EPC Releases 5 kW GaN AC-DC Reference Design for Data Centers

In response to the surging demands of AI server racks and high‑power data‑center infrastructure, EPC has introduced a benchmark reference design: a 5 kW AC-to-48 V DC conversion system based on enhancement‑mode gallium nitride (eGaN) power devices. The solution uses a front‑end four‑level totem‑pole PFC stage plus an isolation stage of modular LLC converters. It achieves up to 96.5 % system efficiency and a power density of 116 W/in³, targeting the form‑factor constraints of OCP ORv3 racks.

This development is important because, as AI and cloud compute escalate, power conversion has become a bottleneck in size, thermal management, efficiency, and cost. By leveraging GaN’s capability for high‑frequency switching, low on‑resistance, and compact electromagnetic components, EPC’s reference design addresses those bottlenecks head‑on.

The 5 kW, 4-level totem-pole PFC evaluation board. Image used courtesy of EPC

Totem‑Pole PFC and ISOP LLC Modular Conversion

The reference design splits the conversion into two segments: the front‑end AC to 400 V DC bus, and the isolation stage stepping down to a 48 V (or approximately 50 V) load rail.

In the front end, EPC uses the EPC91107KIT module implementing a 4‑level flying‑capacitor totem‑pole PFC topology, engineered with EPC2304 (200 V, 5  megaohms) GaN FETs. In this configuration, the inductor requirements shrink dramatically, with the design claiming a 9x smaller PFC inductor and a 40% smaller EMI filter compared to conventional two‑level designs. It also supports a switching frequency of ~140 kHz at the nominal input of 240 V AC and ~25 A input current. Peak efficiency of the PFC stage reaches up to ~98.5% at 5 kW.

The EPC91110KIT power schematic. Image used courtesy of EPC

On the isolation side, EPC deploys the EPC91110KIT, which uses four modular 1.375 kW LLC converters in an Input‑Series Output‑Parallel arrangement. Each module uses EPC2305 (150 V, 3 megaohms) GaN FETs and achieves 98.2% peak efficiency, delivering a combined ~5.5 kW output. The overall system efficiency aggregates to ~96.5% for the full AC‑to‑48 V chain, with a footprint power‑density of 116 W/in³.

The high switching frequency and reduced passive component size enabled by GaN enable this density uplift with smaller inductors, smaller EMI filters, better thermal headroom, and overall system compactness.

Powering the AI Age

As artificial intelligence workloads push server power requirements to new heights, power conversion systems’ efficiency and density have become critical design constraints in data center infrastructure. The rising adoption of 48 V distribution rails reflects the industry's response to these challenges, offering reduced I2R losses and enabling higher overall rack efficiency. EPC’s 5 kW reference design directly addresses these evolving demands, offering a high-efficiency, compact, and scalable blueprint for next-generation compute environments.

The EPC91110KIT board. Image used courtesy of EPC

With total system efficiency approaching 96.5%, the design drastically reduces conversion losses relative to legacy silicon-based systems. This efficiency curtails wasted energy and significantly reduces thermal dissipation, translating into smaller heatsinks, reduced reliance on active cooling, and improved overall system reliability. These gains are particularly valuable in AI applications, where rack-level power densities are already near their thermal and spatial limits.

At a power density of 116 W/in³, the design enables a compact power shelf footprint, opening the door to higher server density within standard ORv3 racks. Instead of sacrificing valuable rack space to accommodate bulky power components, engineers can leverage the small form factor to either increase compute density or simplify cooling infrastructure. Meanwhile, the four-module ISOP configuration of the isolation stage further enhances scalability, allowing designers to extend the system from 5 kW to 33 kW, 48 kW, or even 108 kW with minimal architectural changes.

Additionally, the AC-to-48 V topology aligns seamlessly with industry trends. Many modern data centers are moving away from traditional 12 V rails in favor of higher voltage distribution, particularly 48 V or higher, to reduce transmission losses over long cable runs and within dense rack environments. By integrating a GaN-based four-level totem-pole PFC with a modular LLC architecture, EPC provides an electrically congruent solution aligned with the direction the industry is heading.