Current Sense Amplifier Calibration for Common-Mode Rejection
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Solution Overview
Problem
Conventional current sense amplifier systems face issues with common-mode voltage feedthrough due to resistor mismatches and a narrow common-mode input range, which are not effectively addressed by existing calibration methods that rely on pre-determined gain settings, as component characteristics can change over time.
Innovation Solution
A method and system for calculating a calibration gain for common-mode rejection in real-time by measuring different common-mode voltage values and corresponding output values, allowing for dynamic adjustment of the calibration gain to compensate for mismatches and enhance the common-mode input range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pre-determined calibration gain is stored during product test, then calibration is simplified for end use, but component characteristic changes over time cause calibration to become ineffective
Solution Approach 1:
The patent transitions from static pre-determined calibration gain to dynamic real-time calibration gain calculation. The system continuously measures common-mode voltage and calculates calibration gain based on current operating conditions, allowing the calibration to adapt to component characteristic changes over time and temperature variations.
Solution Approach 2:
The system implements feedback by measuring the actual common-mode voltage at the amplifier inputs and using this measurement to calculate the calibration gain. This closed-loop approach ensures that the calibration gain is always based on actual system conditions rather than historical data from product testing.
2Device complexity
If conventional current sense amplifier is used, then simple structure is maintained, but common-mode voltage feedthrough occurs due to resistor mismatch
Solution Approach 1:
The patent introduces an intermediary calibration gain calculation mechanism that mediates between the differential input signals and the amplifier output. By measuring the common-mode voltage and calculating a correction factor, the system eliminates the harmful effect of resistor mismatch without requiring precision-matched resistors or complex circuit topologies.
Solution Approach 2:
The system dynamically changes the calibration gain parameter based on measured common-mode voltage conditions. This allows the system to compensate for resistor mismatch effects under varying operating conditions without requiring physical changes to the amplifier structure or resistor values.
3Use of energy by moving object
If sense voltage is small compared to common-mode voltage, then power consumption is reduced, but slight resistor mismatch results in significant common-mode feedthrough
Solution Approach 1:
The patent uses feedback to measure the actual common-mode voltage present at the amplifier inputs and calculates calibration gain based on this measurement. This allows the system to maintain small sense voltages for low power consumption while dynamically compensating for common-mode feedthrough effects that become significant when sense voltage is small.
Data Source
AI summary
A method for calculating a calibration gain used for common-mode rejection in a current sensing system may include measuring a first value of a common-mode voltage associated with the current sensing system and a first output value of the current sensing system occurring at the first value of the common-mode voltage, measuring a second value of the common-mode voltage associated with the current sensing system and a second output value of the current sensing system occurring at the second value of the common-mode voltage, and based on a difference between the second output value of the current sensing system and the first output value of the current sensing system and a difference between the second value of the common-mode voltage and the first value of the common-mode voltage, calculating the calibration gain.