Wireless Power Transmitter Foreign Object Detection via Receiver Response Analysis
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in reliably distinguishing between foreign object detection and coil misalignment, leading to unnecessary power transfer interruptions.
Innovation Solution
The system employs a calibration method where the transmitter changes power levels and records receiver responses for different coil alignment conditions, allowing it to differentiate between foreign object presence and misalignment by matching recorded responses during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional FOD methods monitor WPT parameters such as transmitted power or coil coupling coefficient, then foreign object detection capability is provided, but coil misalignment is mistakenly detected as foreign object presence causing unnecessary power transfer interruptions
Solution Approach 1:
The system performs preliminary calibration by sending calibration signals at different power levels and storing the receiver's responses before actual power transfer begins. This pre-established baseline of normal operation patterns enables the system to distinguish between misalignment and foreign object presence during actual operation, preventing false detections and unnecessary interruptions.
Solution Approach 2:
The system periodically sends test signals at varying power levels during operation to compare against stored calibration responses. This periodic verification allows continuous monitoring of the magnetic coupling environment while maintaining power transfer, enabling detection of foreign objects without causing unnecessary interruptions due to transient misalignments.
2Reliability
If the transmitter changes transmitted power and measures receiver response for foreign object detection, then foreign object detection is enabled, but the system cannot distinguish between receiver response due to foreign object and receiver response due to coil misalignment
Solution Approach 1:
The system changes the power level parameter of transmitted signals during calibration and operation. By sending calibration signals at different power levels and storing the corresponding receiver responses, the system creates a pattern baseline that accounts for power-level-dependent behavior. During operation, comparing actual responses against this power-level-aware baseline enables distinction between foreign object presence and misalignment without requiring complex additional sensors.
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 reduces false positives in foreign object detection, maintaining power transfer efficiency and preventing unnecessary interruptions due to coil misalignment.
Implementation Method 1
a transmitter driving a transmit coil to produce a time-varying magnetic field, and a receiver with a receive coil placed proximate to the transmit coil
Implementation Method 2
The receive coil receives the wireless power generated by the transmit coil and uses that received power to drive a load
Implementation Method 3
an electrically conductive (e.g. metallic) foreign object—such as a coin, a key, a paper clip, a screw, a tinfoil, etc.—located proximate to the transmit and receive coils to absorb a significant part of the transmitted magnetic energy
Implementation Method 4
the foreign object (FO) can be heated by the absorbed energy, creating fire or other hazards
Data Source
AI summary
A wireless power transmitter pulses the transmit power level unresponsively to the wireless power receiver's power requests in order to perform foreign object detection (FOD). The FOD is performed by the transmitter analyzing the receiver's responses to the pulsed power. Some embodiments avoid mistaking FOD for coil misalignment. Other features are also provided.