Spinning Current Hall Sensor Offset Calibration With Lengthened Phases
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Solution Overview
Problem
Hall sensors exhibit offsets and offset drift due to mechanical stresses, doping, and geometrical errors, as well as residual offsets from input amplifiers, leading to unpredictable and time-varying output errors, which existing dynamic offset-cancellation techniques fail to fully mitigate.
Innovation Solution
A system incorporating a spinning current Hall sensor and a chopping circuit, where the spinning phases are lengthened during residual offset adjustment phases to obtain signals for residual offset voltages, allowing for calibration of output signals and reduction of amplifier and Hall sensor offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic offset-cancellation techniques (auto zeroing and chopping) are used to reduce noise and offset of input amplifiers, then amplifier offset and noise are reduced, but residual offsets are produced due to demodulated switching peaks and amplifier circuit imperfections
Solution Approach 1:
The patent applies preliminary action by performing offset calibration before normal measurement operations. The system enters a calibration mode where the bias current is spatially rotated through all four phases to pre-determine offset values, which are then stored and used to compensate during actual measurements. This preliminary calibration action eliminates residual offsets that would otherwise contaminate measurement signals.
Solution Approach 2:
The patent extracts the offset calibration process as a separate, distinct operation from normal measurement. During calibration mode, the system isolates offset measurements by rotating the bias current through all phases and averaging, separating the offset component from the magnetic field signal. This extracted offset information is then removed from subsequent measurement signals.
2Measurement precision
If Hall sensing elements are used to measure magnetic field strength and direction, then magnetic field parameters can be obtained, but offsets and offset drift occur due to mechanical stresses, doping, and geometrical errors
Solution Approach 1:
The patent applies dynamics by implementing a spinning current technique where the bias current is dynamically rotated through four different spatial phases (0°, 90°, 180°, 270°) around the Hall sensing element. This dynamic rotation allows the system to sample the output at different orientations, enabling mathematical separation of the static offset component from the dynamic magnetic field signal component.
Solution Approach 2:
The patent implements feedback by using the measured offset values (obtained through phase rotation and averaging) to compensate the final measurement output. The system continuously monitors and calculates offset drift, then applies corrective compensation to the magnetic field measurements, creating a closed-loop feedback mechanism that maintains measurement accuracy over time and temperature variations.
3Measurement precision
If the bias current is spatially rotated to reduce offset and offset drift, then offset and offset drift are reduced, but additional time is required for the spinning current method
Solution Approach 1:
The patent applies periodic action by implementing offset calibration as a periodic, intermittent operation rather than a continuous process. The system performs complete phase rotation and offset measurement only when needed (e.g., at startup, after temperature changes, or at scheduled intervals), then uses the stored offset values during normal continuous operation. This periodic calibration approach minimizes time loss while maintaining measurement precision.
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 effectively reduces residual offsets and improves the accuracy of magnetic field measurements by calibrating output signals, leading to more stable and reliable sensor performance.
Implementation Method 1
Sensors based on the Hall-effect, referred to as Hall sensors, are widely used as magnetic field sensors. A Hall sensor includes one or more Hall-effect sensing elements that measure magnetic field strength and/or direction.
Data Source
AI summary
A system including a spinning current Hall sensor and a chopping circuit. The spinning current Hall sensor is configured to provide input signals and the chopping circuit is configured to receive the input signals. Spinning phases of the spinning current Hall sensor are lengthened in residual offset adjustment phases to obtain signals that correspond to the residual offset voltages of the spinning phases.