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Applications for GaN

Power Semiconductors

Eric Persson

GaN Applications & Marketing

October 2014

Why GaN for Power Electronics?

Today’s Silicon Options for 600 V Switch:

SuperJunction FET (CoolMOS, MDMesh)

• Pro: Low Rds(on) per area; reasonable cost

• Con: Very poor body diode; nonlinear Qoss

• Typical applications: Power Supplies

Traditional Planar FET (FREDFET)

• Pro: low cost process; performance similar to superjunction

• Con: large die area for a given Rds(on)

• Typical applications: Legacy power supplies

IGBT (with co-packaged diode)

• Pro: Very low $/A; short-circuit capable

• Con: High Vce(on); no sync rect; switching loss limits freq.

• Typical applications: Motor drives, UPS inverters

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Different GaN Switch Structures

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Avogy Vertical GaN FET

Panasonic GIT

EPC eGaN FET

IR, Fujitsu/Transphorm

Depletion GaN HEMT

The “Normally Off” Cascode

Native GaN HEMT (depletion mode) has best performance

• Performance is compromised to shift threshold positive

Cascode has easy gate drive

Cascode includes excellent body diode

2-chip solution no more difficult than IGBT

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D

S

G

Low Voltage Si FET

SK

GaN HEMT

GaN: First Generation 600 V Cascode

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Parameter IRGAN

60S002HTR

IPP65R150CFD

CoolMOS™ CFDII

STB25NM60ND

FDMesh II™

Package 6x8 mm PQFN TO-220 TO-220

Vdss 600 V 650 V 600 V

Rdson typ 25°C 135 mΩ 135 mΩ ƒ(ID) 130 mΩ ƒ(ID)

Rdson typ 125°C 225 mΩ +67% 300 mΩ +122% 244 mΩ +88%

Qg (10 V Vgs, 480 V Vds) 7.9 nC 86 nC 80 nC

Qrr (100A/µs, 25°C) 49 nC 700 nC 1,000 nC

Qrr (100A/µs, 125°C) 51 nC 1,600 nC 2,000 nC

• Better Rds(on) characteristic in much smaller footprint

• 10X lower Qg than best superjunction

• 40X lower Qrr than best superjunction

• 3-4X lower Coss (nonlinear, depends on measurement method)

Best SuperJunction Available

CoolMOS is a registered trademark of Infineon Corp. FSMesh is a registered Trademark of ST Microelectronics Corp.

Comparing Qoss of GaN vs SuperJunction

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REF: M. Treu, E. Vecino, M. Pippan, O. Häberlen, G. Curatola, G. Deboy, M. Kutschak, U. Kirchner,” The role of silicon,

silicon carbide and gallium nitride in power electronics,” IEEE International Electron Devices Meeting, December, 2012

Why GaN Cascode - Summary

• Outstanding body diode performance

• Much lower turn-on (switching) loss

• Much lower conducted EMI (-45 dB measured)

• Enables many more half-bridge applications

• Low, linear output capacitance Coss

• Enables much higher soft-switching frequency

• Well-behaved dv/dt further mitigates EMI

• Low gate charge

• 5-10X lower gate driver power loss

• Bidirectional conduction (sync. rect. capable)

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Traditional Boost PFC Topology

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REF: L. Huber, Y. Jang, M. Jovanovic, “Performance Evaluation of Bridgeless PFC Boost Rectifiers,” IEEE TRANSACTIONS

ON POWER ELECTRONICS, VOL. 23, NO. 3, MAY 2008

Qoss Stored Energy versus Vds

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0

5

10

15

20

25

30

35

40

0 100 200 300 400 500 600

Sto

red

En

erg

y (

µJ)

Vds (Volts)

IPW65R045C7

18.6µJ @ 400V

IPW60R045CP

25.7µJ @ 400V

50mΩ GaN Cascode

17.1µJ @ 400V

Company Confidential

Synchronous Bridgeless Boost Topology

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ACLINE

EMI Filter

High Frequency Half-Bridge

60Hz Polarity Switch

DC Bus

Q1

Q2

Q3

Q4

600 V Device Trr Performance Comparison

GaN Qrr independent of temperature

Pulse

Switching

FET

DUT

vS

coaxial

DC

Bus

+

–

shunt

L

iS

iDiL

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Synchronous Bridgeless Boost Demo Board

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Driver

IC GaN

Cascode

Switches

Synchronous Bridgeless Boost Performance

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Output Power (W)

η

ZVS Half Bridge Building Block

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Vout

Q1

Q2+

-Vin

Input Caps

Output

Caps

RF Inductor

Gate

Driver

GaN Cascode

Switches

Half-Bridge Voltage and Current @ 3.3 MHz

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+6 A

+4 A

+2 A

0 A

-2 A

0 V

100 V

200 V

300 V

400 V

Inductor Current

Switch Voltage

Performance of Half-Bridge Boost

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80%

82%

84%

86%

88%

90%

92%

94%

96%

98%

100%

0 100 200 300 400 500

Eff

icie

ncy

Po [W]

Boost Converter Efficiency, No Heatsink, 400 V Out

2.5 MHz

3.3 MHz

High Efficiency Possible by Frequency Control

High-Frequency ZVS Boost Summary

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• 500 W, 2.5 MHz, 97% efficiency – NOT Possible with Silicon

• Very small magnetic – 18 mm toroid inductor

• No heatsink – convection cooled

• Very low gate drive power – 0.72 W consumed by gate driver

• Enables ZVS Boost PFC

LLC Resonant DC-DC Power Supply

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Nonlinear Qoss Causes Time Delay

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0

50

100

150

200

250

300

350

400

450

500

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Vo

lts

Time (µs)

3.3X longer charge-up time

Qoss Measurement Circuit

Company Confidential

LLC – GaN vs SuperJunction @ 1 MHz

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• GaN losses are significantly lower than SuperJunction

IPP65R150CFD2 GaN Vds

Vgs

iprim

icentertap

I2 Primary I2 Secondary Gate Drive

GaN 3.84 A2 48.0 A2 0.24 W

SuperJunction 4.93 A2 64.6 A2 1.88 W

Difference +28.3% +34.6% +685%

Conducted EMI Benefits of GaN

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GaN IR 20 kHz IGBT 20 kHz Rg = 2 Ω

• Test condition: single half-bridge 1.5 A phase current 20 kHz

• No EMI filter

• GaN is up to 45 dB improvement over Si IGBT

45 dB Improvement at 1.5 MHz

Test data courtesy of Schneider Electronic ,Technology & Strategy Department

The Future?

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• Integration – IPMs

• Multiphase Architectures

• Short-circuit capability

• 900 V GaN

• VHF Optimized 30 MHz+