Core loss predictions for general PWM waveforms from a simplified set of measured data

A method to generalize square-wave core-loss data to predict core loss with any common rectangular voltage waveform is proposed. An automated measurement system was used to collect the required square-wave core characterization data for ferrite and powdered-iron cores, and to collect additional data to assess the accuracy of the method for other voltage waveforms. Measurement data is presented and the application of the method in power-electronics design is discussed.

I. Introduction

Core-loss data published by core manufacturers is based on sinusoidal excitation, whereas most applications in switching power supplies and other types of power electronics circuits use rectangular voltage waveforms. Rectangular waveforms can be described by the voltage, period, and duty cycles of the positive and negative portions of the waveform. This leads to a wide diversity of different possible test conditions, and it is not practical for manufacturers to test all possible waveforms that might be used by customers. Approximate methods to estimate expected core loss with rectangular waveforms based on sinusoidal data [1]–[8] exist, but are difficult to use, are inherently limited in accuracy, and are not in wide use in industry.