A circuit for an oscillator structured to drive a control device of a switching resonant converter; the converter having a switching circuit structured to drive a resonant load provided with at least one transformer with at least a primary winding and at least a secondary winding. The control device structured to drive the switching circuit, and the converter structured to convert an input signal into an output signal, the integrated circuit includes a first circuit structured to charge and discharge a capacitor by a first current signal such that the voltage at the ends of the capacitor is between first and second reference voltages, the current signal having a second current signal indicating the output voltage of the converter; the integrated circuit including a second circuit structured to rectify a signal indicating the current circulating in the primary winding.