Measuring Resistor Group for Accurate Load Current Determination
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Solution Overview
Problem
Existing methods for determining load current in battery systems, such as those used in car batteries, are costly due to the need for high-precision resistors like copper-nickel-manganese alloys, and recalibrating cheaper alternatives is difficult, especially during varying high currents.
Innovation Solution
A method using a measuring resistor group with multiple branches, each with a first and second shunt resistor, where calibration currents are applied to calculate load current by measuring voltages across these resistors, allowing for precise determination of load current through mathematical calculations during calibration periods and extrapolation outside these periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision resistors (e.g., copper-nickel-manganese alloys) are used to measure load current, then measurement precision is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent divides the measuring resistor into multiple branches (first branch with first measuring resistor, second branch with second measuring resistor). By segmenting the single high-precision resistor into multiple lower-precision resistors arranged in parallel branches, the system achieves equivalent measurement precision while using cheaper components, directly resolving the contradiction between measurement precision and manufacturing cost.
2Ease of manufacture
If cheaper shunt resistors are used instead of high-precision resistors, then manufacturing cost is reduced, but recalibration difficulty increases during varying high currents
Solution Approach 1:
The patent implements a calibration current injection mechanism that provides feedback for recalibration. During calibration periods, a known calibration current is injected into the measuring resistor group, and the system measures the resulting voltages to calculate and store calibration factors. This feedback loop enables automatic recalibration of cheaper resistors under varying current conditions, resolving the contradiction between manufacturing cost and recalibration difficulty.
Solution Approach 2:
The patent performs calibration measurements during dedicated calibration periods before normal operation. By preliminarily determining calibration factors during these periods when calibration current is injected, the system prepares the measurement system in advance, enabling accurate load current measurement during subsequent operation without requiring complex real-time recalibration, thus reducing recalibration difficulty.
3Measurement precision
If calibration current is applied for recalibration, then measurement accuracy is maintained, but power consumption increases and calibration can only occur during short periods
Solution Approach 1:
The patent implements periodic calibration by injecting calibration current only during dedicated calibration periods rather than continuously. The system alternates between calibration periods (when calibration current flows and accuracy is maintained) and measurement periods (when normal load current is measured). This periodic approach maintains measurement precision while significantly reducing average power consumption compared to continuous calibration, resolving the contradiction between measurement accuracy and power consumption.
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 approach enables accurate and cost-effective determination of load current, reducing the need for expensive high-precision resistors and simplifying recalibration, while maintaining high accuracy in current measurement.
Implementation Method 1
measuring a first measurement voltage, which drops across the first measurement resistor, and a second measurement voltage, which drops across the second measurement resistor
Data Source
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AI summary
The invention relates to a method for determining a load current, which is based on the passage of a calibration current in a specific manner and on specific calculation methods.