In cell touch display device and common voltage generating method thereof

This application claims the priority benefit of China application serial no. 201710690538.3, filed on Aug. 14, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

The invention relates to an in cell touch display device and particularly relates to a common voltage generating method of the in cell touch display device.

In cell touch display device is the goal that panel manufacturers in the field of touch products have been trying to reach in recent years. The layered structure design that directly embeds the touch detector in the display panel enables the in cell touch display device to integrate image display and touch detection and provides a product type that is more competitive.

Under the condition that the display device and the touch device are integrated with each other, the display scanning operation and the touch detection scanning operation need to be performed separately, so as to prevent mutual interference. However, in the in cell touch display device, the same common voltage is used when the display scanning operation and the touch detection scanning operation are performed. In the process of switching between the display scanning operation and the touch detection scanning operation, the common voltage needs to be adjusted corresponding to the scanning operation that is to be performed. Due to influence of the parasitic capacitance and resistance value inside the in cell touch display device, a certain settling time is needed for switching the common voltage to the required voltage value. Hence, as the panel resolution increases, the settling time may cause the effect of at least one of the touch detection and image display to be affected and impair the performance.

The invention provides an in cell touch display device and a common voltage generating method thereof for quickly providing a stable common voltage and improving the efficiency of touch scanning without affecting the efficiency of display scanning.

The in cell touch display device of the invention includes a timing controller and a common voltage generator. The timing controller generates a control signal, divides a time section into a display scanning time section and a touch scanning time section according to the control signal, and divides the touch scanning time section into a touch start time section, a touch execution time section, and a touch end time section sequentially. The common voltage generator raises a common voltage to a first voltage in the touch start time section, provides a periodical pulse signal in the touch execution time section to generate the common voltage, and lowers the common voltage to a second voltage in the touch end time section. The pulse signal oscillates between a third voltage and a fourth voltage. The first voltage is not smaller than the third voltage, the second voltage is not greater than the third voltage, and the third voltage is smaller than the fourth voltage.

The common voltage generating method of the invention is adapted for the in cell touch display device. The common voltage generating method includes: generating a control signal, dividing a time section into a display scanning time section and a touch scanning time section according to the control signal, and dividing the touch scanning time section into a touch start time section, a touch execution time section, and a touch end time section sequentially; and raising a common voltage to a first voltage in the touch start time section, providing a periodical pulse signal in the touch execution time section to generate the common voltage, and lowering the common voltage to a second voltage in the touch end time section. The pulse signal oscillates between a third voltage and a fourth voltage. The first voltage is not smaller than the third voltage, the second voltage is not greater than the third voltage, and the third voltage is smaller than the fourth voltage.

Based on the above, the invention provides a method for quickly setting the common voltage and makes it possible to set the common voltage to the required voltage levels quickly in the touch start time section and the touch end time section to reduce the settling time for the common voltage, by which the efficiency of touch detection is improved without compromising the display quality.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, several embodiments accompanied with figures are described in detail below.

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a schematic diagram of the in cell touch display device according to an embodiment of the invention.

FIG. 2 is a waveform diagram of an embodiment of a common voltage generating method for the in cell touch display device of the embodiment of the invention.

FIG. 3A and FIG. 3B are waveform diagrams respectively illustrating the common voltage in the touch start time section and the touch end time section according to the embodiment of the invention.

FIG. 4 is a waveform diagram of another embodiment of the common voltage generating method for the in cell touch display device of the embodiment of the invention.

FIG. 5 is a schematic diagram of the common voltage generator according to an embodiment of the invention.

FIG. 6A , FIG. 6B , and FIG. 7 are schematic diagrams illustrating the voltage selector according to several embodiments of the invention.

FIG. 8 is a flowchart illustrating the common voltage generating method according to an embodiment of the invention.

Referring to FIG. 1 , FIG. 1 is a schematic diagram of an in cell touch display device according to an embodiment of the invention. The in cell touch display device 100 includes a timing controller 110 and a common voltage generator 120 . The timing controller 110 and the common voltage generator 120 are coupled to each other, wherein the timing controller 110 generates a control signal CTRL, divides a time section into a display scanning time section and a touch scanning time section according to the control signal CTRL, and divides the touch scanning time section into a touch start time section, a touch execution time section, and a touch end time section sequentially. The common voltage generator 120 receives the control signal CTRL, and according to the control signal CTRL, raises a common voltage VCOM to a first voltage in the touch start time section, provides a periodical pulse signal in the touch execution time section to generate the common voltage VCOM, and lowers the common voltage VCOM to a second voltage in the touch end time section. The pulse signal is a periodical signal that oscillates between a third voltage and a fourth voltage, wherein the first voltage is not smaller than the third voltage, the second voltage is not greater than the third voltage, and the third voltage is smaller than the fourth voltage.

