Light emitting device and method for driving thereof

• US 9,099,020 B2
• Filed: 03/25/2013
• Issued: 08/04/2015
• Est. Priority Date: 04/26/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Umezaki, Atushi
• Primary Examiner(s): Leiby, Christopher E
• Application Number:
  US13/849,689
• Publication Number:
  US 20130249887A1
• Time in Patent Office: 862 Days
• Field of Search: 345 55-100, 345204-205, 345211-213
• US Class Current: 1/1
• 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 display device comprising:

a plurality of pixels;

a plurality of source signal lines electrically connected to the plurality of pixels; and

a source driver electrically connected to the plurality of source signal lines, wherein the source driver includes a shift register, an image signal input line configured to input a video signal, a wiring configured to input a control signal, a plurality of first switches, a plurality of second switches, and a plurality of third switches,

wherein each of the plurality of third switches includes a control terminal and is configured to turn 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 connectable to an output terminal of the shift register through a corresponding one of the plurality of first switches and is also connectable to a power source through a corresponding one of the plurality of second switches,

wherein the image signal input line is connectable to the plurality of source signal lines through the plurality of third switches,

wherein the wiring is electrically connected to a control terminal of each of the plurality of first switches and a control terminal of each of the plurality of second switches so that when the plurality of first switches is turned on, the plurality of second switches is turned off, and when the plurality of first switches is turned off, the plurality of second switches is turned on,

wherein the control terminal of each of the plurality of first switches is electrically connected to the control terminal of each of the plurality of second switches through an inverter,

wherein one of the plurality of second switches is connected to the control terminal of only one of the plurality of third switches, and

wherein the one of the plurality of second switches is directly connected to the control terminal of only one of the plurality of third switches.

2. The display device according to claim 1, further comprising a control circuit for outputting the 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.

3. The display device according to claim 1, wherein in a case where all of signals corresponding to all of the plurality of pixels in one row of the plurality of pixels are equal to one another, and the plurality of first switches is turned off, the plurality of second switches is turned on.

4. The display device according to claim 1, wherein, in a case where video signals corresponding to at least two pixels of the video signals corresponding to the plurality of pixels in one row of the plurality of pixels are different from each other, the plurality of first switches is turned on, and the plurality of second switches is turned off.

5. The display device according to claim 1, 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.

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

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

8. The display device according to claim 1, wherein each of the plurality of pixels comprises a thin film transistor, the thin film transistor using a compound semiconductor including indium, gallium, zinc and oxygen.

9. A display device comprising:

a plurality of pixels;

a plurality of source signal lines electrically connected to the plurality of pixels; and

a source driver electrically connected to the plurality of source signal lines,

wherein the source driver includes a shift register, an image signal input line configured to input a video signal, a plurality of first switches, a plurality of second switches, and a plurality of third switches,

wherein each of the plurality of third switches includes a control terminal and is configured to turn 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 connectable to an output terminal of the shift register through a corresponding one of the plurality of first switches and is also connectable to power source through the plurality of second switches,

wherein the image signal input line is connectable to the plurality of source signal lines through the plurality of third switches,

wherein the plurality of first switches and the plurality of second switches 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 plurality of second switches is turned off, and when the plurality of first switches is turned off, the plurality of second switches is turned on,

wherein in a case where all of signals corresponding to all of the plurality of 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,

wherein the control terminal of each of the plurality of first switches is electrically connected to the control terminal of each of the plurality of second switches through an inverter,

wherein one of the plurality of second switches is connected to the control terminal of only one of the plurality of third switches, and

wherein the one of the plurality of second switches is directly connected to the control terminal of only one of the plurality of third switches.

10. The display device according to claim 9, further comprising a control circuit for outputting the 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.

11. The display device according to claim 9, wherein in a case where all of signals corresponding to all of the plurality of pixels in one row of the plurality of pixels are equal to one another, and the plurality of first switches is turned off, the plurality of second switches is turned on.

12. The display device according to claim 9, wherein, in a case where video signals corresponding to at least two pixels of the video signals corresponding to the plurality of pixels in one row of the plurality of pixels are different from each other, the plurality of first switches is turned on, and the plurality of second switches is turned off.

13. The display device according to claim 9, wherein each of the plurality of first switches and the plurality of second switches are digital switches, and wherein each of the plurality of third switches is an analog switch.

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

15. The display device according to claim 9, wherein the display device is an EL display.