Magnetoresistance Sensor with Non-Zero Reference Output
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Solution Overview
Problem
Existing magnetic sensors face limitations in flexibility of magnetic circuit design due to the requirement for the Hall element output to be zero when the magnetic field intensity is zero, restricting the arrangement relationship between the magnet and the Hall element.
Innovation Solution
A magnetic sensor design incorporating a bridge circuit with four magnetoresistance effect elements, each with specific magnetization states of their magnetized fixed layers, allowing for varied resistance changes upon signal magnetic field application, thereby displacing the output value from zero even when the magnetic field intensity is zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Hall element is used with a magnet arranged to achieve zero output at reference position, then the driver IC can perform driving control based on output changes, but the flexibility in designing the magnetic circuit arrangement is reduced
Solution Approach 1:
The patent changes the fundamental operating parameter of the magnetic sensor from Hall effect (which requires zero output at reference position) to magnetoresistance effect with non-zero output at reference position. This is achieved by using magnetoresistance effect elements with specific magnetization configurations that produce a non-zero baseline output, thereby enabling flexible magnetic circuit design while maintaining reliable driving control through differential output detection
2Measurement precision
If the Hall element output is required to be zero when magnetic field intensity is zero, then the driver IC can accurately detect changes, but the arrangement relationship between magnet and Hall element is restricted
Solution Approach 1:
The patent transitions from Hall effect elements that require zero-output calibration to magnetoresistance effect elements that inherently provide non-zero output at reference position. The magnetoresistance effect elements with pinned layers having specific magnetization directions produce a baseline resistance difference that translates to non-zero output, eliminating the need for zero-output arrangement constraints while maintaining precise change detection capability
Solution Approach 2:
The patent uses a bridge circuit configuration with four magnetoresistance effect elements arranged in differential pairs. This segmentation into multiple elements with different magnetization orientations allows the system to detect changes relative to a non-zero baseline, providing both measurement precision and design flexibility simultaneously
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 design enhances the flexibility in arranging magnetic circuits by ensuring non-zero output values, facilitating better control and positioning accuracy through improved detection sensitivity.
Implementation Method 1
a first magnetoresistance effect element, a second magnetoresistance effect element, a third magnetoresistance effect element
Implementation Method 2
a magnetization direction of the magnetized free layer changes according to the signal magnetic field
Data Source
AI summary
An output value of a magnetic sensor when an intensity of a signal magnetic field is zero is displaced from zero due to a difference between a magnetization state of magnetized fixed layers of magnetoresistance effect stacks in each of a first magnetoresistance effect element and a fourth magnetoresistance effect element and a magnetization state of magnetized fixed layers of magnetoresistance effect stacks in each of a second magnetoresistance effect element and a third magnetoresistance effect element.