Display device and driving method based on the number of pixel rows in the display

• US 8,223,179 B2
• Filed: 07/27/2007
• Issued: 07/17/2012
• Est. Priority Date: 07/27/2007
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Kwan, Kin Yip Kenneth, Nguyen, Andrea, Ng, Sunny Yat-san, Zuravleff, William K.
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): Amadiz, Rodney
• Application Number:
  US11/881,732
• Publication Number:
  US 20090027360A1
• Time in Patent Office: 1,817 Days
• Field of Search: 345 89-100, 345/103, 345/204, 345690-693
• US Class Current: 345/693
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• CPC Class Codes: G09G 2310/0272 Details of drivers for data electrodes, the drivers communicating data to the pixels by means of a current
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence

Abstract

A novel method for driving a display having an array of pixels arranged in a plurality of columns and a plurality of rows includes the steps of defining a modulation period for a row of pixels, dividing the modulation period into a number of coequal time intervals equal to n times the number of rows in the array, receiving a multi-bit data word that indicates an intensity value, and updating the signal asserted on the pixel during a plurality of the time intervals such that the intensity value is displayed by the pixel. Note that n is an integer greater than zero. The method can be applied to all rows, which can be driven asynchronously. A display driver for performing the novel methods is also disclosed. The present invention facilitates driving the display at 100% bandwidth efficiency during each time interval in the modulation period.

Claims

1. A method for driving a display device including an array of pixels arranged in a plurality of columns and a plurality of rows, said method comprising:

defining a modulation period during which an electrical signal corresponding to a particular intensity value will be asserted on a pixel in a row of said array;

dividing said modulation period into a plurality of time intervals, the number of said time intervals equal to n times the number of said rows to which data is to be written in said array, n being an integer greater than zero;

receiving a multi-bit data word indicative of said intensity value, each bit of said multi-bit data word having a weighted value and the sum of the weighted values of said bits being equal to n times the number of said rows to which data is to be written in said array and not equal to (2^y−

1), where y is a positive integer; and

updating said electrical signal asserted on said pixel during at least some of said time intervals in said modulation period such that said intensity value is displayed by said pixel.

2. A method according to claim 1, further comprising:

grouping said time intervals into n groups, n being greater than one; and

wherein said step of updating said signal asserted on said pixel includes updating said signal asserted on said pixel during a predetermined number of said time intervals, said predetermined number of said time intervals being evenly distributed among said groups.

3. A method according to claim 2, further comprising:

defining a second modulation period during which an electrical signal corresponding to another particular intensity value will be asserted on a pixel in another row of said array;

dividing said second modulation period into a plurality of time intervals equal to the number of time intervals in said modulation period;

receiving another multi-bit data word indicative of an intensity value to be asserted on said pixel in said another row;

associating each of said time intervals in said second modulation period with one of said groups; and

updating said signal asserted on said pixel in said another row during at least some of said time intervals of said second modulation period such that said another intensity value is displayed by said pixel in said another row, the time periods intervals during which said signal on said pixel in said another row is updated being evenly distributed among said groups.

4. A method according to claim 3, wherein said second modulation period is temporally offset from said modulation period by n said time intervals.

5. A method according to claim 4, further comprising:

defining a third modulation period during which and electrical signal corresponding to a third particular intensity value will be asserted on a pixel in a third row of said array, said third modulation period being temporally offset from said second modulation period by n said time intervals;

dividing said third modulation period into a plurality of time intervals equal to the number of time intervals in said modulation period;

receiving a third multi-bit data word indicative of a third intensity value to be asserted on said pixel in said third row;

associating each of said time intervals in said third modulation period with one of said groups; and

updating said signal asserted on said pixel in said third row during at least some of said time intervals of said third modulation period such that said third intensity value is displayed by said pixel in said third row, the time intervals during which said signal on said pixel in said third row is updated being evenly distributed among said groups.

6. A method according to claim 2, wherein the number of said time intervals during which said electrical signal is updated is equal to the number of bits in said multi-bit data word.

7. A method according to claim 1, further comprising:

defining a plurality of modulation periods during which electrical signals corresponding to particular intensity values will be asserted on said pixels in said rows of said array;

dividing each of said plurality of modulation periods into a plurality of time intervals;

receiving a plurality of multi-bit data words each indicative of an intensity value to be asserted on a corresponding one of said pixels in said array; and

updating the electrical signals asserted on said pixels in an equal number of said rows during each of said time intervals such that each of said intensity values is displayed by said corresponding pixel.

