Modeling And Design Of EMI Active Filter For Switching Converter

With the continuous development and wide application of switching converters,the switching speed of switching converters is getting faster and faster,and the power density is also getting higher and higher,which leads to serious electromagnetic interference problems when switching converters are working.Electromagnetic interference will interfere with nearby sensitive equipment.Therefore,when using switching converters,it is necessary to consider electromagnetic compatibility.EMI filter is one of the most widely used EMI suppression measures.It is of great significance to study EMI filter.Therefore,this paper studies analog active EMI filter and digital active EMI filter for DCDC switching converter,and the main work includes the following aspects:First,the research status of EMI filter at home and abroad is investigated,the research status of passive EMI filter,analog active EMI filter and digital active EMI filter is summarized,and the research direction of active EMI filter is determined.The principle and topology of analog active EMI filter and digital active EMI filter are studied,their advantages and disadvantages are summarized,and common circuit structures and application scenarios are summarized.Secondly,the analog active EMI filter is studied.First,using a new method to measure the noise source impedance of DC-DC switching converters,the source impedance is measured,and the EMI noise level of switching converters is also measured.Then,a new analog active EMI filter is designed and modeled.After selecting the parameters,its stability and insertion loss are analyzed.Then,based on the analog active EMI filter,the hybrid active EMI filter is designed and analyzed.Finally,the hybrid active EMI filter is optimized to meet the requirements of filtering in high-power scenarios.The effectiveness of the filter design is proved by experiments.Thirdly,the digital active EMI filter is studied.First of all,based on the principle of digital active EMI filter,a new schematic diagram of digital active EMI filter is proposed,and its modeling is analyzed.Then,based on the designed schematic diagram,the detection injection scheme and the digital system scheme are designed.Because the digital system will inevitably introduce delay,the delay algorithm is used to solve the problem of delay.The open-loop transfer function of the digital system is measured,and it is verified that the digital system will not have a great impact on EMI suppression.Finally,the filtering effect of the designed digital active EMI filter is proved by experiments.