Improvement of phase-shifted full-bridge converter for electric vehicle

In order to improve efficiency of the on-board power supply of electric vehicles, an improved phase-shifted full-bridge topology was proposed to solve the problems of secondary-side duty cycle loss, transformer magnetic saturation, and secondary-side parasitic oscillation of traditional phase-shifted full-bridge DC / DC converters. By reducing the loss of duty cycle by increasing the ratio of the primary and secondary sides, series DC blocking capacitors prevent the transformer from magnetic saturation, and a diode clamping circuit was used to suppress the voltage oscillation of the secondary side diodes. Based on a detailed analysis of the phase-shifted full-bridge zero-voltage-switch (ZVS) control strategy, the working principle of the clamping diode was analyzed for the different operating states of the topology, and effect of the transformer and resonant inductor position on the circuit was clarified. The role of secondary-side synchronous rectification in the topology was discussed. It is concluded that the topology can restrain the stress of the MOS tube within the input voltage range. Finally, a prototype of 3 kW was developed. The PI control strategy was used to verify correctness of the theoretical analysis through simulation and experimental results. © 2021, Harbin University of Science and Technology Publication. All right reserved.