A probe for measuring the propagation of conducted EMI in powerconverters

摘要

Conducted EMI compliance is based on a single frequencymeasurement at the mains input of a power converter, using a lineimpedance stabilisation network (LISN). A measurement method based on anew probe is proposed with which the sources and propagation of noisecan be measured. The characteristics of the probe are compatible withthe LISN. The method adds time and frequency measurements within theconverter circuit, to the standard LISN measurement. This addedmeasurement flexibility assists in the identification of the noisyswitching transients. Attenuation is added in the probe as a means tocontain the power dissipation in the 50 Ω instrument inputimpedance. The working of the EMI probe is illustrated with somepractical measurements