Design And Study Of EMI Source Filter

With expanding switch power product, electromagnetic compatibility (EMC) design has been one of the most important components during the research and development process of switch power. Corresponding standards of EMC have been required which switch power should satisfy. Switch power of high frequency is serious electromagnetic interference (EMI) source, so EMI source filter usually should be added in switch power. Traditional EMI source filter design has been complex calculation, complex design and times long of the research and development. In order to improve the performance of filter and shorten the research and development time, a simple and good effect filter design method is presented in this dissertation for DC-DC switch power.On the basis of the switch powers' EMI primary characteristic analysis, conducted rugged technology for power is proposed. Basic theory of EMI source filter, topological structure, principle of design and high frequency performance of filtering components are illustrated in this dissertation. Moreover network theory and application in EMI source filter is analyzed.EMI source filter is designed on the basis of DC-DC switch power item of one aviation product. By knowing EMC standards that switch power should be satisfy, characteristics of EMI signal are tested and analyzed and performance indexes of filter are presented. Filter circuit is analyzed by network theory and filter circuit parameters are designed by programming. Then filter insertion loss (I.L) simulation model is established, simulation program is compiled and design results are analyzed. Finally, correction of design method is verified by practice test. At the same time, on the basis of design of EMI source filter, continuation function circuit of filter is designed. It is main against surge voltage by switch motion.By discussing characteristics of soft magnetism ferrite material that apply to EMI source filter, selection principle and application method of ferrite magnetic core are proposed. Then, the key and packaging technique of EMI source filter in engineering are studied in details. At last, testing method in packaging process and some very important problems in the engineering application are also proposed.