Augmented power system for implantable medical device

Abstract

Example systems, devices, and techniques are disclosed. An example implantable medical device (IMD) includes a power source, a receive antenna configured to receive an induced electrical current from a wireless power transmission system, and power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to power operation of the IMD from at least one of the power source or the induced electrical current. The IMD includes processing circuitry coupled to the power control circuitry. The processing circuitry is configured to control the power control circuitry to power operation of the IMD from the power source, determine a presence of the induced electrical current and based on the presence of the induced electrical current, control the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

Description

AUGMENTED POWER SYSTEM FOR IMPLANTABLE MEDICAL DEVICECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Patent Application 63 / 593,713 filed 27 October 2023, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The disclosure relates to wireless power transfer, and more particularly, inductive power transfer to power an implantable medical device.BACKGROUND

[0003] An implantable medical device (IMD) may include an on-board power supply such as a primary (e.g., non-rechargeable) battery, a secondary (e.g., rechargeable) battery, or some other electrical energy storage device. In some examples, the IMD may receive wireless power via a transcutaneous power transfer method configured to recharge the secondary battery.SUMMARY

[0004] In general, the disclosure is directed to an augmented power system for an IMD. The IMD includes a primary battery and a receive antenna that receives radiofrequency (RF) power from a transmit antenna for powering operations of the IMD when an induced electrical current is present on the receive antenna from the received RF power. For example, an IMD may at times perform one or more operations that require a relatively high current drain, for example, a current drain that may exceed a threshold, such as in the order of 6 micoAmps to 30 microAmps. Such current drain conditions may arise, for example, when the IMD is transferring data, performing an artificial intelligence (Al) application, administering therapy for a condition, such as the condition known as Heart Failure preserved Ejection Fraction (HFpEF), administering Atrial Ventricular Neural Stimulation (AVNS), administering therapy for reducing heart wall thickening, and / or performing another power-demanding procedure. As such it may be desirable to provide at least a portion of operational power for the IMD wirelessly from an external source, so as to lower the drain of the primary battery. For example, the receive antennais used to receive operational power (e.g., induced electrical current) to power the implantable device in lieu of, or in addition to, the primary battery. In response to the receive antenna no longer receiving operational power wirelessly, such as when the patient moves out of range of the transmit antenna, operations of the IMD are powered using the primary battery. As used herein, “operational power” means power that may be used to power the operational functions of the IMD, such as the delivery of therapy, the monitoring of physiological parameters, the transmission of data, or the like. As used herein, “recharge power” means power that may be used to recharge a secondary battery. It should be understood that the term “operational power” does not include “recharge power.”

[0005] In some examples described herein, a transmit antenna of an external device, such as a wireless power transmission system, includes an externally-applied coil (e.g., external to a patient) and configured to transfer RF power to the receive antenna of an IMD, with the transferred RF power including an induced electrical current including operational power to be employed when operational power is received by the receive antenna. In a further example, the receive antenna may include a coil positioned in proximity to a perimeter of an assembly frame of the IMD. The amount of transferred RF power (e.g., induced electrical current providing operational power) may be low when compared to recharging a typical battery-powered IMD. The relatively low amount of transferred RF power, in some examples, such as in the United States of America, may not exceed Specific Absorption Rate (SAR) standards promulgated by the Office of Engineering and Technology (OET) of the Federal Communications Commission (FCC), and thereby avoids tissue heating concerns.

[0006] In another example disclosed herein, the transmit antenna and receive antenna use a standardized wireless power transfer protocol known as Qi. Whereas conventional systems may use the Qi protocol to recharge batteries, in some examples disclosed herein, the Qi protocol is used to augment IMD operational power needs when operational power is received by the receive antenna. For example, a Qi device may be provided as or take the form of a sticker, sheet or mat with its own replaceable primary or secondary power source. In some examples, the transmit antenna may employ a large external coil that is configured to not physically touch the patient, but rather be part of a mattress pad, a pillow, an armrest, or other supporting device.

[0007] In some examples disclosed herein, a system comprises: an IMD, the IMD comprising: a power source; a receive antenna configured to receive an induced electricalcurrent from a wireless power transmission system; power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to control a powering of operation of the IMD from at least one of the power source or the induced electrical current; processing circuitry coupled to the power control circuitry and being configure to: control the power control circuitry to power operation of the IMD from the power source; determine a presence of the induced electrical current on the receive antenna; and based on the presence of the induced electrical current on the receive antenna, control the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

[0008] In some examples disclosed herein, a method operable by an IMD comprises: controlling power control circuitry to power operation of the IMD from a power source, the power source being internal to the IMD; determining a presence of an induced electrical current on a receive antenna, the induced electrical current being received from a wireless power transmission system; and based on the presence of the induced electrical current on the receive antenna, controlling the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

[0009] In some examples disclosed herein, a system comprises: an implantable medical device (IMD) comprising: a power source; a receive antenna configured to receive an induced electrical current from a wireless power transmission system; power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to power operation of the IMD from at least one of the power source or the induced electrical current; processing circuitry coupled to the power control circuitry and being configure to: control the power control circuitry to power operation of the IMD from the power source; determine a presence of the induced electrical current; and based on the presence of the induced electrical current, control the power control circuitry to power at least one high-power operation of the IMD from the power source to the induced electrical current; and the wireless power transmission system comprising: a transmit antenna; and driver circuitry configured to energize the transmit antenna with radio-frequency energy to generate a magnetic field to transmit the induced electrical current to the receive antenna.

[0010] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. l is a conceptual diagram illustrating an example a wireless power transmission system according to various examples described in this disclosure.

[0012] FIG. 2 is a functional block diagram illustrating an example configuration of an implantable medical device according to various examples described in this disclosure.

[0013] FIG. 3 is a functional block diagram illustrating an example inductive power supply system according to various examples described in this disclosure.

[0014] FIG. 4 includes diagrams showing various examples of techniques that may be used to construct the antenna coils for use in the systems described in this disclosure.

[0015] FIG. 5 is a conceptual block diagram illustrating an example system for powering operation of an implantable medical device implanted in a patient according to various examples described in this disclosure.

[0016] FIG. 6 is a graphic diagram illustrating examples graphs of representative waveforms that may be generated by a signal generator according to various examples described in this disclosure.

[0017] FIGS. 7 A and 7B are conceptual diagrams illustrating an example wireless power transmission system including coils, according to one or more techniques of this disclosure.

[0018] FIG. 8 is a flowchart illustrating example techniques for powering a high- power operation of an IMD.DETAILED DESCRIPTION

[0019] Devices, systems, and techniques are described related to a wireless power transfer system for powering operation of an implantable medical device (IMD), such as when wireless power is available to the IMD. For example, wirelessly powering operations of an IMD may be desirable when operational power is received by the receive antenna. The IMD includes a primary battery and a receive antenna that receives radiofrequency (RF) power from a transmit antenna of an external device for powering the IMD such RF power is received by the receive antenna when operational power is received by the receive antenna. The IMD may have a primary therapy function, such as pacing, conduction system pacing, cardiac resynchronization therapy, or the like, that has a normal demand function on the power source of the IMD. The IMD may also have secondary operational functions that alone, or in combination with the primary therapyfunction, may cause the IMD to be in a relatively high-power demand state. For example, when the IMD is transferring data, performing an artificial intelligence (Al) application, administering secondary therapy, such as therapy for a condition known as Heart Failure preserved Ejection Fraction (HFpEF), administering Atrial Ventricular Neural Stimulation (AVNS), administering therapy for reducing heart wall thickening, and / or performing another power-demanding procedure, it may be desirable to utilize wirelessly delivered operation power from an external device to power one or more functions of the IMD. In some examples, when operational power is received by the receive antenna, operational power received by the receive antenna may be used to power the IMD in lieu of, or in addition to, the primary battery. In response to the receive antenna no longer receiving RF power (such as when the patient moves out of range of the transmit antenna), the operations of the IMD are powered using the primary battery.

[0020] In some examples described herein, the receive antenna includes a coil. The transmit antenna includes an externally-applied coil (e.g., external to a patient) of an external device and is configured to transfer RF power to the receive antenna of the IMD, with the transferred operational power being employed when the RF power is present on the receive antenna. In a further example, the receive antenna may include a coil positioned in proximity to a perimeter of an assembly frame of the IMD. The amount of transferred RF power (e.g., induced electrical current providing operational power) may be relatively low when compared to recharging a typical battery-powered IMD. For example, in the United States of America, the relatively low amount of transferred RF power may not exceed Specific Absorption Rate (SAR) standards promulgated by the Office of Engineering and Technology (OET) of the Federal Communications Commission (FCC), and thereby avoids tissue heating concerns.

[0021] In another example disclosed herein, the transmit and receive antennas use a standardized wireless power transfer protocol known as Qi. Whereas conventional systems may use the Qi protocol to recharge batteries, in some examples disclosed herein, the Qi protocol is used to augment IMD operational power needs when operational power is wirelessly received by the IMD. For example, a Qi power transmitting device may be provided as a sticker, sheet or mat with its own replaceable primary or secondary power source. In some examples, the transmit antenna may employ a large external coil that is configured to not physically touch the patient, but rather be incorporated into a mattress pad, a pillow, an armrest, or other supporting device.

[0022] FIG. l is a conceptual diagram illustrating a wireless power transmission system 100 including a coil and housing according to one or more techniques of this disclosure. Wireless power transmission system 100 may include a housing comprising a front housing 136A and a back housing 136B that enclose and protect a transmit antenna 102, e.g., which may include a coil, and circuitry mounted to a circuit board 104. In the example of FIG. 1, front housing 136A and back housing 136B may be formed using a type of rubber, plastic, metal, or similar material. In some examples, a system (e.g., system 300 of FIG. 5) may include the wireless power transmission system 100 and an implantable medical device (IMD) 15. IMD 15 may receive wireless power through a patient’s tissue 132, which may include skin, adipose tissue, muscle tissue and so on, depending upon the location of IMD 15. In some examples, wireless power transmission system 100 may be mounted or otherwise incorporated in a cushion, a bed, a seat, such as an automobile seat, or a piece of furniture and may conform and flex with the shape of the cushion, bed, seat, or furniture when occupied, e.g., by a person.

[0023] Circuitry on circuit board 104 may include processing circuitry 110, driver circuitry 114, memory 124, other circuitry 118, circuit traces, vias, connection points, and power source 120. In some examples, transmit antenna 102, which may include a coil, is a power transmit antenna. For example, transmit antenna 102 may include several loops of wire enclosed by a material and configured to generate an electromagnetic field 122 when driven by driver circuitry 114 mounted on circuit board 104. Electromagnetic field 122 may transfer power, such as operational power, to IMD 15. In some examples, electromagnetic field 122 may additionally, or alternatively, transfer power to a secondary device, e.g., a power receiving unit (PRU), which may also be described as a power receiving device. Examples of secondary devices may include a mobile computing device, a mobile phone, portable audio device, a medical device, including IMD 15, and so on.

[0024] In the example of FIG. 1, processing circuitry 110 may access and execute instructions and store and retrieve information stored at memory 124, control the operation of driver circuitry 114 and send and receive digital communications, e.g., from the secondary unit, or from another computing device. Examples of processing circuitry 110 may include any one or more of a microcontroller (MCU), e.g. a computer on a single integrated circuit containing a processor core, memory, and programmable input / output peripherals, a microprocessor (pP), e.g. a central processing unit (CPU) on a single integrated circuit (IC), a controller, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on chip (SoC) or equivalent discrete or integrated logic circuitry. A processor may be integrated circuitry, i.e., integrated processing circuitry, and that the integrated processing circuitry may be realized as fixed hardware processing circuitry, programmable processing circuitry and / or a combination of both fixed and programmable processing circuitry. Accordingly, the terms "processing circuitry," “processor” or “controller,” as used herein, may refer to any one or more of the foregoing structures or any other structure operable to perform techniques described herein.

