A power supply device includes a power input unit, a voltage converting unit, a communication unit, a control unit. The power input unit is used for receiving an external power source. The voltage converting unit is used for converting the voltage of the external power source to a predetermined voltage. The communication unit is used for obtaining working voltage information of a power receiving device connected to the power supply device. The control unit is used for controlling the voltage converting unit to output a working voltage indicated by the working voltage information to the power receiving device.