JPH0574588A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To reduce distortion of higher harmonic waves in an input current waveform and to improve the input power factor, by using a simple structure. CONSTITUTION:A full-wave rectifier circuit 23 is connected to an AC power source 21 through an antinoise circuit 22, and a series circuit consisting of a smoothing capacitor 24, a 1st. choke coil 25 and a diode 26 is connected to the full-wave rectifier circuit 23. And a high frequency inverter circuit 27 is connected to the series circuit in parallel. To the output terminals of the inverter circuit, respective one ends of filament electrodes 33a, 33b of a discharge lamp 33 are connected through a low frequency cutoff capacitor 32, and a capacitor 34 is connected between the other ends of the respective filament electrodes. The other ends of respective filament electrodes of the discharge lamp are connected to the AC power source 21 through the antinoise circuit 22 and a 2nd choke coil 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a discharge lamp lighting device.

[0002]

2. Description of the Related Art Conventionally, a discharge lamp lighting device shown in FIG. 3 has been known. This connects an input terminal of a full-wave rectifier circuit 3 to an AC power source 1 via a noise prevention circuit 2, and an output terminal of the full-wave rectifier circuit 3 includes a smoothing capacitor 4, a choke coil 5 and the full-wave rectifier circuit 3. A series circuit of diodes 6 having a polarity opposite to the output polarity is connected. The high frequency inverter circuit 7 is connected in parallel to this series circuit.

The high frequency inverter circuit 7 is provided with an inverter transformer 8 and a switching transistor 9.
The resonance capacitor 10 is connected in parallel to the primary winding 8p of the inverter transformer 8. Then, one end of the primary winding 8p of the inverter transformer 8 is connected to the positive electrode side end of the smoothing capacitor 4, and the other end is connected to the anode of the diode 6 via the switching transistor 9.

The connection point between the choke coil 5 and the diode 6 is connected to the connection point between the primary winding 8p of the inverter transformer 8 and the switching transistor 9 through the diode 11 in the forward direction. Then, one end of each filament electrode 12a, 12b of the discharge lamp 12 is connected to the secondary winding 8s of the inverter transformer 8, and the capacitor 13 is connected between the other ends of the filament electrodes 12a, 12b.

In this conventional device, when the switching transistor 9 is turned on and off, a charging current flows through the smoothing capacitor 4 accordingly. The charging current at this time flows as a constant current by the choke coil 5. The resonant operation of the primary winding 8p of the inverter transformer 8 and the resonant capacitor 10 causes the secondary winding 8 of the inverter transformer 8 to operate.
High frequency power is generated in s and is supplied to the discharge lamp 12.

This high frequency power further causes a resonance current to flow through the filament electrodes 12a and 12b of the discharge lamp 12 due to the resonance operation of the secondary winding 8s of the inverter transformer 8 and the capacitor 13, thereby preheating. At the same time, a high voltage is applied between the filament electrodes 12a and 12b of the discharge lamp 12, so that the discharge lamp 12 starts high frequency lighting.

[0007]

As described above, in the conventional device, since the output current from the rectifier circuit 3 flows only during the charging period of the smoothing capacitor 4 accompanying the switching operation of the switching transistor 9, the input voltage waveform shown in FIG. As indicated by "a" and the input current waveform "b", there is a problem that harmonic distortion occurs in the input current waveform and the input power factor decreases. Then, this invention aims at providing the discharge lamp lighting device which can reduce the harmonic distortion of an input current waveform with a simple structure and can improve an input power factor.

[0008]

The present invention relates to a series circuit of a smoothing capacitor connected to an AC power source via a rectifier circuit, a first choke coil, and a diode having a polarity opposite to that of the output polarity of the rectifier circuit, and a series circuit thereof. A high-frequency inverter circuit provided with a switching transistor connected to the series circuit,
A discharge lamp is provided which is connected to the output terminal of the inverter circuit via a low frequency cutoff capacitor and is connected to the AC power source via a second choke coil.

[0009]

In the present invention having such a structure, when the switching transistor is turned on and off, a charging current flows through the smoothing capacitor accordingly. Then, the inverter circuit oscillates and high frequency power is supplied from the inverter circuit to the discharge lamp through the low frequency cutoff capacitor.
When the discharge lamp is lit, low frequency power is also supplied from the AC power supply to the discharge lamp via the second choke coil.

