The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Harriet T Daviesmostert - One of the best experts on this subject based on the ideXlab platform.
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heading for the hills risk avoidance drives den site selection in african wild dogs
PLOS ONE, 2014Co-Authors: Craig R Jackson, John R Power, Rosemary J Groom, Emmanuel H Masenga, Ernest E Mjingo, Robert D Fyumagwa, Eivin Roskaft, Harriet T DaviesmostertAbstract:Compared to their main competitors, African wild dogs (Lycaon pictus) have inferior competitive abilities and interspecific competition is a serious fitness-limiting factor. Lions (Panthera leo) are the dominant large carnivore in African savannah ecosystems and wild dogs avoid them both spatially and temporally. Wild dog young are particularly vulnerable and suffer high rates of mortality from lions. Since lions do not utilize all parts of the landscape with an equal intensity, spatial variation in lion densities can be exploited by wild dogs both during their general ranging behaviour, but more specifically when they are confined to a den with vulnerable young. Since patches of rugged terrain are associated with lower lion densities, we hypothesized that these comparatively safe habitats should be selected by wild dogs for denning. We investigated the relationship between the distribution of 100 wild dog den sites and the occurrence of rugged terrain in four wild dog populations located in Tanzania, Zimbabwe and South Africa. A terrain Ruggedness index was derived from a 90 m digital elevation model and used to map terrain Ruggedness at each site. We compared characteristics of actual and potential (random) den sites to determine how wild dogs select den sites. The distributions of wild dog dens were strongly associated with rugged terrain and wild dogs actively selected terrain that was more rugged than that available on average. The likelihood of encountering lions is reduced in these habitats, minimizing the risk to both adults and pups. Our findings have important implications for the conservation management of the species, especially when assessing habitat suitability for potential reintroductions. The simple technique used to assess terrain Ruggedness may be useful to investigate habitat suitability, and even predict highly suitable denning areas, across large landscapes.
Josef Lutz - One of the best experts on this subject based on the ideXlab platform.
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Ruggedness of 1200 v sic mps diodes
Microelectronics Reliability, 2015Co-Authors: Susanne Fichtner, Thomas Basler, Josef Lutz, Roland Rupp, Sophia Frankeser, Rolf GerlachAbstract:Abstract SiC merged-pin-Schottky (MPS) diodes possess fast switching ability combined with low losses. Compared to conventional Schottky diodes they also provide a high surge current capability making them rugged against surge current pulses of more than seventeen times the rated current for a 10 ms half-sine pulse. In this paper further aspects of device Ruggedness are presented such as the surge current capability of two diodes in parallel and the turn-off behavior at application condition and at overcurrent. It was found that the turn-off characteristics are almost independent from the applied voltage. Further, the diode could withstand turn-off from fifteen times the rated current.
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switching Ruggedness and surge current capability of diodes using the self adjusting p emitter efficiency diode concept
Iet Circuits Devices & Systems, 2014Co-Authors: Thomas Basler, Roman Baburske, Hans Joachim Schulze, Franz Josef Niedernostheide, Hanspeter Felsl, Manfred Pfaffenlehner, Frank Pfirsch, Josef LutzAbstract:The surge-current Ruggedness of free-wheeling diodes can be improved by implementing the self-adjusting p emitter efficiency diode concept (SPEED). Simulations indicate that the switching Ruggedness is reduced because of the occurrence of cathode-side filaments during reverse-recovery. Experiments confirm the weak switching performance of such a diode in comparison to a conventional diode. By implementing the controlled injection of backside holes concept cathode-side filaments can be suppressed. However, this measure is not sufficient to regain the switching Ruggedness of a conventional diode. It is also necessary to fully embed the p + -areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths at the p + p-junction and pinning of anode-side filaments. However, anode-side adjustments for improving the switching Ruggedness can reduce the benefit of the SPEED concept regarding the surge-current capability.
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some aspects on Ruggedness of sic power devices
Microelectronics Reliability, 2014Co-Authors: Josef Lutz, Roman BaburskeAbstract:Abstract This article is on effects that can destroy SiC power semiconductor devices. The failure physics in SiC devices are discussed based on the well understood effects in silicon devices. In some device properties, such as surge current, short circuit, static avalanche and dynamic avalanche, SiC has significant possible advantages compared to silicon. For cosmic ray stability, there are no unique results. Regarding thermal mechanical stress on interface materials, SiC is more challenging. The same may hold for electrical stress in passivation layers at the junction termination.
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Short-circuit Ruggedness of high-voltage IGBTs
2012 28th International Conference on Microelectronics Proceedings, 2012Co-Authors: Josef Lutz, Thomas BaslerAbstract:The IGBT can run into different short-circuit types (SC I, SC II, SC III). Especially in SC II and III, an interaction between the gate drive unit and the IGBT takes place. A self-turn-off mechanism after short-circuit turn on can occur. Parasitic elements in the connection between the IGBT and the gate unit as well as asymmetrical wiring of devices connected in parallel are of effect to the short-circuit capability. In high-voltage IGBTs, filament formation can occur at short-circuit condition. Destructive measurements with its failure patterns and short-circuit protection methods are shown.
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influence of buffer structures on static and dynamic Ruggedness of high voltage fwds
International Symposium on Power Semiconductor Devices and IC's, 2005Co-Authors: B Heinze, Hanspeter Felsl, Anton Mauder, H J Schulze, Josef LutzAbstract:It is required to design free wheeling diodes (FWDs) to be robust against static and dynamic avalanche. Therefore we investigate the effect of different buffer structures and the influence of various bulk parameters. By numerical device simulation the effect of the buffer doping, base doping and base width on the static and dynamic behaviour of FWDs is analysed. We show the promising features of well designed buffers for Ruggedness and their coherences to the static reverse characteristics.
