Light emitting device and method for driving thereof

• US 8,405,650 B2
• Filed: 06/21/2011
• Issued: 03/26/2013
• 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): Leiby, Christopher E
• Application Number:
  US13/165,208
• Publication Number:
  US 20110310084A1
• Time in Patent Office: 644 Days
• Field of Search: 345 55-100, 345204-205, 345211-213
• US Class Current: 345/213
• 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 signals 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, sequentially outputting video signals 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 video 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 to the shift register and simultaneously outputting the video signals input to the image signal input line to all of the plurality of source signal lines.

2. The method according to claim 1, wherein an input of a clock pulse is also stopped together with the start pulse 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.

3. The method according to claim 1, wherein the display device is a liquid crystal display.

4. The method according to claim 1, wherein the display device is an EL display.

5. 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, a plurality of image signal input lines to which a digital video signal is input, a plurality of first latch circuits, a plurality of second latch circuits to which a signal output from each of the plurality of first latch circuits is input, and a plurality of D/A converter circuits to which a signal output from each of the plurality of the second latch circuits is input, the method comprising:

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

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

in a case where the digital video 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 to the shift register and simultaneously outputting digital video signals input to the plurality of image signal input lines to all of the plurality of first latch circuits.

6. The method according to claim 5, wherein the display device is a liquid crystal display.

7. The method according to claim 5, wherein the display device is an EL display.

8. 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, a plurality of image signal input lines to which a digital video signal is input, a plurality of first latch circuits, a plurality of second latch circuits to which a signal output from each of the plurality of first latch circuits is input, and a plurality of D/A converter circuits to which a signal output from each of the plurality of the second latch circuits is input, the method comprising:

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

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

in a case where the digital video 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 digital video signals input to the plurality of image signal input lines to all of the plurality of first latch circuits.

9. The method according to claim 8, wherein the display device is a liquid crystal display.

10. The method according to claim 8, wherein the display device is an EL display.

11. A display device comprising:

a plurality of pixels;

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

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

a means for controlling whether or not a start pulse is input to the source driver,

wherein the source driver includes a shift register, an image signal input line to which a video signal is input, a plurality of first switches, a second switch, a plurality of third switches, and a power source terminal kept at predetermined potential,

wherein each of the plurality of third switches includes a control terminal and is turned on or off in accordance with a signal input to the control terminal,

wherein the control terminal of each of the plurality of third switches is connected to an output terminal of the shift register through a single first switch of the plurality of first switches and is also connected to the power source terminal through the second switch,

wherein the image signal input line is connected to a single source signal line of the plurality of source signal lines through a single third switch of the plurality of third switches,

wherein the plurality of first switches and the second switch are selectively turned on or off in accordance with a control signal input to the source driver, 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 plurality of pixels are arranged in a matrix form and the means for controlling comprises a control circuit outputting a control signal, the control circuit comprising a determination circuit for determining whether or not video signals corresponding to all of pixels in one row of the plurality of pixels are equal to one another, and in a case where all of 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 shift register is stopped and the control signal is output to turn on the second switch.

12. The display device according to claim 11, wherein the display device is a liquid crystal display.

13. The display device according to claim 11, wherein the display device is an EL display.

15. A display device according to any one of claim 11 or 14,

wherein each of the plurality of first switches and the second switch are digital switches, and

wherein each of the plurality of third switches is an analog switch.

16. A display device according to any one of claim 11 or 14,

wherein each of the plurality of first switches and the second switch are digital switches, and

wherein each of the plurality of third switches is an analog switch.

