High-precision Digital Sampling Strategy Design For MHz Primary Feedback Flyback Resonant Converter

At present,the switching power supply is developing towards the trend of high frequency miniaturization.The primary feedback flyback resonant converter has the advantages of simple circuit structure and small switching loss,and is very suitable for high frequency medium and small power AC-DC power supplies.Since the converter realizes soft switching control by using parasitic resonance,the irregularity of the auxiliary winding voltage waveform is large,which leads to a large error with the conventional digital sampling method.Therefore,the high-precision voltage digital sampling strategy of this structure converter needs in-depth research and optimization.Aiming at the above problems,this thesis designs a high-precision digital sampling strategy for a MHz-level primary feedback flyback single-switched resonant converter.Firstly,the basic principles of digital sampling technology are introduced from three perspectives: main topology,primary digital sampling technology and soft switching control.On this basis,the following work is mainly done:(1)Designed for single-switched resonant flyback The primary side digital sampling strategy of the converter;(2)designed the continuous conduction mode(CCM)and the discontinuous conduction mode(DCM)dual output DAC inflection point sampling algorithm,which replaces the ADC directly sampling the output voltage,saving the cost of the sampling circuit;(3)Designed a high-precision sampling compensation algorithm suitable for CCM and DCM mode,correcting and compensating the sampling voltage,thus achieving accurate and constant voltage output of the voltage.According to the proposed algorithm,the MATLAB-Simulink simulation platform is built,and the algorithm behavior level simulation is carried out.The loop function of RTL level simulation verification system is carried out by using MATLAB and Modelsim joint platform.Finally,the main topology prototype and control board are designed.Based on FPGA hardware platform,the effectiveness of the designed high-precision digital sampling algorithm is verified.The simulation and measured results show that the double-output DAC inflection point sampling algorithm designed in this thesis has a precision of ±1.4% in the full load input voltage range and ±1.67% in the constant voltage accuracy of the converter system.