Wireless Charging Coil Mutual Inductance for Foreign Object Detection

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Solution Overview

Problem

Existing wireless charging systems face inaccuracies in detecting foreign conductors due to the correlation between power loss and distance, leading to mistaken determinations and poor user experience.

Innovation Solution

A conductor foreign object detection method that calculates mutual inductance values for both transmitting and receiving coils based on voltage and current values, determining the presence of a foreign object by comparing these values and setting a reference deviation to account for environmental interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If power loss detection is used for foreign object detection, then the detection can be implemented, but the detection accuracy deteriorates due to correlation between power loss and distance

Engineering Contradiction:

Improveforeign object detection accuracyVSAvoiddetection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces mutual inductance as an intermediary parameter to detect foreign objects. Instead of directly detecting power loss (which correlates with distance), the system measures mutual inductance between transmitting and receiving coils, which provides a more reliable indicator of foreign object presence that is less affected by distance variations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the detection parameter from power loss to mutual inductance. By calculating mutual inductance values based on voltage and current measurements and comparing them against reference values, the system achieves more accurate foreign object detection that is not confounded by the distance-power loss correlation.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If wireless charging operates over larger distances, then user convenience is improved, but false positive detection increases due to environmental interference

Engineering Contradiction:

Improvecharging distance flexibilityVSAvoidforeign object detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent performs preliminary measurement of mutual inductance under reference conditions (without foreign objects) to establish baseline values before actual charging operation. This preliminary action allows the system to distinguish between mutual inductance changes caused by distance and those caused by foreign objects, enabling accurate detection even at larger charging distances.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors mutual inductance values during charging operation and compares them against reference values. When deviations exceed predetermined thresholds, the system provides feedback to stop charging, preventing false positives while maintaining flexibility for legitimate larger-distance charging operations.

Inventive Principle:

Principle #23Feedback

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 increases the accuracy of foreign conductor detection, allowing wireless charging to operate over a larger distance without false positives, thereby enhancing user experience and safety by preventing overheating due to eddy currents.

Implementation Method 1

Wireless charging uses the coupling between a transmitting coil and a receiving coil to achieve the purpose of energy transfer

Methodology Applied

Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Implementation Method 2

If there is a metal foreign object between the transmitting coil and the receiving coil, the metal foreign object will result in eddy current in the changing magnetic field and the metal foreign object will be heated up

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Data Source

PatentUS11843263B2Charging system, foreign object detection method and component, charging control method and device

Publication Date: 2023.12.12 BOE TECHNOLOGY GROUP CO LTD

AI summary

The present disclosure relates to a charging system, a foreign object detection method and component, and a charging control method and device, which belong to the wireless technical field. The foreign object detection method includes receiving a voltage value and a current value of the transmitting coil, and determining a mutual inductance value of the transmitting coil according to the voltage value and the current value of the transmitting coil; receiving a voltage value and a current value of the receiving coil, and determining a mutual inductance value of the receiving coil according to the voltage value and the current value of the receiving coil; and determining whether there is a conductor foreign object between the receiving coil and the transmitting coil according to the mutual inductance value of the transmitting coil and the mutual inductance value of the receiving coil.