Foreign Object Detection in Wireless Power Transfer Systems
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Solution Overview
Problem
Wireless power transfer systems face inefficiency and potential foreign object detection failures due to early Q-factor measurements when devices are brought into proximity, leading to erroneous enablement of power transfer despite the presence of foreign objects.
Innovation Solution
Implementing a method that performs a plurality of Q-factor or self-resonant frequency measurements at different times, analyzing these measurements to determine a minimum, average, or median value, and using a variable threshold based on expected transmitter-receiver pair characteristics to reliably detect foreign objects before initiating power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Q-factor measurements are performed early when devices are brought into proximity, then power transfer can be enabled quickly, but foreign object detection accuracy deteriorates leading to erroneous enablement
Solution Approach 1:
The system performs multiple preliminary Q-factor measurements at different power levels before finalizing the foreign object detection result. Initial measurements are taken at low power levels, then additional measurements are performed at higher power levels to confirm the absence of foreign objects, ensuring accurate detection before enabling power transfer.
Solution Approach 2:
The measurement process is made dynamic by adjusting power levels adaptively. The system starts with low power measurements and progressively increases power levels based on initial results. This dynamic approach allows the system to balance between quick detection and accurate foreign object identification, resolving the contradiction between speed and precision.
2Measurement precision
If multiple FOD measurements are performed at different times, then foreign object detection accuracy is improved, but measurement time and system complexity increase
Solution Approach 1:
The system performs a minimum required number of measurements (partial action) to achieve sufficient detection accuracy without unnecessary additional measurements. By determining when enough measurements have been taken to confidently detect or rule out foreign objects, the system avoids excessive measurement time while maintaining adequate precision.
Solution Approach 2:
Measurements are performed periodically at different power levels rather than continuously. The system takes measurements at structured intervals (initial low power, then higher power levels), which reduces total measurement time compared to continuous monitoring while still achieving accurate foreign object detection through strategic sampling.
3Device complexity
If a fixed threshold is used for FOD measurements, then the detection process is simple, but adaptability to different transmitter-receiver pairs deteriorates
Solution Approach 1:
The threshold is made dynamic and adaptive rather than fixed. The system determines appropriate thresholds based on characteristics of the specific transmitter-receiver pair being measured, including their coupling conditions and baseline Q-factor values. This adaptive thresholding maintains detection simplicity while significantly improving adaptability across different device combinations.
Solution Approach 2:
The detection threshold parameter is changed adaptively based on measured system characteristics. Instead of using a single fixed threshold value, the system adjusts the threshold according to the specific transmitter-receiver pair's performance characteristics, enabling versatile detection across different devices while keeping the detection process relatively simple through parameter adaptation.
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 ensures accurate foreign object detection, preventing power transfer when foreign objects are present and optimizing efficiency by avoiding early measurements that might miss foreign objects, thus enhancing the reliability and safety of wireless power transfer.
Implementation Method 1
The plurality of FOD measurements may be Q-factor measurements or self-resonant frequency measurements
Implementation Method 2
The plurality of FOD measurements may be Q-factor measurements or self-resonant frequency measurements
Implementation Method 3
magnetic induction (MI) systems
Implementation Method 4
magnetic resonance (MR) systems
Data Source
AI summary
Methods, apparatus and computer-readable storage media for performing foreign object detection (FOD) in a wireless power transfer system. A plurality of FOD measurements may be performed and processed to perform FOD.