Abstract: Optimal power switching circuitry for use in a closed system such as a TET system including an internal device separated from an external device by a boundary. The internal and external devices being powered by separate power sources. During telemetric communication from the external device to the internal device an external RF energy source is produced. If the power supplied by the external RF energy source produced during communication from the external device to the internal device exceeds that required for powering of the internal device, then the power switching circuitry cuts off power to the internal power source and instead draws power from the external RF energy source thereby conserving power consumed from the internal power source. The power switching circuitry may be implemented using either passive components (e.g., diodes) or active components (e.g., an analog switch).

Abstract: A power transfer system for an implanted device, such as an implanted medical device. The implanted device and a power transfer device each include a coil with a magnetically permeable core, so that operatively the coils are magnetically coupled, so as to improve the efficiency of power transfer. The coil resides in an electrically conductive implant case.

Abstract: An implantable transcutaneous energy transfer device secondary coil module includes a housing, a secondary coil, power conditioning circuitry, and a low voltage, high power connector. The transcutaneous energy transfer secondary coil is disposed outside the housing and is configured to receive a time-varying magnetic field provided by a transcutaneous energy transfer primary coil, and to convert the time-varying magnetic field into a high voltage, alternating current electric signal within the coil. The power conditioning circuitry is mounted within the housing and is electrically coupled to the secondary coil. The power conditioning circuitry including electronics for converting the high voltage, alternating current electric signal from the secondary coil into a high power, low voltage direct current electric signal.

Abstract: An implanted coil supplies energy or control signals to, or provides information from, a medical device implanted in a human or animal patient. Preferably, the coil is implanted subcutaneously in the patient at a location suitable for easy access to the coil. The implanted coil is wound from a wire that is formed into a plurality of smaller diameter coils connected in series and positioned perpendicular to the larger implanted coil. Preferably, the wire used to form the implanted coil is a helically-shaped wire that is very resilient, and, thus, capable of handling even extreme movements of a patient in whom it is implanted without the risk of breaking.

Abstract: A system for treating chronic inflammation may include an implantable microstimulator, a wearable charger, and optionally an external controller. The implantable microstimulator may be implemented as a leadless neurostimulator implantable in communication with a cervical region of a vagus nerve. The microstimulator can address several types of stimulation including regular dose delivery. The wearable charger may be worn around the subject's neck to rapidly (<10 minutes per week) charge an implanted microstimulator. The external controller may be configured as a prescription pad that controls the dosing and activity of the microstimulator.

Abstract: A system and method for contactless power transfer in implantable devices for charging rechargeable batteries disposed within the implantable devices are provided. The system includes a first coil electrically couplable to a power source, wherein the first coil is configured to produce a magnetic field. The system further includes a second coil electrically coupled to the rechargeable battery disposed within the implantable device and configured to receive power from the first coil via the magnetic field and to transfer the power to the rechargeable battery. The system also includes a field focusing element disposed between the first coil and the second coil and configured as a self resonant coil having a standing wave current distribution to focus the magnetic field onto the second coil and enhance the coupling between the first coil and the second coil.

Abstract: An implantable device (10) is used to emit electrical stimulation signals to surrounding tissue by means of at least one stimulation electrode (17). The device (10) has an input stage which is connected to a supply unit (12) by a cable, by means of which the input stage is supplied with at least one substantially square electrical AC voltage which is, averaged over time, at least virtually free of a DC voltage with respect to an external ground (29), which can be connected to the tissue (64) (FIG. 1).

Abstract: Systems and methods of the invention generally involve a convertible power transfer system for supplying wireless energy to an implant. According to certain aspect, a system of the invention includes a convertible inductive coil and a receiver inductive coil. The convertible inductive coil may be disposed externally on a body of a patient and to inductively transmit electromagnetic power. The convertible inductive coil transitions between direct electromagnetic power transfer and passive electromagnetic power transfer. The receiver inductive coil can be implanted within the body and provides received electromagnetic power to the implant. The convertible inductive coil, during passive electromagnetic power transfer, couples to the receiver inductive coil such that the convertible inductive coil and receiver inductive coil operate together as single receiver inductive coil that receives inductively transferred electromagnetic power from a distant transmitter inductive coil.

