Current Sensor Offset Calibration for Accurate Open-Loop Sensing
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Solution Overview
Problem
Current sensors in battery pack power supply systems face challenges in accurately compensating for offset voltages, leading to reduced sensing accuracy due to close loop structures and voltage mismatches.
Innovation Solution
A current sensor configuration that includes an input corrector, input amplifier, output amplifier, and controller, which adjusts the input voltages to cancel out offset errors by switching to an open-loop structure and using a correction circuit to equalize input voltages, thereby reducing the absolute difference between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a close loop structure is used for output amplifier compensation, then stability is improved, but measurement precision deteriorates due to offset voltage errors
Solution Approach 1:
The patent applies preliminary action by performing offset voltage compensation before the main current measurement function. The controller executes a calibration routine that grounds the sensing input and adjusts the offset compensation voltage in advance, ensuring that subsequent measurements are performed with pre-corrected offset values, thereby eliminating the trade-off between stability and precision
Solution Approach 2:
The patent segments the current sensor operation into distinct functional modes: a calibration mode for offset compensation and a measurement mode for current sensing. This segmentation allows the system to optimize each function independently - using close-loop compensation during calibration for stability, then switching to open-loop measurement for high precision, thus resolving the contradiction between the two requirements
2Device complexity
If offset compensation is performed in close loop, then device complexity is reduced, but manufacturing precision deteriorates due to inaccurate compensation
Solution Approach 1:
The patent introduces an intermediary calibration routine that mediates between the simple close-loop compensation structure and the requirement for high precision. The controller acts as an intermediary by implementing a software-based calibration process that grounds the input, measures the actual offset voltage, and applies corrective voltage through the DAC, thereby achieving high compensation accuracy without increasing hardware complexity
Solution Approach 2:
The current sensor performs self-calibration through an automated routine executed by the controller. The system grounds its own sensing input, measures its own offset voltage, and adjusts its own compensation parameters without external intervention. This self-service approach maintains simple device architecture while achieving manufacturing-level precision through intelligent self-adjustment
Data Source
AI summary
A current sensor automatically adjusting an offset voltage, includes an input corrector, upon receiving a first voltage, a second voltage, and a control signal, configured to correct either one or both of the first voltage and the second voltage to reduce an absolute value of a difference between the first voltage and the second voltage based on the control signal, and output a correction result; an input amplifier configured to amplify a voltage output from the input corrector; an output amplifier configured to generate an output voltage when a voltage amplified by the input amplifier is input; a controller including a switch connected to one of voltages amplified by the input amplifier to be grounded when a difference between the first voltage and the second voltage is larger than a first threshold value; and a correction circuit controller configured to generate the control signal to input to the input corrector.