Patent Publication Number: US-2021192304-A1

Title: Power supply management method

Description:
PRIORITY CLAIM 
     This application claims the priority benefit of French Application for Patent No. 1914965, filed on Dec. 19, 2019, the content of which is hereby incorporated by reference in its entirety to the maximum extent allowable by law. 
     TECHNICAL FIELD 
     The present disclosure generally relates to electronic devices and, more specifically, to cards powered by an external electromagnetic field. 
     BACKGROUND 
     There are many applications where an electronic device comprises no internal power supply, so that circuits embarked on this device can only be activated when a sufficient power is supplied thereto, externally, by another device. This is particularly true for certain contactless cards which draw, generally from an electromagnetic field emitted by a reader located within their range, the electric power necessary to power their circuits. Such circuits may have a limited electric power which should be managed at best to guarantee an optimal operation of the device to which they belong. 
     There is a need to improve methods for managing the power supply of electronic devices comprising no internal power supply. 
     There is a need to overcome all or part of the disadvantages of known power supply management methods. 
     SUMMARY 
     An embodiment provides a method of management of the power supply of one or first elements by a second element of a same first device, comprising the steps of: sending, to a second device, a time extension request; evaluating, during the time extension, a power available from an electromagnetic field radiated by the second device; and adjusting the power supply of the second element and of the first element(s) according to the available power. 
     According to an embodiment, the second element is remotely supplied via the electromagnetic field. 
     According to an embodiment, the second element is a secure electronic circuit. 
     According to an embodiment, the second element executes the steps of sending the time extension request, of evaluating the power, and of adjusting the power supply. 
     According to an embodiment, the first device comprises exactly two first elements, the first elements preferably being a microcontroller and a fingerprint sensor. 
     According to an embodiment: the first device is a card, preferably a contactless payment card; and the second device is a reader, preferably a contactless payment terminal. 
     According to an embodiment, the first element(s) are powered with a voltage in the range from 1 V to 5.5 V. 
     According to an embodiment, the second element comprises a component configured to evaluate a current available from the electromagnetic field radiated by the second device. 
     According to an embodiment, the second element comprises a switch configured to cut off the power supply of the first element(s). 
     According to an embodiment, the switch is driven by a voltage regulator activated according to a state of the current evaluation component. 
     According to an embodiment, the first element(s) are powered: by a capacitor when the switch is off; and by the voltage regulator when the switch is on. 
     According to an embodiment, the second element turns off the switch in case of an excessive power consumption of the second element(s). 
     According to an embodiment, the second element is set to a low power consumption mode during the evaluation of the available power. 
     According to an embodiment, the available power is evaluated after other time extensions, the power supply of the first element(s) being adjusted according to each evaluation of the available power. 
     According to an embodiment, when the first element(s) are powered, the second element adjusts an operating frequency of the second element and an operating frequency of the first element(s) according to the available power. 
     An embodiment provides a secure electronic circuit configured to implement the method such as described. 
     An embodiment provides a contactless electronic card comprising at least one circuit such as described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments and implementation modes in connection with the accompanying drawings, in which: 
         FIG. 1  very schematically shows in the form of blocks an example of a near-field communication system of the type to which the described embodiments apply as an example; 
         FIG. 2  is a timing diagram of an example of a radiofrequency communication; 
         FIG. 3  is a timing diagram of another example of a radiofrequency communication; 
         FIG. 4  schematically shows in the form of blocks an example of a card; 
         FIG. 5  is a timing diagram of an example of the state variation of an element of the card of  FIG. 4  during a radio frequency communication with a reader; 
         FIG. 6  very schematically shows in the form of blocks an embodiment of a card; 
         FIG. 7  is a timing diagram of an implementation mode of a method of managing the power supply of the card of  FIG. 6 ; 
         FIG. 8  schematically shows in the form of blocks an embodiment of a power supply architecture of the card of  FIG. 6 ; 
         FIG. 9  is another timing diagram of the power supply management method of  FIG. 7  according to an embodiment; and 
         FIG. 10  is still another timing diagram of the power supply management method of  FIG. 7  according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Like features have been designated by like references in the various figures. In particular, the structural and/or functional elements common to the different embodiments and implementation modes may be designated with the same reference numerals and may have identical structural, dimensional, and material properties. 