Abstract: A particular method of providing power to an implantable medical device includes providing a first signal to a primary coil that is inductively coupled to a secondary coil of an implantable medical device. The method also include determining a first alignment difference between a voltage corresponding to the first signal and at least one of a current corresponding to the first signal and a component voltage at a component of a primary coil circuit. The method further includes determining a frequency sweep range based on the first alignment difference. The method also includes performing a frequency sweep over the frequency sweep range.

Abstract: It is necessary to periodically replace a cell of an implantable-type cardiac pacemaker device, which causes suffering to a patient as often as a cell is replaced. Thus, it is an object of the present invention to dispense with cell replacement of the cardiac pacemaker device. A cardiac pacemaker device of the present invention has an antenna and a battery built-in, and an electric power is transmitted to the built-in antenna from outside a body by an electromagnetic wave to store the electric power in the battery. With the use of the electric power stored in the battery, a main body of the pacemaker device can operate. If necessary, the electric power can be supplied wirelessly from outside and a surgery for exchanging a cell becomes unnecessary; therefore, a patient's suffering can be relieved.

Abstract: An external processor device is described for a hearing implant system. An external processor housing has a generally planar skin contacting surface and a central axis perpendicular to the skin contacting surface. A signal processor is located within the processor housing for developing an implant data signal. The processor housing also contains a transmitter coil for coupling the implant data signal across the skin to the implantable prosthetic system. A battery container forms an annular compartment around the central axis and contains a battery arrangement to provide electrical power to the signal processor and the transmitter coil.

Abstract: A system includes at least one active energy transfer coil and a first passive energy transfer coil. The active energy transfer coil is configured to couple with a power supply. The at least one active energy transfer coil has an active coupling range. The first passive energy transfer coil is magnetically coupled to the active energy transfer coil and is located within the active coupling range. The first passive energy transfer coil has a passive coupling range. The first passive energy transfer coil is configured to provide energy to a first device located within the passive coupling range and based on energy received from the at least one active energy transfer coil.

Abstract: For supplying energy to a medical implant (100) in a patient's body a receiver (102) cooperates with an external energizer (104) so that energy is wirelessly transferred. A feedback communication system (109) sends feedback information from the receiver to the energizer, the feedback information being related to the transfer of energy to the receiver. The feedback communication system communicates using the patient's body as an electrical signal line. In particular, the communication path between the receiver and the external energizer can be established using a capacitive coupling, i.e. the feedback information can be capacitively transferred over a capacitor having parts outside and inside the patient's body. An energy balance between the amount of energy received in the receiver and the energy used by the medical implant can be followed over time, and then the feedback information is related to the energy balance.

Abstract: In a method and apparatus for controlling transmission of wireless energy to a medical device (100) implanted in a mammal patient, the wireless energy is transmitted from an external energy source (104) located outside a patient and is received by an internal energy receiver (102) located inside the patient, for directly or indirectly supplying received energy to the medical device. An ultrasonic feedback control signal (S) is transmitted from an internal ultrasonic signal transmitter (110) located inside the patient to an external ultrasonic signal receiver (112) located outside the patient. The feedback control signal relates to the energy for operating the medical device and is used for controlling the transmission of wireless energy from the external energy source.

Abstract: A leadless intra-cardiac medical device (LIMD) includes a housing configured to be implanted entirely within a single local chamber of the heart.

Abstract: A neural prosthesis includes a centralized device that can provide power, data, and clock signals to one or more individual neural prosthesis subsystems. Each subsystem may include a number of individually addressable, programmable modules that can be dynamically allocated or shared among neural prosthetic networks to achieve complex, coordinated functions or to operate in autonomous groups.

Abstract: An improved external charger for an implantable medical device is disclosed in which charging is at least partially controlled based on a sensed pressure impingent on its case, which pressure is indicative of the pressure between the external charger and a patient's tissue. The improved external charger includes pressure detection circuitry coupled to one or more pressure sensors for controlling the external device in accordance with the sensed impingent pressure. The sensed pressure can be used to control charging, for example, by suspending charging, by adjusting a maximum set point temperature for the external charger based on the measured pressure, or by issuing an alert via a suitable user interface. By so controlling the external charger on the basis of the measured pressure, the external charger is less likely to create potentially problematic or uncomfortable conditions for the user.

