Method for driving display device and liquid crystal display device

• US 8,817,009 B2
• Filed: 01/13/2011
• Issued: 08/26/2014
• Est. Priority Date: 01/20/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hayakawa, Masahiko, Wakimoto, Kenichi
• Primary Examiner(s): Dharia, Prabodh M
• Application Number:
  US13/005,763
• Publication Number:
  US 20110175895A1
• Time in Patent Office: 1,321 Days
• Field of Search: 345/76, 345/77, 345 87-102, 345204-214, 345/589, 345/630, 345/690, 348/51, 348/744, 315/169.3
• US Class Current: 345/212
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 3/36 using liquid crystals
• 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: G11C 19/28 using semiconductor elements G11C19/14, G11C19/36 take precedence

Abstract

The still image display mode includes a first period of writing the data of the image signal from the driver circuit portion into the pixel; after the first period, a second period of stopping supply of a signal or voltage for operating the driver circuit portion to the driver circuit portion; and after the second period, a third period of restarting the supply of a signal or voltage for operating the driver circuit portion to the driver circuit portion and writing the data of the image signal into the pixel from the driver circuit portion, so that the pixel keeps displaying a still image. A length of a period from the stop of the supply of the signal for operating the driver circuit portion to the driver circuit portion to the restart is set in accordance with a temperature of the display device.

Claims

1. A method for driving a display device comprising the steps of:

supplying an image signal of a still image from a display control circuit to a driver circuit portion;

writing a data of the image signal from the driver circuit portion into a pixel;

after writing the data of the image signal, holding the data written into the pixel by stopping a supply of a signal for operating the driver circuit portion from the display control circuit to the driver circuit portion for a period; and

after the period, restarting the supply of the signal for operating the driver circuit portion from the display control circuit to the driver circuit portion to write the data of the image signal of the still image from the driver circuit portion into the pixel;

wherein a length of the period from a step of stopping the supply of the signal for operating the driver circuit portion to a step of restarting the supply of the signal for operating the driver circuit portion is set in accordance with a temperature of the display device detected by a temperature detection circuit in the display device, and

wherein the pixel is configured to display the still image in the period.

2. The method for driving a display device according to claim 1,

wherein the length of the period from the step of stopping the supply of the signal for operating the driver circuit portion to the step of restarting the supply of the signal for operating the driver circuit portion is set on a basis of a control signal generated using a data of the temperature detected by the temperature detection circuit.

3. The method for driving a display device according to claim 2,

wherein a supply of a start signal, a clock signal, and a power supply voltage from the display control circuit to the driver circuit portion is stopped when stopping the supply of the signal for operating the driver circuit portion to the driver circuit portion.

4. The method for driving a display device according to claim 2,

wherein a supply of a start signal, a clock signal, and a power supply voltage from the display control circuit to the driver circuit portion is restarted when restarting the supply of the signal for operating the driver circuit portion to the driver circuit portion.

5. The method for driving a display device according to claim 3,

wherein the supply of the start signal, the clock signal, and the power supply voltage from the display control circuit to the driver circuit portion is restarted when restarting the supply of the signal for operating the driver circuit portion to the driver circuit portion.

6. The method for driving a display device according to claim 1,

wherein a supply of a start signal, a clock signal, and a power supply voltage from the display control circuit to the driver circuit portion is stopped when stopping the supply of the signal for operating the driver circuit portion to the driver circuit portion.

7. The method for driving a display device according to claim 6,

wherein the supply of the start signal, the clock signal, and the power supply voltage from the display control circuit to the driver circuit portion is restarted when restarting the supply of the signal for operating the driver circuit portion to the driver circuit portion.

8. The method for driving a display device according to claim 1,

wherein a supply of a start signal, a clock signal, and a power supply voltage from the display control circuit to the driver circuit portion is restarted when restarting the supply of the signal for operating the driver circuit portion to the driver circuit portion.

9. A liquid crystal display device comprising:

a display panel comprising a driver circuit portion and a pixel; and

a display control circuit configured to receive an image signal, a first control signal, a power supply voltage and a second control signal, and selectively start or stop an output of a start signal, an output of a clock signal, and an output of the power supply voltage to the display control circuit sequentially on a basis of the first control signal and the second control signal,

wherein the driver circuit portion is configured to receive the output of the image signal, the start signal, the clock signal, and the power supply voltage from the display control circuit,

wherein the pixel is configured to receive the image signal from the driver circuit portion,

wherein the first control signal is a signal based on the image signal, and

wherein the second control signal is a signal based on a temperature of the liquid crystal display device.

10. The liquid crystal display device according to claim 9,

wherein the pixel includes a liquid crystal element and a transistor which controls whether to output a data of the image signal to the liquid crystal element, and

wherein the transistor includes an oxide semiconductor layer which functions as a channel formation layer and has a carrier concentration of less than 1×

10¹⁴/cm³.

11. A liquid crystal display device according to claim 9,

wherein the display control circuit is configured to selectively start or stop the output of the image signal, the output of the start signal, the output of the clock signal, and the output of the power supply voltage to the driver circuit portion sequentially on the basis of the first control signal and the second control signal.

12. The liquid crystal display device according to claim 9,

wherein the pixel includes a liquid crystal element and a transistor including an oxide semiconductor layer,

wherein the transistor is provided between an electrode of the liquid crystal element and a wiring which is configured to be supplied with the image signal, and

wherein an off-state current density per a channel width of 1 μ

m of the transistor is less than or equal to 1×

10<sup>−

17</sup> A.

