High Efficiency Power Converters Using Gallium Nitride Transistors Marl Nakmali Mentors: Dr. Leon Tolbert Yutian Cui

Room for Improvement 5-2

Material Properties and Limitations 5-3

Size Minimization 5-4

Data Sheet Comparison 5-5 Gallium NitrideSilicon V DS [V] 30 R DS(on) [Ω] I D [A] 6042 V GS [V] -4<V GS <6-20<V GS <20 Size [mm 2 ]

But what about the price? 5-6

How it works 5-7

The Buck Converter 5-8

The Buck Converter 5-9

The Buck Converter 5-10

Loss Analysis 5-11 These losses are: Switching Loss Conduction Loss

Results 5-12

Efficiency Graphs 5-13 GaN:Silicon: 200kHz 600kHz 1MHz 200kHz 600kHz 1MHz

Efficiency Graphs 5-14 GaN:Silicon: 200kHz 600kHz 1MHz 200kHz 600kHz 1MHz

Efficiency Graphs 5-15 GaN:Silicon: 200kHz 600kHz 1MHz 200kHz 600kHz 1MHz

Efficiency Graphs 5-16 GaN:Silicon: 200kHz 600kHz 1MHz 200kHz 600kHz 1MHz

Silicon Switching Period 5-17

GaN Switching Period 5-18

GaN Physical Switching Period 5-19

Conclusion 5-20 Gallium Nitride has: Desirable material properties in a transistor. High frequency, allowing smaller circuits. Development into becoming cheaper. Applications: Smaller, more efficient power converters. Faster, more reliable data transfer.

Acknowledgements This work was supported primarily by the ERC Program of the National Science Foundation and DOE under NSF Award Number EEC Other US government and industrial sponsors of CURENT research are also gratefully acknowledged. 21

Questions and Answers 22

5-23

Power Converters A power converter converts electrical energy from: AC to AC AC to DC DC to AC DC to DC Types of DC to DC converters: Step Down (Buck) Converters Step Up (Boost) Converters

Result Analysis Put in efficiency of simulation versus efficiency of measured values Compare these efficiencies with data from Silicon  OptiMOS  directFET

What is existing technology? Silicon MOSFETs Currently the industry is mostly reliant on Silicon MOSFETs It has a cheap price Its manufacturing processes are matured It is already in enhancement mode, which is easier and safer GaN MOSFETs GaN MOSFETs are not as cheap Its manufacturing processes are not yet mature It is not inherently in enhancement mode and steps must be taken for it to be in that mode

Switching Loss 5-27

Conduction Loss 5-28

Gate Loss 5-29