JPH0564462A - Discharge lamp lighting device - Google Patents

Abstract

(57) [Abstract] [Object] The present invention improves the power factor by a chopper circuit and simplifies the circuit configuration to reduce the cost. A half-bridge inverter circuit 36 has a pair of switching elements 37, 38 and a pair of DC cut capacitors 39, 40, and one end of an AC power source 31 has a high voltage side terminal of one switching element 37 as a first diode. 32 through the first choke coil 33, the low voltage side terminal of the other switching element 38 is connected through the second diode 34 and the second choke coil 35, and the other end of the AC power supply 31 is switched. The connection points of the elements 37 and 38 are connected. Further, the third diode 50 is connected to the DC cut capacitor 39 via the first choke coil 33.
And the fourth diode 51 is connected to the DC cut capacitor 40 via the second choke coil 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device using a half-bridge type inverter circuit.

[0002]

2. Description of the Related Art Conventionally, as a discharge lamp lighting device using, for example, a half-bridge type inverter circuit, one shown in FIG. 2 is known. This is a full-wave rectification of an AC power supply 1 with a full-wave rectification circuit 2 composed of a diode bridge, and a pulsating voltage output from the full-wave rectification circuit 2 is choke coil 3
It is supplied to the smoothing capacitor 4 via the to smooth it. The output of the smoothing capacitor 4 is supplied to the half bridge type inverter circuit 5.

This inverter circuit 5 includes a series circuit of a pair of transistors 6 and 7, a series circuit of a pair of capacitors 8 and 9, feedback diodes 10 and 11 respectively connected in parallel to the transistors 6 and 7, and an oscillation transformer 12. , Start-up resistors 13 and 14 for starting the respective transistors 6 and 7. That is, the primary winding 12p of the oscillation transformer 12 is connected between the connection point of the transistors 6 and 7 and the connection point of the capacitors 8 and 9, and the feedback windings 12b1 and 12b2 attached to the oscillation transformer 12 are connected. The transistors 6 and 7 are switching-driven by the voltage generated at each of them. Then, the secondary winding 12 of the oscillation transformer 12
A discharge lamp 16 is connected to s via a choke coil 15. In such a discharge lamp lighting device, since the DC voltage is obtained by using the smoothing capacitor 4, there is a problem that the input power factor is poor.

In order to improve this, as shown in FIG.
A discharge lamp having a power factor improved by connecting a transistor 17, a switch control circuit 18 for switching control of the transistor 17, a chopper circuit 21 including a choke coil 19 and a diode 20 between the full-wave rectifier circuit 2 and the smoothing capacitor 4. Lighting devices are known.

However, in this discharge lamp lighting device,
Since the chopper circuit 21 is provided completely independently of the inverter circuit, there are problems that the circuit configuration becomes complicated and the cost increases.

[0006]

As described above, the conventional discharge lamp lighting device using the half-bridge type inverter circuit has a poor power factor, and the power factor is not improved by using the chopper circuit. There is a problem that the circuit configuration becomes complicated and the cost increases.

The present invention has been made in view of the above circumstances. The power factor can be improved by combining a half-bridge type inverter circuit and a chopper circuit, and the circuit structure can be simplified and the cost can be reduced. An object of the present invention is to provide a discharge lamp lighting device that can be designed.

[0008]

In order to achieve the above object, the present invention has a series circuit of a pair of switching elements and a series circuit of a pair of DC cut capacitors having a smoothing function. A half-bridge type inverter circuit in which both ends of one switching element are connected to an AC power supply, a discharge lamp connected to the output terminal of this inverter circuit, a high voltage side terminal of one switching element and one end of an AC power supply. A series circuit of a first diode and a first choke coil, which is interposed between the first diode and the first choke coil, and a connection point between the AC power supply and the first diode and a low-voltage side terminal of the other switching element of the pair of switching elements. A series circuit of a second diode and a second choke coil having a polarity opposite to that of the inserted first diode, the first diode and the first diode, A third diode connected in reverse polarity to the first diode between the connection point with the arc coil and the connection point with each DC cut capacitor, and the connection point between the second diode and the second choke coil. And a connection point of each DC cut capacitor is composed of a fourth diode connected in reverse polarity to the second diode, and is turned on and off by each switching element to form a first and a second choke coil. The stored energy is superimposed on each DC cut capacitor.

[0009]

According to the present invention, the circuit including the first and second diodes, the first and second choke coils, and the pair of DC cut capacitors is a half-wave voltage doubler rectifying / smoothing circuit. Function as. In addition, a circuit composed of the first and third diodes, the first choke coil, one DC cut capacitor and one switching element of the inverter circuit, the second and fourth diodes, the second choke coil, The other DC cut capacitor and the circuit composed of the other switching element of the inverter circuit function as a booster chopper circuit, respectively.

