JPS6345834Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gate trigger circuit for a switching element that controls a load connected to an AC power source, and aims to reduce power consumption and improve safety of the circuit.

In general, gate trigger circuits for bidirectional three-terminal thyristors (hereinafter referred to as thyristors) mainly use pulse transformers, but the gate sensitivity of thyristors is generally poor, so the gate trigger circuit that drives the pulse transformer The power consumption of the trigger circuit increases. Further, the pulse transformer requires a relatively large area due to its shape, which sometimes poses a problem in mounting.

Furthermore, as shown in FIG. 4, an AC power supply 21 is provided with a load circuit in which a thyristor 22 and a load 23 are connected in series, and the gate of the thyristor 22 is directly triggered by a switching transistor 24 and a current limiting resistor 25. In this case, the current required for the gate trigger of the thyristor 22 is required in the DC power supply 26, and the power capacity of the DC power supply 26 becomes a problem as well as the circuit current of the load control circuit 27. As a result, the necessity of a power transformer is determined due to implementation. It becomes a problem.
If the switching transistor 24 is short-circuited again, it will be out of the control range of the load control circuit 24, and as a result, the thyristor 22 will continue to be in the gate-triggered state and turn on.

The present invention solves the above conventional problems by configuring a capacitor charging/discharging circuit in the gate trigger circuit.

Hereinafter, the present invention will be explained based on drawings showing embodiments thereof. In FIG. 1, reference numeral 1 denotes an AC power supply, to which a load 2 and a switching element 3 consisting of a bidirectional three-terminal thyristor are connected in series to form a load circuit. 4 is a DC power supply, and a switching transistor 7 is connected in series to the positive side of the DC power supply 4 via resistors 5 and 6. 8 is a load control circuit, and this load control circuit 8
is for controlling the switching transistor 7. A capacitor 9 is connected to the connection point between the resistors 5 and 6, and a diode 10 is connected in series with the capacitor 9. Further, the anode of the diode 10 is connected to the gate terminal of the switching element 3. The emitter of the switching transistor 7, the cathode of the diode 10, and the _T1 terminal of the switching element 3 are all connected to the negative side of the DC power supply 4.

In the above configuration, when the load control circuit 8 outputs an off signal for the switching element 3, the switching transistor 7 is turned off, and as a result, the resistor 5, the capacitor 9, the diode 10, and the DC power source 4 are connected from the positive side of the DC power source 4. A charging circuit A is configured to pass through to the negative side of the capacitor 9, and charge is accumulated in the capacitor 9. Next, the load control circuit 8 switches the switching element 3
When the on signal is output, the switching transistor 7 is turned on, so that the charge in the capacitor 9 is transferred to the discharge circuit B via the resistor 6, the switching transistor 7, the _T1 terminal of the switching element 3, and the gate. discharged through. Due to this discharge, the switching element 3 is turned on in the minus gate trigger mode. When the switching element 3 is turned on, the load 2 is energized.
Note that if the load control circuit 8 outputs an output at zero volts of the AC power supply, the charging time constant of the capacitor 9 and the resistor 5 may be set to the half cycle time of the AC power supply.

Figure 2 shows another embodiment of the present invention.
That is, in FIG. 2, the resistor 6, which was connected to the collector of the switching transistor 7 in FIG. 1, is connected to the gate terminal of the switching element 3. Therefore, it can be inserted into the discharge path.

As described above, in the case of FIGS. 1 and 2, the gate trigger of the switching element 3 is connected to the capacitor 9.
Since the discharge current is set to 1, the circuit current of the DC power source 4 can be reduced, and the switching transistor 7 is safe from short-circuit failure.

FIG. 3 shows still another embodiment of the present invention, in which a diode 11 is connected to the gate terminal of the switching element 3, and the cathode of the diode 11 is connected to the capacitor 9.
and the connection point of the diode 10. In the configuration shown in FIG. 3, when a charging current flows to the capacitor 9 due to the switching transistor 7 being turned off, there is a situation where the diode 10 is open-circuited or a mis-trigger occurs due to variations in the gate sensitivity of the switching element 3. diode 11 prevents current from flowing into the gate terminal of switching element 3.
This can be reliably prevented. Note that since the switching element 3 is a gate trigger circuit that is triggered only by the discharge current of the capacitor 9,
Safety is greatly improved.

As described above, according to the present invention, since the switching element connected in series with the load is triggered by discharging the charge stored in the capacitor, it is possible to reduce the current consumption of the gate trigger circuit. In addition, the gate trigger circuit can be fail-safe against short-circuit failures of switching transistors, open failures of diodes, and the like. That is, if the switching transistor 7 is opened or shot, the capacitor 9 cannot be charged or discharged, and no trigger current can be obtained. An open failure of the capacitor 9 causes the gate circuit to open, and a short failure causes the discharge current to disappear, and at the same time, the forward voltage of the diode 10 suppresses the gate voltage of the bidirectional three-terminal thyristor to a non-trigger voltage. The short failure of the diode 10 is the same as described above, and the charging circuit of the capacitor 9 is immediately cut off in the case of an open failure. Therefore, the bidirectional three-terminal thyristor 3 is connected to the capacitor 9
Since the configuration is triggered only by the discharge current, it is possible to obtain a gate trigger circuit for a switching element with high reliability and high safety.

[Brief explanation of the drawing]

Fig. 1 is a gate trigger circuit diagram showing one embodiment of the invention, Fig. 2 is a gate trigger circuit diagram showing another embodiment of the invention, and Fig. 3 is a gate trigger circuit diagram showing another embodiment of the invention. Trigger Circuit Diagram: FIG. 4 is a gate trigger circuit diagram showing a conventional example. 1... AC power supply, 2... Load, 3... Switching element, 4... DC power supply, 5, 6... Resistance, 7
...Switching transistor, 9...Capacitor, 10, 11...Diode.

Claims (1)

[Scope of utility model registration request] A load circuit in which a load and a bidirectional 3-terminal thyristor are connected in series to an AC power source, an anode connected to the gate side of the bidirectional 3-terminal thyristor, and a cathode connected to the cathode of the bidirectional 3-terminal thyristor. a series circuit having a diode connected to the diode, a capacitor connected in parallel with the diode and an anode of the diode, and an NPN transistor, a collector of the NPN transistor including the capacitor, and the bidirectional three-terminal thyristor. a discharge current limiting resistor provided between the gates of the transistor, a load control circuit connected to the base of the NPN transistor, and a circuit position on the circuit from the collector of the NPN transistor to the capacitor and adjacent to the capacitor. A gate trigger circuit consisting of a DC power supply connected to the gate via a resistor.