One of the open problems in the design of power converters is related to the selection of components, and the effects that these choices may have, beyond steady-state properties, in the dynamical behaviour of the system. This paper describes a numerical method that may help in finding appropriate components. The method is based on Lyapunov functions that are efficiently manipulated to derive linear matrix inequality (LMI) based conditions. With the proposed approach, the domain of component values that verify given dynamical properties can be estimated. The resulting parametric domain can then be used by the practicing engineer to optimise other factors, such as weight, cost or volume. The advantages of the proposed approach have been illustrated with the design of two different input filters for power converters operating as constant power loads.