Inductive wireless power transmitter

Abstract

Presented herein are techniques for charging a battery within an implantable component (implant) in a manner that optimizes (e.g., maximizes, increases) recharging efficiency while ensuring compliance with applicable regulatory safety limits. More specifically, presented herein is an inductive wireless power transmitter (WPT) that includes at least two drivers and at least two overlapping flat spiral coils configured to normalize the specific absorption rate (SAR) of human exposure to the generated electromagnetic (EM) / radio-frequency (RF) fields.

Description

Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 INDUCTIVE WIRELESS POWER TRANSMITTER BACKGROUND Field of the Invention

[0001] The present invention relates generally to charging of implantable medical devices. Related Art

[0002] Medical devices have provided a wide range of therapeutic benefits to recipients over recent decades. Medical devices can include internal or implantable components / devices, external or wearable components / devices, or combinations thereof (e.g., a device having an external component communicating with an implantable component). Medical devices, such as traditional hearing aids, partially or fully-implantable hearing prostheses (e.g., bone conduction devices, mechanical stimulators, cochlear implants, etc.), pacemakers, defibrillators, functional electrical stimulation devices, and other medical devices, have been successful in performing lifesaving and / or lifestyle enhancement functions and / or recipient monitoring for a number of years.

[0003] The types of medical devices and the ranges of functions performed thereby have increased over the years. For example, many medical devices, sometimes referred to as “implantable medical devices,” now often include one or more instruments, apparatus, sensors, processors, controllers or other functional mechanical or electrical components that are permanently or temporarily implanted in a recipient. These functional devices are typically used to diagnose, prevent, monitor, treat, or manage a disease / injury or symptom thereof, or to investigate, replace or modify the anatomy or a physiological process. Many of these functional devices utilize power and / or data received from external devices that are part of, or operate in conjunction with, implantable components. SUMMARY

[0004] In one aspect, an inductive power transmitter system is provided. The inductive power transmitter system comprises: at least two substantially flat spiral transmit coils, wherein the at least two substantially flat spiral transmit coils are at least partially overlapping and substantially parallel the at least two substantially flat spiral transmit coils, respectively.

[0005] In another aspect, a wireless charging device for an implantable medical device is provided. The wireless charging device comprises:Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 and a second substantially flat spiral transmit coil at least partially overlapping the first substantially flat spiral transmit coil, the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil comprising a plurality of coil windings each having a different radial spacing therebetween.

[0006] In another aspect, a system is provided. The system comprises: an implantable medical device including an implantable coil and a rechargeable battery; and an external charging device configured to recharge the rechargeable battery via an inductive power link, wherein the external charging device comprises at least two substantially flat spiral transmit coils that are at least partially overlapping and that each comprise a plurality of coil windings each having a different radial spacing therebetween.

[0007] In another aspect, a method is provided. The method comprises: generating, via at least two transmit coils of an inductive power transmitter device, a magnetic field towards an implantable medical device, wherein the magnetic field is substantially uniform over an area of the at least two transmit coils. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present invention are described herein in conjunction with the accompanying drawings, in which:

[0009] FIG. 1A is a schematic diagram illustrating a cochlear implant system with which aspects of the techniques presented herein can be implemented;

[0010] FIG. 1B is a side view of a recipient wearing a sound processing unit of the cochlear implant system of FIG.1A;

[0011] FIG.1C is a schematic view of components of the cochlear implant system of FIG.1A;

[0012] FIG.1D is a block diagram of the cochlear implant system of FIG.1A;

[0013] FIG. 2 is a block diagram illustrating a system including an external charging device and a cochlear implant, in accordance with embodiments presented herein;

[0014] FIG. 3 is a schematic diagram illustrating spiral coil antennas of the external charging device of FIG.2, in accordance with embodiments presented herein;

[0015] FIG.4 is a schematic diagram illustrating non-constant spacing between turns (unequal winding clearance) of the spiral coil antennas of FIG. 3, in accordance with embodiments presented herein;Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1

[0016] FIG. 5 is a graph illustrating contributions to the magnetic field of a coil in which the windings are at the same circumference of the coil;

[0017] FIG. 6 is a graph illustrating contributions to the magnetic field of a spiral coil having windings that are non-equally spaced with respect to each other, in accordance with embodiments presented herein;

[0018] FIG. 7 is a flowchart of a method for wireless power transfer for charging an implantable medical device, in accordance with embodiments presented herein; and

[0019] FIG. 8 is a schematic diagram illustrating a vestibular stimulator system with which aspects of the techniques presented herein can be implemented. DETAILED DESCRIPTION

[0020] Presented herein are techniques for charging a battery within an implantable component (implant) in a manner that optimizes (e.g., maximizes, increases) recharging efficiency while ensuring compliance with applicable regulatory safety limits. More specifically, presented herein is an inductive wireless power transmitter (WPT) that includes at least two drivers and at least two overlapping flat spiral coils configured to normalize the specific absorption rate (SAR) of human exposure to the generated electromagnetic (EM) / radio-frequency (RF) fields. The use of “spiral” coils, specifically, results in a more homogeneous magnetic field relative to, for example, traditional transmit coils that have windings concentrated near the outer circumference. In one aspect, the spiral transmit coils are arranged to be partially overlapping in a specific way so as to minimize a coupling factor (k) between the coils (e.g., so as to achieve the lowest possible coupling factor k, or a “close-to-zero” coupling factor k).

[0021] There are a number of different types of devices in / with which embodiments of the present invention may be implemented. Merely for ease of description, the techniques presented herein are primarily described with reference to a specific device in the form of a cochlear implant system. However, it is to be appreciated that the techniques presented herein may also be partially or fully implemented by any of a number of different types of devices, including hearing devices, implantable medical devices, consumer electronic devices (e.g., mobile phones), wearable devices (e.g., smart watches), etc. As used herein, the term “hearing device” is to be broadly construed as any device that acts on an acoustical perception of an individual, including to improve perception of sound signals, to reduce perception of sound signals, etc. In particular, a hearing device can deliver sound signals to a user in any form,Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 including in the form of acoustical stimulation, mechanical stimulation, electrical stimulation, etc., and / or can operate to suppress all or some sound signals. As such, a hearing device can be a device for use by a hearing-impaired person (e.g., hearing aids, middle ear auditory prostheses, bone conduction devices, direct acoustic stimulators, electro-acoustic hearing prostheses, auditory brainstem stimulators, bimodal hearing prostheses, bilateral hearing prostheses, dedicated tinnitus therapy devices, tinnitus therapy device systems, combinations or variations thereof, etc.), a device for use by a person with normal hearing (e.g., consumer devices that provide audio streaming, consumer headphones, earphones, and other listening devices), a hearing protection device, etc. In other examples, the techniques presented herein can be implemented by, or used in conjunction with, various implantable medical devices, such as visual devices (i.e., bionic eyes), sensors, pacemakers, drug delivery systems, defibrillators, functional electrical stimulation devices, catheters, seizure devices (e.g., devices for monitoring and / or treating epileptic events), sleep apnea devices, electroporation devices, etc.

[0022] FIGs.1A-1D illustrates an example cochlear implant system 102 with which aspects of the techniques presented herein can be implemented. The cochlear implant system 102 comprises an external component 104 that is configured to be directly or indirectly attached to the body of the user, and an internal / implantable component 112 that is configured to be implanted in or worn on the head of the user. In the examples of FIGs.1A-1D, the implantable component 112 is sometimes referred to as a “cochlear implant.” FIG. 1A illustrates the cochlear implant 112 implanted in the head 154 of a user, while FIG.1B is a schematic drawing of the external component 104 worn on the head 154 of the user. FIG.1C is another schematic view of the cochlear implant system 102, while FIG. 1D illustrates further details of the cochlear implant system 102. For ease of description, FIGs.1A-1D will generally be described together.

