Method for detecting parasitic metal objects on a charging surface and associated charging device

Abstract

A method for detecting parasitic metal objects on a charging surface and an associated charging device. The invention provides a method for detecting a foreign metal object by a charging device (D'), the charging device (D') comprising a microcontroller (10') and a transmitting circuit (E), the transmitting circuit (E) comprising at least one transmitting antenna (B1), the transmitting antenna (B1) being adapted to transmit a parasitic metal object at an operating frequency (F RF ) for charging a portable item (P) of user equipment placed on a charging surface (S), the method being characterized in that it comprises the steps of: a) transmitting a signal at a parasitic resonant frequency (F) at the terminals of a transmitting antenna (B1) RP ) transmitting a predetermined number (N) of voltage pulses (P1), the parasitic resonance frequency being different from and distinct from the operating frequency, b) determining the oscillation frequency (F) of the transmitting circuit E ), c) If the oscillation frequency (F E ) is higher than the parasitic resonant frequency (F RP ), a foreign metal object is detected on the charging surface (S).

Description

Technical Field

[0001] The technical field of the invention is the technical field of magnetic induction charging devices. In particular, the invention relates to a method for detecting parasitic metal objects on a charging surface of a magnetic induction charging device and to an associated charging device. Background Art

[0002] The magnetic induction charging technology is implemented in a system comprising a wireless charging device and a battery to be charged in a mobile terminal, such as, for example, a portable item of user equipment, such as a mobile phone. The charging device comprises a transmission antenna or a transmitting antenna. The battery comprises a receiving antenna to be charged. When the transmission antenna and the receiving antenna are positioned relative to each other, the change in the magnetic field generated by the transmission antenna causes a current to flow in the receiving antenna, thereby charging the battery.

[0003] Inductive charging technology meets the requirements of a standard, in this case, the Wireless Power Consortium’s Qi® standard, also known as the WPC standard.

[0004] In order to detect the presence of a foreign metallic object on the charging surface or to detect the presence of a battery comprising a receiving antenna positioned opposite to a transmitting antenna of a charging device, three steps are currently implemented.

[0005] In a first step, the prior art method seeks to detect the presence of an object positioned relative to the charging device. To this end, an electrical pulse, also called a "ping", is sent via the transmission antenna of the charging device to the receiving antenna at the charging frequency. The ping is a continuous signal that exhibits periodic oscillations with a period of, for example, 300 ms and with an oscillation time of 5 to 20 ms. The voltage or impedance at the terminals of the transmission antenna is observed. If a change in the voltage at the terminals of the transmission antenna or a change in the impedance of the transmission antenna is detected, an object is present relative to the transmission antenna.

[0006] The detected object may be a parasitic metal object or a mobile device, such as a mobile phone equipped with a receiving antenna for inductive charging. In a second step, an effort is then made to establish digital communication with the detected object in order to identify its characteristics. More specifically, in this second step, an effort is made to conclude whether the detected object comprises a receiving antenna for inductive charging in order to charge the latter and that the object is not a parasitic metal object. This communication is performed by modulating the voltage amplitude of the transmitting antenna.

[0007] When digital communication is established between the receiving antenna and the transmitting antenna of the detected object, then the third step begins. The third step allows the receiving antenna of the detected object to be charged.

[0008] If communication cannot be established, a foreign metal object is involved and charging is not initiated.

[0009] The disadvantages of this detection method are the high power consumption caused during the transmission of the ping and also the amount of harmful radiation close to the human body. In some cases, when the human body is close (within a few centimeters) to the transmitting antenna, this radiation may exceed the international recommendations for continuous exposure to magnetic fields.

[0010] Another method known from the prior art is to use one or more NFC (Near Field Communication) antennas located in the inductive charger in order to detect the presence of a battery. This method consists in transmitting a signal at a fixed frequency of 13.56 MHz; if a battery is positioned close to an NFC antenna, the impedance and / or consumption of said NFC antenna changes.

[0011] However, this method consumes a lot of power and requires the presence of an NFC antenna in the inductive charger, which is not always possible.

[0012] The object of the present invention is to overcome all or some of the disadvantages of the prior art, in particular those outlined above, by providing a method for detecting foreign metal objects on the charging surface of an inductive recharging device, which method also allows detection of any type of portable equipment, regardless of the size of the receiving antenna, and also of power receivers used in certification tests of the Qi standard. Summary of the invention

[0013] The present invention provides a method for detecting a foreign metal object by a charging device, the charging device comprising a microcontroller and a transmitting circuit, the transmitting circuit comprising at least one transmitting antenna, which is suitable for charging a portable item of user equipment placed on a charging surface at an operating frequency, the method being characterized in that it comprises the following steps:

[0014] 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 from and distinct from the operating frequency,

[0015] b. Determine the oscillation frequency of the transmitting circuit,

[0016] c. If the oscillation frequency is higher than the parasitic resonance frequency, a foreign metal object is detected on the charging surface.

