INPUT/OUTPUT DEVICE AND DRIVING METHOD THEREOF

• US 20120001874A1
• Filed: 06/22/2011
• Published: 01/05/2012
• Est. Priority Date: 07/02/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: KUROKAWA, Yoshiyuki, IKEDA, Takayuki
• Granted Patent: US 8,605,059 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G06F 1/3206 Monitoring of events, devices or parameters that trigger a change in power modality
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 1/3287 by switching off individual functional units in the computer system
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

An object is to reduce power consumption. An input/output device including: a display selection signal output circuit outputting a display selection signal during a first display mode and stopping outputting the display selection signal during a second display mode; a photodetection reset signal output circuit outputting N (N is a natural number) photodetection reset signals during a first photodetection mode and outputting M (M is a natural number smaller than N) photodetection reset signals during a second photodetection mode; an output selection signal output circuit outputting N output selection signals during the first photodetection mode and outputting M output selection signals during the second photodetection mode; and a photodetector circuit being reset in accordance with a photodetection reset signal, generating data according to an intensity of light entering the photodetector circuit subsequently, and outputting the data as a data signal in accordance with the output selection signal.

Claims

1. A method for driving an input/output device comprising the steps of:

performing a first photodetection;

performing a second photodetection after the first photodetection;

detecting an object closed to the input/output device by the second photodetection;

performing a third photodetection after the second photodetection; and

performing a fourth photodetection after the third photodetection,

wherein a time interval between the first photodetection and the second photodetection is longer than a time interval between the third photodetection and the fourth photodetection.

2. The method for driving the input/output device according to claim 1, further comprising the steps of:

performing supply of a first image signal to the input/output device to display a first image;

performing supply of a second image signal to the input/output device to display a second image after the supply of the first image signal;

performing supply of a third image signal to the input/output device to display a third image after the second photodetection; and

performing supply of a fourth image signal to the input/output device to display a fourth image after the supply of the third image signal;

wherein a time interval between the supply of the first image signal and the supply of the second image signal is longer than a time interval between the supply of the third image signal and the supply of the fourth image signal.

3. The method for driving the input/output device according to claim 2,

wherein the input/output device comprises a first transistor, and

wherein the first transistor comprises an oxide semiconductor.

4. The method for driving the input/output device according to claim 3,

wherein each of the first photodetection, the second photodetection, the third photodetection, and the fourth photodetection comprises the steps of:

performing a reset operation in a pixel of the input/output device;

performing a photocurrent detecting operation in the pixel of the input/output device; and

performing a select operation in the pixel of the input/output device,

wherein the pixel comprises a photoelectric transducer and a second transistor.

5. The method for driving the input/output device according to claim 4,

wherein the second transistor comprises an oxide semiconductor.

6. The method for driving the input/output device according to claim 3,

wherein each of the first photodetection, the second photodetection, the third photodetection, and the fourth photodetection comprises the steps of:

performing a reset operation in each of pixels of the input/output device sequentially;

performing a photocurrent detecting operation in each of the pixels of the input/output device sequentially; and

performing a selecting operation in each of the pixels of the input/output device sequentially,

wherein each of the pixels comprises a photoelectric transducer and a second transistor.

7. The method for driving the input/output device according to claim 6,

wherein the second transistor comprises an oxide semiconductor.

8. The method for driving the input/output device according to claim 3,

wherein each of the first photodetection, the second photodetection, the third photodetection, and the fourth photodetection comprises the steps of:

performing a reset operation in each of pixels of the input/output device simultaneously;

performing a photocurrent detecting operation in each of the pixels of the input/output device simultaneously; and

performing a selecting operation in each of the pixels of the input/output device sequentially,

wherein each of the pixels comprises a photoelectric transducer and a second transistor.

9. The method for driving the input/output device according to claim 8,

wherein the second transistor comprises an oxide semiconductor.

10. A method for driving an input/output device comprising pixels, the method for driving comprising the steps of:

performing a first photodetection in M pixels;

detecting an object closed to the input/output device by the first photodetection; and

performing a second photodetection in N pixels,

wherein N is a natural number of 2 or more, and

wherein M is a natural number smaller than N.

11. The method for driving the input/output device according to claim 10, further comprising the steps of:

performing supply of a first image signal to at least one of the pixels to display a first image;

performing supply of a second image signal to at least one of the pixels to display a second image after the supply of the first image signal;

performing supply of a third image signal to at least one of the pixels to display a third image after the first photodetection;

performing supply of a fourth image signal to at least one of the pixels to display a fourth image after the supply of the third image signal;

wherein a time interval between the supply of the first image signal and the supply of the second image signal is longer than a time interval between the supply of the third image signal and the supply of the fourth image signal,

wherein at least one of the pixels comprises a first transistor comprising an oxide semiconductor.

