The Design Of Led Drive Power Supply Based On A Half-Bridge LLC Resonant Converter

With the increasingly serious energy and environmental issues, energy saving and high efficiency become the pursuit of power electronics, the scheme of efficiency of traditional LED drive power supply is low and performance is not stable, in order to achieve the purpose of environmental protection and high efficiency, resonant converter gradually become research hot spot, the converter has ZVS, ZCS, disconnect the advantages of low loss, high power density and high efficiency, etc., which is widely used in LED lighting driver power supply. The working principle of LLC resonant converter, the design of main circuit and resonant parameter selection is analysis in detailed. The AC small signal modeling and digital PID controller is built, a 24V/350W half-bridge LLC resonant converter is made. The main work and results are summarized as follows:(1) The working process and key issues of half-bridge LLC resonant are researched. Since the resonant parameter uncertainty and the problem of the output voltage is not stable, the principle of the half bridge LLC resonant converter is described in detailed, resonance parameters is optimized, the leakage inductance of the transformer instead of excitation inductance is used to stable working frequency, the diode clamp circuit is used to reduce the output voltage ripple,which increase efficiency of the converter and stabilize the output voltage.(2) The selection and design of main circuit of Half-bridge resonant converter are obtained. According to the performance of LLC half-bridge resonant converter, the main parameters of resonant half-bridge circuit DC/DC converter are calculated in detailed, including the selection, resonant inductance, capacitance and inductance of the excitation power MOS tube design and selection, the design of frequency transformer, the selection of output rectifier diode and clamp diode, the selection of output filter capacitor and inductor. The simulation results show that the parameter selection and design is rational, circuit design is reasonable, which agreement with the requirements of the converter efficiency.(3) The digital control circuit and compensation controller are achieved. The paper design the control circuit by DSP TMS320F2812, including the drive circuit, sampling circuit, EMC design and so on, and design the specific algorithm of digital PID and the software structure of the system, in order to achieve high static and dynamic performance of the LLC resonant converter, the equivalent circuit model, the small signal model of the LLC resonant converter is established. The analog PID parameters of peak current mode is obtained by saber.. Based on the analysis of the control output characteristics, the design of the controller by PID strategy are accomplished.(4) The Circuit is simulated and prototype is made. The circuit is simulated by saber, and the experimental wave forms and data are analyzed. The results show that the theoretical analysis is correct and the design method is reasonable.Finally, the experimental prototype of 24V/350W is built, the stress test of the key components of the resonant converter is carried out, and the input and output state of the circuit is tested. The test results show that the experimental prototype performance is stable and can quickly achieve ZVS and ZCS, output ripple less than IV, the efficiency is higher than 80% at light load and reached 95% at full load.The half bridge LLC resonant converter of LED driver power supply can realize high efficiency and low expansion, which has a good engineering application prospects.