The problem of output feedback control for a class of second-order nonlinear systems is investigated in this paper. Using the techniques of finite-time control and finite-time convergent observers, an observer-based finite-time output feedback controller is proposed, which can guarantee that the state of system converges to the equilibrium in a finite time. As an application of the proposed theoretical results, the problem of finite-time control without current signal for the DC–AC converters is solved. Simulation results demonstrate the effectiveness of the proposed method.