Pressure Sensing Circuit with Temperature Compensation and Pressure Detection Device

Abstract

The present application relates to a pressure sensing circuit with temperature compensation and a pressure detection device. By arranging a piezoresistive sensing element at the sensing part of the probe head, the first end thereof is used to receive an external voltage; a constant voltage is provided to the reference sensing element through a voltage supply module to generate a loop current flowing through the reference sensing element, and then the loop current is mirrored to the conductive path of the piezoresistive sensing element by a current mirror module to generate a pressure sensing signal at the second end of the piezoresistive sensing element. Since the reference sensing element and the piezoresistive sensing element are in the same ambient temperature, and the change in the resistance of the reference sensing element with the temperature rise of the ambient temperature is positively correlated with the change in the resistance of the piezoresistive sensing element with the temperature rise of the ambient temperature, the error generated in the pressure sensing signal caused by the influence of the resistance of the piezoresistive sensing element due to temperature change can be compensated, and finally the accuracy of pressure detection can be improved.

Description

Technical Field

[0001] This application relates to the field of pressure detection, and more particularly to a pressure sensing circuit with temperature compensation and a pressure detection device. Background Art

[0002] A pressure sensor, as a contact sensing device, is an output device that converts pressure information into an electrical signal. For a piezoresistive pressure sensor, when subjected to an external pressure, the resistance of the pressure sensor changes. After being connected to a conductive path, it is manifested as a change in the output electrical signal.

[0003] However, due to material reasons, the resistance value of a piezoresistive sensor is affected by the external ambient temperature, resulting in a temperature drift phenomenon. As a result, there is an error in the output pressure detection signal, which affects the accuracy of pressure detection. Summary of the Invention

[0004] This application provides a pressure sensing circuit with temperature compensation that can improve the accuracy of pressure detection.

[0005] A pressure sensing circuit with temperature compensation is applied to a pressure detection device. The pressure detection device includes a probe head. The pressure sensing circuit includes:

[0006] A reference sensing element;

[0007] A pressure supply module is respectively connected to the first end and the second end of the reference sensing element, and is used to provide a constant voltage to the reference sensing element to generate a loop current flowing through the reference sensing element;

[0008] A piezoresistive sensing element is disposed at a sensing portion of the probe head. The resistance value of the piezoresistive sensing element is used to characterize the pressure value received by the sensing portion. The first end of the piezoresistive sensing element is used to receive an external voltage;

[0009] A current mirror module is respectively connected to the second end of the piezoresistive sensing element, the second end of the reference sensing element, and the pressure supply module, and is used to mirror the loop current to the conductive path of the piezoresistive sensing element to generate a pressure sensing signal at the second end of the piezoresistive sensing element;

[0010] Wherein, the reference sensing element and the piezoresistive sensing element are at the same ambient temperature, and the change in the resistance value of the reference sensing element with the temperature rise of the ambient temperature is positively correlated with the change in the resistance value of the piezoresistive sensing element with the temperature rise of the ambient temperature.

[0011] In one embodiment, the number of the probe heads and the piezoresistive sensing elements are respectively multiple, and each piezoresistive sensing element is respectively disposed at the sensing portion of each probe head in one-to-one correspondence.

[0012] In one embodiment, the current mirror module includes an input - side switching transistor and at least one output - side switching transistor;

[0013] The first connection end and the control end of the input - side switching transistor are commonly connected, and are respectively connected to the control ends of the output - side switching transistors, the second end of the reference sensing element, and the voltage supply module; the second connection end of the input - side switching transistor is connected to the ground end; the first connection ends of the output - side switching transistors are respectively connected to the second ends of the piezoresistive sensing elements; the second connection ends of the output - side switching transistors are respectively connected to the ground end.

[0014] In one embodiment, the current mirror module further includes a first pull - down resistor and at least one second pull - down resistor; the first end of the first pull - down resistor is connected to the second connection end of the input - side switching transistor, and the second end of the first pull - down resistor is connected to the ground end; the first ends of the second pull - down resistors are respectively and correspondingly connected to the second connection ends of the output - side switching transistors, and the second ends of the second pull - down resistors are respectively connected to the ground end; the first pull - down resistor and each of the second pull - down resistors have the same resistance value.

