Touch controller, touch sensing device and touch sensing module

Abstract

A touch controller coupled to a touch sensing panel includes a sensing circuit. The sensing circuit includes an integrator circuit and a reference voltage control circuit. The integrator circuit includes a first input node, a second input node, and an output node, wherein the first input node is coupled to a sensing node to receive a sensing signal, the second input node is coupled to a guard trace, and the output node is to output an integrated signal. The reference voltage control circuit includes a switch coupled between the second input node of the integrator circuit and a voltage source to provide a reference voltage, wherein the switch is to be closed during a pre-charge period to charge the voltage on the guard trace to the reference voltage in a starting stage of a sensing period, and the switch is to be opened after the pre-charge period. The present disclosure also relates to a touch sensing device and a touch sensing module.

Description

TECHNICAL FIELD

[0001] The present application relates to a touch controller, and more particularly to a touch controller capable of reducing noise interference. BACKGROUND

[0002] Many types of input devices are available for practicing the present application, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch pads, touch screens, and the like. In particular, touch sensor devices and touch screens are increasingly popular in consumer electronics because of their ease and versatility of operation and decreasing price. Touch sensor devices can include a touch sensor panel, which can be a transparent panel with a touch sensor surface, and a display device, such as a liquid crystal display (LCD), which can be partially or entirely behind the touch sensor panel or integrated in the touch sensor panel, such that the touch sensor surface substantially covers at least a portion of the viewable area of the display device. Touch sensor devices generally allow a user to perform different functions by touching or hovering over a location on the touch sensor panel with one or more fingers, a stylus, or other object, which is generally designated by a user interface (UI) displayed by the display device, including virtual buttons, keys, bars, displays, or other elements. Generally, touch sensor devices can recognize a touch event, the location of the touch event on the touch sensor panel, a hover event, and the location of the hover event on the touch sensor panel, and the computing system can interpret the touch or hover event according to the display condition at the time of the event and can perform one or more operations based on the event.

[0003] As consumer electronics become thinner, the distance between the touch sensor panel and the display panel becomes closer, and the parasitic capacitance between the two becomes larger. As a result, when the display panel switches pictures, a large amount of noise is generated and coupled to the touch sensor panel due to the large parasitic capacitance, which can affect the accuracy of the recognition of the touch or hover event, or can even increase the voltage of the sensing signal and exceed the operating range of the touch sensing circuit.

[0004] Therefore, there is a need for a novel circuit design of a touch controller capable of reducing noise interference to solve the above problems. SUMMARY

[0005] One of the objectives of the present application is to provide a novel circuit design of a touch controller that is capable of reducing or even canceling noise interference.

[0006] According to an embodiment of the present application, a touch controller is provided. The touch controller is coupled to a touch sensing panel and is configured to detect a touch event on the touch sensing panel, and includes a sensing circuit. The sensing circuit includes an integrator circuit and a reference voltage control circuit. The integrator circuit includes a first input node, a second input node, and an output node. The first input node is coupled to a sensing node to receive a sensing signal. The second input node is coupled to a guard trace disposed adjacent to the touch sensing panel. The output node is configured to output an integrated signal. The reference voltage control circuit includes a switch coupled between the second input node of the integrator circuit and a voltage source configured to provide a reference voltage. The switch is configured to be closed during a pre-charge period to charge the voltage on the guard trace to the reference voltage at a beginning of a sensing period, and is configured to be opened after the pre-charge period.

[0007] According to another embodiment of the present application, a touch sensing device is provided. The touch sensing device includes a guard trace disposed adjacent to a touch sensing panel, and a touch controller coupled to the touch sensing panel and configured to detect a touch event on the touch sensing panel. The touch controller includes a sensing circuit. The sensing circuit includes an integrator circuit and a reference voltage control circuit. The integrator circuit includes a first input node, a second input node, and an output node. The first input node is coupled to a sensing node to receive a sensing signal. The second input node is coupled to the guard trace. The output node is configured to output an integrated signal. The reference voltage control circuit includes a switch coupled between the second input node of the integrator circuit and a voltage source configured to provide a reference voltage. The switch is configured to be closed during a pre-charge period to charge the voltage on the guard trace to the reference voltage at a beginning of a sensing period, and is configured to be opened after the pre-charge period.

