Hard Switched Silicon IGBTs Cut Switching Losses in Half

Hard-Switched Silicon IGBTs?
Cut Switching Losses in Half with Silicon Carbide Schottky Diodes
by Jim Richmond
Replacing the Si Ultrafast soft-recovery diode used as the freewheeling component in hard-switched IGBT applications
with a Silicon Carbide (SiC) Schottky diode reduces the switching losses in the diode by 80% and the switching
losses in the IGBT by 50%.
Introduction
The Silicon IGBT, which combines the output and switching characteristics of a bipolar transistor and the ease
of control of a MOSFET, has become the power switch of choice for hard-switched, high-voltage (greater than
500 V) and high-power (greater than 500 watts) applications. Typical applications include motor-control inverters,
uninterruptible power supplies, welding equipment and switched-mode power supplies (SMPS).
The ever-increasing demand in power electronics for improved efficiency, reduced cooling, decreased size and
weight, and stricter EMI/RFI and power quality requirements present new challenges to the designer. All of these
requirements are greatly influenced by the high transient losses during IGBT turn-on when switching the inductive
load found in hard-switched topologies. The reverse-recovery current present at turn-off of the silicon freewheeling
diode directly affects this IGBT turn-on transient. To compound matters, the diode reverse-recovery current increases
with increasing operating temperature, diode current, and di/dt.
The diode reverse-recovery current and the IGBT switching losses can be drastically reduced by replacing the silicon
freewheeling PiN diode with a SiC Schottky barrier diode (SBD). Due to the material properties of silicon, silicon
Schottky diodes are not possible in the 200-plus volt range.
SiC Schottky Diodes
, Rev. B
e: CPWR-AN03
Application Not
The SiC SBD is commercially available with 600-volt and 1200-volt ratings. The 600-volt diodes are available with 1-,
4-, 6-, 10-, and 20-amp current ratings. The 1200-volt diodes are available with 5- and 10-amp current ratings. The
main advantage of a high-voltage SiC SBD lies in its superior dynamic performance. The reverse-recovery charge in
the SiC SBD is extremely low and is the result of junction capacitance, not stored charge. Furthermore, unlike the Si
PiN diode, it is independent of di/dt, forward current and temperature. The maximum junction temperature of 175°C
in the SiC SBD represents the actual useable temperature. The ultralow Qrr in SiC SBDs results in reduced switching
losses in a typical hard-switched IGBT based application. This lowers the case temperature of the IGBT, improving
the system efficiency and possibly allowing for a reduction in size of the silicon IGBT. In order to measure the benefit
of these high-performance rectifiers, an inductive switching test circuit was used to measure the IGBT and diode
switching losses. This allowed for a switching-loss comparison between an Ultrafast soft-recovery silicon diode and
the Cree Zero Recovery® SBD, as well as the impact their reverse recovery has on the switching losses of an IGBT.
Switching Measurement
Figure 1 shows the inductive test circuit used for making the switching measurements. During operation, a double
pulse is used to drive the IGBT gate. For the 600-volt device testing, a 10-ohm gate drive resistor is used to set the
di/dt to 750 A/µs. A 22-ohm resistor was used with the 1200-volt devices for a di/dt of 250 A/µs.
At time T1, the IGBT is turned on and current through the inductor ramps up until it reaches the desired test current
at time T2. At time T2, the IGBT is turned off and the inductor current is transferred to the diode. The IGBT turn-off
losses and diode turn-on losses are measured at the T2 transition. The inductor current continues to flow through
the diode until the IGBT is turned back on at time T3. Now inductor current is transferred from the diode back to the
IGBT. The IGBT turn-on losses and diode turn-off losses are measured at the T3 transition.
Subject to change without notice.
www.cree.com/power
measurements.
operation,
a double
volt devicesDuring
for a di/dt
of 250 A/µs.
pulse is used to drive the IGBT gate. For the
600 volt device testing a 10 ohm gate drive
resistor is used to set the di/dt to 750 A/µs.
A 22 ohm resistor was used with the 1200
volt devices for a di/dt of 250 A/µs.
0
300
25
-5
200
20
-10
100
15
600
0
10
500
-100
400
300
200
100
0
5
0
20
Power (kW)
-5
15
-15
5
-20
0
-100
-50
0
50
inductor current is transferred to the diode.
600-Volt
Switching
Comparison
At time
T1, the
IGBT
is turned
on and
The
IGBT
turn-off
losses
and diode
turn-on
current
through
the
inductor
ramps
up
it
losses are measured at the T2until
transition.
reaches
the
desired
test
current
at
time
T2.
Switching parameters
werecurrent
measured
for a 15-A,
The inductor
continues
to 600-V
flow
Ultrafast
soft-recovery
silicon
(similar
to what
would
At time
T2, the
isdiode
turned
and
theturned
through
theIGBT
diode
until
theoffIGBT
is
be co-packaged
in a 40-A
Ultrafast IGBT)
and diode.
a 10-A, 600inductor
current
transferred
the
back
on at istime
T3. Now to
inductor
current is
V SiC SBD, along with the switching losses of a 40-A, 600The IGBT turn-off losses and diode turn-on
V silicon IGBT. The losses were measured at a voltage of
losses
are measured
500 V
and current
of 20 A. at the T2 transition.
The inductor current continues to flow
CPWR-AN03, Rev A
through
the diode
until the voltage,
IGBT is current
turned and
Figure
2 shows
the turn-off
instantaneous
power
measured
at
a
junction
temperature
back on at time T3. Now inductor current
is
15
10 Figure
Figure
2: 600
600-volt
Ultrafastdiode
diode
turn2.
volt SiSiUltrafast
turn-off
voltage,
current
and instantaneous
voltage,
current
and instantaneous
power at
0 power at 150°C.
150°C.
5 off
-50
0
50
100
150
0
-100
-50
0
50
250
300
150
200
250
300
Page 2/9
Figure
3: 600
600-volt
SBD turn-off
Figure 3.
volt SiC SiC
SBD turn-off
voltage,
voltage,
current
and instantaneous
power
current and
instantaneous
power at 150°
C.
at 150˚C.
pea
diss
freq
cau
am
F
curr
at a
IGB
SBD
50%
pow
freq
are
resu
8
7
6
5
4
3
2
1
800
45
-1
700
40
-2
600
35
500
30
400
25
300
200
0
CPWR-AN03, Rev. B
100
Time (ns)
Copyright © 2003-2006 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree
100
and the Cree logo are registered trademarks of Cree, Inc.
200
(ns)
2 Time
shows
the turn-off
Figure 3Figure
is the turn-off
waveforms
for thevoltage,
SiC SBD at
current
and
instantaneous
power
measured
150°C. This shows a peak reverse recovery
current of 4
Figure 2. 600 volt Si Ultrafast diode turn-off
junction temperature
of 150°time
C of of
the33Sins, a
amps,ataareduction
of 83%, a recovery
voltage, current and instantaneous power at
reduction
of
67%,
and
a
peak
instantaneous
power
ultrafast diode. This shows a peak reverseof 0.5
150°C.
power is of
due
to the
SiC
SBD
only having
to
kW, a recovery
reduction
93%.
