Implantable medical device with wireless coil configured to receive wireless power from an external charger

Abstract

An implantable medical device is disclosed that is capable of wirelessly receiving power from a magnetic field to power the IMD or charge its battery, but without using a wire-wound coil for magnetic field reception. The IMD may include a housing that houses control circuitry of the IMD, wherein at least a portion of the housing is conductive, wherein a housing current is formed in the conductive housing portion in response to the magnetic field. The IMD includes power receiving circuitry within the housing, and includes various examples of first and second electrical connections for transferring at least some of the housing current to the power receiving circuitry as a power current, thereby allowing the power receiving circuitry to use the power current to power the IMD or charge its battery.

Description

Technical Field

[0001] The present invention relates to implantable medical devices and apparatus for wirelessly receiving power from an external charger. Background Art

[0002] Implantable stimulation devices are devices that generate electrical stimulation and deliver it to the body's nerves and tissues for the treatment of various biological diseases, such as pacemakers for treating arrhythmias, defibrillators for treating cardiac fibrillation, cochlear stimulators for treating deafness, retinal stimulators for treating blindness, muscle stimulators for producing coordinated limb movements, spinal cord stimulators for treating chronic pain, cortical and deep brain stimulators for treating movement and psychological disorders, and other neurostimulators for treating urinary incontinence, sleep apnea, shoulder subluxation, etc. The following description will generally focus on the use of the present invention in a Spinal Cord Stimulation (SCS) system (such as the system disclosed in U.S. Patent 6,516,227). However, the present invention may find application in any implantable medical device system (including a Deep Brain Stimulation (DBS) system).

[0003] As shown in Figures 1A to 1B, the SCS system generally includes an implantable pulse generator (IPG) 10 (more generally, an implantable medical device (IMD) 10) that includes a biocompatible device housing 12 formed, for example, of a conductive material (such as titanium). The housing 12 generally holds a control circuit system 86 (Figure 3) and a battery 14 (Figure 1B) necessary for the IMD 10 to function. The IMD 10 is coupled to electrodes Ex 16 via one or more electrode leads 18, so that the electrodes 16 form an electrode array 20. The electrodes 16 are carried on a flexible body 22, which also accommodates individual signal lines 24 coupled to each electrode. In the illustrated embodiment, there are eight electrodes (Ex) on two leads 18, although the number of leads and electrodes is application-specific and can therefore vary. Leads 18 are coupled to lead connectors 26 in IMD 10, which are secured in a non-conductive header material 28 (such as epoxy). Feedthrough pins 23 are connected to electrode contacts (not shown) in lead connector 26, which pass through sealed feedthroughs 25 on the top of housing 12, where they are connected to stimulation circuitry inside the housing of IMD 10. Control circuitry 86 may include stimulation circuitry configured to provide stimulation current to selected ones of the electrodes, and may include, for example, circuitry disclosed in USP 6,181,969, 8,606,362, 8,620,436, U.S. Patent Application Publications 2018 / 0071520, and 2019 / 0083796. The conductive housing 12 material may also operate as housing electrode Ec, thereby providing a return current path for current provided at lead-based electrode Ex.

[0004] As shown in the cross-section of FIG. 1B , the IMD 10 typically includes a printed circuit board (PCB) 29 and various electronic components 32 mounted to the PCB 29, some of which will be discussed later. The IMD 10 conventionally includes a charging coil 30 for charging or recharging the battery 14 of the IMD using an external charger. The housing 12 is typically formed of two clam-shell-like portions 12i and 12o, which are designed to face the interior and exterior of the patient, respectively, when implanted. These portions 12i and 12o are typically welded (11) together along the periphery of the housing and include a flange welded to the feedthrough 25. When so formed, the housing 12 includes flat, parallel major surfaces formed in the outer and inner housing portions 12o and 12i, and a substantially flat top surface 12t perpendicular to the major surfaces that includes the feedthrough 25.

[0005] 2A and 2B show an IMD 10 in communication with an external charger and show two different examples of chargers 40 and 60. Both types of chargers 40 and 60 are used to wirelessly deliver power to the IMD 10 in the form of an electromagnetic field 55 (referred to as a "magnetic field"), which power can be used to recharge the battery 14 of the IMD. The transmission of power from the external charger 40 is achieved through the primary charging coil 44 in FIG. 2A and through the primary charging coil 66 in FIG. 2B. FIG. 2A shows an example in which the charging coil 44 is integrated into the same housing as the other charger electronics, while in FIG. 2B, the charging coil 66 and the charger electronics are separated into different housings and connected by a cable 68.

[0006] In FIG2A , the integrated charger 40 includes a PCB 46 on which electronic components 48 are placed, some of which will be discussed later. A charging coil 44 can be mounted to the PCB 46, and is preferably mounted on the side of the PCB facing the IMD 10, as shown. A user interface including touchable buttons, LEDs (not shown), and possible displays and speakers (not shown) allows a patient or clinician to operate the external charger 40. In FIG2A , the user interface is simply shown as including an on / off button 42 for turning the magnetic field 55 on or off. A battery 50 provides power to the external charger 40, which itself can be rechargeable. The charger 40 is typically configured to be handheld and portable, and is further described in U.S. Patent Application Publication 2017 / 0361113.

[0007] In FIG. 2B , charger 60 includes a charging coil assembly 62 and an electronics module 64 in separate housings connected by a cable 68. Charging coil assembly 62 includes a charging coil 66, while electronics and user interface elements are provided by electronics module 64. Electronics housing 64 may include a PCB 70, a battery 72, various control circuit systems 74, and user interface elements 76 (such as those mentioned above). Charger 60 (although typically in the form of two pieces 62 and 64) is also typically configured to be handheld and portable, and is further described again in the 2017 / 0361113 publication referenced above.

[0008] The transmission of magnetic field 55 from one of chargers 40 or 60 to IMD 10 occurs wirelessly and percutaneously through the patient's tissue via inductive coupling. FIG3 shows details of the circuitry used to implement this functionality. Primary charging coil 44 or 66 in an external charger is energized with AC current Icharge by charging circuit 64 to generate an AC magnetic charging field 55. A tuning capacitor 45 is provided to form a resonant LC tank with charging coil 44 or 66 that generally sets the frequency of AC magnetic field 55.

[0009] The magnetic portion of the electromagnetic field 55 induces a current Icoil in the secondary charging coil 30 within the IMD 10, which is received at the power receiving circuit system 81. The power receiving circuit system 81 may include a tuning capacitor 80 for tuning the resonance of the LC circuit in the IMD to the frequency of the magnetic field. Those skilled in the art will appreciate that the capacitors 45 or 80 may be placed in series or in parallel with their respective coils (inductors) 44 / 66 or 30, although it is preferred that the capacitor 45 is placed in series with the coil 44 / 66 in the charger 40 / 60 and the capacitor 80 is placed in parallel with the coil 30 in the IMD 10. The power receiving circuit system 81 also includes a rectifier 82 for converting the AC voltage on the coil 30 into a DC voltage Vdc. The power receiving circuit system 81 may also include other regulation circuit systems (such as charging and protection circuit systems 84) to generate a voltage Vbat, which may be used to provide regulated power to the IMD 10 and generate a current Ibat for charging the battery 14. The frequency of the magnetic field 55 may be around 80 kHz.

[0010] The IMD 10 may also communicate data back to the external charger 40 or 60, and this may be done in different ways. As explained in the 2017 / 0361113 publication referenced above, the IMD 10 may employ reflected impedance modulation to transmit data to the charger, which is sometimes referred to in the art as Load Shift Keying (LSK) and involves modulating the impedance of the charging coil 30 with data bits provided by the control circuitry 86 of the IMD 10. The IMD may also use a communication channel separate from the communication channel used to provide power to transmit data to the charger, although such an alternative channel and the required antenna are not shown for simplicity. The charger 40 or 60 may include a demodulation circuitry 68 to recover the transmitted data and send such data to the charger's control circuitry 72. Such data telemetered from the IMD 10 to the charger 40 / 60 may include useful information for the charger to know during charging, such as the temperature of the IMD (sensed by the temperature sensor 87), the voltage Vbat of the battery 14 of the IMD, or the charging current Ibat provided to the battery. Charger 40 / 60 may use this telemetry data to control the generation of magnetic field 55, such as by increasing or decreasing the magnitude of magnetic field 55 (by increasing or decreasing Icharge), or by starting or stopping the generation of magnetic field 55. As explained in the 2017 / 0361113 publication referenced above, charger 40 / 60 may also be used to determine the alignment of charging coil 44 / 66 with IMD 10, and may include an alignment indicator (LED or sound) that a user may view to determine how to reposition the charger to better align with IMD 10 for more efficient power transfer. Summary of the invention

[0011] An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field is disclosed, which may include: a shell that houses a control circuit system of the IMD, wherein at least a portion of the shell is conductive and wherein a shell current is formed in the conductive shell portion in response to the electromagnetic field; a power receiving circuit system inside the shell; and a first electrical connection portion and a second electrical connection portion for transferring at least some of the shell current to the power receiving circuit system as a power current, wherein the power receiving circuit system is configured to use the power current to provide power to the IMD.

