Detection chip and active pen

Abstract

The utility model discloses a detection chip and an active pen. The detection chip is connected with a strain circuit in the active pen through a switching circuit; the strain circuit is used for sensing the pressure of a pen point; the strain circuit comprises a first resistance bridge arm and a second resistance bridge arm; the first end of the first resistance bridge arm is connected with the power supply end, and the second end is grounded; the first end of the second resistor bridge arm is connected with the power supply end, and the second end of the second resistor bridge arm is grounded; when the switching circuit is in a first state, the first end of the detection chip is connected with the first resistor bridge arm, and the second end of the detection chip is connected with the second resistor bridge arm to receive a first forward voltage; and when the switching circuit is in a second state, the second end of the detection chip is connected with the first resistor bridge arm, the first end of the detection chip is connected with the second resistor bridge arm, the first backward voltage is received, and a signal output by the strain circuit to the detection chip is modulated to form a square wave signal, so that demodulation and noise reduction processing are facilitated, a noise signal is removed, and the detection accuracy is improved.

Description

Technical Field

[0001] This utility model relates to the field of pressure detection technology, and in particular to a detection chip and an active pen. Background Technology

[0002] Currently, during the amplification process of the active pen in the amplifier circuit, noise signals are introduced. After being amplified by the amplifier circuit, the noise signals are also input to the ADC converter for conversion. This significantly affects the number of recognizable levels of the pressure value detected by the active pen, resulting in low accuracy of the detected pressure value and impacting the user experience of touch devices equipped with active pens. Summary of the Invention

[0003] This invention provides a detection chip and an active pen to solve the problem that noise signals are introduced during the signal amplification process of the existing pressure detection circuit, resulting in low accuracy of the detected pressure value of the active pen.

[0004] A detection chip is used in an active pen. The detection chip is connected to a strain circuit in the active pen via a switching circuit. The strain circuit is used to sense the pressure of the pen tip.

[0005] The strain gauge circuit includes a first resistor bridge arm and a second resistor bridge arm; the first end of the first resistor bridge arm is used to connect to the power supply terminal, and the second end of the first resistor bridge arm is used to connect to ground; the first end of the second resistor bridge arm is used to connect to the power supply terminal, and the second end of the second resistor bridge arm is used to connect to ground.

[0006] When the switching circuit is in the first state, the first end of the detection chip is connected to the midpoint of the first resistor bridge arm, the second end of the detection chip is connected to the midpoint of the second resistor bridge arm, and the detection chip receives the first positive voltage output by the strain circuit.

[0007] When the switching circuit is in the second state, the second end of the detection chip is connected to the midpoint of the first resistor bridge arm, the first end of the detection chip is connected to the midpoint of the second resistor bridge arm, and the detection chip receives the first reverse voltage output by the strain circuit.

[0008] Preferably, the detection chip includes an amplifier circuit, the non-inverting input terminal of which is connected to the midpoint of the first resistor bridge arm or the midpoint of the second resistor bridge arm via the switching circuit; the inverting input terminal of which is connected to the midpoint of the first resistor bridge arm or the midpoint of the second resistor bridge arm via the switching circuit.

[0009] When the switching circuit is in the first state, the non-inverting input terminal of the amplifier circuit is connected to the midpoint of the first resistor bridge arm, the inverting input terminal of the amplifier circuit is connected to the midpoint of the second resistor bridge arm, and the amplifier circuit receives the first positive voltage output by the strain circuit.

[0010] When the switching circuit is in the second state, the non-inverting input terminal of the amplifier circuit is connected to the midpoint of the second resistor bridge arm, and the inverting input terminal of the amplifier circuit is connected to the midpoint of the first resistor bridge arm. The amplifier circuit receives the first reverse voltage output by the strain circuit.

[0011] Preferably, the switching circuit includes a first switching branch and a second switching branch;

[0012] The midpoint of the first resistor bridge arm is connected to the non-inverting input terminal of the amplifier circuit or the inverting input terminal of the amplifier circuit through the first switch branch.

[0013] The midpoint of the second resistor bridge arm is connected to the non-inverting input terminal or the inverting input terminal of the amplifier circuit through the second switch branch;

[0014] When the first switch branch is connected to the non-inverting input terminal of the amplifier circuit and the midpoint of the first resistor bridge arm, and the second switch branch is connected to the inverting input terminal of the amplifier circuit and the midpoint of the second resistor bridge arm, the amplifier circuit receives the first positive voltage output by the strain circuit.

[0015] The first switch branch is connected to the inverting input terminal of the amplifier circuit and the midpoint of the first resistor bridge arm. The second switch branch is connected to the non-inverting input terminal of the amplifier circuit and the midpoint of the second resistor bridge arm. The amplifier circuit receives the first reverse voltage output by the strain circuit.

[0016] Preferably, the first switch branch includes a first switch and a second switch, the midpoint of the first resistor bridge arm is connected to the non-inverting input terminal of the amplifier circuit through the first switch, and the midpoint of the first resistor bridge arm is connected to the inverting input terminal of the amplifier circuit through the second switch.

[0017] The second switch branch includes a third switch and a fourth switch. The midpoint of the second resistor bridge arm is connected to the non-inverting input terminal of the amplifier circuit through the third switch, and the midpoint of the second resistor bridge arm is connected to the inverting input terminal of the amplifier circuit through the fourth switch.

[0018] When the first switch and the fourth switch are turned on, the amplifier circuit receives the first positive voltage output by the strain circuit;

[0019] When the second switch and the third switch are turned on, the amplifier circuit receives the first reverse voltage output by the strain circuit.

[0020] Preferably, the first switch branch includes a first single-pole double-throw switch, the moving end of the first single-pole double-throw switch is connected to the midpoint of the first resistor bridge arm, the first stationary end of the first single-pole double-throw switch is used to connect to the non-inverting input terminal of the amplifier circuit, and the second stationary end of the first single-pole double-throw switch is used to connect to the inverting input terminal of the amplifier circuit.

[0021] The second switch branch includes a second single-pole double-throw switch. The moving end of the second single-pole double-throw switch is connected to the midpoint of the second resistor bridge arm. The first stationary end of the second single-pole double-throw switch is used to connect to the non-inverting input terminal of the amplifier circuit, and the second stationary end of the second single-pole double-throw switch is used to connect to the inverting input terminal of the amplifier circuit.

[0022] When the moving end of the first single-pole double-throw switch is connected to the first stationary end, and the moving end of the second single-pole double-throw switch is connected to the second stationary end, the amplifier circuit receives the first positive voltage output by the strain circuit.

[0023] When the moving end of the first single-pole double-throw switch is connected to the second stationary end, and the moving end of the second single-pole double-throw switch is connected to the first stationary end, the amplifier circuit receives the first reverse voltage output by the strain circuit.

[0024] Preferably, the detection chip is connected to the strain circuit in the active pen via a switching circuit, and the strain circuit is used to sense the pressure of the pen tip;

[0025] The strain circuit includes a first resistor bridge arm and a second resistor bridge arm. The midpoint of the first resistor bridge arm is used to detect the first end of the chip, and the midpoint of the second resistor bridge arm is used to detect the second end of the chip.

[0026] The first end of the first resistor bridge arm and the first end of the second resistor bridge arm converge to form a first bus terminal, which is connected to the power supply terminal or ground through the switching circuit.

[0027] The second end of the first resistor bridge arm and the second end of the second resistor bridge arm converge to form a second bus terminal, which is connected to the power supply terminal or ground through the switching circuit;

[0028] When the switching circuit is in the first state, the first bus terminal is connected to the power supply terminal, the second bus terminal is connected to ground, and the detection chip receives the first positive voltage output by the strain circuit.

[0029] When the switching circuit is in the second state, the first bus terminal is connected to ground, the second bus terminal is connected to the power supply terminal, and the detection chip receives the first reverse voltage output by the strain circuit.

[0030] Preferably, the detection chip includes an amplifier circuit, wherein the non-inverting input terminal of the amplifier circuit is connected to the midpoint of the first resistor bridge arm, and the inverting input terminal of the amplifier circuit is connected to the midpoint of the second resistor bridge arm.

[0031] When the switching circuit is in the first state, the first bus terminal is connected to the power supply terminal, the second bus terminal is connected to ground, and the amplifier circuit receives the first positive voltage output by the strain circuit.

[0032] When the switching circuit is in the second state, the first bus terminal is connected to ground, the second bus terminal is connected to the power supply terminal, and the amplifier circuit receives the first reverse voltage output by the strain circuit.

[0033] Preferably, the switching circuit includes a first switching branch and a second switching branch;

[0034] The first bus terminal is connected to the power supply terminal or ground through the first switch branch;

[0035] The second bus terminal is connected to the power supply terminal or ground via the second switch branch;

[0036] When the first switch branch is connected to the first bus terminal and the power supply terminal, and the second switch branch is connected to the second bus terminal and ground, the amplifier circuit receives the first positive voltage output by the strain circuit;

[0037] When the first switch branch is connected to the first bus terminal and ground, and the second switch branch is connected to the second bus terminal and the power supply terminal, the amplifier circuit receives the first reverse voltage output by the strain circuit.

[0038] Preferably, the first switch branch includes a first switch and a second switch, the first bus terminal is connected to the power supply terminal through the first switch, and the first bus terminal is connected to ground through the second switch;

[0039] The second switch branch includes a third switch and a fourth switch. The second bus terminal is connected to the power supply terminal through the third switch, and the second bus terminal is connected to ground through the fourth switch.

[0040] When the first switch and the fourth switch are turned on, the amplifier circuit receives the first positive voltage output by the strain circuit;

[0041] When the second switch and the third switch are turned on, the amplifier circuit receives the first reverse voltage output by the strain circuit.

[0042] Preferably, the first switch branch includes a first single-pole double-throw switch, the moving end of the first single-pole double-throw switch is connected to the first bus terminal, the first stationary end of the first single-pole double-throw switch is used to connect to the power supply terminal, and the second stationary end of the first single-pole double-throw switch is used to connect to ground;

[0043] The second switch branch includes a second single-pole double-throw switch. The moving end of the second single-pole double-throw switch is connected to the second bus terminal. The first stationary end of the second single-pole double-throw switch is used to connect to the power supply terminal, and the second stationary end of the second single-pole double-throw switch is used to connect to ground.

[0044] When the moving end of the first single-pole double-throw switch is connected to the first stationary end, and the moving end of the second single-pole double-throw switch is connected to the second stationary end, the amplifier circuit receives the first positive voltage output by the strain circuit.

[0045] When the moving end of the first single-pole double-throw switch is connected to the second stationary end, and the moving end of the second single-pole double-throw switch is connected to the first stationary end, the amplifier circuit receives the first reverse voltage output by the strain circuit.

[0046] Preferably, the detection chip further includes an ADC converter and a controller;

[0047] The amplifier circuit is used to amplify the first positive voltage and the noise voltage to output a second positive voltage, and to amplify the first reverse voltage and the noise voltage to output a second reverse voltage.

