Air-LEGO: A Magnetic-Free Ultra-Thin 24V-to-1V 120A VRM with Air-Coupled Inductors

This paper presents a magnetic-free ultra-thin 24 Vto-1 V 120 A linear-extendable group-operated point-of-load (LEGO-PoL) voltage regulation module (VRM) with air-coupled inductors (Air-LEGO). The thickness of the Air-LEGO converter is very low (about 3 mm), facilitating compact packaging, relaxed thermal constraints, and magnetic-free integration. The module operates by initially stepping down the 24 V input voltage using three series-stacked 2:1 switched-capacitor submodules, resulting in an average voltage of 4 V on the virtual intermediate buses. This virtual bus voltage is then further stepped down to below 1 V through three two-phase buck submodules. Each of these six phases is capable of delivering a peak current of 20 A and regulating the output voltage. Buck submodules are implemented with air-coupled inductors, where designs based on both PCB and Litz-wire windings are explored and compared. Experimental results highlight the viability and potential of incorporating air-coupled inductors into VRM designs, while also addressing associated drawbacks and essential design considerations.