Multi-mode synchronous buck converter with non-uniform current distribution for portable applications

Nowadays, portable applications are very important in telecommunications, business and entertainment markets. Handheld devices like Ultra Mobile PCs (UMPCs), cell phones, PDAs and mobile Internet devices (MIDs) are battery-dependant. In order to decrease the battery voltage level and supply components like the processor, synchronous buck converter (SBC) is extensively used as voltage regulator (VR) in mobile devices. Synchronous buck converter has good efficiency at medium or high load conditions, but at very light-load operation, the converter efficiency is severely reduced. That condition is normal in these converters, but in battery operated systems, it becomes critical. In this paper, some already known techniques to improve efficiency converter at light load operation are presented and discussed. Additionally, a multiphase synchronous buck converter with non-uniform current distribution between phases and load-dependant operation modes is proposed. The basic concept, as well as the analysis and simulation results of the proposed VR, is presented.