[0048] The ADC converter is connected to the amplifier circuit and is used to demodulate and reduce noise on the second forward voltage and the second reverse voltage to determine the third forward voltage and the third reverse voltage.

[0049] The controller, in conjunction with the switching circuit and the ADC converter, controls the switching circuit to alternately enter a first state and a second state, and determines the pressure value of the active pen based on the third positive voltage and the third reverse voltage.

[0050] Preferably, the controller is used to interleave a first control signal and a second control signal to the switching circuit based on the target frequency, so that the switching circuit interleaves into a first state and a second state, and outputs the target frequency to the ADC converter;

[0051] The ADC converter performs quadrature demodulation or square wave demodulation on the second forward voltage and the second reverse voltage based on the target frequency to determine the third forward voltage and the third reverse voltage, and sends the third forward voltage and the third reverse voltage to the controller.

[0052] Preferably, the detection chip further includes an ADC converter, the ADC converter being adapted to connect to a controller, the controller being connected to the switching circuit, and used to control the switching circuit to alternately enter a first state or a second state;

[0053] The amplifier circuit is used to amplify the first positive voltage and the noise voltage to output a third positive voltage, and to amplify the first reverse voltage and the noise voltage to output a third reverse voltage.

[0054] The ADC converter is connected to the amplifier circuit and is used to demodulate and reduce noise on the third positive voltage and the third reverse voltage, determine the third positive voltage and the third reverse voltage, and send the third positive voltage and the third reverse voltage to the controller so that the controller can determine the pressure value of the active pen based on the third positive voltage and the third reverse voltage.

[0055] Preferably, the switching circuit is disposed inside the detection chip or outside the detection chip.

[0056] An active pen includes a strain circuit and the aforementioned detection chip;

[0057] The strain gauge circuit is used to sense the pressure of the pen tip;

[0058] The detection chip is connected to the strain circuit via a switching circuit, and is used to determine the pressure value of the active pen based on the first positive voltage and the first reverse voltage alternately output by the strain circuit through the switching circuit.

[0059] The aforementioned detection chip and active pen are connected. The detection chip is connected to the strain circuit via a switching circuit. The switching circuit can change the conduction direction between the strain circuit and the detection chip, so that when the strain circuit is forward-biased, it outputs a first positive voltage to the detection chip, and when the strain circuit is reverse-biased, it outputs a first reverse voltage to the detection chip. The first positive voltage and the first reverse voltage are alternately output to the detection chip, which is equivalent to modulating the signal output from the strain circuit to the detection chip to form a square wave signal. This allows the detection chip to perform demodulation and noise reduction processing to remove noise signals introduced during the operation of the detection chip, thereby ensuring the accuracy of the pressure value detected by the active pen. Attached Figure Description

[0060] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 This is a schematic diagram of a typical active pen structure;

[0062] Figure 2 This is a typical circuit diagram of an active pen;

[0063] Figure 3 This is a circuit diagram of the active pen in Embodiment 1 of this utility model;

[0064] Figure 4 This is a circuit diagram of the active pen in Embodiment 2 of this utility model;

[0065] Figure 5 This is a circuit diagram of the active pen in Embodiment 3 of this utility model;

[0066] Figure 6 This is a circuit diagram of the active pen in Embodiment 4 of this utility model;

[0067] Figure 7 This is a circuit diagram of the active pen in Embodiment 5 of this utility model;

[0068] Figure 8 This is a circuit diagram of the active pen in Embodiment 6 of this utility model;

[0069] Figure 9 This is a circuit diagram of the active pen in Embodiment 7 of this utility model;

[0070] Figure 10 This is a circuit diagram of the active pen in Embodiment 8 of this utility model.

[0071] In the diagram: 101, pen casing; 102, pen electrode; 103, strain gauge; 1, strain circuit; 11, first resistor bridge arm; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; 12, second resistor bridge arm; 2, switch circuit; 21, first switch branch; K1, first switch; K2, second switch; K5, first single-pole double-throw switch; 22, second switch branch; K3, third switch; K4, fourth switch; K6, second single-pole double-throw switch; 3, amplifier circuit; 4, ADC converter; 5, controller. Detailed Implementation

[0072] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model.

[0073] It should be understood that this invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this invention to those skilled in the art. In the drawings, for clarity, the dimensions of layers and regions, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0074] To fully understand this utility model, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by this utility model. Preferred embodiments of this utility model are described in detail below; however, in addition to these detailed descriptions, this utility model may have other embodiments.

[0075] See Figure 1 The active pen includes a pen housing 101, a pen electrode 102, and a strain gauge 103. The pen electrode 102 is disposed inside the pen housing 101 and connected to the pen tip; the strain gauge 103 is disposed inside the pen housing 101 and connected to the pen electrode 102, i.e., the strain gauge 103 is connected to the pen tip through the pen electrode 102. The active pen also includes a strain circuit 1 and a detection chip. The strain circuit 1 is disposed on the strain gauge 103 connected to the pen tip and is used to sense the pressure of the pen tip; the detection chip is connected to the strain circuit 1 and can receive the voltage signal output by the strain circuit 1 that reflects the pressure strain of the pen tip, and determine the pressure value of the active pen based on the voltage signal. The strain circuit 1 is a circuit formed by multiple resistors disposed on the strain gauge 103, which can cause the resistance of the strain gauge 103 to change when the pressure applied to the strain gauge 103 changes.

[0076] See Figure 2The detection chip generally includes an amplifier circuit 3 connected to the strain circuit 1 and an ADC converter 4 connected to the amplifier circuit 3. In the strain circuit 1, the first ends of the first resistor bridge arm 11 and the second resistor bridge arm 12 are connected to the power supply terminal VCC, and the second ends of the first resistor bridge arm 11 and the second resistor bridge arm 12 are both connected to ground GND. The midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3. The two input terminals are fixedly connected, so that the strain circuit 1 outputs a fixed voltage (i.e., Vip-Vin) to the amplifier circuit 3. That is, the input signal from the strain circuit 1 to the amplifier circuit 3 is free from fluctuation. The amplifier circuit 3 amplifies the received input signal, which introduces noise signal. After amplification, the noise signal will seriously affect the accuracy of the pressure value of the active pen sampled and identified by the subsequent ADC converter 4.

[0077] This utility model embodiment provides a detection chip suitable for use in an active pen, such as... Figures 3-10 As shown, the detection chip is connected to the strain circuit 1 in the active pen through the switch circuit 2. The strain circuit 1 is used to detect the pressure of the strain gauge 103. The detection chip receives the first positive voltage output by the strain circuit 1 through the switch circuit 2 at the first time. The detection chip receives the first reverse voltage output by the strain circuit 1 through the switch circuit 2 at the second time. The detection chip determines the pressure value of the active pen based on the first positive voltage and the first reverse voltage.

[0078] The first positive voltage is the voltage when the strain circuit 1 is forward-biased, which can be represented by V1(+); the first reverse voltage is the voltage when the strain circuit 1 is reverse-biased, which can be represented by V1(-). Generally, during the forward and reverse conduction of the strain circuit 1, the first positive voltage and the first reverse voltage output by the strain circuit 1 to the detection chip have opposite signs (i.e., opposite polarities) but the same absolute value.

[0079] The first time period is the time used to acquire the first positive voltage, and the second time period is the time used to acquire the first reverse voltage.

[0080] As an example, the detection chip can receive the first positive voltage output by the strain circuit 1 through the switching circuit 2 at the first moment, and the first reverse voltage output by the strain circuit 1 through the switching circuit 2 at the second moment. When the strain circuit 1 outputs the first positive voltage and the first reverse voltage alternately, since the first positive voltage and the first reverse voltage have opposite signs (i.e. opposite polarities) and the same absolute value, it is equivalent to the strain circuit 1 outputting a modulated square wave signal to the detection chip. After detecting the square wave signal output by the strain circuit 1, the detection chip can demodulate and reduce the noise of the square wave signal to determine the pressure value of the active pen, which can improve the detected pressure level and ensure the accuracy of pressure detection.

[0081] In this example, the detection chip is connected to the strain circuit 1 via the switching circuit 2. The switching circuit 2 can change the conduction direction between the strain circuit 1 and the detection chip, so that when the strain circuit 1 is forward-biased, it outputs a first positive voltage to the detection chip, and when the strain circuit 1 is reverse-biased, it outputs a first reverse voltage to the detection chip. The first positive voltage and the first reverse voltage are alternately output to the detection chip, which is equivalent to modulating the signal output from the strain circuit 1 to the detection chip to form a square wave signal. This allows the detection chip to remove noise signals introduced during the operation of the detection chip through demodulation and noise reduction processing, thereby ensuring the accuracy of the pressure value detected by the active pen.

[0082] In one embodiment, such as Figures 3-6 As shown, the detection chip is connected to the strain gauge circuit 1 in the active pen via the switching circuit 2. The strain gauge circuit 1 is used to detect the pressure of the strain gauge 103. The strain gauge circuit 1 includes a first resistor bridge arm 11 and a second resistor bridge arm 12. The first end of the first resistor bridge arm 11 is connected to the power supply terminal VCC, and the second end of the first resistor bridge arm 11 is connected to ground GND. The first end of the second resistor bridge arm 12 is connected to the power supply terminal VCC, and the second end of the second resistor bridge arm 12 is connected to ground GND. When the switching circuit 2 is in the first state, the first end of the detection chip is connected to the midpoint of the first resistor bridge arm 11, and the second end of the detection chip is connected to the midpoint of the second resistor bridge arm 12. The detection chip receives the first positive voltage output by the strain gauge circuit 1. When the switching circuit 2 is in the second state, the second end of the detection chip is connected to the midpoint of the first resistor bridge arm 11, and the first end of the detection chip is connected to the midpoint of the second resistor bridge arm 12. The detection chip receives the first positive voltage output by the strain gauge circuit 1.

[0083] As an example, the strain gauge circuit 1 includes a first resistor bridge arm 11 and a second resistor bridge arm 12. The first resistor bridge arm 11 includes a first resistor R1 and a second resistor R2 connected in series. The first end and the second end of the first resistor bridge arm 11 are its beginning and end points, respectively. The midpoint of the first resistor bridge arm 11 is the connection node between the first resistor R1 and the second resistor R2. The second resistor bridge arm 12 includes a third resistor R3 and a fourth resistor R4 connected in series. The first end and the second end of the second resistor bridge arm 12 are its beginning and end points, respectively. The midpoint of the second resistor bridge arm 12 is the connection node between the third resistor R3 and the fourth resistor R4.

[0084] The first state of the switching circuit 2 is used to control the strain circuit 1 to conduct in the forward direction, and the second state of the switching circuit 2 is used to control the strain circuit 1 to conduct in the reverse direction.

