JPS5937898B2 - GTO thyristor gate control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate control circuit for a GTO (gate turn off) thyristor, and more particularly to a control circuit for turning on and off a large capacity GTO thyristor using an auxiliary thyristor.

GTO thyristors turn on when a positive current is passed between the gate and cathode, and turn off when a negative current is passed between the gate and cathode. I need.

In addition, the ignition and extinguishing currents need to have steep rising slopes. FIG. 1 illustrates the gate current waveform.

As described above, since the GTO thyristor requires a large gate current and a steep slope, the gate control circuit has a problem in that its control power is large and the control element also requires a large capacity.

In addition, it is possible to use an auxiliary ignition thyristor as a control element to supply large ignition current and extinguishing current, but the gate-cathode voltage of the GTO thyristor is limited to 10 to 20 volts. be done.

Therefore, if the ignition current is supplied from a low voltage source through the ignition thyristor, the VF of the ignition thyristor becomes large and the turn-on time becomes long, making it impossible to supply a gate current with a steep rise. For this purpose, it is possible to use a transistor instead of a thyristor, but the transistor has a small ratio between the rated current and the permissible pulse current, and requires an expensive, large-capacity transistor with a small amplification factor. In addition, transistors have a low breakdown voltage and require a separate power supply for the drive, making it difficult to miniaturize and reduce cost of the control circuit. The present invention aims to provide a gate control circuit with low power consumption, small size, and low cost by utilizing the high voltage applied between the anode and cathode of a GTO thyristor as an ignition/extinguishing power source. .

FIG. 2 shows an embodiment of the invention.

In addition to the feedback diode 2, the GTO thyristor 1 has a D
A capacitor 3 for preventing v/Dt, a diode 4 for charging this capacitor 3, and a resistor 5 for limiting discharge current are provided. D
Between the high voltage side terminal of the v/Dt suppression capacitor 3 and the gate of the GTO thyristor 1, there is a current limiting resistor 6, a diagonal 7 as a negative resistance element that operates at 0N at a predetermined voltage,
It includes a series circuit of an ignition thyristor 8 and a capacitor 9. This series circuit and the trigger circuit 10 of the thyristor 8 constitute the ignition circuit of the GTO thyristor 1. Now, GT
When O thyristor 1 is in 0FF state, capacitor 3
is charged through the diode 4 to the anode-cathode voltage of the thyristor 1.

In this state, the trigger circuit 10 causes the thyristor 8 to
When igniting, if the voltage of capacitor 3 is higher than the breakover voltage of diac 7, the charge of capacitor 3 is transferred to resistor 6, diac 7, thyristor 8, capacitor 9.
The ignition current of the GTO thyristor 1 is discharged through the GTO thyristor 1, and the thyristor 1 is ignited. The discharge current of the capacitor 3 flows as a charging current of the capacitor 9 until its voltage becomes lower than the voltage of the capacitor 9, during which time the ignition current of the thyristor 1 is supplied. Also, the charge of capacitor 3 is G
From the point at which the TO thyristor 1 shifts to the 0N state, it is discharged through the discharge resistor 5, and the voltage of the capacitor 3 decreases to the 0N voltage VF (2 to 3 V) of the thyristor 1. During this discharging process, the voltage of the capacitor 3 increases to the voltage of the capacitor 9. When the voltage becomes lower than the voltage, the current in the thyristor 8 and the dielectric 7 becomes zero, and the thyristor 8 is turned off. next,
Between the gate and cathode of the thyristor 1, a dielectric 11 and an arc-extinguishing thyristor 1 are connected via the capacitor 9.
2 and a backflow blocking diode 13 in series. This series circuit and the trigger circuit 14 of the thyristor 12 constitute an arc extinguishing circuit for the thyristor 1. Now, when the GTO thyristor 1 is in the ON state, the capacitor 9 is charged to the illustrated polarity during the ignition operation, as described above.

