In this paper, a total sliding-mode control (TSMC) scheme is designed for voltage tracking control of a conventional dc-dc buck-boost converter. This control strategy is derived in the sense of Lyapunov stability theorem such that the stable tracking performance can be ensured under the occurrence of system uncertainties. The major feature of this control scheme is that the controlled system has a total sliding motion without a reaching phase as in conventional sliding-mode control (CSMC). Moreover, the effectiveness of the proposed TSMC scheme is verified by numerical simulations, and the advantages of good transient response and robustness to uncertainties are indicated in comparison with a conventional proportional-integral control (PIC) system.