     For clarity, only those steps and elements which are useful to the understanding of the described embodiments and implementation modes have been shown and will be detailed. In particular, the commands which are executed are not detailed, the described embodiments and implementation modes being compatible with usual commands executed by contactless cards. 
     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 description, when reference is made to terms qualifying absolute positions, such as terms “front”, “back”, “top”, “bottom”, “left”, “right”, etc., or relative positions, such as terms “above”, “under”, “upper”, “lower”, etc., or to terms qualifying directions, such as terms “horizontal”, “vertical”, etc., unless otherwise specified, it is referred to the orientation of the drawings. 
     Unless specified otherwise, the expressions “around”, “approximately”, “substantially” and “in the order of” signify within 10%, and preferably within 5%. 
       FIG. 1  very schematically shows, in the form of blocks, an example of a near-field communication system of the type to which the embodiments which will be described apply as an example. 
     In the example of  FIG. 1 , a first device or reader  100  (Reader), for example, a payment terminal, a cell phone, a readout terminal, etc., radiates a radiofrequency electromagnetic field EMF captured by a second device or card  102  (Card), for example, a contactless payment card, a personal access card, a transport card, etc. 
     In the case of a radio frequency communication, reader  100  detects the presence of card  102  in its EMF field, and then starts a communication procedure comprising exchanges of requests by reader  100  and of answers by card  102 . Such a communication, be it performed in the field of bank transactions, of identification, of transports, of access management, etc., is generally based on the ISO 14443 standard, for example, in its  2018  version, and implements standardized protocols of exchange between reader  100  and the card  102  located within its range. 
       FIG. 2  is a timing diagram of an example of a radio frequency communication between the reader  100  (Reader) and the card  102  (Card)  102  of  FIG. 1 . 
     After a powering-on  202 R,  202 C (PowerOn) of reader  100  and of card  102 , reader  100  starts a communication phase  200  by sending  204 R (RF command) a radiofrequency command (RF) to card  102 , which is waiting  204 C (Wait command) for the reception of a command. Then, card  102  executes  206 C (Processing command) the command, reader  100  waiting  206 R (Wait answer) for a response from card  102 . Once the command has been executed, card  102  sends  208 C (Send answer) an answer to reader  100 , which receives  208 R (Receive answer) this answer. This ends communication phase  200 . One or a plurality of other communication phases  200  may then take place before a powering-off  210 R,  201 C (PowerOff) of reader  100  and of card  102 . 
     Generally, reader  100  assigns to card  102  a maximum duration, for example, 38 ms, for the execution  206 C of each command. It is, however, generally provided for card  102  to sometimes ask reader  100  to grant it a time extension WTX (Wait Time eXtension), in other words an additional delay, as discussed hereafter in relation with  FIG. 3 . 
       FIG. 3  is a timing diagram of another example of a radio frequency communication between the reader  100  (Reader) and the card  102  (Card) of  FIG. 1 . The timing diagram of  FIG. 3  comprises elements common with the timing diagram of  FIG. 2 . The common elements will not be described again hereafter. 
     In the timing diagram of  FIG. 3 , as compared with the timing diagram of  FIG. 2 , the phase of execution  206 C (Processing command) of the command by card  102  is extended. Such an extension, on the initiative of card  102 , results from a sending  302 C (Send WTX) of a request for a time extension WTX to reader  100 , which receives  302 R (Receive WTX req) the request. As a response, reader  100  sends  304 R (Send WTX ACK) an acknowledgement ACK to card  102 , which waits  304 C (Wait WTX ACK) for acknowledgement ACK. Card  102  carries on the execution  206 C of the command, reader  100  waiting  206 R (Wait answer) for the answer of card  102 . 
