1

Wide Bandgap Semiconductors

Burak Ozpineci

Oak Ridge National Laboratory

2

Why not Si?

Today ⇒ All Si-based power semiconductor switches

• Limited breakdown voltages and limited power ratings• Limited operation temperature (<150°C)• Limited switching frequency (≤ 20kHz) for power levels

of more than a few tens of kW

∴ The current Si technology is approaching the material’s theoretical limits, and it cannot meet all the requirements of the transportation industry

3

Why Wide Bandgap Semiconductors

• Advantages– Wide bandgap semiconductor based power

devices,• Operate at higher temperatures, 600 °C (SiC) reported

compared to 150°C of Si ⇒ less cooling requirement; saves space and weight; no heatsink? (1/3 the converter size)

– They have a higher electric breakdown field; much higher doping levels can be achieved; therefore they are

• Thinner ⇒ occupy less space• Low on resistance (~a few hundred times less)

⇒ lower conduction losses, and higher efficiency• Higher breakdown voltages (no need to connect devices in

series)

4

Why Wide Bandgap Semiconductors (cont’d)

– They have higher thermal conductivities ⇒ lower thermal resistance; the device dissipates heat to the surrounding faster

– Forward and reverse electrical characteristics vary only slightly with temperature and time ⇒ reliable

– Excellent reverse recovery characteristics ⇒ less EMI; less snubbing required; lower switching losses; higher efficiency

◊ High temp operation capability and lower switching losses ⇒ high frequency operation (more than 20 kHz at > 1 MW) ⇒ less filtering; smaller passive components; saves space

∴ WBG semiconductor-based converters are compact, light, reliable, efficient, and have a high power density

5

Physical Characteristics

2.72.22211Saturated Electron Drift Velocity, vsat (×107 cm/s)

221.34.94.90.461.5Thermal Conductivity, λ(W/cm⋅K)

850850115101400600Hole Mobility, µp (cm2/V⋅s)

220012501000 5008085001500Electron Mobility, µn

(cm2/V⋅s)

10000200022002500400300Electric Breakdown Field, Ec(kV/cm)

5.5910.19.6613.111.9Dielectric constant, εr1

5.453.453.263.031.431.12Bandgap, Eg (eV)

DiamondGaN4H-SiC6H-SiCGaAsSiProperty

6

Figures of Merit

1426711560.5458.1748.91.41.0BTFM

59410.735.457.30.91.0BPFM

53044591973.63424.81470.540.71.0FTFM

147630.456.048.33.61.0FPFM

240252.512.913.11.61.0BSFM

359565.061.230.511.41.0FSFM

25106186.7223.1125.314.81.0BFM81000215.1215.1277.81.81.0JFM

DiamondGaN4H-SiC6H-SiCGaAsSi

7

Breakdown Voltage

d

crB qN

EV2

2ε≈

where

q is the charge of an electron andNd is the doping density

8

Drift RegionWidth Resistance

( )c

BB E

VVW 2≈ ( )

ncs

Bspon E

VR

µε 3

2

, )(

4=

To calculate the device on resistance, contact resistance and channel resistance are also required.

9

SiC

• Most mature technology among WBG semiconductors

• SiC Schottky diodes are commercially available

• Many companies and universities all over the world are working on SiC power devices: 4H-SiC and 6H-SiC PiN diodes, Schottky diodes, IGBTs, thyristors, BJTs, various MOSFETs, GTOs, MCTs, MTOs, etc. in kV range with reduced on-resistances.

10

SiC Availability

• As of today, only four companies have advertised the commercial availability of SiC power devices:• Infineon (Schottky diodes, 600V up to 12A or

300V up to 10A)• Microsemi (Schottky diodes, 200/400/600V,

1A/4A)• Cree (Schottky diodes, 600V up to 20A)• IXYS (H-bridge Schottky diodes, 600V 3A/5A)

– Experimental controlled SiC VJFET cascodeswitches (4A max) can be obtained from SiCED of Germany.

11

GaN

• GaN device applications focus on optoelectronics and radio frequency uses

• Some experimental GaN Schottky diodes available

• Better reverse recovery compared with SiC; lower switching losses

• Higher forward voltage drop compared with SiC because of wider bandgap; higher conduction losses (diodes)

12

GaN compared with SiC

Malay Trivedi and Krishna Shenai, J. Appl. Phys., Vol. 85, No. 9, 1 May 1999

13

GaN compared with SiC (cont’d)

• GaN does not have a native oxide (for MOS devices); SiC uses the same oxide as Si, SiO2.

• GaN boules cannot be grown; instead GaN is grown on sapphire or SiC.

• Thick GaN substrates are not commercially available; GaN wafers are more expensive.

• GaN thermal conductivity is one-fourth of that of SiC

14

Diamond

• Best theoretical performance.• Its processing problems have not been

solved yet.• Processing is more difficult than the

other WBG materials• In the literature, diamond is used in

only sensors and field emission devices.

15

Conclusions• WBG materials have the promise to surpass Si in

the near future.• Diamond is the ultimate material for the power

devices in utility applications. Diamond power devices are expected to be abundant in 20-50 years.

• GaN and SiC power devices have similar performance improvements compared to Si power devices; however, they both have processing issues.

• SiC power devices are at a more advanced stage than GaN power devices.

• SiC is the best suitable transition material for future power devices.

16

System Impact of Silicon Carbide Power Electronics on Hybrid Electric Vehicle

Applications

Burak Özpineci

Electrical and Computer Engineering DepartmentThe University of Tennessee, Knoxville

17

Outline

SiC MATERIALDEVICESSYSTEMS

CONCLUSIONS

18

Transportation Requirements

• Compactness• Lightweight• High power density• High efficiency• High reliability under harsh conditions• Low cost

19

SiC compared with Si (cont’d)

• Disadvantages– Low processing yield – micropipes (<1/cm2)– Expensive - $7 for 600 V, 4 A SiC Schottky diode

(similar Si pn diode << $1)– Limited availability – High temperature packaging techniques not yet

developed– Compatible passive components and gate drivers do

not exist

20

SiC vs. Si diode I-V characteristics

0.6 0.8 1 1.2 1.4 1.6 1.70

1

2

3

4

5

6

7

Diode Forward Voltage, V

Dio

de F

orw

ard

Cur

rent

, A

Si SiC

0.5

Arrows point at the increasingtemperature 27-250C

R

DUTVdc

IF

+

VF

-

IDUT

CurrentProbe

oven

• Forward voltage drop of Si diode is smaller than that of the SiC diode at the same forward current.

• I-V characteristics of the SiC diodes do not vary much with temperature

21

SiC vs. Si diode I-V characteristics (cont’d)

• Find the diode parameters IS , RS , and n using the genetic algorithm (GA) curve fitting method

• Use the piece wise linear (PWL) approximate model of a diode and find the PWL parameters, RD and VD using GA curve fitting method

( )

−=

− 1nkTIRVqs

seII

A

K

VD

RD

+

vF

-

iF

vF

iF

1

RD

VD

22

SiC vs. Si diode PWL Model

0 50 100 150 200 2500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Toven, °C

V D, V

SiC

Si

• RD and VD expressed as functions of temperature

7042.02785.0 0046.0 += − TSiCD eV

2023.01108.0 0072.0 +−= − TSiCD eR

5724.03306.0 0103.0 += − TSiD eV

0 50 100 150 200 2500

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Toven, °C

RD, Ω

SiC

Si

0529.02136.0 0293.0 += − TSiD eR

• VD of the Si diode is smaller than that of the SiC diode at any temperature.

• Si : RD decreases • SiC: RD increases with temperature

23

SiC vs. Si diode conduction lossesDrmsDDavDcond RIVIP ⋅+⋅= 2

,,Diode conduction loss expression

DDCDDCcond RIVIP ⋅+⋅= 2For dc operation, ID,av=ID,rms=IDC

•For low temperatures the conduction loss of the SiC diode is less than that of the Si diode and vice versa for higher temperatures.

