Herein described is a control device of a device for the correction of the power factor in forced switching power supplies; said device for the correction of the power factor comprises a converter and said control device is coupled to the converter to obtain from an alternating input line voltage a regulated output voltage. The control device comprises generating means associated to a capacitor for generating a signal representative of the root-mean-square value of the alternating line voltage; the generating means are associated to means for discharging said capacitor. The control device comprises further means for discharging the capacitor suitable for discharging said capacitor when the signal representative of the root-mean-square value of the alternating line voltage goes below a given value.