SELF-REGULATING TRANSCUTANEOUS ENERGY TRANSFER

• US 20110046699A1
• Filed: 08/20/2009
• Published: 02/24/2011
• Est. Priority Date: 08/20/2009
• Status: Active Grant

• Current Assignee: Envoy Medical Corporation
• Original Assignee: Envoy Medical Corporation
• Inventors: Mazanec, Paul Richard
• Granted Patent: US 9,782,600 B2
• Time in Patent Office: Days
• US Class Current: 607/61
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/00716 in response to integrated charge or discharge current
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

A rechargeable battery system and method are disclosed, in which an implantable medical device (IMD) regulates its transfer of energy from a separate charger unit. For recharging, a charger unit is brought into proximity to the implanted device. An oscillating current is generated in a primary coil, located in the charger. By inductive coupling through an oscillating magnetic field, an alternating current is generated in a secondary coil, which is implanted in or near the implanted device. The alternating current then passes through a half-wave or full-wave rectifier to form a one-sided current, then passes through a regulator to form an essentially direct current, which is in turn directed to the rechargeable battery in the implanted device. The secondary coil has a controllable damped resonant frequency, which can be dynamically tuned away from the driving frequency of the primary coil by a variable resistor and/or by varying a duty cycle of a rapidly switched electrical element. If a control loop in the implant senses that more power is being received at the second coil than is actually being used to recharge the battery, the control loop temporarily changes the variable resistance. When this happens, the resonant frequency of the secondary coil is detuned slightly away from the driving frequency, so that less of the incoming power is absorbed by the secondary coil. Alternatively, the secondary coil may be temporarily short-circuited. With less or no excess power entering the circuitry of the implant, the problem of overheating is mitigated.

Claims

1. An implantable device for receiving electrical power from an external charger unit, the external charger unit producing an oscillating current in a primary coil at a driving frequency, the oscillating current producing an oscillating magnetic field proximate the external charger unit, the implantable device comprising:

a secondary coil for receiving the oscillating magnetic field and producing an alternating current at the driving frequency, the amplitude of the alternating current depending in part on a resonant profile of the secondary coil, on the driving frequency, on an amplitude of the oscillating current in the primary coil, and on the relative orientations of the primary and secondary coils;

a rectifier for receiving the alternating current from the secondary coil and producing a single-sided current;

a regulator for receiving the single-sided current from the rectifier and producing an essentially direct current;

a rechargeable battery charged by the essentially direct current; and

a control loop for controlling the resonant profile of the secondary coil in response to the amplitude of the alternating current in the secondary coil.

2. The implantable device of claim 1,

wherein the resonant profile of the secondary coil comprises a damped resonant frequency;

and

wherein the damped resonant frequency depends in part on a controllable parasitic resistance.

3. The implantable device of claim 2, wherein the damped resonant frequency, ω

_d, is given by;

4. The implantable device of claim 3, wherein the undamped resonant frequency equals the driving frequency of the primary coil.

5. The implantable device of claim 2, wherein the parasitic controllable resistance comprises a resistance from a variable resistor.

6. The implantable device of claim 2, wherein the parasitic controllable resistance comprises a time-average of at least two discrete resistance values.

7. The implantable device of claim 2, wherein the parasitic controllable resistance varies as a duty cycle of two discrete resistance values.

8. The implantable device of claim 7, wherein the parasitic controllable resistance is switched with a frequency that varies with the amplitude of the current in the secondary coil.

9. The implantable device of claim 2, wherein the amplitude of the alternating current in the secondary coil decreases as the damped resonant frequency of the secondary coil varies away from the driving frequency of the primary coil.

10. The implantable device of claim 1,

wherein the resonant profile of the secondary coil further comprises a quality factor;

and

wherein the quality factor depends in part on a controllable parasitic resistance.

11. The implantable device of claim 10, wherein the quality factor, Q, is given by:

12. The implantable device of claim 1, wherein the rectifier is a full-wave rectifier.

13. The implantable device of claim 1, wherein the rectifier is a half-wave rectifier.

14. A method of recharging a battery in a surgically implanted device, comprising:

bringing an external charger unit into proximity with the implanted device;

producing an oscillating current at a driving frequency in a primary coil within the external charger,

producing an oscillating magnetic field proximate the external charger unit, extending the oscillating magnetic field into the implanted device;

producing an alternating current at the driving frequency in a secondary coil electrically connected to the implanted device; and

adjusting a damped resonant frequency of the secondary coil in response to an amplitude of the alternating current.

15. The method of claim 14, wherein the damped resonant frequency of the secondary coil is adjusted away from the driving frequency, so that for a particular strength of oscillating magnetic field, the amplitude of the alternating current produced in the secondary coil is decreased.

16. The method of claim 14, further comprising limiting the amplitude of the alternating current to a prescribed value.

17. The method of claim 14, further comprising temporally varying a controllable parasitic resistance, the damped resonant frequency of the secondary coil depending in part on the controllable parasitic resistance.

18. The method of claim 17, wherein temporally varying the controllable parasitic resistance comprises varying a resistance of a variable resistor.

19. The method of claim 17, wherein temporally varying the controllable parasitic resistance comprises varying a duty cycle of a rapidly switched electrical element.

20. The method of claim 14, further comprising:

producing a single-sided current from the alternating current;

producing an essentially direct current from the single-sided current; and

directing the essentially direct current to the rechargeable battery.

21. An implantable device for receiving electrical power from an external charger unit, the external charger unit producing an oscillating current in a primary coil at a driving frequency, the oscillating current producing an oscillating magnetic field proximate the external charger unit, the implantable device comprising:

a secondary coil for receiving the oscillating magnetic field and producing an alternating current at the driving frequency, the amplitude of the alternating current depending in part on the driving frequency, on an amplitude of the oscillating current in the primary coil, and on the relative orientations of the primary and secondary coils;

a rectifier for receiving the alternating current from the secondary coil and producing a single-sided current;

a regulator for receiving the single-sided current from the rectifier and producing an essentially direct current at a regulated voltage;

a rechargeable battery charged by the essentially direct current; and

a control loop for temporarily short-circuiting both ends of the secondary coil to ground.

22. The implantable device of claim 21, wherein the control loop comprises a comparator for comparing the regulated voltage to a reference voltage.

23. The implantable device of claim 22, wherein when the regulated voltage is greater than the reference voltage, the control loop connects both ends of the secondary coil to ground.

24. The implantable device of claim 23, wherein after the control loop connects both ends of the secondary coil to ground, the secondary coil stops receiving the oscillating magnetic field, and the regulated voltage drops.

25. The implantable device of claim 24, wherein when the regulated voltage drops below a threshold, the control loop disconnects both ends of the secondary coil from ground and from each other.

26. The implantable device of claim 21,

wherein the control loop operates in pulse-width modulation to simulate a desired resistance;

and

wherein the desired resistance depends on a duty cycle of the pulse-width modulation.

27. The implantable device of claim 26, wherein the frequency of the pulse-width modulation depends on the duty cycle.