New SiC Power Devices Bring Power
Density and Efficiency to the Next Level
March, 2011
Agenda
• Introduction to SiC material
• Industry’s First SiC MOSFET
– Key features
– Comparison with silicon devices
– Application examples
• SiC Shottky Diode
– Key features
– Application in PFC and Inverter
– 1700V SiC diode
• Summary
Copyright © 2007, Cree, Inc.
pg. 2
Introduction to SiC material
Copyright © 2007, Cree, Inc.
pg. 3
A Global Company
Founded in 1987
Global Reach
•Public since 1993 (Nasdaq: CREE)
•Headquartered in Durham, NC
•Strong patent portfolio
•11 Major Locations
•4,500 Employees
•Fiscal 2010 Revenues $867M
• 601 U.S. patents and 1094 foreign patents
Copyright © 2010, Cree, Inc.
pg. 4
Why SiC Power?
SiC’s Material Difference
• 10X Breakdown Field of Si
– Lower specific on-resistance and faster switching
for the same breakdown voltage
• 3X Thermal Conductivity of Si
– Higher current densities
• 3X Bandgap of Si
– Higher temperature operation
Copyright © 2010, Cree, Inc.
pg. 5
The Power Markets and Applications
10,000
HVDC/Power
Transmission
Tractio
Solar, Wind, n/Rail
Motor Control
1,000
Device 100
Current
(A)
10
1
Automotive
Electronics
Power Supplies
10
Product
focus for SiC
100
1,000
10,000
100,000
Device Blocking Voltage (V)
• Today unit volumes dominated by Server Power Supply PFC
• 600V JBS Diodes, >500W supplies
• 1200V JBS diodes growing rapidly in Solar Inverters
SiC Market Projection
Source: Cree estimates, IMS, Yole
Copyright © 2010, Cree, Inc.
pg. 7
Industry’s First SiC MOSFET
Copyright © 2007, Cree, Inc.
pg. 8
Cree Introduces the Industry’s First SiC MOSFET
D
CMF20120D
G
Silicon Carbide Power MOSFET
N-Channel Enhancement Mode
Features:
•
•
•
•
•
Small RDSon change over temp.
Fast switching times
Low capacitances
Easy to Parallel
Simple to Drive TO-247
S
VDS
1200
V
RDS(on)@ VGS = 20 V
80
m
ID
20
A
Set to replace silicon MOSFETs and IGBTs in high
efficiency, high switching speed power applications
Copyright © 2010, Cree, Inc.
pg. 9
Snapshot on the key parameters
Copyright © 2007, Cree, Inc.
pg. 10
Snapshot on the key parameters
Copyright © 2007, Cree, Inc.
pg. 11
SiC Power MOSFET Positioning
2400
1800
SiC MOSFET
(3 - 5yrs)
1200
Si IGBT
600
Si MOSFET
Holdoff voltage and current for SiC MOSFET
and Si MOSFET and IGBT
Copyright © 2010, Cree, Inc.
pg. 12
Power MOSFET basics: (Body Diode)
20
Drain
IF (A)
15
MOSFET
body diode
10
5
Gate
Source
0
0
1
2 V (V)
3
F
4
5
 Due to the physics of these particular types of power MOSFETs (Si and SiC), a
PiN diode is intrinsic to the device
 In Si MOSFETs these diodes are very slow due to their poor recovery
characteristics and additional external circuitry is required to defeat them,
particularly in inverter applications
 Our SiC MOSFET’s body diode has much better recovery characteristics but it
turns ON at a higher voltage (2.5V – 3V)
 Because of this we are recommending customers to use a SiC schottky (1200V
10A) in anti parallel to defeat the internal body diode
Copyright © 2007, Cree, Inc.
pg. 13
Power MOSFET basics: (Body Diode)
Si MOSFET
Body Diode Defeating Circuit
SiC DMOS
Body Diode Defeating Circuit
SCHOTTKY DIODE
EXTERNAL DIODE
Si MOSFET
SiC DMOS
BODY DIODE
SiC JBS
BODY DIODE
Body diode VF ~ external diode VF
• Additional Schottky diode required
Copyright © 2007, Cree, Inc.