[0015] In one embodiment, the voltage supply module includes:

[0016] A power supply unit for outputting a power supply voltage;

[0017] A voltage holding unit is respectively connected to the first end and the second end of the reference sensing element, the power supply unit, and the current mirror module, and is used to generate and output the constant voltage to the reference sensing element according to the power supply voltage, and maintain the voltage drop of the reference sensing element equal to the constant voltage.

[0018] In one embodiment, the constant voltage is equal to the power supply voltage.

[0019] In one embodiment, the voltage holding unit includes resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, operational amplifier U1, operational amplifier U2, and switching transistor Q1;

[0020] The first end of the resistor R11 is connected to the power supply unit, and the second end of the resistor R11 is respectively connected to the non-inverting terminal of the operational amplifier U1 and the first end of the resistor R12; the inverting terminal of the operational amplifier U1 is respectively connected to the first end of the resistor R13 and the first end of the resistor R14, and the output terminal of the operational amplifier U1 is connected to the first end of the resistor R15; the second end of the resistor R15 is connected to the control terminal of the switching transistor Q1; the first connection end of the switching transistor Q1 is used to receive the input voltage; the second end of the resistor R13 is connected to the ground terminal; the second end of the resistor R14 is respectively connected to the second connection end of the switching transistor Q1 and the first end of the reference sensing element; the second end of the resistor R12 is respectively connected to the inverting terminal and the output terminal of the operational amplifier U2; the non-inverting terminal of the operational amplifier U2 is respectively connected to the second end of the reference sensing element and the current mirror module; wherein, the resistor R11 and the resistor R12 have equal resistance values; the resistor R13 and the resistor R14 have equal resistance values.

[0021] In one embodiment, the resistance value of the reference sensing element changes with the temperature rise of the ambient temperature in the same manner as the resistance value of the piezoresistive sensing element changes with the temperature rise of the ambient temperature.

[0022] In one embodiment, both the piezoresistive sensing element and the reference sensing element are strain sensors.

[0023] A pressure detection device, comprising:

[0024] A pressure detection device;

[0025] And the pressure sensing circuit with temperature compensation according to any one of the above embodiments.

[0026] In one embodiment, the pressure detection device is further connected to the second end of the piezoresistive sensing element, and is configured to collect the pressure sensing signal and obtain the pressure value received by the sensing part according to the pressure sensing signal.

[0027] The above pressure sensing circuit with temperature compensation sets the piezoresistive sensing element at the sensing part of the probe head, and its first end is used to receive an external voltage; the supply voltage module provides a constant voltage to the reference sensing element to generate a loop current flowing through the reference sensing element, and then the current mirror module mirrors the loop current to the conductive path of the piezoresistive sensing element to generate a pressure sensing signal at the second end of the piezoresistive sensing element. Since the voltage value of the constant voltage remains unchanged, the reference sensing element and the piezoresistive sensing element are in the same ambient temperature, and the change in the resistance of the reference sensing element with the temperature rise is positively correlated with the change in the resistance of the piezoresistive sensing element with the temperature rise. In this way, the influence of temperature on the resistance change of the piezoresistive sensing element can be transferred to the current flowing through the piezoresistive sensing element, thereby compensating for the error in the generation of the pressure sensing signal caused by the influence of the resistance of the piezoresistive sensing element due to temperature change, and finally improving the accuracy of pressure detection. Description of the Drawings

[0028] Figure 1 It is a structural block diagram of a pressure sensing circuit with temperature compensation according to an embodiment of the present application;

[0029] Figure 2 It is a structural block diagram of a pressure sensing circuit with temperature compensation according to another embodiment of the present application;

[0030] Figure 3 It is a circuit structure diagram of a traditional Wheatstone bridge circuit;

[0031] Figure 4 It is a circuit structure diagram of a pressure sensing circuit with temperature compensation according to an embodiment of the present application;

