An exemplary power supply circuit for a motherboard includes a control circuit, a self-locking circuit, and an unlocking circuit. The control circuit is configured for receiving a working mode signal. The self-locking circuit is arranged to receive a power ok signal and a power supply on signal from a power supply, and is connected to the control circuit and a standby power. The unlocking circuit is connected to the control circuit, the self-locking circuit and the standby power, and is also arranged to receive the power ok signal. When the motherboard is placed in an energy-saving mode, the unlocking circuit unlocks the standby power from the motherboard when the computer is turned off to achieve energy savings.