JP2585463B2 - Driving method of liquid crystal display device - Google Patents

Description

The present invention relates to a method for driving a liquid crystal display device, and more particularly, to a liquid crystal display device capable of performing display with different numbers of effective scanning lines of an input video signal. Driving method.

(Related Art) In recent years, liquid crystal display devices have come to be widely used as displays for televisions, personal word processors, personal computers, etc., taking advantage of their small size and low power consumption.

In particular, an active matrix type liquid crystal display device in which a non-linear element is provided for each pixel can perform high-quality display even when the number of scanning lines is increased by switching the non-linear element provided for each pixel. Because of that, it is attracting attention.

This active matrix type liquid crystal display device will be described with reference to FIG.

FIG. 1 is a schematic configuration diagram of an active matrix type liquid crystal display device (1), in which n signal electrodes Xi (i = 1, 2,...) Connected to a signal electrode driving circuit (101).
n) (11) and m connected to the scan electrode drive circuit (201)
The scan electrodes Yj (j = 1, 2,..., M) (21) are arranged in a matrix, and each intersection is provided with a thin film transistor (3
The pixel electrode (41) connected to 1) is provided.

Then, a plurality of pixel electrodes (41) connected to one scanning electrode Yj (21) form m scanning lines Pj (j = 1, 2,...,
m) is composed.

The thin-film transistor (31) has a gate electrode (31a)
Is the scanning electrode Yj (21) and the source electrode (31b) is the signal electrode X
i (11), the drain electrode (31c) is connected to the pixel electrode (41), and the source electrode (31c) is input to the gate electrode (31a) in response to a gate pulse GP from the scan electrode drive circuit (201). On / off control between the drain electrode (31b) and the drain electrode (31c) is performed.

Then, such a liquid crystal display device (1) operates as follows. That is, the video signal SIG is input to the signal electrode driving circuit (101), and one display pixel signal subjected to digital or analog processing is applied to each signal electrode Xi (1) every scanning period.
Applied to 1).

In this video signal SIG, one frame period Tf is equal to display period Td.
And a blanking period Tb. The blanking period Tb is provided in consideration of a time required for the cathode ray to return to the scanning start position, assuming a CRT display.

The scan electrode drive circuit (201) also supplies a scan start signal ST and this scan start signal ST to each scan electrode Yj (2
The shift clock CK for transfer in 1) is input. Thereby, each scanning electrode Yj (21) is sequentially selected,
One screen is constituted by one frame period Tf.

(Problems to be Solved by the Invention) In recent years, the number of scanning lines (hereinafter referred to as effective scanning lines) constituting a display area varies from 200 to 480 depending on software used. It is.

The self-luminous CRT or plasma display does not need to perform scanning because black is automatically displayed for scanning lines other than the effective scanning lines. But,
Since the liquid crystal display device is not of a self-luminous type, it is necessary to apply some voltage to scanning lines other than the effective scanning lines in order to prevent malfunction of the liquid crystal.

For this reason, in the liquid crystal display device, it is necessary to scan also the scanning lines constituting the non-display area and apply the non-display signal.

For example, in a liquid crystal display device having 400 scanning lines, when displaying by using half of all the scanning lines as 200 effective scanning lines, a CRT scans only 200 effective scanning lines. On the other hand, in the liquid crystal display device, it is necessary to scan a scanning line not used for display.

For this reason, if all the scanning lines are sequentially scanned in one scanning period for scanning the 200 scanning lines, it becomes impossible to scan all the scanning lines within one frame period Tf.

Therefore, when the number of effective scanning lines is smaller than the total number of scanning lines of the liquid crystal display device, there is a method of shortening one scanning period and scanning all the scanning lines, that is, a method of scanning by changing the time axis.

However, such a method involving a change in the time axis requires a time axis changing means in the apparatus, and furthermore, after storing a video signal SIG of one display screen once by providing a storage element such as a frame memory. It is necessary to output sequentially.

For this reason, in the driving method involving the change of the time axis as described above, since it is necessary to provide a time axis changing means or a storage element, the size and cost of the apparatus are increased, and therefore, it is not a preferable method. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has a liquid crystal display device that does not cause an increase in the size or cost of the device even when performing display with a smaller number of effective scanning lines than the total number of scanning lines. It is an object of the present invention to provide a driving method.