Body diode VF > SiC JBS VF
• No Schottky diode required
• SiC JBS must be properly selected
pg. 14
Comparative devices in Si:
SiC DMOS
TO-247
0.166 cm2
TFS IGBT
~ 0.25 cm2
NPT IGBT
Si MOS8
~ 0.44 cm2
~ 2.60 cm2
TO-3P
TO-247
SOT-227
 In the next sections we will be referencing the devices above for
comparison purposes
Copyright © 2007, Cree, Inc.
pg. 15
Features:
1200V SiC MOSFETs have 3 main advantages over 1200V Si
devices (MOSFETs, ESBTs & IGBTs)
1. Lower RDSon with much lower variation over temperature
leading to far superior forward voltage drop or conduction loss
2. Unipolar device with much lower gate charge and capacitance
thereby leading to far superior switching loss
3. Wide bandgap material leads to much lower leakage currents
Copyright © 2007, Cree, Inc.
pg. 16
1. Lower RDSon :
Channel
JFET
Drift thickness
d
Copyright © 2007, Cree, Inc.
pg. 17
1. Lower RDSon : (cont.)
RDSon = Rdrift + Rjfet + Rchannel
RDrift 
For SiC and Si
MOSFETs
d
q n N D
 For SiC: d is 1/10th the thickness of the equivalent Si device
 For SiC: ND (doping factor) can be up to 100 times higher
 Theoretically for SiC: Rdrift can be 103 times lower but in
reality its closer to the order of 102
** RDSon (SiC) <<< RDSon (Si) **
Copyright © 2007, Cree, Inc.
pg. 18
1. Lower RDSon : (cont.)
1.4
Total
1.2
Normalized RDS(on)
1.0
Drift + JFET
0.8
0.6
Channel
0.4
Resultant positive
temperature coefficient
allows safe and easy
paralleling of devices
for higher power
systems
0.2
0.0
0
25
50
75
100
125
150
175
TJ (°C)
 Normalized RDSon @ 25C = 80mΩ (1.0 pu)
 At 25C the RDSon is 50% due to (Drift + JFET) and 50% due to channel resistance
 As temperature increases (Drift + JFET) component increases while the channel
component decreases
 Overall the total increase in RDSon over temperature is only 20% (1.2 pu)
 In Si MOSFETs the increase over temperature is ~250%!!
Copyright © 2007, Cree, Inc.
pg. 19
1. Lower RDSon : (cont.)
Normalized RDSon vs Temp (Si v SiC)
3.0
Normalized RDS(on)
2.5
Si MOSFET RDS(on) varies
> 250 %
2.0
1.5
1.0
SiC MOSFET R DS(on)
varies ~ 20 %
0.5
0.0
0
50
100
150
TJ (°C)
Copyright © 2007, Cree, Inc.
pg. 20
200
2. Lower Switching Loss:
SiC DMOSFET inductive switching test setup.
L1
856 uH
D1
JBS
VDD
800V
20V
R1
DRIVE
M1
SiC DMOS
10
Copyright © 2007, Cree, Inc.
pg. 21
2. Lower Switching Loss: (cont.)
2.5
1
Turn-off Loss (mJ)
Turn-on Loss (mJ)
1.2
Si MOS 8
0.8
NPT IGBT
0.6
0.4
0.2
0
2
1.5
1
0.5
0
0
25
50
75
100
125
150
175
0
25
TJ (°C)
50
75
100
125
150
TJ (°C)
 Note the much lower turn ON and turn OFF losses of the SiC
MOSFET make it the clear choice
 Note the bigger increase in turn OFF loss with the bipolar
IGBTs due to tail currents as opposed to the unipolar SiC
MOSFET which is a majority carrier device
Copyright © 2007, Cree, Inc.
pg. 22
175
3. Lower Leakage Current:
Drain
Gate
Source
 Leakage current is the very small current that flows between the drain and source when the
device is completely OFF
 Ideally leakage current should be zero but the presence of doped semiconductor material
means there will always be very small current flow even in the OFF state
 This leakage current increases with temperature and also reverse blocking voltage
 At high temperature and full blocking this leakage current can account for extra power loss
during the device OFF state which leads to lower efficiency and reliability
 SiC MOSFETs have up to 100 times lower leakage at high temperature due to the wide bandgap material advantage
 This means higher reliability and efficiency and ultimately higher temperature capability
Copyright © 2007, Cree, Inc.
