Theoretical and experimental analysis of ferrite inductors for applications in DC-DC converters

Inductors represent the energy storage elements in the majority of DC/DC power converters topologies. One of the current trends in the application of these devices is the demand for higher power density. A feasible path in this direction is the use of inductors in the saturation region. In fact, recent studies have demonstrated that by using inductors in saturation region, it is possible to reduce dimensions, weight and cost of the core materials without dramatically worsening the performances of the devices. Another trend is the demand for higher efficiency of DC/DC converters, which can also be achieved by minimizing the losses of soft magnetic materials employed. The aim of the thesis is to provide a methodology for the analysis of saturated inductor in DC/DC power converters, investigating the behaviour of soft ferrites in high frequency buck converters. To this end, a method for the experimental characterization and parameterization of the inductance curve of saturated inductors is defined and a method for the simulation of experimental inductor current waveforms under saturation conditions is developed. The second target of the thesis is the understanding of loss processes of soft ferrites employed in DC/DC power converters. On the basis of experimental measurements made under symmetrical flux density waveforms, it is defined a basic predictive model of the core losses under asymmetrical triangular flux density waveforms.