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High Efficiency Power Converters Using Gallium Nitride (GaN) Transistors Authors: Mark Nakmali, Yutian Cui, Dr. Leon Tolbert Affiliation: University of Oklahoma, University of Tennessee Description The aim of this project is to show the switching and efficiency capabilities of Gallium Nitride transistors through simulation and physical testing. Material Properties GaN Material Properties The properties of GaN outweigh silicon and silicon carbide in terms of high voltage operation and high frequency switching. This allows the stoppage of high voltages and allows switching times. With higher switching frequencies, the other passive components in the circuit can be smaller. Cross-sectional Diagram Of An eGaN Field Effect Transistor Operation And Efficiency Capacitor And Inductor Size With Respect To Frequency Typical Losses In A Transistor GaN is grown on a silicon or silicon carbide substrate using AlGaN as a buffer layer. AlGaN also creates the 2-dimensional electron gas (2DEG) which is highly conductive, allowing fast switching and low resistance. It is because of the 2DEG that the switching and conduction losses are minimized. Efficiency And Switching Period Testing The performances of GaN (green) and silicon (blue) converters are tested with varying input voltages (3-6V), switching frequencies (200kHz dark, 600kHz medium, and 1MHz dark) and output powers (12-36W). Their on-transient waveforms are compared to each other and then to actual measurements of a physical circuit. As seen above, the efficiency goes down with the increase in voltage, frequency and output power. In all cases, GaN outperforms silicon. As seen below, the switching period of silicon is about thirteen times larger than GaN. When compared to the real switching speed of GaN, the simulation is about 1.3ns too fast, but in either case the considerable difference in switching speed when compared to silicon is still valid. Silicon GaN (simulated) GaN (real) Applications With high stopping voltages and high frequencies, Gallium Nitride has the potential to make power converters that are more efficient and smaller, as well as the ability to provide faster and more reliable data transfer than the current products that we have today. SPONSORS: This work was supported primarily by the Engineering Research Center Program of the National Science Foundation and the Department of Energy under NSF Award Number EEC-1041877 and the CURENT Industry Partnership Program.