NFC charging

Abstract

NFC Charging The present description relates to a device comprising: an NFC controller (26); a microcontroller (10); a charger circuit (34) of an external battery; an energy harvesting device (32); an antenna (22); and a switch (36), controllable by the NFC controller (26), coupling the energy harvesting device (32) to the charger circuit (34). Abstract figure: figure 1

Description

Description Title of the invention: NFC charging technical field This description generally concerns Near Field Communication (NFC) devices, such as IoT (Internet of Things) devices or others. More specifically, this description focuses on wireless charging (WLC) of these devices. Previous technique In conventional devices, different antennas are used for NFC communications and for wireless charging. More recently, attempts have been made to implement WLC wireless charging using NFC technology. However, conventional circuits are not suitable for small devices such as IoT devices. Summary of the invention It would be desirable to have an NFC charging solution suitable for small devices such as IoT devices. One implementation method overcomes all or part of the drawbacks of known solutions. One embodiment provides for a device comprising: an NFC controller; a microcontroller; an external battery charging circuit; an energy recovery device; an antenna; and a switch, controllable by the NFC controller, coupling the energy harvesting device to the charging circuit. One embodiment provides a method for using a device comprising: an NFC controller; a microcontroller; an external battery charging circuit; an energy recovery device; an antenna; and a switch coupling the energy recovery device to the charging circuit, in which the switch is controlled by the NFC controller. According to one embodiment, said switch is in an open state during NFC communications in reader mode or card mode. D According to one embodiment, said switch is in a closed state during wireless charging cycles. According to one embodiment, the microcontroller generates a control signal to the charger circuit in order to regulate the charging current. According to one embodiment, said charging current is adjusted on the basis of the available energy of the field. According to one embodiment, in the presence of a field emitted by an external charging device, at least the NFC controller and the charging circuit are powered by the field. According to one embodiment, the microcontroller is also powered by the field. According to one embodiment, in the presence of a field emitted by an external charging device, as long as the battery charge level is below a threshold, the NFC controller and / or microcontroller cannot switch to NFC reader mode. According to one embodiment, in the presence of a field emitted by an external charging device, when the battery charge level is above a threshold, the microcontroller and / or the NFC controller is powered by the battery. According to one embodiment, in the presence of a field emitted by an external charging device, the NFC controller enters standby mode during charging cycles. According to one embodiment, in the presence of a field emitted by an external charging device, the microcontroller monitors the power available at the input of the charging circuit. According to one embodiment, the switch is of the normally open type. According to one embodiment, when the NFC controller detects an external wireless charging device emitting a field, it closes the switch coupling the energy harvesting device to the charging circuit. According to one embodiment, the switch is of the normally closed type. One embodiment provides for a device comprising: an NFC controller; a microcontroller; a battery charger; an energy recovery device; an antenna; and a switch coupling the energy recovery device to the battery charger. One embodiment provides a method for implementing the described device, in which the switch is controlled by the NFC controller. According to one embodiment, when the NFC controller detects a wireless charging transmitter (poller) emitting a field, it closes the switch coupling the energy recovery device for the battery charger. According to one embodiment, the microcontroller generates a control signal to the battery charger in order to regulate the charging current. According to one embodiment, said charging current is adjusted on the basis of the available energy of the field. According to one embodiment, in battery off mode, the fault state of the switch is "on" so that the charger is connected to the energy recovery device. According to one embodiment, in battery off mode, at least the NFC controller and battery charger are powered by the field. According to one embodiment, the microcontroller is also powered by the field. According to one embodiment, as long as the battery level is below a threshold, the charger requests the NFC controller and / or microcontroller to remain in "static mode". According to one embodiment, when the battery level is above the threshold, the battery powers the microcontroller, which is no longer powered by the field through the charger. According to one embodiment, during charging phases, the NFC controller enters standby mode. According to one embodiment, the NFC controller monitors the strength of the received signal. According to one embodiment, the microcontroller monitors the power available at the input of the charger. According to one embodiment, if the field falls below a threshold, the microcontroller and the NFC controller