Abstract: A system and method for determining, during a recharge session, an amount of time until a subsequent recharge session is required to charge a rechargeable power source of an implantable medical device. A model allows a determination of the time until recharge without suspending charging during the recharge session by basing the determination on an initial measured battery voltage and a present current into the rechargeable power source. Alternatively, charging is suspended during the recharge session, and voltage measurements are taken, after which time charging is resumed, without patient input or suspending the recharge session.

Abstract: An improved external charger for a battery in an implantable medical device (implant), and technique for charging the battery using such improved external charger, is disclosed. In one example, simulation data is used to model the power dissipation of the charging circuitry in the implant at varying levels of implant power. A power dissipation limit is chosen to constrain the charging circuitry from producing an inordinate amount of heat to the tissue surrounding the implant, and duty cycles are determined for the various levels of input intensities to ensure that the power limit is not exceeded. A maximum simulated average battery current determines the optimal (i.e., quickest) battery charging current, and at least an optimal value for a parameter indicative of that current, for example, the voltage across the battery charging circuitry, is determined and stored in the external charger.

Abstract: A wireless electrostimulation system can comprise a wireless energy transmission source, and an implantable cardiovascular wireless electrostimulation node. A receiver circuit comprising an inductive antenna can be configured to capture magnetic energy to generate a tissue electrostimulation. A tissue electrostimulation circuit, coupled to the receiver circuit, can be configured to deliver energy captured by the receiver circuit as a tissue electrostimulation waveform. Delivery of tissue electrostimulation can be initiated by a therapy control unit.

Abstract: A wireless system for brain monitoring/mapping of neurological-disorder patients includes a plurality of electrodes each configured for surface abutment of brain tissue and main circuitry for placement outside a body of a patient and configured to transmit power at radio frequencies and send and receive data using infrared energy. Remote circuitry is provided for subcutaneous implantation in a head of the patient. The remote circuitry is connected to the plurality of electrodes and includes a multiplexer sampling signals from the plurality of electrodes. The multiplexer outputs electrode signals to an amplifier and A/D converter for transmission to the main circuitry. The remote circuitry is configured to (a) receive transmitted power at radio frequencies from the main circuitry, (b) capture and digitize full-bandwidth EEG signals from each of the electrodes, and (c) send data to and receive data from the main circuitry using infrared energy.

Abstract: A mechanism for transferring energy from an external power source to an implantable medical device is disclosed. A sensor may be used to measure a parameter that correlates to a temperature of the system that occurs during the transcutaneous coupling of energy. For example, the sensor may measure temperature of a surface of an antenna of the external power source. The measured parameter may then be compared to a programmable limit. A control circuit such as may be provided by the external power source may then control the temperature based on the comparison. The programmable limit may be, for example, under software control so that the temperature occurring during transcutaneous coupling of energy may be modified to fit then-current circumstances.

Abstract: Method and systems for optimizing acoustic energy transmission in implantable devices are disclosed. Transducer elements transmit acoustic locator signals towards a receiver assembly, and the receiver responds with a location signal. The location signal can reveal information related to the location of the receiver and the efficiency of the transmitted acoustic beam received by the receiver. This information enables the transmitter to target the receiver and optimize the acoustic energy transfer between the transmitter and the receiver. The energy can be used for therapeutic purposes, for example, stimulating tissue or for diagnostic purposes.

Abstract: Far field telemetry operations are conducted between an external device and an implantable medical device while power is being transferred to the implantable medical device for purposes of recharging a battery of the implantable medical device. The far field operations may include exchanging recharge information that has been collected by the implantable medical device which allows the external device to exercise control over the recharge process. The far field operations may include suspending far field telemetry communications for periods of time while power continues to be transferred where suspending far field telemetry communications may include powering down far field telemetry communication circuits of the implantable medical device for periods of time which may conserve energy. The far field operations may further include transferring programming instructions to the implantable medical device.

Abstract: The present disclosure involves a charging system for charging an implanted medical system. The charging device includes a replenishable power supply. The charging device includes a coil assembly electrically coupled to the power supply. The coil assembly includes a primary coil and a plurality of sense coils positioned proximate to the primary coil. The charging device includes electrical circuitry operable to: measure an electrical parameter of the coil assembly; and determine a position of the coil assembly relative to a position of the implanted medical device based on the measured electrical parameter. The charging device includes a visual communications interface operable to: receive an input from the electrical circuitry; and visually display on a screen the position of the coil assembly relative to the position of the implanted medical device based on the input received from the electrical circuitry.

