Driving circuit and method for light emitting device

• US 6,680,580 B1
• Filed: 11/05/2002
• Issued: 01/20/2004
• Est. Priority Date: 09/16/2002
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Sung, Chih-Feng
• Primary Examiner(s): Lee, Wilson
• Application Number:
  US10/065,631
• Time in Patent Office: 441 Days
• Field of Search: 315/169--16, 345/82-86, 345/55, 345/62, 345/65, 345/72, 345/75, 345/76, 345/92
• US Class Current: 315/169.3
• 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 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

A driving circuit for a light emitting device is suitable for use in an active matrix organic light emitting diode (AMOLED) display, which has a scanning line to be input with a scanning clock signal, so as to control the driving circuit. The driving circuit includes a driving circuit main part which includes a light emitting device driven by a driving transistor as well as a scan line connection terminal and a data line connection terminal. The scan line connection terminal receives a scanning clock signal. A first transistor has a gate connected to this scan line connection terminal, a source. connected to the data line connection terminal, and a drain connected to a gate electrode of the driving transistor. A second transistor has a gate electrode connected to the scan line connection terminal, a source connected to a common voltage, and a drain connected to an anode of the light emitting device. The common voltage has a high voltage level and a low voltage level, alternating by a frequency, wherein the high voltage level of the common voltage is higher than a system low voltage and the low voltage level is smaller than the system low voltage. When the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line can be input with an image digital data voltage or a negative turning-off voltage. When the common voltage is at the low voltage level, the turning-off voltage is input, so as to turn off the driving transistor and the light emitting device.

Claims

1. A driving circuit for a light emitting device, suitable for use in an active matrix organic light emitting diode (AMOLED) display, which has a scanning line to be input with a scanning clock signal, so as to control the driving circuit, the driving circuit comprising:

a driving transistor, having a gate connected to a first node;

a light emitting device, serially connected to the driving transistor at a second node, so as to constitute a light emitting path, wherein, the light emitting path is connected in between a system high voltage and a system low voltage, when the driving transistor is activated, the system high voltage drives the light emitting device to make it emit the light;

maintain capacitor, connected to the first node, is able to maintain the driving transistor in an ON/OFF state according to a potential;

a first transistor, having a gate connected to a scanning line, a source connected to a data line, and a drain connected to the first node; and

a second transistor, having a gate connected to the scanning line, a source connected to a common voltage, and a drain connected to the second node, wherein, the common voltage has a high voltage level and a low voltage level, alternating by a frequency, and the high voltage level of the common voltage is higher than a system low voltage and the low voltage level is smaller than the system low voltage,

wherein, when the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line is input either with an image digital data voltage or a negative turning-off voltage, when the common voltage is at the low voltage level, the negative turning-off voltage is input, so as to turn off the driving transistor and the light emitting device.

2. The driving circuit for the light emitting device of claim 1, wherein the high voltage level of the common voltage is 0V, and the low voltage level is a negative voltage.

3. The driving circuit for the light emitting device of claim 2, wherein the low voltage level is about −

10 V, the system low voltage is about −

5 V, and the turning-off voltage is about −

20 V.

4. The driving circuit for the light emitting device of claim 1, wherein the negative turning-off voltage is smaller than the low voltage level of the common voltage.

5. The driving circuit for the light emitting device of claim 1, wherein when the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line is input with the image digital data voltage, so as to display an image.

6. The driving circuit for the light emitting device of claim 1, wherein the frequency of the common voltage is varied with a period of one frame, so as to drive an ON/OFF state of the corresponding multiple scanning lines to achieve a frame inversion operation.

7. The driving circuit for the light emitting device of claim 1, wherein the frequency of the common voltage is based on the scanning clock signal, so as to use the scanning line as a unit to achieve a line inversion operation.

8. The driving circuit for the light emitting device of claim 1, wherein the light emitting device comprises an organic light emitting diode.

