EL DISPLAY PANEL DRIVING METHOD

• US 20100277401A1
• Filed: 07/13/2010
• Published: 11/04/2010
• Est. Priority Date: 04/26/2002
• Status: Active Grant

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology Co Ltd (Japan Display Incorporated)
• Inventors: Takahara, Hiroshi, Tsuge, Hitoshi
• Granted Patent: US 7,932,880 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/02 Addressing, scanning or driving the display screen or processing steps related thereto
• CPC Class Codes: G09G 2310/0218 with collection of electrodes in groups for n-dimensional addressing
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• 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 2310/0283 Arrangement of drivers for different directions of scanning
• 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 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0261 : in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/043 : Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0606 : Manual adjustment
• CPC Class Codes: G09G 2320/0626 : for control of overall brightness
• CPC Class Codes: G09G 2320/066 : for control of contrast
• CPC Class Codes: G09G 2320/08 : Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 2330/02 : Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 2330/12 : Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/006 : Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/20 : for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2014 : by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/22 : using controlled light sources
• CPC Class Codes: G09G 3/3241 : the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/325 : the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3266 : Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3283 : in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H10K 50/844 : Encapsulations
• CPC Class Codes: H10K 50/846 : comprising getter material or desiccants
• CPC Class Codes: H10K 50/85 : Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/86 : Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 50/87 : Arrangements for heating or cooling
• CPC Class Codes: H10K 59/12 : Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/131 : Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/351 : comprising more than three subpixels, e.g. red-green-blue-white [RGBW]
• CPC Class Codes: H10K 59/353 : characterised by the geometrical arrangement of the RGB subpixels
• CPC Class Codes: H10K 59/873 : Encapsulations
• CPC Class Codes: H10K 59/874 : including getter material or desiccant
• CPC Class Codes: H10K 59/875 : Arrangements for extracting light from the devices
• CPC Class Codes: H10K 59/8791 : Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/8794 : Arrangements for heating and cooling
• CPC Class Codes: H10K 59/88 : Dummy elements, i.e. elements having non-functional features
• CPC Class Codes: H10K 71/861 : Repairing

Abstract

In order to charge and discharge parasitic capacitance of a source signal line sufficiently and program a predetermined current value into a pixel transistor, it is necessary to output a relatively large current from the source driver circuit. However, if such a large current is passed through the source signal line, the value of this current is programmed into the pixel, causing a larger than desired current to flow through an EL element. For example, if a 10 times larger current is used for programming, a 10 times larger current flows through the EL element, and thus the EL element illuminates 10 times more brightly. To obtain predetermined emission brightness, the time during which the current flows through the EL element can be reduced to 1/10 of one frame (1 F). This way, the parasitic capacitance of the source signal line can be charged and discharged sufficiently and the predetermined emission brightness can be obtained.

Claims

1. An EL display apparatus comprising:

gate signal lines and source signal lines which are arranged so as to intersect each other;

a display screen having pixels arranged in a matrix; and

a source driver circuit supplying video signal to said source signal lines,

wherein;

said pixel has an EL element, a driver transistor which supplies a light-emitting current to said EL element, a first condenser, a first switching transistor and a second switching transistor;

said first condenser has a first terminal and a second terminal;

said first switching transistor has a first terminal, a second terminal and a gate terminal;

said second switching transistor has a first terminal, a second terminal and a gate terminal;

said gate signal lines include a first gate signal line and a second gate signal line;

said first terminal of said first switching transistor is connected to a gate terminal of said driver transistor;

said second terminal of said first switching transistor is connected to a first electrode or wiring to which a first voltage is impressed;

said first gate signal line is connected to said gate terminal of said first switching transistor;

said first terminal of said first condenser is connected to said gate terminal of said driver transistor;

said second terminal of said first condenser is connected to a second electrode or wiring to which a second voltage is impressed;

said first voltage is impressed to said gate terminal of said driver transistor by applying a turn-on-voltage to said first gate signal line,

said first terminal of said second switching transistor is connected to said source signal line;

said second gate signal line is connected to said gate terminal of said second switching transistor;

said second switching transistor is turned on by applying a turn-on-voltage to said second gate signal line;

a video signal applied to said source signal line is output from said second terminal of said second switching transistor and is supplied to said drive transistor;

after the turn-on-voltage is applied to said first gate signal line and said first voltage is applied to said driver transistor, the turn-on-voltage is applied to said second gate signal line and said video signal is supplied to said driver transistor.

2. The EL display apparatus according to claim 1, further comprising:

a second condenser which has a first terminal and a second terminal, wherein said first terminal of said second condenser is connected to said second gate signal line,

said second terminal of said second condenser is connected to said gate terminal of said driver transistor, and

an electric potential of said gate terminal of said driver transistor is changed based on a change of voltage level of said second gate signal line.

3. The EL display apparatus according to claim 1, further comprising:

a second condenser which has a first terminal and a second terminal, wherein said first terminal of said second condenser is connected to said second gate signal line,

said second terminal of said second condenser is connected to said gate terminal of said driver transistor,

a capacity of said second condenser is smaller than a capacity of said first condenser, and

an electric potential of said gate terminal of said driver transistor is changed based on a change of voltage level of said second gate signal line.

4. The EL display apparatus according to claim 1, further comprising:

a second condenser which has a first terminal and a second terminal, wherein said first terminal of said second condenser is connected to said second gate signal line,

said second terminal of said second condenser is connected to said gate terminal of said driver transistor, and

said driver transistor and said second switching transistor are transistors of the same conductivity type.

5. The EL display apparatus according to claim 1, further comprising:

a gate driver circuit which selects said gate signal line based upon a control signal supplied from said source driver circuit.

