Characterization of power electronics EMI emission

In this paper, the relationship between the switching pattern of a power electronic system and its electromagnetic interference (EMI) noise emission is investigated. It is concluded that the complicated EMI emission from a power electronic system is determined by only two types of basic switching transitions, namely the positive-going transitions and the negative-going ones. By capturing noise emissions originated from these basic processes under different load currents, EMI spectrums in complicated pulse width modulation (PWM) can be predicted. To verify this concept, the well-known two-pulse test technique was used to reproduce those switching transitions, and then the transient responses were recorded. Based on the saved data, actual EMI emissions under the PWM mode at various load conditions were precisely predicted. To explain this concept in detail, this paper thoroughly examines the PWM operation of a power converter, followed by insightful analysis, and finally confirmed by solid test results.