In this work, the authors present their investigations of the benefits of combining the latest silicon carbide MOSFETs with novel packages for electronic ballasts of inductively coupled plasmas. Such plasmas require MHz inverters with output powers above 2 kW. Additionally, for a breakthrough of the technology efficiencies >90% have to be realised. It has been shown that a combination is achievable with SiC FETs. Nevertheless, even though the transistors have undergone significant development in recent years, one limiting factor has mostly remained untouched. The common TO-247 package does not fit to the requirements of a fast switching application. Within the latest launch of the new generations of SiC MOSFETs, some are available in novel packages with kelvin source connection, like 4pin TO-247 and 7pin D2Pak. The authors compare three versions of the latest generation in a resonant full-bridge inverter and in application-oriented test. Thereby, the 7pin D2Pak and one of the 4pin TO-247 transistors were 65 mΩ devices and the second 4pin TO-247 FET was a 45 mΩ device. For the investigations, the authors made simulations, built three MHz inverters, and conducted measurements. Consequently, efficiencies of 93.9% could be achieved at a switching frequency of 2.5 MHz and an output power of P out =2.6 kW.
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. The radiometric characterization of the lamp was carried out by means of spatially resolved radiance measurements with a fully automated x-y-table, array spectrometer and telescopic optical probe. The measured radiance values were converted to line emission coefficients by means of inverse Abel transform [5]. The radiant flux of the plasma was calculated by the integration of the line emission coefficients over the whole discharge volume for the determination of plasma efficiency. The plasma parameters were determined by comparison of measured values with the calculated values from the model.
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