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

• US 8,237,756 B2
• Filed: 01/28/2008
• Issued: 08/07/2012
• 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:
  US12/011,520
• Publication Number:
  US 20090027361A1
• Time in Patent Office: 1,653 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 the number of said rows to which data is to be written in said array divided by (m);

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 not being 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; and

wherein (m) is an integer greater than one and a divisor of the number of said rows to which data is to be written in said array that leaves no remainder.

2. A method according to claim 1, wherein:

the sum of the weighted values of said bits in said multi-bit data word is equal to the number of said rows to which data is to be written in said array divided by (m).

3. A method according to claim 1, wherein the number of said time intervals during which said electrical signal is updated in said modulation period is equal to the number of bits in said multi-bit data word.

4. 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 equal to the number of said rows to which data is to be written in said array divided by (m);

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.

5. A method according to claim 4, wherein:

each of said plurality of multi-bit data words contains (b) bits; and

the number of said rows that are updated during each of said time intervals is equal to the product of (m) and (b).

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

associating each of said rows with one of said plurality of modulation periods; and

wherein said modulation period is temporally offset with respect to at least some of the other of said plurality of modulation periods.

7. A method according to claim 6, wherein:

m ones of said rows are associated with a particular modulation period; and

said particular modulation period is temporally offset with respect to every other one of said plurality of modulation periods.

8. A method according to claim 4, wherein said step of defining said plurality of modulation periods includes defining a number of modulation periods equal to the number of rows to which data is to be written in said array divided by (m).

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

associating each of said rows to which data is to be written in said array with one of a plurality of sets of rows; 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.

10. A method according to claim 9, wherein:

the number of bits in each of said multi-bit data words is evenly divisible by an integer (s); and

(s) is equal to the number of said sets of said rows.

11. A method according to claim 9, wherein:

the sum of the weighted values of the bits in each of said multi-bit data words is evenly divisible by an integer (s); and

(s) is equal to the number of said sets of said rows.

12. A method according to claim 9, wherein each pixel control unit updates the same number of said rows to which data is to be written in said array as every other said pixel control unit during each of said time intervals.

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

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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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 not being 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 the number of rows to which data is to be written in said array divided by (m), (m) being an integer greater than one and a divisor of the number of said rows to which data is to be written in said array that leaves no remainder, 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.

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

the sum of the weighted values of said bits in said multi-bit data word is equal to the number of said rows to which data is to be written in said array divided by (m).

20. A display driver according to claim 18, wherein said control logic updates said signal during a number of said time intervals in said modulation period equal to the number of bits in said multi-bit data word.

21. A display driver according to claim 18, 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 the number of said rows to which data is to be written in said array divided by (m), 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.

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

each of said plurality of multi-bit data words contains (b) bits; and

the number of said rows that said control logic is operative to update during each of said time intervals is equal to the product of (m) and (b).

23. A display driver according to claim 21, wherein said control logic is further operative to:

associate each of said rows with one of said plurality of modulation periods; and

temporally offset said modulation period from at least some of said plurality of modulation periods.

24. A display driver according to claim 23, wherein said control logic is operative to:

associate (m) ones of said rows with a particular modulation period; and

temporally offset said particular modulation period with respect to every other one of said plurality of modulation periods.

25. A display driver according to claim 21, wherein said control logic is operative to define a number of modulation periods equal to the number of said rows to which data is to be written in said array divided by (m).

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

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

said control logic is further operative to

associate each row to which data is to be written 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.

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

the number of bits in each of said multi-bit data words is evenly divisible by an integer (s); and

(s) is equal to the number of said sets of said rows.

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

the sum of the weighted values of the bits in each of said multi-bit data words is evenly divisible by an integer (s); and

(s) is equal to the number of said sets of said rows.

29. A display driver according to claim 26, wherein each pixel control unit updates the same number of said rows to which data is to be written in said array as every other said pixel control unit during each of said time intervals.

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

said multi-bit data word is a binary-weighted data word; and

said control logic is further operative to convert said binary-weighted data word into a data word having at least one binary-coded bit and at least one thermometer-coded bit.

31. A display driver according to claim 18, 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 to 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.

32. A display driver according to claim 18, 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.

33. A display driver according to claim 18, 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.

34. A display driver according to claim 18, 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.

35. 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, each bit of each of said multi-bit data words having a weighted value and the sum of the weighted values of said bits not being equal to (2^y−

1), where y is a positive integer; 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 the quotient between the number of rows to which data is to be written in said array and a divisor of the number of rows in said array, said divisor being an integer greater than one and being selected such that said quotient has no remainder.

36. 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 the number of said rows to which data is to be written in said array divided by (m);

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 not being 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; and

wherein (m) is an integer greater than one and is a divisor of the number of said rows to which data is to be written in said array that leaves no remainder.

37. The non-transitory, electronically-readable storage medium of claim 36, wherein:

the sum of the weighted values of said bits in said multi-bit data word is equal to the number of said rows to which data is to be written in said array divided by (m).

38. The non-transitory, electronically-readable storage medium of claim 36, wherein the number of said time intervals during which said electrical signal is updated in said modulation period is equal to the number of bits in said multi-bit data word.

39. The non-transitory, electronically-readable storage medium of claim 36, wherein said code additionally causes said electronic device 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;

divide each of said plurality of modulation periods into a plurality of time intervals equal to the number of said rows to which data is to be written in said array divided by (m);

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

update 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.

40. The non-transitory, electronically-readable storage medium of claim 39, wherein:

each of said plurality of multi-bit data words contains (b) bits; and

the number of said rows that are updated during each of said time intervals is equal to the product of (m) and (b).

41. The non-transitory, electronically-readable storage medium of claim 39, wherein said code additionally causes said electronic device to:

associate each of said rows with one of said plurality of modulation periods; and

wherein said modulation period is temporally offset with respect to at least some of the other of said plurality of modulation periods.

42. The non-transitory, electronically-readable storage medium of claim 41, wherein:

m ones of said rows are associated with a particular modulation period; and

said particular modulation period is temporally offset with respect to every other one of said plurality of modulation periods.

43. The non-transitory, electronically-readable storage medium of claim 39, wherein said code additionally causes said electronic device to define a number of modulation periods equal to the number of rows to which data is to be written in said array divided by (m).

44. The non-transitory, electronically-readable storage medium of claim 39, wherein said code additionally causes said electronic device to:

associate each of said rows to which data is to be written in said array with one of a plurality of sets of rows; and

update 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.

45. The non-transitory, electronically-readable storage medium of claim 44, wherein:

the number of bits in each of said multi-bit data words is evenly divisible by an integer (s); and

(s) is equal to the number of said sets of said rows.

46. The non-transitory, electronically-readable storage medium of claim 44, wherein:

the sum of the weighted values of the bits in each of said multi-bit data words is evenly divisible by an integer (s); and

(s) is equal to the number of said sets of said rows.

47. The non-transitory, electronically-readable storage medium of claim 44, wherein each pixel control unit updates the same number of said rows to which data is to be written in said array as every other said pixel control unit during each of said time intervals.

48. The non-transitory, electronically-readable storage medium of claim 36, wherein said code additionally causes said electronic device to:

receive a binary-weighted data word; and

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.

49. The non-transitory, electronically-readable storage medium of claim 36, 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.

50. The non-transitory, electronically-readable storage medium of claim 36, 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.

51. The non-transitory, electronically-readable storage medium of claim 36, wherein:

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

said code additionally causes said electronic device to

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

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

52. The non-transitory, electronically-readable storage medium of claim 36, 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

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