[0017] More specifically, if the oscillation frequency is below the parasitic resonant frequency, then a portable item of user equipment to be charged is detected on the charging surface.

[0018] Conveniently, the simultaneous presence of the portable item of user equipment to be charged and the foreign metallic object is detected if the transmit circuit oscillates at the second resonant frequency when the frequency of the transmit circuit is above the parasitic resonant frequency.

[0019] Advantageously, the predetermined number is equal to three.

[0020] More specifically, the parasitic resonant frequency is between 200 kHz and 1 MHz.

[0021] The invention also relates to any charging device for a portable item of user equipment, comprising a microcontroller and a transmitting circuit, the transmitting circuit comprising at least one transmitting coil adapted to charge the portable item of user equipment at an operating frequency, the device being characterized in that the transmitting circuit further comprises means for generating a parasitic resonant frequency different and distinct from the operating frequency, and characterized in that the device further comprises:

[0022] a. a device for measuring the oscillation frequency of the transmitting circuit, and

[0023] b. Means for detecting a portable item of user equipment to be charged from the oscillation frequency thus measured.

[0024] More specifically, the detection means comprises means for comparing the oscillation frequency and the parasitic resonance frequency.

[0025] Conveniently, the apparatus further comprises means for measuring the second resonant frequency of the transmit circuit and means for detecting a compatible portable item of equipment to be charged in dependence on the second frequency provided thereby.

[0026] Advantageously, the means for generating the parasitic resonant frequency are in the form of means for generating a predetermined number of voltage pulses at the terminals of the transmitting antenna at the parasitic resonant frequency.

[0027] The generating means may comprise a switch, a capacitor and a resistor connected to a voltage source.

[0028] More specifically, the parasitic resonant frequency is between 200 kHz and 1 MHz.

[0029] The invention relates to any motor vehicle comprising a charging device according to any of the preceding features. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features and advantages of the present invention will become more apparent by reading the following description. This description is purely illustrative and must be read with reference to the accompanying drawings, in which:

[0031] [ Figure 1 ]: Figure 1 A prior art charging device D is schematically shown, above which there is a portable item of user equipment P to be charged,

[0032] [ Figure 2 ]: Figure 2schematically shows a device according to the invention for generating voltage pulses at a parasitic resonance frequency,

[0033] [ Figure 3 ]: Figure 3 A charging device D' according to the invention is schematically shown,

[0034] [ Figure 4 ]: Figure 4 is a graph showing a voltage pulse emitted at a parasitic resonant frequency,

[0035] [ Figure 5 ]: Figure 5 is a flow chart showing the various steps of the detection method according to the present invention,

[0036] [ Figure 6 ]: Figure 6 is a graph showing the parasitic resonant frequency as a function of the impedance of the transmitting circuit,

[0037] [ Figure 7 ]: Figure 7 is a graph showing the second resonant frequency and the variation of the resonant frequency as a function of the impedance of the transmit circuit when a portable item of user equipment is placed on a charging surface,

[0038] [ Figure 8 ]: Figure 8 is a graph showing the second resonant frequency and the variation of the resonant frequency as a function of the impedance of the transmitting circuit in a case where a foreign metal object and a portable item of user equipment are placed simultaneously on the charging surface,

[0039] [ Fig. 9 ]: Fig. 9 is a graph showing the second resonant frequency and the change in the resonant frequency as a function of the impedance of the transmitting circuit when a foreign metal object is placed on the charging surface. DETAILED DESCRIPTION

[0040] Figure 1 A prior art charging device D is shown which comprises a transmitting antenna Bl and a charging surface S on which a portable item of user equipment P comprising a receiving antenna B2 is placed.

[0041] The charging device D or inductive charging device may, for example but in a completely non-limiting manner, be intended to be installed in a motor vehicle.

[0042] As previously described, when the transmitting antenna B1 and the receiving antenna B2 are positioned relative to each other, the change in the magnetic field generated by the transmitting antenna B1 causes current to flow in the receiving antenna B2, thereby charging the portable item P of user equipment.

[0043] The present invention provides Figure 2 and 3 A charging device D' is shown in , which allows to overcome the disadvantages of the prior art.

