The innermost part of the ATLAS (A Toroidal LHC Apparatus) experiment at the LHC (Large Hadron Collider), CERN (Conseil Eurpeenne pour la Recherche Nucleaire), will be a pixel detector, which is presently under construction. To operate the approx. 1700 detector modules and their related readout electronics a sophisticated power supply system is required. Its design constraints are the high power density and the sensitivity of the read out chips developed in deep sub-micron technology. A high granularity of the system is desired to allow individual adjustment and to minimize the number of elements out of service. We describe the layout of the full power supply system and concentrate on the components designed in-house: the supply system for the optical link, which offers the possibility of handling a high number of channels at a reasonable price and the remotely-programmable regulator stations, which protect the sensitive front end electronics.