JPH0945489A - Inverter circuit for fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the inverter circuit for a fluorescent lamp, which is compact, and low in noise by turning a switching transistor on when terminal voltage at the output side is high, and however, turning the switching transistor off when terminal voltage at the output side is low. SOLUTION: Voltage at the output terminal of an inductance is compared with a reference voltage by a control circuit 3. And a transistor is driven in such a way that a switching transistor is turned off when terminal voltage at the output side is high, and the switching transistor is turned on when terminal voltage at the output side is low. By this constitution, a main switching transistor is synchronized with the oscillation frequency of a resonance type Royal inverter circuit, and furthermore, since the output side voltage of an inductance corresponding to input voltage is compared with a reference voltage so as to be controlled, two switching circuits can be synchronously operated by letting one circuit be so constituted that one smoothing coil can be commonly used by two switching circuits.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter circuit for driving a fluorescent lamp.

[0002]

2. Description of the Related Art Fluorescent lamps have about three times the luminous efficiency of incandescent lamps and have a long life. Therefore, fluorescent lamps are now the mainstream of luminaires mainly for home lighting. At present, a method of driving a fluorescent lamp with a high-frequency inverter has been widely used for the purpose of improving the luminous efficiency of the fluorescent lamp, reducing flicker, and expanding the application range of the power source.

A conventional fluorescent lamp inverter circuit will be described below with reference to the drawings. FIG. 3 shows a conventional fluorescent lamp inverter circuit. 1 is a DC power supply, 2 is a main switch transistor which constitutes a chopper regulator, 3 is a chopper regulator drive circuit, 4 is a flywheel diode which circulates the current of the chopper regulator, 5 is a current smoothing coil which constitutes the chopper regulator, and 6 is a chopper It is a voltage smoothing capacitor that constitutes a regulator. Reference numeral 7 is an inductance that makes the input current of the resonance type Royer inverter constant, and 10 is a capacitor that forms an LC resonance circuit with the inductance component of the inverter transformer. 8 and 9 are switch transistors forming a resonance type Royer inverter, 11 is an inverter transformer forming a resonance type Royer inverter,
Reference numeral 12 is a ballast capacitor that stabilizes the discharge current of the fluorescent lamp, 13 and 14 are resistors that supply a drive current to the switch transistors 8 and 9, and 15 is a fluorescent lamp.

First, when power is supplied from the DC power supply 1, the chopper regulator drive circuit 3 drives the main switch transistor 2 to drive and control the chopper regulator so that the voltage of the smoothing capacitor 6 becomes a reference voltage value. The resonance type Royer inverter supplied with a constant voltage from the chopper regulator supplies currents from the resistors 13 and 14, and the switch transistors 8 and 9 are formed by the inverter transformer 11 and the capacitor 10.
The resonance type Royer inverter is operated by driving at the resonance frequency.

Electric power is supplied to the primary side of the resonance type Royer inverter, and electric power is supplied from the filament preheating winding of the fluorescent lamp of the inverter transformer 1 to the filaments of both electrodes of the fluorescent lamp 15 to preheat the filament. At the same time, a high voltage is applied from the main winding of the inverter transformer 11 to both electrodes of the fluorescent lamp via the ballast capacitor 12. When the filament is preheated, thermoelectrons are generated from the filament and, at the same time, a high voltage is applied to both electrodes of the fluorescent lamp, so that the fluorescent lamp starts and lights up soon. When the fluorescent lamp is started, the voltage of both electrodes of the fluorescent lamp drops, but a stable discharge state is determined by the voltage across the fluorescent lamp, the voltage generated from the main winding of the inverter transformer 11 and the ballast capacitor 12.

As described above, even if the voltage of the DC power supply 1 fluctuates, a constant voltage is applied to the resonance type Royer inverter by the action of the chopper regulator, so that the fluorescent lamp can always be lit stably.

[0007]

However, the above configuration requires two types of switching circuits, that is, a chopper regulator and a resonance type Royer inverter,
The number of parts is large, and in particular, two inductances are required. Further, there are problems such as beat generation and interference noise due to the difference in operating frequency between the two switching circuits.

In view of the above problems, the present invention provides a compact and low-noise fluorescent lamp inverter circuit that shares the inductance of two switching circuits with a simple circuit configuration and enables synchronous operation of the two switching circuits. is there.

[0009]

In order to achieve this object, a fluorescent lamp inverter circuit of the present invention has a resonance having an input side constant inductance, an inductance component of an inverter transformer, and a capacitor forming an LC resonance circuit. Type Royer inverter, flywheel diodes connected to both ends of the input circuit of the resonance type Royer inverter, a main switch transistor for cutting off the input power source, and a control circuit for driving the main switch transistor. A circuit compares the voltage at the output terminal of the inductance with a reference voltage, and if the voltage at the output terminal is high, the main switch transistor is turned off.
In the F state, when the voltage of the output side terminal is low, the main switch transistor is driven so as to turn on the main switch transistor.

