Research Of High Frequency Isolated Low Voltage High Current DC Converter

With the development of communication system, computer and consumer electronics, more efficient and smaller switching power supplies become a widely demand of customers. In some applications, such as special power supply, the capability of low voltage and high current output is required, so the research of low voltage high current power technology has become one of research hotsports in the field of power electronics at present. PSFB(phase shifted full bridge) converter is widely used in medium-high-power application, since it can realize ZVS for the power switches by utilizing the transformer leakage inductor or an additional resonant inductor and intrinsic capacitances of switches. According to the technical requirements, a 12 kW low voltage and high current DC-DC converter based on PSFB is designed in this paper, and the design principles for magnetic components, power component selection, SiC drive circuit,and RCD snubber circuit are explained in detail.In order to eliminate the voltage oscillation of the rectifier diodes, the two clamping diodes can be introduced to the primary side. According to the location of the transformer and the additional resonant inducotr in the converter, PSFB converter with clamping diode can be divided into two types:Tr-Lead type and Tr-lag type phase-shifted full-bridge converter. The working principles and the ZVS boundaries of this two converter are analyzed and compared considering the junction capacitance of the clamping diode compared in this paper. For the Tr-Lead type phase-shifted full-bridge converter, the junction capacitance of clamping diode increases the ZVS operation range, which improves the efficiency of the converter. Finally, the secondary voltage oscillation of Tr-Lead type phase-shifted full-bridge converter is studyed, and a method that suppressing the volatage oscillation caused by the leakage inductance of the transformer and rectifier diode junction capacitance by increasing the resonant inductor and the junction capacitance of clamping diode is proposed.According to the results of the design, a prototype is built in the lab. The study and analysis is verified by the experimental results.