Design Of Wideband Hybrid EMI Power Filter

In recent years,the frequency band involved in electronic equipment is becoming wider and wider,the integration and complexity of equipment and system are becoming higher and higher,and the electromagnetic environment faced by electronic equipment is becoming increasingly severe,resulting in the increasing demand for wideband and high shielding effectiveness of shielding facilities.It should be noted that the shielding facilities with high shielding effectiveness are not only related to the structural shielding design,but also need to install high-performance EMI power filter for the power lines entering and leaving the shielding body,so as to achieve the insertion loss corresponding to the shielding effectiveness index.Aiming at the requirements of wideband and high insertion loss of EMI power filter for shielding facilities,this thesis studies the filtering characteristics of active EMI filter,improves the design method of active EMI filter,and finally designs a wideband EMI power filter based on active compensation,which can achieve the high insertion loss requirements as low as 1k Hz and as high as 18 GHz.The research results are of great significance to improve the shielding effectiveness of shielding facilities.Firstly,according to the design index of wideband EMI filter and considering the advantages and disadvantages of active and passive EMI filter,the overall design scheme of filter based on active compensation is determined,including active filter module and passive filter module.Then,the controlled source models of each topology of active EMI filter are analyzed by two port network,and the analytical expressions of insertion loss of each topology are obtained.Through the quantitative analysis of the analytical expressions of insertion loss,the universal topology selection rules of active EMI filter are established.At the same time,the typical circuits of each link of active EMI filter are analyzed.According to the actual engineering requirements,topology selection rules and index requirements,the topology selection and parameter design of active EMI filter are carried out.The rationality of active EMI filter design is verified by ADS software simulation.Then,the compensation ability and stability of the active EMI filter are analyzed.It is clear that the compensation ability design and stability design are indispensable parts in the design process of the active EMI filter.The design method of the active EMI filter is further improved,which lays a foundation for the design of the active filter module in the wideband combined EMI filter.According to the overall design scheme of wideband EMI filter,the circuit structure design,parameter design and device selection of active filter module and passive filter module are carried out.And then the filtering performance is analyzed by theory,simulation and test,which verifies the rationality of the design.Subsequently,the combination method of passive filter module and active filter module is studied,and the design of wideband combined filter is completed successfully.Finally,the further optimization strategy of active EMI filter is explored.