Current Source Parallel Resonant Converter For Plastic Film Surface Treatment

In the industrial or daily applications, the plastic film can hardly meet the needs if it is not surface-treated. Thus the surface treatment has been one part of the production of the plastic film. Nowadays the chemical corrosion, flame treating and corona surface treatment are three available methods to realize surface treatment of the plastic film. The corona surface treatment is widely employed because of its high efficiency and environmental-friendly features. Dielectric barrier discharge (DBD) is a high voltage discharge phenomenon, and it is needed in the corona surface treatment. This technique is widely utilized in the applications such as material surface treatment, ozone generating, lighting and decontamination. Thanks to its significant chemical and physical characteristics, DBD is of great value in the scientific researches and industrial applications.In this paper, the configurations and the characteristics of the DBD load are introduced in the first place. And then, the features of the low temperature plasma which is generated by the dielectric barrier discharge. Besides, the importance of the low temperature plasma for the plastic surface treatment is explained in the paper. According to the specific requirements for the plastic film surface treatment, the technical difficulties of designing a suitable converter is analyzed in this paper. And it turns out that the resonant converter is promising. In order to find out a competent resonant converter, some widely used resonant converters are analyzed including voltage source type and current source type. Finally, the current source parallel resonant converter is found to be appropriate in this case due to the features of anti-short circuit ability and resonant frequency variation characteristics.The configuration of the current source parallel resonant converter and the commutation of its full-bridge inverter are investigated in this paper. For stability and safety consideration, the inductive commutation state is preferred. In order to accurately describe the behavior of the converter and optimize the converter, the operating modes in the time domain are defined and the mathematical expressions are obtained. An optimized design method is developed based on the acquired expressions, and an8kW DBD power supply for the surface treatment is designed. Both simulation and experimental results can verify the proposed analysis and design.To guarantee the reliable operation of the current source parallel resonant converter, a suit of control strategy is developed. The configuration of the control system are listed and analyzed. Detailed introduction of the deployment of the DSP hardware is given, and the crucial program flow charts are plotted which illustrate the important control strategies of the system.