Pulse generator having an efficient fractional voltage converter and method of use
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 method of operating an implantable pulse generator (IPG) for generating electrical pulses for application to tissue of a patient, the method comprising:
providing a voltage conversion module coupled to a battery for generating an output voltage that is selected from a range of voltage levels including non-integer multiples of a battery voltage according to a control signal, wherein during pump phase operation, (i) the voltage conversion module charges a first storage capacitor to a first voltage level that is less than the battery voltage, and (ii) the voltage conversion modules charges a second storage capacitor to a second voltage level that is greater that the battery voltage;
operating pulse generating circuitry for generating electrical pulses, wherein the pulse generating circuitry receives the output voltage from the voltage conversion module for pulse generation operations; and
operating a controller for controlling the pulse generating circuitry to generate electrical pulses according to a stimulation program, the stimulation program comprising a first amplitude value and a second amplitude value, wherein during operation according to the stimulation program, the controller causes the pulse generating circuitry to repeatedly alternate between generating one or more pulses at the first amplitude value and generating one or more pulses at the second amplitude value;
wherein, during operation according to the stimulation program, the controller sends a control signal to the voltage conversion module to select different voltage levels for the second voltage according to the first and second amplitude values;
wherein during operation according to the stimulation program, the voltage conversion module controls one or more switches to connect multiple storage capacitors to directly provide the output voltage according to the control signal from the controller without discharging the first and second capacitors.
2. The implantable pulse generator of claim 1 wherein the voltage conversion module further connects storage capacitors in series with the battery to directly provide the output voltage.
3. The implantable pulse generator of claim 1 wherein the voltage conversion module charges a third storage capacitor to a third voltage level that is less than the battery voltage.
4. The implantable pulse generator of claim 3 wherein the first voltage level is ½ of the battery voltage and the third voltage level is ¼ of the battery voltage level.
5. The implantable pulse generator of claim 1 wherein the second voltage level is 2 times the battery voltage.
6. The implantable pulse generator of claim 1 wherein the controller selects a lowest voltage level from the range of voltage levels sufficient for an amplitude value of a given pulse.