The
drastic
reduction
in switching
current
of 23
amps,
a recovery
dissipate
a
small
capacitive
charge,
which
power
is due
to the SiC
SBD
to dissipate only a
Figure
2of shows
turn-off
voltage,
time
100
ns, the
and
a having
peak instantaneous
small capacitive
charge,
happens
while
diode
happens
while
thewhich
diode
voltage
is low.the
The
current
and
instantaneous
power
measured
power
ofThe
7 kW.
Alsoovershoot
shown isseen
the in200
voltage
is low.
voltage
thevolt
Si is
diode
voltage
overshoot
seen
in
the
Si
diode
at
junction
temperature
of the
150°
C SBD.
of the
overshoot
causedwith
by
the SiC
high
di/dtSiduring
is a
completely
eliminated
completely
eliminated
thereverse
SiC SBD.
ultrafast
showssnap-off.
awith
peak
thediode.
reverseThis
recovery
recovery 900
current of 23 amps, a recovery 25
3 and
is thea turn-off
waveforms for
800 ns,
20 the
time of Figure
100
peak instantaneous
SiC
SBD
at
150°
C.
This
shows
a
700
power of 7 kW. Also shown is the 200 volt 15peak
600
10
reverse
recovery
of 4
amps,
a
overshoot
caused
by thecurrent
high di/dt
during
500
5
reduction
of
83%,
a
recovery
time
of
33
ns,
the reverse
400recovery snap-off.
0
a 300
reduction of 67% and a -5peak
Figure
3200is the turn-off
the -10
instantaneous
powerwaveforms
of 0.5 kW,for
a reduction
SiC SBD
at
150°
C.
This
shows
a
peak
100
-15
of 93%.
The drastic reduction in switching
0
reverse recovery
current of 4 amps, a -20
reduction -100
of 83%, a recovery time of 33 ns, -25
20
Page 2/9
a reduction
of 67% and a peak
15
instantaneous
power of 0.5 kW, a reduction
10
of 93%. The
drastic reduction in switching
5
V IGBT (volts)
of 150°C of the Si Ultrafast diode. This shows a peak
reverse-recovery current of 23 amps, a recovery time of
100 ns, and a peak instantaneous power of 7 kW. Also
shown
is the 200-voltRev
overshoot
caused by the high di/dt
CPWR-AN03,
A
during the reverse-recovery snap-off.
300
I diode (A)
reaches the desired test current at time T2.
Figure 1. Inductive Test Circuit with
At time
T2, the IGBT is turned off and the
operating
waveforms.
-25
250
-100
-200
20
I IGBT (A)
T1, the test
IGBT circuit
is turnedwith
on and
Figure At
1: time
Inductive
current
through
the
inductor
ramps
up
until it
operating waveforms.
200
V diode (volts)
with
150
Power (kW)
Circuit
100
Time (ns)
-100
Test
-25
V IGBT (volts)
Power (kW)
20
Figure 1. Inductive
operating waveforms.
-20
-10
10
-100
-15
Cree, Inc.
460015
Silicon Drive
Durham, NC 27703
10
USA Tel: +1.919.313.5300
5
Fax: +1.919.313.5778
www.cree.com/power
Power (kW)
V diode (volts)
700
I diode (A)
800
400
I diode (A)
900
V diode (volts)
diode (similar to what would be copackaged
in a 40 A Comparison
ultrafast IGBT) and a 10
600 volt Switching
A, 600 V SiC SBD, along with the switching
Switching
wereV measured
for The
losses parameters
of a 40A, 600
Silicon IGBT.
a 15 A,
600
V
ultrafast
soft
recovery
silicon
losses were measured at a voltage of 500 V
diode and
(similar
what
currentto
of 20
A. would be copackaged900in a 40 A ultrafast IGBT) and a 10 25
A, 600 V800
SiC SBD, along with the switching 20
losses of700a 40A, 600 V Silicon IGBT. The 15
600 measured at a voltage of 500 V 10
losses were
500
5
and current
of 20 A.
0
-5
Figu
0
50
100
150
200
250
300
Time (ns)
800
45
700
40
600
35
500
30
400
25
300
20
200
15
100
10
0
5
-100
0
-200
-5
Power (kW)
15
0
5
I diode (A)
0
0
5
0
5
10
peak
instantaneous power of 15 kW is
5
dissipated
in the IGBT. Also shown are high
0
frequency
IGBT
-200 -150oscillations
-100 -50
0 in 50the100
150 voltage
200
(ns)
caused when the SiTime
diode
snaps off. This is
a major cause
of RFI/EMI
generation.
Figure
600-volt
IGBT
turn-on
with Si
Figure 4.4:600
volt IGBT
turn-on
w/ Si Ultrafast
current and instantaneous power measured
at a junction
temperature
of 150°C of the
shows
the turn-on
Figure Figure
4 shows4 the
turn-on
voltage, voltage,
current and
IGBT
with
ainstantaneous
SiC SBD.
Thepower
use of
the
SiC
current
and
measured
instantaneous power measured at a junction
temperature
SBD
results
in
a
peak
current
of
22
amps,
at aofjunction
of 150°
C ofDuring
thea the
of 150°C
the IGBTtemperature
with a Si Ultrafast
diode.
50%
reduction,
and
a
peak
instantaneous
IGBT IGBT
turn-on,
the adiode
reverse-recovery
current the
is added
with
Si ultrafast
diode. During
power
of
7.5 kW,
a diode
50% reduction.
The
highof 44
to theIGBT
IGBT turn-on
current,
resulting
inreverse
a peak recovery
current
the
amps.frequency
A peak instantaneous
of IGBT
15 kW voltage
is dissipated
inthethe
current
is oscillations
added topower
IGBT
current,
in theare
IGBT.also
Also eliminated
shown are high-frequency
oscillations
in
with
the
SiC
SBD,
resulting
a peak
current
44 amps.
A This
the IGBT
voltageincaused
when
the Siofdiode
snaps off.
resulting in reduced RFI/EMI generation.
is a major cause of RFI/EMI generation.
800
30
400
25
300
20
200
15
100
10
0
5
Figure
5 shows the turn-on voltage,0 current and
-100
instantaneous
power measured at a junction
temperature
-200
-5
of 150°C of the IGBT with a SiC SBD. The use of the SiC SBD
20 in a peak current of 22 amps, a 50% reduction, and
results
15 instantaneous power of 7.5 kW, a 50% reduction.
a peak
The 10
high-frequency oscillations in the IGBT voltage are
5
also eliminated
with the SiC SBD, resulting in reduced RFI/
0
EMI generation.
-150
-100
0
50
100
150
200
A comparison of the switching parameters of the SiC SDB
with the Si Ultrafast diode are shown for measurements
Figureat5.a 600
volt temperature
IGBT turn-on
SiCinSBD,
taken
junction
of w/
25°C
Table 1 and for
voltage,
current
and
instantaneous
power atof 150°C in
measurements taken at a junction temperature
150°C.
