Folded AMR Current Sensor for High-Frequency EMI Reduction
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Solution Overview
Problem
Current current sensors face challenges in accurately measuring high-frequency currents due to electromagnetic interference (EMI) and limited bandwidth, which affects their sensitivity and response time, especially in miniaturized high-power electronics applications.
Innovation Solution
The proposed solution involves folding the current carrying trace around the anisotropic magneto-resistive (AMR) sensor to amplify and normalize the magnetic field, enhancing sensitivity and bandwidth by creating a uniform magnetic field distribution and shielding the sensor from stray fields, allowing for detection of currents up to >10 MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current carrying trace is folded around the AMR sensor, then the magnetic field is amplified and normalized, improving sensitivity and bandwidth, but the device complexity increases
Solution Approach 1:
The current carrying trace is folded into a curved configuration around the AMR sensor, transforming a straight linear trace into a bent path that encircles the sensor. This curvature concentrates the magnetic field lines through the sensor, amplifying the magnetic field strength and improving sensitivity without requiring additional active components
Solution Approach 2:
The trace is folded from a two-dimensional planar layout into a three-dimensional configuration that wraps around the sensor in the vertical dimension. This dimensional transformation creates a magnetic field concentration effect that passes the trace above and below the sensor, normalizing the field distribution and enhancing the sensor response across a wide bandwidth
2Reliability
If the current carrying trace is folded around the AMR sensor, then the magnetic field is normalized and EMI shielding is improved, but the area occupied by the sensor increases
Solution Approach 1:
The folded trace configuration converts the potentially harmful stray magnetic fields and EMI into a beneficial shielding effect. By wrapping the trace around the sensor, the structure creates a magnetic field concentration zone that shields the sensor from external interference while the return path cancels out external magnetic noise, improving reliability without requiring separate shielding components
3Power
If miniaturized high-power electronics are used, then the power density increases, but electromagnetic interference between current traces and components increases
Solution Approach 1:
The folded trace structure acts as an intermediary magnetic field management system between the high-power current path and the sensitive AMR sensor. The configuration creates a controlled magnetic field zone that mediates the interaction, concentrating the desired signal field while the return path serves as a shield against external EMI, enabling miniaturized high-power applications without compromising sensor performance
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 significantly improves the sensor's bandwidth and sensitivity, enabling accurate detection of high-frequency currents with faster response times, reducing EMI effects and enhancing performance in high-frequency power converters and other applications.
Implementation Method 1
Oersted discovered in 1820 that the flow of current through a conductor produces a magnetic field, and that the strength of the magnetic field produced depends on the amount of current flow. Because of this effect, it is possible to measure the amount of current flowing through a conductor by measuring the strength of the magnetic field the current flow produces.
Implementation Method 2
The proposed solution involves folding the current carrying trace around the anisotropic magneto-resistive (AMR) sensor to amplify and normalize the magnetic field, enhancing sensitivity and bandwidth
Data Source
AI summary
A technique for an AMR-based sensing circuit allows current measurements over a wide frequency range. This is accomplished by folding the current carrying trace around the AMR sensor to concentrate and normalize the magnetic field generated by the current over a wide frequency range. Experimental results show that the sensor, when implemented with the proposed method, has an improved bandwidth of >10 MHz and enhanced sensitivity to high frequency currents evinced by the sensor output at DC or lower frequencies. The method is applicable for example in high frequency power converters where inductor current is used to control the ripple and transient response.