–Note that Si diode cannot withstand Tj > 150 °C

0 1 2 3 4 5 6 7 8 9 100

0.25

0.5

0.75

1

1.25

1.5

Dio

de C

ondu

ctio

n Lo

ss, W

Diode Forward Current, A

Si

25°C

225°C

0 1 2 3 4 5 6 7 8 9 100

0.255

0.5

0.75

1

1.25

1.5

Dio

de C

ondu

ctio

n Lo

ss, W

Diode Forward Current, A

SiC

25°C

225°C

0 1 2 3 4 5 6 7 8 9 10 0

0.25

0.5

0.75

1

1.25

1.5

Dio

de C

ondu

ctio

n Lo

ss, W

Diode Forward Current, A

Si

SiC25°C

225°C

25°C

225°CDirection of temperature

increase

24

SiC vs. Si diode switching losses

Derivation of the switching losses

∫=b

cddrr dtivE

ab

-dIF/dt trrta tbc

IR

-VRVRM

IF

0

0

Turn-onloss

Turn-offloss

Reverse recoveryloss

c-a region a-b region

( )

2

1

bRR

b

a bRR

tIV

dtt

atIV

=

−+−⋅⋅−= ∫

2bRR

srrtIVfP =

a

b

ttS ≡

2

12

+

=

SSt

dtdI

SVfP rrFR

srr

25

SiC vs. Si diode switching losses

R1

L1

D=DUTVdc

iDUT=id

CurrentProbe id

+vd-

Q

iL

oven

+

vQ

- iQ

1kHz25% duty

SiC Schottky diode

Si pn diode

Typical reverse recovery waveforms of the Si pn and SiC Schottky diodes

Reverse recovery loss measurement circuit

26

SiC vs. Si diode switching losses (cont’d)

1 1.5 2 2.5 3 3.5 4 4.50

1

2

3

4

5

6Pe

ak R

ever

se R

ecov

ery

Cur

rent

, A

Peak Forward Current, A

Si

SiC

27°C

61°C

107°C

151°C

27, 61, 107, 151, 200, 250°C

1 1.5 2 2.5 3 3.5 4 4.50

0.25

0.5

0.75

1

1.25

1.5

1.75

2

2.25

2.5

Peak Forward Current, A

Dio

de S

witc

hing

Los

s, W

Si

151°C

61°C

107°C

27°C

27, 61, 107, 151, 200, 250°C

SiC

• Switching characteristics of the SiC diode do not change much with temperature

• Maximum operating conditions– Si diode: 150°C and 4.5 A– SiC diode: 250°C and 4 A ⇔ (datasheet: 175 °C )

27

SiC vs. Si diode switching losses (cont’d)

• Modeling

SiC Schottky

Si pn diode

∫=b

cddsrr dtivfP

∫=b

adRsrr dtiVfP

diode

Calculated experimentally

• The integral above varies linearly with the forward current

βα +⋅=∫ F

b

ad Idti

31.2138 105.2105.3 T⋅×+×= −−α53.3158 103.21025.1 T⋅×+×= −−β

SiC: α=2.167×10-8

β=2.33×10-8

— Assume 20 of 10A diodes in parallel. This means 20 times the losses

+⋅⋅⋅= βα

2020200 F

RsA

rrIVfP

α-β model

• For 200A diode

Si:

28

SiC vs. Si MOSFET conduction lossesonDSrmsQQcond RIP ,

2,, ⋅=MOSFET conduction loss expression

• At 300°K for a 1 cm2 device Ron,sp = 0.18Ω for Si andRon,sp = 0.61x10-3 Ω for 6H-SiCRon,sp = 0.305x10-3 Ω for 4H-SiC (calculated)

α

=

300300

,,TRR K

sponT

spon

300 320 340 360 380 400 420 440 460 480 500

0.01

1

RD

S-on

, Ω

300 320 340 360 380 400 420 440 460 480 5000.01

1

10

P con

d,Q

1, W

Temperature, K

0.0001

Si

SiC

Si

SiC

423

29

SiC vs. Si MOSFET switching losses• The switching losses are mostly during the charging and

discharging of two device capacitances: drain-to-source and drain-to-gate

Drain

( )

