An apparatus for improving the pressure detection accuracy of a capacitive pressure-sensitive touchpad

Abstract

The application discloses a device for improving the pressure detection precision of a capacitive pressure touch panel and relates to the technical field of input devices. The device comprises a capacitive pressure sensor, a touch control chip, a DC-DC voltage boosting circuit and a TX signal amplitude amplification circuit. The touch control chip is connected with the DC-DC voltage boosting circuit and the TX signal amplitude amplification circuit. The DC-DC voltage boosting circuit and the TX signal amplitude amplification circuit are connected with each other. A TX pad ring-welded TX pad is arranged on the back of the pressure touch panel. The TX signal amplitude amplification circuit is connected with the TX pad and the pad ring. An RX pad is arranged on the back of the pressure touch panel and is connected with the touch control chip. The DC-DC voltage boosting circuit, the TX signal amplitude amplification circuit and the capacitive pressure sensor for improving the capacitive change amount greatly improve the sensitivity, consistency and linearity of the pressure detection of the capacitive pressure touch panel. The device has the functions of pressure detection and touch detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of input devices, and in particular to a device for improving the pressure detection accuracy of a capacitive pressure-sensitive touchpad. BACKGROUND

[0002] In the application of existing laptop touchpad technology with pressure sensing function, general pressure detection can adopt resistance type, inductance type and capacitance type. The three pressure detection principles are different, and the amplification, sampling and detection of pressure signals are also different. The resistance type pressure detection chip needs to support a Wheatstone bridge circuit, differential input, multi-stage pre-processing signal amplification and high-precision ADC (16 bits or more); while the pressure-sensitive pressure detection chip needs to output a PWM signal with certain driving capability and a conventional ADC (12 bits); the capacitance type pressure detection adopts the parallel plate capacitance principle, converts the deformation generated when the touchpad is pressed into a change in capacitance, and then calculates the pressure size by detecting the capacitance change.

[0003] The requirements for the pressure sensor are that the piezoresistive type can use strain gauges or piezoresistive sensors, the pressure-sensitive type can directly design the detection coil on the PCB board without the need for special sensor devices, and the capacitance type can use a pot sensor designed with stainless steel material. Although the piezoresistive pressure detection has high detection accuracy, it has high cost and complex structure, while the inductance type pressure detection has low cost but requires very high structure and calibration complexity, and has poor consistency.

[0004] The capacitance type pressure detection has the lowest cost, simple structure and less calibration positions, and most importantly, the capacitance type pressure detection does not need to increase other chips, only needs to connect the capacitance type pressure detection sensor to the capacitance detection channel of the touchpad chip, to realize the change in the size of the parallel plate capacitance formed between the pot sensor and the PCB board.

[0005] However, the existing capacitance type pressure sensor is a pot structure designed with stainless steel, the distance between the pot and the PCB board is generally between 0.1mm-0.15mm, and the deformation surface and the fixed surface of the pot structure are connected in a closed manner, which has extremely weak deformation stroke, making the capacitance change very small, thus causing the problems of low capacitance detection accuracy, poor consistency and linearity, which is the main reason why there are few mass-produced products of the capacitance type pressure detection scheme touchpad.

[0006] Therefore, a new capacitance type pressure-sensitive touchpad system scheme is needed to improve the capacitance detection accuracy of the pot structure pressure sensor and solve the consistency and linearity problems. SUMMARY

[0007] The device for improving the pressure detection accuracy of a capacitive pressure touch panel provided by the application can improve the capacitive detection accuracy of a pressure sensor, and solve the technical problems of poor consistency and linearity.

[0008] To achieve the above-mentioned purpose, the application provides the following technical solutions.

[0009] The device for improving the pressure detection accuracy of a capacitive pressure touch panel provided by the application can improve the capacitive detection accuracy of a pressure sensor, and solve the technical problems of poor consistency and linearity.

