Analog front-end circuit for touch display device and method of operation

Abstract

The invention provides an analog front-end circuit for touch display equipment and an operation method. The analog front-end circuit comprises a receiving circuit and an amplifying circuit. The receiving circuit receives a first noise located in the touch display device to generate an input signal. The amplifying circuit receives a touch sensing signal of the touch display device and receives an input signal from the receiving circuit. The amplifying circuit uses the first noise to reduce a second noise in the touch sensing signal to generate an output signal.

Description

Technical Field

[0001] The present invention relates to an analog front-end circuit and an operating method for an electronic device, and in particular to an analog front-end circuit and an operating method for a touch display device. Background Art

[0002] like Figure 1 As shown, Figure 1 It is a schematic diagram and signal timing diagram of the current touch display device. The touch display device 10 includes a touch panel 11, a cathode 12, a display panel 13 and an analog front-end circuit 14. There is a parasitic capacitance Cd between the cathode 12 and the display panel 13. The data signal SD located at the display panel 13 will interfere with the voltage ELVSS located at the cathode 12 based on the coupling of the parasitic capacitance Cd. Therefore, the voltage ELVSS has noise. There are also parasitic capacitances Ctx and Crx between the cathode 12 and the touch panel 11. The parasitic capacitance Ctx is a parasitic capacitance located between the touch electrode TX1 and the cathode 12. The parasitic capacitance Crx is a parasitic capacitance located between the touch electrode RX1 and the cathode 12. Therefore, the touch sensing signal STS provided by the touch panel 11 according to the touch drive signal STD also has noise. It should be noted that as the touch display device 10 becomes thinner, the parasitic capacitances Ctx, Crx, and Cd will become more obvious.

[0003] The controller 14 compares the touch sensing signal STS with the common mode voltage VCM (or common voltage) and gains the comparison result to generate an output signal OPOUT. It should be noted that the common mode voltage VCM is a constant voltage value, so the output signal OPOUT has a gain signal of the touch sensing signal STS and a gain noise corresponding to the noise of the touch sensing signal STS. The gain noise of the output signal OPOUT occupies most of the dynamic range VR of the output signal OPOUT. Therefore, the signal-to-noise ratio (SNR) of the controller 14 is reduced. In addition, in order to prevent the output signal from being saturated, the gain of the output signal OPOUT can only be reduced.

[0004] It can be seen that how to reduce the noise of the output signal OPOUT is one of the research focuses of those skilled in the art. Summary of the invention

[0005] The present invention provides an analog front-end circuit and an operation method for a touch display device, which can reduce the noise of an output signal.

[0006] In one embodiment of the present invention, the analog front-end circuit includes a receiving circuit and an amplifying circuit. The receiving circuit receives a first noise located in a touch display device to generate an input signal. One end of the amplifying circuit is connected to the receiving circuit to receive the input signal from the receiving circuit. The other end of the amplifying circuit receives a touch sensing signal of the touch display device. The amplifying circuit uses the first noise to reduce a second noise in the touch sensing signal to generate an output signal. The first noise and the second noise are respectively generated by coupling a data signal with a voltage of a cathode of the touch display device.

[0007] In one embodiment of the present invention, the operation method includes receiving a first noise located in a touch display device by a receiving circuit to generate an input signal; receiving an input signal from the receiving circuit by an amplifying circuit and receiving a touch sensing signal of the touch display device; and reducing a second noise in the touch sensing signal by the amplifying circuit using the first noise in the input signal to generate an output signal. The first noise and the second noise are respectively generated by coupling a voltage of a cathode of the touch display device to a data signal.

[0008] Based on the above, the amplifier circuit uses the first noise in the input signal to reduce the second noise in the touch sensing signal to generate an output signal. The noise of the output signal can be reduced. The signal-to-noise ratio (SNR) of the analog front-end circuit is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of a current touch display device and a signal timing diagram;

[0010] Figure 2 is a schematic diagram of a touch display device according to an embodiment of the present invention;

[0011] Figure 3 is a schematic diagram of a touch display device according to an embodiment of the present invention;

[0012] Figure 4 is a signal timing diagram according to an embodiment of the present invention;

[0013] Figure 5 is an impedance schematic diagram according to an embodiment of the present invention;

[0014] Figure 6 is a schematic diagram of an analog front-end circuit according to an embodiment of the present invention;

[0015] Figure 7 is a schematic diagram of a touch display device according to an embodiment of the present invention;

[0016] Figure 8is a signal timing diagram according to an embodiment of the present invention;

[0017] Fig. 9 is a flow chart of an operating method according to an embodiment of the present invention.

