Switched Capacitor-Coupled Buck: A Regulated IBC Solution for 48V-to-5V

The increasing power demands of modern data centers have made 48V power distribution essential for improving efficiency and reducing losses. However, the wide voltage variation of the 48V bus (40-60V) creates challenges for point-of-load (PoL) VRMs, which must account for the full range of input voltages, leading to design complexity and reduced system performance. This paper presents a regulated 48 V-to-5 V Intermediate Bus Converter (IBC) based on a novel Switched Capacitor - dual-phase Coupled Buck (SC-CB) topology specifically developed to address these challenges. The architecture combines a switched-capacitor front stage with an inversely-coupled dual-phase buck stage operating in soft-switching mode, enabling high efficiency within a compact footprint and eliminating the need for a large mid-rail decoupling capacitor. Balanced current sharing between phases is achieved inherently via the flying-capacitor charge/discharge mechanism and magnetic coupling, without additional control circuitry.A 450 W prototype measuring 28.75×28.4×14.7 mm3 (613 W/in3) was built and tested, achieving a stable 5V output across a wide input voltage range of 24-60 V and a peak efficiency of 96.2% at 48 V input. Comparative analysis against state-of-the-art 48 V bus converters confirms that the SC-CB topology offers competitive performance, reduced semiconductor count, and superior power density, making it an attractive solution for space-constrained, high-efficiency data center applications.