An approach to a broad range of power control in voltage-source series-resonant inverters for corona discharge treatment-pulse-density-modulation

This paper implements a wide range of power control with pulse-density-modulation (PDM) in a voltage source series-resonant inverter which realizes a corona discharge for the surface treatment of films. The use of the PDM inverter enables the employment of a three-phase diode bridge rectifier as an electric utility interface. The PDM inverter produces either a square-wave AC voltage state or a zero voltage state at its AC terminals to control the discharge power of a corona surface treater. Moreover, it can achieve zero-current-switching (ZCS) and zero-voltage-switching (ZVS) under all the operating conditions, thus leading to a significant reduction of switching losses and electromagnetic noise. A 80 kHz, 6 kW surface treatment system consisting of a voltage-source PDM inverter, a step-up transformer and a corona discharge treater shows the establishment of a stable corona discharge in an extremely wide range of power control from 0.5 to 100 %, and therefore succeeds in performing both strong and weak surface treatment processes for films.