Wide Band-Gap (SiC and GaN) Devices Characteristics and ... · Richard McMahon University of...
Transcript of Wide Band-Gap (SiC and GaN) Devices Characteristics and ... · Richard McMahon University of...
Richard McMahon University of Cambridge
Wide Band-Gap (SiC and GaN)
Devices – Characteristics and
Applications
Wide band-gap power devices
SiC :
GaN :
• MOSFET
• JFET
• Schottky Diodes
Unipolar
• BJT?
Bipolar
• Enhancement mode
• Depletion mode (in cascode) FET
• Schottky diodes Diode
GaN power devices
EPC :30-450 V
E-mode HEMTs (normally-off)
(commercial)
Infineon (IR)
600 V HEMTs
(Cascode ) +
Panasonic (normally-off
GIT)
Transphorm : 600 V HEMTs
(Cascode)
Gan Systems : 100 & 650 V HEMTs
(Cascode)
DC to DC converters for automotive 48 V / 12 V
systems using GaN HEMTs
• Typical power density 1.5
kW/l - 2 kg
• Reduce mass and volume
• Increase efficiency
Low voltage semiconductor
technologies
Si MOSFET GaN FET
Fast switching
efficiency
Temperature
Cost
Easy to use /
Experience
Switching Considerations
Low threshold voltage issue (low-side turn-off)
Negative gate drive in half
bridges may be needed
Increases reverse conduction
voltage drop
Dead time must be kept
extremely short
Limits choice of driver IC
Converter development
August 2013 January 2015
Max power 100 W 420 W
Efficiency 88 % – 90 % 93 % to 94 %
Robustness dV/dt Problems Solved
Active Temperature
monitoring
No Yes
Version 1 3
Key findings to date
• GaN offers benefits for DC-DC converters
• GaN matches silicon losses at 10 to 20 times the
switching speed
• Power density however will be limited by cooling
constraints.
High voltage (ca. 600 V) opportunities for GaN
• Data centres
• Wireless charging
• Electric vehicles
• Drives
• Power factor correction
• Point of load dc-dc converters
• AC voltage regulators
• Solar inverters?
GaN based half-bridge
Transphorm 600 V devices
Design issues with E-mode devices
(low-side turn-off)
• Tight gate threshold margin
• Accurate gate supply voltage
• Stringent dead time requirements
• dv/dt undesired turn-on
• Ringing increases for fr >1MHz
• Parasitic and loop inductances
HEMT Cascode structure
(Infineon,GaN Systems & Transphorm)
Switching waveforms turn-on and turn-off
• Switching node voltage: 400 V
• Gate voltage: 5 V (yellow trace)
• Switching frequency 50 kHz
• Output rise time: 3 ns, fall time: 4 ns
(standard gate drive with tighter
layout & forced commutation )
First design rise time : 31ns and fall time : 25ns
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Commercial SiC devices
Schottky Diodes:
Rohm
Cree
GeneSiC
STMicroelectronics
United SiC
Infineon
Transistors:
Rohm
Cree
GeneSiC
STMicroelectronics
United SiC
Power Modules:
Cree
Mitsubishi
Semikron
Rohm
SiC applications
Distribution networks
Drives for automotive
Aerospace
High temperatures
Power converters for wind, solar etc.
HVDC
Breakdown Voltage
On State
Switching – Dependence of Turn off
Energy loss with temperature
Switching current = 20 A
High temperature tests - 110ºC
heatsink/hotplate
Half-bridge inverter (2 kW)
Step-up converter
Measurements on a boost converter with a
SiC JFET and a Si CoolMOS.
800 W and100 kHz switching frequency
SiC JFET
Si CoolMos
SiC Cascode
SiC MOSFET and JFET
SiC MOSFET
Cascode
SiC MOSFET Cascode
Challenges
Circuit layout
EMC
Thermal design
Packaging
Device reliability
Device availability
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Conclusions
• GaN & SiC devices are emerging
• GaN looks good up to 600 V
• SiC offers advantages at high voltage
• Both are relatively expensive – cost must be justified
• Silicon design techniques are not necessarily
transferable
• Reliability and supply remain concerns
GaN based half-bridge
(Transphorm 600 V devices)
Switching waveforms(turn-on&off)
Switching node voltage: 400 V
Gate Voltage: 5 V
Switching frequency 50 kHz
Rise time: 31 ns, fall time: 25 ns
Transfer characteristic of EPC 100 V GaN FET
EPC 2022 E-GaN (100 V)
HEMT Cascode structure
(Infineon,GaN Systems &Transphorm)
GaN power devices
EPC :30-450 V
HEMTs (commercial)
Infineon (IR) :
600 V HEMTs
Panasonic :
650 V GITs
Transphorm : 600 V HEMTs
and SBDs
Gan Systems : 100 V HEMTs
Gan Systems : 650 V HEMTs
GaN HEMTs are lateral devices
E-GaN HEMT (EPC)
Cascode characteristics
Courtesy : Transphorm TPH3002LD 600 V
Issues with cascodes
• Overshoot during turn-on
• Upper side gate ringing
• Voltage mismatch
• Parasitic inductances