To keep shrinking the form factor of portable and wearable devices, high current density power converter solutions are highly favorable. Most of these smart devices are powered by a battery or USB port, while the digital processors require a supply dynamic voltage scaling range of 0.5 V to 1.2 V (Fig. 1 top left). A conventional buck converter has difficulties in achieving high power density and high efficiency, mainly because the power inductor has a large DCR and therefore a large conduction loss when placed on the output (low-voltage highcurrent) side of the converter. To reduce the inductor DCR loss, there are mainly two different methods. One is to put the inductor on the input (high-voltage low-current) side [1] -[3], while other methods add one or more flying capacitor(s) connected in-series and/or in-parallel with the inductor to reduce its AC and also DC currents [4] -[6].