Hall Sensor Offset Cancellation via Asymmetric Spinning Current
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Solution Overview
Problem
Current Hall electromotive force signal detection circuits face challenges in achieving high accuracy and fast responsiveness due to spike error signals and offset cancellation issues, particularly in continuous-time signal processing systems, where the order and sequence of selecting terminal pairs for applying drive currents in the spinning current method affect the extent of spike error occurrence.
Innovation Solution
A Hall electromotive force signal detection circuit is designed with two or more Hall elements, each with four terminals, where the switching circuits select different terminal pairs for applying drive currents based on a two-phase chopper clock, allowing for simultaneous addition of Hall electromotive force signals from each element to reduce spike errors and effectively cancel offset voltages, considering the impurity concentration distribution in each Hall element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the spinning current method is used to cancel offset voltage in a Hall element, then offset cancellation is achieved, but spike error signals occur due to switching operations
Solution Approach 1:
The patent divides the Hall element into multiple segments (first Hall element and second Hall element) and applies different switching sequences to each segment. The first Hall element switches terminal pairs in one sequence while the second Hall element switches in a different sequence, allowing the spike errors from each segment to cancel each other out when their outputs are combined, thereby reducing overall spike error signals while maintaining offset cancellation capability
Solution Approach 2:
The patent introduces asymmetry in the switching sequences between the two Hall elements. The first Hall element uses a specific terminal pair switching sequence while the second Hall element uses a different sequence, creating asymmetric switching patterns that generate complementary spike errors. When these asymmetric outputs are combined, the spike errors cancel each other while the useful Hall signals are preserved
2Device complexity
If discrete-time signal processing is used, then sampling is simplified, but folding noise occurs due to discrete-time processing
Solution Approach 1:
The patent employs continuous-time signal processing circuits instead of discrete-time processing. The signal processing maintains continuity from the Hall element output through the switching circuits to the final output, avoiding sampling operations that would cause folding noise. This continuous processing approach preserves signal quality while still enabling the spinning current method for offset cancellation
3Object-generated harmful factors
If the terminal pair switching sequence is optimized to reduce spike errors, then spike error reduction is achieved, but the switching complexity increases
Solution Approach 1:
The patent combines the outputs of two Hall elements with different switching sequences to achieve spike error cancellation. By merging the output signals from the first Hall element and second Hall element, the beneficial spike error cancellation effect is obtained while the switching circuits themselves remain relatively simple, avoiding the need for complex switching sequences in a single Hall element
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 configuration significantly reduces spike error signals, enabling high-accuracy and fast offset cancellation, suitable for continuous-time signal processing, and enhances the responsiveness of magnetic sensors like current sensors for inverter applications.
Implementation Method 1
A magnetic sensor using a Hall element is not only used in a proximity sensor, a linear position sensor, a rotation angle sensor, and the like as a sensor for detecting position information of a magnet, but also widely used in a current sensor for detecting a magnetic field induced by a current flowing through a current conductor
Data Source
AI summary
A Hall electromotive force signal detection circuit combines offset cancellation means by a spinning current method of a Hall element with a continuous-time signal processing circuit. A Hall element includes first to fourth terminals, and generates a Hall electromotive force signal voltage Vhall1. Another Hall element generates another Hall electromotive force signal voltage Vhall2. A first switching circuit selects a terminal position for applying a drive current from the four terminals of the Hall element. A second switching circuit selects a terminal position for applying a drive current from the four terminals of the another Hall element, which is different from the terminal position selected by the first switching circuit. A chopper clock generation circuit supplies a chopper clock signal φ1, φ2 having two different phases to the switching circuit, and also supplies the chopper clock signal φ1, φ2 to the first and second switching circuits.