Hybrid-Switched-Capacitor VRM with Zero-Voltage-Switching Intermediate Voltage Rails

The paper presents a novel hybrid-switched-capacitor voltage regulator module (HSC-VRM) design with Zero-voltage-switching (ZVS) intermediate voltage rails for CPU power supply. This approach combines a switched-capacitor stage to split the input voltage into multiple switched voltage rails, along with a multiphase buck stage connected in parallel at the output terminal. The proposed topology improves the utilization rate of components. It integrates flying capacitors as input filters for the buck stage and reuses switches for both two stages, thus enhancing power density. An LC network controls the slew rate of each intermediate voltage rail and enables ZVS of the switched-capacitor stage. Moreover, this design is scalable to a wide range of input voltages and output currents. The operational principle of this topology is introduced, and a 1-MHz/2-rail-2-phase prototype for 12-V-to-1-V conversion is built to verify the design's performance. The peak efficiency is 91.5% at 30 A and the full-power efficiency is 85.7% at 80 A.