In this paper, a polytopic control approach is applied to a PV-fed single-ended primary-inductance (SEPIC) dc-dc converter. In a clear-cut-contrast with conventional control techniques based on averaging procedures, the polytopic control approach is applied to the switched model of the system. In particular, the switching control signal is synthesized using a Lyapunov function which has polytopic level sets. The validity of the approach is illustrated and verified using numerical simulations showing that the controller can achieve good performance in terms of fast recovery due to input voltage variations.