Method of controlling a stylus for a touch screen

Abstract

A method of controlling a stylus for a touch screen includes outputting an up control signal to a sense electrode of the touch screen during an up control period to control the stylus, and outputting a DC voltage to a gate line of the touch screen during the up control period.

Description

Technical Field

[0001] This invention relates to a method for controlling a stylus of a touchscreen, and more particularly to a method for controlling a stylus of a touchscreen during uplink control of an output uplink control signal. Background Technology

[0002] An active stylus is a common peripheral device used in electronic devices with touchscreens, such as mobile phones or laptops. Generally, a touchscreen includes multiple sensing electrodes that can be integrated or placed on the touchscreen and have both finger touch sensing and stylus sensing capabilities.

[0003] Modern active styluses all have two-way communication capabilities. The touchscreen can output uplink control signals to the active stylus, which are used to control the stylus's operating mode and / or set its frequency. The active stylus can then send downlink signals to at least one sensing electrode based on its position, so as to report the stylus's position information back to the touchscreen's control circuitry.

[0004] Generally, to improve the efficiency of uplink control, the pen shell of an active stylus can be grounded. Since touchscreens are frequently used in large-size display devices, when a user uses an active stylus to draw or write on the touchscreen, the palm of another hand, other fingers, or part of the body may simultaneously contact the touchscreen, such as... Figure 1 As shown. In this situation, the uplink control signal output by the touchscreen will be coupled to the pen shell through the part touched by the user. The uplink control signal coupled to the pen shell reduces the accuracy and efficiency of uplink control. In other words, the signal coupled to the pen shell cancels out part of the energy of the uplink control signal received by the active stylus, which may cause the active stylus to disconnect from the touchscreen during operation.

[0005] To solve this problem, the uplink control signal can be transmitted only to a portion of the sensing electrodes. Figure 2 This is a schematic diagram of a pixel array on a touchscreen, illustrating an exemplary implementation of an uplink control signal. (See diagram for reference.) Figure 2 As shown, the display screen is a Liquid Crystal Display (LCD), where each pixel includes a liquid crystal capacitor and / or a storage capacitor driven by a driving transistor (such as a Thin-Film Transistor (TFT)). Each driving transistor is controlled by a gate driving device via its respective gate line to receive display data via its respective data line. The aforementioned capacitors are also coupled to a common electrode, which can serve as a sensing electrode for finger and stylus sensing. Figure 2As shown, the uplink control signal UL is only transmitted to the sensing electrodes of some columns, while the sensing electrodes of other columns receive a ground voltage GND.

[0006] Sending the uplink control signal UL to some sensing electrodes and grounding the other sensing electrodes to reduce the coupling effect of the pen casing can improve the transmission efficiency of the uplink control signal UL. However, this method leads to visual problems, where the sensing electrode area used to transmit the uplink control signal UL and the grounded sensing electrode area may exhibit different brightness, such as... Figure 3 As shown. Generally, the display function must be turned off during uplink control. However, abnormal light emission may occur in the area where the sensing electrode is connected to the ground terminal and receives the ground voltage GND, causing brightness differences between different areas on the display screen.

[0007] Therefore, there is a real need to improve the existing technology. Summary of the Invention

[0008] Therefore, the main objective of this invention is to propose a novel active stylus control method and its touchscreen to solve the above-mentioned problems.

[0009] An embodiment of the present invention discloses a method for controlling a stylus on a touchscreen. The method includes the following steps: outputting an uplink control signal to a sensing electrode of the touchscreen during an uplink control period to control the stylus; and outputting a DC voltage to a gate line of the touchscreen during the uplink control period.

[0010] Another embodiment of the present invention discloses a method for controlling a stylus on a touchscreen. The method includes the following steps: outputting an uplink control signal to a sensing electrode of the touchscreen to control the stylus. The uplink control signal originates from a downward pulse having a decreasing voltage.

[0011] Another embodiment of the present invention discloses a method for controlling a stylus on a touchscreen. The method includes the following steps: outputting an uplink control signal to a first sensing electrode of the touchscreen during an uplink control period to control the stylus; and outputting a first voltage to a second sensing electrode of the touchscreen during the uplink control period. The first voltage is greater than a ground voltage.

