Built-In Switch Current Sensing With Stray-Field Rejection
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Solution Overview
Problem
Existing sensors, particularly those used in automobile control systems, face challenges in meeting stringent safety and quality requirements due to issues with electromagnetic interference and stray field sensitivity, which affect their reliability and accuracy in measuring electrical current.
Innovation Solution
A current sensor apparatus is designed with a substrate, a switching device, and magnetic field sensing elements arranged in specific patterns to form a sensing circuit, encapsulated in a semiconductor package, which measures electrical current through a contact member using magnetic field sensing elements like TMR or Hall elements, providing immunity to stray fields and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional electromagnetic flux sensing elements are used, then the sensor can detect current, but it becomes sensitive to stray fields and electromagnetic interference
Solution Approach 1:
The sensing element is divided into multiple segments arranged in a ring around the contact member. Each segment detects magnetic flux in a specific direction, and the segmented structure allows the sensor to distinguish between stray fields and the actual current-generated magnetic field through differential measurement.
Solution Approach 2:
The magnetic sensing elements are arranged asymmetrically in a ring configuration with specific orientations. This asymmetric arrangement creates a measurement pattern that is inherently insensitive to uniform stray fields while maintaining sensitivity to the rotational magnetic field generated by current flow through the contact member.
2Reliability
If magnetic field sensing elements are arranged in a ring pattern, then immunity to stray fields is achieved, but the device complexity increases
Solution Approach 1:
Multiple magnetic sensing elements are merged into a unified ring structure around the contact member. The sensing elements are integrated with shared circuitry and common signal processing paths, reducing overall complexity compared to using separate sensors. The ring configuration allows the elements to work together as a single functional unit for stray field rejection.
Solution Approach 2:
The ring-shaped sensing circuit serves multiple functions: it detects current magnitude, determines current direction, and simultaneously rejects stray fields. The same physical structure and sensing elements perform all these functions, eliminating the need for separate circuits for each measurement task and reducing overall 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
The solution provides a reliable and accurate measurement of electrical current, immune to stray fields, thereby meeting safety and quality standards in safety-critical applications.
Implementation Method 1
Some sensors include one or more electromagnetic flux sensing elements, such as a Hall effect element
Implementation Method 2
a magnetoresistive element
Implementation Method 3
a receiving coil to sense an electromagnetic flux
Data Source
Figure 1A
Figure 1B~1D
Figure 1E~1F
AI summary
An apparatus, comprising: a substrate; a switching device that is formed over the substrate, the switching device including a gate layer, a source layer, and a drain layer; a first layer of dielectric material that is formed over the switching device; a first contact member that is electrically coupled to one of the gate layer, the source layer, and the drain layer, the first contact member being formed of at least one electrically-conductive material, the first contact member extending through the first layer of dielectric material; a plurality of first magnetic field sensing elements, the plurality of first magnetic field sensing elements being arranged to at least partially surround the first contact member, the plurality of first magnetic field sensing elements being arranged, at least in part, to form a sensing circuit for measuring a level of electrical current through the first contact member.