Display device
A display device may perform frequency down dimming or frequency up dimming based on a measurement count value generated by counting a number of pulses of an emission signal in frame period. Accordingly, the frequency down dimming or the frequency up dimming may be possible, and the display panel may be driven in a variable refresh rate in which the driving frequency of the display panel changes without a frame memory.
1. A display device, comprising:
a display panel including a pixel;
an emission driver configured to provide an emission signal to the pixel; and
a driving controller configured to receive input image data and a vertical synchronization signal from a host processor to generate output image data based on the input image data, and to control the emission driver,
wherein the driving controller is configured to:
count a number of pulses of the emission signal in an N-th frame to generate a measurement count value in the N-th frame, where N is a natural number equal to or greater than 2,
perform a frequency down dimming and generate a calculation count value in the N-th frame when the measurement count value in the N-th frame is greater than a measurement count value in an N−1-th frame,
sequentially increase the number of the pulses of the emission signal in first to M-th dimming frames, where M is a natural number equal to or greater than 2, the first dimming frame being a frame in which the frequency down dimming starts and the M-th dimming frame being a maximum dimming frame in which the frequency down dimming is performed to a maximum limit, and
determine the M-th dimming frame as a dimming end frame in which the frequency down dimming ends when the M-th dimming frame reaches the maximum dimming frame or when the measurement count value in the N-th frame which follows the M-th dimming frame is less than the calculation count value in the N-th frame.
2. The display device of claim 1 , wherein, when a driving frequency of the display panel in the N-th frame is a maximum driving frequency, input image data in the N-th frame includes a vertical back porch period, a vertical active period, and a vertical front porch period, and
wherein, when the driving frequency of the display panel in the N-th frame is not the maximum driving frequency, the input image data in the N-th frame includes the vertical back porch period, the vertical active period, and the vertical front porch period, and a variable vertical front porch period.
3. The display device of claim 2 , wherein, when the driving frequency of the display panel in the N-th frame is not the maximum driving frequency, the driving controller counts the number of the pulses of the emission signal during the variable vertical front porch period of the N-th frame.
4. The display device of claim 3 , wherein the measurement count value in the N-th frame is the number of the pulses of the emission signal during the variable vertical front porch period of the N-th frame.
5. The display device of claim 2 , wherein, when the input image data in the N-th frame does not include the variable vertical front porch period, the driving controller resets the measurement count value in the N-th frame.
6. The display device of claim 1 , wherein the calculation count value in the N-th frame is determined by using an Equation 1 below:
CC1 [N ]=MC[ N −1]+RV,
where CC 1 [N] denotes the calculation count value in the N-th frame, MC[N−1] denotes the measurement count value in the N−1-th frame, and RV denotes a reference value.
7. The display device of claim 1 , wherein, when the measurement count value in the N-th frame is equal to the calculation count value in the N-th frame, the driving controller transmits a synchronization signal to the host processor.
8. The display device of claim 7 , wherein, when the driving controller transmits the synchronization signal to the host processor, the host processor transmits the input image data in an N+1-th frame to the driving controller.
9. The display device of claim 1 , wherein, when the N-th frame starts, the vertical synchronization signal is transmitted to the driving controller.
10. A display device, comprising:
a display panel including a pixel;
an emission driver configured to provide an emission signal to the pixel; and
a driving controller configured to receive input image data and a vertical synchronization signal from a host processor, to generate output image data based on the input image data, and to control the emission driver,
wherein the driving controller is configured to:
count a number of pulses of the emission signal in an N-th frame to generate a measurement count value in the N-th frame, where N is a natural number equal to or greater than 2,
perform a frequency up dimming and generate a calculation count value in an M-th dimming frame when the measurement count value in the N-th frame is less than a measurement count value in an N−1-th frame,
sequentially decrease the number of the pulses of the emission signal in first to the M-th dimming frames, where M is a natural number equal to or greater than 2, the first dimming frame being a frame in which the frequency up dimming starts and the M-th dimming frame being a maximum dimming frame in which the frequency up dimming is performed to a maximum limit, and
determine the M-th dimming frame as a dimming end frame in which the frequency up dimming ends when the M-th dimming frame reaches the maximum dimming frame or when the measurement count value in the N-th frame which follows the M-th dimming frame is the same as the measurement count value in the M-th dimming frame.
11. The display device of claim 10 , wherein, when a driving frequency of the display panel in the N-th frame is a maximum driving frequency, input image data in the N-th frame includes a vertical back porch period, a vertical active period, and a vertical front porch period, and
wherein, when the driving frequency of the display panel in the N-th frame is not the maximum driving frequency, the input image data in the N-th frame includes the vertical back porch period, the vertical active period, and the vertical front porch period, and a variable vertical front porch period.
12. The display device of claim 11 , wherein, when the driving frequency of the display panel in the N-th frame is not the maximum driving frequency, the driving controller counts the number of the pulses of the emission signal during the variable vertical front porch period of the N-th frame.
13. The display device of claim 12 , wherein the measurement count value in the N-th frame is the number of the pulses of the emission signal during the variable vertical front porch period of the N-th frame.
14. The display device of claim 10 , wherein, when the driving controller performs the frequency up dimming in the M-th dimming frame, the driving controller self-skips remaining input image data except for first input image data in the M-th dimming frame to generate output image data in the M-th dimming frame.
15. The display device of claim 10 , wherein the driving controller sets a threshold frequency, and
wherein, when a current frequency of the display panel before start of the frequency up dimming is greater than the threshold frequency, the calculation count value in the first dimming frame which is the N-th frame is determined by using an Equation 2 below:
CC2=MC[ N −1]−(residual(MC[ N −1]/TP))×TP,
where CC 2 denotes the calculation count value in the first dimming frame, MC[N−1] denotes the measurement count value in the N−1-th frame, TP denotes the number of the pulses of the emission signal during a frame period of a target frequency of the host processor, and residual denotes a function for obtaining a fractional part among an integer part and the fractional part.
16. The display device of claim 15 , wherein the driving controller sets the threshold frequency, and wherein, when the current frequency of the display panel before the start of the frequency up dimming is greater than the threshold frequency, the calculation count value in the M-th dimming frame except for the first dimming frame is determined by using an Equation 3 below:
CC3 [M ]=CC2−(TP×( M −1)),
where CC 3 [M] denotes the calculation count value in the M-th dimming frame except for the first dimming frame and M denotes a number of dimming frames from the first dimming frame to the M-th dimming frame.
17. The display device of claim 10 , wherein the driving controller sets a threshold frequency, and
wherein, when a current frequency of the display panel before start of the frequency up dimming is less than the threshold frequency, the calculation count value in the first dimming frame is determined by using an Equation 4 below:
CC4=TP×MF,
where CC 4 denotes the calculation count value in the first dimming frame, TP denotes the number of the pulses of the emission signal during a frame period of a target frequency of the host processor, and MF denotes a number of dimming frames from the first dimming frame to the maximum dimming frame.
18. The display device of claim 17 , wherein the calculation count value in the M-th dimming frame except for the first dimming frame is determined by using an Equation 5 below:
CC5 [M ]=CC4−(TP×( M −1)),
where CC 5 [M] denotes the calculation count value in the M-th dimming frame except for the first dimming frame and M denotes a number of dimming frames from the first dimming frame to the M-th dimming frame.
19. The display device of claim 10 , wherein, in the M-th dimming frame, the driving controller transmits a synchronization signal to the host processor.
20. The display device of claim 19 , wherein, when the driving controller transmits the synchronization signal to the host processor, the host processor transmits the input image data in an N+1-th frame to the driving controller.