[0085] As an example, the active pen needs to perform steps one and two alternately as follows:

[0086] Step 1: Switching circuit 2 enters a first state based on the first control signal output by controller 5, connecting the first terminal of the detection chip to the midpoint of the first resistor bridge arm 11 and the second terminal of the detection chip to the midpoint of the second resistor bridge arm 12. At this time, the detection chip can receive the first positive voltage output by strain circuit 1. The controller 5 can be located inside or outside the detection chip; its location can be determined according to the actual situation. Specifically, it can be a central processing unit (CPU) located inside the active pen or a microcontroller unit (MCU). The first control signal here is used to control the strain circuit 1 to output the first positive voltage to amplification circuit 3.

[0087] Step 2: Switching circuit 2 enters a second state based on the second control signal output by controller 5, so that the second terminal of the detection chip is connected to the midpoint of the first resistor bridge arm 11, and the first terminal of the detection chip is connected to the midpoint of the second resistor bridge arm 12. At this time, the detection chip can receive the first reverse voltage output by strain circuit 1. The second control signal here is used to control strain circuit 1 to output the first reverse voltage to amplifier circuit 3.

[0088] In this example, either the first control signal or the second control signal is a high-level signal, and the other is a low-level signal. By switching between the high-level and low-level signals, the switching circuit 2 alternately enters the first state and the second state, thereby causing the strain circuit 1 to alternately output the first positive voltage and the first reverse voltage to the detection chip. This modulates the fixed voltage signal output by the strain circuit 1 to the detection chip into a square wave signal, which can be demodulated and noise-reduced by the detection chip to ensure the accuracy of the pressure value of the active pen detected by the detection chip.

[0089] In one embodiment, the first resistor bridge arm 11 includes a first resistor R1 and a second resistor R2 connected in series, with the connection point between the first resistor R1 and the second resistor R2 being the midpoint of the first resistor bridge arm 11; the second resistor bridge arm 12 includes a third resistor R3 and a fourth resistor R4 connected in series, with the connection point between the third resistor R3 and the fourth resistor R4 being the midpoint of the second resistor bridge arm 12; the detection chip includes an amplifier circuit 3, the non-inverting input terminal Vip of the amplifier circuit 3 being connected to the midpoint of the first resistor bridge arm 11 or the midpoint of the second resistor bridge arm 12 via a switching circuit 2; the inverting input terminal Vin of the amplifier circuit 3 is connected to the midpoint of the first resistor bridge arm 11 or the midpoint of the second resistor bridge arm 12 via the switching circuit 2. Connect the midpoint of the first resistor bridge arm 11 or the midpoint of the second resistor bridge arm 12; when the switching circuit 2 is in the first state, the non-inverting input terminal Vip of the amplifier circuit 3 is connected to the midpoint of the first resistor bridge arm 11, and the inverting input terminal Vin of the amplifier circuit 3 is connected to the midpoint of the second resistor bridge arm 12, and the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1; when the switching circuit 2 is in the second state, the non-inverting input terminal Vip of the amplifier circuit 3 is connected to the midpoint of the second resistor bridge arm 12, and the inverting input terminal Vin of the amplifier circuit 3 is connected to the midpoint of the first resistor bridge arm 11, and the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0090] As an example, such as Figure 3 and Figure 4 As shown, the first ends of both the first resistor bridge arm 11 and the second resistor bridge arm 12 are connected to the power supply terminal VCC, and the second ends of both are connected to ground GND. When the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3, the strain gauge circuit 1 outputs a first positive voltage to the amplifier circuit 3; when the midpoint of the first resistor bridge arm 11 is connected to the inverting input terminal Vin of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3, the strain gauge circuit 1 outputs a first positive voltage to the amplifier circuit 3. When the non-inverting input terminal Vip is connected, the strain gauge circuit 1 outputs a first reverse voltage to the amplifier circuit 3; or, when the midpoint of the first resistor bridge arm 11 is connected to the inverting input terminal Vin of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, the strain gauge circuit 1 outputs a first positive voltage to the amplifier circuit 3; when the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3, the strain gauge circuit 1 outputs a first reverse voltage to the amplifier circuit 3.

[0091] As an example, the active pen needs to perform steps one and two alternately as follows:

[0092] Step 1: Switching circuit 2 enters a first state based on the first control signal output by controller 5, connecting the midpoint of the first resistor bridge arm 11 to the non-inverting input terminal Vip of amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 to the inverting input terminal Vin of amplifier circuit 3. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of amplifier circuit 3 is the first positive voltage. Controller 5 can be located inside or outside the detection chip; its location can be determined according to the actual situation. Specifically, it can be a central processing unit (CPU) located inside the active pen, or a microcontroller unit (MCU). The first control signal here is used to control the strain circuit 1 to output the first positive voltage to amplifier circuit 3.

[0093] Step Two: Switching circuit 2 enters a second state based on the second control signal output by controller 5, connecting the midpoint of the second resistor bridge arm 12 to the non-inverting input terminal Vip of amplifier circuit 3, and the midpoint of the first resistor bridge arm 11 to the inverting input terminal Vin of amplifier circuit 3. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of amplifier circuit 3 is the first reverse voltage. The second control signal here is used to control the strain gauge circuit 1 to output the first reverse voltage to amplifier circuit 3.

[0094] In this example, either the first control signal or the second control signal is a high-level signal, and the other is a low-level signal. By switching between the high-level and low-level signals, the switching circuit 2 alternately enters the first state and the second state, thereby causing the strain circuit 1 to alternately output the first positive voltage and the first reverse voltage to the detection chip. This modulates the fixed voltage signal output by the strain circuit 1 to the detection chip into a square wave signal, which can be demodulated and noise-reduced by the detection chip to ensure the accuracy of the pressure value of the active pen detected by the detection chip.

[0095] For example, when the first end of the two resistor bridge arms is connected to the power supply terminal VCC and the second end of the two resistor bridge arms is grounded, the switching circuit 2 is connected between the midpoint of the two resistor bridge arms and the two input terminals of the amplifier circuit 3. When the switching circuit 2 receives the first control signal input from the controller 5, it connects the midpoint of the first resistor bridge arm 11 to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 to the inverting input terminal Vin of the amplifier circuit 3. Then, the voltage Vip at the non-inverting input terminal Vip of the amplifier circuit 3 is 0.9V, and the voltage Vin at the inverting input terminal Vin of the amplifier circuit 3 is 0.8V. Therefore, the first positive voltage input to the amplifier circuit 3 is Vip - Vin = 0.1V. When the switching circuit 2 receives the second control signal input from the controller 5... When the midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the first resistor bridge arm 11 is connected to the inverting input terminal Vin of the amplifier circuit 3, the voltage Vip at the non-inverting input terminal Vip of the amplifier circuit 3 is 0.9V, and the voltage Vin at the inverting input terminal Vin of the amplifier circuit 3 is 1V. Then, the first reverse voltage input to the amplifier circuit 3 is Vip - Vin = -0.1V, which makes the first positive voltage and the first reverse voltage input to the amplifier circuit 3 have opposite signs (i.e., opposite polarities) and the same absolute value. This is equivalent to outputting a square wave signal to the detection chip, so that the detection chip can remove the noise signal brought in during the operation of the detection chip through demodulation and noise reduction processing, thereby ensuring the accuracy of the detected pressure value of the active pen.

[0096] In one embodiment, such as Figures 3-6 As shown, the switching circuit 2 includes a first switching branch 21 and a second switching branch 22. The midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip or the inverting input terminal Vin of the amplifier circuit 3 through the first switching branch 21. The midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip or the inverting input terminal Vin of the amplifier circuit 3 through the second switching branch 22. When the first switching branch 21 connects the non-inverting input terminal Vip of the amplifier circuit 3 and the midpoint of the first resistor bridge arm 11, and the second switching branch 22 connects the inverting input terminal Vin of the amplifier circuit 3 and the midpoint of the second resistor bridge arm 12, the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1. When the first switching branch 21 connects the inverting input terminal Vin of the amplifier circuit 3 to the midpoint of the first resistor bridge arm 11, and the second switching branch 22 connects the non-inverting input terminal Vip of the amplifier circuit 3 to the midpoint of the second resistor bridge arm 12, the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0097] The first switching branch 21 here is a switching branch located between the first resistor bridge arm 11 and the amplifier circuit 3. The first switching branch 21 can be a branch composed of a single switching device or a branch composed of multiple switching devices. The midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip or the inverting input terminal Vin of the amplifier circuit 3 through the first switching branch 21. That is, under the control of the controller 5, the first switching branch 21 can control the midpoint of the first resistor bridge arm 11 to be connected to the non-inverting input terminal Vip or the inverting input terminal Vin of the amplifier circuit 3.

[0098] The second switching branch 22 here is a switching branch located between the second resistor bridge arm 12 and the amplifier circuit 3. The second switching branch 22 can be a branch composed of a single switching device or a branch composed of multiple switching devices. The midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip or the inverting input terminal Vin of the amplifier circuit 3 through the second switching branch 22. That is, under the control of the controller 5, the second switching branch 22 can control the midpoint of the second resistor bridge arm 12 to be connected to the non-inverting input terminal Vip or the inverting input terminal Vin of the amplifier circuit 3.

[0099] As an example, the active pen needs to perform steps one and two alternately as follows:

[0100] Step 1: Switching circuit 2 enters the first state based on the first control signal output by controller 5, so that the non-inverting input terminal Vip of amplifier circuit 3 is connected to the midpoint of the first resistor bridge arm 11 through the first switching branch 21, and the inverting input terminal Vin of amplifier circuit 3 is connected to the midpoint of the second resistor bridge arm 12 through the second switching branch 22. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of amplifier circuit 3 is the first positive voltage.

[0101] Step 2: Switching circuit 2 enters the second state based on the second control signal output by controller 5, so that the non-inverting input terminal Vip of amplifier circuit 3 is connected to the midpoint of the second resistor bridge arm 12 through the second switching branch 22, and the inverting input terminal Vin of amplifier circuit 3 is connected to the midpoint of the first resistor bridge arm 11 through the first switching branch 21. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of amplifier circuit 3 is the first reverse voltage.

[0102] Compared to the typical approach where the midpoints of the first resistor bridge arm 11 and the second resistor bridge arm 12 are fixedly connected to the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3, respectively, to output a fixed voltage to the amplifier circuit 3, this example places the first switching branch 21 between the midpoint of the first resistor bridge arm 11 and the amplifier circuit 3, and the second switching branch 22 between the midpoint of the second resistor bridge arm 12 and the amplifier circuit 3, alternately controlling the connection of either the midpoint of the first resistor bridge arm 11 or the midpoint of the second resistor bridge arm 12 to the non-inverting input terminal of the amplifier circuit 3. One terminal, Vip, is connected to the other terminal, Vin, which is the inverting input terminal of the amplifier circuit 3. This causes the strain gauge circuit 1 to output a first positive voltage and a first reverse voltage to the amplifier circuit 3 alternately. The first positive voltage and the first reverse voltage have opposite signs (i.e., opposite polarities) but the same absolute value. This achieves the effect of outputting voltage signals with opposite signs (i.e., opposite polarities) and the same absolute value to the amplifier circuit 3 alternately. This is equivalent to outputting a square wave signal to the detection chip, so that the detection chip can remove the noise signal brought in during the operation of the detection chip through demodulation and noise reduction processing, thereby ensuring the accuracy of the pressure value detected by the active pen.

