278 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 45, NO. 1, JANUARY/FEBRUARY 2009

A 55-kW Three-Phase Inverter With Si IGBTs andSiC Schottky Diodes

Burak Ozpineci, Senior Member, IEEE, Madhu Sudhan Chinthavali, Leon M. Tolbert, Senior Member, IEEE,Avinash S. Kashyap, Student Member, IEEE, and H. Alan Mantooth, Senior Member, IEEE

Abstract—Silicon carbide (SiC) power devices are expected tohave an impact on power converter efficiency, weight, volume, andreliability. Currently, only SiC Schottky diodes are commerciallyavailable at relatively low current ratings. Oak Ridge NationalLaboratory has collaborated with Cree and Semikron to builda Si insulated-gate bipolar transistor–SiC Schottky diode hybrid55-kW inverter by replacing the Si p-n diodes in Semikron’sautomotive inverter with Cree’s made-to-order higher current SiCSchottky diodes. This paper presents the developed models ofthese diodes for circuit simulators, shows inverter test results, andcompares the results with those of a similar all-Si inverter.

Index Terms—DC–AC conversion, hybrid electric vehicle,insulated-gate bipolar transistors (IGBTs), inverter, Schottkydiode, silicon carbide (SiC).

I. INTRODUCTION

THERE IS a growing demand for more efficient, higherpower density, and higher temperature operation of thepower converters in transportation applications. In spite of theadvanced technology, silicon (Si) power devices cannot meetsome transportation requirements. Silicon carbide (SiC) hasbeen identified as a material with the potential to replace Sidevices in the near term because of its superior material ad-vantages, such as wider bandgap, higher thermal conductivity,and higher critical breakdown field strength. SiC devices arecapable of operating at high voltages, high frequencies, andat higher junction temperatures. Significant reduction in theweight and size of SiC power converters with an increase inthe efficiency is projected [1]–[5]. SiC unipolar devices, suchas Schottky diodes, vertical-junction field-effect transistors,MOSFETs, etc., have much higher breakdown voltages com-pared with their Si counterparts, which makes them suitable for

Paper IPCSD-08-002, presented at the 2006 IEEE Applied Power ElectronicsConference and Exposition, Dallas, TX, March 19–23, and approved forpublication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS bythe Power and Electronics Devices and Components Committee of the IEEEIndustry Applications Society. Manuscript submitted for review November 3,2006 and released for publication April 9, 2008. Current version publishedJanuary 21, 2009.

B. Ozpineci and M. S. Chinthavali are with the Power Electronics and Elec-tric Machinery Research Center, Oak Ridge National Laboratory, Oak Ridge,TN 37831-6472 USA (e-mail: ozpinecib@ornl.gov; chinthavalim@ornl.gov).

L. M. Tolbert is with the Oak Ridge National Laboratory, Oak Ridge, TN37831-6472 USA, and also with The University of Tennessee, Knoxville, TN37996-2100 USA (e-mail: tolbert@utk.edu).

A. S. Kashyap and H. A. Mantooth are with the Department of ElectricalEngineering, University of Arkansas, Fayetteville, AR 72701 USA (e-mail:akashya@uark.edu; mantooth@uark.edu).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIA.2008.2009501

use in traction drives replacing Si p-n diodes and insulated-gatebipolar transistors (IGBTs) [6]–[14].

Presently, SiC Schottky diodes are the most mature andthe only commercially marketed SiC devices available. Thesediodes are commercially available up to 1200 V/50 A or600 V/20 A.

SiC Schottky diodes have been proven to have better perfor-mance characteristics when compared with their equivalent Sip-n diodes [1], [15], particularly with respect to the switchingcharacteristics. SiC devices can also operate at higher tempera-tures and thereby results in reduced heatsink volume.

It is expected that the first impact of SiC power devices onautomotive traction drives will be observed when SiC Schottkydiodes replace Si p-n diodes in inverters [16]. Oak RidgeNational Laboratory (ORNL) has collaborated with Cree andSemikron to build a Si IGBT–SiC Schottky diode hybrid 55-kWinverter by replacing the Si p-n diodes in Semikron’s automo-tive inverter with Cree’s SiC Schottky diodes. This paper showsthe results obtained from testing this inverter and comparing itwith a similar all-Si inverter.

