A display apparatus, comprising: a display panel; and a display controller, configured to receive a video signal from a host, and display the video signal on the display panel; wherein the display controller calculates an image average brightness of each image in the video signal, wherein in response to an absolute difference between a first image average brightness of a current image in the video signal and a second image average brightness of a previous image in the video signal being smaller than a predetermined value, the display controller activates a timer to obtain a timer value, wherein in response to the timer value reaching a first duration, the display controller reduces brightness of each pixel in the current image of the video signal displayed on the display panel by a first ratio, wherein in response to the timer value reaching a second duration, the display controller reduces the brightness of each pixel in the current image of the video signal displayed on the display panel by a second ratio, wherein the second duration is longer than the first duration, and the second ratio is higher than the first ratio, and wherein in response to the timer value being greater than or equal to a third duration, the display controller reduces the brightness of each pixel in the current image of the video signal displayed on the display panel to 0, wherein the third duration is longer than the second duration, wherein the display controller further dynamically adjusts the predetermined value according to the image average brightness of the current image, wherein when the image average brightness of the current image is in a first brightness interval, the display controller sets the predetermined value to a first predetermined value, wherein when the image average brightness of the current image is in a second brightness interval, the display controller sets the predetermined value to a second predetermined value, wherein when the image average brightness of the current image is in a third brightness interval, the display controller sets the predetermined value to a third predetermined value, wherein a brightness selected within the first brightness interval is higher than a brightness selected within the second brightness interval, and a brightness selected within the second brightness interval is higher than a brightness selected within the third brightness interval, wherein the first predetermined value is greater than the second predetermined value, and the second predetermined value is greater than the third predetermined value. a display panel; and a display controller, configured to receive a video signal from a host, and display the video signal on the display panel; wherein the display controller calculates an image average brightness of each image in the video signal, wherein in response to an absolute difference between a first image average brightness of a current image in the video signal and a second image average brightness of a previous image in the video signal being smaller than a predetermined value, the display controller activates a timer to obtain a timer value, wherein in response to the timer value reaching a first duration, the display controller reduces brightness of each pixel in the current image of the video signal displayed on the display panel by a first ratio, wherein in response to the timer value reaching a second duration, the display controller reduces the brightness of each pixel in the current image of the video signal displayed on the display panel by a second ratio, wherein the second duration is longer than the first duration, and the second ratio is higher than the first ratio, and wherein in response to the timer value being greater than or equal to a third duration, the display controller reduces the brightness of each pixel in the current image of the video signal displayed on the display panel to 0, wherein the third duration is longer than the second duration, wherein the display controller further dynamically adjusts the predetermined value according to the image average brightness of the current image, wherein when the image average brightness of the current image is in a first brightness interval, the display controller sets the predetermined value to a first predetermined value, wherein when the image average brightness of the current image is in a second brightness interval, the display controller sets the predetermined value to a second predetermined value, wherein when the image average brightness of the current image is in a third brightness interval, the display controller sets the predetermined value to a third predetermined value, wherein a brightness selected within the first brightness interval is higher than a brightness selected within the second brightness interval, and a brightness selected within the second brightness interval is higher than a brightness selected within the third brightness interval, wherein the first predetermined value is greater than the second predetermined value, and the second predetermined value is greater than the third predetermined value.