JP3379263B2 - Fluorescent lamp lighting device - Google Patents

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.

[0002]

2. Description of the Related Art In recent years, it has been desired to make a lighting circuit small and simple in structure in order to make an efficient illuminating device small-sized, inexpensive and popularized.

As a conventional fluorescent lamp lighting device, a general series inverter as shown in FIG. 5 is known.

In FIG. 5, before starting the fluorescent lamp 8, the AC voltage is rectified from the AC power source 1 via the rectifier circuit 3 to charge the smoothing capacitor 4, and at the same time, the capacitor 20 is charged via the resistor 19. When the voltage reaches the breakdown voltage of the trigger diode 21 of the trigger circuit, the electric charge of the capacitor 20 is supplied to the base of the transistor 23 and the transistor 23 is turned on.

When the transistor 23 is turned on, the capacitor 7 and the fluorescent lamp 8 are supplied from the AC power source 1 via the rectifier circuit 3.
A current flows through the electrodes of the capacitor, the capacitor 9, the choke coil 10, the current transformer 11, and the transistor 23 while increasing. Next, the primary winding 11B of the current transformer 11
A voltage is generated in the secondary winding 11C of the current transformer 11 by the current flowing in the current transformer 11, supplies the base current of the transistor 23, and the transistor 23 is kept on.

However, when the current flowing through each winding of the current transformer 11 increases, the current transformer 1 will eventually be released.
1 core is magnetically saturated. When the core of the current transformer 11 is magnetically saturated, the output of the secondary winding 11C disappears,
Since the base current supplied to the transistor 23 can no longer be supplied, the transistor 23 is turned off.

At the same time, the current due to the energy accumulated in the choke coil 10 flowing to the capacitor 7 through the current transformer 11 and the transistor 22 is a current that changes with time, and therefore, the secondary winding of the secondary winding is interrupted at a certain point. The output polarity is inverted, and the transistor 22 is turned on eventually. Then, this current resonates with the choke coil 10 and the capacitors 7 and 9, and when this current is inverted and the core of the current transformer 11 is magnetically saturated again, the secondary winding 11
Since the output of A disappears and the base current that has been supplied to the transistor 22 cannot be supplied, the transistor 22 turns off, and then the transistor 23 turns on again. After that, this operation is repeated.

The above current flows through the electrodes of the fluorescent lamp 8 and thus heats the electrodes. At the same time, a large voltage is applied to the fluorescent lamp 8 due to resonance, so that the electrode temperature of the fluorescent lamp 8 rises and the fluorescent lamp 8 is turned on.

[0009]

As described above, in the conventional fluorescent lamp lighting device, it is known that the trigger means for lighting the fluorescent lamp, that is, the trigger circuit uses the trigger diode.

However, in general, the characteristic of the trigger diode has a large change with respect to the ambient temperature, and in particular, when the trigger diode itself is at a low temperature at the time of starting, there is a problem that the operating voltage is insufficient and normal operation cannot be performed.

An object of the present invention is to provide a fluorescent lamp lighting device capable of reliably lighting a fluorescent lamp without using a trigger diode.

[0012]

A fluorescent lamp lighting device according to the present invention comprises a series capacitor formed by connecting a resonance capacitor, a fluorescent lamp, an inductance element, a current transformer and an FET in series, and both ends of the series capacitor. In a fluorescent lamp lighting device including a smoothing capacitor connected to the FET, a series body of a secondary winding of the current transformer and a trigger capacitor connected between the gate and the source of the FET, and a drain of the FET. A first resistor connected between the gate and the gate of the FET to charge the trigger capacitor, and a second resistor connected between the gate and the source of the FET to charge or discharge the trigger capacitor. And a starting means consisting of a resistor.

