Display drive device and display device

• US 20070229933A1
• Filed: 03/28/2007
• Published: 10/04/2007
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Yamaguchi, Tomoharu
• Granted Patent: US 7,724,415 B2
• Time in Patent Office: Days
• US Class Current: 359/242
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 3/04 for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions
• CPC Class Codes: G09G 3/19 using electrochromic devices
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant

Abstract

A display drive device comprises a display element being colored by injecting an electric charge into an electrolyte via an display electrode due to an oxidation-deoxidization reaction and being decolored by injecting an electric charge having an inverse polarity of the electric charge into the electrolyte, at least one constant current supply circuit which supplies a constant current as a decoloration current pulse having a predetermined pulse width to the display electrode upon the decoloration, a voltage detection circuit which detects a voltage value generated in the display electrode, and a control circuit which controls an operation of the constant current supply circuit intermittently and repeatedly supplying the decoloration current pulse from the constant current supply circuit to the display electrode upon the decoloration, and ending the decoloration on the basis of a voltage value to be detected by the voltage detection circuit.

Claims

1. A display drive device comprising:

a display element including at least one display electrode and one counter electrode disposed opposite to the display electrode, and an electrolyte between the display electrode and the counter electrode, the display element being colored by injecting an electric charge into the electrolyte via the display electrode due to an oxidation-deoxidization reaction and being decolored by injecting an electric charge having an inverse polarity of the electric charge into the electrolyte;

at least one constant current supply circuit which supplies a constant current as a decoloration current pulse having a predetermined pulse width to the display electrode upon the decoloration and injects the electric charge having the inverse polarity into the electrolyte;

a voltage detection circuit which detects a voltage value generated in the display electrode; and

a control circuit which controls an operation of the constant current supply circuit intermittently and repeatedly supplying the decoloration current pulse from the constant current supply circuit to the display electrode upon the decoloration, and ending the decoloration on the basis of a voltage value to be detected by the voltage detection circuit.

2. The display drive device according to claim 1,

wherein the control circuit controls the constant current supply circuit repeatedly supplying the decoloration current pulse from the constant current supply circuit to the display electrode at predetermined supply intervals, and ending the supply operation of the decoloration current pulse to the display electrode when the voltage value to be detected by the voltage detection circuit when the decoloration current pulse is not supplied from the constant current supply circuit to the display electrode exceeds a preset first reference value.

3. The display drive device according to claim 2,

wherein the first reference value is set to a value of a voltage in response to an electromotive force generated in the display electrode when the decoloration current pulse is supplied once to the display electrode, supply of the decoloration current pulse is ended, and after a time in response to the supply interval of the decoloration current pulse has passed in the state that an initial property is kept by the display element.

4. The display drive device according to claim 2,

wherein the control circuit controls the constant current supply circuit repeating an operation of supplying the decoloration current pulse from the constant current supply circuit to the display electrode when the voltage value to be detected by the voltage detection circuit reaches a preset second reference value after the decoloration current pulse is supplied to the display electrode by the constant current supply circuit and before a preset determination time has passed, and ending the supply operation of the decoloration current pulse to the display electrode when the voltage value to be detected by the voltage detection circuit does not reach the preset second reference value before the first determination time has passed.

5. The display drive device according to claim 4,

wherein the second reference value is set to a value of a voltage in response to an electromotive force generated in the display electrode when the decoloration current pulse is supplied once to the display electrode, supply of the decoloration current pulse is ended, and after a time in response to the supply interval of the decoloration current pulse has passed in the state that an initial property is kept by the display element.

6. The display drive device according to claim 1,

wherein the control circuit controls the constant current supply circuit repeating an operation of supplying the decoloration current pulse from the constant current supply circuit to the display electrode when the voltage value to be detected by the voltage detection circuit reaches a preset third reference value when the decoloration current pulse is not supplied to the display electrode by the constant current supply circuit, and ending the supply operation of the decoloration current pulse to the display electrode when the number of times the voltage value of the display electrode to be detected by the voltage detection circuit exceeds the preset determination value when supplying the decoloration current pulse to the display electrode exceeds a predetermined number of times.