wake up and: If a charging phase ends and a communication phase begins, the microcontroller, via the NFC controller, communicates with the transmitter (poller) to negotiate the charging protocol; or If there is no available field, charging stops. According to one embodiment, an adjustment of an adaptation circuit which includes the device is made while the switch is open and the energy recovery device is “on”. According to one embodiment, the device is configured to implement the described process. Brief description of the drawings These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, provided by way of non-limiting example. relationship with the attached figures, among which: [Fig.1] represents, in a very schematic way and in block form, an embodiment of a device 1 adapted to exploit NFC communications and NFC recharging; Figures ZA and 2B illustrate, in a very schematic and block-like manner, overviews of an NFC communication system and a WLC wireless charging system respectively; [Fig.3] illustrates, schematically and in the form of a chronogram, a battery charging cycle; [Fig.4] represents, in more detail than in [Fig.1], an embodiment of a device adapted to exploit NFC communications and WLC recharging; [Fig.5] schematically illustrates a state of the architecture illustrated in [Fig.4]; [Fig.6] illustrates, schematically, another state of the architecture illustrated in [Fig.4]; [Fig.7] illustrates, schematically, another state of the architecture illustrated in [Fig.4]; [Fig.8] illustrates, schematically, another mode of operation of a device according to the architecture of [Fig.4]; Figure 9 schematically illustrates another mode of operation for a device based on the architecture of Figure 4; and [Fig.10] illustrates, by means of a chronogram, different modes of operation or states of a device according to the architecture of [Fig.4]. Description of the implementation methods The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties. For the sake of clarity, only the steps and elements useful for understanding the implementation methods described have been represented and are detailed. Unless otherwise specified, when referring to two connected elements, this means directly connected without any intermediate elements other than conductors, and when referring to two linked or coupled elements, this means that these two elements can be connected or linked or coupled through one or more other elements. In the description that follows, when referring to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to Orientation qualifiers, such as the terms "horizontal", "vertical", etc., refer, unless otherwise specified, to the orientation of the figures. Unless otherwise specified, the expressions 'approximately', 'roughly', 'significantly', and 'on the order of' mean within 10%, preferably within 5%. Many near-field communication devices, such as battery-powered smartphones, can also be recharged using an electromagnetic field. Most often, these devices use a different technology than NFC (developed by the NFC Forum) for charging; namely, a lower-frequency technology commonly known as Qi. This requires equipping the device with antennas and circuits dedicated to each function. Such a solution is, due to space constraints, unsuitable for small devices such as those generally referred to as IoT (Internet of Things). According to the described embodiments, solutions are planned that enable near-field communication (NFC) and wireless charging (WLC) functions in a smaller footprint and compatible with small objects. Small objects are defined as those that must integrate, in addition to their primary function (e.g., a watch, a temperature sensor, etc.), NFC and charging circuits within a volume of less than one cubic centimeter, preferably between 0.3 and 0.5 cubic centimeters, and even more preferably on the order of 0.4 cubic centimeters. It should be noted that, although the embodiments are described more specifically in relation to an application to IoT devices, they apply more generally to any type of NFC device regardless of its dimensions. Wireless charging using NFC technology is emerging. The NFC Forum defines criteria for wireless charging, known as WLC, using NFC technology in the "NFC Forum wireless charging" section. According to the embodiments described, a 13.56 MHz radio frequency field is used for: - NFC near field communications in reader mode and card mode; - charging without (WLC in charger mode or receiver mode. The described embodiments provide for a new electronic device architecture adapted to allow both NFC communications and NFC (WLC) charging, as well as operating modes allowing both NFC communications and NFC (WLC) charging. Taking the example of an IoT device, NFC charging can be used to recharge the IoT device using a smartphone. The IoT device includes, among other things: - an NFC controller to implement NFC communications in reader mode or card mode (generally referred to as legacy mode) and a wireless charging protocol; - a charging path to convert the received 13.56 MHz radio frequency signal into a continuous signal to recharge a battery via a charging circuit or chip; - a microcontroller to control the exchanges or communications between the charging chip and the NFC controller, and preferably with the other functions of the IoT device. Fig. 1 represents, in a very schematic way and in block form, an embodiment of a device 1 adapted to exploit NFC communications and NFC recharging. According to this embodiment, device 1, in the