Essential-coupling-path models for non-contact EMI in switching power converters using lumped circuit elements

N. K. Poon, Bryan M H Pong, C. P. Liu, Chi Kong Tse

Research output: Journal article publicationJournal articleAcademic researchpeer-review

31 Citations (Scopus)


This paper proposes a simple lumped circuit modeling approach for describing noncontact EMI coupling mechanisms in switching power converters. The resulting model assumes a minimum number of noise sources and contains essential coupling paths that allow easy physical interpretations. Essentially, all capacitive couplings are represented by an equivalent noise voltage source and six coupling impedances, whereas all inductive couplings are represented by an equivalent noise current source and three coupling impedances. The resulting coupled noise appears as currents flowing into the terminals of the Line-Impedance-Stabilization-Network (LISN). The equivalent voltage source can be conveniently approximated as the switching-node-to-zero voltage, which is typically a rectangular pulse of a few hundred volts. The equivalent current source can be modeled as the current flowing around a loop containing the equivalent voltage source and parasitics such as winding capacitance of the power transformer, the snubber capacitance and connection inductances. Also, the coupling impedances can be estimated by making simplifying assumptions about the geometry of the components and tracks, or by direct measurements. Simulations and experiments verify how inductive and capacitive couplings through each path may produce substantial EMI measured by the LISN. Being based on a lumped circuit approach, the proposed model is easy to apply in practice for understanding, diagnosing and approximating EMI behaviors.
Original languageEnglish
Pages (from-to)686-695
Number of pages10
JournalIEEE Transactions on Power Electronics
Issue number2
Publication statusPublished - 1 Mar 2003


  • Capacitive coupling
  • Electromagnetic interference
  • Inductive coupling
  • Lumped circuit models
  • Modeling

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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