[0012] Another embodiment of the present invention discloses a method for controlling a stylus on a touchscreen, the touchscreen being configured to have a gate low voltage, the gate low voltage having a preset level during a display period or a sensing period to turn off a driving transistor on the touchscreen. The method includes the following steps: outputting an uplink control signal to a sensing electrode of the touchscreen during an uplink control period to control the stylus; and setting the gate low voltage to a first level during the uplink control period, wherein the first level is lower than the preset level. Attached Figure Description

[0013] Figure 1 This illustrates a situation where the active stylus disconnects from the touchscreen when the user touches it.

[0014] Figure 2 This is a schematic diagram of a pixel array on a touchscreen.

[0015] Figure 3 The brightness differences between different areas on the display screen are shown.

[0016] Figure 4 This demonstrates the root cause of the abnormal display during uplink control signal transmission.

[0017] Figure 5 This is a schematic diagram of a display device according to Embodiment 1 of the present invention.

[0018] Figure 6 This is a timing diagram for active pen control.

[0019] Figure 7 This is a timing diagram of active pen control in an embodiment of the present invention.

[0020] Figure 8 This is a schematic diagram of an output circuit of a control circuit used to control the gate lines.

[0021] Figure 9 This is a flowchart of a first embodiment of the present invention.

[0022] Figure 10A This is a waveform diagram of a typical uplink control signal and the signal coupled to the gate line.

[0023] Figure 10B This is a waveform diagram of a novel uplink control signal and a signal coupled to the gate line, according to an embodiment of the present invention.

[0024] Figure 11 This is a flowchart of a first embodiment of the present invention.

[0025] Figure 12A This is a schematic diagram of the sensing electrode in a pixel being pulled to ground voltage.

[0026] Figure 12B This is a schematic diagram of a sensing electrode in a pixel receiving a voltage greater than the ground voltage in an embodiment of the present invention.

[0027] Figure 13 This is a flowchart of a first embodiment of the present invention.

[0028] Figure 14A This is a waveform diagram of an uplink control signal and the voltage coupled to or applied to the gate line.

[0029] Figure 14B This is a waveform diagram of the uplink control signal and the voltage coupled to or applied to the gate line in Embodiment 1 of the present invention.

[0030] Figure 15 This shows that the gate low voltage is set to a low level throughout the entire frame.

[0031] Figure 16 This shows that the gate low voltage is set to a lower level during the uplink control period.

[0032] Figure 17 This is a flowchart of a first embodiment of the present invention.

[0033] The reference numerals in the attached figures are explained as follows:

[0034] UL, UL1, UL2 uplink control signals

[0035] GND grounding voltage

[0036] P1 First pixel

[0037] P2 Second Pixel

[0038] Vg gate voltage

[0039] Vs Source Voltage

[0040] Vgs Gate-to-source voltage

[0041] 50 display devices

[0042] 500 touchscreens

[0043] 502 Control Circuit

[0044] VGHO gate high voltage

[0045] VGLO gate low voltage

[0046] Vsync vertical synchronization signal

[0047] VCOM common voltage

[0048] DL downlink sensing signal

[0049] Tx touch sensing signal

[0050] HiZ Floating

[0051] LFD load-resistant drive

[0052] DC voltage

[0053] 80 Output Circuit

[0054] 802 voltage regulator

[0055] 804 Multiplexer

[0056] SW1 and SW2 switches

[0057] SEL Select Signal

[0058] LDO (Low Dropout Linear Regulator)

[0059] C1 capacitor

[0060] 90, 110, 130, 170 Process

[0061] 900~906, 1100~1104, 1300~1306, Steps

[0062] 1700–1706 Detailed Implementation

[0063] Figure 4 This illustrates the root cause of the abnormal display during uplink control signal transmission. For example... Figure 4 As shown, the display screen has a first pixel P1 whose corresponding sensing electrode is subjected to an uplink control signal UL, and a second pixel P2 whose capacitor is capacitively coupled to ground (GND). The first pixel P1 and the second pixel P2 each include a driving transistor and at least one capacitor, including a liquid crystal capacitor and / or a storage capacitor.