[0032] Figure 5 It is a circuit structure diagram of a pressure sensing circuit with temperature compensation according to another embodiment of the present application;

[0033] Figure 6 It is a structural block diagram of a pressure sensing circuit with temperature compensation according to another embodiment of the present application;

[0034] Figure 7 It is a circuit structure diagram of a pressure sensing circuit with temperature compensation according to another embodiment of the present application;

[0035] Figure 8 It is a circuit structure diagram of a pressure sensing circuit with temperature compensation according to another embodiment of the present application. Detailed Embodiments

[0036] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0038] It should be noted that all directional indications (such as up, down, left, right, front, back,...) in the embodiments of the present application are only used to explain the relative position relationship and movement situation between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly. The connection described herein can be a direct connection or an indirect connection.

[0039] In addition, the descriptions such as "first" and "second" in the present application are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0040] Figure 1 A pressure sensing circuit with temperature compensation for an embodiment. The pressure sensing circuit is applied to a pressure detection device. The pressure detection device includes a probe head. The pressure sensing circuit includes a reference sensing element 110, a pressure supply module 120, a piezoresistive sensing element 130, and a current mirror module 140. The pressure supply module 120 is respectively connected to the first end and the second end of the reference sensing element 110, and is used to provide a constant voltage V1 to the reference sensing element 110 to generate a loop current I1 flowing through the reference sensing element 110. The piezoresistive sensing element 130 is disposed at the sensing portion of the probe head. The resistance value of the piezoresistive sensing element 130 is used to characterize the pressure value received by the sensing portion. The first end of the piezoresistive sensing element 130 is used to receive an external voltage VCC. The current mirror module 140 is respectively connected to the second end of the piezoresistive sensing element 130, the second end of the reference sensing element 110, and the pressure supply module 120, and is used to mirror the loop current I1 to the conductive path of the piezoresistive sensing element 130 to generate a pressure sensing signal Vout at the second end of the piezoresistive sensing element 130. Wherein, the reference sensing element 110 and the piezoresistive sensing element 130 are in the same ambient temperature, and the change in the resistance value of the reference sensing element 110 with the rise in ambient temperature is positively correlated with the change in the resistance value of the piezoresistive sensing element 130 with the rise in ambient temperature.

[0041] Among them, the reference sensing element 110 and the piezoresistive sensing element 130 can both be piezoresistive pressure sensing elements. For example, they can be strain sensors that can be directly pasted on the sensing part of the probe head, or they can be diffused piezoresistive sensors. The piezoresistive sensing element 130 is arranged on the sensing part of the probe head of the pressure detection device. When the sensing part is subjected to an external force, the piezoresistive sensing element 130 deforms, resulting in a change in its internal resistance. The reference sensing element 110 is used as a reference and is not arranged on the sensing part of the probe head, so it will not deform. It is only in the same ambient temperature as the piezoresistive sensing element 130. Since the change in the resistance of the reference sensing element 110 with the temperature rise in the ambient temperature is positively correlated with the change in the resistance of the piezoresistive sensing element 130 with the temperature rise in the ambient temperature, when the ambient temperature changes, the change direction of the resistance change of the reference sensing element 110 is the same as that of the resistance change of the piezoresistive sensing element 130, that is, the resistance values both increase or decrease. The power supply module 120 is connected to both ends of the reference sensing element 110 to provide a constant voltage to the reference sensing element 110. It can be understood that the voltage value of the constant voltage remains fixed. The change in the resistance of the reference sensing element 110 caused by temperature is completely reflected in the loop current I1 flowing through the reference sensing element 110. Under the action of the current mirror module 140, the current I2 flowing through the piezoresistive sensing element 130 is equal to the loop current I1. In this way, the influence of temperature on the resistance change of the reference sensing element 110, that is, the influence of temperature on the resistance change of the piezoresistive sensing element 130, can be transferred to the current I2 flowing through the piezoresistive sensing element 130, thereby compensating for the error in the pressure sensing signal Vout caused by the influence of the resistance of the piezoresistive sensing element 130 due to temperature change.