[0023] In the examples of FIGs. 1A-1D, the external component 104 comprises a sound processing unit 106, an external coil 108, and generally, a magnet fixed relative to the external coil 108. The cochlear implant 112 includes an implantable coil 114, an implant body 134, and an elongate stimulating assembly 116 configured to be implanted in the user’s cochlea. In one example, the sound processing unit 106 is an off-the-ear (OTE) sound processing unit, sometimes referred to herein as an OTE component, that is configured to send data and power to the implantable component 112. In general, an OTE sound processing unit is a component having a generally cylindrically shaped housing 111 and which is configured to be magnetically coupled to the user’s head 154 (e.g., includes an integrated external magnet 150 configured toAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 be magnetically coupled to an internal / implantable magnet 152 in the implantable component 112). The OTE sound processing unit 106 also includes an integrated external (headpiece) coil 108 (the external coil 108) that is configured to be inductively coupled to the implantable coil 114.

[0024] It is to be appreciated that the OTE sound processing unit 106 is merely illustrative of the external devices that could operate with implantable component 112. For example, in alternative examples, the external component 104 may comprise a behind-the-ear (BTE) sound processing unit configured to be attached to, and worn adjacent to, the recipient’s ear. In general, a BTE sound processing unit comprises a housing that is shaped to be worn on the outer ear of the user and is connected to the separate external coil assembly via a cable, where the external coil assembly is configured to be magnetically and inductively coupled to the implantable coil 114. It is also to be appreciated that alternative external components could be located in the user’s ear canal, worn on the body, etc.

[0025] Although the cochlear implant system 102 includes the sound processing unit 106 and the cochlear implant 112, as described below, the cochlear implant 112 can operate independently from the sound processing unit 106, for at least a period, to stimulate the user. For example, the cochlear implant 112 can operate in a first general mode, sometimes referred to as an “external hearing mode,” in which the sound processing unit 106 captures sound signals which are then used as the basis for delivering stimulation signals to the user. The cochlear implant 112 can also operate in a second general mode, sometimes referred as an “invisible hearing” mode, in which the sound processing unit 106 is unable to provide sound signals to the cochlear implant 112 (e.g., the sound processing unit 106 is not present, the sound processing unit 106 is powered-off, the sound processing unit 106 is malfunctioning, etc.). As such, in the invisible hearing mode, the cochlear implant 112 captures sound signals itself via implantable sound sensors and then uses those sound signals as the basis for delivering stimulation signals to the user. Further details regarding operation of the cochlear implant 112 in the external hearing mode are provided below, followed by details regarding operation of the cochlear implant 112 in the invisible hearing mode. It is to be appreciated that reference to the external hearing mode and the invisible hearing mode is merely illustrative and that the cochlear implant 112 could also operate in alternative modes.

[0026] In FIGs.1A and 1C, the cochlear implant system 102 is shown with an external device 110, configured to implement aspects of the techniques presented. The external device 110 is a computing device, such as a personal computer (e.g., laptop, desktop, tablet), a mobile phoneAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 (e.g., smartphone), remote control unit, etc. The external device 110 and the cochlear implant system 102 (e.g., sound processing unit 106 or the cochlear implant 112) wirelessly communicate via a bi-directional communication link 126. The bi-directional communication link 126 may comprise, for example, a short-range communication, such as Bluetooth link, Bluetooth Low Energy (BLE) link, a proprietary link, etc.

[0027] Returning to the example of FIGs.1A-1D, the sound processing unit 106 of the external component 104 also comprises one or more input devices configured to capture and / or receive input signals (e.g., sound or data signals) at the sound processing unit 106. The one or more input devices include, for example, one or more sound input devices 118 (e.g., one or more external microphones, audio input ports, telecoils, etc.), one or more auxiliary input devices 128 (e.g., audio ports, such as a Direct Audio Input (DAI), data ports, such as a Universal Serial Bus (USB) port, cable port, etc.), and a short-range wireless transmitter / receiver (wireless transceiver) 120 (e.g., for communication with the external device 110), each located in, on or near the sound processing unit 106. However, it is to be appreciated that one or more input devices may include additional types of input devices and / or less input devices (e.g., the short- range wireless transceiver 120 and / or one or more auxiliary input devices 128 could be omitted).

[0028] The sound processing unit 106 also comprises the external coil 108, a charging coil 130, a closely-coupled radio frequency transmitter / receiver (RF transceiver) 122, at least one rechargeable battery 132, and an external sound processing module 124. The external sound processing module 124 can be configured to perform a number of operations, and can be formed by one or more processors (e.g., one or more Digital Signal Processors (DSPs), one or more uC cores, etc.), firmware, software, etc. arranged to perform operations described herein. That is, the external sound processing module 124 can be implemented as firmware elements, partially or fully implemented with digital logic gates in one or more application-specific integrated circuits (ASICs), partially or fully in software, etc.

[0029] Returning to the example of FIGs. 1A-1D, the implantable component 112 comprises an implant body (main module) 134, a lead region 136, and the intra-cochlear stimulating assembly 116, all configured to be implanted under the skin (tissue) 115 of the user. The implant body 134 generally comprises a hermetically-sealed housing 138 that includes, in certain examples, at least one power source 125 (e.g., one or more batteries, one or more capacitors, etc.), and in which RF interface circuitry 140 and a stimulator unit 142 are disposed. The implant body 134 also includes the internal / implantable coil 114 that is generally externalAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 to the housing 138, but which is connected to the RF interface circuitry 140 via a hermetic feedthrough (not shown in FIG.1D).

[0030] As noted, stimulating assembly 116 is configured to be at least partially implanted in the user’s cochlea. Stimulating assembly 116 includes a plurality of longitudinally spaced intra-cochlear electrical stimulating contacts (electrodes) 144 that collectively form a contact array (electrode array) 146 for delivery of electrical stimulation (current) to the recipient’s cochlea. Stimulating assembly 116 extends through an opening in the recipient’s cochlea (e.g., cochleostomy, the round window, etc.) and has a proximal end connected to stimulator unit 142 via lead region 136 and a hermetic feedthrough (not shown in FIG.1D). Lead region 136 includes a plurality of conductors (wires) that electrically couple the electrodes 144 to the stimulator unit 142. The implantable component 112 also includes an electrode outside of the cochlea, sometimes referred to as the extra-cochlear electrode (ECE) 139.

[0031] As noted, the cochlear implant system 102 includes the external coil 108 and the implantable coil 114. The external magnet 150 is fixed relative to the external coil 108 and the internal / implantable magnet 152 is fixed relative to the implantable coil 114. The external magnet 150 and the internal / implantable magnet 152 fixed relative to the external coil 108 and the internal / implantable coil 114, respectively, facilitate the operational alignment of the external coil 108 with the implantable coil 114. This operational alignment of the coils enables the external component 104 to transmit data and power to the implantable component 112 via a closely-coupled wireless link 148 formed between the external coil 108 with the implantable coil 114. In certain examples, the closely-coupled wireless link 148 is a radio frequency (RF) link. However, various other types of energy transfer, such as infrared (IR), electromagnetic, capacitive and inductive transfer, may be used to transfer the power and / or data from an external component to an implantable component and, as such, FIG. 1D illustrates only one example arrangement.

