Abstarct: In this thesis, simulation and implementation of nonlinear control buck converter is offered in four seasons. Govern the buck converter and case studies done on this converter is included in this treatise. In addition, a control method to get the average output voltage to achieve a desired voltage level is expressed. The control method is provided, including a series of advantages and disadvantages are. To improve the disadvantages as well as better results and to achieve an output voltage with a constant level by reducing the voltage ripple in the output of the converter, linear controller (PI) introduced a nonlinear control method (sliding mode control) combined each three controller is simulated in the MATLAB environment in the fourth quarter, and the results are visible. At the end of this research a controller PI, SMC and PISMC each individually simulated and are compared against sudden load changes.