As a result, the voltage charged in the pair of DC cut capacitors of the half-bridge type inverter circuit becomes a double voltage of the AC power supply. Moreover, since it functions as a step-up chopper circuit, the voltage is further boosted, and the discharge lamp maintains a stable lighting state even with a low input power supply voltage.

Further, the step-up chopper circuit allows the input current to flow along the envelope of the sinusoidal waveform of the power supply voltage, and the input current is a high power factor and approximates to a sine wave with few odd harmonics.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a series circuit of a first diode 32 and a first choke coil 33 in an AC power supply 31 and a second diode 34 and a second diode 34 having a polarity opposite to that of the first diode. A half-bridge type inverter circuit 36 is connected through a series circuit with the choke coil 35.

The half-bridge type inverter circuit 3
Reference numeral 6 is a series circuit of first and second switching transistors 37 and 38, which are a pair of switching elements, and first and second DC cut capacitors 39 and 4 having a smoothing function.
0 series circuits are connected in parallel with each other. The collector, which is the high voltage side terminal of the first transistor 37, is connected to the first choke coil 33 and the first diode 3.
The second choke coil 35 and the second diode 34 are connected to one end of the AC power source 31 via the cathode and the anode of the second transistor 38, respectively. It is connected to one end of the AC power supply 31 via the above, and the connection point of the first and second transistors 37 and 38 is connected to the other end of the AC power supply 31.

In the inverter circuit 36, a connection point of the transistors 37 and 38 is connected to a current transformer 41.
Is connected to one end of one filament electrode 47a of a discharge lamp 47 via a primary winding 41a of the discharge circuit 47 and a choke coil 48 of a lighting circuit 42, and a connection point of the DC cut capacitors 39 and 40 is connected to the discharge lamp. It is connected to one end of the other filament electrode 47b of 47.

The current transformer 41 has a primary winding 4
A pair of feedback windings 41b1 and 41b2 magnetically coupled to 1a
Is attached, and one of the feedback windings 41b1 has a resistor 43
Is connected between the base and the emitter of the first transistor 37 via the, and the other feedback winding 41b2 is connected between the base and the emitter of the second transistor 38 via the resistor 44. The first transistor 37
A starting resistor 52 is connected between the base and collector of the. Feedback diodes 45 and 46 are connected in parallel to the transistors 37 and 38, respectively, with their cathodes on the collector side of the transistors. The discharge lamp 4
A starting capacitor 49 is connected between the other ends of the filament electrodes 47a and 47b of No. 7.

The connection point between the first diode 32 and the first choke coil 33 and each DC cut capacitor 3
The third diode 50 has a polarity opposite to that of the first diode 32 between the connection point of 9 and 40, that is, the cathode is set to the connection point side of the first diode 32 and the first choke coil 33. Connected. Further, a fourth diode 51 is provided between the connection point of the second diode 34 and the second choke coil 35 and the connection point of the DC cut capacitors 39 and 40, and has a polarity opposite to that of the second diode 34. , That is, the anode is connected to the second diode 34 and the second
The choke coil 35 is connected to the connection point side.

In the present embodiment configured as described above, when the AC power supply 31 is turned on, the first diode 3
2, a current flows through the first choke coil 33, the first DC cut capacitor 39, and the lighting circuit 42, and the first DC cut capacitor 39 is charged. In addition, in the inversion half cycle of the AC power supply 31, the lighting circuit 42, the second DC cut capacitor 40, the second choke coil 35,
A current flows through the second diode 34 and the second DC cut capacitor 40 is charged. As a result, the AC power supply 31 is connected to both ends of the DC cut capacitors 39 and 40.
The double voltage of the peak value of is charged. That is, the first and second diodes 32 and 34, the first and second choke coils 33 and 35, and the first and second DC cut capacitors 3
9 and 40 function as a half-wave voltage doubler rectifying and smoothing circuit.

Now, when the first transistor 37 is turned on, a current flows from the AC power supply 31 through the first diode 32, the first choke coil 33, and the transistor 37, and at a certain stage, the first transistor 37 flows to the first transistor 37. On the other hand, a current is supplied from the first DC cut capacitor 39.

At this time, the DC cut capacitor 39, the first
A current flows in a loop of the transistor 37, the primary winding 41a of the current transformer 41, the lighting circuit 42, and the DC cut capacitor 39. This current causes the lighting circuit 42
The choke coil 48 and the starting capacitor 49 resonate with each other to generate a high voltage across the starting capacitor 49.
7 lights up. The resonance current is fed back to the first and second transistors 37 and 38 by the current transformer 41 to drive both transistors 37 and 38.