[0008] According to still another embodiment of the present application, a touch control module is provided. The touch control module includes a touch control panel, a protection trace disposed adjacent to the touch control panel, and a touch controller coupled to the touch control panel and configured to detect a touch event on the touch control panel. The touch controller includes a sensing circuit including an integrator circuit and a reference voltage control circuit. The integrator circuit includes a first input node coupled to a sensing node to receive a sensing signal, a second input node coupled to the protection trace, and an output node to output an integrated signal. The reference voltage control circuit includes a switch coupled between the second input node of the integrator circuit and a voltage source to provide a reference voltage. The switch is closed during a pre-charge period to charge a voltage on the protection trace to the reference voltage at a beginning of a sensing period, and the switch is opened after the pre-charge period.

[0009] By introducing the reference voltage control circuit in the touch controller and the protection trace, the noise in the sensing signal can be reduced or even cancelled by the noise coupled to the protection trace, and the problems in the prior art designs can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 A schematic diagram of a touch control module according to an embodiment of the present application.

[0011] Figure 2 A circuit diagram of a portion of the touch control panel coupled to the sensing circuit.

[0012] Figure 3 A waveform diagram of signals on the transmission lines and the sensing node and the signal output by the sensing circuit.

[0013] Figure 4 A top view of an electronic device according to an embodiment of the present application.

[0014] Figure 5 A block diagram of a touch controller according to an embodiment of the present application.

[0015] Figure 6 A side view of an electronic device according to an embodiment of the present application.

[0016] Figure 7 A waveform diagram of signals during a sensing period according to an embodiment of the present application.

[0017] Figure 8 A block diagram of a touch controller according to another embodiment of the present application.

[0018] In the drawings, like reference numerals refer to like elements throughout.

[0019] 100: touch sensing module

[0020] 120, 420, 500, 800: touch controller

[0021] RX_1 ~ RX_N: reception line

[0022] TX_1 ~ TX_N: transmission line

[0023] Cm, C-self: capacitance

[0024] 200, 510, 810: sensing circuit

[0025] 250: noise

[0026] 400: electronic device

[0027] 401, 402, 550, 601, 602, 850: guard line

[0028] 410: display and touch area

[0029] 511, 811: integrator circuit

[0030] 512, 812: reference voltage control circuit

[0031] 520, 820: analog-to-digital converter

[0032] 530, 830: signal processing circuit

[0033] 560: switch

[0034] 570: resistor

[0035] P1, P2: pad

[0036] C-self1, C-self2: parasitic capacitance

[0037] PRE_VR: pre-charge control signal

[0038] VR: voltage source

[0039] INT_OUT: integrated signal

[0040] CK: clock signal

[0041] 610: touch sensing panel

[0042] 620: layer DETAILED DESCRIPTION

[0043] Figure 1This is a schematic diagram of a touch sensing module 100 according to an embodiment of the present invention. The touch sensing module 100 may include a touch sensing panel 110 and a touch controller 120. The touch sensing panel 110 may include a touchscreen, which includes multiple transmitting (TX) channels (e.g., Figure 1 The transmission lines TX_1, TX_2, ... and TX_M shown, and multiple receiving (RX) channels (e.g.) Figure 1 The receiver lines RX_1, RX_2, ..., and RX_N shown, along with multiple capacitors (formed at the intersection of the transmit and receive channels; for example...) Figure 1 The capacitor Cm is shown.

