Remote device identification using resonant frequency

SUMMARY OF THE INVENTION

The present invention provides a method for controlling an inductive power supply to supply power to at least one remote device, comprising the steps of: selecting an identification frequency from among a plurality of identification frequencies, wherein at least one of the plurality of identification frequencies is associated with each of the at least one remote device, wherein each of the at least one remote device has a resonant frequency at or near at least one frequency from among the plurality of identification frequencies; applying an inductive field to the at least one remote device at the identification frequency; determining whether the at least one remote device has the resonant frequency substantially at the applied identification frequency to identify the at least one remote device; and operating the inductive power supply to supply operating wireless power to the identified at least one remote device according to an operating parameter based on an outcome of said determining step, wherein the operating parameter corresponds to the identified at least one remote device.

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The term “comprising” as used in this specification means “consisting at least in part of’. When interpreting each statement in this specification that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.

The present invention further provides a method for securely controlling an inductive power supply to supply operating wireless power to at least one of a plurality of remote devices, comprising the steps of: determining a common identification profile for the plurality of remote devices to be powered by the inductive power supply, the common identification profile including one or more resonant frequencies; applying an inductive field to the at least one of the plurality of remote devices at the one or more resonant frequencies of the common identification profile; determining whether the at least one of the plurality of remote devices has a resonant frequency profile corresponding with the common identification profile; and operating the inductive power supply according to an operating parameter to supply the operating wireless power to the at least one of the plurality of remote devices if the at least one of the plurality of remote devices has a resonant frequency profile corresponding to the common identification profile.

There is described herein a method for operating an inductive power supply to supply power to at least one of a plurality of remote devices comprising the steps of:

storing a plurality of identification profiles and at least one inductive power supply operating parameter associated with each identification profile in a memory associated with an inductive power supply, each of the plurality of identification profiles corresponding to the at least one of the plurality of remote devices; applying inductive power to the at least one of the plurality of remote devices at one or more frequencies to determine the identification profile of the at least one of the plurality

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Received at IPONZ on 27 March 2012 of remote devices contained within the inductive field; comparing the determined profile with the stored identification profiles to determine an identity of the at least one of the plurality of remote devices; retrieving an operating parameter for an inductive power supply from the memory upon determination of the identity of the at least one of the plurality of remote devices, wherein the operating parameter is selected as a function of the identification profile of the at least one of the plurality of remote devices; and operating the inductive power supply to supply operating wireless power to the identified at least one of the plurality of remote devices in accordance with the retrieved operating parameter.

There is further described herein an inductive power supply for supplying power to at least one remote device comprising: inductive field generating circuitry;

frequency control circuitry electrically connected to said inductive field generating circuitry, said control circuitry capable of operating said inductive field generating circuitry at a plurality of different frequencies; reflected impedance sensing circuitry to sense a characteristic of power in the inductive power supply, said characteristic being indicative of a reflected impedance of the at least one remote device; identification circuitry to determine an identification profile of the at least one remote device as a function of an output of said reflected impedance sensing circuitry; memory storing a plurality of identification profiles for different remote devices and a plurality of operating parameters each corresponding to one or more of the plurality of identification profiles; and power supply control circuitry for supplying operating wireless power to the at least one remote device according to an operating parameter selected as a function of the identification profile of the remote device.

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There is further described herein an inductive power supply and remote device combination comprising: a remote device having an identification profile, said identification profile including one or more resonant frequencies; and an inductive power supply having: a driver; a tank circuit having a primary; a sensor in said tank circuitadapted to sense a characteristic of power in said tank circuit indicative of a reflected impedance of said remote device; identification circuitry to determine said identification profile of said remote device as a function of output of said sensor; a memory storing at least one identification profile and at least one operating parameter associated with said identification profile; and control circuitry for controlling operation of said inductive power supply to supply operating wireless power to the remote device according to an operating parameter selected as a function of said identification profile of said remote device.

The present invention provides an inductive power supply system and associated method in which an adaptive inductive power supply (“AIPS”) identifies the remote device through reflected impedance, and controls operation as a function of the identity of the remote device. The present invention also provides the AIPS with the ability to assess fault conditions by recognizing when the secondary circuit is operating outside of normal operating conditions for the identified device.

