A new "model-free" control methodology is applied for the first time to power converters, and in particular to a buck converter, and to aĆuk converter. We evaluate its performances regarding load and supply variations. Our approach, which utilizes "intelligent" PI controllers, does not require any converter identification while ensuring the stability and the robustness of the control synthesis. Simulation and experimental results show that, with a simple control structure, insensitivity to power supply fluctuations and to large load variations is ensured. Index Terms-dc/dc converters, buck converters,Ćuk converters, model-free control, intelligent PI controllers, numerical differentiation.