Pulse generator having an efficient fractional voltage converter and method of use

Abstract

Disclosed are systems and methods which provide voltage conversion in increments less than integer multiples of a power supply (e.g., battery) voltage. A representative embodiment provides power supply voltage multipliers in a binary ladder distribution to provide a desired number of output voltage steps using a relatively uncomplicated circuit design. By using different sources in various combinations and/or by “stacking” different sources in various ways, the voltage multiplier circuit may be used to provide desired voltages. In order to minimize the number of components used in a voltage converter of an embodiment, a capacitive voltage converter circuit uses one or more storage capacitors in place of pump capacitors in a voltage generation cycle. Also, certain embodiments do not operate to generate an output voltage until the time that voltage is needed.

1 . A pulse generator, for delivering electrical stimulation to a patient, comprising: 
 a battery operable to power the pulse generator;    circuitry for generating and delivering electrical pulses to tissue of the patient according to a plurality of controllable output levels; and    a voltage conversion module operable to convert from a voltage level from the battery to a variable converted voltage level for provision to the circuitry for generating and delivering, wherein the voltage conversion module comprises a plurality of capacitive voltage multipliers including at least one fractional capacitive voltage multiplier, and the voltage conversion module including a voltage combining element that combines the voltages output from the plurality of capacitive voltage multipliers to produce the converted voltage level.    
   
   
       2 . The pulse generator of  claim 1 , wherein the voltage conversion module provides converted voltage levels in ¼ increments of the voltage level from the battery.  
   
   
       3 . The pulse generator of  claim 1 , wherein the voltage conversion module comprises a logic element for receiving multiple control bits, the control bits identifying a desired voltage level for the converted voltage level.  
   
   
       4 . The pulse generator of  claim 1 , wherein the voltage conversion module comprises: 
 switching circuitry that is operable to controllably arrange a plurality of capacitors into a stacked circuit configuration to achieve a desired fractional voltage level.    
   
   
       5 . The pulse generator of  claim 4 , wherein the switching circuitry of the voltage conversion module is implemented in at least one integrated circuit disposed between a plurality of capacitors.  
   
   
       6 . The pulse generator of  claim 4 , wherein lower voltage capacitors are disposed at a bottom portion of the stacked circuit configuration and higher voltage capacitors are disposed at a top portion of the stacked circuit configuration.  
   
   
       7 . The pulse generator of  claim 1 , wherein the voltage conversion module is operable to partition a plurality of controllable switches to minimize a number of components of the voltage conversion module experiencing high voltage levels.  
   
   
       8 . The pulse generator of  claim 1  further comprising: 
 control circuitry for causing delivery of multiple pulses to tissue of the patient in succession, the control circuitry (i) causing the converted voltage level to equal a first voltage level before causing the circuitry for delivering to deliver a first electrical pulse at a first amplitude; and shortly thereafter (ii) causing the converted voltage level to equal a second voltage level before causing the circuitry for delivering to deliver a second electrical pulse at a second amplitude.    
   
   
       9 . The pulse generator of  claim 8 , wherein at least one storage capacitor in the plurality of capacitive voltage multipliers is not discharged between the first and second electrical pulses.  
   
   
       10 . The pulse generator of  claim 1 , wherein at least one capacitor in the voltage conversion module is used in a charge phase, a pump phase, and a source phase.  
   
   
       11 . The pulse generator of  claim 1 , wherein the battery is a rechargeable battery.  
   
   
       12 . The pulse generator of  claim 1 , wherein the pulse generator device is a neurostimulator device.  
   
   
       13 . A method of operating a pulse generator for delivering electrical stimulation to a patient, the method comprising: 
 powering the pulse generator using a battery;    generating electrical pulses according to a plurality of controllable output levels;    delivering the generated electrical pulses to tissue of the patient; and    converting from a voltage level from the battery to a variable converted voltage level for use by the generating, wherein the converting includes (i) multiplying the voltage level from the battery by multiple capacitive multipliers including at least one fractional capacitive multiplier and (ii) combining voltages output from the multiple capacitive multipliers to produce the converted voltage level.    
   
   
       14 . The method of  claim 13 , wherein the converting is performed in ¼ increments of the voltage level from the battery.  
   
   
       15 . The method of  claim 13 , further comprising: 
 communicating multiple control bits to identify a desired voltage level for the converted voltage level.    
   
   
       16 . The method of  claim 13 , wherein the converting comprises: 
 configuring switching circuitry between a plurality of capacitors to achieve the converted voltage level.    
   
   
       17 . The method of  claim 16 , wherein a plurality of switches are controlled to create a stacked circuit configuration of capacitors to achieve a desired fractional voltage level.  
   
   
       18 . The method of  claim 13  further comprising: 
 causing the converted voltage level to equal a first voltage level before causing the generation and delivery of a first electrical pulse at a first amplitude, and shortly thereafter causing the converted voltage level to equal a second voltage level before causing the generation and delivery of a second electrical pulse at a second amplitude.    
   
   
       19 . The method of  claim 18 , wherein at least one storage capacitor in the plurality of capacitive voltage multipliers is not discharged between the first and second electrical pulses.  
   
   
       20 . The method of  claim 13 , wherein at least one capacitor in the multiple capacitive voltage multipliers is used in a charge phase, a pump phase, and a source phase.