In this paper, the output voltage of a DC-DC boost converter with pulse-width modulator (PWM) has been controlled using an output feedback H-infinity (H_∞) controller. The H_∞ controller for the converter has been designed applying the concept of Linear Matrix Inequality (LMI) technique. The main target of this study is to regulate the output voltage of the non-linear boost converter in presence of parameter variations and external noise. The designed H_∞ controller regulates different reference voltages in presence of sensor noise and parameter variations. The proposed H_∞ controller is also very simple and does not require any inner current loop with the outer voltage loop like the other designed controller reported earlier.