Patent Publication Number: US-2023133688-A1

Title: Optimized low power mode for nfc/rfid systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority to French Patent Application No. 2111452, filed on Oct. 28, 2021, which application is hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present disclosure generally relates to electronics, and in particular embodiments, to an optimized low-power mode for near field communication (NFC) and radio frequency identification (RFID) systems. 
     BACKGROUND 
     The energy consumption of circuits, devices, and systems is currently a key issue in most technical fields. 
     Many electronic circuits, devices, and systems are adapted to adjust their energy consumption according to the operations that they have to implement. For this purpose, many have power supply modes, such as full power, low-consumption, or standby modes. 
     It would be desirable to improve at least partly certain aspects of the power supply of electronic circuits, devices, and systems. 
     SUMMARY 
     There is a need for electronic circuits, devices, and systems to consume less energy. 
     There exists a need for electronic devices consuming less energy adapted to receive radio frequency waves. 
     There is a need for such electronic devices to consume less energy during the implementation of a standby mode. 
     An embodiment overcomes all or part of the disadvantages of such known electronic devices. 
     An embodiment provides an electronic device including at least: an antenna adapted to, at least, receive a radio frequency signal; and a control unit, wherein, when the control unit is off and the antenna receives a radio frequency signal, the antenna delivers a first voltage representative of the radio frequency signal and powers the control unit with the voltage for the duration of the booting of the control unit. 
     Another embodiment provides a method of booting an electronic device including at least: an antenna adapted to, at least, receive a radio frequency signal; and a control unit, wherein, when the control unit is off and the antenna receives a radio frequency signal, the antenna delivers a voltage representative of the radio frequency signal and powers the control unit with the voltage for the duration of the booting of the control unit. 
     According to an embodiment, the control unit is a processor, a microprocessor, or a microcontroller. 
     According to an embodiment, when the booting of the control unit is over, the control unit is powered with a second voltage delivered by a circuit for powering the electronic device. 
     According to an embodiment, the voltage representative of the radio frequency signal is converted into a power supply voltage by a conversion circuit. 
     According to an embodiment, the power supply voltage is a DC voltage. 
     According to an embodiment, the conversion circuit includes a voltage rectifying diode bridge. 
     According to an embodiment, when the control unit is not used, it is turned off. 
     According to an embodiment, the booting of the central unit includes the soft start of the central unit, the booting of clock systems of the central unit, and communication of the central unit. 
     According to an embodiment, the device further includes a selection circuit adapted to select a reference potential applied to the different elements of the device. 
     According to an embodiment, the selection circuit is adapted to select a first reference potential when the control unit is powered with the voltage representative of the radio frequency signal, and is adapted to select a second reference potential when the power supply circuit powers the control unit. 
     According to an embodiment, the control unit is a monostable circuit. 
     According to an embodiment, the device further includes a circuit adapted to wireless communication. 
     According to an embodiment, the circuit adapted to wireless communication is adapted to near-field communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a schematic of an embodiment electronic device; 
         FIG.  2    is a flow chart of an embodiment method of operation; 
         FIG.  3    is a block diagram of an embodiment electronic device; and 
         FIG.  4    is a timing diagram of an embodiment operation. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Like features have been designated by like references in the various figures. In particular, the structural or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties. 
     For clarity, only the steps and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail. In particular, the computer protocols used to implement the embodiments described in the description are not described but are accessible to those skilled in the art based on the indications present in the following description. 
     Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other than conductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements. 
     In the following disclosure, unless otherwise specified, when reference is made to absolute positional qualifiers, such as the terms “front,” “back,” “top,” “bottom,” “left,” “right,” etc., or to relative positional qualifiers, such as the terms “above,” “below,” “upper,” “lower,” etc., or to qualifiers of orientation, such as “horizontal,” “vertical,” etc., reference is made to the orientation shown in the figures. 
     Unless specified otherwise, the expressions “around,” “approximately,” “substantially,” and “in the order of” signify within 10% and preferably within 5%. 
       FIG.  1    is a very schematic and simplified block diagram of an embodiment of an electronic device  100 . 
     Electronic device loo includes a control unit  101  (PROC) adapted to implement different operations and functions of electronic device  100 . According to an embodiment, the control unit  101  is a processor, a microprocessor, or a microcontroller. According to an embodiment, the control unit  101  is a monostable circuit or simply monostable in the rest of the description. 
     In an embodiment, a monostable circuit continuously delivers an output voltage at a first level, for example, at a low level, and which, on the reception of a control pulse, modifies the value of its output voltage to a second level, for example, a high level, for a determined period, before changing back its output voltage to the first level. 
