Pressure sensing device, pressure sensing method and electronic terminal

Abstract

The pressure sensing device (100) comprises a substrate (10) and a pressure sensor (20). The pressure sensor (20) used is a thin film piezoresistive sensor (21) having a certain area, and a power line VCC, a ground line GND and two differential lines Vm+ and Vm- are respectively led out at the end of the thin film piezoresistive sensor (21). The pressure sensor (20) is arranged on the substrate (10). The pressure sensor (20) has the advantages of small area, small initial pressure difference, high sensitivity, small temperature drift, strong anti-interference ability, high anti-drop coefficient, stable reliability, etc. The substrate (10) is simply pressed against the object (200) to be tested that is subjected to pressure, and the pressure sensor (20) is connected to a pressure sensing detection circuit. The object (200) to be tested is deformed by the pressure, and the substrate (10) is deformed. The thin film piezoresistive sensor (21) follows the deformation. The deformation of the substrate (10) is detected by detecting the voltage drop between the two differential lines Vm+ and Vm‑, and the pressure of the object (200) to be tested is converted to realize a pressure sensing touch function. The pressure sensing method using the pressure sensing device (100) and the electronic terminal having the pressure sensing device (100) can realize the pressure sensing touch function.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure sensing, and relates to a pressure sensing device, a pressure sensing method using the pressure sensing device, and an electronic terminal having the pressure sensing device. Background Art

[0002] A pressure sensor is a device that can sense pressure signals and convert them into usable output electrical signals according to certain rules. At present, the pressure sensing devices on the market are mainly composed of strain gauges, such as typical electronic scales, which require relatively large structural space and have low sensitivity. Summary of the invention

[0003] The purpose of the present invention is to provide a pressure sensing device, a pressure sensing method and an electronic terminal to solve the technical problems in the prior art that the pressure sensing device requires a relatively large structural space and has low sensitivity.

[0004] An embodiment of the present invention provides a pressure sensing device, comprising a substrate for abutting against an object to be measured, and a pressure sensor arranged on the substrate; the pressure sensor comprises at least one thin film piezoresistive sensor and at least four signal lines respectively led out from four corners of the thin film piezoresistive sensor, one side of the thin film piezoresistive sensor is attached to the substrate and when the substrate is deformed, the resistivity distribution of the thin film piezoresistive sensor changes with the deformation, wherein two opposite signal lines are a power line and a ground line, respectively, and the other two opposite signal lines are differential lines; the pressure of the object to be measured is detected by detecting the voltage drop between the two differential lines.

[0005] An embodiment of the present invention provides a pressure sensing method, which uses the above-mentioned pressure sensing device and includes the following steps:

[0006] Placing the substrate against the object to be measured;

[0007] The thin film piezoresistive sensor is equivalent to a first equivalent circuit, wherein the first equivalent circuit includes a bridge circuit having two pairs of bridge arms, a first resistor connected between the two differential lines, and a second resistor connected between the power line and the ground line, two ends of the bridge circuit are respectively connected to the power line and the ground line, and the other two ends of the bridge circuit are respectively connected to the two differential lines;

[0008] The second resistor in the first equivalent circuit has a negligible effect on the signal quantity, and the second equivalent circuit is obtained by deleting the second resistor; the second equivalent circuit includes a bridge circuit having two pairs of bridge arms, and a first resistor connected between the two differential lines, two ends of the bridge circuit are respectively connected to the power line and the ground line, and the other two ends of the bridge circuit are respectively connected to the two differential lines;

[0009] The first resistor in the second equivalent circuit and the delta-shaped circuit formed by the two bridge arms connected to the power line are equivalent to a Y-shaped circuit to obtain a third equivalent circuit;

[0010] According to Kirchhoff's law, the voltage equation of the center point of the Y-shaped circuit and the voltage equation of the two differential lines are obtained; then the voltage drop formula between the two differential lines is obtained; the deformation of the substrate is converted through the voltage drop formula, and the pressure of the object under test is converted.

[0011] An embodiment of the present invention provides an electronic terminal, comprising a detected object, the pressure sensing device described above, and a pressure sensing detection circuit electrically connected to the pressure sensor, wherein the substrate abuts against the detected object.