[0042] Specifically, let the constant voltage be V1. When there is no temperature drift, the resistance of the reference sensing element 110 is Rc. At the same time, when the piezoresistive sensing element 130 has no deformation, the resistance of the piezoresistive sensing element 130 is Ro. When the temperature changes, the change in the resistance of the reference sensing element 110 caused by temperature drift is ΔR T1 , the change in the resistance of the piezoresistive sensing element 130 is ΔR T2 , and the change in the resistance of the reference sensing element 110 caused by deformation is ΔR N . When there is no temperature drift, the loop current I1 can be expressed as V1 / Rc, that is, it is also equal to the current I2 flowing through the piezoresistive sensing element 130. The potential value at the first end of the piezoresistive sensing element 130 is equal to the voltage value of the external voltage VCC. The voltage value of the pressure sensing signal Vout is equal to the potential value at the second end of the piezoresistive sensing element 130, that is, equal to VCC - (Ro + ΔR N )I2 = VCC - (Ro + ΔR N )V1 / Rc; when there is temperature drift, the loop current I1 can be expressed as V1 / (Rc + ΔR T1 ), and the voltage value of the pressure sensing signal Vout is equal to VCC - (Ro + ΔRN +ΔR T1 )I2 = VCC - (Ro + ΔR N +ΔR T2 )V1 / (Rc + ΔR T1 ),where ΔR T1 is much smaller than Rc, and ΔR T2 is much smaller than Ro. Since the temperature rise change of the reference sensing element with the ambient temperature is positively correlated with the temperature rise change of the piezoresistive sensing element with the ambient temperature, so ΔR T1 changes synchronously with ΔR T2 in the same change direction, weakening the ΔR T2 's influence on the subtraction term (Ro + ΔR N +ΔR T2 )V1 / (Rc + ΔR T1 ) in the formula, thus compensating for the error of the pressure sensing signal Vout caused by the influence of the temperature change on the resistance value of the piezoresistive sensing element 130, and finally improving the accuracy of pressure detection.

[0043] The pressure sensing circuit with temperature compensation according to the embodiment of the present invention includes a reference sensing element 110, a voltage supply module 120, a piezoresistive sensing element 130, and a current mirror module 140; the piezoresistive sensing element 130 is disposed on the sensing part of the probe head, and the resistance value of the piezoresistive sensing element 130 is used to represent the pressure value received by the sensing part, and the first end of the piezoresistive sensing element 130 is used to receive an external voltage; a constant voltage is provided to the reference sensing element 110 through the voltage supply module 120 to generate a loop current I1 flowing through the reference sensing element 110, and then the current mirror module 140 mirrors the loop current I1 to the conductive path of the piezoresistive sensing element 130 to generate a pressure sensing signal Vout at the second end of the piezoresistive sensing element 130. Since the voltage value of the constant voltage remains unchanged, the reference sensing element 110 and the piezoresistive sensing element 130 are in the same ambient temperature, and the change of the resistance value of the reference sensing element 110 with the temperature rise of the ambient temperature is positively correlated with the change of the resistance value of the piezoresistive sensing element 130 with the temperature rise of the ambient temperature. In this way, the influence of temperature on the resistance value change of the piezoresistive sensing element 130 can be transferred to the current I2 flowing through the piezoresistive sensing element 130, thereby compensating for the error of the pressure sensing signal Vout caused by the influence of the temperature change on the resistance value of the piezoresistive sensing element 130.

[0044] In one embodiment, the change of the resistance value of the reference sensing element with the temperature rise of the ambient temperature is the same as the change of the resistance value of the piezoresistive sensing element with the temperature rise of the ambient temperature.

[0045] It can be understood that when the resistance change of the reference sensing element with the temperature rise of the ambient temperature is the same as that of the piezoresistive sensing element with the temperature rise of the ambient temperature, the influence of temperature on the resistance change of the piezoresistive sensing element 130 can be equally transferred to the current I2 flowing through the piezoresistive sensing element 130, thereby compensating for the error of the pressure sensing signal Vout caused by the influence of the resistance of the piezoresistive sensing element 130 on the temperature change.

