DBD tranformerless power supplies: impact of the parasitic capacitances on the power transfer

A new transformerless power supply for DBD application is presented here. The power supply is built with 10kV SiC MOSFET. This high voltage switches allow holding the high voltage required by the DBD. An analytical study of the converter's operation is presented to deduce the power transmitted to the DBD. A comparison between the experimental and theoretical electrical waveforms is shown. The experimental waveforms are particularly affected by all the parasitic capacitances. When all the switches are in OFF state, oscillations cause over-voltages across the switches. An analysis of the effect of each capacitance is presented and demonstrates that the parasitic capacitances of the switches and of the inductance play a key role in the actual power transfer

The ThomX project status

Work supported by the French Agence Nationale de la recherche as part of the program EQUIPEX under reference ANR-10-EQPX-51, the Ile de France region, CNRS-IN2P3 and Université Paris Sud XI - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/wepro052.pdfA collaboration of seven research institutes and an industry has been set up for the ThomX project, a compact Compton Backscattering Source (CBS) based in Orsay - France. After a period of study and definition of the machine performance, a full description of all the systems has been provided. The infrastructure work has been started and the main systems are in the call for tender phase. In this paper we will illustrate the definitive machine parameters and components characteristics. We will also update the results of the different technical and experimental activities on optical resonators, RF power supplies and on the electron gun

Transformerless power supply for dielectric barrier discharge (DBD) device

Cette thèse porte sur le développement d'une structure d'alimentation sans transformateur pour des décharges à barrière diélectrique (DBD). Une DBD est une charge permettant d'obtenir des plasmas froids à la pression atmosphérique. Ce dispositif est fortement capacitif et son alimentation doit délivrer plusieurs kilovolts pour allumer et entretenir la décharge. Cette haute tension est classiquement obtenue à l'aide d'un transformateur élévateur. Dans une première partie, nous montrons que les éléments parasites du transformateur impactent fortement le transfert d'énergie vers la décharge. C'est pourquoi dans une seconde partie, nous proposons une nouvelle topologie d'alimentation sans transformateur élévateur. Les caractéristiques fondamentales et le dimensionnement de notre alimentation sont obtenus par une analyse théorique. Dans cette topologie, les interrupteurs sont directement connectés à la DBD ; ils doivent donc supporter des tensions de plusieurs kilovolts. Il y a encore quelques années, il n'existait pas de semi-conducteur capable de supporter ce niveau de tension, à moins d'utiliser des interrupteurs fonctionnant à très basse fréquence. De récents progrès sur les matériaux semi-conducteurs ont permis d'élaborer des transistors et des diodes à base de carbure de silicium (SiC) capables de supporter des tensions allant jusqu'à 10 kV. Ce niveau de tension est tout à fait compatible avec la topologie d'alimentation proposée ici.Nous consacrerons la troisième partie du manuscrit à la mise en œuvre de notre convertisseur. Ce dernier, conçu à base de semi-conducteurs SiC, est fonctionnel et permet d'allumer une décharge. Cependant le fonctionnement initialement prévu est fortement affecté par la présence des capacités parasites notamment celles des interrupteurs. Nous détaillerons le rôle de chacune d'entre elles. Nous proposerons enfin des solutions permettant d'améliorer le transfert de puissance : mise en série de semi-conducteurs basses tensions, utilisation sur DBD de forte puissance...This thesis focuses on the development of a dielectric barrier discharge (DBD) transformerless power supply. A DBD can produce cold plasma at atmospheric pressure. This device is a capacitive load, which must be supplied by a high voltage alternative source. This high voltage is classically obtained by amplifying a low level voltage with a step up transformer. In the first part, we show that the parasitic elements of the transformer limit the power transfer to the DBD load. This is why, in a second part, we propose a new topology without step-up transformer. A theoretical study of the converter allows to size our power supply and to deduce the fundamental characteristics of the latter. In our topology, the power switches are directly connected to the high voltage. A few years ago, it was inconceivable to connect directly a transistor to a high level of voltage (5kV), unless using very low frequency switches. Recent progress on semiconductor devices led to the development of transistors and diodes based on silicon carbide (SiC), which are able to hold up to 10kV. This voltage level is compatible with our topology.In the third part, we focus on the realization of our transformerless power supply and its operation. Our power supply based on 10 kV SiC semiconductors can ignite the discharge; however the parasitic capacitance and particularly those of the switches affect the power transfer. The role of each one of them is analyzed in detail.In the last part we propose solutions to improve the power delivered by this supply: series connection of lower voltage switches, supplying a high power DBD..

