The Switched-Capacitor step-down DC-DC converter with improved voltage stability and load range

A 5V to 1.1V Switched-Capacitor (SC) DC-DC converter with a novel PFM control is proposed here to achieve a steady output voltage with wide load range. The advantage is through PFM control, the duty cycle of the converter can be fixed to obtain the optimum efficiency even in wide load condition. For the novel PFM control, it uses an error amplifier to sense the output voltage and produce an error signal to change the switching frequency of the converter. Besides, a digital circuit is used to fix the duty-cycle to obtain the best efficiency. This paper will then prove the proposed PFM control has better performance than other control methods.