Method for determining the position of a metal object on an inductive charging support relative to a transmitter antenna and a receiver antenna

Abstract

A method for determining the relative position of a metal object in relation to a user device and to a transmitter antenna of an inductive charging support when charging the user device. The method includes measuring the quality factor of the transmitter antenna, measuring the quality factor of the receiver antenna, and comparing the measured quality factor of the transmitter antenna with a predetermined quality factor threshold of the transmitter antenna and comparing the measured quality factor of the receiver antenna with a predetermined quality factor threshold of the receiver antenna so as to deduce therefrom the relative position of the metal object in relation to the user device and to the transmitter antenna or the absence of an interfering metal object.

Claims

1. A method for determining a position of a metal object, placed on a support of an inductive charging apparatus, in relation to a user device and to a transmitter antenna of said inductive charging apparatus when charging said user device, said user device comprising a battery and a receiver antenna for receiving an inductive charging signal transmitted by the transmitter antenna in order to charge said battery, said method comprising: measuring a quality factor of the transmitter antenna, measuring a quality factor of the receiver antenna, and comparing, during a transmitter quality factor comparison, the measured quality factor of the transmitter antenna with a predetermined quality factor threshold of the transmitter antenna and comparing, during a receiver quality factor comparison, the measured quality factor of the receiver antenna with a predetermined quality factor threshold of the receiver antenna so as to deduce therefrom the position of the metal object in relation to the user device and to the transmitter antenna, and determining that: the metal object is aligned with both the transmitter antenna and the receiver antenna when the quality factor of the transmitter antenna is lower than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is lower than the predetermined quality factor threshold of the receiver antenna, the metal object is aligned with the transmitter antenna and not aligned with the receiver antenna when the quality factor of the transmitter antenna is lower than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is greater than the predetermined quality factor threshold of the receiver antenna, the metal object is aligned with the receiver antenna and not aligned with the transmitter antenna when quality factor of the transmitter antenna is greater than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is lower than the predetermined quality factor threshold of the receiver antenna, and the metal object is not aligned with the transmitter antenna and not aligned with the receiver antenna when the quality factor of the transmitter antenna is greater than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is greater than the predetermined quality factor threshold of the receiver antenna.

2. The method as claimed in claim 1, further comprising a preliminary step of determining the predetermined quality factor threshold of the transmitter antenna.

3. The method as claimed in claim 1, further comprising a preliminary step of determining the predetermined quality factor threshold of the receiver antenna.

4. A charging apparatus for inductively charging a user device, said charging apparatus comprising a transmitter antenna and a support for receiving said user device, situated above said transmitter antenna, the user device comprising a battery and a receiver antenna for receiving an inductive charging signal transmitted by the transmitter antenna and making it possible to charge said battery, the charging apparatus being configured so as to: measure a quality factor of the transmitter antenna, measure a quality factor of the receiver antenna, and compare, during a transmitter quality factor comparison, the measured quality factor of the transmitter antenna with a predetermined quality factor threshold of the transmitter antenna and compare, during a receiver quality factor comparison, the measured quality factor of the receiver antenna with a predetermined quality factor threshold of the receiver antenna so as to deduce therefrom a position of a metal object in relation to the user device and to the transmitter antenna, and determine that: the metal object is aligned with both the transmitter antenna and the receiver antenna when the quality factor of the transmitter antenna is lower than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is lower than the predetermined quality factor threshold of the receiver antenna, the metal object is aligned with the transmitter antenna and not aligned with the receiver antenna when the quality factor of the transmitter antenna is lower than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is greater than the predetermined quality factor threshold of the receiver antenna, the metal object is aligned with the receiver antenna and not aligned with the transmitter antenna when the quality factor of the transmitter antenna is greater than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is lower than the predetermined quality factor threshold of the receiver antenna, and the metal object is not aligned with the transmitter antenna and not aligned with the receiver antenna when the when the quality factor of the transmitter antenna is greater than the predetermined quality factor threshold of the transmitter antenna and when the quality factor of the receiver antenna is greater than the predetermined quality factor threshold of the receiver antenna.

