Paralleling of Gallium Nitride transistors for 48V high ...
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Nikola Boskovic, MSc Prof. ir. Korneel Wijnands Dr. ir. Maurice Roes Prof. dr. Elena Lomonova June 14 th 2018 Paralleling of Gallium Nitride transistors for 48V high current automotive applications
Transcript of Paralleling of Gallium Nitride transistors for 48V high ...
Nikola Boskovic, MSc
Prof. ir. Korneel Wijnands
Dr. ir. Maurice Roes
Prof. dr. Elena Lomonova June 14th 2018
Paralleling of Gallium Nitride transistors for
48V high current automotive applications
Outline
• Introduction
• Motivation
• Approach
• Measurement results
• Conclusion
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Application – Mild hybrid system2
• Specificationso 48 V
o 500 Apeak
• Key performanceso Cost [€/kW]
o Efficiency [%]
battery pack48 V
dc-ac converter
electrical motor
combustion engine
Source: Federalmogul.com
Power converter topology
• Standard 3-phase 2-level inverter
• No transistors available for high currents (500 A)
• Type of low voltage transistors? Si MOSFET or GaN.
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– solution: PARALLELING
Gallium Nitride transistors
• Lower losses compared to silicon devices
• Extremely fast switching
• Paralleling GaN transistors?
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Source: EPC white paper
10 V/div
2 ns/div
80 V/ns
GaN transistor(100V, 90A)6,05 mm x 2,3 mm
• Static current sharing (DC)
• Dynamic current sharing(Transient)
Current sharing5
Static current sharing
• Steady state
• Resistance RDS(ON)
• Negative feedback
• Self-balancing
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• Transients
• Transistor parameters
• Threshold voltage VGS(th)
• Positive feedback
• Avalanche effect
Dynamic current sharing7
Dynamic current sharing
• Asymmetric layout – unavoidable when paralleling more then two transistors
o Circuit parameters – mainly parasitic inductances
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Power loopGate loop
Approach of modelling
• Extraction of the parameters values
• Simulation
• Measurements
• Verifying
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• Wide frequency range
Model of passive components10
Si MOSFET
GaN
Relevant for:
• Models for needed frequency (GHz) range don’t exist!
11Models
40 Hz 110 MHz55 MHz 110 MHz
• Five slightly different circuits
• Most important two are:
Boost Converter
Transistor is in BGA package, 0.9 mm x 0.9 mm
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Boost Converter13
Prototype14
Measurements15
~1 ns (1 GHz)
16Conclusions
• Gallium Nitride transistors are beneficial in terms of lower losses.
• Measurement uncertainty – 1 GHz oscillation!
• Impossible to verify parameters.
• Prediction of current for very high number of paralleled transistors.
• Too many uncertainties for the generalized conclusions.
• Different route should be taken.
Alternative approach
• Paralleling of half bridges by inductances
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Thank you for your attention!
Nikola Boskovic
Electromechanics & Power Electronics (EPE) group
