High-frequency models of ferrite core inductors

Abstract

A model of ferrite core inductors is presented. The skin and proximity effects which increase the ac resistance of the inductor winding are considered. The core losses are studied. Power losses of the inductor are modeled by means of a frequency dependent series resistance. Parasitic capacitances which affect the inductor high-frequency operation are also considered. The model is applicable to cores with and without an air gap. Calculated and measured inductor parameters such as equivalent series inductance (ESL), reactance, equivalent series resistance (ESR), impedance magnitude and phase, and quality factor are plotted as functions of the operating frequency and compared. Calculated results were in good agreement with the measured ones up to the inductor self-resonant frequency. As a consequence, the discussed model is suitable to represent the frequency response of ferrite core inductors and can be effectively used for designing inductors