II. SIC SCHOTTKY DIODES

Semikron has built 55-kW automotive integrated power mod-ules (AIPMs) for the U.S. Department of Energy’s Freedom-CAR Program’s hybrid electric vehicle traction drives. Thesemodules contain three-phase inverters with 600-V/600-A SiIGBTs and p-n diodes.

For an ORNL project, Cree has developed 600-V/75-A SiCSchottky diodes, as shown in Fig. 1. Semikron has replacedeach 150-A Si p-n diode in their AIPM with two of these 75-ASiC Schottky diodes.

A. Static Characteristics

After extensive testing, the I−V characteristics of thesediodes were obtained at different temperatures in the−50 ◦C–175 ◦C ambient temperature range (Fig. 2). Consid-ering the piecewise linear (PWL) model of a diode, whichincludes a dc voltage drop VD and a series resistor RD, thediode I−V curves can be approximated with the following:

Vd = VD + RD · Id (1)

where Vd and Id are the diode forward voltage and current,respectively, and VD and RD are the diode PWL modelparameters.

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OZPINECI et al.: THREE-PHASE INVERTER WITH Si IGBTs AND SiC SCHOTTKY DIODES 279

Fig. 1. The 600-V/75-A SiC Schottky diodes on a wafer next to a quarter.

Fig. 2. Experimental I−V curves of the 75-A SiC Schottky diode.

Fig. 3. RD and VD obtained from the experimental data in Fig. 2.

Fig. 3 shows RD and VD values of the 600-V/75-A SiCSchottky diodes with respect to temperature. As shown inFig. 3, VD decreases with temperature, and RD increases withtemperature. An increase in RD is a sign of the positive temper-ature coefficient the SiC Schottky diodes have, which implies

Fig. 4. (Solid) Measured and (dotted) simulated ON-state waveforms of theSiC Schottky diode at different temperatures.

TABLE ISiC POWER DIODE MODEL PARAMETERS AND EXTRACTION

CHARACTERISTICS FOR CREE 75-A DIODE

that these devices can be paralleled easily. The following showthe temperature dependence of the SiC Schottky diode PWLmodel parameters:

VD = − 0.001 · T + 0.94 (2)

RD =8.9 × 10−5 · T + 0.013 (3)

where T is the temperature in degree Celsius.Another model of this SiC diode has also been developed

for use in circuit simulators. The model, which was constructedin MAST hardware description language and simulated in theSaber simulator, was based on a diode model [17] developedat the University of Arkansas. Fig. 4 shows how the staticcharacteristics of the model fit the experimental results. Thepercentage error is approximately 0.3%–0.4% in the 100 ◦C and150 ◦C curves and approximately 2%–3% in the 25 ◦C curve.Table I contains the values of the modeling parameters for thisdiode.

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280 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 45, NO. 1, JANUARY/FEBRUARY 2009

Fig. 5. Reverse-Recovery current waveforms of the SiC Schottky diode fordifferent forward current values.

Fig. 6. (Solid) Measured and (dotted) simulated reverse-recovery waveformsof the SiC Schottky diode.

B. Dynamic Characteristics

The SiC Schottky diode was also tested in a chopper circuitto observe its dynamic properties. The chopper was switchedat 1 kHz with a 40% duty cycle. The reverse-recovery currentwaveforms obtained for different forward currents are shown inFig. 5, where the reverse-recovery current does not change withthe forward current. Note that, theoretically, Schottky diodes donot display a reverse-recovery phenomenon.

Required junction capacitance for the diode model listedin Table I is obtained from the experimental reverse-recoverycurrent waveforms. The corresponding fit of the model to theexperimental waveform is shown in Fig. 6 for a forward currentof 3 A. Note that the reverse-recovery current is larger in thisplot compared with the ones in Fig. 5. This is because theforward current is selected to be much smaller to observe thefit in detail.

Fig. 7. Static characteristics of the packaged 600-V/450-A SiC Schottky andSi p-n diodes at room temperature.

Fig. 8. Reverse-recovery current waveforms of the Si p-n diode for differentforward current values.

Fig. 9. Experimental turnoff energy losses of a 75-A SiC Schottky diode anda 150-A Si p-n diode at room temperature.

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OZPINECI et al.: THREE-PHASE INVERTER WITH Si IGBTs AND SiC SCHOTTKY DIODES 281

Fig. 10. Inverter output voltage and current during the inductive load test for two different conditions. (a) Vdc = 325 V; ia,peak = 80 A; and fo = 50 Hz.(b) Vdc = 325 V; ia,peak = 60 A; and fo = 100 Hz.

