Voltage control circuitry for charging ouput capacitor

• US 6,799,070 B2
• Filed: 01/23/2002
• Issued: 09/28/2004
• Est. Priority Date: 07/27/1999
• Status: Expired due to Term

• Current Assignee: Alfred E. Mann Foundation For Scientific Research
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Wolfe, James H., Schulman, Joseph H., Gord, John C.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US10/056,848
• Publication Number:
  US 20020068957A1
• Time in Patent Office: 979 Days
• Field of Search: 607/2, 607/7, 607/1, 607/3, 607/61, 607/72, 607/48, 607/50, 607/52, 607/59, 607/46, 600/554, 600/377, 363/59, 363/60, 363/65, 323/282, 307/38, 307/41
• US Class Current: 607/7
• CPC Class Codes: A61N 1/025 Digital circuitry features of electrotherapy devices, e.g. memory, clocks, processors
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371
• CPC Class Codes: A61N 1/378 Electrical supply
• CPC Class Codes: A61N 1/3782 producing a voltage above the power source level
• CPC Class Codes: A61N 1/3981 High voltage charging circuitry
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

Battery driven voltage control circuitry charges an output capacitor, which periodically supplies a current pulse. The circuitry converts battery voltage VBAT to a charging voltage VUPC based upon programmed parameters and the voltage VCOMPL at the capacitor. The circuitry includes a voltage converter for multiplying VBAT to produce VUPC. VCOMPL is sampled to determine its “droop” at the end of an output current pulse. If the droop is lower than a threshold, then the voltage converter increases the charging voltage. If the droop is above a threshold, then the voltage converter reduces the charging voltage. This feedback maintains the output voltage within an acceptable operating range to produce an efficacious output current pulse for stimulation without causing unproductive energy loss. In order to avoid premature depletion of battery energy, VUPC is compared with VCOMPL to determine the optimum clock rate to be used to convert VBAT to VUPC.

Claims

1. An apparatus for supplying a current pulse to a load impedance, said apparatus comprising;

a stimulator capacitor;

an output current control device for selectively discharging said stimulator capacitor to produce an output current pulse through said load impedance;

a battery supplying a battery voltage;

voltage converter circuitry for producing an output voltage signal to charge said stimulator capacitor; and

wherein

said voltage converter circuitry comprises;

a plurality of converter capacitors;

a plurality of switches configured for directing charge from said battery to said converter capacitors in a first mode of operation and configured for directing charge from said converter capacitors to said stimulator capacitor in a second mode of operation;

wherein the selection of switches in said first and second modes of operations determines a voltage multiplication factor;

clock circuitry for periodically switching said switches from said first to said second modes of operation; and

measurement circuitry for periodically adjusting said voltage multiplication factor in response to a voltage measured across said stimulator capacitor.

2. The apparatus of claim 1 wherein said output current control device defines the duration of said output current pulse.

3. The apparatus of claim 2 wherein said voltage across said stimulator capacitor is measured proximate to the end of said output current pulse;

and wherein

said voltage multiplication factor is adjusted in response to said measured voltage.

4. The apparatus of claim 2 wherein said output current control device is programmable to define the duration and/or frequency of said output current pulse.

5. The apparatus of claim 1 wherein said clock circuitry is responsive to said measurement circuitry for determining the rate of adjustment of said multiplication factor.

6. The circuit apparatus of claim 1 further including a recharge current control device responsive to said output voltage for supplying a current to charge said stimulator capacitor.

7. The circuit apparatus of claim 6 further including a programmed controller for controlling said recharge current control device.

8. The circuit apparatus of claim 1 wherein said battery is rechargeable.

9. An apparatus suitable for supplying a current pulse to a load impedance, said apparatus comprising;

a stimulator capacitor;

a battery supplying a battery voltage;

voltage converter circuitry for producing an output voltage signal to charge said stimulator capacitor; and

wherein

said voltage converter circuitry comprises;

a plurality of converter capacitors;

a plurality of switches configured for directing charge from said battery to said converter capacitors in a first mode of operation and configured for directing charge from said converter capacitors to said stimulator capacitor in a second mode of operation;

wherein the selection of switches in said first and second modes of operations determines a voltage multiplication factor;

clock circuitry for periodically switching said switches from said first to said second modes of operation at a clock rate; and

measurement circuitry for periodically adjusting said voltage multiplication factor in response to a voltage measured across said stimulator capacitor.

10. The apparatus of claim 9 wherein said multiplication factor is increased when said voltage measured across said stimulator capacitor is below a threshold voltage.

11. The apparatus of claim 9 wherein said multiplication factor is decreased when said voltage measured across said stimulator capacitor is above a threshold voltage.

12. The apparatus of claim 9 wherein said clock rate is adjustable according to said voltage measured across said stimulator capacitor.

13. A method for generating a voltage across a stimulator capacitor suitable for supplying a current pulse to a load impedance, said method comprising the steps of:

periodically supplying charge from a voltage source to a plurality of converter capacitors via a plurality of switches configured to be activated in a first mode of operation;

periodically supplying charge from said plurality of converter capacitors to said stimulator capacitor via said plurality of switches configured to be activated in a second mode of operation;

wherein the relationship between the voltage supplied by the voltage source and the voltage supplied to said stimulator capacitor defines a multiplication factor that is determined by the configuration of switches activated in said first and second modes of operation;

periodically measuring a voltage across said stimulator capacitor; and

altering said switches activated in said first and second modes of operations in response to said voltage measured across said stimulator capacitor.

14. The method as in claim 13 further comprising the step of increasing said multiplication factor when said voltage measured across said stimulator capacitor is below a certain threshold voltage.

15. The method as in claim 13 further comprising the step of decreasing said multiplication factor when said voltage measured across said stimulator capacitor is above a threshold voltage.

16. The method as in claim 13 wherein the rate of switching between said first and second modes of operations is adjustable in response to said voltage measured across said stimulator capacitor.