Common Mode Choke Layered Winding for High-Frequency Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing common mode chokes face challenges when wound in two or more layers, as the increased parasitic capacitance between layers affects the resonance frequency and impedance, leading to poor common mode noise reduction at higher frequencies.
Innovation Solution
The common mode choke is designed with windings arranged in at least two layers, where the turns of each winding are numbered consecutively, and the second layer is wound around a section of the first layer, ensuring that the difference between the highest and lowest turn numbers in the second layer does not exceed 50% of the first layer's turns, thereby minimizing parasitic capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the windings are wound in two or more layers, then the inductance increases and common mode noise reduction improves at lower frequencies, but parasitic capacitance between layers increases causing resonance frequency to decrease and impedance to drop at higher frequencies
Solution Approach 1:
The patent applies local quality by making different sections of the winding have different structures. Specifically, the winding is divided into a first section and a second section with different numbers of turns, allowing different local regions to contribute differently to the overall inductance while controlling parasitic capacitance. The first section has more turns than the second section, creating localized variations in electrical properties that optimize the balance between inductance and parasitic capacitance.
Solution Approach 2:
The patent segments the winding into multiple distinct sections (first section and second section) rather than using a uniform winding structure. This segmentation allows independent optimization of each section's characteristics - the first section provides higher inductance with more turns, while the second section helps control parasitic capacitance with fewer turns, resolving the contradiction between achieving high inductance and minimizing parasitic effects.
2Reliability
If the number of turns is increased to achieve high inductance, then common mode noise reduction improves, but the resonance frequency decreases due to increased parasitic capacitance
Solution Approach 1:
The patent uses local quality by creating sections with different turn densities. The first section has higher turn density for inductance, while the second section has lower turn density to limit parasitic capacitance growth. This localized variation in winding density allows the overall structure to achieve high inductance without proportionally increasing parasitic capacitance, thereby maintaining higher resonance frequency.
Solution Approach 2:
By segmenting the winding into sections with different numbers of turns, the patent prevents the uniform increase in parasitic capacitance that would result from simply increasing total turns. The segmented structure allows the first section to contribute most of the inductance while the second section provides a controlled contribution that limits overall capacitance, thus preserving resonance frequency.
3Reliability
If a larger magnetic core is used to accommodate more turns, then inductance increases, but the device size and cost increase
Solution Approach 1:
The patent applies local quality by optimizing the winding structure itself rather than relying on core size increases. By creating sections with different turn densities and configurations, the patent achieves higher effective inductance from the same physical space, eliminating the need for a larger magnetic core and thus reducing device size and cost.
Solution Approach 2:
The patent changes the winding parameters (number of turns in different sections, winding density, layer configuration) to optimize inductance without increasing core size. By adjusting these winding parameters rather than scaling up the core, the patent achieves the desired inductance improvement while maintaining compact device dimensions.
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 design minimizes the increase in parasitic capacitance between layers, maintaining a higher resonance frequency and improved impedance at higher frequencies, resulting in effective common mode noise reduction without the need for a larger magnetic core.
Implementation Method 1
common mode currents will flow in the same winding direction... creating equal and in-phase magnetic fields, which add together. This means that to common mode signals, the windings act as inductors, which present a high impedance to these signals
Implementation Method 2
by differential mode signals, including the desired signal such as the supply current delivered to the converter, the two currents will be equal and flow in opposite directions, and the magnetic flux produced in the core by these currents will subtract and tend to cancel each other out
Implementation Method 3
parasitic capacitance or stray capacitance between the individual turns of the windings due to their proximity to each other, and the inductor will act as though it includes a parallel capacitor. The parasitic capacitance changes the impedance of the choke by causing parallel resonance between the inductance and the capacitance at a resonance frequency
Data Source
AI summary
A common mode choke (64) comprises a magnetic core (58) and a first (Wab) and a second (Wcd) winding of insulated wire having the same number of turns wound on the magnetic core. The turns of each winding are numbered consecutively and arranged in at least two layers, of which a first layer of turns is wound directly on the magnetic core and a second layer of turns is wound around a section of the first layer. The two layers are arranged such that the difference between the highest number of a turn in the second layer and the lowest number of a turn in the section of the first layer on which the second layer is wound is less than or equal to 50% of the number of turns in the first layer. In this way, the effect of the parasitic capacitance between the layers is minimized.