A pulse width modulated pulse signal is generated and its duty cycle adjusted according to at least two different schedules, for example, a coarse tuning cycle and a fine tuning cycle. The target duty cycle is derived according to an offset between output voltage and target voltage, as well as the rate of changes in the offset. In the coarse tuning cycle, large changes in the control signal pulse width is used to drive output voltage to target at a fast pace. As output voltage approaches target voltage, smaller adjustment are made to the duty cycle of the control pulse width in the fine tuning cycle. The rate of pulse width change is also taken into consideration, to further improve operation of the DC-DC converter.