Closed Loop Current Sensor Stray Field Immunity
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Solution Overview
Problem
Conventional current sensors face challenges in accurately sensing currents due to immunity to stray magnetic fields, which can affect the accuracy of magnetic field-based current sensing systems, especially in closed loop configurations where differential or gradient sensing is required.
Innovation Solution
A closed loop current sensor system utilizing multiple magnetic field sensing elements with a feedback conductor that generates a feedback magnetic field to modify the outputs of these elements, allowing for differential or gradient sensing by adjusting the coupling factors to bring the magnetic field levels experienced by the sensing elements to zero or a desired equilibrium point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensors use magnetic field transducers positioned near current-carrying conductors, then current sensing capability is achieved, but immunity to stray magnetic fields deteriorates
Solution Approach 1:
The patent implements a closed-loop feedback system where a feedback current is generated based on the difference between sensed magnetic field and desired magnetic field levels. This feedback current flows through a feedback conductor to produce a compensating magnetic field that actively counteracts stray field interference, thereby maintaining measurement precision while rejecting harmful external magnetic fields.
Solution Approach 2:
The patent introduces a feedback conductor as an intermediary element that carries a compensating current to generate a magnetic field opposing stray fields. This intermediary component mediates between the harmful external magnetic environment and the sensitive magnetic field transducer, protecting the sensing function without requiring direct shielding of the transducer itself.
2Adaptability or versatility
If multiple magnetic field sensing elements are spaced at different distances from the primary conductor, then differential sensing capability is improved, but device complexity increases
Solution Approach 1:
The patent divides the sensing function into multiple discrete magnetic field transducers positioned at different spatial locations around the current-carrying conductor. Each transducer independently senses the magnetic field at its specific position, enabling differential or gradient sensing capabilities. This segmentation allows the system to extract more information from the magnetic field distribution while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent combines multiple magnetic field transducers and a feedback conductor into an integrated closed-loop sensing system. The outputs of multiple transducers are processed together with the feedback signal to produce a unified current measurement. This merging approach achieves enhanced differential sensing capability while avoiding the complexity of completely separate sensing systems.
3Reliability
If feedback conductor is positioned proximate to magnetic field sensing elements, then feedback magnetic field coupling is improved, but stray field immunity deteriorates
Solution Approach 1:
The patent positions the feedback conductor in close proximity to specific magnetic field transducers to create strong local feedback coupling at those locations. This local quality enhancement ensures effective feedback control where needed most, while the overall distributed arrangement of multiple transducers and feedback conductors maintains immunity to stray fields by not concentrating all sensing and feedback elements in a single vulnerable location.
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 enhances the accuracy and reliability of current sensing by effectively canceling out stray magnetic fields and achieving precise differential or gradient sensing, improving the overall performance of current measurement systems.
Implementation Method 1
a feedback conductor configured to carry a feedback current generating a feedback magnetic field
Implementation Method 2
magnetic field sensing elements spaced from each other and configured to sense the direct magnetic field at different magnitudes
Data Source
AI summary
A current sensor for sensing a direct magnetic field generated by a current through a conductor includes at least one first magnetic field sensing element spaced from at least one second magnetic field sensing element, with the magnetic field sensing elements configured to sense the direct magnetic field at different magnitudes. The direct magnetic field has a first direct coupling factor with respect to the at least one first magnetic field sensing element and a second direct coupling factor with respect to the at least one second magnetic field sensing element. A feedback conductor configured to carry a feedback current generates a feedback magnetic field that has a first feedback coupling factor with respect to the at least one first magnetic field sensing element and a second feedback coupling factor with respect to the at least one second magnetic field sensing element. A circuit generates the feedback current based on the direct and feedback magnetic fields and a sense element senses the feedback current.