Enhanced Permeability of Fe-Based Amorphous Powder Cores Realized through Selective Incorporation of Carbonyl Iron Powders at Inter-Particle Voids

In this study, we demonstrate a hybrid multimodal soft magnetic composite (SMC) comprising gas-atomized spherical amorphous powder (AP) and carbonyl-iron powder (CIP), and present its enhanced electromagnetic properties. CIP is selectively incorporated into voids between AP, and deforms during compression, effectively reducing the pores, resulting in high packing density of the core, where CIP magnetically bridges AP and helps magnetic domain rotation much efficiently. The hybrid SMC with the addition of 20 wt.% CIP showed constant effective permeability of 57 up to 1 MHz, a remarkable 63% increase compared with the AP core, while DC bias superimposing retention level of 61% was secured with the help of high magnetization of CIP. In addition, the effect of SiO2 surface insulation, prepared by the sol-gel process, on the high-frequency magnetic properties of hybrid SMCs, was also evaluated. It is thus revealed that the high-frequency dynamic loss of the hybrid core, originating from intra-particle eddy current loss and anomalous loss component, and inter-particle eddy currents are negligibly small. We believe that our approach using AP/CIP multimodal hybrid SMCs is an effective way of achieving high permeability as well as high DC bias characteristics at high frequencies. This process will be highly beneficial for the miniaturization of power inductors.

Non-Linear Inductors Characterization in Real Operating Conditions for Power Density Optimization in SMPS

The exploitation of power inductors outside their linear region in switching converters can be achieved by raising the current until a decrease in the inductance can be noticed. This 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 was 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 temperatures up to 105 °C. The magnetic core was then characterized by the saturation current vs. inductance, obtaining an expression for the whole family of inductors sharing the same core. Finally, we experimentally analyzed the thermal transient of the inductors in operating conditions, confirming the fundamental role of the temperature in changing the current profiles and the core saturation condition.

Identification of DC Thermal Steady-State Differential Inductance of Ferrite Power Inductors

In this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the magnetization curve up to the saturation. The obtained inductance profile can be adopted to simulate the current waveform of a saturable inductor in a DC–DC converter, providing accurate results under a wide range of switching frequency, input voltage, duty cycle, and output current values.

Non-Linear Inductors Characterization in Real Operating Conditions for Power Density Optimization in SMPS

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.

Temperature Impact on Non-Linear Inductors in Operating Conditions for SMPS

The exploitation of power inductors outside their linear region in switching converters requires a detailed description of the magnetization curve that is often not included in the datasheets; besides, the temperature of the inductor must be taken into account. This paper shows how to characterize 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 includes 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 temperatures 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 confirming the fundamental role of temperature in changing the current profiles and the core saturation condition.

Temperature Impact on Non-Linear Inductors in Operating Conditions for SMPS

The exploitation of power inductors outside their linear region in switching converters requires a detailed description of the magnetization curve that is often not included in the datasheets; besides, the temperature of the inductor must be taken into account. This paper shows how to characterize 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 includes 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 temperatures 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 confirming the fundamental role of temperature in changing the current profiles and the core saturation condition.

Metallic Glasses and Their Composites

Metallic glasses and their crystal/glass composites find ever more applications in such fields as mini transformers, microelectromechanical devices, pressure sensors, precision surgical instruments, biological implants and sportive goods (springs, diaphragms, membranes, knife blades, electromagnetic wave shields, optical mirrors, power inductors, Coriolis flow meters, etc.). The book reviews recent research and suggests future developments, e.g. in the area of dual-phase composite/hybrid materials.