Modeling High-Frequency Multiwinding Magnetic Components Using Finite-Element Analysis

This paper presents a magnetic component equivalent circuit as well as a methodology to extract its parameters by using a finite- element analysis tool. The model is valid for any kind of magnetic component-transformers and gapped and nongapped inductors-and takes into account frequency and geometry effects such as skin, proximity, interleaving, gap, and end effects. An additional model for capacitive effects may be coupled with the previous one to obtain a more precise result. The impedances in this model represent not only the self terms, but also all mutual terms shared between the windings. Because the simplification of concentrating impedances in one winding is not invoked, simultaneous conduction of all windings (such as forward-like converters) or in alternate conduction of the windings (such as flyback-like converters) can be accurately simulated. The parameters of these self and mutual impedances are frequency dependent, so the model represents the frequency behavior of windings in detail. This allows simulating components with nonsinusoidal currents like the ones present in switched-mode power supplies, provided there is no saturation of magnetic materials. This is not a serious limitation of the model because this kind of power supply works in linear (no-saturation) mode. When there is saturation, the core model determines the component behavior. Applying the model to several actual components has shown its usefulness and accuracy. Details concerning model parameters extraction are presented here with simulation and measurement results.