     On execution  206 C of a same command by card  102 , a plurality of time extensions WTX, comprising operations  302 C,  302 R,  304 C, and  304 R, may be successively granted by reader  102 . Further, each communication between reader  100  and card  102  may comprise any number of communication phases  200 , with or without time extension WTX, before the powering-off  210 R,  210 C (PowerOff) of reader  100  and of card  102 . 
       FIG. 4  schematically shows in the form of blocks an example of a card  102  (Card) comprising: a near-field communication antenna  402  (Antenna); a first secure element  404  (SE), for example, a secure circuit or microcontroller; and an electronic processing module  406  (μModule). 
     First secure element  404  comprises: a power management macrocell or unit  408  (BPMU) according to power supply needs of the first secure element of card  102 ; another frequency adjustment macrocell or unit  410  (AFC) enabling to adjust, according to the EMF field ( FIG. 1 ), an operating frequency of the first secure element of card  102 ; and still another communication macrocell or unit  412  (TART), for example, an asynchronous receiver transmitter. 
     Electronic processing module  406  is coupled or connected: to first secure element  404  over a connection  414  (L1) conveying a power supply voltage for example in the range from 1 V to 5.5 V; and to communication macrocell  412  over another connection  416  (L2) in accordance, for example, with the requirements of the 2013 ISO 7816 standard and used for contact communications. 
     During a contactless communication of the type of those discussed in relation with  FIGS. 2 and 3 , card  102  is particularly capable of managing: the operating frequency of first secure element, due to frequency adjustment macrocell  410 , which adjusts this frequency according to an energy available from the EMF field ( FIG. 1 ); the power supply voltage of first secure element, due to power management macrocell  408 , which adjusts the power supply voltage according to the power supply needs of first secure element; and a plurality of power supply modes, for example, a nominal mode, a low power consumption mode, etc. 
     During operations  204 C,  208 C,  302 C,  304 C ( FIG. 3 ) comprising receiving or sending data, for example, commands, answers, time extension requests WTX, etc., between reader  100  and card  102 , the EMF radiofrequency field ( FIG. 1 ) is modulated. The first secure element of card  102  is set to the low power consumption mode, or standby mode, during these operations, that is, outside of the operations of execution  206 C of a command and of powering-on  202 C. During the operations of execution  206 C of a command and of powering-on  202 C, first secure element is in nominal mode. Due to interoperability constraints, it is generally made sure that card  102 , particularly first secure element, does not cause noise or electronic disturbances during operations  204 C,  208 C,  302 C,  304 C ( FIG. 3 ) comprising exchanging information with reader  100 . 
       FIG. 5  is a timing diagram of an example of state variation (SE state) of the first secure element  404  of the card  102  (Card) of  FIG. 4  during a radio frequency communication with reader  100  ( FIG. 1 ). 
     In this example, first secure element is set: to the nominal power supply mode  502  (Processing), during the powering-on  202 C (PowerOn) of card  102  and during operations of execution  206 C (Processing command) of commands; and to the low power consumption mode  504  (Standby) the rest of the time, in other words, during the operations of: waiting  204 C for a command (Wait command); time extension (WTX), in other words, sending  302 C of a time extension request (Send WTX) and then waiting  304 C for an acknowledgement ACK (Wait WTX ACK) confirming that reader  100  grants time extension WTX; and sending  208 C of an answer (Send answer). 
     First secure element manages its power supply needs each time it is switched from or to the low power consumption mode  504 . In particular: at each switching to the low power consumption mode  504 , frequency adjustment macrocell  410  ( FIG. 4 ) is deactivated and power management macrocell  408  ( FIG. 4 ) adjusts or regulates the power supply voltage so that it corresponds to low power consumption mode  504 ; and at each switching to the nominal mode  502 , frequency adjustment macrocell  410  is activated and power management macrocell  408  adjusts or regulates the power supply voltage so that it corresponds to nominal mode  502 . 
       FIG. 6  schematically shows in the form of blocks an embodiment of a card  602  (Smartcard), for example, a contactless payment card, an identity card, a transport card, a personal access card, etc. 
     Card  602  is particularly configured to communicate with a reader, preferably a payment terminal, for example, the reader  100  of  FIG. 1 . The card  602  of  FIG. 6  comprises elements common with the card  102  of  FIG. 4 . These common elements will not be described again hereafter. 
