An AC adapter that allows a lower power rating while still providing the necessary power to a load which is substantially constant over a varying voltage range and to charge a discharged Ni-Cad battery in a desired time. The AC adapter regulates its output power to a maximum level just greater than the maximum of the load rather than providing a controlled current until a predetermined fully charged voltage is attained. In this manner, the output voltage and current are allowed to vary inversely with respect to each other in order to maintain the desired power level, allowing the output current level to be reduced as the voltage level increases. A regulated voltage mode is also provided to keep the output voltage from rising above a predetermined maximum level should the Ni-Cad battery be disconnected. One preferred embodiment includes a regulated current mode wherein the current through the Ni-Cad battery is maintained at the desired trickle level once the battery is fully charged.