The cyclic PWM pattern of a power controller typically dictates the timing according to which the controller measures voltage and issues commands to control that voltage; at the beginning of each PWM cycle, a power controller measures the voltage at the load device and controls the power delivery by the converter that is active during that PWM cycle based on that measurement. The PWM period is typically determined by the operating efficiencies of the converter(s) used in the power-delivery system (i.e., the PWM period is set close to or equal to the value that results in the most efficient converter performance).

However, because a power controller only reacts to the measurement at the device once per PWM cycle, a longer PWM cycle (e.g., for the sake of converter efficiency) results in a potential for more time between a voltage change at a device and the ability of a power controller to react. This is not ideal, because large, sudden changes in voltage (i.e., the voltage changes that can be dangerous to sensitive devices) often require faster reaction than smaller, gradual changes in voltage. For the purposes of fast reaction time to voltage changes, the shortest possible PWM cycle is ideal.

While adding more converters (and thus, phases) into a power-deliver system may make shorter PWM cycles more feasible, in typical applications it is not cost effective to add in a sufficient amount of phases for ideal reaction to changes in voltage. Even assuming that cost were not an issue, it may also be impractical to add a significant amount of converters, as each converter typically is paired with an inductor and capacitor to smooth out power delivered to a device, and space considerations may limit the amount of converters that may be added to the system.