[0012] In one example, the IMD also includes a non-conductive head attached to the shell. In one example, at least one of the first electrical connection and the second electrical connection includes an antenna portion in or on the head, resulting in at least one antenna portion in or on the head. In one example, the IMD also includes one or more lead connectors in the head, a feedthrough between the head and the shell, and a plurality of electrode feedthroughs, wherein the electrode feedthroughs are connected to contacts in the lead connector and pass through the feedthrough inside the shell. In one example, at least one of the first electrical connection and the second electrical connection includes a feedthrough line connected to at least one antenna portion passing through the feedthrough. In one example, at least one antenna portion is formed by the material of the shell. In one example, the shell includes a flat surface configured to face the outside of the patient when implanted, wherein at least one antenna portion is offset toward the external flat surface in or on the head. In one example, there is a first antenna portion in or on the head including a first electrical connection, and there is a second antenna portion in or on the head including a second electrical connection. In one example, the first antenna portion includes a first end and a second end, and wherein the second antenna portion includes a first end and a second end. In one example, the first electrical connection also includes a first wire connected to a first end of the first antenna portion, wherein the second end of the first antenna portion is connected to the conductive housing portion, wherein the second electrical connection also includes a second wire connected to the first end of the second antenna portion, wherein the second end of the second antenna portion is connected to the conductive housing portion. In one example, there is a single antenna portion in or on the head including the first electrical connection. In one example, the single antenna portion includes a first end and a second end, wherein the first electrical connection also includes a first wire connected to the first end of the single antenna portion, wherein the second end of the single antenna portion is connected to the conductive housing portion. In one example, the second electrical connection includes a second wire connected to the conductive housing portion. In one example, there is a single antenna portion in or on the head including the first electrical connection and the second electrical connection. In one example, the single antenna portion includes a cross member connected to the conductive housing portion along its length. In one example, the first electrical connection includes a first wire connected to the first end of the single antenna portion, and wherein the second electrical connection includes a second wire connected to the second end of the single antenna portion. In one example, the single antenna portion includes a cross member connected to the conductive housing portion at a first contact and at a second contact, wherein there is a space between the cross member and the housing between the first contact and the second contact. In one example, the first electrical connection includes a first contact and a first line connected to a first end of the single antenna portion, and wherein the second electrical connection includes a second contact and a second line connected to a second end of the single antenna portion. In one example, the first connection and the second connection are not formed in or on the header.In one example, at least one of the first electrical connection and the second electrical connection includes a wire connected to the conductive housing portion. In one example, the first electrical connection includes a first wire connected to the conductive housing portion at a first contact, and wherein the second electrical connection includes a second wire connected to the conductive housing portion at a second contact. In one example, the first electrical connection and the second electrical connection are separated by a portion of the housing having a first conductivity, and wherein the conductive housing portion forming the housing current has a second conductivity higher than the first conductivity. In one example, the power receiving circuit system includes a rectifier configured to convert the power current into a DC voltage for providing power to the IMD. In one example, the IMD also includes a battery within the housing, wherein the power receiving circuit system is configured to use the power current to provide power to the IMD to charge the battery. In one example, the conductive housing portion includes a conductive layer applied to the housing. In one example, the IMD does not include a header. In one example, the housing includes a dielectric material, and wherein the conductive housing portion includes a conductive window. In one example, the dielectric material includes a ceramic. In one example, the conductive window is attached to the dielectric material in a manner that covers a hole in the dielectric material. In one example, the conductive window comprises a plate attached to or in a dielectric material. In one example, the control circuit system further comprises a stimulation circuit system for forming a stimulation current at a selected electrode of a plurality of electrodes in contact with the patient's tissue, wherein the conductive window comprises one of the plurality of electrodes. In one example, the conductive window is configured to contact the patient's tissue and is further configured to operate as a housing electrode. In one example, the power receiving circuit system is not coupled to a wire wound coil configured to receive an electromagnetic field.

[0013] An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field is disclosed, which may include: a shell that houses a control circuit system for the IMD, wherein at least a portion of the shell is conductive and wherein a shell current is formed in the conductive shell portion in response to the electromagnetic field; a power receiving circuit system inside the shell; a non-conductive head attached to the shell; and a first electrical connection and a second electrical connection for transferring at least some of the shell current to the power receiving circuit system as a power current, wherein the first electrical connection includes a first antenna portion in or on the head, and wherein the second electrical connection includes a second antenna portion in or on the head, wherein the power receiving circuit system is configured to provide power to the IMD using the power current.

[0014] In one example, the IMD also includes one or more lead connectors in the head, a feedthrough between the head and the shell, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines are connected to contacts in the lead connector and pass through the feedthrough inside the shell. In one example, the first electrical connection includes a first feedthrough line connected to the first antenna part passing through the feedthrough, wherein the second electrical connection includes a second feedthrough line connected to the second antenna part passing through the feedthrough. In one example, the first antenna part and the second antenna part are formed by the material of the shell. In one example, the shell includes a flat surface configured to face the outside of the patient when implanted, wherein the first antenna part and the second antenna part are offset toward the external flat surface in or on the head. In one example, the first antenna part includes a first end and a second end, and wherein the second antenna part includes a first end and a second end. In one example, the first electrical connection also includes a first wire connected to the first end of the first antenna part, wherein the second end of the first antenna part is connected to the conductive shell part, wherein the second electrical connection also includes a second wire connected to the first end of the second antenna part, wherein the second end of the second antenna part is connected to the conductive shell part. In one example, the first wire and the second wire pass through the feedthrough in the shell. In one example, the first and second wires are connected to the first end of the first antenna portion and the first end of the second antenna portion through one or more openings in the housing. In one example, the housing includes a flat surface configured to face the outside of the patient when implanted, wherein one or more openings are formed in the flat surface. In one example, the second end of the first antenna portion and the second end of the second antenna portion are connected to the top of the housing. In one example, the housing includes a flat surface configured to face the outside of the patient when implanted, wherein the second end of the first antenna portion and the second end of the second antenna portion are connected to the flat surface. In one example, the power receiving circuit system includes a rectifier configured to convert the power current into a DC voltage for providing power to the IMD. In one example, the IMD also includes a battery within the housing, wherein the power receiving circuit system is configured to use the power current to provide power to the IMD to charge the battery. In one example, the conductive housing portion includes a conductive layer applied to the housing. In one example, the conductive layer is also applied to the first antenna portion and the second antenna portion. In one example, the conductive layer is applied inside the housing. In one example, the housing includes a window of a material different from the material of the housing, wherein the conductivity of the window material is less than the conductivity of the material of the housing. In one example, the conductive housing portion at least partially surrounds the window. In one example, the housing includes a planar surface configured to face exteriorly of the patient when implanted, wherein the window is formed in the planar surface. In one example, the power receiving circuitry is not coupled to a wire wound coil configured to receive an electromagnetic field.

[0015] An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field is disclosed, which may include: a shell that houses a control circuit system for the IMD, wherein at least a portion of the shell is conductive and wherein a shell current is formed in the conductive shell portion in response to the electromagnetic field; a power receiving circuit system inside the shell; a non-conductive head attached to the shell; and a first electrical connection and a second electrical connection for transferring at least some of the shell current to the power receiving circuit system as a power current, wherein at least the electrical connection includes a single antenna portion in or on the head, and wherein the power receiving circuit system is configured to provide power to the IMD using the power current.

[0016] In one example, the IMD also includes one or more lead connectors in the head, a feedthrough between the head and the shell, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines are connected to contacts in the lead connector and pass through the feedthrough inside the shell. In one example, at least one of the first connection and the second connection includes a feedthrough line connected to a single antenna portion passing through the feedthrough. In one example, the single antenna portion is formed by the material of the shell. In one example, the shell includes a flat surface configured to face the outside of the patient when implanted, wherein the single antenna portion is offset toward the external flat surface in or on the head. In one example, the single antenna portion includes only a first electrical connection and does not include a second electrical connection. In one example, the single antenna portion includes a first end and a second end, wherein the first electrical connection also includes a first line connected to the first end of the single antenna portion, wherein the second end of the single antenna portion is connected to the conductive shell portion. In one example, the second electrical connection includes a second line connected to the conductive shell portion. In one example, the single antenna portion in or on the head includes a first electrical connection and a second electrical connection. In one example, the single antenna portion includes a cross member connected to the conductive shell portion along its length. In one example, the first electrical connection includes a first wire connected to a first end of a single antenna portion, and wherein the second electrical connection includes a second wire connected to a second end of the single antenna portion. In one example, the single antenna portion includes a cross member connected to a conductive housing portion at a first contact and at a second contact, wherein there is a space between the housing between the cross member and the first contact and the second contact. In one example, the first electrical connection includes a first contact and a first wire connected to a first end of the single antenna portion, and wherein the second electrical connection includes a second contact and a second wire connected to a second end of the single antenna portion. In one example, the power receiving circuit system includes a rectifier configured to convert a power current into a DC voltage for providing power to the IMD. In one example, the IMD also includes a battery within the housing, wherein the power receiving circuit system is configured to use the power current to provide power to the IMD to charge the battery. In one example, the conductive housing portion includes a conductive layer applied to the housing. In one example, the conductive layer is also applied to the single antenna portion. In one example, the conductive layer is applied inside the housing. In one example, the housing includes a window of a material different from the material of the housing, wherein the conductivity of the window material is less than the conductivity of the material of the housing. In one example, the conductive housing portion at least partially surrounds the window. In one example, the housing includes a planar surface configured to face exteriorly of the patient when implanted, wherein the window is formed in the planar surface. In one example, the power receiving circuitry is not coupled to a wire wound coil configured to receive an electromagnetic field.

