Display device

• US 7,221,338 B2
• Filed: 04/13/2001
• Issued: 05/22/2007
• 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:
  US09/833,673
• Publication Number:
  US 20010033252A1
• Time in Patent Office: 2,230 Days
• Field of Search: 345/87, 345/88, 345/98, 345/99, 345/100, 345/209, 345/204, 345 44- 46, 345 76- 80, 345/36, 315/169.1, 315/169.3
• US Class Current: 345/76
• 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 display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises a switching circuit for switching a polarity of an output signal,

a polarity of a digital video signal input to said switching circuit is inverted by means of a shift signal to he input into said switching circuit and a resultant digital signal is then input into said plurality of pixels,

said switching circuit comprises an inverter, a first analog switch, and a second analog switch,

said digital video signal input into said switching circuit is input into an input terminal of said first analog switch through said inverter,

said digital video signal input into said switching circuit is input into an input terminal of said second analog switch,

said shift signal input into a first control input terminal of said first analog switch and a second control input terminal of said second analog switch,

a signal obtained by inverting a polarity of said shift signal is input into a first control input terminal of said second analog switch and a second control input terminal of said first analog switch, and

signals output from output terminals of said first analog switch and said second analog switch are output from said switching circuit.

2. A display device according to claim 1, wherein said display device is a light emitting device.

3. A display device according to claim 1, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

4. A display device according to claim 1, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

5. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises a shift register, one or more latches, and a switching circuit,

a polarity of a digital video signal input from said one or more latches into said switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into the plurality of pixels,

said switching circuit comprises an inverter, a first analog switch, and a second analog switch,

said digital video signal input into said switching circuit is input into an input terminal of said first analog switch through said inverter,

said digital video signal input into said switching circuit is input into an input terminal of said second analog switch,

said shift signal is input into a first control input terminal of said first analog switch and a second control input terminal of said second analog switch,

a signal obtained by inverting a polarity of said shift signal is input into a first control input terminal of said second analog switch and a second control input terminal of said first analog switch, and

signals output from output terminals of said first analog switch and said second analog switch are output from said switching circuit.

6. A display device according to claim 5, wherein said display device is a light emitting device.

7. A display device according to claim 5, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

8. A display device according to claim 5, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

9. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises a shift register, and a switching circuit,

a polarity of a digital video signal input into said switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into the plurality of pixels,

said switching circuit comprises an inverter, a first analog switch, and a second analog switch,

said digital video signal input into said switching circuit is input into an input terminal of said first analog switch through said inverter,

said digital video signal input into said switching circuit is input into an input terminal of said second analog switch,

said shift signal is input into a first control input terminal of said first analog switch and a second control input terminal of said second analog switch,

a signal obtained by inverting a polarity of said shift signal is input into a first control input terminal of said second analog switch and a second control input terminal of said first analog switch, and

signals output from output terminals of said first analog switch and said second analog switch are output from said switching circuit.

10. A display device according to claim 9, wherein said display device is a light emitting device.

11. A display device according to claim 9, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

12. A display device according to claim 9, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

13. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises one or more latches, and a switching circuit,

a polarity of a digital video signal input from said one or more latches into said switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into the plurality of pixels,

said switching circuit comprises an inverter, a first analog switch, and a second analog switch,

said digital video signal input into said switching circuit is input into an input terminal of said first analog switch through said inverter,

said digital video signal input into said switching circuit is input into an input terminal of said second analog switch,

said shift signal is input into a first control input terminal of said first analog switch and a second control input terminal of said second analog switch,

a signal obtained by inverting a polarity of said shift signal is input into a first control input terminal of said second analog switch and a second control input terminal of said first analog switch, and

signals output from output terminals of said first analog switch and said second analog switch are output from said switching circuit.

14. A display device according to claim 13, wherein said display device is a light emitting device.

15. A display device according to claim 13, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

16. A display device according to claim 13, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

17. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises a switching circuit for switching a polarity of an output signal,

a polarity of a digital video signal input to said switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into said plurality of pixels,

said switching circuit comprises an inverter, a first NAND, a second NAND, and a NOR,

said first NAND is supplied with said digital video signal through said inverter and said shift signal,

said second NAND is supplied with said digital video signal and a signal obtained by inverting a polarity of said shift signal,

a signal output from said first NAND and a signal output from said second NAND are input onto said NOR, and

a signals output from said NOR is output from said switching circuit.

18. A display device according to claim 17, wherein said display device is a light emitting device.

19. A display device according to claim 17, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

20. A display device according to claim 17, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

21. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises a shift register, one or more latches, and a switching circuit,

a polarity of a digital video signal input from said one or more latches into said switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into the plurality of pixels,

said switching circuit comprises an inverter, a first NAND, a second NAND, and a NOR,

said first NAND is supplied with said digital video signal through said inverter and said shift signal,

said second NAND is supplied with said digital video signal and a signal obtained by inverting a polarity of said shift signal,

a signal output from said first NAND and a signal output from said second NAND are input onto said NOR, and

a signal output from said NOR is output from said switching circuit.

22. A display device according to claim 21, wherein said display device is a light emitting device.

23. A display device according to claim 21, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

24. A display device according to claim 21, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

25. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises a shift register, and a switching circuit,

a polarity of a digital video signal input into switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into the plurality of pixels,

said switching circuit comprises an inverter, a first NAND, a second NAND, and a NOR,

said first NAND is supplied with said digital video signal through said inverter and said shift signal,

said second NAND is supplied with said digital video signal and a signal obtained by inverting a polarity of said shift signal,

a signal output from said first NAND and a signal output from said second NAND are input onto said NOR, and

a signal output from said NOR is output from said switching circuit.

26. A display device according to claim 25, wherein said display device is a light emitting device.

27. A display device according to claim 25, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

28. A display device according to claim 25, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.

29. A display device comprising:

a plurality of pixels, each comprising a light emitting element, the light emitting element comprising an anode, a cathode and an organic compound layer provided therebetween; and

a source signal line driver circuit,

wherein;

said source signal line driver circuit comprises one or more latches, and a switching circuit,

a polarity of a digital video signal input from said one or more latches into switching circuit is inverted by means of a shift signal to be input into said switching circuit and a resultant digital signal is then input into the plurality of pixels,

said switching circuit comprises an inverter, a first NAND, a second NAND, and a NOR,

said first NAND is supplied with said digital video signal through said inverter and said shift signal,

said second NAND is supplied with said digital video signal and a signal obtained by inverting a polarity of said shift signal,

a signal output from said first NAND and a signal output from said second NAND are input into said NOR, and

a signals output from said NOR is output from said switching circuit.

30. A display device according to claim 29, wherein said display device is a light emitting device.

31. A display device according to claim 29, wherein said display device is incorporated in at least one selected from the group consisting of a video camera, an image reproduction apparatus, a head mount display, a portable telephone, a personal computer, and a portable information terminal.

32. A display device according to claim 29, wherein said polarity of said video signal is inverted by means of said shift signal when an average of a time period during which all of said light emitting elements emit light in one frame period becomes longer than a half of a time period during which the light emitting elements emit light in one frame period in the case where a totally white image is to be displayed.