Letteratura scientifica selezionata sul tema "Semiconductor opening switch"

We describe the operation of a repetitive semiconductor opening switch in conjunction with inductive energy storage systems. Different materials and switch configurations are examined. A new method of generating square pulses of nanosecond duration is implemented. It utilizes the opening switch and a current charged transmission line.

Mesa-epitaxial 4H-SiC p+-p-no-n+-diodes were fabricated and their reverse recovery characteristics were measured in pulse regimes to be relevant to DSRD- and SOS-modes of operation [I.V. Grekhov, G.A. Mesyats, Physical basis for high-power semiconductor nanosecond opening switches, IEEE Transactions on Plasma Science 28 (2000) 1540-1544]. It has been found that after short pumping the diodes by forward current pulse (5-ns duration, 200-A/cm2 peak current density) followed by applying the reverse voltage pulse (rise time 2 ns) the diodes are able to interrupt the reverse current density of 3.5 - 25 kA/cm2 in a time less than 0.3 ns.

Dans les systèmes de hautes puissances pulsées, le stockage inductif présente un avantage indéniable vis-à-vis du stockage capacitif du fait de sa plus forte densité d’énergie. L’exploitation de cet avantage nécessite toutefois l'utilisation d'un interrupteur à ouverture pour générer l'impulsion de tension. En outre, compte tenu de la demande croissante de générateurs impulsionnels fiables, en particulier pour les applications industrielles, il devient indispensable de recourir aux composants semi-conducteurs. La diode SOS (Semiconductor Opening Switch), développée dans les années 1990 à l'Institute of Electrophysics en Russie, est un candidat idéal pour la commutation état solide à ouverture, de par sa capacité à générer des impulsions de haute puissance de manière fiable et répétitive, tout en offrant une longue durée de vie et un fonctionnement exempt de maintenance. Cependant, le manque de fabricants de diodes SOS limite leur utilisation à grande échelle. Par conséquent, cette thèse se concentre sur l’étude de diodes disponibles dans le commerce (OTS : Off-The-Shelf) capables de commuter rapidement des courants élevés et de générer des tensions nanosecondes pouvant atteindre 500 kV. Plusieurs types de diodes, incluant les diodes de redressement, à avalanche, à temps de récupération rapide et de suppression de tension transitoire (TVS) ont été étudiés en tant qu’interrupteurs à ouverture, en comparaison avec les diodes SOS de référence. Pour mener à bien cette étude, des bancs d’essai à basse, moyenne et haute énergie (respectivement 25 mJ, 10 J et 40 J) ont été mis au point. Afin d’augmenter leur efficacité énergétique, ces bancs utilisent un circuit basé sur un élément magnétique unique : un transformateur impulsionnel saturable. Plusieurs noyaux magnétiques nanocristallins ont été examinés sur le banc de 10 J dans le but d’optimiser les performances du transformateur. Parmi les diodes étudiées sur les bancs de 25 mJ et 10 J, les diodes TVS et les diodes de redressement ont émergé du lot, démontrant des performances de temps de commutation de l'ordre de la nanoseconde et de tensions générées de plusieurs kilovolts. Enfin, un prototype de générateur de hautes puissances pulsées de 40 J (GO-SSOS) basé sur un interrupteur OTS composé de diodes de redressement a été développé. Le rendement énergétique du système varie de 35% à 70% selon la valeur de la charge, et la puissance crête obtenue est supérieure à 300 MW. Sur une charge de 1 kΩ, l'impulsion de tension générée atteint une amplitude de 500 kV avec un temps de montée de 36 ns et une largeur à mi-hauteur de 80 ns. La reproductibilité des impulsions à une fréquence de répétition de 60 Hz est démontrée, ainsi qu’une application de génération de décharges couronnes. Les travaux prouvent la fiabilité des diodes OTS en mode SOS, ne révélant aucune dégradation après quelques milliers d'impulsions générées. Ils ouvrent également la voie à l’utilisation de cette technologie pour des applications industrielles telles que la stérilisation par faisceau d’électrons
In pulsed power systems, inductive energy storage has an advantage over capacitive storage because of its higher energy density. Exploiting this advantage requires the use of an opening switch to generate the voltage pulse. Moreover, the growing need for reliable pulsed power generators, particularly for industrial applications, strongly supports the adoption of solid-state solutions. The Semiconductor Opening Switch (SOS) diode developed in the 1990s at the Institute of Electrophysics in Russia is an ideal candidate for solid-state opening switching because of its ability to reliably generate high-power pulses at high repetition rates while offering long lifetime and maintenance-free operation. However, the lack of SOS diode manufacturers prevents their widespread use. This thesis is therefore devoted to the study of off-the-shelf (OTS) diodes capable of rapidly switching high currents and generating nanosecond voltages of up to 500 kV. The research includes the investigation of various diode types including rectifier, avalanche, fast recovery, and transient voltage suppression (TVS) diodes as opening switches in comparison with state-of-the-art SOS diodes. Low, medium, and high-energy (25 mJ, 10 J, and 40 J respectively) test benches are developed for the experiments. Their circuits use a single magnetic element – a saturable pulse transformer – resulting in high energy efficiency. Several nanocrystalline cores are examined for optimum transformer performance at an energy of 10 J. Among the diodes investigated at 25 mJ and 10 J energy, the TVS and rectifying diodes stand out particularly promising with nanosecond switching time and generated voltages in the kilovolt range. Finally, a 40 J pulsed power generator prototype (GO-SSOS) based on an OTS opening switch consisting of rectifier diodes is developed. The GO-SSOS achieves a peak power of more than 300 MW with an energy efficiency ranging from 35% to 70% depending on the load value. Across a 1 kΩ load, the voltage pulse generated reaches 500 kV amplitude with a rise time of 36 ns and a pulse width of 80 ns. The system shows high reproducibility at a repetition rate of 60 Hz and is used to demonstrate a corona discharge application. The work proves the reliability of the OTS diodes in SOS mode, revealing no degradation after thousands of pulses. It also offers the prospect of using this technology in industrial applications such as electron-beam sterilization

