EL display apparatus, driving circuit of EL display apparatus, and image display apparatus

• US 7,528,812 B2
• Filed: 02/27/2007
• Issued: 05/05/2009
• Est. Priority Date: 09/07/2001
• Status: Expired due to Fees

• Current Assignee: JOLED Inc.
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Takahara, Hiroshi, Tsuge, Hitoshi
• Primary Examiner(s): LEWIS, DAVID LEE
• Application Number:
  US11/710,919
• Publication Number:
  US 20070146251A1
• Time in Patent Office: 798 Days
• Field of Search: 345 55-100, 345690-697
• US Class Current: 345/78
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/0232 Special driving of display border areas
• 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 2310/0262 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 2310/0278 Details of driving circuits arranged to drive both scan and data electrodes
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 : for control of overall brightness
• CPC Class Codes: G09G 2330/08 : Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 3/2018 : by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3233 : with pixel circuitry controlling the current through the light-emitting element
• 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: 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: G09G 3/3426 : the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: H10K 59/12 : Active-matrix OLED [AMOLED] displays

Abstract

The EL display apparatus according to this invention is provided with an EL light emitting element, a current driving device for driving the EL light emitting element by a current responsive to a source signal represented by a current, and a signal current source (634) for outputting the source signal in response to image signal to the current driving device via a source signal line, the EL display apparatus being further provided with a precharge voltage source (631) for outputting a predetermined voltage and a switching and connecting unit (636, 637) capable of selectively connecting either the signal current source or the precharge voltage source to the source signal line (638).

Claims

1. An EL display apparatus comprising:

a display screen including a plurality of gate signal lines and a plurality of source signal lines which are arranged to intersect with each other, and pixels in each of which an EL light emitting element is formed to correspond to an intersection point of each of the gate signal lines and each of the source signal lines;

a current driving device formed for each of the pixels for driving the EL light emitting element by a second current responsive to a source signal represented by a first current;

a signal current source for outputting the source signal in response to an image signal to the current driving device via the source signal line; and

a precharge voltage source for outputting a predetermined voltage to the source signal line, wherein

the current driving device is configured to drive the EL light emitting element by the second current responsive to a voltage of a control terminal connected to the source signal line; and

the predetermined voltage corresponds to gray scale data of the image signal.

2. The EL display apparatus according to claim 1, further comprising a switching and connecting unit capable of selectively connecting either the signal current source or the precharge voltage source to the source signal line, wherein

the switching and connecting unit connects the precharge voltage source and the signal current source to the source signal line such that the source signal is output to the source signal line after the predetermined voltage is applied to the source signal line in one horizontal scan period.

3. The EL display apparatus according to claim 2, wherein

a duration of applying the predetermined voltage is 0.2 μ

s or more and 3 μ

s or less.

4. The EL display apparatus according to claim 2, wherein

the current driving device drives the EL light emitting element by the second current responsive to the voltage of the control terminal connected to the source signal line;

and

the predetermined voltage is a voltage by which the current driving device so drives the EL light emitting element as to achieve black display.

5. The EL display apparatus according to claim 1, further comprising a switching and connecting unit capable of selectively connecting either the signal current source or the precharge voltage source to the source signal line, wherein

the switching and connecting unit connects the precharge voltage source to the source signal line when the gray scale data of the image signal is a predetermined one.

6. The EL display apparatus according to claim 1, wherein

a plurality of the EL light emitting elements emitting a plurality of types of colors are connected to a plurality of the source signal lines, respectively, and

the precharge voltage source outputs the predetermined voltages for the colors respectively to the source signal lines.

7. The EL display apparatus according to claim 1, wherein the current driving device comprises a transistor.

8. The EL display apparatus according to claim 1, wherein the current driving device comprises a current mirror circuit.

9. The EL display apparatus according to claim 1, further comprising a switching and connecting unit capable of selectively connecting either the signal current source or the precharge voltage source to the source signal line, wherein

a plurality of pixels are disposed in matrix;

each of the pixels is provided with the EL light emitting element and the current driving device;

each of columns or rows of the pixels is provided with the source signal line;

the current driving devices of the rows or the columns are connected selectably to the source signal lines;

each of the source signal lines is provided with the signal current source, the precharge voltage source, and the switching and connecting unit;

a plurality of gate lines for transmitting a gate signal to select the current driving devices per column or row are provided; and

a gate driver for outputting the gate signal to the gate lines is provided.

10. An electronic display appliance comprising:

an image display unit comprising the EL display apparatus according to claim 1, the EL display apparatus further comprising a switching and connecting unit capable of selectively connecting either the signal current source or the precharge voltage source to the source signal line, wherein a plurality of pixels are disposed in matrix;

each of the pixels is provided with the EL light emitting element and the current driving device, each of columns or rows of the pixels is provided with the source signal line, the current driving devices of the columns or the rows are connected selectably to the source signal lines, each of the source signal lines is provided with the signal current source, the precharge voltage source, and the switching and connecting unit, a plurality of gate lines for transmitting a gate signal to select the current driving devices per row or column are provided, and a gate driver for outputting the gate signal to the gate lines is provided;

a receiver; and

a speaker.

14. The EL display apparatus according to claim 1, wherein

the precharge voltage source has an output impedance smaller than an output impedance of the signal current source.

11. A driving circuit of EL display apparatus, comprising:

a plurality of unit current sources;

a reference current generation circuit for defining a current to be output from the unit current sources;

a plurality of current switching circuits disposed on output ends of the unit current sources;

a current wiring having one end connected to the current switching circuits via a first change over switch and the other end connected to a source signal line; and

a precharge voltage source which outputs a predetermined voltage and is connected to the current wiring via a second change over switch, wherein

the current switching circuits are turned on and off depending on gray scale data of an image signal, and

the first and the second change over switches selectively connect either the current switching circuits or the precharge voltage source to the source signal line.

12. The driving circuit of EL display apparatus according to claim 11, wherein

the unit current sources are connected to the current switches in such a fashion that the number of the unit current sources to be aligned parallel and connected to each of the current switches is a number from 2 raised to the 0th power to 2 raised to the nth power (n is a natural number).

13. The driving circuit of EL display apparatus according to claim 11, wherein

the reference current generation circuit has an operation amplifier, the operation amplifier defining a current output from the unit current sources.