Organic light emitting display and driving method thereof

Patent metadata

Field	Value
Publication number	US-9336713-B2
Application number	US-201213668038-A
Country	US
Kind code	B2
Filing date	Nov 2, 2012
Priority date	Aug 30, 2012
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

An organic light emitting display comprises: a driving TFT comprising a gate connected to a node B, a drain connected to an input terminal of high-potential cell driving voltage, and a source connected to the organic light emitting diode through a node C; a first switching TFT for switching the current path between a node A and the node B in response to a light emission control signal; a second switching TFT for initializing the node C in response to an initialization signal; a third switching TFT for initializing either the node A or the node B in response to the initialization signal; a fourth switching TFT for switching the current path between a data line and the node B in response to a scan signal; a compensation capacitor connected between the node B and the node C.

First claim

What is claimed is:

1. An organic light emitting display comprising:
an organic light emitting diode;
a driving thin film transistor (TFT) comprising a first electrode connected to a first node, a second electrode connected to an input terminal of high-potential cell driving voltage, and a third electrode connected to the organic light emitting diode through a second node, and the driving TFT configured to control current through the organic light emitting diode;
a first switching TFT comprising a first electrode connected to a gate driver to receive a light emission control signal, a second electrode connected to a third node, and a third electrode connected to the first node and the first electrode of the driving TFT, the first switching TFT configured to provide a current path between the third node and the first node in response to the light emission control signal at a first light emission level;
a second switching TFT comprising a first electrode connected to the gate driver to receive an initialization signal, a second electrode connected to the second node and the third electrode of the driving TFT, and a third electrode connected an initialization voltage, the second switching TFT configured to initialize the second node to the initialization voltage by connecting the second node to the third electrode of the second switching TFT in response to the first electrode of the second switching TFT receiving the initialization signal at a first initialization level from the gate driver;
a third switching TFT comprising a first electrode connected to the gate driver to receive the initialization signal, a second electrode connected to the first node, the first electrode of the driving TFT, and the third electrode of the first switching TFT, and a third electrode connected to a reference voltage, the third switching TFT configured to initialize either the first node or the third node to the reference voltage that is higher than the initialization voltage in response to the first electrode of the third switching TFT receiving the initialization signal at the first initialization level from the gate driver;
a fourth switching TFT comprising a first electrode connected to the gate driver to receive a scan signal, a second electrode connected to a data line, and a third electrode connected to the third node and the second electrode of the first switching TFT, the fourth switching TFT configured to provide a current path between the data line and the third node in response to the first electrode of the fourth switching TFT receiving the scan signal from the gate driver when the fourth switching TFT is turned on;
a compensation capacitor including a first end and a second end, wherein the first end connected to the first node, the first electrode of the driving TFT, the third electrode of the first switching TFT, and the second electrode of the third switching TFT, and wherein the second end is connected to the second node, the second electrode of the second switching TFT, the third electrode of the driving TFT, and the organic light emitting diode, the compensation capacitor configured to store a threshold voltage of the driving TFT in response to the first switching TFT being turned off after the first electrode of the first switching TFT receives the light emission control signal at a second light emission level from the gate driver, the second switching TFT being turned off after the first electrode of the second switching TFT receives the initialization signal at a second initialization level from the gate driver, and the third switching TFT being turned off after the first electrode of the third switching TFT receives the initialization signal at the second initialization level from the gate driver, and the compensation capacitor being distinct from parasitic capacitance of the driving TFT; and
a storage capacitor including a first end and a second end, the first end of the storage capacitor connected to the third node, the third electrode of fourth switching TFT, and the second electrode of the first switching TFT, and the second end of the storage capacitor connected to the second node, the second electrode of the second switching TFT, and the organic light emitting diode.

2. The organic light emitting display of claim 1 , wherein during an initialization period of a frame the first node is initialized to the reference voltage, the second node is initialized to the initialization voltage, and third node is initialized to the reference voltage, and wherein during a sensing period of the frame the compensation capacitor stores the threshold voltage of the driving TFT, and wherein during a programming period of the frame a data voltage is applied to the third node, and wherein during an emission period of the frame the driving current applied to the organic light emitting diode is compensated using the threshold voltage and the data voltage; and
wherein the first node floats during the sensing period.

3. The organic light emitting display of claim 2 , wherein, during the sensing period, a potential of the second node rises to an intermediate source voltage based on a difference between the threshold voltage and a sum of the reference voltage and an amplification compensation factor voltage for preventing distortion of the threshold voltage, and wherein a potential of the first node rises to an intermediate gate voltage based on a sum of the reference voltage and the amplification compensation factor voltage.

4. The organic light emitting display of claim 3 , wherein the value of the amplification compensation factor voltage is adjusted by a parasitic capacitor of the driving TFT.

5. The organic light emitting display of claim 3 , further comprising an adjustment capacitor including a first end connected to the first node and a second end connected to the input terminal of the high-potential cell driving voltage, the adjustment capacitor configured to adjust the value of the amplification compensation factor voltage.

6. The organic light emitting display of claim 2 , wherein the light emission control signal is at the first light emission level for a first duration during the initialization period and the light emission control signal is at the first light emission level for a second duration during the emission period.

7. The organic light emitting display of claim 6 , wherein during a first emission period of the emission period a first driving current is applied to the organic light emitting diode and during a second emission period of the emission period a second driving current, which is lower than the first driving current, is applied to the organic light emitting diode, the second emission period longer than the first emission period.

8. The organic light emitting display of claim 6 , wherein the first duration is shorter than the second period.

9. The organic light emitting display of claim 1 , wherein the first electrode of the third switching TFT is connected to a signal line to which the initialization signal is supplied by the gate driver and the third electrode of the third switching TFT is connected to an input terminal of the reference voltage.

10. A driving method of an organic light emitting display comprising a driving thin film transistor (TFT) comprising a first electrode connected to a first node, a second electrode connected to an input terminal of high-potential cell driving voltage, and a third electrode connected to an organic light emitting diode through a second node, and the driving TFT controlling the current applied to the organic light emitting diode, a first switching TFT configured to provide the current path between a third node and the first node in response to a light emission control signal, a se

Assignees

• Lg Display Co Ltd

Inventors

• Nam Woojin
• Shim Jongsik
• Shin Hongjae
• Chang Minkyu

Classifications

• G09G2320/0223

  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 title

• G09G2320/043

  Preventing or counteracting the effects of ageing · CPC title

• G09G2310/067

  Special waveforms for scanning, where no circuit details of the gate driver are given · CPC title

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G3/3266

  Details of drivers for scan electrodes · CPC title