++

−=

+⋅=

⋅=

11

11

31

21

21

1

KKBVVVEf

EEf

Efp

csc

offonc

totcQ

ε

Source

Gate Cds

Cdg

Cgs

Drain-to-sourcecapacitance

Gate-to-sourcecapacitance

Drain-to-gatecapacitance

( )J

VVgK thGHm −=1

( )J

VVgK GLthm −=2

30

1. DC-DC POWER SUPPLY

2. ELECTRIC TRACTION DRIVE

31

Dc-dc Power Supply

Q1

Q4

Q2

Q3

D1

D2

ab N1

N2

N2

vo1

v1

Vdc /2

Vdc /2

Id

Io

IL+

-

+-

+ -vL+

-voC

Input Voltage: 300 - 450VOutput voltage: 42V (regulated)

Output Power: 2 - 5kW

voi

v1

iL

Vo

Io

Pout (kW) Vdc (V) VMOSFET (V) IMOSFET (A) VDIODE (V) IDIODE (A)2 300 300 6.67 84 472 450 450 4.44 84 475 300 300 16.67 84 1195 450 450 11.11 84 119

Isolated full-bridge dc-dc converter

32

Device losses• MOSFET conduction loss

d is the duty ratio

• MOSFET switching loss – same as the loss of a single MOSFET given earlier

• Diode conduction loss

• Diode switching loss – same as the loss of a single diode (α-β model )given earlier with VR = 84V

( )onDSQ

onDSQonDSrmsQcond

RId

RIdRIP

,2

,

2

,2

)(

⋅⋅=

⋅⋅==

( )( )DDDD

DDDDDrmsDDavDcond

RIVId

RIdVIdRIVIP

⋅+⋅=

⋅⋅+⋅⋅=⋅+⋅=2

22,,

33

SIMULINK model of the dc-dc converter

.5

d

TjQ

TjD

Ptotal D4

TATj

Thermal Model w/ Heatsink1

Ptotal Q1

TATj

Thermal Model w/ Heatsink

I PswQ1

Q1 switching

Tj

I

d

PcondQ1

Q1 conduction

Ptotal

PQ1

PD4

7 N1/N2

16.67

IMOSFET

6

Gain

I

TjPswD4

D4 switching

Tj

I

d

PcondD4

D4 conduction

TA

Constant7273

Constant6

273

Constant5

TA

Constant4

150

Constant3

150

Constant2

w/

34

Simulation results of the dc-dc converter

412347

549

41

1197

775

626

205

0

200

400

600

800

1000

1200

1400

1 2

Si 20kHzSiC 20kHzSi 100kHzSiC 100kHz

Diodes MOSFETs

Heatsink Volume

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

50

100

Con

duct

ion

loss

, W

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

10

20

Switc

hing

lo

ss, W

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

50

100

Tota

l lo

ss, W

SiC

Si

SiC

Si

Si

SiC

Time, s

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

50

100

Con

duct

ion

loss

, W

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

20406080

Switc

hing

lo

ss, W

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

50

100

150

Tota

l lo

ss, W

SiC

SiC

SiC

Si

Si

Si

Time, s

Diode losses

412 549775 626

347 41

1197

205

0

500

1000

1500

2000

2500

1 2 3 4

20kHz 100kHz

35

Passive Components• High frequency transformer

– SiC power devices can be operated at higher switching frequencies.

– As the switching frequency increases, the size of the high frequency transformer decreases, because

– fc⋅N ⋅A needs to stay constant to keep the maximum flux density without saturation.

– If the switching frequency is increased from 20kHz to 100kHz, then N ⋅A has to be decreased five times.

∴ The size of the high frequency transformer is inversely proportional to the switching frequency

NAfVB

c

14max ⋅=

36

Passive Components (cont’d)

• Output filter capacitor

– For a constant dc , C ∝ A.– C is inversely proportional to the

switching frequency∴ The size of the filter capacitor is

inversely proportional to the switching frequency

• Output filter inductor– The same reasoning as the high

frequency transformer with

C

L

Vin(jω) Vout(jω)

0 50 100 150 200 250 300 0

50

100

150

200

250

300

350

400

fc, kHz L

( µH

) and

C ( µ

F)

L

C

cdAC ε=

NALIB max

max =

37

Electric Vehicle Traction Drive

Q1

Q4

Q3

Q6

Q5

Q2

D1

D4

D3

D6

D5

D2

Vdc /2

AC MOTOR

Vdc /2a

bco

PHASE LEG A

ibia

ic

Federal Urban Driving Schedule

• The electric traction drive system is analyzed for system level benefits such as reduction in size and volume, increase in efficiency, etc.

