Wireless Power Transmitter Foreign Object Detection
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Solution Overview
Problem
Current foreign object detection methods in wireless power transfer systems, such as those based on the Qi specification, face challenges in achieving accurate detection due to uncertainties in operating conditions and the influence of friendly metals, leading to suboptimal performance with high false detection rates and missed detections.
Innovation Solution
A power transmitter system that incorporates a test coil and a driver to generate an electromagnetic test signal during a dedicated foreign object detection time interval, with parameters adjusted based on messages from the power receiver to improve detection accuracy and reliability, allowing for a more controlled and predictable foreign object detection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If foreign object detection is performed using conventional methods during power transfer, then safety is improved, but detection accuracy deteriorates due to high false detection rates and missed detections caused by uncertainties in operating conditions and friendly metal influence
Solution Approach 1:
The system performs foreign object detection during an initialization phase before actual power transfer begins. This preliminary detection allows the system to identify foreign objects when the electromagnetic field conditions are more stable and predictable, avoiding the interference and uncertainties that arise during active power transfer operations
Solution Approach 2:
The system adjusts electromagnetic field parameters during the initialization phase to optimize foreign object detection. By controlling the field strength and characteristics before power transfer commences, the system can achieve more accurate detection measurements without the variability introduced by dynamic power transfer conditions
2Device complexity
If the power transmitter uses a simple detection method, then device complexity is reduced, but detection reliability deteriorates due to suboptimal performance under varying operating conditions
Solution Approach 1:
The system performs foreign object detection during an initialization phase before actual power transfer begins. This preliminary detection allows the system to identify foreign objects when the electromagnetic field conditions are more stable and predictable, avoiding the interference and uncertainties that arise during active power transfer operations
Solution Approach 2:
The system uses feedback from the power receiver about operating conditions to adjust and optimize foreign object detection parameters. This feedback mechanism allows the detection system to adapt to specific operational contexts, improving reliability without requiring a fundamentally complex detection architecture
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 accuracy and reliability of foreign object detection, reducing false and missed detections by adapting the test signal parameters to account for specific power receiver properties and operating conditions, thereby improving the overall performance of the wireless power transfer system.
Implementation Method 1
power is inductively transferred from a transmitter inductor in a power transmitter device to a receiver coil in the individual devices
Implementation Method 2
a test coil for generating an electromagnetic test signal; a test generator arranged to generate a test drive signal for the test coil to provide the electromagnetic test signal
Implementation Method 3
the magnetic flux generated by the transmitter coil will introduce eddy currents in the metal objects which will cause the objects to heat up
Data Source
AI summary
A power transmitter (101) for a wireless power transfer system comprises a transmitter coil (103) and a driver (201) generates a drive signal for the transmitter coil (103) employing a repeating time frame with a power transfer time interval and a foreign object detection time interval. A test generator (211) generates a test drive signal for a test coil (209) during the foreign object detection time interval. A foreign object detector (207) performs a foreign object detection test based on a measured parameter for the test drive signal. Prior to entering a power transfer phase, an adapter (213) controls the power transmitter (101) to operate in a foreign object detection initialization mode in which a preferred value of a signal parameter for the test drive signal is determined in response to at least a first message received from the power receiver (105). During the foreign object detection time interval the signal parameter of is set to the preferred value.