Power supply system with energy-saving function

A power supply system to save energy for a computer system, the power supply system comprising:

• a power supply comprising an input terminal, and a system voltage output terminal;
• and
• an energy-saving circuit connected between the input terminal of the power supply and an alternating current (AC) power source, the energy-saving circuit comprising:
• a switch control circuit connected between the AC power source and the input terminal of the power supply, and connected to the system voltage output terminal of the power supply;
• a voltage rectifying circuit connected between the AC power source and the switch control circuit to rectify an AC voltage into a direct current (DC) voltage to power the switch control circuit;
• and
• a trigger switch connected to the switch control circuit;
• wherein when the computer system is powered off, the system voltage terminal of the
• power supply fails to output a system voltage, and the trigger switch fails to be triggered, the switch control circuit disconnects the input terminal of the power supply from the AC power source, wherein when the computer system is powered off, the system voltage terminal of the power supply fails to output a system voltage, and when the trigger switch is triggered, the switch control circuit connects the input terminal of the power supply to the AC power source;
• the energy-saving circuit further comprises a switch unit, the switch unit is connected between the AC power source and the switch control circuit, the switch unit is also connected between the AC power source and the input terminal of the power supply, the switch unit is used to selectively connect the AC power source to the input terminal of the power supply or connect the AC power source to the switch control circuit, wherein when the switch unit connects the AC power source to the switch control circuit and the computer system is powered off, the trigger switch fails to be triggered, the switch control circuit disconnects the AC power source from the input terminal of the power supply, when the trigger switch is triggered, the switch control circuit connects the AC power source to the input terminal of the power supply;
• the switch control circuit comprises a relay, and first to fourth transistors, a control terminal of the first transistor is connected to a voltage output terminal of the voltage rectifying circuit, a first terminal of the first transistor is connected to the voltage output terminal of the voltage rectifying circuit, and
• connected to a control terminal of the second transistor, a second terminal of the first transistor is grounded through the trigger switch, a first terminal of the second transistor is connected to the voltage output terminal of the voltage rectifying circuit, and connected to a control terminal of the third transistor, a second terminal of the second transistor is grounded, a first terminal of the third transistor is connected to a first terminal of a coil of the relay, a second terminal of the third transistor is grounded, a control terminal of the fourth transistor is connected to the system voltage output terminal of the power supply, a first terminal of the fourth transistor is connected to the first terminal of the coil of the relay,
• a second terminal of the fourth transistor is grounded, a second terminal of the coil of the relay is connected to the voltage output terminal of the voltage rectifying circuit, a first contact of the relay is connected to the switch unit, a second contact of the relay is connected to the input terminal of the power supply, wherein when the switch unit connects the AC power supply to the switch control circuit, and the trigger switch fails to be triggered, the first transistor is turned off, the second transistor is turned on, the third transistor is turned off, the first contact is disconnected from the second contact of the relay,
• the input terminal of the power supply is disconnected from the AC power source, the fourth transistor is turned off, wherein when the switch unit connects the AC power supply to the switch control circuit, and the trigger switch is triggered, the first transistor is turned on, the second transistor is turned off, the third transistor is turned on, the first contact is connected to the second contact of the relay, the input terminal of the power supply is connected to the AC power source, the fourth transistor is turned on to keep the input terminal of the power supply being connected to the AC power source.