TWI869068B - Common voltage generating circuit, touch display driver chip, liquid crystal touch display and information processing device - Google Patents

Abstract

A common voltage generating circuit has a negative feedback voltage regulating circuit composed of a differential input amplifier, a gain stage amplifier and a disconnectable Miller capacitor compensation circuit to generate a common voltage, wherein when the common voltage is coupled to a liquid crystal display panel, the Miller capacitor compensation circuit is disconnected; and when the common voltage is disconnected from the liquid crystal display panel, the Miller capacitor compensation circuit is turned on to keep the common voltage in a stable state.

Description

Common voltage generating circuit, touch display driver chip, liquid crystal touch display and information processing device

The present invention relates to a driving chip of a liquid crystal display, and in particular to a common voltage generating circuit of a driving chip of a liquid crystal touch display.

The liquid crystal unit of the liquid crystal panel can be regarded as a liquid crystal capacitor composed of two parallel electrodes, one of which is a pixel electrode and the other is a common electrode. Please refer to Figure 1a and Figure 1b, where Figure 1a shows an equivalent circuit diagram using a liquid crystal unit to provide a display function; and Figure 1b shows an equivalent circuit diagram using the liquid crystal unit to provide a touch function.

As shown in FIG. 1a, the equivalent circuit has a liquid crystal capacitor 11, a first switch 12 that is turned on, and a second switch 13 that is turned off, wherein a common voltage V _COM is coupled to one end of the liquid crystal capacitor 11 via the first switch 12, and the other end of the liquid crystal capacitor 11 is coupled to a source voltage _VS so that the liquid crystal unit provides a display function. In addition, as shown in FIG. 1b, the equivalent circuit has a liquid crystal capacitor 11, a first switch 12 that is turned off, and a second switch 13 that is turned on, wherein an excitation voltage V _STIM is coupled to one end of the liquid crystal capacitor 11 via the second switch 13, and the other end of the liquid crystal capacitor 11 is pressed by a finger so that the liquid crystal unit provides a touch sensing function.

Generally speaking, the common voltage V _COM is provided by an LDO (low dropout regulator). Please refer to FIG. 2 , which shows a circuit diagram of a common voltage generating circuit of a conventional liquid crystal touch display driver chip. As shown in FIG. 2 , a touch display driver chip 20 is used to provide a common voltage V _COM to a liquid crystal panel 30 in the display stage, wherein the common voltage generating circuit of the touch display driver chip 20 includes an LDO 21, a switch 22, and an external capacitor 40 coupled to a pin 23; and the equivalent load of the common voltage generating circuit seen in the liquid crystal panel 30 can be represented as a plurality of series resistors 31 and a plurality of grounding capacitors 32. When the touch display driver chip 20 works in the touch mode, the switch 22 is turned off, and the LDO 21 obtains a low frequency pole without oscillation through its output resistor and the external capacitor 40. Accordingly, when the touch display driver chip 20 switches to the display mode, it can provide a stable common voltage V _COM to the liquid crystal panel 30 to avoid affecting the image quality of the liquid crystal panel 30.

However, this approach not only requires adding a pin to the touch display driver chip 20, but also requires adding an external capacitor 40, thereby increasing the cost of the entire driver circuit.

In order to solve the above problems, a novel common voltage generating circuit structure is urgently needed in the art.

One object of the present invention is to provide a common voltage generating circuit which can maintain a common voltage in a stable state through a Miller capacitor after being disconnected from a liquid crystal touch display panel, thereby avoiding the common voltage from oscillating and generating unnecessary dynamic power consumption.

Another object of the present invention is to provide a common voltage generating circuit which can maintain a common voltage in a stable state through a Miller capacitor after being disconnected from a liquid crystal touch display panel, so as to minimize the instability period of the common voltage when re-coupled with the liquid crystal touch display panel, thereby improving the picture quality of the liquid crystal touch display panel.

Another object of the present invention is to provide a touch display driver chip that can maintain a common voltage in a stable state during the touch scanning phase to prevent the common voltage from oscillating and generating unnecessary dynamic power consumption.

Another object of the present invention is to provide a touch display driver chip that can minimize the instability period of a common voltage during the display scanning phase, thereby improving the image quality of a liquid crystal touch display panel.

Another object of the present invention is to provide a liquid crystal touch display, which can maintain a common voltage in a stable state during the touch scanning stage by using the aforementioned touch display driver chip to avoid the common voltage from oscillating and generating unnecessary dynamic power consumption.

