A control device for a QR switching power converter is described; said power converter is adapted to convert an input signal to a DC output signal and comprises a power switch connected to said input signal and adapted to regulate said DC output signal and magnetic storage means. The control device is able to determine the switching frequency of the power switch and it is supplied by a feedback signal deriving from a feedback circuit coupled to the output signal of the power converter; said control device performs a control loop regulating the DC output signal by controlling a control variable. The control device comprises modulating means adapted to modulate said control variable as a function of at least one modulating signal having a frequency higher than the control loop bandwidth.