[0013]

With this configuration, at the time of starting the fluorescent lamp, while the smoothing capacitor is being charged with the voltage up to the power supply voltage peak value, the charging current of the smoothing capacitor is such that the resonance capacitor 7, one electrode 8A of the fluorescent lamp 8 and the preheating capacitor. 9, the trigger capacitor 14 is charged via the other electrode 8B of the fluorescent lamp 8, the inductance element 10, the primary winding 11B of the current transformer 11, the resistor 12, and the secondary winding 11C of the current transformer 11, and its voltage is changed. When the gate threshold voltage of FET6 is reached, the trigger capacitor 14
Is supplied to the gate of the FET 6 to turn on the FET 6 and start driving the high frequency inverter circuit.

[0014]

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, the fluorescent lamp lighting device according to the embodiment of the present invention has a resonance capacitor 7, a fluorescent lamp 8, an inductance element 10, a current transformer 11, and a drain of a FET 6 as a first switching element. The source circuits are sequentially connected in series to form a series body. The smoothing capacitor 4 is provided between both ends of the series body, that is, between one end of the resonance capacitor 7 and the source terminal of the FET 6.
Are connected to form a closed circuit. Connection point between current transformer 11 and FET 6 and resonance capacitor 7
The drain-source circuit of the FET 5, which is the second switch element, is connected between the connection point between the smoothing capacitor 4 and the smoothing capacitor 4.

Both ends of the smoothing capacitor 4 are connected to the output terminals of the rectifier circuit 3 connected to the AC power supply 1, respectively. The input end of the rectifier circuit 3 is connected to the AC power supply 1 via the noise prevention capacitor 2. Further, a preheating capacitor 9 is provided between the pair of electrodes 8A and 8B of the fluorescent lamp 8.
Is connected to the side opposite to the power source, and constitutes a high frequency inverter circuit as a whole.

That is, a DC input obtained by rectifying and smoothing commercial AC power supplied from the AC power supply 1 is connected in parallel between the smoothing capacitor 4 and the fluorescent lamp 8 and oscillates at high frequency. The fluorescent lamp 8 is supplied with high-frequency power generated by a series circuit of FETs 5 and 6 that are elements, and an LC resonant circuit that is connected to the FET 6 and that is connected in series to the fluorescent lamp 8 and that includes a resonant capacitor 7 and an inductance element 10. It is an inverter circuit.

Furthermore, the current transformer 11 is provided with a series body of the secondary winding 11C of the current transformer 11 and the trigger capacitor 14 which forms a closed circuit between the gate and the source of the FET 6 as a starting means of the high frequency inverter circuit.
One end of the secondary winding 11C is connected to the gate terminal of the FET 6, and one end of the trigger capacitor 14 is connected to the source terminal of the FET 6. A pair of, that is, two constant voltage diodes 17 and 18 are connected to face each other between both ends of the secondary winding 11C of the current transformer 11. The middle point of the constant voltage diodes 17, 18 and the trigger capacitor 14 and F
A resistor 13 for discharging the voltage charged in the trigger capacitor 14 is connected between the connection point of the ET6 and the source terminal. In addition, the gate terminal of the FET6 and the FET6
And a connection point between the primary winding 11B of the current transformer 11 and
That is, the resistor 12 that charges the trigger capacitor 14 is connected between the gate and drain of the FET 6.

The current transformer 11 has a pair of secondary windings 11A and 11C.
1A and 11C function as self-excited oscillation means for the FETs 5 and 6, respectively. The secondary winding 11A of the current transformer 11 is connected to the gate terminal of the FET 5,
A pair of constant voltage diodes 15 and 16 are also connected to face each other between the gate and the source of the FET 5.

Next, the operation of the fluorescent lamp lighting device according to the embodiment of the present invention will be described. Before starting the fluorescent lamp 8,
AC power supply 1 to commercial AC power is noise prevention capacitor 2
Is supplied to the rectifier circuit 3, and a pulsating voltage is generated through the rectifier circuit 3. The current due to this pulsating voltage flows into the next closed circuit while the smoothing capacitor 4 is charged to the peak value of the power supply voltage. That is, the current is the resonant capacitor 7, one electrode 8A of the fluorescent lamp 8, the preheating capacitor 9, the other electrode 8B of the fluorescent lamp 8, the inductance element 10, the primary winding 11B of the current transformer 11, the resistor 12, the current. Trigger capacitor 1 via secondary winding 11C of transformer 11
4 and the trigger capacitor 14 is charged.

