Transformer Winding Layout for Higher Common-Mode Rejection
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Solution Overview
Problem
Conventional common-mode filters have inferior mode conversion characteristics, leading to a lower yield due to their inadequate common-mode rejection ratio when converting common-mode signals to differential-mode signals.
Innovation Solution
A transformer design with an iron core and multiple coils wound in specific patterns around the core, including alternating layers of first and second coils with strategically placed gaps, enhances the common-mode rejection ratio, thereby improving mode conversion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional common-mode filter coils are wound around an iron core, then the common-mode impedance is increased and common-mode noise is filtered, but the mode conversion characteristic (Ssd/Sds) is inferior
Solution Approach 1:
The patent divides the winding structure into multiple discrete sections with alternating first and second coils arranged in a specific sequence. Each coil section is positioned at a distinct location around the iron core, creating segmented magnetic paths that prevent unwanted mode conversion while maintaining common-mode rejection. The segmentation of the winding structure into alternating coil pairs is the key to resolving the contradiction between noise filtering and mode conversion characteristics.
Solution Approach 2:
The patent employs asymmetric winding patterns where the first and second coils are arranged with specific asymmetry in their positioning and connection patterns. The alternating arrangement of different coil types creates an asymmetric magnetic field distribution that suppresses common-mode to differential-mode conversion while maintaining effective common-mode noise filtering. This asymmetric configuration is crucial for achieving both high common-mode impedance and good mode conversion characteristics.
2Ease of manufacture
If simple coil winding is used, then manufacturing is easy, but common-mode rejection ratio is insufficient
Solution Approach 1:
The complex winding pattern is segmented into repeating units of alternating first and second coils, which can be manufactured using standardized processes. Each segment follows a consistent pattern that can be replicated along the iron core, making the manufacturing process systematic and controllable despite the overall complexity of the winding structure.
Solution Approach 2:
Different regions of the winding structure have specialized functions: the alternating first and second coils in specific positions provide enhanced common-mode rejection, while maintaining overall structural consistency. The local quality of each coil section is optimized for its specific position in the sequence, allowing the entire structure to achieve high common-mode rejection ratio without requiring completely custom manufacturing for each section.
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 enhanced common-mode rejection ratio improves production yield by reducing the mode conversion characteristic, specifically Ssd/Sds, through optimized winding patterns of the coils around the iron core.
Implementation Method 1
When noise current such as common-mode current flows through the common-mode filter, magnetic fields of a same direction are produced on the first and second coil, thereby increasing the inductive reactance of the first and second coil
Data Source
AI summary
The transformer includes iron core and coils. The iron core includes a first flange, a second flange, and a central column having a first face and a second face. The coils include a first coil and a second coil wound around the central column from the first flange towards the second flange. Within a first layer of coils along the first face, there are sequentially arranged at least a first coil, a first coil, a second coil, a first coil, a second coil, a gap, a second coil, a first coil, and multiple rounds of first coil. Within the first layer along the second face, there are sequentially arranged multiple rounds of the first coil, a first coil, a second coil, a gap, a second coil, a first coil, and multiple rounds of the first coil. Within a second layer there are multiple rounds of the second coil.