[0103] In one embodiment, such as Figure 3 and Figure 5 As shown, the first switch branch 21 includes a first switch K1 and a second switch K2. The midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the first switch K1, and the midpoint of the first resistor bridge arm 11 is connected to the inverting input terminal Vin of the amplifier circuit 3 through the second switch K2. The second switch branch 22 includes a third switch K3 and a fourth switch K4. The midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the third switch K3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3 through the fourth switch K4. When the first switch K1 and the fourth switch K4 are turned on, the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1. When the second switch K2 and the third switch K3 are turned on, the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0104] In this circuit, the first switch K1 and the second switch K2 are two switches in the first switch branch 21, and the specific switch type is not limited. As an example, the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the first switch K1, and the midpoint of the first resistor bridge arm 11 is connected to the inverting input terminal Vin of the amplifier circuit 3 through the second switch K2. When the first switch K1 is on and the second switch K2 is off, the midpoint of the first resistor bridge arm 11 is electrically connected to the non-inverting input terminal Vip of the amplifier circuit 3. When the first switch K1 is off and the second switch K2 is on, the midpoint of the first resistor bridge arm 11 is electrically connected to the inverting input terminal Vin of the amplifier circuit 3.

[0105] In this circuit, the third switch K3 and the fourth switch K4 are two switches in the second switch branch 22, and the specific switch type is not limited. As an example, the midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the third switch K3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3 through the fourth switch K4. When the third switch K3 is on and the fourth switch K4 is off, the midpoint of the second resistor bridge arm 12 is electrically connected to the non-inverting input terminal Vip of the amplifier circuit 3. When the third switch K3 is off and the fourth switch K4 is on, the midpoint of the second resistor bridge arm 12 is electrically connected to the inverting input terminal Vin of the amplifier circuit 3.

[0106] As an example, the active pen needs to perform steps one and two alternately as follows:

[0107] Step 1: In response to the first control signal output by the controller 5, control the first switch K1 and the fourth switch K4 to be turned on, and the second switch K2 and the third switch K3 to be turned off, so that the midpoint of the first resistor bridge arm 11 is electrically connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the first switch K1, and the midpoint of the second resistor bridge arm 12 is electrically connected to the inverting input terminal Vin of the amplifier circuit 3 through the fourth switch K4. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first positive voltage.

[0108] Step 2: In response to the second control signal output by controller 5, control the second switch K2 and the third switch K3 to be turned on, and the first switch K1 and the fourth switch K4 to be turned off, so that the midpoint of the second resistor bridge arm 12 is electrically connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the third switch K3, and the midpoint of the first resistor bridge arm 11 is electrically connected to the inverting input terminal Vin of the amplifier circuit 3 through the second switch K2. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first reverse voltage.

[0109] In this example, the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 via the first switch K1 and the second switch K2, respectively; the midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 via the third switch K3 and the fourth switch K4, respectively; the switch circuit 2 formed by the four switches has a simple circuit structure, which allows the strain gauge circuit 1 to output a first positive voltage and a first reverse voltage with opposite signs (i.e., opposite polarities) and the same absolute value to the amplifier circuit 3 in an alternating manner, so as to modulate the signal output by the strain gauge circuit 1 to the amplifier circuit 3 into a square wave signal, so that the detection chip can receive the square wave signal, and the square wave signal can be demodulated by the detection chip to achieve noise reduction.

[0110] In one embodiment, such as Figure 4 and Figure 6 As shown, the first switch branch 21 includes a first single-pole double-throw switch K5. The moving end of the first single-pole double-throw switch K5 is connected to the midpoint of the first resistor bridge arm 11. The first stationary end of the first single-pole double-throw switch K5 is used to connect to the non-inverting input terminal Vip of the amplifier circuit 3, and the second stationary end of the first single-pole double-throw switch K5 is used to connect to the inverting input terminal Vin of the amplifier circuit 3. The second switch branch 22 includes a second single-pole double-throw switch K6. The moving end of the second single-pole double-throw switch K6 is connected to the midpoint of the second resistor bridge arm 12. The first stationary end of the second single-pole double-throw switch K6 is used to connect to the non-inverting input terminal Vin of the amplifier circuit 3. The second stationary terminal of the second single-pole double-throw switch K6 is connected to the non-inverting input terminal Vin of the amplifier circuit 3, and the moving terminal of the first single-pole double-throw switch K5 is connected to the first stationary terminal, and the moving terminal of the second single-pole double-throw switch K6 is connected to the second stationary terminal. When the moving terminal of the first single-pole double-throw switch K5 is connected to the first stationary terminal, and the moving terminal of the second single-pole double-throw switch K6 is connected to the second stationary terminal, the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1. When the moving terminal of the first single-pole double-throw switch K5 is connected to the second stationary terminal, and the moving terminal of the second single-pole double-throw switch K6 is connected to the first stationary terminal, the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0111] The first single-pole double-throw switch K5 here is used to connect the midpoint of the first resistor bridge arm 11 to the amplifier circuit 3, and the second single-pole double-throw switch K6 is used to connect the midpoint of the second resistor bridge arm 12 to the amplifier circuit 3.

[0112] As an example, the active pen needs to perform steps one and two alternately as follows:

[0113] Step 1: In response to the first control signal output by the controller 5, the moving end of the first single-pole double-throw switch K5 is connected to the first stationary end, and the moving end of the second single-pole double-throw switch K6 is connected to the second stationary end. This causes the midpoint of the first resistor bridge arm 11 to be electrically connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the first single-pole double-throw switch K5, and the midpoint of the second resistor bridge arm 12 to be electrically connected to the inverting input terminal Vin of the amplifier circuit 3 through the second single-pole double-throw switch K6. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first positive voltage.

[0114] Step 2: In response to the second control signal output by controller 5, the moving end of the first single-pole double-throw switch K5 is connected to the second stationary end, and the moving end of the second single-pole double-throw switch K6 is connected to the first stationary end. This causes the midpoint of the first resistor bridge arm 11 to be electrically connected to the inverting input terminal Vin of the amplifier circuit 3 through the first single-pole double-throw switch K5, and the midpoint of the second resistor bridge arm 12 to be electrically connected to the non-inverting input terminal Vip of the amplifier circuit 3 through the second single-pole double-throw switch K6. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first reverse voltage.

[0115] In this example, the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 through the first single-pole double-throw switch K5; the midpoint of the second resistor bridge arm 12 is connected to the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 through the second single-pole double-throw switch K6; the switching circuit 2 formed by the two single-pole double-throw switches has a simple circuit structure, which allows the strain gauge circuit 1 to output a first positive voltage and a first reverse voltage with opposite signs (i.e., opposite polarities) and the same absolute value to the amplifier circuit 3 in an alternating manner, so as to modulate the signal output by the strain gauge circuit 1 to the amplifier circuit 3 into a square wave signal, so that the detection chip can receive the square wave signal, and the square wave signal can be demodulated by the detection chip to achieve noise reduction.

[0116] In one embodiment, such as Figures 7-10 As shown, the detection chip is connected to the strain gauge circuit 1 in the active pen via a switching circuit 2. The strain gauge circuit 1 is used to detect the pressure of the strain gauge 103. The strain gauge circuit 1 includes a first resistor bridge arm 11 and a second resistor bridge arm 12. The midpoint of the first resistor bridge arm 11 is used to connect to the first end of the detection chip, and the midpoint of the second resistor bridge arm 12 is used to connect to the second end of the detection chip. The first end of the first resistor bridge arm 11 and the first end of the second resistor bridge arm 12 converge to form a first bus terminal, which is connected to the power supply terminal VCC or ground GND via the switching circuit 2. The second end of the first resistor bridge arm 11 and the second end of the second resistor bridge arm 12 converge to form a second bus terminal, which is connected to the power supply terminal VCC or ground GND via the switching circuit 2. When the switching circuit 2 is in the first state, the first bus terminal is connected to the power supply terminal VCC, and the second bus terminal is connected to ground GND. The detection chip receives the first positive voltage output by the strain gauge circuit 1. When the switching circuit 2 is in the second state, the first bus terminal is connected to ground GND, and the second bus terminal is connected to the power supply terminal VCC. The detection chip receives the first reverse voltage output by the strain gauge circuit 1.

[0117] As an example, the strain gauge circuit 1 includes a first resistor bridge arm 11 and a second resistor bridge arm 12. The first resistor bridge arm 11 includes a first resistor R1 and a second resistor R2 connected in series. The first end and the second end of the first resistor bridge arm 11 are its two ends, respectively, and the midpoint of the first resistor bridge arm 11 is the connection node between the first resistor R1 and the second resistor R2. The second resistor bridge arm 12 includes a third resistor R3 and a fourth resistor R4 connected in series. The first end and the second end of the second resistor bridge arm 12 are its two ends, respectively, and the midpoint of the second resistor bridge arm 12 is the connection node between the third resistor R3 and the fourth resistor R4. In this example, the first end of the first resistor bridge arm 11 and the first end of the second resistor bridge arm 12 merge to form a first bus terminal, and the second end of the first resistor bridge arm 11 and the second end of the second resistor bridge arm 12 merge to form a second bus terminal.

[0118] As an example, the active pen needs to perform steps one and two alternately as follows:

[0119] Step 1: Switching circuit 2 enters the first state based on the first control signal output by controller 5, so that the first bus terminal is connected to the power supply terminal VCC and the second bus terminal is connected to ground GND, so that the current of strain circuit 1 flows from the first bus terminal to the second bus terminal. At this time, the voltage between the first terminal and the second terminal of the detection chip is the first positive voltage, so that the detection chip can receive the first positive voltage output by strain circuit 1.

[0120] Step 2: Switching circuit 2 enters the second state based on the second control signal output by controller 5, so that the second bus terminal is connected to the power supply terminal VCC and the first bus terminal is connected to ground GND, so that the current of strain circuit 1 flows from the second bus terminal to the first bus terminal. At this time, the voltage between the first terminal and the second terminal of the detection chip is the first reverse voltage, so that the detection chip can receive the first reverse voltage output by strain circuit 1.

