JPS62133698A - Fluorescent lamp burner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fluorescent lamp lighting device for lighting a fluorescent lamp at high frequency.

BACKGROUND OF THE INVENTION It is well known that by lighting a fluorescent lamp at a high frequency, the lighting setup can be made smaller and lighter, and the luminous efficiency can be improved. A single-stone self-excited inverter circuit shown in FIG. 5 is generally used as a high-frequency lighting device. In this circuit, a smoothing capacitor 2 is connected to a rectifier 1 connected to a commercial power source to form a power supply circuit, and a resonance capacitor 3 and a switching transistor 8 are connected in series.

Furthermore, the primary winding 4 of the current limiting inductance element 4
A and a fluorescent lamp 5 having a pair of electrodes sa and sb are connected in series, and the starting circuit is composed of a series body of a diode 6 and a bidirectional semiconductor control element 7 between the electrodes sa and sb of the fluorescent lamp 5. is connected. One end of the secondary winding 4b of the current limiting inductance element 4 is connected to the transistor 80 through the capacitor 9, and the other end is connected to the negative terminal of the power supply circuit. In addition, a starting resistor 10. A diode 11 and a resistor 12 are constructed.

Problems to be Solved by the Invention Problems encountered when starting a fluorescent lamp using the circuit shown in FIG. 5 will be described below. When commercial power is turned on, a power supply circuit consisting of a rectifier 1 and a smoothing capacitor 2 converts it into a DC power supply.
A current flows to the base of the transistor 8 via the starting resistor 1Q, and the transistor 8 is turned on. At that time, the collector current changes from the positive electrode of the smoothing capacitor 2 to the primary winding a4a of the current limiting inductance element to the electrode 6 of the fluorescent lamp 5.
a → diode 6 → bidirectional semiconductor control element 7 → electrode 5b of fluorescent lamp 5 → collector emitter of transistor 8 → negative electrode of smoothing capacitor 2.

Furthermore, the secondary winding 4 of the current limiting inductance element 4
Since an electromotive force is generated in the transistor 6 in the direction of turning on the transistor 8, the transistor 8 remains on. Next, the collector current of transistor 8 increases. )h
When f, ・IB (I.: collector current, hfo = current amplification factor, two base current), the collector current tends to saturation, and the starting force of the secondary winding a4b becomes opposite, so
Transistor 8 quickly turns off. At this time, due to the energy i − accumulated in the primary winding 4a of the current limiting inductance element for blocking the reverse voltage of the diode 6, −Lτ,0 (L: 1
A high voltage (the inductance value of the next winding 4a) is generated. This high voltage causes the fluorescent lamp 5 to
Cold cathode discharge starts before the battery is sufficiently preheated. As a result, problems arise such as early blackening of the inner surface of the glass tube due to the scattering of the electron radioactive material on the electrodes 5a and 5b of the fluorescent tube 5, and a shortened service life.

Means for Solving the Problems The present invention provides a transistor inverter circuit having a current-limiting inductance element between a pair of electrodes of a fluorescent lamp connected via the current-limiting inductance element.
The present invention is characterized by a fluorescent lamp lighting device in which a diode and a bidirectional semiconductor control element are connected in series, and a positive temperature coefficient thermistor is connected in parallel with the diode.

Operation First, during transistor operation of the transistor inverter circuit, the preheating current of the fluorescent lamp flows through the series body of the diode and the bidirectional semiconductor control element. Next, when the transistor is in operation, a current flows through the bidirectional semiconductor control element and the positive temperature coefficient thermistor due to the electromagnetic energy stored in the current limiting inductance element. This electromagnetic energy is absorbed by a positive temperature coefficient thermistor, so
High voltages are not generated between the fluorescent lamp electrodes. and,
A positive temperature coefficient thermistor self-heats due to the preheating current, and its resistance value increases rapidly.

