New application of an LLC full bridge inverter topology for corona generation in plastic industry

Corona generation is necessary in plastic industry application where the surface of plastic has to be treated in order to fix ink to the plastic´s surface. For the generation of corona effect a blade-like electrode is used and high voltage is applied (18 kV). In this paper we propose an LLC inverter topology to easily achieve this high voltage by including the parasitic elements of the high voltage transformer in the resonant circuit. The control circuit includes a main loop to control DC output voltage and two additional protection loops to protect against too high currents in the IGBTs and a too large phase shift which means operation of the circuit beyond its resonant frequency and in the capacitive operation mode