The common voltage VCOM generated by the common voltage generator 120 is provided onto a touch display panel (not shown) of the in cell touch display device 100 . Operations of image display and touch detection are executed in the display scanning time section and the touch scanning time section respectively.

Regarding details of implementation of the embodiment of the invention, please refer to FIG. 1 and FIG. 2 , wherein FIG. 2 is a waveform diagram of an embodiment of a common voltage generating method for the in cell touch display device of the embodiment of the invention. First, the timing controller 110 may divide a time section into a display scanning time section DST 1 and a touch scanning time section TST 1 . In the display scanning time section DST 1 , a display scanning operation is performed according to a gate clock signal GIPCLK that transits continuously. Moreover, in the touch scanning time section TST 1 , the gate clock signal GIPCLK stops transiting and the display scanning operation is stopped. In the meantime, the in cell touch display device 100 performs a touch scanning operation for touch detection.

In addition, the timing controller 110 generates the control signal CTRL, so as to divide a touch start time section TA 1 , a touch execution time section TA 2 , and a touch end time section TA 3 that sequentially take place in the touch scanning time section TST 1 . According to the control signal CTRL, the common voltage generator 120 raises the common voltage VCOM in the touch start time section TA 1 to raise the common voltage VCOM from a fifth voltage V 5 to a first voltage V 1 , so as to quickly raise the voltage value of the common voltage VCOM and reduce a rise time required for the common voltage VCOM. Then, in the touch execution time section TA 2 , the common voltage generator 120 makes the common voltage VCOM become a periodical pulse signal that transits between a third voltage V 3 and a fourth voltage V 4 according to the control signal CTRL. According to the periodical pulse on the common voltage VCOM in the touch execution time section TA 2 , a plurality of touch plates on the touch display panel may be scanned to complete an operation of touch point report.

Next, after the touch execution time section TA 2 ends, the common voltage generator 120 quickly lowers the common voltage VCOM from the third voltage V 3 to the second voltage V 2 in the touch end time section TA 3 according to the control signal CTRL, so as to reduce the time for the common voltage VCOM to drop. After the touch end time section TA 3 ends, the common voltage VCOM recovers and becomes equal to the fifth voltage V 5 , and enters the following display scanning time section DST 2 .

It should be noted that, when the in cell touch display device 100 is in the display scanning time sections DST 1 and DST 2 , the voltage value of the common voltage VCOM is set to the fixed fifth voltage V 5 . In this embodiment, the fifth voltage V 5 may be a voltage smaller than 0V, e.g., equal to −2V. When the in cell touch display device 100 enters the touch scanning time section TST 1 , in order to quickly raise the voltage value of the common voltage VCOM, the common voltage generator 120 provides the first voltage V 1 that is greater than the third voltage V 3 in the touch start time section TA 1 , so as to raise the voltage value of the common voltage VCOM. Based on that the first voltage V 1 is greater than the third voltage V 3 , the common voltage VCOM is quickly raised to be greater than the third voltage V 3 . Accordingly, in the touch execution time section TA 2 , the common voltage VCOM is successfully set to the periodical pulse signal that transits between the third voltage V 3 and the fourth voltage V 4 . In other words, the touch scanning operation may be executed quickly and stably in the touch execution time section TA 2 .

In this embodiment, the third voltage V 3 may be equal to a reference ground voltage, i.e., the voltage of 0V.

On the other hand, when the touch execution time section TA 2 ends, it means that the touch scanning operation has been completed, and the process is to enter the following display scanning time section DST 2 . In order to perform the following display scanning operation successfully, the common voltage generator 120 may provide the second voltage V 2 in the touch end time section TA 3 to lower the voltage value of the common voltage VCOM. Based on that the voltage value of the second voltage V 2 is smaller than the voltage value of the fifth voltage V 5 , the common voltage VCOM is quickly lowered to be smaller than the fifth voltage V 5 in the touch end time section TA 3 . Accordingly, the common voltage VCOM is stably set to be equal to the fifth voltage V 5 after the touch end time section TA 3 ends and before entering the following display scanning time section DST 2 , and the common voltage VCOM is provided stably in the display scanning time section DST 2 to render stable image display quality.

Hereinafter, referring to FIG. 3A and FIG. 3B , FIG. 3A and FIG. 3B are waveform diagrams respectively illustrating the common voltage in the touch start time section and the touch end time section according to the embodiment of the invention. In FIG. 3A , in the touch start time section, the common voltage generator 120 generates the common voltage VCOM based on a waveform 311 , and based on the parasitic capacitance and resistance effect in the touch display panel, a waveform 312 is the waveform of the common voltage VCOM that is actually measured. It is known from FIG. 3A that, due to the relatively high first voltage V 1 , the voltage value of the common voltage VCOM is raised more quickly to the required voltage value (equal to the third voltage V 3 ).

