Design of Soft-Charging Switched-Capacitor DC-DC Converters Using Stage Outphasing and Multiphase Soft-Charging

In this paper, two techniques, called stage-outphasing (SO) and multiphase soft-charging (MSC), are introduced, which make use of the advanced multiphasing concept to soft-charge charge transfers between flying capacitors. As such, the charge sharing losses of fully integrated switched-capacitor (SC) converters are reduced, leading to better capacitance utilization, higher efficiency, and higher power density. Furthermore, when used in combination with the Dickson converter, the relative improvement gets better with increasing voltage conversion ratio (VCR), making them an excellent choice to reduce power delivery network-induced losses in modern microchips. The impact of the proposed techniques on the performance is discussed. A 3:1 Dickson SC converter is realized, which implements SO and MSC and achieves a state-of-the-art 1.1-W/mm(2) power density and 82% efficiency combination using common capacitor technologies. Finally, two figures of merit for monolithic SC dc-dc converters are proposed that include the VCR and power density, to allow fair comparison of the converter's performance to the literature.