Table
2. The total switching-loss reduction (IGBT + Diode)
is calculated to be 52% at 25°C and 56% at 150°C.
A
comparison of
the
switching
= 20A,
V = 500V,
10 ohmthe Si
parameters of Ithe
SiC
SDBRg =with
Parameter diode are shown
Units for measurements
Si Pin
SiC
% Reduction
ultrafast
Peak Reverse
(A)
13 of 25°
4 C in
69%
taken
at current
a junction Ipr
temperature
Reverse recovery
Trr (nS)
83 taken
30 at a
64%
Table
1 andtimefor measurements
Recovery
Charge
Qrr
(nC)
560
78
junction temperature of 150°C in Table 2. 86%
Diode loss
turn-off
Eoff Diode
0.11
0.02
The
total
switching
loss(mJ)
reduction
(IGBT
+ 82%
Diode loss is
turn-on
Eon Diode
(mJ)52%
0.03
0.02
Diode)
calculated
to be
at 25°
C and 33%
Diode loss
0.14
0.04
71%
56%
at total
150°C. Ets Diode (mJ)
C
CC
IGBT loss turn-on
Eon IGBT (mJ)
0.63
0.23
63%
IGBT loss turn-off
Eoff IGBT (mJ)
0.46
0.32
30%
IGBT loss total
Ets IGBT (mJ)
1.09
0.55
50%
Ets (mJ)
1.23
0.59
52%
loss total
Table 1: 600 volt-switching parameter comparison
between Si Ultrafast and SiC SBD at 25°C.
IC = 20A, VCC = 500V, Rg = 10 ohm
45
CPWR-AN03, Rev A
-50
Time (ns)
Ultrafast
diode,
current
instantaneous
diode,
voltage,
current
and
instantaneous
Figure
5 shows
theand
turn-on
voltage,
power
at
150˚C.
power at 150°C.
5
35
500
-200
APPLICATION NOTE
20
ing to
which
w. The
ode is
D.
I IGBT (A)
V IGBT (volts)
Figure 3. 600 volt SiC SBD turn-off voltage,
current and instantaneous power at 150°C.
600
I IGBT (A)
-50
V IGBT (volts)
0
-100
Power (kW)
P
5
SiC
Page
3/9% Reduction
Parameter
Units
Si Pin
600
35
Peak Reverse current
Ipr (A)
23
4
83%
500
30
Reverse recovery time
Trr (nS)
100
33
67%
400
25
300
20
Recovery Charge
Qrr (nC)
1220
82
93%
200
15
Diode loss turn-off
Eoff Diode (mJ)
0.23
0.02
91%
100
10
Diode loss turn-on
Eon Diode (mJ)
0.03
0.02
33%
0
5
Diode loss total
Ets Diode (mJ)
0.26
0.04
85%
45
-100
0
IGBT loss turn-on
Eon IGBT (mJ)
0.94
0.24
74%
40
-200
-5
IGBT loss turn-off
Eoff IGBT (mJ)
0.89
0.64
28%
20
IGBT loss total
Ets IGBT (mJ)
0.89
0.64
28%
15
loss total
Ets (mJ)
2.09
0.92
56%
oltage,
°C.
25
20
15
10
5
0
-5
I IGBT (A)
30
Power (kW)
35
I IGBT (A)
40
V IGBT (volts)
700
10
Table 2: 600-volt switching parameter comparison
between Si Ultrafast and SiC SBD at 150°C.
5
0
-200
-150
-100
-50
0
50
100
150
200
Time (ns)
Figure
5: 600
600-volt
IGBT
turn-on
w/ SBD,
SiC
Figure 5.
volt IGBT
turn-on
w/ SiC
SBD,
voltage,
current
and
instantaneous
voltage, current and instantaneous power at
power
150°C. at 150°C.
Figure 6 shows the turn-off currents of the Si Ultrafast
diode and the SiC SBD at 25°C and 150°C superimposed
on one plot. The SiC SBD is unchanged with temperature,
with a peak reverse current of 5 amps. The Si Ultrafast
diode shows strong temperature dependence, increasing
from 13 amps at 25°C to 23 amps at 150°C.
A
comparison of
the
switching
parameters of the SiC SDB with the Si
0
ultrafast diode are shown for measurements
taken at a junction temperature of 25°C in
Table 1 and for measurements taken at a
rafast
© 2003-2006
Cree, Inc. All rightsof
reserved.
The
in this
temperature
150°
C information
in Table
2.document is subject to change without notice. Cree
neous Copyrightjunction
and the Cree logo are registered trademarks of Cree, Inc.
The total switching loss reduction (IGBT +
CPWR-AN03,
Rev. B to be 52% at 25°C and
Diode)
is calculated
ltage,
56% at 150°C.
Cree, Inc.
4600 Silicon Drive
Durham, NC 27703
USA Tel: +1.919.313.5300
Fax: +1.919.313.5778
www.cree.com/power
APPLICATION NOTE
25
-5
20
-10
15
-15
Si Ultrafast Diode @ 25°C
SiC SBD @ 25°C and 150°C
I Diode (A)
10
-20
5
-25
0
-30
-5-200
-10
Si Ultrafast Diode @ 150°C
-150
-100
-50
0
50
100
150
200
Time (ns)
Si Ultrafast Diode @ 25°C
-15
Figure
6: 600
600-volt
turn-off
current
Figure
6:
volt turn
off current
of of
thethe
Si
Si Ultrafast
diode
atC25°C
Ultrafast
diode
andand
the the
SiC SiC
SBDSBD
at 25°
and
-20
and 150°C.
150°C.
Si Ultrafast Diode @ 150°C
-25
-30
Figure 7 50shows
the-100
turn-on
currents
of
the150IGBT
with
-200
-150
-50
0
50
100
200
w/ Si Ultrafast
Diode
150°CSBD at 25°C and 150°C,
a Si Ultrafast diode
and
a @SiC
Time (ns)
45
superimposed
on one plot. The peak current in the IGBT
w/ Si Ultrafast Diode @ 25°C
40 SBD is unchanged with temperature. The peak
with the
SiC
Figure
6: 600 volt turn off current of the Si
current
of
the IGBT
with
thethe
Si Ultrafast
shows
strong
35
Ultrafast
diode
and
SiC SBDdiode
at 25°
C and
temperature
dependence
due
to
the
reverse-recovery
150°C.
30
temperature
dependence of the diode.
25
50
20
w/ Si Ultrafast Diode @ 150°C
45
15
40
10
w/ Si Ultrafast Diode @ 25°C
w/ SBD @ 25°C and 150°C
35
5
30
0
25
-5
20
-10
15-200
-150
-100
-50
10
0
50
100
150
200
Time (ns)
w/ SBDof
@ 25°C
150°C w/
Figure 7: 600 volt turn-on current
theandIGBT
5
the Si Ultrafast diode and the SiC SBD at 25°C and
0
150°C.