14. A display device comprising:

a plurality of pixels;

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

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

a means for controlling whether or not a start pulse and a clock pulse are input to the source driver,

wherein the source driver includes a shift register, an image signal input line to which a video signal is input, a plurality of first switches, a second switch, a plurality of third switches, and a power source terminal kept at predetermined potential,

wherein each of the plurality of third switches includes a control terminal and is turned on or off in accordance with a signal input to the control terminal,

wherein the control terminal of each of the plurality of third switches is connected to an output terminal of the shift register through a single first switch of the plurality of first switches and is also connected to the power source terminal through the second switch,

wherein the image signal input line is connected to a single source signal line of the plurality of source signal lines through a single third switch of the plurality of third switches,

wherein the plurality of first switches and the second switch are selectively turned on or off in accordance with a control signal input to the source driver, 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 plurality of pixels are arranged in a matrix form and the means for controlling comprises a control circuit outputting a control signal, the control circuit comprising a determination circuit for determining whether or not video signals corresponding to all of pixels in one row of the plurality of pixels are equal to one another, and in a case where all of 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 shift register is stopped and the control signal is output to turn on the second switch.

17. The display device according to claim 14, wherein the display device is a liquid crystal display.

18. The display device according to claim 14, wherein the display device is an EL display.

19. 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 signal to each of the plurality of source signal lines; and

a control circuit determining whether or not a start pulse is input to the source driver,

wherein the source driver includes a shift register, a plurality of image signal input lines to which a digital video signal is input, a plurality of first switches, a second switch, a power source terminal kept at predetermined potential, a plurality of first latch circuits, a plurality of second latch circuits, and a plurality of D/A converter circuits,

wherein each of the plurality of first latch circuits includes a control terminal and an input terminal of each of the plurality of first latch circuits is selectively connected to the plurality of image signal input lines in accordance with a signal input to the control terminal,

wherein the control terminal of each of the plurality of first latch circuits is connected to an output terminal of the shift register through a single first switch of the plurality of first switches, and is also connected to the power source terminal through the second switch,

wherein when a latch pulse is input to an output terminal of a single first latch circuit of the plurality of first latch circuits, the output terminal of the single first latch circuit of the plurality of first latch circuits is connected to an input terminal of a single second latch circuit of the plurality of second latch circuits,

wherein an output terminal of a single second latch circuit of the plurality of second latch circuits is connected to an input terminal of a single D/A converter circuit of the plurality of D/A converter circuits,

wherein an output terminal of a single D/A converter circuit of the plurality of D/A converter circuits is connected to a single source signal line of the plurality of source signal lines,

wherein the plurality of first switches and the second switch are selectively turned on or off in accordance with a control signal input to the source driver, 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 digital video signals corresponding to all of pixels in one row of the plurality of pixels are equal to one another, and in a case where the digital 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 shift register is stopped and the control signal is output to turn on the second switch.

20. The display device according to claim 19, wherein the display device is a liquid crystal display.

21. The display device according to claim 19, wherein the display device is an EL display.

22. 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 signal to each of the plurality of source signal lines; and

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

wherein the source driver includes a shift register, a plurality of image signal input lines to which a digital video signal is input, a plurality of first switches, a second switch, a power source terminal kept at predetermined potential, a plurality of first latch circuits, a plurality of second latch circuits, and a plurality of D/A converter circuits,

wherein each of the plurality of first latch circuits includes a control terminal and an input terminal of each of the plurality of first latch circuits is selectively connected to the plurality of image signal input lines in accordance with a signal input to the control terminal,

wherein the control terminal of each of the plurality of first latch circuits is connected to an output terminal of the shift register through a single first switch of the plurality of different first switches, and is also connected to the power source terminal through the second switch,

wherein when a latch pulse is input to an output terminal of a single first latch circuit of the plurality of first latch circuits, the output terminal of the single first latch circuit of the plurality of first latch circuits is connected to an input terminal of a single second latch circuit of the plurality of second latch circuits,

wherein an output terminal of a single second latch circuit of the plurality of second latch circuits is connected to an input terminal of a single D/A converter circuit of the plurality of D/A converter circuits,

wherein an output terminal of a single D/A converter circuit of the plurality of D/A converter circuits is connected to a single source signal line of the plurality of source signal lines,

wherein the plurality of first switches and the second switch are selectively turned on or off in accordance with a control signal input to the source driver, 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 digital video signals corresponding to all of pixels in one row of the plurality of pixels are equal to one another, and in a case where the digital video signals corresponding to all of 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.

23. The display device according to claim 22, wherein the display device is a liquid crystal display.

24. The display device according to claim 22, wherein the display device is an EL display.