Modelling non Linear Magnetic Cores at High Frequencies for PSpice Simulation

Abstract

(Dissertation is written in Spanish.) Using PSpice of MiscroSim to simulate power converters sometimes brings awkward complications such as the simulation of real magnetic components. It deals a little bit of work to bring a good agreement between experimental and simulated results. Simulation with linear inductors or transformers does not produce good results. The reason is that real magnetic components present saturation and hysteresis, a phenomenon that characterises magnetic materials.

The hysteresis or B-H loop of a magnetic component is highly dependent on frequency, waveform (not very important for ferrite material), temperature, excitation level, etc. Although PSpice includes in its magnetic library a list of non-linear components, rarely these parameters are coincident with our working conditions or simply they are not specified. In all of these cases it is necessary the modelling of non-linear magnetic cores for each particular application.

Here we present a systematic procedure to obtain real PSpice parameters to model magnetic materials using the Jiles & Atherton theory. The procedure is totally general and models the static B-H loop given by any manufacturer as well as the one that can be obtained in accordance with some specific working conditions. This is really important, since it helps the designer in obtaining model parameters for any high frequency applications, which are not correctly presented in PSpice libraries.

The modelled magnetic material is used for power electronics circuit simulation, which uses magnetic materials, working at frequencies in the region of kH, to construct transformers and inductors. Magnetic materials are the most critical components in electronics simulators due to their non-linear behaviour. This work examines the modelling of the magnetic core hysteresis for high-frequency applications. As example of application, a buck converter with their inductor working near saturation is implemented and their experimental waveforms are compared with the simulated ones obtained with this model.

With this procedure a good concordance between experimental and simulated B-H loop is obtained and the simulation of the power converter is reached properly.