[0018] Description of Figure Numbers

[0019] 10, 100, 200, 400: Touch display devices

[0020] 11: Touch panel

[0021] 12: Cathode

[0022] 13: Display Panel

[0023] 14: Controller

[0024] 110, 210, 410: Receiving circuit

[0025] 120, 220: Amplification circuit

[0026] 330: Low pass filter

[0027] 340: Analog-to-digital converter

[0028] 350: Signal Processor

[0029] C1, CS: capacitor

[0030] CC1, CC2, CC3, CC4: Analog front-end circuit

[0031] Cd, Cm, Crx, Ctx: parasitic capacitance

[0032] CEQ: Equivalent Circuit

[0033] ELVSS: Voltage

[0034] IDN: Equivalent noise current

[0035] OPIP: Input signal

[0036] OPOUT: Output signal

[0037] P1, P2: receiving end

[0038] R1: Resistor

[0039] Rtx, Rrx: equivalent resistance

[0040] RX1, TX1: Touch electrodes

[0041] S1, S2: control signal

[0042] S100: How to operate

[0043] S110, S120, S130: Steps

[0044] SD: Data signal

[0045] STD: Touch drive signal

[0046] STS: Touch sensing signal

[0047] SW1, SW2, SW3, SW4: switches

[0048] t1, t2, t3, t4: time points

[0049] TD1: First period

[0050] TD2: Second period

[0051] VCM: Common mode voltage

[0052] VR: Dynamic Range

[0053] ZTP: Equivalent Impedance DETAILED DESCRIPTION

[0054] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0055] Please refer to Figure 2 , Figure 2 1 is a schematic diagram of a touch display device according to an embodiment of the present invention. In this embodiment, the touch display device 100 includes a touch panel 11, a cathode 12, a display panel 13, and an analog front-end circuit CC1. In this embodiment, there is a parasitic capacitance Cd between the cathode 12 and the display panel 13. The data signal (e.g., Figure 1 The data signal SD) will interfere with the voltage ELVSS at the cathode 12 based on the coupling of the parasitic capacitor Cd. Therefore, the voltage ELVSS has a first noise. There are also parasitic capacitors Ctx and Crx between the cathode 12 and the touch panel 11. Therefore, the touch sensing signal STS provided by the touch panel 11 has a second noise from the data signal SD. In this embodiment, the parasitic capacitor Ctx is a parasitic capacitor located between the touch electrode TX1 and the cathode 12. The parasitic capacitor Crx is a parasitic capacitor located between the touch electrode RX1 and the cathode 12.

[0056] In the present embodiment, the analog front-end circuit CC1 includes a receiving circuit 110 and an amplifier circuit 120. The receiving circuit 110 is connected to the cathode 12. The receiving circuit 110 receives the first noise to generate an input signal OPIP. The amplifier circuit 120 is connected to the receiving circuit 110. The amplifier circuit 120 receives the touch sensing signal STS and receives the input signal OPIP from the receiving circuit 110. The amplifier circuit 120 uses the first noise in the input signal OPIP to reduce the second noise in the touch sensing signal STS to generate an output signal OPOUT. One end of the amplifier circuit 120 is connected to the receiving circuit 110 to receive the input signal OPIP from the receiving circuit 110. The other end of the amplifier circuit 120 receives the touch sensing signal STS of the touch display device 100.

[0057] It is worth mentioning here that, in the present embodiment, the cathode 12 is connected to the receiving circuit 110 and provides a first noise. The first noise and the second noise are respectively generated by coupling the voltage of the cathode 12 to the data signal. Further, the first noise and the second noise are generated in response to the falling edge of the data signal and the rising edge of the data signal, respectively. The first noise and the second noise have similar waveforms, so the amplifier circuit 120 uses the first noise in the input signal OPIP to reduce the second noise in the touch sensing signal STS to generate the output signal OPOUT. In this way, the noise of the output signal OPOUT can be reduced. The signal-to-noise ratio (SNR) of the analog front-end circuit CC1 is improved.

