Cryogenic rds(on) of a GaN power transistor at high currents

The dramatic reduction in the on-state resistance of Gallium Nitride (GaN) HEMTs at cryogenic temperatures can be exploited to reduce conduction losses in power converters. In this paper, we present a low-cost and easily implementable methodology for the characterisation of the on-state resistance of power transistors below room temperature. Experimental results for a 650 V 30 A GaN HEMT are compared to measurements in the existing literature. In addition, the variation of the onstate resistance to drain-source current at currents in excess of the datasheet rating of the transistor is examined. Thermal equilibrium is obtained with continuous high currents. The conditions for the onset of thermal instability are analysed and compared to experimental results. Thermally stable operation at three times the room-temperature rating of the transistor is demonstrated at cryogenic temperatures

A comparison of the hard-switching performance of 650V power transistors with calorimetric verification

We compare the switching losses of four equivalent silicon and wide-bandgap 650V power transistors operated in a hard-switched half-bridge configuration, switching 400V at 40A. Each transistor is mounted on an identical PCB and driven by a gate drive circuit matched to its requirements. Switching speed is maximised by a PCB design featuring very low parasitic inductance and the use of zero external gate resistance (where possible). Switching losses are measured electrically using a Double Pulse Test (DPT) method. However, high-bandwidth electrical measurements are prone to error and so we assess the gain accuracy, offset accuracy, and the bandwidth requirements of the DPT measurements, and then verify the DPT results by calorimetry. The electrical and calorimetric measurements are shown to agree to within 5%. Comprehensive plots of gate-source voltage, drain-source voltage, and source current are provided for all transistors over a junction temperature range of 50-150°C. The ratio of the total half-bridge switching losses is 1:3.2:14:31 for the GaN HEMT, SiC MOSFET, Si IGBT, and Si superjunction MOSFET, respectively

Fast switching of high current WBG power devices

Wide-band-gap power devices, such as Gallium Nitride High Electron Mobility Transistors and Silicon Carbide Field-effect Transistors, offer impressively fast switching performance compared to their traditional Silicon counterparts. However, Si designs have not stood still, and new generations of these devices offer good switching performance at competitive prices. This paper makes a comparative study between a representative selection of 650 V SiC MOSFET, GaN HEMT, and Si IGBT power switching devices. The devices are switched as fast as possible using a low inductance PCB design and no external gate resistors. A mathematical analysis of switching energy losses is presented, along with SPICE simulation and experimental test results for comparison

Toward community standards in the quest for orthologs

The identification of orthologs—genes pairs descended from a common ancestor through speciation, rather than duplication—has emerged as an essential component of many bioinformatics applications, ranging from the annotation of new genomes to experimental target prioritization. Yet, the development and application of orthology inference methods is hampered by the lack of consensus on source proteomes, file formats and benchmarks. The second ‘Quest for Orthologs' meeting brought together stakeholders from various communities to address these challenges. We report on achievements and outcomes of this meeting, focusing on topics of particular relevance to the research community at large. The Quest for Orthologs consortium is an open community that welcomes contributions from all researchers interested in orthology research and applications. Contact: [email protected]

A Comparison of the Hard-Switching Performance of 650 V Power Transistors With Calorimetric Verification

We compare the switching losses of four equivalent silicon and wide-bandgap 650 V power transistors operated in a hard-switched half-bridge configuration, switching 400 V at 40 A. Each transistor is mounted on an identical PCB and driven by a gate drive circuit matched to its requirements. Switching speed is maximised by a PCB design featuring very low parasitic inductance and the use of zero external gate resistance (where possible). Switching losses are measured electrically using a Double Pulse Test (DPT) method. However, high-bandwidth electrical measurements are prone to error and so we assess the gain accuracy, offset accuracy, and the bandwidth requirements of the DPT measurements, and then verify the DPT results by calorimetry. The electrical and calorimetric measurements are shown to agree to within 5%. Comprehensive plots of gate-source voltage, drain-source voltage, and source current are provided for all transistors over a junction temperature range of 50–150°C. The ratio of the total half-bridge switching losses is 1:3.2:14:31 for the GaN HEMT, SiC MOSFET, Si IGBT, and Si superjunction MOSFET, respectively

The Challenges of Linking Ecosystem Services to Biodiversity:Lessons from a Large-Scale Freshwater Study

We explore some of the key challenges and opportunities that lie in assessing the role of freshwater biodiversity in sustaining ecosystem services, using the recent large interdisciplinary NERC-DURESS project (www.nerc-DURESS.org) as an exemplar case study of wider issues. The conceptual and methodological challenges raised are identified, explored and a range of methods are proposed to quantify how freshwater ecoservices, such as fish production or water quality regulation, depend on river organisms, and how we might identify biodiversity thresholds under which a service is likely to be compromised. We conclude that interdisciplinary, large scale, in situ approaches like these are needed to (i) fully understand how river biodiversity sustains ecosystem services; (ii) help evaluate if, where, and how the ecosystem approach can benefit long-term resource management and (iii) maximise impacts on policy, practice and decision making, which can be especially effective where strong ‘co-production’ partnerships with a broad range of stakeholders are developed and nurtured from a project's outset