The bidirectional dc-dc converters are capable of reversing the direction of current flow and thereby the power flow between two dc sources while maintaining the voltage polarity of both dc sources. In order to significantly reduce reactive component size and cost, high-frequency operation of bidirectional converters is desirable. However, in a hard-switching converter, as the switching frequency increases, switching losses and electromagnetic interference increase. To solve these problems, soft-switching converters are employed. Among the soft switching techniques, the zero voltage transition technique (ZVT) is widely applied to the bidirectional converters due to its prevalent features. However, in ZVT bidirectional converters, the major problems such as missing the soft switching condition at duty cycles ( D ) below 0.5, high voltage stress of the auxiliary switches and using two auxiliary switches exist. In this dissertation, to extend the soft-switching range to D 0.5 in a conventional type of ZVT bidirectional converters, the ideas of using the diode reverse recovery and applying two auxiliary voltage sources are proposed. Besides, to reduce the auxiliary voltage stress in ZVT bidirectional converters, the coupled inductors are applied in the auxiliary circuit. Moreover, a soft switching bidirectional converter without auxiliary switches is introduced. In all the proposed converters, the circuit operation and design considerations are presented, and to confirm the feasibility of the proposed converters, the experimental results for a wide range of duty cycle or load variations are shown. Key Words Bidirectional dc-dc converter (BDC), soft switching techniques, zero voltage switching (ZVS), zero voltage transition (ZVT)