5. An inductive charging system comprising the charging apparatus as claimed in claim 4, the device positioned on the support of the charging apparatus and the metal object positioned between said user device and said support.

6. A motor vehicle comprising the charging apparatus as claimed in claim 4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of aspects of the invention will become apparent from the following description, given with reference to the appended figures that are given by way of non-limiting example and in which identical references are given to similar objects.

(2) FIG. 1 schematically illustrates one embodiment of the vehicle according to an aspect of the invention.

(3) FIG. 2 illustrates an exemplary semi-functional circuit diagram of the vehicle according to an aspect of the invention in a first mode of operation.

(4) FIG. 3 schematically illustrates an example of the four possible configurations of the assembly formed by the transmitter antenna, the metal object and the receiver antenna.

(5) FIG. 4 schematically illustrates one embodiment of the method according to the invention.

(6) FIG. 5 illustrates the semi-functional circuit diagram of FIG. 2 in a second mode of operation.

(7) FIG. 6 is an example of the change in the amplitude of the inductive charging signal as a function of frequency.

(8) FIG. 7 is a graph showing examples of measurements of the quality factor of the transmitter antenna and of the receiver antenna.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) FIGS. 1, 2 and 5 schematically show a motor vehicle 1 comprising a charging apparatus 10 (or charger) according to an aspect of the invention. The charging apparatus 10 may for example be installed in the central console, between the driver's seat and the front passenger seat of the vehicle 1. The charging apparatus 10 is an apparatus for inductively charging a user device 20, using for example Qi technology.

(10) The charging apparatus 10 comprises a transmitter antenna 100, a support 110 for receiving a user device 20, installed above said what is called “transmitter” antenna 100 and intended to receive the user device 20 in order to allow it to be inductively charged. In this example, the charging apparatus 10 also comprises a memory area 120 and a processor 130 (or a microcontroller). It will be noted that the memory area 120 and the processor 130 could be external to the charging apparatus 10.

(11) The user device 20 comprises what is called a “receiver” antenna 200, a processor 210 (or a microcontroller), a memory area 220 and a battery 230. The receiver antenna 200 makes it possible to receive an inductive charging signal transmitted by the transmitter antenna 100 of the charging apparatus 10 and making it possible to charge said battery 230.

(12) The terms “transmitter antenna” 100 and “receiver antenna” 200 are understood within the meaning of inductive charging, that is to say that the transmitter antenna 100 transmits the inductive charging signal, this being received by the receiver antenna 200 in order to allow the battery 230 to be charged. However, it goes without saying that the transmitter antenna 100 may also receive signals and that the receiver antenna 200 may also transmit signals, in particular in the context of communication between the charging apparatus 10 and the user device 20 in order for example to configure the transmission power of the charging signal or to exchange data, such as for example the apparatus reference quality factor Q.sub.0T.sub.X and the user device reference quality factor Q.sub.0R.sub.X, as will be described below.

(13) The memory area 220 of the user device 20 contains a reference value of a quality factor of the transmitter antenna 100 of a calibration charger (not shown), measured beforehand when the user device 20 was present, for example in the factory in a preliminary calibration process. This reference value, called apparatus reference quality factor, is denoted Q.sub.0T.sub.X.

(14) The memory area 220 of the user device 20 also contains a reference value of a quality factor of the receiver antenna 200 said user device 20, measured beforehand on a calibration charger (not shown), for example in the factory in a preliminary calibration process on the model of the user device 20. This reference value, called user device reference quality factor, is denoted Q.sub.0R.sub.X.

(15) The memory area 120 of the charging apparatus 10 also contains a value of a quality factor of the transmitter antenna 100 of the charging apparatus 10, measured when the user device 20 is absent from the reception support 110. This reference value, called no-load quality factor of the charging apparatus 10, is denoted Q.sub.DC.