[0017] An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field is disclosed, which may include: a shell that houses a control circuit system of the IMD, wherein at least a portion of the shell is conductive and wherein a shell current is formed in the conductive shell portion in response to the electromagnetic field; a power receiving circuit system inside the shell; and a first electrical connection and a second electrical connection for transferring at least some of the shell current to the power receiving circuit system as a power current, wherein the first electrical connection includes a first contact formed on the conductive shell portion, and wherein the second electrical connection includes a second contact formed on the conductive shell portion, wherein the power receiving circuit system is configured to provide power to the IMD using the power current.

[0018] In one example, the IMD also includes a non-conductive head attached to the housing. In one example, the IMD also includes one or more lead connectors in the head, a feedthrough between the head and the housing, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines are connected to contacts in the lead connector and pass through the feedthrough inside the housing. In one example, the first connection portion and the second connection portion are not formed in or on the head. In one example, the first electrical connection portion includes a first line connected to a conductive housing portion at a first contact, and wherein the second electrical connection portion includes a second line connected to the conductive housing portion at a second contact. In one example, the first contact and the second contact are separated by a portion of the housing having a first conductivity, and wherein the conductive housing portion forming the housing current has a second conductivity higher than the first conductivity. In one example, the conductive housing portion includes a conductive layer applied to the housing. In one example, the conductive layer is applied outside the housing. In one example, the conductive layer is applied inside the housing. In one example, the portion of the housing having a first conductivity includes a window of a material different from the material of the housing. In one example, the conductive housing portion at least partially surrounds the window. In one example, the housing includes a flat surface configured to face the outside of the patient when implanted, wherein the window is formed in the flat surface. In one example, the window includes a dielectric material, and the conductive housing portion includes a metal material. In one example, the window and the conductive housing portion include a metal material. In one example, the first contact is formed outside the conductive housing portion through an opening in the conductive housing portion, and wherein the second contact is formed outside the conductive housing portion through an opening in the conductive housing portion. In one example, the first contact and the second contact include conductive pins, respectively. In one example, the first contact is formed inside the conductive housing portion, and wherein the second contact is formed inside the conductive housing portion. In one example, the power receiving circuit system includes a rectifier configured to convert the power current into a DC voltage for providing power to the IMD. In one example, the IMD also includes a battery in the housing, wherein the power receiving circuit system is configured to use the power current to provide power to the IMD to charge the battery. In one example, the IMD does not include a head. In one example, the housing includes a dielectric material, and wherein the conductive housing portion includes a conductive window. In one example, the dielectric material includes ceramic. In one example, the conductive window is attached to the dielectric material in a manner covering the hole in the dielectric material. In one example, the conductive window includes a plate attached to or in the dielectric material. In one example, the control circuit system also includes a stimulation circuit system for forming a stimulation current at a selected electrode of a plurality of electrodes in contact with the patient's tissue, wherein the conductive window includes one of the plurality of electrodes. In one example, the conductive window is configured to contact the patient's tissue and is also configured to operate as a housing electrode.In one example, the power receiving circuitry is not coupled to a wire wound coil configured to receive an electromagnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 1A and 1B show different views of an implantable pulse generator, ie, an implantable medical device (IMD), according to the prior art.

[0020] 2A and 2B illustrate different examples of an external charger for wirelessly charging a battery of an IMD or providing power to the IMD.

[0021] FIG. 3 shows an external charger and related charging circuitry in an IMD according to the prior art.

[0022] 4A to 4D A first example of an improved IMD without a wire wound coil but capable of receiving wireless power from an external charger by utilizing eddy currents generated in a conductive housing of the IMD is shown, wherein one or more antenna portions are disposed in a head region of the IMD.

[0023] Figure 5 A second example of an improved IMD is shown in which the antenna portion is differently connected to the housing of the IMD.

[0024] FIG. 6A to FIG. 6C A third example of an improved IMD using a single antenna section is shown.

[0025] Figure 7 A fourth example of an improved IMD is shown in which the antenna portion is formed using the material of the housing.

[0026] Figure 8 A fifth example of an improved IMD is shown in which a conductive layer is used to enhance the flow of eddy currents.

[0027] Fig. 9 A sixth example of an improved IMD is shown in which a lower conductivity window is used in the housing to enhance the flow of eddy currents.

[0028] Fig. 10A and Fig. 10B A seventh example of an improved IMD is shown which does not use an antenna portion in the head region but uses a conductive layer to intensify the flow of eddy currents.

[0029] Fig.11 An eighth example of an improved IMD is shown that does not use an antenna portion in the head region but uses a lower conductivity window in the housing to enhance the flow of eddy currents.

[0030] FIG. 12A to FIG. 12C A ninth example of an improved IMD in a smaller form factor is shown.

[0031] Fig.13 A tenth example of an improved IMD including two conductive housing modules is shown.

[0032] Fig.14 An eleventh example of an improved IMD lacking a head attached to the housing is shown. DETAILED DESCRIPTION

[0033] The inventors see room for improvement in wireless charging of IMDs. In particular, the inventors have found that, unfortunately, conventional IMDs like IMD 10 require a mechanically wound secondary coil 30 to pick up the magnetic field 55. Such coils are relatively expensive, difficult to operate, and may be subject to reliability issues. Typically, such charging coils 30 are made of multiple strands of copper Litz wire, which increases wire conductivity and improves AC performance, but is complex and expensive. Such coils 30 are usually wound and formed on a mandrel before being assembled to the IMD 10. It may be difficult to connect the coil 30 to the PCB 29, and such a connection may be disconnected and become unreliable. In addition, the coil 30 may occupy a large volume in the housing 12 of the IMD, which may hinder making the IMD 10 smaller and more convenient for the patient. The inventors desire to provide an IMD that is capable of wirelessly receiving power from an external charger, but does not include a wound coil 30.

[0034] The inventors note that, as already mentioned, the housing 12 of the IMD 10 is generally conductive, and thus it is reactive to the incoming magnetic field 55. Specifically, the magnetic portion of the AC magnetic field 55 will induce AC eddy currents in the housing 12. As is well known, eddy currents include current loops induced within conductive materials according to Faraday's law of induction. The eddy currents flow in a closed loop in a plane perpendicular to the magnetic field 55, and thus will flow significantly in the external housing portion 12o of the IMD facing the external charger. The amplitude of the current in a given loop is proportional to the strength of the magnetic field, the area of ​​the loop, and the rate of change of the flux, and is proportional to the conductivity of the material. The eddy currents flow in the conductive material at skin depth, and thus are more prevalent at the outer surface of the housing portion 12o facing the impinging magnetic field 55.

[0035] Eddy currents are generally considered an undesirable effect when charging an IMD. When eddy currents are induced, some of the power in magnetic field 55 is lost in housing 12, thereby reducing the power reaching charging coil 30 inside the housing. In short, housing 12 generally attenuates the power that can reach coil 30 to the point where it is useful for charging battery 14 of the IMD. In addition, the eddy currents generated in housing 12 are generally lost as heat, and therefore charging by magnetic induction presents a risk that the housing may overheat, which is a unique safety issue when one considers that IMD 10 is designed to be implanted in a patient.

[0036] Despite such conventional wisdom, the inventors desire to provide an improved IMD that harnesses the power of eddy currents generated at least in part in the housing 12 of the IMD during magnetic induction charging, and uses such harnessed power to charge the battery 14 of the IMD (or, more generally, to provide power to the IMD). In doing so, the inventors' improved IMD design does not require a wire-wound secondary charging coil 30, which reduces manufacturing cost and complexity, and reduces reliability issues inherent in using wire-wound coils. Furthermore, the lack of a secondary charging coil 30 allows the IMD to be made smaller and more convenient for the patient.

[0037] A first example of such an improved IMD 100 is shown in Figure 4A In this example, antenna portions 102a and 102b are included in header 28 of IMD 100. At this point, note that such antenna portions are not strictly required in all embodiments (as described later in Fig. 10A As explained at the beginning) is useful.

[0038] Antenna portions 102a and 102b are not wound coils and are preferably not made of wire, but they can be. Instead, antenna portions 102a and 102b are preferably formed of metal sheets into the shapes shown. Portions 102a and 102b are preferably conductive and can be made of any number of conductive materials or alloys, such as those containing titanium, copper, gold, silver, etc. Portions 102a and 102b can also include a combination of alloys formed in different layers, and in this regard, these portions can be coated, plated, or clad with conductive materials, as discussed further below.

