IEEE Electrification Magazine - June 2020 - 10

detrapping that is responsible for the dynamic Rdson can
be measured and given high-level confidence for its usage
as the values are getting better and are now around 10%.
We need to continuously look at the different failure
modes and take the devices to failure and understand the
GaN
GaN GaN
FET
FET FET
physics of failure.
Beyond AEC Q101 qualifications for validating the GaN
s
FETs' reliability in actual operating conditions, several identical
Cable
PMSM
half-bridge circuits (with continuous current conduction mode)
GaN
GaN GaN
were prepared using one high-side and one low-side GaN063FET
FET FET
650WSA. These were operated continuously for 1,000 h as synTraction Inverter
chronous-boost converters with the conditions voltage input
Vin = 200 V, Vout = 480 V, Pout = 800 W, Tj = 175 °C, and freFigure 6. The traction inverter. PMSM: permanent magnet synchro= 300 KHz. There is no indication of any degradation
quency
nous motor.
in the performance of any circuits for
all samples for the entire 1,000-h
duration of the test. Following high100
100
temperature switching tests, all devic90
99
es were tested for shifts in dynamic
80
98
Rdson, leakage current, and threshold
70
97
voltage. All parameters were found to
60
96
be stable, with any parametric shifts
50
95
V0
below the allowed levels.
40
94
GaN
SI
Q2
The device specification includes
30
93
Vin L1
800-V transient capability and is
20
92
C
2
VS
guaranteed by tests to eliminate
10
91
C1
any concerns on GaN over voltage
0
90
Q1
spikes. Similarly, many other over
GND
stresses like voltage and temperaOutput Power (W)
tures are used and different accel(a)
(b)
eration factors are defined for the
end-of-life and failure-in-time rates
Figure 7. The half-bridge boost converter (GaN FETs versus Si CoolMOS). Vin = 240 V, Vout = 400 V,
estimated for the application situFsw = 100 kHz. (a) The efficiency curve for GaN FETs versus Si FETs. (b) The schematic for the
ations. As the volume of products
half-bridge boost converter.
shipped increases, real field failure
and being worked on. Currently, using GaN devices in a
rates will be determined.
traction inverter means slowing it down significantly to
Power GaN technology is ready to take its place as effisave the motor windings. They are nearly limited to a dV/dt
cient power conversion. We are beginning to see its adopof 10 V/ns, which holds significant potential to improve the
tion in the nonauto segments and it will soon be used in
motors and take the frequency up to 40 kHz to improve the
automotive applications and we can take advantage of
power density significantly. The development of new electric
lower losses and higher power densities. Si technology is
motor technology with improved ability is on the way to
well established in the market but reaching its limit.
make the system more efficient.
Power GaN technology will be the norm in the future as
fear of the unknown is reduced going forward.
0

Loss (W)

Efficiency (%)

Vdc Bus

Quality and Reliability
Power GaN FET technology currently shows good quality
and reliability as multiple vendors demonstrated Joint
Electron Device Engineering Council and Automotive Electronics Council (AEC) Q101 quality standards. To demonstrate the reliability of power GaN technology, these are
minimums and must be fulfilled. For GaN, only the existing quality standards are not enough as the material is
new and operates differently. Dynamic Rdson or current
collapse phenomena is well known for power GaN FETs
and this method for testing is introduced and devices are
verified. Material quality, trapping, and appropriate

I E E E E l e c t r i f i cati o n M agaz ine / J UN E 2020

For Further Reading
"Understanding power GaN FET datasheet parameters," Nexperia, Nijmegen, The Netherlands, AN9005, 2019.
"Circuit design and PCB layout recommendations for GaN
FET half-bridges," Nexperia, Nijmegen, The Netherlands, AN9006,
2019.

Biography
Dilder Chowdhury (dilder.chowdhury@nexperia.com) is a
device architect with Nexperia, Manchester, U.K.

IEEE Electrification Magazine - June 2020

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