[0046] Specifically, if ΔR T1 and ΔR T2 are the same, and both are assumed to be equal to ΔR T , then the voltage value of the pressure sensing signal Vout is equal to VCC - (Ro + ΔR N + ΔR T )V1 / (Rc + ΔR T ). Since ΔR T is much smaller than Rc and Ro, the voltage value of the pressure sensing signal Vout can be approximately equal to VCC - (Ro + ΔR N )V1 / Rc. Therefore, the deviation of the pressure sensing signal Vout caused by the temperature drift can be ignored, thereby greatly improving the accuracy of pressure detection.

[0047] In one embodiment, the number of the probe heads and the piezoresistive sensing elements are respectively multiple, and each piezoresistive sensing element (1301,..., 130N) is respectively and correspondingly arranged in the sensing part of each probe head.

[0048] As Figure 2 shown, the piezoresistive sensing elements 1301 to 130N are respectively and correspondingly arranged in the sensing part of each probe head. In this way, multi-channel pressure sensing can be achieved through multiple probe heads. The first ends of each piezoresistive sensing element (1301,..., 130N) are respectively used to receive the external voltage VCC, and the second ends are respectively connected to the current mirror module 140. The current mirror module 140 mirrors the loop current I1 to the conductive paths where each piezoresistive sensing element (1301,..., 130N) is located, so that the current flowing through each piezoresistive sensing element (1301,..., 130N) is equal to the loop current I1. In this way, the influence of temperature on the resistance change of each piezoresistive sensing element 130 is transferred to the current I2 flowing through each piezoresistive sensing element (1301,..., 130N), thereby compensating for the error of each pressure sensing signal (Vout1,..., VoutN) caused by the influence of the resistance of each piezoresistive sensing element (1301,..., 130N) on the temperature change.

[0049] Among them, according to actual requirements, the resistance values of each piezoresistive sensing element (1301,..., 130N) and the voltage values of the external voltage VCC respectively received by each piezoresistive sensing element (1301,..., 130N) can be the same or different; when they are the same, the external voltage can be the same voltage.

[0050] The traditional method usually uses a Wheatstone bridge circuit to achieve pressure detection. For example, Figure 3 as shown, the series circuit of strain resistors R21 and resistor R24, and the series circuit of strain resistors R22 and resistor R23 are respectively connected in parallel across the power supply to receive the power supply voltage VS. Resistors R23 and R24 have equal resistance values, and strain resistors R22 and R22 have equal resistance values and are respectively arranged on the front and back sides of the deformation probe. Thus, when the probe is stressed, the two strain resistors respectively undergo positive and negative deformations, that is, the resistance value of one of the two strain resistors increases, and the resistance value of the other decreases. The output Vo is equal to the potential difference between the potential between strain resistor R22 and resistor R24 and the potential between strain resistor R22 and resistor R23; the temperature drift characteristics of strain resistors R21 and R22 are the same, that is, under the influence of the same ambient temperature, their resistance values both increase by ΔR. When a temperature drift phenomenon occurs, the output voltage Vo = R24 / (R24 + R22 + ΔR)*VS - R23 / (R23 + R22 + ΔR)*VS = 0V (taking the case of no deformation as an example). In this way, the influence of temperature drift on the output voltage Vo can be eliminated. However, for each additional pressure detection channel in this method, two strain resistors need to be added, which increases the hardware cost and the occupied volume. In contrast, in this application, by sharing the same reference sensing element 110, for each additional pressure detection channel, only one piezoresistive sensing element needs to be added, with a smaller increase in the number of sensing elements, lower hardware cost, and smaller occupied volume.