C. Comparison With Si P-N Diode

The automotive inverter used in this paper has 600-V/450-Adiodes. For this reason, six 75-A SiC Schottky diodes are usedto replace three 150-A Si p-n diodes. The static characteristicsof the packaged 600-V/450-A SiC Schottky and Si p-n diodes atroom temperature are shown in Fig. 7, where both diodes havesimilar characteristics. At low currents, the Si p-n diode has alower voltage drop, while at higher currents, the SiC Schottkydiode has a lower voltage drop; therefore, for higher poweroperations, the SiC Schottky diodes will have lower conductionlosses.

Switching losses of the 75-A SiC Schottky diode have beenshown in Fig. 5. Similar tests have been done on the 150-ASi p-n diodes. The results of these tests are shown in Fig. 8.It can be observed that the peak reverse-recovery current ofthe Si p-n diode is much higher than that of the SiC Schottkydiode at the same forward current and increases further withincreasing forward current. This corresponds to high reverse-recovery losses that increase with the forward current [18].Fig. 9 shows the comparison of the energy losses per turnoffof a 75-A SiC Schottky diode and a 150-V Si p-n diode. Asthe diode forward current increases, the energy losses of theSi p-n diode increase exponentially, while those of the SiCSchottky diode are negligible.

As a summary, the static characteristics of both of the testeddiodes are similar; however, the dynamic characteristics aremuch different. The Si p-n diode has high peak reverse-recoverycurrents that result in high diode switching losses and extraIGBT losses since the reverse current has to go through amain switch. Consequently, it is expected the Si IGBT–SiCSchottky diode inverter will perform better than the similarall-Si inverter.

III. INDUCTIVE LOAD TEST

Both the Si–SiC hybrid and the all-Si inverters were testedwith an inductive load and a dynamometer set with the sameprocedure and the same conditions.

Fig. 11. R−L load test efficiency curves for various load conditions.

For the inductive load test, the output leads of the inverterare connected to a three-phase wye-connected variable resistorbank with a three-phase inductor in series. The dc inputsare connected to a voltage source capable of supplying themaximum rated operating voltage and current levels for theinverter.

The dc link voltage was varied from the minimum operatingvoltage of 200 V to the maximum bus voltage of 450 V.

The load resistance was set to the minimum value, and theoutput current was varied. The inverter operates with a 20 ◦Ccoolant at a flow rate of 9.46 L/min. The open-loop frequencyof operation and the PWM frequency (10 kHz) were fixed,and the current command was varied for a particular dc-linkvoltage. For each value of the current command and open-loopfrequency, the dc-link voltage, dc-link current, input/outputpower, efficiency, and output line currents and voltages were

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282 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 45, NO. 1, JANUARY/FEBRUARY 2009

Fig. 12. Inverter output voltage and current during the dyn test for twodifferent conditions. (a) One-thousand revolutions per minute and 50 N · m.(b) One-thousand revolutions per minute and 150 N · m.

recorded. The three-phase power was measured using the two-wattmeter method.

The command current was increased in steps of 10 A withoutexceeding the power rating of the inverter or the power rating ofthe load. The procedure was repeated by increasing the open-loop frequency in steps of 25 Hz.

The coolant temperature was changed to 70 ◦C and the afore-mentioned procedure was repeated to observe the operation athigher temperatures.

The operating waveforms for two specific operating condi-tions of the Si–SiC hybrid inverter are shown in Fig. 10.

The data obtained for both of the inverters were analyzed, andthe corresponding efficiencies were calculated. The efficiencyversus output power plots for several operating conditions areshown in Fig. 11.

The average loss reduction resulting from using SiC Schottkydiodes instead of Si p-n diodes was calculated as

%loss reduction =P Siloss − P SiCloss

P Siloss× 100. (4)

The Si–SiC hybrid inverter losses are up to 33.6% less than theall-Si inverter.

Fig. 13. Dynamometer test. Motoring mode efficiency plots with 70 ◦Ccoolant and (a) 100-N · m, (b) 150-N · m, and (c) 200-N · m load torques.

