TMR Current Sensor Differential Bridge Insensitivity
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Solution Overview
Problem
Conventional magnetic current sensors based on tunnel magnetoresistive (TMR) technology require differential thermal-assisted programming and are sensitive to external uniform magnetic fields, limiting their scalability and accuracy due to the need for individual device programming and distortion from orthogonal sensing magnetic fields.
Innovation Solution
A differential magnetic current sensor using a magnetoresistive full bridge configuration with TMR sensor elements having pinned reference magnetizations oriented in the same direction, and a field line generating a radial magnetic field that orients sense magnetizations oppositely in each half-bridge, allowing for a single-step programming and insensitivity to external uniform magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential thermal-assisted programming is used to program reference magnetization in opposed directions, then the sensor can detect field current, but the manufacturing complexity increases and mass production bandwidth is limited
Solution Approach 1:
Instead of programming reference magnetizations in opposed directions as in conventional sensors, this invention programs all reference magnetizations in the same direction. The differential detection is achieved by arranging sense magnetizations in opposite directions relative to the reference, eliminating the need for complex differential programming while maintaining detection capability.
Solution Approach 2:
The reference magnetization is programmed once in the same direction for all TMR sensor elements during manufacturing. This preliminary action eliminates the need for subsequent differential programming steps, enabling mass production and reducing manufacturing complexity while maintaining the ability to detect field current direction.
2Measurement precision
If conventional TMR sensor elements with opposed reference magnetization are used, then the sensor can measure field current, but the sensor becomes sensitive to external uniform magnetic fields
Solution Approach 1:
Each TMR sensor element has locally configured magnetization orientations where the reference magnetization is uniformly oriented in the same direction, while the sense magnetization is oriented to be opposite to the reference in diagonally opposed elements. This local quality differentiation enables the sensor to respond to field current while rejecting external uniform magnetic fields through the differential bridge configuration.
3Measurement precision
If orthogonal component of sensing magnetic field is present in curved part of current line, then the sensor can detect current, but the linearity of the sensor is distorted
Solution Approach 1:
The sensor employs an asymmetric bridge configuration where diagonally opposed TMR sensor elements have sense magnetizations oriented opposite to each other relative to the reference magnetization. This asymmetric arrangement creates differential responses that cancel out orthogonal components from curved current lines, maintaining linearity while enabling accurate current detection.
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 enables mass production scalability and improved linearity by eliminating the need for thermal programming and external magnetic field sensitivity, ensuring a differential voltage output proportional to the field current while maintaining resistance variation linearity.
Implementation Method 1
A conventional current sensor 1 based on tunnel magnetoresistive (TMR) sensors is schematically illustrated in FIG. 1
Implementation Method 2
a field line configured to pass a field current generating a magnetic field adapted for orienting the sense magnetization
Data Source
AI summary
Magnetic current sensor, including: a sensor bridge circuit including a first and second half-bridges, each including two series-connected and diagonally opposed tunnel magnetoresistive (TMR) sensor elements, the TMR sensor elements including a reference layer oriented a single predetermined direction and a sense layer having a sense magnetization; a field line configured for passing a field current generating a magnetic field adapted for orienting the sense magnetization of the diagonally opposed TMR sensor elements of the first half-bridge and of the diagonally opposed TMR sensor elements of the second half-bridge in an opposite direction; such that a non-null differential voltage output between the TMR sensor elements of the first half-bridge and the TMR sensor elements of the second half-bridge is measurable when the field current is passed in the field line; the differential voltage output being insensitive to the presence of an external uniform magnetic field.