proposed architecture, includes a microcontroller 10 (MCU) whose role is, among other things, to construct (generate) the messages to be transmitted, to provide the rest of the system with information on the battery charge level and field strength requirements in order to update data packets in a format known by the acronym NDEF (NFC Data Exchange Format). The microcontroller communicates, in particular, with the NFC transceiver circuits, the other functions of device 1, represented by a block 12 (FCT), and the battery charging circuits 14 (BAT). The charging circuits are internal to device 1. In an IoT device, the battery 14 is also internal to device 1. The NFC transmit-receive circuits or NFC communication chain include an antenna 22 (ANTENNA) connected, via an impedance matching circuit or network 24 (MATCHING), to an NFC controller 26 (NFCC) or contactless communication head (CLF - Contactless Front-end) responsible for shaping the signals received from the antenna 22 for the microcontroller 10 (or directly for other functions of the device 1) and the data to be transmitted provided by the microcontroller 10 (or directly by other functions of the device 1). Depending on the operating conditions, the NFC circuits draw the energy required for their operation from the battery 14 or directly from the field captured by the antenna 22. According to the described embodiments, the charging circuits use the same antenna 22 as the NFC communication circuits to extract energy from a charging field. To do this, a power recovery circuit 32 (POWER RECOVERY) or AC / DC converter is connected, on the one hand, to the antenna 22 and, via a switch 36, to a charging circuit 34 (CHARGER) for the battery 14. The circuit 32 converts, from a radio frequency field, for example A DC voltage VIN, emitted by a device in charger mode, powers, among other things, the charger circuit 34. Circuit 32, for example, is simplified to a diode bridge. The role of switch 36, as will be detailed later, is to disconnect the charging branch, particularly when the device is in NFC communication mode. Figures 2A and 2B illustrate, in a very schematic and block-like manner, overviews of an NFC communication system and a wireless charging system respectively. In both cases, the system uses a device 1 of the type described in relation to [Fig.1], that is to say an architecture sharing the same antenna 22 and preferably the same energy recovery circuit 32 between an NFC communication branch and an NFC charging branch. For simplicity, not all the circuits of device 1 have been represented in [Fig.2A] and 2B. Only the antenna 22, the adaptation circuit 24, the NFC controller 26, the energy recovery circuit or AC / DC converter 32, the switch 36 and the charger circuit 34 have been represented. Figure [Fig. 2A] illustrates the two operating modes (CE / RW) in NFC communication in which device 1 can be found. Device 1 can operate in card mode, also called card emulation (CE) mode, when it is within range of a device 42 (NFC READER) emitting a field operating in read or read / write (RW) mode. In this case, switch 36 is open to disconnect the charging branch. The NFC communication branch is active, and the NFC controller and other circuits are powered by the battery, as will be explained in more detail in relation to [Fig. 4]. Device 1 can also operate in reader mode, also known as read / write (RW). In this mode, it generates a radio frequency field directed towards a tag 44 (NFC TAG) operating in card mode (CE). Switch 36 is also open to disconnect the charging branch. The NFC communication branch is active and draws the energy required for its operation from the battery of device 1. Figure 2B illustrates a charging mode in which device 1 is within range of an NFC charging field emitted by a device 46 (WLC-P - Wireless Charging Poller) operating in wireless charging transmitter mode or by a “charger” or “poller” device. Device 46 is, for example, a smartphone intended to charge a connected object (IoT). Since device 46 is configured to perform NFC-type wireless charging, it includes, among other things, an NFC controller 466 (NFCC), an impedance matching circuit 464, and an antenna 462. (ANTENNA). On device 1, this device operates as a wireless charging listener (WLC-L), i.e., as the device to be charged. In this configuration, switch 36 is closed to allow converter 32 to supply energy from the field radiated by the charging device 46 to the charging circuit 34 to recharge the battery (not shown in [Fig. 2B]). The communication branch (in particular network 24 and controller 26) remains active, notably to determine that the remote device is a charging device and thus close switch 36 and, if necessary, establish the charging level according to the charger's capabilities.In particular, device 1 can exchange its wireless charging capabilities with the NFC charger device 46 in an NFC data exchange format, known by the acronym NDEF (NFC Data Exchange Format), which can then be interpreted by the NFC controller 26. The architecture described for device 1 is compatible with standard NFC communication operation, whether in card or reader mode. However, to prevent the presence of the charging path from disrupting communications and, in particular, causing losses, switch 36 is opened as soon as the operating mode is NFC communication, whether in reader or card mode. Figure 3 illustrates, schematically and in the form of a chronogram, a battery charging cycle. The graph in Fig. 3 represents examples of the evolution of the current (Battery current) and voltage (Battery voltage) on the battery side and shows the current (Charger current) supplied by the charger circuit 34 and the voltages (Charger voltages) of the charger circuit 34 as a function of time (Time) for three different states (State 1, State 2, State 3). State 1 corresponds to a state in which the charger 34 is off. This can also correspond to a state in which the battery is off, meaning its charge is insufficient to power the circuits of device 1. In the example in [Fig. 3], which illustrates a charging cycle, the OFF state (charger 34 not supplying power to the battery) is present when the battery is discharged (battery voltage at a VLOW level). The OFF state is also found after the battery is fully charged. The battery voltage is then at a VFLOAD level and the charging current is zero. State 2 corresponds to a pre-charge state in which the battery voltage level is low, i.e., below a VPRE threshold. In this state, a pre-charge step (PRE-CHARGE) can be implemented with limited current (IPRE) and under limited voltage (VPRE) to avoid damaging the battery. State 3 corresponds to a fast-charge state when the battery voltage level is sufficiently high, i.e., above the VPRE threshold. In this state, a fast-charge stage (FAST-CHARGE) can be implemented with a higher constant current (ISET), exceeding the IPRE current, to reach a VFLOAD or maximum voltage. When the battery reaches the VFLOAD voltage, the charger switches to a constant-voltage phase. The charging current drawn by the battery from the charger 34 gradually decreases until an IEND level is reached, at which point charging is considered complete. We then return to a state where the charger is off (OFF), by opening switch 36 (zero charging current). In the implementation and embodiment modes described below, it is planned to take advantage of the presence of the switch 36 to share the same antenna 22 for wireless charging of the battery 14 and for near field communications. Figure 4 represents, in more detail than Figure 1, one embodiment of a device 1. In particular, [Fig.4] details certain connections between the circuits of device 1 for the implementation of the solutions described. For simplicity, only the connections necessary for understanding the power and charging functionalities have been shown and will be described. Other connections between the circuits in [Fig. 4] and other circuits not shown in device 1 exist but have not been detailed. Also for the sake of simplicity, the same terminology and reference will sometimes be used to designate a signal and an input terminal to which it is applied, or an output terminal providing that signal. According to the described embodiments, the same antenna 22 is connected to the impedance matching network 24 for NFC communications and to the energy harvesting device 32, for example a rectifier bridge with an output smoothing capacitor (not shown). These connections are considered to arbitrarily define an NFC communication branch and a wireless charging branch, respectively. On the charging branch side, the output of the energy recovery circuit 32 is connected, via switch 36, to an input or power supply terminal IN of the charger 34. A voltage limiting element 42, simplified to a Zener diode, limits (clipses) the rectified voltage from device 32 to a value VIN, for example, on the order of 6.0 volts, with the anode of diode 42 connected to ground. The voltage VIN is also supplied to an ADCI input of an analog-to-digital converter of the microcontroller 10 to determine the VIN voltage level and allow, when device 2 is in WLC-L mode, it to regulate the power supplied by the charger device operating in WLC-P mode according to the voltage VIN. Where applicable, the measurement is carried out via a voltage divider not shown (the microcontroller is for example supplied with a voltage of around 3 volts while the VIN voltage can typically reach around 6 volts). According to the embodiment shown, diode 42 is downstream of switch 36, so that it is connected to antenna 22 only in battery charging mode. The charger 34 receives control signals from the microcontroller 10, and more specifically a WU (Wake-Up) signal for very low power mode output (typically around 10 nA, often referred to as shipping mode), a BATMS-EN signal to activate the charger 34, an SD (ShutDown) signal to deactivate the charger and switch to very low power mode, and a CEN signal to reset the charger's state machine or suspend charging. These signals are provided by the microcontroller 10 via general-purpose input / output (GPIO) pins, specifically GPIO5S, GPIO4, GPIO3, and GPIO2. The charger 34 provides, on its energy outputs VBAT, Vsys, and LDO, respectively, a voltage to the battery, a system voltage Vsys having either the value VIN from device 32 or the value VBAT supplied by battery 10, and a regulated nominal voltage Vnom (for example, 3.0 volts) from the energy supplied by the battery. The voltage Vnom is, for example, supplied by a linear regulator (LDO – Low Drop-Out) included in the charger 34. The VBAT terminal is an input / output terminal VBAT of the charger 34 connected to the battery (to its positive terminal) to charge it or draw energy from it. The nominal voltage (Vnom) is supplied to, among others, the microcontroller 10 and the NFC controller 26. The system voltage (Vsys) is supplied only to the NFC controller. This separation of supply voltages is primarily due to the fact that the linear regulator LDO has a limited current capacity (for example, on