Another object of the present invention is to provide a liquid crystal touch display, which can minimize the instability period of a common voltage during the display scanning phase by using the aforementioned touch display driver chip, thereby improving the image quality of the display screen.

Another object of the present invention is to provide an information processing device that can maintain a common voltage in a stable state during the touch scanning stage through the aforementioned liquid crystal touch display to avoid the common voltage from oscillating and generating unnecessary dynamic power consumption.

Another object of the present invention is to provide an information processing device that can minimize the instability period of a common voltage during the display scanning phase of the aforementioned liquid crystal touch display, thereby improving the image quality of its display screen.

To achieve the above-mentioned purpose, a common voltage generating circuit is proposed, which has: an amplifier circuit having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is used to couple with a reference voltage, the output terminal is used to output a common voltage, and the negative input terminal is used to couple with a proportional voltage of the common voltage; a disconnectable capacitor circuit having a first switch and a capacitor connected in series, and coupled between an intermediate contact of the amplifier circuit and the output terminal, wherein the first switch turns on or off its channel according to the control of a first switching signal, and when the first switch is turned on, the capacitor provides a Miller compensation effect for the amplifier circuit; and A second switch is coupled between the second inverting output terminal and a voltage output terminal, and is controlled by a second switching signal to turn on or off its channel, wherein the voltage output terminal is used to couple with a liquid crystal display panel;

In one embodiment, when the liquid crystal display panel operates in a touch detection period, (the first switching signal, the second switching signal) corresponds to presenting (active state, inactive state) to turn on the first switch and disconnect the second switch, and when the liquid crystal display panel operates in a display period, (the first switching signal, the second switching signal) corresponds to presenting (inactive state, active state) to disconnect the first switch and turn on the second switch.

In one embodiment, the amplifier circuit has: a differential input amplifier having a first positive input terminal, a first negative input terminal and a first inverting output terminal, the first positive input terminal is coupled to the positive input terminal, the first negative input terminal is coupled to the negative input terminal, and the first inverting output terminal is coupled to the intermediate connection point; and a gain stage amplifier having an input terminal and a second inverting output terminal, the input terminal is coupled to the intermediate connection point, and the second inverting output terminal is coupled to the output terminal.

In one embodiment, the differential input amplifier is a transconductance amplifier.

In one embodiment, the gain stage amplifier is a transconductance amplifier.

To achieve the above-mentioned purpose, the present invention further proposes a touch display driver chip having a common voltage generating circuit, the common voltage generating circuit having: An amplifier circuit having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is used to couple with a reference voltage, the output terminal is used to output a common voltage, and the negative input terminal is used to couple with a proportional voltage of the common voltage; A disconnectable capacitor circuit has a first switch and a capacitor connected in series, and is coupled between an intermediate contact of the amplifier circuit and the output terminal, wherein the first switch is controlled by a first switching signal to turn on or off its channel, and when the first switch is turned on, the capacitor provides a Miller compensation effect for the amplifier circuit; and A second switch is coupled between the second inverting output terminal and a voltage output terminal, and is controlled by a second switching signal to turn on or off its channel, wherein the voltage output terminal is used to couple with a liquid crystal display panel.

When the liquid crystal display panel operates in a touch detection period, (the first switching signal, the second switching signal) corresponds to presenting (active state, inactive state) to turn on the first switch and turn off the second switch, and when the liquid crystal display panel operates in a display period, (the first switching signal, the second switching signal) corresponds to presenting (inactive state, active state) to turn off the first switch and turn on the second switch.

In one embodiment, when the liquid crystal display panel operates in a touch detection period, (the first switching signal, the second switching signal) corresponds to presenting (active state, inactive state) to turn on the first switch and disconnect the second switch, and when the liquid crystal display panel operates in a display period, (the first switching signal, the second switching signal) corresponds to presenting (inactive state, active state) to disconnect the first switch and turn on the second switch.

In one embodiment, the amplifier circuit has: a differential input amplifier having a first positive input terminal, a first negative input terminal and a first inverting output terminal, the first positive input terminal is coupled to the positive input terminal, the first negative input terminal is coupled to the negative input terminal, and the first inverting output terminal is coupled to the intermediate connection point; and a gain stage amplifier having an input terminal and a second inverting output terminal, the input terminal is coupled to the intermediate connection point, and the second inverting output terminal is coupled to the output terminal.

In one embodiment, the differential input amplifier is a transconductance amplifier.

In one embodiment, the gain stage amplifier is a transconductance amplifier.