7. The display drive device according to claim 6,

wherein the control circuit further controls the constant current supply circuit ending the supply operation of the decoloration current pulse to the display electrode when the voltage value to be detected by the voltage detection circuit does not reach the preset third reference value after the decoloration current pulse is supplied to the display electrode by the constant current supply circuit upon decoloration till the preset determination time passes.

8. The display drive device according to claim 6,

wherein the third reference value is set to a value of a voltage in response to an electromotive force generated in the display electrode when the decoloration current pulse is supplied once to the display electrode, supply of the decoloration current pulse is ended, and after the determination time has passed in the state that an initial property is kept by the display element.

9. The display drive device according to claim 6,

wherein, by supplying the decoloration current pulse to the display electrode with the initial property kept by the display element, the determination value is set to a value obtained by increasing the value of the voltage of the display electrode to be detected at that time by the voltage detection circuit predetermined times.

10. The display drive device according to claim 6,

wherein the control circuit controls the constant current supply circuit upon the decoloration, at first, continuously supplying the constant current to the display electrode, and when the voltage value to be detected by the voltage detection circuit exceeds a preset threshold value, supplying the decoloration current pulse intermittently and repeatedly to the display electrode, and

the determination value is set to a value higher than the threshold value.

11. The display drive device according to claim 1,

wherein the control circuit further comprises a current value setting circuit which sets a current value of the constant current, to be supplied to the display electrode by the decoloration current pulse, to a value in proportion to the area of the display electrode by the constant current supply circuit.

12. The display drive device according to claim 1,

wherein the control circuit controls the constant current supply circuit upon the decoloration, at first, continuously supplying the constant current to the display electrode, and when the voltage value to be detected by the voltage detection circuit exceeds a preset threshold value, supplying the decoloration current pulse intermittently and repeatedly.

13. The display drive device according to claim 12,

wherein the threshold value is set on the basis of the voltage value generated in the display electrode during a period of time when the resistance value of the display electrode is not changed largely in a period of time when the constant current is continuously supplied to the display electrode upon the decoloration.

14. The display drive device according to claim 12,

wherein the threshold value is set to a value obtained by increasing the voltage value generated in the display electrode predetermined times during a period of time when the resistance value of the display electrode is not changed largely.

15. The display drive device according to claim 12,

wherein the threshold value is set to a value obtained by adding a predetermine value to the voltage value generated in the display electrode during a period of time when the resistance value of the display electrode is not changed largely.

16. The display drive device according to claim 12,

wherein the threshold value is updated every time the decoloration is made.

17. The display drive device according to claim 12,

wherein the threshold value is updated every time the decoloration is made a predetermined number of times.

18. The display drive device according to claim 12,

wherein the control circuit controls the current value of the constant current to be supplied to the display electrode from the constant current supply circuit, and set the current value of the constant current upon supply of the decoloration current pulse to a value which is smaller than the current value at the time of continuous supply of the constant current.

19. A display drive device comprising:

a display element including at least one display electrode and one counter electrode disposed opposite to the display electrode, and an electrolyte between the display electrode and the counter electrode, the display element being colored by injecting an electric charge into the electrolyte via the display electrode due to an oxidation-deoxidization reaction and being decolored by injecting an electric charge having an inverse polarity of the electric charge into the electrolyte,

at least one constant current supply circuit which supplies a constant current as a decoloration current pulse having a predetermined pulse width to the display electrode upon the decoloration and injects the electric charge having the inverse polarity into the electrolyte;

a voltage detection circuit which detects a voltage value generated in the display electrode; and

a control circuit which controls an operation of the constant current supply circuit intermittently and repeatedly supplying the decoloration current pulse at predetermined supply intervals from the constant current supply circuit to the display electrode upon the decoloration, and ending the supply operation of the decoloration current pulse to the display electrode when the voltage value to be detected by the voltage detection circuit when the decoloration current pulse is not supplied from the constant current supply circuit to the display electrode exceeds a preset first reference value.