[0064] When an uplink control signal UL is applied to the sensing electrode during an uplink control period, the uplink control signal UL is coupled to the gate line through the parasitic capacitance on the touchscreen. For the first pixel P1, the uplink control signal UL can be coupled to the source terminal of the driving transistor through the pixel's internal capacitance, and the same uplink control signal UL is also coupled to the corresponding gate line. Therefore, the gate voltage Vg of the driving transistor oscillates with the source voltage Vs at the same frequency and phase, keeping the gate-to-source voltage Vgs of the driving transistor constant. Under these circumstances, the driving transistor in the first pixel P1 will not turn on during the uplink control period, thus preventing abnormal light emission.

[0065] For the second pixel P2, its corresponding sensing electrode is coupled to ground, so the source voltage Vs of the driving transistor remains constant. Simultaneously, the gate voltage Vg of the driving transistor rises because the uplink control signal UL is coupled to the corresponding gate line. In this situation, the gate-to-source voltage Vgs of the driving transistor rises and tends to be positive, potentially causing the driving transistor to turn on and resulting in abnormal light emission during uplink control. Figure 4 As shown, abnormal light emission occurs in the area where the sensing electrode is grounded.

[0066] To avoid abnormal light emission, the present invention can control the voltage used for the gate line and / or the voltage and signal output to the sensing electrode to reduce the possibility that the driving transistor is accidentally turned on during the uplink control period.

[0067] Figure 5 This is a schematic diagram of a display device 50 according to an embodiment of the present invention. The display device 50 includes a touch screen 500 and a control circuit 502. The touch screen 500 has one or more Gate-On-Array (GOA) circuits disposed in the non-active area, and includes multiple sensing electrodes for performing touch sensing and stylus sensing. The control circuit 502 may be a separate touch sensing chip or a Touch and Display Driver Integrated Circuit (TDDI IC) integrated with the display function. Figure 5 As shown, the display device 50 can be a mobile phone, but is not limited thereto. For example, in another embodiment, the display device can also be a laptop computer, a touchpad, a signature pad, or any device with a touchscreen that integrates display and touch functionality.

[0068] An array gate driving circuit is coupled to the gate line on the touchscreen 500 and is used to output gate control signals to the touchscreen 500. The gate control signal output to the gate line can switch between two voltage levels, such as high level and low level. Since the driving transistors in the pixels of the touchscreen are NMOS transistors, a high level can be used to turn on the driving transistors and a low level can be used to turn off the driving transistors. In the array gate driving circuit, the high level of the gate control signal comes from a gate high voltage VGHO, and the low level of the gate control signal comes from a gate low voltage VGLO, wherein the gate high voltage VGHO and the gate low voltage VGLO are provided by the control circuit 502. For example, the control circuit 502 can determine the values ​​of the gate high voltage VGHO and the gate low voltage VGLO, and output these voltages to the array gate driving circuit through a voltage regulator. Generally, the control circuit 502 can also provide a gate clock signal and a start pulse signal to the array gate driving circuit to realize the scanning operation on the touchscreen during the display period. Without affecting the description of this embodiment, these signals are omitted. Figure 5 .

[0069] In addition, the control circuit 502 can output a control signal and / or voltage to the sensing electrodes on the touchscreen, and correspondingly receive sensing signals from the sensing electrodes. On the touchscreen 500, the common electrodes of several pixels can be coupled to each other to form a sensing electrode, and the sensing electrode on the touchscreen 500 can be used to realize touch sensing operations. In this example, the touchscreen 500 supports finger touch sensing and stylus sensing functions, so the control circuit 502 needs to output an uplink control signal to an active stylus (hereinafter referred to as an active stylus), for example, by outputting an uplink control signal through the sensing electrodes to realize stylus sensing.