IV. DYNAMOMETER TEST

The inverters were connected individually to an inductionmachine set up in a dynamometer test cell to test them for theirdynamic performance in the motoring and regeneration modes.The induction motor used was a four-pole induction motorwith a base speed of 2500 r/min, and the dynamometer had a100-hp capacity. The tests were performed with the in-verter being supplied with 70 ◦C coolant and a flow rate of9.46 L/min.

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OZPINECI et al.: THREE-PHASE INVERTER WITH Si IGBTs AND SiC SCHOTTKY DIODES 283

Fig. 14. Inverter output voltage and current during the regeneration test fortwo different conditions. (a) One-thousand revolutions per minute and 50 N · m.(b) One-thousand revolutions per minute and 150 N · m.

A. Motoring Mode

In this mode, the speed set point, the magnetizing current, thedirection of rotation, and the current limit were the parametersthat could be adjusted. The dc voltage input to the inverterwas set at the nominal battery operating voltage (325 V dc).The closed-loop speed controller gains were adjusted for agiven magnetizing current value and current limit to achievea stable operation of the system for a wide range of speeds.The direction of rotation was set to forward, and the motorspeed was increased from 750 r/min to the rated base speed fora specific continuous load torque. The load torque was variedgradually from zero to the required torque and then decreasedto zero. The data were obtained for a wide range of speedand torque values by changing the load torque (100, 150, and200 N · m) using the dynamometer controller. The followinginformation was recorded at each speed increment: motor shaftspeed, motor torque, input and output voltages, and currents.

The operation waveforms for two different load conditionsare shown in Fig. 12. The efficiency plots for various speeds and

Fig. 15. Dynamometer test. Regeneration mode efficiency plots with 70 ◦Ccoolant and (a) 100-N · m, (b) 150-N · m, and (c) 200-N · m load torques.

load torques are shown in Fig. 13. The average loss reductionwas obtained as described in the previous section. In this case,up to 10.7% reduction in the losses is observed.

B. Regeneration Mode

In this mode, the torque limit and the operating current canbe adjusted. The dc voltage input to the inverter was set at thenominal battery operating voltage. The direction of rotation wasset to be forward. The dynamometer controller was adjusted

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284 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 45, NO. 1, JANUARY/FEBRUARY 2009

to control the speed, while the inverter controller controlledthe current. Data had been collected for the 100-, 150-, and200-N · m torque produced by the drive.

The procedure was repeated to obtain the data for a widerange of speed and torque values. The following information ateach speed increment was recorded: motor shaft speed, motortorque, input and output voltages, and currents.

The operating waveforms for the regeneration mode areshown at two different speeds in Fig. 14. The curves comparingthe efficiency of the inverters with the 70 ◦C coolant areshown in Fig. 15. In this mode, the reduction in the losses iscomparable to the motoring case.

V. CONCLUSION

The testing of both the Si–SiC hybrid and all-Si inverterswas completed successfully. The inverters were able to operateat peak power levels with efficiencies greater than 90%. Theinverters were tested for a peak power of 47 kW and continuousrating of up to 35 kW.

The test results show that, by merely replacing Si p-n diodeswith their SiC Schottky diode counterparts, the losses of aninverter decrease considerably. As the device tests showed,the main reason for this is the high reverse-recovery lossesof Si p-n diodes, which are negligible for SiC Schottkydiodes.

Note that both inverters were tested in the exact same condi-tions with the same controller. Since SiC Schottky diodes have anegligible reverse recovery, they do not stress the main switchesas much as Si p-n diodes. Therefore, it is possible for the Si–SiChybrid inverter to operate at higher switching frequencies thanthe one used in these tests.

ACKNOWLEDGMENT

The authors would like to thank Dr. A. Agarwal andDr. S.-H. Ryu of Cree and Dr. J. Mookken of Semikron for theirpart in building the hybrid inverter.

Prepared by the Oak Ridge National Laboratory, Oak Ridge,TN 37831, managed by UT-Battelle for the U.S. Department ofEnergy under Contract DE-AC05-00OR22725.

This paper has been authored by a contractor of the U.S. Gov-ernment under Contract DE-AC05-00OR22725. Accordingly,the U.S. Government retains a nonexclusive royalty-free licenseto publish from the contribution, or allow others to do so, forU.S. Government purposes.

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[3] S. Hodge, “SiC Schottky diodes in power factor correction,” Power Elec-tron. Technol. Mag., vol. 40, pp. 14–23, Aug. 2004.