When the voltage charged in the trigger capacitor 14 reaches the gate threshold voltage of the FET 6, the charge of the trigger capacitor 14 is supplied to the gate of the FET 6 and the FET 6 turns on. When the FET 6 is turned on, since the initial voltage of the smoothing capacitor 4 is lower than the voltage value of the AC power supply 1, the AC power supply 1 is further connected to the rectifier circuit 3.
Via the resonance capacitor 7, one electrode 8A of the fluorescent lamp 8, the preheating capacitor 9, the other electrode 8B of the fluorescent lamp 8, the inductance element 10, the current transformer 11
The current flows through the primary winding 11B and the FET 6 while increasing.

Next, the primary winding 1 of the current transformer 11
A voltage is generated in the secondary winding 11C of the current transformer 11 by the current flowing in 1B, supplies a gate current to the FET 6, and the FET 6 is kept on.

At this time, the current flowing through the primary winding 11B of the current transformer 11 also continues to increase, but at some point the core of the current transformer 11 is magnetically saturated and loses its function as an inductance.

When the core of the current transformer 11 is magnetically saturated, the output of the secondary winding 11C of the current transformer 11 disappears, the voltage supplied between the gate and the source of the FET 6 falls below the threshold voltage, and the FE
T6 turns off.

Since the current due to the energy accumulated in the current transformer 11 is a current that changes with time, the output polarity of the secondary winding is inverted at the magnetic saturation of the core of the current transformer 11.

That is, since the voltage supplied between the gate and the source of the FET 5 rises, the FET 5 turns on in due course.

When the FET5 is turned on, the current is FET5,
It flows through a closed circuit composed of the current transformer 11, the inductance element 10, the fluorescent lamp 8 and the resonance capacitor 7, and this current resonates with the choke coil 10, the resonance capacitor 7 and the preheating capacitor 9.

This current is inverted and the current transformer 11
When the core of the current transformer is magnetically saturated again, the output of the secondary winding 11A of the current transformer 11 disappears, and the gate of the FET5-
Since the voltage supplied between the sources becomes equal to or lower than the threshold voltage, the FET 5 is turned off, and then the output polarity of the secondary winding of the current transformer 11 is inverted, so that the FE is again fed.
T6 turns on. After that, this operation is repeated.

The above current is applied to the electrodes 8A,
8B to heat the electrodes 8A and 8B. At the same time, a large voltage is applied between the electrodes 8A and 8B of the fluorescent lamp 8 due to resonance, the electrode temperature of the fluorescent lamp 8 rises, and the fluorescent lamp 8 is turned on.

As described above, by using the starting means, that is, the trigger circuit shown in the above-mentioned embodiment, the fluorescent lamp can be reliably started and lit with an extremely simple structure, so that the fluorescent lamp lighting device is smaller and less expensive. Can be obtained.

As an example, in the circuit configuration shown in FIG. 1, the inductance of the choke coil 10 is 0.47 mH, the capacitance of the resonance capacitor 7 is 0.1 μF, and the capacitance of the preheating capacitor 9 is 100 V under an input condition of an AC power supply voltage of 100 V. Is 6
Good results were obtained with 800 pF, the smoothing capacitor 4 having a capacitance of 33 μF and the trigger capacitor 14 having a constant of 0.01 μF.

In the above embodiment, the resistor 13 for discharging the voltage charged in the trigger capacitor 14 is provided with a pair of constant voltage diodes provided so as to face the connection point between the source terminal of the FET 6 and the trigger capacitor 14. Although the example of connecting between the midpoints of 17 and 18 has been described, the trigger capacitor 14 is discharged as shown in FIG. 2 as the starting means of the fluorescent lamp lighting device according to the second embodiment of the present invention. The same effect can be obtained by connecting the resistor 13 between the gate and source of the FET 6 and removing the series body of the constant voltage diode.

