Rainer Kling

Switching speed-control of an optimized capacitor-clamped normally-on Silicon Carbide JFET cascode

This paper presents the results of controlling the switching speed (dv/dt) of an optimized version of the capacitor-clamped normally-on Silicon Carbide (SiC) JFET cascode. The cascode circuit is an easy way to employ the normally-on SiC JFET in a normally-off configuration using a low-voltage Silicon (Si) MOSFET in series connection. The traditional cascode circuit exhibits some disadvantages, namely limited control of the switching speed and high frequency oscillations on the drain-source-voltage of the low-voltage Si MOSFET. The optimized capacitor-clamped cascode reduces the oscillations and enables control of the voltage and current slopes as well as implements a protection of the JFET gate. The theoretical background of the capacitor-clamped cascode and the control of voltage slope are explained and investigated experimentally.

Universal resonant topology for high frequency pulsed operation of Dielectric Barrier Discharge light sources

This paper reports about emerging techniques for the efficient drive of Dielectric Barrier Discharge (DBD) plasma light sources in pulsed operation mode. Besides a classification of pulse topologies, the novel Universal Sinusoidal Pulse topology, that provides high voltage amplification and high frequency operation, is presented. Transformer equipped and transformerless variations of the topology are presented. Experiments prove electrical efficiencies of more than 80%, while power measurements are cross-checked by thermal measurements. Additionally, frequency domain characteristics of the used DBD-lamp were analyzed and magnetic storage devices with distributed center gap are presented.

Modelling of indium(I) iodide-argon low pressure plasma

A new collisional-radiative model for a mercury-free low pressure plasma based on an indium(I) iodide-argon system is presented. The electron impact cross sections and rate coefficients for ionization, excitation and dissociation, as well as de-excitation, three-body recombination and dissociative recombination, of studied fillings have been calculated. Additionally, the coefficients for free and ambipolar diffusion were determined. The rate balance equations for individual generation and loss processes have been created. Densities of ions, electrons and neutral particles (ground or metastable state) are presented as a function of electron temperature for varied lamp parameters, such as argon buffer gas pressure and cold spot temperature (coldest point of discharge vessel). With the help of the presented model, the line emission coefficients of essential emission lines of indium for given electron temperatures and densities can be predicted.

Capacitively Coupled High-Pressure Lamp Using Coaxial Line Networks

This paper describes the development of a capacitively coupled high-pressure lamp with input power between 20 and 43 W at 2.45 GHz, using a coaxial line network. Compared with other electrodeless lamp systems, no cavity has to be used and a reduction in the input power is achieved. Therefore, this lamp is an alternative to the halogen incandescent lamp for domestic lighting. To serve the demands of domestic lighting, the filling of the lamp is optimized over all other resulting requirements, such as high efficacy at low induced powers and fast startups. A workflow to develop RF-driven plasma applications is presented, which makes use of the hot S-parameter technique. Descriptions of the fitting process inside a circuit and FEM simulator are given. Results of the combined ignition and operation network from simulations and measurements are compared. An initial prototype is built and measurements of the lamps lighting properties are presented along with an investigation of the efficacy optimizations using large signal amplitude modulation. With this lamp, an efficacy of 135 lmW-1 is achieved.

High-Intensity Discharge Lamps With High Color Rendering Indices Based on Molecular Radiation of Indium Iodide

This paper deals with mercury-free high-intensity discharges based on indium iodide, that are driven by guided microwaves at 2.45 GHz. The influences of different additives to the lamp on the luminous efficacy as well as on the color rendering index will be shown. Furthermore, the spectral output of pure indium iodide lamps, using argon as auxiliary gas, will be explained by a combination of indium line radiation and molecular emission of the indium iodide molecules. A theoretical model for the molecular emission is shown, which uses the semiclassical description of molecular radiation.

Integrated PFC and series resonant frequency converter analysis and control

A control algorithm for an integrated power factor correction (PFC) and series resonant converter (SRC) using only two switches is presented, allowing to open loop control the AC input current and the DC output current independently. The theory for this approach is analyzed in time domain and a novel approach for open loop regulation is presented and verified. The software defined power (SDF) control algorithms determines the switching frequency and duty cycle of the converter.