[0044] The touch controller 120 is coupled to the touch sensing panel 110 and is used to sense or detect touch events on the touch sensing panel 110. The touch sensing module 100 may further include a transmission drive circuit (in Figure 1 (Not shown in the image) It is used to provide a drive signal to each transmission channel to sense or detect touch events. The touch controller 120 is coupled to the receiving channel and is used to receive a sensing signal that indicates a voltage or charge on the relevant receiving channel. The touch controller 120 can determine whether a touch event has occurred on the touch sensing panel 110, and can further recognize the touch event and the location of the touch event on the touch sensing panel based on the voltage or charge on the relevant receiving channel (or a change in voltage or charge).

[0045] The touch controller 120 may include multiple sensing circuits, each of which is a sensing node coupled to a receiving channel to receive sensing signals.

[0046] Figure 2 This is a circuit diagram of the touch sensing panel portion coupled to the sensing circuit. (Example) Figure 2 As shown, in addition to the capacitor Cm formed at the intersection of a transmission line and a receiving line, another capacitor is also coupled to the sensing circuit 200, such as... Figure 2 The capacitor C-self shown is a parasitic capacitor, which exists between the touch sensing panel and the display panel. Figure 2 (Not shown in the text) forms between them.

[0047] When the display panel is switching the image to be displayed, a lot of noise is generated (e.g., Figure 2The noise shown is 250), and the noise is coupled to the sensing node and the input node of the sensing circuit 200 through the capacitor C-self.

[0048] Figure 3 This is a waveform diagram of the signals on the transmission line and sensing nodes, as well as the signal output by the sensing circuit 200. Figure 3 In this diagram, the signal labeled "TX" is a drive signal supplied to a transmission line by the transmission drive circuit; the signal labeled "RX" is a sensing signal generated at the sensing node and received by the sensing circuit 200; and the signal labeled "OUT" is a signal output by the sensing circuit 200. Figure 3 As shown, noise 250 will appear in the sensing signal received by the sensing circuit 200 and the signal output by the sensing circuit 200, and will eventually affect the accuracy of the recognition of touch events. The larger the capacitance, the greater the noise will be coupled to the sensing circuit.

[0049] Therefore, there is a great need for a novel circuit design for use in touch controllers that can reduce noise interference in order to solve this problem.

[0050] According to one embodiment of the present invention, a reference voltage control circuit and a guard trace (located adjacent to the touch sensing panel) are introduced into the touch controller to help reduce noise. In this embodiment, the guard trace located adjacent to the touch sensing panel can also be used to eliminate electromagnetic interference (EMI).

[0051] Figure 4 This is a top view of an electronic device 400 according to an embodiment of the present invention. The electronic device 400, having touch control and display functions, may include one or more protective traces (e.g., protective traces 401 and 402), distributed around the display and touch area 410 of the electronic device 400 and / or adjacent to the touch sensing panel and the display panel (not shown on the screen). Figure 4 For example, protective traces may be disposed near at least one side of the touch sensing panel and / or the display panel, and may extend along at least one side of the touch sensing panel and / or the display panel. The touch sensing panel and the display panel are both disposed under and / or covered by the display and touch area 410. According to an embodiment of the present invention, one or more protective traces may be coupled to the touch controller 420 and may be further introduced into the touch controller 420 to connect to the sensing circuit in the touch controller 420. In this embodiment, the protective traces may be connected to an input node of the sensing circuit to help reduce noise.

[0052] Figure 5 Figure 5 shows a block diagram of a touch controller 500 according to an embodiment of the present application. The touch controller 500 can be coupled to a touch sensing panel (not shown in Figure 5 ), and can be used to detect touch events on the touch sensing panel. The touch controller 500 can include a plurality of sensing circuits (e.g., sensing circuit 510), analog-to-digital converters (ADC; labeled as "ADC" in Figure 5 for brevity) 520, and signal processing circuits 530. Each sensing circuit is coupled to a sensing node of the touch sensing panel to receive a sensing signal from a receive channel, where the text labeled as "TX" in Figure 5 represents the corresponding transmit channel, and the text labeled as "RX" in Figure 5 represents the corresponding receive channel. It should be noted that, for the purpose of illustrating the concept of the present application, only the elements related to the present application are shown in the simplified block diagram of the touch controller in Figure 5 , for example, only a single sensing circuit is shown in Figure 5 , since those skilled in the art are familiar with the fact that the touch controller can include other elements (not shown in Figure 5 ) configured to perform the functions of touch sensing, detection and recognition, and related signal processing.

