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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
Avogy Vertical GaN FET
IR, Fujitsu/Transphorm
Depletion GaN HEMT
Panasonic GIT
EPC eGaN FET
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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
D
GaN
HEMT
Low
Voltage
Si FET
G
SK
S
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GaN: First Generation 600 V Cascode
Best SuperJunction Available
•
•
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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)
CoolMOS is a registered trademark of Infineon Corp. FSMesh is a registered Trademark of ST Microelectronics Corp.
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Comparing Qoss of GaN vs SuperJunction
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
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Why GaN Cascode - Summary
•
Outstanding body diode performance
•
•
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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
•
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5-10X lower gate driver power loss
Bidirectional conduction (sync. rect. capable)
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Traditional Boost PFC Topology
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
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Qoss Stored Energy versus Vds
40
35
IPW60R045CP
25.7µJ @ 400V
Stored Energy (µJ)
30
25
IPW65R045C7
18.6µJ @ 400V
20
15
50mΩ GaN Cascode
17.1µJ @ 400V
10
5
0
0
100
200
300
Vds (Volts)
400
Company Confidential
500
600
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Synchronous Bridgeless Boost Topology
High Frequency
Half-Bridge
Q1
60Hz
Polarity
Switch
Q3
DC
Bus
AC
LINE
EMI
Filter
Q2
Q4
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600 V Device Trr Performance Comparison
GaN Qrr independent of temperature
shunt
coaxial
DUT
iS
L
vS
Switching
FET
Pulse
iD
iL
+
DC
Bus
–
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Synchronous Bridgeless Boost Demo Board
GaN
Cascode
Switches
Driver
IC
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Synchronous Bridgeless Boost Performance
η
Output Power (W)
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ZVS Half Bridge Building Block
Input Caps
Output
Caps
Gate
Driver
RF Inductor
Q1
Vout
GaN Cascode
Switches
+
Vin
-
Q2
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Half-Bridge Voltage and Current @ 3.3 MHz
+6 A
Inductor Current
+4 A
+2 A
400 V
0A
300 V
-2 A
200 V
100 V
Switch Voltage
0V
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Performance of Half-Bridge Boost
Boost Converter Efficiency, No Heatsink, 400 V Out
100%
High Efficiency Possible by Frequency Control
98%
96%
Efficiency
94%
3.3 MHz
92%
2.5 MHz
90%
88%
86%
84%
82%
80%
0
100
200
300
400
500
Po [W]
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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
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LLC Resonant DC-DC Power Supply
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Nonlinear Qoss Causes Time Delay
500
450
3.3X longer charge-up time
400
350
Volts
300
250
200
150
Qoss Measurement Circuit
100
50
0
0
10
20
30
40
50
60
70
80
Time (µs)
90
100
Company Confidential
110
120
130
140
150
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LLC – GaN vs SuperJunction @ 1 MHz
•
GaN losses are significantly lower than SuperJunction
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%
GaN
IPP65R150CFD2
Vds
icentertap
iprim
Vgs
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Conducted EMI Benefits of GaN
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•
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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
GaN IR 20 kHz
IGBT 20 kHz Rg = 2 Ω
45 dB Improvement at 1.5 MHz
Test data courtesy of Schneider Electronic ,Technology & Strategy Department
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The Future?
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Integration – IPMs
Multiphase Architectures
Short-circuit capability
900 V GaN
VHF Optimized 30 MHz+
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