JPH0624426B2 - Thyristor firing circuit - Google Patents

Description

The present invention relates to a thyristor ignition circuit adapted to obtain ignition energy of a thyristor from a main circuit power source of the thyristor.

FIG. 1 is a circuit diagram showing a conventional thyristor firing circuit of this kind. In the figure, a resistor (2) for a surge absorber and a capacitor (between the anode (1a) and the cathode (1b) of the thyristor (1) are shown. 3) and the series body of the auxiliary thyristor (4) are connected in parallel, the above resistance increases as the potential of the anode (1a) becomes higher than the cathode (1b) of the main thyristor (1).
At the same time when current flows through (2) and capacitor (3),
A current flows through the series body of the diode (6) and the capacitor (7) connected in parallel between the anode and the cathode of the auxiliary thyristor (4), and the voltage of the capacitor (7) begins to gradually increase with the polarity shown. At the same time, the anode voltage of the diode (6) also rises, and the rising voltage increases the auxiliary thyristor.
When the threshold voltage Vz of the Zener diode (5) connected in parallel between the anode and gate of (4) is exceeded, the current flowing in the diode (6) is transferred to the Zener diode (5) side. It is configured to commutate and ignite the auxiliary thyristor (4), and after this thyristor (4) is ignited,
The current flowing through the resistor (2) and the capacitor (3) flows to the auxiliary thyristor (4), making the anode potential of the thyristor (4) almost equal to the potential of the cathode (1b) of the main thyristor (1),
This condition is maintained while the current continues to flow.

Then, a transistor (11) is inserted between the cathode of the diode (6) and the gate of the main thyristor (1),
Further, between the base and collector of the transistor (11), a light receiving element for conducting the transistor (11) by receiving a light command signal (10) to be fired through the light guide (9). (8) is provided, auxiliary thyristor
After (4) is ignited, in the state where the voltage across the capacitor (7) maintains a predetermined voltage determined by the Zener diode (5), the optical command signal (10) to be ignited is output as described above. The charge stored in the capacitor (7) is applied to the light receiving element (8), which makes the transistor (11) conductive.
Discharge to the gate of the main thyristor (1) via (11),
It is configured to provide the ignition pulse energy for the main thyristor (1).

However, in the conventional ignition circuit according to the configuration shown in FIG.
If the power supply voltage of the main thyristor (1) drops or the timing of the firing command signal shifts, the charging voltage of the capacitor (7) is not established up to the threshold of the Zener diode (5), In this state, if the main thyristor (1) is ignited, the ignition energy will be small and the ignition will be inadequate.
There was a risk of destroying (1).

The present invention has been made to eliminate the drawbacks of the conventional circuit as described above, and even if the call command is input while the capacitor has not established a sufficient voltage for supplying the ignition pulse energy to the gate of the main thyristor. (EN) A thyristor ignition circuit which prohibits the output of an ignition pulse and outputs sufficient pulse energy for ignition after the voltage is established.

An embodiment of the present invention will be described below with reference to FIG. 2 showing the same parts as those in FIG. In Fig. 2, the charge accumulated in the capacitor (7) is transferred to the main thyristor (1).
As a switching element provided between the gate of the thyristor (1) and one end of the capacitor (7),
A PNP transistor (12) is used, and a light receiving element (8) and a resistor (1) are provided between the base of the transistor (12) and the emitter.
3), the second auxiliary thyristor (14) is connected to the light receiving element (8), and the cathode of the thyristor (14) is connected so as to face the cathode of the main thyristor (1), and The gate pole of the second auxiliary thyristor (14) is connected in series with the cathode of the first auxiliary thyristor (4), and the diodes (15) and (16) connected in series to the cathode of the first auxiliary thyristor (4) to adjust the voltage drop to a required value. It is connected to the connection point with the body through a current limiting resistor (17).