[0053] Furthermore, it should be noted that, although the analog-to-digital converters shown in Figure 5 are not included in the sensing circuits, the present application is not limited thereto, and in some embodiments of the present application, the analog-to-digital converters can be included in the sensing circuits as part of the sensing circuits.

[0054] According to an embodiment of the present application, the sensing circuit 510 can include an integrator circuit 511 and a reference voltage control circuit 512. The integrator circuit 511 can include a first input node coupled to a sensing node (for receiving a sensing signal indicative of a voltage or a charge quantity on a corresponding receiving channel), a second input node coupled to a guard trace 550 (disposed adjacent to the touch sensing panel), and an input node for outputting an integrated signal INT OUT. According to an embodiment of the present application, the touch controller 500 can be implemented as an integrated circuit (IC) and can be coupled to the touch sensing panel (e.g., one or more sensing nodes of the touch sensing panel) through one or more nodes, pins or pads (e.g., pad P1), and coupled to the guard trace 550 through other nodes, pins or pads (e.g., pad P2).

[0055] The integrator circuit 511 can be configured to accumulate an input quantity (e.g., a voltage or a charge quantity received from the sensing node) over a predetermined time to generate a representative output (e.g., the integrated signal INT OUT). The analog-to-digital converter 520 can be coupled to the output node of the integrator circuit and can be configured to receive the integrated signal INT OUT and a clock signal CK, and convert the integrated signal INT OUT according to the clock signal CK to generate a converted signal. The signal processing circuit 530 can be coupled to the analog-to-digital converter 520 and can be configured to receive the converted signal and process the converted signal to determine whether there is any touch event on the touch sensing panel, further identify the touch event and the location of the touch event on the touch sensing panel. The determination and identification results can be further provided to a processor of an electronic device to interpret the touch event and perform one or more operations according to the touch event.

[0056] According to a first embodiment of the present application, the reference voltage control circuit 512 can include a switch 560 and a resistor 570 coupled in parallel between the second input node of the integrator circuit 511 and a voltage source VR providing a reference voltage. It should be noted that in some embodiments of the present application, the voltage source VR can be included in the reference voltage control circuit as a part of the reference voltage control circuit, and the present application is not limited to any particular implementation method, and furthermore, in some embodiments of the present application, the reference voltage control circuit 512 can be disposed outside the sensing circuit 510, and can be a common reference voltage control circuit coupled to all sensing circuits in the touch controller and can be shared by all sensing circuits, and the present application is not limited to any particular implementation method.

[0057] According to an embodiment of the present application, the reference voltage control circuit 512 can be used to control the voltage provided at the second input node of the integrator circuit 511 to bias at the reference voltage, and in this embodiment, by further connecting the second input node of the integrator circuit 511 to the guard trace 550, the noise present in the sensing signal can be reduced or even cancelled by utilizing the noise coupled to the guard trace 550.

[0058] Figure 6 A side view of an electronic device according to an embodiment of the present application. In Figure 6 , the parasitic capacitance C-self1 represents the parasitic capacitance between the touch sensing panel 610 and a layer 620 (for example but not limited to, the cathode layer of the display panel) of the display panel, and the parasitic capacitance C-self2 represents the parasitic capacitance between the guard trace 601 and the layer 620 of the display panel and between the guard trace 602 and the layer 620 of the display panel, where the guard trace 601 and the guard trace 602 are disposed adjacent to or surrounding the touch sensing panel 610. When noise is generated (for example when the display panel switches the picture to be displayed), the noise will be coupled to the touch sensing panel 610 through the parasitic capacitance C-self1, and will be coupled to the guard trace 601 and the guard trace 602 through the parasitic capacitance C-self2, and the amount of noise generated on the touch sensing panel and the amount of noise generated on the guard trace can be different but similar, or substantially the same. In this embodiment, the noise on the guard trace can be utilized to reduce or even cancel the noise in the sensing signal.