     As compared with the card  102  of  FIG. 4 , the card  602  of  FIG. 6  particularly comprises one or a plurality of second additional elements (Companion chips). Card  602  preferably comprises two second elements: a second element or microcontroller  604  (BioMCU); and another second element or sensor  606  (Sensors) preferably corresponding to a biometric sensor, more preferably a fingerprint sensor. 
     It is said that the second elements  604  and  606  form together a “biometric environment”, card  602  being then called a biometric card. 
     As compared with the first secure element of  FIG. 4 , the first secure element (SE) of  FIG. 6  comprises: an available current macrocell or unit  608  (RAC) for evaluating the current available from the EMF electromagnetic field ( FIG. 1 ); and input-output terminals  610  (GPIO), preferably universal (General Purpose Input-Output). 
     The first secure element of card  602  is remotely supplied via the EMF field radiated by reader  100  ( FIG. 1 ). 
     In the first secure element of  FIG. 6 , power management macrocell  408  ( FIG. 4 ) is replaced with a management and energy harvesting macrocell or unit  612  (BPMU+Energy Harvesting) combining functionalities similar to those of the power management macrocell  408  of  FIG. 4  and additional energy harvesting and/or distribution functionalities. 
     Each second element  604 ,  606  is coupled, preferably connected, to the management and energy harvesting macrocell  612  of first secure element by a connection  614  (L3) preferably conveying a power supply voltage in the range from 1 V to 5.5 V. A switch  616  placed downstream of management and energy harvesting macrocell  612  is configured to establish or cut off the power supply of second elements  604  and  606 . Although switch  616  is shown in  FIG. 6  as not belonging to management and energy harvesting macrocell  612 , switch  616  may in practice be integrated to management and energy harvesting macrocell  612 . In other words, switch  616  is, in  FIG. 6 , functionally shown. 
     Microcontroller  604  is coupled, preferably connected, to the general purpose input-output terminals  610  of first secure element by another connection  618  (L4). Connection  618  conveys, preferably, one or a plurality of communication and/or power supply signals between first secure element and microcontroller  604 . 
     Fingerprint sensor  606  is coupled, preferably connected, to microcontroller  604  by still another connection  620  (L5). Link  620  for example enables sensor  606  to send to microcontroller  604  data representative of a fingerprint acquired in the form of an image by sensor  606 . 
     The presence, in card  602 , of second elements  604  and  606  complicates the power management with respect to the card  102  of  FIG. 4 . Indeed, biometric card  602  is configured to manage not only the energy needs of first secure element, but also those of second elements  604  and  606 . Biometric card  602  thus manages the energy needs of three elements, in the case in point first secure element and the two second elements  604  and  606 , while card  102  manages the energy needs of a single element, in the case in point first secure element. 
       FIG. 7  is a timing diagram of an implementation mode of a method of managing the biometric card  602  (Smartcard) of  FIG. 6  during a communication with reader  100  (Reader) of  FIG. 1 . The timing diagram of  FIG. 7  comprises elements common with the timing diagram of  FIG. 5 . These common elements will not be described again hereafter. In the timing diagram of  FIG. 7 , a line (BIO state) symbolizes a variation of a state of the biometric environment formed by second elements  604 ,  606  ( FIG. 6 ). 
     According to this embodiment, it is made sure that a communication or transaction using biometric environment  604 ,  606  ( FIG. 6 ) is perceived, by reader  100  ( FIG. 1 ), as being identical to a standard communication or transaction, for example, such as that discussed in relation with  FIG. 3 . This provides an advantageous backward compatibility of card  602  ( FIG. 6 ) with the existing readers  100 . 
     Biometric card  602  is configured to evaluate the power supply available from the EMF field emitted by reader  100 . According to this evaluation, advantageously managed transparently for reader  100 , card  602  chooses whether to power or not the second elements  604  and  606 . The evaluation of the power supply available from the EMF field emitted by reader  100  is preferably performed during a period when first secure element is set to the low power consumption mode  504  (Standby). A more accurate evaluation of the available power supply is thus obtained. 