[0025] Examples of memory 124 may include any type of computer-readable storage media, include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), one-time programable (OTP) memory, electronically erasable programmable read only memory (EEPROM), flash memory, or another type of volatile or non-volatile memory device. In some examples the computer readable storage media may store instructions that cause the processing circuitry to execute the functions described herein. In some examples, the computer readable storage media may store data, such as configuration information, temporary values and other types of data used to perform the functions of this disclosure. Though shown as separate from processing circuitry 110 in the example of FIG. 1, in other examples, memory 124 may be on the same component, e.g., the same integrated circuit (IC) as processing circuitry 110. In some examples, processing circuitry 110 controls driver circuitry 114 to provide RF energy to transmit antenna 102.

[0026] In some examples described herein, HMD 15 performing certain operations may cause a current drain of HMD 15 may exceed a threshold, such as a threshold in the range of 6 microAmps to 30 microAmps. Such operations may be referred to as high- power operations. The threshold may be exceeded, for example, when IMD 15 is performing one or more power-demanding activities (e.g., high-power operations) including, but not limited to, transferring data, performing an artificial intelligence (Al) application, administering secondary therapy, such as therapy for a condition known as Heart Failure preserved Ejection Fraction (HFpEF), administering Atrial Ventricular Neural Stimulation (AVNS), administering therapy for reducing heart wall thickening, and / or performing another power-demanding procedure. When induced electrical current is present on receive antenna 96, IMD 15 may use such induced electrical current as operational power to power operation of IMD 15 in lieu of, or in addition to, a powersource 89 (FIG. 2). In some examples, power source 89 is a primary battery (e.g., non- rechargeable). Thus, in this example, the receive antenna 96 need not be used to recharge a secondary, rechargeable battery of IMD 15, which may not be present. In such a case, IMD 15 may be considered a non-rechargeable IMD.

[0027] In some examples, IMD 15 may be configured to not perform one or more high-power operations unless induced electrical current is present on receive antenna 96. In some examples, IMD 15 may be configured to not perform the one or more high-power operations unless sufficient induced electrical current is present on receive antenna 96. For example, IMD 15 may determine whether an induced electrical current on receive antenna 96 is sufficient (e.g., is equal to or greater than the threshold and / or a current required to perform the one or more high-power operations) before initiating the one or more high-power operations. In some examples, such one or more high-power operations may be non-essential, or optional, therapy operations of IMD 15.

[0028] Without the wireless power transmission system 100 (FIG. 1) described herein, the primary battery of IMD 15 would drain much more quickly, and / or device life would be shortened. Examples of therapies that may require IMD 15 current drains above a threshold include reduction of heart wall thickening by pacing the heart at a higher rate, such as using dual chamber His bundle pacing. In some examples, pacing rates are estimated to be 110 beats / min over a 12-hour period each day; much of this during a patient sleep period. This increased rate may reduce the lifespan of IMD 15 by about 1 / 3. Another potential power-hungry, current-draining operation is Atrial Ventricular Neurological Stimulation (AVNS). This technique may include placing a lead of IMD 15 in a region of the atrium that allows pacing and stimulation of part of the Vagus system. Stimulation of this region may counteract the stiffening and thickening of the heart wall via an anti-inflammatory effect. Nervous stimulation capture may also be a power-demanding, current-draining process. While this therapy option is still being investigated, it is estimated that, under best-case conditions, the therapy would span about 8 hours per day, where each pacing pulse is followed immediately by seven pulses at approximately 50Hz. This approach demands about 8 times higher current drain that of a conventional pacer system.

[0029] Some illustrative current drains for IMD 15 may be as follows. When IMD 15 is a pacer device, the rated capacity of the primary battery may be approximately 923 mAh with a discharge rate of 6-11 microamps for a standard pacer conducting routine pacing functions. In some examples, this discharge rate may be considered to be belowthe current drain threshold of IMD 15. For applications that may result in current drains exceeding the threshold, in some examples the current drain may be on the order of 2-3 times greater than 6-11 microamps, or approximately 15-30 microamps. The techniques of this disclosure may be particularly desirable when the current drain exceeds the threshold.

[0030] When IMD 15 is a spinal shunt or a pressure sensor, in some examples the total operational power consumption may be 270uW while routine functions are being performed, such that the current drain is considered to be below the threshold.

[0031] In some examples described herein, the receive antenna 96 includes a coil. An externally supplied transmit antenna 102 (FIG. 1) is used to transfer RF power to receive antenna 96, with the transferred RF power including operational power being employed to power operations of IMD 15. In a further example, the receive antenna may include a coil positioned in proximity to a perimeter of an assembly frame of IMD 15. In some examples, the amount of transferred RF power (e.g., induced electrical current providing operational power) may be low when compared to recharging a rechargeable battery of a typical battery-powered IMD 15. In some examples, the relatively low amount of transferred RF power does not exceed Specific Absorption Rate (SAR) standards promulgated by the Office of Engineering and Technology (OET) of the Federal Communications Commission (FCC), and thereby avoids tissue heating concerns.

[0032] When IMD 15 is a pacer device, in some examples, transmit antenna 102 may operate at any of two frequencies, with a first frequency being below lOOKHz and a second frequency being in a range from approximately 100 - 200KHz. In another example, 102 may operate at a frequency in a range from approximately 800KHz to 2MHz. When IMD 15 is a grain of rice device or a smart screw device, transmit antenna 102 may operate at a frequency in an approximate range of 880 KHz to 2 MHz.

[0033] In another further example disclosed herein, the transmit antenna 102 (FIG. 1) and the coil (receive antenna 96 of FIG. 2) use a standardized wireless power transfer protocol known as Qi. Whereas conventional systems may use the Qi protocol to recharge batteries, in some examples disclosed herein, the Qi protocol is used to augment IMD 15 operational power needs, such as when the current drain of IMD 15 exceeds the threshold. For example, a Qi device may be provided as a sticker with its own replaceable primary or secondary (e.g., rechargeable) power source. In some examples, the transmit antenna 102 (FIG. 1) may employ a large external coil that is not physicallytouching the patient, but rather in or on a mattress pad, a pillow, an armrest, or other supporting device.

[0034] Driver circuitry 114 (FIG. 1) may include switches, amplifier circuits, tuning circuitry, communication circuitry, and so on, configured to send driving signals 112 to transmit antenna 102 to generate electromagnetic field 122 per instructions from processing circuitry 110. Tuning circuitry may include one or more capacitors, inductors, or similar components. In some examples driver circuitry 114 may include logic circuitry or other processing circuitry to receive one or more feedback signals, or communication signals from transmit antenna 102. In some examples, driver circuitry may receive instructions from processing circuitry 110 that controls the operation of driver circuitry 114.

[0035] Power source 120 may include an electrical energy storage device that stores and provides electrical energy to the circuitry of wireless power transmission system 100. In some examples power source 120 may include a primary battery, such as a non- rechargeable battery. In some examples, power source 120 may also include a secondary batter, such as a rechargeable battery. In other examples, power source 120 may be another type of electrical energy storage device, such as a fuel cell, capacitor and so on. In some examples, power source 120 may include a power converter, such as an AC -DC converter, DC-DC converter and so on. In some examples, wireless power transmission system 100 may include connections external to housing 136A and 136B (not shown in FIG. 1) configured to receive external power, such as from a wall outlet, to provide operational power to wireless power transmission system 100, and, optionally to provide recharge power to recharge power source 120. In some examples, electromagnetic field 122 may influence the operation of power source 120. In other examples, circuitry of power source 120 may impact the loading of electromagnetic field 122 and transmit antenna 102.

[0036] Because transmit antenna 102, may be implemented as a coiled conductor, transmit antenna 102 may include properties of an inductor. An inductor may include at least some resistance in addition to its inductance, e.g., because of the length of the conductor, e.g., wire. The type of material, length, cross-sectional area, and other factors may impact the amount of resistance. The lower the value of this resistance R, the better the quality of the coil. The ratio between the resistance components and the frequencydependent inductance is the loss factor (loss factor = R / 27tf L). The inverse of loss factor is the quality factor or Q-value (Q = 2jtf L / R = coL / R). Here “f’ is the frequency of thecurrent flowing through transmit antenna 102, “L” is the effective inductance of the coil in Henrys and “R” is the effective resistance of the coil in Ohms. Therefore, the Q-value will differ according to the frequency. Another way to describe Q-value at the operating frequency is the ratio of reactance of transmit antenna 102 to its resistance.

[0037] In some examples, processing circuitry 110 may determine the impedance of transmit antenna 102 to calculate an estimate for the amount of heating of the power receiving unit, e.g., the secondary device, according to the following equation. In the following equations the “Q” refers to an amount of heat in units of Watts and is not the same as the Q-value described above.Qreceive ~ ^tank ~ Q transmit ~ Precieve-batt where:Qreceive The amount of heat for the receiving unit Prank The power in the transmit antenna 102 and in the tuning capacitorQtransmit The amount of heat for the transmitting unit Precieve-batt The power received by the battery of IMD 15 or the secondary deviceProcessing circuitry 110 may determine the amount of heat of transmit antenna 102, according to:where:Qtransmit The amount of heat, in watts, of the transmitting unitLank The current through transmit antenna 102 from driver circuitry114R transmit The AC impedance of transmit antenna 102, e.g., loading of transmit antenna 102

[0038] Qtransmit may include any heating associated with transmitting the wireless power. In some examples, Qtransmit may include eddy currents in the main circuit board or other circuit boards of wireless power transmission system 100. Though shown as a single circuit board 104, the circuitry of wireless power transmission system 100 may be split among several circuit boards, such as a separate user interface circuit board.Wireless power transmission system 100 may include other components not shown in FIG. 1, such as shielding material, ferrite material and so one that may absorb some of the transmitted energy. Eddy currents may also cause heating, losses in ferrite, and / or eddy currents in a battery, e.g., power source 120, or other components. Similarly, Qreceive may include all the heats in the power receiving unit, e.g., IMD 15, including eddy currents inshielding, a header, a ground plane, rectification circuit losses, battery path impedance, and so on (not shown in FIG. 1).

[0039] The impedance of transmit antenna 102 may be affected by several factors.For example, the material, and cross-sectional area of the conductors of transmit antenna 102 may have a certain resistance per unit distance, e.g., Ohms per millimeter. Changes in temperature may also impact the resistance of a conductor based on the temperature coefficient of resistance for transmit antenna 102. Also, as described above, the spatial relationship between at least the driver circuitry and transmit antenna 102 may impact the loading of transmit antenna 102. In some examples, electromagnetic field 122 may generate eddy currents in the driver circuitry. The eddy currents in the circuitry, e.g., in the traces in circuit board 104 as well as in electrical components mounted to circuit board 104, may cause a change in a driving signal that is output from the driver circuitry to the antenna. In other words, the signal path, e.g., 112, for the driving signal may be positioned with respect to the transmit antenna 102 such that the eddy currents in the signal path may cause a change in the current magnitude, voltage magnitude or other characteristics of the driving signal. As described above, other signal paths on circuit board 104, e.g., between power source 120, processing circuitry 110, sensing circuitry 116 and so on (not shown in FIG. 1) may also be configured with respect to transmit antenna 102, such that electromagnetic field 122 may cause the driving signal output to change due to the eddy current changes at different spatial relationships between transmit antenna 102 and the circuitry. A mathematical model for the transmit coil impedance may be based on the tank current (Itank), the coil temperature, the driver signal frequency (f), which impacts the Q-value, and the spatial relationship between transmit antenna 102 and the circuitry as measured by the degree of deformation. Therefore, the impedance of transmit antenna 102 may be described according to:R transmit - A + B X I tank + C X Transmit + D X D e f O nCltiO l where:Ttransmit The temperature of transmit antenna 102Lank The current through transmit antenna 102 from driver circuitry114Rtransmit The total AC impedance of transmit antenna 102 Deformation The deformation based on sensors 126A A coefficient based on the resistance of the coilB A coefficient for the coil currentC A coefficient for the coil temperatureD A coefficient for the coil deformation

[0040] In some examples, the coefficient “A” may be based on zero tank current (Itank), nominal temperature, and nominal deformation or position. In some examples, processing circuitry 110 may adjust the amount of power output by transmit antenna 102 to ensure the estimated temperature stays within a predetermined temperature range. In the example of an IMD, should the temperature of the IMD rise above a predetermined temperature threshold, the tissue around the IMD may become uncomfortable for a patient. In other examples, the power receiving device may include circuitry that is sensitive to temperatures outside of the predetermined range.

