In this study, an improved fast terminal sliding-mode control (FTSMC) is presented to control the output voltage of the DC-DC step-down converter. It has been compared to other techniques in the literature, including traditional sliding mode control (SMC) and terminal sliding mode control TMSC to demonstrate its performance. The proposed method and all other mentioned methods have been tested in simulation environment. The obtained simulation results are compared in terms of performance of converging error to zero for various conditions such as input voltage variations, step load change and tracking process. The obtained results show that the proposed improved FTSMC method provides the fastest convergence, the smallest rising time, and the smallest steady-state error than the SMC and TSMC method. In addition, no capacitor current was used in the simulations. The backward-euler method was integrated into the sliding surface used and thus only one sensor was used to control the state variables of the respective converter.