(16) This no-load quality factor Q.sub.DC of the charging apparatus 10 makes it possible to estimate the losses generated by just the charging apparatus 10 during operation thereof, for example due to its internal components. More precisely, the ratio of this no-load quality factor Q.sub.DC of the charging apparatus 10 to the no-load quality factor of the calibration charger (denoted Q.sub.CC) corresponds to the loss percentage of the charging apparatus 10 in the absence of a user device 20. This ratio, called loss factor and denoted K, makes it possible to determine the efficiency of the charging apparatus 10 in comparison with the calibration charger. For example, if, when the charging apparatus 10 is calibrated in the absence of a user device 20, a no-load quality factor Q.sub.DC of the charging apparatus 10 of 80 is measured and the no-load quality factor Q.sub.CC of the calibration charger is 100, then it is considered that the loss factor of the charging apparatus is (80/100)=0.8, i.e. 80%, that is to say that the charging apparatus 10 generates losses of 20% due to its operation.

(17) The processor 130 of the charging apparatus 10 is configured so as to perform a plurality of tasks. The processor 130 is in particular configured so as to receive the reference quality factor of the apparatus Q.sub.0T.sub.X from the user device 20 and to calculate a quality factor threshold of the transmitter antenna, denoted ST.sub.X, from said received reference quality factor of the apparatus Q.sub.0T.sub.X and from the stored loss factor K of the charging apparatus 10.

(18) The processor 130 is configured so as to receive the user device reference quality factor Q.sub.0R.sub.X from the user device 20 and to calculate a quality factor threshold of the receiver antenna, denoted SR.sub.X, from said received reference quality factor of the user device and from the stored loss factor K of the charging apparatus 10.

(19) With reference to FIGS. 1 and 2, the processor 130 is configured so as to measure the quality factor of the transmitter antenna, denoted QT.sub.X, to measure the quality factor of the receiver antenna, denoted QR.sub.X, and to compare firstly the measured quality factor QT.sub.X of the transmitter antenna 100 with the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100, and to compare secondly the measured quality factor QR.sub.X of the receiver antenna 200 with the predetermined quality factor threshold SR.sub.X of the receiver antenna 200 so as to deduce therefrom a position of a metal object 30 in relation to the transmitter antenna 100 and to the receiver antenna 200 or to deduce therefrom the absence of an interfering metal object 30.

(20) With continuing reference to FIGS. 1 and 2, the processor 130 is configured so as to determine that the transmitter antenna 100, the metal object 30 and the receiver antenna 200 are aligned when the measured quality factor QT.sub.X of the transmitter antenna 100 is lower than the predetermined quality factor threshold ST.sub.X of the transmitter antenna and when the measured quality factor QR.sub.X of the receiver antenna 200 is lower than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(21) With continuing reference to FIGS. 1 and 2, the processor 130 is configured so as to determine that the transmitter antenna 100 and the metal object 30 are aligned with one another but are not aligned with the receiver antenna 200 when the measured quality factor QT.sub.X of the transmitter antenna 100 is lower than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the measured quality factor QR.sub.X of the receiver antenna 200 is greater than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(22) With continuing reference to FIGS. 1 and 2, the processor 130 is configured so as to determine that the metal object 30 and the receiver antenna 200 are aligned with one another but are not aligned with the transmitter antenna 100 when the measured quality factor QT.sub.X of the transmitter antenna 100 is greater than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the measured quality factor QR.sub.X of the receiver antenna 200 is lower than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(23) With continuing reference to FIGS. 1 and 2, the processor 130 is configured so as to determine that the metal object 30 is not aligned with the transmitter antenna 100 or with the receiver antenna 200 when the measured quality factor QT.sub.X of the transmitter antenna 100 is greater than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the measured quality factor QR.sub.X of the receiver antenna 200 is greater than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(24) In the embodiment illustrated in FIGS. 2 and 5, the charging apparatus 10 furthermore comprises an RFID (radiofrequency identifier or radio identification) communication circuit 140, operating for example at 13.56 MHz when the charging apparatus 10 uses a near-field communication (NFC) function, an inductive charging circuit 150, an RFID communication antenna 160 (for example an NFC one) and a variable-frequency generator 170. In this example, the point S corresponds to the point at which the voltage or the current is measured on the RFID communication antenna 160.