In one embodiment, the present invention includes an AIPS having a controller capable of supplying power to the secondary circuit at various frequencies and a current sensor capable of directly or indirectly sensing the current in the tank circuit. In this embodiment, each remote device or type of remote device includes one or more resonant frequencies that individually or collective provide a signature that is unique to that device or type of remote device. For example, the identification frequency(ies) may uniquely identify a specific model of cell phone or a specific model of personal digital assistant. The system may also include a look-up table or other data collection containing operating information for

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PCT/IB2007/055339 one or more recognizable remote devices. This information can be used to establish operating parameters and recognize fault conditions.

In operation, the AIPS applies a short pulse of power to the secondaiy circuit at a frequency that is uniquely associated with a specific remote device. If the remote device has a resonant frequency at the frequency of the pulse, the remote device will draw a material amount of current, which will be reflected back into the tank circuit through reflected impedance. The controller will recognize the presence of the remote device when input from the current sensor shows the increased power draw. This permits the AIPS to recognize that a specific remote device is present and to obtain its operating parameters from the look-up table. Once the operating parameters have been retrieved, the AIPS can use the retrieved parameters to more efficiently power the device and to recognize that a fault condition has occurred when actual operating conditions fall outside the retrieved operating parameters.

In some applications, the remote device may inherently include a resonant frequency (or plurality of resonant frequencies) that is sufficiently unique to permit it to function as an identification frequency. In such application, the remote device will operate at resonance when the corresponding identification frequency is applied, thereby uniquely identifying the remote device.

In other applications, the remote device may not inherently have a resonant frequency at a frequency that will uniquely identify the remove device. With remote devices of this nature, the remote device can be provided with an identification capacitor that is selected to provide the remote device with a unique resonant frequency (or pattern of frequencies) that can be identified using an identification ping. In some applications, the main circuitry of the remote device may mask the identification capacitor. Accordingly, in some applications, the remote device may include a load delay circuit that isolates the main circuit of the remote device from the secondary coil and the identification capacitor for a

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PCT/IB2007/055339 sufficient period of time to allow resonance to be established by the identification capacitor and reflected back to the tank circuit.

In applications where the number of potential remote devices is large, a plurality of capacitors may be used to provide the remote devices with a plurality of resonant frequencies that collectively provide each remote device with a unique resonant “signature” in response to pings at different frequencies. For example, the use of two different capacitors can be used to provide three separate resonant frequencies—one for each capacitor individually and a third for the combination of the two capacitors. In one embodiment, the presence or absence of resonance at select frequencies can be used as the bits in a binary code that can unique identify a large number of remote devices with only a limited number of frequencies.

In one embodiment, the method generally includes the steps of applying a short pulse of power to the secondary circuit at an identification frequency, waiting a period of time and sensing the current in the tank circuit to determine if a remote device is present that has a resonant frequency at the frequency of the short pulse of power. If so, the remote device is identified and the operating parameters can be pulled from a lookup table or other memory device. If not, the AIPS can move to the next identification frequency and repeat the process. In some applications, a small delay may be implemented between each identification ping to allow the circuit to settle so that residual energy from one identification ping does not impact the remote device’s response to the next identification ping. The system may repeatedly cycle through all of the possible identification frequencies until a remote device is positively identified.

In another embodiment, each remote device capable of being powered by an inductive power supply is provided with a capacitor with the same common resonant frequency. The inductive power supply is programmed to send a short power pulse at that .4.

WO 2008/081405

PCT/IB2007/055339 single common resonant frequency. A response from the device, as described above, indicates that the device is capable of receiving power from the power supply.

In another embodiment, each device capable of being powered by an inductive power supply is equipped with a capacitor with a common resonant frequency, and one or more additional capacitors with unique secondaiy and / or tertiary resonant frequencies. According to this embodiment, the inductive power supply is programmed to send a short power pulse at the single common resonant frequency. When the supply senses a response at that frequency, the inductive power supply sends out additional short pulses at different frequencies, or over a range of frequencies. Depending on the responses at the various frequencies, the power supply is able to distinguish the type of device, and the specific device model.

Once a remote device has been identified, the AIPS can provide power to the remote device in accordance with the operating parameters pulled from memory. Additionally, the AIPS can use information from the lookup table to help identify fault conditions. For example, the lookup table can include minimum and maximum operating frequencies, as well as minimum and maximum current usage. If the current draw on the primary exceeds the maximum current retrieved from the lookup table, the AIPS will recognize a fault condition and take appropriate action, such as powering down the primary.