     Control unit  101  includes at least one power supply terminal VCC on which control unit  101  is adapted to receive a power supply voltage. Control unit  101  further includes a reference terminal, not shown in  FIG.  1   , on which control unit  101  is adapted to receive a reference voltage, for example, the ground. Control unit  101  further includes a plurality of communication terminals enabling control unit  101  to communicate with other elements of device  100 . These communication terminals are detailed hereafter, along with the description of the other elements of electronic device  100 . 
     Electronic device loo includes an antenna  102  (ANT) adapted to receive and emit radio frequency signals. In embodiments, the radio frequency signal is a signal with a frequency ranging from 3 kHz to 300 GHz; these signals are currently used for radio communication. 
     Antenna  102  includes at least one output terminal, ANT-IO adapted to deliver a voltage representative of a radio frequency signal received by antenna  102 . Output terminal ANT-IO may in practice be formed of two electric nodes delivering potentials having as a difference the voltage representative of the radio frequency signal received by antenna  102 . 
     Electronic device  100  further optionally includes a wireless communication circuit  103  (RFID). According to an example, circuit  103  may be a circuit adapted to wireless radio frequency communication or radio frequency identification (RFID), or more particularly, to wireless near field communication (NFC). Circuit  103  includes at least one RFID-IO input terminal coupled, for example, connected, to the output terminal ANT-IO of antenna  102 , and at least one communication terminal RFID-COMM coupled to a communication terminal RFID-COMM 2  of control unit  101 . According to an example, circuit  103  communicates with control unit  101  by using an electronic bus of I2C (Inter-Integrated Circuit) type. According to an example, circuit  103  does not need to be powered, receiving the voltage delivered by antenna  102  is sufficient for its operation. According to a variant, circuit  103  has a power supply terminal. 
     Electronic device  100  further optionally includes one or a plurality of circuits  104  for implementing applications of device  100 . A single circuit  104  is shown in  FIG.  1   . Circuit  104  may be a measurement circuit, a sensor, a display circuit, a cipher circuit, etc. Each circuit  104  includes at least one power supply terminal VCCAPP on which circuit  104  is adapted to receive a power supply voltage. Each circuit  104  further includes a reference terminal, not shown in  FIG.  1   , on which circuit  104  is adapted to receive a reference voltage, for example, the ground. Each circuit  104  further includes a communication terminal APP-COMM coupled, for example, connected, to a communication terminal APP-COMM 2  of control unit  101 . 
     Electronic device  100  further includes means for powering control unit  101  and circuit(s)  104 . These power supply means include a power supply circuit  105 , a conversion circuit  106 , and selection means  107 . 
     Power supply circuit  105  is adapted to power the elements of electronic device  100 . More particularly, power supply circuit  105  is adapted to deliver a power supply voltage or a plurality of different power supply voltages to the elements. In  FIG.  1   , circuit  105  is adapted to deliver a first power supply voltage to control unit  101 , and a second power supply voltage to circuit  104 . Power supply circuit  105  may further be adapted to communicate with control unit  101 , and may thus include at least one communication terminal ALIM-COMM coupled, for example, connected, to a communication terminal ALIM-COMM 2  of control unit  101 . According to another embodiment, power supply circuit  105  does not communicate with control unit  101 . 
     Conversion circuit  106  is adapted to convert the voltage representative of a radio frequency signal received by antenna  102  into a voltage adapted to power control unit  101 . According to an example, the voltage adapted to power control unit  101  is a rectified AC voltage, or even a DC voltage. Conversion circuit  106  includes an input terminal CONV-IN receiving the output voltage of antenna  102  and an output terminal CONV-OUT delivering the voltage adapted to power control unit  101 . 
     Selection means  107  enable control unit  101  to select a power supply source. In particular, selection means  107  enables the control unit to select whether its power supply terminal VCC receives a power supply voltage originating from power supply circuit  105 , or a power supply voltage originating from conversion circuit  106 . According to an example, selection means  107  is a selector controlled by control unit  101 . According to another example, selection means  107  is internal to control unit  101 . 
     According to an embodiment, control unit  101  is adapted to implement a plurality of operating modes. In a first operating mode, or an active mode, control unit  101  operates at full power and is adapted to control all the elements of electronic device  100 . In a second operating mode, a standby mode, or a low-consumption mode, control unit  101  is off, and may be booted at any time if antenna  102  receives a radio frequency signal. In other words, during a standby mode, the control unit receives no power supply voltage. The power supply method implemented on reception of a radio frequency signal by antenna  102  is described in relation with  FIG.  2   . 