[Configuration of the Invention] (Means for Solving the Problems) The present invention has a first area including a display area constituted by a plurality of scanning lines, wherein the number of scanning lines is equal to the number of effective scanning lines of an input video signal. A method for driving a liquid crystal display device comprising a display mode and a second display mode in which the number of effective scanning lines is smaller than the number of scanning lines, wherein the second display mode is provided within a retrace period within one frame period. A plurality of scanning lines other than the effective scanning lines are simultaneously scanned.

(Operation) As described above, when performing display with fewer effective scanning lines than all scanning lines, the driving method of the liquid crystal display device of the present invention employs a method other than the effective scanning lines within the retrace period Td within one frame period Tf. Are scanned at the same time.

By driving the liquid crystal display device in this way,
Even when the number of effective scanning lines of the input video signal is smaller than that of all the scanning lines, there is no need to change the time axis. Thus, according to the driving method of the present invention, it is possible to sufficiently scan all the scanning lines within one frame period Tf without having to provide a time axis changing unit or a storage element inside the device.

For a scanning line other than the effective scanning line, for example, in the case of a liquid crystal display device that performs black display when 0 V is applied, by applying a voltage of 0 V to the non-display region, a high contrast between the display region and the non-display region is obtained. Characteristics can be obtained, which is particularly preferable for the driving method of the present invention.

The timing for scanning a scanning line other than the effective scanning line may be any time within the retrace period Tb within one frame period Tf. Further, the scanning may be performed by scanning all the scanning lines other than the effective scanning line at once, or may be performed by dividing into a plurality of scanning lines. Is preferred.

(Example) Hereinafter, a driving method of a liquid crystal display device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a liquid crystal display device (1) according to an embodiment for realizing a method of driving a liquid crystal display device according to the present invention, wherein 640 lines connected to a signal electrode driving circuit (101) are shown. And 480 scan electrodes Yj (j = 1, 2) connected to the scan electrode drive circuit (201).
2,…, 480) (21) are arranged in a matrix.
At each intersection, a pixel electrode (41) connected to the thin film transistor (31) is provided.

The scanning lines Pj (j = 1, 2,..., 480) are formed by a plurality of pixel electrodes (41) connected to one scanning electrode Yj (21).
(Not shown).

The thin-film transistor (31) has a gate electrode (31a)
Is the scanning electrode Yj (21) and the source electrode (31b) is the signal electrode X
i (11), the drain electrode (31c) is connected to the pixel electrode (41), and the source electrode (31c) is input to the gate electrode (31a) in response to a gate pulse GP from the scan electrode drive circuit (201). On / off control between the drain electrode (31b) and the drain electrode (31c) is performed. Further, the liquid crystal composition (61) is sandwiched between the counter electrode (51) corresponding to each pixel electrode (41), and when the potential difference between the pixel electrode (41) and the counter electrode (51) is 0V. The liquid crystal display device (1) for displaying black was used.

By using this liquid crystal display device (1), as shown in FIG. 2, the display area (24) of 400 display lines out of all 480 lines Pj (j = 1, 2,..., 480) (22) Effective scanning line Pj (j = 1,2, ..., 40
0) will be described.

A video signal SIG having a display signal (83) and a non-display signal (81) shown in FIG. 3 is input to the signal electrode drive circuit (101), and one scan line Pj (22) for each operation period. Is sequentially output to each signal electrode Xi (11). Also,
From the scan electrode driving circuit (201), the gate pulse GP shown in FIG. 3 is sequentially applied to each scan electrode Yj (21) every scanning period.

As a result, the effective scanning lines Pj are sequentially scanned within the display period Td, and a display signal is displayed in the display area (24).

Also, the scanning line Pj of the non-display area (25) is set within the retrace period Tb.
(J = 401, 402,..., 480) are scanned collectively, and the non-display area (25) is displayed in black.

In this manner, all the scanning lines Pj within one field period Tf
(J = 1, 2,..., 480) (22) is scanned to form one display screen.

