Patent ID: 7746044

Claim:
A power supply system for a motherboard, comprising: a voltage regulator circuit comprising a system power source, and a voltage output terminal; a sampling circuit having an input, and an output, the input of the sampling circuit being connected to the voltage output terminal of the voltage regulator circuit, the output of the sampling circuit receiving a high level sleep signal from a south bridge of the motherboard; a switching circuit having an input, and an output, the input of the switching circuit being connected to the output of the sampling circuit; a power connector having a control terminal connected to the output of the switching circuit; and a power source being connected to the power connector, configured to provide power to the motherboard via the power connector; when the voltage regulator circuit outputs a predetermined stable voltage provided by the system power source, the sampling circuit has no signal output at the output, the switching circuit receives the high level sleep signal from the south bridge and outputs a low level signal to the control terminal of the power connector to make the power source provide power to the motherboard normally; when the voltage regulator circuit outputs an output voltage greater than the stable voltage, the sampling circuit outputs a low level signal, the switching circuit receives the low level signal from the sampling circuit and outputs a high level signal to the control terminal of the power connector to make the power source shut off the system power source of the voltage regulator circuit.