[0010] In some embodiments, the DC-DC voltage boosting circuit boosts the input voltage to a set value and then outputs the voltage to the TX signal amplitude amplification circuit, and includes a voltage boosting converter U1, a first resistor R1, a second resistor R2, a first capacitor C1, a second capacitor C2, a third capacitor C3, and an inductor L; the 6th pin of the voltage boosting converter U1 is connected to the input voltage, the 2nd pin is connected to the 6th pin and the 4th pin through the inductor L, the 2nd pin, the 4th pin, and the 6th pin are grounded through the first capacitor C1, the 5th pin of the voltage boosting converter U1 is connected between the first resistor R1 and the second resistor R2 in series; one end of the first resistor R1 is connected to the 3rd pin of the voltage boosting converter U1, and one end of the second resistor R2 is grounded; one pole plate of the second capacitor C2 is connected between the first resistor R1 and the second resistor R2 in series, and the other pole plate is connected to the 3rd pin of the voltage boosting converter U1; one pole plate of the third capacitor C3 is connected to the 3rd pin of the voltage boosting converter U1, and the other pole plate is grounded; and the 3rd pin of the voltage boosting converter U1 is the output end of the DC-DC voltage boosting circuit.

[0011] In some embodiments, the TX signal amplitude amplification circuit amplifies the voltage amplitude of the input TX signal to a preset amplitude and then outputs the signal to the TX pad, and includes a comparator U2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a fourth capacitor C4.

[0012] The pin 1 and the pin 7 of the comparator U2 are two output terminals of the TX signal amplitude amplification circuit, the pin 1 is pulled up to 15V through the third resistor R3, and the pin 7 is pulled up to 15V through the sixth resistor R6, the pin 2 of the comparator U2 is connected to the comparison voltage VDD through the fourth resistor R4, the pin 6 of the comparator U2 is connected to the comparison voltage VDD through the seventh resistor R7, the pin 3 and the pin 5 of the comparator U2 are connected to the input TX signal through the fifth resistor R5 and the eighth resistor R8 respectively, the pin 8 of the comparator U2 is connected to the output terminal of the DC-DC voltage boosting circuit and grounded through the fourth capacitor C4, the TX signal is a 5V square wave signal, and the comparison voltage VDD is a 3.3V voltage signal.

[0013] In some embodiments, the frequency of the TX signal sent by the touch chip to the TX signal amplitude amplification circuit is 100K-200KHz, and the frequency of the amplified TX signal of the TX signal amplitude amplification circuit is 100K-200KHz.

[0014] In some embodiments, the pad ring of the capacitive pressure sensor also enhances electrostatic protection through the TVS tube D when connecting the TX signal amplitude amplification circuit.

[0015] In some embodiments, the device for improving the pressure detection accuracy of the capacitive pressure touchpad further comprises a master control chip connected with the touch chip and the DC-DC voltage boosting circuit.

[0016] In some embodiments, the device for improving the pressure detection accuracy of the capacitive pressure touchpad further comprises a motor drive chip and a linear motor connected with the motor drive chip, and the motor drive chip is connected with the touch chip and the master control chip.

[0017] In some embodiments, the capacitive pressure sensor comprises a pad ring arranged on the periphery, a pot piece arranged in the pad ring, and a connecting part arranged between the pad ring and the pot piece, the connecting part lifts the pot piece from the plane where the pad ring is located, forming a stroke with a set height; the connecting part comprises a hollow structure and a connecting rib arranged in sequence, the connecting rib and the pot piece form a deformable structure, and the pad ring, the pot piece and the connecting rib constitute a conductor as a whole; when the pad ring is welded on the TX pad of the pressure touchpad, the pot piece and the corresponding RX pad of the pressure touchpad constitute a parallel plate capacitor, the pad ring and the RX pad constitute a fixed plate, and the pot piece is a deformation plate.

[0018] In some embodiments, when the pad ring is welded on the TX pad of the pressure touchpad, the RX pad of the pressure touchpad corresponding to the pot piece to form a parallel plate capacitor is coated with insulating green oil.

[0019] In some embodiments, the pressure surface of the pot piece is provided with a soft silicone pressure head.