The present invention provides a simple and effective method and apparatus for identifying remote devices. The lookup table permits the AIPS to retrieve information regarding the remote devices, such as normal operating parameters. This allows the AIPS to more efficiently power the remote device and to more readily identify fault conditions. In applications where a single resonant frequency does not provide a sufficient number of unique identifications, each device may be provided with a pattern of identification frequencies. In applications where a remote device inherently includes a uniquely identifying

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PCT/IB2007/055339 resonant frequencies (or frequency pattern), the present invention requires no modification to the remote device. In applications where a remote device does not include an inherent uniquely identifying resonant frequency, the remote device may be provide with one or more identification capacitors that provide the remote device with an identification frequency or an identification frequency pattern. In another aspect, the present invention provides a set of standards from which a class of remote devices may be identified by predetermined identification frequencies. This permits intelligent operation of the AIPS for an essentially unlimited numbers of remote devices that fit within one of the predetermined classes of remote devices.

These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the current embodiment and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of an inductive power supply system in accordance with an embodiment of the present invention.

Fig. 2 is a circuit diagram of the inductive power supply system of one embodiment.

Fig. 3 A is a circuit diagram of an alternative remote device having an identification capacitor.

Fig. 3B is a circuit diagram of an alternative remote device having a plurality of identification capacitors.

Fig. 4 is a circuit diagram of a second alternative remote device.

Fig. 5 is a table showing various capacitor values and associated resonant frequencies available from select capacitor combinations.

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Fig. 6 is a flow chart showing the general steps of a method for identifying a remote device.

DESCRIPTION OF THE CURRENT EMBODIMENT

An inductive power supply system in accordance with an embodiment of the present invention is shown in Fig. I. The inductive power supply system 10 generally includes an adaptive inductive power supply (“AIPS”) 12 and one of a plurality of remote devices 14. The AIPS 12 generally includes a tank circuit 48 with a primary coil 18 (See Fig. 2) capable of inductively transmitting power. The AIPS also includes a controller 20 for selectively controlling the frequency at which power is generated by the primary coil 18, and a sensor 16 capable of sensing reflected impedance from a remote device 14. The AIPS 12 is intended for use with one or more remote devices 14, each of which has a unique resonant frequency or unique pattern of resonant frequencies. In operation, the AIPS 12 applies power to the primary 18 at an identification frequency and then evaluates the reflected impendence of the remote device 14 using the current sensor 16. If the remote device 14 has a resonant frequency at the identification frequency, then the AIPS 12 knows what type of remote device is inductively coupled to AIPS 12 and the AIPS 12 can recover operating parameters from a look-up table or other memory device. The recovered information can be used by the AIPS to provide efficient operation of the remote device and to identify fault conditions.

I. Adaptive Inductive Power Supply.

The present invention is suitable for use with a wide variety of adaptive inductive power supplies. As used herein, the term “adaptive inductive power supply” is intended to broadly include any inductive power supply capable of providing power at a plurality of different frequencies. For purposes of disclosure, the present invention is described in connection with a particular AIPS 12. The illustrated AIPS 12 is merely

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PCT/IB2007/055339 exemplary, however, and the present invention may be implemented with essentially any AIPS capable of providing inductive power at varying frequencies.

In the illustrated embodiment, the AIPS 12 generally includes a frequency controller 20 and a tank circuit 48. In operation, the frequency controller 20 applies power to the tank circuit 48 to generate a source of electromagnetic inductive power. The frequency controller 20 of the illustrated embodiment generally includes a microcontroller 40, an oscillator 42, a driver 44 and an inverter 46. The microcontroller 40 may be a microcontroller, such as a PIC18LF1320, or a more general purpose microprocessor. The oscillator 42 and driver 44 may be discrete components or they may be incorporated into the microcontroller 40, for example, in the embodiment illustrated in Fig. 2, the oscillator 42 is a module within the microcontroller 40. The frequency controller 20 may also include a low voltage power supply 26 for supplying low voltage power to the microprocessor 40 and the driver 44. In this embodiment, the various components of the frequency controller 20 collectively drive the tank circuit 48 at a frequency dictated by the microcontroller 40, More specifically, the microcontroller 40 sets the timing of the oscillator 42. In certain modes of operation, the microprocessor 40 may establish the operating frequency as a function of input from the current sensor 16. The oscillator 42, in turn, operates the driver 44 at the frequency established by the microcontroller 40. The driver 44 provides the signals necessary to operate the switches 47a-b within the inverter 46. As a result, the inverter 46 provides AC (alternating current) power to the tank circuit 48 from a source of DC (direct current) power

50.

