A light emitting device includes a light source unit, a connection controller, and a driving controller. The light source unit includes a first LED array including a plurality of first LEDs connected in series and a second LED array including a plurality of second LEDs connected in series. The connection controller selectively sets a connection structure between the first and second LED arrays as a series connection, a parallel connection, or a series-parallel connection based on a peak value of a driving voltage driving the light source unit. The driving controller controls the number of LEDs driven in the light source unit according to a magnitude of the driving voltage. Each of the first and second LED arrays is connected between a plurality of first nodes and a plurality of second nodes.