pg. 23
3. Lower Leakage Current: (cont.)
TJ = 150 °C
1E-1
1E-2
ID, IC (A)
1E-3
x100 difference
TFS IGBT
1E-4
1E-5
x10 difference
1E-6
1E-7
0
200
400
600
800
1000
1200
VDS, VCE (V)
Copyright © 2007, Cree, Inc.
pg. 24
4. Gate charge and gate energy comparison
Copyright © 2007, Cree, Inc.
pg. 25
5. Qg*RDS(on) Figure of Merit Comparison
Copyright © 2007, Cree, Inc.
pg. 26
Benefits Summary:
1. Lower RDSon :




2.
Lower Switching Losses:



3.
Lower ON state or conduction losses
Significantly lower loss over temperature
Higher efficiency and cooler running systems
Increased reliability
Allows significantly higher switching frequencies with
equivalent or higher efficiency
Significant reduction in size, weight and cost of system
magnetic and EMI filter components
Significant power density and system size advantage
Lower Leakage Currents:

Increased system reliability particularly at higher
temperatures
Copyright © 2007, Cree, Inc.
pg. 27
Application Examples:
1. Solar Inverter
7kW 750V DC link 3Phase solar inverter
(Fraunhofer Institute, Freiberg
Germany)
Copyright © 2007, Cree, Inc.
pg. 28
Application Examples:
~ 2% Efficiency
Improvement (2008)
CMF20120D
Announced (1/16/2009)
record efficiency (99.05 %)
Key factor = SiC
 The original system configuration had a 1200V module containing Si IGBTs
 Note the dramatic improvement in efficiency when replaced with our SiC MOSFETs
 This is an industry where even a 0.1% increase in efficiency is a big improvement.
SiC MOSFETs have a big future in the fast expanding solar industry!
Copyright © 2007, Cree, Inc.
pg. 29
Application Examples:
ABB Drive
2. Industrial Motor Drive
1200V SiC MOSFETs
 The test unit was an ABB ACS50, 230V 2.2kW AC motor drive
 3- phase output (6 switch inverter), PWM = 16kHz, using Si IGBT co-packs
 Tests were run as standard out of box drive and then the unit’s IGBTs
were replaced with our SiC MOSFETs and retested
 For these test the only modification to the gate drive was a reduction in
gate resistance
Copyright © 2007, Cree, Inc.
pg. 30
Application Examples:
Load vs Efficiency
97
SiC MOSFET
Inverter Efficiency (%)
96.5
96
2.3% Improvement
1.9% Improvement
2.0% Improvement
95.5
95
Si IGBT
94.5
Motor Speed = 1500RPM
94
0.5
1
1.5
2
2.5
3
3.5
Motor Load (HP)
 Note the dramatic improvement in efficiency through the whole load range
 At 1HP a 2.3% improvement in efficiency equates to a 40% reduction in overall
losses
 The drive could now triple its switching frequency (16kHz to 48kHz) and still be
slightly more efficient than the standard off the shelf unit
 This means the system magnetic components and EMI filter can effectively be
reduced in size, weight and cost by 1/3
Copyright © 2007, Cree, Inc.
pg. 31
Application Examples:
Load vs Heatsink Temp
Temperature, Heatsink - Ambient
(Degree C)
45
Motor Speed = 1500RPM
40
35
Si IGBT
30
51.6% Reduction
25
55.8% Reduction
20
53.8% Reduction
15
SiC MOSFET
10
5
0
0.5
1
1.5
2
2.5
3
3.5
Motor Load (HP)
 Note the greater than 50% reduction in heatsink temperature throughout the full
load range
 This means much reduced cooling requirements (heatsink and fan sizing) and
significant increase in reliability
 Also shows the possibility of increasing the power output of the drive
significantly in the same physical package i.e potential for significant power density
improvement
Copyright © 2007, Cree, Inc.
pg. 32
SiC Shottky Diode
Copyright © 2007, Cree, Inc.
pg. 33
Z-RecTM Rectifier Features
• Essentially zero forward and reverse recovery
– reduced switch and diode switching losses
• Temperature independent switching behavior
– stable high temperature performance
• Usable 175oC Junction Temperature
– safely operate at higher temperatures
• Positive temperature coefficient of VF
– ease of parallel operation
Copyright © 2009, Cree, Inc.
