Power loss analysis of active clamp forward converter in continuous conduction mode and discontinuous conduction mode operating modes

In order to improve the light-load efficiency of active clamp forward converter with synchronous rectifier (SR), power loss analysis of the converter operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are presented in this study. The light-load efficiency of normal ACF converter with SR is low because the output inductor current can go negative when operating in CCM. Considering the fixed frequency control only, to shift the converter´s operating mode from CCM to DCM at a critical point of output current at light-load is a solution for efficiency improvement. Based on the CCM and DCM power dissipation models proposed in this study, the power loss characteristics of the converter are analysed, and the critical shift point of output current can be derived, which has also been verified by an experimental prototype.