Differential Detection Coil Layout for Wireless Power FOD
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Solution Overview
Problem
Existing wireless power transfer systems face inefficiencies and safety hazards due to inadequate detection of foreign metal objects, which can lead to undesired heating and disruption of power transfer, particularly in high-power applications.
Innovation Solution
A detection apparatus using multiple detection coils to measure differential currents during a foreign object detection period, with a control unit generating signals based on impedance changes to accurately identify and locate foreign objects, and dynamically adjusting detection zones to account for misalignment and movement of the power reception apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional detection techniques are used, then device complexity is reduced, but foreign object detection accuracy and reliability are insufficient
Solution Approach 1:
The detection system is divided into multiple independent detection coils arranged in a grid pattern, each coil independently detecting foreign objects in its specific zone. This segmentation allows the system to achieve comprehensive coverage and high detection accuracy without requiring a single complex detection mechanism, as each coil operates independently and can be individually optimized.
Solution Approach 2:
The patent introduces detection coils as intermediary elements between the power transfer coils and the control system. These coils act as sensors that indirectly detect foreign objects through electromagnetic coupling, converting the presence of foreign objects into measurable electrical signals without direct contact or complex mechanical detection mechanisms.
2Reliability
If detection is performed continuously, then foreign object detection reliability is improved, but interference with power transfer increases
Solution Approach 1:
The system performs foreign object detection periodically at predetermined time intervals rather than continuously. The control unit activates detection coils only during these periodic detection cycles, allowing normal power transfer to occur during non-detection periods. This periodic operation maintains detection reliability while minimizing interference with power transfer efficiency.
Solution Approach 2:
The system performs foreign object detection before initiating power transfer and during predetermined intervals throughout the power transfer process. By detecting foreign objects in advance and at regular intervals, the system ensures safety without requiring continuous detection that would constantly interfere with power transfer operations.
3Adaptability or versatility
If detection coil area is increased to cover misalignment, then detection coverage is improved, but device complexity and size increase
Solution Approach 1:
The detection system uses multiple smaller detection coils arranged in a grid pattern rather than a single large detection coil. Each coil covers a specific zone, and together they provide comprehensive coverage that adapts to misalignment between power transfer coils. This segmented approach achieves extended coverage without requiring a single large, complex detection structure.
Solution Approach 2:
The detection coils are arranged in a two-dimensional grid pattern, adding spatial dimensionality to the detection coverage. This multi-dimensional arrangement allows the system to detect foreign objects across a wider area and adapt to misalignment in multiple directions, effectively increasing coverage without simply enlarging a single detection element.
4Measurement precision
If multiple detection coils are used, then foreign object location precision is improved, but device complexity increases
Solution Approach 1:
The detection system divides the detection area into multiple zones, each monitored by a separate detection coil. When a foreign object is detected, the control unit identifies its location by determining which specific coil(s) are affected. This segmentation provides precise location information without requiring a single complex detection mechanism, as the grid arrangement naturally encodes spatial information.
Solution Approach 2:
The system uses identical detection coils repeated in a grid pattern throughout the detection area. Each coil is a copy of the others, simplifying the design and manufacturing process. This replication approach achieves comprehensive coverage and precise location detection without requiring each detection element to be uniquely complex.
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
Enhances the accuracy and speed of foreign object detection, minimizing interference with power transfer and ensuring safe operation by preventing overheating of foreign objects, even in misaligned or high-power scenarios.
Implementation Method 1
when a foreign metal object (such as a key, a coin, a metallic can, or aluminum foil, among other examples) is in proximity of the electromagnetic field, the foreign metal object may be undesirably heated up due to eddy currents
Implementation Method 2
a wireless power transmission apparatus may include a primary coil that produces an electromagnetic field
Implementation Method 3
The wireless power may be transferred using inductive coupling or resonant coupling between a primary coil of the wireless power transmission apparatus and a secondary coil of the wireless power reception apparatus
Implementation Method 4
The wireless power may be transferred using inductive coupling or resonant coupling between a primary coil of the wireless power transmission apparatus and a secondary coil of the wireless power reception apparatus
Data Source
AI summary
This disclosure provides systems, methods and apparatuses for foreign object detection (FOD) in a wireless power transfer (WPT) system. Some implementations relate generally to the use of detection coils that are excited to measure and compare a differential current through a coil pair that includes at least two detection coils. A foreign object may cause a change in impedance for one or more detection coils compared to one or more other detection coils. By detecting the differential current of the coil pair, a detection apparatus may determine that a foreign object is in proximity to one of the detection coils of the coil pair. This disclosure provides several options for the design, construction, layout, and operations of detection coils to improve foreign object detection.