Wireless Charging Coil FOD Using Q Factor and Inductance
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Solution Overview
Problem
Existing wireless charging systems face challenges in accurately detecting foreign objects, leading to reduced efficiency, overheating, and potential damage due to foreign objects in the charging area.
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 according to the reference quality factor and potentially incorporating weights or tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If wireless power transmission is performed using electromagnetic induction or resonance, then power can be transferred wirelessly to devices, but foreign objects in the charging area may be heated due to induced electromagnetic signals
Solution Approach 1:
The system performs foreign object detection before initiating full wireless power transmission. By measuring quality factor and inductance values in advance (before the ping phase), the system identifies foreign objects and prevents power transmission that would cause heating, thus eliminating the harmful effect before it occurs.
Solution Approach 2:
The patent uses quality factor and inductance measurements as intermediary parameters to detect the presence of foreign objects. These measurements serve as mediators between the electromagnetic field and the control system, enabling indirect detection of foreign objects without direct contact or additional sensors in the charging area.
2Measurement precision
If foreign object detection sensitivity is increased to prevent heating, then detection accuracy improves, but false detections may occur reducing charging availability
Solution Approach 1:
The system dynamically adjusts detection parameters including quality factor thresholds and inductance reference values based on the specific receiver being charged. By adapting these parameters to each receiver's characteristics, the system achieves high detection sensitivity while minimizing false positives that would reduce charging availability.
Solution Approach 2:
The system uses feedback from the wireless power receiver to establish reference quality factor values and adjust detection thresholds. This feedback mechanism allows the system to learn the normal operating parameters of each receiver and distinguish between actual foreign objects and normal variations in the charging environment.
3Loss of time
If quality factor and inductance measurements are performed before the ping phase, then foreign object detection occurs earlier, but the detection process becomes more complex
Solution Approach 1:
The patent combines quality factor measurement and inductance measurement into a unified detection process that occurs before the ping phase. By merging these measurements and using them together for foreign object detection, the system achieves early detection without proportionally increasing complexity, as both measurements can be performed using the existing resonant circuit infrastructure.
Solution Approach 2:
The resonant circuit in the wireless power transmitter serves multiple functions: it enables wireless power transmission, provides quality factor measurements for foreign object detection, and provides inductance measurements for receiver identification. This multi-functionality allows early foreign object detection without adding separate dedicated detection hardware, thus limiting the increase in device 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 thresholds based on the quality factor and inductance values, thereby improving the reliability of wireless charging systems.
Implementation Method 1
wireless power transmission technology... 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
Data Source
AI summary
A method of transmitting power by a wireless power transmitter, the method including sequentially transmitting a sensing signal a plurality of times to a wireless power receiver through a plurality of transmission coils to sense the presence of the wireless power receiver; identifying transmission coils that receive a signal strength indictor transmitted by the wireless power receiver in response to the plurality of sensing signals; and selecting, as a power transmission coil, the transmission coil that has received the signal strength indicator having the largest amount or the largest value among the transmission coils that have received the signal strength indicator, receiving a plurality of packets including a foreign object detection (FOD) status packet from the 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.