Design And Implementation Of Active Clamp Flyback Converter Based On LM5025

With the development of power electronic technology, switching power supply tendsto be more and more high frequency. The weight of inductor and capacitor is reduced asthe switching frequency increases. So high frequency can increase power density andreduce the weight of material, but the switching loss of power device is proportional to theswitching frequency. In order to solve this problem; people put forward the technology ofsoft switch.The research object of thesis is active clamp flyback converter. Using the technologyof soft switch and synchronous rectification, the converter solves the problems ofconventional flyback converter, such as high switching stress, high switching losses, lowswitching frequency and low efficiency.Active clamp flyback converter’s working principle is analyzed in the paper. Theprocess of the converter is divided into nine intervals.The necessary conditions about theconverter’s power device to realize ZVS is proposed. According to practical applicationrequirements, the parameter values of the converter is designed. Based on theMatlab/Simulink, the simulation model of the converter is builded. The simulation resultsare provided to verify the correctness of parameters’ calculation. A small-signal model ofthe converter is established. The amplitude-frequency characteristics of the converter isanalyzed. A design method of the compensation network in feedback control is introduced.Feedforward control based on the characteristics of LM5025PWM controller is studied.The main losses of the converter is analyzed. The value of the efficiency of the converteris estimated. Several ways to improve the efficiency of the converter is introduced.According to theoretical analysis and designed circuit, an18V~30V input,15V/25Woutput,300KHz frequency prototype is implemented. The experimental results areprovided to verify the effectiveness of the converter.