[0039] exist Figure 4AIn the example of , antenna portions 102a and 102b are generally C-shaped, with the outer ends attached to the housing 12 (110) and the inner ends attached to the antenna feedthrough lines 104a and 104b, respectively. More specifically, and as shown in the cross-sectional view on the right, the outer ends of portions 102a and 102b (only portion 102a is shown) are mechanically and electrically connected to the top surface 12t of the housing, and more specifically to the top surface 12t of the outer housing portion 12o. Such attachment can be made by welding or brazing the outer ends to the top surface 12t, as shown by welding point 110. The cross-sectional view on the left shows the inner ends of portions 102a and 102b (again, only 102a is shown), and shows the attachment of the inner ends to the antenna feedthrough lines 104a and 104b (only 104a is shown), which attachment can be made by solder or welding point 108. In this example, antenna feedthroughs 104a and 104b pass through the same feedthroughs 25 as electrode feedthroughs 23, which connect to electrode contacts in lead connectors 26. This example shows four lead connectors 26 arranged in a 2x2 pattern in header 28, but more or fewer lead connectors may be used.

[0040] like Figure 4A As shown in the cross-section of FIG. 1 , antenna portions 102a and 102b are preferably offset in head 28 toward a major surface of external housing portion 12o of IMD 100 (to the left as shown), while lead connector 26 in the head is offset toward a major surface of internal housing portion 12i (to the right). This preferably places antenna portions 102a and 102b closer to magnetic field 55 of external charger and minimizes interference of conductive structures in lead connector 26 with magnetic field reception. Once lead connector 26 is attached to electrode feedthrough 23 and antenna portions 102a and 102b are connected to housing 12 and antenna feedthroughs 104a and 104b, head 28 can be formed over these structures, such as by encapsulating or overmolding with a suitable head material (e.g., a polymer, epoxy, or thermosetting plastic). However, it is not strictly necessary for antenna portions 102a and 102b to be located in head 28 or encapsulated in the head material for normal operation. For example, antenna portions 102 and 102b can also extend from head 28 or be on an outer surface of head 28. In IMD designs where leads are not required, header 28 may not include lead connectors.

[0041] Figure 4B100 and the formation of current Ipower. As discussed above, magnetic field 55 will induce eddy currents in conductive housing 12. These circular currents will tend to oppose each other in the center of the housing, but will reinforce each other toward the periphery of the housing, thereby generating current Icase with the highest current density near the periphery, as shown. This current Icase will generally return toward the top of the housing as current Ix.

[0042] However, at least some (and in other designs, possibly all) of the current Icase will also be transferred to the antenna portions 102a and 102b as the current Ipower through the electrical connection 110. The flow of the current Ipower is facilitated in different ways. First, the outer end connections (110) of the antenna portions 102a and 102b are near the periphery of the housing 12, where Icase is highest. Second, the antenna portions 102a and 102b are preferably formed of a high conductivity (low resistance) material, as described above. In this regard, it is preferred that the antenna portions 102a and 102b (e.g., silver) have a higher conductivity than the conductive material used to form the housing (e.g., titanium), which enhances the magnitude of Ipower relative to the return current Ix. Third, as just discussed, the eddy currents' tendency to flow to the periphery of the conductive structure means that the current will tend to flow through the antenna portions 102a and 102b, which are more peripheral in the IMD 100 than the housing portion in which the return current Ix is formed. In short, and by these means, a significant AC current Ipower is generated, which may be approximately 0.5 to 3.0 amps and is suitable for charging the battery 14 .

[0043] Antenna feed-through lines 104a and 104b are connected to antenna portions 102a and 102b, and to PCB 29 inside housing 12 to provide power to power receiving circuitry 101. As before, power receiving circuitry 101 may include tuning capacitor 105, which may be connected in series, but is shown as being connected in parallel between antenna feed lines 104a and 104. The capacitance value of tuning capacitor 105 may be modified to tune reception to the frequency of magnetic field 55, as discussed further below. As before, rectifier 82 may derive a DC voltage Vdc, which may optionally be provided to charging and protection circuitry 84 for deriving Vbat and Ibat to charge battery 14 of IMD 100, or more generally, to provide power to IMD 100.

[0044] In short, the first and second electrical connections transfer at least a portion of the power in Icase as Ipower, thereby allowing the power receiving circuit system 101 to provide power to the IMD using Ipower. These electrical connections can include different structures, such as antenna parts, wires, contacts, or a combination of these, as explained in various other embodiments below.

[0045] exist Figure 4A In the example of , antenna portions 102a and 102b are similarly sized and include a gap 103 therebetween, which is generally centered from left to right in IMD 100. However, antenna portions 102a and 102b may have different sizes, and gap 103 may be located in different locations without affecting the current path for forming Ipower. Figure 4C In IMD 100', gap 103 has been moved to the left, so that antenna portion 102b is smaller than antenna portion 102a.

[0046] exist Figure 4D In the IMD 100", only a single antenna portion 102 is present in the head 28 region, with the right end attached to the top surface 12t of the housing (110) and the free end attached to the antenna feedthrough line 104a as before. In this example, the antenna line 104b does not pass through the feedthrough 25, but is connected 107 to the outer housing portion 12o. This connection 107 can be established in different ways, such as Figure 4D. In the left cross section, the antenna line 104b is connected to the inner surface of the outer housing part 12o, that is, the inside of the housing, at the solder or welding point 111. In the right cross section, the antenna line 104b is finally electrically connected to the outer surface of the outer housing part 12o. This is facilitated by using a conductive pin 113 that passes through an opening (not marked) in the main surface of the outer housing part 12o. This pin 113 can be soldered to the outer surface and soldered to the antenna line 104b inside the housing. The connection 107 in the right cross section may be better than the left cross section because it is more conductive to increase the amplitude of Ipower. This is because eddy currents (through the skin depth phenomenon) as described above will tend to form on the outer surface of the outer housing part 12o, and the pin 113 in the right cross section is directly connected to the outer surface. When the connection 107 is established on the inner surface, as in the left cross section, the thickness of the outer housing part 12o is between the eddy currents on the outer surface and the connection 107 on the inner surface, thereby generating a body resistance that may adversely affect the flow of Ipower. Additional steps may be desired to ensure that the connection 107, shown in cross-section to the right, is properly sealed to prevent fluid ingress. For example, and as discussed in other examples below, a glass ferrule may be used to secure the pin 113 in the opening in the outer housing portion 12o, and / or the head 28 may be overmolded to cover the connection.

[0047] In any case, in IMD 140″, and regardless of the manner in which connection 107 is connected to housing 12, the circuit is actually connected to Figure 4B The same as described in : a certain amount of Icase is provided to capacitor 105 and related circuit systems (not shown) as Ipower through antenna line 104b, while antenna line 104a and antenna portion 102 return Ipower to Icase.

[0048] Figure 5 Another example of an improved IMD 120 having antenna portions 122a and 122b is shown, which differs from the previous examples in the manner in which the antenna portions are connected. In this example, and as best seen in cross section, antenna portions 122a and 122b are connected to a major surface of outer housing portion 12o, rather than to top surface 12t. The right side cross section shows the connection of the outer ends of the antenna portions (only 122a is shown) at the periphery of the housing, and shows that the outer ends have been soldered (128) to the major surface of outer housing portion 12o to establish electrical connection.

[0049] The left side cross section shows the inner end of the antenna portion (again only 122a is shown). In this example, the inner end is not connected to the antenna feed-through line that passes through the feed-through 25 of the IMD (compare Figure 4A104a in the outer housing portion 12o). Instead, the conductive path from the inner end passes through an opening 127 formed in a major surface of the outer housing portion 12o. This can be done in different ways, but as shown, the inner end of the antenna portion 122a includes or is connected to a conductive pin 125 that passes through the opening 127 in the outer housing portion 12o. A glass ferrule 126 can be inserted into the opening 127 between the pin 125 and the outer housing portion 12o and melted in a manner similar to how the electrode feedthrough line 23 is conventionally sealed and insulated when passing through the feedthrough 25. The glass ferrule 126 insulates the signal from the housing 12 at the inner end and also provides an airtight seal to prevent liquid from entering at the entry point of the pin 125. The antenna line 124a (124b for antenna portion 122b) can then be connected to the pin 125 by soldering, welding, etc. As before, the antenna lines 124a and 124b are connected to the PCB 29, tuning capacitor 105, rectifier 82 and other circuitry 84, similar to Figure 4A and Figure 4B The content described in .

[0050] Note that Figure 5 Attaching antenna portions 122a and 122b to or through a major surface of outer housing portion 12o may slightly increase the thickness of the device, and as shown, may warrant increasing the thickness of header 28 so that such a structure can be packaged. Antenna portions 122a and 122b are separated by gap 123 as previously described, which is shown as being centered in IMD 120. However, the location of this gap 123 may be similar to Figure 4C and Figure 4D , although this change is not described for simplicity.

[0051] The manner in which the antenna portion is connected to the IMD may vary, and Figure 4A and Figure 5 The methods shown in can be used together. For example, Figure 4A As shown, the outer end of the antenna portion can be connected to the top surface 12t of the housing 12, while the inner end is connected through the opening 127 in the main surface of the outer housing portion 12o, as shown in FIG. Figure 5 Similarly, Figure 5 As shown, the outer end can be connected to the main surface, while the inner end is connected to the antenna feed-through line passing through the feed-through 25, as shown in FIG. Figure 4A shown.

