JPH03250599A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To lower loss and widen the control range by controlling the time constant of time constant circuits connected to control terminals of switching devices respectively in series by a level shifting means to agree the potential difference. CONSTITUTION:At the starting time, a capacitor 52 is charged with d.c. current of a d.c. power source 21, a SSS54 is broken-over turn a transistor 24 on, and after that, transistors 24, 23 are reciprocally turned on and off by a transformer 27 and time constant circuits 43, 31 to induce high frequency a.c. and light a discharge lamp 60. At the time of output control of a half-bridge-type inverter 22, the voltage of a variable voltage power source 62 is changed to convert it into pulse width signals by a V-PWM conversion circuit 63, the potential differences to be applied to each time constant are made same by a level shifting circuit 38, FET 33, 45 are turned on according to the pulse width signals, the on-time of the transistors 23, 24 is changed by controlling the electric charge to be charged in capacitors 32, 44, and the output of the inverter 22 is changed.

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 fourth discharge lamp lighting device is used.
The structure shown in the figure is known.

The device shown in FIG. 4 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 the saturable current transformer 9 is connected to the transistor 5.6, and the secondary winding of the saturable current transformer 9 is connected to the base of the transistor 5.6. 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 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) The discharge lamp lighting device of the present invention has two switching elements constituting a half-bridge inverter that is connected to a DC power source and energizes the discharge lamp, and a control terminal of each of these switching elements. The device includes time constant circuits connected in series, and control means for controlling the time constants of these time constant circuits via level shift means for matching potential differences.

(Function) The present invention controls switching elements according to the time constant of a time constant circuit, and converts direct current from a direct current power source into high-frequency alternating current using a half-bridge inverter.

When controlling the output of the half-bridge inverter, the control means changes the time constant of the time constant circuit via the level shift 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 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 the DC power supply 21, and these transistors 23. 24 have feedback diodes 25 and 26, respectively, and a transformer 2 is connected to the connection point of the emitter of the transistor 23 and the collector of the transistor 24.
7 is connected to one end of the primary winding 27a. Further, the collector and emitter of a transistor 28 which is an auxiliary switching element are connected between the base and emitter which are control terminals of the transistor 23, and the base of the transistor 23 is connected to the resistor 29 and the first secondary winding of the transformer 27. line 27
Through b, the − next winding 27! connected to one end of the

Further, the base of the transistor 28 is connected to a time constant circuit 31 via a Zener diode 30. This time constant circuit 31 is connected from the Zener diode 30 to the drain of the field effect transistor 33 via the capacitor 32.
A resistor 34 is connected between the connection point of the Zener diode 30 and the capacitor 32, and the source of the field effect transistor 33. , and a capacitor 35 are connected. Furthermore, an electrolytic capacitor 36 is connected between the gate and source of the field effect transistor 33, and the gate is connected via a resistor 37 to a level shift circuit 38 as a level shift means for keeping the potential difference constant. On the other hand, the collector and emitter of a transistor 40 which is an auxiliary switching element are connected between the base and emitter of the control terminal of the transistor 24, and the base of the transistor 24 is connected to the resistor 41 and the second secondary winding of the transformer 27. It is connected to one end of the -order winding 2La via the wire 27c. Further, the base of the transistor 40 is connected to a time constant circuit 43 via a Zener diode 42. This time constant circuit 43 is connected to a field effect transistor 45 via a Zener diode 42 and a capacitor 44.
A resistor 46 is connected between the connection point of the Zener diode 42 and the capacitor 32, and the resistor 41 and the second secondary winding 27c, and the connection point of the Zener diode 42 and the capacitor 44, A capacitor 47 is connected between the source of the field effect transistor 45 and the source thereof. Furthermore, the field effect transistor 4
An electrolytic capacitor 49 is connected between the gate and source of 5, and is connected to a level shift circuit via a +i resistor 49. Further, a series circuit of a resistor 51 and a capacitor 52 is connected between the output terminals of the DC power supply 21, and a connection point between the resistor 51 and the capacitor 52 and a connection point between the emitter of the transistor 23 and the collector of the transistor 24. is connected to diode 53,
A 5SS 54 is connected between the connection point of the resistor 51 and the capacitor 52 and the base of the transistor 24.

Further, voltage dividing capacitors 56 and 57 are connected in parallel to the two transistors 23 and 24, and the transformer 2
The filaments 60a and 60b of the discharge lamp 60 are connected via the reactor 58 between the other end of the primary winding 25a of the discharge lamp 56 and the connection point of the capacitor 56 and the capacitor 57. A capacitor 61 for this purpose is connected.

Furthermore, a V-PWM conversion circuit 63 that converts a voltage from a variable voltage source 62 as a control means into a pulse width signal is connected to the level shift circuit 3G.

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

First, when starting the DC power supply 21, the capacitor 52 is charged, the 5SS54 is caused to break over, the base current is passed to the base of the transistor 24, and the transistor 24 is turned on. Zener diode 42.3 alternately by .31
0 is turned on, transistor 40°28 is turned on,
The base current of transistors 24 and 23 is transferred to transistor 4.
0.28, and alternately turn on and off the transistors 23 and 24 to induce high frequency alternating current and light the discharge lamp 60.

Furthermore, when controlling the output of the half-bridge inverter 22, the voltage of the variable voltage source 62 is varied to
The PWM conversion circuit 63 converts it into a pulse width signal, the level shift circuit 36 equalizes the potential difference applied to each time constant, turns on the field effect transistor 33 and the field effect transistor 45 according to the pulse width signal, and converts the capacitor 30 The transistor 2
3 and the off time of the transistor 24,
By changing the oscillation frequency, the output of the half-bridge inverter 22 is changed.

