Foreign Object Sensor Array With Decoupled Resonant Cells
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Solution Overview
Problem
Existing foreign object detection systems for wireless power transfer systems face challenges in maintaining detection accuracy while reducing hardware costs, particularly due to cross-talk between detection cells and increased hardware effort with larger detection arrays.
Innovation Solution
The implementation of a sensor arrangement with decoupling elements connected in series to each resonant tank, allowing for separate stimulation and evaluation of each detection cell using a common power source and evaluation unit, along with a stimulus circuit and measurement unit for determining time response data to detect foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multitude of detection cells are used to increase detection area and sensitivity, then detection accuracy is improved, but hardware complexity and cost increase due to more leads and selection switches
Solution Approach 1:
The patent combines multiple detection cells into groups that share common input and output leads. By arranging detection cells in a matrix configuration where rows share common output leads and columns share common input leads, the system reduces the total number of leads from N individual leads to M+N leads for N detection cells, significantly reducing hardware complexity while maintaining detection accuracy
Solution Approach 2:
The patent makes leads and selection circuits serve multiple functions by having them shared across multiple detection cells. The same input leads and output leads are used to connect multiple detection cells, and the selection circuits can selectively activate any detection cell within the group, making the hardware resources universal and multi-functional rather than dedicated to single cells
2Device complexity
If detection cells are connected in parallel to reduce hardware effort, then hardware complexity is reduced, but cross-talk between detection cells increases reducing detection accuracy
Solution Approach 1:
The patent segments the detection cell array into row groups and column groups, where each detection cell is uniquely identified by the intersection of a specific row and column. This segmentation allows independent addressing of each detection cell through the combination of row selection and column selection, enabling parallel connection of multiple cells while preventing cross-talk through selective activation
Solution Approach 2:
The patent introduces selection circuits as intermediary components between the control system and the detection cells. These selection circuits act as mediators that selectively connect the common leads to specific detection cells, allowing multiple cells to be connected to the same leads without causing cross-talk, as only one cell is connected at a time through the switching action of the selection circuits
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 approach achieves high detection accuracy with reduced hardware effort by minimizing parasite currents and cross-talk, enabling efficient detection of foreign objects with fewer selection switches and leads, thus lowering overall hardware requirements.
Implementation Method 1
Each detection cell comprises a sense coil and a capacitive element, forming a resonant tank
Implementation Method 2
Inductive sensors are more commonly used, because they are robust against environmental influences such as dirt and provide precise results in the near range at the same time. One kind of inductive sensors detects the reduction of the inductance of a coil due to induced eddy currents in the object to be detected
Implementation Method 3
at least one detection cell includes a decoupling element connected in series to its resonant tank
Data Source
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AI summary
The invention relates to a sensor arrangement (140) for a foreign object detection device which includes a current input (142) and a current output (143), a multitude of detection cells (144.1 - 144.9), each comprising a sense coil and a capacitive element, forming a resonant tank. The sensor arrangement (140) further has a multitude of inputs leads (148a-148c) and a multitude of output leads (150a - 150c), the total number of input and output leads being equal or smaller than the number of detection cells (144.1 - 144.9). Each detection cell is connected between one of the input leads (148a - 148c) and one of the output leads (150a-150c), in a way that each of the detection cells (144.1 - 144.9) is connected to a different pair of input and output leads (148a - 148c, 150a - 150c). An input selection circuit (152) allows to selectively establish an electrical connection between the current input (142) and one or more of the input leads (148a - 148c) and an output selection circuit to (153) selectively establish an electrical connection between one or more of the output leads (150a - 150c) and the current output (143). According to the invention at least one detection cell (144.1 - 144.9) includes a decoupling element (D1 - D9) connected in series to its resonant tank. The invention further relates to foreign object detection device for a wireless power transfer system, a primary part of a wireless power transfer system, a wireless power transfer system and a method for detecting a foreign object.