[0041] FIG. 2 is a functional block diagram illustrating an example configuration of IMD 15 according to various examples described in this disclosure. IMD 15 may correspond to IMD 15 described and illustrated with respect to FIG. 1, or another IMD, any of which may be configured to be operationally powered using the devices, systems, and methods as described in this disclosure. IMD 15 includes power source 89 that may be coupled to the electronic circuitry provided in IMD 15, and may be configured to provide operational electrical power to these circuits through a power control circuitry 91. IMD 15 may be inductively powered by providing received electromagnetic energy to the IMD 15, wherein energy from these imposed fields may induce an electrical energy into an antenna 94 (which may be used as a telemetry antenna) coupled to communication circuitry 90 and to power control circuitry 91, or into a receive antenna 96 that may be provided in addition to antenna 94 and that when provided, is coupled directly to power control circuitry 91. Power control circuitry 91 is coupled to power source 89. During the high-power load condition as determined by a processing circuitry 85, power control circuitry 91 is configured to receive electrical energy induced in antenna 94 (or in receive antenna 96 when provided) by one or more electromagnetic fields imposed on the antenna(s), and to operationally power IMD 15 from this received electrical energy. Power control circuitry 91 is generally configured to operationally power IMD 15 from power source 89 when the high-power load condition does not exist or when not receiving RF power from transmit antenna 102, such as when IMD 15 is out of RF power transmission range of wireless power transmission system 100. For example, power source 89 may provide electrical energy to IMD 15 to provide primary therapy function (e.g., CRT or conventional pacing therapy) or sensing function, while the high-power load setting may represent a secondary therapy function that requires higher energy demands. In some such examples, power source 89 may include a primary battery such that IMD 15 may be considered a non-rechargeable device. Power control circuitry 91 may beconfigured to regulate the energy to provide a level of electrical power that is provided by power source 89, receive antenna 96, or both for the purpose of powering operation of other circuitry included as part of IMD 15. In other examples, power control circuitry 91 also may be configured to regulate the energy to provide a level of recharge electrical power and operational electrical power that is provided to power source 89 for the purpose of recharging a secondary battery of power source 89 and powering the other circuitry included as part of IMD 15, respectively. Power control circuitry 91 can be controlled by processing circuitry 85.

[0042] Power control circuitry 91 may perform various energy conditioning functions to the energy inductively generated in antenna 94 (or receive antenna 96 when provided), for example by providing rectification, voltage level regulation, current level regulation, and / or other signal processing functions in order to generate the “recharging energy” provided to power source 89. IMD 15 may be configured to couple electromagnetic energy captured by an antenna (including, but not necessarily antenna 94 or receive antenna 96), and direct the captured energy into a suitable rectifying circuit that delivers the electrical energy to a power supplying device. A switch 95, which may be a transistor switch, may be included in IMD 15 that is controlled to select whether the telemetry or the power transfer system is active, and whether antenna 94 is coupled to communication circuitry 90 or power control circuitry 91. In other examples, receive antenna 96 is coupled to power control circuitry 91, and is configured to receive the inductively coupled energy provided t, and to provide the inductively coupled energy to power control circuitry 91 to provide operational power to IMD 15 and to optionally provide recharge power to recharge power source 89.

[0043] In the illustrated example, IMD 15 includes processing circuitry 85 and an associated memory 86, sensing circuitry 87, therapy delivery circuitry 88, one or more sensors 92, and the communication circuitry 90 coupled to antenna 94 as describe above. However, IMD 15 need not include all of these components, or may include additional components. For example, IMD 15 may not include therapy delivery circuitry 88 in some examples. Memory 86 includes computer-readable instructions that, when executed by processing circuitry 85, causes IMD 15 and processing circuitry 85 to perform various functions attributed to IMD 15 and processing circuitry 85 as described herein, e.g., preparing information for transmission from IMD 15 regarding a level of remaining life present in a power source, such as a battery management system information (BMS), configured to provide information including a state of charge / discharge, and / ortemperature information related to power source 89, e.g., a battery, located in IMD 15. The instructions may also cause IMD 15 and processing circuitry to determine a level of inductive coupling, e.g., energy level being generated in antenna 94 or receive antenna 96 located in IMD 15 as a result of an electromagnetic field or fields being imposed on IMD 15, and generate information related to this inductively received energy for transmission by the communication antenna or separate antenna and associated power conditioning circuitry of IMD 15.

[0044] In some examples described herein, processing circuitry 85 determines a presence of operational power on receive antenna 96. In response to determining the presence of operational power on receive antenna, processing circuitry 85 may control power control circuitry 91 to use the operational power for powering operational activities of IMD 15.

[0045] For example, operational activities of IMD 15 may cause a current drain to exceed a threshold, for which it may be desirable to utilize wireless operational power provided by an external device, in addition to, or in lieu of, operational power from power source 89. The current drain of IMD 15 may exceed the threshold, for example, when IMD 15 is transferring data, performing an artificial intelligence (Al) application, administering secondary therapy, such as therapy for a condition known as Heart Failure preserved Ejection Fraction (HFpEF), such as tachycardia pacing therapy, administering Atrial Ventricular Neural Stimulation (AVNS) therapy, administering therapy for reducing heart wall thickening, and / or performing another power-demanding procedure. When the operational power is received by receive antenna 96 of IMD 15, the operational power is used to power operation of the IMD in lieu of, or in addition to, power source 89. In some examples, power source 89 includes a primary battery, such as a non-rechargeable battery.

[0046] In some examples described herein, receive antenna 96 includes a coil. An externally supplied transmit antenna 102 (FIG. 1) is used to transfer RF power to the receive antenna 96, with the transferred RF power including induced electrical current including operational power being employed to power operation of IMD 15. In a further example, receive antenna 96 (FIG. 2) may include a coil positioned in proximity to a perimeter of an assembly frame of IMD 15. In some examples, the amount of transferred RF power (e.g., induced electrical current providing operational power) may be low when compared to recharging a typical battery-powered IMD 15. In some examples, the relatively low amount of transferred RF power does not exceed Specific Absorption Rate(SAR) standards promulgated by the Office of Engineering and Technology (OET) of the Federal Communications Commission (FCC), and thereby avoids tissue heating concerns.

[0047] In another further example disclosed herein, the transmit antenna 102 (FIG. 1) and receive antenna 96 (FIG. 2) use a standardized wireless power transfer protocol known as Qi. Whereas conventional systems may use the Qi protocol to recharge batteries, in some examples disclosed herein, the Qi protocol is used to augment IMD 15 (FIGs. 1 and 2) operational power needs, such as when the current drain of IMD 15 exceeds the threshold. For example, a Qi device may be provided as a sticker with its own replaceable primary or secondary (e.g., rechargeable) power source. In some examples, the transmit antenna 102 (FIG. 1) may employ a large external coil that is not physically touching the patient, but rather in or on a mattress pad, a pillow, an armrest, or other supporting device.

[0048] Memory 86 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media. Memory 86 may store threshold(s) for time of day, posture, heart rate, activity level, respiration rate, and other parameters. Memory 86 may also store data indicating cardiovascular pressure measurements.

[0049] Processing circuitry 85 may include fixed function circuitry and / or programmable processing circuitry. Processing circuitry 85 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry 85 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 85 herein may be embodied as software, firmware, hardware or any combination thereof.

[0050] As illustrated, sensing circuitry 87 and therapy delivery circuitry 88 are coupled to electrodes 97. Sensing circuitry 87 may monitor signals from a selected two or more of electrodes 97 in order to monitor electrical activity of heart, impedance, or some other electrical phenomenon. Sensing of a cardiac electrical signal may be done to determine heart rates or heart rate variability, or to detect arrhythmias (e.g., tachyarrhythmias or bradycardia) or other electrical signals. In some examples, sensingcircuitry 87 may include one or more filters and amplifiers for filtering and amplifying a signal received from electrodes 97.

[0051] In some examples, sensing circuitry 87 may sense or detect physiological parameters, such as heart rate, blood pressure, respiration, and other physiological parameters associated with a patient. The resulting cardiac electrical signal may be utilized by a cardiac event detection circuit that detects a cardiac event when the cardiac electrical signal crosses a sensing threshold. In some examples, the cardiac event detection circuit is part of sensing circuitry 87, processing circuitry 85, or both. The cardiac event detection circuit may include a rectifier, filter and / or amplifier, a sense amplifier, comparator, and / or analog-to-digital converter. Sensing circuitry 87 may output an indication to processing circuitry 85 in response to sensing of a cardiac event (e.g., detected P-waves or R-waves).

[0052] Sensing circuitry 87 may also include a switch module to select which of the available electrodes 97 (or electrode polarities) are used to sense the heart activity. In examples with several electrodes 97, processing circuitry 85 may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch module within sensing circuitry 87. Sensing circuitry 87 may also pass one or more digitized EGM signals to processing circuitry 85 for analysis, e.g., for use in cardiac rhythm discrimination.

[0053] In the example of FIG. 2, IMD 15 includes one or more sensors 92 coupled to sensing circuitry 87. Although illustrated in FIG. 2 as included within IMD 15, one or more of sensors 92 may be external to IMD 15, e.g., coupled to IMD 15 via one or more leads, or configured to wirelessly communicate with IMD 15. In some examples, sensors 92 transduce a signal indicative of a patient parameter, which may be amplified, filtered, or otherwise processed by sensing circuitry 87. In such examples, processing circuitry 85 determines values of patient parameters based on the signals. In some examples, sensors92 determine the patient parameter values, and communicate them, e.g., via a wired or wireless connection, to processing circuitry 85.

[0054] In some examples, sensors 92 include one or more accelerometers 93, e.g., one or more three-axis accelerometers. Signals generated by the one or more accelerometers93 may be indicative of, as examples, gross body movement (e.g., activity) of the patient, patient posture, heart sounds or other vibrations or movement associated with the beating of the heart, or coughing, rales, or other respiration abnormalities. Accelerometers 93 may produce and transmit signals to processing circuitry 85 for a determination as to theposture of the patient. In various examples, signals from the accelerometers 93 are processed to determine an activity, such as when the patient is taking a step or steps, or for example when the patient is running, used to provide an activity count associated with patient initiated physical activity of the patient. In some examples, sensors 92 may include sensors configured to transduce signals indicative of blood flow, oxygen saturation of blood, or patient temperature, and processing circuitry 85 may determine patient parameters values based on these signals. In various examples, sensors 92 may include one or a combination of sensors 18 as previously described. In some examples, processing circuitry 85 determines one or more patient parameter values based on pressure signals. Patient parameter values determined based on pressure may include, as examples, systolic or diastolic pressure values, such as pulmonary artery diastolic pressure values.

[0055] Therapy delivery circuitry 88, when provided as part of IMD 15, may be configured to generate and deliver electrical therapy to the heart. Therapy delivery circuitry 88 may include one or more pulse generators, capacitors, and / or other components capable of generating and / or storing energy to deliver as pacing therapy, defibrillation therapy, cardioversion therapy, other therapy or a combination of therapies. In some instances, therapy delivery circuitry 88 may include a first set of components configured to provide pacing therapy and a second set of components configured to provide anti-tachyarrhythmia shock therapy. In other instances, therapy delivery circuitry 88 may utilize the same set of components to provide both pacing and antitachyarrhythmia shock therapy. In still other instances, therapy delivery circuitry 88 may share some of the pacing and shock therapy components while using other components solely for pacing or shock delivery.

[0056] Therapy delivery circuitry 88 may include charging circuitry, one or more charge storage devices, such as one or more capacitors, and switching circuitry that controls when the capacitor(s) are discharged to electrodes 97 and the widths of pulses. Charging of capacitors to a programmed pulse amplitude and discharging of the capacitors for a programmed pulse width may be performed by therapy delivery circuitry 88 according to control signals received from processing circuitry 85, which are provided by processing circuitry 85 according to parameters stored in memory 86. Processing circuitry 85 controls therapy delivery circuitry 88 to deliver the generated therapy to the heart via one or more combinations of electrodes 97, e.g., according to parameters stored in memory 86. Therapy delivery circuitry 88 may include switch circuitry to select whichof the available electrodes 97 are used to deliver the therapy, e.g., as controlled by processing circuitry 85. In some examples, therapy delivery circuitry 88 may be configured to deliver therapy for Heart Failure preserved Ejection Fraction (HFpEF), deliver therapy for Atrial Ventricular Neural Stimulation (AVNS), and / or deliver therapy for reducing heart wall thickening.

