In this paper, a new observer‐based controller is proposed for a photovoltaic DC–DC buck converter; both photovoltaic (PV) voltage and current regulation are considered. In order to deal with the complex and nonlinear PV mathematical model and adapt it to the control purpose, a hybrid PV current observer model is proposed; three modes are defined and the stability of the observer is discussed using the hybrid dynamical system approach (HDS). The observer‐based controller is designed for both voltage and current regulation of the PV system; the closed loop of the full system stability is demonstrated through Lyapunov analysis. Experimental results are also presented showing the feasibility of the proposed observer‐based controller.