A New LLSC Series Quasi-Resonant Converter With Narrow Switching Frequency Variation

In this paper, the FHA model including the stray capacitance is analysed. The causes of the voltage gain distortion are studied. Limiting the working frequency is an effective method to solve the voltage gain distortion problem. A new type of the LLSC converter is proposed in the paper. It can regulate the voltage at a constant frequency. At the same time, the soft switch can be realized if the parameter design is reasonable. The proposed converter can overcome the voltage gain distortion problem and obtain the high efficiency at the light load condition. Some mathematical analyses are used to prove that the proposed converter can avoid the voltage gain distortion problems. The simulation and experimental results based on a 200W LLSC converter prototype confirm the correctness of the topology.