Frequency variable display device and flicker compensation method of the same
A frequency variable display apparatus includes a display panel where a plurality of subpixels are provided, an image driving circuit configured to write an input image in the plurality of subpixels in a vertical active period, where a data enable signal swings, of one frame to implement target luminance in the plurality of subpixels, and a flicker compensation circuit configured to cause a leakage current flowing from the plurality of subpixels to signal lines corresponding thereto in a vertical blank period, where the data enable signal does not swing, of the one frame to implement flicker compensation luminance which is lower than the target luminance in the plurality of subpixels.
1 . A frequency variable display apparatus, comprising:
a display panel including a plurality of subpixels;
an image driving circuit configured to write an input image in the plurality of subpixels in a vertical active period of a frame to implement a target luminance in the plurality of subpixels, in response to that a data enable signal swings; and
a flicker compensation circuit configured to cause a leakage current to flow from the plurality of subpixels to signal lines corresponding thereto in a vertical blank period of the frame to implement a flicker compensation luminance which is lower than a target luminance in the plurality of subpixels, in response to that the data enable signal does not swing,
wherein the flicker compensation circuit is configured to output a gate-off control voltage so as to cause a leakage current to flow from the plurality of subpixels to the signal lines corresponding thereto in the vertical blank period, and
wherein the gate-off control voltage is used to generate a 3-level scan signal along with a gate on voltage and a gate off voltage, and the gate-off control voltage is lower than the gate on voltage and higher than the gate off voltage.
2 . The frequency variable display apparatus of claim 1 , wherein the vertical blank period comprises a vertical back porch arranged previously to the vertical active period in the frame and a vertical front porch arranged next to the vertical active period in the frame,
a length of the vertical back porch is a constant value regardless of a length variation of the frame, and
a length of the vertical front porch varies in proportion to a length of the frame.
3 . The frequency variable display apparatus of claim 2 , further comprising a sensing circuit configured to sense an electrical characteristic of each of the plurality of subpixels, in the vertical back porch.
4 . The frequency variable display apparatus of claim 2 , wherein the flicker compensation circuit is configured to cause the leakage current to flow from the plurality of subpixels to the signal lines corresponding thereto in the vertical front porch to implement the flicker compensation luminance which is lower than the target luminance in the plurality of subpixels.
5 . The frequency variable display apparatus of claim 4 , wherein the flicker compensation circuit is configured to output the gate-off control voltage in the vertical front porch.
6 . The frequency variable display apparatus of claim 5 , wherein the flicker compensation circuit is configured to increase a level of the gate-off control voltage in proportion to a length of the vertical front porch, and
the leakage current increases as the level of the gate-off control voltage increases.
7 . The frequency variable display apparatus of claim 6 , wherein the flicker compensation circuit is configured to increase the level of the gate-off control voltage step by step in real time in proportion to the length of the vertical front porch.
8 . The frequency variable display apparatus of claim 7 , wherein the flicker compensation circuit is configured to:
during a vertical front porch of a first frame, increase step by step the level of the gate-off control voltage up to a first target value, based on a real-time count value of a first length of the vertical front porch,
during a vertical front porch of a second frame, increase step by step the level of the gate-off control voltage up to a second target value, based on a real-time count value of a second length of the vertical front porch,
wherein the second length of the vertical front porch is longer than the first length of the vertical front porch, and the second target value of the gate-off control voltage is greater than the first target value of the gate-off control voltage, and
the leakage current increases more in the second frame than in the first frame.
9 . The frequency variable display apparatus of claim 6 , wherein the level of the gate-off control voltage increases linearly in real time in proportion to the length of the vertical front porch.
10 . The frequency variable display apparatus of claim 9 , wherein the flicker compensation circuit is configured to:
during a vertical front porch of a first frame, increase linearly the level of the gate-off control voltage up to a first target value, based on a real-time count value of a first length of the vertical front porch,
during a vertical front porch of a second frame, increase linearly the level of the gate-off control voltage up to a second target value, based on a real-time count value of a second length of the vertical front porch,
wherein the second length of the vertical front porch is longer than the first length of the vertical front porch, and the second target value of the gate-off control voltage is greater than the first target value of the gate-off control voltage, and
the leakage current increases more in the second frame than the in first frame.
11 . The frequency variable display apparatus of claim 5 , wherein the flicker compensation circuit is further configured to output a first fixed voltage to data lines of the signal lines during the vertical front porch and output a second fixed voltage to reference voltage lines of the signal lines, so as to implement the flicker compensation luminance in the plurality of subpixels during the vertical front porch,
the first fixed voltage is lower than data voltages provided the plurality of subpixels in the vertical active period, and
the second fixed voltage is lower than a reference voltage provided to the plurality of subpixels in the vertical active period.
12 . The frequency variable display apparatus of claim 4 , wherein each of the plurality of subpixels comprises:
a driving transistor including a gate electrode connected to a first node, a drain electrode connected to a high level source voltage, and a source electrode connected to a second node;
a light emitting device including an anode electrode connected to the second node and a cathode electrode connected to a low level source voltage;
a first switch transistor configured to control a flow of a current between the first node and a data line, based on a 3-level scan signal from a gate line; and
a second switch transistor configured to control a flow of a current between the second node and a reference voltage line, based on the 3-level scan signal from the gate line,
wherein the 3-level scan signal swings between a gate on voltage and a gate off voltage in the vertical active period and maintains a gate-off control voltage between the gate on voltage and the gate off voltage in the vertical front porch.
13 . The frequency variable display apparatus of claim 12 , wherein a level of the gate-off control voltage is configured to increase in proportion to a length of the vertical front porch, and
the leakage current is configured to increase as a level of the gate-off control voltage increases.
14 . A flicker compensation method of a frequency variable display apparatus including a display panel that include a plurality of subpixels, the flicker compensation method comprising:
writing an input image in the plurality of subpixels in a vertical active period of a frame to implement a target luminance in the plurality of subpixels, when a data enable signal swings; and
outputting a gate-off control voltage so as to cause a leakage current to flow from the plurality of subpixels to signal lines corresponding thereto in a vertical blank period of the frame to implement a flicker compensation luminance which is lower than the target luminance in the plurality of subpixels, when the data enable signal does not swing,
wherein the gate-off control voltage is used to generate a 3-level scan signal along with a gate on voltage and a gate off voltage, and the gate-off control voltage is lower than the gate on voltage and higher than the gate off voltage.