A power source switching apparatus is provided. The example power source switching apparatus may include a voltage adjuster outputting a first power source voltage having a voltage level, corresponding to the output voltage of a battery, during an external power source mode where the battery is being charged, the first power source voltage based at least in part on the external power source and the output voltage of the battery, a controller outputting a first control signal and a second control signal, the first control signal enabled if the battery is operating in the external power source mode and the second control signal is enabled if the battery is not operating in the external power source mode, a first switch outputting the first power source voltage if the first control signal is enabled and a second switch outputting the output voltage of the battery if the second control signal is enabled.