Simulation Bits: A SPICE Behavioral Model of Non-Linear Inductors©

Simulation Bits: A SPICE Behavioral Model of Non-Linear Inductors© Sam Ben-Yaakov and Mor Mordechai Peretz SPICE simulation is already recognized as a viable tool in Power Electronics. Simulation is particularly useful when dealing with a non-linear behavior that cannot be easily handled analytically. Such a case is the analysis of a switching power converter that includes a non-linear inductor that might affect the inrush current, magnitude of the current ripple, small signal transfer functions and others. Modern SPICE simulation packages, such as ORCAD (Cadence, CA, USA) include a non-linear magnetic core model that is based on the Jiles and Atherton model [1]. However, unless the vendor already provides a model for a given core, developing your own model for your specific application may prove to be very frustrating if not practically impossible. Here we demonstrate how a SPICE compatible behavioral model of a non-linear inductor can be developed easily using core manufacturer’s data or simple laboratory measurements. The resulting model is by no means perfect. It does not include core losses, temperature effects, or frequency dependence of the permeability, and it does not show the hysteresis effect. Nonetheless, one may still find it useful in many applications such as the examination of the current ripple of iron powder core inductors under various operating conditions or in small signal analysis based an behavioral average modeling [2]. The basic idea of the proposed inductor model is to reflect the behavior of a linear inductor via a non-linear ‘transformer’ that is realized by (E1, G1) dependent sources (Fig. 1) defined by: