Research On High Power Hybrid Common Mode EMI Filter With Parasitic Inductance Cancellation

The rapid development of power electronics technology leading to faster switching speed,shorter rise time,lower switching loss,as well as higher power density and efficiency of switching mode power supply(SMPS)based on wide band gap semiconductor material gallium nitride(GAN)devices,and it has been widely used in various power conversion devices.The faster switching speed leads to the spread of the common mode noise spectrum to the high frequency band,that is,the common mode noise in the high frequency range will rise to the intolerable level,which makes the electromagnetic compatibility of the whole system more complicated.In order to ensure the stable and reliable operation of the system,these electromagnetic interference must be effectively suppressed.The most direct and effective way to suppress electromagnetic interference is to connect a passive EMI filter to a switching mode power supply system.However,the volume of inductance and capacitance in passive EMI filter is generally very large,and it increases as the power level increases.In order to enhance the power density of the system,the complementation of active EMI filter and passive EMI filter are considered.The hybrid EMI filter balances three properties:volume,weight and performance.However,since the effect of parasitic parameters,their performance in the high frequency range is out of expectation.In high power applications,this problem is more serious.Therefore,how to effectively reduce the influence of parasitic parameters on the hybrid EMI filter and ensure the performance of the filter are problems that must be considered.Effective suppression of high power and high frequency electromagnetic noise is a challenging obstacle in EMC.With the use of Ga N devices and the increase of switching frequency,this problem becomes more serious.This thesis firstly introduces the research background of EMC,the research status of EMI filter and the significance of the subject.Then,the topology and working principle of common EMI filters are analyzed in detail,and the analysis methods and expressions of insertion loss in different topologies are given.Thirdly,considering the influence of parasitic parameters,analyzes the limitations ofπtype PEF and V_SC_C AEF in high frequency and high power,the degree of impact is illustrated by means of insertion loss expressions and simulations.A hybrid EMI filter structure with parasitic inductance cancellation is proposed to deal with this problem,including aπtype PEF and a V_SC_C AEF.The principle on magnetic flux cancellation to reduce the equivalent series inductance(ESL)on common mode(CM)capacitors of the passive EMI filter(PEF)and active EMI filter(AEF)simultaneously is highlighted.Then,the effects of current-carrying conditions,parasitic inductance,and coupling conditions on coupling cancellation in the two branches are analyzed in detail.The optimization problem about the CM capacitance calculation and placement is also addressed.Finally,we use a prototype to prove the effeteness of our method.The hybrid EMI filter with parasitic parameter cancellation is proposed in this thesis,which can effectively solve the electromagnetic compatibility problem caused by switching mode power supply based on Ga N device.It can improve the optimization strategy of high frequency parasitic parameter in filter design,and promote the development of power conversion device to miniaturization and lightweight.