A PSR CC/CV Flyback Converter With Accurate CC Control and Optimized CV Regulation Strategy

This paper presents a primary-side regulation constant current constant voltage (CC-CV) Flyback ac-dc converter characterized by high efficiency and high precision of constant current control. In CC mode, a novel ring detection and demagnetization portion control technique is proposed, with which the ending time of demagnetization can be accurately determined and the portion of demagnetization in switching periods remain precisely the same, which enable the accuracy of constant current output that can reach a level as high as ±0.8%. In CV mode, a power stage model based on steady-state analyzing method is established, according to which the expression of static power loss is first obtained. After that total power loss expression including switching loss is derived as well. By MATLAB simulation, power loss mechanism is revealed and analysis is made in detail. According to which, optimized parameters of Flyback converter system and an effective CV regulation strategy are obtained eventually. Simulation as well as experimental results verifies the efficiency of the ac-dc converter system after optimization that can be more than 84.7% at 5 V/1 A application.