20. A display drive device comprising:

a display element including at least one display electrode and one counter electrode disposed opposite to the display electrode, and an electrolyte between the display electrode and the counter electrode, the display element being colored by injecting an electric charge into the electrolyte via the display electrode due to an oxidation-deoxidization reaction and being decolored by injecting an electric charge having an inverse polarity of the electric charge into the electrolyte;

at least one constant current supply circuit which supplies a constant current as a decoloration current pulse having a predetermined pulse width to the display electrode upon the decoloration and injects the electric charge having the inverse polarity into the electrolyte;

a voltage detection circuit which detects a voltage value generated in the display electrode; and

a control circuit which controls an operation of the constant current supply circuit repeating the supply operation of the decoloration current pulse from the constant current supply circuit to the display electrode when the voltage value to be detected by the voltage detection circuit reaches a preset second reference value after the decoloration current pulse is supplied from the constant current supply circuit to the display electrode and before a preset determination time has passed upon the decoloration, and ending the supply operation of the decoloration current pulse to the display electrode by the constant current supply circuit when the voltage value to be detected by the voltage detection circuit does not reach the preset second reference value before the first determination time has passed.

21. A display device, comprising:

a display unit including at least one display electrode and one counter electrode disposed opposite to the display electrode, and an electrolyte between the display electrode and the counter electrode, and the display unit being colored by injecting an electric charge into the electrolyte via the display electrode due to an oxidation-deoxidization reaction and being decolored by injecting an electric charge having an inverse polarity of the electric charge into the electrolyte;

at least one constant current supply circuit which supplies a constant current as a decoloration current pulse having a predetermined pulse width to the display electrode of the display unit upon the decoloration and injects the electric charge having the inverse polarity into the electrolyte;

a voltage detection circuit which detects a voltage value generated in the display electrode of the display unit; and

a control circuit which controls an operation of the constant current supply circuit intermittently and repeatedly supplying the decoloration current pulse from the constant current supply circuit to the display electrode of the display unit upon the decoloration, and ending the decoloration on the basis of a voltage value of the display electrode to be detected by the voltage detection circuit.

22. The display device according to claim 21,

wherein the control circuit controls the constant current supply circuit repeatedly supplying the decoloration current pulse from the constant current supply circuit to the display electrode at predetermined supply intervals, and ending the supply operation of the decoloration current pulse to the display electrode when the voltage value of the display electrode to be detected by the voltage detection circuit when the decoloration current pulse is not supplied from the constant current supply circuit to the display electrode exceeds a preset first reference value.

23. The display device according to claim 22,

wherein the first reference value is set to a value of a voltage in response to an electromotive force generated in the display electrode when the decoloration current pulse is supplied once to the display electrode, supply of the decoloration current pulse is ended, and after a time in response to the supply interval of the decoloration current pulse has passed in the state that an initial property is kept by the display unit.

24. The display device according to claim 22,

wherein the display electrode is a display segment to form a predetermined display pattern and a plurality of display segments are aligned on the display unit, and

the first reference value is set for each display segment.

25. The display device according to claim 21,

wherein the control circuit controls the constant current supply circuit repeating an operation of supplying the decoloration current pulse from the constant current supply circuit to the display electrode when the voltage value of the display electrode to be detected by the voltage detection circuit reaches a preset second reference value after the decoloration current pulse is supplied to the display electrode by the constant current supply circuit and before a preset determination time has passed, and ending the supply operation of the decoloration current pulse to the display electrode when the voltage value of the display electrode to be detected by the voltage detection circuit does not reach the preset second reference value before the first determination time has passed.

26. The display device according to claim 25,

wherein the second reference value is set to a value of a voltage in response to an electromotive force generated in the display electrode when the decoloration current pulse is supplied once to the display electrode, supply of the decoloration current pulse is ended, and after the determination has passed in the state that an initial property is kept by the display unit.

27. The display device according to claim 25,

wherein the display electrode is a display segment to form a predetermined display pattern and a plurality of display segments are aligned on the display unit, and

the second reference value is set for each display segment.

