| Flyback converters have been widely used in low-power power supplies,especially adapters,due to their simple structure,small number of components,high reliability,and electrical isolation characteristics.After years of research,although all aspects of its performance have been significantly improved,there is still room for optimization.In addition,with the continuous improvement in the miniaturization and portability of electronic equipment in recent years,Flyback converters have put forward higher requirements due to their huge number in the environment of the global energy crisis.Based on the research status of Flyback converters at home and abroad,this paper firstly studies the most widely used quasi-resonant Flyback converter,analyzes its working principle and characteristics,and analyzes its main circuit,transformer,and feedback compensation network.And auxiliary circuits are designed.Based on the establishment of quasi-resonant Flyback and hard-switched Flyback simulation models,considering the isolation requirements,an experimental prototype with an output power of 65W using an optocoupler feedback network was built.The optocoupler in the isolated feedback network is a part of the control circuit.Its own temperature characteristics and parasitic parameters will not only have a certain impact on the performance of the compensator,but the transmission delay of the optocoupler also limits the increase in the switching frequency.Therefore,this paper also studies the Flyback converter based on the secondary side control to eliminate the influence of the transmission delay of the optocoupler and its parasitic parameters on the performance and realize the Q-ZVS turn-on of the primary side switch and the secondary side synchronous rectification technology.In view of the problem of the optimal turn-on voltage of the primary side switch tube of the secondary-side control Flyback converter,the theoretical analysis is carried out and the selection method of the optimal Q-ZVS turn-on voltage is obtained.At the same time,part of the software and hardware design of the secondary-side control Flyback converter is carried out.,Including the design of the main circuit,drive circuit,transformer,detection circuit,auxiliary power supply module and key algorithms,and built a secondary-side control Flyback 65W prototype platform using FPGA.For the research content of this article,firstly,the switch-on voltage of the switching tube under the same working conditions is compared through simulation.The simulation results reflect the advantages of the quasi-resonant Flyback "valley turn-on" and also verify its startup and dynamic performance.The simulation results reflect the design.Reasonableness.The quasi-resonant Flyback prototype was further tested,and the experimental results also proved the rationality of the design.Finally,the hardware circuit and key algorithm of the secondary side control Flyback platform designed in this paper are also tested and experimented,and the experimental results also reflect the correctness and rationality. |
