Non-Linear Inductors Characterization in Real Operating Conditions for
Power Density Optimization in SMPS
Abstract
The exploitation of power inductors outside their linear region in
switching converters can be achieved by raising the current until a
decreasing of the inductance can be noticed. It allows using a smaller
magnetic core increasing the power density of the converter. On the
other hand, a detailed description of the magnetization curve including
the temperature is required. Since this information is often not
included in the inductor’s datasheets, this paper shows how to identify
the behavior of an inductor when it is operated up to saturation and its
temperature rises. In order to characterize the inductor in real
operating conditions, a dedicated measurement rig has been developed. It
consists of a switching converter that encompasses the inductor under
test and is controlled by a virtual instrument developed in LabVIEW. The
characterization system was tested by retrieving the inductance and the
magnetization curves vs. current for two commercial inductors at core
tem-peratures up to 105°C. The magnetic core is then characterized by
the saturation current versus inductance, obtaining an expression for
the whole family of inductor sharing the same core. Finally, we analyzed
experimentally the thermal transient of the inductors in operating
conditions con-firming the fundamental role of temperature in changing
the current profiles and the core saturation condition.