Many information technologies for numerical analysis of electrical circuit parameters have been developed. The peculiarity of these methods is their applicability not only to DC but also AC circuits, not only to linear but also nonlinear circuits. This paper introduces the special mathematical model for rectifier circuits using semiconductor diodes. In previous studies, the rectifier circuit has been modelled by differential inclusions. However, the inclusions cannot be solved by the applied programs of information technology. In this paper, the new model writing by differential equation with a special right hand side is studied to replace the classical model. The main result of this is presented in a theorem that gives the correctness of the new model. The usefulness of this study is illustrated via a concrete example.