Patent Description:
<CIT> relates to an electronic key that can operate a vehicle. An electronic control key, or "key fob," is a keyless entry remote device which may be used to perform one or more authorized functions, such as locking or unlocking doors or the like for controlling access to vehicles or other controlled locations (e.g., hotel rooms, apartments, buildings, secure areas, etc.), opening a trunk, activating an alarm, starting an engine, etc. Modem key fobs may include wireless communication technology, such as <NUM>, Wi-Fi, Bluetooth, Bluetooth Low Energy (BLE), etc., for communicating with a corresponding access control system or the like at the vehicle or other secure location. The key fob and the access control system may include additional wireless technologies, such as ultra-wide band (UWB) or the like, for performing secure distance measurements such as proximity determinations between the key fob and the access control system. A UWB device, for example, may be used to determine when the key fob is within a predetermined threshold distance to facilitate access or other control decisions. The key fob typically includes a battery that provides power to the wireless communication devices. The term "key fob" as used herein contemplates many different configurations of electronic control devices, including conventional vehicle key fob devices and various other electronic Smart Device configurations, such as SmartFOBs, Smart cards, Smart watches, mobile or cellular phones, etc..

When the battery of the key fob is dead or otherwise disconnected, the battery-powered primary communication circuitry of the key fob may be disabled or otherwise unavailable. For this reason, key fobs may include backup communication circuitry remotely powered and controlled. The backup communication circuitry may be independent and secure so that it independently performs the same functions and applications of the primary communication circuitry including secure cryptographic and key store functions. An inductive element may be provided on the key fob that inductively links with the access control system to establish an inductive power and communication link. Existing automotive systems, for example, may use low frequency (LF) technologies in which the cable length to the central base station is critical, or may use near-field communication (NFC) technologies in which the reader electronics are integrated into each coupling device.

There are several issues with current and proposed backup communication devices. The backup communication device must include its own microcontroller and flash memory and must be stand-alone so that it can perform the full application set of the primary communication device. In addition, each of the communication nodes, including the primary communication circuit, the backup communication circuit, and corresponding circuitry in the access control system, is classified as radio equipment requiring related compliance tests and certification. The resulting key fob is relatively complex, expensive to manufacture, and requires significant development time to design and implement appropriate functionality of each microcontroller for each separate communication interface, including, for example, wake up, connection, communications for transferring information, secure distance checks, etc. The inductively linked backup communication devices typically must perform all of these functions except secure distance checks.

According to the invention, there is provided a key fob system as defined by the appended claims.

Embodiments of the present invention are illustrated by way of example and are not limited by the accompanying figures. Similar references in the figures may indicate similar elements.

The inventors have recognized the need to provide backup functionality for battery-powered electronic control keys (a. , key fobs) when the battery is absent, disconnected, or otherwise not useful (e.g., dead or substantially discharged). They have therefore developed a system and method of optimized backup functionality for key fobs including an inductive link that provides power to the primary circuitry of the key fob but that does not perform communications.

<FIG> is a simplified block diagram of an electronic key-based control system <NUM> implemented according to one embodiment of the present disclosure. An electronic control key, or key fob <NUM>, is configured to establish authorized wireless communications with an access controller <NUM> contained within a vehicle <NUM>, such as an automobile, van, SUV, truck or the like. The vehicle <NUM> may also represent any type of controlled location, such as, for example, hotel rooms, apartments, buildings, secure areas, etc. The key fob <NUM> may be used to perform a variety of different functions, such as locking/unlocking doors, opening a trunk, activating an alarm, starting an engine of the vehicle <NUM>, etc. The key fob <NUM> and the access controller <NUM> may each be equipped with wireless communication circuitry that are configured to wirelessly communicate with each other to perform wake up, connection, and communication tasks for access, control and data transfer functions and the like, and for also performing distance measurements between the key fob <NUM> and the vehicle <NUM>.

As shown, each includes a communication (COM) antenna coupled to internal communication circuitry for performing the primary communications. In one embodiment, for example, each may include a wireless Bluetooth device configured to operate according to the Bluetooth wireless standard including low power versions, such as Bluetooth Low Energy (BLE). Although Bluetooth and BLE are commonly used for such functions, alternative wireless communication technologies are also contemplated for performing the same or similar functions, such as <NUM> or Wi-Fi and the like. In addition, the key fob <NUM> and the access controller <NUM> may each be equipped with additional wireless communication circuitry configured to wirelessly communicate with each other to perform distance (DIST) measurements or and the like for localization functions including determining the relative proximity of the key fob <NUM>. As shown, for example, each includes a distance antenna DIST coupled to internal communication circuitry for performing wireless communications associated with measuring a distance between the key fob <NUM> and the access controller <NUM>. In one embodiment, for example, each may include an ultra-wideband (UWB) device configured to operate using UWB technology.

