Accurate extraction of noise source impedance of an SMPS under operating conditions

Abstract

An accurate measurement method to extract the common

mode (CM) and the differential mode (DM) noise source

impedances of a switched-mode power supply (SMPS) under its

operating condition is developed and validated. With a proper

premeasurement calibration process, the proposed method allows

extraction of both the CM and the DM noise source impedances

with very good accuracy. These noise source impedances come in

handy to design an electromagnetic interference filter for an SMPS

systematically with minimum hassle.