FET Controlled thyristor

Claim 1

In a thyristor of the type having a semiconductor body comprising a first base of a first conductivity type contacting a second base of a second conductivity type, a first emitter of the second conductivity type on the first base carrying a first electrode at a boundary surface of the semiconductor body, a second emitter of the first conductivity type carried on the second base, and, for internal current gain, an auxiliary emitter of the second conductivity type spaced laterally from the first emitter and extending from the boundary surface into the first base toward the pn junction of the first and second bases, the auxiliary emitter being a first auxiliary emitter and forming a first semiconductor structure, together with the first and second bases, which has a current transfer ratio α 2 , the improvement therein comprising: a second auxiliary emitter extending into the first base from the boundary surface, spaced from the first auxiliary emitter, and forming a second semiconductor structure, together with the first and second bases, having a current transfer ratio α 1 ; and a semiconductor switch operable to selectively connect and disconnect the first and second auxiliary emitters, the current transfer ratio α 1 of the second semiconductor structure, with the application of a blocking voltage to the thyristor, being greater than the current transfer ratio α 2 of the first semiconductor structure in the conductive state of said semi-conductor switch, relative to the charge carriers emitted by said second auxiliary emitter due to the recombination rate of the first auxiliary emitter being significantly greater than that of the second auxiliary emitter because of the greater distance of the first auxiliary emitter to the pn junction of the first and second bases.