Wireless Power Transfer Foreign Object Detection Using Q Factor Feedback
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Solution Overview
Problem
The accuracy of foreign object detection in wireless power transfer systems decreases due to the inability to detect foreign objects that enter during the time between measuring the Q factor and calculating the estimated power loss.
Innovation Solution
A power transmitting apparatus that measures a Q factor and obtains additional index values regarding physical amounts different from the Q factor, allowing for more accurate foreign object detection by comparing these values before and after initiating wireless power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If foreign object detection is performed only based on Q factor measurement before power transmission starts, then the detection process is simple, but foreign objects that enter during the time until estimated power loss calculation cannot be detected, decreasing detection accuracy
Solution Approach 1:
The system performs preliminary foreign object detection using Q factor before power transmission starts, establishing a baseline state. This preliminary detection is complemented by subsequent detection using estimated power loss during transmission, creating a multi-stage detection approach that maintains both simplicity and accuracy.
Solution Approach 2:
The system continuously monitors power loss during transmission and compares it against estimated values to detect foreign objects that enter after the initial Q factor measurement. This feedback mechanism ensures that foreign objects entering during the transmission process are detected, resolving the accuracy issue while maintaining procedural simplicity.
2Measurement precision
If foreign object detection is performed continuously during power transmission, then detection accuracy is improved, but the time required for power transmission increases
Solution Approach 1:
Instead of continuous monitoring, the system performs foreign object detection periodically at key stages: before power transmission using Q factor, and during transmission using estimated power loss comparisons. This periodic approach maintains detection accuracy while minimizing time loss by only checking at critical moments rather than continuously.
3Measurement precision
If multiple detection methods (Q factor and power loss) are used, then foreign object detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The power transmitting apparatus performs multiple functions using the same hardware components: Q factor measurement for preliminary detection, power loss calculation for ongoing detection, and both methods work together to provide comprehensive foreign object detection. This multi-functionality approach improves accuracy without significantly increasing device complexity.
Solution Approach 2:
The system merges Q factor-based detection and power loss-based detection into a unified foreign object detection framework. Both methods complement each other, with Q factor providing pre-transmission baseline detection and power loss providing during-transmission detection, creating a cohesive system that improves accuracy without duplicating hardware.
Data Source
AI summary
A power transmitting apparatus measures a Q factor of a power transmitting unit that performs wireless power transfer to a power receiving apparatus, and determines presence/absence of an object different from the power receiving apparatus based on the Q factor. The power transmitting apparatus obtains a first index value regarding a predetermined physical amount different from the Q factor after measurement of the Q factor, obtains a second index value regarding the predetermined physical amount before wireless power transfer to the power receiving apparatus starts after the it is determined in the above determination that an object different from the power receiving apparatus does not exist; and determines presence/absence of an object different from the power receiving apparatus based on the first index value and the second index value.