Circuit for driving self-luminous display device and method for driving the same

• US 20070152934A1
• Filed: 08/03/2004
• Published: 07/05/2007
• Est. Priority Date: 08/05/2003
• Status: Active Grant

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology Co Ltd (Japan Display Incorporated)
• Inventors: Maeda, Tomoyuki
• Granted Patent: US 7,592,981 B2
• Time in Patent Office: Days
• US Class Current: 345/92
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0439 Pixel structures
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/062 Waveforms for resetting a plurality of scan lines at a time
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2320/046 Dealing with screen burn-in prevention or compensation of the effects thereof
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/103 : Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/021 : Power management, e.g. power saving
• CPC Class Codes: G09G 2330/025 : Reduction of instantaneous peaks of current
• CPC Class Codes: G09G 2330/028 : Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 2340/16 : Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 2360/16 : Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3233 : with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3241 : the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror

Abstract

An organic EL has a problem of element life. Causes of the element life include a temperature and an amount of current. As for a display using an organic EL element, light is emitted by using a current so that an amount of light emission of a screen is proportional to the amount of current passing through a device. Therefore, there are problems that an image of a large amount of light emission has a large current passing through the device causing deterioration of the element and that a high-capacity power supply is required in order to pass a maximum amount of current. As for the display using an organic EL element, the amount of light emission of the screen is proportional to the amount of current passing through the device. Therefore, the higher a maximum amount of light emission of the element is set, the larger the current becomes when all the elements of the screen emit maximum light. If the maximum amount of light emission of the element is suppressed, the entire screen becomes darker. For that reason, a drive to control the amount of light emission of the element is performed according to a display status of the screen.

Claims

1. A driving method of a self-luminous display apparatus having a plurality of self-luminous elements comprising each of pixels placed like a matrix in a pixel row direction and a pixel line direction and driving a display portion by passing a current between an anode and a cathode of each of the self-luminous elements and thereby emitting light from each of the pixels, the driving method comprising:

a first process of acquiring a first amount of current to be passed between the anode and the cathode correspondingly to video data inputted from outside, and acquiring a predetermined single value as the first amount of current irrespective of a status of video data value distribution around the video data;

a second process of acquiring a second amount of current to be passed between the anode and the cathode correspondingly to the video data inputted from outside, where, regarding the second amount of current, a value, which has the first amount of current suppressed at a predetermined ratio according to the status of video data value distribution around the video data, is prepared, and of performing a processing in which the ratio of suppression is variable according to the status of video data value distribution,

wherein the amount of current passing through each pixel line is controlled based on a result of the first or second processing instrument so as to emit light from the display portion.

2. The driving method of a self-luminous display apparatus according to claim 1, wherein the first amount of current applied between the anode and the cathode of each of the corresponding self-luminous elements is determined by the first process when a gradation value of the video data inputted from outside is on a lower gradation side of performing a black display than a first predetermined gradation value.

3. The driving method of a self-luminous display apparatus according to claim 1, wherein the second amount of current x applied between the anode and the cathode of each of the corresponding self-luminous elements is determined by the second process when a gradation value of the video data inputted from outside is on a higher gradation side of performing a white display than a first predetermined gradation value, and if the first amount of current in the case of performing the first process to the gradation value is y, the following relation holds between the first amount of current y and the second amount of current x:

0.20y≦

x≦

0.60y.

4. The driving method of a self-luminous display apparatus according to claim 1, wherein the applied amount of current is determined by acquiring a current value i1 which is a maximum value of the image data inputted from outside in a first period, acquiring a proper current value i2 by calculation from the image data inputted in a second period, and sequentially calculating the amount of current applied to each of the pixels displayed based on the predetermined image data inputted in the second period based on a ratio i2/i1.

5. The driving method of a self-luminous display apparatus according to claim 1, wherein the applied amount of current is determined by acquiring a third current value i3 which is a maximum value of the inputted image data, actually applying a current between the anode and the cathode of each of the self-luminous display elements, acquiring an optimum value as a second current value i4 and multiplying the inputted image data by a ratio i4/i3 and thereby sequentially calculating amount of current applied to each of the pixels displayed based on the predetermined image data.

