Modeling And Simulation Of Conducted EMI In AC/DC Converter

By the continuous development of power electronic technology, the frequency ofswitching power supply and power density has been greatly improved, as a result itcauses higher du/dt and di/dt. The corresponding electromagnetic compatibilityproblem is increasingly serious, especially the conduction interference in theelectromagnetic compatibility of switching power. In this paper, the AC/DC converteris taken as an example to study the modeling and simulation of conduction EMI ofswitching power supply, and some results are achieved.First of all, according to the test standard of conduction EMI, the test platform isbuilt. And it is used to test the conduction EMI of AC/DC converter under severaltypical working conditions, and the results of the test are analyzed. The reason for theseveral important peaks in the test of the frequency-domain of conduction EMI isfound out by testing the voltage and current waveforms of the main devices in thecircuit and theoretical calculation. Provide directions for the modeling and simulationconducted EMI.Secondly, the high frequency model of the circuit is established, including thehigh frequency model of the converter by the method of the combination of theexperiments and calculations, the high frequency models of diode and powerMOSFET by using the modeling tools in Saber. The impedance characteristic curveof capacitance resistance is obtained through the test of the network analyzer, as wellas the high frequency parameters. The distribution parameters of the PCB areachieved by using Ansoft Q3D software.Thirdly, the Saber simulating model of the whole circuit is established, and thenthe time domain waveform of the conducted EMI is obtained. The influence of thebandwidth measurement by using frequency analyzer is considered for FFT transformof the time domain simulation results, and obtained the spectrum of conducted EMI isobtained, which is similar to the test results of frequency analyzer.Finally, the simulation results are evaluated by feature selective vadiationmethod, and the low frequency characteristics and high frequency characteristics ofthe data are obtained. Through the mathematical calculation, the amplitude differencemeasure, feature difference measure and global difference measure of the data arefurther achieved. More detailed and precise results are obtained, which makes up forthe deficiency of the visual assessment, and then the validity of the model is verified.