Approximating Non-linear Inductors Using Time-variant Linear Filters

In this paper we present an approach to modeling the non-linearities of analog electronic components using time-variant digital linear filters. The filter coefficients are computed at every sample depending on the current state of the system. With this technique we are able to accurately model an analog filter including a nonlinear inductor with a saturating core. The value of the magnetic permeability of a magnetic core changes according to its magnetic flux and this, in turn, affects the inductance value. The cutoff frequency of the filter can thus be seen as if it is being modulated by the magnetic flux of the core. In comparison to a reference nonlinear model, the proposed approach has a lower computational cost while providing a reasonably small error.