[0044] The device D' comprises a printed circuit 10' equipped with a microcontroller connected to the transmitting antenna B1 and also to the impedance matching capacitor C1. The microcontroller 10 is suitable for managing the operation at the operating frequency F RF The operating frequency F RF is the frequency used for charging portable items of user equipment P according to the Qi standard of the WPC® (Wireless Power Consortium) and is between 90 kHz and 205 kHz. To this end, the microcontroller comprises hardware and software means suitable for managing the transmission and reception of data and also the control of the operation of the transmitting antenna B1. This is known from the prior art and will not be described in more detail here.

[0045] According to the present invention, in a first embodiment of the present invention, the charging device D' is equipped so that it further comprises:

[0046] a. Device M1 for generating a parasitic resonant frequency F via the transmitting antenna B1 RP , the parasitic resonance frequency is, for example, in the window between 200 kHz and 1 MHz,

[0047] b. Device M2, for measuring the oscillation frequency F of the transmitting circuit E E ,as well as

[0048] c. means M3 for measuring the oscillation frequency F of the transmitting circuit E in accordance with the above E Detects foreign metal objects.

[0049] Generator M1 Figure 2 is shown in FIG. 1 and is an example for a parasitic resonant frequency F RP The voltage V bounded by the transmitting coil B1 1 The device for generating a predetermined number of pulses P1 is in the form of a device and comprises:

[0050] a. Switch S1, one side of which is connected to the branch of the transmitting antenna B1,

[0051] b. A capacitor C2 connected to ground, on the other side of the switch S1 and connected in parallel with the transmitting antenna B1, allows the resonant frequency F RP is adjusted to the desired value and is itself connected to

[0052] c. a resistor R1 connected in parallel with the capacitor C2 and in parallel with the voltage source Vcc, and

[0053] d. means M0 for controlling said switch S1 so as to open or close said switch, said control means M0 being in the form of software, for example.

[0054] The means M1 for generating a resonant frequency are in the form of a generator of a voltage signal, for example in the form of a square wave.

[0055] By controlling the opening and closing of the switch S1 connected to the voltage source Vcc, the parasitic resonant frequency F RP A voltage V1 pulse P1 is generated at the terminals of the transmitting antenna B1. Figure 4 Shown in. Figure 5 Three voltage pulses in the form of square waves are shown.

[0056] Used to measure parasitic resonance frequency F RP The changing means M2 is, for example, in the form of software.

[0057] "Transmitter Circuit E" (see Figure 2 ) is intended to mean a transmitting antenna B1, an impedance matching capacitor C1 and a capacitor for generating a parasitic resonant frequency F RP A collection of components of the device M1.

[0058] The measuring device M2 may include the following means: B1 (between the transmitting circuit E and electrical ground) and within a predetermined period Δt the voltage V B1 A comparison is made with two threshold voltages, a minimum voltage V− and a maximum voltage V+, in order to determine the oscillation frequency of said transmitting circuit E. These means for temporal analysis of the voltage B1 of the transmitting circuit E so as to allow its oscillation frequency to be deduced therefrom are known to a person skilled in the art and will not be described in greater detail here.

[0059] Alternatively, the measuring means M2 may comprise means for frequency analysis, such as the voltage V B1 Fourier transform in order to determine the oscillation frequency F of the circuit E E .

[0060] A time or frequency analysis of the voltage at the terminals of the transmitting coil B1 or of the voltage at the terminals of the resistor R1 may also be used.A person skilled in the art may determine the oscillation frequency of the transmitting circuit E by analyzing the voltages at the terminals of components of said circuit.

[0061] The device M3 for detecting foreign metallic objects also comprises a device for comparing the oscillation frequency F of the transmitting circuit E thus measured. E and parasitic resonant frequency F RP device.

[0062] Said detection means M3 are adapted to determine the presence of a metal object and / or a portable item of user equipment P. Said detection means M3 may be in the form of software.

[0063] The generating means M1 , the measuring means M2 and the detecting means M3 can be included in the printed circuit 10 ′ in the form of discrete components with a microcontroller or in the form of an ASIC (Application Specific Integrated Circuit) and / or in the form of software.

[0064] In a second embodiment of the invention, the device D' further comprises a device for measuring the second resonance frequency F RR means M4 and for providing a second frequency F in accordance with the RR Device M5 to detect compatible portable items of equipment to be charged.

[0065] Used to measure the second resonant frequency F RR The means M4 and also the detection means M5 may be in software form and each comprise a voltage V for the transmitting circuit E B1 means of time or frequency analysis, such as those described above for the measuring means M2, which make it possible to detect whether the transmitting circuit E is transmitting at the second resonant frequency F RR oscillation in order to determine the value of the frequency, and for converting the second frequency F RR A device that compares with a predetermined value.

