A device corrects the power factor in forced switching power supplies and includes a converter and a control device to obtain a regulated voltage on an output terminal. The control device comprises an error amplifier having an inverting terminal (Vout) and a non-inverting terminal receiving a reference voltage. The device includes first and second resistances coupled in series with a conduction element positioned between the first resistance and the inverting terminal of the error amplifier and a fault detector suitable for detecting the electrical connection of the conduction element with the output terminal and suitable for detecting an output signal of the second resistance. The fault detector is suitable for supplying a malfunction signal upon detecting an electric disconnection of the conduction element from the output terminal or when the output signal of the second resistance tends to zero.