A power supply system includes a power source and a power extending board detachably connected between the power source and an electronic device. The power source includes at least two outputs. The power extending board includes at least two first transmitting terminals and a second transmitting terminal connected to the two first transmitting terminals. Each of the two outputs transmits a first driving voltage from the power source to the second transmitting terminal via a corresponding first transmitting terminal. The first driving voltages from the power source are identical to each other. The second transmitting terminal transmits a second driving voltage to the electronic device. The second driving voltage is identical to each of the first driving voltages.