Analyzing of Passive Filter applied to Power Supply

Conductive EMI of the high frequency power supply is one of the main EMI source in the power and elec-tric device, and the parameter of the power products from the international EMC rules has become one of the most critical parameters of the power supply. How to analyze the EMI of the power supply and take appropriate filter measure are the foundation for the power supply designing. This paper presents a method to reduce EMI in power supply by use of passive filter technology based on the comprehensive analysis of the conductive EMI in power supply by means of EMI mode, in-troduces insertion-loss of filter, derives the models of different mode EMI and common mode EMI of high quality passive filter, and designs the passive filter based on the principle that the insertion-loss to the EMI is most. The passive filter has been used in the special driving power supply of the EV inverter, and it is validated that the passive filter can help reduc-ing high frequency EMI of the power supply.