Driving circuit and method of driving an organic electroluminescence device

• US 6,956,547 B2
• Filed: 06/24/2002
• Issued: 10/18/2005
• Est. Priority Date: 06/30/2001
• Status: Expired due to Term

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Bae, Sung-Joon, Lee, Myung-Ho, Lee, Han-Sang, Park, Joon-Kyu
• Primary Examiner(s): Awad, Amr A.
• Application Number:
  US10/176,537
• Publication Number:
  US 20030001806A1
• Time in Patent Office: 1,212 Days
• Field of Search: 345 76- 81, 345 88- 89, 345690-691, 345/213, 315/169.1, 315/169.3
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• 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 2310/0275 Details of drivers for data electrodes, other than drivers for liquid crystal, plasma or OLED displays, not related to handling digital grey scale data or to communication of data to the pixels by means of a current
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• 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 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

A driving circuit in an organic electroluminescent device includes a gate driver unit for sequentially outputting a control signal to select gate lines in a luminescent array unit and a current driver unit for supplying picture data to a data lines in the luminescent array unit corresponding to the gate lines selected by the gate driver unit and selectively driving organic electroluminescent devices of the selected line. The driving circuit includes a minimum gray level judgment unit for determining whether the picture data is of a predetermined minimum gray level; and a switching unit for receiving a control signal according to the determination made by the minimum gray level judgment unit and for selectively supplying a reference voltage or a reference current to the selectively driven organic electroluminescent devices.

Claims

1. A driving circuit of an organic electroluminescent device having a gate driver unit for sequentially outputting a control signal to select gate lines within a luminescent array unit, the driving circuit comprising:

a current driver receiving picture data;

a minimum gray level judgment unit connected to an output of the current driver, the minimum gray level judgement unit determining whether the picture data is of a predetermined minimum gray level; and

a switching unit connected to an output of the minimum gray level judgement unit and to the output of the current driver, the switching unit receiving a control signal corresponding to the determination made by the minimum gray level judgment unit and selectively supplying a reference voltage or the picture data to the selected organic electroluminescent device in correspondence with the received control signal.

2. The circuit of claim 1, wherein the minimum gray level judgment unit comprises a NOR gate for receiving a digital value of a predetermined gray level from the current driver unit, performing a NOR operation on the received digital value, and outputting the control signal to the switching unit.

3. The circuit of claim 1, wherein the minimum gray level judgment unit comprises:

an inverter for receiving a digital value of a predetermined gray level from the current driver unit and for inverting the received digital value; and

an AND gate for performing an AND operation of the output of the inverter and for outputting the control signal to the switching unit.

4. The circuit of claim 1, further comprising a voltage driver for supplying the reference voltage.

5. A driving circuit of an organic electroluminescent device having a gate driver unit for sequentially outputting a control signal to select gate lines within a luminescent array unit, the driving circuit comprising:

a current driver receiving picture data;

a minimum gray level judgment unit connected to an output of the current driver, the minimum gray level judgement unit determining whether the picture data is of a predetermined minimum gray level; and

a switching unit connected to an output of the minimum gray level judgement unit and to the output of the current driver, the switching unit receiving a control signal corresponding to the determination made by the minimum gray level judgment unit and selectively supplying a reference signal or the picture data to the selected organic electroluminescent device in correspondence with the received control signal.

6. The circuit of claim 5, wherein the minimum gray level judgment unit comprises a NOR gate for receiving a digital value of a predetermined gray level from the current driver unit, performing a NOR operation on the received digital value, and outputting the control signal to the switching unit.

7. The circuit of claim 5, wherein the minimum gray level judgment unit comprises:

an inverter for receiving a digital value of a predetermined gray level from the current driver unit and for inverting the received digital value; and

an AND gate for performing an AND operation of the output of the inverter and for outputting the control signal to the switching unit.

8. The circuit of claim 5, wherein the reference signal comprises a reference voltage.

9. The circuit of claim 5, wherein the reference signal comprises a reference current.

10. A driving circuit of an organic electroluminescent device having a gate driver unit for sequentially outputting a control signal to select lines within a luminescent array unit, the driving circuit comprising:

a current driver receiving picture data;

a minimum gray level judgment unit connected to an output of the current driver, the minimum gray level judgement unit determining whether the picture data is of a predetermined of a predetermined minimum gray level; and

a switching unit connected to an output of the minimum gray level judgement unit and to the output of the current driver, the switching unit receiving a control signal corresponding to the determination made by the minimum gray level judgment unit and selectively supplying a reference current or the picture data to the selected organic electroluminescent device in correspondence with the received control signal.

11. The circuit of claim 10, wherein the minimum gray level judgment unit comprises a NOR gate for receiving a digital value of a predetermined gray level from the current driver unit, performing a NOR operation on the received digital value, and outputting the control signal to the switching unit.

12. The circuit of claim 10, wherein the minimum gray level judgment unit comprises:

an inverter for receiving a digital value of a predetermined gray level from the current driver unit and for inverting the received digital value; and

an AND gate for performing an AND operation of the output of the inverter and for outputting the control signal to the switching unit.

13. The circuit of claim 10, further comprising:

a current source for supplying the reference current.

14. A method of driving an organic electroluminescent device, comprising:

reading picture data supplied to predetermined organic electroluminescent devices within a luminescent array unit, wherein the predetermined organic electroluminescent devices are selected by a gate driver unit and a current driver unit;

determining whether the read picture data is of a predetermined minimum gray level; and

using the picture data to drive the organic electroluminescent devices with the current driver unit, wherein the current driver unit supplies current to predetermined organic electroluminescent devices if the picture data is not of the predetermined gray level, wherein the current driver unit cuts off the current supplied to the predetermined organic electroluminescent devices if the picture data is of the predetermined gray level, wherein a reference voltage is supplied to the predetermined organic electroluminescent devices when the picture data is of the predetermined gray level.

15. A method of driving an organic electroluminescent device, comprising:

reading picture data supplied to predetermined organic electroluminescent devices within a luminescent array unit, wherein the predetermined organic electroluminescent devices are selected by a gate driver unit and a current driver unit;

determining whether the read picture data is of a predetermined minimum gray level; and

using the picture data to drive the organic electroluminescent devices with the current driver unit, wherein the current driver unit supplies current to the predetermined organic electroluminescent devices if the picture data is not of the predetermined gray level, wherein the current driver unit cuts off the current supplied to the predetermined organic electroluminescent devices if the picture data is of the predetermined gray level, wherein a reference current is supplied to the predetermined organic electroluminescent devices when the picture data is of the predetermined gray level.

16. A method of driving an organic electroluminescent device, comprising:

receiving picture data to be supplied to predetermined organic electroluminescent devices within a luminescent array unit, wherein the predetermined organic electroluminescent devices are selected by a gate driver unit and a current driver unit;

determining whether the received picture data is of a predetermined minimum gray level; and

using the picture data to drive the organic electroluminescent devices with the current driver unit, wherein the current driver unit supplies current to predetermined organic electroluminescent devices if the picture data is not of the predetermined gray level, wherein the current driver unit cuts off the current supplied to the predetermined organic electroluminescent devices if the picture data is of the predetermined gray level, wherein a reference voltage is supplied to the predetermined organic electroluminescent devices when the picture data is of the predetermined gray level.