Study On The EMC Of PCB Layout Of Switching Mode Power Supply

The EMC design of Switching Mode Power Supply has increasingly become a major difficulty because of its Electromagnetic Compatibility issues caused by the increase of power density and switching frequency. Conventional design approach, relying on experience in dealing with EMC design issues, consider the Electromagnetic Compatibility only after the prototype established, it may cause a re-design of the entire system of the worst case.Therefore, considering the EMC issues of PCB in the design stage of switching mode power supply is of great importance.Based on the status of the simulation of conductive EMI in switching mode power supply simulation both in china and abroad, the time-domain simulation and frequency domain simulation methods are comparative analyzed. The frequency-domain simulation method based on the noise source and propagation concept is used to analyze the conductive EMI,the noise source model was also studied. Parasitic parameters of a switching power supply PCB are extracted using parasitic parameter extraction tool, after that, the frequency domain equivalent circuit model of the flyback Switching Mode Power Supply is established. Both the power Differential Mode interference and Common Mode interference under different conditions are simulated using the frequency-domain simulation method, the essential means of conducted EMI are proposed by the spectral waveform analysis of Electromagnetic Interference: provide a low impedance path for the noise to go back to the noise source; make use of some parasitic element to reduce the noise; avoid increase of noise caused by resonance.In this paper, we analyzed the mechanism of conducted EMI of Switching Mode Power Supply based on the simulation of a flyback switching power supply. Consideration of EMC problems are given at the PCB design stage of switching mode power supply.