6. The EL display apparatus according to claim 1, further comprising:

a selection circuit, and

a gate driver circuit which selects said gate signal line,

wherein;

said source driver circuit is an semiconductor IC chip,

said selection circuit is formed on a substrate on which said display screen is disposed using polysilicon technology,

said selection circuit has one input terminal and a plurality of output terminals,

said input terminal of said selection circuit is connected to an output terminal of said source driver circuit, and

said source signal line is connected to each of said output terminals of said selection circuit.

7. The EL display apparatus according to claim 1, wherein said display screen comprises:

at least a first color pixel and a second color pixel arranged in matrix state, a size of said first color pixel is different from a size of said second color pixel.

8. The EL display apparatus according to claim 1, further comprising:

an encapsulation film sealing said EL element.

9. An EL display apparatus comprising:

a gate signal line and a source signal line which are arranged so as to intersect each other, a display screen having pixels arranged in a matrix state,

and a source driver circuit supplying video signal to said source signal line;

wherein;

said pixel has an EL element, a driver transistor which supplies a light-emitting current to said EL element, a first switching transistor and a second switching transistor,

said first switching transistor has a first terminal, a second terminal and a gate terminal,

said second switching transistor has a first terminal, a second terminal and a gate terminal,

said gate signal line includes a first gate signal line and a second gate signal line,

said first terminal of said first switching transistor is connected to a gate terminal of said driver transistor,

said second terminal of said first switching transistor is connected to a first electrode or wiring to which a first voltage is impressed,

said first gate signal line is connected to said gate terminal of said first switching transistor,

said first voltage is impressed to said gate terminal of said driver transistor by impressing a turn-on-voltage to said first gate signal line,

said first terminal of said second switching transistor is connected to said source signal line,

said second gate signal line is connected to said gate terminal of said second switching transistor,

said second switching transistor is turned on by impressing a turn-on-voltage to said second gate signal line, a video signal impressed to said source signal line is output from said second terminal of said second switching transistor and is supplied to said driver transistor,

a gate signal line of a first pixel row is connected to a gate signal line of a second pixel row which is arranged before said first pixel row and is separated from said first pixel row more than one pixel row, and

said video signal is supplied to said gate signal line of said second pixel row and said first voltage is supplied to said first pixel row by impressing a turn-on-voltage to said gate signal line of said second pixel row.

10. The EL display apparatus according to claim 9, further comprising:

a second condenser having a first terminal and a second terminal,

wherein said first terminal of said second condenser is connected to said second gate signal line,

said second terminal of said second condenser is connected to said gate terminal of said driver transistor, and

an electric potential of said gate terminal of said driver transistor is changed based on a change of voltage level of said second gate signal line.

11. The EL display apparatus according to claim 9, further comprising:

a second condenser having a first terminal and a second terminal, wherein said first terminal of said second condenser is connected to said second gate signal line,

said second terminal of said second condenser is connected to said gate terminal of said driver transistor, and

said driver transistor and said second switching transistor are transistors of the same conductivity type.

12. The EL display apparatus according to claim 9, further comprising:

a gate driver circuit which selects said gate signal line based upon a control signal supplied from said source driver circuit.

13. The EL display apparatus according to claim 9, further comprising:

a selection circuit, and

a gate driver circuit which selects said gate signal line,

wherein;

said source driver circuit is a semiconductor IC chip,

said selection circuit is formed on a substrate on which said display screen is disposed using polysilicon technology,

said selection circuit has one input terminal and a plurality of output terminals,

said input terminal of said selection circuit is connected to an output terminal of said source driver circuit, and

said source signal line is connected to each of said output terminals.

14. The EL display apparatus according to claim 9, wherein said display screen comprises:

at least a first color pixel and a second color pixel are arranged in matrix state, a size of said first color pixel is different from a size of said second color pixel.

15. The EL display apparatus according to claim 9, further comprising:

an encapsulation film sealing said EL element.

16. An EL display apparatus comprising:

gate signal lines and source signal lines which are arranged so as to intersect each other, a display screen having pixels arranged in a matrix state and a source driver circuit supplying a video signal to said source signal lines;

wherein;

said pixel has an EL element, a driver transistor which supplies a light-emitting current to said EL element, a condenser and a switching transistor,

said condenser has a first terminal and a second terminal,

said switching transistor has a first terminal, a second terminal and a gate terminal,

said first terminal of said condenser is connected to a gate terminal of said driver transistor,

said second terminal of said condenser is connected to said gate terminal of said switching transistor,

a first terminal of said switching transistor is connected to said source signal line,

said gate terminal of said switching transistor is connected to said gate signal line, said switching transistor is turned on by impressing a turn-on-voltage to said gate signal line, a video signal impressed to said source signal line is output from said second terminal of said switching transistor and is supplied to said driver transistor,

said condenser changes electric potential of said gate terminal of said driver transistor based on a change of voltage level of said gate signal line.

17. The EL display apparatus according to claim 16, wherein said driver transistor and said switching transistor are transistors of the same conductivity type.

18. The EL display apparatus according to claim 16, further comprising:

a gate driver circuit which selects said gate signal line based upon a control signal supplied from said source driver circuit.

19. The EL display apparatus according to claim 16, further comprising:

a selection circuit, and

a gate driver circuit which selects said gate signal line;

wherein;

said source driver circuit is a semiconductor IC chip,

said selection circuit is formed on a substrate on which said display screen is disposed using polysilicon technology,

said selection circuit has one input terminal and a plurality of output terminals,

said input terminal of said selection circuit is connected to an output terminal of said source driver circuit, and

said source signal line is connected to each of said output terminals of said selection circuit.

20. The EL display apparatus according to claim 16, wherein said display screen comprises:

at least a first color pixel and a second color pixel arranged in matrix state, a size of said first color pixel is different from a size of said second color pixel.