     At the powering-on  202 R,  202 C of reader  100  and of card  602 , first secure element is in an active state  702  (SE Processing), or nominal mode, of first secure element, similar to the state  502  of the timing diagram of  FIG. 5 . The biometric environment  604 ,  606  then is powered off  704  (BIO OFF) and is held in the powered-off state  704  until further notice. During the waiting  204 C (Wait command) for the sending  204 R (RF command) of a command, first secure element is in low power consumption mode  504  (Standby). 
     According to a preferred implementation mode, first secure element triggers the sending  302 C (Send WTX) of a time extension request WTX during the execution  206 C (Processing command) of a command. This causes the switching of first secure element to the low power consumption mode  504 . First secure element takes advantage of such a switching to the low power consumption mode  504  to evaluate the power supply available from the EMF field. 
     Before the sending  302 C of time extension request WTX, first secure element is in a state  706  (SE Processing (Bio setup)) of configuration of the biometric environment where it: determines a value of the power supply voltage of second elements  604  and  606  and configures management and energy harvesting macrocell  612  ( FIG. 6 ) so that it delivers, as soon as it is come out of the low power consumption mode  504  after the time extension request WTX, a power supply voltage equal to this value; evaluates, via available current macrocell  608 , the current potentially available from the EMF field to power elements  404 ,  604 , and  606  and particularly decides, according to the evaluation, whether to power or not (state  710 , BIO ON/OFF) second elements  604 ,  606  as soon as it is come out of the low power consumption mode  594  after time extension request WTX; and deactivates frequency adjustment macrocell  410  as soon as it is come out of low power consumption mode  504  after time extension request WTX, due to the fact that the power consumption of second elements  604  and  606  is not predictable. 
     At the coming out of low power consumption mode  504 , after time extension request WTX, the first secure element of card  602  switches to another state  708  (SE BIO Processing (Bio evaluation)) of evaluation of the available power, where: second elements  604  and  606  are powered if the state of available current macrocell  608  is compatible with the energy needs of second elements  604  and  606 ; and frequency adjustment macrocell  410  is deactivated. 
     In a case where the available power is sufficient to power second elements  604  and  606 , second elements  604  and  606  are then powered on. According to an embodiment, when second elements  604  and  606  are powered, first secure element adjusts the operating frequency of first secure element and/or the operating frequency of second elements  604  and  606  according to the available power. 
     It could have been devised to activate second elements  604  and  606  and to manage their energy needs while first secure element is in nominal mode  702 . However, this would be less reliable and more complex to achieve than when first secure element is in low power consumption mode  504 . 
     It could also have been devised to attempt activating second elements  604 ,  606  as soon as the powering on  202 C of card  602 . However, if the available power is insufficient at the powering on  202 C, card  602  risks being inoperative, which tends to degrade the user experience. 
     Before card  602  answers reader  100 , first secure element is switched back to the nominal mode  702  due to another time extension request WTX. 
     The described embodiment allows a good reliability of radio frequency communications through: a power supply architecture enabling to manage radio frequency noise, isolated from the power supply of second elements  604 ,  606 , and an evaluation of the radio frequency field by the dedicated available current macrocell  608 ; a management of the power supply, supplied externally, during time extension requests WTX during which second elements  604 ,  606  are powered; and a preservation of the exchanges between first secure element and reader  100  even when second elements  604 ,  606  are powered. 
       FIG. 8  schematically shows in the form of blocks an embodiment of a power supply architecture of the card  602  of  FIG. 6 . 
     According to this embodiment, first secure element (SE) comprises: a block  802  (AFC RAC) schematizing the macrocells  410  and  608  of  FIG. 6 ; a voltage regulator  804  (Reg MV) for the contact power supply of first secure element and of second elements  604  (BioMCU) and  606  (Sensors) from a terminal of application of a potential noted VCC via a connection (TOP_ANA); and another voltage regulator  806  (Reg MV) for the contactless power supply, from antenna  402  connected to terminals (AC 0 , AC 1 ), of second elements  604  and  606 . 
