JPS58189986A - Device for firing discharge lamp - 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] The present invention provides a first closed circuit in which a power source, an inductive ballast, and a discharge lamp are connected in series, and a first closed circuit in which a power source, an inductive ballast, and a switch circuit are connected in series. The present invention relates to an improvement of the above-mentioned circuits S, B, and T in a discharge lamp lighting device, which is constructed of a second closed circuit with a closed circuit and a second closed circuit.

This 2i! The operation of the electric lamp lighting device repeats the operation of a discharge lamp. With this operation, the discharge lamp can be stably lit even when the power supply voltage is relatively low compared to the pressure of the discharge lamp 11 of the discharge lamp.

The key point of the switching circuit of this lighting device is that it can quickly interrupt the current flowing through the inductive ballast. To achieve this purpose.

It is easiest and cheapest to use a gate turn-off thyristor as the switch (due to the small current, high voltage resistance element and low frequency operation).

In the conventional lighting device shown in FIG. 1, the switch circuit 11 includes a gate turn-off thyristor 5 (hereinafter referred to as "gate turn-off thyristor") connected between the DC output terminals of the rectifier 4 via a full-wave rectifier 4 for functioning as an AC switch. (abbreviated as GT080B),
It consists of a series circuit with a circuit element for generating a voltage approximately proportional to the current 11 flowing through the GTO8CR5, and this voltage generating circuit element consists of a parallel circuit of a resistor 7 and a capacitor 8. In order to anode the gate of the GT080R5, a switch is quickly made conductive at a constant voltage across a voltage generating circuit element consisting of a parallel circuit of the resistor 7 and capacitor 8 described above.

10 (eg V18BS or 8U8) is connected.

The operation of this circuit is as follows. When the discharge lamp 3 is lit, the switch element 10 is conductive, and at this time, all the current flowing through the resistor 9 flows through the switch element 10, so that the GTO8OR5 remains non-conductive. Then, when the discharge of the discharge lamp ends and the voltage across the discharge lamp 3 becomes zero.

The current flowing through the switch element 100 becomes zero, and the switch elements 10i-j become non-conductive. Subsequently, the voltage across the discharge lamp 30 increases, and in the period before reaching the breakover voltage of the switch element 10, the voltage '1 of the resistor 9 → ballast 2 → full-wave rectifier 4 → GTO 8 OR 5 → resistor 7 and capacitor 8 A parallel circuit with → full-wave rectifier 4 → and a closed circuit with source 1 are formed.
The flow flows. During this period, when the voltage applied to the switch element 10 reaches the resistance breakover voltage, the switch element IO rapidly becomes conductive, and the resistance 7. The voltage of the parallel circuit of the capacitor 8 is applied as a reverse voltage between the gate and cathode of the GTO 8C through the switch element 10, and the GTO
80R5 becomes non-conductive quickly.

In the following period, 'IN,'wt: lamp 3 is inductive ballast 2
The light is turned on by the energy stored in the power source 1 and the energy supplied from the power supply 1 via the ballast 2, and the current flowing through the resistor 9 due to this discharge voltage causes the switch element 10 to be turned on.
continuity is maintained. This operation is repeated every half cycle to keep the discharge lamp lit.

However, the problem here is the current interrupting ability of the GTO80R5, which generally has a characteristic that the current cannot be interrupted when the current exceeds a certain value. This maximum interruptible current is approximately proportional to the 1.5th power of the reverse voltage value applied between the gate and the cathode.

It is almost inversely proportional to the junction temperature of GT080R5. Therefore, it is necessary to set the current as high as possible so that the GTO80R5 can always cut off the current.

If you increase the reverse voltage that can be applied between the gate and cathode until it exceeds the reverse withstand voltage between the gate and cathode,
Applying a reverse voltage no longer than -1 (4, GTO80
Voltage breakdown occurred at the R5 junction, and the GTO80as
can no longer be shut off. Therefore, the setting of the applied reverse voltage value is.

The reverse withstand voltage between the gate and cathode of the GT080R5 must be set to a certain level lower than that of the GT080R5, and in this sense, the range of applications in which the GTO80R5 can be used is limited.Therefore, one object of the present invention is to solve the above-mentioned problems. An object of the present invention is to provide a discharge lamp lighting device that solves the problem. In order to achieve the above object, in the present invention, a high speed diode is connected in series with the cathode of ()TO80R5.

11) The present invention, which is characterized in that it is configured to make maximum use of the blocking ability of GT080R, will be explained in detail with reference to the drawings.

FIG. 2 shows a circuit configuration of a discharge lamp lighting device according to the present invention. In the figure, the applied reverse voltage in the operation of the conventional lighting device described above is set to be approximately equal to or higher than the reverse breakdown voltage between the gate and cathode of GTO8OR5.

The switch element 10 is applied to the voltage drop value of the parallel circuit of the resistor 7 and the capacitor 8 and the series circuit of the cathode and gate of the GTO 80R, 5 via the switch element 10. Then, the fast diode 6 immediately becomes non-conductive, and therefore the cathode current of GTO80R5 immediately becomes zero.
The cathode holder becomes open. Therefore, the cutoff mode of GTO80R5 at this time is.

It becomes unrelated to the reverse breakdown voltage between the gate and cathode, and becomes the same as the fast-acting mode of a three-layer junction diode between the anode and gate, and the fast-acting ability of GTO80R,5 increases significantly.
This is 2 to 3 times the case without the high-speed diode 6.

Due to the above effects, GTO8, which originally has a small fast-acting capacity,
It also becomes possible to use 0R, and its practical value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional discharge lamp lighting device, and FIG. 2 is a circuit diagram of an embodiment of the lighting device according to the present invention. In the figure, 1
: Power supply, 2: Inductive ballast, 3: Discharge lamp, 4: Full wave rectifier, 5: Cyrisk, 6: High speed diode, 7: Resistor,
8: Capacitor. 9: Resistor, 10: Switch element. +1 figure/ll +2 figure? 7

Claims (1)

[Claims] 1 from a first closed circuit in which a source, an inductive ballast, and a discharge lamp are connected in series, and a second closed circuit in which the power source, the ballast, and a switch are connected in series. In the discharge lamp lighting device, a unidirectional thyristor with a gate turn-off characteristic is used as the switch, and a circuit element is provided at the cathode end of the thyristor that generates a voltage approximately proportional to the current flowing through the thyristor via a high-speed diode. and a switch element is connected between the gate end of the thyristor and the other end of the voltage generating circuit element, such that the generated voltage value of the voltage generating circuit element is equal to or equal to the cathode-to-gate reverse breakdown voltage value of the thyristor. The discharge lamp is characterized in that the switch element is rapidly turned on when the above value reaches one above, and the cathode end of the thyristor is substantially opened by the high-speed diode. lighting device.