The paper deals with the sizing of controlled converter applications, with possibly, closed control loops, by combining several tools. The approach proposes to use symbolic calculation to perform sizing times, but also numerical calculation when symbolic expressions do not exist. The sizing model is deduced from criteria on the components (control values, average values, losses, rms values, maximum values, durations, etc.). The approach is based on two development environments: Gentiane for the modelling and simulation and Eden for the optimisation.