-5
100°C
20
0
15 10
Si Ultrafast Diode
150°C
25
5
SiC SBD
50°C
20
30
40
50
60
70
80
90
100
Switching Frequency (kHz)
10
Figure 8: 600 volt switching power loss of
the 5Si Ultrafast diode and theSiCSBD
at 50°C,
SBD
100°C, and 150°C.
0
Figure
shows
the
IGBT
10
20 930
40
50 total
60
70
80 switching
90
100
(kHz)in watts at
losses (turn-onSwitching
and Frequency
turn-off)
switching frequencies from 10 kHz to 100
Figure
600
volt switching
loss of
Figure 8:
600-volt
switching power
of
kHz at8:50,
100 and
150°C.power
Theloss
IGBT
the Si
Si Ultrafast
diode and
and the
the SBD at
the
Ultrafast diode
at 50°C,
50°C,
switching
loss
with the SiC SBD is about
100°C,
and
150°C.
100°C,
and
150°
C.
half that of the IGBT with the Si ultrafast
Figurediode.
9 shows
total with
IGBT
switching
lossesalso
(turn-on
Figure
9 IGBT
shows
the total
IGBT
switching
Thethe
the
SiC SBD
and turn-off)
in
watts
at
switching
frequencies
from
losses
(turn-on
andinturn-off)
wattswith
at 10
shows less
increase
switchinginlosses
kHz to 100 kHz at 50, 100 and 150°C. The IGBT switching
switching
frequencies
from 10 dependence
kHz
to 100
temperature.
The
loss with
the SiC SBD
is temperature
about half that
of the IGBT with
kHz
50,diode.
100losses
andIGBT
150°
C.IGBT
Thewith
ofUltrafast
theatswitching
in the
the also
the Si
The
with
the
SiCIGBT
SBD
switching
loss
SBD
about
shows
lessSBD
increase
inwith
switching
losses
withis
SiC
is due
tothe
theSiC
increase
intemperature.
IGBT
The temperature
of
the
losses
half
that time
of dependence
the
IGBT
theswitching
Si
ultrafast
turn-off
since
thewith
turn-on
losses
are in
the IGBT
withThe
the IGBT
SiC SBD
is due
toSiC
the increase
in IGBT
diode.
with
the
SBD
also
unchanged with temperature. This dramatic
turn-off time since the turn-on losses are unchanged with
shows
less increase
with
improvement
in in
theswitching
IGBT losses
switching
temperature.
This dramatic
improvement
in the IGBT
temperature.
The
temperature
dependence
performance
is due
to thetoabsence
of of
switching
performance
is solely
due solely
the absence
of
the
switching
in
IGBT with the
reverse
recovery
in the
SiCthe
SBD.
reverse
recovery
in thelosses
SiC
SBD.
SiC SBD is due to the increase in IGBT
200
turn-off time since the turn-on
losses are
Si Ultrafast Diode
180
150°C
unchanged with temperature.
This dramatic
160
improvement 100°C
in the IGBT switching
140
performance50°C
is due solely to the absence of
120
reverse recovery in the SiC SBD.
100
160
40
400
1400
200
1200
0
1000
-200
800
12
600
10
8
400
6
4
200
2
0
0
-200
200
80
180
60

meas
recov
be co
and
1200
switc
The l
meas
1000
recov
temp
be
co
since
and
a
runaw
switch
The l
curre
1000
at a j
tempe
ultraf
since
recov
runaw
of 14
of 2.8
curre
the 6
at
a ju
due
t
ultrafa
lower
recov
1400
of 14
1200
of 2.8
1000
the 60
800
due to
600
lower
V diode (volts)
30
0
30
10
1200
150°C
Si Ultrafast Diode
Power (kW)
I Diode (A)
5
Diode Switching LossesDiode
(watts)
Switching Losses (watts)
APPLICATION NOTE
10
IGBT Switching Losses IGBT
(watts)
Switching Losses (watts)
SiC SBD @ 25°C and 150°C
15
I IGBT (A)
nts of
BD at
plot.
meter
with
d
entSiC
of
trong
from
nts of
BD at
of
ents
plot.
a with
SiC
ed
enton
of
T
with
strong
with
from
IGBT
trong
nts of
verse
a SiC
f the
ed on
T with
with
IGBT
strong
verse
f the
20
I IGBT (A)
7%
3%
meter
1%
d3%SiC
5%
4%
8%
2%
eduction
6%
83%
67%
meter
93%
d91%SiC
33%
85%
74%
28%
52%
56%
25
Figure 8 shows the total diode switching losses (turn-on
Si Ultrafast Diode
and turn-off)
in watts 150°C
at switching frequencies from 10
25
kHz to 100 kHz and 100°C
temperatures of 50, 100 and 150°C.
The SBD20 has significantly lower switching losses (up to
50°C
an 85% reduction)
and shows no change with increased
temperature.
15
V diode (volts)
Power (kW)
30
30
duction
9%
4%
6%
2%
3%
1%
3%
0%
0%
eduction
2%
69%
64%
meter
86%
d82%SiC
33%
71%
63%
30%
50%
duction
52%
3%
12
10
Figur8
6
off vo
4
at 125
2
100°C
SiC SBD
Figure 8 shows the total diode
140
20
-10
50°C
switching
losses (turn-on and turn-off) in
1200
0
-200
-150
-100
-50
0
50
100
150
200
watts at switching frequencies
from
10
kHz
20
30
40
50
60
70
80
90
100
100 10
Time (ns)
to
100
kHz
and
temperatures
of
50,
100
and
Switching Frequency (kHz)
80
Figure 7:7:600
volt turn-on
current
of the IGBT
w/
Figure
600-volt
turn-on
current
of the
150°
The
SBDand
has
the SiC.
Ultrafast
diode
the significantly
SiC SBD at 25°lower
C and
60
Figure
9:600
600-volt
IGBT
switching
power
Figure
9:
volt IGBT
switching
power
loss
IGBT w/ the Si Ultrafast diode and the SiC
Figure
switching
losses (up to an 85% reduction)
150°C.
40with
loss
the Si Ultrafast
diode
and
the
SiC
SBD at 25°C and 150°C.
w/
the
Si Ultrafast
diode and
the
SiC
SBD
at
off vo
SiC SBD
and shows no change with increased
20 at
SBD
50°C,
100°C,
and 150°C.
50°
C,
100°
C, and
150°C.
Figure 8 shows the total diode
at 125
temperature.
0
switching losses (turn-on and turn-off) in
10
20
30
40
50
60
70
80
90
100
watts at switching frequencies from 10 kHz
Switching Frequency (kHz)
to 100 kHz and temperatures of 50, 100 and
Figure 9: 600 volt IGBT switching power loss
150°C. The SBD has significantly lower
w/
the Si Ultrafast diode and the SiC SBD
atCree, Inc.
switching losses (up to an 85% reduction)
4600 Silicon Drive
CPWR-AN03,
Rev
A
Copyright © 2003-2006 Cree, Inc. All rights reserved. The information
in4/9
this document is subject50°
to change
without
Cree C.