In the illustrated embodiment, the current sensor 16 is a current transformer having its primary coil disposed in the tank circuit 48 and its secondary coil connected to the microcontroller 40. The AIPS may include conditioning circuitry 28 for conditioning the current transformer output before it is supplied to the microcontroller 40. Although the

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PCT/IB2007/055339 illustrated embodiment includes a current transformer for sensing the reflected impedance of the remote device, the AIPS 12 may include essentially any alternative type of sensor capable of providing information regarding reflected impedance from the remote device 14. Further, although the current sensor 16 ofthe illustrated embodiment is located in the tank circuit, the current sensor (or other reflected impedance sensor) can be located in essentially any location where it is capable of providing readings indicative of the presence or absence of resonance in the remote device.

In the illustrated embodiment, the AIPS further includes a lookup table 24 or other memory device capable of storing information relating to the operating parameters of a plurality of remote devices 14. The stored information may be used to permit the AIPS 12 to more efficiently power the remote device 14 and more readily recognize fault conditions. In some applications, the AIPS 12 may be intended for use with a specific set of remote devices

14. In these applications, the lookup table 24 includes the unique resonant frequency (or pattern of frequencies) for each remote device 14, along with the desired collection of associated information, such as maximum and minimum operating frequencies and current usage. The lookup table 24 may, however, include essentially any information that may be useful to the AIPS 12 in operating the remote device 14. For example, in applications where it is desirable to establish wireless communications with the remote device 14, the lookup table 24 may include information regarding the wireless communication protocol of the remote device 14.

The tank circuit 48 generally includes the primary coil 18 and a capacitor 52. The capacitance of capacitor 52 may be selected to balance the impedance of the primary coil 18 at anticipated operating parameters. The tank circuit 48 may be either a series resonant tank circuit (as shown) or a parallel resonant tank circuit (not shown). The present invention may be incorporated into the AIPS shown in U.S. Patent 6,825,620, which as noted above is

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PCT/IB2007/055339 incorporated herein by reference. As another example, the present invention may be incorporated into the AIPS shown in U.S. Patent Application Publication US 2004/130916A1 to Baarman, which is entitled “Adapted Inductive Power Supply” and was published on July 8, 2004 (U.S. Serial No. 10/689,499, filed on October 20, 2003), which is also incorporated herein by reference. Further, it may be desirable to use the present invention in connection with an AIPS capable of establishing wireless communications with the remote device, such as the AIPS shown in U.S. Patent Application Publication US 2004/130915A1 to Baarman, which is entitled “Adapted Inductive Power Supply with Communication” and was published on July 8, 2004 (U.S. Serial No. 10/689,148, filed on October 20, 2003), which is incorporated herein by reference.

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II. Remote Devices.

The present invention is intended for use with a wide variety of remote devices of varying designs and constructions. It is anticipated that these various remote devices will require power at varying frequency and will have different current requirements.

In some applications, the remote device may inherently include a unique resonant frequency or pattern of resonant frequencies. For example, a specific type of remote device may include a resonant frequency at 195 kHz. If none of the other remote devices to be identified by the AIPS include a resonant frequency at 195 kHz, then 195 kHz can operate as the identification frequency for this type of remote device. On the other hand, if the remote device does not include a resonant frequency that is unique among the set of remote devices that may need to be identified, then it may be possible to use the presence of a unique pattern of resonant frequencies to identify the remote device. For example, a remote device may have one resonant frequency at 195 kHz and another resonant frequency at 215 kHz. Even if other remote devices have a resonant frequency at 195 kHz or at 215 kHz, the combination of the two resonant frequencies in a single type of remote device may be sufficient to uniquely identify the type of remote device. If two resonant frequencies are not sufficient to uniquely identify a type of remote devices, then even more resonant frequencies may be considered until a unique pattern of identification frequencies emerges.

