This work deals with reduced-order Luenbergerlike observer design and control for switched affine systems. Formulation of state-dependent and dynamic outputdependent switching laws for those systems was already addressed, however, in a full-order treatment. The proposed procedure defines an estimator system only for the unmeasured part of the system state. Linear matrix inequalities for obtaining output gain matrices and for composing a reduced-order Luenberger observer-based switching law are proposed. Finally, the results are validated by design and simulation for DC-DC converters.