[0070] Figure 6 This is a timing diagram for active pen control. (Example) Figure 6 As shown, its operation has three states (or periods): uplink control, display, and pen / touch sensing. In this example, a frame period defined by the vertical synchronization signal Vsync begins with an uplink control period, followed by alternating display and pen / touch sensing periods. During the uplink control period, the control circuit 502 can output an uplink control signal UL to the sensing electrode. If the active pen approaches or touches the touchscreen 500, the uplink control signal UL can be transmitted to the active pen. The uplink control signal UL can provide instructions for the active pen and / or control the operating mode of the active pen. During the display period, the control circuit 502 can output a common voltage VCOM to the sensing electrode. It should be noted that the sensing electrode is the common electrode of the pixel; therefore, the display data voltage relative to the common voltage VCOM can be used to drive the liquid crystal capacitor in the pixel to achieve display operation. The detailed operation should be well known to those skilled in the art and will not be described here. During pen / touch sensing, the control circuit 502 may receive a downlink sensing signal DL from the sensing electrodes to perform active pen sensing, and / or output a touch sensing signal Tx to the sensing electrodes to perform touch sensing. The downlink sensing signal DL originates from an active pen, while the touch sensing signal Tx may be generated by a touch control circuit.

[0071] Generally, during uplink control and pen / touch sensing, the source and gate lines are either set to floating (i.e., high impedance, or HiZ) or subjected to a load-free driving (LFD) signal. The load-free driving signal is a signal whose frequency, phase, and / or amplitude are approximately the same as the touch driving signal. The load-free driving signal and floating control avoid or reduce capacitive load on touch sensing operations. More specifically, the voltage of the sensing electrodes is perturbed by the uplink control signal UL, the downlink sensing signal DL, or the touch sensing signal Tx, which may be a series of square or sine waves. To avoid or reduce capacitive load caused by parasitic capacitance between the sensing line, gate line, and data line, a load-free driving signal needs to be applied to the gate and data lines, and / or the gate and data lines need to be set to floating.

[0072] During the display period, the array gate driving circuit can output a gate control signal to the gate line, wherein the gate control signal switches between a gate high voltage VGHO and a gate low voltage VGLO. The control circuit 502 can correspondingly output display data to the source line (or data line) on the touch screen 500, and each display data can be received by the corresponding pixel according to the control of the gate control signal.

[0073] It should be noted that, Figure 6 The arrangement of periods for different states described herein is only one of many embodiments of the present invention. In another embodiment, the period arrangement and related operations can also be performed in other ways. For example, multiple uplink control periods for transmitting uplink control signals UL can be set within a single frame period, or only one uplink control period can be set within multiple consecutive frame periods.

[0074] As described above, this invention proposes several methods to reduce the probability of driver transistors turning on erroneously, thereby avoiding abnormal light emission during the uplink control period when the uplink control signal UL is transmitted. In a first embodiment, during the uplink control period, the load-resistant drive signal or floating operation previously applied to the gate line is replaced by a DC voltage (denoted as DC), such as... Figure 7 As shown. Therefore, when the control circuit 502 outputs the uplink control signal UL to the sensing electrode to control the active pen, it can also simultaneously output a DC voltage to the gate line, instead of outputting an anti-load drive signal or controlling the gate line to float.

[0075] The DC voltage output to the gate line can be at any level that controls the pixel's driving transistor to remain off, thus preventing abnormal light emission during uplink control. Please refer back to [link / reference]. Figure 4The accidental turn-on of the drive transistor occurs when the common electrode is pulled to ground and the floating gate line is coupled upward by the uplink control signal UL. Conversely, a gate line receiving DC voltage can maintain the gate-to-source voltage Vgs of the drive transistor at a constant level to prevent the drive transistor from being turned on.

[0076] In one exemplary embodiment, the DC voltage applied to the gate line can be the gate low voltage VGLO, which is the voltage used to generate the gate control signal during display. In fact, the DC voltage can be any sufficiently low voltage that controls the drive transistor to remain off.

[0077] Figure 8 This is a schematic diagram of an output circuit 80 of the control circuit 502 used to control the gate lines. Figure 8 As shown, the output circuit 80 can be used to output a gate low voltage VGLO to the touch screen 500 (such as to the array gate drive circuit on the touch screen 500). It includes a voltage regulator 802, a multiplexer (MUX) 804, and switches SW1 and SW2. The voltage regulator 802 can generate the gate low voltage VGLO. In a preferred embodiment, the voltage regulator 802 can be a low-dropout regulator (LDO regulator). The multiplexer 804 can receive a selection signal SEL to select either the output ground voltage GND or the load-insensitive drive signal LFD. A capacitor C1 is coupled between switches SW1 and SW2. This capacitor C1 can be located in the output circuit 80, on the touch screen 500, or on a circuit board on which the output circuit 80 is located.

