Vertical Power Flow 48 V to PoL VRM Architectures With Hybrid Pre-Regulator

The rack-level 54/48 V bus architecture is spreading as modern data center architectures move toward 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 through soft-switching resonant topologies such as nonregulated LLCs, while core voltage regulation is achieved through a multi-phase buck voltage regulation module (VRM). Isolated IBCs have lower power density with respect to novel architectures such as nonisolated switched capacitor converters (SCCs), while classic VRMs suffer from the so- called critical inductance bottleneck. In this article, the novel fully-coupled buck (FCB) converter is used inside two different topologies to achieve the 48–1.8 V conversion, while obtaining dc magnetic flux cancellation and leakage inductance minimization, breaking the limit of critical inductance at the VRM stage. In particular, a soft-switched quasi-dc solution is compared against a resonant conversion by means of a single prototype.