Cascaded step-up converter and charge pump for efficient compliance voltage generation in an implantable stimulator device

• US 20070097719A1
• Filed: 11/03/2005
• Published: 05/03/2007
• Est. Priority Date: 11/03/2005
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Parramon, Jordi, Marnfeldt, Goran
• Granted Patent: US 7,872,884 B2
• Time in Patent Office: Days
• US Class Current: 363/72
• CPC Class Codes: A61N 1/37205 Microstimulators, e.g. implantable through a cannula
• CPC Class Codes: A61N 1/378 Electrical supply
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/155 using semiconductor devices only

Abstract

Disclosed herein are circuits and methods for generating a compliance voltage from a battery voltage in an implantable stimulator device. In one embodiment, the battery voltage is boosted to form the compliance voltage for driving the current sources (DACs) that provide therapeutic current to the electrodes on the device. Such improved boosting circuitry is preferably cascaded and comprises two stages. The first stage is preferably a step-up converter, which is used to generate an intermediate voltage from the battery voltage. The second stage is preferably a charge pump, which is used to generate the compliance voltage from the intermediate voltage. By splitting the boosting into stages, power efficiency during generation of high voltages is improved compared to the use of step-up converters and resolution in setting the compliance voltage is improved compared to the use of charge pumps alone. Moreover, depending on the compliance voltage to be produced by the boosting circuitry, the various stages can be selectively activated.

Claims

1. A method for boosting a battery voltage to a compliance voltage in an implantable medical device, comprising:

boosting a battery voltage to an intermediate voltage using at least a first boosting stage; and

boosting the intermediate voltage to a compliance voltage using at least a second boosting stage.

2. The method of claim 1, wherein the first boosting stage comprises a different circuit than the second boosting stage.

3. The method of claim 1, wherein one of the first or second boosting stages comprises a step-up converter, and wherein the other comprises a charge pump.

4. The method of claim 3, wherein the step-up converter comprises a switched LC circuit, and wherein the charge pump comprises a doubler.

5. The method of claim 1, wherein the compliance voltage drives a current source for passing a current through an electrode of the device for stimulating a patient'"'"'s tissue.

6. The method of claim 1, wherein the first boosting stage comprises a step-up converter, and wherein the second boosting stage comprises a charge pump.

7. A method for boosting a battery voltage to a compliance voltage in an implantable medical device, the device comprising a battery voltage coupled to an intermediate voltage using at least a first boosting stage, and the intermediate voltage coupled to a compliance voltage using at least a second boosting stage, comprising:

assessing the magnitude of the compliance voltage;

depending on the magnitude of the compliance voltage, generating control signals; and

selectively activating none, some, or all of the boosting stages in accordance with the control signals, wherein failure to activating a boosting stage comprises bypassing that boosting stage.

8. The method of claim 7, wherein the first boosting stage comprises a different circuit than the second boosting stage.

9. The method of claim 7, wherein one of the first or second boosting stages comprises a step-up converter, and wherein the other comprises a charge pump.

10. The method of claim 9, wherein the step-up converter comprises a switched LC circuit, and wherein the charge pump comprises a doubler.

11. The method of claim 7, wherein the compliance voltage drives a current source for passing a current through an electrode of the device for stimulating a patient'"'"'s tissue.

12. The method of claim 7, wherein bypassing a boosting stage comprises use of a multiplexer.

13. The method of claim 7, wherein assessing the magnitude of the compliance voltage comprises determining if the compliance voltage is less than or equal to the battery voltage, and if so, activating none of the boosting stages in accordance with the control signals.

14. The method of claim 7, wherein assessing the magnitude of the compliance voltage comprises comparing the compliance voltage against a threshold, and if the compliance voltage is less than a threshold, activating only some of the boosting stages in accordance with the control signals.

15. The method of claim 14, wherein if the compliance voltage is greater than or equal to the threshold, activating all of the boosting stages in accordance with the control signals.

16. Converter circuitry for an implantable medical device, comprising:

at least a first boosting stage, wherein the first boosting stage receives a battery voltage at its input and is capable of producing a boosted intermediate voltage at its output; and

at least a second boosting stage, wherein the second boosting stage receives the intermediate voltage at its input and is capable of producing a boosted compliance voltage at its output.

17. The circuitry of claim 16, wherein the first boosting stage comprises a different circuit than the second boosting stage.

18. The circuitry of claim 16, wherein one of the first or second boosting stages comprises a step-up converter, and wherein the other comprises a charge pump.

19. The circuitry of claim 18, wherein the step-up converter comprises a switched LC circuit, and wherein the charge pump comprises a doubler.

20. The circuitry of claim 16, further comprising a current source powered by the compliance voltage, wherein the current source passes a current through an electrode of the device for stimulating a patient'"'"'s tissue.

21. The circuitry of claim 16, further comprising level detector circuitry for sensing the magnitude of the compliance voltage, and for generating a first control signal for selectively activating the first boosting stage, and a second control signal for selectively activating the second boosting stage.

22. The circuitry of claim 21, wherein the level detector circuitry compares the magnitude of the compliance voltage to at least one threshold, and depending on the comparison, selectively activates none, some, or all of the control signals to selectively activate none, some, or all of the boosting stages.

23. The circuit of claim 22, wherein the level detector circuitry activates only one of the first or second control signals if the magnitude of the compliance voltage is less than the threshold, and wherein the level detector circuitry activates both of the first and second control signals if the magnitude of the compliance voltage is greater than or equal to the threshold.