PCB Current Sensing Circuit Using MTJ Bridge for DC Measurement
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Solution Overview
Problem
Existing current sensing methods for printed circuit boards face challenges such as power loss and unsuitability for miniaturization, especially with direct current measurements, and non-contact methods like current transformers and Hall-effect sensors have limitations in measuring DC currents and size constraints.
Innovation Solution
A contactless current sensing circuit using magnetic tunneling junction (MTJ) structures is implemented on a printed circuit board (PCB), with MTJ structures positioned on both sides of a conductive wire to measure magnetic field changes induced by current flow, utilizing a Wheatstone bridge circuit to determine current based on resistance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current measurement using shunt resistor is used, then current measurement is achieved, but power loss occurs and miniaturization is not suitable
Solution Approach 1:
The patent introduces a magnetic field as an intermediary to transfer the current measurement function. Instead of directly measuring current through electrical contact (shunt resistor), the system uses magnetic field coupling between the conductive trace and sensor to enable indirect measurement, eliminating power loss while maintaining measurement accuracy
Solution Approach 2:
The patent replaces the electrical contact-based measurement system (shunt resistor requiring physical connection in current path) with a magnetic field-based sensing system. This substitution allows contactless current measurement, eliminating the power loss and mechanical contact issues associated with traditional shunt resistors
2Loss of energy
If current transformer is used for non-contact measurement, then power loss is avoided, but DC current measurement is not possible and device size is large
Solution Approach 1:
The patent changes the operating parameters of the sensing system by using MTJ structures that respond to magnetic field direction and strength. This allows the system to detect DC currents (unlike AC-based current transformers) while maintaining contactless measurement and miniaturized form factor through the use of magnetic tunneling junction physics
3Loss of energy
If Hall-effect sensor is used for non-contact measurement, then power loss is avoided, but device size is not suitable for miniaturization
Solution Approach 1:
The patent changes the sensing mechanism from Hall-effect (which requires larger structures) to magnetic tunneling junction effect. This parameter change in the underlying physics enables miniaturization while maintaining contactless operation and eliminating power loss, as MTJ structures can be fabricated at much smaller dimensions compared to traditional Hall-effect sensors
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 accurate and efficient current measurement without power loss, suitable for miniaturized applications, by leveraging the magnetic field-induced resistance changes in MTJ structures within a Wheatstone bridge circuit.
Implementation Method 1
By measuring such a magnetic field, information on the value of the current that produced it can be obtained
Implementation Method 2
magnetic tunneling junction (MTJ) structures... measure magnetic field changes induced by current flow, utilizing a Wheatstone bridge circuit to determine current based on resistance differences
Data Source
AI summary
A contactless current sensing circuit for sensing current in a conductive wire on a dielectric substrate of a printed circuit board (PCB) includes a plurality of magnetic tunneling junction (MTJ) structures including first and second MTJ structures on a first side of the conductive wire, and third and fourth MTJ structures on a second side of the conductive wire opposite to the first side. The MTJ structures are located within the H-field induced by a current flowing through the conductive wire.