Justin D. Moses

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Modern switch-mode power supply (SMPS) applications have embraced the benefits realized through the use of gallium nitride (GaN) HEMT technology as it allows switching speeds to increase drastically with respect to silicon parts. Since GaN HEMT devices are a relatively new technology in the power electronics realm, the manufacturing processes have not been(More)
Transformer loss, comprised of core loss and winding loss, is a critical part in the LLC resonant converter loss. Different winding structures lead to different winding losses and winding capacitances. High winding capacitance will impact the design of the LLC resonant converter. The reason is that high winding capacitance means high winding charge, which(More)
The energy efficiency of typical data centers is less than 50% because more than half of the power is consumed during power conversion, distribution, cooling, etc. In this paper, a combination of two approaches to improve power supply efficiency is implemented and experimentally verified. One approach uses a high voltage DC architecture, designed to reduce(More)
In designing high efficiency, large step down buck converters, the power semiconductors contribute a significant loss mechanism through switching losses. Minimizing these losses can be achieved by running at lower frequencies, decreasing the actual switching time, or performing soft switching. However, soft switching converters introduce extra components,(More)
A 12-1 V Gallium Nitride based POL converter demonstrates over 96% efficiency and under 4 ns switching time. This is accomplished through a layout technique that does not require costly microvias but still minimizes parasitic inductance to support fast switching. A single-sided synchronous buck converter phase operates up to 30 A in a 5.6 cm<sup>2</sup>(More)
The impact of parallel GaN HEMTs on efficiency of a non-isolated point of load (POL) converter is investigated. The test results indicate how many parallel GaN HEMTs should be used to achieve maximum efficiency based on load current. Loss calculations and simulations provided initial direction, and ten POL converters were tested-only varying the number of(More)
The Very-high-resolution Advanced ULtraviolet Telescope (VAULT) experiment was successfully launched on 7 May 1999 on a Black Brant sounding rocket vehicle from White Sands Missile Range. The instrument consists of a 30 cm UV diffraction limited telescope followed by a two-grating, zero-dispersion spectroheliograph tuned to isolate the solar Lα emission(More)
We review the history of ultraviolet and extreme ultraviolet spectroscopy with a specific focus on such activities at the Naval Research Laboratory and on studies of the extended solar corona and solar-wind source regions. We describe the problem of forecasting solar energetic particle events and discuss an observational technique designed to solve this(More)
As transistors rapidly move to smaller packages, reliable prototyping becomes increasingly difficult. Ideally, high accuracy placement machines are preferred for device placement but are not practical for low-volume production. Here, a novel manual assembly process is applied to the 400 &#x03BC;m pitch EPC GaN FETs that has resulted in near 100% yield and(More)
With the growing popularity of GaN HEMTs, the reliability of the transistors after prolonged exposure and use at high temperatures is of increasing importance. Previous work has shown that GaN FETs can operate at temperatures higher greater than 500&#x00B0;C for short amounts of time, but need to be tested at rated operating temperatures. In order to(More)
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