Sensor Device Stray Field Suppression Using Pixel Cell Segmentation
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Solution Overview
Problem
Existing sensor devices for determining rotation angles of shafts are limited in accuracy and are susceptible to magnetic stray fields, such as those from the Earth's magnetic field or power cables in electric/hybrid vehicles, which can interfere with the measurement.
Innovation Solution
A sensor device with a semiconductor body and integrated pixel cells equipped with magnetic field sensors in the x, y, and z directions, utilizing a quadrupole magnet arrangement with four magnetic poles to detect rotation angles by processing signal differences between pixel cells, and suppressing stray fields with dual magnetic field sensors in orthogonal directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single magnetic field sensor is used to detect rotation angle, then the device structure is simple, but the measurement precision is reduced and the device becomes susceptible to magnetic stray fields
Solution Approach 1:
The sensor device is divided into multiple pixel cells (first and second pixel cells) with each containing magnetic field sensors oriented in different directions. This segmentation allows independent detection of magnetic field components in x and y directions, enabling suppression of stray fields while maintaining measurement precision for rotation angle detection.
Solution Approach 2:
Different magnetic field sensors within the pixel cells are oriented in specific local directions (x-direction and y-direction) to detect specific magnetic field components. This local orientation strategy enables the device to distinguish between the magnetic field signal from the magnet and stray fields from external sources like the Earth's magnetic field or power cables.
2Measurement precision
If pixel cells are placed close together to reduce device size, then the device complexity is reduced, but the measurement precision of rotation angle determination is lowered
Solution Approach 1:
The patent introduces a spatial dimension by arranging pixel cells at different positions along the connecting line and orienting magnetic field sensors in multiple directions (x, y, and z components through vector sum). This dimensional approach allows accurate rotation angle determination even with increased distance between pixel cells, as the system utilizes the spatial relationship and directional information from multiple sensors.
3Measurement precision
If the distance between pixel cells is increased to enhance accuracy, then the measurement precision improves, but the device complexity and size increase
Solution Approach 1:
The magnetic field sensors in each pixel cell serve multiple functions: detecting the magnetic field component in their specific direction, contributing to the vector sum for rotation angle calculation, and providing data for stray field suppression. This multi-functionality allows the system to achieve high measurement precision with appropriate pixel cell spacing without unnecessary complexity.
4Reliability
If dual magnetic field sensors in orthogonal directions are implemented to suppress stray fields, then the reliability improves, but the device complexity increases
Solution Approach 1:
The patent merges multiple magnetic field sensors (first and second magnetic field sensors in each pixel cell) into integrated pixel cells that work together as a unified detection system. The sensors are combined through signal processing that calculates vector sums and differences, enabling simultaneous detection of rotation angle and suppression of stray fields from the Earth's magnetic field or power cables.
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 device accurately determines rotation angles of both stationary and rotating shafts, enhancing accuracy with increased distance between pixel cells and effectively suppresses magnetic DC field components, facilitating easier engine startup and precise position determination in automotive systems.
Implementation Method 1
each pixel cell has a first magnetic field sensor and a second magnetic field sensor, and whereby the first magnetic field sensor detects a magnetic field in the x-direction and the second magnetic field sensor a magnetic field in the y-direction
Implementation Method 2
A permanent magnet whose magnetic flux penetrates the sensor is arranged adjacent to the package
Data Source
AI summary
A sensor device for suppressing a magnetic stray field, having a semiconductor body, a first pixel cell and a second pixel cell integrated into a surface of the semiconductor body together with a circuit arrangement. Each pixel cell has a first magnetic field sensor and a second magnetic field sensor to detect a magnetic field in the x-direction and a magnetic field in the y-direction. The first pixel cell is spaced apart from the second pixel cell along a connecting line, and the substrate and the semiconductor body are disposed in the same IC package. A magnet is provided that has a planar main extension surface in the direction of an x-y plane and has a magnetization with four magnetic poles in the direction of the x-y plane. The IC package is spaced apart from the main extension surface of the magnet in the z-direction and at least partially within a ring magnet.