[0078] In detail, during the uplink control period, the control circuit 502 can output an uplink control signal UL and / or a ground voltage GND to the sensing electrodes. The uplink control signal UL is transmitted to some sensing electrodes, while the ground voltage GND is transmitted to other sensing electrodes, such as... Figure 2 The embodiment shown. A DC voltage is applied to the gate line, in Figure 8 In this embodiment, the DC voltage is the gate low voltage VGLO, so switches SW1 and SW2 are turned on, and multiplexer 804 outputs ground voltage GND according to selection signal SEL, so that output circuit 80 can output a constant gate low voltage VGLO to array gate drive circuit, thereby causing array gate drive circuit to output DC voltage to gate line.

[0079] During the display period, the sensing electrodes receive a common voltage VCOM, and the gate line receives a gate control signal. Therefore, the output circuit 80 needs to provide a gate low voltage VGLO to the array gate drive circuit. In this case, switches SW1 and SW2 remain on, and the multiplexer 804 outputs a ground voltage GND according to the control of the selection signal SEL, causing the output circuit 80 to output the gate low voltage VGLO. It should be noted that the gate control signal switches between a gate high voltage VGHO and a gate low voltage VGLO. The gate low voltage VGLO is output by the output circuit 80, and the control circuit 502 may include another regulator to generate and output the gate high voltage VGHO.

[0080] During pen / touch sensing, the sensing electrode can receive a downlink sensing signal DL or output a touch sensing signal Tx. The gate line can receive an anti-load drive signal or be controlled to float (i.e., HiZ) to reduce the capacitive load of the touch sensing operation. The anti-load drive signal and float control can be executed by the output circuit 80. When an anti-load drive signal is applied, switch SW1 is closed and switch SW2 is open, and multiplexer 804 outputs an anti-load drive signal (labeled LFD) according to the control of selection signal SEL. The anti-load drive signal can be coupled to the output terminal of output circuit 80 through capacitor C1, thereby outputting to the gate line. When float control is performed, switch SW1 is closed and switch SW2 is closed, so the output terminal of output circuit 80 is in a floating state, thus controlling the gate line to float.

[0081] The above-described operation of control circuit 502 can be summarized into a process 90, such as... Figure 9 As shown. Process 90 includes the following steps:

[0082] Step 900: Begin.

[0083] Step 902: During the uplink control period, an uplink control signal UL is output to a sensing electrode of the touch screen 500 to control the stylus.

[0084] Step 904: Output a DC voltage to a gate line of the touchscreen 500 during the uplink control period.

[0085] Step 906: End.

[0086] In the second embodiment, the uplink control signal UL output by the control circuit 502 to the sensing electrode starts with a downlink pulse having a falling voltage. Figure 10A This is a waveform diagram of the typical uplink control signal UL1 and the signal coupled to the gate line. During the uplink control period, the uplink control signal UL1 is transmitted to a sensing electrode. Figure 10AAs shown, the uplink control signal UL1 typically starts with an upward pulse. Generally, when the timing enters the uplink control period, the sensing electrode is at the common voltage VCOM, which is equal to -1V. At this time, the pulse of the uplink control signal UL1 rises from -1V to +5V. If the gate line is floating, the rising pulse is coupled to the gate line, increasing the voltage of the gate line (and the gate voltage Vg of the driving transistor), thereby increasing the probability that the driving transistor in the pixel is accidentally turned on and produces abnormal light emission.

[0087] Figure 10B This is a waveform diagram of a novel uplink control signal UL2 and a signal coupled to the gate line, according to an embodiment of the present invention. Figure 10B As shown, the novel uplink control signal UL2 begins with a downward pulse. That is, when the timing enters the uplink control period, the sensing electrode is at the common voltage VCOM, which is equal to -1V. At this time, the uplink control signal UL2 output by the control circuit 502 has a downward pulse, which drops from -1V to -7V. If the gate line is floating, the falling pulse is coupled to the gate line, reducing the voltage of the gate line. In this case, the gate voltage Vg is pulled to a lower level, so the gate-to-source voltage Vgs of the driving transistor will be further away from its turn-on level. In this way, the driving transistor will not be accidentally turned on.

