This paper presents a systematic approach to synthetize constant power loads using switching converters under sliding-mode control. The generation of sliding motions is analyzed in converters with a series inductor in the input port and a switching function representing the error between the input power and a suitable power reference. The analysis establishes the existence conditions for sliding-mode and the stability of the resulting ideal dynamics. Simulation and experimental results verifying the theoretical predictions in boost, Ćuk and SEPIC converters illustrate the proposal. The design procedure yields a simple, economical and small-size prototype that can be useful in the experimental validation of converters supplying constant power loads.