Multilayer Film Inductor Core for High-Frequency Low-Loss Operation
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Solution Overview
Problem
The miniaturization of power supply circuits in mobile devices is hindered by the difficulty in miniaturizing inductors, particularly due to challenges in increasing the driving frequency with conventional silicon-based switching elements and achieving high saturation magnetic flux density and low magnetic loss in magnetic cores for high-frequency applications.
Innovation Solution
A multilayer film magnetic core structure is developed, comprising alternately stacked nanogranular magnetic films and soft magnetic alloy films, where the nanogranular films have a structure with dispersed nano-domains of a first phase in a second phase, and the soft magnetic alloy films contain Fe, Co, and Ni, with a volume ratio of the first phase to the total volume of 65% or less, to achieve high saturation magnetic flux density and specific resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a nanogranular film with high specific resistance is used as a magnetic core, then magnetic loss during high-frequency driving is reduced, but saturation magnetic flux density decreases
Solution Approach 1:
The patent applies composite materials by combining nanogranular magnetic film and soft magnetic alloy film in a multilayer structure. The nanogranular film provides high specific resistance to reduce magnetic loss, while the soft magnetic alloy film contributes high saturation magnetic flux density. This composite approach allows both properties to coexist in different layers, resolving the contradiction between reducing magnetic loss and maintaining saturation magnetic flux density.
2Quantity of substance
If the thickness of nanogranular film is increased to improve saturation magnetic flux density, then the required characteristics are achieved, but process load increases
Solution Approach 1:
The patent segments the magnetic core into multiple thin layers alternating between nanogranular magnetic film and soft magnetic alloy film. This segmentation allows each layer to be thin and easy to manufacture using standard thin film processes, while the cumulative effect of multiple layers achieves the required saturation magnetic flux density. This avoids the need to manufacture a single thick nanogranular film, thereby reducing process load.
3Ease of manufacture
If conventional silicon-based switching elements are used in power supply circuit, then manufacturing cost is controlled, but driving frequency cannot be increased
Solution Approach 1:
The patent changes the material parameter of the switching element from conventional silicon-based semiconductor to GaN-based semiconductor. This parameter change enables the power supply circuit to operate at higher driving frequencies (e.g., 100 kHz to several MHz), which in turn enables miniaturization of the inductor. The higher frequency operation allows the inductor to achieve the same performance with smaller size, addressing the miniaturization requirement.
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
This configuration enhances the saturation magnetic flux density while maintaining high specific resistance, reducing magnetic loss, and allowing for efficient high-frequency operation, thus facilitating the miniaturization of inductors for power supply circuits in mobile devices.
Implementation Method 1
a magnetic loss tan δ during high-frequency driving increases
Implementation Method 2
the magnetic film is required to have a high specific resistance
Implementation Method 3
the inductor for a power supply is required to have a DC superimposition characteristic. Therefore, the material of the magnetic core included in the inductor for a power supply, that is, the magnetic film included in the inductor for a power supply is required to have a high saturation magnetic flux density Bs
Implementation Method 4
a coil portion (4)
Data Source
AI summary
An inductor includes a magnetic core portion and a coil portion. The magnetic core portion is a multilayer film in which a nanogranular magnetic film and a soft magnetic alloy film are alternately stacked. The nanogranular magnetic film has a structure in which nano-domains of a first phase are dispersed in a second phase. The first phase contains one or more selected from Fe and Co, and the second phase contains one or more selected from O, N, and F. The volume ratio of the first phase to the total volume of the first phase and the second phase is 60% or less. The soft magnetic alloy film contains one or more selected from Fe and Co. The total amount of Fe, Co, and Ni in the soft magnetic alloy film is 70 at % or more.