Inductor with Thermally Stable Resistive Element for Accurate Current Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inductors in DC/DC converters face challenges with thermal instability of winding resistance, leading to inaccurate current sensing and increased power loss, which complicates the design of smaller, more complex systems with higher power demands and elevated operating temperatures.
Innovation Solution
Combining an inductor with a thermally stable resistive element into a single unit, using materials like nickel-chrome or manganese-copper alloys with low Temperature Coefficient of Resistance (TCR), to reduce part count and power loss, and enable accurate current sensing without external compensating circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the DCR of an inductor is used for current sensing, then part count is reduced, but measurement precision deteriorates due to 3900 ppm/°C TCR of copper winding
Solution Approach 1:
The patent combines the inductor winding and current sense resistor into a single integrated component. The resistive element is positioned through the inductor body, creating a unified structure that functions as both an energy storage inductor and a current sensing resistor, thereby eliminating the need for separate components while achieving thermal stability through low-TCR materials
Solution Approach 2:
The patent changes the material parameter of the resistive element from conventional copper (3900 ppm/°C TCR) to low-TCR materials such as nickel-chrome or manganese-copper alloys (≤100 ppm/°C TCR). This parameter change in material composition maintains the resistance value stability across temperature variations, enabling accurate current sensing without requiring compensation circuitry
2Measurement precision
If external compensating circuitry is added to maintain stable current sense point, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The inductor integrates a self-service current sensing capability through its low-TCR resistive element. The component automatically maintains stable resistance characteristics across temperature changes without requiring external compensation circuitry, thereby achieving both measurement precision and simplicity simultaneously
3Ease of manufacture
If copper winding is used for inductor, then ease of manufacture is improved, but thermal stability deteriorates due to high TCR
Solution Approach 1:
The patent employs composite material construction where the inductor body is formed of distributed gap magnetic material (such as MPP, HI FLUX, SENDUST, or powdered iron) and the resistive element is made of low-TCR alloy materials. This composite approach combines the magnetic properties needed for inductance with the thermal stability required for accurate current sensing
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 provides a low-profile, high-current inductor with improved thermal stability, reducing power loss and part count, while enabling accurate current sensing and energy storage, thus addressing the competing needs of reduced size and increased power in DC/DC converters.
Implementation Method 1
A thermally stable resistive element is positioned through the void and turned toward the top surface to form opposite surface mount terminals
Implementation Method 2
the current sensing abilities of its resistance still vary significantly due to the 3900 ppm/° C. Thermal Coefficient of Resistance (TCR) of the copper in the inductor winding
Implementation Method 3
Inductors have long been used as energy storage devices in non-isolated DC/DC converters
Data Source
AI summary
An inductor includes an inductor body having a top surface and a first and second opposite end surfaces. There is a void through the inductor body between the first and second opposite end surfaces. A thermally stable resistive element positioned through the void and turned toward the top surface to forms surface mount terminals which can be used for Kelvin type sensing. Where the inductor body is formed of a ferrite, the inductor body includes a slot. The resistive element may be formed of a punched resistive strip and provide for a partial turn or multiple turns. The inductor may be formed of a distributed gap magnetic material formed around the resistive element. A method for manufacturing the inductor includes positioning an inductor body around a thermally stable resistive element such that terminals of the thermally stable resistive element extend from the inductor body.