Implementation and Analysis of Unipolar High-Voltage Pulse Modulator for 172-nm VUV Excilamp

Abstract

Dielectric barrier discharge (DBD)-based excimer sources have found diverse applications in biomedical, agriculture, pharmacy, surface treatment, and industrial processes. The radiation ability of DBD-based 172-nm excimer radiation source to break molecular bonds in organic matter is beneficial for processes, such as ultracleaning and surface activation, improving adhesion. The high-voltage pulsed power modulator plays a critical role in generating efficient plasma discharge for a 172-nm VUV excimer lamp. The precise control of output pulsed amplitude voltage and pulse repetition frequency (PRF) is required for generating efficient and uniform plasma inside the plasma tube. In this article a two switch forward converter (S2FC) topology with snubber at the output is proposed to generate unipolar pulse output for 172-nm VUV excimer source. The developed prototype of high-voltage unipolar impulse power modulator (HVU-IPM) has a 32-kHz PRF and a 1- $\mu $ s pulsewidth with adjustable output pulse voltage. The mathematical model for calculating the DBD pulse voltage and current is developed through mode analysis of the proposed HVU-IPM system. The experimental verifications of the developed prototype of HVU-IPM system are carried out to evaluate the system performance. The DBD plasma generated by the developed HVU-IPM remains stable across a broader range of operating parameters, such as gas pressure and applied voltages, and generates VUV light of absolute irradiance up to 11.24 mW/cm2. The achieved rise time/fall time of output pulse is below 400 ns.