Display device and driving method

• US 20090027364A1
• Filed: 01/28/2008
• Published: 01/29/2009
• 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: Ng, Sunny Yat-san, Zuravleff, William K., Kwan, Kin Yip, Nguyen, Andrea
• Granted Patent: US 8,237,748 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• 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 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;

associating each of said modulation periods with at least one of said rows;

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 one of said intensity values to be asserted on said corresponding one of said pixels in said array; and

updating said electrical signals asserted on said pixels in an equal number of said rows during each of said time intervals such that each of said pixels displays said corresponding one of said intensity values; and

wherein less than all of said rows in said array are updated during each of said plurality of time intervals.

2. A method according to claim 1, wherein:

said step of dividing each of said plurality of modulation periods into said plurality of time intervals further includes dividing each of said modulation periods into a number of time intervals equal to n times the number of said rows in said array; and

n is an integer greater than zero.

3. A method according to claim 2, wherein:

each row in said array is assigned one of a plurality of values; and

said step of updating said signals further includes updating said signals on said pixels in an equal number of said rows having each of said plurality of values during each of said time intervals.

4. A method according to claim 3, wherein:

said first value is one of even and odd; and

said second value is the other of said even and odd.

5. A method according to claim 2, wherein:

said step of updating said signals asserted on said pixels includes updating said signals asserted on said pixels in (b/n) of said rows during each of said time intervals; and

b equals the number of bits in each of said plurality of multi-bit data words.

6. A method according to claim 2, wherein each of said modulation periods is temporally offset from every other one of said modulation periods by at least n said time intervals.

7. A method according to claim 2, wherein:

each bit in each of said multi-bit data words has a weighted value; and

the sum of said weighted values of said bits in each of said multi-bit data words is equal to n times the number of said rows in said array.

8. A method according to claim 2, wherein:

each bit in each of said multi-bit data words has a weighted value; and

the sum of said weighted values of said bits in each of said multi-bit data words is an even number.

9. A method according to claim 2, wherein:

each bit in each of said multi-bit data words has a weighted value; and

the sum of said weighted values of said bits in each of said multi-bit data words is evenly divisible by 2n.

10. A method according to claim 2, wherein the number of said time intervals is evenly divisible by 2n.

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

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

receiving a binary-weighted data word; and

converting said binary-weighted data word into one of said plurality of multi-bit data words, said multi-bit data words 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 frame synchronization signal at the beginning of a particular one of said modulation periods;

receiving a first-of-frame signal indicating the beginning of a first one of said time intervals in said particular 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 based on said phase difference in order to synchronize receipt of a subsequent frame synchronization signal and a subsequent first-of-frame signal.

14. 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 signals on said pixels relative to said common electrode in a first bias direction during a first group of said time intervals; and

asserting said signals on said pixels in a second bias direction during a second group of said time intervals.

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

discarding at least one bit of one of said multi-bit data words prior to the end of said modulation period associated with said pixel displaying said intensity value defined by said one of said multi-bit data words; and

wherein said step of updating said signal on said associated pixel includes updating said signal based on any remaining bits of said one of said multi-bit data words.

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

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

updating the electrical signals asserted on said pixels in said plurality of 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.

17. An electronically readable medium having code embodied thereon for causing an electronic device to perform the method of claim 1.

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

control logic operative to

define a plurality of modulation periods during which electrical signals corresponding to said particular intensity values will be asserted on said pixels in said rows of said array, each of said modulation periods including a plurality of said time intervals,

associate each of said modulation periods with at least one of said rows, 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 pixels displays said corresponding one of said intensity values; and

wherein said control logic updates less than all of said rows during each of said plurality of time intervals.

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

each of said plurality of modulation periods includes a number of time intervals equal to n times the number of said rows in said array; and

n is an integer greater than zero.

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

each row in said array is assigned one of a plurality of values; and

said control logic is further operative to update said signals on said pixels in an equal number of said rows assigned to each of said plurality of values during each of said time intervals.

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

the number of said values is two;

said first value is one of even and odd; and

said second value is the other of said even and odd.

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

said control logic is further operative to update signals asserted on pixels in (b/n) ones of said rows during each of said time intervals; and

b equals the number of bits in each of said multi-bit data words.

23. A display driver according to claim 19, wherein said control logic is further operative to temporally offset each modulation period from every other one of said plurality of modulation periods by at least n said time intervals.

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

each bit in each of said multi-bit data words has a weighted value; and

the sum of said weighted values of said bits in each of said multi-bit data words is equal to n times the number of said rows in said array.

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

each bit in each of said multi-bit data words has a weighted value; and

the sum of said weighted values of said bits in each of said multi-bit data words is an even number.

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

each bit in each of said multi-bit data words has a weighted value; and

the sum of said weighted values of said bits in each of said multi-bit data words is evenly divisible by 2n.

27. A display driver according to claim 19, wherein the number of said time intervals in each of said modulation periods is evenly divisible by 2n.

28. A display driver according to claim 19, wherein the number of bits in each of said multi-bit data words is evenly divisible by 2n.

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

at least one of said multi-bit data words 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.

30. 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 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 one of said modulation periods and a next frame synchronization signal over a subsequent one of said plurality of modulation periods.

31. 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.

32. A display driver according to claim 18, wherein said control logic is further operative to:

discard at least one bit from one of said multi-bit data words prior to the end of said modulation period associated with said pixel displaying said intensity value defined by said one of said multi-bit data words; and

update said signal asserted on said pixel associated with said one of said multi-bit data words based on any remaining bits of said one of said multi-bit data words such that said associated pixel displays said intensity value defined by said one of said multi-bit data words.

33. A display driver according to claim 18, 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; and

said control logic is further operative to 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.

34. 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 plurality of multi-bit data words, each of said multi-bit data words indicative of an intensity value to be asserted on a corresponding one of said pixels;

means for defining a plurality of modulation periods each including a plurality of time intervals; and

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