[0057] Communication circuitry 90 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as an external device, a transceiver, another IMD, or sensors. Referring again to FIG. 2, under the control of processing circuitry 85, communication circuitry 90 may receive downlink telemetry from and send uplink telemetry to external device 11 or another device with the aid of an antenna, such as antenna 94, which may be internal and / or external. In some examples, communication circuitry 90 may communicate with a local external device, for example through transceiver 16, and processing circuitry 85 may communicate with a networked computing device via the local external device and a computer network, such as the Medtronic® CareLink® Network developed by Medtronic, pic, of Dublin, Ireland.

[0058] As described above, in some examples (i.e., where a single antenna is used) the antenna signal can be switched from communication circuitry 90 to power control circuitry 91 to provide operational power to IMD 15. In other examples the receive antenna (receive antenna 96) is separate from the communication / telemetry antenna (e.g., antenna 94). For example, antenna 94 may be switched between being coupled to communication circuitry 90 and power control circuitry 91 by switch 95, wherein switch 95 may be controlled by processing circuitry 85 to determine when antenna 94 is coupled to communication circuitry 90 and when antenna 94 is to be coupled to power control circuitry 91.

[0059] As described previously, in some examples, processing circuitry 85 controls power control circuitry 91 to determine a presence of induced electrical current on receive antenna 96. When operational power (in the form of induced electrical current) is present on receive antenna 96, that operational power is used to operationally power operation of IMD 15 in lieu of, or in addition to, power source 89. In some examples, power source 89 is a primary battery such that IMD 15 may be characterized as a non-rechargeable device.

[0060] For example, processing circuitry 85 may refrain from initiating one or more high-power operations until processing circuitry 85 determines the presence of induced electrical current on receive antenna 96. Once processing circuitry 85 determines thatinduced electrical current is present on receive antenna 96, processing circuitry 85 may control power control circuitry 91 to power and may initiate one or more high-power operations. Such one or more high-power operations may cause the current drain of IMD 15 to exceed a threshold so that it may not be desirable to perform the one or more high- power operations without using operation power from the induced electrical current. For example, the current drain of IMD 15 may exceed the threshold, for example, when IMD 15 is transferring data, performing an artificial intelligence (Al) application, administering secondary therapy, such as therapy for a condition known as Heart Failure preserved Ejection Fraction (HFpEF), administering Atrial Ventricular Neural Stimulation (AVNS), administering therapy for reducing heart wall thickening, and / or performing another power-demanding procedure.

[0061] In various examples, processing circuitry 85 is coupled to power control circuitry 91, and receives information, such as a level of current, that is being induced in antenna 94 or receive antenna 96 as a result of electrical energy received by the antenna via electromagnetic energy imposed on IMD 15 for the purpose of operationally powering IMD 15. Processing circuitry 85 may provide this and other information, for example current consumption rate and temperature information associated with IMD 15, in the form of an output signal to communication circuitry 90 for transmission from IMD 15 to one or more external devices, such as transceiver 16. For example, positioning and / or orientation of a pair of coils located externally to IMD 15 and generating the electromagnetic fields imposed on IMD 15 may be controlled using this information transmitted from IMD 15.

[0062] The setting of electrical parameters used to energize the coils generating the electromagnetic fields imposed on IMD 15 for the purpose of providing induced electrical current to IMD 15 may be controlled using this information transmitted from IMD 15. In addition, other information such as temperature and field intensity information transmitted from IMD 15 may be used to control the electrical parameters, for example by regulating the field strength being generated by the transmit antenna of the wireless power transmission system, or for example to shut off the transmit antenna to stop the transmission of wireless power.

[0063] A clinician or other user may retrieve data from IMD 15 using an external device or another local or networked computing device configured to communicate with processing circuitry 85 via communication circuitry 90, for example through thetransceiver. The clinician may also program parameters of IMD 15 using an external device or another local or networked computing devices.

[0064] In various examples, processing circuitry 85 is configured to receive signals from sensing circuitry 87, sensors 92, and / or sensor signals provided by sensors external to IMD 15, to process these sensor signals to generate one or more input parameters based either directly on or derived from the sensor signals. The input parameters are associated with current value(s) for one or more physiological parameters associated with a patient, such as patient 12. The physiological parameters associated with the input parameters may include activity counts, respiration rates, breathing rates, movements, postures, and changes in postures associated with a patient. The current values associated with these input parameters can be values measured directly from the input parameters, or derived for these input parameters. For example, a value of a heartrate, measured for example in heartbeats per minute or cardiac cycle length, may be determined as the current value (e.g., the most recent value) for the input parameter associated with the heart rate of the patient measured over some predefined time period. Similarly, a value of a breathing rate, measured for example in breaths per minute or breathing cycle length, may be determined as the current value (e.g., the most recent value) for the input parameter associated with the breathing rate of the patient as measured over some predefined time period.

[0065] Similarly, current values can be determined for other input parameters, such as activity count (e.g., based on movement of the patient measured for example in steps taken by the patient per minute), body temperature, and for example a current value for a posture of the patient (e.g., lying down, standing, sitting). A current value of a physiological parameter may be, in some examples, a mean or median of measured values over a period of time. These parameters may be used to monitor the physical condition of a patient, and / or to determine the efficacy of a therapy being applied to the patient, and / or the need to apply a new or different therapy, such as a new or different electrical stimulation therapy, to the patient based on analysis if the sensed parameters and / or instructions received by IMD 15 from one or more external devices.

[0066] FIG. 3 is a functional block diagram illustrating an example inductive power supply system 400 according to various examples described in this disclosure. System 400 includes power control circuitry 401 electrically coupled to a coil 402, located externally to a patient 12, according to various examples described in this disclosure. When energized, coil 402 may be configured to provide a time-varying electromagnetic field that may be imposed on an implanted medical device, such as IMD 15 (FIGs. 1 and2), for the purpose of operationally powering IMD 15 under the high-power load condition. Power control circuitry 401 may be coupled to a computing device 406 that includes a display 406A and one or more input devices 406B, such as a keyboard and / or a computer mouse, that allow a user to interact with power control circuitry 401 through computing device 406. Computing device 406 may be communicatively linked to power control circuitry 401 by a wired connection 406C, and / or by a wireless connection 406D.

[0067] In various examples, computing device 406 is configured to operate and control power control circuitry 401 in a manner that, during the high-power load condition, applies an alternating electrical current to coil 402, to thereby generate an electromagnetic field to provide power transfer to receive antenna 96 (FIG. 2) located within IMD 15 that is positioned in the electromagnetic field generated by coil 402. Further, feedback received from IMD 15, for example received by computing device 406 (FIG. 3), may be used to control and adjust various aspects of power control circuitry 401, based on any feedback provided by IMD 15.

[0068] For example, coil 402 may be arranged so that the position of the coil can be moved, for example up and down, left or right, and / or tilted or rotated around one or more axes, in order to position receive antenna 96 (FIG. 2) of IMD 15 within an estimated optimal envelope formed by the electromagnetic field being generated through the energization of coil 402 (FIG. 3). When the receive antenna is positioned within the estimated optimal envelope, a positional angle O (theta) of rotation of the third coil around a longitudinal axis extending between the pair of coils may be irrelevant with respect to a coupling efficiency of the level of the electrical current being induced in the third coil by the resultant magnetic field. In a further example, power control circuitry 401 may be configured to control a physical orientation of coil 402, relative to IMD 15 (FIG. 2) to steer the direction of the resultant magnetic field imposed on receive antenna 96 of IMD 15, and angle of orientation <p (phi) between a normal axis of receive antenna 96 and a longitudinal reference axis, thus increasing the level of inductive coupling and the power transfer provided to receive antenna 96 by the power control circuitry 401 (FIG. 3). Such transferred RF power (e.g., induced electrical current) includes operational power. In examples where IMD 15 also includes a secondary, rechargeable power source, the transferred RF power may optionally include recharge power.

[0069] Feedback from IMD 15 in some examples includes a value for the level of current that is being induced in the receive coil of IMD 15 through the inductive coupling of the energy being provided by coil 402 (FIG. 3). Other information provided by IMD15, such as temperature, may be transmitted from IMD 15 to computing device 406 and / or other external devices, and used by power control circuitry 401 to control the energization of coil 402, and / or to determine when to terminate the wireless power transmission process being performed by power control circuitry 401 on IMD 15.

[0070] System 400 further includes external computing devices, such as a server 408 and one or more other computing devices 411A-411N, that may be communicatively coupled to IMD 15, computing device 406, and / or external device 404 via a network 407. In this example, IMD 15 may use its communication circuitry, at different times and / or in different locations or settings, to communicate with external device 404 via a first wireless connection, and / or to communicate with an access point 405 via a second wireless connection. In the example of FIG. 3, computing device 406, access point 405, external device 404, server 408, and computing devices 411A-411N are interconnected, and able to communicate with each other, at least through network 407.

[0071] Access point 405 may include a device that connects to network 407 via any of a variety of connections, such as telephone dial-up, digital subscriber line (DSL), or cable modem connections. In other examples, access point 405 may be coupled to network 407 through different forms of connections, including wired or wireless connections. In some examples, access point 405 may be co-located with the patient. Access point 405 may interrogate IMD 15, e.g., periodically or in response to a command from the patient or from network 407, to retrieve physiological measurements and / or other operational or patient data from IMD 15. Access point 405 may provide the retrieved data to server 408 via network 407. In various examples, access point 405 may be a transceiver and / or an external device. In some cases, server 408 may be configured to provide a secure storage site for data that has been collected from IMD 15, from power control circuitry, and / or from external device 404. In some cases, server 408 may assemble data in web pages or other documents for viewing by trained professionals, such as clinicians, via computing devices 411A-411N. The illustrated system 400 of FIG. 3 may be implemented, in some aspects, with general network technology and functionality similar to that provided by the Medtronic® CareLink® Network developed by Medtronic pic, of Dublin, Ireland.

[0072] In some examples, one or more of computing device 406, access point 405, server 408, or computing devices 411A-411N may be configured to perform, e.g., may include processing circuitry configured to perform, some or all of the techniques described herein, e.g., with respect to processing circuitry of IMD 15 and external device404, relating to the transmission of power from wireless power transmission system 100 (FIG. 1) to IMD 15. In the example of system 400 as shown in FIG. 3, server 408 includes a memory 409, which may be configured to store physiological and other data received from IMD 15 and / or external device 404, and processing circuitry 410, which may be configured to provide some or all of the functionality ascribed to processing circuitry of IMD 15 as described herein. For example, processing circuitry 410 may provide programming and / or parameters that are used by power control circuitry 401 that may be used in the process of providing power, such as operational power, and, optionally, recharge power to a power source located within IMD 15. Configurations for and operational features of coil 402, and power control circuitry 401, are further described with respect to FIG. 4 of this disclosure.

[0073] FIG. 4 includes diagrams showing various examples of techniques that may be used to construct antenna coils for use in the systems described in this disclosure. The illustrations provided in FIG. 4 are not necessarily drawn to scale, are intended to illustrate techniques for providing antenna coils, and do not necessary illustrate relative sizes, dimensions, and / or scales of the devices illustrated. In diagram 150D as shown in FIG. 4, an antenna coil is illustrated as viewed from a direction having a longitudinal axis 170 turned so that longitudinal axis 170 is orientated directly into the plane of the drawing sheet, perpendicular to both a vertical axis 175 and a horizontal axis 176 that are substantially co-planar with the winding 152 of the antenna coil, and perpendicular to each other. Winding 152 may be formed form from a length of an electrical conductor, such as a wire, formed around support structure 153 by a plurality of windings encircling the longitudinal axis 170 at a distance of radius 154. A cutaway view A-A of the windings 152 of an antenna coil having a thickness 172 is further illustrated and described with respect to diagram 150G. Details shown in diagrams 150E, 150F, and 150G will be described below using the axes shown in diagram 150D of the antenna coil for orientation purposes relative to the views illustrated in these further diagrams as shown in FIG. 4.