[0012] The above one or more technical solutions provided by the embodiments of the present application have at least one of the following technical effects: the pressure sensor used is a thin film piezoresistive sensor with a certain area, and a power line, a ground line and two differential lines are respectively led out at the ends of the thin film piezoresistive sensor, and the pressure sensors are arranged and distributed on the substrate. The pressure sensor has the advantages of small area, small initial pressure difference, high sensitivity, small temperature drift, strong anti-interference ability, high anti-drop coefficient, stable reliability, etc. The substrate is simply pressed against the object under pressure, and the pressure sensor is connected to the pressure sensing detection circuit. The object under pressure is deformed, and the thin film piezoresistive sensor follows the deformation. The voltage drop between the two differential lines is detected to detect the deformation of the substrate, and the pressure of the object under test is converted to realize the pressure-sensitive touch function. The pressure sensing method using the pressure sensing device and the electronic terminal with the pressure sensing device can realize the pressure-sensitive touch function. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0014] Figure 1 A front view of a pressure sensing device provided by an embodiment of the present invention;

[0015] Figure 2 A cross-sectional view of an electronic terminal provided by an embodiment of the present invention;

[0016] Figure 3 A cross-sectional view of an electronic terminal provided by another embodiment of the present invention;

[0017] Figure 4 for Figure 1 A first equivalent circuit diagram of a thin film piezoresistive sensor used in a pressure sensing device;

[0018] Figure 5 Reason Figure 4 A second equivalent circuit diagram obtained by converting the first equivalent circuit into a second equivalent circuit diagram;

[0019] Figure 6 for Figure 5 The equivalent resistance change diagram of the second equivalent circuit after the object under test is pressed;

[0020] Figure 7 Reason Figure 5 A third equivalent circuit diagram obtained by converting the second equivalent circuit into a third equivalent circuit diagram;

[0021] Figure 8 It is a simulation diagram of the voltage drop between the two differential lines when the first resistor Rx changes;

[0022] Fig. 9 It is a simulation diagram when the voltage drop between the two differential lines changes in the bridge arms Rm1 and Rm2. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] In the description of the embodiments of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present invention.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0026] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0027] Please also read Figures 1 to 3 The embodiment of the present invention provides a pressure sensing device 100, which includes a substrate 10 for contacting with a measured object 200, and a pressure sensor 20 provided on the substrate 10; the pressure sensor 20 includes at least one thin film piezoresistive sensor 21 and at least four signal lines respectively led out from four corners of the thin film piezoresistive sensor 21, one side of the thin film piezoresistive sensor 21 is attached to the substrate 10 and when the substrate 10 is deformed, the resistivity distribution of the thin film piezoresistive sensor 21 changes with the deformation, wherein two relative signal lines are a power line VCC and a ground line GND, and the other two relative signal lines are differential lines Vm+ and Vm-; the pressure of the measured object 200 is detected by detecting a voltage drop △V between the two differential lines Vm+ and Vm-.

[0028] The pressure sensor 20 used is a thin film piezoresistive sensor 21 with a certain area, and the power line VCC, the ground line GND and the two differential lines Vm+ and Vm- are respectively led out at the ends of the thin film piezoresistive sensor 21, and the pressure sensor 20 is arranged on the substrate 10. The pressure sensor 20 has the advantages of small area, small initial pressure difference, high sensitivity, small temperature drift, strong anti-interference ability, high anti-drop coefficient, stable reliability, etc. The substrate 10 is simply pressed against the object 200 under pressure, and the pressure sensor 20 is connected to the pressure sensing detection circuit. The object 200 under pressure is deformed, and the thin film piezoresistive sensor 21 of the substrate 10 deforms and follows the deformation. The voltage drop △V between the two differential lines Vm+ and Vm- is detected to detect the deformation of the substrate 10, and the pressure of the object 200 under test is converted to realize the pressure-sensitive touch function.

