Research On Phase-shifted Full-bridge Low-voltage High-current DC Power Supply

A high-current low-voltage DC/DC converter is commonly used in Computer communication technology, electric vehicle, aviation, electrolytic plating and magnetic power supply. With the increasing demanding power of the converter, switching losses and conduction losses of the semiconductor switch reduce the transmission efficiency, while the bulky transformer and filter device in low frequency converter restrict the miniaturization of the whole machine. So high efficiency and high power density have become the new development directions of low voltage high current DC / DC converter.PSFB converter can achieve zero voltage switching(ZVS) by utilizing the transformer leakage inductance and parasitic paralleled capacitance of the MOSFETs without any additional circuitry, that the efficiency will be improved significantly and the electromagnetic interference(EMI) will be reduced dramatically. However, ZVS of the lag leg switches is affected by different factors. The relationship among the load current, dead time, resonant inductor and parasitic capacitance of the switch in ZVS operation is derived, and the design method of dead time is introduced. Utilizing the low impedance MOSFET instead of rectifier diode with appropriate control achieve synchronous rectifier during both conducting and current changing. Winds arrangement effects the loss and leakage inductance of PCB planar transformer. Three different kinds of arrangements are compared, and the best one is chosen. Simulation on performance and ZVS operation of the converter has been confirmed base on MATLAB/Simulink.A 100 kHz 3000W PSFB ZVS converter with SR has been constructed and all the analysis has been confirmed by the test result. Over 95% efficiency can be achieved which is better than the traditional converter.