Noise Source Impedance Measurement in SMPS

Abstract

An accurate measurement method to extract common mode (CM) and differential mode (DM) noise source impedances of a switched-mode power supply (SMPS) under operating condition is presented in this chapter. With a proper pre-measurement 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 systematically design an electromagnetic interference filter for a SMPS with minimum hassle.