How can a 3kW AC/DC converter increase power without increasing PSU volume?

AI server racks need more power at the point of load, but the power supply cannot keep taking more space from compute hardware. Once large passive components and heatsinks define the converter envelope, higher power output becomes as much a packaging problem as an electrical one.

• Planar printed circuit board (PCB) layouts can limit power density even when the switching devices can support higher power output.
• Moving selected switching stages onto daughterboards changes how the converter uses available volume.
• Surface-mount silicon carbide (SiC) packages make that layout practical, but only when thermal paths are designed around them.
• Toshiba’s whitepaper shows how a 3kW AC/DC reference design achieved higher density through packaging, layout and thermal engineering.

Rack power demand is exposing layout limits

A conventional high-power AC/DC converter often starts with a single PCB. Transformers, capacitors and heatsinks then dictate the volume around it.

That arrangement works until the application needs several kilowatts from almost the same space. In an AI server, adding PSU volume competes directly with processors, memory and airflow. A more efficient switching device helps, but it does not automatically solve the mechanical constraint.

The design challenge moves from topology to volume

The design question becomes where each circuit section should physically sit.

Keeping all components on one board simplifies the layout, but it leaves little room to increase output power without increasing footprint. Moving switching circuitry onto vertical daughterboards can free up board area, but only if the packages, heatsinks and airflow path remain low enough to avoid creating a larger structure elsewhere.

Toshiba’s reference design uses SiC packaging to enable a multi-board layout

Toshiba’s 3kW AC/DC reference design separates key power-factor correction (PFC) and phase-shifted full-bridge (PSFB) switching functions onto daughterboards while larger passive components remain on the main PCB.

The design uses surface-mount SiC devices to keep those daughterboards compact and thermally manageable. Heatsinks mounted behind the switching devices provide a defined thermal path.

The result is a multi-board converter architecture that increases output power from an earlier 1.6kW design to 3kW with a 34% improvement in power density (Figure 1).