White Paper: Power Architecture Evolution in Datacenters

Overview

This document is a white paper published by the Open Compute Project (OCP) and authored by Renesas. It asks how data center power architecture is changing, and needs to change, as AI workloads push rack power sharply upward. The paper describes a move from a 48 V in-rack bus to an 800 V DC bus fed from a sidecar rack.

The starting point of the paper is the growth of xPU power. GPU rack power is projected to reach several hundred kW, with NVL144-class racks given as an example and said to need more than twice the power of NVL72. At that level a 48 V in-rack bus cannot carry the load without large losses or a great deal of copper. Moving to a higher voltage is therefore presented as the natural way to cut current, and with it conductor size and losses.

The paper compares two conductor arrangements. Two-wire 800 V makes better use of copper, while three-wire +/-400 V lowers insulation requirements but needs load-balancing control. According to the document, an 800 V DC bus can cut busbar copper weight by almost 50%. The high-voltage DC bus is generated in an external sidecar rack from 3-phase 480 V AC, and the AC/DC building blocks of that rack are trending towards about 20 kW or more each.

The conversion chain covers a GaN bidirectional-switch Vienna PFC front end, a 16:1 DCX stage from 800 V to 48 V, stages from 48 V to 12 V/6 V, and core-voltage stages. The two-stage 48 V path is said to reach about 96% efficiency today, while core-voltage converters need more than 90%. As a limit, this is an architecture white paper written from a supplier's perspective; it contains no field operating data or independent verification.

Key points

1. GPU rack power is projected to reach several hundred kW; NVL144-class racks need more than twice the power of NVL72.
2. A 48 V in-rack bus cannot carry such power without large losses or a lot of copper.
3. An 800 V DC bus can reduce busbar copper weight by almost 50%.
4. Two-wire 800 V uses copper better; three-wire +/-400 V lowers insulation requirements but needs load-balancing control.
5. The HVDC bus is generated in an external sidecar rack from 3-phase 480 V AC; AC/DC building blocks are trending to about 20 kW or more each.
6. In-rack 16:1 DCX converts 800 V to 48 V; a two-stage 48 V path reaches about 96% today.
7. Core-voltage converters need more than 90% efficiency.

Using it in design

• Use as background for the 800 VDC and sidecar topology option.
• Include per-stage conversion efficiencies in power-chain estimates: AC/DC front end, 800-to-48 V DCX and 48 V IBC.
• Explain the two-wire 800 V versus three-wire +/-400 V choice when a user selects DC distribution.
• Read alongside related specifications (OCP Mt. Diablo, DCF LVDC).

Who should read it

Electrical designers and architects planning power distribution for high-density AI racks.

Related standards

• OCP Mt. Diablo Disaggregated Power Rack Specification
• OCP DCF LVDC Power Distribution white paper

Publication details

Authors

Open Compute Project Foundation

Publisher

Open Compute Project Foundation

Year

2026

Document language

English

Source type

Industry body

Access

Free to read

Licence

Bibliographic reference only — the document is not redistributed here; confirm reuse terms at the original source

Citation