Spee

d, m

ph

60

00 1369Time, s

38

Why average modeling?• Because of the huge difference between the required sampling times

of the simulation components.

FUDS Cyclesampled at 1Hz

(1 s)

0s 1369s

InductionMachine

Three-PhaseInverter

Electric Traction Drivefo=0-200 Hz

SiC Power devicesfc>20kHz

(switching period<50 µs)

Battery

ADVISOR

ωr, Te I, M

– Vehicle simulation~seconds

– Three phase inverter simulation with switching frequency of 20kHz

~microseconds– Device loss simulation included

~nanoseconds

• For device loss simulation, – without average modeling ~109 simulation points per second of

simulation is required.– with average modeling 2×104 simulation points per second of

simulation is required (for 20kHz switching). ~50000 times less points

39

Verification of average modeling

0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9-

0

200

i a, i b

,and

i c (

A)

0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9-50

0

50

T e (N

.m)

0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9200

250

300

Time, s

ωr (

rad/

s)

1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 1.16 1.18 1.2

-

0

200

i a, i b

,and

i c (

A)

1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 1.16 1.18 1.2

0

100

200

T e (N

.m)

1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 1.16 1.18 1.2200

250

300

Time, s

?r (

rad/

s)

2*pi*40we

vco*

vbo*

vao*

300/2

Vdc/2

TorqueLoad

Scope

vref

vao*

vbo*

vco*

vao

vbo

vco

Inverter

vao

vbo

vco

Tl

we

ia

ib

ic

Te

wr

InductionMachine Model

vao

vbo

vco

Tl

we

ia

ib

ic

Te

wr

InductionMachineModel

vref1k

40

Average device loss modelingMOSFET Losses

•Conduction Losses

Dn = duty ratio in the nth intervalio,n = average output current in the nth interval

I = peak output current

φ = phase angle of the current

onDSrmsQQcond RIP ,2

,11, ⋅=

∑=−

=

1

0

2,,1

1 N

nnnormsQ Di

NI

co

oc

TT

ffN ==

−= φθnInoi sin,

If N >> 1, then

Thus,

D

+= nMn θsin121

φπ

φππ

φπ

φθθφθπ

cos31

81

cos34

241

sin12sin221

,1

MI

MI

dMII rmsQ

+=

+=

∫+

+−⋅

≅

+⋅⋅= φπ cos3

1812

,1, MRIP onDSQcond

41

Average device loss modeling (cont’d)

Averaging over the outputperiod, To,

MOSFET Losses (cont’d)

•Switching Losses

Energy loss during switching

Q1 switching loss in one Tcperiod is

( ) ( )

++

−=

++

−=

+=

JG

J

JG

JH

BV

VVcEs

KBV

VVcEs

K

offEonEtotE

21

21

2

21

1 13

1

13

1εε

totEcfcToffEonE

pQ =+

=1

( )

−

−+−−

+

−

−+−

≅

∫+

≅∑=

=

222

22

2

221

221

1

1,

'

'1tan22'

'

'1tan2'2

2

1

1

1

JG

J

JG

G

JG

J

JG

GcHf

dtotEcfN

nntotEcf

NP Qsw

π

ππ

φπ

φθ

π

21

31

=

BVVVEfH csc ε

( )thGHm VVgG −=1 ( )GLthm VVgG −=2

42

Average device loss modeling (cont’d)

Thus,

Diode Losses

•Conduction Losses

The diode conducts when the MOSFET is not conducting; therefore, the duty ratio of the diode is

And,

DrmsDDavDDcond RIVIP ⋅+⋅= 2,4,44,

−=− nMnD θsin1211

φπ cos31

81

,4 MII rmsD −=

−=

∫+

−−≅

∑ −=−

=

8cos

21

sin121sin2

1

1,1 1

0,4

φπ

φπ

φθθφθπ

MI

dMI

nDnoiNIN

navD

−⋅⋅+−⋅⋅= φπφπ cos8

121cos3

181

4,2 MVIMRI

DcondP DD

•Switching Losses

−Use the α-β model

43

Algorithm to find I, M, and φ1. Get Te and we profiles from ADVISOR

2. Machine input power, 3. Output frequency, 4. V/Hz constant,

5. where fb is the base frequency

6.7.8.