       FIG.  2    is a block diagram illustrating a method of powering the control unit  101  of the device  100  described in relation with  FIG.  1   , when the control unit is in a standby mode, and antenna  102  receives a radio frequency signal. 
     At the beginning of the power supply method, control unit  101  is in an initial state  201 , shown by a block “OFF,” where control unit  101  is off, that is, is not powered. As for antenna  102 , it is also in an initial state  202 , shown by a block “NO RF,” where antenna  102  has not received a radio frequency signal yet. It can also be the that, during states  201  and  202 , electronic device  100  is in a standby mode. No function of electronic device  100  is implemented. According to an example, power supply circuit  105  is functional but is not used when control unit  101  is off. 
     At a state  203 , shown by a block “RF,” subsequent to initial state  202 , antenna  102  receives a radio frequency signal. Antenna  102  converts this signal into a voltage representative of the radio frequency signal. This voltage is transmitted to conversion circuit  106 , which then generates a power supply voltage adapted to power control unit  101 . This voltage may further be sent to wireless communication circuit  103 , which processes this voltage, for example, so as to supply circuit  103  with energy. 
     According to an embodiment, once conversion circuit  106  generates a power supply voltage and since control unit  101  is off, selection means  107  deliver the power supply voltage of conversion circuit  106  to the power supply terminal VCC of control unit  101 . 
     Control unit  101  then enters a boot state  204 , represented by a block “BOOT”. During state  204 , the control unit performs all the operations necessary for its booting, such as a soft start, and the booting of its internal circuits and components, the booting of power supply circuit  105 , but also, optionally, for the booting of the other elements of electronic device  100 , such as that of application circuit(s)  104 . More particularly, the operations necessary to the booting of the control unit include the booting of its internal clocks, of its communication units, the booting of its internal software or program, etc. 
     Once the booting of control unit  101  is over, control unit  101  switches to a state  205 , shown by a block “ACTIVE,” where control unit  101  is in an active mode. Selection means  107  no longer deliver the power supply voltage originating from conversion circuit  106 , but deliver a power supply voltage originating from power supply circuit  105 , which is now booted. 
     In other words, during its boot phase, control unit  101  is powered by conversion circuit  106 , and once its boot phase is over, control unit  101  is powered by power supply circuit  105 . 
     Control unit  101  remains in active mode as long as necessary, whether antenna  102  receives a radio frequency signal or not. If antenna  102  no longer receives a radio frequency signal, control unit  101  chooses whether it continues to be in an active mode or whether it switches to standby mode. 
     An advantage of this embodiment is that, during a standby mode, control unit  101  consumes no energy since it is not powered and thus off. Indeed, electronic devices generally have a low-consumption mode where they consume less energy than in their active consumption mode. During this low-consumption mode, the control unit remains “on alert” to be able to process a radio frequency signal, or more generally, any event capable of causing its booting, and for this purpose it needs to be always powered, but generally with a lower power. This is not the case with device  100 . 
       FIG.  3    is an electric diagram, partially in the form of blocks, of an example of embodiment of an electronic device  300  of the type of the electronic device loo described in relation with  FIG.  1   . 
     Like electronic device  100 , electronic device  300  includes: a control unit  301  (PROC) of the type of the control unit  101  of  FIG.  1   ; an antenna  302  (ANT) of the type of the antenna  102  of  FIG.  1   ; an optional wireless communication circuit  303  (RFID), of the type of the wireless communication circuit  103  of  FIG.  1   ; one or a plurality of optional circuits  304  (APP) of implementation of applications of device  300 , of the type of the circuit(s)  104  of  FIG.  1   ; a power supply circuit  305  (ALIM), of the type of the power supply circuit  105  of  FIG.  1   ; a conversion circuit  306  (CONV) of the type of the conversion circuit  106  of  FIG.  1   ; and selection means  307 , of the type of the selection means  107  of  FIG.  1   . 
     In  FIG.  3   , control unit  301  includes: a power supply terminal VCC coupled, for example, connected, to selection means  307  and receiving a power supply potential VCC; a terminal GND on which control unit  301  receives a reference potential GND, for example, the ground; three communication terminals ALIM-COMM 2 , APP-COMM 2 , and RFID-COMM 2  coupled, for example, connected, respectively to power supply circuit  305 , to circuit  306 , and to circuit  303 ; a reset terminal N_RST enabling to control a booting or a rebooting, or a resetting, of control unit  101 . 
     Antenna  302  includes two terminals ANT-IO 1  and ANT-IO 2 , each delivering a potential. The potential difference of terminals ANT-IO 1  and ANT-IO 2  is a voltage VANT representative of a radio frequency signal received by antenna  302 . 
