Design And Implementation Of LLC Resonant SMPS Based On PFC

There are some problems with the traditional switching power supply,such as distortion of the input current waveform,higher harmonics,low power factor,and hard switching,which makes the switching loss large.In order to improve the situation,the paper research and design a regulated output switching power supply based on power factor correction technology and LLC resonant converter.The switching power supply adopts cascading mode and the design requirements are as follows: the wide range AC input voltage between 85 Vac and 265 Vac,output DC voltage of AC-DC converter is 380 V,the output DC voltage of DC-DC converter is 12 V,the maximum power is 120 W.At first,The research analyzes the development status of power factor correction technology and resonant converter,and selects the appropriate topology and implementation method according to the designed switching power supply.Secondly,the working principle of LLC half-bridge resonant converter and Boost-PFC circuit are explained clearly.In the part of LLC half-bridge resonant converter,the thesis expounds the specific working conditions of the different states and establish FHA equivalent circuit model.And then analyzing the gain of the model.In the part of Boost-PFC circuit,the thesis descripts the principle of Boost-PFC circuit and the principle of single-cycle control.Thirdly,according to power system specifications,the thesis designs the PFC circuit which selects the Boost topology based on single-cycle control,the soft-switching technology which selects the LLC half-bridge resonant converter,and the auxiliary switching power supply which choose the fly-back topology,and then simulating the design.The thesis briefly designs the main circuit,the peripheral circuit of control chip,input EMI filter of Boost-PFC circuit,main circuit,transformer,peripheral circuit of control chip,SR circuit of LLC half-bridge resonant converter and transformer,RCD absorption circuit,control loop of fly-back auxiliary switching power supply.Finally,according to the designed circuit board soldering components and selecting the appropriate heat sink to make the prototype and test it.The results verify that the designed switching power supply can achieve power factor correction,zero voltage switching and synchronous rectification,and work with relatively higher efficiency.