Disclosed is a display apparatus including: a display; a transformer configured to boost an input alternating current (AC) first voltage and output a second voltage; a switch configured to allow an electric current to flow or stop in the transformer based on a control signal; a power factor correction (PFC) converter configured to correct a power factor of the output second voltage, and output a direct current (DC) third voltage to the display; and a controller configured to modulate a frequency of the control signal so that the second voltage has a target level, and increase or decrease the frequency of the control signal within a specified range to synchronize with an AC period of the first voltage.