Output buffer and source driver utilizing the same

1. Field of the Invention

The invention relates to an output buffer, and more particularly to an output buffer applied in a source driver.

2. Description of the Related Art

FIG. 1 is a schematic diagram of a conventional output buffer. The output buffer 100 comprises input stage circuits 111 and 113 , output stage circuits 131 and 133 , and an output multiplex unit 150 . The output buffer 100 increases the driving capability of the input signals IN 1 and IN 2 to successfully drive the load units L 1 and L 2 . However, the transistor sizes of the output stage circuit 131 and 133 and the output multiplex unit 150 are increased as a result. Thus, the size of the output buffer is increased.

In addition, when the output signals of the output stage circuit 131 and 133 approach a target, the voltage difference between the drain and the source of the transistor of the output multiplex unit 150 approaches 0V. If the load units L 1 and L 2 become heavier, when the output signals of the output stage circuits 131 and 133 approach the target, the driving speed of the output is reduced.

Output buffers are provided. An exemplary embodiment of an output buffer comprises a first input stage circuit, a first output stage circuit, a second output stage circuit, a first switching module, and a second switching module. The first output stage circuit is coupled to a first data line. The second output stage circuit is coupled to a second data line. The first switching module is coupled between the first input stage circuit and the first output stage circuit. The second switching module is coupled between the first input stage circuit and the second output stage circuit.

Source drivers are also provided. An exemplary embodiment of a source driver comprises a digital-to-analog converter and an output buffer. The digital-to-analog converter generates a first analog signal and a second analog signal. The output buffer comprises a first input stage circuit, a first output stage circuit, a second output stage circuit, a first switching module, and a second switching module. The first input stage circuit receives the first analog signal. The first output stage circuit is coupled to a first data line. The second output stage circuit is coupled to a second data line. The first switching module is coupled between the first input stage circuit and the first output stage circuit. The second switching module is coupled between the first input stage circuit and the second output stage circuit.

Another exemplary embodiment of a source driver comprises a digital-to-analog converter and an output buffer. The digital-to-analog converter generates a first analog signal and a second analog signal. The output buffer comprises a first input stage circuit, a first output stage circuit, a second output stage circuit, a first switching module, a second switching module, a second input stage circuit, a third output stage circuit, a fourth output stage circuit, a third switching module, and a fourth switching module. The first input stage circuit receives the first analog signal. The first output stage circuit is coupled to a first data line. The second output stage circuit is coupled to a second data line. The first switching module is coupled between the first input stage circuit and the first output stage circuit. The second switching module is coupled between the first input stage circuit and the second output stage circuit. The second input stage circuit receives the second analog signal. The third output stage circuit is coupled to the second data line. The fourth output stage circuit is coupled to the first data line. The third switching module is coupled between the second input stage circuit and the third output stage circuit. The fourth switching module is coupled between the second input stage circuit and the fourth output stage circuit.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

The invention can be more fully understood by referring to the following detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of a conventional output buffer;

FIG. 2 is a schematic diagram of an exemplary embodiment of a display device;

FIG. 3A is a schematic diagram of an exemplary embodiment of an output buffer;

FIG. 3B is a schematic diagram of another exemplary embodiment of the output buffer; and

FIG. 4 is a schematic diagram of another exemplary embodiment of the output buffer.

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.

FIG. 2 is a schematic diagram of an exemplary embodiment of a display device. The display device 200 comprises a gate driver 210 , a source driver 230 , and pixels P 11 ˜P mn . The gate driver 210 provides scan signals to the pixels P 11 ˜P mn via the scan lines SL 1 ˜SL n . The source driver 230 provides data signals to the pixels P 11 ˜P mn via the data lines DL 1 ˜DL m . The pixels P 11 ˜P mn receive the data signals according to the scan signals and display brightness according to the data signals.

To drive the pixels P 11 ˜P mn , the source driver 230 comprises an output buffer. FIG. 3A is a schematic diagram of an exemplary embodiment of an output buffer. The output buffer 300 as shown in FIG. 3 is capable of driving the pixels of two data line. The data lines DL 1 and DL 2 are given as an example.

As shown in FIG. 3A , the output buffer 300 comprises an input stage circuit 310 , switching modules 330 and 350 , and output stage circuits 370 and 390 . The input stage circuit 310 receives an input signal IN 1 . The switching module 330 is coupled between the input stage circuit 310 and the output stage circuit 370 . The output stage circuit 370 is coupled to the data line DL 1 . The switching module 350 is coupled between the input stage circuit 310 and the output stage circuit 390 . The output stage circuit 390 is coupled to the data line DL 2 .

