Zero crossing synchronous switching circuits for power semiconductors

Claim 1

AN ALTERNATING CURRENT POWER CONTROL CIRCUIT INCLUDING IN COMBINATION AT LEAST ONE POWER SEMICONDUCTOR LOAD CURRENT CARRYING BIDIRECTIONAL GATE CONTROLLED CONDUCTING DEVICE ADAPTED TO BE CONNECTED IN SERIES WITH A LOAD ACROSS A PAIR OF ALTERNATING CURRENT POWER SUPPLY TERMINALS, AND SYNCHRONOUSLY OPERABLE CONTROL CIRCUIT MEANS COUPLED TO SAID BIDIRECTIONAL CONDUCTING DEVICE, THE SYNCHRONOUSLY OPERABLE CONTROL CIRCUIT MEANS COMPRISING A GATING TRANSISTOR HAVING AN OUTPUT TERMINAL OPERATIVELY COUPLED TO THE CONTROL GATE OF THE BIDIRECTIONAL GATE CONTROLLED CONDUCTING DEVICE FOR GATING ON THE DEVICE, RECTIFYING MEANS ADAPTED TO BE CONNECTED ACROSS THE ALTERNATING CURRENT POWER SUPPLY TERMINALS IN PARALLEL WITH A BIDIRECTIONAL CONDUCTING DEVICE AND LOAD FOR DERIVING A RELATIVELY LOW VALUE DIRECT CURRENT CONTROL POTENTIAL, CIRCUIT MEANS OPERATIVELY COUPLED BETWEEN THE OUTPUT OF SAID RECTIFYING MEANS AND SAID GATING TRANSISTOR FOR CONTINUOUSLY APPLYING A TURN-ON SIGNAL TO THE GATING TRANSISTOR, A FIRST SHUNT TRANSISTOR OPERATIVELY COUPLED TO SAID GATING TRANSISTOR FOR SHUNTING THE BASE-EMITTER OF THE GATING TRANSISTOR FOR ONE POLARITY OF A SUPPLY ALTERNATING CURRENT POTENTIAL APPLIED ACROSS THE POWER SUPPLY TERMINALS, A SECOND SHUNT