Research On Zero-Voltage-transition For Wide Range Soft-switching Full-bridge Converter

In recent years,phase-shift full-bridge(PSFB)converter benefits from simple circuit structure,reliable structural characteristics,low electromagnetic interference and high power density.Thus,it is widely used in distributed generation,battery charging and renewable energy applications.However,this PSFB converter suffers from a narrow zerovoltage-switching(ZVS)range of lagging-leg switches under wide load variation which severely affects its light load efficiency,and severe duty cycle losses,large circulating losses and severe parasitic oscillations on the secondary side of the power transformer.In this thesis,based on the defects mentioned above,combining with the auxiliary parallel inductor network,the wide-range soft-switching zero-voltage-transition(ZVT)fullbridge converter is researched.In this thesis,the topology of the conventional PSFB converter is presented.The operating principle,loss analysis and operating characteristic are given.Moreover,the requirement of the ZVS,duty cycle losses of the secondary side,circulation loss and the parasitic oscillations of the rectifier diodes are presented.The analysis results indicate that the conventional PSFB converter suffer from limited soft-switching range,duty cycle losses on the secondary side,rectifier diodes parasitic oscillations and large circulating losses due to its own circuit structure defects.In order to overcome the problems mentioned above,a hybrid control wide-range ZVT full-bridge converter with an auxiliary parallel inductor networks is presented in this thesis.The soft switching range of the switches can be increased with the help of auxiliary parallel inductor networks where ZVS can be realized if the load above 10%.Moreover,due to the use of the auxiliary inductors,the series inductor in the primary side can be chosen very small and thus,the duty cycle losses is reduced.Furthermore,in order to reduce the voltage oscillations between the rectifier diodes caused by the leakage,an RCD absorption circuit is adopted.In order to solve the parasitic oscillation on rectifier diodes and realize a wide range ZVS,a wide-range zero-voltage zero-current switching(ZVZCS)full-bridge converter is proposed in this thesis.Wide range soft switching can be realized and the parasitic oscillation of the rectifier diodes can be solved by adding two auxiliary parallel inductor networks to the primary side and adopting capacitive filtering.Furthermore,with the help of the capacitive filtering scheme,the circulating losses in the secondary side can be elimilatied.Finally,the experimental platforms are built to verify the results,and the correctness of the theoretical analysis are verified by the results.