GaN Transistors Successes and Challenges Ahead€¦ · Alex Lidow Efficient Power Conversion Corporation ... 0 50 100 150 200 250 300 350) ) Output Power (W) 4 MHz Efficiency 1 MHz

EPC - The Leader in eGaN® FETs | April, 2013 | www.epc-co.com

The eGaN® FET Journey Continues

Alex Lidow

Efficient Power Conversion Corporation

GaN Transistors – Successes and

Challenges Ahead

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=SmsXddFlZiLrWM&tbnid=yftikwFazUBmcM:&ved=0CAUQjRw&url=http://www.mse.vt.edu/Default.aspx?tabid=378&ei=dVVRUcPzJIbe8AS7woFI&bvm=bv.44158598,d.eWU&psig=AFQjCNGn0s895RLAHPF828Qq06rYVi-Iaw&ust=1364371166025930


Agenda

• GaN Device Structure

• Envelope Tracking

• Wireless Power

• What is in the future?

2


EPC - The Leader in eGaN® FETs | April, 2013 | www.epc-co.com 3

Dielectric

GaN

- - - - - - - - - - - - - - -

Si

AlGaN Electron Generating Layer

Aluminum Nitride Isolation Layer

D G S - - - -

eGaN® FET Structure

Two Dimensional Electron Gas (2DEG)



Printed Circuit Board Copper Traces

Silicon Substrate

Active GaN Device Region

Solder Bars

4

LGA Construction



Key Applications • RF DC-DC “Envelope Tracking”

• Wireless Power Transmission

• RadHard

• Power Over Ethernet

• RF Transmission

• Network and Server Power Supplies

• Point of Load Modules

• Solar Micro-inverters

• Energy Efficient Lighting

• Class D Audio

5



Envelope Tracking (ET)

6



Peak to Average Power Ratio

Reference: Nujira.com website

Same average

Normalized

to same peak

7



Effect of PAPR

Peak Power Average Power

Output Power (dBm)

Output Probability

Fixed supply

Average efficiency only 25 %

PAPR = 0dB Peak efficiency

up to 65%

Increasing PAPR

8



Effect of Envelope Tracking

Output Power (dBm)

Average Power

Output Probability

Only 1/3 the losses Average efficiency > 50 % (incl. ET)

Envelope Tracking

9



Envelope Tracking Supply

Buck ~ 10% Bandwidth ~ 90% Power

Linear AMP ~ 10% Power Highest 90% of Bandwidth

*Reference: V. Yousefzadeh, et al, Efficiency optimization in linear-assisted switching power converters for envelope tracking in RF power amplifiers, ISCAS 2005

10



Efficiency Results

0

2

4

6

8

10

12

14

16

90%

91%

92%

93%

94%

95%

96%

97%

98%

0 50 100 150 200 250 300 350

Pow

er lo

ss (W

)

Effic

ienc

y (%

)

Output Power (W)

4 MHz Efficiency

1 MHz Efficiency

4 MHz Losses

1 MHz Losses

11

45 VIN – 22VOUT



Wireless Power

12



Wireless Power

13



⁺ Resonant design is in the coil set ⁺ Switch voltage rating = to supply value

Class D Wireless Power

+

VDD

Crp Crs Lrp

Cmrp

Cmp

Lp Ls Cms

⁻ COSS plays an important role in losses

QRF2

QRF1 V / I

VDS_QRF ID_QRF

time

VDD

50%

14

Load

Co



System Setup

Device Board

Source Coil Source Board

Coil Feedback

Device Coil

25m

m

25m

m

eGaN FETs RF connection

RF connection

50mm 50mm

15

MOSFETs RF connection



Efficiency

54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Efficiency [%]

Output Power [W]

6.639 MHz, 23.6 Ω load

Vin =8V

Vout=6.8V

Vin =22V

Vout=18.3V

16



What’s in the Future?

17



Breaking Down the Barriers

• Does it enable significant new capabilities?

• Is it easy to use?

• Is it VERY cost effective to the user?

• Is it reliable?

18






• Is it reliable?

19




0

10

20

30

40

50 500

Gai

n (d

B)

Frequency [MHz]

EPC1012 Maximum Gain Vs Frequency

High Frequency High Voltage and High Power

1000

EPC 2012 Maximum Gain vs Frequency 200 V eGaN FETs

20






• Is it reliable?

21




It’s just like a MOSFET

Is an eGaN FET Easy to Use?

except

The high frequency capability makes circuits using eGaN FETs sensitive to layout

The lower VG(MAX) of 6 V makes it advisable to have VGS regulation in your gate drive circuitry

22



What Other Advances are Needed?

• High speed digital controller ICs and integrated controller/driver ICs.

– Application specific controllers to reduce time-to-market

– Dynamic deadtime control with ~1 ns resolution

– Envelope Tracking Controllers

• Improved measurement systems

23






• Is it reliable?

24




Silicon vs. eGaN Wafer Costs

Starting Material

Epi Growth

Wafer Fab

Test

Assembly

OVERALL

2012 2015

same same

higher

same

same

lower

lower

same

lower

~same?

lower! higher

25






• Is it reliable?

26




eGaN FETs are Reliable

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 200 400 600 800 1000

No

rma

lize

d R

dso

n

Stress Hours

EPC2001 RDS(ON) after 100VDS HTRB at 125oC

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 200 400 600 800 1000

Vth

(V)

Stress Hours

EPC2001 VGS(TH) after 100VDS HTRB at 125oC

0.0E+00

1.0E-04

2.0E-04

3.0E-04

4.0E-04

5.0E-04

0 200 400 600 800 1000

Idss

@40

V (A

)

Stress Hours

EPC2015 Idss after 40V H3TRB at 85oC/85%RH

datasheet spec: 500uA max

0.9

0.95

1

1.05

1.1

0 1000 2000 3000

No

rmal

ized

Eff

icie

ncy

Stress Hours

EPC9001 Efficiency after Op Life Test at 85oC TJ

board a

board b

board c

board d

board e

27



Driver On Board

Beyond Discrete Devices

Full-Bridge with Driver and Level Shift

Discrete FET with Driver

28



Summary

• GaN transistors improve efficiency compared with power MOSFETs in power conversion.

• eGaN FETs are straightforward to use, but you can’t just drop them into a MOSFET socket.

• GaN transistors enable exciting new applications such as RF Envelope Tracking and Wireless Power Transmission.

29


EPC - The Leader in eGaN® FETs | April, 2013 | www.epc-co.com 30

The end of the road

for silicon…..

is the beginning of

the eGaN FET

journey!


GaN Transistors Successes and Challenges Ahead€¦ · Alex Lidow Efficient Power Conversion Corporation ... 0 50 100 150 200 250 300 350) ) Output Power (W) 4 MHz Efficiency 1 MHz

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