[0088] The above-mentioned operation mode of control circuit 502 can be summarized as a process 110, such as... Figure 11 As shown. Process 110 includes the following steps:

[0089] Step 1100: Begin.

[0090] Step 1102: Output an uplink control signal UL to a sensing electrode of the touchscreen 500 to control the stylus, wherein the uplink control signal UL is initiated by a downward pulse with a falling voltage.

[0091] Step 1104: End.

[0092] In the third embodiment, the sensing electrode can be pulled to a higher level to increase the source voltage Vs of the driving transistor, thereby reducing the gate-to-source voltage Vgs of the driving transistor.

[0093] Generally, before the uplink control period begins, the sensing electrodes are at the level of the common voltage VCOM. When the uplink control period begins, the sensing electrodes at the common voltage VCOM level (e.g., -1V) are pulled to ground voltage GND. Subsequently, some sensing electrodes remain at ground voltage GND, such as... Figure 12AAs shown, other sensing electrodes receive the uplink control signal UL. It should be noted that the common electrode of the pixel can be used as a sensing electrode to perform stylus and finger touch sensing. As described above, for the driving transistor in a pixel coupled to a sensing electrode pulled to ground (GND), its source voltage Vs remains constant while its gate voltage Vg rises due to the coupling of the uplink control signal UL, causing the gate-to-source voltage Vgs to rise. Therefore, this driving transistor may be accidentally turned on during uplink control, resulting in abnormal light emission.

[0094] Figure 12B This is a schematic diagram illustrating how a sensing electrode in a pixel receives a voltage greater than the ground voltage GND in an embodiment of the present invention. During uplink control, when the uplink control signal UL is transmitted to other sensing electrodes, a voltage greater than the ground voltage can be output to a specific sensing electrode. In this case, the gate-to-source voltage Vgs of the driving transistor can be reduced, thereby reducing the probability of the driving transistor turning on erroneously.

[0095] The voltage output to the common electrode (i.e., the sensing electrode) can be controlled by a regulator in the control circuit 502. In one embodiment, the regulator can output a common voltage VCOM during the display period and a positive voltage greater than the ground voltage GND during the uplink control period.

[0096] exist Figure 12A In the example, when the voltage at the common electrode rises from the common voltage VCOM to the ground voltage GND, this rising pulse is coupled to the source terminal of the driving transistor to generate a rising level ΔV at the source terminal. In contrast, in Figure 12B In this embodiment, the voltage of the common electrode rises from the common voltage VCOM to a positive voltage greater than the ground voltage GND and having an offset ΔVos. Therefore, the source terminal of the driving transistor can be upwardly coupled via a rising level ΔV+ΔVos. Even though the gate voltage Vg of the driving transistor may still be upwardly coupled by the uplink control signal UL, the increased upward coupling capability from the common voltage VCOM can increase the source voltage Vs of the driving transistor, thereby reducing the gate-to-source voltage Vgs of the driving transistor, thus reducing the probability of the driving transistor turning on erroneously and generating abnormal light emission.

[0097] In one exemplary embodiment, all sensing electrodes (i.e., the common electrodes of all pixels on the touchscreen) rise to a first voltage at the start of uplink control, which is any suitable positive voltage greater than the ground voltage GND. The sensing electrodes used to receive the constant voltage remain at the first voltage during uplink control; while the sensing electrodes used to receive the uplink control signal UL rise from the first voltage at the start of uplink control, i.e., the uplink control signal UL starts at the level of the first voltage. In other words, the uplink control signal UL can be switched at a higher level. In this case, the source voltage Vs of the driving transistor in each pixel can be coupled to a higher level.

[0098] The above-described operation of control circuit 502 can be summarized as a process 130, such as... Figure 13 As shown. Process 130 includes the following steps:

[0099] Step 1300: Begin.

[0100] Step 1302: During the uplink control period, an uplink control signal UL is output to a first sensing electrode of the touch screen 500 to control the stylus.