[0121] In one embodiment, the first resistor bridge arm 11 includes a first resistor R1 and a second resistor R2 connected in series, with the connection node between the first resistor R1 and the second resistor R2 being the midpoint of the first resistor bridge arm 11; the second resistor bridge arm 12 includes a third resistor R3 and a fourth resistor R4 connected in series, with the connection node between the third resistor R3 and the fourth resistor R4 being the midpoint of the second resistor bridge arm 12; the detection chip includes an amplifier circuit 3, with the non-inverting input terminal Vip of the amplifier circuit 3 connected to the midpoint of the first resistor bridge arm 11 and the inverting input terminal Vin of the amplifier circuit 3 connected to the midpoint of the second resistor bridge arm 12; when the switching circuit 2 is in the first state, the first bus terminal is connected to the power supply terminal VCC, the second bus terminal is connected to ground GND, and the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1; when the switching circuit 2 is in the second state, the first bus terminal is connected to ground GND, the second bus terminal is connected to the power supply terminal VCC, and the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0122] As an example, when the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3, if the first bus terminal formed by the confluence of the first end of the first resistor bridge arm 11 and the first end of the second resistor bridge arm 12 is connected to the power supply terminal VCC, and the second bus terminal formed by the confluence of the second end of the first resistor bridge arm 11 and the second end of the second resistor bridge arm 12 is connected to ground GND, the current flows from the first end to the second end of the two resistor bridge arms. At this time, the strain gauge circuit 1 can output a first positive voltage to the amplifier circuit 3. If the first bus terminal formed by the confluence of the first end of the first resistor bridge arm 11 and the first end of the second resistor bridge arm 12 is connected to ground GND, and the second bus terminal formed by the confluence of the second end of the first resistor bridge arm 11 and the second end of the second resistor bridge arm 12 is connected to the power supply terminal VCC, the current flows from the second end to the first end of the two resistor bridge arms. At this time, the strain gauge circuit 1 can output a first reverse voltage to the amplifier circuit 3. Generally, during the forward and reverse conduction processes of strain gauge circuit 1, the first positive voltage and the first reverse voltage output to amplifier circuit 3 have opposite signs (i.e. opposite polarities) but the same absolute value.

[0123] As an example, the active pen needs to perform steps one and two alternately as follows:

[0124] Step 1: Switching circuit 2 enters the first state based on the first control signal output by controller 5, so that the first bus terminal is connected to the power supply terminal VCC and the second bus terminal is connected to ground GND, so that the current of strain circuit 1 flows from the first bus terminal to the second bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of amplifier circuit 3 is the first positive voltage.

[0125] Step 2: Switching circuit 2 enters the second state based on the second control signal output by controller 5, so that the second bus terminal is connected to the power supply terminal VCC and the first bus terminal is connected to ground GND, so that the current of strain circuit 1 flows from the second bus terminal to the first bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of amplifier circuit 3 is the first reverse voltage.

[0126] For example, when the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3, if the first bus terminal formed by the first ends of the two resistor bridge arms is connected to the power supply terminal VCC, and the second bus terminal formed by the second ends of the two resistor bridge arms is connected to ground GND, then the voltage Vip at the non-inverting input terminal Vip of the amplifier circuit 3 is 0.9V, and the voltage Vin at the inverting input terminal Vin of the amplifier circuit 3 is 0.8V. Therefore, the first positive voltage input to the amplifier circuit 3 is = Vip - Vin = 0.1V. If the first bus terminal formed by the first ends of the two resistor bridge arms is connected to ground GND... D. The second bus terminal formed by the second ends of the two resistor bridge arms is connected to the power supply terminal VCC. At this time, the voltage Vip at the non-inverting input terminal Vip of amplifier circuit 3 is 0.9V, and the voltage Vin at the inverting input terminal Vin of amplifier circuit 3 is 1V. Therefore, the first reverse voltage input to amplifier circuit 3 is Vip - Vin = -0.1V, which makes the first positive voltage and the first reverse voltage input to amplifier circuit 3 opposite in sign (i.e., opposite in polarity) but the same in absolute value. This is equivalent to outputting a square wave signal to the detection chip, so that the detection chip can remove the noise signal introduced during the operation of the detection chip through demodulation and noise reduction processing, thereby ensuring the accuracy of the detected pressure value of the active pen.

[0127] In one embodiment, such as Figures 7-10 As shown, the switching circuit 2 includes a first switching branch 21 and a second switching branch 22; a first bus terminal is connected to the power supply terminal VCC or ground GND through the first switching branch 21; a second bus terminal is connected to the power supply terminal VCC or ground GND through the second switching branch 22; when the first switching branch 21 is connected to the first bus terminal and the power supply terminal VCC, and the second switching branch 22 is connected to the second bus terminal and ground GND, the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1; when the first switching branch 21 is connected to the first bus terminal and ground GND, and the second switching branch 22 is connected to the second bus terminal and the power supply terminal VCC, the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0128] The first switching branch 21 here is a switching branch located between the first resistor bridge arm 11 and the amplifier circuit 3. The first switching branch 21 can be a branch composed of a single switching device or a branch composed of multiple switching devices. The first bus terminal is connected to the power supply terminal VCC or ground GND through the first switching branch 21. That is, the first switching branch 21 can control the first bus terminal to be connected to the power supply terminal VCC or ground GND under the control of the controller 5.

[0129] The second switching branch 22 here is a switching branch located between the second resistor bridge arm 12 and the amplifier circuit 3. The second switching branch 22 can be a branch composed of a single switching device or a branch composed of multiple switching devices. The second bus terminal is connected to the power supply terminal VCC or ground GND through the second switching branch 22. That is, the second switching branch 22 can control the second bus terminal to be connected to the power supply terminal VCC or ground GND under the control of the controller 5.

[0130] As an example, the active pen needs to perform steps one and two alternately as follows:

[0131] Step 1: In response to the first control signal output by the controller 5, the first bus terminal is connected to the power supply terminal VCC through the first switch branch 21, and the second bus terminal is connected to ground GND through the second switch branch 22, so that the current of the strain gauge circuit 1 flows from the first bus terminal to the second bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first positive voltage.

[0132] Step 2: In response to the second control signal output by the controller 5, the second bus terminal is connected to the power supply terminal VCC through the second switch branch 22, and the first bus terminal is connected to ground GND through the first switch branch 21, so that the current of the strain circuit 1 flows from the second bus terminal to the first bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first reverse voltage.

[0133] Compared to the typical approach where the first and second bus terminals are fixedly connected to the power supply terminal VCC and ground GND respectively, so that they output a fixed voltage to the amplifier circuit 3, in this example, the first switch branch 21 is set between the first bus terminal, the power supply terminal VCC, and ground GND, and the second switch branch 22 is set between the second bus terminal, the power supply terminal VCC, and ground GND. Either the first or second bus terminal is alternately connected to the power supply terminal VCC, and the other is connected to ground GND. This causes the strain gauge circuit 1 to alternately output a first positive voltage and a first reverse voltage to the amplifier circuit 3. The first positive voltage and the first reverse voltage have opposite signs (i.e., opposite polarities) but the same absolute value. This achieves the alternate output of voltage signals with opposite signs (i.e., opposite polarities) and the same absolute value to the amplifier circuit 3, modulating the signal output from the strain gauge circuit 1 to the amplifier circuit 3 into a square wave signal. This square wave signal can be received by the detection chip and demodulated by the detection chip to achieve noise reduction.

[0134] In one embodiment, such as Figure 7 and Figure 9As shown, the first switch branch 21 includes a first switch K1 and a second switch K2. The first bus terminal is connected to the power supply terminal VCC through the first switch K1, and the first bus terminal is connected to ground GND through the second switch K2. The second switch branch 22 includes a third switch K3 and a fourth switch K4. The second bus terminal is connected to the power supply terminal VCC through the third switch K3, and the second bus terminal is connected to ground GND through the fourth switch K4. When the first switch K1 and the fourth switch K4 are turned on, the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1. When the second switch K2 and the third switch K3 are turned on, the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0135] In this circuit, the first switch K1 and the second switch K2 are two switches in the first switch branch 21, and the specific switch type is not limited. As an example, the first bus terminal is connected to the power supply terminal VCC through the first switch K1, and the first bus terminal is connected to ground GND through the second switch K2. When the first switch K1 is turned on and the second switch K2 is turned off, the first bus terminal is electrically connected to the power supply terminal VCC. When the first switch K1 is turned off and the second switch K2 is turned on, the first bus terminal is electrically connected to ground GND.

[0136] In this circuit, the third switch K3 and the fourth switch K4 are two switches in the second switch branch 22, and the specific switch type is not limited. As an example, the second bus terminal is connected to the power supply terminal VCC through the third switch K3, and the second bus terminal is connected to ground GND through the fourth switch K4. When the third switch K3 is on and the fourth switch K4 is off, the second bus terminal is electrically connected to the power supply terminal VCC; when the third switch K3 is off and the fourth switch K4 is on, the second bus terminal is electrically connected to ground GND.

[0137] As an example, the active pen needs to perform steps one and two alternately as follows:

[0138] Step 1: In response to the first control signal output by the controller 5, control the first switch K1 and the fourth switch K4 to be turned on, and the second switch K2 and the third switch K3 to be turned off, so that the current of the strain circuit 1 flows from the first bus terminal to the second bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first positive voltage.

[0139] Step 2: In response to the second control signal output by the controller 5, control the second switch K2 and the third switch K3 to turn on, and the first switch K1 and the fourth switch K4 to turn off, so that the current of the strain circuit 1 flows from the second bus terminal to the first bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first reverse voltage.

[0140] In this example, the first bus terminal is connected to the power supply terminal VCC and ground GND through the first switch K1 and the second switch K2, respectively; the second bus terminal is connected to the power supply terminal VCC and ground GND through the third switch K3 and the fourth switch K4, respectively. The switch circuit 2 formed by the four switches has a simple circuit structure, which allows the strain gauge circuit 1 to output first positive voltage and first reverse voltage with opposite signs (i.e., opposite polarities) to the amplifier circuit 3 in an alternating manner. The first positive voltage and the first reverse voltage have opposite signs (i.e., opposite polarities) but the same absolute value, so as to realize the alternating output of voltage signals with opposite signs (i.e., opposite polarities) and the same absolute value to the amplifier circuit 3, so as to modulate the signal output by the strain gauge circuit 1 to the amplifier circuit 3 into a square wave signal, so that the detection chip can receive the square wave signal. The square wave signal can be demodulated by the detection chip to achieve the purpose of noise reduction.

[0141] In one embodiment, such as Figure 8 and Figure 10 As shown, the first switch branch 21 includes a first single-pole double-throw switch K5. The moving end of the first single-pole double-throw switch K5 is connected to the first bus terminal. The first stationary end of the first single-pole double-throw switch K5 is used to connect to the power supply terminal VCC, and the second stationary end of the first single-pole double-throw switch K5 is used to connect to ground GND. The second switch branch 22 includes a second single-pole double-throw switch K6. The moving end of the second single-pole double-throw switch K6 is connected to the second bus terminal. The first stationary end of the second single-pole double-throw switch K6 is used to connect to the power supply terminal VCC, and the second stationary end of the second single-pole double-throw switch K6 is used to connect to ground GND. When the moving end of the first single-pole double-throw switch K5 is connected to the first stationary end, and the moving end of the second single-pole double-throw switch K6 is connected to the second stationary end, the amplifier circuit 3 receives the first positive voltage output by the strain gauge circuit 1. When the moving end of the first single-pole double-throw switch K5 is connected to the second stationary end, and the moving end of the second single-pole double-throw switch K6 is connected to the first stationary end, the amplifier circuit 3 receives the first reverse voltage output by the strain gauge circuit 1.

