Inductors For DC-DC Converters Research Articles

Large-Signal Characterization of Power Inductors in EV Bidirectional DC–DC Converters Focused on Core Size Optimization

This paper is focused on core size optimization of power inductors in bidirectional dc-dc converters. It presents an experimental large-signal characterization procedure for power inductors in electric vehicle applications and a method to obtain an inductance reference value for the power inductor in dc-dc converters' simulation studies. It discusses the importance of the inductor design project by describing important constraints such as core size and saturation. The main contribution of this paper is related to the proposed dc flux cancelation technique in the bidirectional converter. A variable inductor prototype is used to replace the power inductor in order to decrease core size by improving the ripple content of the inductor current. The saturation level of the core is controlled by means of an auxiliary winding whether the converter operates in buck or boost mode. Experimental results validate the proposed methodology showing more than 50% reduction in magnetic material for similar current levels.

Effect of nitrogen contents on the high-frequency characteristics and magnetic properties of FeHfN films

High permeability magnetic films can enhance the inductance of thin-film inductors in DC-DC converters. In order to obtain high permeability, uniaxial anisotropy and coercivity should be as low as possible. This study employed dc reactive magnetron sputtering to fabricate the nanocrystalline FeHfN thin films. The influence of nitrogen flows on composition, microstructure, permeability characteristics, as well as magnetic properties was investigated. Increasing nitrogen contents can alter the FeHfN films from amorphous-like to crystalline phases, and the magnetic properties and permeability depend on the variations of microstructures. With this optimum condition of the nitrogen flows at 1.2 sccm, low anisotropy (HK = 20 Oe), low coercivity (HC = 1.1 Oe) and permeability (μ' > 600 at 50 MHz) were obtained for the nanocrystalline FeHfN film with a thickness around 700 nm. The as-fabricated FeHfN films with permeability over 600 at 50 MHz should be promising for high-permeability ferromagnetic material applications.