Simulation is a key issue in the design of control electrical systems. Simulation packages using component library, such as PSIM®, are very useful to achieve this goal. The simulation model is thus easily built from the system topology (structural model). But the deduction of the control scheme is more difficult, because a functional model is more suitable. Some graphical descriptions, such as EMR (Energetic Macroscopic representation) are recently been developed to help the user in the control scheme design. But they are generally associated with functional software, such as Matlab-Simulink®. In this paper, a structural modeling software is combined with a functional modeling method. An original and new control of a DC/DC converter is taken as an example.