Common mode filter
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Solution Overview
Problem
Drum-core type common mode filters face challenges in achieving high noise-reduction performance and stable characteristics for in-vehicle Ethernet applications due to limitations in mode conversion characteristics and inductance, particularly with existing winding methods that increase capacitance between different turns.
Innovation Solution
A common mode filter design incorporating a drum core with sparsely-wound and closely-wound portions, where the first and second wires are wound in a specific pattern to reduce capacitance between different turns, allowing for higher inductance and improved noise-reduction performance by optimizing the winding configuration and arrangement of sparsely-wound and closely-wound portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a drum core is used with conventional winding methods, then mass production is enabled through automatic coil winding, but noise-reduction performance is insufficient due to high capacitance between different turns
Solution Approach 1:
The winding structure is segmented into multiple layers with intentional spacing. The patent divides the continuous winding into discrete sections where air gaps are introduced between layers, reducing the capacitance between different turns while maintaining the drum core structure suitable for automatic winding.
Solution Approach 2:
Air gaps are introduced as intermediary spaces between different wire layers. These air gaps act as insulating mediators that reduce the electrical capacitance between adjacent turns while maintaining mechanical stability of the winding structure.
2Quantity of substance
If wires are wound closely together to increase inductance, then higher inductance is achieved, but mode conversion characteristics worsen due to increased capacitance between different turns
Solution Approach 1:
The winding is segmented into layers with controlled air gaps between them. This segmentation allows the inductance to be maintained through sufficient number of turns while the air gaps reduce the parasitic capacitance between turns, improving mode conversion characteristics.
Solution Approach 2:
Different regions of the winding have different properties: within each layer wires are closely wound to maximize inductance, while between layers air gaps are introduced to reduce capacitance. This local differentiation of winding density optimizes both inductance and mode conversion characteristics.
3Object-affected harmful factors
If a toroidal core is used to suppress leakage flux and improve noise-removal performance, then high noise-reduction performance is obtained, but automatic coil winding becomes difficult requiring manual winding
Solution Approach 1:
Instead of using a toroidal core that requires manual winding, the patent inverts the approach by using a drum core with optimized winding structure. The drum core geometry is specifically chosen because it accommodates automatic winding mechanisms while the winding pattern compensates for the higher leakage flux through careful spacing and layering.
Solution Approach 2:
The patent changes the geometric parameters of the core from toroidal to drum shape, and adjusts winding parameters such as layer spacing and air gaps. These parameter changes enable automatic winding while maintaining noise-reduction performance through optimized inductance and reduced capacitance between turns.
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 proposed design effectively reduces mode conversion characteristics and increases inductance, enhancing noise-reduction performance while minimizing variations in characteristics, making it suitable for high-performance in-vehicle Ethernet applications.
Implementation Method 1
first and second wires that are wound around the winding core portion so as to form a pair-wire for each turn
Data Source
AI summary
Disclosed herein is a common mode filter that comprises a drum core including a winding core portion and a pair of flange portions provided at both ends of the winding core portion, and first and second wires wound around the winding core portion so as to form a pair-wire for each turn. The first and second wires includes one or a plurality of sparsely-wound portions in which the first and second wires are wound with adjacent pair-wires spaced from each other, and one or a plurality of closely-wound portions in which the first and second wires are wound with adjacent pair-wires in close contact with each other.