Power converter

The present invention is related to a power converter, and more particularly, the present invention is related to a frequency modulation circuit which implements the input-current shaping function at the central tap of the transformer in a power supply. A power converter, and more particularly a switched AC/DC converter, is provided with an input current shaping (ICS) function. The ICS function is carried out by adjusting the conducting angle of the input current for a rectifier coupled to a central tap of a main transformer, thereby obtaining a higher power factor. Owing to the action of the ICS, the ripples in the feedback signal are usually larger. The ripples are used to modulate the switching frequency to effectively disperse and planarize the electromagnetic energy distribution of the power supply, and to suppress the electromagnetic interference problems of the power supply.