Organic electroluminescent display and driving method thereof

• US 7,187,354 B2
• Filed: 09/19/2002
• Issued: 03/06/2007
• Est. Priority Date: 01/30/2002
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Cheol-Woo, Jeong, Ho-Yong, Min, Woong-Kyu
• Primary Examiner(s): Shalwala; Bipin
• Assistant Examiner(s): Kovalick; Vincent E.
• Application Number:
  US10/503,026
• Publication Number:
  US 20050078064A1
• Time in Patent Office: 1,629 Days
• Field of Search: 345/36, 345/45, 345/63, 345/76, 345/77, 345/87, 345/89, 313/483, 313/504, 315/169.3
• US Class Current: 345/89
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2033 with splitting one or more sub-frames corresponding to the most significant bits into two or more sub-frames
• CPC Class Codes: G09G 3/2077 by a combination of two or more gradation control methods
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 5/399 using two or more bit-mapped memories, the operations of which are switched in time, e.g. ping-pong buffers

Abstract

The present invention relates to an organic electroluminescent display and a driving method thereof, which divides one frame into a plurality of subframes. Since the present invention divides one frame into several subframes, and drives an organic EL device with the subframes assigned to the upper bits and with the corrected gray data for representing the detailed grays between the basic grays during the subframes assigned to the lower bits, it is possible to represent sufficient number of grays regardless of the unstable luminescence characteristics of an organic EL device.

Claims

1. An organic electroluminescent (EL) display comprising:

a panel including a plurality of data lines, a plurality of scan lines intersecting the data lines, and a plurality of pixels provided on areas defined by the data lines and the scan lines, each pixel including an organic EL device;

a scan driver applying scan signals to the scan lines;

a data driver applying data voltages corresponding to gray data to the data lines; and

a subframe generator receiving a data signal and a synchronization signal for one frame, dividing the frame into a plurality of subframes, and outputting a corrected gray data and a corrected synchronization signal for each subframe.

2. The organic EL display of claim 1, further comprising a timing controller receiving the corrected gray data and the corrected synchronization signal for each subframe from the subframe generator and generating a control signal for driving the scan driver and the data driver.

3. The organic EL display of claim 1 or claim 2, wherein the subframe generator outputs a first corrected data for subframes assigned to upper bits of an input data signal to represent a basic gray, and outputs a second corrected data for a subframe corresponding to lower bits of the input data signal to represent a detail gray between basic grays.

4. The organic EL display of claim 3, wherein the number of the subframes corresponding to the upper bits is 2^m when a bit number of the upper bits is m.

5. The organic EL display of claim 3, wherein on and off of the subframes for representing the basic gray are determined by the upper bits.

6. The organic EL display of claim 3, wherein the subframe generator comprises:

a frame memory unit storing input data signal by frame;

a lookup table storing the first corrected data and the second corrected data;

a controller reading the data signal stored in the frame memory unit in response to the synchronization signal, analyzing the data read from the frame memory unit into upper-bit data and lower-bit data, assigning the upper-bit data and the lower-bit data to subframes, and bringing gray data for the respective subframes from the lookup table.

7. The organic EL display of claim 6, wherein the frame memory unit comprises a fist frame memory for storing data signal of odd frame and a second frame memory for storing data signal of even frame.

8. The organic EL display of claim 7, wherein the controller reads the data signal of odd frame stored in the first frame memory and simultaneously stores the data signal of even frame from an external device to the second frame memory.

9. A method of driving an organic electroluminescent (EL) display including a plurality of data lines, a plurality of scan lines intersecting the data lines, and a plurality of pixels formed on areas defined by the data lines and the scan lines and including respective organic EL devices, the method comprising:

a fist step receiving a data signal and a synchronization signal for a frame;

a second step driving the frame into a plurality of subframes and outputting a corrected gray data and a corrected synchronization signal for each subframe;

a third step applying scan signals to the scan lines by subframe unit; and

a fourth step applying data voltages corresponding to the corrected gray data outputted in the second step to the data lines by subframe unit.

10. The method of claim 9, wherein the second step comprises:

outputting a first corrected data used in subframes corresponding to upper-bit data of an input data signal and representing a basic gray; and

outputting a second corrected data used in subframes corresponding to lower-bit data of the input data signal and representing a detailed gray between basic grays.