Next, a specific configuration of the scan electrode driving circuit (201) for generating such a gate pulse GP will be described with reference to FIG.

FIG. 4 is an equivalent circuit diagram of a main part of the main scanning electrode drive circuit (201), in which a scan start signal ST from an ST signal terminal (213) is sequentially transferred by a clock signal CK from a CK signal terminal. It has a shift register having a set / reset function composed of 480 connected D flip-flops D1j (203) (j = 1, 2,..., 480).

The output from the D flip-prop D1j (203) is controlled by a level shifter (209) so as to have a predetermined voltage, and then connected to each scan electrode Yj (21) so as to be applied as a gate pulse GP. . The D flip-flop D1j (203) has the D flip-flop D1j (2
AND gate (20) for set / reset control of 03)
7) The output is connected. And AND gate (20
One input terminal of 7) is connected to the SET signal terminal (215) and the other input terminal of the D flip-flop D2j (2) that operates using the output of the D flip-flop D1j (203) as a clock.
05) (j = 1, 2,..., 480) is connected to the output to constitute the scan electrode drive circuit (201).

CK of the scan electrode drive circuit (201) having such a circuit configuration
Signal terminal (211), ST signal terminal (213), SET signal terminal (2
15) The shift clock signal CK, scan start signal ST, set signal SE as shown in FIG.
By applying T and the clear signal CLR, the above-described display operation can be performed.

That is, the scan start signal ST is sequentially transferred to the D flip-flop D1j (203) by the shift clock signal CK, and is output to each scan electrode Yj (21) as a gate pulse GP.
As a result, all the effective scanning lines Pj (j = 1, 2,
.. 400) are scanned to display information.

When the selection of the 400th scan electrode Yj (21) is completed, the set signal SE input from the SET signal terminal (215) is set.
According to T, only 401 to 480 scan electrodes Yj (21), that is, only the scan electrodes Yj (21) in the non-display area (25) can be set at the same time. As a result, the set signal ST transferred by the next shift clock signal CK becomes 4
A predetermined voltage is output by the level shifter (209) so as to be a gate pulse GP of each of the 80th scan electrodes Yj (21) and output. As a result, the non-display area (2
The non-display signal (81) (see FIG. 3) is applied collectively to the scanning line Pj of 5).

Then, all the D flip-flops D1j (203) are reset by the clear signal CLR, and the next display becomes possible.

As described above, according to the driving method of the liquid crystal display device of the present embodiment, even if the driving in which the number of effective scanning lines Pj is smaller than the number of all the scanning lines Pj (22) is not performed within the retrace period Tb. By applying the non-display signal (81) collectively to the scanning lines Pj (22) in the display area (25), the operation can be easily performed with a simple circuit configuration without shortening the time axis.

Next, a driving method of a liquid crystal display device according to another embodiment of the present invention will be described.

FIG. 5 shows 400 effective scanning lines Pj (j = 41, 42,.
0) shows a display screen in the second display mode in which the display area (24) is formed by the non-display areas (23), (40) formed by the upper and lower 40 scanning lines Pj of the display area (24). Two
5).

Such a display is performed, for example, by the gate pulse shown in FIG.
This can be easily achieved by selecting each scanning electrode Yj (21) by GP and applying the video signal SIG.

In the video signal SIG shown in FIG. 6, one frame period Tf includes a display period Td and a blanking period Tb, and the display period Td
Is composed of a display signal (83) and a non-display signal (81).

The gate pulse GP shown in FIG. 6 is sequentially applied to the scanning electrode Yi (21) every scanning period, and the effective scanning line Pj (j = 4) is applied.
, 440), display information is displayed.

Then, during the retrace period Tb within one frame period Tf, the sixth
The effective scanning line Pj (j =
Scan lines Pj (j = 1, 2, ..., 40) other than 41, 42, ..., 440), Pj
(J = 441,..., 480) are scanned at once and a non-display signal (81) is applied. Thus, one frame period
All the scanning lines Pj (22) are scanned within Tf, and one display screen is constituted.

Next, an embodiment of the scan electrode drive circuit (201) of the liquid crystal display device (1) for enabling such a drive will be described with reference to an equivalent circuit diagram of the scan electrode drive circuit (301) in FIG. I will explain.

