Pixel and organic light emitting display using the same

• US 20080036704A1
• Filed: 01/19/2007
• Published: 02/14/2008
• Est. Priority Date: 08/08/2006
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung SDI Company Limited
• Inventors: Eom, Ki Myeong, Choi, Michael, Kim, Yang Wan
• Granted Patent: US 8,059,071 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• 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 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• 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 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

A pixel and an organic light emitting display using the same, which reduces the number of output lines in a data driver and stably express black gradation. The pixel includes an organic light emitting diode; a storage capacitor coupled between a first power supply and an initialization power supply and being charged with a voltage corresponding to a data signal; a first transistor controlling an amount of an electric current supplied to the organic light emitting diode corresponding to the voltage charged in the storage capacitor; a second transistor coupled between a data line and a current scan line, supplying a data signal to be provided to the data line when a scan signal is supplied to the current scan line; a third transistor coupled between a gate electrode and a second electrode of the first transistor, and being turned-on when the scan signal is supplied to the current scan line; and a boosting capacitor coupled between the current scan line and the gate electrode of the first transistor, boosting a voltage of the gate electrode of the first transistor when a supply of the scan signal to the current scan line stops.

Claims

1. A pixel comprising:

an organic light emitting diode;

a storage capacitor coupled between a first power supply and an initialization power supply and being charged with a voltage corresponding to a data signal;

a first transistor controlling an amount of an electric current supplied to the organic light emitting diode corresponding to the voltage charged in the storage capacitor;

a second transistor coupled between a data line and a current scan line, supplying the data signal to a first electrode of the first transistor when a scan signal is supplied to the current scan line;

a third transistor coupled between a gate electrode and a second electrode of the first transistor, and being turned-on when the scan signal is supplied to the current scan line; and

a boosting capacitor coupled between the current scan line and the gate electrode of the first transistor, boosting a voltage of the gate electrode of the first transistor when a supply of the scan signal to the current scan line stops.

2. The pixel of claim 1, further comprising:

a fourth transistor coupled between the first power supply and the first electrode of the first transistor, and being turned-on or turned-off according to an emission control signal supplied to an emission control line; and

a fifth transistor coupled between the second electrode of the first transistor and the organic light emitting diode, and being turned-on or turned-off according to the emission control signal supplied to the emission control line.

3. The pixel of claim 2, further comprising a sixth transistor coupled between the initialization power supply and the storage capacitor, and being turned-on when the scan signal is supplied to a previous scan line.

4. The pixel of claim 1, wherein a capacitance of the boosting capacitor is set to be less than the capacitance of the storage capacitor.

5. An organic light emitting display comprising:

a data driver supplying data signals to respective output lines during a data period of a horizontal time period;

a scan driver sequentially supplying a scan signal to scan lines during a scan period of the horizontal time period which is a time period other than the data period, respectively, and supplying an emission control signal to emission control lines during at least two horizontal time periods;

demultiplexers installed at the respective output lines supplying the data signals to data lines during the data period;

data capacitors installed at the data lines storing the data signals; and

pixels generating light of predetermined luminance corresponding to the data signals,

wherein each of the pixels includes;

an organic light emitting diode;

a storage capacitor coupled between a first power supply and an initialization power supply and being charged with a voltage corresponding to one of the data signals;

a first transistor controlling an amount of an electric current supplied to the organic light emitting diode corresponding to the voltage charged in the storage capacitor;

a second transistor coupled between one of the data lines and one of the scan lines, supplying one of the data signals to a first electrode of the first transistor when the scan signal is supplied to the one of the scan lines;

a third transistor coupled between a gate electrode and a second electrode of the first transistor, and being turned-on when the scan signal is supplied to the one of the scan lines; and

a boosting capacitor coupled between the one of the scan lines and the gate electrode of the first transistor, boosting a voltage of the gate electrode of the first transistor when a supply of the scan signal to the current scan line stops.

6. The organic light emitting display of claim 5, further comprising:

a fourth transistor coupled between the first power supply and the first electrode of the first transistor, and being turned-on or turned-off according to an emission control signal supplied to an emission control line; and

a fifth transistor coupled between the second electrode of the first transistor and the organic light emitting diode, and being turned-on or turned-off according to the emission control signal supplied to the emission control line.

7. The organic light emitting display of claim 6, further comprising a sixth transistor coupled between the initialization power supply and the storage capacitor, and being turned-on when the scan signal is supplied to a previous scan line.

8. The organic light emitting display of claim 5, wherein a capacitance of the boosting capacitor is set to be less than the capacitance of the storage capacitor.

9. The organic light emitting display of claim 5, wherein a voltage of the initialization power supply is set to be less than a voltage of one of the data signals.

10. The organic light emitting display of claim 5, wherein one of the data capacitors is selected from a parasitic capacitor equivalently formed at one of the data lines and a separately constructed capacitor.

11. The organic light emitting display of claim 5, further comprising a demultiplexer controller sequentially outputting a plurality of control signals to the demultiplexers during the data period, respectively, so that the data signals to be supplied to one of the output line is provided to one of the plurality of data lines.

12. The organic light emitting display of claim 5, wherein the demultiplexers divide the data signals supplied by the output lines and output the divided data signals to the data lines.

13. The organic light emitting display of claim 11, wherein the demultiplexer controller sequentially provides the plurality of control signals so that the plurality of control signals do not overlap with each other during the data period.

14. The organic light emitting display of claim 11, wherein each of the demultiplexers includes at least one switching element couple to a respective one of the output lines and a respective one of the data lines.

15. The organic light emitting display of claim 14, wherein the at least one switching element is turned-on to provide the data signals to the respective one of the data lines, when one of the control signals from the demultiplexer controller is supplied.

16. The organic light emitting display of claim 15, wherein when one of the control signals is supplied to the at least one switching element, the data signals provided to the respective one of the data lines are temporarily stored in a first data capacitor.

17. A method of expressing black gradation in a pixel comprising:

charging a storage capacitor coupled between a first power supply and an initialization power supply with a voltage corresponding to a data signal;

controlling an amount of an electric current supplied to an organic light emitting diode corresponding to the voltage charged in the storage capacitor through a first transistor;

supplying the data signal to the first transistor when a scan signal is supplied to a scan line;

turning-on a second transistor coupled between a gate electrode and a second electrode of the first transistor, when the scan signal is supplied to the scan line; and

boosting a voltage of the gate electrode of the first transistor when a supply of the scan signal to the current scan line stops.