     Wireless communication circuit  303  includes two terminals RFID-IO 1  and RFID-IO 2  coupled, for example, connected, respectively, to terminals ANT-IO 1  and ANT-IO 2  of antenna  302 . Circuit  303  further includes a terminal RFIDGND receiving a reference potential, for example, the ground, and a communication terminal RFID-COMM coupled, for example, connected to the terminal RFID-COMM 2  of control unit  101 . 
     In  FIG.  3   , circuit  304  of implementation of applications includes: a communication terminal APP-COMM coupled, for example, connected, to the communication terminal APP-COMM 2  of control unit  301 ; a power supply terminal VCAPP receiving a power supply potential VCCAPP from power supply circuit  305 ; and a terminal APPGND receiving a reference potential, for example, the ground. 
     In  FIG.  3   , power supply circuit  305  includes: a power supply terminal VCC delivering power supply potential VCC; a power supply terminal VCCAPP delivering power supply potential VCCAPP; a terminal ALIMGND receiving a reference potential, for example, the ground; and a communication terminal ALIM-COMM coupled, for example, connected, to the communication terminal ALIM-COMM 2  of control unit  302 . 
     According to an example, power supply potentials VCC and VCCAPP are identical. 
     In the example of  FIG.  3   , conversion circuit  306  includes two input terminals CONV-IN 1  and CONV-IN 2  coupled, for example, respectively connected, to the terminals ANT-IO 1  and ANT-IO 2  of antenna  302 ; an output terminal CONV-OUT delivering a power supply potential VCC-ANT; and a terminal delivering a reference potential GND-ANT. 
     According to an example of embodiment, circuit  306  includes three elements coupled in parallel between terminals CONV-OUT and CONV-GND. Circuit  306  more particularly, includes a voltage rectifying diode bridge receiving as an input voltage VANT, and delivering as an output the power supply voltage being the difference of potential VCC-ANT and of potential GND-ANT corresponding to rectified voltage VCCANT. The diode bridge is formed of four diodes D 1 , D 2 , D 3 , and D 4 . According to an example, the anode of diode D 1  is coupled, preferably connected, to terminal CONV-IN 1 , and the cathode of diode D 1  is coupled, preferably connected, to terminal CONV-OUT. The anode of diode D 2  is coupled, preferably connected, to terminal CONV-OUT, and the cathode of diode D 2  is coupled, preferably connected, to terminal CONV-IN 2 . The anode of diode D 3  is coupled, preferably connected, to terminal CONV-IN 2 , and the cathode of diode D 3  is coupled, preferably connected, to terminal CONV-GND. The anode of diode D 34  is coupled, preferably connected, to terminal CONV-GND, and the cathode of diode D 4  is coupled, preferably connected, to terminal CONV-IN 1 . Circuit  306  further includes a diode D-CONV, for example, a Zener diode, having its anode coupled, preferably connected, to terminal CONV-GND, and its cathode coupled, preferably connected, to terminal CONV-OUT. Circuit  306  further includes a capacitor C-CONN having a first electrode coupled, preferably connected, to terminal CONV-GND, and its second electrode is coupled, preferably connected, to terminal CONV-OUT. 
     Electronic device  300  further includes an RC-type circuit enabling to protect the reset terminal N-RST of control unit  301 . This circuit includes a resistor R-RST and a capacitor C-RST. A first terminal of resistor R-RST is coupled, preferably connected, to the terminal CONV-OUT of conversion circuit  306 , and a second terminal of resistor R-RST is coupled, preferably connected, to the terminal N-RST of control unit  301 . A first electrode of capacitor C-RST is coupled, preferably connected, to the terminal N-RST of control unit  301 , and a second electrode of capacitor C-RST receives a reference potential GND-PERM. 
     Electronic device  300  further includes a selection circuit GND-SELECT adapted to select the reference potential applied to the different elements of device  300 . Indeed, since the main power supply source of device  300 , and more particularly of control unit  301 , is modifiable, the reference potential also is. Selection circuit GND-SELECT includes an input node A coupled to terminals GND of control unit  301 , APPGND of circuit  304 , ALIM-GND of circuit  305 , and RFID-GND of circuit  303 . Selection circuit GND-SELECT is adapted to deliver either the reference potential GND-ANT delivered by conversion circuit  306  on its terminal CONV-GND, or reference potential GND-PERM. 
