A display device includes a display panel, and a power management circuit including a switching regulator for supplying a power in a discontinuous conduction mode or in a continuous conduction mode, and a sensing circuit for sensing whether the switching regulator is operated in the discontinuous conduction mode, the switching regulator including a comparator for monitoring the supplied power, and an RS latch for receiving an output signal from the comparator, and the sensing circuit including a phase lock loop circuit for generating a first clock signal, a phase delay circuit for generating a second clock signal having a phase delayed from the first, and a determination circuit for outputting a first value when a pulse width of the output signal from the RS latch is small, and for outputting a second value when the pulse width of the output signal from the RS latch is not small.