[0032] As noted above, sound processing unit 106 includes the external sound processing module 124. The external sound processing module 124 is configured to process the received input audio signals (received at one or more of the input devices, such as sound input devices 118 and / or auxiliary input devices 128), and convert the received input audio signals into output control signals for use in stimulating a first ear of a recipient or user (i.e., the external sound processing module 124 is configured to perform sound processing on input signals received at the sound processing unit 106). Stated differently, the one or more processors (e.g., processing element(s) implementing firmware, software, etc.) in the external sound processing moduleAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 124 are configured to execute sound processing logic in memory to convert the received input audio signals into output control signals (stimulation signals) that represent electrical stimulation for delivery to the recipient.

[0033] As noted, FIG. 1D illustrates an embodiment in which the external sound processing module 124 in the sound processing unit 106 generates the output control signals. In an alternative embodiment, the sound processing unit 106 can send less processed information (e.g., audio data) to the implantable component 112 and the sound processing operations (e.g., conversion of input sounds to output control signals 156) can be performed by a processor within the implantable component 112.

[0034] In FIG. 1D, according to an example embodiment, output control signals (stimulation signals) are provided to the RF transceiver 122, which transcutaneously transfers the output control signals (e.g., in an encoded manner) to the implantable component 112 via external coil 108 and implantable coil 114. That is, the output control signals (stimulation signals) are received at the RF interface circuitry 140 via implantable coil 114 and provided to the stimulator unit 142. The stimulator unit 142 is configured to utilize the output control signals to generate electrical stimulation signals (e.g., current signals) for delivery to the user’s cochlea via one or more of the stimulating contacts (electrodes) 144. In this way, cochlear implant system 102 electrically stimulates the user’s auditory nerve cells, bypassing absent or defective hair cells that normally transduce acoustic vibrations into neural activity, in a manner that causes the recipient to perceive one or more components of the input audio signals (the received sound signals).

[0035] As detailed above, in the external hearing mode the cochlear implant 112 receives processed sound signals from the sound processing unit 106. However, in the invisible hearing mode, the cochlear implant 112 is configured to capture and process sound signals for use in electrically stimulating the user’s auditory nerve cells. In particular, as shown in FIG.1D, an example embodiment of the cochlear implant 112 can include a plurality of implantable sound sensors 165(1), 165(2) that collectively form a sensor array 160, and an implantable sound processing module 158. Similar to the external sound processing module 124, the implantable sound processing module 158 may comprise, for example, one or more processors and a memory device (memory) that includes sound processing logic. The memory device may comprise any one or more of: Non-Volatile Memory (NVM), Ferroelectric Random Access Memory (FRAM), read only memory (ROM), random access memory (RAM), magnetic disk storage media devices, optical storage media devices, flash memory devices, electrical, optical,Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 or other physical / tangible memory storage devices. The one or more processors are, for example, microprocessors or microcontrollers that execute instructions for the sound processing logic stored in memory device.

[0036] In the invisible hearing mode, the implantable sound sensors 165(1), 165(2) of the sensor array 160 are configured to detect / capture input sound signals 166 (e.g., acoustic sound signals, vibrations, etc.), which are provided to the implantable sound processing module 158. The implantable sound processing module 158 is configured to convert received input sound signals 166 (received at one or more of the implantable sound sensors 165(1), 165(2)) into output control signals 156 for use in stimulating the first ear of a recipient or user (i.e., the implantable sound processing module 158 is configured to perform sound processing operations). Stated differently, the one or more processors (e.g., processing element(s) implementing firmware, software, etc.) in implantable sound processing module 158 are configured to execute sound processing logic in memory to convert the received input sound signals 166 into output control signals 156 that are provided to the stimulator unit 142. The stimulator unit 142 is configured to utilize the output control signals 156 to generate electrical stimulation signals (e.g., current signals) for delivery to the user’s cochlea, thereby bypassing the absent or defective hair cells that normally transduce acoustic vibrations into neural activity.

[0037] It is to be appreciated that the above description of the so-called external hearing mode and the so-called invisible hearing mode are merely illustrative and that the cochlear implant system 102 could operate differently in different embodiments. For example, in one alternative implementation of the external hearing mode, the cochlear implant 112 could use signals captured by the sound input devices 118 and the implantable sound sensors 165(1), 165(2) of sensor array 160 in generating stimulation signals for delivery to the user.

[0038] As noted, presented herein is an inductive wireless power transmitter with multiple flat spiral coils for charging a battery within an implantable component (implant) of an implantable medical device system in a manner that optimizes (e.g., maximizes, increases) recharging efficiency while ensuring compliance with applicable regulatory safety limits. Various implementation details will now be described with reference to FIGs.2, 3, and 4, respectively.

[0039] FIG.2 is a block diagram of an exemplary system 202 in which embodiments presented herein are implemented. The system 202 comprises an implantable component, referred to as cochlear implant 212, and an external charging device 203, sometimes referred to herein asAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 a wireless or external charger 203. The external charger 203 may have a number of different forms, such as a pillow charger, charging mat, mattress, headrest, etc.

[0040] As described below, the cochlear implant 212 comprises a rechargeable battery 225 that is configured to be recharged using power signals received from the external charger 203 via an inductive radio frequency (RF) link, and the external charger 203 is a multi- loop (multi-antenna) device that includes two or more coil antennas (antenna loops) that each emit a magnetic field.

[0041] It is to be appreciated that the cochlear implant 212 of FIG. 2, as well as the external charger 203 of FIG. 2, may each have a number of different arrangements. In the example arrangement of FIG. 2, the cochlear implant 212 is a totally implantable cochlear implant in which all components of the cochlear implant are configured to be implanted under the skin / tissue 215 of a recipient. Because all components are implantable, cochlear implant 212 operates, for at least a finite period of time, without the presence of an external device (e.g., without external charger 203).

[0042] Generally, the cochlear implant 212 of FIG. 2 comprises the same or similar components as the cochlear implant 112 of FIG. 1D, where like numbers refer to like parts in FIG. 1D and FIG. 2, respectively. As such, a similar description for similar components and similar functions in relation to FIG. 1D will not be repeated here in connection with FIG. 2. As shown in FIG. 2, the cochlear implant 212 also includes an implant controller 268 (i.e., battery and power management component or battery processor) in connection with the rechargeable battery 225 disposed within the housing 238. The implant body 234 also includes one or more implantable microphones 265 and an internal / implantable coil 214 located external to the housing 238. The implantable coil 214 is connected to elements within the housing 238 via a hermetic feedthrough (not shown in FIG. 2). Implantable coil 214 is typically a wire antenna coil comprised of multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire. It is to be appreciated that cochlear implant 212 may include one or more other components that, for ease of illustration, have been omitted from FIG.2.

[0043] The implantable coil 214 enables cochlear implant 212 to receive power / current signals from an external charger (e.g., external charger 203) via an RF link 248, sometimes referred to herein as an inductive power link 248. The rechargeable battery 225 is configured to store the energy needed to power the other elements of the cochlear implant 212, as well asAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 to provide the current needed to electrically stimulate the recipient's cochlea. The RF interface circuitry 240 is configured to operate under the control of the implant controller 268 and contains the necessary switches so as to charge the rechargeable battery 225 using the power received via the inductive power link 248.