[0101] Step 1304: During the uplink control period, output a first voltage to a second sensing electrode of the touch screen 500, wherein the first voltage is greater than the ground voltage GND.

[0102] Step 1306: End.

[0103] It should be noted that the touchscreen 500 is provided with a first sensing electrode in a region for transmitting the uplink control signal UL during uplink control, and a second sensing electrode in a region coupled to a first voltage greater than the ground voltage GND during uplink control, in order to reduce the coupling effect on the stylus shell and improve signal transmission efficiency. In process 130, the first sensing electrode is located in the first region used to transmit the uplink control signal UL to the stylus, while the second sensing electrode is located in the second region used to receive the first voltage greater than the ground voltage GND.

[0104] In the above embodiments, the source voltage Vs of the driving transistor is coupled to a higher level through the sensing electrode. In another embodiment, to avoid the driving transistor from being accidentally turned on, the gate voltage Vg can also be lowered to a lower level. More specifically, during the uplink control period of transmitting the uplink control signal UL, the gate low voltage VGLO can be set to a level lower than its preset level. This preset level is the level used to turn off the driving transistor of the pixel during the display period or the pen / touch sensing period in a typical touchscreen. It should be noted that a typical touchscreen is configured to have a gate high voltage VGHO and a gate low voltage VGLO, wherein the preset level of the gate high voltage VGHO output to the gate line can be used to turn on the driving transistor, and the preset level of the gate low voltage VGLO output to the gate line can be used to turn off the driving transistor.

[0105] Figure 14A This is a waveform diagram of an uplink control signal UL and the voltage coupled to or applied to the gate line. Similar to... Figure 10A For example, the voltage of the gate line and the gate voltage Vg of the driving transistor are upward coupled via an uplink control signal UL, which consists of a series of pulses rising from -1V to 5V. In this example, at the start of the uplink control period, the gate line is pulled to a preset level of the gate low voltage VGLO, and then controlled to float or be applied an anti-load drive signal. Alternatively, the gate line may be pulled to a preset level of the gate low voltage VGLO at the end of the display period preceding the uplink control period, and then controlled to float or be applied an anti-load drive signal when the timing enters a subsequent pen / touch sensing period or uplink control period. Therefore, during the uplink control period, the voltage of the gate line (or the gate voltage Vg of the driving transistor) is upward coupled or pulled up from the preset level of the gate low voltage VGLO.

[0106] Figure 14B This is a waveform diagram of the uplink control signal UL and the voltage coupled to or applied to the gate line according to Embodiment 1 of the present invention. In this example, when the timing enters the uplink control period, the gate low voltage VGLO is set to a specific level below its preset level. Therefore, when the gate line is upwardly coupled or pulled up during the uplink control period, the starting point is this specific level. In this case, even if the gate voltage Vg is upwardly coupled by the uplink control signal UL1 or pulled up by the load drive signal, it is still at a relatively low level, making the gate-to-source voltage Vgs of the driving transistor far from its turn-on level, making it difficult to turn on the driving transistor and generate abnormal light emission.

[0107] In one embodiment, the gate low voltage VGLO can be set to remain at a specific level below its preset level. More specifically, during uplink control, display, and pen / touch sensing, the gate low voltage VGLO is set to have the same voltage level below the preset level. For example, as Figure 15As shown, the gate low voltage VGLO is set to remain at a low level (with a voltage drop of ΔV) throughout the entire frame.

[0108] In another embodiment, the gate low voltage VGLO can be set to a specific level below its preset level only during uplink control. For example, such as Figure 16 As shown, the gate low voltage VGLO is set to a low level (with a voltage drop of ΔV) during the uplink control period; during display and pen / touch sensing periods, the gate low voltage VGLO can return to its preset level. In this case, the effect of reducing the false start-up rate of the drive transistors during the uplink control period can still be achieved.

[0109] The aforementioned implementation of gate low voltage VGLO can also be achieved using the voltage regulator in control circuit 502. For example, please refer back to [reference needed]. Figure 8 The regulator 802 can be used to generate a gate low voltage VGLO. If the gate low voltage VGLO is set to have a selectable output at a preset level and a lower level, an additional selection mechanism can be provided in the regulator 802 to change its output level. For example, the control circuit 502 can generate a control signal to control the regulator 802 to output a gate low voltage VGLO with a lower level during uplink control periods and to output a gate low voltage VGLO with a preset level during other periods.

