Development of GaN-based Power Electronics for PV Inverters ---...

Development of GaN-based Power Electronics for PV Inverters

----an important BoS cost driver

Umesh K MishraUC Solar co-Director and Professor ECE, UC Santa Barbara

Chairman and CTO, Transphorm Inc., (a UCSB Start-up)

UC Solar Review, October 7, 2016

“Moore’sLaw”ofPowerElectronics

GaN is the next significant semiconductor alongside Silicon

3

• GaN has a direct and large bandgap • Enormous and growing photonics market which develops a large eco-system

of infrastructure and human resources

• GaN is a lucky semiconductor; it performs reliably (in photonics and electronics) • Even while being an imperfect material (high dislocation density)

• In electronics it can also serve a large market • From KHz (power conversion) to GHz (RF amplification and communication)

• It has been proven reliable in both power conversion and RF applications• It is market ready

• GaN has a clear roadmap to lower cost and higher performance• Necessary for mass adoption

• Vertical GaN-on-GaN devices• Attractive for high power applications (>50kW)

Proprietary&Confidential

FormandfunctionisdrivenbyfrequencyHomeSatelliteCommunication

C-Band4-8GHz Ku-Band

12-18 GHz

http://www.satsig.net/pointing/dish-pointing-images.htm

Widespreaddistributionenabledbyhigherfrequency

Proprietary&Confidential

WithHighEfficiencyatHighFrequencyTransphorm’s EZ-GaNDisruptsPVInvertersbyProvidingEnhancedEfficiencyand

ReducedSizeatReducedCost

HighEfficiency– ReducesMechanicalSize

HighFrequency–ReducesElectricalSize

SystemSizeGaN,

2520in3

72%

Saved,1000in3

28%

SystemCostGaN,$586.791%

Saved,$54.779%

WithGaN

Analysisdoneforoneclassofinverters,willapplytootherinverterclassesingeneral

Proprietary&Confidential

CurrentInverterTechnology(20kHz)TopCostDrivers

Mechanical ElectricalHeatsink,$50.36,24%

Enclosure$63.5330%

SwitchBox$36.5117%

Other,$61.71,29%

BoostInductor$47.0219%

InverterInductor$72.1029%

ElectrolyticCapacitors$35.5214%

CommonModeChokes$12.485%

Other$84.5333%

Proprietary&Confidential

Transphorm’s EZ-GaN ProvidesHighEfficiencywithSimpleTopology:ReducesSizeandCost

Enables:• ShrinkingofHeatsink• ShrinkingofEnclosure System

SizeGaN,

2520in3

72%

Saved,1000in3

28%

Efficiency(%) 96.8 97.5(Current) 98.5(2013)

Heatsinkininches

Length 12 8.4 5.5

Width 12 7.2 3.3

Height 3 2.5 2.0

WithGaN

WithGaN 15%systempricereduction

Breakdown of PV system costs for a residential system

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TheAdvantageofGaN-on-SiforPowerConversion

• GaNenablesincreasedoutputpowerdensity• Higherefficienciesathigherpowerandhigherfrequencies

• PVinverter:4.5kW>98%efficiencyat50KHz(Yaskawa)• 10L(50%ofYaskawa’s SiIGBT-basedproduct)

• 1Userversolution:2.2kWat98%efficiency• Today’scurrentdesignis1.2kW

Si-IGBT-basedsystem

GaNFET-basedsystem45%smaller

99

94

93

Efficie

ncy

(%)

Power (W)

98

97

96

95

500 1000 2000 3000 4000 4500

GaNIGBT

1500 2500 3500

9

10

HVGaNHEMTLVSi

FET

G

DNormallyoffNormallyon

Advantage:o Robusto Highperformanceo Compatiblewith

SidriversDisadvantageo Two-chipsolution

Substrate(SiC orSi)

GaN Buffer

AlGaN BarrierSource Insulator Drain

Gate

DeviceCellCross-section

2DEG

Cascode Approachtoachievenormallyoff

GD

S

EffectiveCKT

Normallyoff

Cascode HEMTimplementation

HighTemperatureOperatingLife

Circuit:Boostconverter• InputVoltage:200V• OutputVoltage:400V• Operatingfrequency:300kHz

06

3000

9.5

Time (hrs)

Loss

(W

)

1500

8.5

7.5

6.5

9

8

7

750 2250

High Temperature Operating Life Test

Reference device (Si)

GaN FETs

Operating conditions:200/400V converter operation@ 175oC/300kHz/410W Tested in hard-switched boost converter

• OperatingTemperature:Tcase =150°C

• OutputPower:410W

• Testtime:3000hours

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QualityandReliability

• TransphormhasdemonstratedJEDEC-qualified650VGaNdevices• ExtendedreliabilitytestingaboveandbeyondJEDEC• Establishedintrinsiclifetimefor650VratedGaNpowerchips

Over 1500 V breakdown voltage

With little dynamic R(on) collapse

Stable switching up to 1000 Volts

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ProprietaryandConfidentialInformation13

Current,Temperature:HighTemperatureDCTestingVoltage:HighVoltageOff-StateTesting

TemperatureandCurrentAcceleration§ Devicestestedat“high”rangeofnominalcurrentlevels§ Tj rangedfrom330to380°C§ Resultsconsistentwithreporteddata

