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 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 through soft-switching resonant topologies such as non-regulated LLCs, while core voltage regulation is achieved through a multi-phase buck VRM. Isolated IBCs have lower power density with respect to novel architectures such as non-isolated Switched Capacitor converters, while classic VRMs suffer from the so-called critical inductance bottleneck. In this paper, the novel Fully Coupled Buck Converter is used inside two different topologies to achieve the 48 V-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.