[0052] Fig. 6A Another example of an improved IMD 140 is shown, and in this example, there is only a single antenna portion in the head 28. The antenna portion as before includes two C-shaped portions 142a and 142b, but also includes a cross member 145 connecting them at the bottom. In this example, similar to Figure 4A The cross member 145 is attached to the top surface 12t of the housing 12 using welds 110 in the same manner as the outer ends of the antenna portions 102a and 102b are connected to the top of the housing. The design of IMD 140 may be easier to manufacture because there is only a single antenna portion 142 and because that portion is connected to the housing 12 along the length of the top surface 12t, making the connection more stable. Nevertheless, the current still flows in a manner similar to that described above with respect to Figure 4B At first glance, it would appear that cross member 145 would act as a short circuit, sending all current Icase through Ix, and thus reducing Ipower to zero. However, the tendency explained above to force eddy currents to the periphery of the conductive structure prevents this from happening, so that Ipower remains significant and has a suitable magnitude to charge battery 14 of IMD 140.

[0053] Although not shown, note that the antenna portion 142, and in particular the cross member 145 thereof, may also be attached to a major surface of the outer housing portion 12o, such as Figure 5 (128), although such a variation is not depicted. The inner end of antenna portion 142 may be connected to antenna feedthrough lines 144a and 144b that pass through feedthrough 25, as depicted (e.g., FIG. 4a), or may be connected to circuitry (e.g., FIG. 4b) through opening (127) in outer housing portion 12o. Figure 5 The gap 143 between the antenna portions 142a and 142b can also be moved to different positions (see, for example, Figure 4C and Figure 4D ),and Figure 6B IMD 140' shows an example where gap 143 has been moved to the left. Note that antenna line 144b is shown connected to the cross member via a feed-through, but it can also be connected to the housing, such as Figure 4D shown.

[0054] Figure 6CAnother example of an improved IMD 140" is shown in which antenna portions 142a and 142b are connected by a cross member 145. However, in this example, cross member 145 is not connected to housing 12 (e.g., top surface 12t) along its length. Instead, in this example, cross member 145 is connected at the left and right ends using welds 110. This leaves a space 147 between cross member 145 and housing 12. This space 147 will be filled with header 28 material, or it may be left as an air gap within header 28. Experiments have shown that the use of space 147 increases the inductance in the Ipower current path, which means that a lower Ipower will establish a higher voltage across capacitor 105 and rectifier 82, making the circuit more efficient in delivering power to IMD 140".

[0055] Figure 7 Another example of an improved IMD 160 is shown. In this example, antenna portions 162a and 162b are not formed from separate structures, but are formed using material from the housing 12 itself. Specifically, the conductive material of the outer housing portion 12o continues into the head 28 region to form antenna portions 162a and 162b with a gap 163 therebetween. The material of the inner housing portion 12i may also continue into the head region if desired, although this is not shown. The right cross section shows the antenna portion 162a being allowed to pass from the outer housing portion 12o into the head 28 region, while the left cross section shows the connection (168) of the inner end to the antenna feedthrough line 164a that passes through the feedthrough 25, as shown. Figure 4A This inner end may also be connected via an opening in the outer housing portion 12o (not shown), such as Figure 5 As shown. Once the structure is connected, the header material 28 can be formed within the antenna portions 162a and 162b by mold injection, and although not shown, the header material 28 can also completely surround or encapsulate these portions. The current Ipower and the charging of the battery 14 of the IMD 160 will occur as previously explained. As appeared in the earlier example, the position of the gap 163 between the antenna portions 162a and 162b can vary.

[0056] Figure 8Another example of an improved IMD 180 is shown. In this example, the conductivity of the current path carrying Icase and Ipower is increased by applying a conductive layer 185. As shown, this conductive layer 185 is applied to the periphery of the housing 12, and in particular to the periphery of the major surface of the outer housing portion 12o, where Icase will tend to form. The conductive layer 185 preferably includes a material that is more conductive than the material used to form the outer housing portion 12o, and thus the conductive layer 185 surrounds a less conductive region 186 in the middle of the outer housing portion 12o. This promotes Icase ( Figure 4B ) conduction. Additionally, a conductive layer 185 may also be applied to the antenna portions 122a and 122b, which facilitates the conduction of Ipower. ( Figure 8 The example is based on Figure 5 , but the conductive layer 185 can also be applied to any of the previously described examples, although this variation is not described for simplicity).

[0057] Conductive layer 185 can be formed in different ways. For example, region 186 and other important structures (e.g., lead connector 26) can be masked, and conductive layer 185 formed by sputtering, chemical vapor deposition (CVD), electroplating, and similar techniques. Conductive layer 185 can also include an applied coating. Note that conductive layer 185 can be applied once the relevant portions of IMD 180 are assembled, or conductive layer 185 can be applied separately before the various pieces (12o, 122a, 122b) are assembled into IMD 180. Conductive layer 185 can include any number of conductive materials, such as copper, gold, silver, etc., or a mixture of different compounds, and can be formed to have a thickness suitable for facilitating the flow of currents Icase and Ipower. Although Figure 8 Conductive layer 185 is shown formed on both outer housing portion 12o and antenna portions 122a and 122b, but this layer may be formed on only one of these structures. For example, if antenna portions 122a and 122b are already formed of a suitable conductive material, then conductive layer 185 may only need to be applied to outer housing portion 12o. To the extent that conductive layer 185 is not biocompatible, it may be coated or even covered by the head material, but this detail is not shown.

[0058] The application of the conductive layer 185 means that the housing 12 can be formed from materials other than the commonly used titanium alloys. Figure 8The housing 12 in the example can be formed of a dielectric material, such as ceramic, glass, epoxy resin or various plastics. Although such materials are generally not easy to form eddy currents in response to the magnetic field 55, the conductive layer 185 will allow the eddy currents to flow, thereby ultimately providing the currents Icase and Ipower required for powering and charging the IMD.

[0059] Fig. 9 Another example of an improved IMD 200 is shown that is functionally similar to an IMD in that it promotes the conduction of Icase and Ipower by increasing the conductivity in the region where Icase and Ipower flow. Figure 8 IMD 180. (Again, this example is based on Figure 5 , but may be applied to any of the previously described examples). However, in this example, different materials are used to form the outer housing portion 12o, resulting in a conductivity difference, which again facilitates the flow of currents Icase and Ipower. Specifically, the outer housing portion 12o includes a "window" 206 formed of a material that is separated from the rest of the outer housing portion 12o. The window 206 is formed of a material having a lower conductivity than the rest of the outer housing portion 12o (and preferably also lower than the conductivity of the antenna portions 122a and 122b). This is relative to the return current Ix ( Figure 4B ) promotes the flow of current Icase, which in turn increases Ipower.

[0060] In one example, the window 206 may include a dielectric material, such as ceramic, glass, epoxy, or various plastics. In another example, the window 206 may include a metal structure or alloy, but a metal structure or alloy having a lower conductivity than the rest of the housing 12 or the outer housing portion 12o. For example, the window 206 may be formed of a lower conductivity titanium-aluminum-vanadium alloy (such as Ti-6Al-4V (e.g., grade 5 or 23), while the rest of the housing 12 or the outer housing portion 12o is formed of higher conductivity pure titanium (e.g., grade 1). Brazing, laser welding, or similar techniques may be used to attach the window 206 to the hole formed in the outer housing portion 12o. Preferably, the conductivity of the material used for the window 206 is one-third or less of the conductivity of the material used for the rest of the housing 12 or the outer housing portion 12o. Although not shown, the conductivity difference between the window 206 and the portion carrying Ipower and Icase may be further enhanced by applying a conductive layer 185, such as Figure 8 As is done in .

[0061] Fig. 10A and Fig. 10BAnother example of an improved IMD 220 is shown which, like the other examples, utilizes eddy currents in the case 12 to facilitate IMD powering and charging. However, in this example, no antenna portion is provided in the region of the head 28 of the IMD, and the head 28 may be formed as in conventional designs. Instead, the associated currents Icase and Ipower are generated entirely using the case, as described in reference Fig. 10B As further explained. Fig. 10A In the example of , a conductive layer 185 is provided, which is positioned around a portion of the housing periphery. Specifically, the conductive layer 185 is formed on the outer housing portion 12o, and in particular, on its main surface around the periphery, and along a portion close to the top surface 12t, leaving a gap 223. The conductive layer 185 can be as previously described with reference to Figure 8 Conductive layer 185 also preferably comprises a more conductive material than the material used to form outer housing portion 12o, and thus surrounds a less conductive region 186 in the middle of outer housing portion 12o and in gap 223.

[0062] Fig. 10B The related currents Icase, Ix, and Ipower formed at the IMD 220 are shown. In this example, Icase is formed by eddy currents in response to the magnetic field 55 as previously explained, wherein Icase is preferentially formed in the conductive layer 185. The return current Ix appears in the gap 223 and is thus formed within the lower conductivity material of the outer housing portion 12o. Antenna lines 224a and 224b provide electrical connections to the conductive layer 185 near the gap 223, as explained later, and thus transfer at least some of Icase as Ipower. Antenna lines 224a and 224b carrying Ipower as above are connected to the power receiving circuit system 101, which can be the same as described previously.