A shift register is configured by D flip-flops D1j (j = 1, 2,..., 480) (303), and an input signal input from an input terminal (317) is input to the first-stage D flip-flop D11 (303). D13 is input and sequentially transferred by the shift clock CK2 input from the input terminal (319).

Each output terminal Q of each D flip-flop D1j (303)
Is the input of the next-stage D flip-flop D1j (303) and the switch element Sj (j =
1,2, ..., 480) (305) to control each switch element S
j (305). One input terminal of the first-stage switch element S1 (305) is connected to receive the signal DI1 from the input terminal (311), and is connected to the input terminal of the other switch element Sj (305). The output terminal Q of the D flip-flop D2j (j = 1, 2,..., 479) (307) is connected. Further, the other input terminal of the switch element Sj (305) is connected to receive the signal D12 from the input terminal (315).

Further, the input terminal D of the D flip-flop D2j (307) is connected to the output terminal of the adjacent switch element Sj (305), and is connected via buffers BFj (j = 1, 2,..., 480) (309). The scan electrode drive circuit (201) is connected to the scan electrode Yj (21) to constitute a scan electrode drive circuit (201).

Then, by inputting a predetermined signal DI3 to the input terminal (317), the switching elements Sj (j = 1,..., 40), Sj (j =
441,…, 480) (305) is the input signal from the input terminal (315)
Control is performed to select DI2, and switch element Sj (j = 4
1, ..., 440) (305) is the D flip-flop D2j (j = 40,
.., 439) so as to be connected to the output terminal Q of (207). Thereby, the gate pulse GP as shown in FIG.
Can be easily output.

Here, the scanning line Pj (j = 41,..., 440) is displayed in the display area (2
4) as scanning lines Pj (j = 1,..., 40), Pj (j = 441,.
480) as the non-display areas (23) and (25), the display mode of 400 effective scanning lines (see FIG. 5) has been described. However, various modes are provided depending on the signal DI3 input to the input terminal (217). It is possible to correspond to the display mode of the number of effective scanning lines Pj.

Also, according to the signal DI3 input to the input terminal (217),
The display position can also be easily changed variously.

Next, another embodiment of the present invention will be described with reference to the drawings.

Similar to the above-described embodiment, a second display mode in which the number of effective scanning lines Pj is 400 out of the total of 480 scanning lines Pj as shown in FIG. 5 will be described.

FIG. 8 is a timing chart showing one embodiment of the driving method of the liquid crystal display device of the present embodiment. The driving method of the liquid crystal display device (1) of the present embodiment employs an effective scanning line Pj (j = 41, 42). ,…, 44
0) is sequentially scanned for each scanning period and a display signal (83) is applied, and then, except for the effective scanning lines Pj (j = 41, 42,..., 400) within a retrace period Tb within one frame period Tf. Scan line Pj (j = 1,
, 40) to scan the non-display signal (81a) and further scan line Pj
(J = 441,..., 480) to apply a non-display signal (81b).

As described above, in the second display mode in which the number of effective scanning lines Pj is smaller than that of all the scanning lines Pj, the scanning lines Pj other than the effective scanning lines Pj are divided into two within the retrace period Tb, and the non-display signals (81a), ( 81b) may be applied.

Even in this case, it is not necessary to provide a storage element such as a frame memory or a time axis changing means in the liquid crystal display device (1) in the same manner as in the above-described embodiment, and the liquid crystal display device (1) can easily correspond to various effective scanning lines. Display can be performed.

Next, an embodiment of a scan electrode drive circuit (401) of the liquid crystal display device (1) for enabling such a drive will be described with reference to an equivalent circuit diagram of the scan electrode drive circuit of FIG. I do.

In FIG. 9, a serial / parallel conversion circuit (403)
, Each switch element S1j (j = 1, 2,..., 48
0) and (405) are configured to be controlled. This first stage switch element S11 (405) has three input terminals (42
1), (425), and (427), and the inputs DI1, DI2, and DI3 can be selected.

Then, the other switch elements S1j (j = 2,..., 480) (40
5) is a D flip-flop instead of the input terminal (421)
Dj (j = 1, 2,..., 479) (407).