(25) The charging apparatus 10 also comprises two switching circuits I1, I2 in order to switch between what is called an “NFC communication” mode via the RFID communication antenna 160 and what is called a “measurement” mode in which the processor 130 measures the voltage at the point S in order to estimate the quality factor QR.sub.X of the receiver antenna 200. The charging apparatus 10 also comprises a switching circuit 13 for deactivating the charging mode and activating the variable-frequency generator 170.

(26) Remaining in the embodiment illustrated in FIGS. 2 and 5, the user device 20 comprises a series resonant capacitor Cs, a parallel resonant capacitor Cp, a switching circuit 14 activated only in the event of inductive charging, and a rectifier circuit 240 for transforming the received AC current into a DC current for charging the battery 230.

(27) By way of example, the switching circuits I1, I2, I3 and I4 may take the form of switches, for example implemented by transistors.

(28) An aspect of the invention will now be described in terms of its implementation with reference to the figures, in particular to FIG. 4.

(29) It is considered as a prerequisite that the user device 20 has undergone a test phase beforehand in order to determine its apparatus reference quality factor Q.sub.0T.sub.X and its user device 20 reference quality factor Q.sub.0R.sub.X, the values of these two factors being stored in the memory area 220 of the user device 20. It is also considered as a prerequisite that the charging apparatus 10 has undergone a test phase beforehand in order to determine its loss factor K representative of its loss percentage in comparison with the calibration charger.

(30) In a preliminary step E0, the user device 20 communicates its apparatus reference quality factor Q.sub.0T.sub.X and its user device 20 reference quality factor Q.sub.0R.sub.X to the charging apparatus 10, the processor 130 stores the values of these two factors in the memory area 120 of the charging apparatus 10 and calculates a quality factor threshold ST.sub.X of the transmitter antenna 100 and a quality factor threshold SR.sub.X of the receiver antenna 200 on the basis of these values (Q.sub.0T.sub.X, Q.sub.0R.sub.X) and of its loss factor K, this being described further below. The processor 130 uses these threshold values each time the user device 20 is charged.

(31) It will be noted that the processor 130 may calculate and store values of a quality factor threshold ST.sub.X of the transmitter antenna 100 and of a quality factor threshold SR.sub.X of the receiver antenna 200 for several different types of user device 20 and use the appropriate values depending on the type of user device 20 during charging.

(32) In a step E1, the processor 130 measures the quality factor QT.sub.X of the transmitter antenna 100.

(33) First of all, the switching circuits I1, I2 and I3 are activated in order to connect the RFID communication circuit 140 and the inductive charging circuit 150 to the RFID communication antenna 160 and to the transmitter antenna 100, respectively.

(34) The generator 170 generates a variable-frequency electrical signal so as to be able to measure the signal at the measurement point S. This measured signal corresponds to the frequency image of the resonance of the charging apparatus 10 and of the user device 20, illustrated in FIG. 6.

(35) In this FIG. 6, the frequency band B1, for example [0.02-0.08 MHz], corresponds to the operating band of the transmitter antenna 100 and the frequency band B2, for example [0.7-2.0 MHz], corresponds to the operating band of the receiver antenna 200.

(36) The quality factor QT.sub.X of the transmitter antenna 100 is then calculated from a frequency bandwidth at −3 dB around the resonant frequency fr_T.sub.X of the transmitter antenna 100 using the following equation:

(37) ${\mathrm{QT}}_X=\frac{{\mathrm{fr\_T}}_X}{\mathrm{W\_fr}{\mathrm{\_T}}_X}$

(38) where fr_T.sub.X is the resonant frequency of the transmitter antenna 100 and W_fr_T.sub.X is the frequency bandwidth at −3 dB, centered on the resonant frequency of the transmitter antenna 100.

