A ringing converter of the type having an output voltage stabilizing circuit connected on the primary side of a transformer. The converter is further provided with a circuit for detecting the primary current, which is proportional to the load current on the secondary side of the transformer. This enables detection of a change in the output voltage due to fluctuation in the load current on the secondary side, as detected by the detecting circuit. A signal indicative of the detected change is fed back to an oscillator circuit in order to stabilize the output voltage.