Coupled Inductor Leakage Inductance via Magnetic Core Segmentation
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Solution Overview
Problem
Coupled inductors in multi-level power converters face challenges in meeting performance requirements such as system stability, ripple current, and total harmonic distortion due to relatively low leakage inductance, which is insufficient to replace the filter inductor effectively.
Innovation Solution
The design includes a magnetic core with three first magnetic cylinders and two second magnetic cylinders, arranged between opposite magnet yokes, where the magnetic permeability of the first cylinders is greater than that of the second cylinders, and the second cylinders have an interior air gap, increasing leakage inductance to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coupled inductor uses multiple windings or coils in a conventional configuration, then the output ripple current is reduced and output frequency is improved, but the leakage inductance remains relatively low and cannot effectively replace the filter inductor
Solution Approach 1:
The patent applies local quality by creating different magnetic path characteristics in different regions of the magnetic core. Specifically, it designs separate magnetic paths with different reluctance characteristics - one path providing low reluctance for main flux while another path provides high reluctance for leakage flux. This is achieved through the asymmetric arrangement of magnetic cores and air gaps, where certain regions have intentionally increased magnetic resistance to enhance leakage inductance locally without affecting the overall coupling efficiency
Solution Approach 2:
The patent introduces a new dimension to the magnetic circuit design by adding a third magnetic core component and creating a three-dimensional magnetic path structure. Instead of conventional planar arrangements, it stacks magnetic cores vertically and creates multiple magnetic paths in different spatial dimensions. This dimensional expansion allows independent control of main flux and leakage flux paths, enabling enhanced leakage inductance while maintaining effective coupling
2Ease of manufacture
If the coupled inductor is designed with conventional magnetic core structures, then the manufacturing process is simple, but additional filter inductors are required increasing system costs and losses
Solution Approach 1:
The patent applies universality by designing a coupled inductor that simultaneously performs multiple functions: power transfer, ripple current reduction, and filtering. By enhancing the leakage inductance through its special magnetic core structure, the coupled inductor replaces the need for separate filter inductors. The device maintains its primary function of electromagnetic coupling while its leakage inductance is optimized to provide filtering capability, eliminating additional components and reducing system losses
3Reliability
If conventional coupled inductor designs are used, then the structure is compact, but the leakage inductance is insufficient to meet performance requirements for system stability and harmonic distortion
Solution Approach 1:
The patent applies segmentation by dividing the magnetic circuit into distinct segments with different functions. It separates the magnetic core into multiple components (first magnetic core, second magnetic core, third magnetic core) with different roles: some segments provide main magnetic flux paths while others are specifically designed to create leakage flux paths. Air gaps are strategically placed in specific segments to control magnetic reluctance. This segmentation allows independent optimization of coupling efficiency and leakage inductance without requiring complete structural redesign
Solution Approach 2:
The patent introduces air gaps as intermediary elements between magnetic core segments to control magnetic flux distribution. These air gaps act as mediators that increase magnetic reluctance in specific paths, thereby enhancing leakage inductance. The air gaps are positioned strategically to create high-reluctance paths for leakage flux while maintaining low-reluctance paths for main flux. This intermediary approach allows precise control of magnetic circuit characteristics without fundamentally changing the overall compact structure
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 increases leakage inductance, improving system stability and meeting performance requirements while reducing system costs and losses, and simplifying the manufacturing process by eliminating the need for additional windings.
Implementation Method 1
the magnetic permeability of the first cylinders is greater than that of the second cylinders
Implementation Method 2
increasing leakage inductance to enhance performance
Implementation Method 3
the second cylinders have an interior air gap
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A coupled inductor and a power converter are disclosed. The coupled inductor includes a magnetic core and at least two windings. The magnetic core includes at least two first magnetic cylinders (111, 112), at least one second magnetic cylinder (121), and two opposite magnet yokes (131, 132), the at least two first magnetic cylinders and the at least one second magnetic cylinder are disposed between the two opposite magnet yokes, the at least two windings (151, 152) are respectively located on the at least two first magnetic cylinders, and the at least two windings are in a one-to-one correspondence with the at least two first magnetic cylinders. Leakage inductance of the coupled inductor is increased by adding a second magnetic cylinder between the opposite magnet yokes of the coupled inductor, thereby meeting a requirement on system stability when the coupled inductor is connected to the power converter.