Digitally Controlled Low-Power DC-DC Converter with Instantaneous On-Line Efficiency Optimization

This paper introduces a digital controller and a segmented power stage that dynamically change mode of operation to maximize power processing efficiency when highly dynamic loads are supplied. The controller operates as a mixed-signal peak current program mode voltage regulator, where a digital current reference is created and used for the efficiency optimization. The losses of the power stage are minimized by combining power stage segmentation and gate swing variation. Based on the current reference, in each switching cycle, the optimal number of power switch segments and gate drive voltages are set through a sequence controller and a novel dual-output switch-capacitor circuit. The effectiveness of the system is verified on a 1.8 V, 5 W, 1 MHz buck converter prototype. The results show that the on-line optimization raises and flattens the efficiency curve and that, for dynamic loads, improves energy utilization by up to 20%.