[0044] Certain regulatory safety limits apply to the specific absorption rate (SAR) of human exposure to electromagnetic / radio-frequency fields emanating from hand-held and body- mounted wireless communication devices. These limits also apply to pillow power transmitter devices (i.e., pillow chargers are also evaluated with respect to SAR). As such, the techniques and example embodiments described herein further address issues relating to charging efficiency (i.e., optimize charging power and speed of charging) and human safety while charging.

[0045] The SAR limits are typically expressed in W / kg (Watt per kilogram). Today, basic restrictions for SAR are defined by: (1) The International Commission on Non-Ionizing Radiation Protection (ICNIRP) in “Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (up to 300 GHz),” as being 2 W / kg averaged over 10 g of tissue; (2) The European Commission in EC1999 / 519 / ec / 1999 “On the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz),” as being 2 W / kg averaged over 10 g of tissue; and / or (3) The US Code for Federal Regulations Title 47 Chapter I Subchapter A Part 1 Subpart I § 1.1310 “radio frequency radiation exposure limits,” May 2021, as being 1.6 W / kg averaged over 1 g of tissue. These SAR limits may be trespassed when charging an implant battery at typical 5 mA within 7 cm range from the loop coil. This may happen especially when regular (non-spiral) transmit coils are used, for example.

[0046] One possible solution to ensure compliance with the regulatory safety limits is to send less power to the implant. However, this has the risk that the implant will not be fully charged by the end of the night, for example, which is not ideal for the implant recipient. Thus, presented herein are techniques to mitigate the risk of trespassing the SAR exposure limits whilst still providing sufficient energy to the implant to recharge a battery during the night or even daytime (i.e., comfort charging, carefree charging). More specifically, in order to address the above and other needs, a system or a device according to the example embodiments described herein is configured to implement wireless power transfer to human implants using an inductive wireless power transmitter (WPT) with at least two drivers and at least two overlapping flat spiral coils, which effectively reduces the specific absorption rate (SAR) of human exposure to these electromagnetic / radio frequency fields. According to one aspect, theAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 specific use of “spiral” coils results in a more homogeneous magnetic field, relative to normal transmit coils that have all windings concentrated near the outer circumference. According to another aspect, the spiral transmit coils are arranged to be partially overlapping in a specific way so as to minimize a coupling factor k (e.g., so as to achieve the lowest possible coupling factor k, or a “close-to-zero” coupling factor k). In addition, spiral transmit coils having the partially overlapping configuration that results in a close-to-zero coupling factor k are easier to tune at resonance because the spiral transmit coils are magnetically isolated, thereby creating impedance independency.

[0047] Referring again to the example arrangement of FIG.2, the external charging device 203 may be a so-called “pillow charger” that comprises a wireless power transmitter module 276 and a plurality (i.e., two or more) of external loop or coil antennas 280 disposed in a pillow structure 272 (also referred to simply as pillow 272). Although the specific example of a pillow charger is described, it should be appreciated that wireless power transmitter module 276 and the external loop or coil antennas 280 may be similarly integrated in various other structures (e.g., a mat, a chair, a mattress, a headrest, etc.) in other example embodiments. The external charging device 203 may have an electrical connection to a power source (not shown), which may include a galvanic isolation element (i.e., a transformer) to insulate the power source from the electronics, and may also include a 12V DC adapter (not shown).

[0048] According to an aspect of the present disclosure, the external loop or coil antennas 280 comprise at least a first spiral transmit coil 280A (spiral coil A) and a second spiral transmit coil 280B (spiral coil B), as shown in FIG.2. In certain embodiments, the first spiral transmit coil 280A and the second spiral transmit coil 280B each have an outer diameter (and / or an outer circumference) that is greater than a diameter (and / or outer circumference) of the implantable coil 214 of the cochlear implant 212, and comprise a plurality (e.g., three or more) of coil windings. The first spiral transmit coil 280A and the second spiral transmit coil 280B are positioned so as to lie substantially parallel (e.g., they are substantially co-planar with respect to each other). In certain example embodiments, the first spiral transmit coil 280A and the second spiral transmit coil 280B are substantially flat, circular or rectangular coils that at least partially overlap each other (as further described below with reference to FIG.3).

[0049] The wireless power transmitter module 276 comprises a first dedicated transmit driver 278A (driver A) for driving the first spiral transmit coil 280A and a second dedicated transmit driver 278B (driver B) for driving the second spiral transmit coil 280B. Although not shown in FIG. 2, it is noted that the first dedicated transmit driver 278A and the second dedicatedAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 transmit driver 278B may each comprise multiple components (e.g., a waveform generator, dedicated amplifiers for each spiral transmit coil, tuning capacitors, current transformers, etc.) for implementing their corresponding functionality.

[0050] The wireless power transmitter module 276 is configured to drive each of the plurality of external loop or coil antennas 280 (i.e., the first spiral transmit coil 280A and the second spiral transmit coil 280B) with different alternating current signals so that the coil antennas 280 (i.e., the first and second spiral transmit coils 280A, 280B) each emit a corresponding magnetic field. That is, the first transmit driver 278A and the second transmit driver 278B can each comprise a dedicated amplifier (which are connected to a waveform generator) configured to provide energy to the corresponding coil antenna 280 (i.e., a first dedicated amplifier for the first spiral transmit coil 280A and a second dedicated amplifier for the second spiral transmit coil 280B), which is placed in resonance with a corresponding tuning capacitor (not shown).

[0051] In addition, corresponding transformers (not shown) insulate the amplifiers and waveform generator from the coil antennas 280 (the first and second spiral transmit coils 280A, 280B), respectively, and can also act as current boosters, thereby avoiding the need for high voltages over the coil antennas 280. The high electrical current flowing in the secondary side of the transformers and through the coil antennas 280 generate corresponding magnetic fields (i.e., such that the first spiral transmit coil 280A emits a first magnetic field, and the second spiral transmit coil 280B emits a second magnetic field). In certain examples, the wireless power transmitter module 276 is configured to drive the coil antennas 280 (the first spiral transmit coil 280A and the second spiral transmit coil 280B) so that at least one characteristic of the corresponding emitted magnetic field varies, over time, with respect to the same characteristic of the other magnetic field. Driving the coil antennas 280 (the first and second spiral transmit coils 280A, 280B) with different signals (e.g., having a non-fixed frequency, phase, or amplitude relationship) causes a difference in frequency, phase, or amplitude between both of the coil antennas (spiral transmit coils). This frequency, phase, and / or amplitude difference can be used to avoid dead zones (i.e., an area or point where the receiving coil / antenna would receive no power, or only a very small amount of power).

[0052] FIG.3 is a schematic diagram illustrating the coil antennas 280 of the external charging device 203 (e.g., pillow charger), which are referred to as a first spiral transmit coil 380A and a second spiral transmit coil 380B in FIG.3. For ease of illustration, FIG. 3 is described with reference to a three-dimensional Cartesian coordinate system formed by three coordinate axes (the x-axis 331, the y-axis 333, and the z-axis 335). In the arrangement shown in FIG. 3, theAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 first spiral transmit coil 380A and the second spiral transmit coil 380B are disposed substantially parallel with respect to each other, e.g., are each in an XY plane (formed by the x-axis 331 and the y-axis 333).

