JPH0955291A - Fluorescent lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorescent lamp lighting device capable of stopping oscillation, when one fluorescent lamp is detached without adding a special circuit for detecting the existence of a fluorescent lamp, in a lighting device for lighting plural fluorescent lamps. SOLUTION: A base drive voltage of the transistor 11 of a selfexciting type half-bridge inverter circuit 100 for lighting fluorescent lamps 3 and 4 by voltage, obtained by rectifiably smoothing an A.C. power source 1, is obtained from a feedback winding 21a wound on a ballast inductor 21 on the fluorescent lamp 3 side. The base drive voltage of a transistor 12 is obtained from a feedback winding 22a wound on a ballast inductor 22 on a fluorescent lamp 4 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp lighting device for turning on a fluorescent lamp by inputting AC power.

[0002]

2. Description of the Related Art Generally, a self-excited half-bridge type inverter circuit is frequently used in a fluorescent lamp lighting device. This is because the circuit configuration is simple and the constant setting is easy. However, when two or more fluorescent lamps are lit by this inverter circuit, the self-excited half-bridge circuit continues to oscillate even if one of the lit lamps is removed, and a high frequency high voltage is generated between the fluorescent lamp sockets. Keep doing FIG. 2 shows a countermeasure circuit in which oscillation is appropriately stopped except for the above problems. Hereinafter, this will be described. In FIG. 2, 1 is an AC power supply, 2 is a rectifier circuit, and 41 is a capacitor that smoothes the output voltage of the rectifier circuit 2. In parallel with the capacitor 41, two cascade-connected transistors 11 and 12 which are switching elements of the self-excited half-bridge type inverter circuit 100 and capacitors 43 and 44 connected in series are respectively connected. Diodes 14 and 15 are connected in antiparallel with the transistors 11 and 12, respectively. Between the connection points of the transistors 11 and 12 and the connection points of the capacitors 43 and 44 in FIG. 2, a series circuit including a ballast inductor 21 which is one load and a parallel circuit of the capacitor 45 and the fluorescent lamp 3 is connected, Further, a series circuit including the ballast inductor 22 which is the other load and the parallel circuit of the capacitor 46 and the fluorescent lamp 4 is connected. Both load and transistor 1 above
The primary winding of the feedback transformer 20 for generating the base voltage of the transistors 11 and 12 is connected between 1 and 12. The secondary winding of the feedback transformer 20 has two transistors 11
-Connected between the 12 bases and emitters via resistors 32 and 33. A series circuit of the resistor 31 and the capacitor 42 is connected to the capacitor 41 of FIG. 2, and the intersection of the resistor 31 and the capacitor 42 is connected to the transistor 1 via the diode 16.
It is connected to the base of the transistor 12 at the intersection of 1 · 12 and via a trigger element (2-terminal thyristor) 13. The filaments on the condenser 43 and 44 sides of the fluorescent lamps 3 and 4 in FIG. 2 are connected to the filament detection circuit 5,
The output signal of the filament detection circuit 5 is the transistor 1
It is supplied via a resistor 34 to the base of the transistor 10 which is connected to the position where the two bases and the emitter are short-circuited. In FIG. 2, the AC voltage of the AC power supply 1 is rectified by the rectifier circuit 2 and smoothed by the capacitor 41.
The smoothed voltage charges the capacitor 42 via the resistor 31,
When the voltage of the capacitor 42 exceeds the breakover voltage of the trigger element 13, the charged charge of the capacitor 42 flows to the base of the transistor 12 via the trigger element 13,
The transistor 12 is turned on. When the transistor 12 is turned on, the current flows through the capacitor 41, the capacitor 43, the filament of the fluorescent lamp 3, the condenser 45, the filament of the fluorescent lamp 3 and the ballast inductor 21, and at the same time, the condenser 43, the filament of the fluorescent lamp 4, and the condenser 4.
6, filament of fluorescent lamp 4, ballast inductor 22
And flows. The current flowing through the ballast inductors 21 and 22 is the primary winding of the feedback transformer 20, the transistor 12,
It flows with the condenser 41. When a current flows through the primary winding of the feedback transformer 20, a current flows through the secondary winding of the feedback transformer 20 in the direction to turn on the transistor 12. And
When a current flows through the primary winding of the feedback transformer 20 above a certain level, the feedback transformer 20 is saturated, the voltage generated in the secondary winding is inverted, and the transistor 12 is turned off and the transistor 11 is turned on. When the transistor 11 is turned on, the current flows through the capacitor 41, the transistor 11, the primary winding of the feedback transformer 20, the ballast inductor 21, which is one of the load circuits, the filament of the fluorescent lamp 3, and the capacitor 4.
5, the filament of the fluorescent lamp 3, the ballast inductor 22 which is the other load circuit, the filament of the fluorescent lamp 4, the capacitor 46, the filament of the fluorescent lamp 4, and the combined current of the load circuit is the capacitor 44 and the capacitor 41.
And flows. Thereafter, the transistors 11 and 12 are alternately turned on and off to apply a high frequency voltage to the load circuit. Due to this high frequency voltage, a resonance voltage is generated in the series circuit of the ballast inductor 21 and the capacitor 45 (ballast inductor 22 and capacitor 46), and the fluorescent lamp 3
The filament of (4) is heated and a high voltage is applied to the fluorescent lamp 3 (4), and the fluorescent lamp 3 (4) starts discharging. The filament detection circuit 5 detects the filament resistance of the fluorescent lamps 3 and 4, and does not output an output signal when the fluorescent lamps 3 and 4 are mounted. Here, when either of the fluorescent lamps 3 and 4 is removed, the output signal of the filament detection circuit 5 is output, the transistor 10 is turned on, the base voltage of the transistor 12 is cut off, and the operation of the inverter circuit 100 is stopped. , Prevents generation of high frequency high voltage between fluorescent lamp sockets.