To achieve the above object, the present invention further provides a liquid crystal touch display having a liquid crystal display panel and the aforementioned touch display driver chip for driving the liquid crystal display panel.

To achieve the above-mentioned object, the present invention further proposes an information processing device having a central processing unit and the liquid crystal touch display as mentioned above, wherein the central processing unit is used to communicate with the liquid crystal touch display.

In possible embodiments, the information processing device may be a personal computer, a portable computer, a car computer or a smart phone.

In order to enable the Review Committee to further understand the structure, features, purpose, and advantages of the present invention, the following are attached with drawings and detailed descriptions of preferred specific embodiments.

Please refer to FIG3 , which is a block diagram of an embodiment of a liquid crystal touch display of the present invention. As shown in FIG3 , a liquid crystal touch display 100 includes a driver chip 110 and a liquid crystal display panel 120 .

The driver chip 110 has a common voltage generating circuit, which has a differential input amplifier 111, a gain stage amplifier 112, a disconnectable capacitor circuit 113, a feedback network 114 and a second switch 115.

The differential input amplifier 111 may be a transconductance amplifier having a first positive input terminal, a first negative input terminal and a first inverting output terminal. The first positive input terminal is coupled to a reference voltage V _REF , and the first negative input terminal is coupled to a feedback voltage V _FB .

The gain stage amplifier 112 may be a transconductance amplifier having an input terminal and a second inverting output terminal. The input terminal is coupled to the first inverting output terminal, and the second inverting output terminal is used to provide a common voltage V _COM .

The disconnectable capacitor circuit 113 has a first switch 113a and a capacitor 113b connected in series, and is coupled between the input terminal and the second inverting output terminal, wherein the first switch 113a is turned on or off according to the control of a first switching signal SW1.

The feedback network 114 is used to generate a feedback voltage V _FB according to a ratio of the common voltage V _COM , so that the common voltage V _COM is proportional to the reference voltage V _REF .

The second switch 115 is coupled between the second inverting output terminal and a voltage output terminal A, and is turned on or off according to the control of a second switching signal SW2, wherein the voltage output terminal A is used to couple with the liquid crystal display panel 120.

Among them, when the liquid crystal display panel 120 works in a touch detection period, (the first switching signal SW1, the second switching signal SW2) corresponds to presenting (active state, inactive state) to turn on the first switch 113a and disconnect the second switch 115, and its equivalent circuit is shown in Figure 4a; and when the liquid crystal display panel 120 works in a display period, (the first switching signal SW1, the second switching signal SW2) corresponds to presenting (inactive state, active state) to disconnect the first switch 113a and turn on the second switch 115, and its equivalent circuit is shown in Figure 4b.

In detail, when the first switch 113a is turned on and the second switch 115 is turned off, the first inverting output terminal of the differential input amplifier 111 will see an output resistance of the differential input amplifier 111 and a Miller equivalent capacitance generated by the gain stage amplifier 112 and the disconnectable capacitor circuit 113. The output resistance can be expressed as R _O1 , and the Miller equivalent capacitance can be expressed as C _M = (1+A ₂ )C, where A ₂ represents the voltage gain of the gain stage amplifier 112, and C represents the capacitance value of the capacitor 113b. In this way, the common voltage generating circuit can generate a low-frequency dominant pole 1/(R _O1 C _M ) to effectively prevent the common voltage V _COM from oscillating.

As can be seen from the above, the present invention discloses a common voltage generating circuit, which has: an amplifier circuit, having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is used to couple with a reference voltage, the output terminal is used to output a common voltage, and the negative input terminal is used to couple with a proportional voltage of the common voltage; a disconnectable capacitor circuit, having a first switch and a capacitor connected in series, and coupled to one of the amplifier circuits; between the intermediate contact and the output terminal, wherein the first switch is controlled by a first switching signal to turn on or off its channel, and when the first switch is turned on, the capacitor provides a Miller compensation effect for the amplifier circuit; and a second switch is coupled between the second inverting output terminal and a voltage output terminal, and is controlled by a second switching signal to turn on or off its channel, wherein the voltage output terminal is used to couple with a liquid crystal display panel.

During operation, when the liquid crystal display panel works in a touch detection period, (the first switching signal, the second switching signal) corresponds to presenting (active state, inactive state) to turn on the first switch and disconnect the second switch, and when the liquid crystal display panel works in a display period, (the first switching signal, the second switching signal) corresponds to presenting (inactive state, active state) to disconnect the first switch and turn on the second switch.