Durham, NC 27703
C, 100°
C, notice.
and 150°
and shows no change with Page
increased
and the Cree logo are registered trademarks of Cree, Inc.
USA Tel: +1.919.313.5300
Fax: +1.919.313.5778
temperature.
www.cree.com/power
CPWR-AN03, Rev. B
0
2
800
0
600
-2
400
-4
200
-6
0
-8
Power (kW)
-200
12
10
8
6
4
2
0
-150
-10
-100
-50
0
50
100
150
200
250
Time (ns)
Figure
10: 1200
1200-volt
Ultrafast
Figure 10.
volt Si Si
Ultrafast
diodediode
turnturn-off voltage, current and instantaneous
off voltage, current and instantaneous power
power at 125°C.
at 125°C.
100
Figure 11 is the turn-off waveforms for the SiC SBD at
125°C. This shows a peak reverse-recovery current of
1 amp, a reduction of 83%, a recovery time of 30 ns, a
er loss reduction of 80%, and a peak instantaneous power of 0.3
SBD at kW, a reduction of 89%. The drastic reduction in switching
power is due to the capacitive charge of the SBD dissipating
while the diode voltage is low.
200
800
0-6
6000
-8
-2
-200
400
-10
-4
Power (kW)

Figure 11 is the turn-off waveforms for
Figure
1200
SiC
voltage,
Figure
11:
1200-volt
SiC turn-off
SBD
the SiC11.
SBD
atvolt
125°
C.SBD
This
showsturn-off
a peak
current
instantaneous
power
C a
voltage,
current
and
instantaneous
power
reverseand
recovery
current
of at
1 125°
amp,
at 125°C.
reduction
of 83%,
time of 30 ns,
Figure 11
is thea recovery
turn-off waveforms
for
a SiC
reduction
of
80%
and
a a peak
peak
the
SBD
at
125°
C.
This
shows
Figureinstantaneous
12 is the turn-on
voltage,
current
and instantaneous
power
of 0.3
kW,
current
of 1aofreduction
amp,
a the
powerreverse
measuredrecovery
at a junction
temperature
125°C for
of
89%. The
drastic
reduction
in switching
of 83%,
a recovery
time
30 ns,
IGBT reduction
with a Si Ultrafast
diode.
During
the of
IGBT
turn-on,
is due to of
the capacitive
theIGBT
the diode
reverse-recovery
current and
is charge
added
the
apower
reduction
80%
a toof
peak
SBD
dissipating
while
the
diode
voltage
current,
resulting in apower
peak current
of 11.7
amps. Aispeak
instantaneous
of 0.3 kW,
a reduction
instantaneous
power
of
11
kW
is
dissipated
in
the IGBT.
low.
of
89%. The drastic reduction in switching
power
1200 is due to the capacitive charge of
12 the
SBD
dissipating while the diode voltage
is
1000
10
low.
800
8
1200
600
12
6
1000
400
10
4
800
200
8
2
600
0
6
0
400
-200
4
-2
200
12
10
0
8
6
-200
4
2
120
10
8-200
2
0
-2
-150
-100
-50
0
50
100
150
200
6
Time (ns)
4
2
Figure
12. 1200-volt
1200 volt IGBT
Si
Figure
12:
IGBT turn-on
turn-on w/
with
0
Ultrafast
diode,
voltage,
current
and
Si
Ultrafast
diode,
voltage,
current
and
-200 -150 -100 -50
0
50
100 150 200
instantaneous
power
125°C.
instantaneous power
atat
125°
C.
Time
(ns)
Figure
12.121200
IGBT
turn-on
w/ Si
Figure
is thevolt
turn-on
voltage,
current
Page 5/9
FigureUltrafast
13 shows
the turn-on
voltage,
current
and
diode,
voltage,
currentat
and instantaneous
power
measured
a and
instantaneous
power power
measured
at aC.junction temperature
instantaneous
at
125°
junction
temperature
for the
of 125°C
for the
IGBT with of
a 125°
SBD.CThe
use IGBT
of the SBD
Figure 12 is the turn-on voltage, current
and instantaneous power measured at a
CPWR-AN03,
Rev A
junction
temperature
of 125°C for the IGBT
Copyright © 2003-2006 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree
and the Cree logo are registered trademarks of Cree, Inc.
CPWR-AN03, Rev A
CPWR-AN03, Rev. B
Cree, Inc.
4600 Silicon Drive
Durham, NC 27703
USA Tel: +1.919.313.5300
Fax: +1.919.313.5778
www.cree.com/power
V IGBT (volts)V IGBT (volts)
2-4
120
60
100
40
80
20
60
40
-20
20
1
1
Power (kW)
4-2
400
1000
I diode (A)
60
600
1200
I diode (A)
V diode (volts)V diode (volts)
800
1400
with
turnis ad
peaka
with
insta
turn-o
in ad
the
is
120
peak
100
insta
80
in the
-20
Power (kW)
4
1000
2
I IGBT (A)
1200
1000
I IGBT (A)
6
I diode (A)
1400
4
Power (kW)
at a junction temperature of 125°C for the Si
Figureultrafast
10 shows
theThis
turn-off
diode.
showsvoltage,
a peak current
reverse and
instantaneous power measured at a junction temperature
recovery current of 6 amps, a recovery time
of 125°C for the Si Ultrafast diode. This shows a peak
of 148 ns, and
a peak
power
reverse-recovery
current
of 6 instantaneous
amps, a recovery
time of
of and
2.8 kW.
The
voltage overshoot
seen
148 ns,
a peak
instantaneous
power of
2.8 with
kW. The
voltage
withisthe
Si diode
is not
theovershoot
600 volt seen
Si diode
not600-volt
pronounced
here
pronounced
the testing
1200-volt
testing
being
due tohere
the due
1200tovolt
being
done
at adone
at a lower
vs.vs.
750
A/µs).
lowerdi/dt
di/dt(250
(250A/µs
A/µs
750
A/µs).
V diode (volts)
tching
tts at
o 100
IGBT
about
rafast
D also
s with
dence
th the
IGBT
s are
amatic
tching
nce of
6
1200
200
-6
12
10
08
-8
-2006
-10
4
122
100
8-150 -100 -50
0
50
100 150 200 250
6
Time (ns)
4
2 11. 1200 volt SiC SBD turn-off voltage,
Figure
0
current
and instantaneous
power at 125°C
-150 -100 -50
0
50
100 150 200 250
Time (ns)
V IGBT (volts)V IGBT (volts)
oss of of 1000 V and current of 5 A. The maximum temperature
Figure 10 shows the turn-off voltage,
50°C, used in this testing was 125°C since the IGBT started going
currentrunaway
and instantaneous
power
measured
into thermal
when biased at
150°C.
1400
Power (kW)
100
The switching parameters were
measured for an 8A, 1200 V ultrafast soft
recovery silicon diode (similar to what would
be co-packaged in an 11 A ultrafast IGBT)
and
a 5Switching
A, 1200 VComparison
SBD, along with the
1200-Volt
switching losses of a 11 A, 1200 V IGBT.
