Research On Quasi Resonant Flyback Synchronous Rectification Converter

With the increasingly widespread application of power electronic equipment in industry,as the power core of the power equipment-the switching power supply,its performance requirements are also increasing,Switching power supplies are evolving toward high power factor,high efficiency and high reliability.Low power factor and harmonic current of the traditional rectifier filter circuit has brought serious pollution to the power grid;As the switching frequency increases,the switching loss increases as well,the efficiency of the whole machine is reduced,so the working frequency is in contradiction with the overall efficiency of the machine.In order to improve the efficiency of power supply in high working frequency,the application of the soft switching technology can effectively solve this contradiction.Therefore,the research of power factor correction(PFC),soft switching and synchronous rectification is an effective method to meet the high requirements of switching power supply.Quasi resonant and synchronous rectification techniques are used to improve the efficiency of the converter as an effective means.The converter overall structure mainly includes the pre-Boost APFC circuit,the power level quasi-resonant flyback converter and the output stage synchronous rectification circuit.First of all,the working process of the Boost APFC circuit in the critical conduction mode and the working principle of the flyback synchronous rectifier topology circuit are analyzed in detail.Secondly,the advantages and disadvantages of the traditional flyback circuit and the quasi resonant flyback circuit are compared.Finally,the resonant flyback circuit is designed,and its working process is explained in detail.According to the main design parameters of prototype,the parameters of APFC circuit,quasi resonant flyback circuit,synchronous rectifier circuit,and input rectifier circuit are designed.For example,the inductance of APFC,transformer and other parameters are calculated in detail,and the schematic of the prototype circuit is given as well.The simulation software Tina was used to simulate and analyze the circuit.At the same time,the main parameter waveforms of the prototype,as well as the main indicators were tested,such as power factor,efficiency and load adjustment rate.The simulation results and prototype experimental results show that all the performance indicators meet the expected design requirements,expected results are achieved,and the feasibility and rationality of the design scheme are proved as well.