Application Of Palanar Integrated LC Unit In Electromagnetic Compatibility

EMI filter plays an important role in restraining conducted EMI. Planar EMI filter has adecreased size and high reliability in high frequency performance compared to passive discrete EMIfilter. Based on the LC unit, the planar EMI filter integrated all the components of a EMI filter in onestructure. The basic units, whole structure, insertion loss, near field parameters are studied in thispaper in order to improve the performance of the planar EMI filter.(1) The effect of parasitic on the insertion loss of the planar EMI filter is studied based on thetypical structure of the planar EMI filter. The relationship between the PCB section of the planar EMIfilter and the equivalent parallel capacitor and the equivalent serial resistor is studied. In order toreduce the parasitic parameters, the parallel bundle structure is proposed to replace the conventionalwire. Based on the different equivalent circuits of different connections of the LC units, four planarEMI structures are proposed under different impedance conditions. These four structures are analyzedin detail. In order to obtain the required DM inductor and the CM inductor, the calculation forums ofthe DM inductor and the CM inductor is studied and the core is improved.(2) The method of scatter parameters is used to measure EMI filter performance in this paper.The relationship between scatter parameter and insertion gain of EMI filter has been derived; themethod to predict the insertion gain of filter under different impedance is proposed. The near fieldcoupling model of the planar filter in high frequency is deduced. The near field coupling between theEMI filter and the switching model power supply is analyzed. The main source of the near field canbe known based on the EMSCAN. The effect of the near field coupling between the EMI filter and theswitching model power supply on the performanece of EMI filter is analzed using saber.(3) The conductor EMI model of a fly back convector is studied and a sample of the planar EMIfilter is designed based on the design steps. The high frequency performance of the planar EMI filteris improved using the parall wire structure; with the increase of the distance between the filter and theconvector, the near field coupling can be reduced and the performance of the insertion loss of the filteris improved effectively.