Compensated Detection Coils for Wireless Power Foreign Object Detection
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Solution Overview
Problem
Current foreign object detection methods in wireless power transfer systems, such as those using the Qi specification, face challenges in achieving accurate detection, especially at higher power levels, due to uncertainties in operating conditions and interference from friendly metals, leading to potential heating issues and suboptimal performance.
Innovation Solution
The implementation of a power transmitter with balanced detection coils and a communication antenna design that compensates for inductive and capacitive couplings, allowing for improved foreign object detection accuracy and reduced interference from communication antennas, enabling more reliable and efficient power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If foreign object detection is performed using conventional methods in wireless power transfer systems, then power transfer functionality is provided, but detection accuracy deteriorates due to interference from friendly metals and operating condition uncertainties
Solution Approach 1:
The detection coil is divided into multiple segments arranged in a specific geometric pattern (e.g., hexagonal or circular arrangement with alternating polarity). This segmentation allows the system to differentiate between signals from foreign objects and signals from friendly metals by analyzing the spatial distribution and polarity patterns of induced currents.
Solution Approach 2:
The detection system uses asymmetric coil configurations and signal processing approaches. By arranging detection coils with specific asymmetric geometries and analyzing asymmetric response patterns, the system can distinguish foreign objects from friendly metals which produce symmetric or predictable interference patterns.
2Volume of moving object
If communication antenna is placed near detection coils for compact implementation, then device size is reduced, but detection accuracy deteriorates due to inductive and capacitive coupling interference
Solution Approach 1:
The patent extracts and separately compensates for the interference signals from the communication antenna. By identifying and removing the specific inductive and capacitive coupling components from the detection signal, the system maintains high detection accuracy despite the close proximity of the communication antenna.
Solution Approach 2:
The system dynamically adjusts operating parameters such as frequency, phase, and amplitude of detection signals to minimize coupling effects. By changing these parameters adaptively, the system optimizes detection performance while maintaining compact antenna placement.
3Power
If higher power levels are used for power transfer, then power transmission capability is improved, but foreign object heating risk increases
Solution Approach 1:
The system implements continuous feedback monitoring using the detection coils to sense the presence and characteristics of objects in real-time. Based on this feedback, the power transmitter dynamically adjusts the power level to prevent foreign object heating while maximizing power transfer to legitimate devices. The feedback loop enables safe operation at higher power levels through active monitoring and control.
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 foreign object detection accuracy, reduces complexity, and improves performance, particularly in higher power level transfers, while allowing for compact implementation and efficient power and communication functionality.
Implementation Method 1
the transmitter coil being arranged to generate an electromagnetic test field for foreign object detection
Implementation Method 2
a set of balanced detection coils comprising two detection coils coupled in series and such that changes in electromagnetic flux linking the two detection coils compensate each other
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
Implementation Method 4
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 comprises a transmitter coil (103) generating an electromagnetic field. A set of balanced detection coils (207, 209) comprises detection coils in series and compensating each other. A foreign object detector (205) performs foreign object detection, by potentially detect a foreign object in response to a property of an output signal from the set of balanced detection coils (207, 209) in response to the electromagnetic test meeting a foreign object detection criterion. A communicator (211) is coupled to a communication antenna (213) communicates with a power receiver (105) via this. The communication antenna (213) comprises a plurality of communication coils (215, 217) coupled in parallel. A first segment of a first communication coil (215) has a first coupling to a first detection coil and a second segment of a second coil (217) has a second coupling to a second detection coil. The couplings are capacitive and/or inductive couplings and the first coupling and the second coupling compensate each other in the output signal.