JPH04174998A - Fluorescent lamp lighting device - Google Patents

Abstract

PURPOSE:To supply sufficient pre-heat current in filament electrodes by operat ing a time constant circuit utilizing the voltage appearing across a pre-heat electrodes so as to control a three-terminal switching element. CONSTITUTION:When an AC tower supply 1 is turned on, a transistor 8 is driven into conduction state by supplying current in the base of the transistor 8 through a resistor 10. Consequently, a pre-heat current flows in a closed circuit comprising a ballast 2, a pre-heat electrode 4, the transistor 8, a diode 7, and a pre-heat electrode 5. In this case, since there exists a voltage drop across the pre-heat electrode 4 due to the pre-heat current, the voltage charges a condenser 13 in a time constant circuit through a resistor 11. The pre-heat state continues until the voltage across the condenser 13 exceeds the voltage across a Zener diode 14, but when exceeding the voltage, since a current flows between the gate and the cathode of a thyristor 12 through a resistor 15, the thyristor 12 turns on, and the transistor 8 turns off, and then the current flowing through the ballast is interrupted so that a lamp 3 turns into the light-on state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a starting device for a fluorescent lamp, and more particularly to a starting device for a fluorescent lamp having a preheating electrode.

BACKGROUND OF THE INVENTION Conventionally, glow starters have been mainly used as starting devices for fluorescent lamps. However, this has drawbacks such as long start-up time and short life. Recently, starting circuits using semiconductor switch elements have been developed.
Due to its high price, demand was limited. Therefore, there is a desire to develop a starting device using a semiconductor switch element and having an inexpensive circuit type. Based on the above requirements, a circuit as shown in FIG. 3 using inexpensive transistors as semiconductor switching elements has been proposed. In Figure 3, 1
is an AC power supply, 2 is a ballast, 3 is a fluorescent lamp, 4 and 5 are preheating electrodes for the fluorescent lamp 3, 6 is a noise prevention capacitor, 7 is a diode, 8 is a transistor, 9.10.11 is a resistor, 12 is a thyristor , 13 is a capacitor, 14 is a Zener diode, and 15 is a resistor.

The operation of the lighting device configured in this way will be explained. When AC power supply 1 is turned on, diode 7 and resistor 10
Since current is supplied to the base of transistor 8 through ballast 2., transistor 8 becomes conductive and ballast 2. Preheating electrode 4. Diode 7, resistor 9. Transistor 8. A preheating current flows through the closed circuit of the preheating electrode 5. At this time, a voltage drop occurs across the resistor 9, and this voltage charges the capacitor 13 of the time constant circuit via the resistor 11. The preheating state of the fluorescent lamp 3 continues until the voltage across the capacitor 13 exceeds the voltage across the Zener diode 14. When the voltage across the capacitor 13 exceeds the voltage across the Zener diode 14, a current flows through the resistor 15 to the gate of the thyristor 12, so the thyristor 12 is turned on and the transistor 8 is turned off. At this time, the current flowing through the ballast 2 is cut off, so a pulse is generated and the fluorescent lamp 3 is turned on. FIG. 4 shows voltage and current waveforms at various parts at this time.

Also, while the lamp is lit, the capacitor 13 of the time constant circuit is always charged by the lamp voltage, so the thyristor 12
remains on, and transistor 8 does not operate.

Problems to be Solved by the Invention However, in a lighting device with such a conventional configuration, since a resistor 9 is connected in series with the transistor 8, the preheating current is insufficient due to this resistor, and cold cathode starting is likely to occur. 4 and 5, there is a risk of short life and blackening due to early wear of the emitter. Furthermore, since the resistor 9 generates heat due to the preheating current, there is a problem that a resistor with a large wattage is required.

Means for Solving the Problems The fluorescent lamp lighting device of the present invention comprises a series circuit of a ballast connected to an AC power source and a fluorescent lamp having a pair of preheating electrodes. A series body of a collector-emitter diode of a transistor is connected between the terminals of the power-supply side preheating electrode, and a terminal of one power-supply side preheating electrode of the fluorescent lamp is connected to the base of the transistor via a resistor, It has a configuration in which the anode and cathode of a three-terminal switch element controlled by a time constant circuit operated by a voltage generated across the preheating electrode are connected between the base and emitter of the transistor.

