Research On A Novel Zero-current And Zero-voltage Switching PWM Asymmetric Half Bridge Converter

Through the circuit control switch opening and closing, DC-DC converter change the DC or AC power into the required voltage of one or more groups. With the rapid development of power electronic technology, the research and application of switching power supply with high efficiency, small volume, light weight and high precision has been greatly promoted. Especially in the low voltage/high current output and low-power conversion places, it is significant to improve the power conversion efficiency and reduce the electromagnetic interference (EMI) by reducing the voltage stress of power switches and the voltage and current rate of change. It is important to research asymmetric half bridge converters (AHBC) owing to its low switch voltage stress and its simple topological structure. In order to improve the switch frequency as well as reduce the switching loss, many scholars have put forward soft-switching technology for AHBC in recent years. Soft-switching technology can improve operating environment and reliability of power switches, reduce power loss, suppress the higher dv/dt and di/dt, cut down EMI and system noise effectively, and so on. So AHBC have aroused wide concern of domestic and foreign researchers.By the research of many typical half bridge converter topologies, the problems that the converter can not achieve soft-switching under light load and the rectifier circuit in secondary side has a high loss are found out. And this is the key problem of applying AHBC to reality and must be resolved in the future. Aiming at overcoming the problem, this thesis presents a zero current quasi resonant asymmetric half bridge converter.In this thesis, a novel asymmetrical half-bridge (AHB) zero-voltage and zero-current switching PWM DC-DC converter topology is presented which consists of a PWM-controlled half bridge inverter with an active auxiliary edge-resonant snubber cell (AERS) and a current doubler rectifier linked with a high frequency (HF) transformer. In order to attain a wide range of soft switching operation in the primary side of HF inverter, the lossless snubber cell composed of an actively-switched capacitor and lossless inductors is adopted in the half-bridge leg, providing Zero Current Switching (ZCS) commutation which is less sensitive to magnitude input current for a wide range of output power under a constant switching frequency. Furthermore, the proposed converter can turn off at Zero Voltage Zero Current Switching (ZVZCS) condition. According to the equivalent circuit in different operation modes, this thesis analyses the operation principle, soft-switching implementation condition and parameter design procedure of the soft-switching inverter. Finally, the practical effectiveness of the proposed converter is illustrated by simulation results using insulated gate bipolar transistor (IGBT).