[0059] Please refer back to Figure 5 , the parasitic capacitance C-self1 and the parasitic capacitance C-self2 are also shown in Figure 5In this embodiment, noise coupled to the first input node of the integrator circuit 511 will also be coupled to the second input node of the integrator circuit 511 through the protection trace.

[0060] According to this embodiment, the state (e.g. closed or opened) of the switch 560 is changed or controlled in response to the pre-charge control signal PRE_VR, and the signal processing circuit 530 can be configured to generate the pre-charge control signal PRE_VR to control the switch 560. In one embodiment of the present application, in response to the pre-charge control signal PRE_VR, the switch 560 is closed in a pre-charge period in a starting stage of a sensing period to charge a voltage on the protection trace 550 to a reference voltage, when the switch 560 is closed, the protection trace 550 and the second input node of the integrator circuit 511 are both connected to the voltage source VR (which provides the reference voltage), and the voltage on the protection trace 550 and the voltage at the second input node of the integrator circuit 511 are both charged to the reference voltage in the pre-charge period.

[0061] After the pre-charge period (e.g. when the pre-charge period ends), the switch 560 is opened, when the switch 560 is opened, the protection trace 550 and the second input node of the integrator circuit 511 are both disconnected from the voltage source VR, thus, when the switch 560 is opened, the second input node of the integrator circuit 511 is only connected to the protection trace 550.

[0062] According to one embodiment of the present application, the protection trace provided adjacent to the touch sensing panel can be designed as a floating trace, which means that it is not connected to any voltage source that provides a predetermined voltage, thus, the voltage on the floating trace is floating.

[0063] In this embodiment, the protection trace (e.g. the protection trace 550) is connected to a voltage source (e.g. the voltage source VR; which provides a predetermined voltage) only when the switch 560 is closed, and the protection trace is a floating trace when the switch 560 is opened.

[0064] When the switch is opened, the voltage of the protection trace 550 is floating and will vary with the induced noise, thus, in this embodiment, the noise appearing in the protection trace is provided to the second input node of the integrator circuit 511 to cancel the noise appearing in the sensing signal.

[0065] It should be noted that in some embodiments of the present application, the guard traces disposed adjacent to the touch sensing panel can also be designed as non-floating traces (which are connected to or coupled to a voltage source providing a predetermined voltage), for example, the guard traces disposed adjacent to the touch sensing panel can be designed as non-floating traces connected or coupled to ground, thus, in some other embodiments of the present application, when the switch 560 is turned on, the guard trace (e.g. the guard trace 550) is connected to another voltage source (e.g. a ground voltage) providing another predetermined voltage.

[0066] Figure 7 A signal waveform diagram during sensing according to an embodiment of the present application. In Figure 7 the signal labeled "TX" is a drive signal supplied by a transmit driving circuit to a transmit line, the signal labeled "RX" is a sense signal generated at a sense node and received by a sense circuit (e.g. the sense circuit 510), the signal labeled "PRE_VR" is a pre-charge control signal, the signal labeled "Guard_Trace" is a voltage signal on a guard trace (e.g. the guard trace 550), and the signal labeled "INT_OUT" is a signal output by the sense circuit.

[0067] As shown in Figure 7 corresponding to a predetermined voltage level (e.g. a high voltage level) of the pre-charge control signal PRE_VR during a pre-charge period Pre_Charge in an initial stage of the sensing period, the switch is turned off to charge a voltage on the guard trace to a reference voltage (which is provided by the voltage source VR), after the pre-charge period Pre_Charge, corresponding to another predetermined voltage level (e.g. a low voltage level) of the pre-charge control signal PRE_VR, the switch is turned on.

