Research And Design Of A High Power LED Constant Current Supplier Based On LLC Resonant Converter

Due to its high efficiency,energy saving,environmental protection,long life and easy control,LED lighting has a wide range of applications.In the LED lighting system,the driving power directly limits the reliability and stability of the entire system.The main function of the LED driver is to convert the power supply to DC that matches the voltage and current required by the LED source.LEDs are semiconductor devices whose V-I characteristics change exponentially.A slight forward voltage fluctuation causes a large change in the forward current,which causes illumination variation.Therefore,the high-quality LED driving power requires constant current output characteristics and good stability,and also requires high conversion efficiency,perfect protection function,long service life and strong electromagnetic compatibility.According to the actual demand,this paper designs a high-efficiency LED constant current driving power with power factor correction,half-bridge LLC resonance and soft switching technology for the problems of large switching loss and low efficiency.The power supply features a wide input voltage range,high power factor,and dimming.The main work of the thesis is as follows:(1)According to the requirements of high-power LED lighting system,based on the analysis and comparison of existing driving power solutions,and combining with the current development trend of AC-DC conversion technology,a high-efficiency LED constant-current driving power supply scheme with the structure of "active power factor correction+half-bridge LLC resonance+constant-current driving module" is designed;(2)The active power factor correction principle and the operating characteristics under different operating modes are analyzed,and the main control circuit design of APFC in critical mode is completed according to the application requirements;(3)The working principle of the half-bridge LLC resonant converter in different modes is analyzed,the equivalent circuit model is established,the design flow of the resonant network parameters is given,and the resonant network parameter calculation and SIMetrix/Simplis simulation verification and control circuit design are completed;(4)The synchronous rectification technology of external drive is used to realize the synchronous rectification of secondary side of transformer,which further reduces the secondary rectification loss.The design of high power constant current drive circuit and the fabrication of experimental prototype are completed.According to the relevant national standards,the designed prototypes were tested for power factor,input current harmonic and system energy conversion efficiency under different load conditions.The test results show that the designed power factor correction circuit can effectively suppress the input current harmonic;when AC 220V input,the prototype power factor can reach 0.98;according to the energy conversion efficiency measured under different load conditions,the average efficiency of the system can reach 0.88.In addition,the system operates stably,and has a wide input voltage range,high output current accuracy and adjustable brightness of the light source,achieving the expected design goals.