[0029] The object 200 to be tested can be a panel or the side of a mobile phone or other. The substrate 10 is in the shape of an elongated strip, and the pressure sensor 20 is arranged on the substrate 10, which can reduce consumables. The elongated substrate 10 has two outer edges 10a and two inner edges 10b located inside the two outer edges 10a. The thin film piezoresistive sensor 21, the signal line and the pad 22 at the end of the signal line of the pressure sensor 20 are located in the area between the two inner edges 10b, and the structure is compact. The substrate 10 is a circuit board, and the pressure sensor 20 is installed on the circuit board, which is easy to assemble and facilitates the thin film piezoresistive sensor 21 to follow the deformation of the substrate 10. The circuit board has a circuit trace connected to the pressure sensing detection circuit for signal processing to achieve pressure touch.

[0030] The pressure sensor 20 may be an NDT pressure sensor. The thin film piezoresistive sensor 21 of the pressure sensor 20 is an integrated structure with a certain area. When force acts on the object 200 to be measured, due to the influence of the tangential strain force, the curvature of the thin film piezoresistive sensor 21 in the long side direction increases, and the curvature of the thin film piezoresistive sensor 21 in the short side direction does not change significantly. According to the characteristics of the pressure sensor 20, that is, the characteristics of the resistor, the resistance value increases when the resistor curvature increases; the resistance value decreases when the resistor curvature decreases. The object 200 to be measured is deformed by pressure, and the substrate 10 is deformed and the thin film piezoresistive sensor 21 follows the deformation. The voltage drop △V between the two differential lines Vm+ and Vm- is used as a signal quantity, and the pressure of the object 200 to be measured is obtained through data processing by the pressure sensing detection circuit.

[0031] The pressure sensing device 100 can be made relatively small and compact, and can be applied to different pressure sensing occasions. For example, the width of the pressure sensing device 100 can be 2 mm or more.

[0032] Further, as a specific embodiment of the pressure sensing device 100 provided by the present invention, the number of the pressure sensor 20 is one; when used in multiple channels, the number of the pressure sensors 20 is at least two, and the pressure sensors 20 are arranged or unevenly distributed. The pressure sensing device 100 is in the shape of a long strip, and will produce a one-dimensional deformation when subjected to pressure.

[0033] Further, as a specific embodiment of the pressure sensing device 100 provided by the present invention, the thin film piezoresistive sensor 21 can be any type of strain sensor, including polycrystalline or amorphous semiconductor materials, polycrystalline silicon, graphene, copper-nickel alloy, carbon nanotubes, metal fine wires, and conductor-insulator composite materials, etc. The above solutions can all achieve pressure sensing.

[0034] Further, as a specific embodiment of the pressure sensing device 100 provided by the present invention, the thin film piezoresistive sensor 21 is a pressure sensor with a certain area, which can be a regular polygon, an irregular polygon, an ellipse, a circle, etc. The above schemes can all achieve pressure sensing. The present invention is described by taking a square resistor as an example.

[0035] For further information, see Figure 3 As a specific embodiment of the pressure sensing device 100 provided by the present invention, the substrate 10 is a printed circuit board 11, the ends of the four signal lines are connected to the printed circuit board 11; the pressure sensor 20 is printed on the printed circuit board 11. The printed circuit board 11 can be a paper substrate, a metal substrate, a composite substrate, a glass fiber cloth substrate, a ceramic substrate, etc. Alternatively, please refer to Figure 2 The substrate 10 includes a flexible circuit board 12 and a reinforcing sheet 13 provided on the flexible circuit board 12, and the ends of the four signal lines are connected to the flexible circuit board 12. The pressure sensor 20 is printed on the flexible circuit board 12. The reinforcing sheet 13 can be a stainless steel sheet, a glass fiber epoxy resin copper-clad sheet (FR-4), an aluminum sheet or other materials with a certain rigidity. Both of the above solutions are easy to assemble, and the thin film piezoresistive sensor 21 follows the deformation of the substrate 10, and can be selected as needed.

[0036] For further information, see Figure 1 As a specific embodiment of the pressure sensing device 100 provided by the present invention, the signal line can be various conductors, such as metals or metal compounds such as Cu (copper), Ni (nickel), Ag (silver), Au (gold), etc., or C (carbon) powder or conductive nanotubes, or oxide powder, etc. The above structure is easy to form, and it is convenient to connect the four ends of the thin film piezoresistive sensor 21 to the circuit board.

