Light emitting device and method for driving thereof

• US 7,965,283 B2
• Filed: 04/21/2006
• Issued: 06/21/2011
• Est. Priority Date: 04/26/2005
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Umezaki, Atsushi
• Primary Examiner(s): Eisen; Alexander
• Assistant Examiner(s): Leiby; Christopher E
• Application Number:
  US11/911,999
• Publication Number:
  US 20090021501A1
• Time in Patent Office: 1,887 Days
• Field of Search: 345 55-100, 345204-205, 345211-213
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 2300/0895 having more than one selection line for a two-terminal active matrix LCD, e.g. Lechner and D2R circuits
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 5/001 Arbitration of resources in a display system, e.g. control of access to frame buffer by video controller and/or main processor
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

An object of the present invention is to provide a display device consuming lower amounts of power. The display device determines whether or not video signals corresponding to all of pixels in one row of a plurality of pixels are equal to one another. In a case where the video signals corresponding to at least two pixels among the video signals corresponding to all of the pixels in one row of the plurality of pixels, are different from each other, video signals input to an image signal input line are sequentially output to a plurality of source signal lines in synchronization with a sampling pulse output from a shift register. On the other hand, when the video signals corresponding to all of the pixels in one row of the plurality of pixels are equal to one another, input of a start pulse to the source driver is stopped, and the video signals input to the image signal input line are simultaneously output to the plurality of source signal line.

Claims

1. A method for driving a display device including a plurality of pixels arranged in a matrix form, a plurality of source signal lines inputting a video signal to the plurality of pixels, and a source driver outputting a signal to each of the plurality of source signal lines, wherein the source driver includes a shift register and an image signal input line to which a video signal is input, the method comprising:

determining whether or not video signals corresponding to all of pixels in one row of the plurality of pixels are equal to one another;

in a case where video signals corresponding to at least two pixels of the video signals corresponding to the pixels in one row of the plurality of pixels are different from each other, outputting a video signal input to the image signal input line to the plurality of source signal lines in synchronization with a sampling pulse output from the shift register; and

in a case where the signals corresponding to all of the pixels in one row of the plurality of pixels are equal to one another, stopping input of a start pulse and a clock pulse to the shift register and simultaneously outputting a predetermined signal input to an output signal line to all of the plurality of source signal lines.

2. A display device comprising:

a plurality of pixels arranged in a matrix form;

a plurality of source signal lines inputting a video signal to the plurality of pixels;

a source driver outputting a video signal to each of the plurality of source signal lines;

a control circuit determining whether or not a start pulse and a clock pulse are input to the source driver;

a plurality of first switches;

a second switch; and

an output signal line kept at predetermined potential,

wherein each of the plurality of source signal lines is connected to an output terminal of the source driver through a single first switch of the plurality of first switches and is also connected to the output signal line through the second switch,

wherein the plurality of first switches and the second switch are selectively turned on or off in accordance with a control signal, when the plurality of first switches is turned on, the second switch is turned off, and when the plurality of first switches is turned off, the second switch is turned on, and

wherein the control circuit includes a determination circuit for determining whether or not video signals corresponding all of pixels in one row of the plurality of pixels are equal to one another, and in a case where the video signals corresponding to all of the pixels in one row of the plurality of pixels are equal to one another, input of a start pulse and a clock pulse to the shift register is stopped and the control signal is output to turn on the second switch.

3. A display device according to claim 2, wherein each of the plurality of first switches and the second switch are analog switches.

4. A display device according to any one of claims 2 and 3, wherein each of the plurality of pixels includes a light emitting element.

5. A display device according to any one of claims 2 and 3, wherein each of the plurality of pixels includes an EL element.

6. A display device according to any one of claims 2 and 3, wherein each of the plurality of pixels includes a liquid crystal element.

7. A display module comprising the display device according to any one of claims 2 and 3.