# US 12,769,022 B2 · Method for detecting a parasitic metal object on a charging surface, and associated charging device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,769,022 B2 - Document ID: US12769022B2 - Status: Granted - Kind: B2 - Application number: 17/523,114 - Filed: 2021-11-10 - Published: 2022-06-09 - Granted: 2026-10-20 - Earliest claimed: 2020-12-03 - Assignees: Continental Automotive Technologies GmbH - Applicants: Continental Automotive GmbH - Inventors: Joao Carlos Vasconcelos De Almeida; Brahim Aloui - Web page: https://patentgrep.com/patent/US12769022B2 ## CPC - G01V 3/12: operating with electromagnetic waves {(operating with millimetre waves G01V8/005)} - H02J 50/12: of the resonant type - H02J 50/60: responsive to the presence of foreign objects, e.g. detection of living beings - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY ## Abstract A method for detecting a foreign metal object, by way of a charging device, including a microcontroller and a transmitting circuit, having at least one transmitting antenna, which are suitable for charging a portable item of user equipment placed on a charging surface at an operating frequency, the method including a) transmitting a predetermined number of voltage pulses at the terminals of the transmitting antenna, at a parasitic resonant frequency, the parasitic resonant frequency being different and distinct from the operating frequency; b) determining an oscillating frequency of the transmitting circuit; c) if the oscillating frequency is higher than the parasitic resonant frequency, then a foreign metal object is detected on the charging surface. ## Claims ### Claim 1 A method for detecting a foreign metal object, by way of a charging device, comprising a microcontroller and a transmitting circuit, said transmitting circuit comprising at least one transmitting antenna, which are suitable for charging a portable item of user equipment placed on a charging surface at an operating frequency, the method comprising: a1) generating a predetermined number of voltage pulses at the terminals of the transmitting antenna at a parasitic resonant frequency, said parasitic resonant frequency being different and distinct from the operating frequency, a2) transmitting the generated predetermined number of voltage pulses at the terminals of the transmitting antenna, at the parasitic resonant frequency, a3) generating plural frequencies at the transmitting circuit, wherein a first oscillating frequency of the plural frequencies is determined by comparing a voltage at the terminals of the transmitting antenna with two threshold voltages for a predetermined period, and a second oscillating frequency of the plural frequencies is generated by a receiver in response to an electromagnetic field transmitted by the transmitting antenna; b) analyzing the plural frequencies of the transmitting circuit that are oscillating simultaneously such that: b1) when the first oscillating frequency is higher than the parasitic resonant frequency, a foreign metal object is detected on the charging surface, b2) when the first oscillating frequency is lower than the parasitic resonant frequency, the portable item of user equipment to be charged is detected on the charging surface, and b3) when the second oscillating frequency oscillates at a second resonant frequency and when the first oscillating frequency is higher than the parasitic resonant frequency, then the simultaneous presence of the portable item of user equipment to be charged and of a foreign metal object are detected on the charging surface, wherein the parasitic resonant frequency is between 200 kHz and 1 MHz, the second resonant frequency is different and distinct from the parasitic resonant frequency, and a value of the second resonant frequency is between 800 KHz and 1200 kHz. ### Claim 2 (depends on 1) The detection method as claimed in claim 1, wherein, the second oscillating frequency is higher than the first oscillating frequency of the transmitting circuit. ### Claim 3 (depends on 1) The detection method as claimed in claim 1, wherein the predetermined number is equal to three. ### Claim 4 (depends on 1) The detection method as claimed in claim 1, wherein the electromagnetic field generated by the transmitting antenna is at the parasitic resonant frequency. ### Claim 5 A charging device for a portable item of user equipment, the charging device comprising: a microcontroller; a charging surface; a transmitting circuit comprising: at least one transmitting coil configured for charging the portable item of user equipment at an operating frequency, and means for generating a parasitic resonant frequency that is different and distinct from the operating frequency, means for generating plural oscillating frequencies at the transmitting circuit, wherein a first oscillating frequency of the plural oscillating frequencies is generated by comparing a voltage at the terminals of the transmitting antenna with two threshold voltages for a predetermined period, and a second oscillating frequency of the plural oscillating frequencies is generated by a receiver in response to an electromagnetic field transmitted by the transmitting antenna; means for analyzing the plural oscillating frequencies of the transmitting circuit that are oscillating simultaneously; and means for detecting a foreign metal object and/or a portable item of user equipment to be charged depending on the oscillating frequency thus measured as follows: i) when the first oscillating frequency is higher than the parasitic resonant frequency, then the foreign metal object is detected on the charging surface, ii) when the first oscillating frequency is lower than the parasitic resonant frequency, then the portable item of user equipment to be charged is detected on the charging surface, and iii) when the second oscillating frequency is oscillating at a second resonant frequency and when the first oscillating frequency of the transmitting circuit is higher than the parasitic resonant frequency, the portable item of user equipment to be charged and the foreign metal object are detected on the charging surface, wherein the parasitic resonant frequency is between 200 kHz and 1 MHz, wherein the second resonant frequency is different and distinct from the parasitic resonant frequency, and wherein a value of the second resonant frequency is between 800 kHz and 1200 KHz. ### Claim 6 (depends on 5) The charging device as claimed in claim 5, wherein the detection means comprise means for comparing the oscillating frequency and the parasitic resonant frequency. ### Claim 7 (depends on 5) The charging device as claimed in claim 5, further comprising means for measuring the second oscillating frequency and means for detecting a compatible portable item of equipment to be charged depending on the second oscillating frequency thus provided. ### Claim 8 (depends on 5) The charging device as claimed in claim 5, wherein the means for generating the parasitic resonant frequency are in the form of means for generating a predetermined number of voltage pulses at terminals of a transmitting antenna at the parasitic resonant frequency. ### Claim 9 (depends on 5) The charging device as claimed in claim 5, wherein the generating means comprise a switch connected at a first side to a branch of a transmitting antenna, a capacitor connected to ground and a second side of the switch, and a resistor connected to a voltage source and to the second side of the switch. ### Claim 10 (depends on 5) A motor vehicle, comprising a charging device as claimed in claim 5. ### Claim 11 (depends on 5) The charging device as claimed in claim 5, wherein the electromagnetic field generated by the transmitting antenna is at the parasitic resonant frequency.