     Selection circuit GND-SELECT includes a switch INT-GND, for example, a transistor of N-channel MOS type. Call MOS-type transistor an insulated gate field effect transistor, more currently called MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Switch INT-GND includes a first terminal, corresponding to a first conduction terminal of the transistor, coupled, preferably connected, to node A, and a second terminal, corresponding to a second conduction terminal of the transistor, coupled, preferably connected, to a node delivering reference potential GND-PERM. The control node of switch INT-GND, corresponding to the transistor gate, is coupled, preferably connected, to the terminal SEL of control unit  301 . 
     Selection circuit GND-SELECT further includes a diode D-GND having its anode coupled, preferably connected, to node A, and having its cathode coupled, preferably connected, to the terminal CONV-GND of conversion circuit  306 . According to an alternative embodiment, diode D-GND may be replaced with a switch of the type of switch INT-GND. According to another alternative embodiment, diode D-GND may be replaced with a switch controlled by the presence or not of a radio frequency field. 
     When control unit  301  is powered by power supply circuit  305 , then switch INT-GND is conductive, and node A delivers potential GND-PERM, otherwise switch INT-GND is off, and node A delivers potential CONV-GND. 
     The application of the power supply method described in relation with  FIG.  2    is described in further detail for device  300  in relation with  FIG.  4   . 
       FIG.  4    illustrates timing diagrams of voltages of electronic device  300  during the power supply method described in relation with  FIG.  2   . In other words, these timing diagrams illustrate the passage of control unit  301  from a standby mode where it is not powered to an active mode on reception of a radio frequency signal by antenna  302 . 
       FIG.  4    more particularly illustrates the time variation: of the output voltage VANT of antenna  302 ; of a power supply voltage VCC received by control unit  301  on its power supply terminal VCC; of a voltage VN_RST being the difference between the potential at the level of terminal N-RST of control unit  301  and potential GND-PERM; and of a voltage VSEL being the difference between the potential at the level of terminal SEL of control unit  301  and potential GND-PERM. 
     At an initial time t 0 , all voltages are in a low state or reference state. In other words, antenna  302  receives no radio frequency signal, and conversion circuit  306  receives no voltage to be converted. The booting of control unit  301  is not requested by its reset terminal N_RST since control unit  301  is not powered. Selection circuit GND-SELECT selects potential GND-PERM as being the reference potential of the elements of device  100 . 
     At a time t 1 , subsequent to time t 0 , antenna  302  receives a radio frequency signal. Voltage VANT then switches from its low state, corresponding to a difference of two substantially equal potentials, to an oscillating state representative of the radio frequency signal received by antenna  302 . Conversion circuit  306  receives voltage VANT and starts its conversion. For this purpose, and until a time t 2 , subsequent to time t 1 , voltage VCC is the voltage VCCANT delivered by conversion circuit  306  and increases, for example, substantially linearly. 
     At time t 2 , voltage VCC, and thus voltage VCCANT, has reached its maximum amplitude, and is then equal to the rectified voltage VANT. Voltage VCCANT is then sufficiently high to power control unit  301 , and to have the voltage VN-RST at the reset terminal N-RST of control unit  301  increase. 
     At a time t 3 , subsequent to time t 2 , voltage VN-RST is at a high level. In other words, the reset terminal N-RST of control unit  301  is activated, and control unit  301  can start its booting. 
     At a time t 4 , subsequent to time t 3 , control unit  301  has ended its booting. As described in relation with  FIG.  2   , control unit  301  is then capable of modifying its power supply source for power supply circuit  305 . Since the power supply source is modified, selection circuit GND-SELECT modifies the reference potential of the elements of device  300 . For this purpose, control unit  301  switches voltage VSEL to a high state, different from its low state. 
     At a time t 5  subsequent to time t 4 , voltage VCC is the voltage VCC-ALIM delivered by power supply circuit  305 . Thus, from time t 5 , voltage VCC is a stable voltage, or even a DC voltage. 
     At a time t 6 , subsequent to time t 5 , antenna  302  no longer receives a radio frequency signal, and no longer delivers a voltage. Thus, voltage VANT switches back to its low state. According to an example of embodiment, control unit  301  here decides to keep on operating and not to stop. It will be within the abilities of those skilled in the aft to imagine different embodiments. 
     At a time t 7 , subsequent to time t 6 , control unit  301  has finished the operations that it should implement, and device  300  can be turned off. All the elements of device  300  are stopped, and voltages VCC, VN-RST, and VSEL are set back to their low state. 
     Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants may be combined, and other variants will occur to those skilled in the art. 
     Finally, the practical implementation of the described embodiments and variations is within the abilities of those skilled in the art based on the functional indications given hereabove.