Then, is it a positive characteristic thermistor? : Since the preheating current of the fluorescent lamp is cut off, a high voltage due to electromagnetic energy is applied between the electrodes of the fluorescent lamp to start discharging the fluorescent lamp.

Embodiment First, the basic configuration of a circuit according to an embodiment of the present invention will be explained with reference to FIG.

As shown in FIG. 1, a series body of a resonance capacitor 3 and a switch S is connected between the positive terminal and the negative terminal of the power supply circuit.
Resonant capacitor 3 and current limiting inductance element 4
A fluorescent lamp 6 having a pair of electrodes 5a and sb is connected to an inverter circuit having a current limiting inductance element 4. and both electrodes 5a of the fluorescent lamp 5.

A series body of a diode 6 and a bidirectional semiconductor control element 7 is connected between the diode 5b, and a positive temperature coefficient thermistor 13 is connected in parallel with the diode 6.

In such a circuit, when the switch S is in the on state,
Positive terminal → primary winding 4a of current limiting inductance element 4
→ Electrode 6a → Diode 6 → Bidirectional semiconductor control element 7
(The positive terminal voltage is higher than the breakover voltage of the bidirectional semiconductor control element 7) -> electrode 5b -> switch S -> the preheating current f1 flows through the closed circuit of the negative terminal. Next, when the switch S is turned off, the electromagnetic energy accumulated in the primary winding 4a of the current limiting inductance element 4 causes the primary winding 4a of the current limiting inductance element 4 to turn off.
Current flows through the closed circuit of the primary winding 4b of the current limiting inductance 4, and the electromagnetic energy is positive. Characteristic thermistor 13
Since the high voltage is absorbed by the electrodes 6a of the fluorescent lamp 5,
It does not occur between 5b. The resistance value of the PTC thermistor 13 when cold is low, but due to the Joule heat caused by the preheating current (when the temperature of the PTC thermistor 13 rises and reaches the switching temperature or higher, the resistance value of the PTC thermistor 13 increases). As a result, a closed circuit through the positive temperature coefficient thermistor 13 is not formed when the switch is turned on, so a high voltage due to the electromagnetic energy is applied between the electrodes sa and sb of the fluorescent lamp 5, and the fluorescent lamp 5 starts discharging.

Next, one embodiment of the present invention will be described using the drawings.

In this circuit, a rectifier 1 and a smoothing capacitor 2 are connected to the commercial power supply.
are connected to form a power supply circuit.

A resonance capacitor 3 and a switching transistor 8 are connected in series.

In addition, the primary winding 4a of the current limiting inductance element 4
and a fluorescent lamp 5 having a pair of electrodes sa and sb are connected in series, and an electrode 5a of the fluorescent lamp 5.

A starting circuit formed by connecting a parallel body of a diode 6 and a positive temperature coefficient thermistor 13 in series with a bidirectional semiconductor control element 7 is connected between 5b and 5b.

Furthermore, the secondary winding 4 of the current limiting inductance element 4
One end of b is connected to the base of transistor 8 via base current limiting capacitor 9, and the other end is connected to the negative terminal of the power supply circuit. In addition, a diode 11. is used as a reset circuit for the base current limiting capacitor 9. A resistor 12 is connected to the base of the transistor 8, and a resistor 10 is connected as a starting resistor.

Next, the operation of this circuit will be explained. When commercial power is turned on, the smoothing capacitor 2 is charged through the rectifier 1, and current flows through the starting resistor 1o to the base of the transistor 8, turning the transistor 8 on. At that time, the collector current of the transistor 8 is as follows: positive electrode of the smoothing capacitor 2 → primary winding 4a of the current limiting inductance element 4 → electrode 5a of the fluorescent lamp 5 → diode 6 → bidirectional semiconductor control element 7 → Electrode 6b of fluorescent lamp 5 → transistor 8
Flows from collector emitter to negative electrode of smoothing capacitor 2.

