Current Sensing Circuit Impedance Mismatch Compensation
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Solution Overview
Problem
Current sensing circuits in electronic devices often face errors due to mismatched equivalent impedances of windings in the sensing path, leading to inaccurate current sensing, which can be critical in safety-critical applications like vehicle electronics.
Innovation Solution
A current sensing circuit that includes a sensing resistor, a current monitor, and a processor, with a digital variable resistor connected in series with one of the windings, allowing the processor to adjust the impedance to match the equivalent impedance of the other winding, ensuring accurate current sensing even with environmental changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equivalent impedances of windings are not matched, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces a variable resistor that can dynamically adjust its resistance value to compensate for impedance mismatches between windings. By changing the resistance parameter of the variable resistor, the system achieves accurate current sensing without requiring perfectly matched winding impedances, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The variable resistor acts as an intermediary component between the windings and the sensing circuit. It mediates the impedance mismatch by providing adjustable resistance that balances the total impedance in each branch, enabling accurate current measurement while maintaining circuit simplicity
2Reliability
If equivalent impedances of windings are not matched, then manufacturing precision requirements are reduced, but reliability deteriorates
Solution Approach 1:
The variable resistor allows the system to dynamically adjust resistance parameters to compensate for manufacturing variations in winding impedances. This ensures reliable and accurate current sensing even when winding impedances vary due to manufacturing tolerances, environmental changes, or aging effects
Solution Approach 2:
The system transitions from a static impedance configuration to a dynamic one where the variable resistor can be adjusted during operation. This dynamic adjustment capability ensures that the sensing circuit maintains high reliability under varying conditions without requiring extremely precise manufacturing
3Measurement precision
If a variable resistor is added to adjust impedance, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The variable resistor serves as a simple intermediary component that provides impedance adjustment functionality. While it adds one component to the circuit, it eliminates the need for complex calibration circuits or multiple fixed resistors, achieving a net reduction in overall circuit complexity while improving measurement precision
Data Source
AI summary
A current sensing circuit includes a sensing resistor, a current monitor, a variable resistor, and a processor. The sensing resistor is disposed on a to-be-sensed circuit and coupled between first and second first voltage terminals of the to-be-sensed circuit. The current monitor includes first and second terminals. A first winding is coupled between the first terminal and the first voltage terminal, and a second winding is coupled between the second terminal and the second voltage terminal. The variable resistor is connected in series with the first winding between the first voltage terminal and the first terminal. The current monitor obtains a sensed current according to a first voltage on the first terminal, a second voltage on the second terminal, and an impedance of the sensing resistor and generates a sensing signal. The processor determines whether to adjust an impedance of the variable resistor according to the sensing signal.