Wireless Power Receiver Q-Factor Calibration for Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transmission systems face challenges in accurately detecting foreign objects in the charging area, which can lead to reduced charging efficiency and potential overheating due to increased ambient temperature, resulting in power waste and damage to the transmitter and receiver.
Innovation Solution
A wireless power receiver that dynamically calibrates the measured quality factor value based on the shift of the current peak frequency from a reference peak frequency, calculates the quality factor slope, and compares it with predetermined thresholds to accurately detect foreign objects, incorporating methods to identify and remove detected objects and adjust power transfer accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a wireless power transmitter uses a simple quality factor measurement method, then the device complexity is reduced, but the measurement precision of foreign object detection deteriorates
Solution Approach 1:
The system performs preliminary action by determining the peak frequency of the transmitter coil before conducting foreign object detection. This preliminary frequency identification enables subsequent correction of quality factor measurements, resolving the contradiction by adding a simple preparatory step that significantly improves detection accuracy without substantially increasing system complexity
Solution Approach 2:
The system applies parameter changes by correcting the quality factor value based on the determined peak frequency. Instead of using a fixed frequency measurement, the system adjusts the quality factor calculation according to the actual peak frequency, which accounts for frequency shifts caused by different receiver devices. This dynamic parameter adjustment maintains operational simplicity while achieving accurate foreign object detection
2Productivity
If the wireless power transmitter continuously monitors quality factor at fixed frequency, then the productivity is improved, but the measurement precision of foreign object detection worsens
Solution Approach 1:
The system performs a preliminary frequency sweep to identify the actual peak frequency before foreign object detection. This preliminary action establishes the correct reference frequency for quality factor measurement, ensuring that subsequent continuous monitoring occurs at the optimal frequency rather than a fixed predetermined frequency, thereby maintaining both speed and accuracy
Solution Approach 2:
The system implements periodic frequency sweeps to update the peak frequency determination at appropriate intervals during power transfer. This periodic recalibration ensures that the quality factor measurements remain accurate even as operating conditions change, while maintaining high productivity by not requiring continuous frequency scanning
3Productivity
If foreign objects are present in the charging area, then power transfer continues without interruption improving productivity, but harmful factors increase due to overheating
Solution Approach 1:
The system employs feedback by continuously monitoring the corrected quality factor value during power transfer and comparing it against reference values. When the corrected quality factor indicates the presence of a foreign object, the system provides feedback to stop power transfer, preventing overheating while maintaining productivity during normal operation through continuous accurate monitoring
Solution Approach 2:
The system replaces simple threshold-based detection with a corrected quality factor measurement system that accounts for frequency variations. This substitution enables more accurate discrimination between legitimate receivers and foreign objects, allowing continuous safe operation by reducing false positives that would unnecessarily interrupt charging
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 of foreign object detection, minimizes power waste, and prevents overheating by adaptively applying detection methods based on quality factor and peak frequency shifts, ensuring safe and efficient charging.
Implementation Method 1
Wireless power transmission or wireless energy transfer refers to technology for wirelessly transmitting electric energy from a transmitter to a receiver using the magnetic induction principle
Implementation Method 2
If a conductor which is not a wireless power receiver, that is, a foreign object (FO), is present in a wireless charging area, an electromagnetic signal received from a wireless power transmitter may be induced in the FO, thereby increasing in temperature
Data Source
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AI summary
The present invention relates to a method for detecting foreign material, and an apparatus and a system therefor, and a method for detecting foreign material in a wireless power transmitter, according to one embodiment of the present invention, comprises the steps of: measuring a quality factor value, which corresponds to a reference operation frequency, when an object is sensed; searching for a current peak frequency having a maximum quality factor value within an operation frequency band; receiving, form a wireless power receiver, a foreign material detection state packet including information on a reference peak frequency; correcting the measured quality factor value by using a difference value between the current peak frequency and the reference peak frequency; and determining whether the foreign material exists by comparing the corrected quality factor value with a predetermined quality factor threshold value. Therefore, the present invention has an advantage of enabling foreign material to be more effectively and accurately detected.