12. The method for driving the input/output device according to claim 11,

wherein each of the first photodetection and the second photodetection comprising the steps of:

performing a reset operation in each of the pixels of the input/output device;

performing a photocurrent detecting operation in each of the pixels of the input/output device; and

performing a selecting operation in each of the pixels of the input/output device,

wherein each of the pixels comprises a photoelectric transducer and a second transistor.

13. The method for driving the input/output device according to claim 12,

wherein the second transistor comprises an oxide semiconductor.

14. The method for driving the input/output device according to claim 11,

wherein each of the first photodetection and the second photodetection comprises the steps of:

performing a reset operation in each of pixels of the input/output device sequentially;

performing a photocurrent detecting operation in each of the pixels of the input/output device sequentially; and

performing a selecting operation in each of the pixels of the input/output device sequentially,

wherein each of the pixels comprises a photoelectric transducer and a second transistor.

15. The method for driving the input/output device according to claim 14,

wherein the second transistor comprises an oxide semiconductor.

16. The method for driving the input/output device according to claim 11,

wherein each of the first photodetection and the second photodetection comprises the steps of:

performing a reset operation in each of pixels of the input/output device simultaneously;

performing a photocurrent detecting operation in each of the pixels of the input/output device simultaneously; and

performing a selecting operation in each of the pixels of the input/output device sequentially,

wherein each of the pixels comprises a photoelectric transducer and a second transistor.

17. The method for driving the input/output device according to claim 16,

wherein the second transistor comprises an oxide semiconductor.

18. An input/output device comprising:

a display selection signal output circuit configured to perform supply of a display selection signal during a first display mode and configured to stop supply of the display selection signal during a second display mode;

a display data signal output circuit configured to receive an image signal and configured to generate a display data signal on a basis of the image signal;

a photodetection reset signal output circuit configured to generate N (N is a natural number of 2 or more) photodetection reset signals during a first photodetection mode and configured to generate M (M is a natural number smaller than N) photodetection reset signals during a second photodetection mode;

an output selection signal output circuit configured to generate N output selection signals during the first photodetection mode and configured to generate M output selection signals during the second photodetection mode; and

a photodetector circuit configured to receive the photodetection reset signal and the output selection signal, configured to perform reset in accordance with the photodetection reset signal, configured to generate data according to an intensity of light entering the photodetector circuit subsequently, and configured to generate the data as a data signal in accordance with the output selection signal.

19. The input/output device according to claim 18, wherein the output selection signal output circuit and the photodetection reset signal output circuit each comprise:

a shift register configured to generate L (L is a natural number of 2 or more) first pulse signals; and

L logic circuits,

wherein one of the L logic circuits is configured to receive a first pulse signal and a second pulse signal and configured to generate the output selection signal,

wherein the first pulse signal is one of the L first pulse signals,

wherein the second pulse signal is one of Z (Z is a natural number of 2 or more and L or less) pulse control signals, and

wherein the output selection signal is determined in accordance with the first pulse signal and the second pulse signal.

20. A method for driving an input/output device comprising:

a display selection signal output circuit;

a pixel data signal output circuit;

a photodetection selection signal output circuit;

a photodetector circuit; and

a reading circuit,

the method for driving comprising the steps of;

performing supply of a photodetection reset signal to the photodetector circuit;

performing reset of the photodetector circuit in accordance with the photodetection reset signal every unit period;

generating data in the photodetector circuit according to an intensity of light entering the photodetector circuit subsequently after the reset of the photodetector circuit;

generating N (N is a natural number of 2 or more) photodetection selection signals from the photodetection selection signal output circuit during a first photodetection mode;

outputting the data as a first data signal from the photodetector circuit in accordance with one of the N photo detection selection signals;

reading the first data signal from the photodetector circuit sequentially by the reading circuit;

generating M (M is a natural number smaller than N) photodetection selection signals from the photodetection selection signal output circuit during a second photodetection mode;

outputting the data as a second data signal from the photodetector circuit in accordance with one of the M photo detection selection signals;

reading the second data signal from the photodetector circuit sequentially by the reading circuit;

generating a display selection signal from the display selection signal output circuit during a first display mode and the first photodetection mode;

generating the display selection signal from the display selection signal output circuit during the first display mode and the second photodetection mode;

stopping generation of the display selection signal from the display selection signal output circuit during a second display mode and the first photodetection mode;

stopping generation of the display selection signal from the display selection signal output circuit during the second display mode and the second photodetection mode;

switching the input/output device from the second photodetection mode to the first photodetection mode in accordance with a value of data generated by the photodetector circuit in successive periods of the second photodetection mode; and

switching the input/output device from the second display mode to the first display mode in accordance with the value of the data generated by the photodetector circuit in successive periods of the first photodetection mode.