Charge-balancing during electrical stimulation

• US 9,295,850 B2
• Filed: 03/14/2013
• Issued: 03/29/2016
• Est. Priority Date: 04/24/2012
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kallmyer, Todd A.
• Primary Examiner(s): Flory, Christopher A
• Application Number:
  US13/827,595
• Publication Number:
  US 20130282079A1
• Time in Patent Office: 1,111 Days
• Field of Search: 607/62, 607/2, 607/66
• US Class Current: 1/1
• CPC Class Codes: A61N 1/36 for stimulation
• CPC Class Codes: A61N 1/3605 Implantable neurostimulators for stimulating central or peripheral nerve system
• CPC Class Codes: A61N 1/3606 adapted for a particular treatment
• CPC Class Codes: A61N 1/36082 Cognitive or psychiatric applications, e.g. dementia or Alzheimer's disease
• CPC Class Codes: A61N 1/36125 Details of circuitry or electric components
• CPC Class Codes: A61N 1/36128 Control systems
• CPC Class Codes: A61N 1/36142 for improving safety
• CPC Class Codes: A61N 1/3615 Intensity
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data

Abstract

In some examples, a device for delivering electrical stimulation to a medical patient includes an electrical stimulation generator, a coupling circuit, and a processing module. The electrical stimulation generator is configured to generate electrical stimulation. The coupling circuit includes a first node connected to the electrical stimulation generator, a second node configured to deliver the electrical stimulation to the patient, and a capacitor. The coupling circuit is configured to operate in a first state to couple the capacitor between the first and second nodes in a first orientation and operate in a second state to couple the capacitor between the first and second nodes in a second orientation that is opposite to the first orientation. The processing module is configured to set the state of the coupling circuit to one of the first and second states.

Claims

1. A device for delivering electrical stimulation to a patient, the device comprising;

a capacitor; and

circuitry configured to;

deliver an electrical stimulation current of a first polarity to the patient via the capacitor; and

switch a terminal of the capacitor into which the electrical stimulation current flows at least twice during delivery of the electrical stimulation current of the first polarity.

2. The device of claim 1, wherein the circuitry is further configured to switch the terminal of the capacitor into which the electrical stimulation current flows based on at least one of a signal indicative of a magnitude of a voltage developed across the capacitor and a signal indicative of a charge stored in the capacitor.

3. The device of claim 2, wherein the circuitry is further configured to switch the terminal of the capacitor into which the electrical stimulation current flows based on a comparison of the at least one of the signal indicative of the magnitude of the voltage developed across the capacitor and the signal indicative of the charge stored in the capacitor to one or more thresholds.

4. The device of claim 3, wherein the one or more thresholds are selected based on at least one of a type of capacitor and a rated voltage of the capacitor.

5. The device of claim 3, wherein the one or more thresholds are selected based on a specified balance between power consumption and charge-balance accuracy.

6. The device of claim 2, wherein the device comprises a voltage detection module that is configured to measure a voltage across the terminals of the capacitor, and generate the signal indicative of the magnitude of the voltage developed across the capacitor.

7. The device of claim 1, wherein the circuitry is further configured to:

deliver an electrical stimulation current of a second polarity to the patient via the capacitor; and

switch the terminal of the capacitor into which the electrical stimulation current flows at least once during delivery of the electrical stimulation current of the second polarity.

8. The device of claim 7, wherein the electrical stimulation current of the first polarity and the electrical stimulation current of the second polarity are both part of a biphasic electrical stimulation waveform, and wherein the circuitry is further configured to:

cease delivering electrical stimulation current of the second polarity in response to detecting that a number of times that the terminal of the capacitor into which electrical stimulation current flows has been switched during delivery of the electrical stimulation current of the second polarity is equal to a number of times that the terminal of the capacitor into which the electrical stimulation current flows has been switched during delivery of the electrical stimulation current of the first polarity and detecting that the capacitor is discharged.

9. The device of claim 1, wherein the circuitry is further configured to:

deliver a biphasic electrical stimulation waveform to the patient during a stimulation cycle via a plurality of capacitors and a plurality of electrodes, each of the capacitors being electrically coupled to a respective one of the plurality of electrodes;

for each of the plurality electrodes, cease delivering electrical stimulation current via the respective electrode during the stimulation cycle in response to detecting that a number of times that a terminal of a respective one of the capacitors into which electrical stimulation current flows has been switched during delivery of a first polarity of the biphasic electrical stimulation waveform is equal to a number of times that a terminal of the respective one of the capacitors into which the electrical stimulation current flows has been switched during delivery of a second polarity of the biphasic electrical stimulation waveform and that the respective one of the capacitors is discharged;

detect if all electrodes that have not ceased delivery of electrical stimulation current during the stimulation cycle are currently delivering electrical stimulation current of the same polarity; and

adjust a magnitude of a recharge waveform for one or more of the electrodes to be delivered during subsequent biphasic electrical stimulation waveforms in response to detecting that all electrodes that have not ceased delivery of electrical stimulation current during the stimulation cycle are currently delivering electrical stimulation current of the same polarity.