[0066] The second resonant frequency F RR The predetermined value of corresponds to a resonance frequency value of a receiver compatible with a charging standard, which is the Qi standard here, and is, for example, between 800 kHz and 1200 kHz.

[0067] The present invention is based on the following observation by the applicant: when the transmitting antenna B1 is at a parasitic frequency F RP When generating electromagnetic waves, the presence of a parasitic metal object on the charging surface S of the device D' and / or a compatible portable item of user equipment P causes the transmitting circuit E to generate electromagnetic waves at a parasitic resonant frequency F RP Change (shift) the oscillation frequency F E Oscillations, which vary downward or upward depending on the characteristics of the object on the surface of the device D'.

[0068] In particular, the Applicant has observed that in the presence of a foreign metallic object (or FO), the oscillation frequency F E has a higher initial parasitic resonant frequency F RP High value.

[0069] In contrast, in the presence of a compatible portable item P or TPR of user equipment, that is to say a test power receiver, that is to say a battery used during the phase of certification of a mobile phone for the Qi standard, the oscillation frequency F E has a higher initial parasitic resonant frequency F RP Low value.

[0070] Furthermore, the Applicant has observed that when a portable item P of user equipment is present on the charging surface S, the transmitting antenna B1 is charged at the parasitic resonant frequency F RP The emitted electromagnetic field additionally leads to the appearance of a second resonance frequency, which is F RR is the resonant frequency of the receiver P.

[0071] Now it will follow Figure 5 The detection method according to the present invention is described according to the flowchart shown in FIG.

[0072] In an initial step E1, a parasitic resonance frequency F is generated at the terminals of the transmitting antenna B1. RP Emit a predetermined number N of voltage pulses P1 (see Figure 4 ), for example, N = 3, that is, three consecutive voltage pulses P1, parasitic resonance frequency F RP That is, in a window of values ​​between 200 kHz and 1 MHz, with a tolerance of + / - 10%, or between approximately 180 kHz and 1.1 MHz. These voltage pulses are at the parasitic resonant frequency F RP The transmitting circuit E is excited. The pulse has a period between 0.91 μs and 5.56 μs. Figure 4 in and Figure 6 Shown in.

[0073] The parasitic resonance frequency F RP Between 200 kHz and 1 MHz and differs from the operating frequency F according to the WPC Qi standard RF , the operating frequency F RF Partially between 90 kHz and 205 kHz.

[0074] In a second step E2 , once the three pulses P1 have been generated, the voltage V of the transmitting circuit E is measured. B1 And then determine the oscillation frequency F of the circuit E E Two implementations are possible, time analysis or frequency analysis.

[0075] In the third step E3, if the oscillation frequency F of the transmitting circuit E E Equal to the parasitic resonant frequency F RP, it is inferred from this that no object has yet been placed on the placement surface S, and the method returns to the first step E1.

[0076] In a fourth step E4, the two frequencies F are compared. E and F RP ; If the oscillation frequency F E Below the parasitic resonance frequency F RP , it is inferred therefrom that a portable item P or TPR of user equipment has been placed on the charging surface (step E5b ) and inductive charging is triggered (step E6b ).

[0077] This is Figure 7 The figure shows the parasitic resonance frequency F below. RP The oscillation frequency F E of charts.

[0078] If the oscillation frequency F E Higher than the parasitic resonance frequency F RP , it is inferred from this that there is a foreign metallic object FO on the charging surface S (step E5a ), which object may be alone on the charging surface or next to or below a portable item of user equipment P.

[0079] In order to distinguish between these two cases, step E6a involves checking whether the transmitting circuit E also operates at the second resonance frequency F RR To this end, a voltage V B1 time or frequency analysis, this voltage is the voltage of the transmitting circuit E relative to electrical ground.

[0080] If the transmitting circuit E is in addition to the frequency F E In addition to oscillation, it also oscillates at the second resonant frequency F RR Oscillation, the second resonant frequency F RR Different from and distinct from the parasitic resonant frequency F RP , and its value is within a predetermined window of values ​​corresponding to the resonance frequency of the Qi receiver, then not only the presence of a foreign metal object FO is inferred from it, but also the simultaneous presence of a portable item P or TPR equipped by the user on the charging surface S. In this case, inductive charging is not triggered, or it is initiated with very low power and the user is warned of the presence of a foreign metal object on the charging surface S by a warning message M, either acoustic or visual (step E7b), so that the user removes the foreign metal object from the surface to allow the inductive charging to be triggered. This Figure 8 It is shown in Figure 2, which shows that the parasitic resonance frequency F RP The oscillation frequency F E and the impedance Z as the transmitting circuit E The second resonant frequency F of the function RR The second resonant frequency FRR corresponds to the resonant frequency of a receiver compatible with the Qi standard and has in this example a value equal to 1 MHz.

