The present invention relates to a power supply device for supplying power, from a battery provided at an electric vehicle, to various types of components, the power supply device enabling current sensing to be performed so as to confirm that an electric vehicle charging facility and an electric vehicle are connected to each other through a connector, and reducing electro-magnetic interference (EMI) noise. The objective of the power supply device of the present invention is to: provide a stable voltage to electric vehicle application components; and reduce the EMI noise according to battery charging, self-switching of the power supply device and the like.