A 93.7% efficient 400A 48V-1V merged-two-stage hybrid switched-capacitor converter with 24V virtual intermediate bus and coupled inductors

This paper presents a 93.7% efficient 400 A 48 V-1 V merged-two-stage hybrid switched-capacitor converter with 24 V virtual intermediate bus and coupled inductors. The first stage of the converter is a 2:1 interleaved charge pump which converts the 48 V input voltage to a virtual intermediate bus at 24 V. The second stage contains multiple paralleled 24:1 four-phase series capacitor buck modules with coupled inductors which have an equivalent voltage conversion ratio of 6:1. The two stages are linked by a 24 V virtual intermediate bus with small decoupling capacitor and voltage ripple. The hybrid switched capacitor architecture enables high efficiency, high power density, and high control bandwidth for ultra-high-current point-of-load applications. The effectiveness of the topology is verified by a 48 V-1 V 400 A prototype with a peak efficiency of 93.7% at 120 A and a full load efficiency of 88.7% at 400 A. The power density of the prototype is 342 W/in3. Compared to a decoupled-two-stage design, the merged-two-stage design reduces the passive component size at the cost of slightly reduced efficiency.