(39) In a step E2, the processor 130 measures the quality factor QR.sub.X of the receiver antenna 200. For this purpose, with the switching circuits I1, I2 and I3 being activated in order to connect the RFID communication circuit 140 and the inductive charging circuit 150 to the RFID communication antenna 160 and to the transmitter antenna 100, respectively, the generator 170 generates a variable-frequency electrical signal so as to be able to measure the signal at the measurement point S. This measured signal corresponds to the frequency image of the resonance of the charging apparatus 10 and of the user device 20.

(40) The quality factor QR.sub.X of the receiver antenna is then calculated from a frequency bandwidth at −3 dB around the resonant frequency fr_R.sub.X of the receiver antenna 200 using the following equation:

(41) ${\mathrm{QR}}_X=\frac{{\mathrm{fr\_R}}_X}{\mathrm{W\_fr}{\mathrm{\_R}}_X}$

(42) where fr_R.sub.X is the resonant frequency of the receiver antenna 200 and W_fr_R.sub.X is the frequency bandwidth at −3 dB, centered on the resonant frequency of the receiver antenna 200.

(43) It will be noted that the order of steps E1 and E2 could be swapped or that steps E1 and E2 could be simultaneous.

(44) These steps E1 and E2 thus make it possible firstly to directly measure the quality factor of the transmitter antenna 100 in its operating band B1 and secondly to indirectly measure the quality factor QR.sub.X of the receiver antenna 200 through feedback by sending a variable signal via the RFID communication antenna 160 and by measuring the voltage or the current at the point S in the operating band B2 of the receiver antenna 200.

(45) In a step E3, the processor 130 compares the measured quality factor QT.sub.X of the transmitter antenna 100 with the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and compares the measured quality factor QR.sub.X of the receiver antenna 200 with the predetermined quality factor threshold SR.sub.X of the receiver antenna 200 so as to deduce therefrom the relative position of the metal object 30 in relation to the transmitter antenna 100 and to the receiver antenna 200 or the absence of an interfering metal object 30.

(46) More precisely, the processor 130 determines, in a step E4A, that the transmitter antenna 100, the metal object 30 and the receiver antenna 200 are aligned (configuration 1) when the measured quality factor QT.sub.X of the transmitter antenna 100 is lower than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the measured quality factor QR.sub.X of the receiver antenna 200 is lower than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(47) The processor 130 determines, in a step E4B, that the metal object 30 and the transmitter antenna 100 are aligned with one another but are not aligned with the receiver antenna 200 (configuration 2) when the measured quality factor QT.sub.X of the transmitter antenna 100 is lower than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the measured quality factor QR.sub.X of the receiver antenna 200 is greater than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(48) The processor 130 determines, in a step E4C, that the metal object 30 and the receiver antenna 200 are aligned with one another but are not aligned with the transmitter antenna 100 (configuration 3) when the measured quality factor QT.sub.X of the transmitter antenna 100 is greater than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the measured quality factor QR.sub.X of the receiver antenna 200 is lower than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

(49) The processor 130 determines, in a step E4D, that the metal object 30 is not aligned with the transmitter antenna 100 or with the receiver antenna 200 (configuration 4) when the measured quality factor QT.sub.X of the transmitter antenna 100 is greater than the predetermined quality factor threshold ST.sub.X of the transmitter antenna 100 and when the quality factor QR.sub.X of the receiver antenna 200 is greater than the predetermined quality factor threshold SR.sub.X of the receiver antenna 200.

Exemplary Implementation

(50) In this purely illustrative example, it is considered as a prerequisite that: the no-load quality factor Q.sub.CC of the calibration charger is 100, the no-load quality factor Q.sub.DC of the charging apparatus 10 is 80 (that is to say a loss factor K of 0.8, corresponding to losses of 20%), the apparatus reference quality factor Q.sub.0T.sub.X is 70, the user device reference quality factor Q.sub.0R.sub.X is 40.