Therefore, in the configuration shown in FIG. 2, the firing command signal (1
0) is input and the light receiving element (8) becomes conductive, the transistor (1
2) is configured so that it does not conduct. This is because the second auxiliary thyristor (14) is connected to the base of the transistor (12) for switching control.
The conduction condition of the auxiliary thyristor (14) is that current flows through the diodes (15) and (16), the anode potential of the diode (15) reaches a predetermined value, and the thyristor passes through the current limiting resistor (17).
Only when current flows to the gate electrode of (14). And
This state is because the first auxiliary thyristor (4) is conducting and the current flows, and the voltage of the capacitor (7) is sufficient for the first auxiliary thyristor (4) to be conducting. It is when the thyristor (4) is ignited after the threshold voltage of the Zener diode (5) is exceeded after the establishment.

That is, after the voltage of the capacitor (7) is sufficiently established, the first auxiliary thyristor (4) is turned on and then the second auxiliary thyristor (14) is turned on. In other words, the power supply for roll call, that is, The voltage across the capacitor (7) is the main thyristor (1)
The second auxiliary thyristor (14) becomes conductive under the condition that it is charged to a predetermined voltage value capable of supplying sufficient ignition pulse energy to ignite. Therefore, in such a state, when the ignition command is input, the transistor (12) naturally becomes conductive and outputs the pulse voltage. At this time, the resistor (13) keeps the conductive state of the thyristor (14) by flowing a current more than the holding current in the thyristor (14) by the voltage of the capacitor (7).

As is apparent from the above, according to the embodiment shown in FIG. 2, it is possible to output the pulse voltage only when the voltage across the power source for ignition, that is, the capacitor (7) reaches a certain value. There is no fear that the main thyristor (1) will be destroyed by outputting the ignition pulse in an insufficient ignition state where the ignition energy is small.

Further, FIG. 3 shows another embodiment of the present invention. In this embodiment, the transistor (12) of the embodiment of FIG.
8) are cascade-connected to form a direct-connection type cascade amplifier, and the firing current from the transistor (18) to the main thyristor (1) is amplified. As in the embodiment of FIG. Since the ignition pulse voltage is output under the condition that is established to a required value, there is no fear of destruction of the main thyristor due to lack of ignition energy, and reliability in ignition is significantly improved.

As described above, according to the present invention, while the capacitor does not establish a sufficient voltage for supplying the ignition pulse energy to the gate of the main thyristor, the ignition pulse output by the capacitor is output even if the ignition command is input. Prohibition and outputting sufficient pulse energy for ignition to the main thyristor gate after the above voltage is established.Therefore, the ignition of the main thyristor in the state of insufficient ignition energy can be reliably prevented and the thyristor may be destroyed. Can be eliminated, and reliability in ignition can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional thyristor firing circuit, and FIG.
FIG. 3 is a circuit diagram showing a diagram of a thyristor firing circuit according to an embodiment of the present invention, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. (1): Main thyristor (2), (3): Surge absorber resistor and capacitor (4): Auxiliary thyristor, (5): Zener diode (6): Diode, (7): Capacitor (8): Light receiving Element, (9): Light guide (10): Optical command signal, (11): Transistor (12): PNP transistor (13): Resistor (14): Second auxiliary thyristor (15), (16): Diode

Front Page Continuation (72) Inventor Shinichiro Hayashi 1-2-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Electric Corporation Control Works (56) Reference JP-A-52-116160 (JP, A)

Claims (1)

[Claims] Claim: What is claimed is: 1. A capacitor for charging ignition energy by obtaining an ignition power source from an anode pole of a main thyristor via a diode, which is connected between a connection point of the diode and the capacitor and a gate of the main thyristor, and an ignition command. A switching element that supplies the charging energy of the capacitor to the gate of the main thyristor in response to an optical signal, a constant voltage diode that conducts when the charging energy of the capacitor becomes a predetermined value or more, and a conduction of this constant voltage diode A first auxiliary thyristor that is ignited and bypasses the charging path of the capacitor, and a second auxiliary thyristor that is made conductive by the conduction of the first auxiliary thyristor and makes the signal switching element conductive by the ignition command light signal. A thyristor ignition circuit characterized by having an auxiliary thyristor.