Convertisseur isolé à large plage de tension d'entrée, utilisant des transistors GaN en commutation douce, pour applications spatiales

This thesis deals with the development of an isolated wide range input voltage converter for a space application. The input voltages vary by a factor close to 6 (20 to 110V) in order to adapt this converter to all existing satellite distribution architectures. In consideration of generating an isolated secondary bus for local power distribution to digital systems, the output voltage is fixed at 3.3V and the maximum power at 50W. The constraints raised by this system are thus multiple. On the one hand, the strong variations of input voltage, output current and the strong ratio of down conversion are electrical difficulties which are highlighted by the strongly constrained environment (radiations and charged particles, temperatures, reliability/lifetime). On the other hand, volume and weight not only affect the thermal (and thus the efficiency) but also the choice of conversion topology and frequencies. In response to this problem, two topologies have been studied. The first one is based on a variation of the FLYBACK ACQR in which the operating modes have been detailed. A dimensioning based on GaN transistors has been proposed and implemented as well as all the necessary components for the final realization. A detailed experimental characterization allied to theoretical laws allowed to identify the distribution of the losses in the cell and thus to propose optimization axes of the converter. In this sense, an optimization of the choice of the components based on precise models allowed to propose a theoretical dimensioning reducing the losses of more than 30 %. The second topology is based on an innovative LLC-PS topology which has been patented. The different operating modes and a theoretical dimensioning is proposed.