[0068] After the pre-charge period Pre_Charge, the guard trace 550 can become a floating trace and the reference voltage on the guard trace 550 is maintained by the path provided by the resistor 570 and connected to the voltage source VR, when noise occurs, the noise appearing in the sense signal received by the first input node of the sense circuit also appears in the voltage signal on the guard trace, in this way, the noise can be reduced, cancelled or excluded, and does not appear in the integrated signal INT_OUT output by the sense signal.

[0069] Figure 8 A block diagram of a touch controller 800 according to another embodiment of the present application. The touch controller 800 can be coupled to a touch sensing panel (not shown in Figure 8(in the middle), and can be used to detect touch events on the touch-sensitive panel. The touch controller 800 may include multiple sensing circuits (e.g., sensing circuit 810), an analog-to-digital converter 820 (for simplicity, in Figure 8 The signal processing circuit 830 and the sensing circuit 810 may include an integrator circuit 811 and a reference voltage control circuit 812. The integrator circuit 811 may include a first input node (coupled to the sensing node and used to receive an indication of a voltage or charge on the corresponding receiving channel), a second input node (coupled to a protection trace 850 disposed adjacent to the touch sensing panel), and an input node (used to output the integrated signal INT_OUT). It should be understood that, due to Figure 8 Most of the components shown are the same or similar Figure 5 For the sake of simplicity, the components shown will not be described in detail here.

[0070] According to a second embodiment of the present invention, the reference voltage control circuit 812 may consist of only a single switch coupled between the second input node of the integrator circuit 811 and the voltage source VR that provides a reference voltage.

[0071] In this embodiment, in response to a predetermined voltage level during the pre-charging period in the initial stage of the sensing period, the switch in the reference voltage control circuit 812 is turned off to charge a voltage on the protection line to the reference voltage (provided by the voltage source VR). After the pre-charging period, in response to another predetermined voltage level of the pre-charging control signal PRE_VR, the switch in the reference voltage control circuit 812 is turned on.

[0072] In this embodiment, although there is no resistor coupled between the protection trace 850 and the voltage source VR, the reference voltage is still maintained on the protection trace through the capacitor C-self2. After the pre-charging period, the protection trace becomes a floating trace. When noise is generated, the noise in the sensing signal received by the first input node of the sensing circuit will also appear on the voltage signal on the protection trace. In this method, the noise can be reduced, canceled or eliminated and will not appear in the integrated signal INT_OUT output by the sensing circuit.

[0073] In some embodiments of the present application, the disclosed circuit design of the touch control panel (which is capable of reducing noise interference), such as the aforementioned touch controller 500 and the touch controller 800, can be included in a touch control device (which further includes one or more protection traces disposed adjacent to the touch control panel). In some other embodiments of the present application, the disclosed circuit design of the touch control panel (which is capable of reducing noise interference), such as the aforementioned touch controller 500 and the touch controller 800, can be included in a touch control module (which further includes a touch control panel and one or more protection traces disposed adjacent to the touch control panel). By introducing the reference voltage control circuit and the protection traces in the aforementioned touch controller, the noise coupled to the protection traces can be utilized to reduce or even cancel the noise present in the sensing signals, and the problems in the aforementioned prior designs can be solved.

[0074] The above descriptions are only the preferred embodiments of the present application, and any equivalent changes and modifications made according to the claims of the present application shall fall within the scope of the present application.

Claims

1. A touch controller coupled to a touch sensing panel and configured to detect touch events on the touch sensing panel, and comprising: a sensing circuit comprising: an integrator circuit comprising: a first input node coupled to a sensing node for receiving a sensing signal; and a second input node coupled to a guard trace disposed adjacent to the touch-sensing panel; an output node for outputting an integrated signal; and a reference voltage control circuit comprising: a switch coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage; and a capacitor coupled between the protection trace and the second input node of the integrator circuit; wherein the switch is closed during a pre-charge period of a sensing period to charge a voltage on the protection trace to the reference voltage, and the switch is opened after the pre-charge period, wherein the pre-charge period occurs in a beginning phase of the sensing period and does not include the entire sensing period.

