Liquid crystal display device
View Patent ↗The liquid crystal display device has a liquid crystal panel in which liquid crystal cells are disposed in intersection areas of scanning lines and data lines, respectively. A picture signal and a synchronous signal are supplied via external terminals, respectively. A timing controller generates a driving timing of the scanning lines and a driving timing of the data lines in response to the synchronous signal. Further, the timing controller varies at least one of the driving timing of the scanning lines and the driving timing of the data lines according to a cycle of the synchronous signal in order to keep a writing time of the picture signal supplied to the liquid crystal cells constant. Therefore, it is possible to keep the writing time constant even when the cycle of the synchronous signal varies, which can prevent the deterioration in display quality.
1. A liquid crystal display device comprising:
external terminals which receives a picture signal and a synchronous signal, respectively; and
a timing controller which generates a driving timing of the scanning lines and a driving timing of the data lines in response to the synchronous signal, and enlarges a difference between the driving timing of the scanning lines and the driving timing of the data lines when a cycle of the synchronous signal is long and diminishes the difference when the cycle is short to keep a writing time of the picture signal supplied to the liquid crystal cells constant.
2. The liquid crystal display device according to claim 1 , further comprising
an oscillator which generates an internal clock signal, wherein
said timing controller includes:
a counter which counts the cycle of the synchronous signal as the number of clocks of the internal clock signal; and
a timing setting circuit which sets at least one of the driving timing of the scanning lines and the driving timing of the data lines according to a counter value of said counter.
3. The liquid crystal display device according to claim 2 , further comprising
an external terminal which receives an external clock signal, wherein
said timing setting circuit sets, according to the counter value of said counter, at least one of the driving timing of the scanning lines and the driving timing of the data lines based on serial number(s) indicating the number(s) of clocks of the external clock signal, and fixes the driving timing of the scanning lines and the driving timing of the data lines to predetermined serial numbers, respectively, when the cycle of the synchronous signal exceeds a predetermined value.
4. The liquid crystal display device according to claim 2 , further comprising
an external terminal which receives an external clock signal, wherein
said timing setting circuit sets, according to the counter value of said counter, at least one of the driving timing of the scanning lines and the driving timing of the data lines based on serial number(s) indicating the number(s) of clocks of the external clock signal.
5. The liquid crystal display device according to claim 4 , wherein
said timing setting circuit assigns the serial number to each of a plurality of counter groups each consisting of the plural continuous counter values and sets each of the driving timings based on each of the serial numbers corresponding to one of the counter groups including the counter value of said counter.
6. The liquid crystal display device according to claim 5 , wherein
said timing setting circuit has a table showing the counter groups and the serial numbers assigned to the respective counter groups.
7. The liquid crystal display device according to claim 4 , wherein:
said timing controller includes a difference detector which detects, as a change in the cycle of the synchronous signal, a difference between a preset standard counter value and the counter value outputted from said counter; and
said timing setting circuit operates said difference to find at least one of the serial numbers indicating the driving timing of the scanning lines and the driving timing of the data lines.
8. The liquid crystal display device according to claim 7 , wherein
said timing setting circuit sets the number of shifts in the serial number indicating the driving timing of the scanning lines to a value (integer) obtained by multiplying a ratio P1/P2 by said difference, P1 being a cycle of the internal clock signal and P2 being a preset standard cycle of the external clock signal.
9. The liquid crystal display device according to claim 7 , wherein
said timing setting circuit sets the number of shifts in the serial number indicating the driving timing of the data lines to a value (integer) obtained by multiplying a ratio P1/P2 by said difference, P1 being a cycle of the internal clock signal and P2 being a preset standard cycle of the external clock signal.
10. The liquid crystal display device according to claim 7 , wherein
said timing selling circuit sets the sum of the number of shifts in the serial number indicating the driving timing of the scanning lines and the number of shifts in the serial number indicating the driving timing of the data lines, to a value (integer) obtained by multiplying a ratio P1/P2 by said difference, P1 being a cycle of the internal clock signal and P2 being a preset standard cycle of the external clock signal.
11. The liquid crystal display device according to claim 1 , further comprising
an oscillator which generates an internal clock signal, wherein
said timing controller includes:
a frame cycle detector which detects a cycle of one frame for displaying one screen based on the synchronous signal to find the cycle of the synchronous signal;
a counter which counts the frame cycle detected by said frame cycle detector as the number of clocks of the internal clock signal; and
a timing selling circuit which sets at least one of the driving timing of the scanning lines and the driving timing of the data lines according to a counter value of said counter.
12. The liquid crystal display device according to claim 11 , further comprising
an external terminal which receives an external clock signal, wherein
said timing setting circuit sets, according to the counter value of said counter, at least one of the driving timing of the scanning lines and the driving timing of the data lines based on serial number(s) indicating the number(s) of clocks of the external clock signal, and fixes the driving timing of the scanning lines and the driving timing of the data lines to predetermined serial numbers, respectively, when the frame cycle exceeds a predetermined value.
13. The liquid crystal display device according to claim 11 , further comprising
an external terminal which receives an external clock signal, wherein
said timing setting circuit sets, according to the counter value of said counter, at least one of the driving timing of the scanning lines and the driving timing of the data lines based on serial number(s) indicating the number(s) of clocks of the external clock signal.
14. The liquid crystal display device according to claim 13 , wherein
said timing setting circuit assigns the serial number to each of a plurality of counter groups each consisting of the plural continuous counter values and sets each of the driving timings based on each of the serial numbers corresponding to one of the counter groups including the counter value of said counter.
15. The liquid crystal display device according to claim 14 , wherein
said timing setting circuit has a table showing the counter groups and the serial numbers assigned to the respective counter groups.
16. The liquid crystal display device according to claim 13 , wherein:
said timing controller includes a difference detector which detects, as a change in the cycle of the synchronous signal, a difference between a preset standard counter value and the counter value outputted from said counter; and
said timing setting circuit operates said difference to find at least one of the serial numbers indicating the driving timing of the scanning lines and the driving timing of the data lines.
17. The liquid crystal display device according to claim 16 , wherein
said timing setting circuit sets the number of shifts in the serial number indicating the driving timing of the scanning lines to a value (integer) obtained by multiplying a ratio P1/P2 by said difference, P1 being a cycle of the internal clock signal and P2 being a preset standard cycle of the external clock signal.
18. The liquid crystal display device according to claim 16 , wherein
said timing setting circuit sets the number of shifts in the serial number indicating the driving timing of the data lines to a value (integer) obtained by multiplying a ratio P1/P2 by said difference, P1 being a cycle of the internal clock signal and P2 being a preset standard cycle of the external clock signal.
19. The liquid crystal display device according to claim 16 , wherein
said timing setting circuit sets the sum of the number of shifts in the serial number indicating the driving timing of the scanning lines and the number of shifts in the serial number indicating the driving timing of the data lines, to a value (integer) obtained by multiplying a ratio P1/P2 by said difference, P1 being a cycle of the internal clock signal and P2 being a preset standard cycle of the external clock signal.