Resonance Current Suppression for AC-DC Active-Clamp Flyback Converter by Triangular Current Mode

This paper proposes the conduction loss reduction control method under Zero Voltage Switching (ZVS) operation of an AC-DC active-clamp flyback (ACF) converter for USB-Power Delivery. The proposed control method reduces the resonance current in the active clamp circuit by the reduction on-time of the clamp switch, while Triangular Current Mode control achieves ZVS to reduce the switching loss of the ACF converter. Moreover, the proposed control method provides the Power Factor Correction (PFC) capability without an additional PFC circuit because the proposed control method controls the input current by adjusting the on-time of the primary-side switch of the flyback converter. The detailed operation mode of both the conventional control method and the proposed control method is described. Experimental results of the 100-W active-clamp flyback converter demonstrate that the proposed method reduces the RMS current in the active-clamp circuit by 52.7% compared with the conventional control method.