[0020] Implementing one of the above technical solutions of the present application has the following advantages or beneficial effects:

[0021] The DC-DC voltage boosting circuit and the TX signal amplitude amplification circuit of the present application can increase the TX coding voltage of the touch chip normal voltage process to more than 15V, and the highest can reach 20V. The high voltage coding voltage can detect the tiny pressure deformation of the capacitive pressure touch panel. At the same time, the capacitive pressure sensor capable of significantly improving the capacitive change amount is set, which greatly improves the sensitivity, consistency and linearity of the capacitive pressure touch panel pressure detection, and effectively makes up for the shortcomings of the existing capacitive pressure detection. At the same time, the capacitive pressure touch panel pressure detection precision device of the present application has the functions of pressure detection and touch detection. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. In the drawings:

[0023] Figure 1 is a capacitive pressure sensor structure schematic diagram of the embodiment of the present application;

[0024] Figure 2 is a capacitive pressure sensor cross section A-A schematic diagram of the embodiment of the present application;

[0025] Figure 3 is a capacitive pressure sensor size schematic diagram of the embodiment of the present application;

[0026] Figure 4 is a front view, side view and back view of a capacitive pressure sensor for comparison of the embodiment of the present application;

[0027] Figure 5 is a device structure diagram for improving the pressure detection precision of the capacitive pressure touch panel of the embodiment of the present application;

[0028] Figure 6 is a mutual capacitance touch chip circuit structure schematic diagram of the embodiment of the present application;

[0029] Figure 7 is a DC-DC voltage boosting circuit structure schematic diagram of the embodiment of the present application;

[0030] Figure 8 is a TX signal amplitude amplification circuit structure schematic diagram of the embodiment of the present application;

[0031] Figure 9 is an exploded view of a capacitive pressure touchpad provided with four capacitive pressure sensors according to an embodiment of the present application;

[0032] Figure 10 is a schematic diagram of a driving and sensing interface of four capacitive pressure sensors of a capacitive pressure touchpad according to an embodiment of the present application;

[0033] Figure 11 is a schematic diagram of a touch chip structure according to an embodiment of the present application.

[0034] In the diagram:

[0035] 1, pad ring; 2, pot piece; 3, connecting part; 31, hollow structure; 32, connecting rib; 4, pressure touchpad; 41, front surface of pressure touchpad; 5, soft silicone pressure head; 51, back shell contact surface; 6, RX pad; 7, TX pad; 8, insulating green oil; 9, tin paste. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the various exemplary embodiments to be described below will be described with reference to the corresponding drawings, which form a part of the exemplary embodiments, and various exemplary embodiments that can be used to implement the present application are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation described in the following exemplary embodiments does not represent all implementations consistent with the present disclosure. It should be understood that they are only examples of processes, methods and devices, etc. consistent with some aspects of the present disclosure as described in the appended claims, and other embodiments can be used, or modifications can be made to the embodiments listed herein in structure and function, without departing from the scope and spirit of the present application.

[0037] In the description of the present application, the term "a plurality of" means two or more. The terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, detachably connected, integrally connected, mechanically connected, electrically connected, communicatively connected, directly connected, indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] In order to illustrate the technical solutions of the present application, the following will be described by specific embodiments, only the parts related to the embodiments of the present application are shown.

[0039] Embodiment one: as Figures 1-2As shown, the capacitive pressure sensor of the embodiment includes a pad ring 1 arranged at the periphery, a diaphragm 2 arranged in the pad ring 1, and a connecting portion 3 arranged between the pad ring 1 and the diaphragm 2. The connecting portion 3 lifts the diaphragm 2 from the plane of the pad ring 1 to form a stroke with a set height.

[0040] In one or more embodiments, the connecting portion 3 lifts the diaphragm 2 from the plane of the pad ring 1 to form a stroke with a height of 0.15 mm.

[0041] Based on the above embodiment, the connecting portion 3 includes hollow structures 31 and connecting ribs 32 arranged in sequence and at intervals. The connecting ribs 32 form a deformable structure with the diaphragm 2, and the pad ring 1, the diaphragm 2, and the connecting ribs 32 constitute a whole conductor. When the pad ring 1 is welded to the TX pad 7 of the pressure touch panel 4, the diaphragm 2 and the corresponding RX pad 6 of the pressure touch panel 4 constitute a parallel-plate capacitor, the pad ring 1 and the RX pad 6 constitute a fixed plate, and the diaphragm 2 constitutes a deformable plate.