[0051] In one embodiment, as Figure 4 shown, the current mirror module 140 includes an input-side switching transistor Qi and at least one output-side switching transistor (Qo1,..., Qo N ); the first connection end and the control end of the input-side switching transistor Qi are commonly connected and are respectively connected to the control ends of each output-side switching transistor (Qo1,..., Qo N ), the second end of the reference sensing element 110, and the pressure supply module 120; the second connection end of the input-side switching transistor Qi is connected to the ground terminal; the first connection ends of each output-side switching transistor (Qo1,..., Qo N ) are respectively connected to the second ends of each piezoresistive sensing element (1301,..., 130N); the second connection ends of each output-side switching transistor (Qo1,..., Qo N ) are respectively connected to the ground terminal.

[0052] Among them, the ground terminals to which each switching transistor in the figure is connected can be the same ground terminal; each switching transistor can be, for example, a triode, and can be of the same type of switching transistor. Among them, the first connection end can be the collector, the second connection end can be the emitter, and the control end can be the base.

[0053] In this embodiment, through one input-side switching transistor and multiple output-side switching transistors (Qo1,..., Qo N)Multiple current mirrors are formed to mirror the current flowing through the input - side switching transistor, i.e., the loop current I1, to each output - side switching transistor (Qo1, …… Qo N ) in the current path where it is located, so that the current flowing through each piezoresistive sensing element (1301, …… 130N) is also equal to the loop current I1, to compensate for the influence of the piezoresistive sensing elements (1301, …… 130N) on the output pressure sensing signals (Vout1, …… VoutN) due to temperature drift.

[0054] In one embodiment, as Figure 5 shown, the current - mirror module 140 further includes a first pull - down resistor RL1 and at least one second pull - down resistor (RL 21 , ……, RL 2N ); the first end of the first pull - down resistor RL1 is connected to the second connection end of the input - side switching transistor Qi, and the second end of the first pull - down resistor RL1 is connected to the ground terminal; the first ends of the second pull - down resistors (RL 21 , ……, RL 2N ) are respectively and correspondingly connected to the second connection ends of the output - side switching transistors (Qo1, …… Qo N ), and the second ends of the second pull - down resistors (RL 21 , ……, RL 2N ) are respectively connected to the ground terminal; the first pull - down resistor RL1 and the second pull - down resistors (RL 21 , ……, RL 2N ) have the same resistance value.

[0055] It can be understood that directly connecting a pull - down resistor between the second connection end of each switching transistor and the ground terminal can protect the switching transistor. Among them, the first pull - down resistor RL1 and the second pull - down resistors (RL 21 , ……, RL 2N ) have the same resistance value, which can ensure that the input - side switching transistor and the output - side switching transistor can form a current mirror, so as to ensure that the loop current I1 can be mirrored to the conductive paths where each output - side switching transistor is located, that is, the conductive paths where each piezoresistive sensing element (1301, …… 130N) is located.

[0056] In one embodiment, as Figure 6 shown, the voltage - supplying module 120 includes a power - supply unit 121 and a voltage - holding unit 122. The power - supply unit 121 is used to output a power - supply voltage; the voltage - holding unit 122 is respectively connected to the first end and the second end of the reference sensing element 110, the power - supply unit 121, and the current - mirror module 140, and is used to generate and output a constant voltage to the reference sensing element 110 according to the power - supply voltage and keep the voltage drop of the reference sensing element 110 equal to the constant voltage.

[0057] Among them, the power supply unit 121 may include a positive terminal and a negative terminal, where the negative terminal is connected to the ground terminal, and the positive terminal is connected to the voltage holding unit 122 to output a power supply voltage; the voltage holding unit 122 can generate a constant voltage according to the power supply voltage, so as to be applied to the reference sensing element 110, and maintain the voltage drop across the reference sensing element 110 equal to the constant voltage, so as to generate a current flowing through the reference sensing element 110 whose value is uniquely related to the resistance of the reference sensing element 110.

[0058] In one embodiment, the constant voltage may be equal to the power supply voltage.

[0059] It can be understood that by reasonably setting the operating parameters of each component in the voltage holding unit 122, the output constant voltage can be made the same as the power supply voltage. In this way, to adapt to more detection scenarios, when it is necessary to change the constant voltage to adjust the loop current I1, it can be achieved by directly changing the power supply voltage, and the adjustment process is more intuitive and simple.