     According to an embodiment, voltage regulators  804 ,  806  form part of management and energy harvesting macrocell  612  (BPMU+Energy Harvesting) which further comprises: a block  808  (Shunt) configured to mask possible electronic disturbances, originating from first secure element and/or second elements  604  and  606  in their different operating modes, capable of propagating to antenna  402 ; still another voltage regulator  810  (Reg  1 V 1 ) powered from block  802  and communication macrocell  412  (TART) by a voltage noted Vdd_ 1 V 1 ; and transformers  812  coupled, preferably connected, to a bus conveying a power supply voltage (VCC_HV). 
     By default, second elements  604  and  606  are not powered. Voltage regulator  806  drives switch  616  configured to establish or cut off the power supply of second elements  604  and  606  when card  602  ( FIG. 6 ) is near-field powered. Regulator  806  is activated according to the state of current evaluation component  802 . In the case of a contact communication, voltage regulator  804  drives another switch  617  configured to establish or cut off the power supply of second elements  604  and  606 . 
     The power supply of second elements  604  and  606  is preferably controlled by software according to the state of macrocell  802 . A capacitor  814  is connected in parallel with second elements  604  and  606 . At the coming out of standby mode  504  ( FIG. 7 ), voltage VCC_HV is adjusted by block  802  according to the power supply needs of second elements  604  and  606 . 
     First elements  604 ,  606  are powered: by capacitor  814 , when switches  616  and  617  are turned off; by voltage regulator  806 , when switch  616  is turned on in the context of a contactless power supply; or by voltage regulator  804 , when switch  617  is turned on in the context of a contact power supply. 
     In  FIG. 8 , the second elements  604  and  606  are powered under a voltage, noted VCC_VOUT, in the range from 1 V to 5.5 V. Second element  604  is coupled, preferably connected, to universal input-output terminals  610  (GPIO). Second elements  604 ,  606  are both coupled, preferably connected, to a terminal of application of a reference potential, for example, the ground (Gnd). 
       FIG. 9  is another timing diagram of the power supply management method of  FIG. 7  according to an embodiment.  FIG. 9  more particularly shows a variation: of the state (SE state) of first secure element ( FIG. 8 ); of the power supply voltage VCC_OUT of second elements  604  and  606  ( FIG. 8 ); and of the state (BIO state) of the biometric environment, that is, of second elements  604  and  606 . 
     According to this implementation mode, second elements  604  and  606  are initially powered  902  (External ICs Processing) and first secure element is in a state  904  (SE Bio-Processing) where it executes biometric processing operations. It is then assumed that first element SE sends  906  (WTX TX) a time extension request to reader  100  ( FIG. 1 ), and then receives  908  (WTX RX) a confirmation indicating that the request has been granted. During operations  906  and  908  of time extension request WTX: first secure element ( FIG. 8 ) is set to the low power consumption mode (SE Standby); and second elements  604  and  606  ( FIG. 8 ) are set to the low power consumption mode  910  (Standby). 
     Second elements  604  and  606  are then preferably not powered from voltage regulator  806  ( FIG. 8 ). For example, the switch  616  driven by voltage regulator  806  is turned off. While they are in low power consumption mode  910 , second elements  604  and  606  are powered, preferably by capacitor  814  ( FIG. 8 ). 
     After time extension request WTX, first secure element ( FIG. 8 ) re-evaluates  912  (RAC), via block  802 , the current available from the field to power second elements  604  and  606 . According to the evaluation performed by block  802 , for example if the available current is sufficient, card  602  may decide to carry on the execution of biometric operations. In this case: first secure element is set back to state  904  (SE Bio-Processing); and second elements  604  and  606  are powered  902  (External ICs Processing). 
     In the opposite case, card  602  may decide to interrupt the execution of the biometric operations, for example, by cutting off the power supply  902  of second elements  604  and  606 . 
     In other words, first secure element: sends, to reader  100  ( FIG. 1 ), a time extension request WTX; evaluates, during time extension WRX, a power available from the electromagnetic field EMF radiated by reader  100 ; and adjusts its power supply and the power supply of second elements  604 ,  606  according to the available power. 