[0037] For further information, see Figure 2 , Figure 3 As a specific embodiment of the pressure sensing device 100 provided by the present invention, a colloid 30 for bonding with the object 200 to be measured is provided on a side of the substrate 10 away from the pressure sensor 20. The colloid 30 is used to facilitate the assembly of the pressure sensing device 100 against the surface of the object 200 to be measured. The colloid 30 can be VHB tape or other colloids.

[0038] Further, as a specific implementation of the pressure sensing device 100 provided by the present invention, the width of the pressure sensing device 100 is greater than or equal to 1 mm. The pressure sensing device 100 can be applied to occasions with relatively small space (less than 1 mm).

[0039] For further information, see Figure 1As a specific embodiment of the pressure sensing device 100 provided by the present invention, one of the side edges of the thin film piezoresistive sensor 21 is parallel to the arrangement direction of the pressure sensor 20. The structure is compact and occupies little space. The thin film piezoresistive sensor 21 can be equivalent to the following first equivalent circuit, second equivalent circuit, and third equivalent circuit, and the long side direction of the bridge arms Rm1 and Rm2 in the first equivalent circuit is parallel to the arrangement direction of the pressure sensor 20, and the long side direction of the bridge arms Rf1 and Rf2 is perpendicular to the arrangement direction of the pressure sensor 20.

[0040] Further, as a specific embodiment of the pressure sensing device 100 provided by the present invention, the deformation direction of the pressure sensor 20 is parallel to the long side direction of the pressure sensing device 100. The pressure sensing device 100 is in the shape of a long strip and will produce a one-dimensional deformation when subjected to pressure. The thin film piezoresistive sensor 21 can be equivalent to the following first equivalent circuit, second equivalent circuit, and third equivalent circuit. The length direction of the signal line is parallel to the arrangement direction of the pressure sensor 20. The structure is compact and occupies little space.

[0041] See also Figures 1 to 3 The embodiment of the present invention provides a pressure sensing method, which uses the pressure sensing device 100 of any of the above embodiments, and includes the following steps:

[0042] Place the substrate 10 against the object 200 to be tested;

[0043] Four wires are drawn out from the four corners of the thin film piezoresistive sensor 21. There is a certain impedance between every two wires. The thin film piezoresistive sensor 21 is equivalent to a first equivalent circuit ( Figure 4 As shown), the first equivalent circuit includes a bridge circuit with two pairs of bridge arms, a first resistor Rx connected between two differential lines Vm+ and Vm-, and a second resistor Ry connected between a power line VCC and a ground line GND, two ends of the bridge circuit are respectively connected to the power line VCC and the ground line GND, and the other two ends of the bridge circuit are respectively connected to the two differential lines Vm+ and Vm-;

[0044] The change of the second resistor Ry will not affect the voltage values ​​of Vm+ and Vm-. The signal amount is the difference between Vm+ and Vm-, which is convenient for calculation. The influence on the signal amount can be ignored. The second resistor Ry in the first equivalent circuit is deleted to obtain the second equivalent circuit ( Figure 5 As shown); the second equivalent circuit includes a bridge circuit having two pairs of bridge arms, and a first resistor Rx connected between two differential lines Vm+ and Vm-, two ends of the bridge circuit are respectively connected to a power line VCC and a ground line GND, and the other two ends of the bridge circuit are respectively connected to the two differential lines Vm+ and Vm-;

[0045] Among them, in the first equivalent circuit, the voltage drop △V between the two differential lines Vm+ and Vm- is used as the signal quantity, and the second resistor Ry is connected between the power line VCC and the ground line GND. Since the signal quantity is equal to the difference in potential between the two differential lines Vm+ and Vm-, the change in the resistance value of the second resistor Ry does not affect the signal quantity. Therefore, the second resistor Ry can be deleted, and the first equivalent circuit can be equivalent to the second equivalent circuit.

[0046] The △-shaped circuit composed of the first resistor Rx and the two bridge arms Rf1 and Rm2 connected to the power line VCC in the second equivalent circuit is equivalent to a Y-shaped circuit, and the third equivalent circuit ( Figure 7 shown);

[0047] According to Kirchhoff's law, the voltage equation of the center point of the Y-shaped circuit and the voltage equation of the two differential lines Vm+ and Vm- are obtained; then the voltage drop formula between the two differential lines Vm+ and Vm- is obtained; the deformation of the substrate 10 is converted through the voltage drop formula, and the pressure of the object 200 is converted.

