Abstract: An uninterruptible power supply (UPS) provides DC output power and uses a plurality of relatively low power DC/DC converters which are of much higher efficiency and lower heat dissipation than inverters normally used in UPS devices to provide AC output power. Power is stored at high voltage in capacitors to provide output power when input power may be interrupted. Since the power dissipation is reduced and use of batteries can be avoided where redundant input power sources are available, the UPS made be made very compact and of light weight as is particularly suited to mobile machinery such as aircraft, water-borne vehicles and the like.