During normal operation, the key fob <NUM> may be used to perform any of one or more different authorized functions, such as locking/unlocking doors, opening a trunk, activating an alarm system, starting an engine of the vehicle <NUM>, etc. Many of these authorized functions may be activated by one or more pushes of one or more buttons other interfaces (not shown) provided on the key fob <NUM>. Other authorized functions, such as passive keyless entry (PKE), may be performed without human action. When the key fob <NUM> is within a predetermined threshold distance <NUM> from the vehicle <NUM>, an authorized wireless communication session may be established to allow wireless communications between the key fob <NUM> and the access controller <NUM> to perform any of the desired authorized functions. The threshold distance <NUM> is a predetermined to ensure that the key fob <NUM> is nearby the vehicle <NUM> for enabling the authorized functions. In one embodiment, the predetermined threshold distance <NUM> is on the order of a few meters, such as <NUM>-<NUM> meters or the like, although any suitable distance threshold less than or greater than <NUM>-<NUM> meters is contemplated. The key fob <NUM> may include memory or the like storing a secure key or code which may be encrypted and transferred for purposes of authentication. The COM and DIST functions are supported by corresponding communication circuitry, described further below, powered by a battery or the like.

When the battery of the key fob <NUM> is absent, disconnected, or dead (or substantially discharged), then the normal wireless communications, including COM and DIST functions, might otherwise be disabled such as is the case for legacy or conventional key fob configurations. The key fob <NUM> includes an inductive element <NUM> which may be used to establish an inductive link with a corresponding inductive element <NUM> located on or within the vehicle <NUM>. The inductive elements <NUM> and <NUM> may each be implemented as physical inductors, although alternative inductive configurations are contemplated. When the inductive elements <NUM> and <NUM> are sufficiently close to one another, such as within a predetermined coupling zone <NUM>, then the inductive link may be established for transferring power and energizing the circuitry of the key fob <NUM>. In one embodiment, the location of the inductive element <NUM> of the vehicle <NUM> is marked or otherwise known by the user, such as at or near a door handle or the like. The coupling zone <NUM> may be a predetermined distance, such as <NUM>-<NUM> centimeters (or <NUM>-<NUM> inches) or the like. The user positions the key fob <NUM> so that the inductive element <NUM> of the key fob <NUM> is within the coupling zone <NUM> of the inductive element <NUM>.

Various methods are contemplated for detection of the presence of the key fob <NUM>. In the illustrated embodiment, a sensor <NUM> is provided on or within the vehicle <NUM>. The sensor <NUM> may be configured according to any suitable method and may include a sensor interface <NUM> configured according to the particular sensor type. The sensor interface <NUM> may a button, an inductive object detector, a capacitive sensor, etc. In one embodiment, the sensor interface <NUM> may be sufficiently close to the inductive element <NUM> for detecting the inductive element <NUM> when within the coupling zone <NUM>. In another embodiment, the sensor interface <NUM> is a button that is pressed by a user. In yet another embodiment, the sensor interface <NUM> may be a touch pad or the like configured as a capacitive sensor. In yet another embodiment, the sensor <NUM> is avoided and the inductive element <NUM> itself may be used as the sensing device. Once proximity is detected indicating a possible inductive link, the sensor <NUM> wakes up or otherwise activates the access controller <NUM>. Either the sensor <NUM> or the access controller <NUM> activates an inductive power generator (IPG) <NUM> electrically interfaced with the inductive element <NUM>. When activated, the IPG <NUM> energizes the inductive element <NUM> to transfer power to the inductive element <NUM> of the key fob <NUM>. As described further herein, once energized, the primary wireless communications (COM) of the key fob <NUM> are powered to enable normal wireless communications to commence.

According to the claimed invention, only limited circuitry of the key fob <NUM> is energized by the inductive link, such as, only the COM functions. In this limited activation embodiment, the DIST communications remain disabled since not necessary for measuring distance of the key fob <NUM> since assumed to be within the coupling zone <NUM> which has a radius much smaller than the threshold distance <NUM>.

