Review of the 800-VDC Power Delivery Architecture and Isolated 800-V to 48-V Converter Solutions for Future AI Data Centers

Overview

The starting question is how far the conventional architecture, fed from 415/480 VAC and using a 48 VDC rack busbar, can be pushed in current, copper and thermal terms as AI workloads move rack power from 120 kW toward 1 MW. The authors answer it through a structured survey of the literature rather than a new measurement campaign. The paper first sets out the case for 800 VDC, its architecture and the transition paths from existing facilities, and then compares candidate circuits for the 800 V to 48 V stage at the heart of the design.

The architecture sections cover medium-voltage rectifier or solid-state transformer (SST) front ends, a staged transition through side power racks, and energy storage layered by time scale: in-rack capacitor banks respond in well under a millisecond, rack battery backup units carry load for minutes, and facility-scale BESS bridges the transfer to generators. The same part compares unipolar 800 VDC with bipolar ±400 VDC and a future 1500 VDC bus in terms of pole count, touch voltage and breaker availability.

The second half explains the LLC resonant DC transformer (DCX) principle, its circuit and magnetic design, and then compares half-bridge, full-bridge, three-level half-bridge and three-phase LLC families on switch voltage stress, power capability, magnetic complexity, modularity and maturity. No single winner emerges; the choice is presented as a trade-off that depends on power level and the maturity the project can accept.

As a review, its figures come from other publications and industry announcements and are not re-measured under common conditions. High secondary-side current, magnetic integration, control and modulation constraints, and thermal management remain the main barriers to high efficiency and power density in the 800 V to 48 V stage. The architecture is also not yet standardised, so the paper offers a roadmap and a comparison framework rather than a ready recipe.

Key points

1. For a conductor with a 48 A continuous rating, moving rack distribution from 415 VAC to 800 VDC carries about 157% more power; 415 to 480 VAC adds only about 16%, and 1500 VDC about 382% (Table 1).
2. 800 VDC is reported to raise end-to-end efficiency by up to about 5% over 48 VDC systems and to cut copper use by up to 45%.
3. MV rectifier or SST front ends converting about 35 kVAC to 800 VDC are cited at roughly 7.5 MVA per unit with 98.5% or better efficiency.
4. The OCP Open Rack V3 PSU specification targets above 97.5% peak efficiency and at least 96.5% across 30%-100% load.
5. AI workloads show short-cycle swings of about 50% of peak (from 20%-40% idle to near full load); in-rack capacitor banks react in as little as 400 µs and rack BBUs hold load for roughly 5-15 minutes.
6. Bipolar ±400 VDC lowers pole-to-ground and touch voltage but needs three-pole breakers and a voltage balancer; 800 VDC works with common two-pole breakers and needs no pole balancing.
7. The LLC candidate families (half-bridge, full-bridge, three-level half-bridge, three-phase) trade off switch voltage stress, power capability, magnetic complexity, modularity and maturity.
8. The main challenges of the 800 V to 48 V stage are high secondary current, magnetic integration, control and modulation limits, and thermal management.

Using it in design

• Define 800 VDC unipolar, ±400 VDC bipolar and 48/54 VDC busbar as separate voltage classes in the single-line diagram, each with its own conductor ampacity, breaker pole count and clearance (IEC 60664-1) checks.
• For a given rack kW, compare how many feeders or whips are needed at 415 VAC, 480 VAC, 800 VDC and 1500 VDC, and read the copper and space benefit from that comparison.
• Model layered storage together in AI rack templates (CBU for milliseconds, BBU for minutes, BESS for seconds to minutes) and warn on generator and UPS sizing when load swings near 50% of peak are not buffered.
• Catalogue the side-power-rack path and the MV rectifier/SST front end as options for an 800 VDC transition, and report efficiency, power density and maturity as separate criteria when selecting converters.

Who should read it

Design engineers, power-electronics teams and decision makers choosing the electrical architecture for high-density AI racks.

Document contents

1. I. Introduction
2. II. 800 VDC Power Delivery Architecture (Motivation to 800 VDC, the architecture schematic, transition pathways, key facility components, other HVDC bus distribution options)
3. III. LLC DCX Resonant Converter (principles of operation, circuit design considerations)
4. IV. Magnetic Design of the LLC DCX Converter (magnetic design considerations, resonant inductor and transformer)
5. V. Half-Bridge LLC Resonant Converter (symmetric half-bridge, AI data center designs)
6. VI. Full-Bridge LLC Resonant Converter (modulation methods)
7. VII. Three-Level Half-Bridge LLC Resonant Converter
8. VIII. Three-Phase LLC Resonant Converter (transformer and resonant tank connections, interleaved structures)
9. IX. Comparison of the Reviewed Topologies
10. X. Conclusion

Related standards

• IEC 60664-1
• IEC 60309
• IEC 62477-1
• NEC Article 690
• OCP Open Rack V3

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Publication details

Authors

Amirhossein Habibi; Mehdi Ferdowsi

Publisher

IEEE Access (Institute of Electrical and Electronics Engineers (IEEE))

Year

2026

Volume

14

Pages

171985-172010

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.1109/ACCESS.2026.3745478

Licence

CC BY 4.0 — share with attribution

Licence evidence

ieeexplore.ieee.org

Citation