Investigations of SMPD SiC-MOSFET phase-leg modules for MHz inverters

In this work we present results of investigations on the usability of ISOPLUS SMPD SiC-MOSFET phase-leg modules for medium-frequency resonant inverters. These modules combine excellent thermal performance, very low parasitic inductances and good switching performance with the benefits of surface-mountable packages. In the first step, a SPICE and a thermal simulation of a half-bridge inverter using the SMPD module and one using discrete SiC-MOSFETs in TO-247 package was performed. Here, the semiconductor losses of the discrete devices were 2.5 times higher than the one of the SMPD module. In the second step, a modular prototype of a resonant MHz half-bridge inverter with the SMPD module was built. A short circuit test and efficiency measurements with an ohmic load showed an excellent switching performance of the SMPD SiC-MOSFET phase-leg module in the MHZ range. With the inverter prototype, an efficiency of > 95% was measured, at a switching frequency of 2.01 MHz and an output power of 5.6 kW delivered to the load resistor.

Characteristics of a surfatron-produced atmospheric-pressure plasma jet at low plasma temperatures

Summary form only given. The need of Atmospheric-Pressure Plasma is becoming increasingly important in several application fields like surface treatment for coating industry or microbicidal treatment. Due to a lot of investigation the discharge at atmospheric pressure has developed a wide range of applications over the last years, such as microbial decontamination. One of the possibly most interesting characteristics of an atmospheric pressure plasma is that it can fill the gap between low pressure and high pressure plasmas as it enables likewise high-temperature plasmas with a thermal equilibrium and low-temperature plasmas with high-energy electrons.High temperature plasmas can be deployed for the disinfection of non-organic materials compatible with these high temperatures, like titanium implants. Surface wave driven plasmas allow high electron and low plasma temperatures at low injected powers. A low plasma temperature enables to also treat materials sensitive to high temperatures or furthermore even the human skin. An optimized Surface-design developed at the Light Technology Institute of the Karlsruhe Institute of Technology enables higher field strengths and by that an stable ionization of the working gas at lower induced powers. Besides the power the effective temperature of the plasma strongly depends on the gas flow rate. This research focuses on the characterization of plasmas with an effective plasma temperature below 50°C. An extension of the detailed understanding of all processes within an Atmospheric-Pressure Plasma Jet at this low temperatures is the main object of this research. In this work all relevant plasma parameters such as the plasma temperature, electron temperature, plasma density and its UV- and ViS-spectrum are studied. The consequent characteristics of the cold plasma jet is then evaluated concerning their possible fields of application.

Diagnostics of surface wave driven low pressure plasmas based on indium monoiodide-argon system

Indium monoiodide is proposed as a suitable alternative to hazardous mercury, i.e. the emitting component inside the compact fluorescent lamps (CFL), with comparable luminous efficacy. Indium monoiodide-argon low pressure lamps are electrodelessly driven with surface waves, which are launched and coupled into the lamp by the ‘surfatron’, a microwave coupler optimized for an efficient operation at a frequency of 2.45 GHz. A non intrusive diagnostic method based on spatially resolved optical emission spectroscopy is employed to characterize the plasma parameters. The line emission coefficients of the plasma are derived by means of Abel’s inversion from the measured spectral radiance data. The characteristic plasma parameters, e.g. electron temperature and density are determined by comparing the experimentally obtained line emission coefficients with simulated ones from a collisional-radiative model. Additionally, a method to determine the absolute plasma efficiency via irradiance measurements without any goniometric setup is presented. In this way, the relationship between the plasma efficiency and the plasma parameters can be investigated systematically for different operating configurations, e.g. electrical input power, buffer gas pressure and cold spot temperature. The performance of indium monoiodide-argon plasma is compared with that of conventional CFLs.

Modeling and characterization of an indium(I)iodide-argon low pressure lamp

Summary form only given. Compact fluorescent lamps are broadly used for general lighting applications [1], yet they still struggle with acceptance problems, since they contain hazardous mercury as an elementary component. The presented work is a part of a project to substitute mercury with non-hazardous materials. For the efficiency increase and further improvement of the lamp, the determination of the plasma parameters is of utmost importance. For this purpose, the mercury free discharge based on indium(I)iodide-argon system is modeled on the basis of an extended corona model. The electron impact ionization and excitation cross sections of atomic components were calculated by means of Gryzinski method [2], while the method from [3] was used for calculation of ionization and dissociation cross sections of molecular indium(I)iodide. Ambipolar and free diffusion coefficients were determined by Chapman-Enskog-theory [4]. The rate equations for individual generation and loss processes were developed. Computational tools to solve the rate equations were programmed with MATLAB. With the help of this model, the plasma parameters like electron temperature, electron density and the line emission coefficients can be predicted at any given lamp configuration like puffer gas pressure or cold spot temperature.