The Improvement For Dynamic Performance Of Digital Control Primary Side Regulated Flyback Conveter

Due to its low cost, simple structure and easy to adjust control parameters, digital control multi-mode primary side regulated flyback converter ia widely used in the power supply scheme of consumer electronics products. However, compared with the secondary side feedback structure, the dynamic response performance of digital control primary side regulated flyback system is not ideal. This thesis will analysis this problem to improve its dynamic performance.Firstly, this thesis analysis the shortcomings of traditional sampling method, and then optimizes the sampling algorithm. The improved sampling algorithm can accurately sampling the output voltage of the system in dynamic state by using different gap value calculation method in different sampling condition. Secondly, this thesis analysis the influences of traditional multi-mode control strategy to the dynamic response of digital control multi-mode primary side regulated flyback converter and propose the dynamic multi-mode control algorithm. Due to the traditional multi-mode control can only switch continuously, the Switching process have a long recovery time and big overshoot. The dynamic multi-mode control algorithm can more rapid transition to the appropriate working mode by inserting dynamic switching mode in the traditional multi-mode control algorithm. Finally, the improved sampling algorithm combined with the dynamic multi-mode control algorithm is proved to improve the dynamic performance of the digital control primary side regulated flyback converter in a 5V/1A system.The experimental results show that the improved sampling algorithm proposed in this thesis has better tracking performance compared with the traditional sampling algorithm. The use of the dynamic multi-mode control algorithm combined with the improved sampling algorithm improved dynamic response performance of the digital control primary side regulated flyback converter, while maintaining other system characteristics unchanged. The maximum voltage overshoot and undershoot voltage in a full load jump is 0.192V and 0.472V. Overshoot recovery time is 53.68ms, undershoot recovery time is 1.29ms. The test results meet the original design specifications.