CN101840673B - amplifier and the source driver applying the amplifier - Google Patents

Abstract

An amplifier and a source driver using the same. The source driver includes an amplifier. The amplifier comprises an input stage, an output stage, a first current source, a second current source, a third current source and a switch module. The first current source is used for providing a first bias current to the input stage, the second current source is used for providing a second bias current to the output stage, and the third current source is used for providing a third bias current. The switch module is used for selectively connecting the third current source to the input stage or the output stage.

Description

amplifier and the source driver applying the amplifier

technical field

The present invention relates to an amplifier, in particular to an amplifier arranged in a source driver.

Background technique

As the resolution and frame refresh rate of liquid crystal displays are gradually improved, it becomes more and more difficult to charge the pixel electrodes to the target potential in time. In order to reduce the charging time, it is necessary to increase the driving current of an output buffer of a source driver in the liquid crystal display to increase the driving capability of the output buffer. However, increasing the current of the output buffer will lead to an increase in power consumption, so how to save power has become an important issue in design.

Contents of the invention

Therefore, one of the objectives of the present invention is to provide an output buffer with better driving capability without wasting power.

According to an embodiment of the present invention, a source driver including an amplifier is disclosed. The amplifier includes an input stage, an output stage, a first current source, a second current source, a third current source and a switch module. The first current source is used to provide a first bias current to the input stage, the second current source is used to provide a second bias current to the output stage, and the third current source is used to provide a third bias current. The switch module is used for selectively connecting the third current source to the input stage or the output stage.

According to another embodiment of the present invention, an amplifier is disclosed. The amplifier includes an input stage, an output stage, a first current source, a second current source, a third current source and a switch module. The first current source is used to provide a first bias current to the input stage, the second current source is used to provide a second bias current to the output stage, and the third current source is used to provide a third bias current. The switch module is used for selectively connecting the third current source to the input stage or the output stage.

Description of drawings

FIG. 1 is a schematic diagram of the present invention applied to an output buffer (amplifier) in a source driver of a display.

FIG. 2 is a schematic diagram of the relationship between the control signal and the conversion pulse signal in the first embodiment of the present invention.

FIG. 3 is a schematic diagram of the relationship between the control signal and the switching pulse signal in the second embodiment of the present invention.

FIG. 4 is a schematic diagram of the relationship between the control signal and the conversion pulse signal in the third embodiment of the present invention.

[Description of main component symbols]

100 Amplifier 110 input stage 120 output stage 130 switch module 132 first switch 134 Second switch M6 The first current source M7 Second current source M8 Third current source

Detailed ways

Certain terms are used throughout the specification and appended claims to refer to particular elements. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This description and the appended claims do not use the difference in name as a way to distinguish components, but use the difference in function of components as a criterion for distinguishing. "Includes" mentioned throughout the specification and appended claims is an open term, so it should be interpreted as "including but not limited to". In addition, the term "coupled" herein includes any direct and indirect means of electrical connection. Therefore, if it is described that a first device is coupled to a second device, it means that the first device may be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means.

Please refer to FIG. 1 . FIG. 1 is a schematic diagram of an output buffer 100 applied in a source driver of a display according to the present invention. As shown in Figure 1, the output buffer 100 is an amplifier, which includes an input stage 110, an output stage 120, a switch module 130, a first current source M6, a second current source M7 and a third current source M8. The input stage 110 includes four transistors M1 - M4 , the output stage 120 includes a transistor M5 , and the switch module 130 includes a first switch 132 and a second switch 134 . In this embodiment, the first current source M6 is used to provide a first bias current _I1 to the input stage 110, the second current source M7 is used to provide a second bias current I2 to the output stage 120, and the second current source M7 is used to provide a second bias current _I2 to the output stage 120. The three current sources M8 are used to provide a third bias current I ₃ . In addition, the first current source M6 , the second current source M7 and the third current source M8 are implemented in a current mirror manner. The switch module 130 is used to selectively connect the third current source M8 to the input stage 110 or the output stage 120, wherein the first switch 132 selectively connects the third current source M8 to the input stage 110, and the second switch 134 selects The third current source M8 is electrically connected to the output stage 120.

During the operation of the amplifier 100, the switch module 130 is controlled by a control signal HDR generated based on a conversion pulse signal TP, wherein the conversion pulse signal TP is used to trigger the source driver to output display data. The first switch 132 is controlled by the control signal HDR, and the second switch 134 is controlled by an inverse control signal HDRB, wherein the phases of the control signal HDR and the inverse control signal HDRB are opposite to each other. FIG. 2 is a schematic diagram of the relationship between the control signal HDR and the pulse conversion signal TP in the first embodiment of the present invention. As shown in FIG. 2 , in a first scanning line period T1 , the conversion pulse signal TP is activated to enable the source driver to drive a row of pixels, and the control signal HDR is correspondingly activated. In this embodiment, the activation time of the control signal HDR is longer than the activation time of the conversion pulse signal TP. Then, in a second scanning line period T2, the conversion pulse signal TP is activated to enable the source driver to drive the pixels of the next row, and the control signal HDR is correspondingly activated.

