Foreign Object Detection Coils for Wireless Power Transfer
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Solution Overview
Problem
Existing contactless electric power transfer systems struggle to detect relatively small foreign objects between power transmission and reception devices due to the size of the coils used for Q factor measurement, which affects the detection accuracy, especially in high-power applications.
Innovation Solution
The implementation of a foreign object detector with a set of smaller first and second coils arranged in a matrix above or below the power transmission or reception coils, allowing for reduced size and enhanced detection capabilities, including a switching device to determine the presence of foreign objects based on power receiving states and resonant frequency management to suppress induced voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power feeding coil is used as the coil for Q factor measurement or a coil of similar size is provided separately, then the power transmission capability is maintained, but the ability to detect relatively small foreign objects deteriorates
Solution Approach 1:
The patent divides the detection function into multiple small coils (first and second coils) arranged in a matrix pattern, rather than using a single large coil. This segmentation allows each small coil to detect small foreign objects effectively while maintaining overall detection coverage through the distributed array
Solution Approach 2:
The patent employs coils of different sizes for different functions: large power feeding coils for power transmission and small detection coils for foreign object detection. Each coil size is optimized for its specific function, allowing simultaneous achievement of high power transmission capability and small foreign object detection accuracy
2Measurement precision
If smaller coils are used for foreign object detection, then the detection accuracy for small foreign objects improves, but the coils become more vulnerable to breakage and contamination
Solution Approach 1:
The patent places the small detection coils inside the housing of the power transmission device, nesting them within the protective structure. This arrangement protects the fragile small coils from external damage and contamination while maintaining their detection functionality
Solution Approach 2:
The patent introduces a housing as an intermediary protective structure between the small detection coils and the external environment. This housing shields the coils from breakage and contamination risks while allowing the detection function to operate effectively
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
Enables the detection of small foreign objects by reducing the size of the coils and improving detection accuracy, while protecting them from breakage and contamination, and suppressing the effect of the magnetic field on the foreign object detector.
Implementation Method 1
a power transmission coil configured to transmit electric power to a power reception coil of the power reception device in a contactless manner
Implementation Method 2
This detection device detects a metallic foreign object present between the power transmission device and the power reception device based on a change in Q factor of a resonant circuit including a coil
Data Source
AI summary
A foreign object detector includes a plurality of first coils and a plurality of second coils. The plurality of first coils are arranged along an upper surface of a power transmission coil. The plurality of second coils are provided to correspond to the plurality of first coils, with the second coils each being arranged to face a corresponding one of the first coils. An outer shape of each of the plurality of first coils and each of the plurality of second coils is smaller than an outer shape of the power transmission coil when the power transmission coil is viewed two-dimensionally from above the power transmission coil.