A display apparatus comprising: an OLED (Organic Light Emitting Diode) panel unit receiving an input of a video signal and a plurality of driving power levels for RGB colors and displaying an image; a video signal providing unit providing the video signal to the OLED panel unit; and a power supply unit supplying the plurality of driving power levels to the OLED panel unit wherein the power supply unit is operable to predict driving currents for the RGB colors to be supplied to the OLED panel unit based on luminance information of the video signal and to perform feed forward control with respect to the plurality of driving power levels based on the predicted driving currents; characterized in that: the power supply unit comprises: a rectifying unit arranged to rectify an external AC power; a power factor correction, PFC, unit arranged to make voltage and current of the rectified AC power to be in the same phase and to transform the AC voltage into a DC voltage; a convertor arranged to convert the DC voltage into a plurality of voltages to output the plurality of voltages through a multi-winding insulation transformer; a plurality of output terminals arranged to output the plurality of voltages; a plurality of switching units arranged to selectively provide the plurality of voltages of the convertor to the plurality of output terminals; and a power control unit arranged to control the plurality of switching units to perform feedback control with respect to the plurality of voltages output from the output unit, wherein each of the plurality of switching units comprises: a switching element having one end connected to the convertor; an inductor having a first end connected to the other end of the switching element and a second end connected to one of the plurality of output terminals; and a diode having an anode commonly connected to the other end of the switching element and the first end of the inductor and also having a cathode grounded. an OLED (Organic Light Emitting Diode) panel unit receiving an input of a video signal and a plurality of driving power levels for RGB colors and displaying an image; a video signal providing unit providing the video signal to the OLED panel unit; and a power supply unit supplying the plurality of driving power levels to the OLED panel unit wherein the power supply unit is operable to predict driving currents for the RGB colors to be supplied to the OLED panel unit based on luminance information of the video signal and to perform feed forward control with respect to the plurality of driving power levels based on the predicted driving currents; characterized in that: the power supply unit comprises: a rectifying unit arranged to rectify an external AC power; a power factor correction, PFC, unit arranged to make voltage and current of the rectified AC power to be in the same phase and to transform the AC voltage into a DC voltage; a convertor arranged to convert the DC voltage into a plurality of voltages to output the plurality of voltages through a multi-winding insulation transformer; a plurality of output terminals arranged to output the plurality of voltages; a plurality of switching units arranged to selectively provide the plurality of voltages of the convertor to the plurality of output terminals; and a power control unit arranged to control the plurality of switching units to perform feedback control with respect to the plurality of voltages output from the output unit, wherein each of the plurality of switching units comprises: a switching element having one end connected to the convertor; an inductor having a first end connected to the other end of the switching element and a second end connected to one of the plurality of output terminals; and a diode having an anode commonly connected to the other end of the switching element and the first end of the inductor and also having a cathode grounded. a rectifying unit arranged to rectify an external AC power; a power factor correction, PFC, unit arranged to make voltage and current of the rectified AC power to be in the same phase and to transform the AC voltage into a DC voltage; a convertor arranged to convert the DC voltage into a plurality of voltages to output the plurality of voltages through a multi-winding insulation transformer; a plurality of output terminals arranged to output the plurality of voltages; a plurality of switching units arranged to selectively provide the plurality of voltages of the convertor to the plurality of output terminals; and a power control unit arranged to control the plurality of switching units to perform feedback control with respect to the plurality of voltages output from the output unit, wherein each of the plurality of switching units comprises: a switching element having one end connected to the convertor; an inductor having a first end connected to the other end of the switching element and a second end connected to one of the plurality of output terminals; and a diode having an anode commonly connected to the other end of the switching element and the first end of the inductor and also having a cathode grounded. a switching element having one end connected to the convertor; an inductor having a first end connected to the other end of the switching element and a second end connected to one of the plurality of output terminals; and a diode having an anode commonly connected to the other end of the switching element and the first end of the inductor and also having a cathode grounded.