Patent ID: 7636862

Claim:
A method for operating an information handling system comprising a plurality of sub-systems including a voltage regulator module, a power supply unit for providing a main power supply and a stand-by power supply, and a power management controller, comprising: upon a sub-system power on request: determining whether the main power supply is available and if not, turning on the main power supply; and enabling the voltage regulator module of the respective sub-system; and upon a sub-system power off request: turning off the voltage regulator module of the respective sub-system; and determining whether no other sub-system is enabled and if yes, then turning off the main power supply; and repeating turning on or off for a pre-defined group of sub-systems, wherein within a sequence of turning off a group of sub-systems, stopping the sequence if a sub-system which has been shut down was the last active sub-system and turning off the main power supply.