A Study on Conducted Emissions fromSwitching Power Converters and a SystematicDesign Procedure for EMI Filters

[摘要] Electromagnetic interference has been a major issue in the case of high frequency and high speed switching in power electronic circuits, especially in launch vehicle power supply system. The EMI generated by switching power converters interferes with the normal operation of other sensitive equipment and may cause operating faults. These effects are critical in the case of electronic packages in launch vehicle and should be carefully examined whether it meets required EMC standard. The EMI can be either conducted EMI or Radiated EMI. Electromagnetic interference (EMI) filters are treated much as the effective equipments for controlling conducted EMI. The Conducted EMI consists of mainly common mode and differential mode noises. In this paper, a study on conducted emissions from a switching power converter is done. Also, a systematic design procedure of EMI Filters conforming to the military standard MIL-STD 461C is presented. The design procedure is based on practically measured conducted emissions. Design procedure discussed in this paper considers common mode and differential mode sections separately. Also, various considerations in fabrication stage to improve the performance of designed filter are discussed. The considerations for filter size optimization include grounding, common mode choke size optimization, magnetic core material, integrated common mode and differential mode inductor etc.

[关键词] Switching power converters;Conducted Emission;EMI filter.