[0042] It can be understood that the pad ring 1, the diaphragm 2, and the connecting ribs 32 constitute a whole conductor. When the pad ring 1 is welded to the TX pad 7 of the pressure touch panel 4, the whole capacitive pressure sensor and the detection channel corresponding to the TX pad 7 constitute a complete capacitive detection channel. When a force is applied to the touch panel or the diaphragm 2, the diaphragm 2 moves towards the RX pad 6, the deformable structure deforms, and the distance between the parallel plates decreases. Thus, the change in capacitance can be calculated according to the deformation, and the pressure can be calculated according to the change in capacitance, thereby realizing the capacitive pressure detection function. When the applied force disappears, the deformable structure returns to its original state.

[0043] It can be understood that the pressure touch panel 4 can also be a PCB, an FPC, or the like. Further, the connecting portion 3 adopts hollow structures 31 and connecting ribs 32 arranged in sequence and at intervals, such as four hollow structures 31 and four connecting ribs 32. The purpose is to reduce the resistance between the fixed surface (pad ring) and the deformable surface (diaphragm), so that the downward stroke is larger. It can be understood that the number of hollow structures 31 and connecting ribs 32 is not limited to four. The number of hollow structures 31 can be six, eight, or ten, and the number of connecting ribs 32 can also be six, eight, or ten.

[0044] In one or more embodiments, when the pad ring 1 is welded to the TX pad 7 of the pressure touch panel 4, the RX pad 6 of the pressure touch panel 4, which forms a parallel-plate capacitor with the diaphragm 2, is coated with insulating green oil 8. Thus, when the diaphragm 2 is pressed towards the RX pad 6 by an external force, no short circuit occurs when the diaphragm 2 contacts the RX pad 6.

[0045] In one or more embodiments, the pressure receiving surface of the piezoelectric disc 2 is provided with a soft silicone pressure head 5. In some specific embodiments, the piezoelectric disc 2 has a diameter of 8.5 mm, and the soft silicone pressure head 5 has a diameter of 5 mm, so that the piezoelectric disc 2 (deformation surface) has a larger pressure receiving area and is more easily subjected to a larger stroke change. Further, since the soft silicone pressure head 5 is elastic, when the pressure on the rear shell contact surface 51 of the soft silicone pressure head 5 (for example, when the capacitive pressure sensor is applied to a pressure-sensitive touchpad of a notebook computer, the rear shell is a structural member for mounting the pressure-sensitive touchpad, and the structural member directly contacts the soft silicone pressure head) disappears, the soft silicone pressure head 5 returns to its original position, thereby quickly returning the piezoelectric disc 2 to its original position.

[0046] It can be understood that the diameter of the piezoelectric disc 2 is 8.5 mm, and the diameter of the soft silicone pressure head 5 is 5 mm, i.e., the diameter of the soft silicone pressure head 5 is smaller than that of the piezoelectric disc 2, and thus the smaller pressure receiving surface is like a punch. For example, if the soft silicone is compared to a user's finger, the distributed pressing force is concentrated on a very small point and then transmitted to the piezoelectric disc 2. The corresponding speed of deformation of the piezoelectric disc 2 can be greatly improved.

[0047] Further, as shown in FIG. 3, as a specific example, the capacitive pressure sensor is welded to the TX pad 7 of the PCB, so that the entire sensor serves as a TX channel. The piezoelectric disc 2 (deformation surface) has a diameter of φ=8.5 mm, and the RX pad 6 of the PCB is directly below the piezoelectric disc 2. The outer diameter of the pad ring is φ=13 mm, and the inner diameter of the pad ring is φ=10.5 mm. When a user presses any point on the touch surface of the PCB, the soft silicone pressure head 5 will squeeze the deformation surface of the piezoelectric sensor to change the distance from the RX pad 6. This causes the distance D between the two electrodes to change, thereby causing a change in the capacitance C. The touch chip detects this capacitance change and can determine whether there is a pressing force or the size of the pressing force according to the following parallel plate capacitance formula.

