Power switching system and method

The present invention discloses a system and method for power switching. Power source switching system for a computer system, comprising a power supply module, according to an external voltage source for generating a system voltage source and a power transistor driving voltage source; a control module, according to a feedback signal to produce a control signal; and a power switch module, coupled to the power supply module and the control module, for driving a voltage source to the power module according to the control signal, and outputting a modulatable source of the system voltage and the power transistor; wherein the feedback signal is used to determine an operating mode of the computer system for a heavy load operating mode or a light-load operation.