egan® fets enable low power high frequency wireless energy

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

The eGaN® FET Journey Continues

eGaN® FETs Enable Low Power High Frequency Wireless Energy Converters

M. A. de Rooij & J. T. Strydom Efficient Power Conversion 1

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

Wireless Power

2


Equivalent Circuit model for the Coils

3

Ideal Transformer Lrp Lrs

Lmp Lms


Highly Resonant Wireless System* Overview

4

Comprises 4 main sections:

1. An amplifier (a.k.a. a power converter).

2. A transmit coil including matching network.

3. A receive coil including matching network.

4. A rectifier with high frequency filtering

* Reference: Highly resonant wireless power transfer is the subject of many WiTricity US and foreign patents. Please refer to http://www.witricity.com/pages/intellectual-property.html for a partial listing of WiTricity patents.

http://www.witricity.com/pages/intellectual-property.html�


Block Diagram of the Wireless System

5

PSU

Gate Driver

Gate Driver

Feedback and Basic Control

PSU Matching

Impedance Network

+

24VDC

Source Unit

Resonant Source

Device Unit

Capture Device

Load

Un-Regulated DC output

Matching Impedance

Network

WiTricity Coils


Experimental System Setup

6

eGaN FETs RF connection

Device Board

Source Coil

Source Board

Coil Feedback

Device Coil

25m

m

RF connection

50mm


Source Board of the Wireless System

7

Coil Voltage Feedback

Ext. Osc.

Control Supply

Main Supply

Coil Connection

eGaN FET Circuit

MOSFET Circuit

eGaN FET Heat-Sink

MOSFET Heat-Sink

eGaN

MOSFET


Capture Board of the Wireless System

8

Kelvin Shunt

Voltage

Coil Connection

Kelvin Output Voltage

Output

* Ammeter connection

* Remove Shunt before using Ammeter


Typical Operating Waveforms

9

Source Coil Input Current

Device Coil Output

Lower Gate

Switch-Node

0

0

22 V input, 6.639 MHz, 23.6 Ω load (15 W)


Efficiency as function of Load Power

10

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


Thermal Performance of the Wireless System

11

28ºC ambient, No forced air cooling, 20 V input, 6.639 MHz, 23.6 Ω load (12.5 W)


Loss Breakdown Considerations

12

FET: • Conduction • Switching • Gate Rectifier: • Conduction losses • Capacitive losses Coil: • Conduction losses (skin and proximity effects)


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

eGaN FET MOSFET Ind. Coil Rectifier

Power [W] Power Loss Break Down 22 V supply, 15 W load

FET Cond. FET SW. Gate Driver Pri. Coil Sec. Coil Rect. Cond. Rect. Cap.

Loss Breakdown of the Wireless System

13

87.3% 93.6% 82.9% 70.4% Efficiency:

eGaN FET System

78.8%

MOSFET System

66.1%


High Efficiency Class-E Wireless Power using eGaN FETs

14

• Tight coupling between source and receive coils • Used EPC1010 • Reported 26.8 W output at 93.6% Drain efficiency

“A 25.6 W 13.56 MHz Wireless Power Transfer System with a 94% Efficiency GaN Class-E Power Amplifier”

W. Chen, R. A. Chinga, S. Yoshida, J. Lin, C. Chen, W. Lo IEEE International Microwave Symposium Digest (MTT) Conference, 17-22 June 2012 Page(s): 1 - 3

RRFload

+ VDD

QRF

C1

Zs/p1

C2 L2

L1

eGaN FET


Current-Mode Class-D eGaN FET RF Source

15

RRFload

+ VSupply

CSupplyACblock

LSuppluACblock1

CoutDCblock2

LoutMatch

QRF1

CoutDCblock1

LSuppluACblock2

QRF2

“Enhancement Mode GaN (eGaN) FETs for On-Coil MRI Transmit Amplifiers”, M. Twieg, M. J. Riffe, N. Gudino, M. A. Griswold, International Society for Magnetic Resonance in Medicine 21st Annual Meeting, April 2013

EPC2012x2

2A rms into 3 turn RF coil 87% Drain efficiency at 123.5 MHz Pout = 18 W

VDS_QRF1 VDS_QRF2

IRFload


Conclusions

16

High Frequency (> 6.78 MHz) Class-D/CMD/E

Wireless Energy Transfer System enabled using

eGaN FETs.

• Low Losses

• Small Size

• Support circuitry available (Texas Instruments

LM5113/4 gate drivers)

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

The end of the road for silicon…..

is the beginning of

the eGaN FET journey!

egan® fets enable low power high frequency wireless energy

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