[0048] The parallel plate capacitance formula is as follows:

[0049] C=ε S / (4 π K D);

[0050] wherein C is the capacitance, ε is the dielectric constant, S is the area of the two parallel plates, K is the electrostatic force constant, and D is the distance from the deformation surface to the RX pad. In specific calculations, the dielectric constant can be 1, and the electrostatic force constant is 8900000000 N.

[0051] For example, Figure 4As shown, as a comparison with the capacitive pressure sensor of the embodiment, another capacitive pressure sensor structure is provided, which is different from the capacitive pressure sensor of the embodiment in that the fixed surface is connected with the deformation surface by a whole ring of connecting ribs, and there is no hollow structure, and the rest is consistent with the capacitive pressure sensor of the embodiment.

[0052] When a force of 100 g is applied to the capacitive pressure sensor of the embodiment, the travel change of the deformation surface is about 0.04 mm, and the distance between the deformation surface of the pot sensor and the RX pad is still 0.11. Among them, in order to facilitate calculation, S is a square with a length of 7.53 mm and a width of 7.53 mm. Substituting the above parallel plate capacitor formula, a 4.61 pF capacitor is obtained, and subtracting the capacitor before deformation 3.38 pF, a change of 1.23 pF is obtained.

[0053] When a force of 100 g is applied to the capacitive pressure sensor structure, a soft silicone pressure head with a diameter of 5 mm is used, the travel change of the deformation surface is about 0.01 mm, and the distance between the deformation surface of the pot sensor and the RX pad is still 0.14. Among them, in order to facilitate calculation, S is a square with a length of 7.53 mm and a width of 7.53 mm. Substituting the above parallel plate capacitor formula, a 3.62 pF capacitor is obtained, and subtracting the capacitor before deformation 3.38 pF, a change of 0.24 pF is obtained.

[0054] Therefore, the capacitive pressure sensor of the embodiment can significantly improve the change of the capacitor, and can better solve the problem of poor consistency and linearity of the existing capacitive pressure sensor.

[0055] Embodiment two: as shown Figure 5 As the same inventive concept, the embodiment provides a device for improving the pressure detection accuracy of a capacitive pressure touch panel, which comprises a capacitive pressure sensor as described in embodiment one, and further comprises a touch control chip, a DC-DC voltage boosting circuit and a TX signal amplitude amplification circuit. Among them, the touch control chip is connected with the DC-DC voltage boosting circuit and the TX signal amplitude amplification circuit, and the DC-DC voltage boosting circuit is connected with the TX signal amplitude amplification circuit; the TX pad welded with the pad ring is arranged on the back of the pressure touch panel, and the TX signal amplitude amplification circuit connects the TX pad with the pad ring; the RX pad is arranged on the back of the pressure touch panel and connected with the touch control chip.

[0056] The DC-DC voltage boosting circuit and the TX signal amplitude amplification circuit of the application can increase the TX coding voltage of the touch control chip to more than 15V, and the highest can reach 20V. The high voltage coding voltage can detect the small pressure deformation of the capacitive pressure touch panel. In combination with the capacitive pressure sensor capable of significantly improving the change of the capacitor as described in embodiment one, the sensitivity, consistency and linearity of the pressure detection of the capacitive pressure touch panel can be effectively improved.

[0057] In one or more embodiments, further comprising a master chip, a motor driving chip, and a linear motor connected with the motor driving chip. Specifically, the master chip is connected with the touch chip and the DC-DC boost circuit, and the motor driving chip is connected with the touch chip and the master chip.

[0058] It can be understood that through the motor design, the user can experience the pressure feeling, and the user's pressure touch experience of products such as notebook computers, smart phones, wearable devices and the like is improved.