Also, as a third embodiment, as shown in FIG. 3, a series body of a pair of constant voltage diodes 17 and 18 facing each other is connected between the gate and source of the FET 6 as a starting means. Between both ends of the series body of the secondary winding 11C of the current transformer 11 and the trigger capacitor 14,
The same effect can be obtained by using the trigger capacitor 14 connected in parallel with the discharging resistor 13.

Further, as a fourth embodiment, FIG.
As shown in FIG. 4, as a starting means, a series body of a pair of facing constant voltage diodes 17 and 18 is connected between the gate and source of the FET 6 to connect the secondary winding 11C of the current transformer 11 and the trigger capacitor 14. The resistor 13 which is connected in series between the secondary windings 11C of the current transformer 11 and discharges the trigger capacitor 14 is connected to the FET.
The same effect can be obtained by using the one connected between the gate terminal of FET 6, the source terminal of FET 6, and the connection point of the trigger capacitor 14.

Although the series inverter is used as the lighting circuit, the same effect can be obtained by using another configuration as long as the switching transistor is driven by the current transformer, for example, a single stone inverter.

Further, in the present embodiment, the preheating capacitor 9 is provided on the side opposite to the power source of the fluorescent lamp 8, but the same effect can be obtained by providing it on the side of the power source. Further, although the trigger circuit is configured to trigger the FET 6, it may be the FET 5.

[0037]

As described above, according to the present invention, it is possible to provide a fluorescent lamp lighting device capable of reliably lighting a fluorescent lamp without using a trigger diode, and having a small size and a simple structure and being inexpensive. It is possible.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a trigger circuit of a fluorescent lamp lighting device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a trigger circuit of a fluorescent lamp lighting device according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a trigger circuit of a fluorescent lamp lighting device according to a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional fluorescent lamp lighting device.

[Explanation of symbols]

4 Smoothing capacitor 5,6 FET 7 Resonant capacitor 8 fluorescent lamps 10 Inductance element 11 Current Transformer 12,13 resistor 14 Trigger capacitor

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Laid-Open No. 5-94893 (JP, A) Japanese Patent Laid-Open No. 53-141429 (JP, A) Actual Flat 4-6200 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) H05B 41/24

Claims (4)

(57) [Claims] 1. A fluorescent lamp lighting device including a resonance capacitor, a fluorescent lamp, an inductance element, a current transformer, and a series body formed by connecting an FET in series, and smoothing capacitors connected to both ends of the series body. In the device, a series body of the secondary winding of the current transformer and a trigger capacitor connected between the gate and the source of the FET, and the trigger capacitor connected between the drain and the gate of the FET are provided. It has a starting means comprising a first resistor for charging and a second resistor for charging or discharging the trigger capacitor connected between the gate and the source of the FET. Fluorescent lamp lighting device. 2. The starting means comprises the series body of the secondary winding of the current transformer and the trigger capacitor, a pair of opposing constant voltage diodes connected between both ends of the series body, and the FET. A first resistor for charging the trigger capacitor connected between the drain and the gate of the second resistor, and a second resistor for charging or discharging the trigger capacitor connected across the series body. The fluorescent lamp lighting device according to claim 1, wherein the fluorescent lamp lighting device comprises: 3. A start-up means includes a series body of the secondary winding of the current transformer and the trigger capacitor, and a pair of opposing constant coils connected between both ends of the secondary winding of the current transformer. A voltage diode; the first resistor for charging the trigger capacitor connected between the drain and the gate of the FET; and the charge or discharge for the trigger capacitor connected across the series body. 2. A second resistor is included.
The fluorescent lamp lighting device described. 4. A start-up means includes a series body of the secondary winding of the current transformer and the trigger capacitor, and a pair of opposing constant coils connected between both ends of the secondary winding of the current transformer. The voltage diode, the first resistor connected between the drain and the gate of the FET to charge the trigger capacitor, and the connection point between the source terminal of the FET and the trigger capacitor are provided to face each other. The fluorescent lamp lighting device according to claim 1, wherein the second resistor for charging or discharging the trigger capacitor is provided between the middle points of the set of the constant voltage diodes.