T32.5 - A 48V to 2.4V-5V 95.8%-Peak-Efficiency 869W/in³-Power-Density Fibonacci Dual-Path Hybrid DC-DC Converter with Inductor Current Reduction and Low Output Resistance

This paper presents a 48V-input and 2.4V-5V-output dual-path hybrid buck converter based on a Fibonacci switched-capacitor topology to provide large voltage conversion ratio with high efficiency and high power density. Among the classic switched-capacitor topologies, Fibonacci topology realizes the maximum achievable voltage gain, and thus a large voltage conversion ratio can be obtained by this converter with fewer capacitors. Moreover, compared with conventional inductive buck converters, the dual-path structure with a capacitor always in parallel with the inductor lowers the inductor current to up to 62.5%, thus significantly reducing inductor DCR loss and relieving the reliance on a bulky inductor. Topology optimization on both the capacitors and the inductor results in a lower output resistance with a minimized power loss. A prototype has been designed with a maximum load of 30A. Measurement results show that the converter achieves a peak efficiency of 95.8% for 48V-to-5V operation and a power density of up to 869W/in3.