[0059] Based on the above embodiment, the master chip can provide the working power VDD for the touch chip, the DC-DC boost circuit and the motor driving chip. Under the premise of providing the working power VDD, the touch chip sends a start signal to the DC-DC boost circuit and sends a TX signal to the TX signal amplitude amplification circuit; the DC-DC boost circuit raises the input voltage provided by the master chip to a set value according to the obtained start signal, and after receiving the boosted voltage, the TX signal amplitude amplification circuit amplifies the voltage amplitude of the TX signal to a preset amplitude. The amplified TX signal is used as a driving signal of the capacitive pressure sensor. The touch chip acquires the RX signal sensed by the capacitive pressure sensor due to the pressure on the front surface of the pressure touch panel in real time, and calculates the size and position corresponding to the pressure according to the acquired RX signal through an algorithm. Finally, the calculated size and position corresponding to the pressure are transmitted to the master chip, and the next step is processed through the master chip.

[0060] It can be understood that the capacitive pressure touch panel has not only a pressure sensing function but also a touch detection function. The touch signal on the front surface of the capacitive pressure touch panel is acquired through the touch sensor connected with the touch chip. This can be the prior art, and will not be described here.

[0061] Further, the master chip described above can be configured according to different products. When the device is used for pressure sensing and touch detection of a notebook computer, the master chip is a computer-side master chip. When the device is used for pressure sensing and touch detection of a wearable device, the master chip is a master chip of the wearable device.

[0062] It can be understood that the touch chip is a mutual capacitance touch chip. The mutual capacitance detection output data of the mutual capacitance touch chip is mainly related to the code voltage of the TX signal, the internal operational amplification multiple of the chip and the change size of the to-be-tested capacitance, that is,

[0063] ;

[0064] Wherein, V0 is the to-be-tested capacitance test output voltage signal, V i is the code voltage of the TX signal, C m is the to-be-tested capacitance, C fThis is the internal feedback capacitor of the chip.

[0065] like Figure 6 As shown in the figure, combined with the above formula, it can be seen that to improve the mutual capacitance detection output data of the touch chip, two directions can be considered: First, increase the coding voltage V of TX. i Secondly, increase the magnitude of the change in the measured capacitance Cm; Cf is the internal feedback capacitance of the chip, which determines the amplification factor of the operational amplifier. Once the chip is determined, the maximum value of this parameter is fixed. Currently, due to factors such as chip manufacturing process and cost, the maximum TX coding voltage of touchpad chips is generally around 12V, and some chips even have a maximum of only around 6V. Therefore, in order to increase the TX coding voltage, a boost circuit and a TX amplitude amplification circuit can be added to the external circuitry of the touch chip to increase the TX coding voltage to above 15V. It should be noted that... Figure 6 TXgen is a signal generator, used in this embodiment to generate a square wave of a specific frequency (such as 200KHz), i.e., the TX signal mentioned above.

[0066] like Figure 7 As shown, in one or more embodiments, the DC-DC boost circuit is used to boost the input voltage to a set value and then output it to the TX signal amplitude amplification circuit. The input voltage is provided by the main control chip mentioned above. The DC-DC boost circuit includes a boost converter U1, a first resistor R1, a second resistor R2, a first capacitor C1, a second capacitor C2, a third capacitor C3, and an inductor L. In this configuration, pin 6 of boost converter U1 is connected to the input voltage. Pin 2 is connected to pins 6 and 4 via inductor L. Pins 2, 4, and 6 are grounded via capacitor C1. Resistors R1 and R2 are connected in series. Pin 5 of boost converter U1 is connected between resistors R1 and R2. One end of resistor R1 is connected to pin 3 of boost converter U1, and one end of resistor R2 is grounded. One plate of capacitor C2 is connected between resistors R1 and R2, and the other plate is connected to pin 3 of boost converter U1. One plate of capacitor C3 is connected to pin 3 of boost converter U1, and the other plate is grounded. Pin 3 of boost converter U1 is the output terminal of the DC-DC boost circuit, which outputs a voltage boosted to the set value.

[0067] Based on the above embodiments, the boost converter U1 can be selected from SGM6602 of Sanbang Microelectronics, with a maximum voltage of 20V. That is, the range of the above-mentioned set value is not lower than 15V and not higher than 20V. The first resistor R1 and the second resistor R2 can be selected with different resistance values ​​to set the optimal output voltage value.