Abstract: By incorporating magnetic field sensing coils in an external charger, it is possible to determine the position of an implantable device by sensing the reflected magnetic field from the implant. In one embodiment, two or more field sensing coils are arranged to sense the reflected magnetic field. By comparing the relative reflected magnetic field strengths of the sensing coils, the position of the implant relative to the external charger can be determined. Audio and/or visual feedback can then be communicated to the patient to allow the patient to improve the alignment of the charger.

Abstract: An improved external charger for a battery in an implantable medical device (implant), and technique for charging batteries in multiple implants using such improved external charger, is disclosed. During charging, values for a parameter measured in the implants are reported from the implants to the external charger. The external charger infers from the magnitudes of the parameters which of the implants has the highest and lowest coupling to the external charger, and so designates those implants as “hot” and “cold.” The intensity of the magnetic charging field is optimized for the cold implant consistent with the simulation to ensure that that the cold implant is charged with a maximum (fastest) battery charging current. The duty cycle of the magnetic charging field is also optimized for the hot implant consistent with the simulation to ensure that the hot implant does not exceed the power dissipation limit.

Abstract: Techniques are disclosed for recharging an Implantable Medical Device (IMD). In one embodiment, a first external coil is positioned on one side of a patient's body, such as on a front side of the torso in proximity to the IMD. A second external coil is positioned on an opposite side of the patient's body, such as on the back of the torso. A recharging device generates a current in each of the coils, inductively coupling the first and the second coils to the secondary recharge coil of the IMD. According to another aspect, each of the two external coils may wrap around a portion of the patient's body, such as the torso or head, and are positioned such that the IMD lies between the coils. According to this aspect, current generated in the coils inductively couples to a second recharge coil that is angled within the patient's body.

Abstract: An improved external charger for an implantable medical device is disclosed in which charging is at least partially controlled based on a sensed pressure impingent on its case, which pressure is indicative of the pressure between the external charger and a patient's tissue. The improved external charger includes pressure detection circuitry coupled to one or more pressure sensors for controlling the external device in accordance with the sensed impingent pressure. The sensed pressure can be used to control charging, for example, by suspending charging, by adjusting a maximum set point temperature for the external charger based on the measured pressure, or by issuing an alert via a suitable user interface. By so controlling the external charger on the basis of the measured pressure, the external charger is less likely to create potentially problematic or uncomfortable conditions for the user.

Abstract: Described is an apparatus and method for increasing a gain of a transmitted power signal in a wireless link when operating in a mid field wavelength that is within a range between wavelength/100 to 100*wavelength and within a medium having a complex impedance between a transmit antenna and a receive antenna. The apparatus and method maximize the gain in the wireless link using simultaneous conjugate matching, to increase power transfer within the transmitted power signal, wherein the simultaneous conjugate matching accounts for interaction between the transmit antenna and the receive antenna, including the complex impedance of the medium between the transmit antenna and the receive antenna.

Abstract: A transcutaneous energy transfer system, transcutaneous charging system, external power source, external charger and methods of transcutaneous energy transfer and charging for an implantable medical device and an external power source/charger. The implantable medical device has a secondary coil adapted to be inductively energized by an external primary coil at a carrier frequency. The external power source/charger has a primary coil and circuitry capable of inductively energizing the secondary coil by driving the primary coil at a carrier frequency adjusted to the resonant frequency to match a resonant frequency of the tuned inductive charging circuit, to minimize the impedance of the tuned inductive charging circuit or to increase the efficiency of energy transfer.

Abstract: Apparatus and methods for charging an implanted medical device.

Abstract: A system for treating chronic inflammation may include an implantable microstimulator, a wearable charger, and optionally an external controller. The implantable microstimulator may be implemented as a leadless neurostimulator implantable in communication with a cervical region of a vagus nerve. The microstimulator can address several types of stimulation including regular dose delivery. The wearable charger may be worn around the subject's neck to rapidly (<10 minutes per week) charge an implanted microstimulator. The external controller may be configured as a prescription pad that controls the dosing and activity of the microstimulator.

