Wireless Charging FOD Using Resonant Peak and Q-Factor Detection

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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 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

VSEngineering Contradiction Analysis

1Loss of energy

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

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidforeign object heating

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

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.

Inventive Principle:

Principle #10Preliminary action

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.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If foreign object detection sensitivity is increased to prevent heating, then detection accuracy improves, but false detections increase causing charging interruptions

Engineering Contradiction:

Improveforeign object detection accuracyVSAvoidcharging system stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system dynamically adjusts the threshold for quality factor changes that trigger foreign object detection. Rather than using a fixed threshold, the detection sensitivity adapts based on measured quality factor variations, allowing the system to distinguish between normal fluctuations and actual foreign object presence, thereby reducing false detections while maintaining detection accuracy.

Inventive Principle:

Principle #15Dynamics

3Reliability

If quality factor measurement is performed continuously to improve detection reliability, then detection reliability improves, but energy consumption increases

Engineering Contradiction:

Improvedetection reliabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system performs quality factor measurements periodically at key stages such as before initiating power transmission and during charging phases, 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.

Inventive Principle:

Principle #19Periodic action

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 factors and inductance values, thereby improving the reliability of wireless charging systems.

Implementation Method 1

The electromagnetic resonance method uses an electric field or a magnetic field instead of using electromagnetic waves or current

Methodology Applied

Scientific EffectElectromagnetic resonance: Resonance

Implementation Method 2

The magnetic induction method uses a phenomenon that, 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

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12444990B2Method for detecting foreign material, and device and system therefor

Publication Date: 2025.10.14 LG INNOTEK CO LTD

AI summary

A method of receiving power by a wireless power receiver, the method including transmitting, to a wireless power transmitter, a plurality of packets including a foreign object detection (FOD) status packet; and receiving, from the wireless power transmitter, a response signal indicating whether a foreign object is present in a charging area of the wireless power transmitter, 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.