Patent ID: 8519940

Claim:
A display apparatus, comprising: a display panel to display an image according to a synchronous signal; and a back light unit to emit a light to the display panel, wherein the back light unit comprises a controller to determine a first number of frames during which a change in a frequency of the synchronous signal is maintained, determine whether the first number of frames has reached a first threshold value, and recognize a change of display mode of the display apparatus from a first mode to a second mode when the first number has reached the first threshold value, wherein the controller comprises: a mode counter to receive the synchronous signal and a count clock comprising a period from an exterior source, the mode counter to transmit a vertical count value of a frame; a register to store a registered vertical count value; a comparator to receive the vertical count value of a previous frame and a current frame from the mode counter and the registered vertical count value from the register, the comparator to transmit a compare signal; and a sync counter to receive the compare signal from the comparator and to transmit the control signal to the driving signal generator, wherein the sync counter is configured to hold a sync counter value at zero or reset to zero when the sync counter receives the compare signal, and the compare signal indicates the vertical count value of the current frame and the registered vertical count value are the same, wherein the sync counter is further configured to increase the sync counter value by one when the vertical count value of the current frame is different from the registered vertical count value and the sync counter value is zero at the previous frame, or when the vertical count value of the current frame is different from the registered vertical count value and the vertical count value of the previous frame and the vertical count value of the current frame are the same, and wherein the sync counter is further configured to hold the sync counter value at a current value when the sync counter value at the previous frame is not zero and the vertical count value of the previous frame and the vertical count value of the current frame are different.