An integrated circuit includes an output terminal a first input terminal is configured to receive a signal proportional to a voltage between first and second terminals of the primary winding, and a second input terminal is configured to receive a signal proportional to a current flowing through the primary winding. A quasi-resonant (QR) circuit has a first input coupled to the first terminal, and a second input coupled to an output of an oscillator circuit. A selector circuit has a first input coupled to the output of the oscillator circuit, a second input coupled to an output of the QR circuit, and a select input. An output control circuit includes a first input coupled to the second input terminal, a second input coupled to an output of the selector circuit, and an output coupled to a control terminal of the switching transistor.