New EMI Filter Design Method for Single Phase Power Converter Using Software-Based Noise Separation Method

The main theme of this paper is to present a new EMI filter design method for single power converter such that the results meet the standard of EN 55022. In previous works, the corner frequency of filter is determined by drawing the 40 dB/decade slope line which is tangent to the required common-mode and differential-mode components. However, the high frequency components, e.g. around 20 MHz, can´t meet the standard. The presented method determines common-mode choke based upon the required impedance of common-mode choke to attenuate the common-mode noise to the desired level. Moreover, the presented method determines the corner frequency of differential EMI filter by the required attenuation amplitude at the frequency of maximum amplitude of differential-mode component. Therefore, the designed EMI filter can reduce the noise to meet the related standard from low frequency to high frequency range, 150 kHz to 30 MHz. A single-phase converter is used as the EUT and the related filter is designed and verified. It will be shown that EMI filter designed by this systematic design method effectively attenuates the EMI components to meet the related standard.