Pulse transformers are often used to couple a trigger pulse generator to a thyristor in order to obtain electrical isolation between the two circuits. The transformers commonly used for thyristor control are either 1:1 two winding or 1:1:1 three winding types.

Above figure shows a complete output circuit to fire a thyristor correctly. The series resistor R either reduces the SCR holding current or balances gate current in a three winding transformer connected to two SCRs. The series diode D prevents reverse gate current in the case of ringing or reversal of the pulse transformer output voltage. The diodes also reduce holding current of the SCR. In some cases where high noise levels are present it may be necessary to load the secondary of the transformer with a resistor to prevent false triggering.