Motor Rotor Position Sensor Ground Layout Against EMI and ESD
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Solution Overview
Problem
Magnetic elements in motor sensors are vulnerable to electromagnetic interference (EMI) and electrostatic discharge (ESD), leading to potential failure during testing.
Innovation Solution
A ground pattern corresponding to a Hall integrated circuit (IC) is formed on a substrate to reduce the likelihood of EMI and ESD failures, with separate ground patterns for Hall and encoder signal magnetic elements positioned strategically on the substrate to enhance electromagnetic interference protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If magnetic elements are mounted on a printed circuit board and disposed in a housing of the motor, then the sensor structure is compact and integrated, but the magnetic elements become vulnerable to electromagnetic interference (EMI) and electrostatic discharge (ESD)
Solution Approach 1:
The patent divides the ground connection system into multiple separate ground patterns (first ground pattern and second ground pattern) on the printed circuit board. The first ground pattern is electrically connected to the Hall signal magnetic element while the second ground pattern is electrically connected to the encoder signal magnetic element. This segmentation isolates the ground paths for different magnetic elements, preventing electromagnetic interference from affecting both elements simultaneously and reducing ESD damage propagation.
2Area of stationary object
If multiple magnetic elements are disposed close to each other on the substrate to reduce space, then the sensor size is minimized, but electromagnetic interference between elements increases
Solution Approach 1:
The patent implements separate ground patterns for different magnetic elements. The first ground pattern serves the Hall signal magnetic element while the second ground pattern serves the encoder signal magnetic element. This ground segmentation creates electrical isolation between the elements, allowing them to be positioned close together on the compact substrate without experiencing mutual electromagnetic interference.
Solution Approach 2:
The patent provides each magnetic element with its own dedicated ground connection pattern tailored to its specific requirements. The first ground pattern is optimized for the Hall signal magnetic element's location and electrical characteristics, while the second ground pattern is optimized for the encoder signal magnetic element. This localized ground design ensures each element has appropriate electromagnetic shielding and reference potential despite close proximity to other elements.
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 the risk of EMI and ESD failures, enhancing the reliability of motor sensors and improving their operational stability.
Implementation Method 1
a Hall signal magnetic element mounted on the substrate, and configured to detect a change in magnetic flux of the sensing magnet assembly
Implementation Method 2
an encoder signal magnetic element mounted on the substrate, and configured to detect a change in magnetic flux of the sensing magnet assembly
Data Source
AI summary
A rotor position detecting apparatus includes a rotor, a stator disposed in correspondence with the rotor and a sensing assembly disposed at one side of the rotor. The sensing assembly includes a substrate, a first magnetic element part and a second magnetic element part disposed on the substrate and a first ground pattern and a second ground pattern disposed on the substrate. The first ground pattern is electrically connected to the first magnetic element part. The second ground pattern is electrically connected to the second magnetic element part, and the first ground pattern is electrically disconnected from the second ground pattern.