[0060] In one embodiment, as Figure 7 shown, the voltage holding unit 122 includes a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, an operational amplifier U1, an operational amplifier U2, and a switching transistor Q1;

[0061] The first end of the resistor R11 is connected to the power supply unit 121, and the second end of the resistor R11 is respectively connected to the non-inverting terminal of the operational amplifier U1 and the first end of the resistor R12; the inverting terminal of the operational amplifier U1 is respectively connected to the first end of the resistor R13 and the first end of the resistor R14, and the output terminal of the operational amplifier U1 is connected to the first end of the resistor R15; the second end of the resistor R15 is connected to the control terminal of the switching transistor Q1; the first connection end of the switching transistor Q1 is used to receive the input voltage VDD; the second end of the resistor R13 is connected to the ground terminal; the second end of the resistor R14 is respectively connected to the second connection end of the switching transistor Q1 and the first end of the reference sensing element 110; the second end of the resistor R12 is respectively connected to the inverting terminal and the output terminal of the operational amplifier U2; the non-inverting terminal of the operational amplifier U2 is respectively connected to the second end of the reference sensing element 110 and the current mirror module 140; among them, the resistance values of the resistor R11 and the resistor R12 are equal; the resistance values of the resistor R13 and the resistor R14 are equal.

[0062] It can be understood that assuming the power supply voltage is Vin, the potential at the non-inverting terminal of the operational amplifier U1 is V2, the potential at the second terminal of the resistor R12 is V4, and the potential at the first terminal of the reference sensing element 110 is V3. On the one hand, due to the virtual short between the non-inverting terminal and the inverting terminal of the operational amplifier U1, the potential between the resistor R13 and the resistor R14 is also V2. Since the resistance values of the resistor R13 and the resistor R14 are equal, the potential at the first terminal of the reference sensing element 110 is V3 = 2V2. On the other hand, since the resistance values of the resistor R11 and the resistor R12 are equal, then Vin - V2 = V2 - V4, that is, Vin = 2V2 - V4 = V3 - V4. Also, due to the virtual short between the non-inverting terminal and the inverting terminal of the operational amplifier U2, the potential at the second terminal of the reference sensing element 110 is also V4. Then the voltage drop across the reference sensing element 110 is V3 - V4 = Vin.

[0063] Among them, the output terminal of the operational amplifier U1 can be connected to the control terminal of the switching transistor Q1 through the resistor R15 to control the closing and opening of the switching transistor. In addition, the power supply terminals of the operational amplifier U1 and the operational amplifier U2 can both be used to receive the input voltage VDD, and the ground terminals are used to connect to the ground terminal.

[0064] In one embodiment, both the piezoresistive sensing element 130 and the reference sensing element 110 can be strain gauges.

[0065] It can be understood that the strain gauge is an adhesive strain gauge, which has high sensitivity and small volume, and is more convenient to be arranged on the sensing part of the probe.

[0066] The embodiment of the present invention also provides a pressure sensing circuit with temperature compensation, which is applied to a pressure detection device. The pressure detection device includes at least one probe, as Figure 8 shown, the pressure sensing circuit includes a reference sensing element, a pressure supply module 120, a current mirror module 140, and at least one piezoresistive sensing element. The change in the resistance value of the reference sensing element with the rise in ambient temperature can be the same as the change in the resistance value of the piezoresistive sensing element with the rise in ambient temperature.

[0067] Among them, each piezoresistive sensing element (whose resistances are Ro1,..., Ro N ) and the reference sensing element (whose resistance is Rc) can both be strain gauges. Each piezoresistive sensing element is arranged on the sensing part of each probe. The resistance value of the piezoresistive sensing element is used to characterize the pressure value received by the sensing part. The first terminals of each piezoresistive sensing element, that is, the first terminals of each resistor Ro1,..., Ro N are respectively used to receive each external voltage VCC.

