Design of a low swing power-efficient output stage for DC-DC converters

DC-DC converter is required to supply various DC voltage levels from battery to logic devices for most of the portable systems, such as cellular phone, portable DVD, CD player, etc. As the energy capacity of a battery is usually very limited, DC-DC converter with high efficiency over the entire load range is necessary to extend the battery life time. In this paper, a low swing gate controlled output stage design with capacitor charge recycling scheme is proposed to improve the light load efficiency. Theoretical calculation and Hspice simulation results prove that the proposed low swing output stage design significantly provides a maximum of 8% improvement in light load efficiency for a 3.6V-to-1.2V low power synchronous buck converter operating in 2MHz PWM CCM mode.