[0003]

In the conventional circuit shown in FIG.
A filament detection circuit 5 for detecting the presence or absence of the fluorescent lamp 3 is provided in order to prevent a high frequency high voltage from being continuously generated between the sockets of the fluorescent lamp (3) when one fluorescent lamp (for example, 3) is removed. It is necessary to provide the oscillation transistor control voltage cutoff transistor 10 for stopping the oscillation of the lighting device, which complicates the circuit. It is an object of the present invention, in a lighting device for lighting a plurality of fluorescent lamps, without adding a special circuit for detecting the presence or absence of fluorescent lamps, oscillation can be easily stopped when one fluorescent lamp is removed. It is an object of the present invention to provide a fluorescent lamp lighting device capable of operating.

[0004]

In order to achieve the above object, as shown in FIG. 1, a self-excited half bridge circuit 10 is provided.
The base driving voltage of the transistor 11 of 0 is obtained from the winding wound around the ballast inductor 21 which is the current control element of the fluorescent lamp 3, and the base driving voltage of the transistor 12 is set to the fluorescent lamp 4 of the fluorescent lamp 4.
It is configured to be obtained from the winding wound around the ballast inductor 22 which is the current control element.

[0005]

As shown in FIG. 1, if the fluorescent lamp 3 is removed from the lighting device while the fluorescent lamp 3 is lit, no current will flow through the ballast inductor 21.
Since no voltage is generated in the feedback winding 21a wound around 1, the on / off operation of the transistor 11 is stopped. As a result, the operation of the transistor 12 also stops, so that the operation of the self-excited half-bridge circuit 100 also stops, and it is possible to prevent generation of a high-frequency high voltage between the fluorescent lamp sockets.

