IEEE Power Electronics Magazine - June 2017 - 43

Summary and Conclusions
This article presented the static and dynamic characterization results for six SiC MOSFETs for a wide range of temperatures, from 25 °C to 200 °C. Following the design of a
double-pulse tester system capable of providing variable
gate-driving voltages, commercial and sample SiC MOSFETs
from Wolfspeed, ROHM, Monolith, and SEI were tested.
Also, the dynamic test circuit design criteria and the necessity of achieving minimum parasitics for the gate loop,
power loop, and load inductor were explained.
In the test procedure, equal conditions were created for
all of the devices to enable an unbiased comparison between
them. The recommended gate voltages were applied to all of
the devices in both the static and dynamic tests. Also, for

Temperature Sensor

Fan
Function
Generator

Hot Plate
Inductor

DESAT
Protection

200
180
160
140
120
100
80
60
40
20
0

Turn-On

FIG 10 The test setup for high-temperature DPTs. DESAT:
desaturation.

25 °C
100 °C
150 °C
200 °C
Turn-Off

To be able to test a device at high temperatures, a hot plate
is used. Referring to Figure 10, the device is bent 90° and
mounted at the bottom of the PCB. In this way, the DUT can
touch the hot plate. In addition, the device leads are as short
as possible to minimize additional inductances in the gate
and power loops. A fan is used to cool the PCB and the
components thereon so they do not experience high temperatures when the device is heated up to 200 °C.
For a high-temperature DPT, the hot plate needs to
be isolated from the DUT. This is due to the fact that the
device case, which has to be in touch with the hot plate,
is connected to the drain, while the hot plate is grounded.
A layer of Kapton tape is applied on the hot plate to provide isolation. For better thermal conductivity and also
to create an even-temperature surface, a layer of thermal
padding is applied both under and above the Kapton tape.
The high-temperature tests are performed at three temperatures other than the room temperature: 100 °C, 150 °C,
and 200 °C. Although the DUTs are not capable of continuous operation at 200 °C, it is assumed that heating the
device to 200 °C for a short time and triggering it twice at
that temperature cannot change its properties in a significant way. High-temperature tests are performed at 5 A up to
20 A, with steps of 5 A, and higher load currents are avoided
for higher reliability and safety purposes.
The high-temperature test results reveal that the temperature dependency of switching losses is negligible for
SiC MOSFETs, an outstanding feature contributing to easier
system design and more reliable operation. Figure 11, for
instance, shows switching-off and switching-on losses for
the Wolfspeed #1 MOSFET as a reference, where the total
switching loss change at 200 °C compared to 25 °C is about
6%. Also, as expected, as temperature increases, the turnoff losses of SiC MOSFETs increase and the turn-on losses
decline. This is mainly due to the reduction of the plateau
and threshold voltages as temperature increases [21], causing faster switching transients in the turn-on phase and
a slower turn-off process. Figure 12 shows the switching
waveforms in the Wolfspeed #1 DUT, where the effect of
temperature on switching transients can be seen.

each MOSFET, the external gate resistance was selected
to have similar switching transients. The static characterization included the acquisition of output characteristics,
transfer characteristics, specific on-resistances, threshold
voltages, and parasitic capacitances. Also, in the dynamic
characterization using the designed chopper circuit, the
MOSFETs' turn-on and turn-off losses were measured at
different load currents and temperatures. Table 3 summarizes key specifications and a summary of the data acquired,
where the blocking voltage, nominal continuous current
rating, specific on-state resistance (at a 20-A drain current),
threshold voltage, junction capacitances (input, output, and
Miller capacitances at 600 V), and switching losses (at a
30-A load current) are shown for all of the semiconductors
at room temperature.

Energy (µJ)

High-temperature DPts

10
15
Load Current (A)

Switching-Off at 25 °C
Switching-Off at 150 °C
Switching-Off at 100 °C
Switching-Off at 200 °C
Switching-On at 25 °C
Switching-On at 150 °C
Switching-On at 100 °C
Switching-On at 200 °C
FIG 11 The turn-on and turn-off switching losses versus
junction temperature for the Wolfspeed X3M0050090G SiC
MOSFET under test at various temperatures.

June 2017

z IEEE PowEr ElEctronIcs MagazInE

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - June 2017