Shiferaw, Dereje (PhD)Tolossa, Zawde2018-06-292023-11-282018-06-292023-11-282017-02http://etd.aau.edu.et/handle/12345678/4882DC-DC converters are non-linear and the most widely used circuits in power electronics. Generally they are used in all situations where there is need of stabilizing a given DC voltage to a desired value. DC-DC buck converter is used in applications for voltage step-down. The output voltage of this converter alone is usually unstable, oscillates, it has large overshoot, and long settling time. Also it is unable to give the desired output voltage under input voltage and load variations. To overcome this problem and obtain constant stable output voltage and fast response various controllers are required. PID controllers have been usually applied to the converters to obtain the desired output voltage because of their simplicity. But application of PID controller is not reliable and satisfactory in the case of non-linear systems. Therefore, non-liner controllers are required to improve system performance. In this thesis second order sliding mode controller based on the prescribed convergence algorithm has been designed to achieve fast and stable performance of buck converter. The proposed controller performance is compared with PID controller based on dynamic response of the system in terms of overshoot, settling time, rise time, and voltage deviation from desired value using MATLAB/Simulink. In order to test the performance of proposed controllers the load resistance increased and decreased by 62.5% from operating point while input voltage decreased by 20.83% and increased up to 41.67% from operating point. Also to test effectiveness of SOSM control the input voltage is varied from operating point (i.e. 24V) up to 200V. Simulation results show that, using SOSM controller the rise and settling time is improved by 5.228% and 46.39% respectively as compared to that obtained using PID controller. The overshoot is reduced from 51.3% to 9.455% using PID controller while SOSM controller totally removes it. Both controllers overcame the effect of load resistance variations. The overshoot is increased from 9.455% to 17.5% for input voltage increased by 41.67% using PID controller is eliminated using SOSM controller. The actual output voltage is not deviated from desired value even for large input voltage variation using SOSM controller. Generally from the result it is possible to conclude that the performance of SOSM controller is better than PID controller. Key words: DC-DC Converter, Buck Converter, PID Control, SOSM Control.enDC-DC Converter; Buck Converter; PID Control SOSM ControlThesis