A Reconfigurable 5-Mode Inductively Assisted Switched-Capacitor DC-DC Converter with 0.5-to-2.5V Output Voltage Range

This paper presents an inductively assisted switched-capacitor (L-SC) converter that employs a small inductor to enable continuous voltage conversion above and below the native n:m conversion ratio of a series-parallel SC converter. Unlike buck and flying-capacitor multilevel converters, the employed inductor in the demonstrated converter delivers only a fraction of the load current rather than its entire value, whereas the embedded SC supplies the remaining amount and lowers the voltage swing across the inductor as well as its current ripple. To maintain high efficiency across a wide output voltage range (i.e., 0.5-to-2.5V), a reconfigurable L-SC converter structure is proposed that enables altering the series-parallel SC conversion ratio between three distinct values, 2:1, 3:1, and 3:2, to facilitate five L-SC operating modes (i.e., <3:1,<2:1,>2:1,<3:2, and >3:2). The five modes specifically allow the converter to avoid operation near the native SC ratios via small duty cycles, which otherwise lead to high discharging currents in the flying capacitors and their associated switches, and hence, low conversion efficiency. Simulation results in 0.18µm CMOS demonstrate that the proposed reconfigurable five-ratio series-parallel L-SC topology achieves a 98% peak efficiency while delivering power at a density of 2.55W/mm3 and a peak power density of 10.18W/mm3 with an efficiency of 96.3%.