<FIG> is a simplified schematic and block diagram of the circuitry of the key fob <NUM> according to one embodiment of the present disclosure. The circuitry includes COM circuitry <NUM>, DIST circuitry <NUM>, and MEMS circuitry <NUM>. The COM circuitry <NUM> establishes primary wireless communications with corresponding COM circuitry (not shown) of the access controller <NUM>, which is otherwise referred to as "authorized" communications. In the illustrated embodiment, COM is the primary communication method between the key fob <NUM> and the access controller <NUM>, although alternative wireless communication technologies are contemplated. The DIST circuitry <NUM> operates according to suitable wireless technology for performing distance measurements for localization of the key fob <NUM>. It is noted that the COM and DIST circuitry of the key fob <NUM> may be combined into a single wireless communication device performing the functions of both. When BLE or the like is used for performing the COM functions, however, BLE may not be able to perform proper localization in a targeted environment with acceptable speed, so that UWB circuitry or the like is better suited for the DIST functions.

The MEMS circuitry <NUM> may be used for various purposes including energy savings and the like. The key fob circuitry further includes a battery <NUM> having a negative terminal coupled to ground (GND) and a positive terminal coupled to an anode of a power diode <NUM>, having its cathode coupled to a power supply node <NUM> developing a supply voltage VDD. The power supply node <NUM> is coupled to power inputs of the COM circuitry <NUM>, the DIST circuitry <NUM>, and the MEMS circuitry <NUM>. A communication bus <NUM> is provided to enable internal communications between the COM circuitry <NUM>, the DIST circuitry <NUM>, and the MEMS circuitry <NUM>, and may be implemented in any suitable manner such as, for example, a serial peripheral interface (SPI) or the like. A COM antenna <NUM> is coupled to the COM circuitry <NUM> and a DIST antenna <NUM> is coupled to the DIST circuitry <NUM>, although a single antenna is contemplated in different embodiments.

The circuitry of the key fob <NUM> further includes an inductive power circuit <NUM>. The inductive power circuit <NUM> includes an LC tank circuit <NUM>, a rectifier circuit <NUM>, and a regulator circuit <NUM>. The LC tank circuit <NUM> includes the inductive element <NUM>, shown as an inductor, and a filter capacitor C1. The inductive element <NUM> has a first terminal coupled to a first terminal of C1 at a first node <NUM> and has a second terminal coupled to a second terminal of C1 at a second node <NUM>. The rectifier circuit <NUM> includes four diodes D1, D2, D3, and D4 coupled in a bridge configuration. Node <NUM> is coupled to the cathode of D1 and to the anode of D2, and node <NUM> is coupled to the cathode of D3 and to the anode of D4. The anodes of D1 and D3 are coupled to GND, and the cathodes of D2 and D4 are coupled to a node <NUM>. The regulator circuit <NUM> is shown coupled between node <NUM> and the power supply node <NUM> and may be referenced to GND. A filter capacitor C2 is coupled between node <NUM> and GND.

In one embodiment, the regulator circuit <NUM> may simply be a Zener diode or a voltage limiter or the like coupled between node <NUM> and GND for limiting voltage of VDD to a predetermined voltage level, in which case node <NUM> may be directly coupled to (or otherwise may be the same as) the power supply node <NUM>. Alternative voltage limiting or voltage protection or regulator devices or circuits are contemplated, such as a low-dropout (LDO) regulator or a DC-DC regulator or the like for converting or limiting the voltage developed on node <NUM> to limit VDD to a desired voltage level or within a desired voltage range.

In operation of the circuitry of the key fob <NUM> shown in <FIG>, when the battery <NUM> is provided and sufficiently charged for battery operation, the battery voltage forward biases the power diode <NUM> and charges the supply voltage VDD to provide power to the COM circuitry <NUM>, the DIST circuitry <NUM>, and the MEMS circuitry <NUM> for normal operation. When the battery <NUM> is absent, disconnected, or otherwise not functional (e.g., dead or substantially discharged) and the inductive elements <NUM> and <NUM> are within the coupling zone <NUM> establishing an inductive link, and when the IPG <NUM> is activated to energize the inductive element <NUM> with alternating current (AC) for inductive power mode, corresponding AC current flows through the inductive element <NUM> generating AC voltage across the nodes <NUM> and <NUM>. The AC voltage is full wave rectified by the rectifier circuit <NUM> and filtered by the capacitor C2 to develop a corresponding voltage on node <NUM>. The regulator <NUM> either limits the voltage or converts the voltage to the desired voltage level of the supply voltage VDD. Rather than providing separate backup communications via the inductive link, the COM circuitry <NUM> is powered to enable primary wireless communications with the access controller <NUM>.

