Semiconductor switching circuit

Details Semiconductor switching circuit Semiconductor switching circuit

1988-03-21

1989-05-23

Wong, Peter S.

Electric power conversion systems

Current conversion

With condition responsive means to control the output...

363 85, 323351, 307633, 307637, H02M 1318

Patent

active

048335878

ABSTRACT:
A fraction of current passing through the P-emitter region and N-base region of a thyristor is by-passed to the base-emitter junction of a PNP transistor. The amount of the base current is dependent on the thyristor current. Thus, as the anode current of the thyristor increases, the base current and hence the collector current of the PNP transistor increases. The collector current by-passed to the PNP transistor is fed, via a switch which is closed during the off-time of the thyistor, to the base-collector path of an NPN transistor whose collector and emitter are respectively connected to the gate and cathode of the thyristor. The turn-on voltage across the collector and emitter of the NPN transistor accordingly becomes lower than the gate-cathode voltage of the thyristor. The base-emitter current of the NPN transistor equals the collector current of the PNP transistor, the collector current being a fraction of the anode current by-passed to the PNP transistor. A fraction of the anode current of the turned-on thyristor is utilized as the control power for driving the NPN transistor so that additional external power for turning off the thyristor becomes almost unnecessary.

REFERENCES:
patent: 4117350 (1978-09-01), Kalfus et al.
patent: 4231083 (1980-10-01), Matsuda et al.
patent: 4581542 (1986-04-01), Steigerwald
patent: 4641231 (1987-02-01), Walker et al.

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