the order of 150mA), while the NFC controller 26 can require up to 400mA in reader mode and 200mA in card mode. Furthermore, the 3V supply provided by the linear regulator LDO limits the radio frequency performance of the NFC controller. Since the Vsys voltage corresponds to the battery voltage VBAT, which is then greater than 3 volts when switch 36 is open (no charging in progress), NFC performance is improved. On the other hand, it is necessary to power the VPSIO input on the NFC 26 controller with the LDO linear regulator because the VPSIO input serves as a voltage reference for the GPIO and I2C inputs / outputs connected to the microcontroller 10. The charger 34 also provides the microcontroller 10 with BÂTMS and CHG signals. The BATMS signal corresponds to the battery voltage measurement used to assess the charge level. To avoid excessive power consumption in a voltage divider (not shown) connected between the BÂTMS terminal and an ADC2 terminal of an analog-to-digital converter of the microcontroller 10, the measurement is activated by BATMS_EN (BATMS only presents the battery voltage if BATMS_EN is at 1). The CHG signal indicates the state of the charger's state machine, typically: invalid VIN / valid VIN / charging / end of charge / charging timeout (after 30 minutes of pre-charge or 5 hours of fast charging) / overload error / low battery voltage error (VBAT < VPRE) during fast charging / charger overheating error / battery overheating error. The states are encoded by high / low levels of the CHG signal at a frequency of a few Hertz. The CHG signal is supplied, for example, to the microcontroller 10 on a GPIO1 (General Purpose Input / Output) pin. The intensity of the battery charging current, between the pre-charge current IPRE and the fast charging current ISET, is conditioned by the connection (internal to the charger 34) of a resistor R1, respectively R2 connecting terminals respectively IPRE and ISET of the charger 34 to ground. On the communication branch side, the impedance matching circuit 24 is connected to the NFC controller 26. The NFC controller is connected to the microcontroller 10 via at least a bidirectional I2C bus, allowing the exchange of received and transmitted data. The controller 26 provides, on a DMP terminal, a control signal for the switch 36, enabling it to be opened or closed depending on the operating conditions. The microcontroller 10 exchanges signals with other circuits not shown in device 1. A bus (BUS) symbolizes the links specific to these exchanges. The architecture described is suitable for different methods of construction and implementation. In particular, the operation and controls will differ depending on whether switch 36 is normally open or normally closed. Preferably, the switch is normally open, which allows for optimal NFC performance in card and reader mode. It closes when a WLC-P charging device is detected through data exchange to initiate battery charging. Figures 5 to 7 illustrate different phases of operation of a device 1 as described above, in the presence of a field generated by a WLC-P charger device captured by the antenna 22. These figures reproduce, in part, certain elements of the architecture described above according to the circuits used in the different situations. Figure 5 schematically illustrates a state of the architecture shown in Figure 4. This figure corresponds to state 1 (State 1, [Fig.3]) in which the battery is off. or is not sufficiently charged to power any of the circuits. For example, the battery has a voltage of less than 2.8 volts across its terminals. In this state, the microcontroller 10 is in a low power mode being powered by the linear regulator and the NFC controller 26 is powered by the field via the circuit 32. The controller 26 emulates a tag operation and sends a WLC_CAP message supporting only static mode in order to initiate a precharge when a WLC-P charging device is within range. If switch 36 is normally open, controller 26 causes it to close by changing the state of the DMP signal. If switch 36 is normally closed, the state of the DMP signal remains unchanged. Figure 6 schematically illustrates another state of the architecture shown in Figure 4. This figure corresponds to State 2 of pre-charge in which the battery 14 cannot support rapid charging by the charger device 34. This corresponds, for example, to a state in which the battery 14 has, at its terminals, a voltage lower than the VPRE voltage (for example, less than 3.0 volts). In this state, the WLC-P charging device sends a static charge level, which is the default field level for a device that has communicated a WLC_CAP message requesting static charging. The battery begins to be recharged by the field. The battery charging current is limited to the IPRE level by resistor R1, which is activated. The microcontroller 10 can begin to draw power from the battery via the charger 34 when the battery level is sufficient, the internal LDO regulator of the charger 34 providing the nominal voltage (Vnom) (e.g., 3.0 volts). The microcontroller 10 can then begin communicating with the charger 34 to monitor (MONITOR) the battery charge level and the charger's operation (BATMS and CHG signals) and to control (CMD) the charger (BAMTS-EN, CEN, SD, and WU signals). Preferably, the NFC 26 controller begins to be powered by the nominal voltage (Vnom), i.e., by the battery, as soon as its charge level is sufficiently high (above a certain threshold). One advantage is that if the state of the microcontroller (10) changes (for example, if