Magnetic Sensor Drift Compensation via Electrode Switching
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Solution Overview
Problem
Existing magnetic sensors, such as integrated Hall sensors, face challenges in eliminating offset and sensitivity variations due to temperature, aging, and magnetic field amplitude, which current compensation circuits and calibration methods are unable to adequately address, especially when power and silicon area are limited.
Innovation Solution
A method and device that isolate the contribution of a reference magnetic field to the output signal of a magnetic sensor without requiring multiple sensors or specific filters, allowing for the evaluation and compensation of sensitivity drift by alternating the reference magnetic field's amplitude and direction in sub-phases, enabling accurate measurement and correction of external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic offset cancellation is used with a single Hall sensor, then offset elimination is achieved, but sensitivity drift due to temperature and aging cannot be compensated
Solution Approach 1:
The measurement process is segmented into multiple phases (first phase with first bias electrodes, second phase with second bias electrodes) where each phase measures different components of the output signal. This segmentation allows separate measurement of offset voltage and sensitivity drift, enabling both to be compensated independently.
Solution Approach 2:
The patent employs periodic switching between different bias electrode configurations at defined phases. The first and second phases are alternated periodically, with the reference magnetic field being applied during specific phases. This periodic action enables continuous monitoring and compensation of both offset and sensitivity drift over time.
2Measurement precision
If multiple Hall sensors are used to compensate sensitivity drift, then measurement accuracy improves, but power consumption and silicon area increase
Solution Approach 1:
A single Hall sensor is made multi-functional by sequentially applying different bias configurations and reference magnetic fields. The same sensor measures both offset voltage and sensitivity drift at different phases, eliminating the need for multiple dedicated sensors while maintaining compensation accuracy.
Solution Approach 2:
The Hall sensor performs self-diagnosis and self-compensation by measuring its own offset and sensitivity drift characteristics through internal switching between bias electrodes and reference field application. This self-service approach eliminates external calibration equipment and multiple sensors.
3Reliability
If reference magnetic field is applied continuously, then sensitivity drift can be monitored, but power consumption increases
Solution Approach 1:
The reference magnetic field is applied periodically only during specific phases (first and/or second phases) rather than continuously. The field application is synchronized with the phase switching, allowing sensitivity drift monitoring at intervals while minimizing power consumption during non-measurement periods.
Solution Approach 2:
Sensitivity drift calibration is performed preliminarily during manufacturing or at startup using the reference magnetic field, storing the calibration data for later use. This preliminary action reduces the need for continuous reference field application during normal operation, lowering power consumption.
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 compensates for sensitivity drift in magnetic sensors, improving measurement accuracy without the need for additional sensors or power-consuming filters, thus enhancing the reliability and efficiency of magnetic field sensing.
Implementation Method 1
A Hall sensor for sensing magnetic fields is advantageously integrated in a semiconductor substrate... When a magnetic field BExt is applied perpendicularly to the doped planar region, a difference of potential VH appears across the plate
Data Source
AI summary
The present invention provides a method to compensate for the sensitivity drift of a magnetic field sensor for sensing a magnetic field. The magnetic field sensor comprises at least four electrodes. The method comprises a first step where a first set of two electrodes is used to bias the sensor and a second set of two electrodes is used to sense an output signal of the magnetic field sensor, and a second step where the second set of two electrodes is used to bias the sensor and the first set of two electrodes is used to sense an output signal of the magnetic field sensor. The method is characterized in that at least one of the first or the second step is subdivided in at least a first sub-step and a second sub-step. A reference magnetic field has first magnetic field parameters, e.g. a first amplitude and/or direction, in the first sub-step and second magnetic field parameters, a second amplitude and/or direction, in the second sub-step. An output signal is sensed in the first and in the second step, and within the first or the second step an output signal is sensed in the first and the second sub-step.