[0063] Fig. 10ADifferent ways in which the conductive layer 185 can be formed and connected to the antenna wires 224a and 224b (only the connection to 224a is shown) are shown. In the left cross-section, the conductive layer 185 is formed on the outside of the outer housing portion 12o. For easier viewing, the thickness of the conductive layer 185 is exaggerated. The connection of the conductive layer 185 to the antenna wire 224a is made through the opening 227 in the outer housing portion 12o. Although the wires 224a and 224b can be directly connected to the conductive layer 185, in the described example, the conductive pin 226 is used as an intermediate and is positioned in the opening 227 and surrounded by the glass ferrule 228, which is useful for providing sealing and preventing fluid ingress as described above. One end of the pin 226 is connected to the antenna wire 224a within the housing 12, and the outer end of the pin 226 is exposed to contact the conductive layer 185 after the conductive layer is applied. Although not shown, it is noted that the material of the head 28 can be overmolded to cover the conductive layer 185, and in particular the opening 227, thereby further improving the sealing. Pin 226 can also be used without the glass ferrule, similar to the previous description of Figure 4D The content described.

[0064] In the right cross section, the conductive layer 185 is formed inside the outer housing portion 12o, so that the conductive layer 185 is inside the housing 12. In this example, there is no need to provide an opening 227 in the outer housing portion 12o, but the antenna line 224a can be directly connected to the conductive layer 185 with a suitable connection 230, such as by welding or soldering. Figure 8 As is also the case with the example of , the application of the conductive layer 185 means that the housing 12 can be formed of different materials and can be formed of a dielectric material as explained previously. In the example shown in the right cross-section where the conductive layer 185 is located inside the housing, the use of a dielectric housing material may be preferred; if the housing 12 material is conductive, eddy currents will form on the outer surface, while the bulk resistance - the thickness of the outer housing portion 12o - is between the eddy currents and the conductive layer 185, as previously described with reference to Figure 4D If the housing material were a dielectric, this would not be a problem since the eddy currents would form directly in the conductive layer 185 .

[0065] Fig.11 Another example of an improved IMD 240 is shown. Similar to IMD 220, IMD 240 does not use the antenna portion in the area of ​​head 28, and the related currents Icase, Ipower, and Ix are completely generated using housing 12, similar to reference Fig. 10B However, in this example, the outer housing portion 12o includes a window 206 of low electrical conductivity material formed of a separate material from the remainder of the outer housing portion 12o, similar to Fig. 9The content described in Fig. 10A Similar to the gap 223 of the embodiment, the lower conductivity window 206 preferably also exists in the gap 243, which is relative to the return current Ix ( Fig. 10B ) facilitates the flow of currents Icase and Ipower. In this example, antenna lines 244a and 244b contact the higher conductivity housing portion 205 near gap 243. This contact can be made on the outside of housing 12 (e.g., see Figure 4D ), or the antenna lines 224a and 224b may be connected to the interior of the outer housing portion 12o at the connection space 250 as shown. Fig. 9 As with the example of , window 206 may include a dielectric material or a metal structure or alloy, but a metal structure or alloy having a lower electrical conductivity than that used for the remainder of housing 12 or outer housing portion 12o.

[0066] Fig. 12A Another example of an improved IMD 260 is shown without a wire-wound charging coil, which, as in other examples, uses housing 262 to form the necessary current to extract power from magnetic field 55. IMD 260 has a smaller form factor and can be as described in U.S. Patent Application Publication 2017 / 0151440. IMD 260 can be significantly smaller than the IMD examples to date. Note that the application of the disclosed technology - which does not require a wire-wound charging coil 30 - greatly facilitates the manufacture of a smaller IMD (IMD 260).

[0067] The IMD 260 includes a housing 262 that contains associated electronics, such as a battery and stimulation circuitry (not shown). One or more lead connectors 268 are formed on the exterior of the housing 262 and are connected to the circuitry inside the housing via electrode feedthroughs (not shown) via feedthroughs 266, similar to previous examples. In this example, the housing 262 and lead connector(s) 268 may be overmolded with a dielectric material 264 such as silicone, although epoxies of other materials may also be used. The housing 262 in this example includes a higher conductivity region 275 around its periphery that surrounds a lower conductivity region 276. As in Fig. 10A and 11 As in the example of FIG. 1 , the lower conductivity region 276 includes a gap 263, which, as previously explained, helps suppress the return current Ix and thus promotes the current Ipower through the antenna lines 284a and 284b. The higher and lower conductivity regions 275 and 276 can be as previously described with reference to FIG. FIG. 10A to FIG. 11The housing 262 may include or contain a dielectric material. The IMD 260 may also include an antenna portion in the header near the lead connector(s) 268 as in the previous examples, although this is not shown.

[0068] Fig. 12B Shows that with Fig. 12A 260. As previously described, the IMD 280 includes one or more lead connectors 268, a feedthrough 266, and an overmolded dielectric material 264. However, the housing is made of a different material. The majority of the housing is made of a dielectric material 282 (such as ceramic). One of the major surfaces of the housing includes a conductive material 283, which may include a conductive window attached to the dielectric housing material 282, as best shown in cross section. The conductive window 283 can be brazed to the ceramic housing material 282.

[0069] In this example, the conductive window 283 serves a dual purpose. First, and as in other examples, the conductive window 283 serves as a means for receiving the magnetic field 55 for powering the IMD 280 and charging the battery. In this regard, the conductive window 283 can include a higher conductive region 285 around its periphery, as in the previous examples, and a lower conductive region 286 at its center, the lower conductive region including a gap 263 useful for generating power that is provided to the power receiving circuit system. As in the earlier examples, the higher and lower conductivity regions 285 and 286 can be formed in different ways. They can be formed of different materials (e.g., different alloys), or the conductivity of region 285 can be enhanced by the use of a conductive layer. The conductive layer can be placed on the outside or inside of the conductive window 283 as before, with the antenna lines 284a and 284b appropriately connected, similar to the previous description for Fig. 10A As explained. Fig. 12A In the embodiment, the conductive layer is applied to the outside of the conductive window while its thickness is exaggerated in the cross section.

[0070] Conductive window 283 can also be used to serve as the purpose of housing electrode Ec. As will be appreciated by those skilled in the art, the use of housing electrodes during neural stimulation is particularly useful for providing a return current path for the stimulation current formed at electrode Ex (e.g., on a lead), which is generally referred to as a monopolar stimulation mode. The stimulation circuit system 298 in the housing for providing stimulation current to a selected electrode in electrode Ex can be connected to conductive window 283 to form housing electrode Ec. This connection can be formed in a higher or lower conductivity region 285 or 286, and is typically made by a wire connected to the interior of the housing. As best seen in cross section, the overmolded dielectric material 264 can be formed with an opening 264a, allowing the exterior of the conductive window 283 to be in physical and electrical contact with the patient's tissue.

[0071] exist Fig. 12B In the example circuit system shown in , one or more of the antenna lines 284a and 284b (which are additionally used to connect the power receiving circuit system 101 to the conductive region 285) can also be used to operate the conductive window 283 as a shell electrode. This can occur in different ways, but in the example shown, one or more switches 297 are connected between the shell electrode output Ec of the stimulation circuit 298 and one or more of the antenna lines 284a and 284b. (In reality, only one switch 297 connected to either 284a or 284b is required, but two switches connected to both are shown). Logic (e.g., the control circuit system 86 of the IMD, FIG. 3) can control the switch(es) 297 so that the switch is open when the IMD 280 receives a magnetic field and is closed when the stimulation circuit 298 is used to drive the conductive window 283 as a shell electrode. The approach of using one or more of antenna lines 284a and 284b, while not required, is advantageous because it allows conductive window 283 to operate as a housing electrode without providing an additional connection to conductive window 283 other than the antenna lines for the housing electrode.

[0072] Fig. 12C An alternative to IMD 280 (IMD 280') is shown in cross-section in which conductive feature 284 does not include conductive window 283 positionable in a hole of dielectric housing 282, but instead includes conductive plate 283' positionable on or in the housing. Fig. 12C In the example of FIG. 2 , the conductive plate 283′ has been positioned outside the dielectric housing 282, thus allowing it to be used as the housing electrode Ec just explained. However, the conductive plate 283′ may also be placed inside the dielectric housing 282. The conductive plate 283′ may have higher and lower conductive regions 285 and 286 as previously described, as shown in reference to FIG. Fig. 12BAlthough not shown, the openings in dielectric housing 282 can allow antenna lines 284a and 284b to connect to higher conductive areas 285, as occurred in the earlier examples. For purposes of this disclosure, a "plate" such as 283' can be considered a type of "window" such as 283, and thus, window 283 or 283' can be placed in a hole in housing 282 ( Fig. 12B ), or placed on or in a housing 282 without a corresponding hole ( Fig. 12C ).

[0073] Note that in the examples described above, a conductive plate attached to or in the housing, such as 283', may also be used. For example, a conductive plate attached to or in the housing may include Figure 8 and Fig. 10A The conductive layer 185 in.

[0074] Although it is useful to form the housing electrode using the same conductive window 283 or plate 283' for power reception in the example, it is noted that this is not strictly necessary. A different conductive window, plate or other electrode formed in conjunction with the housing can be used as a housing electrode separate from the conductive window 283 or plate 283' for power reception.

