Drive method of el display panel

• US 20050168491A1
• Filed: 03/06/2003
• Published: 08/04/2005
• 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 7,777,698 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• 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 15.

For example, if a 10 times larger current is used for programming, a 10 times larger current flows through the EL element 15, and thus the EL element 15 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. A drive method for an EL display panel, the EL display panel comprising:

EL elements arranged in a matrix;

driver transistors which supply current to be passed through the EL elements;

first switching elements placed in current paths of the EL elements;

a gate driver circuit which turns on and off the first switching elements for control; and

a source driver circuit which supplies programming current to the driver transistors,

wherein the driver transistors are p-channel transistors,

unit transistors which generate the programming current in the source driver circuit are n-channel transistors, and

the gate driver circuit turns off the first switching elements at least two or more times during one frame period or one field period.

2. The drive method for an EL display panel according to claim 1, wherein the first switching elements are turned off periodically during one frame period or one field period.

4. The drive method for the EL display panel according to claim 1,

wherein the first switching elements are turned off periodically during one frame period or one field period.

3. A drive method for an EL display panel, the EL display panel comprising:

EL elements arranged in a matrix;

driver transistors which supply current to be passed through the EL elements;

first switching elements placed in current paths of the EL elements;

a gate driver circuit which turns on and off the first switching elements for control; and

a source driver circuit which supplies programming current to the driver transistors,

wherein the driver transistors are p-channel transistors,

unit transistors which generate the programming current in the source driver circuit are n-channel transistors,

a period during which a pixel row is selected and programmed with current is constructed from a first period and second period,

a first current is applied during the first period,

a second current is applied during the second period,

the first current is larger than the second current, and

the source driver circuit outputs the first current during the first period and outputs the second current during the second period which comes after the first period.

5. An EL display panel, comprising:

a source driver circuit which outputs programming current;

EL elements arranged in a matrix;

driver transistors which supply current to be passed through the EL elements;

first switching elements placed in current paths of the EL elements;

second switching elements which constitute paths used to transmit programming current to the driver transistors;

a first gate driver circuit which turns on and off the first switching elements for control;

a second gate driver circuit which turns on and off the second switching elements for control;

a source driver circuit which supplies programming current to the driver transistors,

wherein the driver transistors are p-channel transistors,

unit transistors which generate the programming current in the source driver circuit are n-channel transistors,

the first gate driver circuit turns off the first switching elements a number of times during one frame period or one field period,

the first gate driver circuit is placed or formed on one side of the display panel, and

the second gate driver circuit is placed or formed on another side of the display panel.

6. The EL display panel according to claim 5, wherein the gate driver circuits are formed in a same process as the driver transistors and the source driver circuit is made of a semiconductor chip.

7. An EL display panel, comprising:

gate signal lines;

source signal lines;

a source driver circuit which outputs programming current;

a gate driver circuit;

EL elements arranged in a matrix;

driver transistors which supply current to be passed through the EL elements;

first transistors placed in current paths of the EL elements;

second transistors which constitute paths used to transmit programming current to the driver transistors; and

a source driver circuit which supplies programming current to the driver transistors,

wherein the driver transistors are p-channel transistors,

unit transistors which generate the programming current in the source driver circuit are n-channel transistors,

the source driver circuit outputs programming current to the source signal lines,

the gate driver circuit is connected to the gate signal lines,

gate terminals of the second transistors are connected to the gate signal lines,

source terminals of the second transistors are connected to the source signal lines,

drain terminals of the second transistors are connected to drain terminals of the driver transistors, and

the gate driver circuit selects a plurality of gate signal lines and supplies the programming current to the driver transistors of a plurality of pixels.

9. The EL display panel according to claim 7,

wherein the gate driver circuit selects a plurality of pixel rows at a time and applies the image signal from the source driver circuit to the plurality of pixel rows;

and

a dummy pixel row is selected when the first pixel row or I-th pixel rows is selected.

10. The EL display panel according to claim 7, wherein the gate driver circuit is constructed of p-channel transistors.

8. An EL display panel, comprising:

a display area of I pixel rows (I is an integer larger than

     1) and J pixel columns (J is an integer larger than

     1);

a source driver circuit which applies an image signal to source signal lines in the display area;

a gate driver circuit which applies a turn-on voltage or turn-off voltage to gate signal lines in the display area; and

a dummy pixel row formed outside the display area,

wherein EL elements are arranged in a matrix in the display area and emit light based on the image signal from the source driver circuit, and

the dummy pixel row either does not to emit light or emits light not visible to the eye.

11. An EL display panel, comprising:

EL elements arranged in a matrix;

driver transistors which supply current to be passed through the EL elements;

first switching elements placed in current paths of the EL elements;

a gate driver circuit which turns on and off the first switching elements for control; and

a source driver circuit which supplies programming current to the driver transistors,

wherein the driver transistors and the first switching elements are p-channel transistors,

unit transistors which generate the programming current in the source driver circuit are n-channel transistors, and

unit transistors which generate the programming current in the source driver circuit are n-channel transistors.

12. A drive method for an EL display panel, comprising:

supplying EL elements with a current which makes the EL elements emit light brighter than a predetermined brightness; and

making the EL elements emit light for a period equal to 1/N of one frame period or one field period (N is larger than

     1).

13. The drive method for the EL display panel according to claim 12, wherein the period equal to 1/N of a frame is divided into a plurality of periods.

14. A drive method for an EL display panel which uses a current to program currents to be passed through EL elements, comprising:

making the EL elements emit light brighter than a predetermined brightness;

displaying a display area equal to 1/N(N>

1) of an entire screen; and

shifting the display area of 1/N of the entire screen in sequence to display the entire screen.

15. An EL display apparatus comprising:

an EL display panel comprising EL elements arranged in a matrix;

driver transistors which supply current to be passed through the EL elements;

first switching elements placed in current paths of the EL elements; and

a gate driver circuit which turns on and off the first switching elements, and a receiver.