<p>For a DC-DC buck converter, disturbances are inevitable due to unmodeled uncertainties, fluctuations in load and input voltage and other factors. Moreover, when current sensors malfunction, the traditional state feedback control method falls short in achieving the enhanced control performance. Considering these factors, this work proposes a finite-time output feedback control framework for the current-sensorless DC-DC buck converter with unknown load changes and external disturbances. To begin with, a finite-time state feedback controller is constructed for the converter, deliberately excluding the influence of external disturbances from the initial design considerations. Next, given the absence of inductor current measurements, a finite-time extended state observer is introduced. This observer leverages the nonseparation principle and treats both the unknown load resistor information and external disturbances as components of a generalized state. Its primary objective lies in concurrently estimating both the unmeasured inductor current and the unidentified external disturbances. Building upon this observer, a finite-time output feedback controller is explicitly presented for the converter. By using the Lyapunov method, it is strictly proved that the closed loop converter system achieves finite-time convergence under the designed controller. Finally, to validate the effectiveness of the algorithm, a series of comprehensive hardware experiments were conducted, thus confirming the superiority of the proposed technique.</p>