[0053] A magnetic field (H-field) is the magnetic effect of electric currents and magnetic materials and, at any given point in space, can be represented by a vector quantity (i.e., there is both a direction associated with the field as well as a field strength). Therefore, the magnetic fields generated by the first spiral transmit coil 380A and the second spiral transmit coil 380B can be represented as magnetic field vectors (Hx, Hy, Hz), respectively. Since the first and second spiral transmit coils 380A, 380B are in close proximity to one another, the magnetic field vectors (Hx, Hy, Hz) are summed as vector elements and this summed vector (i.e., the combined magnetic field vector) determines the magnetic flux that is received at the implant coil (e.g., the implantable coil 214 of FIG.2).

[0054] As shown in FIG.3, the first spiral transmit coil 380A comprises a plurality of windings 381A, 382A, and 383A, and the second spiral transmit coil 380B comprises a plurality of windings 381B, 382B, and 383B. As also shown in FIG.3, and described further below with reference to FIG.4, the plurality of windings of the spiral transmit coils are arranged so as to have different radial spacings relative to the other windings. For example, there is a first radial distance between winding 381A and winding 382A, a second radial distance between winding 382A and winding 383A, and a third radial distance between winding 383A and the center of the first spiral transmit coil 380A. Likewise, there is a first radial distance between winding 381B and winding 382B, a second radial distance between winding 382B and winding 383B, and a third radial distance between winding 383B and the center of the second spiral transmit coil 380B. In this example, the first radial distance is smaller than the second radial distance, and the second radial distance is smaller than the third radial distance. That is, the space (gap) between respective windings progressively increases starting from the outermost winding (381A, 381B) to the innermost winding (383A, 383B). However, this example is merely illustrative and non-limiting, and other arrangements are possible, such as smaller radial distances between inner windings and larger radial distances between outer windings (i.e., the opposite of the arrangement shown in FIGs. 3 and 4), or a fixed radial distance between each of the windings (i.e., such that there is a substantially constant gap or equal spacing between each respective winding). Although the example shown in FIG.3 has exactly three windings, other example embodiments may have a greater number of windings (e.g., four or more windings).Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1

[0055] The first spiral transmit coil 380A and the second spiral transmit coil 380B of FIG. 3 have relatively high Q-factors (e.g., a Q value greater than 100), which is beneficial for the power transfer efficiency of the spiral transmit coils. In certain embodiments, the first and second spiral transmit coils 380A, 380B also partially overlap in a common plane in order to limit and / or substantially eliminate mutual coupling between the spiral transmit coils (i.e., a coupling factor k of the spiral transmit coils is zero, substantially close-to-zero, or otherwise below a predetermined threshold coupling factor). That is, the mutual influence between the two spiral transmit coils is dependent on the coil shape and the partial overlap of the two spiral transmit coils.

[0056] In certain examples, the relative phase or amplitude differences between the magnetic fields emitted by the coil antennas 380 (the first and second spiral transmit coils 380A, 380B) can vary continuously or discontinuously (e.g., randomly) to effectuate fluctuations / changes in the direction / orientation of the summed magnetic field vector. More specifically, in accordance with certain embodiments, the external charging device 203 is configured to manipulate the signals sent to each coil antenna 380 to vary the relationship between the phases and / or amplitudes of the emitted magnetic fields such that the direction / orientation of the resulting combined / summed magnetic field vector (corresponding to the summation of the emitted magnetic fields) changes over time. Since the orientation of the combined magnetic field vector changes, the implantable coil will have a non-zero magnetic flux therethrough during different periods of time, regardless of the relative location of the implantable coil to the external coil antennas. Stated differently, if the relative phases or amplitudes of the magnetic field vector Hx, Hy, and / or Hz (FIG.3) vary over time, then the orientation / direction of the combined / summed magnetic field vector (i.e., the sum of Hx, Hy, and Hz) will also fluctuate / change over time (i.e., the orientation / direction rotates). Since the orientation of the combined magnetic field changes over time (e.g., the direction of the vector “moves” around), the implant coil (i.e., the implantable coil 214 of FIG. 2) will, at different times, have a non- zero magnetic flux therethrough than can induce a current in the implant coil that, in turn, can be used to charge a battery (e.g., the rechargeable battery 225 of FIG. 2) in an implantable medical device (e.g., the cochlear implant 212 of FIG.2). This arrangement provides implant recipients more freedom of movement and leads to more reliable charging that is less dependent on head orientation.

[0057] Although FIGs.2 and 3 generally illustrate an example multi-loop external charger that includes at least two coil antennas (a first spiral transmit coil and a second spiral transmit coil)Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 with at least three windings each, it is to be appreciated that the use of two coil antennas (two spiral transmit coils) with three windings is merely illustrative and non-limiting, and that other arrangements may include different numbers of coil antennas (e.g., three spiral transmit coils, etc.) and / or different numbers of windings (e.g., four windings, etc.). Thus, the techniques described herein can also be adapted similarly for a third spiral transmit coil (not shown) in other embodiments, and the third spiral transmit coil can be positioned so as to lie in the same plane as the first and second spiral transmit coils, or can be positioned so as a lie in a different plane relative to the first and second spiral transmit coils. In an alternative arrangement (not shown in FIGs.2 and 3), the first and second spiral transmit coils 380A, 380B could be disposed in the XZ plane (i.e., instead of the XY plane). In another alternative arrangement (not shown), the first and second spiral transmit coils may be disposed in the same plane as each other, and a third spiral transmit coil (not shown) may be disposed in the same plane or a different plane with respect to the first and second spiral transmit coils.

[0058] Although the first spiral transmit coil antenna and the second spiral transmit coil antenna can have a substantially circular shape, as shown in FIGs. 2, 3 and 4, example embodiments are not limited thereto, and the spiral transmit coils could instead have a more square-like shape (e.g., with rounded corners). This variation would further enhance the ability of the two spiral transmit coils to produce magnetic fields that provide even more uniform and complete coverage for targeted implant locations than with a conventional a circular shaped coil or two non-overlapping circular coils (e.g., which would produce magnetic fields in a figure-8 shape). For example, charging an implant located near the joining area in the middle (i.e., a notch) in the example of a figure-8 pattern produced by two non-overlapping circular coils may not deliver sufficient signal / power when the implant coil is located outside the circumference of the coils, which is less than ideal. Providing two partially-overlapping spiral coils (whether having a circular shape or a more square-like shape) according to the techniques described herein can effectively reduce or eliminate that dead zone (i.e., the notch in the middle of the figure-8 pattern where the two loops join) in the area between the two non-overlapping circular coils. The aim of this solution is to more uniformly and completely cover as much of the target area where the implant coil will be located as possible with the combined magnetic field of the partially-overlapping spiral transmit coils described herein.

[0059] FIG.4 illustrates an optimized dual coil design for an external charging device (e.g., a pillow charger, a charging mat, etc.), according to an example embodiment. Similar to FIG.3, the spiral transmit coil 480A shown in FIG. 4 is a planar spiral coil comprising a plurality ofAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 coil windings 481A, 482A, and 483A, with an increasing winding clearance betweenneighboring windings ( 1 < 2 < 3, etc.). FIG. 4 more clearly illustrates the nature of thepositional relationship between the respective windings (i.e., the winding clearances, gaps, spacings, radial distances, etc.) according to one specific example design of a flat spiral transmit coil. Although not shown in FIG.4, it should be appreciated that there is also a second spiral transmit coil with increasing winding clearance between its windings, which at least partially overlaps with the spiral transmit coil 480A (e.g., refer to FIG. 3). As noted above, each of the spiral transmit coils has a separate driver (not shown in FIG.4, refer to FIG.2) in the wireless power transmitter module.