13. A liquid crystal display device comprising:

a display panel comprising a driver circuit portion and a pixel;

a memory circuit configured to sequentially store a data of a first image signal and a data of a second image signal;

a comparison circuit configured to compare the data of the first image signal and the data of the second image signal to generate a first control signal;

a selection circuit configured to read out the data of a third image signal on a basis of the first control signal to output the data of the third image signal;

a correction circuit configured to detect a temperature of the liquid crystal display device to generate a second control signal; and

a display control circuit configured to receive a power supply voltage, the first control signal, the second control signal, and the third image signal, and selectively start or stop an output of the third image signal, an output of a start signal, an output of a clock signal, and an output of the power supply voltage to the driver circuit portion sequentially on a basis of the first control signal and the second control signal ,

wherein the driver circuit portion is configured to receive the output of the third image signal, the start signal, the clock signal, and the power supply voltage from the display control circuit,

wherein the pixel is configured to display an image corresponding to the third image signal,

wherein the first image signal and the second image signal are image signals in successive frame periods, and

wherein the third image signal is the first image signal or the second image signal.

14. The liquid crystal display device according to claim 13,

wherein the correction circuit comprising:

a temperature detection circuit configured to detect the temperature of the liquid crystal display device to generate a first count value in accordance with a detected temperature;

a counting circuit configured to count a number of successive frame periods corresponding to a still image to generate a second count value; and

a counting value comparison circuit configured to compare the first count value with the second count value to generate the second control signal based on a comparison result.

15. The liquid crystal display device according to claim 14,

wherein the pixel includes a liquid crystal element and a transistor which controls whether to output the data of the third image signal to the liquid crystal element, and

wherein the transistor includes an oxide semiconductor layer which functions as a channel formation layer and has a carrier concentration of less than 1×

10¹⁴/cm³.

16. The liquid crystal display device according to claim 14,

wherein the pixel includes a liquid crystal element and a transistor including an oxide semiconductor layer,

wherein the transistor is provided between an electrode of the liquid crystal element and a wiring which is configured to be supplied with the third image signal, and

wherein an off-state current density per a channel width of 1 μ

m of the transistor is less than or equal to 1×

10<sup>−

17</sup> A.

17. The liquid crystal display device according to claim 13,

wherein the pixel includes a liquid crystal element and a transistor which controls whether to output the data of the third image signal to the liquid crystal element, and

wherein the transistor includes an oxide semiconductor layer which functions as a channel formation layer and has a carrier concentration of less than 1×

10¹⁴/cm³.

18. The liquid crystal display device according to claim 13,

wherein the pixel includes a liquid crystal element and a transistor including an oxide semiconductor layer,

wherein the transistor is provided between an electrode of the liquid crystal element and a wiring which is configured to be supplied with the third image signal, and

wherein an off-state current density per a channel width of 1 μ

m of the transistor is less than or equal to 1×

10<sup>−

17</sup> A.

19. A liquid crystal display device comprising:

a display panel comprising a driver circuit portion and a pixel;

a memory circuit configured to sequentially store a data of a first image signal and a data of a second image signal;

a comparison circuit configured to compare the data of the first image signal and the data of the second image signal to generate a first control signal;

a selection circuit configured to read out the data of the first image signal to output the first image signal;

a correction circuit configured to detect a temperature of the liquid crystal display device to generate a second control signal; and

a display control circuit configured to receive a power supply voltage, the first control signal, the second control signal, and the first image signal, and sequentially stop an output of a start signal, an output of a clock signal, and an output of the power supply voltage to the driver circuit portion,

wherein the driver circuit portion is configured to stop an operation while the display control circuit stops at least one of the output of the start signal, the output of the clock signal, and the output of the power supply voltage to the driver circuit portion,

wherein the pixel is configured to display an image corresponding to the first image signal while the display control circuit stops the output of the start signal, the output of the clock signal, and the output of the power supply voltage to the driver circuit portion, and

wherein the first image signal and the second image signal are image signals in successive frame periods.

20. The liquid crystal display device according to claim 19,

wherein the display control circuit is configured to sequentially stop the output of the first image signal, the output of the start signal, the output of the clock signal, and the output of the power supply voltage to the driver circuit portion;

wherein the driver circuit portion is configured to stop the operation while the display control circuit stops the output of the first image signal, the output of the start signal, the output of the clock signal, and the output of the power supply voltage to the driver circuit portion; and

wherein the pixel is configured to display the image corresponding to the first image signal while the display control circuit stops the output of the first image signal, the output of the start signal, the output of the clock signal, and the output of the power supply voltage to the driver circuit portion.

21. A method for driving a display device comprising an image processing circuit, a display control circuit, a correction circuit, a driver circuit and a pixel, the method comprising the steps of:

outputting a first signal from the image processing circuit, the first signal including data for displaying a still image;

outputting a second signal from the correction circuit, the second signal including data of a length of a holding period of the still image;

inputting the first signal and the second signal to the display control circuit;

outputting a third signal from the display control circuit, the third signal including data for displaying the still image,

inputting the third signal to the driver circuit,

outputting a fourth signal from the driver circuit, the fourth signal including data for displaying the still image,

inputting the fourth signal to the pixel and then holding the fourth signal input to the pixel during the holding period whereby the still image is displayed during the holding period,

wherein the display control circuit stops a supply of a power supply voltage to the driver circuit during the holding period, and

wherein the length of the holding period is set based on a temperature of the display device detected by the correction circuit.

22. The method for driving a display device according to claim 21,

wherein the display control circuit restarts the supply of the power supply voltage to the driver circuit after the holding period.