ηωrein

TP ⋅=

πω22

ropf ⋅=

bf

dcV

vK

24

2

3

π=

voL KfV ⋅=

LII 2=

L

inL V

PI3

cos =⋅ φ

mL II =⋅ φsin

( ) ( )

2

2

22

3

sincos

mL

in

LLL

IV

P

III

+

⋅=

⋅+⋅= φφ

9. Peak line current

10.

11. Modulation index L

L

II φφ coscos 1−=

b

o

bv

ov

dc

L

ff

fKfK

VVM =

⋅⋅

==

24

23

π

44

SIMULINK model of the traction drive

TjQ

TjD

Ptotal D4

TATj

Thermal Model w/ Heatsink1

Ptotal Q1

TATj

Thermal Model w/ Heatsink

I PswQ1

Q1 switching

TjIphiM

PcondQ1

Q1 conduction

Ptotal

PQ1

PD4

Te

wr

I

M

phi

I, M, & φ

6

Gain

[t wr]

[t Te]

I PswD4

D4 switching

TjIphiM

PcondD4

D4 conduction

TA

Constant7 273

Constant6

273

Constant5

TA

Constant4

175

Constant3

175

Constant2w/

45

Si vs. SiC - Device Losses for HEV

• SiC diode losses are lower mostly because it has lower reverse recovery losses

• SiC MOSFET losses are lowerbecause– Switching losses are similar– SiC MOSFET conduction losses

are lower (Ron,sp (Si)=180×10−3 Ω-cm2

Ron,sp (SiC)=0.3×10−3 Ω-cm2)

0 200 400 600 800 1000 12000

20

40

60

Dio

de lo

sses

, W

0 200 400 600 800 1000 12000

200

400

600

Time, s

MO

SFET

loss

es, W

Si

SiC

Si

SiC

1369

1369

46

Si vs. SiC - Efficiency

• Energy loss in inverter for FUDS cycle:– Si: 925 W⋅sec – SiC: 338 W⋅sec

• Efficiency:– Si: 80 – 85%– SiC: 90 – 95%

0 200 400 600 800 1000 12000

2000

4000

Tota

l inv

erte

rlo

sses

, W

0 200 400 600 800 1000 12000

50

100

Effic

ienc

y (S

i)

0 200 400 600 800 1000 12000

50

100

Effic

ienc

y (S

iC)

Time, s

SiCSi

Si

SiC

1369

1369

1369

47

Si vs. SiC - Heatsink Requirements

• If natural air cooled heatsinks are used, then – Si inverter needs a heatsink

with a volume of 1998 cm3

and a weight of 5.4 kg.

– Si inverter needs a heatsink with only a volume of 606 cm3

and weight of 1.65 kg.

1200450

4200

1200

5400

1650

0

1000

2000

3000

4000

5000

6000

Diodes MOSFETs Inverter

Heatsink Mass (g)

SiSiC

0 200 400 600 800 1000 12000

50

100

150

200

Dio

de J

unct

ion

Tem

pera

ture

, °C

0 200 400 600 800 1000 12000

50

100

150

200

MO

SFET

Jun

ctio

nTe

mpe

ratu

re, °

C

150 C

175 C

150 C

175 C

Si

SiC

Si

SiC

1369

1369Time, s

48

Conclusions

• SiC devices are in their infancy but they are already surpassing the mature Si device technology

• By replacing Si power devices with their SiC counterparts– power converter losses are decreased– the efficiency of the inverter is increased– less cooling is required– the volume and weight of the converter are decreased– higher switching frequencies can be used; consequently,

the volume and weight of the passive device decrease• The averaging model of an inverter is

– similar to a ‘moving average filter’– a good approximation, which can be used to shorten the

long simulation time.

49

Current and Future Projects

• High frequency gate drivers for SiC switches (JFET) operating at high temperatures (Madhu)

• A 55kW Si-SiC hybrid AIPM/inverter (Cree-Semikron)

• A 7.5kW all-SiC inverter (Rockwell)• High temperature packaging forSiC power devices