Impact of Precision Metrology on the Evaluation of Advanced eGaN FET Power Converters

Benjamin Kromann, Rushi Patel

Abstract


An advanced semiconductor device applications research program at Mississippi State University is exploring metrology methods appropriate for high-efficiency, high-frequency power conditioning systems. In the evaluation of any electronic device, the measurement methods used will have an impact on the reliability of the collected data. This becomes all the more relevant when dealing with high-efficiency, high-frequency devices. The specific topic of this paper details the application and performance evaluation of an enhancement-mode Gallium Nitride field-effect transistor (eGaN FET) in a buck converter operating at several switching frequencies extending into the megahertz band. Advancements in wide band-gap power semiconductor devices (of which the eGaN FET is one) have resulted in dramatic increases in efficiency and system bandwidths as compared to their silicon counterparts. The former advancement leads to increasingly low power loss, which is harder to accurately measure and quantify. The later advancement has pushed operating frequencies into the megahertz spectrum. This means that the time period between high and low levels is extremely short, resulting in fewer data points per period. Conventional metrology methods in this application may result in measurement errors brought about by electromagnetic interference, lack of precision and inherent system losses. For power and efficiency measurements, a synthetic four-point measurement is adopted using four 6.5 digit multi-meters. Kelvin connected voltage measurements are made at the input and output terminals of the system. Similarly, precision shunt measurements capture DC input and output currents. Additionally, a giga-sample capable oscilloscope captures any ripple voltages and currents using compensated high impedance 10x attenuated probes. True RMS values of all voltage and current measurements are calculated in post-process computations. These results are compared against data captured using simpler yet less precise conventional means to fully document the effect that appropriate metrology has on the evaluation of devices of this nature.


Keywords


Power Electronics, Gallium Nitride Transistor, Precision Metrology

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