Resistive Structure Calibration via Node Current Injection
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Solution Overview
Problem
Existing methods for calibrating resistive structures during system operation are limited by their inability to compensate for manufacturing tolerances and long-term drift, require costly temperature coefficient determination, and often compromise accuracy due to load current interference and temperature measurement challenges, especially in switch-mode power supplies.
Innovation Solution
A method and circuit that calibrate resistive structures by injecting a calibration current at a strategic node, using a control circuit to alternate the current between nodes, and employing signal processing to determine resistance without measuring temperature, allowing for uninterrupted system operation and compensation for manufacturing tolerances and drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature measurement and compensation methods are used, then temperature drift can be compensated, but manufacturing tolerances cannot be compensated and individual temperature coefficient determination is costly
Solution Approach 1:
The patent extracts the temperature sensor from the system and eliminates the need for temperature measurement and compensation. Instead of measuring temperature and compensating for drift, the system directly measures resistance at the operating point, making the measurement independent of temperature variations and manufacturing tolerances.
Solution Approach 2:
The system uses the resistive structure itself as the measurement object without requiring external temperature sensors or complex calibration procedures. The resistance measurement is performed directly on the structure during normal operation, allowing the system to self-calibrate using its own operating characteristics.
2Measurement precision
If test current injection methods are used, then resistance can be measured, but load current interference compromises accuracy
Solution Approach 1:
The patent employs periodic switching between measurement mode and normal operation mode. During brief measurement intervals, the resistive structure is isolated from load current and a known test current is injected to measure resistance. This periodic action allows accurate measurement while maintaining continuous system operation.
Solution Approach 2:
The patent introduces switching elements as intermediaries that isolate the measurement circuit from the load current path. These switches act as mediators that redirect current flow during measurement intervals, preventing load current interference while allowing the measurement system to access the resistive structure.
3Reliability
If recalibration is performed periodically, then long-term drift can be compensated, but system operation must be interrupted and cost increases
Solution Approach 1:
The patent enables continuous resistance measurement and drift compensation during normal system operation. By using brief periodic measurement intervals with switching isolation, the system maintains uninterrupted operation while continuously monitoring and compensating for long-term drift, eliminating the need for operational interruptions.
4Measurement precision
If precise temperature measurement is implemented, then temperature compensation improves, but cost increases
Solution Approach 1:
The patent removes the temperature measurement component from the system entirely. By making the resistance measurement independent of temperature, the design eliminates the need for temperature sensors, signal conditioning circuits, and complex compensation algorithms, significantly reducing manufacturing cost and complexity.
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 resistance measurement and compensation for manufacturing tolerances and long-term drift without interrupting system operation, reducing costs by eliminating the need for precise temperature measurement and improving accuracy by minimizing load current interference.
Implementation Method 1
employing signal processing to determine resistance without measuring temperature
Implementation Method 2
A calibration current source is coupled to a third node of the resistive structure to provide a calibration current to the resistive structure
Data Source
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AI summary
Method and system for measuring the resistance of a resistive structure having at least three nodes. A first calibration signal is determined by measuring a voltage at an output of the resistance structure when no calibration current is injected into a third node between the first and second nodes of the structure. A calibration current is then injected into the third node and a second calibration signal is determined. The absolute value of the difference between the first calibration signal and the second calibration signal is determined, the absolute value being proportional to a product of the resistance of the resistive structure and the calibration current.