Optically activated semiconductor opening switches1 are anticipated to have unique characteristics of repetitive operation, fast opening time, and potential scalability. We have demonstrated the operation of optically activated semiconductors2 as fast opening switches. A semiconductor with high dark resistivity is maintained in a conductive state by continuous illumination with argon laser light. The opening of the switch is obtained by interrupting abruptly the light using a Pockels cell placed between two parallel polarizers. The opening speed is given either by the rise time of the Pockels cell (1 ns in our system) or by the recombination time of the carriers optically formed in the semiconductor, whichever is the longest. To demonstrate its operation, the switch was placed in an inductive charging circuit which delivers the stored energy to a load when the switch opens. The shape of the transient current signal was observed on an oscilloscope for different parameters of the circuit and using different switches. The off-to-on resistivity ratio of the switch was always larger than 103. We have achieved a repetitive 1-ns opening time with an lnGaAs:Fe switch of ~300-ps recombination time. The results obtained with different materials (GaAs, InGaAs, GaAs:Cr) and different gap configurations are presented.

Although it is well known that the bandwidth afforded by optical fibers exceeds 1 Tb/s, the bandwidth of networks presently implemented is in the 1-10 Gb/s range. Considerable improvements are required in components used for modulation and demodulation of signals in optical communications networks. A central problem to be solved for the deployment of 100-Gb/s systems is the development of appropriate all-optical switches. A number of optical switches based on semiconductors, in which a control pulse gates a signal pulse, have been demonstrated. However, one of the main problems with switches based on semiconductors has been that while the switch may have a fast opening time, the closing time is very slow since the switch is open for as long as carriers (electrons and holes) are present in the material, limiting the bandwidth quite severely. In this talk we describe a technique which provides for fast closing as well as opening of the switch to give the required bandwidth.