Power Inductor Winding Segmentation for Current Sensing
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Solution Overview
Problem
The high temperature coefficient of resistance (TCR) of pure copper in power inductor windings makes it difficult to accurately detect current over a range of operating temperatures, and using low-TCR alloys like nickel-copper or manganese-copper increases resistivity, leading to larger winding cross-sections and increased power loss in limited size inductors.
Innovation Solution
A power inductor with a winding comprising both pure copper and low-TCR alloy portions, where the alloy portion forms a current sensor, minimizing total resistance and allowing for accurate current detection while maintaining low resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure copper is used as winding material, then electrical conductivity is high, but temperature coefficient of resistance is high causing inaccurate current detection
Solution Approach 1:
The winding is divided into two distinct portions: a first portion made of pure copper for low resistance, and a second portion made of low-TCR alloy for accurate current sensing. This segmentation allows each portion to fulfill its specific function optimally.
Solution Approach 2:
Different materials are used in different portions of the winding based on local functional requirements. The pure copper portion provides low resistance where current flows, while the low-TCR alloy portion provides stable resistance for current detection in the sensing path.
2Measurement precision
If low-TCR alloy is used as winding material, then current detection accuracy is improved, but resistivity is much higher requiring larger winding cross-section
Solution Approach 1:
The winding is segmented into pure copper and low-TCR alloy portions, allowing the low-TCR material to be used only where needed for sensing, rather than throughout the entire winding structure.
Solution Approach 2:
The low-TCR alloy is applied locally only in the current sensing path, while the main current-carrying winding uses pure copper, optimizing both measurement precision and electrical conductivity.
3Measurement precision
If low-TCR alloy is used as winding material, then current detection accuracy is improved, but power loss increases due to higher resistivity
Solution Approach 1:
The winding structure is segmented to separate the current-carrying function (pure copper, low loss) from the current-sensing function (low-TCR alloy, high precision).
Solution Approach 2:
The high-resistivity low-TCR alloy is used only in the sensing portion where accurate measurement is needed, while the main power-carrying winding uses low-resistivity pure copper to minimize power losses.
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 solution enables accurate current detection with minimized winding resistance, optimizing electrical performance in limited size inductors by balancing resistivity and accuracy.
Implementation Method 1
because the temperature coefficient of resistance (TCR) of pure copper is high, the equivalent DC resistance (DCR) of a winding made of pure copper varies much as the temperature varies
Implementation Method 2
Because the winding needs good conductive properties, usually pure copper is chosen as the material of winding
Data Source
AI summary
A power inductor includes a core and winding. The winding has at least two portions, one made of pure copper and the other made of a low-TCR (temperature coefficient of resistance) alloy, wherein the alloy portion is used to form a current sensor. The two portions are joined to provide a unitary winding. The inductor can provide accurate current detection sensor while minimizing total resistance of the winding.