Research And Design On Feedback Loop Based On Half-Bridge LLC Resonant Constant Current/Constant Voltage LED Power Supply

With the rapid development of the intelligent energy-saving lighting industry,LED has become the mainstream lighting source,which is used in various environments.The mature application of LED lighting technology will inevitably promote the rapid development of its driving power.Since the advent of high-power LED driving technology,the research of high-power LED driving power has been restricted by the important problems of high power factor,high efficiency,and high reliability.At present,the research of high-power LED drive power supply is only limited to constant current drive.Although it overcomes the disadvantages of constant voltage drive,the load is too large,the efficiency will be greatly reduced,and even the power supply will be damaged.Therefore,it is necessary to design a high-power LED drive power control feedback circuit based on a half-bridge LLC resonant converter that can achieve constant voltage under low load and constant current drive under full load from the theoretical study of the switching power supply control loop.Firstly,the main circuit topology of LLC resonant converter and its working principle are studied in detail.The working process is analyzed in detail under different switching frequencies and different working modes.The fundamental wave analysis method(FHA)is used to model and study its steady-state characteristics.A necessary condition for achieving zero voltage turn-on(ZVS).Then,the extended description function method(EDF)is used to establish the small signal model of LLC resonant converter.The dynamic characteristics of the LLC resonant converter are studied by deriving the state space model and transfer function,and the frequency domain characteristics of the built small signal model are verified with the help of Math CAD.Secondly,according to the dynamic characteristics of the small signal model and the constant current/constant voltage drive feedback control characteristics of the LED power supply,a dual operational amplifier is used to design a reasonable loop feedback compensation network,and Loop stability criterion verifies that the feedback drive method can Realize the constant current/constant voltage drive characteristics,verify the stability of the compensation network through Math CAD,and further build a simulation model of the constant current/constant voltage drive feedback circuit based on the half-bridge LLC resonant converter with the help of SIMetix/SIMPLIS to verify the rationality of the feedback loop design.Finally,the hardware circuit design is completed,the experimental prototype is built,and the system output voltage,current and ZVS waveforms are analyzed under light load and full load.Under sudden load switching conditions,the overshoot,undershoot voltage and response time have reached the actual ideal standard,which verifies the rationality of the designed constant current/constant voltage drive feedback output circuit.Compared with the traditional constant current driving method,the constant current/constant voltage driving method plays the role of overload protection and short circuit protection,and has good dynamic performance.