In one embodiment, a method of operating an implantable pulse generator comprises: providing power to a voltage converter at a first voltage level; outputting a second voltage level by the voltage converter, the second voltage level being a variable voltage level that is controlled by a control signal provided to the voltage converter, the second voltage level being provided to pulse generating circuitry of the implantable pulse generator, the second voltage level being selectable from a plurality of voltages including non-integer multiples of the first voltage level; generating pulses by the pulse generating circuitry, the pulse generating circuitry including current control circuitry for controlling the pulses to cause the pulses to provide substantially constant current to tissue of the patient; and applying at least two different control signals to the voltage converter during individual pulses to provide successively increasing voltages to the pulse generating circuitry during a respective pulse.