The losses were measured at a voltage of
The switching parameters were measured for an 8-A,
1000 V and current of 5 A. The maximum
1200-V Ultrafast soft-recovery silicon diode (similar to
temperature
used in inthis
was 125°
C and
what would
be co-packaged
an testing
11-A Ultrafast
IGBT)
the
IGBT
started
going
into thermal
a 5-A,since
1200-V
SBD,
along
with the
switching
losses of an
11-A, runaway
1200-V IGBT.
The
losses at
were
measured
at a voltage
when
biased
150°
C.
Power (kW)
0
1200 volt Switching Comparison
1
1
F
SBD,
powe
FF
SBD,
curre
powe
at a
IGBT
Fi
resul
curre
redu
at
a
of
6.2
IGBT
resulF
reduc
the S
of
6.2
25°
C
The F
tempS
the
1
25°am
C
stron
The
from
temp
The
1 am
diode
stron
nS a
from
the
The r
temp
diode
nS a
the
temp
APPLICATION NOTE
4
0
-2
-4
I diode (A)
2
with a Si ultrafast diode. During the IGBT
turn-on the diode reverse recovery current
is added to the IGBT current, resulting in a
peak current of 11.7 amps. A peak
results in a peak current of 6.7 amps, a 42% reduction, and
instantaneous power of 11 kW is dissipated
a peak instantaneous power of 6.2 kW, a 44% reduction.
in the IGBT.
12
-8
1000
10
-10
800
8
600
6
400
4
200
2
0
0
ltage,
°C
Power (kW)
-200
I IGBT (A)
1200
V IGBT (volts)
-6
w/ Si Ultrafast Diode @ 125°C
w/ Si Ultrafast Diode @ 25°C
12
10
8
6
4
2
0
-200
8
2
0
-2
0
w/ Si
and
ent
a
GBT
Figure 14 shows the turn-off currents of
the6 Si ultrafast diode and the SiC SBD at
25°C and 125°C superimposed on one plot.
25°C and 125°C
The4 SiC SBD SiCisSBD @ unchanged
with
temperature, with a peak reverse current of
2
1 amp.
The Si ultrafast diode shows a
strong temperature dependence, increasing
0
from 5 amps at 25°C to 6 amps at 150°C.
The
-2 reverse recovery time of the Si ultrafast
diode increases from 100 nS at 25°C to 148
nS-4at 125°C while reverse recovery time of
Si Ultrafast Diode @ 25°C
the SiC SBD is unchanged
with
-6
temperature.
Si Ultrafast Diode @ 125°C
8
-8
-150
-100
-50
0
50
100
150
200
250
Time (ns)
Figure 14: 1200-volt turn-off current of the
Figure 14: 1200 volt turn-off current of the Si
Si Ultrafast diode and the SiC SBD at 25°C
Ultrafast
diode and the SiC SBD at 25°C and
and 125°C.
125°C.
Page 6/9
6
4
w/ SBD @ 25°C and 125°C
2
0
-2
-200
-150
-100
-50
0
50
100
150
200
Time (ns)
Figure 15:
volt turn-on
current
of the IGBT
w/
Figure
15:1200
1200-volt
turn-on
current
of the
the Si Ultrafast
diode
and the SiCdiode
SBD atand
25°C the
and
IGBT
with the
Si Ultrafast
150°SBD
C.
SiC
at 25°C and 150°C.
A comparison of the
switching parameters
of the SiC SBD
APPLICATION
NOTE
with the Si Ultrafast diode are shown for measurements
taken
atcomparison
a junction temperature
in Table 3, and
A CPWR-AN03,
of A theof 25°C
switching
Rev
for
measurements
a junction
temperature
of
parameters
of thetaken
SiC atSBD
with the
Si
125°C in Table 4. All measured parameters show a major
ultrafast diode are shown for measurements
improvement with the SiC SBD. The value of the SBD
taken at a junction
temperature
of 25°with
C in increased
parameters
are effectively
unchanged
Table 3, andwhile
for measurements
taken
at aparameters
temperature
the Silicon Ultrafast
diode
increase.
The total switching-loss
reduction
junction temperature
of 125°C in
Table 4.(IGBT
All + Diode)
is
51% at 25°C
and 58% at 125°C.
measured
parameters
show a major
improvement with the SiC SBD. The value
of the SBD parameters are effectively
unchanged with increased temperature
while the Silicon Ultrafast diode parameters
increase. The total switching loss reduction
(IGBT + Diode) is 51% at 25°C and 58% at
125°C.
Parameter
Peak reverse current
Reverse recovery time
Recovery charge
Diode loss turn-off
Diode loss turn-on
Diode loss total
IGBT loss turn-on
IGBT loss turn-off
IGBT loss total
loss total
Ic = 5A, Vcc = 1000V, Rg = 22 ohm
Units
Si Pin
SiC % Reduction
Ipr (A)
5.5
1
82%
Trr (nS)
100
30
70%
Qrr (nC)
295
20
93%
Eoff Diode (mJ) 0.08
0.02
75%
Eon Diode (mJ) 0.03
0.02
33%
Ets Diode (mJ) 0.11
0.04
64%
Eon IGBT (mJ) 0.73
0.28
62%
Eoff IGBT (mJ) 0.33
0.25
24%
Ets IGBT (mJ) 1.06
0.53
50%
Ets (mJ)
1.17
0.57
51%
Figure 15 shows the turn on currents of
the IGBT with a Si ultrafast diode and the
Table 3: 1200 volt switching parameter
SiC SBD at 25°C and 125°C superimposed
Cree, Inc.
comparison between Si Ultrafast and SiC
4600 Silicon Drive
on
one
plot.
The
peak
current
in
the
IGBT
Copyright © 2003-2006 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree
Durham, NC 27703
SBD at 25°C.
and the with
Cree logothe
are registered
Inc.
USA Tel: +1.919.313.5300
SiC trademarks
SBD ofisCree,unchanged
with
Fax: +1.919.313.5778
www.cree.com/power
current and reverse
Ic = 5A, Vcc = 1000V, Rg = 22 ohm
temperature.
CPWR-AN03,The
Rev.peak
B
Parameter
Units
Si
Pin
SiC
%
Reduction
recovery time of the IGBT with the Si
Peak reverse current
Ipr (A)
Diode
Diode
Dio
IGBT
IGBT
IGB
Table
comp
SBD
P
Peak r
Revers
Rec
Diode
Diode
Dio
IGBT
IGBT
IGB
Table
comp
SBD
10
-2
I Diode (A)
I IGBT (A)
4
14
12
ms for
peak
-150 -100 -50
0
50
100 150 200
mp, a
Time (ns)
30 ns,
Figure
13: 1200-volt
IGBT
turn-on
with
SiC
peak
Figure
13. 1200 volt
IGBT
turn-on
w/SiC
SBD,
voltage,
current
and
instantaneous
uction
SBD, voltage, current and instantaneous
power
at125°
125°C.
power at
C.
ching
shows the turn-off currents of the Si Ultrafast
of the Figure 14Figure
13 shows the turn-on voltage,
and the SiC SBD at 25°C and 125°C superimposed
ge is diode current
andSiC
instantaneous
power
measured
on one plot. The
SBD is unchanged
with
temperature,
a junction
125°
C for
the
with aatpeak
reversetemperature
current of 1 of
amp.
