A Hybrid Always-Dual-Path Recursive Step-Down Converter Using Adaptive Switching Level Control Achieving 95.4% Efficiency with 288mΩ Large-DCR Inductor

Abstract

Supply voltages of mobile systems have been gradually scaled down, requiring step-down converters with a low voltage conversion ratio (VCR) that can convert a Li-ion battery voltage of 2.8-4.2V to a lower supply voltage around 1V [1]–[4]. Also, the sizes of mobile device are getting smaller, limiting the volume of output components, especially inductors. Smaller-volume inductors suffer from larger DC resistance (DCR), increasing conduction power loss. To address these issues, hybrid topologies, which transfer load currents through both inductor and capacitor in parallel to reduce DCR losses, have been proposed [5], but more aggressive techniques to further improve efficiencies are required. The proposed converter not only reduces the inductor current, $I_{L}$, with an always-dual-path topology, but also minimizes $\Delta I_{L}$ using recursive switching level control that can reduce the switching voltage difference across the inductor in a build-up phase.