In FIG. 3B , in the touch end time section, the common voltage generator 120 generates the common voltage VCOM based on a waveform 321 , and based on the parasitic capacitance and resistance effect in the touch display panel, a waveform 322 is the waveform of the common voltage VCOM that is actually measured. It is known from FIG. 3B that, due to the relatively low second voltage V 2 , the voltage value of the common voltage VCOM is lowered more quickly to the required voltage value (equal to the third voltage V 5 ).

According to FIG. 3A and FIG. 3B , it is easy to notice that, when the in cell touch display device 100 of the embodiment of the invention enters the touch scanning time section TST 1 from the display scanning time section DST 1 , or enters the display scanning time section DST 2 from the touch scanning time section TST 1 , the common voltage VCOM is quickly set to the required voltage value and the settling time required for transition of the common voltage VCOM is reduced to effectively improve the efficiency of the in cell touch display device 100 .

Regarding details of implementation of another embodiment of the invention, please refer to FIG. 1 and FIG. 4 , wherein FIG. 4 is a waveform diagram of another embodiment of the common voltage generating method for the in cell touch display device of the embodiment of the invention. First, the timing controller 110 divides a time section into a display scanning time section DST 1 and a touch scanning time section TST 1 . In the display scanning time section DST 1 , the display scanning operation is performed according to a gate clock signal GIPCLK that transits continuously. Moreover, in the touch scanning time section TST 1 , the gate clock signal GIPCLK stops transiting and the display scanning operation is stopped. In the meantime, the in cell touch display device 100 performs the touch scanning operation for touch detection.

In addition, the timing controller 110 generates the control signal CTRL, so as to divide a touch start time section TB 1 , a touch execution time section TB 2 , and a touch end time section TB 3 that sequentially take place in the touch scanning time section TST 1 . Moreover, according to the control signal CTRL, the common voltage generator 120 provides the first voltage V 1 that is equal to the third voltage V 3 in the touch start time section TB 1 to raise the common voltage VCOM from the fifth voltage V 5 to the third voltage V 3 , so as to quickly raise the voltage value of the common voltage VCOM and reduce the rise time required for the common voltage VCOM. Here, the first voltage V 1 may be equal to the third voltage V 3 to be the reference ground voltage. That is, the first voltage V 1 =the third voltage V 3 =0V. It should be noted that, in the touch start time section TB 1 , the common voltage generator 120 may directly connect a reference ground terminal that provides the reference ground voltage to the common voltage VCOM, and utilize the relatively large current drawability of the reference ground terminal to quickly lower the voltage value of the common voltage VCOM to 0V.

Then, in the touch execution time section TB 2 , the common voltage generator 120 makes the common voltage VCOM become a periodical pulse signal that transits between the third voltage V 3 and the fourth voltage V 4 according to the control signal CTRL. According to the periodical pulse on the common voltage VCOM in the touch execution time section TB 2 , a plurality of touch plates on the touch display panel may be scanned to complete an operation of touch point report.

Next, after the touch execution time section TB 2 ends, the common voltage generator 120 provides the second voltage equal to 0V in the touch end time section TB 3 according to the control signal CTRL to lower the common voltage VCOM from the fourth voltage V 4 to the second voltage V 2 and maintain it stably at the second voltage V 2 (=0V). After the touch end time section TB 3 ends, the common voltage VCOM recovers and becomes equal to the fifth voltage V 5 , and enters the following display scanning time section DST 2 .

Referring to FIG. 5 , FIG. 5 is a schematic diagram of the common voltage generator according to an embodiment of the invention. A common voltage generator 500 includes a voltage generator 510 and a voltage selector 520 . The voltage generator 510 generates the first voltage V 1 , the second voltage V 2 , the third voltage V 3 , the fourth voltage V 4 , and the fifth voltage V 5 . The voltage selector 520 is coupled to the voltage generator 510 . The voltage selector 520 receives the first voltage V 1 , the second voltage V 2 , the third voltage V 3 , the fourth voltage V 4 , the fifth voltage V 5 , and the control signal CTRL, and according to the control signal CTRL, selects one of the first voltage V 1 , the second voltage V 2 , the third voltage V 3 , the fourth voltage V 4 , and the fifth voltage V 5 in different time sections to generate the common voltage VCOM.

