Research On The Radiated EMI Mechanism Of Switching Power Supply Boost PFC

Power Factor Correction(PFC)of switching power supply has been widely applied in reducing harmonic pollution among power grid caused by power electronic equipment.However,the increasing operation frequency of PFC causes strong Electromagnetic interference(EMI)noise of internal switching devices and external wiring,which can affect normal operation of the electronic equipment.This experiment establishes three Boost PFC models under continuous current mode:a circuit radiation EMI model,a cable radiation EMI model,and a shielding model of the shell.The results reveal the generation mechanism of radiated EMI noise and the shielding mechanism of the shell.In addition,an effective suppression method is proposed.In details:This paper analyzes the generation mechanism of radiated EMI noise in Boost PFC circuit of switching power supply,and establishes models based on common-mode radiation and differential-mode radiation.In addition,high-frequency noise current is extracted by circuit simulation software,and is imported to common/differential-mode radiation formula for calculation.Furthermore,different radiated EMI noises generated by high-frequency current under different inductance parameters are analyzed;This paper analyzes the extraction method of cable radiation impedance based on different antenna models,proposes an estimation method of cable radiated EMI noise,and establishes models of different cable length for comparison with CST simulation software.In addition,an experiment is run for comparison between traditional prediction model and the proposed prediction model;This paper analyzes the shielding mechanism of good metal-conductor,and analyzes the influences of different holes(on PFC shell)on shielding effectiveness.A shielding effectiveness simulation comparison is run with CST software for verification of shielding characteristics of the shell and the effectiveness of the shell simulation model;The UCC28180 control chip of Texas Instruments is selected to design the PFC circuit of the switching power supply.Experiments on three suppression methods are run,which are based on circuit radiation,cable radiation,and shell shielding.Results verified the theoretical basis and the effectiveness of proposed suppression methods.