SiC schottky diodes in PFC circuits
SiC Significantly Reduced Losses
• Improved System Efficiency
10
– Lower Switching Losses
8
• Reduced System Size
• Lower System Cost
• Reduced EMI signature
4
I Current (A)
– Fewer / smaller components
Switched Mode Power Supply
AC/DC
Rectifier
DC/DC
System
Powerand
Eliminate
Snubbers
Converter
PFC
SiC Switching
Waveform –
Steady over Temp
6
2
CSD10060
T J = 25, 50, 100, 150°C 0
600V, 10A Si FRED
TJ = 25°C
TJ = 50°C
TJ = 100°C
TJ = 150°C
-2
-4
-6
Wasted
Energy!
-8
Improve Efficiency
-1.0E-07
-5.0E-08
-10
0.0E+00
5.0E-08
1.0E-07
Replaced an 8 Amp “Hyper-fast” Si Diode and 10 snubber components with one
Time (s)
4 Amp SiC Schottky Diode
Simplified PFC Circuit
Without SiC
Copyright © 2007, Cree, Inc.
Efficiency Increase of 3% to 7% *
pg. 35
* Depending on load and input voltage
SiC
Diode
With SiC
1.5E-07
2.0E-07
SiC schottky diodes in PFC circuits
500W PFC Example
90VAC Input Efficiency Measurements
100.0%
97.0%
94.0%
SiC
91.0%
Si
88.0%
85.0%
50W
150W
250W
350W
450W
One Single Component Change Achieves
2% Efficiency Improvement
That Equals a 24% Reduction In Loss
Copyright © 2007, Cree, Inc.
pg. 36
SiC schottky diodes in PFC circuits
Low Frequency Silicon vs. High Frequency Silicon Carbide
Comparisons
PCB Area
Volume
Weight
Density
80kHz
200kHz
23.9 in2
154.1 cm2
47.8 in3
782.8 cm3
18.4 oz.
521.6 gm
10.5 W/ in3
0.64 W/ cm3
14.8 in2
95.5 cm2
29.6 in3
485.1 cm3
10.4 oz
294.8 gm
16.9 W/ in3
1.03 W/cm3
Delta
-38%
-38%
-44%
+61%
90VAC Input Efficiency Measurements
100.0%
97.0%
94.0%
91.0%
80kHz Si
200kHz SiC
88.0%
85.0%
50W
150W
250W
350W
450W
Performance Improvements can be used to Increase
Switching Frequency and keep the Efficiency High
Copyright © 2007, Cree, Inc.
pg. 37
SiC schottky diodes in inverter circuits
 An inverter is an electrical circuit that converts electrical power from DC
to AC by means of switches called IGBTs and free wheeling diodes.
Target Inverter Applications:
• Solar inverters - convert solar panel voltage to a usable AC source.
• Motor drives - convert a DC link voltage to a variable voltage / frequency AC
source to control speed and torque.
• UPS systems - convert a DC battery source to a usable AC line source to
backup system operation when utility power is lost.
Copyright © 2007, Cree, Inc.
pg. 38
SiC schottky diodes in inverter circuits
SiC diode benefits in an Inverter
T1
D1
1. T1 OFF, T2 OFF
(Dead-time)
D2 conducting (Blue)
2. T1 ON, T2 OFF (Red)
D2 turns OFF
T2
D2
D2 Reverse recovery flows
through T1 and D2 (Green)
SiC diodes eliminate recovery current (green line)
Copyright © 2007, Cree, Inc.
pg. 39
SiC schottky diodes in inverter circuits
Si-SiC comparison:
Diode turn-OFF
Vdiode 100V/div
Idiode 5A/div
Diode voltage
Idiode 5A/div
Vdiode 100V/div
Diode current
Diode voltage
Diode current
Trr = 141ns
Recovery time
Trr = 29ns
Recovery time
Standard Si PiN
Cree SiC Schottky
@ 150ºC
@ 150ºC
Copyright © 2007, Cree, Inc.
pg. 40
SiC schottky diodes in inverter circuits
Silicon waveform
SiC waveform
IGBT current
IGBT voltage
Diode
current
Area under curve
equates to IGBT
turn-ON loss
Capacitive
current
Diode Recovery
Current
57% reduction
in turn ON loss
 Note the much larger recovery current in the Si device.
