A Physics-Based Circuit Model for Nonlinear Magnetic Material Characteristics

Nonlinear magnetic properties in power electronics applications, such as permeability and core loss cause significant discrepancies between magnetic designs and prototype measurements, leading to iterative prototyping efforts. To address this issue, a bottom-up approach that is based on the physics of magnetic material is proposed to unveil the fundamental origin of nonlinearity. The physical parameters such as magnetization, gyromagnetic ratio, damping factor, etc., are translated to equivalent circuit parameters. The nonlinear magnetization dynamics of a single magnetic domain are described by an equivalent circuit model derived from the Landau-Lifshitz-Gilbert (LLG) equation. A fictitious magnetic domain is used to demonstrate the developed model's capability on predicting the nonlinearity that includes magnetization dynamics and hysteresis. Then, the model is further validated by a commercial material, TDK N87 toroidal core. The results such as B-H loop and permeability simulated from the circuit model are in close agreement with the datasheet, validating the feasibility of predicting magnetic material's nonlinear performance from physics perspective rather than empirical approaches.