A control circuit for controlling the output voltage of a primary-controlled switched mode power supply. The switched mode power supply includes a primary-side switch and a transformer with a primary winding, a secondary winding and a secondary-side auxiliary winding. The control circuit is connected to the auxiliary winding and a voltage tapping point between the secondary winding and the auxiliary winding. The control circuit includes a secondary-side switch and an RC element. The secondary-side switch short-circuits the connection between the output terminal and the voltage tapping point and the RC element provides positive and negative control pulses having a predefined time constant.