[0048] The width of the pressure sensing device 100 can be 2mm or more. The pressure sensor 20 used is a thin film piezoresistive sensor 21 with a certain area, and the power line VCC, the ground line GND and the two differential lines Vm+ and Vm- are respectively led out at the ends of the thin film piezoresistive sensor 21. The pressure sensor 20 is arranged on the substrate 10. The pressure sensor 20 has the advantages of small area, small initial pressure difference, high sensitivity, small temperature drift, strong anti-interference ability, high anti-drop coefficient, stable reliability, etc. The substrate 10 is simply pressed against the object 200 under pressure, and the pressure sensor 20 is connected to the pressure sensing detection circuit. The object 200 under pressure is deformed, and the thin film piezoresistive sensor 21 of the substrate 10 deforms and follows the deformation. The voltage drop △V between the two differential lines Vm+ and Vm- is detected to detect the deformation of the substrate 10, and the pressure of the object 200 under test is converted to realize the pressure-sensitive touch function. The pressure sensing method using the pressure sensing device 100 can realize the pressure-sensitive touch function.

[0049] Further, as a specific implementation of the pressure sensing method provided by the present invention, the thin film piezoresistive sensor 21 is a square resistor, and the resistance value of each bridge arm (Rf1, Rf2, Rm1, Rm2) is equal, that is, Rf1=Rm1=Rm2=Rf2; the resistance value of the first resistor Rx is equal to the resistance value of the second resistor Ry, that is, Rx=Ry; this is obtained based on the symmetry of the resistor. It can be understood that the thin film piezoresistive sensor 21 can also be other regular polygons, irregular polygons, ellipses or circles or other shapes, and these structures can all use the above-mentioned pressure sensing method for pressure sensing.

[0050] Further, as a specific implementation of the pressure sensing method provided by the present invention, please refer to Figure 4 In the first equivalent circuit, one pair of bridge arms of the bridge circuit is denoted as Rf1 and Rf2, and the other pair of bridge arms is denoted as Rm1 and Rm2. The first resistor is denoted as Rx, and the second resistor is denoted as Ry. The long sides of the bridge arms Rm1 and Rm2 are parallel to the arrangement direction of the pressure sensor 20, and the long sides of the bridge arms Rf1 and Rf2 are perpendicular to the arrangement direction of the pressure sensor 20.

[0051] See also Figure 7 , the three equivalent resistances of the Y-shaped circuit in the third equivalent circuit are recorded as Ra, Rb, and Rc respectively; comparing the voltage-current relationship between the △-shaped circuit and the Y-shaped circuit, we can get:

[0052]

[0053] According to Kirchhoff's law, we get the following equation:

[0054] The voltage equation at the center point of the Y-shaped circuit is:

[0055]

[0056] The voltage equation of one of the differential lines Vm+ is:

[0057]

[0058] The voltage equation of another differential line Vm- is:

[0059]

[0060] The voltage drop formula between the two differential lines Vm+ and Vm- is:

[0061]

[0062] In the above voltage drop formula, there are multiple variables Rm1, Rm2, Rf1, and Rf2. In order to study the influence of each variable on the voltage drop △V, the partial derivatives of the voltage drop △V with respect to each variable are calculated below to examine the monotonicity of each variable on the voltage drop △V.

[0063] (1) Taking the partial derivative of △V with respect to Rm1, we get:

[0064]

[0065] ∵ It's a positive number.

[0066] ∴The function of ΔV with respect to Rm1 is monotonically increasing.

[0067] (2) Taking the partial derivative of △V with respect to Rm2, we get:

[0068]

[0069] ∵ It's a positive number.

[0070] ∴The function of ΔV with respect to Rm2 is monotonically increasing.

[0071] (3) Taking the partial derivative of △V with respect to Rf1, we get:

[0072]

[0073] ∵ It's a negative number.

[0074] ∴The function of ΔV to Rf1 is monotonically decreasing.

