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 48-V-input and 2.4-V-to-5-V-output dual-path hybrid buck converter based on an interleaved Fibonacci switched-capacitor topology. This Fibonacci topology is a more effective switch strategy with well-distributed current and reduced voltage stress compared with a conventional one, and hence high efficiency and high power density can be achieved. Among classic switched-capacitor topologies, the Fibonacci configuration maximizes achievable voltage gain, allowing for a large voltage conversion ratio with fewer capacitors. Moreover, compared with conventional inductive buck converters, the dual-path structure with a capacitor always in parallel with the inductor realizes an inductor current reduction of 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 hardware prototype was designed and built to validate the performance of the proposed converter. It was tested with a maximum load of 30 A, and measurement results show that the converter achieves a peak efficiency of 95.8% for 48-V-to-5-V operation and a power density (by total passive volume) of up to 869 W/in³.