Circular Vertical Hall Sensor DC Offset Reduction
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Solution Overview
Problem
Magnetic field sensors, particularly circular vertical Hall (CVH) sensing elements, face challenges with DC offsets from multiple vertical Hall elements, leading to reduced accuracy in measuring the angle of rotation and speed of a target object.
Innovation Solution
A magnetic field sensor design that includes a circular vertical Hall sensing element with a sequence switch circuit to sequentially select and generate sequenced signal steps from multiple vertical Hall elements, using first and second current sources to provide current signals to these elements, and an amplifier circuit to generate an amplified signal, thereby reducing DC offsets and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple vertical Hall elements are used to sense magnetic field direction, then the sensing coverage and measurement capability are improved, but DC offsets from each element accumulate and reduce measurement accuracy
Solution Approach 1:
The patent segments the sensing function by using multiple vertical Hall elements arranged in a circular pattern, where each element senses magnetic field in a specific angular sector. This segmentation allows comprehensive 360-degree coverage while enabling individual processing of signals from each element to manage and cancel DC offsets systematically
Solution Approach 2:
The patent implements feedback by measuring the DC offset from each vertical Hall element and using this information to compensate for the offset in subsequent measurements. The system continuously monitors and adjusts for offset errors, feeding the offset information back into the signal processing to improve measurement accuracy over time
2Measurement precision
If DC offset compensation techniques are applied, then measurement accuracy is improved, but device complexity increases due to additional circuits and processing
Solution Approach 1:
The patent extracts the DC offset component from the total signal output by each vertical Hall element through sequential measurement techniques. By separating and identifying the offset portion independently from the useful magnetic field signal, the system can remove or compensate for the offset without requiring complex real-time processing circuits
Solution Approach 2:
The patent performs preliminary measurement of DC offsets from each Hall element before actual magnetic field sensing operations. By characterizing and storing offset values in advance, the system prepares compensation data that simplifies subsequent measurement processes and reduces the complexity of real-time offset correction circuits
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 effectively reduces DC offsets and enhances the accuracy of the magnetic field sensor's output signals, providing a more precise representation of the angle of rotation and speed of a target object.
Implementation Method 1
A magnetic field sensing element can be used to detect a direction of a magnetic field... One type of current sensor uses a Hall Effect magnetic field sensing element... A vertical Hall element tends to be responsive to magnetic field parallel to a surface of a substrate
Data Source
AI summary
A magnetic field sensor includes a circular vertical Hall (CVH) sensing element comprising a plurality of vertical Hall elements, each one of the plurality of vertical hall elements comprising respective first and second current receiving contacts. The magnetic field sensor additionally includes a sequence switches circuit coupled to the plurality of vertical Hall elements. The magnetic field sensor also includes a first current source sequentially coupled by the sequence switches circuit to the first current receiving contact of sequentially selected ones of the plurality of vertical Hall elements. The magnetic field sensor further includes a second current source sequentially coupled by the sequence switches circuit to the second current receiving contact of the sequentially selected ones of the plurality of vertical Hall elements. The first and second current sources can swap couplings in half-period intervals for each of a plurality of coupling arrangements. A corresponding method is also described.