[0074] Diagram 150E is an illustrative example of the winding 152 formed from the electrical conductors of an antenna coil being “flat spiral-wound” around the perimeter of support structure 153 to form the antenna coil. As shown in diagram 150E, the antenna coil is illustrated as viewed from a direction having the longitudinal axis 170 of the antenna coil turned so that longitudinal axis 170 is orientated directly into the plane of the drawing sheet, perpendicular to both the vertical axis 175 and the horizontal axis 176 that are substantially co-planar with the winding 152 of the antenna coil, and perpendicular toeach other. As shown in diagram 150E, each layer of the winding 152 of the antenna coil is wound so that all windings are substantially coplanar relative to one another, and starting at the first input lead 157 having an initial winding closest to longitudinal axis 170, and spaced away from longitudinal axis 170 by a distance of radius 154. The additional winding of winding 152 are formed around and surrounding the initial winding closest to first input lead 157, and form a spiral shape surrounding the longitudinal axis 170 at an increasingly larger distance from the longitudinal axis 170 as each winding is added to the antenna coil, extending to a second input lead 158. As shown in diagram 150E, the layers of windings surrounding support structure 153 and extending between the first input lead 157 and the second input lead 158 have a thickness 172 that surrounds the longitudinal axis around an outside perimeter of the support structure 153.

[0075] Diagram 150F in FIG. 4 is an example illustrating the electrical conductor of winding 152 being spiral wound to form a solenoid type winding around support structure 153. The antenna coil is illustrated in diagram 150F as viewed from a direction having the longitudinal axis 170 orientated horizontally across the diagram, and horizontal axis 176 turned so that horizontal axis 176 is orientated directly into the plane of the drawing sheet, perpendicular to both the vertical axis 175 and the longitudinal axis 170. As shown in diagram 150F, first input lead 157 of winding 152 is wound near one end 153 A of the support structure 153, and consecutive windings are formed along support structure 153 in a direction along longitudinal axis 170 toward a second end 153B of support structure 153 to a second input lead 158, so that winding of winding 152 as formed between first input lead 157 and second input lead 158 are substantially a same distance away from longitudinal axis 170. The windings of winding 152 thus extend along support structure 153 for a distance forming a width 173 of the winding.

[0076] In some examples, a combination of the winding techniques of diagram 150E and 150F may be used. For example, a first layer of electrical conductor forming winding 152 may be formed as a solenoid type winding as shown in diagram 150F, and then another layer of windings formed above the first layer of windings, in a manner similar to that shown in diagram 150E, forming layers of windings, but wherein each layer includes a plurality of windings of the electrical conductor that are wound in a solenoid type winding. In various examples, the total number of these layers of solenoid type windings formed as one set of windings surrounding another set of windings is not limited to any particular number of layers of windings, and may include a plurality of layers forming coil 151.

[0077] Diagram 150G in FIG. 4 is a cut-away view A-A illustrative of an example of the winding 152 formed from the electrical conductors of the antenna coil comprising windings using a combination of the spiral windings illustrated in diagram 150F, layered with additional layers of winding as illustrated in diagram 150E. The antenna coil is illustrated in diagram 150G as viewed in cutaway and from a direction having the longitudinal axis 170 orientated horizontally across the diagram, and horizontal axis 176 turned so that horizontal axis 176 is orientated directly into the plane of the drawing sheet, perpendicular to both the vertical axis 175 and the longitudinal axis 170. As shown in diagram 150G, portion 150H of winding 152 is located above longitudinal axis 170 and away from the longitudinal axis by a distance of at least radius 154. The winding 152 having a thickness 172 extending in a directing perpendicular to the longitudinal axis 170, and a width 173 extending in a direction parallel to the longitudinal axis 170. The cross- sectional shape of winding 152 within portion 150H may be defined by a two- dimensional shape such as a square or a rectangle having the thickness 172 and the width 173 dimensions. The shape of the winding 152 in cross-section illustrated in portion 150H is not limited to any particular shape, and may include shapes other than square or rectangular shape, such as a circular or elliptical shape in cross section.

[0078] Similarly, a portion 150J of winding 152 may be located below longitudinal axis 170 and away from the longitudinal axis by a distance of at least radius 154. The winding 152 in portion 150J may be a same shape as the shape of portion 150H, and having a same thickness 172 extending in a directing perpendicular to the longitudinal axis 170, and a same width 173 extending in a direction parallel to the longitudinal axis 170. The cross-sectional shape of winding 152 within portion 150J may be defined by a two-dimensional shape such as a square or a rectangle device by the thickness 172 and the width 173 dimensions. The shape of the winding 152 in cross section illustrate in portion 150J is not limited to any particular shape, and may include a same shape other than square or rectangular shape, such as a circular or elliptical shape in cross section that corresponds to the shape of the winding 152 provided in cross-section by portion 150H.

[0079] In various examples, the electrical conductor used to wind any of the antenna coils shown in FIG. 4 is Litz wire, for example a single or multiple stranded wire, wherein the electrical conductor used to form each winding 152 is insulated along the outer surface of the electrical conductor, for example using a coating, such as enamel, to reduce the skin effect of the electrical conductor. Skin effect is the characteristic of electrical current flowing through an electrical conductor that causes the flow of currentin the electrical conductor to travel though the outer portion, e.g., the “skin” of the conductor, and not through the inner portion of the electrical conductor. The skin effect is more pronounced at higher frequencies. The use of Litz wire helps reduce the skin effect in the electrical conductor at higher frequencies. In addition, the inter-turn capacitance of the respective windings / turns is reduced by increasing inter-turn distances, thus increasing the self-resonant frequency of the assembly and enabling higher modulation frequency to be applied to the coil. Any of the windings illustrated in diagrams 150D, 150E, 150F, and 150G, and other winding techniques as would be understood by one of ordinary skill in the art, are contemplated for use in forming receive antenna 96 for IMD 15 (FIG 2), and / or transmit antenna 102 (FIGs. 1 and 3), and may be used in forming any other examples of coils described throughout this disclosure.

[0080] FIG. 5 is a conceptual block diagram illustrating an example system 300 for operationally powering IMD 15 implanted in a patient 12 according to various examples described in this disclosure. As illustrated in FIG. 5, system 300 may be configured to provide wireless transmission of power to one or more implantable medical devices, illustratively represented as IMD 15, that may be implanted in a patient, illustratively represented as patient 12. System 300 includes power control circuitry 302 that is coupled to a transmit antenna 312. Transmit antenna 312 may include one or more coils. The arrangement of transmit antenna 312 relative to patient 12 as shown in FIG. 5 is not necessarily intended to be illustrative of the actual arrangement, for example with respect to positioning and / or scale of the transmit antenna 312 and patient 12 during a period of time when operational powering of IMD 15 is occurring, and is intended to be illustrative of various features of system 300. The actual arrangements of transmit antenna 312 relative to patient 12 and IMD 15 may be as illustrated and described with respect to transmit antenna 102 as illustrated in FIG. 3, and / or as illustrated and described with respect to coils 150D-150G of FIG. 4.

[0081] As illustrated in FIG. 5, system 300 includes processor control circuitry 320 coupled to power control circuitry 302. Processor control circuitry 320 includes processing circuitry 321, a memory 322 coupled to processing circuitry 321, for example by bus / connections 328 (herein after “bus 328”). Memory 322 may store program instructions that, when retrieve and executed by processing circuitry 321, provides programming steps that allow processing circuitry 321 to control power control circuitry 302 to perform the power control processes associated with inductively and operationally powering IMD 15 implanted in patient 12 under the high-power load condition. Inaddition, memory 322 may also store values, for example charging values, charging times, patient history associated specifically with patient 12, communication protocols, and any other information that may be required or that may be helpful to allow processing circuitry 321 to control the operational powering process being used to operationally power IMD 15 during the high-power load condition, according to any of the techniques described in this disclosure, and any equivalents thereof.

[0082] Processor control circuitry 320 may include communication circuitry 324. Communication circuitry 324 may be used to receive and process signals from IMD 15 implanted in patient 12 for use by processing circuitry 321 in controlling the inductive power transfer processes including, but not limited to a battery management system that monitors and optimizes the inductive power transfer process. Communication circuitry 324 may also provide wireless communications with devices located externally to system 300, for example external device 404, or for example external computing devices 111 A- 11 IN, and / or external server 108 as described and illustrated with respect to FIG. 3. In FIG. 5, communication circuitry 324 as may also be used to download information, such as programing information, to processor control circuitry 320 that may then be stored in memory 322, and accessed by processing circuitry 321. In addition, memory 322 may be used to store information related to the inductive power transfer process performed by system 300, such as the level of energy provided during the inductive power transfer process to transmit antenna 312, any fault conditions that have occurred during the inductive power transfer process, and any other information deemed necessary or helpful that may be related to the inductive power transfer performed by system 300. This information as stored in memory 322 may be provided to computing device 330, and / or uploaded and transmitted through communication circuitry 324 to some other external device or devices, as described above. Processor control circuitry 320 as illustrated in FIG. 5 may also include sensor circuitry 323 configured to be coupled one more different sensors 325, 326, and to receive signals from the sensors that may be further processed by sensor circuitry 323 and / or by processing circuitry 321, to provide and / or derive information that may be further used to control and regulate the inductive power transfer process being performed by system 300.

[0083] In various examples, one or more of the circuits illustrated as comprising processor control circuitry 320 may instead be provided by computing device 330. In various examples, computing device 330 includes a display and one or more input devices, such as a keyboard and / or a computer mouse, that allow a user, such as aphysician or a clinician, to interact with the system 300. This interaction may include interaction to control the inductive power transfer process to be performed or being performed by system 300. In some examples, processor control circuitry 320 and power control circuitry 302 include some or all of power control circuitry 101 as illustrated and described with respect to FIG. 3, and may provide any of the features and be configured to perform any of the function ascribed to power control circuitry 101.

[0084] As shown in FIG. 5, power control circuitry 302 includes a power supply 303, a signal generator 304 (which may include an oscillator and signal generation circuitry), a plurality of power amplifiers 310 and 313, and a corresponding plurality of matching network circuitry 311, 314. The circuits of power control circuitry 302 may be coupled by a bus 306. Bus 306 may be a same bus as bus 328, or communicatively coupled to bus 328. Power control circuitry 302 includes a power amplifier 310 coupled to signal generator 304 and configured to receive a signal from the signal generator 304. Power amplifier 310 is also coupled to matching network circuitry 311, and configured to provide an output signal to the matching network circuitry 311 based on the signal received from the signal generator 304. Matching network circuitry 311 may be configured to provide impedance matching between power amplifier 310 and transmit antenna 312, and to provide outputs that may be coupled to transmit antenna 312 to energize transmit antenna 312.

[0085] Power amplifier 310 in some examples receive a signal including a waveform generated by signal generator 304, and provides power amplification of the received signal that is then applied through matching network circuitry 311 to energize transmit antenna 312. Matching network circuitry 311 provides impedance matching between the output stage of power amplifier 310 that matching network circuitry 311 is coupled to and transmit antenna 312 that is being energized by power amplifier 310. In various examples, a typical range of impedance provided as an output from power amplifier 310 may be in a range of 1 to 100 ohms, in some examples 50 ohms, wherein the real part of the input impedance of transmit antenna 312 would be in a range of 0.1 to 20 ohms, in some examples 0.5 ohms. The imaginary part of a complex impedance of the coils may be in a range of 60 to several hundred ohms, depending on the frequency of the signal or signal applied to the coils. In order to provide maximum power transfer between the power amplifier 310 output and the transmit antenna 312, this output is coupled to matching network circuitry 311. Matching network circuitry is configured to match theimpedance of the output of power amplifier 310 to transmit antenna 312 through matching network 311 circuitry.

[0086] In some examples, matching network circuitry 311 includes an impedance matching transformer configured to match an output impedance of power amplifier 310 to an input impedance of transmit antenna 312 coupled to the output of impedance matching circuitry. In some examples, matching network circuitry 311 includes a transformer and / or a capacitor rated for peak voltage of the assembly and of a capacitance value that the inductive nature of the coil is accommodated. In one implementation, an adjustable vacuum ceramic capacitor is placed in series with a 50 Q to 1 Q transformer. Other configurations and devices may be used to perform the impedance matching function of matching network circuitry 311 are contemplated for using in providing the matching network circuitry 311 and 314 as described in this disclosure.

