Better Understanding EMI Generation of Power Converters

Abstract

This paper describes how the use of a specific signal processing method can help understanding the EMI generation of a switched mode power supply. It provides an equivalent system between a supposed disturbance source and the actual EMI signal. To identify this system, the "Wiener filtering" method is applied. Both experimental and simulation waveforms may be used. This method is illustrated in the simple example of a boost switching cell. The application to more complicated power electronics structures with several switches is also possible.I.

Conducted EMI of Switching Frequency Modulated Boost Converter

“…Theoretical analysis and prediction of conducted EMI of SMPC without SFM has been performed in various papers, e.g. [12] - [16]. Usually EMI is analyzed using computer simulation and fast Fourier transform (FFT) to calculate EMI spectrum.…”

“…Usually EMI is analyzed using computer simulation and fast Fourier transform (FFT) to calculate EMI spectrum. However several papers [12], [16] propose simple analytical models for EMI analysis and prediction in SMPC without SFM.…”

“…Although numerous research papers [6][7][8][9][10][11] are devoted to SMPC conducted EMI reduction with periodic SFM, usually the analysis includes only the investigation of spectra of rectangular pulse trains (representing power component voltages) or power component currents (such as power inductor current). However the conducted EMI noise voltage waveforms highly differ from the power component voltages and currents waveforms [12]. Thus the analysis presented in the papers can omit several important details of the effect of SFM parameters on conducted EMI attenuation.…”

The Wiener Filter Applied to EMI Decomposition

“…Although voltage V d across dc-switch-mode supply [see Fig. 6(b)] changes from 0 to 600 V (higher voltage than power inverter), the perturbations generated are smaller because of the topology of the circuit layout [12]. …”

EMI Estimation for DC/AC Hard Switching Converter Using Wiener Filter

“…• simulation of whole circuit with many simplifications in parasitic calculation [1], [2], [3], • estimation of simplified schema consisted of only the most important components [7], [9]. In previous papers in order to forecast perturbation, authors used only one transfer function between switch and the line impedance stabilization network (LISN) voltage [7], [10].…”