www.epc-co.com EPC - The Leader in eGaN® FETs PCIM Asia 2014 1 1

The eGaN® FET

Journey Continues

Performance Evaluation of eGaN® FETs in Low Power High

Frequency Class E Wireless Energy Converter

Michael de Rooij

Efficient Power Conversion Corporation

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Agenda

• Why GaN?

• Topologies Evaluated

• Wireless Power Figure of Merit

• Device Comparison

• Experimental Verification

• Summary

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Why eGaN FETs for Wireless

• Low CISS and COSS

• Low RDS(on) for equal voltage rating

• Low profile

• Gate Drivers available:

• LM5113 • LM5114 • UCC27611

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Coil Simplification

Lsrc Ldev

Cdevs

RDCload

Cout

Ldevs

Cdevp Zload

Coil Set

Simplified representation of coil-set for easy comparison between topologies

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Single Ended Class E

VDD

Ideal Waveforms

VDS ID

time

3.56 x VDD

V / I

50%

Q1

+

Csh

Cs Le LRFck

Zload

• Switch voltage rating ≥ 3.56·Supply (VDD).

• COSS “absorbed” into matching network.

• Susceptible to load variation - high FET losses.

• Coil voltage ≈ 0.707·VDD [VRMS].

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Class E Topology Variations

VDD

Q1

+

Csh

Cs Le LRFck

Zload

Cam1

Lam

Cam2

Filter Network

Q1

+

Csh1

Cs Le LRFck Zload

Q2

Csh2

LRFck

• Impedance matching filter for load variations.

• Differential mode:

• Increases output power.

• Reduced voltage harmonics.

• Coil voltage ≈ 1.414·VDD [VRMS].

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ZVS Class D

+ VDD

Cs Q2

Q1 Zload

LZVS

CZVS

V / I

VDS ID

time

VDD

50%

Ideal Waveforms ZVS tank

• Switch voltage rating = Supply (VDD).

• COSS voltage is transitioned by the ZVS tank .

• ZVS tank circuit does not carry load current.

• Coil voltage = ½·VDD [VRMS].

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Class E Analysis Comparison

2

6

10

14

18

80

85

90

95

100

0 10 20 30 40 50

Ou

tpu

t P

ow

er

[W]

Effi

cie

ncy

[%

]

DC Load Resistance [Ω]

eGaN FET Eff.

MOSFET Eff.

eGaN FET Pout

MOSFET Pout

EPC2012

MOSFET 95.6%

98.5 %

85.2%

94.4%

Peak Power Device losses = 279 mW No Heat-Sink Required

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Class E Device Comparison

FoMWPT [nC·mΩ]

0

200

400

600

800

1000

1200

1400

1600

EP

C2012

MO

SF

ET

SE-CE

SE-CE

GDGDS(on)WPT QQRFOM

100

200

300

400

500

600

700

800

900

1000

0 100 200 300 400 500 600

Devic

e P

ow

er

[mW

]

RDS(on) [mΩ]

MOSFET

eGaN FET

Gate Power

dominant

Conduction Loss

dominant

Lowest Power Dissipation

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Class E Experimental Setup

Gate Driver LM5113

eGaN® FET EPC2012

Coil Connection RF Choke LRFck

Extra Inductor Le

Shunt Capacitor Csh

Gate Driver

MOSFET

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ZVS Class D Experimental Setup

Gate Driver

ZVS Capacitor CZVS

eGaN FET EPC8009

Coil Connection

ZVS Inductor LZVS

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50

55

60

65

70

75

80

85

0 5 10 15 20 25 30 35 40

Eff

icie

ncy [

%]

Output Power [W]

50

55

60

65

70

75

80

85

0 5 10 15 20 25 30 35 40

Eff

icie

ncy [

%]

Output Power [W]

Peak Performance Results

Fixed DC Load Resistance

η EPC8009 ZVS-CD

η MOSFET 2 ZVS-CD

η MOSFET 3 ZVS-CD

η EPC2012 SE-CE

η MOSFET 1 SE-CE

Variable Supply Voltage

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64

68

72

76

80

84

10 15 20 25 30 35 40 45 50

Eff

icie

ncy [

%]

DC Load Resistance [Ω]

64

68

72

76

80

84

10 15 20 25 30 35 40 45 50

Eff

icie

ncy [

%]

DC Load Resistance [Ω]

Load Variation Results

η EPC8009 ZVS-CD

η MOSFET 2 ZVS-CD

η MOSFET 3 ZVS-CD η EPC2012 SE-CE

η MOSFET 1 SE-CE

Coil becomes Inductive

Coil becomes Capacitive

Fixed Supply Voltage

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Load Regulation Results

64

68

72

76

80

84

10 15 20 25 30 35 40 45 50

Eff

icie

ncy [

%]

DC Load Resistance [Ω]

64

68

72

76

80

84

10 15 20 25 30 35 40 45 50

Eff

icie

ncy [

%]

DC Load Resistance [Ω]

η EPC8009 ZVS-CD

η MOSFET 2 ZVS-CD

η MOSFET 3 ZVS-CD

η EPC2012 SE-CE

η MOSFET 1 SE-CE Design Load

Peak Coil η

Fixed Load Voltage

Coil becomes Inductive

Coil becomes Capacitive

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Class E Thermal Performance

MOSFET UCC27511 eGaN FET LM5113

Pout = 29 W in 20.2 Ω

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Class D Thermal Performance

EPC8009 LM5113 MOSFET 2 LM5113 MOSFET 3 LM5107

Pout = 17 W in 23.6 Ω Pout = 36 W in 23.6 Ω

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Summary

eGaN® FETs are disruptive in wireless energy:

• Enable wireless power

• Yield higher efficiency than MOSFETs

• Can operate at 6.78 MHz and 13.56 MHz

• Are low profile

• Easy to use

• Drive new topologies e.g. ZVS Class D

• Growing support e.g. gate drivers and products use them.

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The end of the road

for silicon…..

is the beginning of

the eGaN FET

journey!