A power supply circuit includes a voltage output controller configured for outputting voltages, a standby controller configured for directing the voltage output controller to provide voltage to a load, and a microprocessor configured for controlling the standby controller according to a mode of the load. The voltage output controller is applied with a direct current voltage. When the load enters active mode from a powered off mode, the standby controller sends a control signal to the voltage output controller to output direct current voltage to the load and the microprocessor. When the load enters standby mode from the active mode, the microprocessor directs the standby controller to prevent the voltage output controller from outputting direct current voltage to the load and the microprocessor.