Research On High Power LED Driver Based On Half-bridge LLC Resonant Converter

As a new type of lighting resources, LED has many advantages, such as environmentalprotection,energy saving, and long service life. However, the technology of LED driver is notmature enough. The LED driver’s problem of low efficiency and reliability has greatlyshortened the service life of LED lamps. Therefore, how to improve the efficiency andstability of LED driver has become the current research hotspot in the field of power supply.As a relatively new soft switch technology, the half-bridge LLC resonant converter canachieve zero voltage switching of primary MOSFETs, and zero current switching ofsecondary rectifiers. Therefore, the switching loss and EMI of LED driver could beeffectively reduced. In the occasion with high output current of LED driver, the application ofsynchronous rectification technology can effectively decrease the secondary conduction loss,and further improve efficiency of LED driver.In this paper, a prototype of320W LED driver is designed according to the actualengineering quality requirements, and it adopts a two-stage circuit topology with half-bridgeLLC and APFC. First of all, an improved FOT control mode is put forward on the basis oftraditional Boost-APFC. And the APFC circuits are designed with the improved FOT scheme.Secondly, it is completed that the design of the resonant network parameters of the resonantconverter. Further more, the resonant converter model is built with the fundamentalapproximation method, and the effect of main parameters on the resonant converterperformance is discussed. Meanwhile, it is determined that the achieving condition of zerovoltage switching of primary MOSFETs. Finally, this paper applies the external drivensynchronous rectifier technology in the driver to improve the efficiency. Because of the highconduction loss of secondary rectifier diode, the external driven synchronous rectifiertechnology can effectively reduce the loss with replacing the traditional rectifier diodescheme.A hardware prototype of320W LED driver is developed according to the design scheme.The parameters of prototype are input AC100V to260V, output DC40V/8A. The powerfactor of the prototype is greater than0.98, and the efficiency is greater than92%.Theaccuracy of output current is within±1%. Therefore, the main parameters of the prototypeverify the feasibility and validity of the design scheme....