[0087] In various examples of system 300, since it is more difficult to dynamically tune the quality factor of the receive coil within an implanted medical device such as IMD 15, or rather, change the frequency at which the quality factor is a maximum, it may significantly improve the maximum power delivered to IMD 15 by fixing the frequency of the system based on the characteristics of the receive coil and using a tunable vacuum capacitor located between power amplifier 310 (and after a following transformer) and a coil, such as transmit antenna 312, in order to match the output of the power amplifiers to the impedance presented by the coils without changing the oscillation frequency, as is practiced in rechargeable wireless power transfer systems such as the RESTORE ULTRA® device from Medtronic pic, of Dublin, Ireland. A frequency -based maximization configuration may result in a non-optimal power transfer if the secondary / receive coil of IMD 15 are tuned to a frequency different than that found to maximize power transfer to the primary / transmit coils providing the inductive energy provide by system 300. Therefore, examples of the systems and methods described herein include tuning the impedance of the system at a fixed frequency, as opposed to varying the frequency of the system, in order to maximize the power delivered to a receive coil in the implanted device.

[0088] As shown in FIG. 5, power supply 303 is coupled to a power input 301, and is configured to receive electrical power from input 301. Power input 301 may be any source of electrical power, such as commercially available electrical power supply by an electrical utility, for example electrical power having 110-120 volts RMS single-phasepower at frequency of 50-60 Hz, as is commonly available in the United States. In other examples, input 301 may provide power in other arrangements, such as but not limited to 480V three-phase in an ungrounded delta configuration at 50-60 Hz, or 208 three-phase “Y” configuration at 50-60 Hz. Other voltages, frequencies, configurations, and numbers of phases are contemplated for use as input power to system 300, as would be understood by one of ordinary skill in the art. Power supply 303 is configured to receive electrical power at input 301, and may perform various operations on the received electrical power, including conditioning, filtering, and conversion of the input power voltage to one or more different voltages, including both different voltages provided as alternating current (AC) voltage supplies and direct current (DC) power supplies as outputs from power supply 303. The outputs are generally represented by the “TO OTHER CIRCUITRY” output arrow illustratively provided as an output from power supply 303, and may include any electrical power outputs required to operationally power the circuitry for operation of the devices included in and powered from system 300.

[0089] In some examples, power supply 303 is also configured to provide one or more separate outputs, illustratively represented by the “TO POWER AMPLIFIERS” output arrow from power supply 303. These outputs from power supply 303 may be coupled to power amplifier 310 provided as part of power control circuitry 302, and wherein the “TO POWER AMPLIFIERS” output is configured to provide the electrical energy used to energize the transmit antenna 312 under the control of the power amplifier 310.

[0090] In FIG. 5, signal generator 304 is coupled to bus 306, wherein signal generator 304 may be configured to generate one or more output signals that are used to control the waveforms of the electrical power used to energize transmit antenna 312. For example, signal generator 304 may generate a signal having sinusoidal voltage waveform and a particular frequency. This signal is provided to the power amplifiers and matching network circuitry of power control circuitry 302. In some examples, the sinusoidal waveform is converted to the square waveform, the frequency of the square wave having a same frequency of the sinusoidal waveform generated by signal generator 304, or in other examples signal generator 304 may change the frequency of the square wave signal. In some examples, the duty cycle of the square wave may be the same as provided with the sinusoidal waveform (e.g., a 50% duty cycle), and in other examples, signal generator 304 may alter the duty cycle to a duty cycle other than a 50% duty cycle.

[0091] In some examples, signal generator 304 amplifies the signal for example to alter the voltage level of the signal. In some examples, signal generator 304 is configured to process the signal to retain the processed signal as a sinusoidal waveform, but for example acts as a buffer or driver to amplify and / or drive the output signal from the signal generator 304 to the power amplifier 310, and for example to prevent the power amplifiers from loading down or otherwise distorting the signal being provided from the signal generator 304. In some examples, one or more of the power amplifiers include a Class D amplifier. In some examples, one or more of the power amplifiers include a Class E amplifier. In some examples, the signal generator 304 may provide frequency tuning (closed loop or open loop), to optimize the wireless power transfer between transmit antenna 312 and receive antenna 96 (FIG. 2) of IMD 15. This tuning may or may not be integrated and coordinated with the battery management system and telemetry / communication systems.

[0092] Once processed by signal generator 304 (FIG. 5), the signal generator 304 is coupled to power amplifier 310 that is configured to control the output of electrical energy provided by matching network circuitry 311 to transmit antenna 312 using the signal processed by signal generator 304, which may be provided by a coupling the power amplifier 310 to the “TO POWER AMPLIFIERS” output of power supply 303. The output from power amplifier 310 is then provided as an output to matching network circuitry 311 to energize transmit antenna 312. Matching network circuitry 311 may also include a feedback loop 311 A that provides a feedback signal, such as a varying voltage level, that is indicative of the level of energy, for example a current flow, being provided to transmit antenna 312 by matching network circuitry 311. This feedback signal may be processed by one or more devices included in system 300, for example processing circuitry 321 or computing device 330, or other battery management systems, to provide information that may be used to control and regulate the output of electrical energy being provided to energize transmit antenna 312.

[0093] In some examples of system 300, a position control circuitry 316 is coupled to bus 306. The position control circuitry 316 is coupled to a structure 340 including one or more mechanical actuators, illustratively represented as motor 341. Structure 340 and motor 341 may be physically coupled to transmit antenna 312, and in some examples to a structure (not shown in FIG. 5), such as a table where patient 12 may lay or sit when positioned proximate to transmit antenna 312. Position control circuitry 316 may be configured to drive the motor 341 in order to control movements of structure 340, andthus the positioning of transmit antenna 312, and / or a structure (not shown in FIG. 5) where the patient 12 is positioned, e.g., lying or sitting. Position control circuitry 316 may receive instructions, for example from processing circuitry 321, and control motor 341 in order to reposition transmit antenna 312, and / or patient 12 having IMD 15. Position control circuitry 316 may for example be configured to operate motor 341 to move transmit antenna 312, and / or patient 12 and IMD 15, in an up or down direction as indicated by arrow 317, and / or in a left or right direction as indicated by arrow 318 in FIG. 5. The actuators controlled by position control circuitry 316 are not limited to any particular type of actuator device or devices, and may be a combination of two or more different types of actuator devices working in conjunction to position transmit antenna 312. Actuator devices may include electrical actuators such as motors, including but not limited to stepper or servo motors, pneumatic or hydraulic actuators such as pneumatic or hydraulic motors, and / or pneumatic or hydraulic cylinders, and mechanical actuators that may include gears, rails, pulleys or other mechanical devices conjured to provide mechanical movement. Actuator devices may include linear actuator devices configured to provide movements in a linear direction, and rotary actuators configured to provide rotary movements.

[0094] In addition, position control circuitry 316 may also be configured to tilt or rotate the position of transmit antenna 312, for example relative to the direction of longitudinal axis 170, as represented by arrow 319 in FIG. 5. As described above, movement and repositioning of the transmit antenna 312 and / or patient 12 and IMD 15 may be based on one or more feedback signals provided from IMD 15 that are indicate of the level of electrical energy being induced into the receive antenna of IMD 15. Position control circuitry 316 may be configured to receive this feedback information, or instructions generated for example by processing circuitry 321 based on the feedback information, and to move transmit antenna 312 and / or patient 12 and IMD 15 to a position providing the most efficient coupling of the magnetic field being provided by transmit antenna 312 to receive antenna 96 (FIG. 2) of IMD 15 based on the feedback being provided.

[0095] In operation, a patient 12 (FIG. 5) with IMD 15 that requires operational powering of the IMD under the high-power load condition is positioned so that the IMD 15 is located within the area of the resultant magnetic fields that will be generated by transmit antenna 312 when the coil is energized. Based on control provided by processing circuitry 321 and / or by instructions received from computing device 330,signal generator 304 generates one or more signals that are provided to the power amplifier 310. Power amplifier 310, based at least in part on the received signal, and in some examples based on instructions received from processing circuitry 321, provide power outputs to energize transmit antenna 312. When energized, transmit antenna 312 generates a magnetic field, such as resultant magnetic field 331, onto receive antenna 96 (FIG. 2) of IMD 15, which begins to provide inductive power to supply IMD 15.

[0096] Signals either provided by IMD 15 (FIG. 5) to communication circuitry 324 and / or signals provided as feedback loop 311 A, are processed, for example by processing circuitry 321 and / or by position control circuitry 316, and may be used to reposition transmit antenna 312 and / or a device where patient 12 is sitting or lying, as described above, if deemed necessary, in order to provide better coupling efficiency between the magnetic field provided by transmit antenna 312, and the receive antenna 96 (FIG. 2) of the IMD 15 being powered. In some examples, positioning of the transmit antenna 312 and / or the IMD 15 may include moving the coils and / or the patient / IMD up or down (as indicated by arrow 317), and / or left or right (as indicated by arrow 318) to position the receive antenna of the IMD 15 within the estimated optimal envelope generated by the resultant magnetic field 331 provided by transmit antenna 312. As described above, control of the positioning of transmit antenna 312 and / or receive antenna 96 (FIG. 2) of IMD 15 to position the receive antenna in the estimated optimal envelope being generated by the resultant magnetic fields in the area of transmit antenna 312 (FIG. 5) may be made based on a feedback signal or signals receive from IMD 15 that is / are indicative of the strength or level of energy being induced into the receive antenna at any given time.

[0097] In some examples, control of the level of electrical energy being provided to transmit antenna 312 may be determined based on the feedback signal receive from IMD 15 that is indicative of the strength and / or level of energy being induced into receive antenna 96 (FIG. 2) at any given time. The feedback signal or instructor generated based on the feedback signal, for example generated by processing circuitry 321 (FIG. 5), may be provided to position control circuitry 316, to cause position control circuitry 316 to reposition transmit antenna 312, and / or to reposition patient 12 to locate the receive antenna of IMD 15 within the estimated optimal power transfer envelope of the resultant magnetic field of transmit antenna 312. The feedback signal or the instructions generated based on the feedback signal may also be provided signal generator 304 and / or power amplifier 310, to cause power control circuitry 302 to control the relative level of electrical energy being provided by the circuitry to transmit antenna 312 in order to steerthe resultant magnetic field (e.g., resultant magnetic field 332 as shown in FIG. 5), to maximize the coupling efficiency being achieved between the resultant magnetic field and the receive antenna of IMD 15.

[0098] During the process of inductively transferring power, such as operational power, to IMD 15, various sensors 325, 326, may be monitored, and the information received from or derived from the sensors may be used to further control the powering process. For example, temperature sensors located at the coils may provide signals indicative of the temperature of transmit antenna 312, and may be monitored during the inductive power transfer process to determine if the coil may be overheating. In some examples, one or more of sensors 325, 326 may sense a magnetic field strength and / or direction of the resultant magnetic field at one or more locations in the area around transmit antenna 312. The information from the one or more sensors 325, 326 may be received at sensor circuitry 323, and may be further processed, for example by processing circuitry 321, to further control the powering process being performed by system 300. For example, the level of the intensity of the magnetic field being generated by transmit antenna 312 as sensed by the one or more sensor 325, 326 may be monitored to assure that a safe level of exposure to the electromagnetic fields provided to the patient are maintained.

[0099] In some examples, a temperature of the patient 12 or of IMD 15 may be monitored during the inductive power transfer process. These sensed temperatures of patient 12 and / or of IMD 15 may be used to control the inductive power transfer process for example by lowering (reducing) the level of energy being provided to transmit antenna 312 if the temperature of the patient 12 or of IMD 15 is rising, and for example shutting off the energy being provided to the coil if the temperature of the patient or of IMD 15 exceeds a temperature considered to be safe for the patient. Further, the strength of the magnetic field being generated and imposed on IMD 15 may be monitored during the inductive power transfer process, and the sensed strength of the magnetic fields may be processed and used to further regulate the process, for example to raise or lower the level of electrical energy being provided to transmit antenna 312. Monitoring of the strength of the magnetic field imposes on patient 12 may be required to assure that the level of the strength of the magnetic field does not exceed a predetermined level, or a predetermined level for more than a predetermined time period. The monitoring may include a reduction, including lower the energy level or shutting off the electrical energy provided to the coil for safety reasons if the strength of the magnetic field exceeds somepredetermined value or values, either instantaneous and / or over some predetermined time period.

