IEEE Power Electronics Magazine - March 2014 - 54

White Hot

(continued from p. 56)

One aspect of GaN HEMTs that
is both a significant advantage and
a significant disadvantage is the
lack of a body diode. We have spent
years mastering circuits that either
minimize the effect of a body diode
or take advantage of it. With GaN
HEMTs, we will need very highspeed adaptive drivers or very fast
diodes in parallel to minimize losses.
The big commercial challenge is
a general lack of availability. Yes, it
is possible to buy some GaN HEMTs
from distributors today, but the selection is limited. In particular, the 600-V
devices we need for off-line power supplies are few and far between.

Also limiting widespread adoption is the lack of standardized device ratings and characteristics-
and that means there are no real
second sources for any of the devices on the market today. This may
be the biggest challenge to the widespread adoption of GaN devices. No
major manufacturer is going to use
a GaN transistor in a high-volume
application until interchangeable
devices are available from multiple
manufacturers.
It may seem that all of these challenges will keep GaN transistors as
exotic curiosities. Well, the situation
looked equally bleak for MOSFETs

in 1980. Just as we learned how to
overcome the challenges of using
MOSFETs and just as manufacturers
converged on standardized devices,
I am confident the same will happen
with GaN. Today's MOSFETs are very
good, and MOSFET manufacturers
will continue to do everything they
can to remain competitive.
But GaN transistors, due to their
high speed and low capacitance,
can switch at megahertz frequencies with high efficiency. GaN device
manufacturers are already showing
impressive results with power factor
correction circuits, dc-dc converters
for computer applications, switching
power amplifiers for audio, and
high-speed dc-dc converters
for envelope tracking in radio
frequency applications. I think
that while GaN has challenges
to overcome, in a few years, GaN
transistors will be the device of
choice for switching power supply design.

About the Author
Robert V. White (bob.white@
ieee.org) has over 30 years of
industry experience as a power
electronics engineer. He has
worked in product design, systems and applications engineering, and technology development.
He has been an active volunteer
with the IEEE Power Electronics
Society, serving several years on
the Administrative Committee,
two terms as technical vice president, and as a Chapter chair. He
earned a B.S.E.E. degree from the
Massachusetts Institute of Technology and an M.S.E.E. degree
from Worcester Polytechnic Institute; he is currently pursuing a
Ph.D. degree in power electronics
at the University of Colorado-
Boulder. Presently, he is the chief
engineer of Embedded Power
Labs, a power electronics consulting company. He is a Fellow
of the IEEE.

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