Patent ID: 8159160

Claim:
An apparatus for controlling fan speed in a power supply, the apparatus comprising: an input power module that measures, over an interval, input power at an input terminal for the power supply and calculates an input power value; an output power module that measures, over the interval, output power at an output terminal for the power supply and calculates an output power value; a fan control apparatus that: receives the input power value from the input power module and the output power value from the output power module; calculates a power value representing the power dissipated by the power supply over the interval based on the difference between the input power value and the output power value; looks up a fan speed associated with the power value in a lookup table that associates increasing power dissipation values with increasing fan speeds such that higher power dissipation values correspond to higher fan speeds; and sends the fan speed to a fan controller of a fan that cools the power supply.