In addition, the amplifier circuit may have: a differential input amplifier having a first positive input terminal, a first negative input terminal and a first inverting output terminal, the first positive input terminal is coupled to the positive input terminal, the first negative input terminal is coupled to the negative input terminal, and the first inverting output terminal is coupled to the intermediate contact; and a gain stage amplifier having an input terminal and a second inverting output terminal, the input terminal is coupled to the intermediate contact, and the second inverting output terminal is coupled to the output terminal.

In addition, the differential input amplifier may be a transconductance amplifier, and the gain stage amplifier may also be a transconductance amplifier.

In addition, according to the above description, the present invention further proposes an information processing device. Please refer to FIG. 5, which shows a block diagram of an embodiment of the information processing device of the present invention. As shown in FIG. 5, an information processing device 200 has a central processing unit 210 and a liquid crystal touch display 220, wherein the central processing unit 210 is used to communicate with the liquid crystal touch display 220, and the liquid crystal touch display 220 is implemented by the liquid crystal touch display 100. In addition, the information processing device 200 can be a personal computer, a portable computer, a car computer or a smart phone.

According to the above-mentioned design, the present invention has the following advantages: (1) After the common voltage generating circuit of the present invention is disconnected from a liquid crystal touch display panel, a Miller capacitor can be used to maintain a common voltage in a stable state, thereby avoiding the common voltage from oscillating and generating unnecessary dynamic power consumption; (2) After the common voltage generating circuit of the present invention is disconnected from a liquid crystal touch display panel, a Miller capacitor can be used to maintain a common voltage in a stable state, so as to minimize the instability period of the common voltage when re-coupling with the liquid crystal touch display panel, thereby improving the picture quality of the liquid crystal touch display panel; (3) The touch display driver chip of the present invention can maintain a common voltage in a stable state during the touch scanning stage to avoid the common voltage from oscillating and generating unnecessary dynamic power consumption; (4) The touch display driver chip of the present invention can minimize the instability period of a common voltage during the display scanning stage, thereby improving the image quality of a liquid crystal touch display panel; (5) The liquid crystal touch display of the present invention can maintain a common voltage in a stable state during the touch scanning stage by means of the aforementioned touch display driver chip to avoid the common voltage from oscillating and generating unnecessary dynamic power consumption; (6) The liquid crystal touch display of the present invention can minimize the instability period of a common voltage during the display scanning stage by means of the aforementioned touch display driver chip, thereby improving the image quality of the display screen; (7) The information processing device of the present invention can maintain a common voltage in a stable state during the touch scanning stage by means of the aforementioned liquid crystal touch display, so as to avoid the common voltage from oscillating and generating unnecessary dynamic power consumption; and (8) The information processing device of the present invention can minimize the instability period of a common voltage during the display scanning stage by means of the aforementioned liquid crystal touch display, thereby improving the image quality of the display screen.

The invention disclosed in this case is a preferred embodiment. Any partial changes or modifications that are derived from the technical concept of this case and are easily inferred by people familiar with the art do not deviate from the scope of the patent rights of this case.

In summary, this case shows that it is very different from the known technology in terms of purpose, means and effect, and it is the first invention that is practical and indeed meets the patent requirements for invention. We sincerely request the review committee to examine this carefully and grant a patent as soon as possible to benefit the society. This is our utmost prayer.

11: Liquid crystal capacitor

12: First switch

13: Second switch

20: Touch display driver chip

21:LDO

22: Switch

23: Pin

30: LCD panel

31: Series resistance

32: Grounding capacitor

40: External capacitor

100: LCD touch display

110:Drive chip

111: Differential Input Amplifier

112: Gain stage amplifier

113: Capacitor circuit can be disconnected

113a: First switch

113b: Capacitor

114: Feedback Network

115: Second switch

120: LCD panel

200: Information processing device

210: Central Processing Unit

220: LCD touch display

FIG. 1a shows an equivalent circuit diagram of a liquid crystal unit providing a display function; FIG. 1b shows an equivalent circuit diagram of a liquid crystal unit providing a touch function; FIG. 2 shows a circuit diagram of a common voltage generating circuit of a conventional liquid crystal touch display driver chip; FIG. 3 shows a block diagram of an embodiment of a liquid crystal touch display of the present invention; FIG. 4a shows an equivalent circuit diagram of the common voltage generating circuit of the liquid crystal touch display of FIG. 3 during a touch detection period; FIG. 4b shows an equivalent circuit diagram of the common voltage generating circuit of the liquid crystal touch display of FIG. 3 during a display period; and FIG. 5 shows a block diagram of an embodiment of an information processing device of the present invention.

