Design Of Digital Constant Voltage Controller For Primary-side Regulation Flyback Converter

Flyback converter is widely used in the field of adapter and charger because of iTs simple structure,small volume and low cost.At the same time,in the field of power management,the development of process conditions makes the digital control technology gradually reveal iTs unique advantages.Compared with analog technology,digital control technology has the advantages of strong anti-interference ability,good programmability and portability.But the reality is that the sampling is not accurate,and the problem of multi mode switching instability affecTs the accuracy and efficiency of the digital control of the primary side feedback flyback converter.In this thesis,a quasi resonant compensation method is proposed to realize the high precision sampling of the output voltage amplitude and a constant voltage multi mode switching method is introduced to improve the whole voltage precision and efficiency.In quasi resonant compensation method,taking the relationship between auxiliary winding voltage and the output voltage,which is derived from the main topology structure of hardware,as the sampling principle,specifically through the auxiliary winding terminal voltage and zero potential,estimated turning potential compare to include two level signal magnetic time information,according to the two signals calculus of quasi resonant cycle,deduce the estimated errors of turning potential,and compensation for the PI,which can sample the precise output voltage.Constant voltage multi-mode switching method,according to the output current and the demagnetization time,switch relationship cycle,primary peak current,the output current reflecting load condition is deduced,and then determine the pulse width modulation/pulse frequency modulation control strategy,as the additional loss of the critical state of frequent switching will be brought,so hysteresis control is added in multimode switch,which makes the switching procedure occurs steadily.Based on this,this thesis uses the Matlab software to realize the system simulation,the main circuit topology of flyback converter is built in Matlab/Simulink,hardware description code to generate control module is written in Modelsim,to realize the high precision constant pressure control.The simulation resulTs show that the input voltage is 85V-264V,the load current is O?IA,and the simulation resulTs show that the output voltage is controlled at 5V,the digital controller designed in this thesis can make the output voltage error less than 1%.Finally,using FPGA to build a digital control constant voltage flyback converter test platform,digital controller designed in this thesis is verified,the test resulTs show that in the whole input voltage(85V-264V)and full load range(0?1A),the voltage error is controlled within 1%by the proposed digital controller,and the accuracy of sampling method proposed in this thesis is 99%,the average efficiency in the full load range reaches more than 75%.