[0110] The above-described operation of control circuit 502 can be summarized as a process 170, such as... Figure 17 As shown. Process 170 includes the following steps:

[0111] Step 1700: Begin.

[0112] Step 1702: During the uplink control period, an uplink control signal UL is output to a sensing electrode of the touch screen 500 to control the stylus.

[0113] Step 1704: During the uplink control period, set the gate low voltage VGLO to a first level, wherein the first level is lower than a preset level.

[0114] Step 1706: End.

[0115] It is worth noting that the purpose of this invention is to provide a method for controlling an active pen and a touchscreen to reduce the probability of the driving transistor being turned on erroneously during uplink control. Those skilled in the art will be able to make modifications or variations accordingly, and are not limited thereto. For example, this invention proposes various methods to minimize the gate voltage Vg of the driving transistor and / or maximize the source voltage Vs of the driving transistor during uplink control, thereby reducing the gate-to-source voltage Vgs. Therefore, any two or more of the above embodiments can be combined to further improve efficiency. For example, in one embodiment, the gate low voltage VGLO can be set to a specific level below its preset level, while the gate line is pulled to a specific level at the beginning of the uplink control period and then receives a DC voltage to maintain a constant level during the uplink control period. In this case, the gate voltage Vg can be maintained at an extremely low level without upward coupling, further minimizing the probability of the driving transistor being turned on erroneously.

[0116] Additionally, when the gate low voltage VGLO is at a low level, the gate line can be controlled to float or an anti-load drive signal can be applied during the uplink control period of the output uplink control signal UL. Alternatively or additionally, a DC voltage greater than the ground voltage level can be applied to the sensing electrode to increase the source voltage Vs, and a series of downward pulses can be used to generate the uplink control signal to form downcoupling on the gate line. Various implementations and operating methods described in this specification can be selectively combined to reduce the false turn-on rate of the driving transistor during the uplink control period and prevent abnormal light emission.

[0117] More specifically, in the first embodiment, a DC voltage can be applied to the gate line during the uplink control period to prevent the gate voltage from being upwardly coupled through the uplink control signal; in the second embodiment, the uplink control signal starts with a down pulse instead of an up pulse, causing the gate voltage to be downwardly coupled to a lower level during the uplink control period; in the third embodiment, at the start of the uplink control period, the voltage of the sensing electrode is pulled to a higher level (e.g., higher than ground voltage), causing the source voltage of the driving transistor to be coupled to a higher level to prevent the driving transistor from turning on; in the fourth embodiment, the gate low voltage is set to a lower level below its preset level (this preset level is used to turn off the driving transistor during display operation), and the reduced gate low voltage can be output to the gate line to reduce the gate voltage of the driving transistor. In another embodiment, two or more of the above embodiments can be combined to further minimize the false turn-on probability of the driving transistor, thereby improving the efficiency of uplink control of the active pen.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling a stylus on a touchscreen, characterized in that, include: During an uplink control period, an uplink control signal is output to a first sensing electrode of the touchscreen to control the stylus; as well as During the uplink control period, a first voltage is output to a second sensing electrode of the touchscreen; The first voltage is greater than a ground voltage.

2. The method as described in claim 1, characterized in that, The pulse of the uplink control signal starts from a voltage level greater than the ground voltage.

3. A method for controlling a stylus on a touchscreen, characterized in that, The touchscreen is configured to have a gate low voltage, which has a preset level during a display period or a sensing period, for turning off a driving transistor on the touchscreen, the method comprising: During an uplink control period, an uplink control signal is output to a sensing electrode of the touchscreen to control the stylus; and During the uplink control period, the gate low voltage is set to a first level, wherein the first level is lower than the preset level.

4. The method as described in claim 3, characterized in that, This also includes performing at least one of the following steps during the uplink control period: The gate low voltage at the first level is output as a DC voltage to a gate line of the touch screen; When the gate low voltage is at the first level, an anti-load drive signal is applied to the gate line; as well as When the gate line is at the first level, the gate line is controlled to be in a floating state.

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