The
Si Ultrafast
diode IGBT
shows with
a strong
temperature
dependence,
12
a SBD.
The use
of the increasing
SBD
from results
5 ampsinata 25°C
6 amps
at 150°C.
reverse
peak to
current
of 6.7
amps, The
a 42%
10
recovery
time of and
the Si
Ultrafast
diode increases
from 100
reduction
a
peak
instantaneous
power
8
ns at 25°C to 148 ns at 125°C while reverse-recovery time
of 6.2 kW, a 44% reduction.
of the SiC SBD is unchanged with temperature.
6
Figure 15 shows the turn on currents of
the IGBT with a Si ultrafast diode and the
SiC SBD at 25°C and 125°C superimposed
Figureon
15one
shows
theThe
turn-on
with a
plot.
peakcurrents
current ofinthe
theIGBT
IGBT
Si Ultrafast
diode
and
the
SiC
SBD
at
25°C
and
with the SiC SBD is unchanged with125°C
superimposed
on one
plot.
Thecurrent
peak current
in the IGBT
temperature.
The
peak
and reverse
with the SiC SBD is unchanged with temperature. The peak
recovery time of the IGBT with the Si
current and reverse-recovery time of the IGBT with the Si
ultrafast
a strong
temperature
Ultrafast
diode diode
showsshows
a strong
temperature
dependence
dependence
due to the
reverse dependence
recovery of
due to
the reverse-recovery
temperature
the diode.
temperature dependence of the diode.
I IGBT (A)
6
Ultrafast diode and the SiC SBD at 25°C and
125°C.
6
1
83%

switc
watts
to 10
125°C
switc
and
temp
IGBT
in wa
kHz
and
SBD
Si Pin
SiC
% Reduction
Peak Reverse current
Ipr (A)
5.5
1
82%
Reverse recovery time
Trr (nS)
100
30
70%
Recovery Charge
Qrr (nC)
295
20
93%
Diode loss turn-off
Eoff Diode (mJ)
0.08
0.02
75%
Diode loss turn-on
Eon Diode (mJ)
0.03
0.02
33%
Diode loss total
Ets Diode (mJ)
0.11
0.04
64%
IGBT loss turn-on
Eon IGBT (mJ)
0.73
0.28
62%
IGBT loss turn-off
Eoff IGBT (mJ)
0.33
0.25
24%
IGBT loss total
Ets IGBT (mJ)
1.06
0.53
50%
Ets (mJ)
1.17
0.57
51%
loss total
Table 3: 1200-volt switching parameter comparison
between Si Ultrafast and SiC SBD at 25°C.
IC = 5A, VCC = 1000V, Rg = 22 ohm
Parameter
Units
Si Pin
SiC
% Reduction
Peak Reverse current
Ipr (A)
6
1
83%
Reverse recovery time
Trr (nS)
148
30
80%
Recovery Charge
Qrr (nC)
540
20
96%
Diode loss turn-off
Eoff Diode (mJ)
0.16
0.02
88%
Diode loss turn-on
Eon Diode (mJ)
0.03
0.02
33%
Diode loss total
Ets Diode (mJ)
0.19
0.04
79%
IGBT loss turn-on
Eon IGBT (mJ)
0.98
0.28
71%
IGBT loss turn-off
Eoff IGBT (mJ)
0.57
0.41
28%
IGBT loss total
Ets IGBT (mJ)
1.55
0.69
55%
Ets (mJ)
1.74
0.73
58%
loss total
Table 4: 1200-volt switching-parameter comparison
between Si Ultrafast and SiC SBD at 125°C.
Figure 16 shows the total diode switching losses (turn-on
and turn-off) in watts at switching frequencies from 10
kHz to 100 kHz for temperatures of 25, 75 and 125°C.
The SBD has significantly lower switching losses (up to
a 79% reduction) and shows no change with increased
temperature. Figure 17 shows the total IGBT switching
losses (turn-on and turn-off) in watts at switching
frequencies from 10 kHz to 100 kHz for temperatures of
25, 75 and 125°C. IGBT switching loss with the SBD is
about half that of the IGBT with the Si Ultrafast diode. The
IGBT with the SBD also shows less increase in switching
losses with temperature. The temperature dependence
of the switching losses in the IGBT with the SBD is due
to the increase in the IGBT turn-off time, since the turnon losses are unchanged with temperature. This dramatic
improvement in the IGBT switching performance is due
solely to the absence of reverse recovery in the SiC SBD.
20
20
Diode Switching Losses (watts)
Diode Switching Losses (watts)
Units
125°C
125°C
15
15
10
10
CPWR-AN03, Rev. B
5
5
4
4
3
3
2
2
1
1
5
5
SiC SBD
SiC SBD
0
0 10
10
20
20
30
30
40
50
60
70
80
40
50
60
70
80
Switching Frequency (kHz)
Switching Frequency (kHz)
90
90
100
100
Figure 16:
16: 1200
1200-volt
switching-power
loss
Figure
volt switching
power loss
of
Figure
16:
volt switching
power
loss
of
of the
Si 1200
Ultrafast
and
the at
SBD
the
Si Ultrafast
diodediode
and the
SBD
25°at
C,
the
Si Ultrafast
diode and the SBD at 25°C,
25°C,
75°C,
and
75°
C, and
125°
C. 125°C.
75°C, and 125°C.
180
180
160
160
140
140
120
120
100
100
80
80
60
60
40
40
20
20
0
0
10
10
125°C
125°C
Si Ultrafast Diode
Si Ultrafast Diode
75°C
75°C
25°C
25°C
SiC SBD
SiC SBD
20
20
30
30
40
50
60
70
80
40
50
60
70
80
Switching Frequency (kHz)
Switching Frequency (kHz)
90
90
100
100
Figure
17: 1200-volt
1200 volt IGBT
IGBT switching power
Figure17:
17: 1200
Figure
volt IGBT switching-power
switching power
loss
w/
the
Si
Ultrafast
diode
and thethe
SBD at
lossw/
w/
the
Ultrafast
diode
loss
the
Si Si
Ultrafast
diode
andand
the SBDSBD
at
25°
C,
75°
C,
and
125°
C.
at C,
25°C,
andC.
125°C.