During the period when the control signal HDR is activated, the first switch 132 connects the third current source M8 to the input stage 110, and the bias current of the input stage 110 is equal to the first bias current _I1 and the third bias current _I3 Overall, therefore, the drive capability of the input stage 110 is increased and the slew rate of the signal carrying the display data is also increased. Furthermore, in the embodiment shown in FIG. 2 , the source driver outputs the display data when the transition pulse signal TP has a negative pulse edge. During the period when the control signal HDR is activated, firstly, a capacitor C located at the output stage 120 is rapidly charged by the current provided by the input stage 110, and then, when the source driver starts outputting a signal with display data, a capacitor C located at a A liquid crystal capacitor of the pixel is charged rapidly. When the control signal HDR is deactivated, the second switch 134 connects the third current source M8 to the output stage 120 to stabilize the amplifier 100. At this time, the bias current of the output stage 120 is the second bias current I ₂ and the sum of the third bias current I ₃ .

It should be noted that in FIG. 2, the start-up time of the control signal HDR is a small part of one period of the control signal HDR itself; that is to say, in most of the time, the second switch 134 turns the third current source M8 Connect to output stage 120 to stabilize amplifier 100 .

3 and 4 are schematic diagrams of the relationship between the control signal HDR and the conversion pulse signal TP in other embodiments (second embodiment and third embodiment) of the present invention. In FIG. 3, the control signal HDR is activated after the switching pulse signal TP is deactivated, while in FIG. 4, the control signal HDR is substantially synchronized with the switching pulse signal TP.

In addition, in the embodiment shown in FIG. 1 , the third bias current I ₃ is much higher than the first bias current I ₁ and the second bias current I ₂ . Therefore, when the capacitor C in the output stage 120 or the liquid crystal capacitor in the pixel starts to be charged, the third current source M8 provides a third bias current _I3 to the input stage 110 to increase the slew rate; then the third current source M8 A third bias current I ₃ is provided to the output stage 120 to stabilize the amplifier 100 .

It should be noted that the input stage 110 and the output stage 120 shown in FIG. -rail) or other types of amplifiers, and these design changes still fall within the scope of the present invention.

Briefly, the amplifier in the source driver includes an input stage, an output stage, a first current source, a second current source, a third current source and a switch module. The switch module is used for selectively connecting the third current source to the input stage or the output end. Most of the time, the switch module connects the third current source to the output stage to stabilize the amplifier, and when driving capability needs to be enhanced, the switch module connects the third current source to the input stage , In this way, there is no need to use additional current to improve the driving capability of the amplifier, so unnecessary power consumption can be reduced.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (14)

1. A source driver comprising: An amplifier, including: an input stage; an output stage coupled to the input stage; a first current source for providing a first bias current to the input stage; a second current source for providing a second bias current to the output stage; a third current source for providing a third bias current; and a switch module for selectively connecting the third current source to the input stage or the output stage, wherein the switch module is controlled by a control signal generated based on a switching pulse signal, and the switching pulse signal The source driver is triggered to output display data. 2. The source driver as claimed in claim 1, wherein the switch module comprises a first switch and a second switch, the first switch selectively connects the third current source to the input stage, and the first switch Two switches selectively connect the third current source to the output stage. 3. The source driver as claimed in claim 1, wherein the control signal is activated when the switching pulse signal is activated, and an activation time of the control signal is longer than an activation time of the switching pulse signal. 4. The source driver as claimed in claim 1, wherein the control signal is activated after the switching pulse signal is deactivated. 5. The source driver as claimed in claim 1, wherein the control signal is substantially synchronous with the switching pulse signal. 6. The source driver as claimed in claim 1, wherein the second current source and the third current source are implemented by current mirrors. 7. The source driver as claimed in claim 1, wherein the third bias current is larger than the first bias current or the second bias current. 8. An amplifier comprising: an input stage; an output stage coupled to the input stage; a first current source for providing a first bias current to the input stage; a second current source for providing a second bias current to the output stage; a third current source for providing a third bias current; and a switch module for selectively connecting the third current source to the input stage or the output stage, wherein the switch module is controlled by a control signal generated based on a switching pulse signal, and the switching pulse signal A source driver including the amplifier is triggered to output display data. 9. The amplifier of claim 8, wherein the switch module comprises a first switch and a second switch, the first switch selectively connects the third current source to the input stage, and the second switch The third current source is selectively connected to the output stage. 10. The amplifier of claim 8, wherein the control signal is activated when the switching pulse signal is activated, and an activation time of the control signal is longer than an activation time of the switching pulse signal. 11. The amplifier of claim 8, wherein the control signal is activated after the switching pulse signal is deasserted. 12. The amplifier of claim 8, wherein the control signal is substantially synchronous with the switching pulse signal. 13. The amplifier as claimed in claim 8, wherein both the second current source and the third current source are implemented by current mirrors. 14. The amplifier of claim 8, wherein the third bias current is larger than the first bias current or the second bias current.

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