Abstract:
An apparatus and method for enabling a Near Field Communications (NFC) equipment integrated into a portable communications device, such that when the portable communications device&#39;s battery is low the residual charge of the battery is used to power the NFC equipment to enable various NFC applications without causing damage to the battery or portable communications device.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure is related to Near Field Communication (NFC), transponders and mobile communications devices having integrated NFC circuitry, and to methods and apparatuses for controlling battery power conditions, particularly when the battery is in a low charge state and power is required to operate the NFC circuitry. 
       BACKGROUND 
       [0002]    Near Field Communication (NFC) a short-range wireless connectivity technology having various standards such as Ecma-340 and ISO/IEC 18092. NFC technology uses magnetic field induction to enable communication between devices that are either touched together, or brought within a few centimeters of each other. NFC technology may be integrated with various devices such as mobile phones. Various applications, for example a credit card, may be securely provisioned to an NFC enabled mobile phone such that customers can pay for goods or services by simply waving their mobile phone at a point-of-sale reader. One of the many uses cases for NFC is to enable transit applications. In a transit application use case, a subscriber would utilize their mobile phones to board metro trains, buses, trams or other modes of transport. 
         [0003]    A problem arises however when the mobile phone&#39;s battery is too low to power up the mobile phone. A user who must use their NFC enabled mobile phone at an NFC reader to board a mode of transport may not be able to make the transaction due to the low battery power. 
         [0004]    One solution proposed to address this problem is to use the power derived from the NFC reader to enable the NFC circuitry of the mobile phone. However, testing has shown that there are many use cases where adequate power cannot be derived from the NFC field alone to power up the NFC circuitry and the other needed mobile phone components, such as a SIM card or SD Card. The size of the NFC coil in the mobile phone and the reader, along with the proximity of the two devices to each other can significantly affect the power derived from the field. 
         [0005]    Operators desire NFC applications such as ticketing to work even when a mobile phone&#39;s battery is insufficient to power up the handset. Thus, what is needed and does not exist today is a solution to allow an NFC application to work when a mobile phone&#39;s battery is too low to power up the mobile phone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a diagram of a portable communication device architecture having an integrated Near Field Communication (NFC) module and circuitry in accordance with the embodiments. 
           [0007]      FIG. 2  is a flow chart illustrating operation of the embodiments with respect to determining a correct voltage of a Subscriber Identity Module (SIM) card. 
           [0008]      FIG. 3  is a flow chart illustrating operation of a battery voltage detector in accordance with the embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    In the embodiments a mobile phone, or other portable device, battery residual charge may be used to supply power to an NFC transceiver and SIM card to allow an NFC application to function without causing damage to the battery. In some embodiments for example, the mobile phone battery residual voltage range may be 2.6 to 3.1 Volts. 
         [0010]    The methodologies of the embodiments as disclosed herein ensure that no damage occurs to the battery due to charge drainage beyond its acceptable operational levels. The embodiments also provide methods for correctly setting voltage to a SIM card and methods such that various batteries having different operating characteristics will be used correctly. 
         [0011]    Turning now to the drawings,  FIG. 1  provides details of a portable communications device architecture, such as a mobile phone architecture, in accordance with an embodiment. A portable communication device  100 , such as a mobile phone, comprises a non-volatile memory  37 , a battery  38 , which may be a lithium-ion battery, a Subscriber Identity Module (SIM) card interface  24 , such that a removable SIM card may be installed within, and a Near Field Communication (NFC) module  39 . The SIM card is represented in  FIG. 1  only by its connection interface, SIM connections  10 . The SIM card interface may be for example an ISO7816 standard interface. 
         [0012]    The portable communication device provides various interfaces to the NFC module  39  such as a supply voltage Vcc  36  and a SIM card supply voltage, SIM Vcc  34 . The supply voltage Vcc  36  provide power to the NFC module  39 , and the various components such as controller  20  which comprises processor  21  and memory  22  and NFC transceiver  27 , through diode  31  at the NFC IC Vcc  30  connection, when the portable communication device  100  is powered on. The portable communication device  100  may further provide various universal asynchronous receiver/transmitter (UART) interfaces for translation of data and communication between the NFC module  39  controller  20  and in some embodiments a Bluetooth™ transceiver  25 , and the portable communication device  100 . Therefore the portable communication device  100  will provide UART interface  35  to the NFC module controller  20  and in some embodiments will also provide UART interface  11  to the Bluetooth™ transceiver  25 . 
