Design and Implementation of Bidirectional DC-DC CLLLC Resonant Converter

An isolated bidirectional resonant converter with digital control is presented in this paper for the energy transferring between the DC bus and the EV battery. The main circuit topology consists of full-bridge structures and a CLLLC resonant tank. Due to the bidirectional symmetrical characteristics of the circuit, the complexity of the bidirectional power flow control can be reduced. This converter can also achieve soft switching to improve the efficiency. A laboratory prototype converter with rated power 4.4 kW, DC bus voltage 400 V and battery voltage 200~410 V is implemented to validate the theoretical analysis. During the bidirectional operation, the maximum conversion efficiency is 96.5%.