Frequency jitter utilizing a fractional valley switching controller

摘要

A method involves determining a target number of valleys of a resonant waveform at a drain node of a main switch of a power converter. The target number of valleys corresponds to a desired off-time of the main switch. A first intermediate valley number of a series of intermediate valley numbers is selected. An average of the series of intermediate valley numbers corresponds to the target number of valleys. A first average off-time of the main switch is controlled, for a duration of a first modulation period, such that the first average off-time corresponds to the first intermediate valley number. Upon expiration of the first modulation period, a second intermediate valley number of the intermediate valley numbers is selected. A second average off-time of the main switch is controlled, for a duration of a second modulation period, such that the second average off-time corresponds to the second intermediate valley number.