Choosing the Right Semiconductor Technology for 800 V AI Data Center Power

This application note compares GaN HEMTs, SiC MOSFETs, and SiC cascode JFETs for high-voltage intermediate bus converters in AI datacenters, highlighting their conduction, switching, and gate-drive characteristics at high frequencies. While all three technologies achieve similar overall efficiency in resonant LLC converters, CJFETs stand out for their lower cost, simpler gate drive, and minimal snubber requirements. The note also shows that a three-phase LLC topology offers the best system-level advantages.

Device-Level Tradeoffs: Compare GaN HEMTs, SiC MOSFETs, and SiC Cascode JFETs

Switching Dynamics at 1 MHz: Understand parasitic capacitances, gate-charge losses, and snubber requirements

Resonant Converter Topologies: Evaluate stacked, single-phase, and three-phase LLC architectures

System-Level Efficiency Analysis: See how semiconductor choice impacts total losses, magnetics, and gate-drive design

Bill of Materials Optimization: Topology selection can reduce component count

Application Note Overview

High-voltage intermediate bus converters (HV IBCs) are becoming essential as AI datacenters shift toward 800 V power distribution and demand higher efficiency in increasingly compact systems. To meet these requirements, designers are turning to wide-band-gap semiconductor technologies capable of operating near 1 MHz. This application note compares three leading options—lateral GaN HEMTs, SiC MOSFETs, and SiC cascode JFETs—focusing on conduction losses, switching behavior, parasitic capacitances, and gate-drive requirements within resonant converter architectures.

Download this application note to see how each device technology performs under realistic high-frequency LLC converter conditions. While all three options deliver comparable overall system efficiency, the analysis highlights important design tradeoffs: GaN excels in low gate-charge losses, SiC MOSFETs incur higher auxiliary losses, and CJFETs offer a compelling cost advantage among other benefits.

The note also evaluates stacked, single-phase, and three-phase LLC topologies, showing how three-phase designs achieve key benefits for high-density power systems. All these insights form the basis for onsemi’s ongoing hardware validation efforts, guiding the development of future HV IBC solutions for modern datacenter power architectures.