Drive method of el display apparatus

• US 20050168490A1
• 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
• Granted Patent: US 7,742,019 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• 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 2300/0842 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 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• 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 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• 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

Abstract

To provide a drive method capable of maintaining gradation display performance regardless of screen display brightness.

Reference numeral 491R denotes a regulator used to control reference current for red (R). By adjusting a reference current for R linearly, it is possible to linearly vary a current flowing through a transistor 472a which constitutes a current mirror with a transistor 471R. This changes a current flowing through a transistor 472b which has received a current-based delivery from the transistor 472a in a transistor group 521a. This in turn causes changes to a transistor 473a in a transistor group 521b which constitutes a current mirror with the transistor 472b, resulting in changes to a transistor 473b which has received a current-based delivery from the transistor 473a. Thus, since drive current of the unit transistor 484 changes, programming current can be changed linearly. Reference numeral 491G denotes a regulator used to control reference current for green (G) and reference numeral 491B denotes a regulator used to control reference current for blue (B).

By adjusting 491R, 491G, and 491B, it is possible to adjust white balance easily and change screen brightness easily. Besides, gradation display performance is maintained at any screen brightness.

Claims

1. A drive method of an EL display apparatus that comprises a switching element which turns on and off a current path between a driver transistor and an EL element, in each pixel, the drive method comprising:

aggregating image data or data equivalent to image data; and

turning off the switching element for a longer period if the aggregated data is large in amount than if the aggregated data is small in amount.

2. An EL display apparatus comprising:

a display panel in which EL elements are formed in a matrix; and

a source driver circuit configured to supply programming current to the display panel,

wherein the source driver circuit comprises an output stage that has a plurality of unit current elements and a variable circuit configured to control current flowing from the unit current elements.

3. A drive method of an EL display apparatus that includes a moving-picture detection circuit that detects moving pictures and a feature extraction circuit that extracts features of video images, the drive method of the EL display apparatus comprising:

first changing a number of selected pixel rows depending on output data from the moving-picture detection circuit; and

second changing the number of selected pixel rows depending on output data from the feature extraction circuit.

4. An EL display apparatus that controls brightness of a screen using a ratio between non-display and display areas on the screen, the EL display apparatus comprising:

a display area in which EL elements and driver transistors that drive the EL elements are formed in a matrix;

gate signal lines configured to transmit voltages that turn on and off the EL elements in each pixel row;

a gate driver circuit configured to drive the gate signal lines;

an aggregation circuit configured to aggregate image data or data equivalent to image data; and

a conversion circuit configured to convert aggregation results produced by the aggregation circuit into a start pulse signal for the gate driver circuit.

5. A control method of an EL display apparatus that controls brightness of a screen using a ratio between non-display and display areas on the screen, the control method comprising:

generating a delay time when changing the ratio between the non-display and display areas on the screen from a first ratio to a second ratio.

6. The drive method of an EL display apparatus according to claim 5, wherein the display area/(the non-display area+the display area on the screen) is from 1/16 to 1/1 both inclusive.

7. An EL display apparatus comprising:

a display panel in which each pixel contains a capacitor, an EL element, and a P-channel driver transistor configured to supply current to the EL element, and wherein the pixels are arranged in a matrix; and

a source driver circuit configured to supply programming current to the display panel,

wherein the source driver circuit comprises an output stage that has an N-channel unit transistor configured to output a plurality of unit currents.

8. The EL display apparatus according to the claim 7, wherein a capacitance of a capacitor is Cs (pF) and one pixel occupies an area of S (square μ

m), and a condition 500/S≦

Cs≦

20000/S is satisfied.

9. The EL display apparatus according to claim 7, wherein a pixel size is A (square mm) and predetermined white raster display brightness is B (nt), and a programming current I (μ

A) from the source driver circuit satisfies a condition (A×

B)/20≦

1≦

(A×

B).

10. The EL display apparatus according to claim 7, wherein a number of gradations is K and a size of the unit transistor is St (square μ

m), and conditions 40≦

K/{square root}{square root over ( )}(St) and St≦

300 are satisfied.

11. The EL display apparatus according to claim 7, wherein a number of gradations is K, channel length of the unit transistor is L (μ

m), and channel width is W (μ

m), and a condition ({square root}{square root over ( )}(K/16))≦

L/W≦

{square root}{square root over ( )}(K/16))×

20 is satisfied.

12. An EL display apparatus comprising:

a first EL display panel including a first display screen;

a second EL display panel including a second display screen; and

a flexible board configured to connect source signal lines of the first EL display panel with source signal lines of the second EL display panel,

wherein a channel width of driver transistors that drive pixels is W (μ

m) and a channel length is L (μ

m), and W/L differs between the driver transistor that drives pixels in the first display screen and the driver transistor that drives pixels in the second display screen.