100: LCD touch display

110:Drive chip

111: Differential input amplifier

112: Gain stage amplifier

113: Capacitor circuit can be disconnected

113a: First switch

113b:Capacitor

114: Feedback network

115: Second switch

120: LCD panel

Claims (11)

A common voltage generating circuit comprises: an amplifier circuit having a positive input terminal, a negative input terminal and an output terminal, wherein the positive input terminal is used to couple with a reference voltage, the output terminal is used to output a common voltage, and the negative input terminal is used to couple with a voltage proportional to the common voltage; a disconnectable capacitor circuit having a first switch and a capacitor connected in series and coupled between an intermediate contact of the amplifier circuit and the output terminal, wherein the first switch turns on or off its channel according to the control of a first switching signal, and when the first switch is turned on, the capacitor provides a Miller compensation effect for the amplifier circuit; and The second switch is coupled between the output terminal and a voltage output terminal, and is controlled by a second switching signal to turn on or off its channel, wherein the voltage output terminal is used to couple with a liquid crystal display panel; wherein, when the liquid crystal display panel works in a touch detection period, (the first switching signal, the second switching signal) is correspondingly presented (active state, inactive state) to turn on the first switch and turn off the second switch, and when the liquid crystal display panel works in a display period, (the first switching signal, the second switching signal) is correspondingly presented (inactive state, active state) to turn off the first switch and turn on the second switch. A common voltage generating circuit as described in claim 1, wherein the amplifier circuit has: a differential input amplifier having a first positive input terminal, a first negative input terminal and a first inverting output terminal, the first positive input terminal is coupled to the positive input terminal, the first negative input terminal is coupled to the negative input terminal, and the first inverting output terminal is coupled to the intermediate connection point; and a gain stage amplifier having an input terminal and a second inverting output terminal, the input terminal is coupled to the intermediate connection point, and the second inverting output terminal is coupled to the output terminal. A common voltage generating circuit as described in claim 2, wherein the differential input amplifier is a transconductance amplifier. A common voltage generating circuit as described in claim 2, wherein the gain stage amplifier is a transconductance amplifier. A touch display driver chip has a common voltage generating circuit, the common voltage generating circuit has: an amplifier circuit, having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is used to couple with a reference voltage, the output terminal is used to output a common voltage, and the negative input terminal is used to couple with a proportional voltage of the common voltage; a disconnectable capacitor circuit, having a first switch and a capacitor connected in series, and coupled between an intermediate contact of the amplifier circuit and the output terminal, wherein the first switch is controlled by a first switching signal to turn on or off its channel, and when the first switch is turned on, the capacitor provides the amplifier circuit with a voltage proportional to the common voltage; A Miller compensation effect; and a second switch coupled between the output terminal and a voltage output terminal, and opening or closing its channel according to the control of a second switching signal, wherein the voltage output terminal is used to couple with a liquid crystal display panel; wherein, when the liquid crystal display panel works in a touch detection period, (the first switching signal, the second switching signal) is correspondingly presented (active state, inactive state) to open the first switch and open the second switch, and when the liquid crystal display panel works in a display period, (the first switching signal, the second switching signal) is correspondingly presented (inactive state, active state) to open the first switch and turn on the second switch. A touch display driver chip as described in claim 5, wherein the amplifier circuit has: a differential input amplifier having a first positive input terminal, a first negative input terminal and a first inverting output terminal, the first positive input terminal is coupled to the positive input terminal, the first negative input terminal is coupled to the negative input terminal, and the first inverting output terminal is coupled to the intermediate contact; and a gain stage amplifier having an input terminal and a second inverting output terminal, the input terminal is coupled to the intermediate contact, and the second inverting output terminal is coupled to the output terminal. A touch display driver chip as described in claim 6, wherein the differential input amplifier is a transconductance amplifier. A touch display driver chip as described in claim 6, wherein the gain stage amplifier is a transconductance amplifier. A liquid crystal touch display having a liquid crystal display panel and a touch display driver chip as described in any one of claims 5 to 8 for driving the liquid crystal display panel. An information processing device having a central processing unit and a liquid crystal touch display as described in claim 9, wherein the central processing unit is used to communicate with the liquid crystal touch display. The information processing device as described in claim 10 is selected from the group consisting of a personal computer, a portable computer, a car computer and a smart phone.

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