[0058] Please refer to Figure 2 , Figure 3 as well as Figure 4 , Figure 3 is a schematic diagram of a touch display device according to an embodiment of the present invention. Figure 4 is a signal timing diagram according to an embodiment of the present invention. In this embodiment, Figure 3 Shown as Figure 2 The equivalent circuit CEQ of the touch panel 11, cathode 12, and display panel 13 and the analog front-end circuit CC2 of this embodiment. The equivalent circuit CEQ includes parasitic capacitances Cd, Ctx, Crx, and Cm and equivalent resistances Rtx and Rrx. The parasitic capacitance Cd is a parasitic capacitance between the cathode 12 and the display panel 13. The parasitic capacitance Ctx is a parasitic capacitance between the touch electrode TX1 and the cathode 12. The parasitic capacitance Crx is a parasitic capacitance between the touch electrode RX1 and the cathode 12. The parasitic capacitance Cm is a parasitic capacitance between the touch electrode RX1 and the touch electrode TX1. The equivalent resistance Rtx is the equivalent resistance capacitance of the touch electrode TX1. The equivalent resistance Rrx is the equivalent resistance of the touch electrode RX1.

[0059] In this embodiment, the analog front-end circuit CC2 includes a receiving circuit 210 and an amplifying circuit 220. The amplifying circuit 220 includes an operational amplifier 221 and a feedback circuit 222. The first input terminal (e.g., the inverting input terminal) of the operational amplifier 221 receives the touch sensing signal STS. The second input terminal (e.g., the non-inverting input terminal) of the operational amplifier 221 receives the input signal OPIP. The output terminal of the operational amplifier 221 is used to output the output signal OPOUT. The feedback circuit 222 is connected between the first input terminal of the operational amplifier 221 and the output terminal of the operational amplifier 221.

[0060] In this embodiment, the feedback circuit 222 includes a resistor R1 and a capacitor C1. The resistor R1 is connected between the first input terminal of the operational amplifier 221 and the output terminal of the operational amplifier 221. The capacitor C1 is connected between the first input terminal of the operational amplifier 221 and the output terminal of the operational amplifier 221. In some embodiments, the feedback circuit 222 may include more than just the resistor R1 and the capacitor C1. The present invention is not limited to the composition of the feedback circuit 222 of this embodiment.

[0061] In this embodiment, the receiving circuit 210 includes a switch SW1 and a capacitor CS. The first end of the switch SW1 receives the common mode voltage VCM. The second end of the switch SW1 is connected to the second input end of the operational amplifier 221. The switch SW1 can be operated according to the control signal S1. For example, the switch SW1 can be turned on according to the first level (e.g., high voltage value or high logic value) of the control signal S1, and can be turned off according to the second level (e.g., low voltage value or low logic value) of the control signal S1. The first end of the capacitor CS receives the first noise of the voltage ELVSS coupled data signal SD. The second end of the capacitor CS is connected to the second input end of the operational amplifier 221.

[0062] In the first period TD1, when the common mode voltage VCM does not have the first noise before the data signal SD is driven, the switch SW1 is turned on to allow the capacitor CS to receive the common mode voltage VCM. Therefore, the voltage value of the input signal OPIP is equal to the common mode voltage VCM.

[0063] In the second period TD2 after the first period TD1, the switch SW1 is turned off. The data signal SD starts to drive and couples the first noise to the first end of the capacitor CS, so the input signal OPIP is the common mode voltage VCM having the first noise. In other words, in the second period TD2 when the switch SW1 is turned off, the capacitor CS couples the voltage ELVSS to the noise of the data signal SD to the second input end of the operational amplifier 221.

[0064] The first input terminal of the operational amplifier 221 receives the touch sensing signal STS. The touch sensing signal STS has a second noise. It should be noted that the first noise and the second noise are generated in response to the falling edge of the data signal SD and the rising edge of the data signal SD, respectively. The operational amplifier 221 can use the virtual short circuit characteristic between the first input terminal and the second input terminal to use the first noise of the input signal OPIP to offset the second noise of the touch sensing signal STS. Therefore, the noise of the output signal OPOUT can be reduced or eliminated.

[0065] It should also be noted that the noise of the output signal OPOUT is reduced. Figure 1 , the noise of the output signal OPOUT of this embodiment occupies a smaller dynamic range VR. Therefore, the amplifier circuit 220 is allowed to have a larger amplification gain. The SNR of the analog front-end circuit CC2 can be improved.

[0066] In this embodiment, the first input terminal of the operational amplifier 221 can receive the touch sensing signal STS via the receiving terminal P1. The receiving circuit 210 can receive the first noise of the data signal SD coupled voltage ELVSS via the receiving terminal P2.

