A 1500-A/48-V-to-1-V Switching Bus Converter for Next-Generation Ultra-High-Power Microprocessors

This paper presents a switching bus converter, an ultra-high-current hybrid switched-capacitor (SC) voltage regulator for single-stage 48-V-to-1-V vertical power delivery, for next-generation ultra-high-power microprocessors (e.g., GPUs, CPUs, ASICs, etc.). The proposed switching bus converter consists of two 2-to-1 SC front-ends and four 10-branch series-capacitor-buck (SCB) modules, merged together through four switching buses. Compared to the existing DC-bus-based architecture, the proposed switching-bus-based architecture does not require DC bus capacitors, reduces the number of switches, and ensures complete soft-charging operation. Through a topological comparison, this paper reveals that the proposed topology achieves the lowest normalized switch stress and the smallest normalized passive component volume compared with existing 48-V-to-1-V hybrid SC demonstrations, showing great potential for both higher efficiency and higher power density than prior solutions. A hardware prototype was designed and built with custom four-phase coupled inductors and gate drive daughterboards to validate the functionality and performance of the proposed switching bus converter. It was tested up to 1500-A output current and achieved 92.7% peak system efficiency, 85.7% full-load efficiency (including gate drive loss), and 759 W/in³ power density (by box volume), pushing the performance limit of the state-of-the-art 48-V-to-1-V works in previous literature.