Furthermore, the current limiting inductance element 40 secondary winding 4
Since a starting force is generated in the direction b that turns on the transistor 8, the on state of the transistor 8 is maintained. At this time, the preheating current If1 (Fig. 3 (
The waveform is shown in a). ) flows. Next, the collector current increases. > hfo” IB (Eng.: Collector current,
= base current, hfo: current amplification factor), the collector current is saturated, so the starting force generated in the secondary winding D4b of the current limiting inductance element 4 is in the cutoff direction of the transistor 8. 8 is rapidly turned off. When transistor 8 is turned off,
The electromagnetic energy accumulated in the primary winding 4a of the current limiting inductance element 4 is absorbed by the closed circuit consisting of the positive temperature coefficient thermistor 13, the bidirectional semiconductor control element 7, and the resonance capacitor 3, so that high voltage is not generated at both ends of the fluorescent lamp 5. At this time, the electrodes sa and sb are
The preheating current f2 shown in b) flows. As the transistor 8 repeats the on-off operation, an alternating current preheating current f1. xf
2 flows and the temperature of the electrode increases. This positive characteristic thermistor 13 has a low resistance value when cold, but the preheating current f
The temperature rises due to Joule heat generated by 2, and its resistance value rises rapidly. Therefore, a closed circuit is not formed through the positive temperature coefficient thermistor 13 when the transistor 8 is off, and as a result, the high voltage due to the electromagnetic energy accumulated in the primary 134a of the current limiting inductance element 4 is applied to the fluorescent lamp. 6, the fluorescent rung 6 starts a main discharge. When the fluorescent lamp 5 is turned on, the voltage across the fluorescent lamp 5 decreases and unless it falls below the breakover voltage of the bidirectional semiconductor control element 7, the starting circuit ceases to function. Therefore, the positive characteristic thermistor 13
No current flows through the circuit, the temperature decreases, and the resistance value decreases. Next, turn off the commercial power and repeat the same operation when turning it back on.

Further, as shown in FIG. 4, a circuit configuration may be provided in which a compensation winding 4C is added in order to increase the preheating current.

Effect of the invention As described above, according to the present invention, the following effects can be obtained.

(1) Since the time during which the preheating current is sufficiently passed can be set by the characteristics of the positive temperature coefficient thermistor, the flashing life of the fluorescent lamp can be significantly extended.

(2) When the fluorescent lamp is turned on, the bidirectional semiconductor control element does not operate, so no preheating current flows, and there is no preheating loss at all times, and no current flows to the positive temperature coefficient thermistor, so the Since the temperature is lower and the resistance value is lower, the engine can be restarted using the same operation as when it was started.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the basic configuration of a fluorescent lamp lighting device of the present invention, FIG. 2 is a circuit diagram of a fluorescent lamp lighting device that is an embodiment of the present invention, and FIG. ). (C) is a waveform diagram of the preheating current in the same fluorescent lamp installation device, FIG. 4 is a circuit diagram of a fluorescent lamp lighting device which is another embodiment of the present invention, and FIG. 6 is a conventional fluorescent lamp lighting device. FIG. 1...- Rectifier, 2... Smoothing capacitor, 3... Resonance capacitor, 4... Current limiting inductance element, 4a... Primary winding, 4b... Secondary winding, 4C... Compensation winding, 5... Fluorescent lamp, s a , 5b.
...Electrode, 6...Diode, 7...
... Bidirectional semiconductor control element, 8 ... Transistor, 9 ... Base current limiting capacitor,
1o... Starting resistor, 11... Diode, 12... Resistor, 13... Positive characteristic thermistor. Name of agent: Patent attorney Toshio Nakao and 1 other person3-
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Claims (1)

[Claims] A series body of a diode and a bidirectional semiconductor control element is connected between a pair of electrodes of a fluorescent lamp connected to a transistor inverter circuit having a current-limiting inductance element via the current-limiting inductance element, and A fluorescent lamp lighting device characterized in that a positive temperature coefficient thermistor is connected in parallel with the diode.