Implementation and analysis of an improved series-loaded resonant dc-dc converter operating above resonance for battery chargers

The well established advantages of resonant converters, including simplicity of circuit configuration, easy of the control scheme, low switching losses, and low electromagnetic interference (EMI), among others, have led to their attracting more interest. This work develops a highly efficient battery charger with an improved series-loaded resonant converter for renewable energy applications to improve the performance of traditional switching-mode charger circuits. The switching frequency of the improved series-loaded resonant battery charger was at continuous conduction mode (CCM). Circuit operation modes are determined from the conduction profiles. Operating equations and operating theory are also developed. This study utilizes the fundamental wave approximation and a battery equivalent circuit to simplify the circuit analyses. The mean charging efficiency of the proposed topology is as high as 87.5%.