         [0013]    The NFC module  39  comprises the controller  20 , which further comprises a processor  21  and a non-volatile memory  22 , the processor coupled to the SIM card via a communication line  23  to the SIM connections  10 . The NFC module contains the NFC transceiver  27  coupled to an NFC antenna  28 , for communicating with NFC reader devices. In some embodiments the NFC module  39  will also have a Bluetooth™ transceiver  25  and a corresponding antenna  26  for communication with various Bluetooth™ devices. 
         [0014]    In accordance with the embodiments a circuitry is integrated into the NFC module  39  to detect the presence of an NFC field, monitor the battery  38  voltage and provide an indication that the battery  38  is within acceptable voltage levels and an indication that the portable communications device  100  is on or off. 
         [0015]    The indications are then used to enable, via AND gate logic  41 , a switch  40  to connect the battery  38  to the NFC components of NFC module  39 . For the switch  40  to be activated by the AND gate  41  logic, the battery  38  must be within acceptable voltage limits as determined by voltage detector  29 , an NFC field must be detected by the NFC transceiver  27 , and the portable communication device  100  must be off as determined by the transistor  32 . 
         [0016]    The battery voltage detector  29  thresholds are programmable via an application processor (not shown) of the portable communication device  100  based on information received from the battery  38  or stored in its non-volatile memory  37  at the time of manufacture. On power up, or alternatively power down, the battery  38  low voltage detector  29  threshold is checked and programmed into the non-volatile memory  22  of the NFC module  39  controller  20 . 
         [0017]    If the battery  38  low voltage detector  29  determines that the battery  38  voltage has fallen too low, the switch  40  is automatically turned off and the battery  38  is thus disconnected from the NFC module  39 . This prevents the battery  38  from being discharged to too low of a voltage level and possibly being damaged. 
         [0018]    In an alternative embodiment, a programmable hang timer (not shown) may be utilized to delay the battery  38  from immediately switching off. The timer is useful for conditions in which the NFC field may be too weak or intermittent. 
         [0019]    Further in accordance with the embodiments, power derived from the NFC field is summed with the residual charge of the battery  38  to minimize the drain from the battery when operating in the low battery mode of operation. A logical “OR” circuitry of an Off Mode Power Manager module  18  consists of a first diode  16  and second diode  17 , where the first diode  16  provides a current path from the battery  38 , when logical switch  40  is in a closed position, and where the second diode  17  provides a current path from an NFC field via the NFC transceiver  27 . 
         [0020]    It is to be understood that the circuit elements or components illustrated by  FIG. 1  are exemplary only and for the purpose of conveying to one of ordinary skill how to make and use the various embodiments disclosed herein. Therefore it will be apparent that such circuit elements, and/or components may be implemented in various ways such as by discrete circuit components, logic circuits, integrated circuits and/or software so as to obtain the results obtained as described using the examples illustrated by  FIG. 1  and therefore any and all such implementations remain in accordance with the embodiments herein disclosed. 
         [0021]    Returning to  FIG. 1 , the Off Mode Power Management module  18  also comprises an NFC IC regulator  14  and a SIM regulator  15  for controlling the specific voltages supplied to the NFC module components and the SIM card, respectively. The summed power from an NFC field and a residual battery  38  voltage may be provided to the NFC module  39  NFC IC Vcc  30  connection from NFC IC regulator  14  through diode  13 . 
         [0022]    When an NFC field is detected, and if the battery  38  voltage level is acceptable as determined by voltage detector  29 , and the portable communication device  100  is powered off as determined by the transistor  32 , then the logical AND gate  41  will close switch  40  so that the battery  38  power is connected to the NFC module  39  circuitry through diode  16 . Diode  17  will remain reversed biased until the NFC field power voltage is higher then the battery  38  voltage. Thus if the NFC field power does not overcome the battery  38  residual voltage then the NFC module  39  will operate solely from the battery  38  residual voltage. However if the NFC field power becomes sufficiently strong and achieves a voltage higher than the battery  38  residual voltage then diode  16  will be reverse biased and will provide power to the NFC module  39 . 