[0075] (4) Taking the partial derivative of △V with respect to Rf2, we get:

[0076]

[0077] ∵ It's a negative number.

[0078] ∴The function of ΔV to Rf2 is monotonically decreasing.

[0079] See also Figures 1 to 3 When the force F acts on the object 200, the curvature of the thin film piezoresistive sensor 21 in the long side direction increases due to the influence of the tangential strain force, and the curvature of the thin film piezoresistive sensor 21 in the short side direction does not change significantly. According to the characteristics of the pressure sensor 20, the curvature of the thin film piezoresistive sensor 21 increases, and the resistance value increases; the curvature of the thin film piezoresistive sensor 21 decreases, and the resistance value decreases. The object 200 is deformed by the pressure, and the substrate 10 is deformed, and the thin film piezoresistive sensor 21 follows the deformation.

[0080] The long sides of the bridge arms Rm1 and Rm2 are parallel to the arrangement direction of the pressure sensors 20 , and the long sides of the bridge arms Rf1 and Rf2 are perpendicular to the arrangement direction of the pressure sensors 20 . Figure 6 2 is a graph showing the change in equivalent resistance of the second equivalent circuit after the object under test 200 is pressed.

[0081] According to symmetry, it is assumed that the resistance change of Rm1 and Rm2 is △R1, and the resistance change of Rx is △R2. Since the curvature change of Rf1 and Rf2 is very small, it is assumed that Rf1 and Rf2 remain unchanged.

[0082] From the above, we can see that the relationship between the voltage drop △V (signal quantity) between the two differential lines Vm+ and Vm- and the bridge resistance is:

[0083]

[0084] And the function of ΔV to Rm1 and the function of ΔV to Rm2 are both monotonically increasing.

[0085] The above voltage drop formula also has an Rx variable, and changes in Rx have very little effect on the voltage drop ΔV.

[0086] The following simulation verifies that the change of Rx has very little effect on the voltage drop ΔV. For example, when pressing, set Rf1 = Rf2 = 5kΩ, Rm1 = Rm2 = 5000.5Ω, and Rx increases from 5k to 1Ω. The simulation results show that the ΔV curve is as follows: Figure 8 As shown in the figure, the horizontal axis is resistance (in Ω). In the above example, when the resistance value of Rx changes by one thousandth, the change of ΔV does not exceed one thousandth. When Rx is simulated with other resistance values, the effect on ΔV is also very small. It can be seen that the change of Rx caused by the voltage-variable effect has very little effect on ΔV.

[0087] The following simulation verifies that the larger the resistance of Rm1 and Rm2, the more the voltage drop ΔV increases monotonically. Set Rf1 = Rf2 = 5kΩ, and increase the resistance of Rm1 and Rm2 by 0.5Ω. The curve of ΔV obtained by simulation is as follows: Fig. 9 As shown, the horizontal axis is resistance (in Ω). It can be seen that the voltage-dependent effect increases the resistance of Rm1 and Rm2, which can make ΔV increase monotonically.

[0088] Therefore, when force is applied to the pressure sensing device 100, Rm1 and Rm2 increase, and Rf1 or Rf2 remains basically unchanged, the signal △V will increase positively. Moreover, the greater the force applied, the greater the signal △V, and after signal processing, pressure touch can be achieved.

[0089] See also Figures 1 to 3 An embodiment of the present invention provides an electronic terminal, including a measured object 200, a pressure sensing device 100 of any of the above embodiments, and a pressure sensing detection circuit electrically connected to the pressure sensor 20, and a substrate 10 is against the measured object 200.

[0090] The width of the pressure sensing device 100 can be 2mm or more. The pressure sensor 20 used is a thin film piezoresistive sensor 21 with a certain area, and the power line VCC, the ground line GND and the two differential lines Vm+ and Vm- are respectively led out at the ends of the thin film piezoresistive sensor 21. The pressure sensor 20 is arranged on the substrate 10. The pressure sensor 20 has the advantages of small area, small initial pressure difference, high sensitivity, small temperature drift, strong anti-interference ability, high anti-drop coefficient, stable reliability, etc. The substrate 10 is simply pressed against the object 200 under pressure, and the pressure sensor 20 is connected to the pressure sensing detection circuit. The object 200 under pressure is deformed, and the thin film piezoresistive sensor 21 of the substrate 10 deforms and follows the deformation. The deformation of the substrate 10 is detected by detecting the voltage drop △V between the two differential lines Vm+ and Vm-, and the pressure of the object 200 under test is converted to realize the pressure-sensitive touch function. The electronic terminal with the pressure sensing device 100 can realize the pressure-sensitive touch function.