In this state, the trigger circuit 14 causes the thyristor 1 to
When 2 is ignited, the voltage across capacitor 9 is increased to 11.
If the breakover voltage of capacitor 9 is higher than the breakover voltage of
3 as the extinguishing current of the GTO thyristor 1, and the thyristor 1 is turned off. The thyristor 1 recovers its cathode-to-gate junction by the turn-off operation and exhibits high impedance. Therefore, the discharge current of the capacitor 9 is reduced by the recovery of the junction between the cathode and gate of the thyristor 1.
and flows through resistor 16. The capacitor 15 is charged by this current, and its terminal voltage increases, causing the thyristor 1
A thyristor 17 and a constant voltage diode 18 are provided to prevent the cathode-to-gate breakdown voltage from exceeding VGK. That is, when the charging voltage of the capacitor 15 is lower than GK, this voltage is detected by the diode 18 and the thyristor 17 is ignited.
5 (reverse voltage between the cathode and the gate of thyristor 1) is regulated to the Zener voltage of diode 18. After the ON operation of the thyristor 17, the discharge current of the capacitor 9 is bypassed through the thyristor 17 and the diode 19. Therefore, GTO thyristor 1 turned off
is reverse biased between its gate and cathode to the Zener voltage of the constant voltage diode 18. Therefore, capacitor 1
The voltage of the GTO thyristor 1 does not rise above one Zener voltage, and the voltage between the gate and cathode of the GTO thyristor 1 does not rise above one Zener voltage, and there is no breakover.

Further, the thyristor 12 receives a reverse bias when the terminal voltage of the capacitor 9 is reversed, and is turned off. that's all,
As clarified, the gate control circuit according to the present invention comprises:
In order to discharge the charge in the Dv/Dt suppression capacitor through the ignition thyristor, the d! /
Dt is reduced, a large-capacity power supply for the control circuit is not required, and a control circuit with low power consumption, small size, and low cost can be realized.

In addition, by continuing to fire the thyristor 8 during the 0N control period of the GTO thyristor, the capacitor 3 can be charged up to the breakover voltage of the sidac 7 even when the GTO thyristor is turned off due to intermittent current that occurs during inductive loads. Once charged, it can be re-ignited. In this case, in the conventional pulse ignition, sufficient ignition current does not flow and element destruction occurs due to insufficient Di/Dt withstand capability, whereas in the control circuit of the present invention, the breakover voltage of the sidac and the limiting resistance 6
Since the ignition current and ignition start voltage can be determined by the above, a sufficient ignition current can be supplied. In addition, since the reverse bias between the gate and cathode when off is regulated to the Zener voltage of the constant voltage diode 18, the voltage of the arc extinguishing circuit can be set high.
Arc extinguishing control using a thyristor becomes possible.

Therefore, a small arc-extinguishing circuit can be constructed using a thyristor that allows a high current to flow at a high gradient, ensures reliable turn-off operation, and has a large capacity to withstand large currents. Also,
Since a negative resistance element such as a diaphragm is connected in series with the ignition and extinguishing thyristors, the ignition and extinguishing current can have a steep rise and a sufficient peak value, reducing GTO due to power loss during switching. Device destruction can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing firing and extinction current waveforms of a GTO thyristor, and FIG. 2 is a circuit diagram showing an embodiment of a gate control circuit according to the present invention. 1...GTO thyristor, 3...d/
Dt suppression capacitor, 7, 11...Diac, 8...Ignition thyristor, 10...
- Ignition trigger circuit, 12... Arc extinguishing thyristor, 14... Arc extinguishing trigger circuit, 18...
... Constant voltage diode.

Claims (1)

[Claims] 1 dv/d of the thyristor in parallel with the GTO thyristor
Connect the t suppression capacitor and connect this capacitor to GTO.
A switching element having a negative resistance element in series between the gates of the thyristor and an ignition circuit having a capacitor are connected in series so that the charging voltage of the dv/dt suppression capacitor becomes higher than the voltage set by the negative resistance element. At some point, the DV
/dt discharges the electric charge of the suppression capacitor as the ignition current of the GTO thyristor, and has a switching element having a negative resistance element in series between the capacitor of the ignition circuit and the cathode of the GTO thyristor. When the switching element of this arc extinguishing circuit is turned on and the voltage charged in the capacitor of the ignition circuit is higher than the voltage set by the negative resistance element, the charge of the capacitor is turned off to extinguish the GTO thyristor. The arc extinguishing circuit is connected in parallel with a voltage regulating capacitor connected between the gate and cathode of the GTO thyristor, and becomes conductive when the voltage of the capacitor reaches a predetermined value. 1. A gate control circuit for a GTO thyristor, comprising a discharging switching element and configured to charge a voltage regulation capacitor with a discharge current of the capacitor of the ignition circuit after the GTO thyristor is turned off.