Abstract
This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)4). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.
Highlights
IntroductionThe wide band-gap SiC/GaN power devices have been applying for high-efficient power electronics systems such as dc-dc converter and dc-ac inverter due to their low on-resistance, fast switching speed and possible operation at ambient temperature over 200 degree-C.1,2
The wide band-gap SiC/GaN power devices have been applying for high-efficient power electronics systems such as dc-dc converter and dc-ac inverter due to their low on-resistance, fast switching speed and possible operation at ambient temperature over 200 degree-C.1,2 The power conversion frequency can be increased beyond 1 MHz to miniaturize the power electronics systems by using SiC/GaN power device, where the power inductor and transformer, used in the SiC/GaN based power electronics operating at 200 degree-C over ambient temperature, must have small power-loss in the MHz band and thermally stable electrical property when exposing it to such high ambient temperature.The authors are currently developing a heat-resistant iron-based metal composite bulk magnetic core for SiC/GaN power device MHz switching dc-dc converter
This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body
Summary
The wide band-gap SiC/GaN power devices have been applying for high-efficient power electronics systems such as dc-dc converter and dc-ac inverter due to their low on-resistance, fast switching speed and possible operation at ambient temperature over 200 degree-C.1,2. The authors are currently developing a heat-resistant iron-based metal composite bulk magnetic core for SiC/GaN power device MHz switching dc-dc converter. The iron-based metal composite magnetic core consists of 1.1 μm diameter carbonyl-iron powder (CIP) and heat-resistant resin. Such the fine CIP is used to suppress the MHz band eddy current inside the CIP body.
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