Optimal High-Efficiency DCM Design of Switched-Inductor CMOS Power Supplies

Abstract

Improving efficiency for switched-inductor (SL) power-supplies is vital for energy-limited battery-supplied microsystems such as wireless microsensors and portable devices. These microsystems idle mostly so efficiency in Discontinuous Conduction Mode (DCM) is crucial. Moreover, limited volumes of these tiny microsystems often lead to using tiny lossy inductors, which further reduce efficiency. Therefore, this paper theorizes how to select the optimal inductor, design the optimal power stage, and optimize the current profile to achieve the highest efficiency in DCM, using insightful derivations. This proposed co-design of inductor and current profile is absent in the state-of-the-art. The theory is accurate, and the percentage error is 0.3–4.9%. Using the proposed theory, with a 1.6 × 0.8 × 0.8 mm3 inductor, efficiency improvement can reach 6.4% compared with the State of the Art.