[0060] That is, the transmit coils described with reference to FIGs. 2, 3, and 4 are “spiral” transmit coils, specifically, and the spiral transmit coils also “overlap” with each other (at least partially). In certain embodiments, the winding clearances (gaps, spacings, radial distances) are different from but are proportional to each other (e.g., 2 is greater than and proportional to 1, and 3 is greater than 2 and proportional to 2 and / or 1). Further, providing two partially overlapping spiral coils with progressively increasing winding clearances (i.e., 1 < 2 < 3) between the neighboring windings, as described above with reference to FIGs.3 and 4, creates a magnetic coupling factor ‘k’ that is close to or at zero. One notable advantage of this arrangement is to avoid (or reduce the occurrence of) high H-field peak levels within a few centimeters from an array of transmit coils (e.g., at least two transmit coils, or three or more transmit coils), as described further below with reference to FIGs.5 and 6.

[0061] Thus, the example embodiments described above with reference to FIGs. 2, 3, and 4 provide an inductive wireless power transfer antenna system that comprises at least two substantially parallel (e.g., quasi co-planar) flat spiral transmit coils, and at least two dedicated transmit drivers for each of the flat spiral transmit coils, respectively. The at least two spiral transmit coils should have a relatively large outer diameter and / or outer circumference in relation to the implant coil (e.g., a diameter or circumference of an outermost winding of the spiral transmit coil could be approximately 2-3x greater than diameter or circumference of the implant coil, in one non-limiting illustrative example). As noted, the flat spiral transmit coils are “partially overlapping” in a specific manner with respect to each other, such that a magnetic coupling factor ‘k’ is close to or at zero. In certain examples, the at least two substantially flat spiral transmit coils are configured to produce magnetic fields with joined enclosed loop area boundaries in an XY plane, so as to provide substantially uniform and complete coverage for (all or most) implant locations within the same XY boundary (i.e., in a Cartesian coordinateAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 system). Preferably, the area covered by the coils, from a magnetic field point of view, should align with where the implant coil will be located for charging purposes.

[0062] According to a preferred example embodiment, and as shown in FIGs. 3 and 4 in particular, each circular flat spiral coil is constructed so as to have non-constant spaced coil windings (e.g., with an increased winding clearance between neighboring coil windings, going inwards to the center of each coil or decreased winding clearance between neighboring coil windings, going inwards to the center of each coil). In an alternative example embodiment (not shown), however, each circular flat spiral coil can be constructed with constant spaced coil windings (i.e., with a fixed / equal winding clearance between neighboring coil windings). Similarly, a constant / fixed spacing or an increasing / decreasing spacing between coil windings could be used in the alternative example in which the flat spiral coils have a more square-like shape.

[0063] As noted, the number of turns (i.e., the number of windings) for each spiral transmit coil can vary in different embodiments. For example, there should be at least three turns (windings), although size and space considerations may effectively place an upper limit on the total amount of turns (the total number of windings). Likewise, the spacing between turns (winding clearance, radial distance) can vary in different embodiments. For example, the spacing between turns (winding clearance, radial distance) can increase proportionally from the outer part of the coil (smaller spacing / clearance / distance) towards the center of the coil (larger spacing / clearance / distance). This spacing / clearance / distance between the respective turns / windings could also be tuned (optimized) in some other manner so as to improve the results for various different configurations or arrangements.

[0064] As noted, the spiral transmit coils can produce a rotating magnetic field (or “H-field”). In certain examples, the continuous magnetic field emanating from each transmit coil is shifted in phase, frequency, or amplitude to avoid radio dead / quiet zones, and the resulting magnetic field is a rotating H-field. Preferably, the spiral transmit coils should be high Q transmit coils (e.g., with a value of at least 100, for energy efficiency purposes).

[0065] In certain embodiments, a low-Rds(on) MOSFET is selected for the transmit coil drivers, such as eGaN FETs (again, for enhanced power efficiency). In some examples, the power transmitter can be powered by a USB battery pack (e.g., for portability, travelling, etc.). In certain embodiments, the transmitter drivers are differential (e.g., differential signalingAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 permits transmission with lower voltages, good SNR, improved immunity to noise, and higher data rates).

[0066] In certain embodiments, an EMC grid / fork (to electrical ground) is placed on the spiral coils. In one example, an EMC grid / fork may be placed on the top side of the spiral transmit coils, or alternatively, on the bottom side of the spiral transmit coils. In another example, EMC grids / forks may be placed on both the top side and the bottom side of the spiral transmit coils.

[0067] It is noted that in some instances, the human tissue could be at very close proximity to the power transmitter loop of the charger device (e.g., less than 1 cm separation distance). In such instances, an extra safeguard layer (e.g., of z = 1 cm) could be applied, according to an example embodiment. For example, an electrical non-conductive coil safeguard enclosure can be disposed around the loops of wire that form the spiral transmit coils, in order to prevent the implantable medical device (e.g., cochlear implant) from being positioned within a predetermined vicinity of the loops of wire. This extra safeguard layer can ensure that no body part / tissue can come too close to the spiral transmit coils (e.g., to further ensure that the SAR limits are not exceeded).

[0068] Next, the contributions to a magnetic field of coils with different arrangements of windings will be described with reference to FIGs.5 and 6, to further illustrate how the example embodiments described above with reference to FIGs.2, 3, and 4 (e.g., the flat spiral transmit coils that are partially overlapping and that have differently spaced coil windings) can optimize charging efficiency (in terms of power and speed) while remaining within the bounds of the SAR limits.

[0069] FIG. 5 is a graph illustrating contributions to the magnetic field (H-field) of a coil in which all of the windings are at the same circumference of the coil. The curves 512, 514, and 516 in the graph of FIG.5 represent the contribution to the H-field of each individual winding, respectively, and the curve 518 represents the overall resulting H-field that would be generated by the coil (via all of the windings) of FIG. 5. The curve 518 corresponds to a spatial summation of the contributions of the individual windings.

[0070] As shown in FIG. 5, the curves 512, 514, and 516 for all three of the windings have peaks 513, 515, and 517 at the same locations in the graph, each having a distance of approximately 130 mm from the center and the same level of approximately 7.5 A / m in this example. Therefore, the peak 519 of the curve 518 representing the total spatial contributionAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 of all of the windings also has a distance of approximately 130 mm from the center, and has a level of approximately 22 A / m at its highest point in the example of FIG.5.

[0071] FIG. 6 is a graph illustrating contributions to the magnetic field (H-field) of a coil having windings that are non-equally spaced with respect to each other, such as shown in FIGs. 3 and 4 and described above, according to an example embodiment. The coil of FIG. 6 otherwise has the same outer diameter as the coil of FIG. 5. The curves 612, 614, and 616 in the graph of FIG. 6 represent the contribution to the H-field of each individual winding, respectively, and the curve 618 represents the overall resulting H-field that would be generated by the coil (via all of the non-equally spaced windings) of FIG. 6. Again, the curve 618 corresponds to a spatial summation of the contributions of the individual windings.

[0072] As shown in FIG.6, each of the curves 612, 614, and 616 for each of the windings have peaks at different locations in the graph, respectively. In this example, the curve 612 for a first winding has a peak 613 at a distance of approximately 130 mm from the center and a level of approximately 7.5 A / m, the curve 614 for a second winding has a peak 615 at a distance of approximately 100 mm from the center and a level of approximately 8 A / m, and the curve 616 for a third winding has a peak 617 at a distance of approximately 70 mm from the center and a level of approximately 8.5 A / m. The peak 619 of the curve 618 representing the total spatial contribution of all of the windings has a distance of approximately 80 mm from the center, and has a level of approximately 18 A / m at its highest point in the example of FIG.6.