[0006]

EXAMPLE An example of the present invention will be described with reference to FIG. In FIG. 1, 1 is an AC power supply, 2 is a rectifier circuit, and 41 is a capacitor that smoothes the output voltage of the rectifier circuit 2. Capacitor 41
In addition, two cascade-connected transistors 11 and 12, which are switching elements of the self-excited half-bridge inverter circuit 100, and a capacitor 43 connected in series.
・ 44 are connected in parallel. Each transistor 11
・ Diodes 14 and 15 are connected in antiparallel with 12. Connection point between transistors 11 and 12 and capacitor 43.4
A pair of load circuits serving as a load of the inverter circuit 100 is connected between the four connection points. One load circuit is fluorescent lamp 3
And a ballast inductor 21 and a preheating capacitor 45 in series with the lighting circuit. The other load circuit is a lighting circuit including the fluorescent lamp 4, a ballast inductor 22 in series with the fluorescent lamp 4, and a preheating capacitor 46. Both lighting circuits are in parallel, and power is supplied from the inverter circuit 100 together. A feedback winding 21a for driving the transistor 11 is wound around one ballast inductor 21 in FIG.
One of the feedback windings 21 a is connected to the emitter of the transistor 11 and the other is connected to the base of the transistor 11 with a resistor 32.
Connected via The other ballast inductor 22 has a feedback winding 22 a for driving the transistor 12.
Is wound, and one side of this feedback winding 22a is the transistor 1
The emitter of 2 is connected to the base of the transistor 12 via the resistor 33. A series circuit of a resistor 31 and a capacitor 42 is connected to the capacitor 41, and an intersection of the resistor 31 and the capacitor 42 is connected to an intersection of the transistors 11 and 12 via the diode 16 and a transistor via a trigger element (thyristor) 13. It is connected to 12 bases.

Next, the operation of the circuit shown in FIG. 1 will be described. The AC voltage of the AC power supply 1 is rectified by the rectifier circuit 2 and smoothed by the capacitor 41. This smoothed voltage is
When the capacitor 42 is charged via the trigger element 13 and the voltage of the capacitor 42 exceeds the breakover voltage of the trigger element 13, the charged charge of the capacitor 42 flows to the base of the transistor 12 via the trigger element 13 and
Turn on. When the transistor 12 is turned on, the current flows through the capacitor 41, the capacitor 43, the filament of the fluorescent lamp 3, the condenser 45, the filament of the fluorescent lamp 3, and the ballast inductor 21, and at the same time, the condenser 43, the filament of the fluorescent lamp 4, the condenser 46, the fluorescent lamp 4 Of the filament, the ballast inductor 22, and the combined current of the ballast inductors 21 and 22 is the transistor 1
2, the capacitor 41 flows. As described above, when current flows through the ballast inductors 21 and 22, the feedback winding 21
The output of a is the operation of turning off the transistor 11, and the output of the feedback winding 22a is the operation of turning on the transistor 12. After that, the ballast inductor 21, the capacitors 45 and 43 (the ballast inductor 22, the capacitor 46
The feedback winding 21a at the resonance frequency determined by 43)
The output voltage of 22a changes, and after a certain time, the transistor 12 is turned off and the transistor 11 is turned on. When the transistor 11 is turned on, the current flows through the capacitor 41, the transistor 11, the ballast inductor 21 which is one of the lighting circuits, the filament of the fluorescent lamp 3, the capacitor 45, the filament of the fluorescent lamp 3, and the ballast inductor 22 which is the other lighting circuit. The combined current of the filament of the fluorescent lamp 4, the condenser 46, the filament of the fluorescent lamp 4, and the load circuit flows through the condenser 44. After that, a high frequency voltage is applied to each lighting circuit circuit by alternately turning on and off the transistors 11 and 12. By this high frequency voltage, the ballast inductor 21 and the capacitor 45
A resonance voltage is generated in the series circuit of the (ballast inductor 22 and the capacitor 46), heats the filament of the fluorescent lamp 3 (4), and a high voltage is applied to the fluorescent lamp 3 (4). Starts discharging.

