Method for determining the presence of a foreign metallic body at the interface between an NFC transmitter and an electrical device to be charged

The method measures MOSFET drain-source voltage and applies digital processing to detect foreign metallic bodies during NFC charging, improving reliability and safety by preventing heating and incorrect charging.

FR3160521A1Active Publication Date: 2025-09-26CONTINENTAL AUTOMOTIVE TECHNOLOGIES GMBH
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Patent Information

Application Number
FR2024002935
Authority / Receiving Office
FR · FR
Patent Type
Applications
Current Assignee / Owner
Filing Date
2024-03-25
Publication Date
2025-09-26
Estimated Expiration
2044-03-25

AI Technical Summary

Technical Problem

Existing methods for detecting foreign metallic bodies during NFC wireless charging are unreliable, particularly at frequencies above 1 MHz, leading to potential user safety risks and degraded charging performance.

Method used

A method involving the measurement of drain-source voltage of a MOSFET within the NFC transmitter, combined with digital processing and Fourier transforms, to determine the presence of a foreign metallic body by analyzing harmonic frequencies and comparing against a predetermined threshold.

Benefits of technology

Enhances detection reliability of foreign metallic bodies without hardware modifications, effectively preventing heating and incorrect charging, especially at higher frequencies.

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Abstract

The invention relates to a method for determining the presence of a foreign metallic body at the interface between an NFC transmitter (1) comprising at least one MOSFET (5) and an electrical device to be charged (11), comprising the steps of: - measuring the drain-source voltage (Vds) of the MOSFET (5), - deducing from this measurement a value (OEi) representative of the presence of said body, - emitting a signal and / or interrupting the charging cycle when said value (OEi) reaches a predetermined threshold (OEseuil). (Fig. 1)
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