8. A method according to claim 1, further comprising:

defining a plurality of modulation periods during which electrical signals corresponding to particular intensity values will be asserted on said pixels in said rows of said array;

dividing each of said plurality of modulation periods into a plurality of time intervals;

associating each of said rows in said array with one of a plurality of sets;

receiving a plurality of multi-bit data words each indicative of an intensity value to be asserted on a corresponding one of said pixels in said array; and

updating the electrical signals asserted on said pixels in a plurality of said rows during each of said time intervals with a plurality of pixel control units; and

wherein each of said plurality of pixel control units updates only the rows associated with a particular one of said sets of said rows during each of said time intervals.

9. A method according to claim 1, wherein:

the sum of said weighted values of said bits is an even number.

10. A method according to claim 1, wherein:

the sum of said weighted values is evenly divisible by 2n.

11. A method according to claim 1, wherein the number of bits in said multi-bit data word is evenly divisible by 2n.

12. A method according to claim 1, wherein said step of receiving said multi-bit data word includes:

receiving a binary-weighted data word; and

converting said binary-weighted data word into said multi-bit data word, said multi-bit data word having at least one binary-coded bit and at least one thermometer-coded bit.

13. A method according to claim 1, further comprising:

receiving a first frame synchronization signal at the beginning of said modulation period;

receiving a second frame synchronization signal that defines a time difference between the end of the last one of said time intervals of said modulation period and receipt of said second frame synchronization signal;

defining a second modulation period;

dividing said second modulation period into said plurality of time intervals; and

adjusting the duration of at least some of said time intervals of said second modulation period to spread said time difference over said second modulation period.

14. A method according to claim 1, further comprising:

receiving a frame synchronization signal at the beginning of said modulation period;

receiving a first-of-frame signal indicating the beginning of a first one of said time intervals in said modulation period;

measuring the phase difference between said frame synchronization signal and said first-of-frame signal; and

adjusting the duration of at least some of said time intervals in said modulation period based on said phase difference in order to synchronize receipt of a subsequent frame synchronization signal and a subsequent first-of-frame signal.

15. A method according to claim 1, wherein each pixel in said array includes a liquid crystal layer disposed between a pixel electrode and a common electrode, said method further comprising:

asserting said signal on said pixel relative to said common electrode in a first bias direction during a first group of said time intervals; and

asserting said signal on said pixel in a second bias direction during a second group of said time intervals.

16. A method according to claim 1, further comprising:

discarding at least one bit of said multi-bit data word prior to the end of said modulation period; and

wherein said step of updating said signal includes updating said signal based on any remaining bits of said multi-bit data word.

17. A display driver for driving an array of pixels arranged in a plurality of columns and a plurality of rows, said display driver comprising:

a timer operative to generate a series of time values each associated with a respective one of a plurality of time intervals;

a data input terminal set for receiving a multi-bit data word indicative of an intensity value to be asserted on one of said pixels, each bit of said multi-bit data word having a weighted value and the sum of the weighted values of said bits being equal to n times the number of said rows to which data is to be written in said array and not equal to (2^y−

1), where y is a positive integer; and

control logic operative to

define a modulation period during which an electrical signal corresponding to said intensity value will be asserted on said pixel, said modulation period including a number of said time intervals equal to n times the number of said rows to which data is to be written in said array, n being an integer greater than zero, and

update said signal asserted on said pixel during at least some of said time intervals in said modulation period such that said pixel displays said intensity value.

18. A display driver according to claim 17, wherein:

n is greater than one; and

said control logic is further operative to group said time intervals into n groups and to update said signal asserted on said pixel during a predetermined number of said time intervals, said time intervals during which said signal is updated being evenly distributed among said groups.

19. A display driver according to claim 18, wherein:

said data input terminal set is further operative to receive a second multi-bit data word indicative of another intensity value to be asserted on a pixel in another row of said array; and

said control logic is further operative to

define a second modulation period during which an electrical signal corresponding to said another intensity value will be asserted on said pixel in said another row, said second modulation period including a number of said time intervals equal to n times the number of said rows to which data is to be written in said array,

associate each of said time intervals in said second modulation period with one of said groups, and

update said electrical signal asserted on said pixel in said another row during at least some of said time intervals of said second modulation period, said time intervals during which said signal asserted on said pixel in said another row is updated being evenly distributed among said groups.