In some embodiments of the invention, the voltage value of the fourth voltage V 4 is greater than the voltage value of the first voltage V 1 , the voltage value of the first voltage V 1 is greater than the voltage value of the third voltage V 3 , the voltage value of the third voltage V 3 is greater than the voltage value of the fifth voltage V 5 , and the voltage value of the fifth voltage V 5 is greater than the voltage value of the second voltage V 2 . In other embodiments, the voltage values of the first voltage V 1 , the second voltage V 2 , and the third voltage V 3 are equal to the voltage value of the reference ground voltage (=0V).

Regarding the hardware architecture of the voltage generator 510 , there is no specific limitation and it is possible to use a voltage generator that those skilled in the art are familiar with, e.g., a voltage regulator, a voltage boost converter, a voltage buck converter, a charge bump circuit, or a combination of the foregoing circuits.

Regarding details of implementation of the voltage selector, FIG. 6A , FIG. 6B , and FIG. 7 are schematic diagrams illustrating the voltage selector according to several embodiments of the invention. In FIG. 6A , the voltage selector 520 includes switches SW 1 to SW 5 , which respectively receive the first voltage V 1 to the fifth voltage V 5 to be turned on or off according to a plurality of bits CTRL[ 1 ] to CTRL[ 5 ] of the control signal respectively. The first voltage V 1 to the fifth voltage V 5 are provided respectively, so as to generate the common voltage VCOM. Any two of the switches SW 1 to SW 5 are not turned on at the same time.

For example, when the touch display device is in the display scanning time section, the switch SW 5 is turned on (the switches SW 1 to SW 4 are turned off), and the voltage selector 520 provides the fifth voltage V 5 to generate the common voltage VCOM. In the touch start time section, the switch SW 1 is turned on (the switches SW 2 to SW 5 are turned off), and the voltage selector 520 provides the first voltage V 1 to generate the common voltage VCOM. In the touch execution time section, the switches SW 3 and SW 4 are alternately turned on (the switches SW 1 , SW 2 , and SW 5 are turned off), and the third voltage V 3 and the fourth voltage V 4 are alternately provided to generate the common voltage VCOM that is a periodical pulse signal. In the touch end time section, the switch SW 2 is turned on (the switches SW 1 and SW 3 to SW 5 are turned off), and the voltage selector 520 provides the second voltage V 2 to generate the common voltage VCOM.

Furthermore, referring to FIG. 6B , an endpoint between the switches SW 3 and SW 4 for generating the common voltage VCOM may be further connected in series to a switch SW 6 . The switch SW 6 is controlled by a bit CTRL[ 6 ] of the control signal, and the switch SW 6 is turned on only in the touch execution time section for transmitting the periodical pulse signal generated according to the switches SW 3 and SW 4 . Moreover, the switch SW 6 is turned off in the other time sections.

In FIG. 7 , the voltage selector 520 only includes the switches SW 1 , SW 3 , SW 4 , and SW 5 . The switch SW 1 is for transmitting the first voltage V 1 and the second voltage V 2 which are equal to 0V, so as to generate the common voltage VCOM. The switch SW 3 is for transmitting the third voltage V 3 to generate the common voltage VCOM. The switches SW 4 and SW 5 respectively transmit the fourth voltage V 4 and the fifth voltage V 5 to generate the common voltage VCOM. The voltage selector 520 of FIG. 7 is for generating the waveform of the common voltage in the embodiment of FIG. 4 . Details of the related operations have been specified in the embodiment of FIG. 4 and thus are not repeated hereinafter.

Hereinafter, referring to FIG. 8 , FIG. 8 is a flowchart illustrating the common voltage generating method according to an embodiment of the invention. The flowchart of FIG. 8 is adapted for the in cell touch display device, wherein Step S 810 is executed to: generate a control signal, divide a time section into a display scanning time section and a touch scanning time section according to the control signal, and divide the touch scanning time section into a touch start time section, a touch execution time section, and a touch end time section sequentially. Then, Step S 820 is executed to: raise a common voltage to a first voltage in the touch start time section, provide a periodical pulse signal in the touch execution time section to generate the common voltage, and lower the common voltage to a second voltage in the touch end time section. The pulse signal oscillates between a third voltage and a fourth voltage. The first voltage is not smaller than the third voltage, the second voltage is not greater than the third voltage, and the third voltage is smaller than the fourth voltage.

Details of the above steps have been specified in the foregoing embodiments and examples and thus are not repeated hereinafter.

To sum up, according to the invention, the common voltage is generated by providing specific voltages in the touch start time section and the touch end time section, and the common voltage may be raised to the required voltage value quickly. Accordingly, the settling time for the common voltage is reduced, and the quality of touch detection is improved without compromising the display quality.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention covers modifications and variations of this disclosure provided that they fall within the scope of the following claims and their equivalents.