[0073] In general, for the examples of FIGs. 5 and 6, the displayed value is the z component of the H-field (or the “Hz field”), which is the magnetic field seen by a receiver coil parallel to the spiral transmit coil (i.e., Tx and Rx having the same orientation). In the example of FIG. 5, the peaks of each winding are located at the same place in the graph, which has a cumulative effect on the peak of the overall Hz field. In the example of FIG.6, however, the peaks of each winding are located at different places in the graph, which has less of a cumulative effect on the peak of the overall Hz field (e.g., reduced from 22 A / m in FIG.5 down to 18 A / m in FIG. 6). As mentioned above, one advantage of the arrangement of FIG.6 is to avoid (or reduce the occurrence of) high H-field peak levels within a few centimeters from an array of transmit coils (e.g., at least two transmit coils, or three or more transmit coils). In addition, it is possible that the Hz field could be made “flatter” by adding more turns (i.e., additional windings) for the spiral transmit coils in this example.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1

[0074] FIG.7 is a flowchart of an example method 700 for wireless transfer of power (e.g., for charging of an implantable medical device), in accordance with embodiments presented herein. At operation 710, the method 700 includes generating, via at least two transmit coils of an inductive power transmitter device, a magnetic field (combined / summed magnetic field) towards an implantable medical device, wherein the combined magnetic field is substantially uniform over an area of the at least two transmit coils.

[0075] As noted, example embodiments described above with reference to FIGs.2, 3, 4, 6, and 7 are applicable to closely coupled inductive wireless power transmitters and many other implant types such as pillow power transmitters, mattress power transmitters, headrest power transmitters (chairs in home, office, cars, planes), etc. One benefit of the techniques described herein is to ensure human safety and regulatory compliance with respect to the specific absorption rate (SAR) of human exposure to RF fields emanating from wireless devices, such as pillow power transmitter devices (i.e., reduce magnetic field towards human body while being under the SAR limits, reduce human exposure to RF fields). Another advantage of the techniques described herein is to enable more convenient charging during the night or even daytime (also sometimes referred to as “comfort charging” or “carefree charging”). The techniques described herein would also serve to improve recipient acceptance of this type of device and technology (e.g., by alleviating user concerns about keeping their head over a radiating source of energy for 6-8+ hours every night), while ensuring compliance with the relevant regulatory standards (safety limits) described above.

[0076] As previously described, the technology disclosed herein can be applied in any of a variety of circumstances and with a variety of different devices. Example devices that can benefit from technology disclosed herein are described in more detail in FIG.8. The techniques of the present disclosure can be applied to other devices, such as neurostimulators, cardiac pacemakers, cardiac defibrillators, sleep apnea management stimulators, seizure therapy stimulators, tinnitus management stimulators, and vestibular stimulation devices, as well as other medical devices that deliver stimulation to tissue. Further, technology described herein can also be applied to consumer devices. These different systems and devices can benefit from the technology described herein.

[0077] FIG. 8 illustrates an example vestibular stimulator system 802, with which embodiments presented herein can be implemented. As shown, the vestibular stimulator system 802 comprises an implantable component (vestibular stimulator) 812 and an external device / component 804 (e.g., external processing device, battery charger, remote control, etc.).Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 The external device 804 comprises a transceiver unit 860. As such, the external device 804 is configured to transfer data (and potentially power) to the vestibular stimulator 812.

[0078] The vestibular stimulator 812 comprises an implant body (main module) 834, a lead region 836, and a stimulating assembly 816, all configured to be implanted under the skin / tissue (tissue) 815 of the recipient. The implant body 834 generally comprises a hermetically-sealed housing 838 in which RF interface circuitry, one or more rechargeable batteries, one or more processors, and a stimulator unit are disposed. The implant body 834 also includes an internal / implantable coil 814 that is generally external to the housing 838, but which is connected to the transceiver via a hermetic feedthrough (not shown).

[0079] The stimulating assembly 816 comprises a plurality of electrodes 844(1)-(3) disposed in a carrier member (e.g., a flexible silicone body). In this specific example, the stimulating assembly 816 comprises three (3) stimulation electrodes, referred to as stimulation electrodes 844(1), 844(2), and 844(3). The stimulation electrodes 844(1), 844(2), and 844(3) function as an electrical interface for delivery of electrical stimulation signals to the recipient’s vestibular system.

[0080] The stimulating assembly 816 is configured such that a surgeon can implant the stimulating assembly adjacent the recipient’s otolith organs via, for example, the recipient’s oval window. It is to be appreciated that this specific embodiment with three stimulation electrodes is merely illustrative and that the techniques presented herein may be used with stimulating assemblies having different numbers of stimulation electrodes, stimulating assemblies having different lengths, etc.

[0081] In operation, the vestibular stimulator 812, the external device 804, and / or another external device, can be configured to implement the techniques presented herein. That is, the vestibular stimulator 812, possibly in combination with the external device 804 and / or another external device, can include an evoked biological response analysis system, as described elsewhere herein.

[0082] As should be appreciated, while particular uses of the technology have been illustrated and discussed above, the disclosed technology can be used with a variety of devices in accordance with many examples of the technology. The above discussion is not meant to suggest that the disclosed technology is only suitable for implementation within systems akin to that illustrated in the figures. In general, additional configurations can be used to practiceAtty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 the processes and systems herein and / or some aspects described can be excluded without departing from the processes and systems disclosed herein.

[0083] This disclosure described some aspects of the present technology with reference to the accompanying drawings, in which only some of the possible aspects were shown. Other aspects can, however, be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Rather, these aspects were provided so that this disclosure was thorough and complete and fully conveyed the scope of the possible aspects to those skilled in the art.

[0084] As should be appreciated, the various aspects (e.g., portions, components, etc.) described with respect to the figures herein are not intended to limit the systems and processes to the particular aspects described. Accordingly, additional configurations can be used to practice the methods and systems herein and / or some aspects described can be excluded without departing from the methods and systems disclosed herein.

[0085] According to certain aspects, systems and non-transitory computer readable storage media are provided. The systems are configured with hardware configured to execute operations analogous to the methods of the present disclosure. The one or more non-transitory computer readable storage media comprise instructions that, when executed by one or more processors, cause the one or more processors to execute operations analogous to the methods of the present disclosure.

[0086] Similarly, where steps of a process are disclosed, those steps are described for purposes of illustrating the present methods and systems and are not intended to limit the disclosure to a particular sequence of steps. For example, the steps can be performed in differing order, two or more steps can be performed concurrently, additional steps can be performed, and disclosed steps can be excluded without departing from the present disclosure. Further, the disclosed processes can be repeated.

[0087] Although specific aspects were described herein, the scope of the technology is not limited to those specific aspects. One skilled in the art will recognize other aspects or improvements that are within the scope of the present technology. Therefore, the specific structure, acts, or media are disclosed only as illustrative aspects. The scope of the technology is defined by the following claims and any equivalents therein.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1

[0088] It is also to be appreciated that the embodiments presented herein are not mutually exclusive and that the various embodiments may be combined with another in any of a number of different manners.

Claims

Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 CLAIMS What is claimed is:

1. A wireless charging device for an implantable medical device, the wireless charging device comprising: and a second substantially flat spiral transmit coil at least partially overlapping the first substantially flat spiral transmit coil, the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil comprising a plurality of coil windings each having a different radial spacing therebetween.

