Efficiency Optimized Single-Stage Reconfigurable DC/DC Converter for Hybrid and Electric Vehicles

This paper proposes a single-stage reconfigurable topology for an isolated dc/dc converter that supplies the 12 V power net from high voltage (HV) battery pack in hybrid and electric vehicles. The proposed topology solves the problem of reduced converter efficiency in the upper range of HV battery voltages. The converter is based on a zero voltage transition (ZVT) phase shift (PS) full bridge dc/dc converter that is during its operation, depending on the instantaneous value of battery voltage, reconfigured into a push-pull converter. The more efficient ZVT PS configuration covers the upper range of input voltages whereas the hard-switching push-pull configuration covers the lower, less significant range. The ZVT PS configuration, due to tighter voltage range, operates with reduced turn-off losses, significantly decreased circulating current in the freewheeling period as well as improved efficiency of the rectifier stage. The point of reconfiguration is chosen to maximize the average efficiency according to the histogram of HV battery voltage during a typical driving cycle. The operation of the proposed converter and the efficiency improvement are validated experimentally.