[0142] The first single-pole double-throw switch K5 here is used to connect the first bus terminal, the power supply terminal VCC and ground GND. The second single-pole double-throw switch K6 is used to connect the second bus terminal, the power supply terminal VCC and ground GND.

[0143] As an example, the active pen needs to perform steps one and two alternately as follows:

[0144] Step 1: In response to the first control signal output by controller 5, the moving end of the first single-pole double-throw switch K5 is connected to the first stationary end, and the moving end of the second single-pole double-throw switch K6 is connected to the second stationary end. This makes the first bus terminal electrically connected to the power supply terminal VCC through the first single-pole double-throw switch K5, and the second bus terminal electrically connected to ground GND through the second single-pole double-throw switch K6. This causes the current of the strain gauge circuit 1 to flow from the first bus terminal to the second bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first positive voltage.

[0145] Step 2: In response to the second control signal output by controller 5, the moving end of the first single-pole double-throw switch K5 is connected to the second stationary end, and the moving end of the second single-pole double-throw switch K6 is connected to the first stationary end, so that the second bus terminal is electrically connected to the power supply terminal VCC through the second single-pole double-throw switch K6, and the first bus terminal is connected to ground through the first single-pole double-throw switch K5, so that the current of the strain gauge circuit 1 flows from the second bus terminal to the first bus terminal. At this time, the voltage between the non-inverting input terminal Vip and the inverting input terminal Vin of the amplifier circuit 3 is the first reverse voltage.

[0146] In this example, the first bus terminal is connected to the power supply terminal VCC and ground GND through the first single-pole double-throw switch K5; the midpoint of the second resistor bridge arm 12 is connected to the power supply terminal VCC and ground GND through the second single-pole double-throw switch K6; the switching circuit 2 formed by the two single-pole double-throw switches has a simple circuit structure, which allows the strain gauge circuit 1 to output first positive voltage and first reverse voltage with opposite signs (i.e. opposite polarities) to the amplifier circuit 3 in an alternating manner. The first positive voltage and the first reverse voltage have opposite signs (i.e. opposite polarities) but the same absolute value, so as to realize the alternating output of voltage signals with opposite signs (i.e. opposite polarities) and the same absolute value to the amplifier circuit 3, so as to modulate the signal output by the strain gauge circuit 1 to the amplifier circuit 3 into a square wave signal, so that the detection chip can receive the square wave signal. The square wave signal can be demodulated by the detection chip to achieve the purpose of noise reduction.

[0147] In one embodiment, the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 are switching transistors of the same type and with the same on-resistance.

[0148] As an example, the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 are switches of the same type and with the same on-resistance, in order to avoid introducing new interference signals due to different types and / or different on-resistances, which would cause the absolute values ​​of the first positive voltage and the first reverse voltage of the interleaved input to be different, affecting the subsequent sampling and recognition process.

[0149] In one embodiment, the switching transistor is a MOSFET or a bipolar transistor.

[0150] In this example, the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 can all be MOSFETs or transistors, depending on the specific circumstances. The MOSFETs can be NMOS or PMOS, again depending on the actual situation.

[0151] In one embodiment, such as Figure 3 , Figure 5 , Figure 7 and Figure 10 As shown, the detection chip also includes an ADC converter 4 and a controller 5; the amplifier circuit 3 is used to amplify the first positive voltage and the noise voltage, outputting a second positive voltage, and to amplify the first reverse voltage and the noise voltage, outputting a second reverse voltage; the ADC converter 4 is connected to the amplifier circuit 3 and is used to demodulate and reduce noise on the second positive voltage and the second reverse voltage to determine the third positive voltage and the third reverse voltage; the controller 5 is connected to the switch circuit 2 and the ADC converter 4 and is used to control the switch circuit 2 to alternately enter the first state and the second state, and to determine the pressure value of the active pen based on the third positive voltage and the third reverse voltage.

[0152] The second forward voltage is the voltage output by amplifier circuit 3 after amplifying the first forward voltage and its inherent noise voltage, and can be represented by V2(+). The second reverse voltage is the voltage output by amplifier circuit 3 after amplifying the first reverse voltage and its inherent noise voltage, and can be represented by V2(-). The noise voltage is the voltage formed by the noise inherent in amplifier circuit 3 during its operation, and can be represented by Vn. Generally speaking, the inherent noise voltages of amplifier circuit 3 are basically similar during the amplification process of the first forward voltage and the first reverse voltage.

[0153] As an example, the detection chip includes an amplifier circuit 3, an ADC converter 4, and a controller 5, and its pressure detection process is as follows:

[0154] Amplifier circuit 3 is connected to strain gauge circuit 1 via switch circuit 2, or directly connected to strain gauge circuit 1. It can receive the first positive voltage and the first reverse voltage output alternately from strain gauge circuit 1. When amplifier circuit 3 receives the first positive voltage, it amplifies the first positive voltage and its inherent noise voltage, outputting a second positive voltage to ADC converter 4. Similarly, when amplifier circuit 3 receives the first reverse voltage, it amplifies the first reverse voltage and its inherent noise voltage, outputting a second reverse voltage to ADC converter 4. In this example, amplifier circuit 3 receives the first positive voltage and the first reverse voltage alternately via switch circuit 2, which is equivalent to receiving a modulated square wave signal and amplifying it. The alternately output second positive voltage and second reverse voltage are equivalent to an amplified square wave signal, which is the superposition of the amplified signal corresponding to the square wave signal and the amplified signal corresponding to the noise voltage.

[0155] For example, after receiving the first positive voltage output by the strain gauge circuit 1, the amplifier circuit 3 amplifies the first positive voltage V1(+) and the noise voltage Vn formed by its own noise. The voltage after amplification is determined as the second positive voltage V2(+), and the second positive voltage V2(+) is output to the ADC converter 4. That is, V2(+) = Amp_V1(+) + Amp_Vn, where Amp_V1(+) is the voltage after amplification of the first positive voltage V1(+), and Amp_Vn is the voltage after amplification of the noise voltage. After receiving the first positive voltage from the interleaved output of the strain circuit 1, the amplifier circuit 3 amplifies the first inverted voltage V1(-) and the noise voltage Vn formed by its own noise. The voltage after amplification is determined as the second inverted voltage V2(-), and the second inverted voltage V2(-) is output to the ADC converter 4. That is, V2(-) = Amp_V1(-) + Amp_Vn, where Amp_V1(-) is the voltage after amplification of the first inverted voltage V1(-), and Amp_Vn is the voltage after amplification of the noise voltage.

[0156] The ADC converter 4 can demodulate and reduce noise in the amplified square wave signal output from the amplifier circuit 3. Specifically, it can perform quadrature demodulation or square wave demodulation on the second forward voltage and the second reverse voltage in the amplified square wave signal, respectively, and output the noise-reduced third forward voltage and third reverse voltage to filter out the interference of the noise signal inherent in the amplifier circuit 3 and improve the signal-to-noise ratio of the output signal of the ADC converter 4. The third forward voltage is the voltage determined after demodulating and reducing noise in the second forward voltage, and can be represented by V3(+). The third reverse voltage is the voltage determined after demodulating and reducing noise in the second reverse voltage, and can be represented by V3(-).

[0157] After receiving the third positive voltage V3(+) and the third reverse voltage V3(-) output by the ADC converter 4, the controller 5 can invoke its built-in pressure calculation logic to calculate the pressure value of the active pen based on these voltages. In this example, since the third positive voltage V3(+) and the third reverse voltage V3(-) output by the ADC converter 4 are demodulated and noise-reduced voltages, the pressure value calculated by the controller 5 is the noise-reduced pressure value, which improves the detected pressure level and ensures the accuracy of pressure detection.

[0158] In one embodiment, the controller 5 is used to perform differential processing on the third positive voltage and the third reverse voltage to determine the voltage difference, and based on half of the voltage difference, determine the pressure value of the active pen.

[0159] The controller 5 performs differential processing on the third positive voltage V3(+) and the third reverse voltage V3(-) output by the ADC converter 4 to determine the voltage difference between the two. Half of this voltage difference is determined as the corresponding sampling voltage, i.e., sampling voltage = (V3(+) - V3(-)) / 2. The sampling voltage is converted from voltage to pressure to determine the pressure value of the active pen. This sampling voltage can eliminate the noise influence of the amplifier circuit 3, improve the detected pressure level, and ensure the accuracy of pressure detection.

[0160] For example, when the first end of the two resistor bridge arms is connected to the power supply terminal VCC and the second end of the two resistor bridge arms is grounded, and the midpoint of the first resistor bridge arm 11 is connected to the non-inverting input terminal Vip of the amplifier circuit 3, and the midpoint of the second resistor bridge arm 12 is connected to the inverting input terminal Vin of the amplifier circuit 3, the voltage Vip at the non-inverting input terminal Vip of the amplifier circuit 3 is 0.9V, and the voltage Vin at the inverting input terminal Vin of the amplifier circuit 3 is 0.8V. Therefore, the first positive voltage input to the amplifier circuit 3 is = Vip - Vin = 0.1V; the voltage at the midpoint of the second resistor bridge arm 12 is connected to the amplifier circuit... When the non-inverting input terminal Vip of amplifier circuit 3 is connected, and the midpoint of the first resistor bridge arm 11 is connected to the inverting input terminal Vin of amplifier circuit 3, the voltage Vip at the non-inverting input terminal Vip of amplifier circuit 3 is 0.9V, and the voltage Vin at the inverting input terminal Vin of amplifier circuit 3 is 1V. Then, the first reverse voltage input to amplifier circuit 3 is Vip - Vin = -0.1V, which makes the first positive voltage and the first reverse voltage input to amplifier circuit 3 have opposite signs and the same absolute value, so that the first positive voltage -0.1V and the first reverse voltage 0.1V can be used for noise reduction processing later. When the amplification factor of amplifier circuit 3 is k and the noise voltage of amplifier circuit 3 is Vn, amplifier circuit 3 amplifies the first positive voltage 0.1V and the noise voltage Vn, and then outputs the second positive voltage V2(+) to ADC converter 4, V2(+) = k * (0.1V + Vn). Amplifier circuit 3 amplifies the first reverse voltage -0.1V and the noise voltage Vn, and then outputs the second reverse voltage V2(-) to ADC converter 4, V2(-) = k * (-0.1V + Vn). ADC converter 4 demodulates and reduces noise from the second positive voltage V2(+) and the second reverse voltage V2(-), and determines the corresponding third positive voltage V3(+) and third reverse voltage V3(-). When the demodulation and noise reduction coefficient of DC converter 4 is s, V3(+)=s*V2(+)=s*k*(0.1V+Vn), V3(-)=s*V2(-)=s*k*(-0.1V+Vn). The difference between V3(+) and V3(-) is calculated so that the calculated voltage difference can eliminate the interference of the amplified noise voltage k*Vn. Half of this voltage difference is determined as the sampling voltage, that is, the sampling voltage is s*k*0.1V or -s*k*0.1V, so that the sampling voltage can eliminate the noise influence of the amplifier circuit 3 itself. The sampling voltage after noise reduction is converted to determine the pressure value of the active pen, which can improve the detected pressure level and ensure the accuracy of pressure detection.