Abstract: The disclosed invention varies the width of the energy pulses with constant frequency and constant amplitude to regulate the amount of energy transferred from an energy transmitting device placed outside a patient to an energy receiver inside the patient. The pulse width is achieved with a modulation technique, PWMT, to control the amount of energy transferred from the external energy transmitting coil in the system to the implanted receiver. The PWMT is used to digitally vary the amount of power from the power amplifier that drives the transmitting coil. Compared to previous analog systems a PWM system is a great deal more efficient and can easily be controlled from a digital domain system such as a microprocessor.

Abstract: Receiver-stimulator with folded or rolled up assembly of piezoelectric components, causing the receiver-stimulator to operate with a high degree of isotropy are disclosed. The receiver-stimulator comprises piezoelectric components, rectifier circuitry, and at least two stimulation electrodes. Isotropy allows the receiver-stimulator to be implanted with less concern regarding the orientation relative the transmitted acoustic field from an acoustic energy source.

Abstract: An injectable leadless heart stimulation and/or monitoring system is provided that includes an device having a sealed housing, one or more electrodes configured to electrically contact heart tissue when in use and electric components arranged within the housing. The electric components are at least in part operationally connected to the at least one electrode. The electric components include a power supply for providing power to the electric components. The power supply includes a rechargeable battery and further includes an implant-based coil that is configured to receive electric power via a tuned magnetic or electromagnetic field.

Abstract: An implantable stimulation system comprises an implantable stimulator and a control device. The control device is configured to transmit acoustic waves to the implantable stimulator, and the implantable stimulator is configured to transform the acoustic waves into electrical current, and generate stimulation energy based on the electrical current. For example, the electrical current can be transformed into electrical energy that can be used to generate the stimulation energy. Or the electrical current can contain signals used to directly or indirectly control the generation of the stimulation energy.

Abstract: Systems and methods are disclosed to stimulate tissue to treat medical conditions involving tissues such as the bone, spine, stomach, nerves, brain and the cochlea. The disclosed invention uses electrical stimulation of the tissue, where vibrational (or acoustic) energy from a source is received by an implanted device and converted to electrical energy and the converted electrical energy is used by implanted electrodes to stimulate the pre-determined tissue sites. The vibrational energy is generated by a controller-transmitter, which could be either implanted or located externally. The vibrational energy is received by a receiver-stimulator, which could be located at or close to the stimulation site.

Abstract: One aspect of the invention relates to an implantable medical device comprising a device housing (100), at least one radio frequency circuit (104) for radio frequency communication, at least one antenna, at least one terminal to electromagnetically couple said at least one antenna to said at least one radio frequency circuit, and a dielectric compartment (101, 1661) that encompasses at least a portion of said at least one antenna. The antenna comprises a conducting pattern, at least a portion of which is shaped as a curve, wherein said curve comprises at least five segments, wherein each of said at least five segments forms an angle with each adjacent segment in said curve, wherein at least three of the at least five segments of said curve are shorter than one-fifth of the longest free-space operating wavelength of the antenna, wherein each angle between adjacent segments is less than 180°, and at least two of the angles between adjacent sections are less than approximately 115°.

Abstract: Power management methods, systems and circuitry are provided for efficiently energizing implanted stimulators. Efficiency is achieved by automatically adjusting the power-supply voltage of the stimulator channel so that the magnitude of the voltage of the current-sink or current-source providing the stimulation current is regulated within a narrow band just above the minimum acceptable level. Adjustment is done once in every cycle of the external high-frequency power source in order to achieve regulation with a very fine time resolution throughout each stimulation period. The power supply voltage is generated and adjusted by rectifying the high-frequency voltage of the secondary coil of a transcutaneous magnetic link by closing and opening a solid-state switch at appropriate times during positive half cycles for a current-sink, and during negative half-cycles for a current-source.

Abstract: The present invention an implantable, sub-cutaneous, bellows-like device with one plate proximal (or superficial) to the skin surface and the other plate distal (or deep) to the skin surface having a component of a pneumatic/hydraulic driver for an implantable medical device such as a cardiac assist, cardiac support, or combined cardiac assist and support device and inducible magnet material on the distal plate of the bellows that can be magnetically drawn towards the proximal plate by the action of a magnet outside the body to contract the bellows or pressurize the fluid in the bellows.

