Power supply for an equipment and equipment power supply system

The device has a branch with a transformation unit (7) to transform an alternating voltage from a supply network into an equivalent direct voltage. Another branch has a transformer (8) to bring a direct voltage supplied by a battery to a direct output voltage. The branches are connected by a switching unit (10) to a converter (9) that transforms the equivalent direct voltage into a direct supply voltage for a server. An independent claim is also included for a system of supplying equipment of an aircraft.