[0161] In one embodiment, the controller 5 is used to alternately output a first control signal and a second control signal to the switching circuit 2 based on the target frequency, so that the switching circuit 2 alternately enters the first state and the second state, and outputs the target frequency to the ADC converter 4; the ADC converter 4 performs quadrature demodulation or square wave demodulation on the second forward voltage and the second reverse voltage based on the target frequency, determines the third forward voltage and the third reverse voltage, and sends the third forward voltage and the third reverse voltage to the controller 5.

[0162] The target frequency is the frequency at which the first control signal and the second control signal are alternately output to the switching circuit 2. The target frequency can be a preset fixed frequency or a dynamic frequency determined autonomously according to the actual situation.

[0163] As an example, the detection chip also includes a controller 5, which is located within the detection chip and needs to be electrically connected to the switching circuit 2 and the ADC converter 4. In this example, the controller 5 can output a first control signal and a second control signal to the switching circuit 2 alternately based on the target frequency. The first control signal can cause the switching circuit 2 to enter a first state, causing the strain gauge circuit 1 to output a first positive voltage to the amplification circuit 3. The second control signal can cause the switching circuit 2 to enter a second state, causing the strain gauge circuit 1 to output a first reverse voltage to the amplification circuit 3. The amplification circuit 3 then amplifies the first positive voltage and the first reverse voltage, and outputs a second positive voltage and a second reverse voltage, respectively. In this example, the controller 5 also needs to output the target frequency to the ADC converter 4, so that the ADC converter 4 can demodulate and reduce the noise of the second positive voltage and the second reverse voltage based on the target frequency, and output a third positive voltage and a third reverse voltage to the controller 5. The controller 5 can then determine the pressure value of the active pen based on the third positive voltage and the third reverse voltage. Understandably, when the controller 5 controls the operation of the switching circuit 2 based on the target frequency, it enables the amplifier circuit 3 to receive the square wave signal corresponding to the target frequency, and sends the target frequency to the ADC converter 4, providing the ADC converter 4 with the preconditions for demodulation and noise reduction, so as to ensure the reliability of the scheme.

[0164] In one embodiment, the target frequency is a first frequency or a second frequency, wherein the first frequency is greater than the second frequency; the controller 5 is also used to obtain the current state of the active pen; when the current state is the working state, the controller outputs a first control signal and a second control signal to the switching circuit 2 in an alternating manner based on the first frequency; when the current state is the sleep state, the controller outputs a first control signal and a second control signal to the switching circuit 2 in an alternating manner based on the second frequency.

[0165] The first frequency and the second frequency are two preset frequencies. The first frequency is greater than the second frequency, which means that the time interval between the interleaved output of the first control signal and the second control signal at the first frequency is less than the time interval between the interleaved output of the first control signal and the second control signal at the second frequency.

[0166] As an example, controller 5 obtains the current state of the active pen through a built-in detection module or detection pin. When the current state is the working state, it outputs the first control signal and the second control signal to the switching circuit 2 alternately based on the first frequency, that is, it outputs the first control signal and the second control signal alternately based on a short time interval, so that the pressure detection process is more frequent, which helps to ensure the timeliness of the response of subsequent control based on the pressure value of the active pen. When the current state is the sleep state, it outputs the first control signal and the second control signal to the switching circuit 2 alternately based on the second frequency, that is, it outputs the first control signal and the second control signal alternately based on a longer time interval, which helps to save energy when the active pen is in the sleep state.

[0167] In one embodiment, such as Figure 4 , Figure 6 , Figure 8 and Figure 9 As shown, the detection chip also includes an ADC converter 4, which is adapted to connect to a controller 5. The controller 5 is connected to a switching circuit 2 and is used to control the switching circuit 2 to alternately enter the first state or the second state. The amplifier circuit 3 is used to amplify the first positive voltage and the noise voltage and output the third positive voltage, and to amplify the first reverse voltage and the noise voltage and output the third reverse voltage. The ADC converter 4 is connected to the amplifier circuit 3 and is used to demodulate and reduce noise from the third positive voltage and the third reverse voltage, determine the third positive voltage and the third reverse voltage, and send the third positive voltage and the third reverse voltage to the controller 5 so that the controller 5 can determine the pressure value of the active pen based on the third positive voltage and the third reverse voltage.

[0168] As an example, the detection chip includes an amplifier circuit 3 and an ADC converter 4. The ADC converter 4 is connected to a controller 5 located outside the detection chip, and its pressure detection process is as follows:

[0169] Amplifier circuit 3 is connected to strain gauge circuit 1 via switch circuit 2, or directly connected to strain gauge circuit 1. It can receive the first positive voltage and the first reverse voltage output alternately from strain gauge circuit 1. When amplifier circuit 3 receives the first positive voltage, it amplifies the first positive voltage and its inherent noise voltage, outputting a second positive voltage to ADC converter 4. Similarly, when amplifier circuit 3 receives the first reverse voltage, it amplifies the first reverse voltage and its inherent noise voltage, outputting a second reverse voltage to ADC converter 4. In this example, amplifier circuit 3 receives the first positive voltage and the first reverse voltage alternately via switch circuit 2, which is equivalent to receiving a modulated square wave signal and amplifying it. The alternately output second positive voltage and second reverse voltage are equivalent to an amplified square wave signal, which is the superposition of the amplified signal corresponding to the square wave signal and the amplified signal corresponding to the noise voltage.

[0170] For example, after receiving the first positive voltage output by the strain gauge circuit 1, the amplifier circuit 3 amplifies the first positive voltage V1(+) and the noise voltage Vn formed by its own noise. The voltage after amplification is determined as the second positive voltage V2(+), and the second positive voltage V2(+) is output to the ADC converter 4. That is, V2(+) = Amp_V1(+) + Amp_Vn, where Amp_V1(+) is the voltage after amplification of the first positive voltage V1(+), and Amp_Vn is the voltage after amplification of the noise voltage. After receiving the first positive voltage from the interleaved output of the strain circuit 1, the amplifier circuit 3 amplifies the first inverted voltage V1(-) and the noise voltage Vn formed by its own noise. The voltage after amplification is determined as the second inverted voltage V2(-), and the second inverted voltage V2(-) is output to the ADC converter 4. That is, V2(-) = Amp_V1(-) + Amp_Vn, where Amp_V1(-) is the voltage after amplification of the first inverted voltage V1(-), and Amp_Vn is the voltage after amplification of the noise voltage.

[0171] The ADC converter 4 can demodulate and reduce noise in the amplified square wave signal output by the amplifier circuit 3. Specifically, it can perform quadrature demodulation or square wave demodulation on the second forward voltage and the second reverse voltage in the amplified square wave signal, and output the noise-reduced third forward voltage and third reverse voltage to the controller 5 to filter out the interference of the noise signal of the amplifier circuit 3 and improve the signal-to-noise ratio of the output signal of the ADC converter 4.

[0172] After receiving the third positive voltage V3(+) and the third reverse voltage V3(-) output by the ADC converter 4, the controller 5 can invoke its built-in pressure calculation logic to calculate the pressure value of the active pen based on these voltages. The specific processing procedure is the same as in the above embodiment, and will not be repeated here to avoid repetition. In this example, since the third positive voltage V3(+) and the third reverse voltage V3(-) output by the ADC converter 4 are demodulated and noise-reduced voltages, the pressure value of the active pen calculated by the controller 5 is the noise-reduced pressure value, which can improve the detected pressure level and ensure the accuracy of pressure detection.

[0173] In one embodiment, the switching circuit 2 is disposed inside the detection chip or outside the detection chip.

[0174] As an example, such as Figure 3 , Figure 4 , Figure 7 and Figure 8 As shown, the switching circuit 2 can be set inside the detection chip, such as... Figure 5 , Figure 6 , Figure 9 and Figure 10 As shown, the switch circuit 2 can also be set outside the detection chip, which can be determined independently according to the actual situation.

[0175] This utility model embodiment provides an active pen, including a strain circuit 1 and a detection chip as described in the above embodiment; the strain circuit 1 is used to detect the pressure of the strain gauge 103; the detection chip is connected to the strain circuit 1 through a switching circuit 2, and is used to determine the pressure value of the active pen based on the first positive voltage and the first reverse voltage alternately output by the strain circuit 1 through the switching circuit 2.

[0176] As an example, the detection chip can receive the first positive voltage output by the strain circuit 1 through the switching circuit 2 at the first moment, and the first reverse voltage output by the strain circuit 1 through the switching circuit 2 at the second moment. When the strain circuit 1 outputs the first positive voltage and the first reverse voltage alternately, since the first positive voltage and the first reverse voltage have opposite signs (i.e. opposite polarities) and the same absolute value, it is equivalent to the strain circuit 1 outputting a modulated square wave signal to the detection chip. After detecting the square wave signal output by the strain circuit 1, the detection chip can demodulate and reduce the noise of the square wave signal to determine the pressure value of the active pen, which can improve the detected pressure level and ensure the accuracy of pressure detection.

[0177] In this example, the detection chip is connected to the strain circuit 1 via the switching circuit 2. The switching circuit 2 can change the conduction direction between the strain circuit 1 and the detection chip, so that when the strain circuit 1 is forward-biased, it outputs a first positive voltage to the detection chip, and when the strain circuit 1 is reverse-biased, it outputs a first reverse voltage to the detection chip. The first positive voltage and the first reverse voltage are alternately output to the detection chip, which is equivalent to modulating the signal output from the strain circuit 1 to the detection chip to form a square wave signal. This allows the detection chip to remove noise signals introduced during the operation of the detection chip through demodulation and noise reduction processing, thereby ensuring the accuracy of the pressure value detected by the active pen.

[0178] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. A detection chip, suitable for use on an active pen, characterized in that, The detection chip is connected with a strain circuit in the active pen through a switch circuit, and the strain circuit is used for sensing pressure of a pen tip; The strain circuit comprises a first resistance bridge arm and a second resistance bridge arm; a first end of the first resistance bridge arm is used for connecting a power supply end, and a second end of the first resistance bridge arm is used for connecting a ground; a first end of the second resistance bridge arm is used for connecting the power supply end, and a second end of the second resistance bridge arm is used for connecting the ground; When the switch circuit is in a first state, a first end of the detection chip is connected with a midpoint of the first resistance bridge arm, and a second end of the detection chip is connected with a midpoint of the second resistance bridge arm, so that the detection chip receives a first forward voltage output by the strain circuit; When the switch circuit is in a second state, the second end of the detection chip is connected with the midpoint of the first resistance bridge arm, and the first end of the detection chip is connected with the midpoint of the second resistance bridge arm, so that the detection chip receives a first reverse voltage output by the strain circuit.