[0010]

With this configuration, the main switch transistor is synchronized with the oscillation frequency of the resonance type Royer inverter circuit, and the output side voltage of the inductance corresponding to the input voltage is compared with the reference voltage and controlled. It is possible to realize a compact and low-noise fluorescent lamp inverter circuit with a simple circuit configuration in which one smoothing coil is shared, and moreover, two switching circuits can be operated synchronously.

[0011]

【Example】

(Embodiment 1) Hereinafter, the first embodiment of the fluorescent lamp inverter circuit of the present invention
Embodiments will be described with reference to the drawings.

FIG. 1 shows a first embodiment of a fluorescent lamp inverter circuit according to the present invention. With reference to FIG. 1, 1 is a DC power supply, 2 is a main switch transistor which constitutes a chopper regulator, 3 is a control circuit which is constituted by a reference voltage realized by a constant voltage element such as a Zener diode and a comparator, and drives a chopper regulator, 4 Is a flywheel diode that circulates the current of the chopper regulator, 5 is an inductance that also serves as a chopper regulator and for making the input current of the resonance type Royer inverter constant, and 10 is a capacitor that forms an LC resonance circuit with the inductance component of the inverter transformer Is. Reference numerals 8 and 9 are switch transistors forming a resonance type Royer inverter, 11 is an inverter transformer forming a resonance type Royer inverter, 12 is a ballast capacitor for stabilizing discharge current of a fluorescent lamp, and 13 and 14 are switch transistors 8 and 9. Resistance for supplying drive current, 15
Is a fluorescent lamp.

First, when power is supplied from the DC power supply 1, the control circuit 3 for driving the chopper regulator turns on the main switch transistor 2 because the output side voltage of the inductance 5 is lower than the reference voltage of the control circuit 3. By this operation, current is supplied through the resistors 13 and 14 to drive the switch transistors 8 and 9, and the resonance type Royer inverter is started from this point. After that, the control circuit 3 drives the main switch transistor 2, and when the output side voltage of the inductance 5 is lower than the reference voltage of the control circuit 3, the main switch transistor 2 is turned on to supply the current from the DC power supply 1, and conversely the inductance. The output side voltage of 5 is the control circuit 3
When the voltage is higher than the reference voltage, the main switch transistor 2 is turned off to cut off the DC power supply 1, and the flywheel diode 4 circulates the energy stored in the inductance 5 and the inverter transformer 11. The resonance type Royer inverter, to which constant power is supplied by the above operation, continuously supplies current from the resistors 13 and 14 to drive the switch transistors 8 and 9 at the LC resonance frequency configured by the inverter transformer 11 and the capacitor 10. ,
Resonant Royer inverter is operated continuously.

When the resonance type Royer inverter is started,
Electric power is supplied from the filament preheating winding of the fluorescent lamp of the inverter transformer 11 to the filaments of both electrodes of the fluorescent lamp 15 to preheat the filament. At the same time, a high voltage is applied from the main winding of the inverter transformer 11 to both electrodes of the fluorescent lamp via the ballast capacitor 12. When the filament is preheated, thermoelectrons are generated from the filament and, at the same time, a high voltage is applied to both electrodes of the fluorescent lamp, so that the fluorescent lamp starts and lights up soon. When the fluorescent lamp is started, the voltage of both electrodes of the fluorescent lamp drops, but a current determined by the voltage across the fluorescent lamp, the voltage generated from the main winding of the inverter transformer 11 and the ballast capacitor 12 flows, and a stable discharge state occurs. become.

(Second Embodiment) A second embodiment of the fluorescent lamp inverter circuit of the present invention will be described below with reference to the drawings.

FIG. 2 shows a second embodiment of the fluorescent lamp inverter circuit according to the present invention. Regarding FIG. 2, 1 to
Reference numeral 15 is the same component as that of the embodiment shown in FIG.

In this embodiment, the control circuit 3 compares the collector voltage of the transistor 8 of the two transistors forming the resonance type Royer inverter with the reference voltage,
When the collector voltage is high, the main switch transistor is turned off, and when the collector voltage is low, the main switch transistor is turned on.

First, in the control circuit 3 for driving the chopper regulator when power is supplied from the DC power source 1, the collector voltage of the switch transistor 8 of the resonance type Royer inverter is lower than the reference voltage of the control circuit 3, so that the main switch transistor 2 is turned on. Turn it on. This action causes resistance 1
A current is supplied via 3 and 14 to drive the switch transistors 8 and 9, and the resonance type Royer inverter is started from this point. After that, the control circuit 3 drives the main switch transistor 2, and when the voltage of the switch transistor 8 is lower than the reference voltage of the control circuit 3, the main switch transistor 2 is turned on to supply a current from the DC power supply 1, and conversely When the collector voltage of 8 is higher than the reference voltage of the control circuit 3, the main switch transistor 2 is turned off.
Set to F to shut off the DC power supply 1 and use the flywheel diode 4 for the inductance 5 and the inverter transformer 11
Recirculate the energy stored in. The resonance type Royer inverter, to which constant power is supplied by the above operation, continuously supplies current from the resistors 13 and 14 to connect the switch transistors 8 and 9 to the inverter transformer 11 and the capacitor 1.
The resonance type Royer inverter is continuously operated by driving at the LC resonance frequency constituted by 0.