[0100] In various examples, processing circuitry 321 regulates various functions related to the inductive power transfer process. Processing circuitry 321 may include a timer function for controlling and limiting the duration of time the patient 12 may be exposed to the magnetic fields being generated transmit antenna 312, during the inductive power transfer process. Timing functions may be provided by one or more timers included in processing circuitry 321, and may timeout based on one or more timer values stored in memory 322. Processing circuitry 321 may also regulate a profile of the levels of electrical energy provided to the coils over the duration of the inductive power transfer process, so that the levels of electrical energy provided to transmit antenna 312 may be set and / or varied over the duration of the transmission of power to receive antenna 96 (FIG. 1) based on a profile that may be stored in memory 322 and retrieved and executed by processing circuitry 321. Processing circuitry 321 may further regulate and / or terminate the inductive power transfer process to IMD 15 based on information received from IMD 15. For example, a wireless signal 327 provided by IMD 15 may indicate that IMD 15 is no longer operating under the high-power load condition, and further exposure to the magnetic fields by both patient 12 and IMD 15 will provide no further benefit. In such instances, processing circuitry 321 may terminate the inductive power transfer process in order to minimize the amount of exposure of patient 12 to the magnetic fields generated by system 300, regardless of whether or not a timer has indicated that the time for the inductive power transfer to IMD 15 has expired.

[0101] FIG. 6 illustrates examples graphs 350, 360 of representative waveforms that may be generated by a signal generator, such as signal generator 304 and / or signal generator 305 as illustrated and described with respect to FIG. 5, and applied to transmit antenna 312 coupled to power control circuitry according to various examples described in this disclosure. Graph 350 (FIG. 6) illustrates an example waveform 351 of a square wave having an amplitude value plotted against the vertical axis 352 over time, time represented by horizontal axis 353. Waveform 351 includes a peak-to-peak amplitude 354, and a period 355. In various examples, the peak-to-peak amplitude 354 of waveform 351 may include a voltage range of 10 mV to 100 volts, in some examples, 5 volts. The peak-to-peak amplitude in some examples is dependent on the power amplifier selected that the waveform 351 is being provided to in order to generate the output used to energize one or both of a pair of electrical coils.

[0102] In some examples, the power amplifier being driven by the waveform 351 is a fixed amplification power amplifier, capable of providing a 400 Watt output signal based on a variable input signal having a peak-to-peak amplitude 10-200 mV. In some examples, a reference voltage level 356 may include a zero-volt reference voltage, wherein a portion of waveform 351 is provided at voltage level that is a higher voltage than the reference voltage 356, and a portion of waveform 351 is provided at a voltage level that is less than the reference voltage level 356. In various examples, the duty cycle of waveform 351 over period 355 provides a fifty-percent duty cycle. In various examples, the duty cycle of waveform 351 over the period 355 provides a duty cycle other than a fifty -percent duty cycle. In various examples, period 355 of waveform 351 is in a range of 100 microseconds to 10 nanoseconds, representative of a frequency range of 10 kHz to 100 MHz for waveform 351.

[0103] In some examples, an electrical current having a waveform corresponding to waveform 351 is applied to transmit antenna 312 (FIG. 5). When waveform 351 as shown in FIG. 6 is applied to transmit antenna 312 (FIG. 5), the resultant magnetic field may have a direction that is perpendicular to the longitudinal axis common to transmit antenna 312. This portion of the resultant magnetic field can be used to induce an electrical current into receive antenna 96 (FIG. 2) positioned within the portions of the resultant magnetic field that include the perpendicular direction. In addition, transmit antenna 312 (FIG. 5) being energized by the application of electrical current in the form of waveform 351 (FIG. 6) may also be tilted so that the direction of the resultant magnetic field aligns with an axis of orientation of receive antenna 96 (FIG. 2) in order to maximize the level of coupling efficiency occurring between the resultant magnetic field and the current being induced into the receive antenna. As a result, a maximum level of coupling efficiency between the electrical power being provided to the transmit antenna 312 (FIG. 5) via waveform 351 (FIG. 6) and the level of current being induced into the receive antenna 96 (FIG. 2) may be achieved using only a single coil to generate the resultant magnetic field. Other and / or different combinations of differences between the electrical parameters of waveform 351 (FIG. 6) applied to transmit antenna 312 is not limited to variation of the peak-to-peak amplitude 354 (FIG. 6) of the waveforms, and may include other variation, such as changes in the duty cycle of the waveform applied for example to transmit antenna 312 (FIG. 5).

[0104] Graph 360 (FIG. 6) illustrates an example waveform 361 of a sinusoidal waveform generated from the signal generator 304, and having a varying amplitude valueplotted against the vertical axis 362 over time, time represented by horizontal axis 363. Waveform 361 includes a peak-to-peak amplitude 364, and having a period 365. In various examples, the peak-to-peak amplitude 364 may include a voltage range of 10 mV to 100 volts, in some examples, 5 volts peak-to-peak depending on the desired peak magnetic field intensity and the capacity of the power amplifier employed. In some examples, the power amplifier is a fixed 400 Watt power amplifier, in other example the power amplifier includes a variable output between 2 Watt and 1 kW. In some examples, a reference voltage level 366 may include a zero-volt reference voltage, wherein a portion of waveform 361 provides a voltage level above the reference voltage level 366, and another portion of each cycle of waveform 361 includes a voltage value that is below the reference voltage level 366. In various examples, the duty cycle of waveform 361 over period 365 provides a fifty-percent duty cycle. In various examples the time period 365 of waveform 361 is in a range of 100 microseconds to 10 nanoseconds, representative of a frequency range of 10 kHz to 100 MHz for waveform 361.

[0105] Other and / or different combinations of electrical parameters of waveform 361 applied to transmit antenna 312 is not limited to variation of the amplitude 364 of the waveforms, and may include other variation, such as differences in the phases of the waveforms applied for example to transmit antenna 312.

[0106] FIGS. 7 A and 7B are conceptual diagrams illustrating an example wireless power transmission system including multiple coils, according to one or more techniques of this disclosure. System 600 is an example of systems 100, 300, and 400 described above in relation to FIGS. 1, 3, and 5, and may have the same or similar functions and characteristics as systems 100, 300 and 400. FIG. 7A represents an A-A sectional view of FIG. 7B.

[0107] FIG. 7A illustrates patient 624 with power receiving device 652 lying on a wireless power transmission system 600 including coils, depicted by 612, 614, 616 and 618, and driver circuitry 610. Wireless power transmission system 600 may generate one or more electromagnetic fields to wirelessly transfer operational power to operationally power receiving device 652. In some examples, power receiving device 652 may be an implantable medical device, such as IMD 15 of FIG. 5. In some examples, power receiving device 652 may be located in the pectoral area, near the clavicle, ankle, buttock area, hip pocket, or any other location on patient 624.

[0108] The example of FIGS. 7A and 7B depict wireless power transmission system600 as a mat or bed in which patient 624 is positioned. In other examples, wireless powertransmission system 600 may be installed in a chair, the seat of an automobile, or other vehicle, and other similar locations. FIG. 7A is an example cross section view and FIG. 7B is a top view of wireless power transmission system 600 of this disclosure. Coil cross-sections 612, 614, 616 and 618 may be implemented as multiple loops of a single coil, in some examples. In other examples, coil cross-sections 612, 614, 616 and 618 may depict separate overlapping coils, or separate coils that do not overlap.

[0109] Driver circuitry 610 may include processing circuitry, coil driving amplifier circuits, tuning circuits, communication circuits, sensing circuitry including filters, amplifiers and so on connected to one or more sensors, along with other circuitry not specifically listed. Driver circuitry 610 may drive each of the one or more coils of system 600 together or separately. Driver circuitry 610 may control the phase angle, frequency, magnitude, and other characteristics of the driving signal to focus, or to broaden, the electromagnetic field generated by the one or more coils.

[0110] In some examples, system 600 may include a single coil, as shown in the example of FIG. 7B. In other examples, system 600 may include multiple coils. In some examples, system 600 may include a first coil near the upper body of patient 624 formed by 612 and 618, along with a second coil near the legs of patient 624 formed by 614 and 616. In other examples, system 600 may include overlapping coils, e.g., a first coil formed by 614 and 618 near the upper body of patient 624 and a second coil formed by 612 and 616 near the lower body of patient 624. In other examples, system 600 may include three or more coils, which may be arranged as overlapping or adjacent coils. The portions of the coils indicated by 612 and 614 are not shown in FIG. 7B.[oni] Driver circuitry 610 may be located such that the coils of system 300 may generate the electromagnetic field that encompasses processing circuitry 110 (FIG. 1), the driver circuitry, and the one or more sensors 325, 326 (FIG. 5). The one or more sensors may include temperature sensors to provide temperature measurements for the one or more coils. Other sensors may generate a signal representative of a spatial relationship between driver circuitry 610 (FIGs. 7A and 7B) and the one or more coils. For example, when patient 624 sits or lies down near driver circuitry 610, the components of system 600 may conform to the surface of patient 624. The spatial relationship between driver circuitry 610 and the coils may change as patient 624 moves. For example, the coils depicted by 614 and 616 may compress and move closer to driver circuitry 610. Changes in the shape and angle of the coils may cause changes in the electromagnetic field surrounding driver circuitry 610 and causes changes in the driving signal and operation ofthe processing circuitry. Based on indications from strain gauges, capacitive sensors, pressure sensors or other sensors, the processing circuitry of driver circuitry 610 may determine the changes in the spatial relationship and cause adjustments to the driving signal that may compensate for the changes in the driving signal caused by the changes in the spatial relationship.

[0112] FIG. 8 is a flowchart illustrating example techniques for powering a high- power operation of an IMD. Although method 800 is described with respect to the devices and systems illustrated with respect to wireless power transmission system 100 of FIG. 1, IMD 15 of FIG. 2, system 400 of FIG. 3, and / or system 300 of FIG. 5, method 800 (FIG. 8) is not limited to being performed by any of these systems, and may be performed, in whole or in part, by any of the example devices and / or systems described in this disclosure, and the equivalents thereof.

[0113] Processing circuitry 85 may control power control circuitry 91 to power operation of IMD 15 from power source 89 (801). For example, processing circuitry 85 may control power control circuitry 91 to power operation of a primary therapy function of IMD 15 from power source 89, which may be internal to IMD 15. Such a primary therapy function may include pacing, conduction system pacing, cardiac resynchronization therapy, or the like. Power source 89 may also power relatively lower- power functions such as sensing physiological parameters or the like.

[0114] Processing circuitry 85 may determine a presence of an induced electrical current on receive antenna 96 (802). For example, processing circuitry 85 may include a current detector configured to detect the induced electrical current. The induced electrical current on receive antenna 96 may be received from a wireless power transmission system 100 (FIG. 1).

[0115] Based on the presence of the induced electrical current on receive antenna 96, processing circuitry 85 may control power control circuitry 91 to power at least one high- power operation of IMD 15 from the induced electrical current (803). For example, processing circuitry 85 may control power control circuitry 91 to begin powering, and thus initiate, the at least one high-power operation.

[0116] In some examples, the at least one high-power operation of IMD 15 includes one or more of a data transfer operation, an artificial intelligence application, or administering cardiac therapy. In some examples, the cardiac therapy includes at least one of therapy for Heart Failure preserved Ejection Fraction, Atrial Ventricular Neural Stimulation, or therapy for reducing heart wall thickness.

[0117] In some examples, processing circuitry 85 may initiate the at least one high- power operation of IMD based on the presence of the induced electrical current. In some examples, processing circuitry 85 may initiate the at least one high-power operation of the IMD based on the induced electrical current at least one of exceeding a threshold or being equal or greater than a current sufficient to power the at least one high-power operation of the IMD. In some examples, the at least one high-power operation causes a current drain of IMD 15 to exceed a threshold. In some examples, the induced electrical current includes operational power and recharge power, and wherein power control circuitry 91 uses the recharge power to recharge a rechargeable battery of the power source.