For purposes of disclosure, one embodiment of a remote device 14 having an inherent identification frequency is shown in Fig. 2. In the embodiment of Fig. 2, the remote device 14 generally includes a secondary 22 for receiving power from the AIPS 12, a bridge 30 (or other rectifier for converting AC power to DC), a charging circuit 32, a battery 34 and a main circuit 36. In operation, the bridge 30 converts the AC power generated in the secondary 22 to DC power, which is required for operation of charging circuit 32 in this embodiment Charging circuits are well-known and are widely used with a variety of

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PCT/IB2007/055339 rechargeable electronic devices. If desired, the charging circuit 32 may be configured to both charge the battery 34 and/or power the remote device 14 (if the remote device 14 is powered on). Charge circuits capable of charging and/or powering an electronic device are wellknown and therefore will not be described in detail. In some applications, the charging circuit 32 will be a part of the main circuit 36. In other applications, the charging circuit 32 will be a separate circuit, and may even be controlled by the AIPS 12, if desired. The term “main circuit” is used loosely to refer to the operating circuitry for the remote device 14.

Although the illustrated embodiment is described in connection with a batterypowered remote device, the present invention may alternatively be used to directly power a remote device by eliminating the battery 34 and charging circuit 32 and connecting the secondary 22 to the main circuit 36, for example, through appropriate power conditioning circuitry, which may include a transformer or rectifier (such as bridge 30).

In another embodiment, a remote device may be provided with one or more identification capacitors that provide resonance at desired identification frequencies.

Although useable with all remote devices, this embodiment is perhaps most useful with remote devices that do not have an inherent identification frequency or inherent identification pattern of frequencies. Fig. 3A shows a circuit diagram of an exemplary remote device 14’ having an identification capacitor 38’. As shown in Fig. 3A, an identification capacitor 38’ is connected in parallel across the secondary 22’. The identification capacitor 38’ has a capacitance selected to establish resonance at the identification frequency. In this embodiment, it is possible that the charging circuit 32’ and/or the main circuit 36’ will mask the identification capacitor 38’ making it difficult or impossible for the AIPS 12 to recognize the presence of the identification capacitor 38’. Accordingly, in this embodiment, the remote device 14’ includes a load enable delay circuit 54’ that prevents the charging circuit 32’ and/or the main circuit 36’ from receiving power for a period of time sufficient for the

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PCT/IB2007/055339 identification capacitor 38’ to establish resonance and for that resonance to be conveyed to the AIPS 12 through reflected impedance. The load enable delay circuit 54’ may include a simple timed switching circuit that connects the bridge 30’ to the charging circuit 32’ only after a sufficient period of time has lapsed. This embodiment is particularly well-suited for incorporating the present invention into remote devices already including a charging circuit. Fig. 4 shows an alternative embodiment intended primarily for use in incorporating the present invention into remote devices not already including charging circuitry or that include charging circuitry having a microprocessor with an enable input. In this embodiment, the load enable delay 54’” is connected to the “enable” input of the microprocessor in the charging circuitry 32”’. In this embodiment, the load enable delay 54’” does not enable the charging circuitry 32”’ until a sufficient amount of time has passed for the AIPS 12 to recognize whether or not the identification capacitor 38’” has established resonance. Although described in connection with two specific embodiment, the load enable delay circuit may be essentially any circuitry capable of preventing the charging circuit and/or main circuit from masking the identification capacitor long enough for the AIPS 12 to recognize whether resonance has been established.

In the embodiment of Fig. 3A, the remote device 14’ includes only a single identification capacitor 38’. In the embodiment shown in Fig. 3B, the remote device 14” is provided with three identification capacitors 38a-c” connected in parallel to the load each providing resonance at a different frequency. In a similar manner, additional identification capacitors can be provided to establish even more additional resonant frequencies, if desired.

For example, Fig. 5 is a table showing the resonance frequencies that may be provided using different combinations of four capacitors. The first four columns labeled C1-C4 list the capacitance (in microfarads) of four different capacitors. In this example, the capacitors are

8.2, 6.8, 3.3, and 2.2 microfarad capacitors. The capacitors used in this table or merely

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PCT/IB2007/055339 exemplary and are not intended to limit the scope of the present invention. The second four columns labeled C1-C4 identify the capacitors included that particular combination, using a “1” to represent the presence of a capacitor and a “0” to represent the absence of a capacitor. The column labeled “Capacitance” provides the combined capacitance of the capacitors in that particular combination. The column labeled “Frequency” provides the resonant frequency of the capacitor combination when the inductance is 0.000000309 as specified in the last column. For example, row four includes a “1” in the Cl and C2 columns to indicate that an 8.2 microfarad capacitor and a 6.8 microfarad capacitor are combined to provide a combined capacitance of 3.7173 microfarad, which will have a resonant frequency of roughly

