Patent Application
20100164930
This Non-provisional application claims priority under 35 U.S.C. ยง119(a) on Patent Application No(s). 097151771, filed in Taiwan, Republic of China on Dec. 31, 2008, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to displays, and in particular relates to drive circuits of the displays.
2. Description of the Related Art
The output voltage Vout on the pixel 102 influences the brightness of the pixel, while the characteristic of the display influences that as well. Taking the carbon nanotube display (CNDP) for example, owing to its particular characteristic, the brightness of the CNDP will increase when it ages. For this case, it is necessary for the drive circuit 100 to comprise a calibration device 130 to calibrate the brightness of the display. For example, in the calibration device 130 in
However, the coupling effect of the transistor T1 (there is a coupling capacitor between the gate and the source/drain) makes the output voltage Vout influencing the bias voltage Vbias. The output voltage Vout on the pixel 102 alternates between the two voltage levels according to the pixel signal SP. When the output voltage Vout switches from the low voltage VGND to the high voltage VH, the output voltage makes the bias voltage Vbias raise rapidly and causes a surge P1 therein; when the output voltage Vout switches from the high voltage VH to the low voltage VGND, the output voltage makes the bias voltage Vbias descend rapidly and causes a surge P2 therein. In addition, the drive circuit 100 of the display is a high voltage device, and the high voltage VH on the pixel 102, for example, could be as high as 110 volt, therefore, the surge P1 and P2 are not negligible. Once the bias voltage Vbias changes, the equivalent resistance of the calibration device 130 changes accordingly and thus results in luminance flickers on the display.
To settle the problems mentioned above, the drive circuit 100 could further comprise a stabilizing device 140. The stabilizing device 140 is coupled to the input end A of the calibration device 130 for suppressing surges in the bias voltage Vbias which occurs due to the switch of the output voltage Vout. For example, the stabilizing device 140 could comprise the voltage pulling down device 141, the voltage pulling up device 142 and the bias transmission device 143.
However, from
The present invention provides a drive circuit of a displayer for driving at least a pixel. The drive circuit comprises an output stage, a calibration device, a stabilizing device and an accelerating device. The output stage is coupled to the pixel and controlled by a pixel signal to switch an output voltage on the pixel between a high voltage and a low voltage; the calibration device is coupled between the output stage and the pixel and comprising an input end controlled by a bias voltage to calibrate the equivalent resistance of the calibration device for further calibrating the brightness of the pixel; the stabilizing device is coupled between the input end of the calibration device and the pixel signal for stabilizing the voltage on the input end of the calibration device to be at the level of the bias voltage after a variation; and the accelerating device is coupled between the stabilizing device and a voltage source for generating the bias voltage and accelerating the speed stabilizing the voltage on the input end of the calibration device to be at the level of the bias voltage.
The present invention also provides a method for calibrating the brightness of a display. The method comprises disposing an output stage, wherein the output stage is coupled to at least a pixel of the display, and the output stage is controlled by a pixel signal to switch an output voltage on the pixel between a high voltage and a low voltage; disposing a calibration device between the output stage and the pixel; imposing a bias voltage on the calibration device to calibrate a equivalent resistance of the calibration device for further calibrating the brightness of the pixel; stabilizing the voltage on the input end of the calibration device to be at the level of the bias voltage after a variation; and accelerating the speed stabilizing the voltage on the input end of the calibration device to be at the level of the bias voltage.
A detailed description is given in the following embodiments with reference to the accompanying drawings.
The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
The accelerating device 460 comprises a bias voltage generator 463 for generating the bias voltage Vbias. For example, the bias voltage generator 463 is composed of a n-MOSFET T3 and a resistor R2, wherein the transistor T3 has a gate coupled to the voltage source 470 for receiving the input voltage Vin, a source coupled to a low level (for convenience, the low level is the same with the grounded voltage VGND here, but the present invention is not limited thereto in other embodiments), and a drain for providing the bias voltage Vbias to the input end B of the stabilizing device 440. The resistor R2 is coupled between a high level (for convenience, the high level is the same with the high voltage VH here, but the present invention is not limited thereto in other embodiments) and the drain of the transistor T3. Those skilled in the art could dispose a proper resistor R2 to generate the bias voltage Vbias.
Besides, the accelerating device 460 in the present invention further comprises a compensating device 461 for compensating the bias voltage Vbias when the bias voltage Vbias does not consist with a standard bias voltage Vo. According to the present invention, the standard bias voltage Vo has to be stable and consisting with the original bias voltage Vbias. In this embodiment, the compensating device 461 is a n-MOSFET T1 which has a gate coupled to the standard bias voltage V0, a drain coupled to a high level (for convenience, the high level is the same with the high voltage VH here, but the present invention is not limited thereto in other embodiments), and a source coupled to the input end B of the stabilizing device 440 and the drain of the bias voltage generator 463. Those skilled in the art understands that when the difference between the standard bias voltage Vo received by the gate of the transistor T1 and the bias voltage Vbias received by the source of the transistor T1 exceeds the threshold voltage VT of the transistor T1, the high voltage VH received by the drain of the transistor T1 will charge and stabilize the bias voltage Vbias immediately.
In an embodiment, the standard bias voltage Vo could be provided by a standard bias voltage generator 462. The standard bias voltage generator 462 could be composed of an n-MOSFET T2 and a resistor R1. The transistor T2 has a gate coupled to the voltage source 470 for receiving the input voltage Vin, a source coupled to a low level (for convenience, the low level is the same with the grounded voltage VGND here, but the present invention is not limited thereto in other embodiments), and a drain for providing the standard bias voltage V0 to the gate of the compensating device 461. Note that, according to the present invention, the standard bias voltage generator 462 has to be the same with the bias voltage generator 463, which means that the transistor T2 and the transistor T3 have to match with each other (both have the same aspect ratio), the resistances of the resistor R1 and R2 are the same with each other and coupled to the same high voltage VH and low voltage VGND. Since the standard bias voltage generator 462 and the bias voltage generator 463 are the same with each other, they output the same voltages respectively on the output ends of themselves after receiving the input voltage Vin from the voltage source 470. Further, with the operation of the compensating device 461, the voltages difference between the output end of the standard bias voltage generator 462 and the bias voltage generator 463 could be compensated immediately.
In addition, the present invention further provides a method for calibrating the brightness of a display.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 097151771 | Dec 2008 | TW | national |