High voltage SiC MOSFET Opportunities for Dielectric Barrier Dis- charge Transformerless Power Supply

International audienceFrom an electrical point of view, cold plasmas are complex loads to control. For ignition, high voltages are required , and once established, the plasma can easily go into the arc regime (thermal plasma). In Dielectric Barrier Discharge (DBD) setups, at least one dielectric is placed between the two metallic electrodes that supply the gas. Current flowing through the plasma also charges these dielectrics: their voltages increase and the gas voltage also decreases. Through this limiting mechanism, the dielectric barriers limit the current and therefore prevent from going into the arc regime. This property makes the DBD particularly appealing in various applications that require plasmas with low temperatures: UV excimer lamps, thin film deposition, surface treatment, disinfection. Our developments are geared toward DBD UV lamps [1], but the approach proposed is applicable to any DBD setup (plane-plane setup for thin film deposit was also tested). The capacitive character of the dielectrics requires supplying DBDs using an alternative source. Furthermore, to ignite the discharge at atmospheric pressure, the required voltage usually reaches several kilovolts. This high alternating voltage is traditionally obtained via amplification using a step-up transformer. Unfortunately, the parasitic capacitances of the latter (inter-turn and inter-winding) limit the power transfer: these capacitances have generally low values but often are of the same order of magnitude as those of the DBD. It is parallel to the DBD, so it diverts a significant proportion of the current transferred. This slows down the voltage rise and delays the ignition. This increases the OFF time, during which the excited species created by the previous discharge disappear. In some processes this can even change the behavior of the discharge. As a matter of fact, the main consequences of the parasitic capacitance of the transformer concern the functioning of the discharge and not the energetic efficiency of the system. These reasons incited us to investigate power supplies for DBD without transformer

10 kV SiC MOSFET Evaluation for Dielectric Barrier Discharge Transformerless Power Supply

International audienceAt low pressure, cold plasmas are used for a wide range of applications such as coating, flow control, or microelectronics. Currently, this industry requires expensive vacuum systems which consume energy and time, and therefore it is very appealing to develop similar processes at atmospheric pressure. Under this condition, dielectric barrier discharge (DBD) is one of the best ways to obtain a cold plasma. The dielectric barriers naturally limit the current, and then the plasma temperature. Unfortunately, at atmospheric pressure the discharge ignition between the electrodes requires high voltage, which is generally obtained through a step-up transformer. The parasitic elements of this device exclude a smart control for the discharge. In order to overcome this default, we analyze the performance of a transformerless power supply developed with a recently released single-chip high-voltage semiconductor. The circuit uses only two high-voltage switches synthesized by means of the 10 kV SiC MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The design and implementation of the electric converter are presented and validated with experiments carried out on UV excimer DBD lamps. Then, the performances of the 10 kV SiC switches are analyzed and the relevance of this device for DBD applications is discussed

Series Resonant Inverter Efficiency Improvement with Valley Switching for Dielectric Barrier Discharges

International audienceThis paper presents the analysis of a Series Resonant Inverter for Dielectric Barrier Discharge (DBD) applications, operating in discontinuous current mode. The study of different factors that can improve the efficiency and behavior of the converter are presented. First, the implementation of the converter is studied with two possible locations of the resonant inductance. The inductance location can be used to decrease the stress voltage of the switching components. Additionally, the effects of the parasitic elements are stated and the use of the Valley Switching technique to reduce the turn-on switching losses is proposed. Experimental results are included, showing the system improvements

Coupled Approach for Reliability Study of Fully Self Aligned SiGe:C 250GHz HBTs.

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Impact of Inside Spacer Process on Fully Self-Aligned 250 GHz SiGe:C HBTs Reliability Performances: a - Si vs. Nitride.

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Assessment of contamination, distribution and chemical speciation of trace metals in water column in the Dakar coast and the Saint Louis estuary from Senegal, West Africa

The water column from Dakar coast and Saint Louis estuary in Senegal, West Africa, was sampled in order to measure the contamination level by trace metals. The speciation of metals in water allowed performing a distribution between dissolved and particulate trace metals. For the dissolved metals, the metallic concentration and repartition between the organic fraction and the inorganic fraction were performed. The results show that the pollution of the estuary was more serious than in Dakar coast for Co, Cr, Ni, Pb and Zn; while, Cd and Cu were higher in Dakar coast. A strong affinity between metals and suspended particles has been revealed. Dissolved metals that have a tendency to form organic metal complexes are in decreasing order: Cd, Zn, Pb, Co = Cr = Mn, Cu and Ni. The results showed that the mobility of trace metals in estuary is controlled by dissolved organic carbon, while in coast it depends on chlorides

Accumulation of PAHs, Me-PAHs, PCBs and total Mercury in sediments and Marine Species in Coastal Areas of Dakar , Senegal: Contamination level and impact

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