Pixel and organic light emitting display using the pixel

• US 20060232678A1
• Filed: 03/17/2006
• Published: 10/19/2006
• Est. Priority Date: 03/19/2005
• Status: Active Grant

• Current Assignee: Industry-University Cooperation Foundation Hanyang University, Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Mobile Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Choi, Sang Moo, Kwon, Oh Kyong
• Granted Patent: US 7,843,442 B2
• Time in Patent Office: Days
• US Class Current: 348/207.110
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than 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 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes

Abstract

A pixel and an organic light emitting display using the pixel capable of displaying an image of uniform luminance. A pixel circuit is coupled with at least one scan line and at least one data line. The pixel circuit first charges a voltage corresponding to a first data signal across at least one capacitor when the first data signal is supplied from the data lines, and second charges the at least one capacitor when a current as a second data signal is provided. The pixel circuit controls an amount of current supplied to a second power supply from the first power supply through the organic light emitting diode according to the voltage charged in the at least one capacitor. Accordingly, an image of uniform luminescence may be displayed.

Claims

1. A pixel comprising:

an organic light emitting diode; and

a pixel circuit electrically connected to at least one scan line and at least one data line, the pixel circuit including a capacitor, wherein the scan line and the data line are configured to charge the capacitor in response to the first data signal with a voltage corresponding to a difference between a first power supply and a first data signal and to charge the capacitor with a voltage corresponding to a current signal when the current signal is being sunk,

wherein the pixel circuit is configured to control the amount of current supplied to a second power supply from the first power supply through the organic light emitting diode according to the voltage stored in the capacitor.

2. The pixel as claimed in claim 1, wherein the pixel circuit comprises:

first and second transistors connected to the data line, each transistor being configured to turn on in response to a scan signal supplied to an n (n is a positive integer)-th scan line;

a third transistor electrically connected to the first power supply and to a second electrode of the first transistor, the third transistor configured to turn on in response to the scan signal supplied to an (n−

1) th scan line;

first and second capacitors connected to the second electrode of the first transistor and the first power supply;

a fourth transistor, comprising a gate connected to a common terminal of the first and second capacitors, and comprising a first electrode connected to the first power supply; and

a fifth transistor connected to the gate and the second electrode of the fourth transistor, configured to diode-connect the fourth transistor in response to the scan signal supplied to the n−

1 th scan line.

3. The pixel as claimed in claim 2, wherein the second transistor is connected to the second electrode of the fourth transistor and is connected to the data lines, and wherein the second transistor provides a current path for the current signal.

4. The pixel as claimed in claim 2, wherein a sixth transistor is connected to the second electrode of the fourth transistor and is connected to the organic light emitting diode, and is configured to turn off in response to the scan signal supplied to the (n−

1) th and n th scan lines.

5. An organic light emitting display, comprising a plurality of pixels;

a scan driver configured to supply a scan signal to scan lines; and

at least one data driving circuit configured to supply a first data signal during a first period of at least one horizontal period, the first data signal being supplied through data lines to the pixels selected by the scan signal , the driving circuit being further configured to provide a current as a second data signal to the pixels during a second period different from the first period, wherein each of the pixels comprise;

an organic light emitting diode; and

a pixel circuit electrically connected to at least one of the scan lines and to at least one of the data lines, the pixel circuit including a capacitor, wherein the scan line and the data line are configured to charge the capacitor in response to the first data signal with a voltage corresponding to a difference between a first power supply and a first data signal and to charge the capacitor with a voltage corresponding to, and in response to, a current signal when the current signal is being sunk,

wherein the pixel circuit is configured to control the amount of current supplied to a second power supply from the first power supply through the organic light emitting diode according to the voltage charged across the capacitor.

6. The organic light emitting display as claimed in claim 5, wherein the pixel circuit comprises:

first and second transistors connected to at least one data line, and each transistor configured to turn on in response to a scan signal supplied to an n (n is a positive integer)-th scan line;

a third transistor electrically connected to the first power supply and to a second electrode of the first transistor, the third transistor being configured to turn on in response to the scan signal supplied to an (n−

1) th scan line;

first and second capacitors connected to the second electrode of the first transistor and the first power supply;

a fourth transistor, comprising a gate connected to a common terminal of the first and second capacitors, and comprising a first electrode connected to the first power supply; and

a fifth transistor connected to the gate and the second electrode of the fourth transistor, configured to diode-connect the fourth transistor in response to the scan signal supplied to the (n−

1) th scan line.

7. The organic light emitting display as claimed in claim 6, wherein the second transistor is connected to the second electrode of the fourth transistor and is connected to the data lines, and wherein the second transistor is configured to provide a current path for the current signal.

8. The organic light emitting display as claimed in claim 6, wherein a sixth transistor is connected to the second electrode of the fourth transistor and is connected to the organic light emitting diode, and is configured to turn off in response to the scan signal supplied to the (n−

1) th and n th scan lines.

9. The organic light emitting display as claimed in claim 5, wherein the data driving circuit includes:

a voltage output digital-analog converter configured to generate the first data signal, wherein the first data signal corresponds to a gray scale of externally supplied data;

a current output digital-analog converter configured to generate the second data signal, wherein the second data signal corresponds to the gray scale of the data; and

a selection block configured to electrically connect the voltage output digital-analog convert with the data lines for the first period during the horizontal period, and to electrically connect the current output digital-analog converter with the data lines during the second period.

10. The organic light emitting display as claimed in claim 9, wherein the selection block comprises a plurality of selectors, each selector comprising:

a first switch element electrically connected to the voltage output digital-analog converter and to the data lines, the first switch element configured to turn on during the first period and and to turn off during the second period; and

a second switch element electrically connected to the current output digital-analog converter and to the data lines, on the second switch element configured to turn on during the second period and to turn off during the first period.

11. The organic light emitting display as claimed in claim 9, further comprising a buffer unit electrically connected to the voltage output digital-analog converter and to the selection block.

12. The organic light emitting display as claimed in claim 9, further comprising

a shift register configured to sequentially generate a sampling signal;

and

a latch section configured to store the data in response to the sampling signal from the shift register, and configured to supply the stored data to the voltage output digital-analog converter and to the current output digital-analog converter.

13. The organic light emitting display as claimed in claim 12, wherein the latch section includes:

a sampling latch configured to sequentially store the data in response to the sampling signal; and

a holding latch configured to store the data stored in the sampling latch, and to supply the stored data to the voltage output digital-analog converter and the current output digital-analog converter.

14. The organic light emitting display as claimed in claim 13, further comprising a level shifter configured to increase a voltage level of the data stored in the holding latch and to supply the increased level data to the current output digital-analog converter.

15. The organic light emitting display as claimed in claim 10, further comprising a third switch element formed by a transistor having a conductive type different from of that of the first switch element, wherein the third switch element is electrically connected to the first and second electrodes of the first switch element, and configured to turn on and turn off substantially simultaneously with the first switch element.

16. A pixel comprising:

an organic light emitting diode; and

a pixel circuit configured to control an amount of current supplied to a second power supply from the first power supply through the organic light emitting diode according to a voltage stored in the pixel circuit, wherein the pixel circuit is configured to receive a voltage data signal and a current data signal and to generate the voltage stored in the pixel circuit based on the current data signal.