Research On Secondary-Side PWM Phase-Shifting Full-Bridge Converter

Switching power supply has been widely used in the field of communications engineering,aerospace and electric power system.Miniaturization and high frequency are the developing trend of switching power supply.In order to deal with energy loss and electromagnetic interference caused by high frequency,soft switching technology began to apply.Phase-shifting full-bridge converter have advantages on low voltage and current stress,fixed switching frequency and primary side switch achieve zero voltage turn-on and turn off,so it is always used in high-power application occasions.But the drawbacks still exist:the soft switching range is narrow,which means when the loads are light,the primary side switch is not easy to achieve zero voltage switching and the secondary-side faces duty loss.The circulation loss is large and rectifier diode voltage is oscillating.To overcome these drawbacks,this thesis presents a novel secondary-side PWM phase-shifting full-bridge converter.The novel converter can achieve a primary side switch zero voltage switching and a secondary-side switch zero current switching under full load range,meanwhile,it also behaves smaller circulation loss and duty loss.This thesis first analyzed the working principles of the traditional converter;secondly,we presented the novel secondary-side PWM phase-shifting converter’s circuit structure,working mode and soft switching condition.We compared the traditional converter with the novel converter comprehensively.The power of 110V/20A was adopted in the example and we figured out an optimally design of device selection and parameters.At the last,the secondary-side PWM phase-shifting full-bridge converter wi th synchronous rectifier has been proposed to decrease rectifier loss and circulation loss.We demonstrated the theory is correct by using the Pspice simulation software.