Switching Power Conducted Interference Simulation Analysis

With the development of electronic technology, EMC's research has attracted more and more people's attention. The research in this dissertation is mainly about the conducted EMI in Switching Mode Power Supllies and radiated electromagnetic interference (EMI) measuring system.This paper takes flyback switching-mode power supply as a research object. Summarized the source of interference and the coupling channel.The rerformance of resistance capacitance and inductance at high frequency range were analyzed in this paper.The simulation models of resistance capacitance inductance transformer MOSFET and diode at high frequency range were established.Using PSpice software simulates switching-mode power supply conducted interference production and coupling channel Analysis of the leakage inductance, C_gdo,C_gso,C_jd, and other parameters on the size ofinterference.when the MOSFET was turned off, leakage inductance will make a electromotive force E = -L_p (di/dt) ,and peak voltage. Leakage inductance greater thelonger decay time, the more serious interference. The fin-to-ground capacitance has a great impact on interference when voltage jumps capacitance kept on charging and discharging. This form a voltage attenuation and interference current waveform.Transformer leakage inductance, the fin-to-ground capacitance are the main reason for electromagnetic interference. the turn-on and turn-off switching time affected by C_gdo,C_gdo have a great impact on EMI According to interference current , the coupling channel is analysised These work is useful to EMC design of switching power supply with a guide.The radiated interference test of EMC is very important. This paper emphatically elaborated EMI radiation test system based on the GPIB in the last chapter, model and method were analyzed.Using Matlab instrument control toolbox,Turntable, antenna height and EMI sets were controled through GPIB. the radiated EMI was tested Influences of three factors - elevation, azimuth and frequency on radiated EMI results are analyzed.