 Note also the effect this recovery current has on the IGBT turn-ON
current overshoot.
Copyright © 2007, Cree, Inc.
pg. 41
SiC schottky diodes in inverter circuits
Summary in 2.4kW system at 16kHz
Parameter
Units
Unit w/Si diode
Rg = 39
Unit w/SiC diode
Rg = 22
IGBT Switching Loss
Watts
12.67
6.23 (-51%)
Diode Switching Loss
Watts
1.36
0.01 (-99%)
Overall Inverter Loss
Watts
121.2
100 (-17%)
Inverter efficiency improved by 0.8%
Equates to a 17.5% reduction in inverter losses
Copyright © 2007, Cree, Inc.
pg. 42
SiC schottky diodes in inverter circuits
EMI Comparison
 Radiated EMI plot from 30MHz to 1GHz.
 Shows the contribution of diode reverse recovery on the EMI spectrum in
these systems. EMI can be a critical challenge during qualification
 Similar reductions achieved in the conducted EMI spectrum (150kHz to
30MHz).
Copyright © 2007, Cree, Inc.
pg. 43
First Commercial 1700V SiC Devices
Copyright © 2010, Cree, Inc.
pg. 44
1700V SiC Devices Go Beyond Si Capability
• Enables up to 10X switching frequency increase vs. silicon!
• Provides design flexibility, performance optimization and higher reliability
L1
Test Circuit
847 uH
D3
DIODE UNDER
TEST
T2
1.2 kV
C1
42.3 uF
GATE DRIVE
INPUT
T1
VCC
DIODE
CURRENT
SENSE
SWITCH
CURRENT
SENSE
99%
Lower Qrr
GATE DRIVER
+
-
10
Z1
IXGX32N170AH1
VEE
Test Conditions:
Test Conditions:
•
•
•
•
•
•
VR = 1.2 kV
IF = 25 A,
di/dt = 400 A/µsec
Copyright © 2010, Cree, Inc.
VR = 1.2 kV
IF = 25 A
di/dt = 800 A/µsec
pg. 45
SiC Schottky Diode Products
• The Z-RecTM Rectifier Product Family
− 600V Z-Rec Diodes
• 1A, 2A, 3A, 4A, 6A, 8A, 10A & 20A
− 650V Z-Rec Diodes
• 4A, 6A, 8A, 10A
− 1200V Z-Rec Diodes
• 5A, 10A, 20A & 50A
− 1700V Schottky Diodes
− 10A & 25A (Die only)
• Packages
– Thru Hole
• TO-220, Fully Molded TO-220, TO-247
– Surface Mount
• TO-252 (D-Pak), TO-263 (D2-Pak)
Copyright © 2010, Cree, Inc.
pg. 46
Summary – SiC Shottky Diode:
 By replacing Si PiNs with SiC Schottkys there will be an instant
increase in system efficiency.
 In addition to lower losses in the diode itself, SiC Schottkys
reduce IGBT and MOSFET junction temperatures by reducing their
turn ON losses. This leads to increased system reliability and
reduced cooling requirements.
 SiC Schottkys permit the designer to increase the system
switching frequency thereby increasing system power density and
reducing filter and boost magnetics size.
 By eliminating diode recovery current “snap” in any power
conversion system, both conducted and radiated EMI levels will be
reduced.
Copyright © 2007, Cree, Inc.
pg. 47
Summary – SiC MOSFET:
1.
SiC MOSFETs have a much lower forward voltage drop, particularly as
temperature increases leading to much lower conduction losses
2.
SiC MOSFETs have industry leading switching losses
3.
SiC MOSFETs have much lower leakage currents leading to increased
reliability
4.
All the above benefits mean significant system efficiency improvements,
cooler system operation and more reliable systems
5.
SiC MOSFETs open the door for much higher system frequencies with
industry leading efficiencies for the future
Copyright © 2007, Cree, Inc.
pg. 48
Thanks for your time
Copyright © 2007, Cree, Inc.
pg. 49