Gallium nitride delivers 97.5% efficiency in PFC-corrected supply

May 14, 2013 // By Graham Prophet
A circuit using 600-V GaN HEMTs combines totem pole PFC circuit with LLC converter to achieve total conversion losses that are claimed to be half of that possible with silicon.

Transphorm Inc. has announced a high-efficiency off-line 1 kW 48-Vdc power supply that has demonstrated peak efficiency of 97.5%. The power supply design uses Transphorm’s JEDEC-qualified GaN-on-silicon 600V high electron mobility transistors (HEMTs) to implement a 99% efficiency totem pole power factor correction (PFC) front end, combined with a 98.6% efficiency LLC converter.

Based on Transphorm’s high-performance EZ-GaN technology, the TPH3006PS HEMT combines low switching and conduction losses to reduce energy loss by a claimed 50% compared to conventional silicon-based power conversion designs. The TO-220-packaged GaN transistor features low on-state resistance (RDS(on)) of 150 mΩ, low reverse-recovery charge (Qrr) of 54 nanocoulombs (nC) and high-frequency switching capability — all of which result in lower loss, more compact, lower cost systems.

“Transphorm’s GaN-based power supply design exceeds the best efficiency results possible with silicon by at least one percent,” said Umesh Mishra, CEO of Transphorm, “And while recent advances in superjunction silicon devices have reduced the output capacitance by 20% and the Qrr of the intrinsic body diode by 25%, these improvements lag far behind the effective Qrr of the new GaN transistors which reduce Qrr by 95%.”

For approved customers, the TPH3006PS and TPH3006PD HEMT devices are available for sale at a price of $5.89 (1,000). The TPS3410PK and TPS3411PK diodes are priced at $2.06 and $1.38 (1,000).