A power supply circuit includes a PWM controller, which is capable of providing pulse signals to the CPU, a temperature feedback circuit coupled to the PWM controller, and a temperature sensor. The temperature sensor is coupled to the temperature feedback circuit, the temperature sensor is located adjacent the CPU, and capable of detects a temperature of the CPU. The PWM controller is capable of adjusting the pulse signals to maintain the pulse signals stably when the temperature sensor detects the temperature of the CPU rising.