[0067] In this embodiment, the switch SW1 may be implemented by any appropriate type of transistor switch.

[0068] Please refer to Figure 6 , Figure 6 is a schematic diagram of an analog front-end circuit according to an embodiment of the present invention. In this embodiment, the analog front-end circuit CC3 includes a receiving circuit 210, an amplifying circuit 220, a low-pass filter 330, an analog-to-digital converter (ADC) 340, and a signal processor 350. The implementation details of the receiving circuit 210 and the amplifying circuit 220 have been described in Figure 3 as well as Figure 4 This is clearly described in the embodiments, so it will not be repeated here.

[0069] In the present embodiment, the low-pass filter 330 is connected to the amplifier circuit 220. The low-pass filter 330 filters out the high-frequency noise of the output signal OPOUT. The analog-to-digital converter 340 converts the analog format of the output signal OPOUT into a digital format. Taking the present embodiment as an example, the analog-to-digital converter 340 is connected to the low-pass filter 330. Therefore, the analog-to-digital converter 340 converts the analog format of the output signal OPOUT from which the high-frequency noise has been filtered out into a digital format. The signal processor 350 determines the touch behavior occurring in the touch display device according to the output signal OPOUT. Taking the present embodiment as an example, the signal processor 350 is connected to the analog-to-digital converter 340. Therefore, the signal processor 350 can be a digital signal processor.

[0070] Please refer to Figure 2 , Figure 7 as well as Figure 8 , Figure 7 is a schematic diagram of a touch display device according to an embodiment of the present invention. Figure 8 is a signal timing diagram according to an embodiment of the present invention. In this embodiment, Figure 3 Shown as Figure 2 The equivalent circuit CEQ of the touch panel 11, cathode 12, display panel 13 and the analog front-end circuit CC4 of this embodiment. The equivalent circuit CEQ is already Figure 3 This is clearly described in the embodiments, so it will not be repeated here.

[0071] In this embodiment, the analog front-end circuit CC4 includes a receiving circuit 410 and an amplifier circuit 220. The amplifier circuit 220 includes an operational amplifier 221 and a feedback circuit 222. The implementation of the operational amplifier 221 and the feedback circuit 222 has been described in detail. Figure 3 The embodiments of the present invention are clearly described in detail, so they are not repeated here. In this embodiment, the receiving circuit 410 includes switches SW1~SW4 and a capacitor CS. The first end of the switch SW1 receives the common mode voltage VCM. The first end of the switch SW2 is connected to the second end of the switch SW1. The second end of the switch SW2 is connected to the second input end of the operational amplifier 221. The first end of the switch SW3 receives the first noise of the voltage ELVSS coupled data signal SD. The first end of the switch SW4 is connected to the second end of the switch SW3. The second end of the switch SW4 is connected to a reference low voltage (for example, ground). The first end of the capacitor CS is connected to the second end of the switch SW1 and the first end of the switch SW2. The second end of the capacitor CS is connected to the second end of the switch SW3 and the first end of the switch SW4.

[0072] In this embodiment, switches SW1 and SW4 can be operated according to control signal S1. Switches SW2 and SW3 can be operated according to control signal S2. For example, switches SW1 and SW4 can be turned on according to a first level of control signal S1, and turned off according to a second level of control signal S1. Switches SW2 and SW3 can be turned on according to a first level of control signal S2, and turned off according to a second level of control signal S2.

[0073] In this embodiment, in the first period TD1, the switches SW2 and SW3 are turned off, and the switches SW1 and SW4 are turned on. Specifically, in the first period TD1, the switches SW2 and SW3 are turned off during the period between the time point t1 and the time point t4, and the switches SW1 and SW4 are turned on during the period between the time point t2 and the time point t3.

[0074] Further, in the first period TD1 of the present embodiment, the operation can be performed when the data signal SD is driven. The voltage ELVSS has noise at the time points of the falling edge of the data signal SD and the rising edge of the data signal SD. In the first period TD1, the time point t1 is earlier than the time point t2. The time point t3 is later than the time point t2 and earlier than the time point t4. The switches SW2 and SW3 are disconnected during the period between the time point t1 and the time point t4, and the switches SW1 and SW4 are turned on during the period between the time point t2 and the time point t3. The first end of the capacitor CS receives the common mode voltage VCM. The second end of the capacitor CS receives the reference low voltage. Therefore, the common mode voltage VCM received by the capacitor CS during the first period TD1 is not affected by the first noise. In other words, the operation of the switches SW1~SW4 during the first period TD1 can ensure that the first noise does not affect the charging of the capacitor CS by the common mode voltage VCM.

