The aim of the present work was to design and simulate a switched mode power supply, to be used in pumping a CO2 laser source. The major parts of switched mode power supply included: input rectifier, smoothing filter, push-pull converter (chopper circuit), high voltage transformer, output rectifier, and output smoothing filter. A (PWM scheme) control circuit for controlling the chopper circuit have been designed and evaluated. Forward and push-pull converters were commonly used, especially with high power applications. A bipolar power transistor as the main switching device in the power circuits (chopper circuit and high voltage transformer circuit) with simple protection network have been implemented to ensure safe operation. The switching frequency was 40 kHz with 3F3 ferrite core material. In this work, three systems of CO2 laser with different specifications as a load for the DC power supply were used. A case study which consists of a switched mode CO2 laser power supply with output power rating of 3000 VA, output voltage (supply voltage) of 30 kV, is presented. The simulation is based on the Electronic Workbench [EWB] version 5.0 and MAT LAB version 6.0 softwares.