Wireless Power Transmitter Foreign Object Detection by Q-Factor Shift
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Solution Overview
Problem
Existing wireless charging technologies face challenges in accurately detecting foreign objects (FO) within the charging area, leading to reduced efficiency, overheating, and potential damage due to power waste.
Innovation Solution
A wireless power transmitter that dynamically calibrates a measured quality factor value based on the shift of a current peak frequency from a reference peak frequency, calculates a quality factor slope, and compares it with predetermined thresholds to accurately detect foreign objects, incorporating a method to identify and remove FOs to prevent overheating and improve detection capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If magnetic induction method is used for wireless power transfer, then power transfer efficiency is high and large power can be transferred, but transmission distance is limited to 1 cm or less requiring the device to be located adjacent to the charger
Solution Approach 1:
The patent combines magnetic induction method and electromagnetic resonance method in a single wireless power transmitter system. The controller selectively activates either the magnetic induction coil or the electromagnetic resonance antenna based on the charging distance, allowing the system to achieve both high power transfer at short distances and extended transmission range at longer distances.
2Device complexity
If quality factor measurement is performed at reference operating frequency only, then measurement process is simple, but detection accuracy is reduced when peak frequency shifts occur
Solution Approach 1:
The patent implements a dynamic foreign object detection process that first measures quality factor at the reference operating frequency, then determines whether peak frequency has shifted. If a shift is detected, the system dynamically adjusts by measuring quality factor at the new peak frequency and using the difference to calibrate the detection threshold, thereby maintaining high detection accuracy under varying operating conditions.
3Device complexity
If foreign object detection is not performed, then device complexity is reduced, but temperature increase and power waste occur when foreign objects are present in the charging area
Solution Approach 1:
The patent performs foreign object detection before initiating the power transfer process. By measuring the quality factor of the resonant circuit in advance and comparing it with calibrated values, the system identifies the presence of foreign objects and prevents power transfer that would cause overheating or energy waste, thereby eliminating harmful effects before they occur.
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
The solution enhances foreign object detection accuracy, minimizing power waste and overheating risks by adaptively applying methods based on quality factor and peak frequency shifts, ensuring safe and efficient wireless charging.
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
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 3
an electromagnetic signal received from a wireless power transmitter may be induced in the FO, thereby increasing in temperature
Data Source
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AI summary
The present invention relates to a method for detecting foreign material, and an apparatus and a system therefor, and a method for detecting foreign material in a wireless power transmitter, according to one embodiment of the present invention, comprises the steps of: measuring a quality factor value, which corresponds to a reference operation frequency, when an object is sensed; searching for a current peak frequency having a maximum quality factor value within an operation frequency band; receiving, form a wireless power receiver, a foreign material detection state packet including information on a reference peak frequency; correcting the measured quality factor value by using a difference value between the current peak frequency and the reference peak frequency; and determining whether the foreign material exists by comparing the corrected quality factor value with a predetermined quality factor threshold value. Therefore, the present invention has an advantage of enabling foreign material to be more effectively and accurately detected.