148.5 kHz. In addition to the resonant frequency created by the combined capacitance of the two capacitors, the identification capacitors will also establish resonance at the individual capacitances of each capacitor in that combination. So, continuing with the row 4 example, the combined capacitors will also have a resonant frequency at roughly 100 kHz (the resonance frequency of the 8.2 microfarad capacitor) and at roughly 109.9 kHz (the resonance frequency of the 6.8 microfarad capacitor). As can be seen, the combination of 8.2 and 6.8 microfarad capacitors provides an identification frequency pattern with resonance at roughly 100 kHz, 109.9 kHz and 148.5 kHz.

The particular remote devices described above are merely exemplary as the present invention is well-suited for use with essentially any remote device having an identification frequency and capable of inductively receiving power within the limits of the

AIPS.

III. Operation.

General operation of the system 10 is described in connection with Fig. 6. In this embodiment, the system 10 is configured to recognize one of a plurality of remote

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PCT/IB2007/055339 devices. Each remote device includes a single resonant frequency that is unique among the remote devices. Accordingly, the AIPS 12 can uniquely identify a remote device by cycling through each of the potential identification frequencies until a remote device is present that establishes resonance at one of the potential identification frequencies.

In the illustrated embodiment, the AIPS 12 is provided with data defining a plurality of potential identification frequencies. For example, a list or table of potential identification frequencies may be stored in onboard memory on the microcontroller 40. The identification process begins by setting 100 the identification frequency to the first frequency in the list. The AIPS 12 then applies 102 power to the tank circuit 48 at the identification frequency. The AIPS 12 continues to apply power to the tank circuit 48 for a period of delay 104. The delay period is selected to provide sufficient time for the remote device 14 to establish resonance and to generate sufficient reflected impedance in the tank circuit 48. The delay period may be a fixed period of time that remains constant throughout the identification process. The delay period may vary from application to application, but in the illustrated embodiment is approximately 6 microseconds. In some applications, a sufficient delay may be inherent in the system and therefore may not require the implementation of a separate deliberate delay step. If the remote device 14 includes a resonant frequency at the identification frequency, the remote device 14 will draw current and this increase in current draw will be reflected back into the tank circuit 48 by reflected impedance. After the delay 104 is complete, the microprocessor 40 obtains 106 input from the current sensor 16. As noted above, the output of the current sensor 16 may be conditioned using conditioning circuitry 28. The microprocessor 40 evaluates the input from the current sensor 16 to determine whether the remote device 14 has a resonant frequency at the current identification frequency. In this embodiment, the microprocessor 40 will conclude that a resonant frequency exists if the current sensor reading is above a threshold value. Typically, the

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PCT/IB2007/055339 threshold value for a specific application will be a value above the noise floor of that application plus an additional deadband. The amount of the deadband may vary from application to application.

If the microprocessor 40 determines that the remote device 14 does not include a resonant frequency at the current identification frequency, then the controller 20 prepares to apply to the next identification frequency to the tank circuit 48. More specifically, the microprocessor 40 enters a delay 114 for a relatively short period of time. The delay period is selected to provide sufficient time for the remote device 14 to settle and for the energy in the remote device 14 to sufficiently dissipate. The delay period may be a fixed period of time that remains constant from throughout the identification process. The settle delay period may vary from application to application, but in the illustrated embodiment is approximately 5 microseconds. In some applications, a sufficient delay may be inherent in the system and therefore may not require the implementation of a separate deliberate settle delay step. After the delay, the microprocessor 40 sets the identification frequency as the next frequency in the list of potential identification frequencies. The process then repeats beginning with the step of applying 102 power to the tank circuit 48 at the new identification frequency.

