A circuit for controlling a thyristor (V1) into conducting state, the thyristor (V1) being in a rectifier, which rectifier is adapted to supply DC voltage to a DC voltage circuit. The circuit comprises a pulse transformer (T1), means for generating voltage pulses on the primary winding of the pulse transformer (T1), a trigger capacitor (C2) adapted to be charged from the voltage pulses in the secondary winding of the pulse transformer, a zener diode (V5) adapted to be triggered with the voltage of the trigger capacitor (C2) when the voltage of the trigger capacitor (C2) exceeds the breakdown voltage of the zener diode (V5), and an auxiliary thyristor (V3) adapted to be triggered with the current from the trigger capacitor (C2) flowing via the zener diode (V5), wherein the cathode of the auxiliary thyristor (V3) is connected to the gate of the thyristor (V1) for triggering the thyristor (V1) with the current from the trigger capacitor (C2) flowing via the auxiliary thyristor (V3).