Active-clamp forward converter with asymmetric transformer turns for reducing transformer DC offset current

An active-clamp forward (ACF) converter is widely used in low-to-medium power applications because of simple structure and high efficiency. However, a transformer of the ACF converter with double-ended rectifier (DER) has a DC offset current to satisfy the current-second balance for a clamp capacitor. The transformer DC offset current can increase the susceptibility to transformer saturation and a size of transformer to prevent saturation. Moreover, it can increase the core loss of transformer. In this letter, to reduce the DC offset current of transformer in the ACF converter with DER, an ACF converter with asymmetric transformer turns (ATTs) is proposed. Since the proposed converter can have a low transformer DC offset current, the size and the core loss of transformer can be reduced. The operational principle of the proposed converter is analyzed and verified experimentally.