Next, another embodiment will be described with reference to FIG. The circuit shown in FIG. 2 is different from the capacitor 3 in FIG.
A resistor 71 is connected between 2 and the negative electrode of the DC power supply 21,
The gate of the field effect transistor 33 is connected to the level shift circuit 38 via a resistor 72, and the gate of the field effect transistor 45 is connected via a resistor 73. This level shift circuit 38 is connected from the positive electrode of the DC power supply 21 to the transistor 7 via a diode 74 and a resistor 75.
The bases of these transistors 76 and 77 are connected together, and the emitters of these transistors 76 and 77 are connected via a diode 78. The emitter is connected to the first secondary winding 27b of the transformer 27 via a parallel circuit of a Zener diode 79 and an electrolytic capacitor 80. Further, the collector of the transistor 76 is connected to the resistor 72, and the collector of the transistor 77 is connected to the diode 81. It is connected to the collector of a transistor 83 via a resistor 82, and the emitter of this transistor 83 is connected to the negative electrode of the DC power supply 21 via a resistor 84. Furthermore, the base of the transistor 83 is connected via a resistor 86 of a voltage conversion circuit 85 to a connection point between a resistor 87 and a resistor 88 that are connected in parallel to the variable voltage source 62 .

Then, the level shift circuit 38 changes the potential difference between the positive electrode of the DC power supply 21 and the emitter of the transistor 23,
Output control is performed in accordance with the potential difference between the collector of transistor 24 and the negative electrode of DC power supply 21.

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

The circuit shown in FIG. 3 is different from the circuit shown in FIG. 2 in that the input winding 91! is connected, and a resonant capacitor 9 is connected in parallel to this input winding 91a.
2 are connected. The output winding 9To has 2
Filament 60 at both ends of two continuously connected discharge lamps 60.60! , 60b are connected, and one discharge lamp 60
filament 60a.

A capacitor 93 for lighting is sequentially connected between the discharge lamps 60 and 60b, and the filaments 60a and 60 are connected between the discharge lamps 60 and 60.
0b is connected to a preheating winding 91c provided in the output transformer 91.

Further, the output transformer 91 is provided with a power winding 91d, which is connected to a rectifier circuit 95 such as a diode bridge, and between the output terminals of the rectifier circuit 95 is an electrolytic capacitor 96 and a Zener diode. 9
7 parallel circuits are connected, and a load of a variable voltage source 62 is connected to the negative electrode of the DC power source 21.

The positive terminal of the variable voltage source 62 is connected to the comparator 102 of the IC circuit 101 of the V-PWM conversion circuit 63, and the other end of the comparator 102 is connected to the negative terminal of the variable voltage source 62 via the resistor 103. A capacitor +0 is connected between the input terminal and output terminal of this comparator 102.
4 and a resistor 105 are connected. Further, the output terminal of the comparator 102 is connected to the output terminal of the comparator 106, and the input terminal of the comparator 106 is
The resistor 10 is connected to the negative terminal of the variable voltage source 62.
7 and a resistor 108 to a connection point between a resistor 103 and a capacitor 104. Further, the negative electrode of the variable voltage source 62 is connected to the comparator 110 via a DC power source 109, and the O8C circuit 110 via a capacitor 111 and a resistor 112 connected in parallel.
Connected to 3. Furthermore, the connection point between the resistor 107 and the resistor 108 is connected to a REF circuit 114, and this REF circuit 114 is connected to a rectifier circuit 95, and is also connected to the collector of a transistor 115 via a resistor 115, and this transistor 116 The emitter of is connected to a resistor 73. Further, the REF circuit 114
Transistor 8 via resistor 117 and resistor 118
3 and the transistor 119
The emitter of this transistor 119 is connected to the negative electrode of the variable voltage source 62.

Then, the voltage from the power supply winding 91d is transferred to the rectifier circuit 95.
and rectify it with an electrolytic capacitor 96 and a Zener diode 97 to supply power to the IC circuit 101, and convert it into a pulse width signal in a V-PWM conversion circuit 63 according to the voltage set by a variable voltage source 62, Level shift circuit 3
8, the half-bridge inverter 22 is controlled by equalizing the potential difference input to the gate of the field effect transistor 33 and the gate of the field effect transistor 40.

Note that the DC power source 20 may be a rectified alternating current, a battery, or the like, and may also be provided with a partial smoothing circuit, a capacitor, or other smoothing circuit.

〔Effect of the invention〕

According to the present invention, a time constant circuit is connected to the control terminal of the switching element of the half-bridge inverter, and the time constant is controlled by the control means, so that the on-time of the switching element is changed to increase the frequency of the half-bridge inverter. can be changed, reducing loss and widening the control range.Also, since the level shift means equalizes the potential difference of the voltage input to the time constant circuit connected to each switching element, it is possible to ensure It is possible to control the

[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, Fig. 3 is a circuit diagram showing another embodiment, and Fig. 4 is a circuit diagram showing another embodiment. 1 is a circuit diagram showing a conventional discharge lamp lighting device. 21..DC power supply, 22..half-bridge inverter, 23.24..transistor as switching element, 31.43..time constant circuit, 38..level shift circuit as level shift means, 60..discharge electric light, 6
2...Variable voltage source as control means.

Claims (1)

[Claims] (1) Two switching elements constituting a half-bridge inverter connected to a DC power supply and energizing the discharge lamp, time constant circuits connected in series to the control terminals of these switching elements, and these time constant circuits. A discharge lamp lighting device comprising: control means for controlling the time constant of through a level shift means for matching the potential difference;