 52a of a photocoupler 52 as a control means is connected in parallel to the photocoupler 52. Furthermore, a series circuit of a diode 53 and a resistor 54 is connected between the base and emitter of the transistor 42, and a second secondary winding 45c of a saturable current transformer 45 is connected in parallel to this series circuit. A series circuit of diodes 55 is connected, and a variable capacitance circuit 56 is connected in parallel to this series circuit. In this variable capacitance circuit 56, a capacitor 57 is connected in parallel to the diode 55, and a capacitor 58 and a phototransistor 59a of a photocoupler 59 as an insulating means are connected in parallel to the capacitor 57. Furthermore, a series circuit of a resistor 61, a capacitor 62, and a resistor 63 is connected between the output terminals of the partial smoothing circuit 30, and a connection point between the resistor 61 and the capacitor 62, and a connection point between the emitter of the transistor 41 and the collector of the transistor 42. A diode 64 is connected between
A 5SS65 is connected between the connection point of the resistor 61 and the capacitor 62 and the base of the transistor 42.

Furthermore, capacitors 66 and 67 for voltage division are connected in parallel to the two transistors 41 and 42, and the connection point between the other end of the primary winding 45a of the saturable current transformer 45 and the capacitor 66 and the capacitor 67 is connected in parallel to the two transistors 41 and 42. Inductor 6 is inserted between
Filament 70 of discharge lamp 70 through 8! , 70
b is connected, filament 70a, ? A starting capacitor 71 is connected between Ob.

Furthermore, a resistor 8 is connected to a variable voltage source 81 as a control means.
A light emitting diode 52b of the photocoupler 52 and a light emitting diode 59b of the photocoupler 59 are connected through the photocoupler 52 and the photocoupler 59, respectively.

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

First, the AC from the commercial AC power supply 21 is rectified by the rectifier circuit 26 and smoothed by the partial smoothing circuit 30. And when starting,
The capacitor 62 is charged, the 5SS65 is caused to break over, the base current is passed to the base of the transistor 42, the transistor 42 is turned on, the saturable current transformer 45 is saturated, and then the transistor 41 and the transistor 42 are turned on alternately. In this way, high frequency alternating current is induced and the discharge lamp 70 is lit.

In addition, when controlling the output of the half-bridge inverter 40, the voltage of the variable voltage source 81 is varied to change the amount of light emitted from the light emitting diodes 52b and 59b, thereby changing the amount of current flowing through the phototransistors 52a and 59a. , by changing the charges charged in capacitors 51 and 50 and capacitors 57 and 58, controlling the on-time of transistors 41 and 42, and changing the frequency to vary the output of half-bridge inverter 40. let

According to the embodiment shown in FIG.
Since it can be varied by 1, it is possible to more efficiently and easily perform control over a wide range.

Note that the DC power source 27 is not limited to a rectified alternating current, and may be a battery or the like, and the partial smoothing circuit 30 may simply be a capacitor, another smoothing circuit, or may not be provided.

Further, the discharge lamp 70 is not limited to the circuit shown in FIG. 2 which is a simplified version of the circuit shown in FIG. 1, but as shown in FIG. 66 and the connection point of the capacitor 67, the primary winding 85a of the saturable current transformer 85 is connected, the discharge lamp 70 is connected to the secondary winding 85b, and the discharge lamp 70 is connected in parallel to the secondary winding 85b. A resonance capacitor 86 may also be connected.

Furthermore, instead of the resonance capacitor 86 connected to the secondary winding 85b shown in FIG. 3, a resonance capacitor 86 may be connected to the -secondary winding 85a as shown in FIG.

Furthermore, as shown in FIG. 4, two discharge lamps 7o connected as shown in FIG. 2 may be connected in parallel.

〔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 type inverter, and the on-time of the switching element is changed by controlling the variable capacitance circuit through the insulating means by the control means. Since the frequency can be changed, loss can be reduced and the control range can be widened.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the discharge lamp lighting device of the present invention, Figs. 2/-5 are circuit diagrams showing other embodiments of the same, and Fig. 6 is a conventional discharge lamp lighting device. FIG. 2 is a circuit diagram showing the device. 27...DC power supply, 40...Half bridge type inverter, 41. , 42... Transistor as a switching element, 45... Saturable current transformer, 45a - Secondary winding, 45h, 45e Secondary winding, 49.56
...Variable capacitance circuit, 52.59.. Photocoupler as control means, 70.. Discharge lamp, 81. Variable voltage source as control means.

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, and a control means for controlling the capacitance of the variable capacitance circuit via an insulating means. discharge lamp lighting device.