SiC MOSFET reference design details totem-pole PFC topology hitting 98% efficiency

Wolfspeed, a Cree Company, has advanced the development of high efficiency data center power supplies through the implementation of an innovative totem-pole PFC topology that employs its latest low-inductance SiC MOSFETs to exceed an 80+ Titanium rating, which is critical for reducing the overall power consumption for data centers, estimated to be more than 70 billion kWh annually in the US.

High-efficiency power supply designs like those employing Wolfspeed’s SiC MOSFETs are vital for data center designers as they strive to meet demanding efficiency standards without increasing costs. According to a 2016 US Department of Energy supported study¹ on US data center energy usage, efficiency improvements in data center power systems have contributed to an estimated 620 billion kWh in energy savings from 2010 to 2020.

Wolfspeed recently developed a comprehensive reference design that demonstrates the implementation of a totem-pole PFC topology in a 2kW bridgeless power supply that is capable of easily exceeding the 80+ Titanium standards, with actual results of 98.7% peak efficiency at half load and 98.55% efficiency at full load – both taken at 230V redundant operation. Power supply design engineers have faced significant challenges in attaining these efficiency levels using conventional silicon switching devices due to their higher losses and the need for more complex topologies.

“Using Wolfspeed’s latest SiC MOSFETs in a totem-pole PFC design allows our server power systems to achieve an 80+ Titanium efficiency rating,” said Nash Chen, staff engineer for cloud computing at Chicony Power Technology. “Wolfspeed’s MOSFETs also enabled higher frequency operation, reduced harmonic distortion, improved thermal management, and smaller overall system size.”

“Our objective was to design the simplest totem-pole PFC topology using our latest generation of 900V SiC MOSFETs, combined with low-cost silicon diodes, that could achieve 80+ Titanium system efficiency levels,” said Guy Moxey, Wolfspeed’s senior director of power products. “Moreover, we set the additional requirements that the design would use only established and proven commercially-available wide bandgap devices in full production, be the most practical circuit to implement and commercialize, as well as be smaller in volume than existing silicon-based systems at the lower 80+ Platinum efficiency level. And finally, the overall system bill-of-materials (BOM) cost had to be comparable or less than silicon.”

The resulting reference design was presented in a webinar entitled, “Achieving High-Efficiency Power Supplies (80+Titanium) Without Increasing Complexity or Cost,” presented by Wolfspeed engineers Dr. Adam Barkley and Edgar Ayerbe.