Duty cycle estimator

A duty cycle estimator determines a nominal duty cycle of an output regulator and comprises at least two modes including a mode one estimator and a mode two estimator. The mode one estimator determines the nominal duty cycle as a function of prior duty cycles. The mode two estimator determines the nominal duty cycle as a function of accumulated error. A mode selector selects one of the at least two modes to generate the nominal duty cycle based on a mode selection criteria.