[0091] The pressure sensing detection circuit, as a signal processing circuit, analyzes and processes the electrical signal of the pressure sensor 20 and transmits it to the main controller of the electronic terminal together with the touch position information detected by the panel, thereby achieving accurate touch pressure while identifying the touch position.

[0092] The pressure sensing detection circuit is used to detect the electrical signal obtained by the pressure sensing component and process and analyze the electrical signal. The thin film piezoresistive sensor 21 of the pressure sensor 20 is connected to the pressure sensing detection circuit through a signal line. Of course, the signal line is only used to describe the combination of the thin film piezoresistive sensor 21 and the pressure sensing detection circuit. As other embodiments, the pressure sensor 20 can also be directly or indirectly electrically connected to the detection circuit in other ways.

[0093] The pressure sensing detection circuit can be used as a control center, which receives the control information transmitted by the pressure sensor 20 and then controls the electronic terminal, etc. It is usually described as a combination of hardware and software with multiple processing methods. The hardware and software are configured to communicate the control information input by the pressure sensor 20 through feedback or a system associated with the customer and perform additional related tasks or functions.

[0094] The pressure sensing detection circuit can be implemented as a general processor, a content addressable memory, a digital signal processor, a digital-to-analog conversion switch, a programmable logic device, a discrete hardware component or other combinations; at the same time, it also has embedded algorithms and software information related to the pressure touch screen / pressure sensing system.

[0095] The hardware and software in the pressure sensing detection circuit are configured to perform a variety of functions, techniques, feedback and processing tasks associated with the client system.

[0096] Furthermore, as a specific implementation of the electronic terminal provided by the present invention, the object 200 to be tested is a panel or a frame, and the pressure-sensitive touch function of the panel or the frame is realized.

[0097] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A pressure sensing device, characterized in that: The invention comprises a substrate for contacting with a measured object, and a pressure sensor arranged on the substrate; the substrate is in an elongated strip shape, and the elongated strip-shaped substrate has two outer edges and two inner edges located inside the two outer edges, and the outer edges and the inner edges both extend along the long side direction of the substrate; the pressure sensor comprises at least one thin film piezoresistive sensor and at least four signal lines respectively led out from four corners of the thin film piezoresistive sensor, and the thin film piezoresistive sensor, the signal line and the pad at the end of the signal line of the pressure sensor are located in the area between the two inner edges; the thin film piezoresistive sensor One of the sides is parallel to the arrangement direction of the pressure sensor; one side of the thin film piezoresistive sensor is attached to the substrate and when the substrate is deformed, the resistivity distribution of the thin film piezoresistive sensor changes with the deformation, wherein the two opposite signal lines are a power line and a ground line, respectively, and the other two opposite signal lines are differential lines; the pressure of the object to be measured is detected by detecting the voltage drop between the two differential lines; when force acts on the object to be measured, the curvature of the thin film piezoresistive sensor in the long side direction increases, and the curvature of the thin film piezoresistive sensor in the short side direction does not change significantly.

2. The pressure sensing device according to claim 1, characterized in that: The number of the pressure sensors is one; or, the number of the pressure sensors is at least two, and the pressure sensors are distributed in an array; or, the number of the pressure sensors is at least two, and the pressure sensors are unevenly distributed.

3. The pressure sensing device according to claim 1, characterized in that: The thin film piezoresistive sensor is made of at least one of polycrystalline semiconductor materials, amorphous semiconductor materials, polycrystalline silicon, graphene, copper-nickel alloy, carbon nanotubes, metal fine wires, and conductor-insulator composite materials; And / or, the signal line is made of at least one material selected from the group consisting of metal, metal compound, carbon powder, conductive nanotube, and oxide powder.