[0075] In the second period TD2 after the first period TD1, the switches SW1 and SW4 are turned off. The switches SW2 and SW3 are turned on. Therefore, the input signal OPIP is the common mode voltage VCM having the first noise. In other words, in the second period TD2, the capacitor CS couples the voltage ELVSS and the noise of the data signal SD to the second input terminal of the operational amplifier 221.

[0076] Compared to Figure 1 , the noise of the output signal OPOUT of this embodiment occupies a smaller dynamic range VR. Therefore, the amplifier circuit 220 is allowed to have a larger amplification gain. The SNR of the analog front-end circuit CC4 can be improved.

[0077] In this embodiment, the analog front-end circuit CC4 may also include: Figure 6 A low pass filter 330 , an analog to digital converter 340 , and a signal processor 350 are shown.

[0078] In this embodiment, the switches SW1 - SW4 can be implemented by any appropriate type of transistor switches.

[0079] Please refer to Figure 2 as well as Fig. 9 , Fig. 9is a flow chart of an operation method according to an embodiment of the present invention. In this embodiment, the operation method S100 is applicable to the touch display device 100. The operation method S100 includes steps S110~S130. In step S110, the receiving circuit 110 receives the first noise of the voltage ELVSS coupled to the data signal SD to generate an input signal OPIP. In step S120, the amplifying circuit 120 receives the touch sensing signal STS having the second noise coupled to the data signal SD, and receives the input signal OPIP from the receiving circuit 110. In step S130, the amplifying circuit 120 uses the first noise in the input signal OPIP to reduce the second noise in the touch sensing signal STS to generate an output signal OPOUT. The implementation details of steps S110~S130 have been described in detail. Figures 2 to 5 , Figure 7 , Figure 8 The invention has been clearly described in the multiple embodiments, so it will not be repeated here.

[0080] In summary, the amplifier circuit of the present invention utilizes the first noise in the input signal to reduce the second noise in the touch sensing signal to generate an output signal. The noise of the output signal can be reduced. In this way, the SNR of the analog front-end circuit can be improved.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An analog front-end circuit for a touch display device, characterized in that: The analog front end circuit comprises: A receiving circuit configured to receive a first noise located in the touch display device to generate an input signal; and an amplifier circuit, one end of the amplifier circuit is connected to the receiving circuit to receive the input signal from the receiving circuit, the other end of the amplifier circuit receives the touch sensing signal of the touch display device, and the amplifier circuit uses the first noise to reduce the second noise in the touch sensing signal to generate an output signal, The first noise and the second noise are respectively generated by the voltage of the cathode of the touch display device coupled with a data signal.

2. The analog front-end circuit according to claim 1, characterized in that: The cathode is connected to the receiving circuit and provides the first noise.

3. The analog front-end circuit according to claim 1, characterized in that: The first noise and the second noise are generated in response to a falling edge of a data signal and a rising edge of the data signal, respectively.

4. The analog front-end circuit according to claim 1, characterized in that: The amplifying circuit comprises: an operational amplifier, wherein a first input terminal of the operational amplifier receives the touch sensing signal, a second input terminal of the operational amplifier receives the input signal, and an output terminal of the operational amplifier is used to output the output signal; and The feedback circuit is connected between the first input terminal of the operational amplifier and the output terminal of the operational amplifier.

5. The analog front-end circuit according to claim 4, characterized in that: The receiving circuit comprises: a switch, wherein a first end of the switch receives a common mode voltage, and a second end of the switch is connected to a second input end of the operational amplifier; and A capacitor, a first terminal of the capacitor receives the first noise, and a second terminal of the capacitor is connected to the second input terminal of the operational amplifier.

6. The analog front-end circuit according to claim 5, characterized in that: During a first period, when the common mode voltage does not have noise before the data signal is driven, the switch is turned on to allow the second input terminal of the operational amplifier to receive the common mode voltage.

7. The analog front-end circuit according to claim 6, characterized in that: During a second period after the first period, the switch is turned off, and the first noise is coupled to the input signal.

