Investigation on the Possible Use of Wavelet Transform in EMC and Power Electronics

The design of Switch Mode Power Supplies (SMPSs) is more and more related to Electromagnetic Compatibility (EMC) matters. The voltage and current signals of a generic converter are normally rich in high-frequency transients. In this work Discrete and Continuous Wavelet Transforms (DWT and CWT) were tested to get information about the evolution of such signals in both time and frequency domains. This tool was used to identify two components in the signal. The first component was the one that is considered in any first order simplified model of the converter; the second component was the remaining part of the signal, which is the result of second order phenomena (parasitic components, layout effects, etc). The paper shows how this time decomposition could be used as an EMC diagnostic tool which will make it possible to separate the effect of noise from the effect of intentional components on the measured conducted noise caused by a converter. Moreover, this EMC analysis will make it possible to relate particular spectrum components to significant time domain events.