Abstract: A continuous uninterrupted power supply (UPS) having microprocessor control DC circuitry is disclosed. The UPS comprises a regulator for converting an AC line signal to a regulated DC signal. The regulator may include an AC/DC converter connected to an AC input line for converting the AC input signal for generating a DC signal from an AC input signal. A filter circuit is provided within the regulator for filtering the converted DC signal. A backup DC source and a series diode are also provided within the regulator for connecting a backup source to the converted DC signal when the DC signal is less than a predetermined signal level. A DC/DC converter is provided within the regulator for controlling the converted DC signal level. A DC/AC converter is connected to the regulator for receiving the regulated DC signal and generating an output AC signal therefrom. A microprocessor controller regulates the operation of the DC/AC converter.