2. The detection chip according to claim 1, characterized in that, The first resistance bridge arm comprises a first resistance and a second resistance arranged in series, and a connection node between the first resistance and the second resistance is the midpoint of the first resistance bridge arm; the second resistance bridge arm comprises a third resistance and a fourth resistance arranged in series, and a connection node between the third resistance and the fourth resistance is the midpoint of the second resistance bridge arm; The detection chip comprises an amplification circuit, a non-inverted input end of the amplification circuit is connected with the midpoint of the first resistance bridge arm or the midpoint of the second resistance bridge arm through the switch circuit, and an inverted input end of the amplification circuit is connected with the midpoint of the first resistance bridge arm or the midpoint of the second resistance bridge arm through the switch circuit; When the switch circuit is in the first state, the non-inverted input end of the amplification circuit is connected with the midpoint of the first resistance bridge arm, and the inverted input end of the amplification circuit is connected with the midpoint of the second resistance bridge arm, so that the amplification circuit receives the first forward voltage output by the strain circuit; When the switch circuit is in the second state, the non-inverted input end of the amplification circuit is connected with the midpoint of the second resistance bridge arm, and the inverted input end of the amplification circuit is connected with the midpoint of the first resistance bridge arm, so that the amplification circuit receives the first reverse voltage output by the strain circuit.

3. The detection chip of claim 2, wherein, The switch circuit comprises a first switch branch and a second switch branch; The midpoint of the first resistance bridge arm is connected with the non-inverted input end of the amplification circuit or the inverted input end of the amplification circuit through the first switch branch; The midpoint of the second resistance bridge arm is connected with the non-inverted input end of the amplification circuit or the inverted input end of the amplification circuit through the second switch branch; When the first switch branch is connected with the non-inverted input end of the amplification circuit and the midpoint of the first resistance bridge arm, and the second switch branch is connected with the inverted input end of the amplification circuit and the midpoint of the second resistance bridge arm, the amplification circuit receives the first forward voltage output by the strain circuit; The midpoint of the first resistance bridge arm is connected to the inverting input end of the amplification circuit through the first switch branch, the midpoint of the second resistance bridge arm is connected to the non-inverting input end of the amplification circuit through the second switch branch, and the amplification circuit receives a first reverse voltage output by the strain circuit.

4. The detection chip of claim 3, wherein, The first switch branch comprises a first switch and a second switch, the midpoint of the first resistance bridge arm is connected to the non-inverting input end of the amplification circuit through the first switch, and the midpoint of the first resistance bridge arm is connected to the inverting input end of the amplification circuit through the second switch. The second switch branch comprises a third switch and a fourth switch, the midpoint of the second resistance bridge arm is connected to the non-inverting input end of the amplification circuit through the third switch, and the midpoint of the second resistance bridge arm is connected to the inverting input end of the amplification circuit through the fourth switch. When the first switch and the fourth switch are turned on, the amplification circuit receives a first forward voltage output by the strain circuit. When the second switch and the third switch are turned on, the amplification circuit receives a first reverse voltage output by the strain circuit.

5. The detection chip of claim 3, wherein, The first switch branch comprises a first single-pole double-throw switch, the moving end of the first single-pole double-throw switch is connected to the midpoint of the first resistance bridge arm, the first stationary end of the first single-pole double-throw switch is used for connecting the non-inverting input end of the amplification circuit, and the second stationary end of the first single-pole double-throw switch is used for connecting the inverting input end of the amplification circuit. The second switch branch comprises a second single-pole double-throw switch, the moving end of the second single-pole double-throw switch is connected to the midpoint of the second resistance bridge arm, the first stationary end of the second single-pole double-throw switch is used for connecting the non-inverting input end of the amplification circuit, and the second stationary end of the second single-pole double-throw switch is used for connecting the inverting input end of the amplification circuit. When the moving end and the first stationary end of the first single-pole double-throw switch are connected, and the moving end and the second stationary end of the second single-pole double-throw switch are connected, the amplification circuit receives a first forward voltage output by the strain circuit. When the moving end and the second stationary end of the first single-pole double-throw switch are connected, and the moving end and the first stationary end of the second single-pole double-throw switch are connected, the amplification circuit receives a first reverse voltage output by the strain circuit.

6. A detection chip suitable for use on an active pen, characterized in that The detection chip is connected to the strain circuit in the active pen through a switch circuit, and the strain circuit is used for sensing the pressure of the pen tip. The strain circuit comprises a first resistance bridge arm and a second resistance bridge arm, the midpoint of the first resistance bridge arm is used for the first end of the detection chip, and the midpoint of the second resistance bridge arm is used for the second end of the detection chip. The first end of the first resistance bridge arm and the first end of the second resistance bridge arm are connected in parallel to form a first parallel connection end, and the first parallel connection end is connected to a power supply end or a ground through the switch circuit. The second end of the first resistance bridge arm and the second end of the second resistance bridge arm are connected in parallel to form a second parallel connection end, and the second parallel connection end is connected to the power supply end or the ground through the switch circuit. In the first state of the switch circuit, the first bus end is connected to the power supply end, the second bus end is connected to the ground, and the detection chip receives a first forward voltage output by the strain circuit; In the second state of the switch circuit, the first bus end is connected to the ground, the second bus end is connected to the power supply end, and the detection chip receives a first reverse voltage output by the strain circuit.

7. The detection chip of claim 6, wherein, The first resistance bridge arm comprises a first resistance and a second resistance arranged in series, and a connection node between the first resistance and the second resistance is a midpoint of the first resistance bridge arm; the second resistance bridge arm comprises a third resistance and a fourth resistance arranged in series, and a connection node between the third resistance and the fourth resistance is a midpoint of the second resistance bridge arm The detection chip comprises an amplification circuit, a non-inverting input end of the amplification circuit is connected to the midpoint of the first resistance bridge arm, and an inverting input end of the amplification circuit is connected to the midpoint of the second resistance bridge arm; In the first state of the switch circuit, the first bus end is connected to the power supply end, the second bus end is connected to the ground, and the amplification circuit receives a first forward voltage output by the strain circuit; In the second state of the switch circuit, the first bus end is connected to the ground, the second bus end is connected to the power supply end, and the amplification circuit receives a first reverse voltage output by the strain circuit.

8. The detection chip of claim 7, wherein, The switch circuit comprises a first switch branch and a second switch branch; The first bus end is connected to the power supply end or the ground through the first switch branch; The second bus end is connected to the power supply end or the ground through the second switch branch; In the first state of the switch circuit, the first bus end is connected to the power supply end, the second bus end is connected to the ground, and the amplification circuit receives a first forward voltage output by the strain circuit; In the second state of the switch circuit, the first bus end is connected to the ground, the second bus end is connected to the power supply end, and the amplification circuit receives a first reverse voltage output by the strain circuit.

9. The detection chip of claim 8, wherein, The first switch branch comprises a first switch and a second switch, the first bus end is connected to the power supply end through the first switch, and the first bus end is connected to the ground through the second switch; The second switch branch comprises a third switch and a fourth switch, the second bus end is connected to the power supply end through the third switch, and the second bus end is connected to the ground through the fourth switch; In the first state of the switch circuit, the first bus end is connected to the power supply end, the second bus end is connected to the ground, and the amplification circuit receives a first forward voltage output by the strain circuit; In the second state of the switch circuit, the first bus end is connected to the ground, the second bus end is connected to the power supply end, and the amplification circuit receives a first reverse voltage output by the strain circuit.

10. The detection chip of claim 8, wherein, The first switch branch comprises a first single-pole double-throw switch, a moving end of the first single-pole double-throw switch is connected to the first bus end, a first fixed end of the first single-pole double-throw switch is used for connecting the power supply end, and a second fixed end of the first single-pole double-throw switch is used for connecting the ground; The second switch branch comprises a second single-pole double-throw switch, a moving terminal of the second single-pole double-throw switch is connected with the second bus terminal, a first stationary terminal of the second single-pole double-throw switch is used for connecting a power supply terminal, and a second stationary terminal of the second single-pole double-throw switch is used for connecting a ground terminal; When the moving terminal of the first single-pole double-throw switch and the first stationary terminal are connected, and the moving terminal of the second single-pole double-throw switch and the second stationary terminal are connected, the amplification circuit receives a first forward voltage output by the strain circuit; When the moving terminal of the first single-pole double-throw switch and the second stationary terminal are connected, and the moving terminal of the second single-pole double-throw switch and the first stationary terminal are connected, the amplification circuit receives a first reverse voltage output by the strain circuit.

11. The detection chip according to any one of claims 2-5, 7-10, wherein, The detection chip further comprises an ADC converter and a controller; The amplification circuit is configured to amplify the first forward voltage and a noise voltage, output a second forward voltage, amplify the first reverse voltage and the noise voltage, and output a second reverse voltage; The ADC converter is connected with the amplification circuit, and is configured to demodulate and denoise the second forward voltage and the second reverse voltage, and determine a third forward voltage and a third reverse voltage; The controller is connected with the switch circuit and the ADC converter, and is configured to control the switch circuit to alternately enter a first state and a second state, and determine a pressure value of the active pen according to the third forward voltage and the third reverse voltage.

12. The detection chip of claim 11, wherein, The controller is configured to output a first control signal and a second control signal to the switch circuit based on a target frequency, so that the switch circuit alternately enters the first state and the second state, and output the target frequency to the ADC converter. The ADC converter is configured to perform quadrature demodulation or square wave demodulation on the second forward voltage and the second reverse voltage based on the target frequency, determine the third forward voltage and the third reverse voltage, and send the third forward voltage and the third reverse voltage to the controller.

13. The detection chip according to any one of claims 2-5, 7-10, wherein, The detection chip further comprises an ADC converter, the ADC converter is adapted to be connected with a controller, and the controller is connected with the switch circuit and is configured to control the switch circuit to alternately enter a first state or a second state; The amplification circuit is configured to amplify the first forward voltage and a noise voltage, output a third forward voltage, amplify the first reverse voltage and the noise voltage, and output a third reverse voltage; The ADC converter is connected with the amplification circuit, and is configured to demodulate and denoise the third forward voltage and the third reverse voltage, determine a third forward voltage and a third reverse voltage, and send the third forward voltage and the third reverse voltage to the controller, so that the controller determines a pressure value of the active pen according to the third forward voltage and the third reverse voltage.

14. The detection chip according to any one of claims 1-10, wherein, The switch circuit is arranged in the detection chip or outside the detection chip.

15. A stylus, characterized by The detection chip comprises a strain circuit and any one of the detection chips in claims 1-14. The strain circuit is configured to sense a pressure of a pen tip. The detection chip is connected with the strain circuit through a switch circuit, and is configured to determine the pressure value of the active pen according to a first forward voltage and a first reverse voltage staggered and output by the strain circuit through the switch circuit.

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