Patent ID: 8344546

Claim:
A power supply apparatus comprising: an AC to DC converter configured to generate a first DC output voltage at an output of the AC to DC converter responsive to receiving an AC input from a primary AC power source or an auxiliary AC power source; a DC to DC converter configured to receive a DC input voltage from a DC backup power source and generate a second DC output voltage responsive to turning on of the DC to DC converter; a controller configured to monitor the AC input, and control at least one of the AC to DC converter and the DC to DC converter, wherein the controller is configured to: determine energy stored in a capacitor of the AC to DC converter, and turn on the DC to DC converter based on the energy determined to be stored in the capacitor or a rate of change in the energy determined to be stored in the capacitor; and an output node coupled to the output of the AC to DC converter or the output of the DC to DC converter, the output node configured to connect to one or more components of the computing device.