Display device

• US 7,623,098 B2
• Filed: 08/18/2004
• Issued: 11/24/2009
• Est. Priority Date: 04/18/2000
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Osame, Mitsuaki, Koyama, Jun, Yamazaki, Shunpei, Osada, Mai
• Primary Examiner(s): OSORIO, RICARDO
• Application Number:
  US10/920,279
• Publication Number:
  US 20050012731A1
• Time in Patent Office: 1,924 Days
• Field of Search: 345 76- 84, 315/169.3
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• 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 2310/0281 Arrangement of scan or data electrode driver circuits at the periphery of a panel not inherent to a split matrix structure
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H10K 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays

Abstract

The present invention is intended to suppress power consumption of an EL display. In accordance with the brightness of an image to be displayed in a pixel portion, the contrast of the image is determined whether to be inverted or not, and the number of bits of the digital video signal to be input into the pixel portion is reduced, and the magnitude of a current to flow through the EL element is allowed to be maintained at a constant level even when a temperature of an EL layer changes by providing the EL display with another EL element to be used for monitoring a temperature.

Claims

1. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a source signal line and a gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit is connected to the other one of the source region and the drain region of the second thin film transistor.

2. A light emitting device according to claim 1, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

3. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a capacitor, a source signal line and a gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of electrodes of the capacitor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit is connected to the other one of the source region and the drain region of the second thin film transistor and to the other one of the electrodes of the capacitor.

4. A light emitting device according to claim 3, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

5. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a first gate signal line, and a second gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit is connected to the other one of the source region and the drain region of the second thin film transistor and to the other one of the source region and the drain region of the third thin film transistor.

6. A light emitting device according to claim 5, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

7. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a capacitor, a source signal line, a first gate signal line, and a second gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, to one of electrodes of the capacitor, and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit is connected to the other one of the source region and the drain region of the second thin film transistor, to the other one of electrodes of the capacitor, and to the other one of the source region and the drain region of the third thin film transistor.

8. A light emitting device according to claim 7, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

9. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a source signal line, a gate signal line, and a power source line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit is connected to the power source line.

10. A light emitting device according to claim 9, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

11. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a capacitor, a source signal line, a gate signal line, and a power source line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of electrodes of the capacitor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit and the other one of the electrodes of the capacitor are connected to the power source line.

12. A light emitting device according to claim 11, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

13. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a first gate signal line, a second gate signal line, a power source line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line, and the other one of the source region and the drain region of the third thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit is connected to the power source line.

14. A light emitting device according to claim 13, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

15. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a capacitor, a source signal line, a first gate signal line, a second gate signal line, and a power source line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, to one of electrodes of the capacitor, and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line, and the other one of the source region and the drain region of the third thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a circuit which outputs a same potential as an input potential,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the circuit are connected with each other, and

wherein an output of the circuit and the other one of the electrodes of the capacitor are connected to the power source line.

16. A light emitting device according to claim 15, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

17. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a source signal line and a gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier is connected to the other one of the source region and the drain region of the second thin film transistor.

18. A light emitting device according to claim 17, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

19. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a capacitor, a source signal line and a gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of electrodes of the capacitor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier is connected to the other one of the source region and the drain region of the second thin film transistor and to the other one of the electrodes of the capacitor.

20. A light emitting device according to claim 19, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

21. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a first gate signal line, and a second gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier is connected to the other one of the source region and the drain region of the second thin film transistor and to the other one of the source region and the drain region of the third thin film transistor.

22. A light emitting device according to claim 21, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

23. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a capacitor, a source signal line, a first gate signal line, and a second gate signal line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, to one of electrodes of the capacitor, and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier is connected to the other one of the source region and the drain region of the second thin film transistor, to the other one of electrodes of the capacitor, and to the other one of the source region and the drain region of the third thin film transistor.

24. A light emitting device according to claim 23, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

25. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a source signal line, a gate signal line, and a power source line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier is connected to the power source line.

26. A light emitting device according to claim 25, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

27. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a capacitor, a source signal line, a gate signal line, and a power source line,

wherein a gate electrode of the first thin film transistor is connected to the gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of electrodes of the capacitor, and

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier and the other one of the electrodes of the capacitor are connected to the power source line.

28. A light emitting device according to claim 27, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

29. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a source signal line, a first gate signal line, a second gate signal line, a power source line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line, and the other one of the source region and the drain region of the third thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier is connected to the power source line.

30. A light emitting device according to claim 29, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.

31. A light emitting device comprising:

a plurality of pixels, each of the plurality of pixels including a light emitting element having a pair of electrodes, a first thin film transistor, a second thin film transistor, a third thin film transistor, a capacitor, a source signal line, a first gate signal line, a second gate signal line, and a power source line,

wherein a gate electrode of the first thin film transistor is connected to the first gate signal line,

wherein one of a source region and a drain region of the first thin film transistor is connected to the source signal line, and the other one of the source region and the drain region of the first thin film transistor is connected to a gate electrode of the second thin film transistor, to one of electrodes of the capacitor, and to one of a source region and a drain region of the third thin film transistor,

wherein one of a source region and a drain region of the second thin film transistor is connected to one of the pair of electrodes of the light emitting element, and the other one of the source region and the drain region of the second thin film transistor is connected to the power source line, and

wherein a gate electrode of the third thin film transistor is connected to the second gate signal line, and the other one of the source region and the drain region of the third thin film transistor is connected to the power source line;

a constant current source;

a monitoring light emitting element having a pair of electrodes; and

a buffer amplifier,

wherein the constant current source, one of the pair of electrodes of the monitoring light emitting element, and the buffer amplifier are connected with each other, and

wherein an output of the buffer amplifier and the other one of electrodes of the capacitor are connected to the power source line.

32. A light emitting device according to claim 31, wherein the light emitting device is incorporated in one selected from the group consisting of a telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer.