Research On ZVZCS DC-DC Converter Using A Passive Resonant Circuit

Currently in the field of power electronics, PWM soft-switching technique is applied widely to achieve the converter's high-frequency and high-efficient operation. Phase-shifted zero-voltage and zero-current switching (ZVZCS) full bridge PWM DC-DC converter is used in middle-to-high power appliances. This paper has a research on zero-voltage and zero-current switching full bridge PWM DC-DC converter.Based on the operation principles of the full bridge PWM DC-DC converter, the operation principles and topology of ZVZCS full bridge PWM DC-DC converter are discussed synthetically. After comparing the advantages and disadvantages of some typical ZVZCS full bridge PWM DC-DC converters, an improved ZVZCS full bridge DC-DC converter with passive resonant is proposed for widening the load range of soft switching, decreasing additional losses for auxiliary resonant circuit and reducing stress of the voltage and current. The converter operating principle and soft switching condition are analyzed detailedly.On the basis of the analysis of equivalent small signal model of PWM switch in Buck converter, using equivalent circuit model law combined with the operation features of ZVZCS FB PWM converter, the small signal model of the ZVZCS FB PWM DC-DC converter is built, then the analysis is made using MATLAB software. According to the request of operating characteristics, the hardware design of the phase shift converter is carried out, including power switches and diodes, high frequency full bridge inverter, output rectifier and filter, the auxiliary resonant circuit, DSP control circuit and protection circuit. Phase- shifted PWM control signals, the duty cycle,phase-shift angle and dead-time are adjusted conveniently by software. Loop control system using current-control system designed digital PID regulator, detailedly analyzed digital PID algorithms and software program to achieve. In the design process, using PSPICE software to simulate the converter.To verify the performance of this improved ZVZCS full bridge DC-DC converter, a prototype was made. After debugging through experiments, the correctness of the theoretical analysis is verified.