Magnetic Field Sensor Self-Testing via Dual-Mode Switching
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Solution Overview
Problem
Conventional magnetic field sensors lack built-in self-test circuits that can effectively test the magnetic field sensing elements and all circuits within the sensor, especially when operating in the presence of varying external magnetic fields, and they do not allow for real-time gain adjustment during normal operation.
Innovation Solution
A magnetic field sensor design that includes at least two magnetic field sensing elements coupled through a switching circuit to alternate between measured-field-sensing and reference-field-sensing configurations, generating both measured-magnetic-field-responsive and reference-magnetic-field-responsive signals, enabling self-testing and gain adjustment while operating in normal conditions, regardless of the external magnetic field magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional built-in self-test circuits are used in magnetic field sensors, then the circuit can be tested, but the magnetic field sensing element and all circuits cannot be effectively tested
Solution Approach 1:
The magnetic field sensing elements are designed to serve dual purposes: normal operation for sensing external magnetic fields and self-test mode for testing all circuits within the sensor. By alternating between measured-field-sensing configuration and reference-field-sensing configuration, the same sensing elements test the entire circuitry including amplifiers and signal processing circuits, eliminating the need for separate test circuits.
Solution Approach 2:
The magnetic field sensor performs self-diagnosis using its own sensing elements to generate test signals. The sensing elements alternately couple to generate measured-field-responsive signals and reference-field-responsive signals, enabling the sensor to self-test all internal circuits without external testing equipment.
2Adaptability or versatility
If magnetic field sensors operate in varying external magnetic fields, then they can perform normal sensing, but real-time gain adjustment and self-testing cannot be performed
Solution Approach 1:
The switching circuit alternates periodically between measured-field-sensing configuration and reference-field-sensing configuration. During each cycle, the sensing elements first sense the external magnetic field, then switch to generate reference-field-responsive signals for self-testing and gain adjustment. This periodic switching enables real-time calibration without interrupting normal operation.
Solution Approach 2:
The circuit configuration dynamically switches between measurement mode and self-test mode. The switching circuit rapidly alternates the coupling of magnetic field sensing elements, allowing the sensor to adapt between normal sensing operation and self-diagnosis mode, enabling real-time gain adjustment during operation.
3Reliability
If separate self-test circuits are added to magnetic field sensors, then testing capability is improved, but device complexity increases
Solution Approach 1:
The magnetic field sensing elements serve multiple functions: normal magnetic field sensing, self-testing of all circuits, and gain adjustment. By making the sensing elements universal, the patent eliminates the need for separate dedicated test circuits, reducing overall device complexity while maintaining comprehensive self-test capability.
Solution Approach 2:
The patent merges the self-test function with the normal sensing function by using the same magnetic field sensing elements for both purposes. The switching circuit combines measurement mode and self-test mode into a single integrated system, eliminating redundant circuitry and reducing device complexity.
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
Enables real-time self-testing and gain adjustment of magnetic field sensors, ensuring accurate operation and reliability even in the presence of varying external magnetic fields, thereby improving the sensor's performance and reliability.
Implementation Method 1
Hall effect elements generate an output voltage proportional to a magnetic field
Implementation Method 2
magnetoresistance elements change resistance in proportion to a magnetic field
Implementation Method 3
magnetic field sensing elements alternately coupled in a measured-field-sensing configuration and in a reference-field-sensing configuration
Data Source
Figure 1~1A
Figure 2
Figure 2A~2C
AI summary
A magnetic field sensor includes a reference-field-sensing circuit channel that allows a calibration or a self-test of the circuitry of the magnetic field sensor. The magnetic field sensor can generate a reference magnetic field to which the magnetic field sensor is responsive.