4. The pressure sensing device according to claim 1, characterized in that: The thin film piezoresistive sensor is in the shape of a regular polygon, an irregular polygon, an ellipse or a circle.

5. The pressure sensing device according to claim 1, characterized in that: The substrate is a printed circuit board, and the ends of the four signal lines are connected to the printed circuit board.

6. The pressure sensing device according to claim 5, characterized in that: The printed circuit board is a paper substrate, a metal substrate, a composite substrate, a glass fiber cloth substrate or a ceramic substrate.

7. The pressure sensing device according to claim 1, characterized in that: The substrate includes a flexible circuit board and a reinforcing sheet arranged on the flexible circuit board, and the ends of the four signal lines are connected to the flexible circuit board.

8. The pressure sensing device according to claim 7, characterized in that: The reinforcing sheet is a stainless steel sheet, a glass fiber epoxy resin copper-clad sheet or an aluminum sheet.

9. The pressure sensing device according to claim 1, characterized in that: A colloid for bonding with a measured object is disposed on a side of the substrate away from the pressure sensor.

10. The pressure sensing device according to claim 1, characterized in that: The width of the pressure sensing device is greater than or equal to 1 mm.

11. The pressure sensing device according to claim 1, characterized in that: The deformation direction of the pressure sensor is parallel to the long side direction of the pressure sensing device.

12. A pressure sensing method, characterized in that: It uses the pressure sensing device according to any one of claims 1 to 11, comprising the following steps: placing the substrate against the object to be measured; The thin film piezoresistive sensor is equivalent to a first equivalent circuit, wherein the first equivalent circuit includes a bridge circuit having two pairs of bridge arms, a first resistor connected between the two differential lines, and a second resistor connected between the power line and the ground line, two ends of the bridge circuit are respectively connected to the power line and the ground line, and the other two ends of the bridge circuit are respectively connected to the two differential lines; The second resistor in the first equivalent circuit has a negligible effect on the signal quantity, and the second resistor is deleted to obtain a second equivalent circuit; the second equivalent circuit includes a bridge circuit with two pairs of bridge arms, and a first resistor connected between the two differential lines, two ends of the bridge circuit are respectively connected to the power line and the ground line, and the other two ends of the bridge circuit are respectively connected to the two differential lines; The first resistor in the second equivalent circuit and the delta-shaped circuit formed by the two bridge arms connected to the power line are equivalent to a Y-shaped circuit to obtain a third equivalent circuit; According to Kirchhoff's law, the voltage equation of the center point of the Y-shaped circuit and the voltage equation of the two differential lines are obtained; then the voltage drop formula between the two differential lines is obtained; the deformation of the substrate is converted through the voltage drop formula, and the pressure of the object under test is converted.

13. The pressure sensing method according to claim 12, wherein: In the first equivalent circuit, of the two pairs of bridge arms of the bridge circuit, one pair of the bridge arms is denoted as Rf1 and Rf2, and the other pair of the bridge arms is denoted as Rm1 and Rm2, the first resistor is denoted as Rx, and the second resistor is denoted as Ry; the long sides of the bridge arms Rm1 and Rm2 are parallel to the arrangement direction of the pressure sensors, and the long sides of the bridge arms Rf1 and Rf2 are perpendicular to the arrangement direction of the pressure sensors; The three equivalent resistances of the Y-shaped circuit in the third equivalent circuit are respectively denoted as Ra, Rb, and Rc; The voltage equation at the center point of the Y-shaped circuit is: The voltage equation for one of the differential lines is: The voltage equation of the other differential line is: The voltage drop formula between the two differential lines is:

14. The pressure sensing method according to claim 12 or 13, characterized in that: The thin film piezoresistive sensor is a square resistor, the resistance value of each bridge arm is equal, and the resistance value of the first resistor is equal to the resistance value of the second resistor.

15. An electronic terminal, characterized in that It comprises a measured object, a pressure sensing device as claimed in any one of claims 1 to 11, and a pressure sensing detection circuit electrically connected to the pressure sensor, wherein the substrate abuts against the measured object.

16. The electronic terminal according to claim 15, characterized in that: The object to be tested is a panel or a frame.

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