A Merged-Two-Stage LEGO-PoL Converter with Coupled Inductors for Vertical Power Delivery

This paper presents a merged-two-stage hybrid-switched-capacitor converter featuring the Linearly Extendable Group Operated Point-of-Load (LEGO-PoL) architecture with coupled inductor-enabled vertical power delivery for ultra-high-current microprocessors. By merging a switched-capacitor stage with a multiphase buck converter stage, the proposed converter achieves reduced device stress, minimized magnetics size, and soft charging. A systematic way of designing coupled inductors in multiphase buck converters, based on an inductance dual model which links the geometry of the magnetic core to a lumped circuit model, is introduced. Coupled inductors in the multiphase buck stage reduce the steady-state per-phase current ripple and improve the transient performance of the system. By delivering power vertically from the motherboard to microprocessors, a high current and power density prototype is designed to minimize the parasitic resistance and enable fast transient with low output current ripple. A 48 V to 1.5 V LEGO-PoL converter rated to deliver 750 A of output current with 100 A/cm
²
current area density and 1125 W with 1725 W/in
³
power density is designed and simulated with customized four-phase coupled inductors.