When the fluorescent lamps 3 and 4 are turned on and the fluorescent lamp 3 is removed from the lighting device, for example, the ballast inductor 2
No current flows through the ballast inductor 21.
The voltage is no longer generated in the feedback winding 21a wound around the coil, and the on / off operation of the transistor 11 is stopped. And
Since the operation of the transistor 12 also stops, the operation of the self-excited half-bridge type inverter circuit 100 also stops. Even when the other fluorescent lamp 4 is removed from the lighting device, no current flows in the ballast inductor 22, so that no voltage is generated in the feedback winding 22a wound around the ballast inductor 22 and the transistor 12 is turned on / off. The operation stops, and the operation of the self-excited half-bridge inverter circuit 100 stops. As a result, even if either of the fluorescent lamps 3 and 4 is removed from the lighting device, it is possible to prevent generation of high-frequency high-voltage between the fluorescent lamp (3.4) sockets. In the embodiment of FIG. 1, when the fluorescent lamps 3 and 4 are removed from the lighting device, the fluorescent lamps 3 and 4 are detected in order to prevent a high-frequency high voltage from being generated between the fluorescent lamp (3.4) sockets. Since it is not necessary to add a circuit, the circuit configuration is simplified and the lighting device can be downsized.

The explanation will be supplemented. The half-bridge type inverter circuit 100 is based on two switching elements 11 and 12 connected in cascade. The pair of capacitors 43 and 44 in series is not essential. Condenser 43
The modified half-bridge circuit in which one of 44 is omitted may be practically used. The half-bridge type inverter circuit 100 oscillates by alternately turning on and off the two switching elements 11 and 12. If either one of the switching elements 11 or 12 is held in the off state, the oscillation stops. The present invention uses this property
Used in combination with the light circuit. The ballast inductor 21 corresponding to the fluorescent lamp 3 is in charge of on / off control of the one switching element 11. The ballast inductor 22 corresponding to the fluorescent lamp 4 is in charge of on / off control of the switching element 12. Under this circumstance, when the fluorescent lamps 3 and 4 are both alive, it is possible to alternately turn on and off the two switching elements 11 and 12, and when either one of the fluorescent lamps 3 or 4 is removed. Alternate on / off control becomes impossible and oscillation stops.

[0010]

According to the present invention, in a lighting device for lighting a plurality of fluorescent lamps, it is possible to reliably perform the operation when one fluorescent lamp is removed without adding a special circuit for detecting the presence or absence of the fluorescent lamps. The effect is that the oscillation can be stopped.
Further, there is an advantage that the circuit is simple and inexpensive because no special circuit for detecting the presence or absence of the fluorescent lamp is added.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a fluorescent lamp lighting device according to the present invention.

FIG. 2 is a circuit diagram of a conventional fluorescent lamp lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Rectifier circuit 3.4 ... Fluorescent lamp 5 ... Filament detection circuit 10/11/12 ... Transistor 14/15/16 ... Diode 21/22 ...・ Ballast inductor 21a ・ 22a ・ ・ ・ Feedback winding 31 ・ 32 ・ 33 ・ ・ ・ Resistance 41 ・ 42 ・ 43 ・ 44 ・ 45 ・ 46 ・ ・ ・ Capacitor 00 ・ ・ ・ Self-excited half-bridge type inverter circuit

Claims (1)

[Claims] 1. An AC power supply, a rectifying circuit for full-wave rectifying the AC power supply, a smoothing circuit for smoothing an output voltage of the rectifying circuit, and two cascade-connected switching elements connected to the smoothing circuit. A fluorescent lamp including a fluorescent lamp and a lighting circuit including a ballast inductor in series with the fluorescent lamp, and another similar set of lighting circuits, wherein each of the lighting circuits is supplied with power from the inverter circuit. In the lighting device, ON / OFF of one of the switching elements is controlled by an output of a feedback winding wound on one of the ballast inductors, and the other switching element is controlled by an output of a feedback winding wound on the other ballast inductor. Fluorescent lamp lighting device characterized by controlling ON / OFF of the.