High density 48V-to-PoL VRM with hybrid pre-regulator and fixed-ratio buck

The rack-level 48 V bus architecture is wide-spreading as modern Data Center architectures move towards the cloud computing and Internet of Things Era. Increasing power demands require low-profile, high-density server board solutions able to efficiently step down the input distribution bus to the digital rails. Intermediate Bus Converters (IBCs) are usually implemented though soft-switching resonant topologies such as non-regulated LLCs, while core voltage regulation is achieved through a multi-phase buck VRM. This paper proposes two different architectures to increase the power density of the 48 V-1.8 V conversion: the IBC is implemented through a regulated switched-capacitor converter, while the Point-of-Load stage is a novel 4:1 fully-coupled buck that enables DC magnetic flux cancellation and leakage inductance minimization to improve the load transient response.