LLC resonant converter for electric vehicle battery chargers

This study presents a new LLC resonant converter with two transformers in parallel for the electric vehicle battery charger. This topology achieves the zero-voltage switching for main switches in the entire charging profile. In addition, the zero-current switching for output rectifier diodes is extended under charging condition. The proposed charger provides a wide range output voltage for the battery system. Moreover, in order to maintain the high efficiency under charging, the charger adopts a bidirectional switch. At low-output power condition, the charger uses one transformer to transfer the energy. Finally, the design procedure is provided and implemented in a prototype charger with the input DC link 400 V and the output voltage of 36-58 V. Experimental results are presented to demonstrate the system performance. The maximum power is up to 700 W and the peak efficiency is as high as 93.6%.