this thesis presents five different nonlinear control techniques for voltage regulation of a dc-dc buck converter operating in continuous conduction mode. a state space averaging model is derived from a non-ideal buck converter circuit with the consideration of resistances of each component. based on this model, different nonlinear control techniques have been developed to control the dc-dc buck converter. these include backstepping control, sliding mode control, backstepping sliding mode control, adaptive backstepping control, and adaptive backstepping sliding mode control. all these proposed controllers have been evaluated by computer simulation and implemented on the dc-dc buck converter which is built for this thesis. simulation and experimental results show that all the proposed controllers are able to stabilize the closed loop system and to achieve satisfactory voltage regulation performances under source voltage variations and load changes.