Co-Located Differential Magnetic Sensor Layout for Stray Field Rejection
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Solution Overview
Problem
Stray magnetic fields from sources like electric motors and other electromagnetic components in automotive applications interfere with the accuracy of magnetic field sensors, causing significant output errors and impacting systems relying on these sensors.
Innovation Solution
A differential current sensor with co-located magnetic field sensing elements is used, comprising groups configured to detect both main and stray magnetic fields, providing redundant channels for each, and utilizing Gilbert cells to process outputs, ensuring fault detection when stray field outputs fall outside a defined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field sensors are used to detect main magnetic fields in automotive applications, then current measurement capability is provided, but stray magnetic fields from electromagnetic components interfere with sensor accuracy
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the same magnetic field sensing elements to detect both the main magnetic field (useful signal) and stray magnetic fields (harmful interference). By measuring both components with identical sensors in identical locations, the system converts the previously harmful stray fields into useful diagnostic information that enables compensation and fault detection, thereby resolving the accuracy interference problem.
Solution Approach 2:
The patent introduces an intermediary processing system that includes differential amplifiers and signal processing circuitry. This intermediary layer processes the raw sensor outputs by subtracting the stray field component from the main field measurement, effectively mediating between the sensor's vulnerable detection capability and the harmful interference to produce accurate compensated measurements.
2Reliability
If redundant sensor channels are added to provide safety backup, then system reliability is improved, but device complexity and sensor area increase
Solution Approach 1:
The patent merges the redundant safety channel with the main measurement channel by using identical magnetic field sensing elements for both functions. Instead of separate sensor assemblies, the system combines multiple sensing elements into a unified structure where the same physical location and sensor type serve both primary measurement and redundancy purposes, thereby reducing overall device complexity while maintaining safety backup capability.
Solution Approach 2:
The patent implements universality by designing the magnetic field sensing elements to serve multiple functions: they simultaneously detect main magnetic fields for measurement, detect stray fields for compensation, and provide redundant safety channels for fault detection. This multi-functionality eliminates the need for separate dedicated redundancy sensors, reducing complexity while ensuring reliability.
3Measurement precision
If multiple magnetic field sensing elements are used to detect both main and stray fields, then measurement accuracy is improved, but sensor area requirements increase
Solution Approach 1:
The patent merges the detection functions for main fields and stray fields into a single integrated sensor area. By using the same magnetic field sensing elements for both detection purposes and processing both signals through the same physical location, the system achieves dual field detection capability without requiring separate sensor areas, thereby maintaining compact footprint while improving 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 configuration effectively removes the influence of stray magnetic fields, ensuring accurate main magnetic field measurements while providing safety redundancy with reduced sensor area requirements.
Implementation Method 1
a first plurality of magnetic field sensing elements in a first region relative to a conductor and configured to detect a main magnetic field produced by current in the conductor
Implementation Method 2
a second plurality of magnetic field sensing elements in a second region relative to the conductor and configured to detect one or more stray magnetic fields
Data Source
AI summary
Systems, structures, packages, circuits, and methods provide magnetic current sensors with redundant magnetic field elements or groups of elements used for current sensing. Such systems, structures, packages, circuits, and methods allow for the measurement of a diagnostic channel to be similar in amplitude to the measurement of the main channel in the case of gradient magnetic fields. Some embodiments can utilize three magnetic sensing elements or groups of elements to provide redundant safety while using less area. The sensors can provide fault indications when comparisons between the measurements made for the main and diagnostic channels are outside of a specified range or do not compare favorably.