Low-volume hybrid tap-connected SC-buck converter with shared output capacitor

This paper introduces a hybrid converter topology for low-power applications that uses a novel connection of a switched capacitor (SC) converter and a buck converter to achieve smaller volume and better power processing efficiency than conventional step-down solutions. Specific advantages of this topology include smaller inductor volume, reduced input filter requirements, and lower voltages stress of the semiconductor components. These advantages are achieved by connecting the buck converter to a tap of a 2:1 ladder SC circuit and both stages share the middle capacitor of the capacitor stack. A direct connection of the stacked input capacitors of the SC to the source acts as a portion of the input filter and reduces the voltage swing across the inductor and switching components, allowing for smaller inductance value and lower voltage stress. The advantages of this topology are verified with a digitally controlled 24 V to 5 V/ 5 A, 1 MHz experimental prototype having about 50% smaller inductor, and about 30% lower voltage stress than a conventional buck converter.