Display device and driving method thereof

• US 20030122773A1
• Filed: 12/11/2002
• Published: 07/03/2003
• Est. Priority Date: 12/18/2001
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Maeda, Kazuhiro, Aoki, Toshiya, Takahashi, Keiji, Kubota, Yasushi, Washio, Hajime, Kaise, Yasuyoshi, Tsujino, Sachio
• Granted Patent: US 7,333,096 B2
• Time in Patent Office: Days
• US Class Current: 345/103
• CPC Class Codes: G09G 2310/0213 controlling the sequence of the scanning lines with respect to the patterns to be displayed, e.g. to save power
• CPC Class Codes: G09G 2310/0232 Special driving of display border areas
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0283 Arrangement of drivers for different directions of scanning
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3666 with the matrix divided into sections
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A control signal generating circuit CTL for controlling the writing into pixels PIX instructs a data signal line drive circuit SD2, which is for driving pixels in a non-display area, to write a voltage VB or a voltage VW which are for non-displaying, not only in the first frame but also once in a predetermined number of frames. In other words, the pixels in the display area is refreshed at intervals longer than those in the case of refreshing the pixels in each frame. Thus, even if the mobility of an active element is high and the leak current on the occasion of OFF-state is large, or even if a large amount of electric charge is accumulated because of the photoelectric effect due to the use of a backlight, it is possible to prevent unnecessary displaying on the display area, which is caused because the writing into the pixels in the display area influences on the pixels in the non-display area, and hence it is possible to improve the quality of partial displaying, while restraining the power consumption.

Claims

1. A driving method of a display device provided with a display section which is composed of a plurality of pixels and includes an active element, comprising the steps of:

setting at least two refresh rates of the plurality of pixels;

dividing the display section into a plurality of areas; and

writing data into the plurality of pixels in the plurality of areas at any one of said at least two refresh rates.

2. The driving method of the display device as defined in claim 1, wherein:

the plurality of areas are composed of a display area and a non-display area;

data is written into pixels in the display area either in each frame or intermittently; and

data is intermittently written into pixels in the non-display area at a refresh rate lower than a refresh rate for writing the data into the pixels in the display area.

3. The driving method of the display device as defined in claim 2, wherein, an interval of intermittent writing of the data into the pixels in the non-display area is determined in accordance with at least one factor selected from the group consisting of a mode of displaying, a type of the active element, a size of the active element, a driving method of an opposed electrode, liquid crystal materials, an auxiliary capacitor, a content of displaying on the display area, and a size of the display area.

4. The driving method of the display device as defined in claim 2, wherein the data is intermittently written into the pixels in the non-display area, with both polarities, so that a difference between (i) an effective value of a voltage of one polarity and (ii) an effective value of a voltage of the other polarity is set to be not more than a predetermined value, during a period of applying the voltages to the pixels.

5. The driving method of the display device as defined in claim 4, wherein the polarities on occasion of writing the data into the pixels in the non-display area are set so as to correspond to polarities of previous writings.

6. The driving method of the display device as defined in claim 4, wherein the polarities on occasion of writing the data into the pixels in the non-display area are automatically adjusted in accordance with polarities of previous writings.

7. The driving method of the display device as defined in claim 1, wherein, the plurality of areas are two display areas, and data is written into pixels in one display area either in each frame or intermittently, while data is intermittently written into pixels in the other display area at a refresh rate lower than a refresh rate for writing the data into the pixels in said one display area.

8. The driving method of the display device as defined in claim 7, wherein, an interval of intermittent writing of the data into the pixels in said the other display area is determined in accordance with at least one factor selected from the group consisting of a mode of displaying, a type of the active element, a size of the active element, a driving method of an opposed electrode, liquid crystal materials, an auxiliary capacitor, a content of displaying on said one display area, and a size of said one display area.

9. The driving method of the display device as defined in claim 7, wherein the data is intermittently written into the pixels in said the other display area, with both polarities, so that a difference between (i) an effective value of a voltage of one polarity and (ii) an effective value of a voltage of the other polarity is set to be not more than a predetermined value, during a period of applying the voltages to the pixels.

10. The driving method of the display device as defined in claim 9, wherein the polarities on occasion of writing the data into the pixels in said the other area is set so as to correspond to polarities of previous writings.

11. The driving method of the display device as defined in claim 9, wherein the polarities on occasion of writing the data into the pixels in said the other area are automatically adjusted in accordance with polarities of previous writings.

12. The driving method of the display device as defined in claim 1, wherein, the plurality of areas are not less than three areas, and data is written into said not less than three areas at each different refresh rate.

13. The driving method of the display device as defined in claim 12, wherein data is intermittently written into the pixels in at least one of said not less than three areas, with both polarities, so that a difference between (i) an effective value of a voltage of one polarity and (ii) an effective value of a voltage of the other polarity is set to be not more than a predetermined value, during a period of applying the voltages to the pixels.

14. The driving method of the display device as defined in claim 13, wherein the polarities on occasion of writing the data into the pixels in said at least one of said not less than three areas are set so as to correspond to polarities of previous writings.

15. The driving method of the display device as defined in claim 13, wherein the polarities on occasion of writing the data into the pixels in said at least one of said not less than three areas are automatically adjusted in accordance with polarities of previous writings.

16. An active matrix display device, comprising a control signal generating circuit for controlling writing of data into pixels of a display section, by driving a data signal line drive circuit and a scanning signal line drive circuit, wherein:

the writing of the data into the pixels can be controlled by not less than two refresh rates;

the display section is divided into a plurality of areas; and

the data is written into the pixels in the plurality of areas at said not less than two refresh rates.