Dieter Silber - One of the best experts on this subject based on the ideXlab platform.
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limitation of the short circuit Ruggedness of high voltage igbts
International Symposium on Power Semiconductor Devices and IC's, 2009Co-Authors: Arnost Kopta, Ulrich Schlapbach, Nando Kaminski, Munaf Rahimo, Dieter SilberAbstract:In this paper, the destruction mechanism, which limits the short-circuit capability of high voltage IGBTs utilizing N-buffer structures will be described. The failure mechanism was studied using a combination of device simulations and experimental investigations of 3.3kV, 4.5kV and 6.5kV IGBTs. It was found that the limiting short-circuit failure in these IGBTs is caused by a current filamentation mechanism, which is associated to a distortion of the electric field triggered by a positive feedback effect between the carrier drift velocities and the electric field and the resulting potential distribution in the IGBT N-base.
J N Burghartz - One of the best experts on this subject based on the ideXlab platform.
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power amplifier pae and Ruggedness optimization by second harmonic control
IEEE Journal of Solid-state Circuits, 2003Co-Authors: M Spirito, L C N De Vreede, L K Nanver, S Weber, J N BurghartzAbstract:Second-harmonic control is applied to optimize power-added efficiency (PAE) and Ruggedness of silicon power amplifiers (PAs). A differential push-pull topology is chosen because it facilitates independent fundamental load and second-harmonic control. Various amplifiers using high-Q passives for fundamental and harmonic matching have been implemented. Experiments demonstrated an increase in PAE and Ruggedness simultaneously even under high mismatch conditions. The amplifiers are operating in class-AB and are intended for use in the digital communication system (DCS) band.
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power amplifier pae and Ruggedness optimization by second harmonic control
Bipolar BiCMOS Circuits and Technology Meeting, 2002Co-Authors: M Spirito, L C N De Vreede, L K Nanver, S Weber, J N BurghartzAbstract:Optimum class-AB power amplifier (PA) operation, with maximum power added efficiency (PAE) and Ruggedness can be obtained by proper 2/sup nd/ harmonic termination at the in- and output. Implementation in a differential push-pull amplifier for DCS band yields significantly higher PAE and Ruggedness even under high mismatch conditions. Various PA implementations using novel balun structures are compared for their performance.
Thomas Basler - One of the best experts on this subject based on the ideXlab platform.
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performance and Ruggedness of 1200v sic trench mosfet
International Symposium on Power Semiconductor Devices and IC's, 2017Co-Authors: Dethard Peters, Thomas Basler, Ralf Siemieniec, Thomas Aichinger, Romain Esteve, Wolfgang Bergner, Daniel KueckAbstract:This paper describes a novel SiC trench MOSFET concept. The device is designed to balance low conduction losses with Si-IGBT like reliability. Basic features of the static and dynamic performance as well as short circuit capability of the 45mΩ/1200 V CoolSiC™ MOSFET are presented. The favorable temperature behavior of the on-state resistance combined with a low sensitivity of the switching energies to temperature simplify the design-in. Long-term gate oxide tests reveal a very low extrinsic failure rate well matching the requirements of industrial applications.
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Ruggedness of 1200 v sic mps diodes
Microelectronics Reliability, 2015Co-Authors: Susanne Fichtner, Thomas Basler, Josef Lutz, Roland Rupp, Sophia Frankeser, Rolf GerlachAbstract:Abstract SiC merged-pin-Schottky (MPS) diodes possess fast switching ability combined with low losses. Compared to conventional Schottky diodes they also provide a high surge current capability making them rugged against surge current pulses of more than seventeen times the rated current for a 10 ms half-sine pulse. In this paper further aspects of device Ruggedness are presented such as the surge current capability of two diodes in parallel and the turn-off behavior at application condition and at overcurrent. It was found that the turn-off characteristics are almost independent from the applied voltage. Further, the diode could withstand turn-off from fifteen times the rated current.
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switching Ruggedness and surge current capability of diodes using the self adjusting p emitter efficiency diode concept
Iet Circuits Devices & Systems, 2014Co-Authors: Thomas Basler, Roman Baburske, Hans Joachim Schulze, Franz Josef Niedernostheide, Hanspeter Felsl, Manfred Pfaffenlehner, Frank Pfirsch, Josef LutzAbstract:The surge-current Ruggedness of free-wheeling diodes can be improved by implementing the self-adjusting p emitter efficiency diode concept (SPEED). Simulations indicate that the switching Ruggedness is reduced because of the occurrence of cathode-side filaments during reverse-recovery. Experiments confirm the weak switching performance of such a diode in comparison to a conventional diode. By implementing the controlled injection of backside holes concept cathode-side filaments can be suppressed. However, this measure is not sufficient to regain the switching Ruggedness of a conventional diode. It is also necessary to fully embed the p + -areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths at the p + p-junction and pinning of anode-side filaments. However, anode-side adjustments for improving the switching Ruggedness can reduce the benefit of the SPEED concept regarding the surge-current capability.
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Short-circuit Ruggedness of high-voltage IGBTs
2012 28th International Conference on Microelectronics Proceedings, 2012Co-Authors: Josef Lutz, Thomas BaslerAbstract:The IGBT can run into different short-circuit types (SC I, SC II, SC III). Especially in SC II and III, an interaction between the gate drive unit and the IGBT takes place. A self-turn-off mechanism after short-circuit turn on can occur. Parasitic elements in the connection between the IGBT and the gate unit as well as asymmetrical wiring of devices connected in parallel are of effect to the short-circuit capability. In high-voltage IGBTs, filament formation can occur at short-circuit condition. Destructive measurements with its failure patterns and short-circuit protection methods are shown.