         [0023]    Another aspect of the embodiments is to ensure that the correct power supply voltage is presented to the SIM card. This is accomplished at the time the portable communication device  100  is powered on. Detection of the appropriate SIM card voltage by a portable communication device is defined in the ETSI standards such as ETSI TS102 221 which is hereby incorporated by reference herein. The portable communication device  100  therefore incorporates a means to detect the correct SIM card voltage, which may be for example 1.8, 3 or 5 volts. Once detected the portable communication device  100  application processor sets the correct SIM card voltage in the NFC power management non-volatile memory  22 . Once the correct SIM card voltage is set in memory  22 , this voltage will be used when the portable communication device  100  is powered off to correctly power up the SIM card when needed by the NFC module  39 . 
         [0024]    Setting the correct SIM card voltage up front, in accordance with the embodiments, speeds the transaction process which is important for low battery use cases. An additional use case may occur wherein the user may swap out the SIM card while the battery  38  is discharged to the extent that the NFC module  39  cannot establish communications with the SIM card. In this case, the NFC module behaves in accordance with, or similar to, the procedures described in the ETSI TS102 221 specification. The procedure, as defined by TS102 221, will first attempt SIM communications at the voltage set in memory  22 . If this is not successful then the NFC module  39  will attempt a different voltage until all possible voltage levels are tried. 
         [0025]    In another embodiment, the portable communication device may also comprise the Bluetooth™ transceiver  25  and antenna  26  in addition to the various NFC components. 
         [0026]    In this embodiment, the Bluetooth™ components will only be powered up while the portable communication device is in the “on” state. The NFC components may be powered up directly from the portable communication device via Vcc  36  or directly from the battery  38  through the logical switch  41  which may also be connected to the Bluetooth™ transceiver  25 . 
         [0027]      FIG. 2  summarizes operation of the embodiments with respect to supplying an appropriate voltage to a SIM card. The method begins at  201  and in block  203  the determination of whether the portable communication device  100  is powered on. If the device is powered on then in  205  the device determines the battery  38  characteristics from either the battery  38  itself or from the portable communication device  100  memory  37 . In  207 , the determined battery  38  threshold is added to the NFC module  39  memory  22 . In  209  the portable communication device  100  or the NFC module  39  will determine the appropriate SIM voltage using standard procedures and set the SIM operating voltage in the NFC module  39  memory  22  as shown in  211 . 
         [0028]      FIG. 3  illustrates operation of the battery voltage detector  29  in accordance with the embodiments. The method begins in  301  and the embodiments determine whether the portable communication device  100  is powered off. As discussed previously, this is accomplished using the circuitry exemplified by transistor  32  in conjunction with logical AND gate  41 . In  305  the voltage detector  29  provides an indication of whether the battery  38  voltage is at an acceptable level, that is, whether the battery voltage is at a critical level such that the battery may be damaged if operated to provide further power. Therefore, an “acceptable level” as used herein is a voltage level, which may be a residual voltage level, determined by the battery  38  characteristics and/or the battery  38  manufacturer specifications, at which the battery  38  may be operated without causing irreversible damage to the battery  38 . Therefore, in  309 , if the switch  40  is in a closed position such that the battery  38  is providing power to the NFC module  39 , and if the battery level detected in  205  is not acceptable, the switch  40  will be disabled, that is, placed in the off state or open condition as shown in  311 . In an alternative embodiment, a hand timer may also be employed in  311  as was discussed previously. Otherwise, if the switch  40  was not activated, no action will occur at  309 , and the method loops back to start  301 . 
         [0029]    Returning to decision block  305 , if the battery  38  level is acceptable, then a determination is made of whether an NFC field is present in  307 . This is accomplished as described previously via logical AND gate  41 , NFC transceiver  27 . Thus the NFC transceiver provides another input to logical AND gate  41 , the input being a logical one if an NFC field is detected. If no field is detected the method continues at  303  as shown. 
         [0030]    If an NFC field is detected then as in  313  the switch  40  is enabled, or placed in a closed position, such that the battery  38  is connected and supplies power to the NFC module  39 . In  315  the appropriate SIM card supply voltage is set as defined in NFC module  39  memory  22  described previously. 
         [0031]    The embodiments herein disclosed may be used in any NFC enabled device for conditions wherein sufficient power cannot be derived from the NFC field to reliably operate a desired NFC application. The embodiments herein disclosed have specifically addressed the handling of low power battery modes of operation to safely protect the battery and the operation of the portable communications device. 
         [0032]    While various embodiments have been illustrated and described, it is to be understood that the invention is not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.