Digitally controlled low-power DC-DC converter with segmented output stage and gate charge based instantaneous efficiency optimization

Abstract

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 two methods. Based on the current reference, in each switching cycle, the optimal number of power switch segments and the gate voltage swing level for power MOSFETS are set through a sequence controller and a gate voltage scaling circuit. A 1.8 V, 5 W, 1 MHz buck converter prototype is built. The results verify the operation of the system and show that on-line optimization raises and flattens the efficiency curve by as much as 18%.