[0075] Fig.13 Another example of an improved IMD 300 is shown. In this example, the housing is separated into different housing modules 302 and 304, which are enclosed within an overmold 306. For simplicity, the lead connectors are not shown in this example, but can be incorporated into the overmold 306 in any number of different ways, with the signaling terminating in the housing module 302. In this example, the housing modules 302 and 304 house different circuit systems of the IMD 300. For example, the housing module 302 may include stimulation circuit systems and other electronics, while the housing module 304 may house the battery 14 (not shown). The circuit system of the IMD 300 can be divided between the two housing modules 302 and 304 in any desired manner.

[0076] In this example, housing modules 302 and 304 are formed and connected in a manner to facilitate the flow of Icase, as previously described, Icase is tapped to Ipower to provide power or charge to battery 14 of IMD 300. To facilitate the flow of current Icase, housing module 302 preferably includes a higher conductivity region 305 around its periphery that at least partially surrounds a lower conductivity region 306. As in the housings of the previous examples, higher and lower conductivity regions 305 and 306 may be formed in different manners, such as by using a conductive layer 185 ( Figure 8 ) or lower conductivity window 206 ( Fig. 9 ), although these details are not shown. Shell module 304 preferably has higher conductivity and is connected to higher conductivity region 305 in shell module 282 to promote the flow of Icase, as shown. In order to promote this flow, shell modules 302 and 304 are connected together in different ways. In the example shown, on the left side, shell modules 302 and 304 are connected by conductive wire 309, and on the right side, these modules are connected by conductive joint 307 (which can also include a conduit for providing power and grounding wire to module 302 from the battery in module 304). The left and right connections can also be carried out similarly. Once shell modules 302 and 304 are connected, Icase will flow through both of shell modules 302 and 304 by eddy current, as shown. As the lower conductivity gap 303 as above is between conductive regions 305, the antenna line is connected to region 305 across the gap. As before these antenna lines will carry Ipower to capacitor 105 and associated circuitry to allow IMD 300 to be powered or charged as previously explained.

[0077] Fig.14 Another example of an improved IMD 320 that is capable of utilizing eddy currents to provide IMD power, but lacks a head connected to the housing, is shown. The IMD 320 is also generally shown in the 2017 / 0151440 publication cited above, which is assumed to be familiar to the reader. The IMD 320 is generally divided into three parts: an electronics portion 322, a connector block portion 324, and an electrode wire portion 326. In this example, portions 324 and 326 are further composed of left and right connector blocks 325a and 325b, each coupled to its own electrode wire cables 327a and 327b, which can be flexible. The proximal end of the lead 18 (Figure 1A) can be coupled to the openings in the connector blocks 325a and 325b. The electrode wires in the electrode cables 327a and 327b are connected to contacts in the connector blocks and to the stimulation circuit system inside the electronic component 322.

[0078] The electronics portion 320 includes a housing 330 which, in this example, is generally cylindrical and has a major flat surface that faces the outside of the patient when implanted. This surface includes a higher conductivity region 335 that surrounds a lower conductivity region 336 that includes a gap 333. These regions 335 and 336 can be formed in any of the ways mentioned above and can be formed from different combinations of materials also mentioned above. The antenna line is connected to the higher conductivity region 335 across the gap 333 and to the capacitor 105 and other aspects of the power receiving circuit system 101 as described above to allow eddy currents formed in the region 335 to provide power to the IMD 320. The IMD 320 may include an overmold 350 that overmolds one or all of the electronics 322, connector block 324, and electrode line 326 portions. This overmold 350 may include openings for the housing electrodes (e.g., 264a, Fig. 12B ), although this is not shown.

[0079] Various disclosed examples of IMDs capable of receiving power using eddy currents and without a wire wound coil can operate using a range of frequencies, and thus, the AC magnetic field 55 generated by the external charger can include a range of frequencies. The frequencies used to provide power to the various disclosed IMDs can be higher than the frequencies conventionally used in IMDs that pick up the magnetic field 55 using a wire wound coil 30. For example, while an IMD with a conventional wire wound coil 30 can be tuned to receive a magnetic field 55 having a frequency of approximately 100kHz, the disclosed examples can be tuned to receive a magnetic field 55 having a frequency of approximately 1 to 10MHz. In a specific example, an ISM band frequency of 6.78MHz or 13.56MHz can be used. It may be preferred to provide power to the disclosed IMD using a higher frequency to reduce heating in the housing where the eddy currents are induced. As will be understood by those skilled in the art, the current Icase flows with a skin depth that is inversely proportional to the frequency. Therefore, a higher frequency will reduce the skin depth, which will tend to reduce Icase, but will also reduce heating. Those skilled in the art will understand that by changing the capacitor 105, the IMD can be tuned to resonate at the frequency of the magnetic field 55. In one example, for the higher frequencies discussed, capacitor 105 may have a value ranging from 1 to 100 nanofarads.

[0080] As will be appreciated by those skilled in the art, the foregoing examples illustrate several different ways in which an IMD may wirelessly receive power from an external charger to power or charge the IMD using housing-induced eddy currents without the need for a wire-wound coil. It should be understood that these different examples are not mutually exclusive, and thus techniques used in certain examples may be combined with different examples. All of these variations are not explicitly shown because doing so would be cumbersome.

[0081] Furthermore, while the foregoing examples are shown in the context of an implantable stimulator device, those skilled in the art will appreciate that many different implantable medical devices may be powered or charged using magnetic induction, and all such implantable devices may therefore benefit from the teachings provided in the present disclosure. This is true even for implantable medical devices that have no head at all. Non-implantable or non-medical devices that have a conductive housing portion and can be powered or charged using magnetic induction may also benefit.

Claims

1. An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field, comprising: a housing housing control circuitry for the IMD, wherein at least a portion of the housing is electrically conductive, and wherein a housing current is established in the electrically conductive housing portion in response to the electromagnetic field; a power receiving circuit system, which is located inside the housing; as well as a first electrical connection and a second electrical connection for transferring at least some of the housing current as power current to the power receiving circuitry, wherein the power receiving circuitry is configured to provide power to the IMD using the power current, wherein the housing comprises a dielectric material, and wherein the conductive housing portion comprises a conductive window, The control circuit system further comprises stimulation circuit system for forming a stimulation current at a selected electrode of a plurality of electrodes in contact with tissue of the patient, wherein the conductive window comprises one of the plurality of electrodes and is further configured to operate as a housing electrode. 2 . The IMD of claim 1 , further comprising a non-conductive header attached to the housing.

3. The IMD of claim 2, wherein at least one of the first electrical connection and the second electrical connection comprises an antenna portion in or on the head, thereby resulting in at least one antenna portion in or on the head.

4. The IMD of claim 3, further comprising one or more lead connectors in the head, a feedthrough between the head and the housing, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines are connected to contacts in the lead connectors and pass through the feedthroughs inside the housing. 5 . The IMD of claim 4 , wherein at least one of the first electrical connection and the second electrical connection comprises a feedthrough line passing through the feedthrough, the feedthrough line connected to the at least one antenna portion. The IMD of claim 3 , wherein the at least one antenna portion is formed from material of the housing.

7. The IMD of claim 3, wherein the housing includes a planar surface configured to face exteriorly of the patient when implanted, wherein the at least one antenna portion is offset in or on the head toward the exterior planar surface.

8. The IMD of claim 3, wherein there is a first antenna portion in or on the head including the first electrical connection, and there is a second antenna portion in or on the head including the second electrical connection.

9. The IMD of claim 3, wherein there is a single antenna portion in or on the head that includes the first electrical connection.

10. The IMD of claim 3, wherein there is a single antenna portion in or on the head that includes the first electrical connection and the second electrical connection.

11. The IMD of claim 2, wherein the first electrical connection and the second electrical connection are not formed in or on the header.

12. The IMD of claim 1, wherein at least one of the first electrical connection and the second electrical connection comprises a wire connected to the conductive housing portion.

13. The IMD of claim 1, wherein the first electrical connection comprises a first wire connected to the conductive housing portion at a first contact, and wherein the second electrical connection comprises a second wire connected to the conductive housing portion at a second contact.

14. The IMD of claim 13, wherein the first electrical connection and the second electrical connection are separated by a portion of the housing having a first conductivity, and wherein the conductive housing portion forming the housing current has a second conductivity higher than the first conductivity.

15. The IMD of any one of claims 1 to 14, wherein the power receiving circuitry comprises a rectifier configured to convert the power current into a DC voltage for providing power to the IMD.

16. The IMD of claim 1, further comprising a battery within the housing, wherein the power receiving circuitry is configured to provide power to the IMD using the power current to charge the battery.

17. The IMD of claim 1, wherein the conductive housing portion comprises a conductive layer applied to the housing.

18. The IMD of claim 1, wherein the dielectric material comprises ceramic.

19. An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field, comprising: a housing housing control circuitry for the IMD, wherein at least a portion of the housing is electrically conductive, and wherein a housing current is established in the electrically conductive housing portion in response to the electromagnetic field; a power receiving circuit system, which is located inside the housing; a non-conductive head attached to the housing; as well as a first electrical connection and a second electrical connection for transferring at least some of the shell current as power current to the power receiving circuit system, wherein the first electrical connection includes a first antenna portion in or on the head, and wherein the second electrical connection includes a second antenna portion in or on the head, Wherein the power receiving circuitry is configured to provide power to the IMD using the power current.