9. The driving circuit for the light emitting device of claim 1, wherein the first transistor, the second transistor, and the driving transistor, are either an N type TFT transistor or a P type TFT transistor.

10. The driving circuit for the light emitting device of claim 1, wherein the maintain capacitor is connected in between the first node and the second node.

11. The driving circuit for the light emitting device of claim 1, wherein the second node is an anode of the light emitting device.

12. A driving circuit for a light emitting device, suitable for use in an active matrix organic light emitting diode (AMOLED) display, which has a scanning line to be input with a scanning clock signal, so as to control the driving circuit, the driving circuit comprising:

a driving circuit main part, including a light emitting device driven by a driving transistor as well as a data line connection terminal and a scan line connection terminal, wherein, the scan line connection terminal receives a scanning clock signal;

a first transistor, having a gate connected to the scan line connection terminal, a source connected to the data line connection terminal, and a drain connected to a gate electrode of the driving transistor; and

a second transistor, having a gate electrode connected to the scan line connection terminal, a source connected to a common voltage, and a drain connected to an anode of the light emitting device;

wherein, the common voltage has a high voltage level and a low voltage level, alternating by a frequency, and the high voltage level of the common voltage is higher than a system low voltage and the low voltage level is smaller than the system low voltage,

when the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line is input either with an image digital data voltage or a negative turning-off voltage, when the common voltage is at the low voltage level, the turning-off voltage is input, so as to turn off the driving transistor and the light emitting device.

13. The driving circuit for the light emitting device of claim 12, wherein the light emitting device comprises an organic light emitting diode.

14. The driving circuit for the light emitting device of claim 12, wherein the high voltage level of the common voltage is 0 V, and the low voltage level is a negative voltage.

15. The driving circuit for the light emitting device of claim 12, wherein the negative turning-off voltage is smaller than the low voltage level of the common voltage.

16. The driving circuit for the light emitting device of claim 12, wherein when the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line is input with the image digital data voltage, so as to display an image.

17. The driving circuit for the light emitting device of claim 12, wherein the frequency of the common voltage is varied with a period of one frame, so as to drive an ON/OFF state of the corresponding multiple scanning lines to achieve a frame inversion operation.

18. The driving circuit for the light emitting device of claim 12, wherein the frequency of the common voltage is based on the scanning clock signal, so as to use the scanning line as a unit to achieve a line inversion operation.

19. A driving method for a light emitting device, suitable for use in an active matrix organic light emitting diode (AMOLED) display, which has a scanning line to be input with a scanning clock signal, so as to control the driving circuit, the driving method comprising:

providing a driving circuit main part, wherein the driving circuit main part includes a light emitting device driven by a driving transistor as well as a data line connection terminal and a scan line connection terminal, and the scan line connection terminal receives a scanning clock signal;

providing a first transistor, wherein the first transistor has a gate connected to the scan line connection terminal, a source connected to the data line connection terminal, and a drain connected to a gate electrode of the driving transistor;

providing a second transistor, wherein the second transistor has a gate electrode connected to the scan line connection terminal, a source connected to a common voltage, and a drain connected to an anode of the light emitting device;

providing a high voltage level and a low voltage level that are alternating by a frequency, and the high voltage level of the common voltage is higher than a system low voltage and the low voltage level is smaller than the system low voltage; and

when the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line is input either with an image digital data voltage or a negative turning-off voltage, when the common voltage is at the low voltage level, the turning-off voltage is input, so as to turn off the driving transistor and the light emitting device.

20. The driving method for the light emitting device of claim 19, wherein the high voltage level of the common voltage is 0 V, and the low voltage level is a negative voltage.

21. The driving method for the light emitting device of claim 19, wherein the negative turning-off voltage is smaller than the low voltage level of the common voltage.

22. The driving method for the light emitting device of claim 19, wherein when the first transistor and the second transistor are simultaneously activated by the scanning clock signal, the data line is input with the image digital data voltage, so as to display an image.