PWM CONTROL SCHEME FOR PROVIDING MINIMUM ON TIME

摘要

According to certain aspects, the present embodiments are based on an improved switched-capacitor (SC) converter topology that typically does not include an inductor. In particular, the topology includes a ladder SC circuit configured as a cap divider. The cap divider can be used to provide an unregulated output voltage Vout that is a certain fraction (e.g. 2) of input voltage Vin, such as Vin/2 (i.e., duty cycle≈50%). In some embodiments of a PWM control scheme for this topology, the PWM OFF pulse is free running, determined by the logic combination of timer and VOUT comparator. The PWM OFF pulse width is measured and used as the reference for a minimum PWM ON timer. The PWM ON pulse is therefore forced to be at least a minimum width that is proportional to the PWM OFF pulse. A UVOV protection window can be added to ignore the minimum PWM ON timer during a load transient.