Symmetric Detection Coil Arrays for Wireless Charging Safety
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Solution Overview
Problem
The existing wireless charging systems face safety issues due to the risk of foreign objects, such as metal objects or living creatures, entering the air gap between the transmit and receive coils, leading to potential overheating and safety hazards.
Innovation Solution
A foreign object detection method and apparatus are introduced, which include a coil array with detection coils arranged in a matrix and a foreign object detection circuit. The method involves obtaining induction signals from the detection coils, determining abnormal-value thresholds, and detecting foreign objects based on these thresholds, thereby improving safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless charging is implemented with an air gap between transmit and receive coils, then convenience and ease of use are improved, but the risk of foreign objects entering the air gap increases, leading to safety hazards
Solution Approach 1:
The patent performs foreign object detection before initiating the wireless charging process. The detection circuit measures the impedance of the transmit coil before power transmission starts, comparing it against reference values to identify foreign objects in advance, preventing potential heating hazards before they occur
Solution Approach 2:
The patent implements continuous monitoring during the charging process by measuring impedance changes of the transmit coil in real-time. The system compares current impedance values with reference values and provides feedback to control the charging process, stopping or adjusting charging when foreign objects are detected
2Reliability
If foreign object detection is performed during wireless charging, then safety is improved, but system complexity increases due to additional detection circuits and measurement requirements
Solution Approach 1:
The patent uses the transmit coil's impedance measurement for dual purposes: both for controlling the wireless power transfer efficiency and for detecting foreign objects. The same measurement circuit and impedance data serve both charging optimization and safety detection functions, avoiding the need for separate dedicated detection hardware
Solution Approach 2:
The system uses its own transmit coil impedance characteristics as the detection mechanism. The wireless charging system detects foreign objects by monitoring changes in its own operational parameters (impedance) rather than requiring external detection devices, making the system self-diagnostic
3Difficulty of detecting and measuring
If impedance-based foreign object detection is used, then detection capability is improved, but measurement precision may be affected by variations in charging conditions and environmental factors
Solution Approach 1:
The patent measures impedance at multiple different frequencies rather than a single frequency. By performing impedance measurements at various frequencies and analyzing the changes, the system can distinguish foreign object effects from variations caused by charging conditions, improving measurement precision through multi-parameter analysis
Solution Approach 2:
The patent measures impedance at multiple frequencies beyond what would be strictly necessary for basic operation. This excessive measurement approach provides redundant data that helps filter out environmental noise and charging condition variations, enhancing detection reliability
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
The proposed solution effectively enhances the safety and efficiency of wireless charging by accurately detecting foreign objects in real-time, preventing potential hazards, and ensuring reliable charging operations.
Implementation Method 1
A transmit coil in the power transmitting apparatus and a receive coil in the power receiving apparatus may transmit energy through electromagnetic induction
Implementation Method 2
When there is a metal foreign object between the transmit coil and the receive coil, the metal foreign object may heat due to an eddy effect
Data Source
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AI summary
This application provides a foreign object detection method and apparatus, and a wireless charging system. The foreign object detection apparatus includes a coil array and a foreign object detection circuit. The coil array includes at least one coil group, and each coil group includes four detection coils whose locations are symmetrical to each other. The foreign object detection circuit may obtain an induction signal generated by each detection coil; determine an abnormal-value threshold of each coil group based on induction signals that are of each coil group and that are obtained in a first time period, and detect, based on the abnormal-value threshold and the induction signals of each coil group, whether there is a foreign object; when it is determined that there is no foreign object, determine a signal threshold of each coil group based on the induction signals of each coil group; and detect, based on the signal threshold of each coil group and induction signals that are of each coil group and that are obtained in a second time period, whether there is a foreign object. The technical solutions provided in this application may improve wireless charging safety.