[4] H. R. Chang, E. Hanna, and A. V. Radun, “Demonstration of siliconcarbide (SiC)-based motor drive,” in Proc. Conf. IEEE Ind. Electron. Soc.,Nov. 2–6, 2003, vol. 2, pp. 1116–1121.

[5] A. M. Abou-Alfotouh, A. M. Radun, V. Arthur, H. R. Chang, andC. Winerhalter, “A 1 MHz hard-switched silicon carbide DC/DC con-verter,” in Proc. IEEE Appl. Power Electron. Conf., Feb. 9–13, 2003,vol. 1, pp. 132–138.

[6] K. Mino, K. S. Herold, and J. W. Kolar, “A gate drive circuit for siliconcarbide JFET,” in Proc. Conf. IEEE Ind. Electron. Soc., Nov. 2–6, 2003,vol. 2, pp. 1162–1166.

[7] M. L. Heldwein and J. W. Kolar, “A novel SiC J-FET gate drive circuitfor sparse matrix converter applications,” in Proc. IEEE Appl. PowerElectron. Conf., Feb. 22–26, 2004, vol. 1, pp. 116–121.

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[13] S. H. Ryu, A. Agarwal, J. Richmond, J. Palmour, N. Saks, and J. Williams,“10 A, 2.4 kV power DiMOSFETs in 4H-SiC,” IEEE Electron DeviceLett., vol. 23, no. 6, pp. 321–323, Jun. 2002.

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[17] T. R. McNutt, “Modeling and characterization of silicon carbide power de-vices,” Ph.D. dissertation, Dept. Elect. Eng., Univ. Arkansas, Fayetteville,AR, 2004.

[18] N. Y. A. Shammas, M. T. Rahimo, and P. T. Hoban, “Effects of externaloperating conditions on the reverse recovery behaviour of fast powerdiodes,” EPE J., vol. 8, no. 1/2, pp. 11–18, Jun. 1999.

Burak Ozpineci (S’92–M’02–SM’05) received theB.S. degree in electrical engineering from the MiddleEast Technical University, Ankara, Turkey, in 1994,and the M.S. and Ph.D. degrees in electrical engi-neering from the University of Tennessee, Knoxville,in 1998 and 2002, respectively.

He is with the Power Electronics and ElectricMachinery Research Center, Oak Ridge NationalLaboratory (ORNL), Knoxville, TN, first with thePostmasters Program in 2001, then as a Full-TimeResearch and Development Staff Member in 2002,

and then as a Technical Program Manager in 2006. Currently, he is also anAdjunct Faculty with the University of Arkansas, Fayetteville. He is doingresearch on the system-level impact of SiC power devices, multilevel inverters,power converters for distributed energy resources and hybrid electric vehicles,and intelligent control applications for power converters.

Dr. Ozpineci was the Chair of the IEEE Power Electronics Society Rectifiersand Inverters Technical Committee and was the Transactions Review Chair-man of the IEEE Industry Applications Society Industrial Power ConverterCommittee. He was the recipient of the 2006 IEEE Industry ApplicationsSociety Outstanding Young Member Award; the 2001 IEEE InternationalConference on Systems, Man, and Cybernetics Best Student Paper Award;and the 2005 UT-Battelle (ORNL) Early Career Award for EngineeringAccomplishment.

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OZPINECI et al.: THREE-PHASE INVERTER WITH Si IGBTs AND SiC SCHOTTKY DIODES 285

Madhu Sudhan Chinthavali received the B.E. de-gree in electrical engineering from BharathidasanUniversity, Tiruchirapalli, India, in 2000, and theM.S. degree in electrical engineering from The Uni-versity of Tennessee, Knoxville, in December 2003.

He is currently with the Power Electronics andElectric Machinery Research Center, Oak RidgeNational Laboratory, Oak Ridge, TN. His areas ofinterest include wide bandgap semiconductor powerelectronics, power system applications, and verylarge scale integration.

Leon M. Tolbert (S’89–M’91–SM’98) received theB.E.E., M.S., and Ph.D. degrees in electrical en-gineering from Georgia Institute of Technology,Atlanta, in 1989, 1991, and 1999, respectively.

