Wireless Charging Foreign Object Detection via Quality Factor Calibration
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Solution Overview
Problem
Current wireless charging technologies face challenges in accurately detecting foreign objects in the charging area, which can lead to reduced efficiency and potential damage due to overheating, as existing methods struggle to reliably differentiate between a wireless power receiver and foreign objects based on quality factor values and peak frequencies.
Innovation Solution
A method and apparatus for detecting foreign objects in a wireless power transmitter that dynamically calibrate quality factor values by comparing measured peak frequencies with reference values, using a quality factor slope calculated from output voltage levels within an operating frequency band, and applying adaptive detection based on these calibrations to determine the presence of foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wireless power transmission is performed in a charging area, then power transfer efficiency is improved, but foreign objects may be heated causing safety hazards and energy waste
Solution Approach 1:
The system performs foreign object detection by measuring quality factor changes before initiating full power transmission. This preliminary detection action identifies potential foreign objects in the charging area, allowing the system to prevent or adjust power transmission to avoid heating foreign objects while maintaining efficient charging when the area is clear.
Solution Approach 2:
The quality factor measurement serves as an intermediary indicator to indirectly detect the presence of foreign objects. Instead of directly detecting foreign objects or their heating, the system uses quality factor changes of the resonant circuit as a mediator to infer foreign object presence, enabling safe power transmission decisions.
2Measurement precision
If foreign object detection sensitivity is increased to prevent heating, then detection accuracy improves, but false detection of legitimate receivers increases causing charging interruptions
Solution Approach 1:
The system applies different quality factor threshold criteria for different detection scenarios. Instead of using a single universal threshold, it establishes specific threshold ranges that account for the different electromagnetic characteristics of foreign objects versus legitimate wireless power receivers, enabling accurate differentiation without false positives.
Solution Approach 2:
The system uses bidirectional communication between transmitter and receiver to verify device identity and status. The receiver provides feedback signals that confirm its legitimacy, allowing the system to distinguish authenticated receivers from foreign objects even when quality factor changes are similar, preventing false detection interruptions.
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 effectively distinguishing between wireless power receivers and foreign objects, thereby ensuring safe and efficient charging operations.
Implementation Method 1
The magnetic induction method uses a phenomenon that, when two coils are located adjacent to each other and then current is applied to one coil, a magnetic flux is generated to cause an electromotive force in the other coil
Implementation Method 2
The electromagnetic resonance method uses an electric field or a magnetic field instead of using electromagnetic waves or current
Implementation Method 3
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
AI summary
A wireless power receiver that receives power from a wireless power transmitter, the wireless power receiver including a wireless communication unit configured to communicate with the wireless power transmitter; and a controller, wherein the wireless communication unit transmits a first foreign object status packet and a second foreign object status packet to the wireless power transmitter, wherein the wireless communication unit receives, from the wireless power transmitter, a first foreign object detection indicator including a positive response signal or a negative response signal to the first foreign object status packet, wherein the wireless communication unit receives, from the wireless power transmitter, a second foreign object detection indicator including a positive response signal or a negative response signal to the second foreign object status packet, and wherein the controller is configured to proceed to a first power transmission procedure when both the first foreign object detection indicator and the second foreign object detection indicator include the positive response signal, or is configured to proceed to a second power transmission procedure that requests termination of power transmission or proceed to a third power transmission procedure different from the termination of the power transmission when at least one of the first foreign object detection indicator and the second foreign object detection indicator includes the negative response signal.