Wireless Power Foreign Object Detection with Adaptive Q-Factor Thresholds
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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 the ping phase, determines a threshold value based on a reference quality factor, and compares these values to accurately identify foreign objects, with the threshold value adjusted by a weight that increases with 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 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 detections increase causing charging interruptions
Solution Approach 1:
The system dynamically adjusts the threshold for quality factor comparison based on reference quality factor values obtained during device pairing. By changing the detection parameter (threshold) according to specific device characteristics, the system achieves high detection sensitivity without excessive false alarms, maintaining both accuracy and charging reliability.
Solution Approach 2:
The system uses feedback from the quality factor measurement to dynamically adjust detection decisions. The measured quality factor is compared against a reference value with a dynamically determined threshold, allowing the system to adapt to different devices and environmental conditions, reducing false detections while maintaining high detection accuracy.
3Device complexity
If a fixed threshold is used for foreign object detection, then the detection process is simple, but detection accuracy varies with different devices and conditions
Solution Approach 1:
The detection threshold transitions from a fixed value to a dynamic value that adapts to different wireless power receivers and environmental conditions. The threshold is calculated based on the reference quality factor specific to each device, making the detection process adaptive rather than static, thereby improving accuracy without excessive complexity.
Solution Approach 2:
The system applies a customized detection threshold tailored to each specific wireless power receiver device rather than using a universal fixed threshold. This localized approach adjusts the detection criteria to match the specific characteristics of each device, improving detection precision while maintaining reasonable system complexity.
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 the threshold values based on the reference quality factor, thereby improving the reliability 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
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
Data Source
AI summary
A method of transmitting power by a wireless power transmitter, the method including receiving a plurality of packets including a foreign object detection (FOD) status packet from a wireless power receiver; determining whether a foreign object is present in a charging area of the wireless power transmitter on the basis of the FOD status packet; and transmitting, 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.