A natural ZVS medium-power bidirectional DC-DC converter with minimum number of devices

This paper introduces a new bidirectional, isolated DC-DC converter. A typical application for this converter can be found in the auxiliary power supply of hybrid electric vehicles. A dual half-bridge topology has been developed to implement the required power rating using the minimum number of devices. Unified zero-voltage switching was achieved in either direction of power flow with neither a voltage-clamping circuit nor extra switching devices and resonant components. All these new features allow high power density, efficient power conversion, and compact packaging. Complete descriptions of operating principle and design guidelines are provided in this paper. An extended state-space averaged model is developed to predict large- and small-signal characteristics of the converter in either direction of power flow. A 1.6-kW prototype has been built and successfully tested under full power. The experimental results of the converter's steady-state operation confirm the soft-switching operation, simulation analysis, and the developed averaged model. The proposed converter is a good alternative to full-bridge isolated bidirectional DC-DC converter in medium-power applications.