A survey of light-load efficiency improvement techniques for low-power dc-dc converters

Maintaining high efficiency at light-load conditions is extremely important in most modern power management applications, where the predominantly digital loads spend the majority of their time in idle mode. The objective of this paper is to review circuit and system-level techniques used to leverage the existing process technologies in order to achieve high efficiency over a wide load range. The main focus is on low-power dc dc converters operating above several MHz. Existing fixed and variable frequency schemes are contrasted in this work, namely pulse-frequency modulation with fixed and adaptive on-time, burst-mode control, adaptive gate swing, segmented power-stage, resonant gate drivers and capacitive charge recovery.