Circular Vertical Hall Element Circuit for Offset Reduction
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Solution Overview
Problem
Existing magnetic field sensors, particularly those using Circular Vertical Hall (CVH) elements, suffer from offset components that reduce accuracy and speed of angle measurement, especially due to varying offset voltages among different magnetic field sensing elements and temperature influences.
Innovation Solution
The proposed solution involves processing output signals from CVH sensing elements or separate magnetic field sensing elements using circuits that combine and sequence the signals to reduce offset components, employing techniques such as current spinning and differential amplification to enhance measurement speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple vertical Hall elements are used to improve angular accuracy, then measurement precision is improved, but offset voltage variations among elements reduce accuracy
Solution Approach 1:
The patent combines multiple vertical Hall elements into a single integrated sensor structure where the elements are arranged in a specific geometric configuration (e.g., triangular, square, or circular patterns). By merging the elements and using common electrical connections, the patent achieves both improved angular accuracy through multiple sensing points and reduced offset voltage impact through differential measurement techniques.
Solution Approach 2:
The patent changes the operational parameters by implementing current spinning techniques where the current direction is periodically reversed through the Hall elements. This parameter change allows for differential measurements that cancel out offset voltage components while maintaining the sensitivity benefits of multiple Hall elements.
2Measurement precision
If offset components are reduced through signal processing, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the signal processing into distinct functional blocks: current spinning circuitry that periodically reverses current direction, differential amplification stages that subtract offset components, and angle calculation units that process the cleaned signals. This segmentation makes the complex processing manageable while maintaining accuracy.
Solution Approach 2:
The patent employs periodic current spinning where the current direction through Hall elements is reversed at regular intervals. This periodic action enables the extraction of offset voltage components through temporal averaging and differential processing, reducing their impact on measurement accuracy without requiring continuous complex processing.
3Measurement precision
If current spinning is used to reduce offset voltage, then measurement accuracy is improved, but speed of measurement may be reduced
Solution Approach 1:
The patent maintains continuous measurement capability by overlapping current spinning cycles with angle calculation operations. While current is being spun through the Hall elements, preliminary angle calculations can be performed on previously acquired data, ensuring that the measurement process continues without interruption despite the periodic current reversal.
Solution Approach 2:
The patent performs preliminary signal conditioning and offset compensation during the current spinning process itself. By preparing the signals in advance through differential amplification and filtering while the current is being spun, the system reduces the processing time needed for final angle calculation, thereby maintaining high measurement speed.
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 approach improves the measurement of angles at high speed by minimizing offset errors and enhancing angular accuracy, even in the presence of temperature variations and other environmental factors.
Implementation Method 1
A vertical Hall element tends to be responsive to magnetic field parallel to a surface of a substrate on which the vertical Hall element is formed
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
A magnetic field sensor can be based upon three element vertical Hall element building blocks, e.g., three element or six element vertical Hall element arrangements, all arranged in a circle. In some embodiments, the circle of vertical Hall elements can be arranged as a CVH sensing element.