Research On Key Technologies Of Switching Power Supply Radiated EMI Noise Analysis And Suppression

With the high integration of electronic equipment,radiated interference generated by high-speed digital printed circuits are becoming increasingly serious.The interference not only affect the normal operation of this circuit,but also cause interference to other circuits around.Therefore,it is urgent to study the electromagnetic interference(EMI)of power electronic devices.In order to reduce the radiated interference noise,the detailed study and discussion have been widely carried out by scholars all over the world,which mainly through grounding,filtering,shielding and other measures to suppress.However,the research on modeling and predicting the radiated EMI noise of typical switching power supply circuit has been lacked,the intelligent algorithms have been not applied to shielding suppression and using electromagnetic simulation softwares to physical model and visualize electronic devices have not been studied.In this paper,the switching power supply was taken as an example,the above three contents were discussed respectively,and specific radiated suppression measures were proposed and verified by experiments.The main contents are as follows:Firstly,the circuit analysis and radiated EMI modeling of typical switching power supply circuits were carried out.The working principle of switching power supply circuit in discontinuous current mode was studied which includ AC-DC,Boost PFC and LLC circuits,and the circuit through simulation software was built;the generation mechanism of radiated EMI noise by switching power supply circuit was researched,which mainly including common mode radiated EMI model and differential mode radiated EMI model;the high-frequency noise current at the incoming line was extracted from the simulation circuit,and which was brought into the noise calculation formula for field circuit collaborative simulation;the effective radiated suppression measures were designed.Secondly,the shielding effectiveness of the electromagnetic radiation shell by the switching power supply was studied.The shielding effectiveness mechanism was researched,which mainly includes the calculation principle of switching power supply apertures,the shielding mechanism of metal good conductors and cavities with apertures;the intelligent optimization algorithm particle swarm algorithm was combined with the switching power supply shielding effectiveness,which can obtain the optimal situation;the effect of different opening methods on the shielding effectiveness of switching power supply was studied by using electromagnetic simulation software,and the correctness of the algorithm results was verified.Thirdly,the key devices of the switching power supply were modeled and the near-field visualization was analyzed.The near-field testing of switching power supply was carried out to find devices with larger radiation influence;seven key devices was selected from filter circuits and boost circuits for physical modeling;the key cevices was studied and the near field visualization between the devices and the devices and the shell was analyzed,which optimize the layout of the PCB board.Finally,the radiated EMI noise suppression experiment by the switching power supply was performed.The switching power supply circuit was built,The suppression experiment is carried out combining the switching power supply suppression measures mentioned above,which verified the correctness of the theoretical simulation and the effectiveness of the suppression measures.