He was with Oak Ridge National Laboratory(ORNL), Oak Ridge, TN, in 1991 and worked onseveral electrical distribution projects at the threeU.S. Department of Energy plants in Oak Ridge, TN.In 1997, he was a Research Engineer with the PowerElectronics and Electric Machinery Research Cen-ter, ORNL. Currently, he is an Associate Professor

with the Department of Electrical and Computer Engineering, University ofTennessee, Knoxville, where he has worked since 1999. He is also currentlyan Adjunct Participant with ORNL and conducts joint research at the NationalTransportation Research Center. He does research in the areas of electric powerconversion for distributed energy sources, motor drives, multilevel converters,hybrid electric vehicles, and application of SiC power electronics.

Dr. Tolbert is a registered Professional Engineer in the state of Tennessee.He was the coordinator of Special Activities for the Industrial Power ConverterCommittee of the Industry Applications Society (IAS) from 2003 to 2006. Hewas the recipient of the 2001 IAS Outstanding Young Member Award. He wasthe Chair of the Education Activities Committee of the IEEE Power ElectronicsSociety from 2003 to 2007. He was an Associate Editor of the IEEE POWERELECTRONICS LETTERS from 2003 to 2006. He is currently an AssociateEditor of the IEEE TRANSACTIONS ON POWER ELECTRONICS.

Avinash S. Kashyap (S’03) received the B. Tech.degree in electrical and electronics engineering fromthe University of Calicut, Kerala, India, in 2001, andthe M.S. degree in electrical engineering from theUniversity of Arkansas, Fayetteville, in 2005, wherehe is currently working toward the Ph.D. degree inthe Department of Electrical Engineering.

His research is primarily focused on modeling(compact and Technology Computer Aided Design),characterization, and study of various semiconductordevices in extreme environments. He was an Intern

with the Wide Bandgap Research Group, Oak Ridge National Laboratory,Knoxville, TN, and also with the SPICE Modeling Group, National Semicon-ductor, Santa Clara, CA.

Mr. Kashyap is the recipient of the Sam Walton Doctoral Academy Fellow-ship and the William E. Clark Endowed Doctoral Fellowship.

H. Alan Mantooth (S’83–M’90–SM’97) receivedthe B.S. (summa cum laude) and M.S. degreesin electrical engineering from the University ofArkansas (UA), Fayetteville, in 1985 and 1987, re-spectively, and the Ph.D. degree from the GeorgiaInstitute of Technology, Atlanta, in 1990.

He was with Analogy in 1990, where he focusedon semiconductor device modeling and the researchand development of hardware-description-language(HDL)-based modeling tools and techniques. Asidefrom HDL-based modeling, his research interests

include analog and mixed-signal IC designs. In 1998, he was a member ofthe faculty of the Department of Electrical Engineering, UA, as an AssociateProfessor, where he has received teaching, service, and/or research awardsevery year since his return and has been a Full Professor since 2002. In 2003,he cofounded Lynguent, an electronic design automation company focused onmodeling and simulation tools. He has published over 100 refereed articleson modeling and IC design. He holds patents on software architecture andalgorithms for modeling tools and has others pending. He is the coauthor ofthe book Modeling with an Analog Hardware Description Language (Norwell,MA; Kluwer, 1994).

Dr. Mantooth is a member of Tau Beta Pi and Eta Kappa Nu and is aregistered Professional Engineer in Arkansas. He was the Technical ProgramChair for the IEEE International Workshop on Behavioral Modeling andSimulation in 2000 and was the General Chair in 2001. He served as the GuestEditor for a Special Issue on Behavioral Modeling and Simulation for the IEEETRANSACTIONS ON COMPUTER-AIDED DESIGN in February 2003 and asan IEEE Circuits and Systems Society Distinguished Lecturer in 2003–2004.He is currently serving the profession in the following roles: IEEE Circuitsand Systems Society (CAS) representative on the IEEE Council on ElectronicDesign Automation and member of the Power Electronics Society AdvisoryCommittee as Chair of the Society’s Standards Committee. In 1996, he wasnamed Distinguished Member of Technical Staff at Analogy (now owned bySynopsys). He was also selected to the Georgia Tech Council of OutstandingYoung Engineering Alumni in 2002 and to the Arkansas Academy of ElectricalEngineers in 2006. He helped establish the National Center for Reliable ElectricPower Transmission, UA in 2005, for which he serves as the Director. In 2006,he was selected as the Inaugural Holder of the 21st Century Chair in Mixed-Signal IC Design and Computer-Aided Design, an endowed chair position. Hehas served on several technical program committees for IEEE conferences.

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