Soft-switching forward DC–DC converter using a continuous current mode for electric vehicle applications

This study presents the analysis and design of a novel technique that improves the efficiency of the conventional forward DC-DC converter by reducing switching losses, along with a comprehensive analysis of the circuit and detailed information for designers. The converter uses the current control mode to trigger the switches. To use this control mode, an equalising circuit is presented in the input port to guarantee that the voltage in each half-switching period will be equal; otherwise, the current control mode cannot be applied. A 5 kW step-down (from 350-500 to 28.8 V) prototype is presented and compared with the traditional hard-switching forward converter for fully electric vehicle applications. In addition, the small-signal characteristics and the dynamic response for load variation are presented. Efficiency improvements of over 2% are obtained.