LEGO-PoL: A 48V-1.5V 300A Merged-Two-Stage Hybrid Converter for Ultra-High-Current Microprocessors

This paper presents a family of 48 V–1.5 V merged-two-stage hybrid-switched-capacitor converters with a Linear Extendable Group Operated Point-of-Load (LEGO-PoL) architecture for high current microprocessors. The proposed LEGO-PoL converter leverages the advantages of switched-capacitor (SC) circuits and multiphase buck circuits and can achieve soft charging, current sharing, and automatic voltage balancing. The SC circuits are connected in series to split the high input voltage into multiple stacked voltage domains, and the multiphase buck circuits are connected in parallel to split the high output current into multiple parallel current paths. The inductors of the multiphase buck converters are used as current sources to soft-charge and soft-switch the switched-capacitor circuits, and the switched-capacitor circuits are utilized to ensure current sharing among the multiphase buck circuits. The voltage balancing and current sharing mechanisms of the LEGO-PoL architecture are investigated in detail. A 450 W, 48 V–1.5 V, 300 A LEGO-PoL converter with a peak efficiency of 96%, a full load efficiency of 87.7%, and a power density of 577 W/in
³
was built and tested to verify the effectiveness of the LEGO-PoL architecture.