Wireless Charging FOD Using Resonant Q Threshold Adjustment
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Solution Overview
Problem
Existing wireless charging systems face challenges in accurately detecting foreign objects, which can lead to reduced charging efficiency, overheating, and potential damage due to increased ambient temperature, as well as unnecessary 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 according to 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 unnecessary power transmission interruptions
Solution Approach 1:
The system dynamically adjusts the threshold for quality factor comparison based on reference quality factor values obtained during the ping phase. Instead of using a fixed threshold, the system modifies the detection parameter (threshold value) according to the specific charging scenario, enabling accurate detection while adapting to different conditions to reduce false positives.
Solution Approach 2:
The system uses feedback from the quality factor measurement and comparison results to adjust power transmission decisions. By continuously monitoring quality factor changes and comparing them against dynamically determined thresholds, the system can distinguish between actual foreign objects and normal variations, reducing false detections while maintaining high detection accuracy.
3Reliability
If quality factor measurement is performed continuously to improve detection reliability, then detection accuracy improves, but energy consumption increases
Solution Approach 1:
The system performs quality factor measurements periodically at specific phases (ping phase before power transfer, and optionally during power transfer phase) rather than continuously. This periodic measurement approach maintains detection reliability by checking for foreign objects at critical moments while significantly reducing energy consumption compared to continuous monitoring.
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 based on reference quality factor values, thereby improving the reliability and safety of wireless charging systems.
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
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
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
Implementation Method 4
an electromagnetic signal received from a wireless power transmitter may be induced in the FO, thereby increasing in temperature
Implementation Method 5
The electromagnetic resonance method uses an electric field or a magnetic field instead of using electromagnetic waves or current
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 the header is configured to identify a type of the each packet.