Wireless Charging FOD Using Resonant Q and Inductance Checks
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Solution Overview
Problem
Existing wireless charging systems face challenges in accurately detecting foreign objects, which can lead to reduced efficiency, overheating, and potential damage due to increased ambient temperature and power waste.
Innovation Solution
A method and apparatus for detecting foreign objects using a wireless power transmitter that measures quality factor and inductance values of a resonant circuit before a ping phase, determines a threshold value based on a reference quality factor, and compares these values to accurately identify foreign objects, with threshold values adjusted dynamically based on the reference quality factor.
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 equipment damage
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 detections increase causing charging interruptions
Solution Approach 1:
The system dynamically adjusts the threshold for quality factor changes that trigger foreign object detection. By changing this parameter based on reference quality factor values obtained during device pairing, the system optimizes detection sensitivity to distinguish actual foreign objects from normal variations, reducing false detections while maintaining detection accuracy.
Solution Approach 2:
The system uses feedback from the quality factor measurements to continuously refine foreign object detection decisions. By comparing real-time quality factor changes against reference values and adjusted thresholds, the system can distinguish between normal charging variations and actual foreign object presence, preventing false interruptions while maintaining reliable detection.
3Adaptability or versatility
If quality factor measurement range is expanded to detect all foreign objects, then detection coverage improves, but measurement complexity and processing time increase
Solution Approach 1:
The system focuses quality factor measurements on the specific resonant frequency of the wireless power transmission system rather than scanning a broad frequency range. This localized measurement approach maintains detection coverage for foreign objects that affect the resonant circuit while significantly reducing measurement complexity and processing requirements compared to wideband scanning.
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, minimizing power waste and equipment damage by dynamically adjusting thresholds and using quality factor and inductance measurements.
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
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 3
The electromagnetic resonance method uses an electric field or a magnetic field instead of using electromagnetic waves or current
Implementation Method 4
The rectenna is a combination of an antenna and a rectifier and means an element for directly converting RF power into DC power
Data Source
AI summary
A wireless power transmitter that transmits power to a wireless power receiver, the wireless power transmitter including a communication unit configured to communicate with the wireless power receiver; and a controller, wherein the communication unit receives a plurality of packets including a foreign object detection (FOD) status packet from the wireless power receiver, wherein the controller determines whether a foreign object is present in a charging area of the wireless power transmitter on the basis of the FOD status packet, wherein the communication unit transmits, to the wireless power receiver, a response signal indicating whether the foreign object is present in the charging area of the wireless power transmitter on the basis of a result of the determination, wherein the response signal is determined using a measured peak frequency of a power signal transmitted by the wireless power transmitter and a reference peak frequency included in the FOD status packet received from the wireless power receiver, wherein each of the plurality of packets includes a preamble, a header, a message, and a checksum for identifying whether an error occurs in each packet, and wherein a size of the message included in the each packet is identified on the basis of a value of the header.