20. A display driver according to claim 19, wherein said control logic is further operative to temporally offset said second modulation period from said modulation period by n said time intervals.

21. A display driver according to claim 20, wherein:

said data input terminal set is further operative to receive a third multi-bit data word indicative of an intensity value to be asserted on a pixel in a third row of said array; and

said control logic is further operative to

define a third modulation period during which an electrical signal corresponding to said intensity value of said third multi-bit data word will be asserted on said pixel in said third row, said third modulation period including a number of said time intervals equal to n times the number of said rows to which data is to be written in said array,

associate each of said time intervals in said third modulation period with one of said groups,

update said electrical signal asserted on said pixel in said third row during at least some of said time intervals of said third modulation period, said time intervals during which said signal asserted on said pixel in said third row is updated being evenly distributed among said groups, and

temporally offset said third modulation period from said second modulation period by n said time intervals.

22. A display driver according to claim 18, wherein the number of time intervals during which said electrical signal is updated is equal to the number of bits in said multi-bit data word.

23. A display driver according to claim 17, wherein:

said data input terminal set is further operative to receive a plurality of multi-bit data words each indicative of an intensity value to be asserted on a corresponding one of said pixels in said array; and

said control logic is further operative to

define a plurality of modulation periods during which electrical signals corresponding to particular intensity values will be asserted on said pixels in said rows of said array, each of said modulation periods including a number of said time intervals equal to n times the number of said rows to which data is to be written in said array, and

update the electrical signals asserted on said pixels in an equal number of said rows during each of said time intervals such that said intensity values are displayed by said corresponding pixels.

24. A display driver according to claim 17, wherein:

said control logic further includes a plurality of pixel control units, each of said pixel control units operative to update the electrical signals asserted on said pixels;

said data input terminal set is further operative to receive a plurality of multi-bit data words each indicative of an intensity value to be asserted on a corresponding one of said pixels in said array; and

said control logic is further operative to

define a plurality of modulation periods during which electrical signals corresponding to particular intensity values will be asserted on said pixels in said rows of said array, each of said modulation periods including a number of said time intervals equal to n times the number of said rows to which data is to be written in said array,

associate each row in said array with one of a plurality of sets of rows, and

cause at least some of said pixel control units to update the electrical signals asserted on said pixels in at least one of said rows during each of said time intervals, each of said pixel control units updating only said rows associated with one of said sets of rows.

25. A display driver according to claim 17, wherein:

the sum of said weighted values of said bits is an even number.

26. A display driver according to claim 17, wherein:

the sum of said weighted values is evenly divisible by 2n.

27. A display driver according to claim 17, wherein the number of bits in said multi-bit data word is evenly divisible by 2n.

28. A display driver according to claim 17, further comprising a data converter and wherein:

said data converter is operative to receive a binary-weighted data word; and

said data converter is further operative to convert said binary-weighted data word into said multi-bit data word indicative of said intensity value, said multi-bit data word having at least one binary-coded bit and at least one thermometer-coded bit.

29. A display driver according to claim 17, wherein said control logic is further operative to define a second modulation period and divide said second modulation period into said plurality of said time intervals, said display driver further comprising:

a synchronization input operative to receive a series of frame synchronization signals; and

a compensator operative adjust the duration of subsequent ones of said time intervals to spread the time difference between the end of the last one of said time intervals in said modulation period and a next frame synchronization signal over said second modulation period.

30. A display driver according to claim 17, further comprising:

a synchronization input operative to receive a series of frame synchronization signals; and

a compensator operative to

measure a phase difference between the receipt of a frame synchronization signal and a first-of-frame signal indicative of the beginning of a first one of said time intervals, and

adjust the duration of at least some of said time intervals in said modulation period based on said phase difference in order to synchronize receipt of a subsequent frame synchronization signal and a subsequent first-of-frame signal.

31. A display driver according to claim 17, wherein:

each pixel in said array includes a liquid crystal layer disposed between a pixel electrode and a common electrode; and

said display driver further includes a debias controller operative to

provide a first debias signal indicative of a first bias direction for a first group of said time intervals, and

provide a second debias signal indicative of a second bias direction for a second group of said time intervals.