28. The display device according to claim 21,

wherein the control circuit controls the constant current supply circuit repeating an operation of supplying the decoloration current pulse from the constant current supply circuit to the display electrode when the voltage value of the display electrode to be detected by the voltage detection circuit reaches a preset third reference value when the decoloration current pulse is not supplied to the display electrode by the constant current supply circuit, and ending the supply operation of the decoloration current pulse to the display electrode when the number of times the voltage value of the display electrode to be detected by the voltage detection circuit exceeds the preset determination value when supplying the decoloration current pulse to the display electrode exceeds a predetermined number of times.

29. The display device according to claim 28,

wherein the control circuit further controls the constant current supply circuit ending the supply operation of the decoloration current pulse to the display electrode when the voltage value of the display electrode to be detected by the voltage detection circuit does not reach the preset third reference value after the decoloration current pulse is supplied to the display electrode by the constant current supply circuit upon the decoloration and before the preset determination time has passed.

30. The display device according to claim 28,

wherein the third reference value is set to a value of a voltage in response to an electromotive force generated in the display electrode when the decoloration current pulse is supplied once to the display electrode, supply of the decoloration current pulse is ended, and after the determination time has passed in the state that an initial property is kept by the display unit.

31. The display device according to claim 28,

wherein, by supplying the decoloration current pulse to the display electrode with the initial property kept by the display unit, the determination value is set to a value obtained by increasing the value of the voltage of the display electrode to be detected at that time by the voltage detection circuit predetermined times.

32. The display device according to claim 28,

wherein the control circuit controls the constant current supply circuit upon the decoloration, at first, continuously supplying the constant current to the display electrode of the display unit, and when the voltage value to be detected by the voltage detection circuit exceeds a preset threshold value, supplying the decoloration current pulse intermittently and repeatedly to the display electrode, and

the determination value is set to a value higher than the threshold value.

33. The display device according to claim 28,

wherein the display electrode is a display segment to form a predetermined display pattern and a plurality of display segments are aligned on the display unit, and

the third reference value and the determination value are set for each display segment.

34. The display device according to claim 21,

wherein the display electrode is a display segment to form a predetermined display pattern and a plurality of display segments are aligned on the display unit, and

the control circuit further comprises a current value setting circuit which sets a current value of the constant current, to be supplied from the constant current supply circuit to the display electrode upon the decoloration, to a value in proportion to the area of each display segment.

35. The display device according to claim 21,

wherein the control circuit controls the constant current supply circuit upon the decoloration, at first, continuously supplying the constant current to the display electrode, and supply the decoloration current pulse intermittently and repeatedly to the display electrode when the voltage value to be detected by the voltage detection circuit exceeds a preset threshold value.

36. The display device according to claim 35,

wherein the display electrode is a display segment to form a predetermined display pattern and a plurality of display segments are aligned on the display unit, and

the threshold value is set for each display segment.

37. The display device according to claim 35,

wherein the threshold value is set on the basis of the voltage value generated in the display electrode during a period of time when the resistance value of the display electrode is not changed largely in a period of time when the constant current is continuously supplied to the display electrode upon the decoloration.

38. The display device according to claim 37,

wherein the threshold value is set to a value obtained by increasing the voltage value generated in the display electrode predetermined times during a period of time when the resistance value of the display electrode is not changed largely.

39. The display device according to claim 37,

wherein the threshold value is set to a value obtained by adding a predetermine value to the voltage value generated in the display electrode during a period of time when the resistance value of the display electrode is not changed largely.

40. The display device according to claim 35,

wherein the threshold value is updated every time the decoloration is made.

41. The display device according to claim 35,

wherein the threshold value is updated every time the decoloration is made a predetermined number of times.

42. The display device according to claim 35, wherein the control circuit controls the current value of the constant current to be supplied to the display electrode from the constant current supply circuit, and set the current value of the constant current upon supply of the decoloration current pulse to a value which is smaller than the current value at the time of continuous supply of the constant current.