Wolfspeed of Research Triangle Park, NC, USA — a Cree Company that makes silicon carbide (SiC) power devices (including MOSFETs, Schottky diodes, and modules) — says that its latest low-inductance SiC MOSFETs have been used to develop high-efficiency data-center power supplies – through the implementation of a totem-pole power factor correction (PFC) topology – to exceed an 80+ Titanium rating, which is critical for reducing the overall power consumption for data centers (which is estimated to be more than 70 billion kWh annually in the USA).
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 US Department of Energy-supported study on US data center energy usage (2016 United States Data Center Energy Usage Report, Lawrence Berkeley National Laboratory, LBNL-1005775), 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, says Wolfspeed.
“Using Wolfspeed’s latest SiC MOSFETs in a totem-pole PFC design allows our server power systems to achieve an 80+ Titanium efficiency rating,” comments 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,” he adds.
“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,” says 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 ‘Achieving High Efficiency Power Supplies (80+Titanium) Without Increasing Complexity or Cost’ by Wolfspeed engineers Dr Adam Barkley and Edgar Ayerbe.