20. The IMD of claim 19, further comprising one or more lead connectors in the head, a feedthrough between the head and the housing, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines connect to contacts in the lead connectors and pass through the feedthroughs inside the housing.

21. The IMD of claim 20, wherein the first electrical connection comprises a first feedthrough line passing through the feedthrough connected to a first antenna portion, wherein the second electrical connection comprises a second feedthrough line passing through the feedthrough connected to a second antenna portion.

22. The IMD of claim 19, wherein the first antenna portion and the second antenna portion are formed from material of the housing.

23. The IMD of claim 19, wherein the housing comprises a planar surface configured to face exteriorly of the patient when implanted, wherein the first antenna portion and the second antenna portion are offset toward the exterior planar surface in or on the head.

24. The IMD of claim 19, wherein the first antenna portion comprises a first end and a second end, and wherein the second antenna portion comprises a first end and a second end, wherein the first electrical connection portion further comprises a first wire connected to the first end of the first antenna portion, wherein the second end of the first antenna portion is connected to the conductive shell portion, wherein the second electrical connection portion further comprises a second wire connected to the first end of the second antenna portion, wherein the second end of the second antenna portion is connected to the conductive shell portion.

25. The IMD of claim 24, wherein the first wire and the second wire pass through a feedthrough in the housing, or wherein the first wire and the second wire are connected to a first end of the first antenna portion and a first end of the second antenna portion through one or more openings in the housing.

26. An IMD according to claim 24, wherein the second end of the first antenna portion and the second end of the second antenna portion are connected to the top of the shell, or wherein the shell includes a flat surface, which is configured to face the outside of the patient when implanted, and wherein the second end of the first antenna portion and the second end of the second antenna portion are connected to the flat surface.

27. The IMD of any one of claims 19 to 26, wherein the power receiving circuitry comprises a rectifier configured to convert the power current into a DC voltage for providing power to the IMD.

28. The IMD of claim 19, further comprising a battery within the housing, wherein the power receiving circuitry is configured to provide power to the IMD using the power current to charge the battery.

29. The IMD of claim 19, wherein the conductive housing portion comprises a conductive layer applied to the housing.

30. The IMD of claim 29, wherein the conductive layer is applied inside the housing.

31. The IMD of claim 19, wherein the housing comprises a window of a material different than a material of the housing, wherein the electrical conductivity of the window material is less than the electrical conductivity of the housing material.

32. The IMD of claim 31 , wherein the conductive housing portion at least partially surrounds the window.

33. The IMD of claim 31 , wherein the housing comprises a planar surface configured to face exteriorly of the patient when implanted, wherein the window is formed in the planar surface.

34. An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field, comprising: a housing housing control circuitry for the IMD, wherein at least a portion of the housing is electrically conductive, and wherein a housing current is established in the electrically conductive housing portion in response to the electromagnetic field; a power receiving circuit system, which is located inside the housing; a non-conductive head attached to the housing; as well as a first electrical connection and a second electrical connection for transferring at least some of the housing current as power current to the power receiving circuit system, wherein at least the electrical connection comprises a single antenna portion in or on the head, Wherein the power receiving circuitry is configured to provide power to the IMD using the power current.

35. The IMD of claim 34, further comprising one or more lead connectors in the head, a feedthrough between the head and the housing, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines connect to contacts in the lead connectors and pass through the feedthroughs inside the housing.

36. The IMD of claim 35, wherein at least one of the first electrical connection and the second electrical connection comprises a feedthrough line passing through the feedthrough, the feedthrough line connected to the single antenna portion.

37. The IMD of claim 34, wherein the single antenna portion is formed from material of the housing.

38. The IMD of claim 34, wherein the housing includes a planar surface configured to face exteriorly of the patient when implanted, wherein the single antenna portion is offset in or on the head toward the exterior planar surface.

39. The IMD of claim 34, wherein the single antenna portion includes only the first electrical connection and not the second electrical connection.

40. The IMD of claim 39, wherein the single antenna portion comprises a first end and a second end, wherein the first electrical connection further comprises a first wire connected to the first end of the single antenna portion, wherein the second end of the single antenna portion is connected to the conductive housing portion.

41. The IMD of claim 40, wherein the second electrical connection comprises a second wire connected to the conductive housing portion.

42. The IMD of claim 34, wherein the single antenna portion in or on the head comprises the first electrical connection and the second electrical connection.

43. The IMD of claim 42, wherein the single antenna portion includes a cross member connected along its length to the conductive housing portion.

44. The IMD of claim 43, wherein the first electrical connection comprises a first line connected to a first end of the single antenna portion, and wherein the second electrical connection comprises a second line connected to a second end of the single antenna portion.

45. The IMD of claim 42, wherein the single antenna portion comprises a cross member connected to the conductive housing portion at a first contact and at a second contact, wherein a space exists between the cross member and the housing between the first contact and the second contact.

46. ​​The IMD of claim 45, wherein the first electrical connection comprises the first contact and a first line connected to a first end of the single antenna portion, and wherein the second electrical connection comprises the second contact and a second line connected to a second end of the single antenna portion.

47. The IMD of any one of claims 34 to 46, wherein the power receiving circuitry comprises a rectifier configured to convert the power current into a DC voltage for providing power to the IMD.

48. The IMD of claim 34, further comprising a battery within the housing, wherein the power receiving circuitry is configured to provide power to the IMD using the power current to charge the battery.

49. The IMD of claim 34 wherein the conductive housing portion comprises a conductive layer applied to the housing.

50. The IMD of claim 34, wherein the housing comprises a window of a material different than a material of the housing, wherein the electrical conductivity of the window material is less than the electrical conductivity of the material of the housing.

51. An implantable medical device (IMD) configured to wirelessly receive power from an electromagnetic field, comprising: a housing housing control circuitry for the IMD, wherein at least a portion of the housing is electrically conductive, and wherein a housing current is established in the electrically conductive housing portion in response to the electromagnetic field; a power receiving circuit system, which is located inside the housing; a first electrical connection and a second electrical connection for transferring at least some of the housing current as power current to the power receiving circuit system, wherein the first electrical connection includes a first contact formed on the conductive housing portion, and wherein the second electrical connection includes a second contact formed on the conductive housing portion, wherein the power receiving circuitry is configured to provide power to the IMD using the power current, wherein the housing comprises a dielectric material, and wherein the conductive housing portion comprises a conductive window, and The control circuit system also includes a stimulation circuit system for forming a stimulation current at a selected electrode of a plurality of electrodes in contact with the patient's tissue, wherein the conductive window includes one of the plurality of electrodes, and wherein the conductive window is also configured to operate as a housing electrode.

52. The IMD of claim 51 further comprising a non-conductive header attached to the housing.

53. The IMD of claim 52, further comprising one or more lead connectors in the head, a feedthrough between the head and the housing, and a plurality of electrode feedthrough lines, wherein the electrode feedthrough lines are connected to contacts in the lead connectors and pass through the feedthroughs inside the housing.

54. The IMD of claim 52, wherein the first and second electrical connections are not formed in or on the header.

55. The IMD of claim 51 wherein the first electrical connection comprises a first wire connected to the conductive housing portion at the first contact, and wherein the second electrical connection comprises a second wire connected to the conductive housing portion at the second contact.

56. The IMD of claim 51 wherein the first and second contacts are separated by a portion of the housing having a first conductivity, and wherein the conductive housing portion forming the housing current has a second conductivity that is higher than the first conductivity.

57. The IMD of claim 56, wherein the conductive housing portion comprises a conductive layer applied to the housing, wherein the conductive layer is applied to the interior or exterior of the housing.

58. The IMD of claim 56, wherein the portion of the housing having the first conductivity comprises a window of a material different than a material of the housing.

59. The IMD of claim 58, wherein the conductive housing portion at least partially surrounds the window, wherein the housing comprises a planar surface configured to face exteriorly of the patient when implanted, wherein the window is formed in the planar surface.

60. The IMD of claim 58 wherein the window comprises a dielectric material and the conductive housing portion comprises a metallic material.

61. The IMD of claim 58 wherein the window and the conductive housing portion comprise a metallic material.

62. The IMD of claim 51 wherein the first contact is formed on the exterior of the conductive housing portion through an opening in the conductive housing portion, and wherein the second contact is formed on the exterior of the conductive housing portion through an opening in the conductive housing portion.

63. The IMD of claim 51 wherein the first contact is formed within the interior of the conductive housing portion, and wherein the second contact is formed within the interior of the conductive housing portion.

64. The IMD of any one of claims 51 to 63, wherein the power receiving circuitry comprises a rectifier configured to convert the power current into a DC voltage for providing power to the IMD.

65. The IMD of claim 51 further comprising a battery within the housing, wherein the power receiving circuitry is configured to provide power to the IMD using the power current to charge the battery.

66. The IMD of claim 51 , wherein the conductive window is secured to the dielectric material in a manner that covers a hole in the dielectric material, or wherein the conductive window comprises a plate attached to or in the dielectric material.

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