Proposing an Improved DC LISN for Measuring Conducted EMI Noise

Switched-mode power supplies are among the sources of emitting electromagnetic interference (EMI) noise for various applications. Several standards specify limits of allowable generated EMI, where special line impedance stabilization network (LISN) has been introduced to measure both differential-mode (DM) and common-mode (CM) conducted noise. This article introduces an improved multistage LISN to measure the conducted noise for dc-dc converters. An analytical approach is suggested to decide on the number of stages. The proposed LISN has a good specification over the specified frequency bandwidth. Simulations are performed by the advanced design system to show the impedance and frequency response of the introduced LISN. Also, an implemented version of the suggested LISN has been set up for the required tests, whose practical measurements verify the performed simulations. Both simulations and experiments confirm the accuracy of the suggested LISN according to the requirements necessitated by standards compared to those of conventional LISN.