Single-Die Angle Sensor Using Bridge Circuits for Stray Field Rejection
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Solution Overview
Problem
Existing angle sensors face challenges in accurately determining the angle of a rotating ring magnet with unique North-South pole pairs, particularly in avoiding cycloid distortion and topological defects, while maintaining sensitivity and precision across a 0° to 360° range.
Innovation Solution
The development of an angle sensor system that includes multiple pairs of magnetic-field sensing elements and processing circuitry, forming bridges to reject stray magnetic fields and determine the angle of a ring magnet with unique pole pairs, utilizing vertical Hall, horizontal Hall, and magnetoresistance elements, and employing specific pitch distributions to minimize distortions and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple pairs of magnetic-field sensing elements are used to determine angle with high precision, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sensor divides the measurement task into multiple independent sensing pairs (first pair for sine, second pair for cosine, third pair for alternative sine, fourth pair for alternative cosine), each pair measuring a specific magnetic field component. This segmentation allows precise angle determination through coordinate transformation while keeping each individual sensing pair relatively simple in structure.
Solution Approach 2:
The patent employs multiple sensing pairs oriented along different axes (first and second pairs along a first axis, third and fourth pairs along a second axis perpendicular to the first axis). This dimensional arrangement enables the system to capture magnetic field components in multiple dimensions, which through coordinate transformation yields precise angular information without requiring a single complex sensing element.
2Reliability
If bridges are formed from sensing elements to reject stray magnetic fields, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple magnetic-field sensing elements into bridge circuits (first bridge from first and second pairs, second bridge from third and fourth pairs). This merging approach enables the bridges to reject common-mode stray magnetic fields while maintaining the individual sensing capabilities of each element, thereby improving reliability without requiring entirely separate sensing systems.
Solution Approach 2:
The bridge circuits act as intermediary structures that process the raw signals from multiple sensing pairs. The bridges transform individual element outputs into differential signals that inherently reject stray magnetic fields, serving as an intermediate processing stage between the sensing elements and the final angle calculation, thus improving reliability while managing complexity through functional decomposition.
3Adaptability or versatility
If off-axis or side-shaft configuration is used, then adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The sensor is designed with universal adaptability by providing multiple installation configurations (off-axis and side-shaft options). The same basic sensing element array and bridge circuit architecture can be deployed in different spatial arrangements depending on the application requirements, making the sensor versatile across various mechanical systems without requiring design modifications.
Solution Approach 2:
The patent accommodates asymmetric installation configurations where the sensing element array is positioned off-axis or at the side of the rotating member rather than at the center. This asymmetric placement provides installation flexibility for various mechanical constraints while the bridge circuits and coordinate transformation algorithms compensate for the non-ideal geometry, maintaining measurement accuracy despite relaxed manufacturing precision requirements compared to perfectly centered configurations.
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
The system effectively determines the angle of a rotating ring magnet with high precision and sensitivity, avoiding cycloid distortions and topological defects, and is capable of operating across a full 360° range with improved accuracy and reliability.
Implementation Method 1
vertical Hall, horizontal Hall, and magnetoresistance elements
Implementation Method 2
vertical Hall, horizontal Hall, and magnetoresistance elements
Data Source
AI summary
In one aspect, an angle sensor includes magnetic-field sensing elements that include a first pair, a second pair, a third pair and a fourth pair of magnetic-field sensing elements; and processing circuitry configured to determine an angle of a rotating ring magnetic having a plurality of North-South pole pairs each having a unique period length. The processing circuitry includes a first bridge formed from the first and second pairs of magnetic-field sensing elements and a second bridge formed from the third and fourth pairs of magnetic-field sensing elements. The angle includes a value from 0° to 360°. The first, second, third and fourth pairs of magnetic-field sensing elements are each disposed on a first axis. The first, second, third and fourth pairs of magnetic-field sensing elements each have a sensitivity in a first direction along the first axis. The angle sensor is formed on a single die.