The Design Of High Efficiency Soft- Switching Control Algorithm For MHz Single-Switched Resonant Flyback Converter

With the development of smart devices,switching power supplies are developing in the direction of high frequency and miniaturization.Combining with soft-switching technology,an isolated single-switched resonant flyback converter realizes the valley switching turn-on and zero current switching turn-off of the switch,and meets the development requirements of the MHz miniaturized power supply.However,under the traditional Pulse Frequency Modulation(PFM)control,the topology cannot guarantee the realization of the soft-switching in the full load range,resulting in a decrease in the overall efficiency of the system.In order to solve the above problems,an efficient soft-switching control algorithm for MHz single-transistor resonant flyback converter is designed in this thesis.Firstly,the traditional loss model of this kind of converter for pulse frequency modulation control is analyzed,and a dynamic loss model for soft-switching control strategy is improved and designed.Under the soft-switching control strategy,the model can calculate the peak efficiency of the system under different load conditions more accurately by multi-switching cycle iteration method.Secondly,combined with the point of peak efficiency and the idea of ONOFF control,an efficient soft-switching control algorithm is designed to ensure the precise realization of soft-switching in the system and improve the conversion efficiency of the converter in the full load range.Then,the circuit simulation model of single-switched resonant flyback converter is built on MATLAB,and the algorithm-level and behavior-level verification are completed respectively.The RTL-level verification is carried out by using Simulink and Modelsim joint simulation platform.Finally,a test prototype of MHz singletransistor resonant flyback converter is built to verify the validity of dynamic loss model and the superiority of high efficiency soft-switching control algorithmThe test results show that the maximum error of the proposed dynamic loss model is 5.78% and the average error is 3.05%.The peak efficiency of the test prototype is increased from 88.8% to 90%,the light load efficiency from 74.9% to 81.1%,and the average efficiency from 81.7% to 85.6%.The measured results meet the design requirements.