6. The driving method of a self-luminous display apparatus according to claim 1, wherein the gradation value of the video data inputted from outside is on a higher gradation side of performing a white display than the first predetermined gradation value, and the amount of current applied between the anode and the cathode of each of the self-luminous elements is controlled by a black insertion rate.

7. The driving method of a self-luminous display apparatus according to claim 6, wherein the black insertion is performed from a first line to a terminal line in turn, and a black area is collectively inserted in one frame.

8. The driving method of a self-luminous display apparatus according to claim 7, wherein the black insertion is performed from the first line to the terminal line, and the black area is inserted into a plurality of areas divided in the one frame.

9. The driving method of a self-luminous display apparatus according to claim 6, wherein the black insertion is performed into a plurality of areas divided in the one frame while interchanging the turn instead of performing it from the first line to the terminal line in turn.

10. The driving method of a self-luminous display apparatus according to claim 1, wherein the gradation value of the video data inputted from outside is on a higher gradation side of performing a white display than the first predetermined gradation value, and the amount of current applied between the anode and the cathode of each of the self-luminous elements is controlled by adjusting the amount of current passing through a group of source lines.

11. The driving method of a self-luminous display apparatus according to claim 10, wherein the adjustment of the amount of current passing through the group of source lines is performed by increasing and decreasing a reference current value.

12. The driving method of a self-luminous display apparatus according to claim 10, wherein the adjustment of the amount of current passing through the group of source lines is performed by increasing and decreasing the number of gradations.

13. The driving method of a self-luminous display apparatus according to claim 1, wherein a difference between a first current passing between the anode and the cathode of each of the self-luminous elements in a first frame period and a second current passing in a second frame period following the first frame period is acquired, an n difference current value of which difference value is 1/n (n is a number of 1 or more) is calculated, and a selection value of a pixel line is determined from the n difference current value.

14. The driving method of a self-luminous display apparatus according to claim 13, wherein the value n is 4≦

n≦

256.

15. The driving method of a self-luminous display apparatus according to claim 1, wherein a γ

constant is corrected to be optimum by the amount of current passing between the anode and the cathode of each of the self-luminous elements.

16. The driving method of a self-luminous display apparatus according to claim 15, wherein the γ

constant is a set of points on a curve configured by sequentially combining intermediate values of a plurality of γ

curves.

17. The driving method of a self-luminous display apparatus according to claim 15, wherein increase and decrease in the γ

constant is adjusted based on whether a light emission period of the self-luminous display element is long or short.

18. The driving method of a self-luminous display apparatus according to claim 1, wherein on and off of the second process is controlled by placing switching instrument for the second processing instrument so as to determine the amount of current passing between the anode and the cathode of each of the self-luminous element by combining the first process and the second process when turned on and determine it only by the first process when turned off.

19. A driving circuit of a self-luminous display apparatus having multiple self-luminous elements constituting each pixel placed like a matrix in a pixel row direction and a pixel line direction and driving a display portion by passing a current between an anode and a cathode of each self-luminous element and thereby emitting light from the pixels, the driving circuit comprising:

a first light emitting instrument which has light emitted by each of the self-luminous elements at a first luminance preset correspondingly to image data inputted from outside;

a second light emitting instrument which has light emitted by each of the self-luminous elements at a second luminance adjusted to suppress the first luminance preset correspondingly to the image data inputted from outside in conformance with light emitting luminance distribution of the pixels in surroundings.

25. The driving circuit of the self-luminous display apparatus according to claim 19, further comprising a switching instrument for the second processing instrument which has operations effected only by the first processing instrument.

27. A controller of a self-luminous display apparatus having the driving circuit according to claim 19.

29. A self-luminous display apparatus comprising the driving circuit according to claim 19, in which the self-luminous elements are formed or placed in a matrix in a pixel row direction and a pixel line direction.

