Asymmetric half-bridge resonant converter having a reduced conduction loss for DC/DC power systems with a low input voltage

A new asymmetric half-bridge (HB) resonant converter for DC/DC power system with a low and wide input voltage is proposed in this paper. The proposed converter is based on the switch integration technique, merging the Active-Clamp Forward (ACF) circuit and the HB LLC resonant converter. By adopting the ACF circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, an asymmetric pulse width modulation (APWM) control is applied to cover wide input voltage range and to mitigate the design limitation for a high efficiency and. Consequently, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36-72VDC input and 300W (12V/25A) output.