JPH0151876B2 - - Google Patents

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 switch circuit in a discharge lamp lighting device comprising a second closed circuit.

The operation of this discharge lamp lighting device is such that the switch circuit short-circuits when the discharge in the discharge lamp ends, and then rapidly opens when the current flowing therethrough reaches an appropriate constant value. This operation allows the discharge lamp to be stably lit even with a power supply voltage that is relatively low compared to the discharge voltage of the discharge lamp.

The key point of the switch circuit in this lighting system is that it can quickly interrupt the current flowing through the inductive ballast. To achieve this purpose, it is simplest and cheapest to use a gate turn-off thyristor as a switch (due to its low 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.
GTOSCR) and a circuit element for generating a voltage approximately proportional to the current flowing through the GTOSCR 5. This voltage generation circuit element consists of a parallel circuit of a resistor 7 and a capacitor 8. ing. A resistor 9 is connected between the gate and anode of GTOSCR5 to trigger the GTOSCR5.
is connected to it, and in order to turn off the GTOSCR 5, a switch element 10 which rapidly conducts at a constant voltage is connected to the gate of the GTOSCR 5, across a voltage generating circuit element consisting of a parallel circuit of the above-mentioned resistor 7 and capacitor 8. (e.g. SBS and SUS) are 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 GTOSCR
5 maintains a non-conducting state. 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 10 becomes zero, and the switch element 10 becomes non-conductive. Subsequently, in the period before the voltage across the discharge lamp 3 increases and reaches the breakover voltage of the switch element 10, all of the current in the resistor 9 flows into the gate of the GTOSCR 5.
This makes GTOSCR5 conductive. Then, power supply 1 → stabilizer 2 → full wave rectifier 4 → GTOSCR 5 → parallel circuit of resistor 7 and capacitor 8 → full wave rectifier 4
→A closed circuit is formed with power supply 1 and current flows. During this period, the voltage applied to the switch element 10 becomes approximately equal to the voltage drop of the parallel circuit of the resistor 7 and capacitor 8. This voltage drop value is the switch element 10
When the breakover voltage reaches the breakover voltage of rapidly becomes non-conductive. In the subsequent period, the discharge lamp 3 is lit by the energy stored in the inductive ballast 2 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 lit. continuity is maintained. Such an operation is repeated every half cycle to keep the discharge lamp lit.

However, the problem here is
This is the current interrupting ability of GTOSCR5, and it generally has the characteristic that current cannot be interrupted when the current exceeds a certain value. This maximum interruptible current is approximately proportional to the 1.5 power of the reverse voltage value applied between the gate and the cathode, and approximately inversely proportional to the junction temperature of the GTOSCR 5.
Therefore, in order for the GTOSCR 5 to be able to always cut off current, it is necessary to keep the junction temperature low and at the same time set the reverse voltage applied between the gate and cathode as high as possible.

If you increase the reverse voltage applied between the gate and cathode so that it exceeds the reverse withstand voltage between the gate and cathode, voltage breakdown will occur at the junction of GTOSCR5 even if a higher reverse voltage is applied. , GTOSCR5 can no longer be shut off. Therefore, the setting of the applied reverse voltage value is
It must be set to a certain level lower than the gate-to-cathode reverse breakdown voltage of GTOSCR5, and in this sense, the range of conditions under which GTOSCR5 can be used is limited.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a discharge lamp lighting device that eliminates the above-mentioned problems. In order to achieve the above object, the present invention provides GTOSCR5
A high-speed diode is connected in series with the cathode of the GTOSCR, thereby making maximum use of the GTOSCR's interrupting ability.

Hereinafter, the present invention will be explained in detail using 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 the GTOSCR 5. The switch element 10 becomes conductive when the voltage drop value of the parallel circuit of the resistor 7 and the capacitor 8 reaches the breakover voltage of the switch element 10. It is added to the circuit via a switch element 10. Then, the high speed diode 6 immediately becomes non-conductive, so the cathode current of the GTOSCR 5 immediately becomes zero, and the cathode end becomes open. Therefore, the cutoff mode of GTOSCR5 at this time becomes unrelated to the reverse withstand voltage between the gate and cathode, and becomes the same as the cutoff mode of a three-layer junction diode between the anode and gate, and the cutoff ability of GTOSCR5 increases significantly. , 2~ without fast diode 6
It will be tripled.

Due to the above effects,
It also becomes possible to use GTOSCR, and its practical value is extremely large.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional discharge lamp lighting device, Figure 2 is a circuit diagram of a conventional discharge lamp lighting device.
The figure is a circuit diagram of an embodiment of a lighting device according to the present invention. In the diagram, 1: power supply, 2: inductive ballast, 3:
Discharge lamp, 4: Full wave rectifier, 5: Thyristor, 6:
High speed diode, 7: resistor, 8: capacitor,
9: Resistor, 10: Switch element.

Claims (1)

[Claims] 1. A series circuit of an inductive ballast and a discharge lamp connected between the AC power supply connection terminals, a full-wave rectifier connected between the non-power supply side electrodes of the discharge lamp, and a DC output terminal of the full-wave rectifier. a one-way thyristor with a gate turn-off characteristic connected between the resistor and the capacitor, which is connected between the cathode end of the thyristor and the DC output end, and generates a voltage approximately proportional to the current flowing through the thyristor. a parallel circuit, a resistor connected between the anode and gate of the thyristor, and a resistor connected between the gate of the thyristor and the DC output terminal, the voltage value generated by the parallel circuit being connected between the cathode and gate of the thyristor; a switch element that rapidly conducts when a reverse breakdown voltage value or a value exceeding it is reached; and a switch element connected in series with the parallel circuit between the cathode of the thyristor and the DC output end of the switch element; A discharge lamp lighting device comprising: a high-speed diode that substantially opens the cathode during rapid conduction.