20. A driving circuit of a self-luminous display apparatus having multiple self-luminous elements constituting each pixel placed like a matrix in a pixel row direction and a pixel line direction and driving a display portion by passing a current between an anode and a cathode of each self-luminous element and thereby emitting light from the pixels, the driving circuit comprising:

a first processing instrument which performs processing of setting a first amount of current which should pass between the anode and the cathode correspondingly to image data inputted from outside and setting the first amount of current at a predetermined single value independently of an image data value distribution status in the vicinity of the image data; and

a second processing instrument which performs processing of setting a second amount of current which should pass between the anode and the cathode correspondingly to the image data inputted from outside and having one value of the second amount of current prepared which is a value of the first amount of current suppressed at a predetermined ratio according to the image data value distribution status in the vicinity of the image data, where the ratio of suppressing is variable according to the image data value distribution status; and

a control instrument which controls the amount of current passing through each of the pixel lines based on results of the first and second processing instrument.

21. The driving circuit of the self-luminous display apparatus according to claim 20, in which the second processing circuit performs processing of deciding the second amount of current for each of the pixel lines by arithmetic processing based on the image data inputted from outside.

22. The driving circuit of the self-luminous display apparatus according to claim 21, in which the arithmetic processing is a process of obtaining a current value i1 which is a maximum value of the image data inputted from outside in a first period, acquiring a proper current value i2 by calculation from the image data inputted from outside in a second period, and sequentially calculating an amount of current applied to each of the pixels displayed based on the predetermined image data inputted from outside in the second period based on a ratio i2/i1.

23. The driving circuit of the self-luminous display apparatus according to claim 20, in which the second processing circuit includes an instrument that measures the image data inputted from outside and performs the arithmetic processing of deciding the second amount of current for each of the pixel lines based on the measurement result.

24. The driving circuit of the self-luminous display apparatus according to claim 23, in which the arithmetic processing is a process of obtaining a third current value i3 which is a maximum value of the image data inputted from outside, actually applying a current between the anode and the cathode of each of the self-luminous display elements, and acquiring an optimum value as a second current value i4 and multiplying the inputted image data by a ratio i4/i3 so as to sequentially calculate the amount of current applied to each of the pixels displayed based on the predetermined image data.

26. The driving circuit of the self-luminous display apparatus according to claim 20, further comprising a switching instrument for the second processing instrument which has operations effected only by the first processing instrument.

28. A controller of a self-luminous display apparatus having the driving circuit according to claim 20.

30. A self-luminous display apparatus comprising the driving circuit according to claim 20, in which the self-luminous elements are formed or placed in a matrix in a pixel row direction and a pixel line direction.

31. A driving method of a self-luminous display apparatus having a plurality of self-luminous elements comprising each of pixels placed in a matrix in a pixel row direction and a pixel line direction and driving a display portion by passing a current between an anode and a cathode of each of the self-luminous elements and thereby emitting light from each of the pixels, wherein:

the light is emitted from the display portion by controlling an amount of current passing each of pixel lines based on results of (1) a first process of acquiring a first amount of current to be passed between the anode and the cathode correspondingly to video data inputted from outside, and acquiring a predetermined single value as the first amount of current irrespective of a status of video data value distribution around the video data, or (2) a second process of acquiring a second amount of current to be passed between the anode and the cathode correspondingly to the video data inputted from outside; and

preparing as the second amount of current a value having the first amount of current suppressed at a predetermined ratio according to the status of video data value distribution around the video data while the ratio of suppression being variable according to the status of video data value distribution, and

in the case where the amount of current equivalent to displaying white is represented as 100, and if a gradation of a low-current region having the predetermined amount of current represented as 30 or less is given a positive number which is N1>

1, N2>

0 and N1≧

N2 as a coefficient, W as the predetermined amount of current, I org as a current value at the time, and T org as a light emitting period, the amount of current satisfying the current value of I org×

N1 and the light emitting period of T org×

1/N2 is applied instead of the predetermined amount of current.