The voltage generated across the preheating electrode of the fluorescent lamp is used to operate the time constant circuit, which controls the three-terminal switch element, making it possible to flow a sufficient preheating current to the filament electrode. can.

EXAMPLE Hereinafter, an example of the present invention will be described 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 series circuit including a ballast 2 connected to an AC power source 1 and a fluorescent lamp 3 having a preheating electrode 4.5 consisting of a pair of filament coils. It is biased towards A series body of the emitter collector of a transistor 8 and a diode 7 is connected between the terminals of the non-power supply side preheating electrode of the fluorescent lamp 3. A noise prevention capacitor 6 is connected to both ends of the fluorescent lamp 30. The base of the transistor 8 is connected to the terminal of one power supply side preheating electrode of the fluorescent lamp 3 via a resistor 1o, and is operated by the voltage generated across the preheating electrodes 4 and 5 between the base and emitter of the transistor 8. resistance 1
The anode and cathode of a thyristor 12, which is a three-terminal switching element controlled by a time constant circuit consisting of a capacitor 1 and a capacitor 13, are connected. A Zener diode 14 and a resistor 15 are connected to the gate of the thyristor 12, one end of which is connected to the connection point between the resistor 11 and the capacitor 13 of the time constant circuit.
The other end of the series body is connected.

Next, the operation of the fluorescent lamp lighting device will be explained.

When the AC power supply 1 is turned on, current is supplied to the base of the transistor 8 via the resistor 1o, so the transistor 8 becomes conductive and the ballast 2, preheating electrode 4. Transistor 8. A preheating current flows through a closed circuit between the diode 7 and the preheating electrode 5. At this time, a voltage drop occurs across the preheating electrode 4 due to the preheating current, and this voltage charges the capacitor 13 of the time constant circuit via the resistor 11. capacitor 13
The preheating state continues until the voltage across the capacitor 13 exceeds the voltage of the Zener diode 14, and when the voltage across the capacitor 13 exceeds the voltage of the Zener diode 14, a voltage is applied between the gate and cathode of the thyristor 12 via the resistor 15. Since current flows, thyristor 12 is turned on and transistor 8 is turned off. At this time, the current flowing through the ballast 2 is cut off, so a pulse is generated and the fluorescent lamp 3 is turned on. The voltage and current waveforms at each part at this time are shown in FIG.

By setting the time constant of the time constant circuit so that a pulse is generated when the preheating electrodes 4 and 5 are sufficiently preheated,
Wearing of the emitter of the preheating electrode can be suppressed.

Also, while the lamp is lit, the capacitor 13 of the time constant circuit is constantly charged by the lamp voltage, so the thyristor 12
In the above embodiment, a thyristor is used as a three-terminal switch element, but the same effect as described above can be obtained when a transistor or the like is used.

As described in detail, the fluorescent lamp lighting device of the present invention allows a sufficient preheating current to flow through the preheating electrode of the fluorescent lamp, thereby suppressing consumption of the emitter of the preheating electrode due to cold cathode starting. It can extend the life of the electrode and reduce the blackening of the electrode. Furthermore, unlike the conventional method, there is no heat generated by the resistor, making it possible to achieve a smaller size and lower cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a fluorescent lamp lighting device which is an embodiment of the present invention, Fig. 2 is a voltage and current waveform diagram of various parts of the same lighting device, Fig. 3 is a circuit diagram of a conventional fluorescent lamp lighting device, and Fig. 4 is a circuit diagram of a fluorescent lamp lighting device according to an embodiment of the present invention. The figure is a diagram of voltage and current waveforms at various parts of a conventional fluorescent lamp lighting device. 1... AC power supply, 2... Ballast, 3.
...Fluorescent lamp, 4,5...Preheating electrode,
8...Transistor, 9.10.11...
...Resistor, 12...Thyristor, 14...
...Zener diode. Name of agent: Patent attorney Haruaki Koebi and two others Figure 2

Claims (1)

[Claims] In a fluorescent lamp lighting device comprising a series circuit of a ballast connected to an AC power supply and a fluorescent lamp having a pair of preheating electrodes, a collector-emitter of a transistor and a diode are connected between terminals of a non-power supply side preheating electrode of the fluorescent lamp. are connected in series, and a terminal of one power supply side preheating electrode of the fluorescent lamp is connected to the base of the transistor via a resistor. A fluorescent lamp lighting device characterized by connecting a switching element controlled by a time constant circuit operated by voltage.