     According to a preferred embodiment, the available power is evaluated after other time extensions, for example, similar to the above-described time extension WTX, the power supply of first element(s)  604 ,  606  being adjusted according to each evaluation of the available power. 
       FIG. 10  is still another timing diagram of the power supply management method of  FIG. 7  according to an implementation mode. 
       FIG. 10  more particularly shows a variation: of the state (SE state) of first secure element ( FIG. 8 ); of a signal (Harvesting sensor) of a sensor, for example, a sensor of voltage VCC_OUT which triggers in case of a crossing of a high threshold beyond which it is considered that the energy consumed by second elements  604  and  606  is too high; of another signal (SE Interrupt) of interruption of first secure element; of the power supply voltage VCC_OUT of second elements  604  and  606  ( FIG. 8 ); and of the state (BIO state) of the biometric environment, that is, of second elements  604  and  606 . 
     According to this embodiment, available current macrocell  608  ( FIG. 6 ) evaluates a generally power supply capacity, that is, for all the elements  404 ,  604 ,  606  of card  602 . Such a power supply capacity is then distributed between first secure element and second elements  604  and  606  according to a maximum power consumption of each element. 
     In case, for example, of a degradation of the fingerprint sensor  606  of card  602  ( FIG. 6 ) or of leakages at the level of the connection pads of microcontroller  604 , this may result in an excessive or unexpected power consumption of sensor  606  or of microcontroller  604 , respectively. In this case, first secure element is advantageously configured to cut off the power supply of second elements  604  and  606 . 
     According to this embodiment, second elements  604  and  606  are initially in state  902  (External ICs Processing) and first secure element is in state  904  (SE Bio-Processing). It is then assumed that it is desired to cut off the power supply of second elements  604 ,  606 . The first element then transmits a command  1002  (SE Bio-Abort) for powering off second elements  604  and  606  and then a time extension request  1004  (WTX). The execution of command  1002  results in the powering off  704  (BIO OFF) of the second elements  604 ,  606 . This is particularly reflected by the fact that signal VCC_OUT is, after the discharge of capacitor  814  ( FIG. 8 ), equal to approximately 0 V. 
     According to this embodiment, it is then switched from state  904 , where first secure element and second elements  604 ,  606  are powered, to state  702  (SE Processing), where only first secure element is powered. The time extension request  1004  here enables to make sure that the communication between card  602  and reader  100  remains active and first secure element switches back to state  702 . 
     In other words, card  602  is configured to give a power supply harvesting priority (Harvesting priority on SE) to first secure element. 
     The component  608  of the first secure element of card  602  ( FIG. 6 ) is thus configured to evaluate the current available from the EMF field radiated by reader  100  ( FIG. 1 ). The power supply of first secure element and of second elements  604 ,  606  is then adjusted according to the evaluation of the current. The adjustment is preferably performed: either by the cutting off of the power supply of second elements  604  and  606 , if the available current is not sufficient to properly power second elements  604  and  606  while keeping an operational communication between first secure element and reader  100 ; or by adjustment of the power supply of first secure element and of second elements  604 ,  606  according to the power supply needs of each element. 
     The above-described embodiments have the advantage of being compatible with current protocols of communication between a card  602  ( FIG. 6 ) and a reader  100  ( FIG. 1 ). The power supply of second elements  604  and  606  is in particular managed by card  602  transparently for reader  100 . Thus, in the case of card  602 , first secure element manages additional elements  604 ,  606  with respect to card  102  ( FIG. 4 ). However, reader  100  may indifferently communicate with card  102  or with card  602  without for this to cause a modification in terms of communication protocol. The existing readers  100  can thus be kept, to communicate with card  602 . 
     Various embodiments, implementation modes, and variations have been described. Those skilled in the art will understand that certain features of these various embodiments, implementation modes, and variants, may be combined and other variants will occur to those skilled in the art. 
     Finally, the practical implementation of the described embodiments, implementation modes, and variants is within the abilities of those skilled in the art based on the functional indications given hereabove. 
     Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.