Abstract: Techniques for transcutaneous transferral of energy to an implantable medical device are disclosed. An embodiment includes a system comprising an implantable medical device having a secondary coil. An external device is provided to transcutaneously transfer energy to the secondary coil. The external device comprises a housing having a side adapted to be positioned in proximity to the secondary coil when the external device is transferring energy to the secondary coil. A temperature sensor is coupled to the side to determine a temperature indicative of heat to which the patient is being exposed during the transfer of energy. A control circuit is adapted to control the transfer of energy to the secondary coil based on the temperature. For instance, the control circuit may limit transfer of energy by controlling times at which transfer of energy occurs or controlling an amplitude of a signal within the external device.

Abstract: By incorporating magnetic field-inducing position determination coils (PDCs) in an external charger, it is possible to determine the position of an implantable device by actively inducing magnetic fields using the PDCs and sensing the reflected magnetic field from the implant. In one embodiment, the PDCs are driven by an AC power source with a frequency equal to the charging coil. In another embodiment, the PDCs are driven by an AC power source at a frequency different from that of the charging coil. By comparing the relative reflected magnetic field strengths at each of the PDCs, the position of the implant relative to the external charger can be determined. Audio and/or visual feedback can then be communicated to the patient to allow the patient to improve the alignment of the charger.

Abstract: A neural prosthesis includes a centralized device that can provide power, data, and clock signals to one or more individual neural prosthesis subsystems. Each subsystem may include a number of individually addressable, programmable modules that can be dynamically allocated or shared among neural prosthetic networks to achieve complex, coordinated functions or to operate in autonomous groups.

Abstract: An implantable stimulation system comprises an implantable stimulator and a control device. The control device is configured to transmit acoustic waves to the implantable stimulator, and the implantable stimulator is configured to transform the acoustic waves into electrical current, and generate stimulation energy based on the electrical current. For example, the electrical current can be transformed into electrical energy that can be used to generate the stimulation energy. Or the electrical current can contain signals used to directly or indirectly control the generation of the stimulation energy.

Abstract: External power source, system for controlling and method for predicting heat loss of implantable medical device during inductive recharging by an external primary coil. A primary coil inductively couples energy to a secondary coil when energized and placed in proximity of the secondary coil. Control circuitry, operatively coupled to said primary coil, determines the energy absorbed in said tissue based on a total applied power by said external power source, power lost in said electronic circuitry, power lost in said electronic circuitry, power lost in said primary coil and power applied to said rechargeable power source and controlling said total applied power based upon said energy absorbed in said tissue.

Abstract: An improved integrated external controller/charger system useable with an implantable medical device is disclosed. The system comprises two main components: an external controller and an external charging coil assembly that is coupleable thereto. When the external charging coil assembly is coupled to the external controller, the system can be used to both send and receive data telemetry to and from the implantable medical device, and to send power to the device. Specifically, the external controller controls data telemetry by energizing at least one coil within the external controller, and the external controller controls power transmission by energizing a charging coil in the external charging coil assembly, which is otherwise devoid of its own control, power, and user interface. The result is a cheaper, simpler, more compact, and more convenient data telemetry and charging solution for the patient having a medical implant.

Abstract: A medical device having a unit in communication with ancillary components wherein the unit and the ancillary components each have a sensory output through which communication with a user of the medical device may be accomplished and to which the user's attention directed. In one aspect, the medical device is an AED unit with associated pads, which are an ancillary component electrically connected to the AED unit. In this illustrative example, the unit has a unit sensory output (e.g., a speaker or a display), and the pads, and/or their associated packaging, have an ancillary sensory output (e.g. a speaker or display). Programming in the AED unit controls output to the sensory outputs such that the user's attention is directed between the unit and the ancillary components.

Abstract: According to some embodiments, a method of treating a subject having diabetes or symptoms associated with diabetes is provided. The method includes delivering a neuromodulation catheter within a vessel (e.g., hepatic artery) having surrounding nerves that innervate the liver (e.g., sympathetic nerves of the hepatic plexus). The method may also include modulating (e.g., disrupting, ablating, stimulating) the nerves by mechanical compression, energy delivery, or fluid delivery.

Abstract: By incorporating magnetic field sensing coils in an external charger, it is possible to determine the position of an implantable device by sensing the reflected magnetic field from the implant. In one embodiment, two or more field sensing coils are arranged to sense the reflected magnetic field. By comparing the relative reflected magnetic field strengths of the sensing coils, the position of the implant relative to the external charger can be determined. Audio and/or visual feedback can then be communicated to the patient to allow the patient to improve the alignment of the charger.