A power supply device for powering equipment from at least one network supplying AC and at least one battery supplying DC, the power supply device comprising: a first branch that is connected to the main network and that comprises a transformation member for transforming the AC voltage into an equivalent DC voltage; a second branch that is connected to the battery and that comprises a voltage booster for raising the DC voltage supplied by the battery to an output voltage close to the DC voltage equivalent to the AC voltage; the first branch and the second branch being connected by a switch member to a converter arranged to transform the DC voltage equivalent to the AC voltage of the network into at least one DC voltage for powering the equipment.