However, by combining the input current supplied from the AC power supply to the inverter circuit via the rectifier circuit and the input current supplied from the AC power supply to the second choke coil, the input having no pause section from the power supply side. An electric current can be passed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an input terminal of a full-wave rectifier circuit 23 is connected to an AC power supply 21 via a noise prevention circuit 22, and a smoothing capacitor 24, a first capacitor, is connected to an output terminal of the full-wave rectifier circuit 23. A series circuit of a choke coil 25 and a diode 26 having a polarity opposite to the output polarity of the full-wave rectification circuit 23 is connected. A voltage resonance type high frequency inverter circuit 27 is connected in parallel to this series circuit.

The high frequency inverter circuit 27 is provided with an inverter transformer 28 and a switching transistor 29, and a resonance capacitor 30 is connected in parallel to a primary winding 28p of the inverter transformer 28. One end of the primary winding 28p of the inverter transformer 28 is connected to the positive electrode side end of the smoothing capacitor 24, and the other end is connected to the anode of the diode 26 via the switching transistor 29.

The connection point between the first choke coil 25 and the diode 26 is connected to the connection point between the primary winding 28p of the inverter transformer 28 and the switching transistor 29 via the diode 31 in the forward direction.

Each filament electrode 33 of the discharge lamp 33 is connected to the secondary winding 28s of the inverter transformer 28 in the inverter circuit 27 through a low frequency cutoff capacitor 32.
a and 33b are connected at one end, and each filament electrode 3
A capacitor 34 is connected between the other ends of 3a and 33b.

Further, the other ends of the filament electrodes 33a and 33b of the discharge lamp 33 are connected to the AC power source 21 through the noise prevention circuit 22 and the second choke coil 35.

In the embodiment having such a configuration, when the switching transistor 29 of the inverter circuit 27 starts the on / off operation, the charging current is constant in the smoothing capacitor 24 via the first choke coil 25 accordingly. It flows like a current.

High frequency power is generated in the secondary winding 28s of the inverter transformer 28 by the resonance operation of the primary winding 28p of the inverter transformer 28 and the resonance capacitor 30. Further, due to the resonance operation between the secondary winding 28s of the inverter transformer 28 and the capacitor 34, a resonance current is generated from the secondary winding 28s via the low frequency cutoff capacitor 32, the filament electrodes 33a and 33b of the discharge lamp 33, and the capacitor 34. Flow each filament electrode 33a, 33b
Is preheated. At the same time, a high voltage is applied between the filament electrodes 33a and 33b of the discharge lamp 33,
Will start high frequency lighting.

When the discharge lamp 33 starts to light up, the internal impedance of the discharge lamp 33 decreases, so that the discharge lamp 3 passes from the AC power source 21 through the second choke coil 35.
Low frequency power will be supplied to 3.

In this way, a high-frequency current flows through the discharge lamp 28 along the low-frequency current waveform, and there is no re-ignition or the like that occurs during low-frequency lighting, and a stable lighting operation without flicker is performed.

As described above, since the input current approximates to the sine wave flows through the second choke coil 35 and the high frequency current flows along the input current, the input current with few odd harmonics can be supplied. That is, in FIG. 2, the input voltage waveform a
And, as shown by the input current waveform b, distortion of harmonics in the input current waveform can be reduced, and the input power factor can be improved. Moreover, the configuration is simple because only the low frequency cutoff capacitor 32 and the second choke coil 35 are added. Needless to say, the structure of the high frequency inverter circuit is not limited to that of the above embodiment.

[0022]

As described in detail above, according to the present invention, the harmonic distortion of the input current waveform can be reduced with a simple structure to improve the input power factor and the high frequency along the low frequency current waveform. It is possible to provide a discharge lamp lighting device that does not cause flicker and a stable lighting operation without a re-ignition that occurs when a current flows and a low frequency lighting is performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of an input voltage and an input current in the embodiment.

FIG. 3 is a circuit diagram showing a conventional example.

FIG. 4 is a waveform diagram of an input voltage and an input current in the conventional example.

[Explanation of symbols]

21 ... AC power supply, 23 ... Full wave rectification circuit, 24 ... Smoothing capacitor, 25 ... First choke coil, 26 ... Diode, 27 ... High frequency inverter circuit, 32 ... Low frequency cutoff capacitor, 33 ... Discharge lamp, 35 ... 2 choke coils.

Claims (1)

[Claims] 1. A series circuit of a smoothing capacitor connected to an AC power source via a rectifier circuit, a first choke coil, and a diode having a polarity opposite to the output polarity of the rectifier circuit,
A high-frequency inverter circuit provided with a switching transistor connected to the series circuit is connected to the output terminal of the inverter circuit via a low-frequency cutoff capacitor, and is also connected to the AC power source via a second choke coil. A discharge lamp lighting device comprising a discharge lamp.