Implantable pulse generator comprising fractional voltage converter

1. An implantable pulse generator for generating electrical pulses for stimulating tissue of a patient, comprising:

pulse generating circuitry for generating pulses and delivering the pulses to outputs of the implantable pulse generator;

a controller for controlling the pulse generating circuitry;

wherein the pulse generating circuitry comprises a voltage multiplier for multiplying a battery voltage, the voltage multiplier including multiple outputs, wherein a first output of the multiple outputs provides a voltage that is programmably selectable from a plurality of voltages including non-integer multiples of the battery voltage, wherein a second output of the multiple outputs provides a voltage that is a fixed multiple of the battery voltage;

wherein the controller controls the pulse generator circuitry to generate a first pulse for stimulation of the patient using a first output of the multiple outputs and controls the pulse generator circuitry to generate a second pulse to discharge output capacitors of residual charge from the first pulse using a second output of the multiple outputs.

2. The implantable pulse generator of claim 1 further comprising:

a variable resistance circuit for controlling the amplitude of an output pulse.

3. The implantable pulse generator of claim 2 wherein the controller modifies a resistance of the variable resistance circuit between the first and second pulses.

4. The implantable pulse generator of claim 1 wherein first pulse and the second pulse are separated by a blanking period.

5. The implantable pulse generator of claim 1 wherein the controller causes the second pulse to discharge the output capacitors to a non-zero level that is sufficiently low to permit passive discharge to substantially remove remaining charge before another stimulation pulse is generated.

6. The implantable pulse generator of claim 1 wherein the voltage multiplier comprises:

a plurality of capacitors; and

switching circuitry for selectively connecting to the plurality of capacitors, wherein said switching circuitry comprises a plurality of controllable switches, wherein the plurality of controllable switches includes at least a first switch having a higher relative voltage characteristic and a second switch having a lower relative voltage characteristic;

wherein the switching circuitry is controlled to provide the first output according to a digital control signal, wherein the voltage multiplier couples the first output to one of the first and second switches in relation to a magnitude corresponding to the digital control signal.

7. The implantable pulse generator of claim 1 wherein the voltage multiplier comprises:

a plurality of capacitors; and

switching circuitry for selectively connecting to the plurality of capacitors, wherein said switching circuitry comprises a plurality of controllable switches, wherein the plurality of controllable switches includes at least a first switch having a higher relative voltage characteristic and a second switch having a lower relative voltage characteristic;

clock conversion circuitry for converting a received clock into respective level-shifted clocks for application to the plurality of controllable switches, wherein the clock conversion circuitry up-shifts the received clock to a maximum level for generation of a level-shifted clock for application to the first switch and, then, down-shifts from the maximum level for generation of a level-shifted clock for application to the second switch.

8. The implantable pulse generator of claim 1 wherein the controller comprises a microprocessor.

9. The implantable pulse generator of claim 1 wherein the controller comprises an output driver integrated circuit.

10. The implantable pulse generator of claim 1 wherein the controller controls the pulse generating circuitry to generate and deliver pulses at a frequency of 250 Hz or greater.

11. A method of operating an implantable pulse generator that is adapted to stimulate tissue of a patient, the implantable pulse generator comprising pulse generating circuitry for generating and delivering electrical pulses, the method comprising:

operating a voltage multiplier for multiplying a battery voltage to provide multiple outputs, wherein a first output of the multiple outputs provides a voltage that is programmably selectable from a plurality of voltages including non-integer multiples of the battery voltage, wherein a second output of the multiple outputs provides a voltage that is a fixed multiple of the battery voltage;

controlling the pulse generating circuitry to generate a first pulse for stimulation of the patient using a first output of the multiple outputs; and

controlling the pulse generator circuitry to generate a second pulse to discharge output capacitors of residual charge from the first pulse using a second output of the multiple outputs.

12. The method of claim 11 wherein the implantable pulse generator further comprises a variable resistance circuit for controlling the amplitude of an output pulse.

13. The method of claim 11 further comprising:

modifying a resistance of the variable resistance circuit between the first and second pulses.

14. The method of claim 11 wherein first pulse and the second pulse are separated by a blanking period.

15. The method of claim 11 wherein the second pulse discharges the output capacitors to a non-zero level that is sufficiently low to permit passive discharge to substantially remove remaining charge before another stimulation pulse is generated.

16. The method of claim 11 wherein the voltage multiplier comprises switching circuitry for selectively connecting to capacitors of the voltage multiplier, wherein said switching circuitry comprises a plurality of controllable switches, wherein the plurality of controllable switches includes at least a first switch having a higher relative voltage characteristic and a second switch having a lower relative voltage characteristic, the method further comprising:

selectively coupling the first output of the multiple outputs to one of the first and second switches in relation to a magnitude of the voltage selected for the first output.

17. The method of claim 11 wherein the voltage multiplier comprises switching circuitry for selectively connecting to capacitors of the voltage multiplier, wherein said switching circuitry comprises a plurality of controllable switches, wherein the plurality of controllable switches includes at least a first switch having a higher relative voltage characteristic and a second switch having a lower relative voltage characteristic, the method further comprising:

converting a received clock into respective level-shifted clocks for application to the plurality of controllable switches, wherein converting up-shifts the received clock to a maximum level for generation of a level-shifted clock for application to the first switch and, then, down-shifts from the maximum level for generation of a level-shifted clock for application to the second switch.

18. The method of claim 11 wherein the pulse generator is controlled by a controller comprising a microprocessor.

19. The method of claim 11 wherein the pulse generator is controlled by a controller comprising an output driver integrated circuit.

20. The method of claim 1 wherein the pulse generating circuitry generates and delivers pulses at a frequency of 250 Hz or greater.