25°
75°C,75°C,
and 125°
0
0
0
0.0
Figur
Figure
1200
1200 v
at 25°
at 25°C
Ta
Tab
losse
losses
a 50%
a 50%
2.5 a
2.5 am
devic
device
used.
used.
the d
the da
With
With t
reduc
reduce
are re
are re
loss
loss r
by sim
by sim
a SiC
a SiC
Diode
Diode
Diode
Diode
Toc
Tota
IGBT
IGBT
IGBT
IGBTToc
Tota
T
Conduction
andTotal
Total
Losses
Conduction
and Total
Losses
Conduction
and
Losses
Table
Table
Figure 18 shows the forward IV of the
a con
Figure the
18 forward
shows IV
theof forward
IV of the
con
Figure1200
18 shows
the
1200-volt
Ultrafast adiode
volt Si ultrafast
diode
and
the SiCSi
SBD
diode
1200
volt
Si
ultrafast
diode
and
the
SiC
SBD
diodeat
and
the
SiC SBD
125°C.
At 5SBD
amps the
25°
C and
125°at
C.25°C
At 5and
amps
the SiC
at 25°
C and
125°
C. At 5lower
amps
the SiC
SBD
SiC SBD
diode
has
0.75-volt
forward
drop
at 25°C
and 0.18-volt lower forward drop at 125°C. This results in
reduced conduction losses for the SiC SBD.
CPWR-AN03, Rev A
CPWR-AN03, Rev A
Copyright © 2003-2006 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree
and the Cree logo are registered trademarks of Cree, Inc.
Si Ultrafast Diode
Si Ultrafast Diode
75°C
75°C
25°C
25°C
IGBT Switching Losses (watts)
IGBT Switching Losses (watts)
IC = 5A, VCC = 1000V, Rg = 22 ohm
Parameter
6
6
Diode Forward Current (amp)
Diode Forward Current (amp)
the IGBT turn-off time, since the turn-on
the IGBT turn-off time, since the turn-on
losses are unchanged with temperature.
losses are unchanged with temperature.
This dramatic improvement in the IGBT
This dramatic improvement in the IGBT
switching performance is due solely to the
switching performance is due solely to the
absence of reverse recovery in the SiC
absence of reverse recovery in the SiC
SBD.
SBD.
Cree, Inc.
4600 Silicon Drive
Durham, NC 27703
USA Tel: +1.919.313.5300
Fax: +1.919.313.5778
www.cree.com/power
APPLICATION NOTE
SBD
sses
ature
n the
se in
rn-on
ature.
GBT
o the
SiC
diode has 0.75 volt lower forward drop at
25°C and 0.18 volt lower forward drop at
125°C. This results in reduced conduction
losses for the SiC SBD.
Diode Forward Current (amp)
5
4
125°C
3
25°C
2
SiC SBD
1
Si Ultrafast Diode
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Diode Forward Voltage (volt)
100
Figure 18: Forward voltage and current of
Figure
18: Forward voltage and current of the
the 1200-volt Si Ultrafast diode and the SiC
1200 volt Si Ultrafast diode and the SiC SBD
SBD at 25°C and 125°C.
at 25°C and 125°C.
ss of
25°C,
90
Conclusions
6
5 shows
theofcalculation
total
Table 5 Table
shows the
calculation
total losses of
for a
100-kHz
converter
operating
at
a
50%
duty
cycle
with
an
losses for a 100 kHz converter operating average
at
current
of 2.5
amps
using
thean
1200-volt
a 50%
duty
cycle
with
averagedevices.
currentAofdevice
junction
125°C
was
used.
The conduction
2.5 temperature
amps usingofthe
1200
volt
devices.
A
loss for the IGBT is the data sheet value of 2.9 volts at 5
device
junction
temperature
of
125°
C
was
amps. With the SiC SBD, the total diode losses are reduced
used.
loss for
IGBTbyis 51%.
by 50%
andThe
the conduction
total IGBT losses
arethe
reduced
the
data
sheet
value
of
2.9
volt
at
5
amps.
This gives a 51% total loss reduction for the
1200-volt
converter
changing
the diode
Si Ultrafast
With by
thesimply
SiC SBD,
the total
lossesdiode
are to a
SiC SBD.
reduced by 50% and the total IGBT losses
100
ower
BD at
s
The turn-on switching losses of the IGBT are strongly
dependent on the reverse-recovery characteristics of its
freewheeling diode. The impact of the SiC SBD on the
switching performance of the freewheeling diode and the
IGBT is of great importance to the hard-switched circuit
designer. Based on the measurements presented above,
there are significant advantages offered by SiC Schottky
diodes. While the reverse-recovery current of the Si
Ultrafast diode shows a strong temperature dependence,
the SiC SBD is unaffected. At a high di/dt, the Si Ultrafast
diode exhibits a voltage overshoot on turn-off due to snapoff during reverse recovery, but the SiC SBD is unaffected.
The snap-off in the Si Ultrafast diode causes oscillations in
the IGBT voltage, which generate RFI/EMI. This oscillation
is not present with the SiC SBD. The 50% reduction in
switching losses can be applied in a number of ways to
optimize the circuit design. The reduction in switching
losses can be applied to increase efficiency, reduce cooling
requirements, or reduce the current rating of the IGBT.
The operating frequency can be increased in order to
allow the use of smaller passive components or to achieve
acoustic requirements. The absence of a voltage overshoot
eliminates the need for snubber networks. The absence of
the high-frequency oscillation reduces the RFI/EMI filter
requirements. The replacement of the Si Ultrafast diode
with a SiC Schottky diode such as the Cree Zero Recovery®
SBD results in a substantial reduction in switching losses
in both the diode and the IGBT, resulting in a significant
system-level performance improvement.
are reduced by 51%. This
givesSiCa SBD
51%,%total
Si Pin
Reduction
loss
reduction
for
the
1200
volt
converter
Diode Switching loss (watt)
19
4
79%
by simply changing the Si
ultrafast
diode to
Diode conduction loss (watt)
12.5
11.7
6%
a SiC SBD.
Total Diode loss (watt)
31.5
15.7
50%
Si PiN
155 SiC SBD69 % Reduction
55%
Diode Switching loss (watt)
19
4
79%
IGBT conduction loss (watt)
14.5
14.5
0%
Diode conduction loss (watt)
12.5
11.7
6%
Total IGBT loss
169.5 15.7 83.5
Total(watt)
Diode loss (watt)
31.5
50% 51%
155201
69 99.2
55% 51%
Total lossIGBT
(watt)Switching loss (watt)
IGBT conduction loss (watt)
14.5
14.5
0%
Table 5:
of169.5
calculated
losses
in a
TotalComparison
IGBT loss (watt)
83.5
51%
lossthe
(watt)1200-volt
201 Si 99.2
converterTotal
with
Ultrafast51%
diode and
IGBT Switching loss (watt)
the SBD at 125°C.
Table 5: Comparison of calculated losses in
a converter with the 1200 volt Si Ultrafast
diode and the SBD at 125°C.
f the
SBD
SBD
Page 8/9
Copyright © 2003-2006 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree
and the Cree logo are registered trademarks of Cree, Inc.
CPWR-AN03, Rev. B
Cree, Inc.
4600 Silicon Drive
Durham, NC 27703
USA Tel: +1.919.313.5300
Fax: +1.919.313.5778
www.cree.com/power