In one embodiment of the inductive power mode, the DIST circuitry <NUM> and the MEMS circuitry <NUM> are both disabled to conserve energy for the COM circuitry <NUM>. In another embodiment of the inductive power mode, only the DIST circuitry <NUM> is disabled and the MEMS circuitry <NUM> is enabled. It is noted that during the inductive power mode when the inductive elements <NUM> and <NUM> are inductively linked, the distance measurement functions of the DIST circuitry <NUM> may be considered superfluous and unnecessary. Also, it is noted that during the inductive power mode when the inductive elements <NUM> and <NUM> are inductively linked, any motion sensor functions of the MEMS circuitry <NUM> may be considered superfluous and unnecessary.

In any event, the inductive link formed by the inductive elements <NUM> and <NUM> is only used to transfer power from the IPG <NUM> to the circuitry of the key fob <NUM> using the inductive power circuit <NUM> and is not used for purposes of communication. Although the key fob <NUM> may include additional circuitry not shown, such as battery charging circuitry for charging the battery <NUM> via the inductive link, in no event is the inductive link used for purposes of communication. In this manner, a separate secure backup communication device is eliminated substantially simplifying the circuitry of the key fob <NUM>. This eliminates the need for a separate microcontroller and corresponding memory for supporting the functions of backup communication configurations. In addition, the inductive link need not be classified as radio equipment requiring related compliance tests and certification since only used for power transfer functions, resulting in reduced effort for compliance tests (radio compliance) and certification. Also, since data communication is avoided on the inductive link, no modulation is done and thus the system can be tuned for highest efficiency, such as a high Q factor and the like.

<FIG> is a flowchart diagram illustrating operation of the circuitry of the vehicle <NUM> including the access controller <NUM>, the sensor <NUM> and the IPG <NUM> according to one embodiment of the present disclosure. Operation begins at block <NUM> to perform a presence inquiry. The presence inquiry is performed by the sensor <NUM> which depends upon its particular configuration. When the sensor interface <NUM> is configured as a button and the button is pressed by a user, then presence is true. When the sensor interface <NUM> is configured as a capacitive sensor configuration and when a user comes close to or touches the sensor interface <NUM>, then presence is true. When the sensor interface <NUM> is configured as an inductive object load detector and when the inductive element <NUM> (or any similar inductive element or device) is sufficiently close to the sensor interface <NUM>, then presence is true. While presence is false, operation loops at block <NUM> representing sensor <NUM> monitoring.

When presence is true, operation advances to block <NUM> in which the sensor <NUM> awakens the access controller <NUM>, and either the sensor <NUM> or the awakened access controller <NUM> then activates the IPG <NUM>. If the key fob <NUM> is present and inductively linked, then activation of the IPG <NUM> provides power to the circuitry of the key fob <NUM> as previously described. At next block <NUM>, it is queried whether authorized communication (AUTH. COMM) with the key fob <NUM> is established. In one embodiment, authorized communication is established between the COM circuitry <NUM> of the key fob <NUM> and corresponding COM circuitry within the access controller <NUM>. When the key fob <NUM> is powered on or otherwise awakened, it attempts to establish a communication session with the access controller <NUM>. At block <NUM>, the access controller <NUM> determines whether the key fob <NUM> is authorized, such as detection of a correct key or code value. If the key fob <NUM> is not present, or if a nearby device or entity triggering presence is not an authorized device, such as a different or unauthorized key fob or simply a nearby foreign inductive or capacitive element or accidental pressing of the sensor button, then operation advances to block <NUM> in which the IPG <NUM> is deactivated, and then operation loops back to block <NUM>. It is noted that a timeout function may be implemented to deactivate the IPG <NUM> to prevent damage to a foreign object.

If the key fob <NUM> is present and an authorized communication session is established, then operation advances to block <NUM> to query whether the IPG <NUM> is needed for providing power. For normal operations in which the battery <NUM> is present and charged, then operation proceeds to block <NUM> in which the IPG <NUM> is deactivated, the communication session is completed per normal operation, and operation is completed. On the other hand, if the IPG <NUM> is needed to provide power to the key fob <NUM>, then operation advances instead to block <NUM> in which the IPG <NUM> remains activated to complete the communication session. When the communication session is completed, operation advances to block <NUM> to deactivate the IPG <NUM>, and operation is completed. In one embodiment, during authorized communication, the key fob <NUM> informs the access controller <NUM> whether the IPG <NUM> is needed or not, such as by setting a bit in a register or control field or the like, or else by sending an instruction or command or the like. In another embodiment, the IPG <NUM> may sense power consumption via the inductive element <NUM> and if authorized communication is established with the key fob <NUM>, then it is assumed that the IPG <NUM> is necessary to provide power to the key fob <NUM>.