communication is required), and consequently the current consumption changes, this will not affect the level of the field radiated by the WLC-P charging device. Therefore, there is no risk of triggering a "foreign object detection" mechanism on the charging device side. In this state, the battery charger provides a constant charging current to the battery, drawn from the field by the voltage (VIN), and the energy required by the system is drawn from the battery via the power outputs (Vsys and LDO). Preferably, as long as the charge level is insufficient, the controller 26 remains in static mode and cannot switch to reader mode. To achieve this, a direct connection (dotted line in [Fig. 6]) is preferably provided between the charger 34 and the controller 26 to allow the charger 34 to indicate to the controller 26 when the charge level becomes sufficient. Similarly, preferably, as long as the charge level is insufficient, the microcontroller 10 remains in static mode (limited power consumption). Figure 7 illustrates, schematically, another state of the architecture illustrated in Figure 4. This figure corresponds to State 3 of fast charging, in which the WLC-P charger can provide sufficient power to charge the battery 14 to its maximum VFLOAD. This corresponds, for example, to a state in which the battery terminals have a voltage between the pre-charge level VPRE and its maximum voltage VFLOAD. In this state, the WLC-P charger can enter a negotiated state with the WLC-L receiver (device 1). To do this, microcontroller 10 instructs the NFC controller to send a WLC_CAP message to the WLC-P device to inform it of the battery's charge capacity. One of the fields in the WLC_CAP message indicates a request to switch to negotiated mode. The battery is then charged by this field. Monitoring of the field is available at the microcontroller 10 level (preferably, microcontroller 10 is powered by the Vnom voltage and the NFC controller 26 is powered by the Vsys voltage). Alternatively, as soon as the charge level is sufficient to power the NFC controller and microcontroller, the microcontroller monitors the incoming power. It then generates a control signal for the charger 34 to regulate the charging current. This maximizes the use of the received power. In other words, it matches the available power generated by the WLC-P charging device to the current drawn by the battery for recharging. Figure 8 schematically illustrates another mode of operation of a device according to the architecture of Figure 4. This figure illustrates a state in which device 1 establishes, during battery charging from a WLC-P charging device, a communication according to the WLC standard with the charging device, i.e., using the WLC protocol as defined in the NFC Forum. In this operating mode, the charger device enters a static field state to enable communication. In other words, it reduces the generated field, but energy is still drawn by the charger 34 to continue charging the battery 14. However, the two resistors R1 and R2 are They are deactivated because they are not useful. Indeed, the battery charge level is, in such a situation, sufficient so that the resistor that would be activated would be resistor R2, but it is not useful since the power of the field radiated by the charging device is controlled by the device itself. In this operating mode, the microcontroller 10 and the NFC controller 26 are powered by the battery. The communication itself uses the NFC controller 26 and the microcontroller 10. Figure 9 illustrates, schematically, another mode of operation of a device according to the architecture of Figure 4. This figure illustrates a state in which device 1 is used as an NFC device in reader mode, i.e. to generate a field and to communicate with an external NFC tag. In this state, known as NFC Tx mode, the controller 26 triggers the switch 36 to disconnect the charging circuitry downstream of the switch 36. The device 1 generates a field (via the NFC controller 24 and the antenna 22) to communicate with an external NFC tag. The NFC controller 26 and the microcontroller 10 are battery-powered. Preferably, according to another embodiment in which the energy recovery circuit 32 consists of rectification elements of the diode type, the parasitic capacitances of the diodes are taken into account when dimensioning the adaptation circuit 24. The operation in NFC reader mode is otherwise standard in terms of communication. The described architecture supports different modes of operation, in particular depending on whether the switch 36 is of the normally open or normally closed type and depending on whether the NFC controller 36 is powered. According to an embodiment where the switch 36 is of the normally open type, the charging path does not disrupt the operation of the device in NFC communication mode (except for adaptation due to the energy recovery circuit). When controller 26 detects that the field is generated by a WLC-P charging device, it closes switch 36 to connect the charger 34 to the energy harvesting circuit. As mentioned above, controller 26 emulates a label (lag) operation and sends a WLC_CAP message that only supports static mode. Typically, the process is as follows. The reader or charger, upon detecting a tag (device 1 emulates a tag), performs an anti-collision procedure according to the ISO14443 / EMVCo contactless standard or the NFC Forum. Then, the reader sends its Application Identifier (AID), which specifies the application. supported by the reader, for example "Payment", "Transport" or "NFC Forum", these identifiers are defined in the ISO7816-4 standard. For example, if the identifier corresponds to the standardized code D2760000850101 (NDEF Tag Application), device 1 presents the NDEF message it desires according to the desired exchange (a WLC-CAP message in the case where it wants to charge). In states 1 and 2 ([Fig. 3]), device 1 will emulate an NDEF WLC_CAP tag when a reader sends an NFC Forum-compliant Application Identifier. In state 3, device 1 is fully functional. Device 1 can therefore send a more complex NDEF message, including, for example, a WLC_CAP message, a pairing request (via Wi-Fi or Bluetooth), a virtual card (vCARD), etc., depending on the user's actions. In one embodiment where the switch 36 is normally closed, the default function is battery charging. The controller 26 then opens the switch to enable NFC communication. Such communication is typically established either in reader mode by drawing energy from the battery, or in card mode by drawing energy from the field in which the device 1 is located. The [Fig.10] is a timing diagram illustrating the operation of a WLC-P charging device in the presence of a WLC-L charging device in its field. This chronogram represents an example of field power as a function of time. At rest, the charging device periodically emits bursts of field (NFC polling). When it detects the presence of an object in its field, it initiates an anti-collision procedure (NFC LE). Then, in an initial activation phase (WCCA — Wireless Charging Control Activation), as mentioned above, the reader emits its application identifier and device 1, emulating a tag, emits an NDEF WLC_CAP message which is read by the reader. Wireless charging then begins and consists of a succession of n charging cycles (WLC cycle #1, WLC cycle #2, WLC cycle #3, …, WLC cycle #tn). Each charging cycle includes a control phase (WCC — Wireless Charging Control) followed by a power transfer phase (WPT — Wireless Power Transfer). Depending on the mode (static or negotiated) contained in the WLC_CAP message transmitted by device 1 during a WCC phase, the power of the field emitted by the reader during the WPT power transfer phase varies. In particular, in negotiated mode, the voltage exceeds a maximum threshold Vov.max, while in static mode, the voltage remains between a minimum threshold Vov.min and the threshold Vov.max. If necessary, at the end of the transfer phase, the reader interposes a period before the next phase of WCC command, an IFOD phase of foreign object detection. Once the loading is complete (end of the nth cycle), the reader returns to polling mode. Regardless of the embodiment, it is preferable that, during battery charging, the controller 26 be switched to standby mode during the charging phases. Indeed, according to the WLC protocol, the charging device transmits successive charging frames separated by command exchange frames that allow for adjustment of the field strength. The controller 26 can then be placed in standby mode at the end of each command exchange frame. This means that at the end of sending a WLC_CAP message in static mode or a WLC_CTL message in negotiated mode, to the charging device, the NFC 26 controller goes into standby mode to reduce energy consumption and increase charging efficiency. During the charging phase, even in standby mode, the NFC controller (or microcontroller 10) monitors the received field to detect the end of the charging cycle and the need to present a new WLC_CAP or WLC_CTL message. If there is a transition in the received field level, and the field falls below a custom threshold (chosen according to the characteristics of device 1), the NFC controller wakes up and: - either it is the end of the charging phase and the beginning of a communication phase: the NFC controller performs the communication to then continue the re-charging protocol; - or, no WLC-P field is detected. The charging process exits. This corresponds to the case where either the device is no longer within range of the WLC-P device, or the WLC-P device has stopped emitting a field. Table 1 below summarizes an example of the LDO and Vsys voltage levels ([Fig. 4]) as a function of a threshold Vth value of the VIN voltage and the VBAT voltage level. As a specific example, the V_PRE value is 3 volts, the V_LOW value is 2.8 volts, and the Vth value is 3.9 volts. [Table 1] (N |VIN > Vih VIN > Vth LDO Vsys 3V (from VIN) |VIN 3V (from VIN) VIN VBAT | VBAT > V_PRE V_LOW <VBAT < V_PRE VBAT<V_LOW VBAT > V_PRE a <VBAT < V_PRE |VBAT < V_LOW VIN > Vth VBAT < V_LOW 3V (from VIN) to VIN VIN < Vth VBAT > V_PRE 3V (from VBAT) VBAT |VIN <vh | |v_low<vbat< vbat (régulateuren … |vbat v_pre mode suiveur) [va < vih v_low 0 (off) en variante, lorsque la tension vin est supérieure à vth et que (première ligne du tableau), vsys="VBAT" fournie par batterie le régulateur ldo tire son énergie de au lieu vin. un avantage des modes réalisation décrits qu'ils permettent mutualiser l'antenne, préférentiellement circuit récupération d'énergie pour un fonc- tionnement en communication nfc recharge nfc. Another advantage of the described embodiments is that they are compatible with the protocols defined by the NFC Forum. Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these embodiments can be combined, and other variations will become apparent to them. Finally, the practical implementation of the described embodiments and variants is within the reach of a person skilled in the art, based on the functional indications given above.< / vh>