8. The analog front-end circuit according to claim 4, characterized in that: The receiving circuit comprises: a first switch, wherein a first end of the first switch receives a common mode voltage; a second switch, wherein a first end of the second switch is connected to a second end of the first switch, and a second end of the second switch is connected to a second input end of the operational amplifier; a third switch, a first end of the third switch receiving the first noise; a fourth switch, wherein a first end of the fourth switch is connected to a second end of the third switch, and a second end of the fourth switch is connected to a reference low voltage; and A capacitor, wherein a first end of the capacitor is connected to the second end of the first switch and the first end of the second switch, and a second end of the capacitor is connected to the second end of the third switch and the first end of the fourth switch.

9. The analog front-end circuit according to claim 8, characterized in that: During the first period, the second switch and the third switch are turned off. The first switch and the fourth switch are turned on to enable the second input terminal of the operational amplifier to receive the common mode voltage, and In a second period after the first period, the first switch and the fourth switch are turned off, the second switch and the third switch are turned on, and the first noise is coupled to the input signal.

10. The analog front-end circuit according to claim 8, characterized in that: During the first period: The second switch and the third switch are turned off during a period between the first time point and the second time point, The first switch and the fourth switch are turned on during a period between the third time point and the fourth time point. The first time point is earlier than the third time point, and The fourth time point is later than the third time point and earlier than the second time point.

11. An operating method for a touch display device, characterized in that: The operation method comprises: The receiving circuit receives a first noise located in the touch display device to generate an input signal; The amplifying circuit receives the input signal from the receiving circuit and receives the touch sensing signal of the touch display device; and The amplifying circuit utilizes the first noise to reduce the second noise in the touch sensing signal to generate an output signal, The first noise and the second noise are respectively generated by the voltage of the cathode of the touch display device coupled with a data signal.

12. The operating method according to claim 11, characterized in that: The cathode is connected to the receiving circuit and provides the first noise.

13. The operating method according to claim 11, characterized in that: The first noise and the second noise are generated in response to a falling edge of a data signal and a rising edge of the data signal, respectively.

14. The operating method according to claim 11, characterized in that: The amplifying circuit comprises: an operational amplifier, wherein a first input terminal of the operational amplifier receives the touch sensing signal, a second input terminal of the operational amplifier receives the input signal, and an output terminal of the operational amplifier is used to output the output signal; and The feedback circuit is connected between the first input terminal of the operational amplifier and the output terminal of the operational amplifier.

15. The operating method according to claim 14, characterized in that: The receiving circuit comprises: a switch, wherein a first end of the switch receives a common mode voltage, and a second end of the switch is connected to a second input end of the operational amplifier; and A capacitor, a first terminal of the capacitor receives the first noise, and a second terminal of the capacitor is connected to the second input terminal of the operational amplifier.

16. The operating method according to claim 15, characterized in that: The step of receiving the common mode voltage to generate the input signal comprises: During a first period, when the common mode voltage does not have noise and the data signal has not been driven, turning on the switch to allow the second input terminal of the operational amplifier to receive the common mode voltage; and In a second period after the first period, the switch is turned off and the first noise is coupled to the input signal.

17. The operating method according to claim 14, characterized in that: The receiving circuit comprises: a first switch, wherein a first end of the first switch receives a common mode voltage; a second switch, wherein a first end of the second switch is connected to a second end of the first switch, and a second end of the second switch is connected to a second input end of the operational amplifier; a third switch, a first end of the third switch receiving the first noise; a fourth switch, wherein a first end of the fourth switch is connected to a second end of the third switch, and a second end of the fourth switch is connected to a reference low voltage; and A capacitor, wherein a first end of the capacitor is connected to the second end of the first switch and the first end of the second switch, and a second end of the capacitor is connected to the second end of the third switch and the first end of the fourth switch.

18. The operating method according to claim 17, characterized in that: The step of receiving the common mode voltage to generate the input signal comprises: During a first period, turning off the second switch and the third switch; Turning on the first switch and the fourth switch to allow the second input terminal of the operational amplifier to receive the common mode voltage; and In a second period after the first period, the first switch and the fourth switch are turned off, and the second switch and the third switch are turned on, so that the first noise is coupled to the input signal.

19. The operating method according to claim 17, characterized in that: During the first period: The second switch and the third switch are turned off during a period between the first time point and the second time point, The first switch and the fourth switch are turned on during a period between the third time point and the fourth time point. The first time point is earlier than the third time point, and The fourth time point is later than the third time point and earlier than the second time point.

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