Control circuit of display device, display device and electronic appliance having the same, and driving method of the same

• US 20050270254A1
• Filed: 06/07/2005
• Published: 12/08/2005
• Est. Priority Date: 06/08/2004
• Status: Abandoned Application

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Ozaki, Tadafumi
• Application Number:
  US11/146,238
• Publication Number:
  US 20050270254A1
• Time in Patent Office: Days
• US Class Current: 345/63
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/2096 Details of the interface to the display terminal specific for a flat panel suitable for both CRT and flat panel G09G5/006; specific for a CRT G09G1/167
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory
• 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
• 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

Downsizing and improvement in operating efficiency of a control circuit of a display device is achieved. Two video data storage units that have conventionally been used in a control circuit are combined into one, and an address area thereof is divided in half. One of the areas is used as a writing area while the other is used as a reading area, and these areas are alternately switched at regular intervals, for example per frame period. Video data reading from the video data storage unit is performed not in synchronous with a half-cycle of a source clock. Instead, a predetermined quantity of video data is read out continuously in a plurality of consecutive clock cycles, and the video data is temporarily held in a read-out video data storage unit and the like so as to be transmitted to a display panel at any time desired. Write-in operation is performed in the period in which the read-out operation is not performed until a write-in video data storage unit is completely rewritten.

Claims

1. A display device having a control circuit, the control circuit comprising:

main video data storage means including first and second areas for storing video data;

read-out means for reading out the video data from one of the first and second areas of the main video data storage means, and supplying the video data to a display panel; and

write-in means for converting a video signal supplied in format to video data enabling a gray scale display in the display device, and writing the video data to one of the first and second areas of the main video data storage means that is not being read out while the read-out operation of the video data is not performed,

wherein the read-out means switches the first and second areas to be read out the video data in each period in which one ore more images are displayed; and

wherein the read-out means reads out from the main video data storage means, a predetermined quantity of video data that is appropriate for the display timing of the display panel in a plurality of consecutive clock cycles.

2. The display device according to claim 1, wherein the readout means includes a read-out video data storage means for holding the predetermined quantity of video data for a fixed hold period

3. The display device according to claim 2, wherein the read-out video data storage means includes first read-out video data storage means for holding video data that is read out from the main video storage means for a fixed period, and second read-out video data storage means for reading out video data from the first read-out video data storage means all at once at regular intervals.

4. The display device according to claim 1, wherein the read-out means is incorporated into one integrated circuit.

5. The display device according to claim 1, wherein the write-in means includes write-in video data storage means for holding the predetermined quantity of video data that is appropriate for being written to the main video data storage means for a fixed write-in video data hold period so as to write the video data to the main video data storage means.

6. The display device according to claim 1, wherein the write-in means includes excess video data storage means for temporarily holding a part of the predetermined quantity of video data held in the write-in video data storage means, which has not been written to the main video data storage means during the write-in video data hold period, and for writing the video data to the main video data storage means while the read-out operation of the video data is not being performed.

7. The display device according to claim 1, wherein the display device includes a display panel having pixels each of which includes a light emitting element.

8. The display device according to claim 7, wherein the light emitting element is an EL element.

9. An electronic appliance comprising the display device according to claim 1, wherein the electronic appliance is selected from the group consisting of a digital camera, a goggle display (head-mounted display), a navigation system, a sound reproducing device, a computer, a game machine, a portable information terminal, and an image reproducing device provided with a recording medium

10. A display device comprising:

main video data storage unit including first and second areas for storing video data;

a read-out circuit for reading out the stored video data from one of the first and second areas of the main video data storage unit; and

a write-in circuit for writing video data to one of the first and second areas of the main video data storage unit that is not being read out while the read-out operation of the stored video data is not performed.

11. The display device according to claim 10, wherein the read-out circuit includes a read-out video data storage circuit for holding the predetermined quantity of video data for a fixed hold period

12. The display device according to claim 11, wherein the read-out video data storage circuit includes a first read-out video data storage unit for holding video data that is read out from the main video storage unit for a fixed period, and a second read-out video data storage unit for reading out video data from the first read-out video data storage unit all at once at regular intervals.

13. The display device according to claim 10, wherein the read-out circuit is incorporated into one integrated circuit.

14. The display device according to claim 10, wherein the write-in circuit includes a write-in video data storage unit for holding the predetermined quantity of video data that is appropriate for being written to the main video data storage means for a fixed write-in video data hold period so as to write the video data to the main video data storage unit.

15. The display device according to claim 10, wherein the write-in circuit includes an excess video data storage unit for temporarily holding a part of the predetermined quantity of video data held in the write-in video data storage unit, which has not been written to the main video data storage unit during the write-in video data hold period, and for writing the video data to the main video data storage unit while the read-out operation of the video data is not being performed.

16. The display device according to claim 10, wherein the display device includes a display panel having pixels each of which includes a light emitting element.

17. The display device according to claim 16, wherein the light emitting element is an EL element.

18. An electronic appliance comprising the display device according to claim 10, wherein the electronic appliance is selected from the group consisting of a digital camera, a goggle display (head-mounted display), a navigation system, a sound reproducing device, a computer, a game machine, a portable information terminal, and an image reproducing device provided with a recording medium

19. A driving method of a control circuit of a display device, which converts a video signal supplied in format to video data enabling a gray scale display in the display device to be supplied to a display panel, and which comprises a main video data storage means including first and second areas for storing the video data, the driving method comprising the steps:

reading out a predetermined quantity of video data appropriate for the display timing of the display panel continuously in a plurality of consecutive clock cycles from one of the first and second areas of the main video data storage means;

supplying video data readout from the main video data storage unit to the display panel;

converting the video signal supplied in format to the video data, and writing the video data to one of the first and second areas of the main video data storage means that is not being read out while the read-out operation of the video data is not performed; and

switching the first and second areas to be read out the video data in each period for displaying one more images.