32. A display driver according to claim 17, wherein said control logic is further operative to:

discard at least one bit of said multi-bit data word prior to the end of said modulation period; and

update said signal based on any remaining bits of said multi-bit data word such that said pixel displays said intensity value.

33. A display driver for driving an array of pixels arranged in a plurality of columns and a plurality of rows, said driver comprising:

a timer operative to define a time period during which a plurality of electrical signals corresponding to particular intensity values can be asserted on said pixels in said rows of said array;

a data input terminal set for receiving a plurality of multi-bit data words, each of said multi-bit data words indicative of an intensity value to be displayed by one of said pixels; and

means for updating said electrical signals asserted on said pixels such that the number of non-zero ones of said intensity values displayable by said pixels in said time period is equal to an integer multiple of the number of rows to which data is to be written in said array and not equal to (2^y−

1), where y is a positive integer.

34. A non-transitory, electronically-readable storage medium having code embodied therein for causing an electronic device to:

define a modulation period during which an electrical signal corresponding to a particular intensity value will be asserted on a pixel in a row of an array of pixels arranged in a plurality of columns and a plurality of rows;

divide said modulation period into a plurality of time intervals, the number of said time intervals equal to n times the number of said rows to which data is to be written in said array, n being an integer greater than zero;

receive a multi-bit data word indicative of said intensity value, each bit of said multi-bit data word having a weighted value and the sum of the weighted values of said bits being equal to n times the number of said rows to which data is to be written in said array and not equal to (2^y−

1), where y is a positive integer; and

update said electrical signal asserted on said pixel during at least some of said time intervals in said modulation period such that said intensity value is displayed by said pixel.

35. The non-transitory, electronically-readable storage medium of claim 34, wherein said code additionally causes said electronic device to:

group said time intervals into n groups, n being greater than one; and

wherein said update of said electrical signal asserted on said pixel includes updating said signal asserted on said pixel during a predetermined number of said time intervals, said predetermined number of said time intervals being evenly distributed among said groups.

36. The non-transitory, electronically-readable storage medium of claim 34, wherein the sum of said weighted values of said bits is an even number.

37. The non-transitory, electronically-readable storage medium of claim 34, wherein the sum of said weighted values is evenly divisible by 2n.

38. The non-transitory, electronically-readable storage medium of claim 34, wherein the number of bits in said multi-bit data word is evenly divisible by 2n.

39. The non-transitory, electronically-readable storage medium of claim 34, wherein said code for causing said electronic device to receive said binary data word includes code for causing said electronic device to convert said binary-weighted data word into said multi-bit data word, said multi-bit data word having at least one binary-coded bit and at least one thermometer-coded bit.

40. The non-transitory, electronically-readable storage medium of claim 34, wherein said code additionally causes said electronic device to:

receive a first frame synchronization signal at the beginning of said modulation period;

receive a second frame synchronization signal that defines a time difference between the end of the last one of said time intervals of said modulation period and receipt of said second frame synchronization signal;

define a second modulation period;

divide said second modulation period into said plurality of time intervals; and

adjust the duration of at least some of said time intervals of said second modulation period to spread said time difference over said second modulation period.

41. The non-transitory, electronically-readable storage medium of claim 34, wherein said code additionally causes said electronic device to:

receive a frame synchronization signal at the beginning of said modulation period;

receive a first-of-frame signal indicating the beginning of a first one of said time intervals in said modulation period;

measure the phase difference between said frame synchronization signal and said first-of-frame signal; and

adjust the duration of at least some of said time intervals in said modulation period based on said phase difference in order to synchronize receipt of a subsequent frame synchronization signal and a subsequent first-of-frame signal.

42. The non-transitory, electronically-readable storage medium of claim 34, wherein said code additionally causes said electronic device to:

assert said signal on a pixel electrode in a first bias direction relative to a common electrode during a first group of said time intervals; and

assert said signal on said pixel electrode in a second bias direction during a second group of said time intervals.

43. The non-transitory, electronically-readable storage medium of claim 34, wherein said code additionally causes said electronic device to:

discard at least one bit of said multi-bit data word prior to the end of said modulation period; and

wherein said update of said signal includes updating said signal based on any remaining bits of said multi-bit data word.