When the first transistor 37 is turned off, the electromagnetic energy stored in the first choke coil 33 during the on period is changed to the first choke coil 3 by the electromagnetic energy.
3, the first DC cut capacitor 39, the third diode 50, and the first choke coil 33 are discharged in a loop. As a result, the first choke coil 3 is applied to the input power supply voltage applied to the first DC cut capacitor 39.
The electromagnetic energy from 3 is superimposed and the voltage across the series circuit of the DC cut capacitors 39 and 40 is boosted. That is, the first diode 32 and the third diode 5
A circuit including 0, the first choke coil 33, the first DC cut capacitor 39, and the first transistor 37 of the inverter circuit 36 functions as a step-up chopper circuit.

Next, when the second transistor 38 is turned on, the AC power source 31 causes the second choke coil 35 and the second
An electric current flows through the diode 34 of FIG. At this time, the second
DC cut capacitor 40, lighting circuit 42, primary winding 41a of current transformer 41, second transistor 3
8. A current flows in the loop of the second DC cut capacitor 40. As a result, a resonance current flows through the lighting circuit 42 in the same manner as above, and the discharge lamp 47 is lit.

When the second transistor 38 is turned off, the electromagnetic energy stored in the second choke coil 35 during the on period of the transistor 38 is changed to the second choke coil 35, the fourth diode 51, and the fourth choke coil 35. It is discharged in the loop of the second DC cut capacitor 40 and the second choke coil 35. Thereby, the electromagnetic energy from the second choke coil 35 is superimposed on the second DC cut capacitor 40 charged with the AC power supply voltage, and the voltage across the second DC cut capacitor 40 is boosted. That is, the second diode 3
4, fourth diode 51, second choke coil 3
5, a circuit including the second DC cut capacitor 40 and the second transistor 38 of the inverter circuit 36 functions as a step-up chopper circuit.

Further, the first and second transistors 37, 3
By the function as a chopper circuit for switching 8 on, the input current along the envelope of the sine waveform of the power supply voltage can be made to flow, and the input current is approximate to a sine wave with a high power factor and few odd harmonics. Become.

As described above, according to the present embodiment, since it functions as a half-wave voltage doubler rectifying and smoothing circuit, the voltage charged between both ends of the DC cut capacitors 39 and 40 is supplied to the AC power supply 31.
The voltage can be doubled to the peak value of the above, and since it further functions because it functions as a boost chopper circuit, the discharge lamp can maintain a stable lighting state even with a low input power supply voltage.

Moreover, the first and second transistors 37 and 38 of the half-bridge type inverter circuit 36 are connected to the first and second transistors 37 and 38.
Since the second DC cut capacitors 39 and 40 are also used as the chopper circuit, the circuit configuration can be simplified and the cost can be reduced.

[0027]

As described above in detail, according to the present invention, the power factor can be improved by combining the half-bridge type inverter circuit and the chopper circuit, and the circuit configuration can be simplified and the cost can be reduced. It is possible to provide a discharge lamp lighting device that can perform

[Brief description of drawings]

FIG. 1 is a configuration diagram of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional discharge lamp lighting device.

FIG. 3 is a configuration diagram of a discharge lamp lighting device having a chopper circuit.

[Explanation of symbols]

31 ... AC power supply, 32 ... First diode, 33 ... First
Choke coil, 34 ... Second diode, 35 ... Second choke coil, 36 ... Half bridge type inverter circuit, 37 ... First switching transistor, 38
Second switching transistor, 39 First DC cut capacitor, 40 Second DC cut capacitor, 42 Lighting circuit, 47 Discharge lamp, 50 Third diode, 51 Fourth diode.

Claims (1)

[Claims] 1. A half circuit having a series circuit of a pair of switching elements and a series circuit of a pair of DC cut capacitors having a smoothing function, wherein both ends of one switching element of the pair of switching elements are connected to an AC power source. A bridge type inverter circuit, a discharge lamp connected to the output terminal of the inverter circuit, a first diode and a first diode inserted between the high voltage side terminal of the one switching element and one end of the AC power supply. A series circuit of one choke coil, the first diode inserted between a connection point of the AC power supply and the first diode, and a low voltage side terminal of the other switching element of the pair of switching elements; Is a series circuit of a reverse polarity second diode and a second choke coil, and the first diode and the first choke coil. A third diode connected between the connection point and the connection point of each of the DC cut capacitors with a polarity opposite to that of the first diode, and a connection point between the second diode and the second choke coil. And a connection point of each of the DC cut capacitors, and a fourth diode connected in reverse polarity to the second diode. The ON / OFF operation of each switching element causes the first and second diodes to operate. A discharge lamp lighting device, characterized in that the energy stored in the choke coil is superposed on each of the DC cut capacitors.