<FIG> is a flowchart illustrating operation of the circuitry of the key fob <NUM> during inductive linking according to one embodiment of the present disclosure. In this case, battery power from the battery <NUM> is not available (disconnected, absent, discharged) and an inductive link is established. When the key fob <NUM> is powered up, operation advances to block <NUM> to query whether power is being provided only by the inductive link of the inductive power circuit <NUM>. Although not explicitly shown, additional detection circuitry, such as a battery detector or inductive field detector or the like, provides an indication to the COM circuitry <NUM> regarding the source of power within the key fob <NUM>, such as either from the battery <NUM> or the inductive power circuit <NUM>. If power is not provided by the inductive link, then the battery <NUM> may be available so that normal operations apply. In this case, the functions of inductive coupling do not apply and operation loops at block <NUM>. If power is only being provided by the inductive link, then operation advances to block <NUM> in which the COM circuitry <NUM> attempts to establish authorized communications with the COM circuitry of the access controller <NUM>. Assuming authorized communications are established as determined at next query block <NUM>, then operation advances to block <NUM> in which the communication session is completed while maintaining activation of the IPG <NUM>. In one embodiment, the key fob <NUM> commands or otherwise indicates whether the IPG <NUM> is needed or not. In another embodiment, power via the inductive link is detected by the IPG <NUM> which communicates to the access controller <NUM> the need to remain activated. The circuitry of the key fob <NUM> then goes back to sleep after communications are completed. Referring back to block <NUM>, if authorized communications are not established with the access controller <NUM>, then power may be provided by another device without the access controller <NUM> and circuitry of the key fob <NUM> goes back to sleep.

A key fob according to one embodiment includes at least one wireless communication circuit, a power supply node coupled to provide power to the at least one wireless communication circuit, a battery node, a battery power circuit, and an inductive power circuit for only providing power. The battery power circuit provides power when a battery with sufficient charge is provided. The inductive power circuit provides power when energized with inductive power when the battery is not provided or is not sufficiently charged, in which the inductive power circuit does not perform wireless communications thereby simplifying circuitry and operation of the key fob and a corresponding access system. The inductive power circuit may include a rectifier circuit and an inductor and may further include regulator circuitry. Since only configured to transfer power, the inductive power circuit may be optimized for power transfer. The access system inductively provides power to the key fob when within a predetermined coupling zone distance.

Although the present invention has been described in connection with several embodiments, the invention is not intended to be limited to the specific forms set forth herein. On the contrary, it is intended to cover such alternatives, modifications, and equivalents as can be reasonably included within the scope of the invention as defined by the appended claims. For example, variations of positive logic or negative logic may be used in various embodiments in which the present invention is not limited to specific logic polarities, device types or voltage levels or the like. For example, logic states, such as logic low and logic high may be reversed depending upon whether the pin or signal is implemented in positive or negative logic or the like. In some cases, the logic state may be programmable in which the logic state may be reversed for a given logic function.

Claim 1:
A key fob system (<NUM>), comprising:
a key fob (<NUM>) and an access system (<NUM>),
the key fob (<NUM>) comprising:
at least one wireless communication circuit;
a power supply node (<NUM>) coupled to provide power to the at least one wireless communication circuit;
a battery node;
a battery power circuit that provides power via the power supply node when a battery (<NUM>) with sufficient charge is coupled to the battery node; and
an inductive power circuit (<NUM>) that, with the key fob in an inductive power mode, only provides power via the power supply node (<NUM>) when energized with inductive power and when the battery node does not provide power,
the access system (<NUM>) comprising:
an inductive power generator (<NUM>) that can inductively couple to the inductive power circuit (<NUM>) of the key fob (<NUM>) when the inductive power circuit (<NUM>) is within a predetermined coupling zone distance of the inductive power generator (<NUM>);
an access controller (<NUM>) comprising at least one wireless communication circuit; and characterized by
a sensor (<NUM>) that senses and reports a presence of the key fob (<NUM>) to the access controller (<NUM>) ,
wherein when the presence of the key fob (<NUM>) is detected, the inductive power generator (<NUM>) is configured to activate and the access controller (<NUM>) is configured to attempt to establish wireless communications with the key fob (<NUM>),
wherein the key fob (<NUM>) comprises COM circuitry (<NUM>) for establishing primary wireless communications with corresponding COM circuitry of the access controller and DIST circuitry (<NUM>) for performing distance measurements for localization of the key fob (<NUM>), the key fob (<NUM>) being configured to enable the COM circuitry (<NUM>) and disable the DIST circuitry (<NUM>) when in the inductive power mode.