Modelling Power Loss of High-Frequency Inductor under Distorted Current Waveforms

Most inductor currents in switch-mode power electronic circuits have distorted waveforms, which makes it difficult to predict the power losses using traditional DC or high frequency AC equivalent resistances. This paper presents a high frequency inductor model that can be used for accurately calculating the power losses at multiple harmonic frequencies. A 2nd order equivalent circuit model is proposed to describe the dynamic characteristics of a high frequency inductor by considering the DC, fundamental and up to 4th order harmonic AC components. A procedure to determine the model parameters is proposed with known fundamental frequency, inductance, DC and equivalent AC resistances. In general, the equivalent circuit model of the inductor can be used for time domain simulation of power converters for more accurate results; and specifically it is applied to model a practical inductor used in a 5MHz Boost dc-dc converter and Class-E inverter respectively. The final power loss results show a good agreement with theoretical analysis.