[0068] like Figure 8As shown, in one or more embodiments, the TX signal amplitude amplification circuit amplifies the voltage amplitude of the input TX signal to a preset amplitude and then outputs it to the TX pad. The input TX signal is provided by the touch chip. The TX signal amplitude amplification circuit includes a comparator U2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a fourth capacitor C4. The pin 1 and pin 7 of the comparator U2 are two output terminals of the TX signal amplitude amplification circuit, the pin 1 is pulled up to 15V through the third resistor R3, and the pin 7 is pulled up to 15V through the sixth resistor R6. The pin 2 of the comparator U2 is connected to the comparison voltage VDD through the fourth resistor R4, and the pin 6 of the comparator U2 is connected to the comparison voltage VDD through the seventh resistor R7. The pin 3 and pin 5 of the comparator U2 are connected to the input TX signal through the fifth resistor R5 and the eighth resistor R8, respectively. The pin 8 of the comparator U2 is connected to the output terminal of the DC-DC voltage boosting circuit and grounded through the fourth capacitor C4. The TX signal is a 5V square wave signal, and the comparison voltage VDD is a 3.3V voltage signal. It should be noted that the third resistor R3 and the sixth resistor R6 are pull-up resistors.

[0069] Based on the above embodiment, the comparator U2 can use RS8920 with high-speed high-voltage performance to amplify the 5V coded square wave signal of the TX signal of the TX channel to 15V (preset amplitude), and the maximum amplitude can reach 20V.

[0070] Based on the above embodiment, the TX signal and RX signal used for pressure detection can be conveniently selected from the regular touch channel pins of the touch chip according to the wiring of the capacitive pressure touch panel. The touch chip selects a regular voltage process, so the cost is relatively low. In addition, according to the size of the touch panel, 4 or 6 capacitive pressure sensors can be selected. If there are 4, 2 TX and 2 RX are used to complete the function; if there are 6, 3 TX and 3 RX are selected to complete the function.

[0071] In one or more embodiments, the TX signal sent by the touch chip to the TX signal amplitude amplification circuit is a square wave signal with a voltage of 5V and a frequency of 100KHz~200KHz. The TX signal generated by the TX signal amplitude amplification circuit is a square wave signal with a voltage of 15V and a frequency of 100KHz~200KHz.

[0072] Based on the above embodiment, the TX signal frequency is set to 100KHz~200KHz, and the signal delay generated by the comparator will not affect the reception of the RX signal of the touch chip, because a signal period of 200KHz is 5us (2.5us high, 2.5us low), and the delay time of the comparator RS8920 is within 100ns, and the total delay time including the load circuit delay is less than 1us. The RX detection of the touch chip is generally set near the front end of the falling edge of the TX square wave signal, so the delay of the comparator will not affect the detection of the RX signal.

[0073] In one or more embodiments, the pad ring of the capacitive pressure sensor, when connected to the TX signal amplitude amplification circuit, also enhances electrostatic protection through the TVS tube D.

[0074] As shown in Figures 9-11 As a specific embodiment, four capacitive pressure sensors FS1-FS4 are arranged on the pressure-sensitive touchpad, and the four capacitive pressure sensors are arranged at the four corners of the pressure-sensitive touchpad. The RX pads corresponding to the sensor FS1 and the sensor FS3 correspond to the common port FRX1, and the RX pads corresponding to the sensor FS2 and the sensor FS4 correspond to the common port FRX2. The TX pads corresponding to the sensor FS1 and the sensor FS2 correspond to the common port FTX2, and the TX pads corresponding to the sensor FS3 and the sensor FS4 correspond to the common port FTX1. The 19th pin and the 20th pin of the touch chip are connected to the common port FRX2 and the common port FRX1 of the capacitive pressure sensor respectively, and the 37th pin and the 38th pin are connected to the input end corresponding to the 3rd pin of the comparator U2 and the input end corresponding to the 5th pin of the comparator U2 of the TX signal amplitude amplification circuit respectively. The output end corresponding to the 1st pin of the comparator U2 of the TX signal amplitude amplification circuit is connected to the common port FTX1, and the common port FTX1 enhances electrostatic protection through the TVS tube D1. The output end corresponding to the 7th pin of the comparator U2 is connected to the common port FTX2, and the common port FTX2 enhances electrostatic protection through the TVS tube D2.