[0118] In some examples, wireless power transmission system 100 includes transmit antenna 102 and driver circuitry 114 configured to energize transmit antenna 102 with radio-frequency energy to generate a magnetic field to transmit the induced electrical current to receive antenna 96 of IMD 15. In some examples, at least one of transmit antenna 102 or receive antenna 96 includes an antenna coil. In some examples, the radio-frequency energy does not exceed a maximum Specific Absorption Rate for absorption of radio-frequency energy by human tissue. In some examples, transmit antenna 102 and receive antenna 96 utilize a Qi power transfer protocol.

[0119] In some examples, transmit antenna 102 is incorporated into a support including any of a mattress pad, a pillow, or an armrest. In some examples, wireless power transmission system 100 further includes one or more sensors operatively coupled to processing circuitry 110 of wireless power transmission system 100. Processing circuitry 110 of wireless power transmission system 100 is further configured to receive, from the one or more sensors 325, 326 (FIG. 5), a signal representative of a spatial relationship between transmit antenna 102 and receive antenna 96. Processing circuitry 110 is further configured to control, based on the signal representative of the spatial relationship between transmit antenna 102 and receive antenna 96, driver circuitry 114 to adjust a driving signal output from driver circuitry 114 to transmit antenna 102.

[0120] In some examples, IMD 15 further includes one or more temperature sensors (e.g., of sensors 92) configured to generate a signal indicative of a temperature of IMD 15. In such examples, processing circuitry 110 of wireless power transmission system 100 is further configured to receive an indication of the temperature of IMD 15 from IMD 15, and control driver circuitry 114 in response to the indication of temperature of IMD 15. For example, IMD 15 may, via communication circuitry 90, send an indication of the temperature of IMD 15, based on the signal from the one or more temperaturesensors, to wireless power transmission system 100. Wireless power transmission system 100 may receive such an indication via communication circuitry 324 (FIG. 5).

[0121] In one or more examples, the functions described above may be implemented in hardware, software, firmware, or any combination thereof. For example, the various components of FIGS. 1, 3, 5, 7A and 7B, such as processing circuitry 110 (FIG. 1), power control circuitry 101 (FIG. 3), power control circuitry 302 (FIG. 5), components of IMD 15 (FIGS. 1, 3, and 5), and driver circuitry 310 (FIG. 7A), without limitation and as an example only, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer- readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0122] The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache). By way of example, and not limitation, such computer-readable storage media, may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magnetic media, optical media, or other computer readable media. In some examples, an article of manufacture may include one or more computer-readable storage media.

[0123] Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Combinations of the above should also be included within the scope of computer-readable media.

[0124] Instructions may be executed by one or more processors, such as one or more DSPs, general purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein, such as processing circuitry 110, may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0125] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and / or firmware.

[0126] Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.

[0127] The following are illustrative of techniques described herein.

[0128] Example 1 : A system comprising: an implantable medical device (IMD), the implantable medical device comprising: a power source; a receive antenna configured to receive an induced electrical current from a wireless power transmission system; power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to control a powering of operation of the IMD from at least one of the power source or the induced electrical current; processing circuitry coupled to the power control circuitry and being configure to:control the power control circuitry to power operation of the IMD from the power source; determine a presence of the induced electrical current on the receive antenna; and based on the presence of the induced electrical current on the receiveantenna, control the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

[0126] Example 2: The system of example 1, wherein the at least one high-power operation of the IMD comprises one or more of a data transfer operation, an artificial intelligence application, or administering cardiac therapy.

[0127] Example 3: The system of example 2, wherein the cardiac therapy comprises at least one of therapy for Heart Failure preserved Ejection Fraction, Atrial Ventricular Neural Stimulation, or therapy for reducing heart wall thickness.

[0128] Example 4: The system of any of examples 1-3, wherein the processing circuitry is further configured to initiate the at least one high-power operation of the IMD based on the presence of the induced electrical current.

[0129] Example 5: The system of example 4, wherein the processing circuitry is further configured to initiate the at least one high-power operation of the IMD based on the induced electrical current at least one of exceeding a threshold or being equal or greater than a current sufficient to power the at least one high-power operation of the IMD.

[0130] Example 6: The system of any of examples 1-5, wherein the at least one high- power operation causes a current drain of the IMD to exceed a threshold.

[0131] Example 7: The system of any of examples 1-6, wherein the induced electrical current comprises operational power and recharge power, and wherein the power control circuitry is further configured to use the recharge power to recharge a rechargeable battery of the power source.

[0132] Example 8: The system of any of examples 1-7, further comprising the wireless power transmission system, the wireless power transmission system comprising: a transmit antenna; and driver circuitry configured to energize the transmit antenna with radio-frequency energy to generate a magnetic field to transmit the induced electrical current to the receive antenna.

[0133] Example 9: The system of any of examples 1-8, wherein at least one of the transmit antenna or the receive antenna includes an antenna coil.

[0134] Example 10: The system of example 8 or example 9, wherein the radiofrequency energy does not exceed a maximum Specific Absorption Rate for absorption of radio-frequency energy by human tissue.

[0135] Example 11 : The system of any of examples 8-10, wherein the transmit antenna and the receive antenna utilize a Qi power transfer protocol.

[0136] Example 12: The system any examples 8-11, wherein the transmit antenna is incorporated into a support comprising any of a mattress pad, a pillow, or an armrest.

[0137] Example 13: The system of any of examples 8-12, wherein the wireless power transmission system further comprises one or more sensors operatively coupled to the processing circuitry of the wireless power transmission system, wherein the processing circuitry of the wireless power transmission system is further configured to:receive, from the one or more sensors, a signal representative of a spatial relationship between the transmit antenna and the receive antenna; and control, based on the signal representative of the spatial relationship between the transmit antenna and the receive antenna, the driver circuitry to adjust a driving signal output from the driver circuitry to the transmit antenna.

[0138] Example 14: The system of any of examples 8-13, wherein the IMD further comprises one or more temperature sensors configured to generate a signal indicative of a temperature of the IMD, and wherein the processing circuitry of the wireless power transmission system is further configured to receive an indication of the temperature of the IMD from the IMD, and control the driver circuitry in response to the indication of temperature of the IMD.

[0139] Example 15: A method operable by an implantable medical device (IMD) comprising: controlling power control circuitry to power operation of the IMD from a power source, the power source being internal to the IMD; determining a presence of an induced electrical current on a receive antenna, the induced electrical current beingreceived from a wireless power transmission system; and based on the presence of the induced electrical current on the receive antenna, controlling the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

[0140] Example 16: The method of example 15, wherein the at least one high-power operation of the IMD comprises one or more of a data transfer operation, an artificial intelligence application, or administering cardiac therapy.

[0141] Example 17: The method of example 16, wherein the cardiac therapy comprises at least one of therapy for Heart Failure preserved Ejection Fraction, Atrial Ventricular Neural Stimulation, or therapy for reducing heart wall thickness.

[0142] Example 18: The method of any of examples 15-17, further comprising initiating the at least one high-power operation of the IMD based on the presence of the induced electrical current.

[0143] Example 19: The method of example 18, wherein initiating the at least one high-power operation of the IMD is further based on the induced electrical current at least one of exceeding a threshold or being equal or greater than a current sufficient to power the at least one high-power operation of the IMD.

[0144] Example 20: A system comprising: an implantable medical device (IMD) comprising: a power source; a receive antenna configured to receive an induced electrical current from a wireless power transmission system; power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to power operation of the IMD from at least one of the power source or the induced electrical current;processing circuitry coupled to the power control circuitry and being configure to:control the power control circuitry to power operation of the IMD from the power source; determine a presence of the induced electrical current; and based on the presence of the induced electrical current, control the power control circuitry to power at least one high-power operation of the IMD from the power source to the induced electrical current; and the wireless power transmission system comprising:a transmit antenna; and driver circuitry configured toenergize the transmit antenna with radio-frequency energy to generate a magnetic field to transmit the induced electrical current to the receive antenna.

Claims

WHAT IS CLAIMED IS:

1. A system comprising: an implantable medical device (IMD), the implantable medical device comprising: a power source; a receive antenna configured to receive an induced electrical current from a wireless power transmission system; power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to control a powering of operation of the IMD from at least one of the power source or the induced electrical current; processing circuitry coupled to the power control circuitry and being configure to: control the power control circuitry to power operation of the IMD from the power source; determine a presence of the induced electrical current on the receive antenna; and based on the presence of the induced electrical current on the receive antenna, control the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

2. The system of claim 1, wherein the at least one high-power operation of the IMD comprises one or more of a data transfer operation, an artificial intelligence application, or administering cardiac therapy.

3. The system of claim 2, wherein the cardiac therapy comprises at least one of therapy for Heart Failure preserved Ejection Fraction, Atrial Ventricular Neural Stimulation, or therapy for reducing heart wall thickness.

4. The system of any of claims 1-3, wherein the processing circuitry is further configured to initiate the at least one high-power operation of the IMD based on the presence of the induced electrical current.

5. The system of claim 4, wherein the processing circuitry is further configured to initiate the at least one high-power operation of the IMD based on the induced electrical current at least one of exceeding a threshold or being equal or greater than a current sufficient to power the at least one high-power operation of the IMD.

6. The system of any of claims 1-5, wherein the at least one high-power operation causes a current drain of the IMD to exceed a threshold.

7. The system of any of claims 1-6, further comprising the wireless power transmission system, the wireless power transmission system comprising: a transmit antenna; and driver circuitry configured to energize the transmit antenna with radio-frequency energy to generate a magnetic field to transmit the induced electrical current to the receive antenna.

8. The system of any of claims 1-7, wherein at least one of the transmit antenna or the receive antenna includes an antenna coil.

9. The system of claim 7 or claim 8, wherein the radio-frequency energy does not exceed a maximum Specific Absorption Rate for absorption of radio-frequency energy by human tissue.

10. The system of any of claims 7-9, wherein the transmit antenna and the receive antenna utilize a Qi power transfer protocol.

11. The system any claims 7-10, wherein the transmit antenna is incorporated into a support comprising any of a mattress pad, a pillow, or an armrest.

12. The system of any of claims 7-11, wherein the wireless power transmission system further comprises one or more sensors operatively coupled to the processing circuitry of the wireless power transmission system, wherein the processing circuitry of the wireless power transmission system is further configured to: receive, from the one or more sensors, a signal representative of a spatial relationship between the transmit antenna and the receive antenna; and control, based on the signal representative of the spatial relationship between the transmit antenna and the receive antenna, the driver circuitry to adjust a driving signal output from the driver circuitry to the transmit antenna.

13. The system of any of claims 7-12, wherein the IMD further comprises one or more temperature sensors configured to generate a signal indicative of a temperature of the IMD, and wherein the processing circuitry of the wireless power transmission system is further configured to receive an indication of the temperature of the IMD from the IMD, and control the driver circuitry in response to the indication of temperature of the IMD.

14. A method operable by an implantable medical device (IMD) comprising: controlling power control circuitry to power operation of the IMD from a power source, the power source being internal to the IMD; determining a presence of an induced electrical current on a receive antenna, the induced electrical current being received from a wireless power transmission system; and based on the presence of the induced electrical current on the receive antenna, controlling the power control circuitry to power at least one high-power operation of the IMD from the induced electrical current.

15. A system comprising: an implantable medical device (IMD) comprising: a power source; a receive antenna configured to receive an induced electrical current from a wireless power transmission system; power control circuitry coupled to the power source and the receive antenna, the power control circuitry being configured to power operation of the IMD from at least one of the power source or the induced electrical current;processing circuitry coupled to the power control circuitry and being configure to: control the power control circuitry to power operation of the IMD from the power source; determine a presence of the induced electrical current; and based on the presence of the induced electrical current, control the power control circuitry to power at least one high-power operation of the IMD from the power source to the induced electrical current; and the wireless power transmission system comprising: a transmit antenna; and driver circuitry configured to energize the transmit antenna with radiofrequency energy to generate a magnetic field to transmit the induced electrical current to the receive antenna.

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