17. The display device as defined in claim 16, wherein, the control signal generating circuit divides the plurality of areas into a display area and a non-display area, causes data to be written into pixels in the display area in each frame, and causes data for non-displaying to be intermittently written into pixels in the non-display area.

18. The display device as defined in claim 17, wherein, an interval of intermittent writing into the pixels in the non-display area is determined in accordance with at least one factor selected from the group consisting of a mode of displaying, a type of an active element, a size of the active element, a driving method of an opposed electrode, liquid crystal materials, an auxiliary capacitor, a content of displaying on the non-display area, and a size of the non-display area.

19. The display device as defined in claim 17, wherein the data is intermittently written into the pixels in the non-display area, with both polarities, so that a difference between (i) an effective value of a voltage of one polarity and (ii) an effective value of a voltage of the other polarity is set to be not more than a predetermined value, during a period of applying the voltages to the pixels.

20. The display device as defined in claim 19, wherein the polarities on occasion of writing the data into the pixels in the non-display area are set so as to correspond to polarities of previous writings.

21. The display device as defined in claim 19, wherein the polarities on occasion of writing the data into the pixels in the non-display area are automatically adjusted in accordance with polarities of previous writings.

22. The display device as defined in claim 16, wherein, the control signal generating circuit divides the plurality of areas into two display areas, causes data to be written into pixels in one of said two display areas in each frame, and causes data to be intermittently written into pixels in the other of said two display areas.

23. The display device as defined in claim 22, wherein, an interval of intermittent writing into the pixels in said the other of said two display areas is determined in accordance with at least one factor selected from the group consisting of a mode of displaying, a type of an active element, a size of the active element, a driving method of an opposed electrode, liquid crystal materials, an auxiliary capacitor, a content of displaying on said one of said two display areas, and a size of said one of said two display areas.

24. The display device as defined in claim 22, wherein the data is intermittently written into the pixels in said the other of said two display areas, with both polarities, so that a difference between (i) an effective value of a voltage of one polarity and (ii) an effective value of a voltage of the other polarity is set to be not more than a predetermined value, during a period of applying the voltages to the pixels.

25. The display device as defined in claim 24, further comprising polarity setting means for setting the polarities on occasion of writing the data into the pixels in said the other of said two display areas, to correspond to polarities of previous writings.

26. The display device as defined in claim 24, further comprising polarity self-adjustment means for automatically adjusting the polarities on occasion of writing the data into the pixels in said the other of said two display areas, in accordance with polarities of previous writings.

27. The display device as defined in claim 16, wherein, the control signal generating circuit divides the plurality of areas into not less than three display areas and causes data to be written into pixels in said not less than three display areas at each different refresh rates.

28. The display device as defined in claim 27, wherein data is intermittently written into pixels in one of said not less than three areas, with both polarities, so that a difference between (i) an effective value of a voltage of one polarity and (ii) an effective value of a voltage of the other polarity is set to be not more than a predetermined value, during a period of applying the voltages to the pixels.

29. The display device as defined in claim 28, further comprising polarity setting means for setting the polarities of writing the data into said one of said not less than three areas, to correspond to polarities of previous writings.

30. The display device as defined in claim 28, further comprising polarity self-adjustment means for automatically adjusting the polarities on occasion of writing the data into said one of said not less than three areas, in accordance with polarities of previous writings.

31. The display device as defined in claim 16, wherein:

the data signal line drive circuit is composed of a multiple gray-scale driver which writes data into pixels in at least one area and a binary driver which writes data into pixels in a plurality of areas other than said at least one area; and

the control signal generating circuit selectively drives either one of the multiple gray-scale driver and the binary driver.

32. The display device as defined in claim 31, wherein the multiple gray-scale driver is composed of a plurality of drivers,

the display device further comprising a switching circuit for transferring a transferred pulse from a last stage of a shift register in a first side of the multiple gray-scale driver to a first stage of a shift register in a second side of the multiple gray-scale driver,

wherein the control signal generating circuit instructs the switching circuit to permit or prohibit transfer of the transferred pulse.

33. The display device as defined in claim 31, wherein the binary driver includes:

a shift register;

a latch circuit which latches binary image signals, responding to an output pulse supplied from the shift register; and

a plurality of selectors which select a voltage applied to liquid crystal, in accordance with an output from the latch circuit,

the display device further comprising a transmission position instructing circuit for causing each of said plurality of selectors to be either active or inactive,

wherein the control signal generating circuit instructs the transmission position instructing circuit to cause said plurality of selectors to be either active or inactive.

34. The display device as defined in claim 16, wherein the scanning signal line drive circuit includes m-stages of shift registers and m first logic circuits, each of said m first logic circuits receives a pulse from a corresponding stage of said m-stages of shift registers and a pulse width control signal for permitting or prohibiting an output of the pulse, and the control signal generating circuit controls a pulse width of the pulse width control signal.

35. The display device as defined in claim 34, wherein, the scanning signal line drive circuit further includes m second logic circuits provided between said m-stages of shift registers and said m first logic circuits, and each of said m second logic circuits generates the pulse supplied from a corresponding stage of said m-stages of shift registers, by means of an input pulse and an output pulse supplied from the corresponding stage of said m-stages of shift registers.

36. The display device as defined in claim 16, wherein the scanning signal line drive circuit includes a plurality of drivers,

the display device further comprising a frame control circuit for transferring a transferred pulse from a last stage of a shift register in a first side of said plurality of drivers to a first stage of the shift register in a second side of said plurality of drivers,

wherein the control signal generating circuit instructs the frame control circuit to permit or prohibit transfer of the transferred pulse.

37. The display device as defined in claim 16, wherein an active element is composed of a polycrystalline silicon thin-film transistor.