Design of switched-mode power supply for TEA CO2 laser.

Bilal Essam Abdul-Razzaq
Dr. Muthana J. Al-Khishali

Abstract:This work is to design and simulate a switched mode power supply (SMPS) with the required pulsating circuits, to be used in pumping a TEA CO2 laser. The main parts of the switched mode power supply included: input rectifier, input smoothing filter, push-pull converter (chopping circuit), high voltage power transformer, output rectifier, and output smoothing filter. The control circuit for controlling the chopper circuit was the PWM scheme control circuit and the main switching device in the power converter circuit was the bipolar power transistor with high voltage rating. A protection network (snubber circuit) was used with the transistor to ensure safe operation. The high voltage power transformer was of the type double-E core (3F3 ferrite core material) with a switching frequency of 50 KHz. In this work, the load was TEA (Transversely Excited Atmospheric) CO2 laser. Four systems of this laser with different specifications were considered. Accordingly, a switched-mode power supply was designed with an output power rating of 3000 VA (DC supplied voltage 30 KV and DC output current 100 mA) to suit one of the four systems of TEA CO2 laser with required conditions. The SMPS was used to charge the pulsating or discharging circuits in order to deliver the required breakdown voltage as well as the glow voltage with the required pulse width and energy. The discharging circuits used were Marx generator and Pulse Forming Network (PFN) circuits. Marx generator was considered the ideal and the best circuit for providing the breakdown voltage for the TEA CO2 laser electrodes because of its ability for voltage multiplication. PFN was used to supply the glow discharge voltage with high energy and with a desired pulse shape and width. Marx generator was also used for supplying the glow voltage. For this high voltage environment and for a repetition rate of 10 Hz (operation in pulsed mode), the best switching device used for discharging the pulsating circuits into the load (TEA CO2 laser) was the spark gap. Full design for the SMPS, Marx generator, PFN, spark gap with its triggering circuit was presented. The simulation of this work is based on the Electronic Workbench (EWB) version 9.0 and MATLAB version 7.0 softwares.