When electric power is supplied to the primary side of the resonance type Royer inverter, electric power is supplied from the filament preheating winding of the fluorescent lamp of the inverter transformer 11 to the filaments of both electrodes of the fluorescent lamp 15 to preheat the filament. At the same time, a high voltage is applied from the main winding of the inverter transformer 11 to both electrodes of the fluorescent lamp via the ballast capacitor 12. When the filament is preheated, thermoelectrons are generated from the filament and, at the same time, a high voltage is applied to both electrodes of the fluorescent lamp, so that the fluorescent lamp starts and lights up soon. When the fluorescent lamp is started, the voltage of both electrodes of the fluorescent lamp drops, but a current determined by the voltage across the fluorescent lamp, the voltage generated from the main winding of the inverter transformer 11 and the ballast capacitor 12 flows, and a stable discharge state occurs. become. In the second embodiment, the operating frequency of the main switch transistor 2 is synchronized with the operating frequency of the transistor 8 forming the resonance type Royer inverter, which is half the operating frequency of the main switch transistor 2 of the first embodiment. It is possible to achieve the same performance as that of the first embodiment by using the switch transistor 2 that is small and uses a relatively low-cost switch element.

Although the transistor has been described as a typical example of the switch element in the present invention, it can be realized by an FET or SIT and is not limited to the transistor.

[0021]

As described above, according to the present invention, a resonance type Royer inverter having an inductance for making a constant current, an inductance component of an inverter transformer and a capacitor forming an LC resonance circuit on the input side, and the resonance type Royer. A flywheel diode connected to both ends of the input circuit of the inverter, a switch transistor for connecting and disconnecting the input power source, and a control circuit for driving the switch transistor, the control circuit 3 including a voltage at the output terminal of the inductance. Compared with a reference voltage, if the output side terminal voltage is high, the switch transistor is turned on.
In the FF state, when the voltage at the output side terminal is low, the switch transistor is driven so as to turn on the switch transistor.
The main switch transistor is synchronized with the oscillation frequency of the resonance type Royer inverter circuit, and the output side voltage of the inductance corresponding to the input voltage is controlled by comparison with the reference voltage. Therefore, the smoothing coils of two switching circuits are shared by one. It is possible to realize a compact and low-noise fluorescent lamp inverter circuit with a simplified and simple circuit configuration and to enable synchronous operation of two switching circuits, and its practical effect is great.

Further, a resonance type Royer inverter having an input side constant inductance, an inductance component of an inverter transformer, and a capacitor forming an LC resonance circuit, and a fly connected to both ends of the input circuit of the resonance type Royer inverter. It is composed of a wheel diode, a main switch transistor that shuts off an input power source, and a control circuit that drives the main switch transistor, and the control circuit is one of two transistors that form the resonance type Royer inverter. Of the collector voltage of the main switch transistor is compared with a reference voltage, and if the collector voltage is high, the main switch transistor is turned off.
In the F state, when the voltage of the collector is low, the main switch transistor is driven so as to turn on the main switch transistor.
The main switch transistor is synchronized with the oscillation frequency of the resonance type Royer inverter circuit, and the output side voltage of the inductance corresponding to the input voltage is controlled by comparison with the reference voltage. Therefore, the smoothing coils of two switching circuits are shared by one. It is possible to realize a compact and low-noise fluorescent lamp inverter circuit with a simplified and simple circuit configuration and to enable synchronous operation of two switching circuits, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a fluorescent lamp inverter circuit of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the fluorescent lamp inverter circuit of the present invention.

FIG. 3 is a circuit diagram showing a conventional fluorescent lamp inverter.

[Explanation of symbols]

 1 DC power supply 2 Main switch transistor 3 Control circuit 4 Flywheel diode 5 Inductance 8 Switch transistor 9 Switch transistor 10 Capacitor 11 Inverter transformer 12 Ballast capacitor 13 Resistor 14 Resistor 15 Fluorescent lamp

Claims (2)

[Claims] 1. A resonance type Royer inverter having an inductance for making a constant current, an inductance component of an inverter transformer and a capacitor forming an LC resonance circuit on an input side, and a fly connected to both ends of the input circuit of the resonance type Royer inverter. It is composed of a wheel diode, a switch transistor for connecting and disconnecting the input power source, and a control circuit for driving the switch transistor, the control circuit comparing the voltage of the output side terminal of the inductance with a reference voltage, and the output side. The fluorescent lamp inverter circuit is characterized in that the switch transistor is turned off when the voltage of the terminal is high, and the switch transistor is turned on when the voltage of the output side terminal is low. 2. A resonance type Royer inverter having an inductance for making a constant current, an inductance component of an inverter transformer and a capacitor forming an LC resonance circuit on an input side, and a fly connected to both ends of the input circuit of the resonance type Royer inverter. It is composed of a wheel diode, a switch transistor for connecting and disconnecting an input power source, and a control circuit for driving the switch transistor, and the control circuit is a collector of one of two transistors forming the resonance type Royer inverter. And a reference voltage, and when the collector voltage is high, the switch transistor is turned off, and when the collector voltage is low, the switch transistor is turned on. .