If the microprocessor 40 determines that the remote device 14 includes a resonant frequency at the current identification frequency, the microprocessor 40 will retrieve

110 the operating parameters from the lookup table 24 and will exit the remote device identification process. The microprocessor 40 may then operate 112 the remote device 14 using the operating parameters retrieved from lookup table 24. The lookup table 24 may include an anticipated operating frequency and may begin operation by applying power to the tank circuit 48 at the recalled operating frequency. The microprocessor 40 may also use maximum and minimum current draws values obtained from the lookup table to determine the presence of a fault condition. For example, if during operation the actual current draw

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PCT/IB2007/055339 sensed by the current sensor exceeds the maximum current draw or falls below the minimum current draw, the microprocessor 40 will conclude that a fault condition exists. The microprocessor 40 may be programmed to take remedial action if a fault condition is encountered. For example, the microprocessor 40 may be programmed to shut down the system if a fault condition arises. Alternatively, the microprocessor 40 may restart the identification process to determine if a different remote device 40 has been placed near the primary 18.

In the embodiment described above, the microprocessor 40 cycles through a list of potential identification frequencies in an effort to identify a remote device. As an alternative to cycling through a list, the AIPS 12 may be programmed to simply cycle through a range of frequencies using a specified step value. For example, by stepping from 100 kHz to 300kHz in 5 kHz increments.

In another aspect, the present invention provides a mechanism for establishing standards for using frequency identification for remote devices. In this embodiment, unique identification frequencies can be specified for each type of remote device and for other identifying features. For example, the standards may specify a different identification frequency for each type of device (e.g. cell phone, personal digital assistant, may digital music player) and/or for each manufacturer (e.g. company name). In applications where a unique identification frequency is assigned to each manufacturer, the manufacturer may be permitted to add additional identification frequencies to specify model numbers and product types.

In an alternative method for establishing standards, identification frequencies can be establish by the class of the remote device rather than the specific model type. For example, all devices operating within a given set of operating parameters can be assigned the same identification frequency (or identification frequency pattern). This alternative method

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PCT/IB2007/055339 is particularly well-suited for use in application where a plurality of remote devices of different types are capable of operating under the operating parameters set forth in a single record in the lookup table.

According to another embodiment, each device capable of being inductively powered or charged by an inductive power supply is provided with at least one common resonant frequency, and at least one unique frequency. For example, referring to the above embodiments and the figures, each device capable of being charged by AIPS 12 is provided with an 8.2 microfarad capacitor, providing the device with a primary identification resonant frequency of 100kHz. AIPS 12 repeatedly sends out a pulse at approximately 100kHz. If a device 14 with a resonant frequency of 100kHz is placed within the field generated by AIPS

12, then AIPS proceeds with a sweep of additional frequencies to identify the type of device

14. According to one embodiment, the charging circuit of each individual battery type is provided with a second unique resonant frequency, or secondary identification frequency.

For example, each lithium ion battery is further comprised of a capacitor or other circuitry to provide a secondary resonant frequency at 109.4 kHz; each nickel cadmium battery is provided with a capacitor or other circuitry to provide a secondary resonant frequency at

148.5 kHz. According to another embodiment, each battery may further equipped with a capacitor or other circuitry to provide a tertiary resonant frequency used to identify the individual manufacturer or supplier of that battery. For example, each inductively charged lithium ion battery manufactured or sold by vendor X is provided with one or more capacitors or other circuitry to provide a primary identification resonant frequency of 100kHz, a secondary identification resonant frequency of 109.4 kHz, and a tertiary identification resonant frequency of 130kHz. Each lithium ion battery manufactured or sold by vendor Y is provided with one or more capacitors or other circuitry to provide a primary identification resonant frequency of 100kHz, a secondary identification resonant frequency of 109.4 kHz,

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PCT/IB2007/055339 and a tertiary identification resonant frequency of 140kHz. According to another embodiment, an additional identification resonant frequency may be added to distinguish, for example, different types of inductively charged lithium ion batteries sold by vendor X or vendor Y. Such identification could allow AIPS to adjust the charging or power control not only according to the requirements of various load types as discussed above, but according to specific requirements of individual manufacturers or suppliers of those load types. It would be obvious that such identification strategies and protocols could be used to identify inductive loads that are not only powered by a rechargeable battery, but also to identify those loads that are directly inductively powered.

The standards discussed above rely on the assignment of a range of identification frequencies. The spacing between identification frequencies may vary from application to application depending of the resolution of the AIPS sensing the present of resonance during the identification process. For example, an AIPS with sufficient resolution to accurately recognize frequency differences of 5 kHz can use a separation of 5 kHz between identification frequencies (e.g. 250 kHz and 255 kHz). An AIPS with lower resolution may require greater separation between identification frequencies (e.g. 250 kHz and 260kHz).

The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.

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