10. The device of claim 1, wherein the circuitry comprises:

an electrical stimulation generator configured to generate the electrical stimulation current;

a coupling circuit comprising a first node connected to the electrical stimulation generator, a second node configured to deliver the electrical stimulation current to the patient, and the capacitor, the coupling circuit being configured to, during delivery of the electrical stimulation current of the first polarity;

operate in a first state to couple the capacitor between the first and second nodes in a first orientation; and

operate in a second state to couple the capacitor between the first and second nodes in a second orientation that is opposite to the first orientation; and

a processing module configured to set the state of the coupling circuit to one of the first and second states.

11. The device of claim 10, wherein the coupling circuit comprises a plurality of switches, wherein the switches are configured to connect the capacitor between the first and second nodes in the first orientation, wherein the switches are configured to connect the capacitor between the first and second nodes in the second orientation, and wherein the processing module is configured to set the states of the switches to set the coupling circuit to one of the first and second states.

12. The device of claim 10, wherein the processing module is configured to set the state of the coupling circuit to maintain the voltage across the capacitor within a threshold voltage range.

13. The device of claim 12, wherein the threshold voltage range is defined by a first threshold voltage and a second threshold voltage, wherein the processing module is configured to change the state of the coupling circuit from the first state to the second state when the voltage across the capacitor reaches the first threshold voltage, and wherein the processing module is configured to change the state of the coupling circuit from the second state to the first state when the voltage across the capacitor reaches the second threshold voltage.

14. The device of claim 10, wherein the electrical stimulation generator is configured to deliver current to the coupling circuit that charges the capacitor to a first voltage polarity when the capacitor is in the first orientation and charges the capacitor to a second voltage polarity that is opposite to the first voltage polarity when the capacitor is in the second orientation.

15. The device of claim 14, wherein the processing module is configured to transition the coupling circuit from the first state to the second state when the capacitor is in the first orientation and the voltage across the capacitor is equal to a positive threshold voltage, and wherein the processing module is configured to transition the coupling circuit from the second state to the first state when the capacitor is in the second orientation and the voltage across the capacitor is equal to a negative threshold voltage.

16. The device of claim 10, wherein the electrical stimulation generator is configured to generate a biphasic electrical stimulation waveform comprising a pulse portion having a first polarity and a subsequent recharge portion having a second polarity that is opposite to the first polarity, wherein the second node is configured to deliver the biphasic electrical stimulation waveform to the patient, and wherein the processing module is configured to transition the coupling circuit between the first and second states during the pulse portion to maintain a voltage across the capacitor within a threshold voltage range.

17. The device of claim 16, wherein the processing module is further configured to:

count a number of transitions during the pulse portion;

transition the coupling circuit between the first and second states during the recharge portion to maintain the voltage across the capacitor within the threshold voltage range;

decrement the number of transitions counted during the pulse portion for each transition during the recharge portion; and

determine that the biphasic electrical stimulation waveform is charge-balanced after the number of transitions has been decremented to zero.

18. The device of claim 10, further comprising a housing configured for implantation in the patient, wherein the housing encloses the electrical stimulation generator, the coupling circuit, and the processing module.

19. The device of claim 10, wherein the second node is configured to electrically connect to an electrode configured for implantation in the patient.

20. A device for delivering electrical stimulation to a patient, the device comprising:

a capacitor;

means for delivering an electrical stimulation current of a first polarity to the patient via the capacitor; and

means for switching a terminal of the capacitor into which the electrical stimulation current flows at least twice during delivery of the electrical stimulation current of the first polarity.

21. The device of claim 20, further comprising:

means for generating electrical stimulation; and

means for capacitively coupling the generated electrical stimulation to the patient using the capacitor, wherein the means for capacitively coupling comprises;

means for orienting the capacitor in a first orientation during delivery of the electrical stimulation of the first polarity to the patient; and

means for orienting the capacitor in a second orientation during delivery of the electrical stimulation of the first polarity to the patient, wherein the second orientation is opposite to the first orientation; and

means for setting the orientation of the capacitor to one of the first and second orientations during delivery of the electrical stimulation of the first polarity.

22. The device of claim 21, further comprising means for setting the orientation of the capacitor based on a magnitude of a voltage developed across the capacitor.

23. A method for delivering electrical stimulation to a patient, the method comprising:

delivering, via a capacitor of a device, an electrical stimulation current of a first polarity to the patient; and

switching a terminal of the capacitor into which the electrical stimulation current flows at least twice during delivery of the electrical stimulation current of the first polarity.

24. The method of claim 23, further comprising

generating electrical stimulation;

capacitively coupling the generated electrical stimulation to the patient using the capacitor, wherein capacitively coupling the generated electrical stimulation comprises;

orienting the capacitor in a first orientation during delivery of the electrical stimulation of the first polarity to the patient; and

orienting the capacitor in a second orientation during delivery of the generated electrical stimulation of the first polarity to the patient, wherein the second orientation is opposite to the first orientation; and

setting the orientation of the capacitor to one of the first and second orientations during delivery of the electrical stimulation of the first polarity.

25. The method of claim 24, further comprising setting the orientation of the capacitor based on a magnitude of a voltage developed across the capacitor.