§ Ea =1.84eV§ Lifetimeat150°C>1X108hrs

Testsprovidescredibleandgoodlifetimeprojections

125⁰C175⁰C 150⁰C

VoltageAcceleration§ Cascode(product)devicestested§ HighVoltagesrangedfrom1000to1300V

§ MTTFat1050V=6800hrs§ Higherthanexpectedvoltagespikesduringoperation

§ Nominaloperatingtemperature=82°C§ Lifetimeat600V>1X108hrs

Updated 8/6/15

20 years

MTTF

600V 480V

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High-voltagePowerTechnology Transitions

$0 M

$50 M

$100 M

$150 M

$200 M

$250 M

$300 M

2016 2017 2018 2019

1200 V

900 V

Broad Industrial

Consumer

Automotive

Motor Drive

PV Inverters

Servers

SignificantinflectionpointinCY18/CY19 timeframe forreliable>650VGaN-on-Siproduct

10

GaN-on-Sibasedpowerconversionisready

Bottoms-up GaN ServableMarket – Near Term

Bottoms-up GaN ServableMarket – Medium Term

$0 M

$150 M

$300 M

$450 M

$600 M

$750 M

$900 M

2019 2020 2021 2022

2014/15WorldWideVehicleSalesbyRegion

• Europeisthefastestgrowing:9.2%growth• Threelargestmarkets:DE,UK,FR,(Nor,SE,NLgov’tprogramssupportingEV’s)

• Chinaisthelargest:9.1%growth• Reducedtaxesonvehicleswithlessthan1.6literengines

• Japancontractedby10.1%

0%5%

10%15%20%25%30%35%

Russia India Brazil Japan Europe USA China

Units(M

)

Region

2014(59.9Mu) 2015(61.7Mu)

-

Source:VDC

-7.8%

-25.6%

-10.3%

9.2%

5.7%

9.1%

WhyisGaNTargetingAuto

http://www.automotive-eetimes.com/content/lateral-gan-transistors-%E2%80%93-replacement-igbt-devices-automotive-applications

GaN’sValueProposition

HigherEfficiency

BridgelessTotemPolePFC

HigherFrequencyIncreasedPower

Density

LowerSystemCost

650V/SMD&TOpackagesAEC-Q101

Transphorm’sSales

Strategy

ValueofGaNisRealizedinDifferentTopologies

Topology HigherPerformance HigherPowerDensity LowerSystemCost

Standardboost PFC XInterleavedboostPFC XBridgelesstotem-

polePFC X X X

GaNValueShownViaCustomerSolution• Project:1.2kWpowersupply• Competition:Superjunction(silicon)• Result:Higherefficiency,lowerBOMcost

• Reductioninpartcount,magnetics,EMIfilter

ParameterResults InterleavedPFC BridgelessTotemPolePFC

Efficiency 97.8% 98.7%Totalcost 100% 93.7%

SiFET

SiFET

SiC Diodes

GaNValueShownViaCustomerSolution• Project:3.3kWpowersupply• Competition:Superjunction(silicon)• Result:Higherefficiency,lowerBOMcost

• Reductioninpartcount,magnetics,EMIfilter

ParameterResults InterleavedPFC BridgelessTotemPolePFC

Efficiency 98.5% 98.7%Totalcost 100% 60%

GaNFET

GaNFET

SiFET

SiFET

SiFET

SiFET

SiC Diodes

SiFETs

Vertical design advantages over lateral design

2

-Grow thick GaN layers: High BV >> 1200V

-Realize high current (>> 20A) devices

-Normally-off operation

-Reduced number of defects: Improved Reliability, Large EC

-Breakdown occurs in bulk Avalanche capability

-GaN on GaN takes less chip area àLowers die cost

*KIZILYALLI et al.: VERTICAL POWER p-n DIODES BASED ON BULK GaN

State of the art vertical devices: CAVET

CAVET (UCSB, ASU, Avogy, Toyota, UC Davis)

Best Performance:- 1.5 kV, 2.2 mΩ.cm2 (Avogy)3

Best Performance:- 380 V, 1.5 mΩ.cm2 (UCSB)

UCSB Data

RON = 2.5 mΩ.cm2

VBR = 990 V

Vertical GaN in a simple device topology is attractive for 1200V markets soon

GaN is the next significant semiconductor alongside Silicon

25

• GaN has a direct and large bandgap • Enormous and growing photonics market which develops a large eco-system

of infrastructure and human resources

• GaN is a lucky semiconductor; it performs reliably (in photonics and electronics) • Even while being an imperfect material (high dislocation density)

• In electronics it can also serve a large market • From KHz (power conversion) to GHz (RF amplification and communication)

• It has been proven reliable in both power conversion and RF applications• It is market ready

• GaN has a clear roadmap to lower cost and higher performance• Necessary for mass adoption

• Vertical GaN-on-GaN devices• Attractive for high power applications (>50kW)

Sustained funding from UC Solar for both the PV module and the PV Inverter will Drive higher performance lower cost systems in the coming decades

Conclusion

Yes we GaN!

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