Patent ID: 7817445

Claim:
A power supply for a computer, comprising: an alternating current (AC) power supply connected to a primary inductance coil of a transformer via a rectifier, a secondary inductance coil of the transformer providing a standby voltage; a pulse width modulation (PWM) controller comprising a voltage terminal, and a pulse terminal, a positive voltage terminal of the rectifier connected to the pulse terminal of the PWM controller via the primary inductance coil of the transformer; and a relay comprising a switch and an inductance coil, the switch connected between the positive voltage terminal of the rectifier and the voltage terminal of the PWM controller, the inductance coil and a power switch connected in series between a battery and ground; wherein the power switch is controlled by powering on or off the computer, when the computer is turned on, the power switch is closed, the battery provides a voltage to the inductance coil of the relay to close the relay, the positive voltage terminal of the rectifier provides voltages to the voltage terminal of the PWM controller via the relay, the pulse terminal of the PWM controller outputs a pulse signal to the primary inductance coil of the transformer to start the transformer, a direct current (DC) voltage is converted from the AC power supply via the rectifier and the transformer, and output to the voltage output terminal; when the computer is turned off, the power switch is opened, the inductance coil of the relay does not receive voltages from the battery and the relay is not conductive, the voltage terminal of the PWM controller receives no voltage, and the pulse terminal of the PWM controller does not output a pulse signal to the transformer and the transformer stop working, the voltage output terminal does not output voltages.