Claims

Demands

1. Device comprising: an NFC controller (26); a microcontroller (10); a charger circuit (34) for an external battery; an energy recovery device (32); an antenna (22); and a switch (36), controllable by the NFC controller (26), coupling the energy recovery device (32) to the charger circuit (34).

2. Device according to claim 1, wherein said switch (36) is in an open state during NFC communications in mode reader or card mode.

3. Device according to claim 1 or 2, wherein said switch (36) is in a closed state during wireless charging cycles (WLO).

4. Device according to any one of claims 1 to 3, in which the microcontroller (10) generates a control signal for the charger circuit (34) so ​​as to regulate the charging current.

5. Device according to claim 5, wherein said charging current is adjusted based on the available energy of the field.

6. A device according to any one of claims 1 to 5, wherein, in the presence of a field emitted by an external charging device (4), at minus the NFC controller (26) and the charger circuit (34) are powered through the field.

7. Device according to claim 7, wherein the microcontroller (10) is also powered by the field.

8. Device according to any one of claims 1 to 7, in which, in the presence of a field emitted by an external charging device (4), as long as the battery charge level (14) is less than one threshold, the NFC controller and / or the microcontroller cannot switch to NFC reader mode.

9. A device according to any one of claims 1 to 8, wherein, in the presence of a field emitted by an external charging device (4), when the battery charge level is above a threshold, the mid- The NFC controller (10) and / or the NFC controller is powered by the battery.

10. A device according to any one of claims 1 to 9, wherein, in the presence of a field emitted by an external charging device (4), in which the NFC controller (26) enters standby mode for charge cycles.

11. | Device according to any one of claims 1 to 10, wherein, in the presence of a field emitted by an external charging device (4), the microcontroller (10) monitors the power available at the input of the charger circuit (34).

12. A device according to any one of claims 1 to 11, in which the switch (36) is of the normally open type.

13. Device according to claim 13, wherein when the controller NFC (26) detects an external wireless charging device (4) emitting a field, it closes the switch (36) coupling the recovery device- energy operation (32) to the charger circuit (34).

14. Device according to any one of claims 1 to 11, in which the switch (36) is of the normally closed type.

15. | Method of using a device according to any one of the claims indication 1 to 14, in which the switch (36) is controlled by the NFC controller (26).