The output Q of the D flip-flop Dj (407) is connected to each scan electrode Yj (21) via an output buffer BFj (j = 1, 2,..., 480) (409), and the switch element S2
The input of the next-stage switch element S2j (j = 1, 2,..., 480) (411) via j (j = 1, 2,..., 480) (411). This switch element S2j (411) is connected to switch element S1j (j = 2,.
480) and (405) as well as the serial / parallel conversion circuit (40
On / off control is performed by the output from 3).

Scan electrode drive circuit (401) thus configured
A predetermined signal is input to the serial / parallel conversion circuit (403) of the switching element S1j (j = 1, 2,..., 40).
(405) is connected to the input DI3 by a switch element S1j (j = 41, 42,...,
440) and (405) are D flip-flops Dj (j = 40, 41,..., 4)
39) The switching element S1j (j = 44) is added to the output Q of (407).
1,442, ..., 480) (405) are connected to the input DI2. Also,
Only the switch S2j (j = 440) (411) is in the connected state.

As a result, the gate pulse GP is applied to the scanning electrodes Yj (21) collectively, and the non-display signal (81b) is applied to the scanning lines Pj (j = 1, 2,... 40) collectively. . And
Scan electrodes forming effective scan lines Pj (j = 41, 42,..., 440)
A gate pulse GP is sequentially applied to Yj (j = 41, 42,..., 440) (21) for each scanning period, whereby the display signal (8
3) is applied to form one display screen. Further, the scanning lines Pj (j = 441, 442,..., 480) are scanned at a time within the flyback period Tb, and the non-display signal (81a) is applied to the non-display area (25).

As the scan electrode driving circuit (401) for realizing the driving method of the liquid crystal display device of the present embodiment, for example, by adopting the above-described configuration, the serial-parallel conversion circuit (403)
The display position can be easily changed by setting various signals to be input to the.

As described in detail above, according to the driving method of the liquid crystal display device of the present embodiment, scanning lines other than the effective scanning lines are collectively or divided into a plurality of groups and scanning is performed within the retrace period Tb of one frame period Tf. By doing so, it becomes possible to scan all the scanning lines within the retrace period Tb of one frame period Tf without having to change the time axis or the like.

Thereby, the circuit configuration for realizing the present invention can be made very easy.

[Effects of the Invention] As described above, according to the driving method of the liquid crystal display device of the present invention, even when a display is performed in which the number of effective scanning lines is smaller than the total number of scanning lines, the scanning lines that are not used for the display. With respect to the above, by changing the non-display signal by simultaneously selecting a plurality of scanning lines during the flyback period Tb, it is not necessary to change the time axis. For this reason, it is possible to effectively drive the apparatus according to various effective scanning lines without increasing the size or cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment for realizing the driving method of the present invention, FIG. 2 is a display screen diagram of the liquid crystal display device in FIG. 1 in a second mode, and FIG. Is a waveform diagram for realizing a display screen in the second mode,
FIG. 4 is an equivalent circuit diagram of a scan electrode driving circuit for outputting the waveform of FIG. 3, FIG. 5 is a display screen in another second mode, and FIG. 6 is a display screen in the second mode. 7 is an equivalent circuit diagram of a scan electrode driving circuit for outputting the waveform of FIG. 5, and FIG. 8 is another waveform for realizing the display screen in FIG. FIG. 9 is an equivalent circuit diagram of a scan electrode drive circuit for outputting the waveform of FIG. (1) Liquid crystal display device (11) Signal electrode (21) Scanning electrode (22) Scanning line (23), (25) Non-display area (24) Display area (101): Signal electrode drive circuit (201), (301), (401): Scan electrode drive circuit

Claims (1)

(57) [Claims] Stomach A first display mode including a display area including a plurality of scanning lines, wherein the number of scanning lines is equal to the number of effective scanning lines of an input video signal; In a method for driving a liquid crystal display device having a second display mode having a small number of scanning lines, the second display mode includes the step of changing the scanning lines other than the effective scanning lines within a retrace period within one frame period. A method for driving a liquid crystal display device, wherein a plurality of lines are simultaneously scanned.