Investigation On Serial Resonant Soft-switching Push-pull Circuits

DC-DC converters with low input voltage and high output voltage are widely used in photovoltaic power systems, wind power systems, fuel cell systems and vehicular power systems, etc. With the development of power electronics, this type of converter is demanded to higher quality.Base on the boost type converter with middle or small power class, the paper does some research, analysis and experiments on the serial resonant soft-switching push-pull circuit.The paper presents the theoretical analysis, simulation and experimental results of serial resonant soft-switching push-pull circuit under ideal working condition. Then, three different kinds of control methods: fixed turn-on time and varied turn-off time PFM modulation, varied turn-on time and fixed turn-off time PFM modulation, PWM modulation, are applied to the circuit. The advantages and disadvantages, especially the characteristic of soft switching, output voltage modulation and application range, of the three are compared through theoretical analysis, simulation and experiments. The transformer, used in the serial resonant soft-switching push-pull circuit, is also analyzed. Based on the basics of transformer, the solutions to the problems of high windings' rate and leakage inductor specified to the circuit are proposed.At last, a serial resonant soft-switching push-pull circuit with double-transformer topology is proposed. The theoretical analysis, simulation and experimental results are presented. This kind of circuit has the advantages of low switching loss, low transformer's loss, and high efficiency compared with single-transformer topology. The conclusions above are all verified by experiments.