Linear Gain Trim for Accurate Current Sensing on PCBs
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Summary
Problems
Existing current sensors face challenges in accurately sensing large currents on printed circuit boards (PCBs) due to high temperature coefficients of materials like copper, and the need for high-resolution digital-to-analog converters (DACs) for gain trimming, which increases cost and complexity.
Innovation solutions
The solution involves moving the gain trim term from the denominator to the numerator of the current sensor control loop, creating a linear gain trim relationship. This allows for the use of lower resolution DACs and simplifies the resistor network, reducing the dynamic range requirements and maintaining stability and accuracy.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If a discrete sense resistor with low temperature coefficient is used, then measurement precision is improved, but device complexity and cost increase due to exotic materials and Kelvin-sense requirements
Why choose this principle:
The patent replaces expensive exotic material sense resistors with a simple copper PCB trace that has known, predictable properties. The copper trace is a standard, inexpensive material already present on the PCB, eliminating the need for special sense resistors while maintaining adequate measurement precision through compensation techniques.
Principle concept:
If a discrete sense resistor with low temperature coefficient is used, then measurement precision is improved, but device complexity and cost increase due to exotic materials and Kelvin-sense requirements
Why choose this principle:
The patent creates an electrical model that copies and simulates the behavior of the ideal low-TCR sense resistor using standard copper traces and compensation circuits. By modeling the temperature effects and compensating for them, the system achieves accurate current sensing without requiring physical exotic materials.
Application Domain
Data Source
AI summary:
The solution involves moving the gain trim term from the denominator to the numerator of the current sensor control loop, creating a linear gain trim relationship. This allows for the use of lower resolution DACs and simplifies the resistor network, reducing the dynamic range requirements and maintaining stability and accuracy.
Abstract
Described are techniques to provide a gain trim term in the numerator for a current sensor control loop. In this manner, a linear gain trim relationship is created with respect to the trim code. This linear relationship reduces the dynamic range needed for the DAC, which allows the use of lower resolution DACs to smoothly adjust the gain while maintaining stability and accuracy.