Hall-Effect Sensor Diagnostics via External Magnet Extraction
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Solution Overview
Problem
Current systems for run time diagnostics in Hall-effect sensors require additional on-chip area and consume significant power, and are not reliable due to challenges in isolating the local magnetic field from the external magnetic field.
Innovation Solution
A method involving a diagnostic sensor that generates a reference voltage by periodically switching the direction of current flow, which includes a non-sinusoidal differential voltage with alternating amplitude, and a circuit with multiplexers and an analog front end to amplify, demodulate, and digitize the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If on-chip coils are used to create a local magnetic field for run time diagnostics, then magnetic field generation is achieved, but additional on-chip area is required and power consumption increases
Solution Approach 1:
The patent extracts the magnetic field generation function from the integrated circuit by using an external magnet instead of on-chip coils. This removes the need for additional on-chip area dedicated to magnetic field generation while maintaining the diagnostic capability through periodic switching of current direction in the external magnet connection
Solution Approach 2:
The existing on-chip coil structure is made multi-functional by using it for both normal sensor operation and diagnostic functions. The coil serves as the sensing element during normal operation and as a diagnostic test element when connected to the external magnet, eliminating the need for separate diagnostic hardware
2Reliability
If on-chip coils are used to create a local magnetic field for run time diagnostics, then magnetic field generation is achieved, but power consumption increases
Solution Approach 1:
The patent implements periodic switching of current direction through the on-chip coil during diagnostic mode, rather than continuous operation. This periodic action (switching between positive and negative voltage levels) enables diagnostic measurement while minimizing average power consumption compared to continuous magnetic field generation
Solution Approach 2:
By removing the on-chip coil from the power consumption equation and using an external magnet instead, the patent eliminates the significant power consumption associated with continuous magnetic field generation, retaining only the minimal power needed for periodic switching and measurement
3Reliability
If local magnetic field is used for diagnostics, then sensor testing is enabled, but isolation from external magnetic field becomes unreliable
Solution Approach 1:
Instead of trying to shield the sensor from external magnetic fields, the patent inverts the approach by using the external magnetic field itself as the diagnostic tool. By periodically switching the current direction through the coil in the known external field, the system creates a controlled, reversible magnetic environment that enables accurate measurement while naturally rejecting static external field interference
Solution Approach 2:
The patent employs feedback through differential measurement techniques that compare sensor output during positive and negative voltage phases. This feedback mechanism cancels out static external magnetic field effects while capturing the dynamic response to the switched current, achieving reliable diagnostics despite external field presence
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 solution enables reliable run time diagnostics with reduced power consumption and on-chip area, effectively validating the integrity of Hall-effect sensors by isolating the diagnostic signal from external magnetic fields.
Implementation Method 1
A magnetic sensor such as a Hall-effect sensor is a device used to measure the strength of a magnetic field. The magnetic sensor provides an output voltage that is directly proportional to the magnetic field strength.
Implementation Method 2
generating a reference voltage by periodically switching direction of current flow in a diagnostic sensor, where the reference voltage is a non-sinusoidal differential voltage of which an amplitude alternates between minimum and maximum values
Implementation Method 3
amplifying the reference voltage to produce an amplified reference voltage, where the amplified reference voltage is a differential voltage having an amplifier offset voltage component
Implementation Method 4
demodulating the amplified reference voltage by filtering the diagnostic sensor offset voltage component and the amplifier offset voltage component to produce a demodulated voltage
Implementation Method 5
digitizing the demodulated voltage to produce a digitized voltage
Data Source
AI summary
A method includes generating a reference voltage by periodically switching direction of current flow in a diagnostic sensor, where the reference voltage is a non-sinusoidal differential voltage of which an amplitude alternates between minimum and maximum values, and where the reference voltage includes a diagnostic sensor output voltage component responsive to an external magnetic field and a diagnostic sensor offset voltage component responsive to a mismatch of the diagnostic sensor. The method also includes amplifying the reference voltage to produce an amplified reference voltage, where the amplified reference voltage is a differential voltage having an amplifier offset voltage component. Additionally, the method includes demodulating the amplified reference voltage by filtering the diagnostic sensor offset voltage component and the amplifier offset voltage component to produce a demodulated voltage. Also, the method includes digitizing the demodulated voltage to produce a digitized voltage.