Research On Two-Stage LED Driver Power Supply Based On Electrolytic Capacitor-less Bridgeless PFC

The fourth generation of light-emitting power LED occupies a dominant position in the lighting field because of its high efficiency,energy saving,long service life and excellent performance.For high-power LED,pulsating power exists at the output of the AC/DC converter in the drive circuit,so electrolytic capacitors are often used to alleviate this problem.However,the poor temperature characteristics,short service life,low voltage and current resistance of electrolytic capacitors lead to the performance of LED drive power supply cannot meet the requirements of long service life of LED.Therefore,the electrolytic capacitor-less of LED drive power supply has become the research focus of lighting field.In view of the above problems,this paper focuses on the research of two-stage LED drive power supply without electrolytic capacitor.Firstly,the front stage of the power supply adopts a double diode bridgeless PFC(Power Factor Correction)converter based on one-cycle control,which is used to realize power factor correction and reduce harmonic pollution.The stability conditions of one-cycle control applied to the bridgeless PFC converter are analyzed.The small signal model is established and the voltage loop controller is designed.Then,aiming at the problem of double-line-frequency pulsation component on the front-end DC bus side,a boost bidirectional Buck/Boost power decoupling converter is connected in parallel at the DC bus end.Its working principle is expounded,its small signal model is established,and a double closed-loop control structure is adopted.The voltage outer loop adopts PI control,and the current inner loop adopts model predictive current control,so that the bidirectional converter absorbs double-line-frequency ripple power,reduces the power ripple at the PFC output end,realizes power decoupling,and achieves the purpose of removing electrolytic capacitors.Finally,the latter stage uses a half-bridge LLC resonant converter to achieve soft switching and reduce switching loss.The working process is analyzed.The equivalent circuit model is established by first harmonic approximation,and the voltage gain expression is derived.The change trend of the gain curve is observed by changing the quality factor,inductance coefficient and ratio,and the zero voltage switching constraint condition of the primary side is derived.On this basis,the design of the resonant parameters is completed.According to the above theoretical analysis,the overall simulation model of electrolytic capacitor-less two-stage LED drive power supply based on bridgeless PFC and half-bridge LLC resonant converter is established.With TMS320F28335 as the control core,the main circuit parameters,drive circuit,auxiliary power supply and sampling circuit are designed.The 200 W experimental platform is built to verify the correctness and effectiveness of the designed LED drive power supply and its control method.