Foreign Object Detection Coils for Wireless Charging Systems
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Solution Overview
Problem
Wireless power transfer systems face inefficiencies and safety concerns due to energy loss and heating caused by foreign objects, particularly small objects like coins and rings, which are not effectively detected by existing methods.
Innovation Solution
The use of smaller foreign object detection coils, often in arrays, that are comparable in size to the foreign objects, along with resonant circuits and adjustable detection distances, allows for precise detection of foreign objects without misidentifying friendly parasitic components, and pre-charging of receiver coils to reduce false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large power transmitter coil is used for wireless power transfer, then power transfer capability is improved, but detection sensitivity for small foreign objects deteriorates
Solution Approach 1:
The system divides the detection function into separate detection coils that are distinct from the power transmitter coil. These detection coils are specifically sized to be comparable to small foreign objects (coins, rings), enabling sensitive detection while the larger power transmitter coil maintains power transfer capability. The detection coils can be arranged in arrays to provide comprehensive coverage.
Solution Approach 2:
Different coils serve different functions with optimized characteristics: the power transmitter coil is sized for maximum power transfer, while separate detection coils are sized specifically for detecting small foreign objects. This local optimization allows each component to perform its specific function effectively without compromising the other.
2Measurement precision
If detection coils are made smaller to detect small foreign objects, then detection sensitivity is improved, but detection distance in the Z-direction deteriorates
Solution Approach 1:
The system compensates for reduced Z-direction detection distance of small coils by using multiple detection coils arranged in arrays across the charging surface. This spatial distribution in the X-Y plane compensates for the limited depth penetration of individual small coils, maintaining comprehensive detection coverage.
3Loss of time
If foreign object detection is performed without pre-charging receiver coils, then detection speed is improved, but false positives from friendly parasitic components increase
Solution Approach 1:
The system performs a pre-charging phase where the receiver coil is charged before foreign object detection begins. This preliminary action ensures that any coupling between the detection coils and the receiver coil is established, allowing the system to distinguish between the receiver (a friendly component) and actual foreign objects. This reduces false positives while maintaining detection speed.
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 enhances the detection sensitivity and accuracy for small foreign objects, reduces false positives, and ensures safe and efficient power transfer by effectively distinguishing between foreign objects and friendly components.
Implementation Method 1
The power is then transferred from the power transmitter coil to a power receiver coil using inductive coupling
Implementation Method 2
The behavior of the resonant circuit is used to identify the presence of foreign objects
Implementation Method 3
The power is then transferred from the power transmitter coil to a power receiver coil using inductive coupling
Implementation Method 4
energy can be lost in the system when the field interacts with metal or electrically conductive parts not configured to power or charge the device... This heating can, in turn, damage the device or pose a threat to the safety of the user
Data Source
AI summary
Methods and systems are described for using detection coils to detect metallic or conductive foreign objects that can interfere with the wireless transfer of power from a power transmitter to a power receiver. In particular, the detection coils are targeted to foreign objects that are smaller than a power transmitter coil in the power transmitter.