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High Efficiency Power Converters Using
Gallium Nitride (GaN) Transistors
Authors: Mark Nakmali, Yutian Cui, Dr. Leon Tolbert
Affiliation: University of Oklahoma, University of Tennessee
Description
The aim of this project is to show the switching and efficiency capabilities of Gallium Nitride transistors through
simulation and physical testing.
Material Properties
GaN Material Properties
The properties of GaN outweigh
silicon and silicon carbide in terms
of high voltage operation and high
frequency switching. This allows
the stoppage of high voltages and
allows switching times. With
higher switching frequencies, the
other passive components in the
circuit can be smaller.
Cross-sectional Diagram Of An
eGaN Field Effect Transistor
Operation And Efficiency
Capacitor And Inductor Size With
Respect To Frequency
Typical Losses In A Transistor
GaN is grown on a silicon or silicon
carbide substrate using AlGaN as a
buffer layer. AlGaN also creates
the 2-dimensional electron gas
(2DEG) which is highly conductive,
allowing fast switching and low
resistance. It is because of the
2DEG that the switching and
conduction losses are minimized.
Efficiency And Switching Period Testing
The performances of GaN (green) and silicon (blue) converters are tested with varying input voltages (3-6V),
switching frequencies (200kHz dark, 600kHz medium, and 1MHz dark) and output powers (12-36W). Their
on-transient waveforms are compared to each other and then to actual measurements of a physical circuit.
As seen above, the efficiency goes down with the increase in voltage, frequency and output power. In all cases,
GaN outperforms silicon.
As seen below, the switching period of silicon is about thirteen times larger than GaN. When compared to the
real switching speed of GaN, the simulation is about 1.3ns too fast, but in either case the considerable difference
in switching speed when compared to silicon is still valid.
Silicon
GaN (simulated)
GaN (real)
Applications
With high stopping voltages and high frequencies, Gallium Nitride has the potential to make power converters
that are more efficient and smaller, as well as the ability to provide faster and more reliable data transfer than
the current products that we have today.
SPONSORS: This work was supported primarily by the Engineering Research Center Program of the National Science Foundation
and the Department of Energy under NSF Award Number EEC-1041877 and the CURENT Industry Partnership Program.