Patent Application
20080042941
The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein:
The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.
In general, the system for displaying an image includes the pixel structures 2, a scan driving circuit and a data driving circuit. The pixel structures 2 are arranged in an array. The plurality of scan lines SL connects the scan driving circuit with the pixel driving circuit 20. The plurality of data lines DL connects the data driving circuit with the pixel driving circuit 20. The data driving circuit operates in conjunction with the scan driving circuit. The scan driving circuit sequentially outputs the scan signals to the scan lines at different time instants and the data driving circuit writes the data into the pixel driving circuit 20 on each scan line through the data lines.
As shown in
When the data writing operation is to be ended, the scan signal on the first scan line SL is disabled to turn off the select switch 24 and the data switch 25 so that the drive element 23 is disconnected from the data line DL and the second scan line SL′. Thus, the drive element 23 is only controlled by the storage capacitor 22 to output the current 1, which is controlled by the voltage difference between the first terminal 221 and the second terminal 222 of the storage capacitor 22. Because the data signal is precisely recorded in the storage capacitor 22, the current 1 can respond precisely with the data signal to drive the organic light-emitting element 21 to precisely achieve the predetermined lighting intensity.
When the data is being written, the two terminals of the drive element 23 are controlled by the data line DL and the second scan line SL′. So, the loading voltage of the organic light-emitting element 21 does not influence the voltage difference between the two terminals of the drive element 23 and the output current 1 thereof. Thus, the rise of the loading voltage caused by the attenuated organic light-emitting element 21 also does not influence the current 1. Furthermore, because the data line DL charges/discharges the storage capacitor 22 when it is writing the data, the voltage at the second terminal 222 of the storage capacitor 22 approaches 0. So, the writing voltage of the data line DL may be below 5V, and the operation voltage of the data driving circuit may be 5V. The data driving circuit may be implemented in an integrated circuit formed using the typical manufacturing processes such as the CMOS manufacturing processes, and does not have to be manufactured using a special, expensive semiconductor manufacturing processes, such as certain high-voltage processes, so the cost of the data driving circuit can be reduced.
In this embodiment, the second scan line SL′ may be a previousor a next scan line adjacent to the first scan line SL, or any other scan line, as long as the scan signal on the second scan line SL′ is disabled when the scan signal on the first scan line SL is enabled.
In addition, the select switch 24 and the data switch 25 can be N-type transistors, which can be thin film transistors. The select switch 24 can have a gate electrically connected with the first scan line SL, a drain electrically connected with the data line DL, and a source electrically connected with the first terminal 221 of the storage capacitor 22. The data switch 25 can have a gate electrically connected with the first scan line SL, a drain electrically connected with the second terminal 222 of the storage capacitor 22, and a source electrically connected with the second scan line SL′.
The drive element 23 can be an N-type transistor having a gate electrically connected with the first terminal 221 of the storage capacitor 22, a source electrically connected with the second terminal 222 of the storage capacitor 22, and a drain electrically connected with a power source VDD. The current 1 outputted from the drive element 23 is controlled by the voltage difference between the two terminals of the storage capacitor 22. When the voltage difference between the first terminal 221 and the second terminal 222 of the storage capacitor 22 increases, the current 1 outputted from the drive element 23 increases such that the lighting intensity of the organic light-emitting element 21 increases. Because the data signal is precisely recorded in the storage capacitor 22, the current 1 can precisely respond with the data signal so as to drive the organic light-emitting element 21 to reach the predetermined lighting intensity precisely.
In addition, each organic light-emitting element 21 may be commonly connected with the power source VSS, and the organic light-emitting element 21 does not have the reverse structure but rather the same structure as that of the typical organic light-emitting element. So, the organic light-emitting element 21 is compatible with present manufacturing processes.
In this embodiment, the power switch 26 is a P-type transistor having a gate electrically connected with the first scan line SL, a source electrically connected with the power source VDD, and a drain electrically connected with the drive element 23. It is to be specified that the transistor of the power switch 26 is complementary to other transistors in the pixel driving circuit 20. If the other transistors, such as the drive element 23, the select switch 24 and the data switch 25, are P-type transistors, the power switch 26 can be an N-type transistor.
Step S01 controls a data signal to be written into the storage capacitor 22 from the data line DL when a signal on the first scan line SL is enabled so as to set the voltage at the first terminal 221 of the storage capacitor 22. Next, step S02 controls the second scan line SL′ to set the voltage at the second terminal 222 of the storage capacitor 22 when the signal on the first scan line SL is enabled. Finally, step S03 controls the drive element 23 to output the current 1 to the organic light-emitting element 21 to drive the organic light-emitting element 21 to emit light according to the voltage difference between the first terminal 221 and the second terminal 222 of the storage capacitor 22.
The driving method for the pixel driving circuit of this embodiment may be applied to the pixel driving circuit 20 according to the embodiment of
In summary, the output current of the drive element is controlled according to the voltage difference between the first terminal and the second terminal of the storage capacitor. The first terminal of the storage capacitor is connected with the data line and receives the data signal and the second terminal of the storage capacitor is connected to the second scan line and receives another scan signal when the first scan signal is enabled. Thus, the loading voltage of the organic light-emitting element does not influence the current outputted from the drive element, and the terminal voltage of the organic light-emitting element connected with the drive element is controlled so that the lifetime of the organic light-emitting element can be extended.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 095130165 | Aug 2006 | TW | national |
