Magnetic Switch Asymmetric Hysteresis Offset Compensation
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Solution Overview
Problem
Conventional two-way drive spinning current methods in magnetic switches fail to achieve a satisfactory symmetric property of magnetoelectric conversion characteristics due to asymmetric offset voltages, leading to fluctuations in rotation speed and vibrations in brushless DC motors, and variations in magnetic detection distance.
Innovation Solution
A semiconductor device with a magnetic switch that includes a Hall element and a control circuit to alternate the direction of drive current based on a latch output signal, ensuring symmetric magnetoelectric conversion characteristics by selecting appropriate switch configurations and reference voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional two-way drive spinning current method is used, then processing time is reduced compared to four-way drive method, but the symmetric property of magnetoelectric conversion characteristic deteriorates due to asymmetric offset voltages
Solution Approach 1:
The patent applies asymmetry principle by intentionally introducing asymmetric hysteresis characteristics through the control circuit to compensate for the asymmetric offset voltages. The control circuit generates different hysteresis widths for S-pole and N-pole detection, creating a controlled asymmetry that counteracts the unwanted asymmetry from offset voltages, thereby achieving line-symmetric magnetoelectric conversion characteristics.
Solution Approach 2:
The patent changes the hysteresis width parameter dynamically based on the detection pole type. The control circuit adjusts the hysteresis width to be wider for S-pole detection and narrower for N-pole detection (or vice versa depending on offset polarity), thereby compensating for asymmetric offset voltages and achieving symmetric overall detection characteristics while maintaining fast processing speed.
2Reliability
If hysteresis width is increased to prevent output signal chattering, then reliability of output signal improves, but detection precision deteriorates due to shift in operating point and returning point
Solution Approach 1:
The patent applies dynamics principle by making the hysteresis width adjustable and adaptive. The control circuit dynamically changes the hysteresis width based on the detected pole type (S-pole or N-pole), allowing the system to have wider hysteresis for noise immunity during pole transitions and narrower hysteresis for precise detection, thereby resolving the contradiction between reliability and precision.
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 stabilizes the symmetric property of magnetoelectric conversion characteristics, reducing residual offset voltage influence and achieving line-symmetric hysteresis characteristics, thus improving detection accuracy and reducing power consumption compared to four-way drive methods.
Implementation Method 1
A Hall element is used for various applications as a magnetic sensor because the Hall element can detect a position and an angle in a non-contact manner.
Data Source
AI summary
The semiconductor device includes a magnetic switch provided to a semiconductor substrate. The magnetic switch includes: a horizontal Hall element including first electrodes and second electrodes arranged at positions perpendicular to the first electrodes; a switch circuit configured to select a drive current direction of the Hall element from four directions; an SH comparator configured to alternately perform a first operation for sampling a signal transmitted from the Hall element and a second operation for sending a signal which is based on a result of comparing a value of the sampled signal and a reference value; a latch circuit configured to hold this sent signal and send the held signal as a latch output signal; and a control circuit configured to select the drive current direction in each of a period for the first operation and a period for the second operation based on the latch output signal.