The presented work aims mainly at simplifying the study of energy transfers involved in converters. A preliminary mathematic study leads to introduce a new element in equivalent circuits. We name it "loss less modulator". This modulator is something like an ideal transformer, the ratio of which cart vary, under control, with time. Such a function is obtained by associating a chopper with low pass filters. Then, we study the association of a ~oss less modulator with a standard reactive element and we named such a dipole "modulated reactive dipole". We show that not only such a device behaves as a time varying reactive element, but it can also behave as an inductive one, even if energy storage is capaci~ive.. Thus, a large part of converters appear as assemblies of a small number of loss less modulators and modulated reactive dipoles. Finally and independently, we show that someconversions require the storage of a minimum energy. It is thus necessary to manage the energy by minimizing the stored amolint, i.e. in "taut flow". This concept,applied to a PFC ac-de converter; leads to reduce by a factor higher than 10 the stored energy as weil as the output rise time. This is supported by a practical realization.
