Magnetic Field Sensor with Pyramid Impedance Characteristic
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Solution Overview
Problem
Magnetic field sensors using magnetic impedance effects face limitations in detection range, sensitivity, and accuracy due to narrow detection ranges, high current consumption, and increased hysteresis when employing magnetic impedance elements with M-shaped characteristics, and issues with phase detection when using pyramid-shaped elements.
Innovation Solution
A magnetic field sensor design incorporating a magnetic detection element with a pyramid-shaped impedance characteristic, a high-frequency oscillation circuit, an AC bias circuit, and a detection circuit with amplitude and phase difference detection capabilities, utilizing a bridge circuit and selection circuit to optimize detection based on external magnetic field strength, allowing for reduced current consumption and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic impedance element with M-shaped characteristic is used, then sensitivity can be improved by applying AC bias at steep inclination positions, but current consumption increases and hysteresis becomes larger
Solution Approach 1:
The patent changes the fundamental parameter of the magnetic impedance element from M-shaped characteristic to pyramid-shaped characteristic. This parameter change allows the element to achieve steep inclination at the center position without requiring large AC bias currents, thereby improving detection accuracy while reducing current consumption. The pyramid shape inherently provides smaller hysteresis compared to M-shape, further enhancing detection accuracy.
2Measurement precision
If AC bias is applied to achieve high sensitivity measurement, then detection accuracy improves, but current consumption increases
Solution Approach 1:
By changing the magnetic impedance characteristic from M-shape to pyramid-shape, the patent enables high sensitivity detection at the center position where AC bias is applied, without requiring excessive bias current. The pyramid shape's geometric parameter allows achieving steep inclination with minimal bias, thus improving detection accuracy while minimizing current consumption.
3Measurement precision
If pyramid-shaped magnetic impedance element is used, then hysteresis is reduced and detection accuracy improves, but detection range becomes limited when using conventional circuits
Solution Approach 1:
The patent employs a dual-mode detection system that dynamically switches between phase difference detection and amplitude detection modes. The phase difference detection circuit handles small magnetic field changes with high precision, while the amplitude detection circuit extends the detection range for larger magnetic field variations. This dynamic adaptation resolves the contradiction between detection accuracy and detection range.
Solution Approach 2:
The patent implements multiple detection circuits (phase difference detection and amplitude detection) that can operate depending on the magnetic field conditions. This multi-functional approach allows the system to maintain high detection accuracy for small signals while extending the detection range for larger signals, making the pyramid-shaped element versatile across different application scenarios.
4Measurement precision
If phase difference detection is used for pyramid-shaped element, then accuracy improves for small fields, but detection fails when external magnetic field increases
Solution Approach 1:
The patent creates a dynamic detection system that automatically switches between phase difference detection and amplitude detection based on the magnitude of the external magnetic field. For small magnetic fields, phase difference detection provides high accuracy. When the magnetic field exceeds a certain threshold and phase detection becomes unreliable, the system transitions to amplitude detection, thereby maintaining detection capability across the entire range from small to large magnetic fields.
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 sensor achieves a wider detection range, improved accuracy, and reduced current consumption by detecting amplitude changes and phase differences, enabling effective magnetic field detection without the need for large bias currents and maintaining stability across voltage and temperature changes.
Implementation Method 1
a magnetic detection element (12) which includes a magnetic material (12b) causing a magnetic impedance effect
Implementation Method 2
a bias coil (14) which applies a bias magnetic field to the magnetic material (12b)
Implementation Method 3
impedance sensitively changes in response to an external magnetic field due to the influence of a skin effect
Data Source
AI summary
A magnetic field sensor includes a magnetic detection element that includes a magnetic material causing a magnetic impedance effect and a bias coil applying a bias magnetic field to the magnetic material, a high-frequency oscillation circuit that supplies a high-frequency current to the magnetic material, an AC bias circuit that supplies an AC bias current to the bias coil, and a detection circuit that sets a reference point corresponding to an extreme impedance position in a characteristic of the magnetic detection element in the state of no application of an external magnetic field and outputs an electric signal changing in response to an impedance change amount from the reference point. The detection circuit includes an amplitude detection circuit which detects an amplitude of the electric signal at a timing of each vertex in which at least a voltage change direction of the electric signal changes.