Student: Rushi PatelFaculty Advisor: Dr. Daniel Costinett

Final Presentation7/14/2016

University of Tennessee

Loss Model for Gallium Nitride DC-DC Buck Converter

Applications

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•Mobile phone charger

•Electric vehicles

•Solar energy

•Wind energy

•Loss model canbe use for different topologies of converters

Background

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Type Silicon Carbide

Vin 12V

Vout 1.2V

fsw 300kHz

Vdd 12V

L 1uH

DCR 1mΩ

Type Gallium Nitride

Vin 12V

Vout 1.2V

fsw 1MHz

Vdd 10V

L 280nH

DCR .29mΩ

Compare

Objective

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•Compare theoretical, LTspice simulation and experimental efficiency data

•Develop a theoretical and experimental loss model for 500kHz and 1MHz

• Find the constant variables that causes difference in theoretical and experimental loss model to reduce the iterative process of hardware prototyping

Method

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• eGaN DC-DC buck converter

• Take measurements at the input and

output terminals for currents and voltages

• Plot efficiency vs output current graph to

compare with theoretical data

Experimental

EPC 9036 Development Board

Method

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Theoretical

•To evaluate different losses, input and output

power using datasheets for transistors, inductor

and capacitor.

•Plot efficiency vs output current graph to

compare with experimental data

Different Types of Losses• Switching loss on high side

• Conduction loss on high side and low side

• Inductor loss

• Capacitor loss

• Gate drive loss

• Dead-time loss

• Output capacitance loss on high side and low side

• Core loss

Method

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Simulation

•Model all the parts with its

parasitic components

• Plot efficiency vs output

current graph to verify

experimental data

Results

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•At lower current, experimental efficiency is higher than theoretical efficiency

Results

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•Efficiency is about 90% at higher current and higher frequency for eGaN buck converter compare to silicon carbide buck converter.

Results

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• Approximately at 10A, the loss difference approaches 0 watts

Results

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• Second order Polynomial fits best in both cases

Results

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• All the equations of second order:

• Conduction loss on high side: Rds_on_HS*Irms_HS^2

• Conduction loss on low side: Rds_on_LS*Irms_LS^2

• Inductor loss : Irms_L^2*DCR

• Capacitor loss: Iripple^2*ESR

Results

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• Rds_on_LS : Measured between 5mΩ and 7mΩ. Theoretical: 6mΩ

• Rds_on_HS: Measured between 1mΩ and 2.2mΩ. Theoretical: 1.5mΩ

• DCR: Measured between 1mΩ and 3mΩ. Theoretical: .29mΩ

• ESR: Requires precise measurement. Theoretical: 2mΩ

Results

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• DCR value for theoretical data changed from .29mΩ to 2mΩ

Results

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• DCR value for theoretical data changed from .29mΩ to 2mΩ

Conclusion/Future work

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• DCR in the inductor causes the difference between theoretical and experimental loss model

•Different frequencies give loss model of same trends

• Complex experiments can be done to get precise measurements for future work

• Analyze the initial difference between experimental and theoretical efficiency

• Create new designs with different inductor and capacitor value to compare

Acknowledgements

This work was supported primarily by the ERC Program of the National Science Foundation and DOE under NSF Award Number EEC-1041877.

Other US government and industrial sponsors of CURENT research are also gratefully acknowledged.

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Questions and Answers

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