Study On Two-stage High Power Factor Dimmable LED Driver Without Low-frequency Flicker

Light Emitting Diode(LED)as a new generation of green light source with high efficiency,long lifetime,small size,environmental protection etc.,is widely used in all kinds of lighting field.Highquality LED driver is a key part of the LED lighting system,which directly affects the overall performance of the LED lighting system.Therefore,the research on high-performance LED drivers has important theoretical significance and engineering application value.In this paper,the LED driver and power factor correction technology are briefly introduced.In view of the shortcomings of traditional BOOST PFC,this paper proposes a PFC output voltage adaptive following controller based on BOOST converter,which realizes the BOOST PFC output voltage adaptive follow input voltage and improves the conversion efficiency of the converter.The adaptive following circuit is composed of an adder and a switching device,which can realize the PFC output voltage adaptive follows input voltage without sampling the input voltage peak,which improves the dynamic response capability of the system.In the thesis,the detailed theoretical analysis of traditional constant voltage PFC and voltage following PFC is presented.The relationship between the output voltage of adaptive following control PFC converter and various parameters of the system is demonstrated in detail.The theoretical basis of parameter design is presented.At the same time,the error source of adaptive following control is analyzed in detail,and a reasonable compensation scheme is provided.An 80 W experimental prototype is designed to prove the correctness of the adaptive following control theory.In order to make up for the shortcomings of the secondary side control Flyback LED driver,this paper presents a quasi-resonant Flyback LED driver scheme based on primary side control.The theoretical prediction of the primary side control is proposed.Meanwhile,the error source of the primary side feedback is analyzed,and a reasonable compensation scheme is provided.An 80 W experimental prototype was designed to verify the theory,and the experimental results show that the primary control has good constant current accuracy.Finally,the two prototypes are jointly tested to obtain a two-stage LED driver experimental prototype.The two-stage LED drivers using PFC constant voltage scheme and adaptive following scheme are tested respectively.The experimental results proved that the adaptive following scheme has better conversion efficiency.Besides,the experimental results of the system's output ripple,PF,THD,linear adjustment rate and dimming curve are presented.