[0075] The above only describes the preferred embodiments of the present application, and those skilled in the art know that various changes or equivalent replacements can be made to the features and embodiments without departing from the spirit and scope of the present application. In addition, the features and embodiments can be modified to adapt to specific conditions and materials under the guidance of the present application without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the protection scope of the present application.

Claims

1. A device for improving the pressure detection accuracy of a capacitive pressure-sensitive touchpad, characterized by The capacitive pressure sensor, the touch chip, the DC-DC voltage boosting circuit, and the TX signal amplitude amplification circuit are connected with each other. The TX pad ring welded with the pad ring is arranged on the back of the pressure touch pad, and the TX signal amplitude amplification circuit connects the TX pad and the pad ring. The TX signal amplitude amplification circuit amplifies the voltage amplitude of the input TX signal to a preset amplitude and then outputs the amplified signal to the TX pad, and includes a comparator U2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a fourth capacitor C4. The 1st pin and the 7th pin of the comparator U2 are two output terminals of the TX signal amplitude amplification circuit, the 1st pin is pulled up to 15V through the third resistor R3, and the 7th pin is pulled up to 15V through the sixth resistor R6.

2. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 1, characterized in that, The DC-DC voltage boosting circuit boosts the input voltage to a set value and then outputs the boosted voltage to the TX signal amplitude amplification circuit, and includes a voltage boosting converter U1, a first resistor R1, a second resistor R2, a first capacitor C1, a second capacitor C2, a third capacitor C3, and an inductor L. The 6th pin of the voltage boosting converter U1 is connected with the input voltage, the 2nd pin is connected with the 6th pin and the 4th pin through the inductor L, the 2nd pin, the 4th pin, and the 6th pin are grounded through the first capacitor C1, and the 5th pin of the voltage boosting converter U1 is connected between the first resistor R1 and the second resistor R2 in series.

3. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 1, characterized in that, The TX signal sent by the touch chip to the TX signal amplitude amplification circuit has a frequency of 100K-200KHz, and the amplified TX signal has a frequency of 100K-200KHz.

4. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 1, characterized in that, The pad ring of the capacitive pressure sensor is also connected with the TVS tube D to enhance the electrostatic protection when connected with the TX signal amplitude amplification circuit.

5. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 1, characterized in that, The main control chip is also connected with the touch chip and the DC-DC voltage boosting circuit.

6. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 5, characterized in that, The motor driving chip is connected with the touch control chip and the main control chip.

7. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 1, characterized in that, The capacitive pressure sensor comprises a peripheral pad ring, a diaphragm arranged in the pad ring, and a connecting part arranged between the pad ring and the diaphragm, the connecting part lifting the diaphragm from the plane of the pad ring to form a stroke with a set height; the connecting part comprises a hollow structure and a connecting rib arranged in sequence and at intervals, the connecting rib and the diaphragm forming a deformable structure, and the pad ring, the diaphragm and the connecting rib forming a whole conductor; when the pad ring is welded on the TX pad of the pressure-sensitive touchpad, the diaphragm and the corresponding RX pad of the pressure-sensitive touchpad form a parallel-plate capacitor, the pad ring and the RX pad form a fixed plate, and the diaphragm is a deformable plate.

8. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 7, characterized in that, When the pad ring is welded on the TX pad of the pressure-sensitive touchpad, the RX pad of the pressure-sensitive touchpad which forms a parallel-plate capacitor with the diaphragm is coated with insulating green oil.

9. The device for improving the pressure detection precision of a capacitive pressure-sensitive touchpad according to claim 7, characterized in that, The pressure receiving surface of the diaphragm is provided with a soft silicone pressure head.

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