Gate circuit of gate turn-off thyristor

Claim 1

A gate circuit of a gate turn-off thyristor comprising: a first circuit means connected across the cathode and the gate of said gate turn-off thyristor for applying thereacross a pulse voltage with a high rate of increase and lower rate of decrease, said first circuit means including a DC power supply and a series circuit connected across said DC power supply, said series circuit being a substantially lossless series circuit, and including: (a) a pulse transformer having first and second primary windings and a secondary winding, with said first primary winding be connected in series with, and magnetically closely coupled to, said second primary winding, (b) a rectifier circuit element connected in series with said secondary winding across the cathode and the gate of said thyristor to apply said pulse voltage, said rectifier circuit element connected with a polarity to conduct current from the gate to the cathode of said thyristor, (c) a diode connected in series with said primary windings of said transformer for preventing a reverse current from flowing into said DC power supply, and (d) a switching element connected in series with said primary windings of said transformer for switching on said series circuit when said thyristor is on so that said thyristor turns off; a second circuit means connected to a junction between said first and second primary windings and one side of said power supply for charging at a low rate a large part of the exciting energy stored in said transformer by way of said first primary winding until the voltage across said second circuit means becomes large enough to bias said diode reversely when said switching element is switched off and for discharging at a high rate to produce a steeply rising edge pulse when said switching element is switched on.