[0081] If the transmitting circuit E does not have a frequency different from and distinct from the parasitic resonant frequency F RP The second resonant frequency F RR oscillates, from which it is concluded that only a foreign metal object FO is present on the charging surface S and no inductive charging is triggered (step E7a). Fig. 9 is shown in Figure 1, which shows the impedance Z of the circuit as E The function of the parasitic resonance frequency F RP The oscillation frequency F E .

[0082] The invention thus ingeniously makes it possible to determine the presence of a foreign metallic object on the charging surface of an inductive charging device in a manner that is simple and less energy intensive than prior art methods; in particular, the voltage pulse consumes much less electrical energy than prior art pings.

[0083] The invention is further advantageous because it makes it possible to detect also the presence of a foreign metallic object simultaneously with the presence of a compatible portable item of user equipment.

[0084] Furthermore, the implementation of the present invention is reliable and simple, because the technical means for embodying the present invention are mainly composed of inexpensive hardware devices or software devices.

Claims

1. A method for detecting a foreign metallic object by means of a charging device (D'), the charging device (D') comprising a microcontroller (10') and a transmitting circuit (E), the transmitting circuit (E) comprising at least one transmitting antenna (B1) adapted to transmit a metallic object at an operating frequency (F RF ) for charging a portable item of user equipment (P) placed on a charging surface (S), the method being characterized in that it comprises the following steps: a) At the terminals of the transmitting antenna (B1) at the parasitic resonant frequency (F RP ) emits a predetermined number (N) of voltage pulses (P1), the parasitic resonance frequency (F RP ) is different from and distinct from the operating frequency (F RF ), b) Determine the oscillation frequency (F) of the transmitting circuit E ), c) If the oscillation frequency (F E ) is higher than the parasitic resonant frequency (F RP ), a foreign metal object is detected on the charging surface (S), If the frequency of the transmitting circuit (F E ) is higher than the parasitic resonant frequency (F RP ) when the transmitting circuit (E) is at the second resonant frequency (F RR ) oscillates, the simultaneous presence of a portable item of user equipment to be charged and a foreign metal object is detected.

2. The detection method according to claim 1, characterized in that: If the oscillation frequency (F E ) is lower than the parasitic resonant frequency (F RP ), then a portable item of user equipment to be charged is detected on the charging surface (S).

3. The detection method according to any one of claims 1 to 2, characterized in that: The predetermined number (N) is equal to three.

4. The detection method according to any one of claims 1 to 2, characterized in that: Parasitic resonant frequency (F RP ) between 200kHz and 1MHz.

5. A charging device (D') for a portable item of user equipment (P), comprising a microcontroller (10') and a transmitting circuit (E), the transmitting circuit (E) comprising at least one transmitting coil (B1) adapted to charge a portable item (P) at an operating frequency (F RF ) for charging a portable item of user equipment, the device (D') being characterized in that the transmitting circuit (E) also includes a circuit for generating a signal having an operating frequency (F RF ) Different and distinct parasitic resonant frequencies (F RP ) and is characterized in that The device (D') also comprises: a) Used to measure the oscillation frequency (F) of the transmitting circuit E ) of the device (M2), b) used to measure the oscillation frequency (F E ) for detecting means (M3) for detecting a portable item (P) of user equipment to be charged, For measuring the second resonant frequency (F) of the transmitting circuit (E) RR ) device (M4), and For the second frequency (F RR ) to detect a compatible portable item of equipment to be charged.

6. The charging device (D') according to claim 5, characterized in that The detection device (M3) comprises a device for comparing the oscillation frequency (F E ) and parasitic resonant frequency (F RP ) device.

7. The charging device (D') according to claim 5 or 6, characterized in that: Used to generate parasitic resonant frequency (F RP ) is used to generate a parasitic resonant frequency (F RP ) generates a predetermined amount of voltage (V B1 ) The form of the pulse (P1) device.

8. The charging device (D') according to claim 5 or 6, characterized in that: The generating means (M1) comprises a switch (S1) connected to a voltage source (Vcc), a capacitor (C2) and a resistor (R1).

9. The charging device (D') according to claim 5 or 6, characterized in that: Parasitic resonant frequency (F RP ) between 200kHz and 1MHz.

10. A motor vehicle, characterized in that: It comprises a charging device (D′) according to any one of claims 5 to 9.

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