Mini-LEGO CPU Voltage Regulator

Youssef Elasser, Jaeil Baek, Kaladhar Radhakrishnan, Houle Gan, Jonathan P. Douglas, Harish K. Krishnamurthy, Xin Li, Shuai Jiang, Vivek De, Charles R. Sullivan, Minjie Chen

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


This article presents the design and optimization of a miniaturized 48-V-to-1-V, 240-A linear-extendable group operated point-of-load (LEGO-PoL) CPU voltage regulator module (VRM) - Mini-LEGO - with a volume of 30 mm×11.2 mm × 8.4 mm. The Mini-LEGO converter provides vertical power delivery, and it achieves a peak efficiency of 87.1%, a full load efficiency of 84.1%, and a power density of 1390 W/in3 when stepping down a 48 V input voltage to an output voltage of 1 V. The Mini-LEGO offers compact device implementation, simple gate drive circuitry, and a fast regulation-stage switching frequency of 1.5 MHz. The 9-mm-by-9-mm, 4-phase, 20-A-per-phase vertical coupled inductor has a per-phase transient inductance of 10.3 nH, with its coupling reducing the ripple by a factor of six, and a height of 2.5 mm. This vertical coupled inductor structure is designed following a systematic approach to minimizing its height while achieving significant current ripple reduction and maintaining sufficient saturation margin. Thermal simulations are performed to verify the cooling feasibility. A measurement characterization method for vertical coupled inductor structures is introduced and used to characterize the designed vertical coupled inductor.

Original languageEnglish (US)
Pages (from-to)3391-3410
Number of pages20
JournalIEEE Transactions on Power Electronics
Issue number3
StatePublished - Mar 1 2024

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering


  • Coupled inductor
  • dc-dc power conversion
  • point-of-load
  • switched-capacitor (SC)
  • vertical power delivery
  • voltage regulator module (VRM)


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