Dust Core Inductor with Composite Particle Distribution
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Solution Overview
Problem
Existing inductor elements for high frequency bands suffer from low permeability, insufficient DC superimposition characteristics, and high core loss, hindering miniaturization and efficiency in power supply applications.
Innovation Solution
A dust core composed of large and small particles of soft magnetic material powder with a saturation magnetic flux density of 1.4 T or more, where the ratio of the area occupied by large particles to small particles in the cross section is between 9:1 to 5:5, and the small particles have an electrical resistance of 40 μΩ·cm or more, made from alloys containing Fe, Si, Ni, Co, and Cr, which reduces eddy current loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dust cores are used for high frequency applications, then the inductor can operate at several MHz, but the permeability is low and DC superimposition characteristics are insufficient
Solution Approach 1:
The dust core uses a composite material structure combining large particles (3-15 μm) and small particles (300 nm-900 nm) of soft magnetic material powder with specific saturation magnetic flux density (1.4 T or more). This composite particle size distribution optimizes both permeability and DC superimposition characteristics by creating efficient magnetic flux paths while maintaining high frequency performance
Solution Approach 2:
The invention applies different particle sizes in specific proportions (area ratio 9:1 to 5:5) to different regions of the magnetic field distribution. The large particles provide structural stability and high saturation flux density, while the small particles fill interstitial spaces to enhance permeability and reduce air gaps, achieving optimized local magnetic properties throughout the core
2Reliability
If conventional dust cores are used for high frequency applications, then the inductor can operate at several MHz, but the core loss is large
Solution Approach 1:
The dust core is segmented into particles of two distinct size ranges (large: 3-15 μm, small: 300 nm-900 nm) with insulated surfaces. This segmentation disrupts continuous eddy current paths that would form in larger solid cores, forcing currents to follow shorter, higher-resistance paths through the particle network, thereby reducing eddy current loss at high frequencies
Solution Approach 2:
The invention changes the electrical resistance parameter of the small particles to 40 μΩ·cm or more through material composition control (Fe-Si alloys with Ni, Co, and Cr). This parameter change directly reduces eddy current loss by increasing the electrical resistance of the particle material itself, complementing the segmentation effect and improving overall efficiency
3Volume of moving object
If the particle size is reduced for miniaturization, then the inductor size can be reduced, but the permeability becomes low
Solution Approach 1:
The dust core employs a composite particle system where small particles (300 nm-900 nm) provide high surface area and fill voids between larger particles, maximizing material density and permeability in a compact volume. The specific area ratio (9:1 to 5:5) ensures optimal packing and magnetic coupling, achieving high permeability despite the use of fine particles that enable miniaturization
Solution Approach 2:
The small particles nest within the interstitial spaces between large particles, creating a hierarchical structure that maximizes space utilization. This nesting arrangement ensures continuous magnetic flux paths through both particle sizes, maintaining high permeability while reducing the overall inductor volume through efficient space filling
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides excellent DC superimposition characteristics and low eddy current loss at high frequency bands, enabling miniaturization and efficiency improvements in inductor elements.
Implementation Method 1
large particles and small particles of insulated soft magnetic material powder, wherein the large particles and the small particles have a saturation magnetic flux density of 1.4 T or more
Implementation Method 2
the small particles have an electrical resistance of 40 μΩ·cm or more
Implementation Method 3
low in eddy current loss (core loss) for increasing the efficiency of the power supply
Data Source
AI summary
A dust core excellent in DC superimposition characteristics and low in eddy current loss at a high frequency band of several MHz, and an inductor element using the dust core. A dust core contains large and small particles of insulated soft magnetic material powder, wherein the large and small particles have a saturation magnetic flux density of 1.4 T or more, and wherein in the soft magnetic material powder observed in a cross section of the dust core, a ratio of an area occupied by large particles to an area occupied by small particles in the cross section is 9:1 to 5:5, when a group of particles having particle size of 3 μm or more and 15 μm or less is defined as the large particles, and group of particles having a particle size of 300 nm or more and 900 nm or less is defined as the small particles.