Wireless Charging Foreign Object Detection Using Q-Factor Calibration
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Solution Overview
Problem
Existing wireless charging technologies face challenges in accurately detecting foreign objects in the charging area, leading to reduced efficiency and potential overheating due to increased ambient temperature, which can cause power waste and damage to the charger and receiver.
Innovation Solution
A method for detecting foreign objects using calibrated quality factor values and peak frequency shifts, involving the measurement of quality factor slopes and comparison with predetermined thresholds, to accurately identify and respond to foreign objects in the charging area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If wireless power transmission is performed using electromagnetic resonance method, then power can be transmitted over longer distances compared to magnetic induction method, but energy transmission efficiency is reduced
Solution Approach 1:
The patent adjusts resonance frequency and impedance parameters of the coils to optimize the balance between transmission distance and efficiency. By tuning the resonant frequency of both transmitting and receiving coils to match, the system achieves extended transmission distance while minimizing energy loss through parameter optimization.
2Productivity
If foreign object detection is not performed accurately, then charging can continue without interruption, but power waste and overheating occur causing damage to charger and receiver
Solution Approach 1:
The system continuously monitors the quality factor (Q-factor) of the resonant circuit and compares it against reference values. When the Q-factor changes indicate the presence of a foreign object, the system provides feedback to stop or reduce power transmission, preventing energy waste and overheating while maintaining charging continuity when safe.
Solution Approach 2:
The patent replaces physical inspection methods with electromagnetic field-based detection. By measuring changes in the electromagnetic resonance characteristics (Q-factor and frequency shift) caused by foreign objects, the system detects anomalies without mechanical contact, enabling continuous monitoring during charging.
3Device complexity
If quality factor measurement is performed without calibration, then detection process is simpler, but detection accuracy is reduced
Solution Approach 1:
The system performs preliminary calibration by measuring the quality factor at the resonant frequency before actual foreign object detection. This preliminary measurement establishes a baseline Q-factor value that accounts for system-specific characteristics, improving subsequent detection accuracy without significantly increasing overall complexity.
Solution Approach 2:
The patent uses the same resonant circuit and measurement infrastructure for both power transmission and quality factor measurement. By multi-functioning the resonant circuit as both the power transfer medium and the detection sensor, the system achieves accurate calibrated detection without adding separate complex measurement systems.
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 method enhances the accuracy of foreign object detection, minimizing power waste and overheating, thereby improving the safety and efficiency of wireless charging systems.
Implementation Method 1
a coil electromagnetically coupled to the external, a resonant circuit that includes at least the coil
Implementation Method 2
a resonant circuit that includes at least the coil, and a detecting section that superimposes a measurement signal for measuring the Q-factor of the resonant circuit
Implementation Method 3
wireless power transfer technology for wirelessly transmitting electric energy from a transmitter to a receiver using the magnetic induction principle
Implementation Method 4
The electromagnetic resonance method uses an electric field or a magnetic field instead of using electromagnetic waves or current
Implementation Method 5
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
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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.