PCB Current Sensor Using MTJ Bridge for Contactless Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing current sensing methods for printed circuit boards face challenges such as power loss and unsuitability for miniaturization, particularly with direct current measurements and large current transformers, while contactless methods like Hall-effect and AMR/GMR sensors are limited in application and size.
Innovation Solution
A current sensing circuit utilizing magnetic tunneling junction (MTJ) structures on a printed circuit board, configured in a Wheatstone bridge circuit to measure current non-contactually by exploiting the resistance changes induced by magnetic fields around conductive wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current measurement using shunt resistor is implemented, then current measurement is achieved, but power loss occurs and measurement accuracy is affected
Solution Approach 1:
The patent introduces a magnetic field as an intermediary to transfer information about current flow without direct electrical contact. The MTJ sensor detects the magnetic field generated by the current-carrying wire, enabling indirect measurement that eliminates power loss while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces the electrical contact-based measurement system (shunt resistor) with a magnetic field-based detection system (MTJ sensor). This substitution allows current measurement without electrical contact, eliminating power loss and improving measurement accuracy.
2Loss of energy
If current transformer is used for contactless measurement, then power loss is minimized, but device size becomes large and miniaturization is not suitable
Solution Approach 1:
The patent changes the operating parameters and physical principles of the sensor. Instead of using traditional current transformers that rely on electromagnetic induction with large cores, the MTJ sensor uses quantum mechanical tunneling effects in magnetic layers, enabling miniaturization while maintaining contactless measurement capability and low power loss.
Solution Approach 2:
The patent employs composite magnetic layer structures (MTJ) combining ferromagnetic layers with non-magnetic spacer layers. This composite structure enables miniaturized sensor design while maintaining the ability to detect magnetic fields without direct electrical contact, solving both the size and measurement accuracy requirements.
3Loss of energy
If Hall-effect sensor is used for non-contact measurement, then contactless current measurement is achieved, but measurement accuracy and sensitivity are limited
Solution Approach 1:
The patent changes the detection mechanism from Hall-effect (measuring magnetic field strength) to MTJ effect (measuring resistance changes due to magnetic field orientation). This parameter change enables higher measurement precision and sensitivity while maintaining contactless operation and low power loss.
Solution Approach 2:
The patent uses composite magnetic layer structures with ferromagnetic layers and non-magnetic spacers to create MTJ sensors. This composite material approach provides superior magnetic field sensitivity and measurement accuracy compared to single-material Hall-effect sensors, while enabling miniaturization.
4Measurement precision
If AMR or GMR sensor is used for non-contact measurement, then measurement capability is improved, but device complexity and integration difficulty increase
Solution Approach 1:
The patent merges the MTJ sensor structure directly with the PCB trace structure, integrating the sensing element into the circuit layout. This merging approach simplifies device integration and reduces overall system complexity while maintaining high measurement precision through the magnetic field detection capability.
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
Enables accurate and efficient contactless current measurement with minimal power loss, suitable for miniaturized applications, by leveraging the resistance differences in MTJ structures responsive to magnetic fields.
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... exploiting the resistance changes induced by magnetic fields around conductive wires
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.