A power source module is assembled on a main printed circuit board. The power source module comprises an input processing circuit, a PFC/PWM control circuit, a conversion circuit, and an output processing circuit. The input processing circuit is for rectifying an alternating current voltage to be a primary direct current voltage. The PFC/PWM control circuit is for modulating the primary direct current voltage. The PFC/PWM control circuit is assembled on a subsidiary printed circuit board electrically connected to the main printed circuit board. The conversion circuit is for converting the primary direct current voltage to be a secondary direct current voltage. The output processing circuit is for rectifying and filtering the secondary direct current voltage.