2. The touch controller of claim 1, further comprising: an analog-to-digital converter coupled to the output node of the integrator circuit and configured to receive the integrated signal and convert the integrated signal to generate a converted signal; and a signal processing circuit coupled to the analog-to-digital converter and configured to receive the converted signal and process the converted signal to determine whether any touch event is on the touch sensing panel.

3. The touch controller of claim 1, wherein the reference voltage control circuit further comprises: a resistor coupled between the second input node of the integrator circuit and the voltage source.

4. The touch controller of claim 1, wherein the protection trace is a floating trace when the switch is opened.

5. The touch controller of claim 2, wherein the signal processing circuit is further configured to generate a pre-charge control signal to control the switch.

6. A touch sensing device comprising: a protection trace disposed adjacent to a touch sensing panel; and a touch controller coupled to the touch sensing panel and configured to sense touch events on the touch sensing panel, and comprising: a sensing circuit comprising: an integrator circuit comprising: a first input node coupled to a sensing node for receiving a sensing signal; and an output node for outputting an integrated signal; and a reference voltage control circuit comprising: a second input node coupled to the guard trace; a switch coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage; and a capacitor coupled between the protection trace and the second input node of the integrator circuit; wherein the switch is closed during a pre-charge period of a sensing period to charge a voltage on the protection trace to the reference voltage, and the switch is opened after the pre-charge period, wherein the pre-charge period occurs in a beginning phase of the sensing period and does not include the entire sensing period.

7. The touch sensing device of claim 6, wherein the touch controller further comprises: ​ ​ ​ ​ an analog-to-digital converter coupled to the output node of the integrator circuit and configured to receive the integrated signal and convert the integrated signal to generate a converted signal; and a signal processing circuit coupled to the analog-to-digital converter and configured to receive the converted signal and process the converted signal to determine whether any touch event occurs on the touch sensing panel.

8. The touch sensing device of claim 6, wherein the reference voltage control circuit further comprises: a resistor coupled between the second input node of the integrator circuit and the voltage source.

9. The touch sensing device of claim 6, wherein the guard trace is a floating trace when the switch is turned on.

10. The touch sensing device of claim 7, wherein the signal processing circuit is further configured to generate a pre-charge control signal to control the switch.

11. A touch sensing module, comprising: a touch sensing panel; a guard trace disposed adjacent to the touch sensing panel; and a touch controller coupled to the touch sensing panel and configured to detect touch events on the touch sensing panel, and comprising: a sensing circuit comprising: an integrator circuit comprising: a first input node coupled to a sensing node to receive a sensing signal; a second input node coupled to the guard trace; and an output node to output an integrated signal; and a reference voltage control circuit comprising: a switch coupled between the second input node of the integrator circuit and a voltage source providing a reference voltage; a capacitor coupled between the guard trace and the second input node of the integrator circuit; wherein the switch is turned off during a pre-charge period of a sensing period to charge a voltage on the guard trace to the reference voltage, and the switch is turned on after the pre-charge period, wherein the pre-charge period occurs in a beginning stage of the sensing period and the pre-charge period does not include the entire sensing period.

12. The touch sensing module of claim 11, wherein the touch controller further comprises: an analog-to-digital converter coupled to the output node of the integrator circuit and configured to receive the integrated signal and convert the integrated signal to generate a converted signal; and a signal processing circuit coupled to the analog-to-digital converter and configured to receive the converted signal and process the converted signal to determine whether any touch event occurs on the touch sensing panel.

13. The touch sensing module of claim 11, wherein the reference voltage control circuit further comprises: a resistor coupled between the second input node of the integrator circuit and the voltage source.

14. The touch sensing module of claim 11, wherein the guard trace is a floating trace when the switch is turned on.

15. The touch sensing module of claim 12, wherein the signal processing circuit is further configured to generate a pre-charge control signal to control the switch. ​

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