2. The wireless charging device of claim 1, further comprising: a first transmit driver configured to drive the first substantially flat spiral transmit a second transmit driver configured to drive the second substantially flat spiral transmit coil.

3. The wireless charging device of claim 1, wherein the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil are circular or square shaped flat coils that are both positioned in a same plane.

4. The wireless charging device of claim 1, 2, or 3, wherein the plurality of coil windings have an increasing radial spacing towards a center of the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil, respectively.

5. The wireless charging device of claim 1, 2, or 3, wherein the different radial spacing between the plurality of coil windings are configured to generate a substantially uniform magnetic field over an area of the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil.

6. The wireless charging device of claim 1, 2, or 3, wherein a coupling factor between the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil is below a predetermined threshold.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 7. The wireless charging device of claim 6, wherein the coupling factor is substantially close to or equal to zero, such that the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil are substantially uncoupled.

8. The wireless charging device of claim 1, 2, or 3, wherein an outermost coil winding of the plurality of coil windings of each of the first substantially flat spiral transmit coil and the second substantially flat spiral transmit coil has a first outer circumference that is greater than a second outer circumference of an implant coil of the implantable medical device.

9. An inductive power transmitter system comprising: at least two substantially flat spiral transmit coils, wherein the at least two substantially flat spiral transmit coils are at least partially overlapping and substantiallyparallelat least two dedicated transmit drivers configured to drive each of the at least two substantially flat spiral transmit coils, respectively.

10. The inductive power transmitter system of claim 9, wherein a coupling factor between the at least two substantially flat spiral transmit coils is below a predetermined threshold.

11. The inductive power transmitter system of claim 9, wherein the at least two substantially flat spiral transmit coils are substantially uncoupled.

12. The inductive power transmitter system of claim 11, wherein a coupling factor between the at least two substantially flat spiral transmit coils is substantially close to, or equal to, zero.

13. The inductive power transmitter system of claim 9, wherein the at least two substantially flat spiral transmit coils are configured to produce magnetic fields with joined enclosed loop area boundaries in an XY plane, so as to provide substantially uniform and complete coverage for implant locations within a same XY boundary in a Cartesian coordinate system.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 14. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, wherein each of the at least two substantially flat spiral transmit coils comprises three or more coil windings, and an outermost coil winding of the three or more coil windings has a first outer circumference that is greater than a second outer circumference of an implant coil of an implantable medical device coupled with the inductive power transmitter system.

15. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, wherein each of the at least two substantially flat spiral transmit coils comprises three or more coil windings with a fixed radial spacing between the three or more coil windings.

16. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, wherein each of the at least two substantially flat spiral transmit coils comprises three or more coil windings with a different radial spacing between the three or more coil windings.

17. The inductive power transmitter system of claim 16, wherein the three or more coil windings have an increasing radial spacing towards a center of each of the at least two substantially flat spiral transmit coils.

18. The inductive power transmitter system of claim 16, wherein the different radial spacing between the three or more coil windings of the at least two substantially flat spiral transmit coils are configured generate a substantially uniform magnetic field over an area of the at least two substantially flat spiral transmit coils.

19. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, wherein the at least two dedicated transmit drivers are configured to drive each of the at least two substantially flat spiral transmit coils to produce a rotating magnetic field.

20. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, wherein the at least two dedicated transmit drivers are differential drivers.

21. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, further comprising: one or more EMC forks disposed on one or more of the at least two substantially flat spiral transmit coils.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 22. The inductive power transmitter system of claim 9, 10, 11, 12, or 13, wherein the inductive power transmitter system is integrated in at least one of a pillow, a mattress, a chair, or a headrest, and is configured to charge a battery of an implantable medical device coupled with the inductive power transmitter system.

23. A system comprising: an implantable medical device including an implantable coil and a rechargeable an external charging device configured to recharge the rechargeable battery via an inductive power link, wherein the external charging device comprises at least two substantially flat spiral transmit coils that are at least partially overlapping and that each comprise a plurality of coil windings each having a different radial spacing therebetween.

24. The system of claim 23, wherein the external charging device further comprises at least two dedicated transmit drivers that are configured to deliver at least two current signals to the at least two substantially flat spiral transmit coils, respectively, so as to produce at least two magnetic fields.

25. The system of claim 24, wherein the external charging device is configured to transmit the at least two magnetic fields towards the implantable coil of the implantable medical device via the at least two substantially flat spiral transmit coils, respectively.

26. The system of claim 25, wherein the implantable medical device is configured to receive a combined magnetic field via the implantable coil, wherein the combined magnetic field is comprised of the at least two magnetic fields that are transmitted via the at least two substantially flat spiral transmit coils of the external charging device, respectively.

27. The system of claim 23, 24, 25, or 26, wherein the plurality of coil windings have an increasing radial spacing towards a center of each of the at least two substantially flat spiral transmit coils.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 28. The system of claim 23, 24, 25, or 26, wherein an outermost coil winding of the plurality of coil windings of each of the at least two substantially flat spiral transmit coils each has a first outer circumference that is greater than a second outer circumference of the implantable coil of the implantable medical device.

29. The system of claim 23, 24, 25, or 26, wherein a coupling factor between the at least two substantially flat spiral transmit coils is substantially close to or equal to zero, such that the at least two substantially flat spiral transmit coils are substantially uncoupled.

30. A method for wireless power transfer, comprising: generating, via at least two transmit coils of an inductive power transmitter device, a magnetic field towards an implantable medical device, wherein the magnetic field is substantially uniform over an area of the at least two transmit coils.

31. The method of claim 30, wherein the at least two transmit coils are substantially flat spiral transmit coils that are substantially parallel and at least partially overlap with each other.

32. The method of claim 30 or 31, wherein generating the magnetic field towards the implantable medical device via the at least two transmit coils comprises: generating, via a first substantially flat spiral transmit coil of the at least two transmit coils, a first magnetic field towards the implantable medical device; and generating, via a second substantially flat spiral transmit coil of the at least two transmit coils that at least partially overlaps with the first substantially flat spiral transmit coil, a second magnetic field towards the implantable medical device.

33. The method of claim 32, further comprising: delivering, via a first dedicated transmit driver of the inductive power transmitter device, a first current signal to the first substantially flat spiral transmit coil so as to produce the first magnetic field; and delivering, via a second dedicated transmit driver of the inductive power transmitter device, a second current signal to the second substantially flat spiral transmit coil so as to produce the second magnetic field.Atty. Docket No.3065.0751i Client Ref. No. CID03751WOPC1 34. The method of claim 32, further comprising: receiving, via an implantable coil of the implantable medical device, the magnetic field comprised of the first magnetic field and the second magnetic field; and generating, at the implantable coil, a third current signal from the magnetic field to recharge a battery of the implantable medical device.

35. The method of claim 34, wherein the at least two transmit coils each have a first outer circumference that is greater than a second outer circumference of the implantable coil of the implantable medical device.

36. The method of claim 30 or 31, wherein each of the at least two transmit coils is comprised of a plurality of coil windings each having a different radial spacing therebetween.

37. The method of claim 36, wherein the plurality of coil windings have an increasing radial spacing towards a center of the at least two transmit coils, respectively.

38. The method of claim 36, wherein at least an outermost winding of the plurality of coil windings of each of the at least two transmit coils partially overlap with each other.

39. The method of claim 30 or 31, wherein a coupling factor between the at least two transmit coils is substantially close to or equal to zero, such that the at least two transmit coils are substantially uncoupled.

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