Asymmetric Dual-Channel Current Sensor for Interference Cancellation
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Solution Overview
Problem
Conventional current sensors face challenges in accurately detecting current in multiple pathways due to mutual interference of magnetic flux, especially in miniaturized inverter control systems for three-phase motors, where magnetic shielding is difficult and dual-channel sensors are ineffective.
Innovation Solution
A current sensor design featuring pairs of magnetic sensors arranged at equal distances from each current pathway, with a signal processor generating signals based on the differences between the outputs of opposing sensors to cancel out mutual interference, allowing for accurate current detection in multiple channels without the need for magnetic shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic shielding is introduced to reduce mutual interference between multiple current pathways, then measurement precision is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent applies asymmetry by positioning magnetic sensors at different distances from current pathways. Specifically, the first magnetic sensor is positioned at a first distance from the first current pathway, while the second magnetic sensor is positioned at a second distance from the second current pathway, where these distances are intentionally made asymmetric to differentiate and eliminate mutual interference effects through differential measurement
Solution Approach 2:
The patent uses the difference in magnetic flux detection between two asymmetrically positioned sensors as an intermediary mechanism. By calculating the difference between the first magnetic flux detected by the first sensor and the second magnetic flux detected by the second sensor, the system creates a differential measurement that acts as an intermediary to cancel out mutual interference from adjacent current pathways
2Measurement precision
If magnetic sensors are arranged at fixed intervals to avoid mutual interference, then measurement precision is maintained, but the space reserved for current detection increases
Solution Approach 1:
The patent transitions from a single-dimensional arrangement where sensors are placed at fixed intervals along a line, to a two-dimensional asymmetric arrangement where sensors are positioned at different distances and lateral positions relative to current pathways. This dimensional change allows for more flexible space utilization while maintaining measurement precision through differential measurement
3Volume of moving object
If coreless current sensors are used to achieve miniaturization, then device volume is reduced, but the ability to apply magnetic shielding and reduce external magnetic field effects is weakened
Solution Approach 1:
The patent employs differential measurement as an intermediary mechanism that cancels out external magnetic field interference. By calculating the difference between magnetic flux detected by two asymmetrically positioned sensors, the system creates a measurement process that inherently rejects common-mode external magnetic field effects, compensating for the lack of magnetic shielding in coreless sensor design
4Volume of moving object
If dual-channel sensors are used to realize further miniaturization, then device volume is reduced, but magnetic flux from one current pathway affects the magnetic sensor of the other channel
Solution Approach 1:
The patent applies asymmetry in the dual-channel sensor design by positioning the first magnetic sensor at a first distance from the first current pathway and the second magnetic sensor at a second distance from the second current pathway. This asymmetric positioning, combined with differential measurement, allows the compact dual-channel structure to reject mutual interference and maintain high measurement precision
Solution Approach 2:
The differential measurement process serves as an intermediary mechanism that eliminates mutual interference between channels. By calculating the difference between the first magnetic flux and the second magnetic flux, the system creates a measurement process that cancels out the magnetic flux from adjacent current pathways, enabling accurate measurement in the compact dual-channel configuration
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 design effectively reduces mutual interference of magnetic flux, enabling accurate current detection in multiple pathways, even in compact configurations, thereby improving the precision and miniaturization of current sensors.
Implementation Method 1
a magnetic sensor, for example, and outputs a signal whose magnitude is proportional to a magnetic field produced by current flowing through a conductor
Data Source
AI summary
A current sensor includes a first current pathway, a first magnetic sensor arranged near the first current pathway, a second magnetic sensor arranged opposite the first magnetic sensor with the first current pathway in between, a second current pathway, a third magnetic sensor arranged near the second current pathway, a fourth magnetic sensor arranged opposite the third magnetic sensor with the second current pathway in between, and a signal processor that generates a signal based on a quantity of the first measured current from output of the first magnetic sensor and output of the second magnetic sensor, and also generates a signal based on a quantity of the second measured current from output of the third magnetic sensor and output of the fourth magnetic sensor.