Two-Stage Power Delivery Architecture Using Hybrid Converters for Data Centers and Telecommunication Systems

Overview

The study asks whether the power chain from AC distribution voltage to processor core voltage can be done in two stages instead of four. The conventional chain after an online UPS has four stages: PFC rectifier to a high-voltage DC link, DC link to a nominal 48 V bus, 48 V to 12 V, and 12 V to 0.8-3.3 V core voltages. The proposed architecture replaces it with a switched-capacitor (SC) step-down PFC rectifier producing a 48-60 V bus and a GaN multi-phase hybrid point-of-load converter producing about 1 V.

Prototypes of both stages were built and tested separately and together. The first-stage SC PFC rectifier (90-110 VAC to 48-60 VDC) reached 96.1% peak efficiency at 0-4.5 A output, with 73 W/in³ peak power density. The second-stage hybrid PoL converter reached 90.7% peak efficiency over 0-220 A at 1 V, with 2020 W/in³ peak power density. For the multi-phase multi-inductor hybrid (MP-MIH) converter a new phase sequence giving a wider output voltage range was proposed and verified experimentally.

End to end, direct conversion from about 110 VAC to 1 VDC peaked at 84.1% efficiency at 50 A and fell to 73.5% at 160 A. This shows the two-stage structure works as a concept, but efficiency may lag production-grade multi-stage chains.

Limits: it is a converter-level hardware paper, efficiency falls at high current and the input is a low 90-110 VAC range; facility-scale use, thermal management and reliability are not assessed. Its relevance to facility design is the efficiency of the 48 V rack-to-chip chain and the argument for fewer stages.

Key points

1. The conventional rack chain after an online UPS has four stages: PFC rectifier to a high-voltage DC link, DC link to a nominal 48 V bus, 48 V to 12 V, and 12 V to 0.8-3.3 V core voltages.
2. The first-stage SC PFC rectifier (90-110 VAC to 48-60 VDC) reached 96.1% peak efficiency at 0-4.5 A output, with 73 W/in³ peak power density.
3. The second-stage hybrid PoL converter reached 90.7% peak efficiency over 0-220 A at 1 V, with 2020 W/in³ peak power density.
4. End to end, direct conversion from about 110 VAC to 1 VDC peaked at 84.1% efficiency at 50 A and fell to 73.5% at 160 A.
5. A new phase sequence for an extended output voltage range was proposed and verified experimentally.

Using it in design

• In rack power-chain efficiency calculations, treat the number of stages and each stage's efficiency as separate inputs, and show the benefit of fewer stages at load points (low and high current).
• Account for the efficiency fall at high current (73.5% at 160 A) in rack heat-load calculations; do not use peak efficiency as typical operating efficiency.
• Label such two-stage architectures as prototype-maturity options and do not compare them with production-grade solutions as if at the same maturity.

Who should read it

Power-electronics engineers evaluating the number of stages and efficiency in in-rack power conversion and the 48 V chain.

Document contents

1. 1. Introduction
2. 2. Step-Down PFC Converter (2.1 Topology and Operation, 2.2 Modified Operation for Capacitor Balancing, 2.5 Control and Sensing Circuits)
3. 3. Multi-Phase, Multi-Inductor Hybrid Converter
4. 4. Experimental Results (4.1 Step-Down PFC Converter, 4.2 MP-MIH Converter, 4.3 Full System Verification)
5. 5. Conclusions

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Publication details

Authors

Ratul Das; Hanh-Phuc Le

Publisher

Electronics (MDPI AG)

Year

2025

Volume

14

Issue

16

Pages

3169

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.3390/electronics14163169

Licence

CC BY 4.0 — share with attribution

Licence evidence

www.mdpi.com

Citation