(51) In the preliminary step E0, the charging apparatus 10 receives the values of the apparatus reference quality factor Q.sub.0T.sub.X and of the user device 20 reference quality factor Q.sub.0R.sub.X from the user device 20 and calculates the quality factor threshold ST.sub.X of the transmitter antenna 100 and the quality factor threshold SR.sub.X of the receiver antenna 200 as follows: the quality factor threshold ST.sub.X of the transmitter antenna 100 corresponds to the product of the apparatus reference quality factor Q.sub.0T.sub.X and the loss factor K of the user device 20, that is to say in this case: ST.sub.X=70×0.8=56, the quality factor threshold SR.sub.X of the receiver antenna 200 corresponds to the product of the user device 20 reference quality factor Q.sub.0R.sub.X and the loss factor K of the user device 20, that is to say in this case: SR.sub.X=40×0.8=32.

(52) When the user device 20 is charged on the reception support 110, the processor 130 measures the quality factor QT.sub.X of the transmitter antenna 100 and the quality factor QR.sub.X of the receiver antenna 200 (steps E1 and E2) and compares these two values with their respective threshold ST.sub.X and SR.sub.X.

(53) FIG. 7 shows a graph of the quality factor QR.sub.X of the receiver antenna 200 as a function of the quality factor QT.sub.X of the transmitter antenna 100 for the four configurations illustrated in FIG. 3.

(54) For example, if the measured value of the quality factor QT.sub.X of the transmitter antenna 100 is lower than 56 (quality factor threshold ST.sub.X of the transmitter antenna 100) and if the measured value of the quality factor QR.sub.X of the receiver antenna 200 is lower than 32 (quality factor threshold SR.sub.X of the receiver antenna 200), then the processor 130 deduces therefrom that the transmitter antenna 100, the metal object 30 and the receiver antenna 200 are aligned, this corresponding to configuration 1, illustrated in FIG. 3. This corresponds to area A of the graph in FIG. 7.

(55) In this case, the charging apparatus 10 may reduce the charging power or stop charging and signal the presence of a metal object to the user.

(56) If the measured value of the quality factor QT.sub.X of the transmitter antenna 100 is lower than 56 (quality factor threshold ST.sub.X of the transmitter antenna 100) and if the measured value of the quality factor QR.sub.X of the receiver antenna 200 is greater than 32 (quality factor threshold SR.sub.X of the receiver antenna 200), then the processor 130 deduces therefrom that the transmitter antenna 100 and the metal object 30 are aligned with one another but are not aligned with the receiver antenna 200. This corresponds to configuration 2 in FIG. 3 and to area D in FIG. 7. In this case, the charging apparatus 10 may reduce the charging power or stop charging and signal the presence of a metal object to the user.

(57) If the measured value of the quality factor QT.sub.X of the transmitter antenna 100 is greater than 56 (quality factor threshold ST.sub.X of the transmitter antenna 100) and if the measured value of the quality factor QR.sub.X of the receiver antenna 200 is lower than 32 (quality factor threshold SR.sub.X of the receiver antenna 200), then the processor 130 deduces therefrom that the metal object 30 and the receiver antenna 200 are aligned with one another but are not aligned with the transmitter antenna 100. This corresponds to configuration 3 in FIG. 3 and to area B in FIG. 7. In this case, the charging apparatus 10 may reduce the charging power or stop charging and signal the presence of a metal object to the user.

(58) If the measured value of the quality factor QT.sub.X of the transmitter antenna 100 is greater than 56 (quality factor threshold ST.sub.X of the transmitter antenna 100) and if the measured value of the quality factor QR.sub.X of the receiver antenna 200 is greater than 32 (quality factor threshold SR.sub.X of the receiver antenna 200), then the processor 130 deduces therefrom that the metal object 30 is not aligned with the transmitter antenna 100 or with the receiver antenna 200 or is absent from the reception support 110. This corresponds to configuration 4 in FIG. 3 and to area C in FIG. 7.

(59) In this case, the charging apparatus 10 transmits or continues to transmit the power required by the user device 20.

(60) The method according to an aspect of the invention thus makes it possible to easily determine whether a metal object is present on the reception support 110, between the transmitter antenna 100 of the charging apparatus 10 and the receiver antenna 200 of the user device 20, and to specify in which of the four configurations they are positioned in order to take the appropriate measures depending on the configuration, for example reduce the power of the charging signal or else interrupt charging.