HF Characterization and Nonlinear Modeling of a Gapped Toroidal Magnetic Structure

The frequency dependent characteristics of a gapped toroidal structure are extracted empirically over a bandwidth that exceeds 30MHz. The analysis is complicated due to nonlinear flux distributions, magnetic properties of the core material, leakage inductance, stray capacitances, and eddy currents in the windings. A permeance model of the core is implemented to model the magnetic circuit. The model includes a linear lumped element equivalent circuit to approximate the nonlinear complex permeability of the core, which was measured empirically. Stray capacitance and inductance of the winding are also modeled. A gyrator is used to couple the electric and magnetic models for circuit simulation. The measured and simulated results of open-circuit impedance from the secondary winding and the transimpedance gain (V/A) of the current sensor are compared and discussed

I. Introduction

The wide-band characteristics of passive components are becoming increasingly important even for high power applications, for which there has been a steady increase in switching frequencies over recent years. Present microprocessors are more able to cope with high frequencies and enable tighter control bandwidth. The ability to predict conducted electromagnetic interference (EMI) in power electronics circuitry before even constructing a prototype has also become a reality. These are only some of the reasons why high frequency behavior will gain increasing interest for the accurate characterization, modeling, and design of circuit components, such as filters, inductors, capacitors, and sensors, for frequencies typically up to 30MHz.