A circuit may generate a clock signal with a variable period given by a ratio between an initial switching period and a number of phase circuits through which a current of a multi-phase PWM voltage converter flows. The circuit may include an adjustable current generator driven by a signal representing the number of phase circuits through which the current flows and configured to generate a current proportional to the number of phase circuits through which the current flows, and a tank capacitor charged by the adjustable current generator. The circuit may include a comparator of a voltage on the tank capacitor with a threshold value configured to generate a pulse of the clock signal when the threshold value is attained, and a discharge path of the tank capacitor, the discharge path being enabled during the pulses of the clock signal.