When the switching module 330 transmits the input signal IN 1 to the output stage circuit 370 , the output stage circuit 370 generates a first data signal to the data line DL 1 according to the input signal IN 1 . When the switching module 350 transmits the input signal IN 1 to the output stage circuit 390 , the output stage circuit 390 generates a second data signal to the data line DL 2 according to the input signal IN 1 . In this embodiment, when the switching module 330 transmits the input signal IN 1 , the switching module 350 stops transmitting the input signal IN 1 . When the switching module 350 transmits the input signal IN 1 , the switching module 330 stops transmitting the input signal IN 1 .

In FIG. 3A , the structures of the switching modules 330 and 350 are provided as an example. The switching modules 330 and 350 respectively transmit the input signal to the output stage circuits 370 and 390 . Thus, the switching modules 330 and 350 can be replaced by other transmitting circuits or switches in other embodiments.

Similarly, the structures of the output stage circuits 370 and 390 are provided as an example. The output stage circuits 370 and 390 generate data signals to the data lines DL 1 and DL 2 respectively. Thus, the output stage circuits 370 and 390 as shown in FIG. 3A can be replaced by other circuits in other embodiments.

FIG. 3B is a schematic diagram of another exemplary embodiment of the output buffer. FIG. 3B is similar to FIG. 3A except for the additions of the feedback modules 320 and 340 and the control modules 360 and 380 . In some embodiment, the feedback modules 320 and 340 and/or the control modules 360 and 380 can be omitted.

The feedback module 320 provides the first data signal generated by the output stage circuit 370 to the input stage circuit 310 . The feedback module 340 provides the second data signal generated by the output stage circuit 390 to the input stage circuit 310 . In this embodiment, the input stage circuit 310 does not receive the first and the second data signals simultaneously.

In this embodiment, the control modules 360 and 380 control the output stage circuits 370 and 390 respectively. When the switching module 330 transmits the input signal IN 1 to the output stage circuit 370 , the control module 360 activates the output stage circuit 370 and the control module 380 de-activates the output stage circuit 390 . Thus, the first data signal is generated by the output stage circuit 370 . At this time, the feedback module 320 transmits the first data signal to the input stage circuit 310 .

When the switching module 350 transmits the input signal IN 1 to the output stage circuit 390 , the control module 380 activates the output stage circuit 390 and the control module 360 de-activates the output stage circuit 370 . Thus, the second data signal is generated by the output stage circuit 390 . At this time, the feedback module 340 transmits the second data signal to the input stage circuit 310 .

FIG. 4 is a schematic diagram of another exemplary embodiment of the output buffer. FIG. 4 is similar to FIG. 3B except for the additions of an input stage circuit 410 b , feedback modules 420 b and 440 b, switching modules 430 b and 450 b, control modules 460 b and 480 b, and output stage circuits 470 b and 490 b. The input stage circuit 410 b, the feedback modules 420 b and 440 b, the switching modules 430 b and 450 b, the control modules 460 b and 480 b, and the output stage circuits 470 b and 490 b are the same as the input stage circuit 310 , the feedback modules 320 and 340 , the switching modules 330 and 350 , the control modules 360 and 380 , and the output stage circuits 370 and 390 as shown in FIG. 3B .

The input circuits 410 a and 410 b respectively receive the input signals IN 1 and IN 2 . The input signals IN 1 and IN 2 may be differential signals. In one embodiment, the input signals IN 1 and IN 2 are generated by a digital-to-analog converter (DAC), such as a resistor-string DAC.

Assuming that the input signal IN 1 is positive and the input signal IN 2 is negative, when the switching module 430 a transmits the input signal IN 1 to the output stage circuit 470 a, the data signal generated by the output stage circuit 470 a is positive. When the switching module 450 b transmits the input signal IN 2 to the output stage circuit 490 b, the data signal generated by the output stage circuit 490 b is negative. Similarly, when the switching module 450 a transmits the input signal IN 1 to the output stage circuit 490 a, the data signal generated by the output stage circuit 490 a is positive. When the switching module 430 b transmits the input signal IN 2 to the output stage circuit 470 b, the data signal generated by the output stage circuit 470 b is negative. Thus, the polarity of the data signal is controlled by the switching modules 430 a, 450 a, 430 b, and 450 b.

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.