Coupled Inductor Rail Structure for Low-Leakage Power Conversion
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Solution Overview
Problem
Conventional coupled inductors face challenges in achieving high coupling coefficients, leading to limited figure of merit, increased leakage inductance, and reduced efficiency in multi-phase switching power converters, which affects transient response and ripple current management.
Innovation Solution
The design of coupled inductors with magnetic cores free of leakage structures, featuring a high ratio of magnetic rail cross-sectional area to connecting element cross-sectional area, enhances coupling coefficients, reduces leakage inductance, and increases magnetizing inductance, thereby improving transient performance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coupled inductors are used, then the basic energy storage function is achieved, but the coupling coefficient is limited and leakage inductance is high
Solution Approach 1:
The patent removes leakage structures (air gaps, magnetic shields, and other features that create leakage flux paths) from the magnetic core. By extracting these harmful elements, the magnetic flux is forced to couple more effectively between windings, increasing the coupling coefficient and reducing leakage inductance. The core becomes a continuous magnetic path that promotes flux linkage.
Solution Approach 2:
The patent changes the geometric parameters of the magnetic core, specifically the ratio of magnetic rail cross-sectional area to connecting element cross-sectional area. By optimizing this ratio and ensuring continuous magnetic paths without gaps, the magnetic permeability and coupling characteristics are improved, leading to higher coupling coefficients and lower leakage inductance.
2Speed
If coupled inductors with high coupling coefficients are designed, then transient response improves, but manufacturing complexity increases
Solution Approach 1:
The magnetic core is divided into modular components: magnetic rails and connecting elements. These segments can be manufactured separately using standard techniques and then assembled. This segmentation allows for simplified manufacturing of each component while achieving the complex overall geometry needed for high coupling coefficients and fast transient response.
Solution Approach 2:
By defining specific geometric parameters (cross-sectional area ratios, continuous magnetic paths), the patent simplifies the design space. Instead of complex arbitrary shapes, the core uses standardized geometric relationships that are easier to manufacture while maintaining the performance benefits of high coupling and fast transient response.
3Loss of energy
If leakage structures are included in the magnetic core, then flux distribution is controlled, but coupling coefficient decreases and efficiency is reduced
Solution Approach 1:
The patent explicitly removes leakage structures from the magnetic core design. By taking out air gaps, magnetic shields, and other features that create controlled leakage flux paths, the design achieves higher coupling coefficients and improved efficiency. The removal of these structures eliminates the trade-off between flux distribution control and coupling performance.
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 results in higher coupling coefficients, reduced ripple current, and increased saturation current ratings, enhancing the overall performance and manufacturability of coupled inductors while reducing manufacturing costs.
Implementation Method 1
A coupled inductor is an electromagnetic device including two or more windings that are magnetically coupled together. Leakage inductance results from magnetic flux generated by current flowing through a winding of the coupled inductor which does not couple to any other winding of the coupled inductor. Thus, leakage inductance is associated with energy storage in the coupled inductor.
Implementation Method 2
Magnetizing inductance results from magnetic flux generated by current flowing through one winding of the coupled inductor which couples to each other winding of the coupled inductor. Thus, magnetizing inductance is associated with magnetic coupling of the windings.
Data Source
AI summary
A coupled inductor includes first and second magnetic rails, a plurality of connecting magnetic elements, and a plurality of windings. The first and second magnetic rails are separated from each other in a first direction, and the first magnetic rail has a first cross-sectional area A1 as seen when viewed in the first direction. Each connecting magnetic element is disposed between the first and second magnetic rails in the first direction. The plurality of connecting magnetic elements collectively have a second cross-sectional area A2 as seen when viewed in the first direction, and a ratio of A2/(A1−A2) is at least 1.5. A respective winding is wound at least partially around each connecting magnetic element.