A simple method to plot online B-H curve and calculate core loss of the inductor in a conventional buck-boost converter is developed. In order to obtain a reliable loss data, measurement error and phase shift error are analyzed and then quantified. A new method to minimize measurement error is given. A new core loss model in terms of switching duty cycle is presented. This model predicts variation of core loss of an inductor operating .in various conditions in a switching converter. This inductor model can be generalized to inductors in other switching converter topologies.

A simplified physical model concludes a minimum of six equivalent physical coupling paths, Least Coupling Paths (LCP), using lump elements approach through non-contact EM1 coupling mechanism to the terminals of LISN. Simulation shows both inductive and capacitive coupling through each path may produce substantial EM1 measured by a LISN. This physical model is good for understanding, diagnosis and emission estimation.