[0068] The supply voltage module 120 includes a power supply unit 121 and a voltage holding unit 122. The power supply unit 121 is used to output a power supply voltage. The voltage holding unit 122 is connected to the first end and the second end of the reference sensing element 110, the power supply unit 121, and the current mirror module 140 respectively, and is used to generate and output a constant voltage to the reference sensing element 110 according to the power supply voltage, and maintain the voltage drop of the reference sensing element 110 equal to the constant voltage to generate a loop current I1 flowing through the reference sensing element 110. Among them, the voltage holding unit 122 includes a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, an operational amplifier U1, an operational amplifier U2, and a switching transistor Q1. The first end of the resistor R11 is connected to the power supply unit 121, and the second end of the resistor R11 is respectively connected to the non-inverting terminal of the operational amplifier U1 and the first end of the resistor R12. The inverting terminal of the operational amplifier U1 is respectively connected to the first end of the resistor R13 and the first end of the resistor R14, and the output terminal of the operational amplifier U1 is connected to the first end of the resistor R15. The second end of the resistor R15 is connected to the control terminal of the switching transistor Q1. The first connection terminal of the switching transistor Q1 is used to receive an input voltage. The second end of the resistor R13 is connected to the ground terminal. The second end of the resistor R14 is respectively connected to the second connection terminal of the switching transistor Q1 and the first end of the reference sensing element 110. The second end of the resistor R12 is respectively connected to the inverting terminal and the output terminal of the operational amplifier U2. The non-inverting terminal of the operational amplifier U2 is connected to the second end of the reference sensing element 110. Among them, the resistance values of the resistor R11 and the resistor R12 are equal; the resistance values of the resistor R13 and the resistor R14 are equal.

[0069] The current mirror module 140 includes an input side switching transistor Qi, a first pull-down resistor RL1, at least one output side switching transistor (Qo1,..., Qo N ) and at least one second pull-down resistor (RL 21 ,..., RL 2N ). The first connection terminal and the control terminal of the input side switching transistor Qi are commonly connected, and are respectively connected to the control terminals of the output side switching transistors (Qo1,..., Qo N ), the second end of the reference sensing element 110, and the non-inverting terminal of the operational amplifier U2. The second connection terminal of the input side switching transistor is connected to the ground terminal through the first pull-down resistor. The first connection terminals of the output side switching transistors (Qo1,..., Qo N ) are respectively connected to the second ends of the piezoresistive sensing elements (1301,..., 130N). The second connection terminals of the output side switching transistors (Qo1,..., Qo N ) are respectively connected to the ground terminal through the second pull-down resistors.

[0070] For the specific principle and beneficial effects of this embodiment, reference can be made to the above pressure sensing circuit embodiment, and details will not be elaborated here.

[0071] An embodiment of the present invention further provides a pressure detection device, including a pressure detection means and the pressure sensing circuit with temperature compensation in any of the above embodiments.

[0072] It can be understood that the pressure detection means includes a probe head, and the piezoresistive sensing element 130 of the pressure sensing circuit is arranged at the sensing part of the probe head to sense the external pressure. The number of the probe head and the piezoresistive sensing element 130 can be multiple respectively, so as to realize multi-channel pressure measurement. The specific circuit, principle and beneficial effects can be referred to Figure 2 、 Figure 4 、 Figure 5 and Figure 8 the embodiments, which will not be elaborated here.

[0073] In one embodiment, the pressure detection means is also connected to the second end of the piezoresistive sensing element 130, for collecting the pressure sensing signal Vout, and obtaining the pressure value received by the sensing part according to the pressure sensing signal Vout.

[0074] It can be understood that the pressure detection means can also have the functions of collection and data processing, so as to collect and process the pressure sensing signal Vout. Since the resistance value of the piezoresistive sensing element 130 represents the pressure value received by the sensing part, when the resistance value changes due to the pressure, the pressure sensing signal Vout will also change. Therefore, the pressure value received by the sensing part can be correspondingly obtained according to the pressure sensing signal Vout.

[0075] Among them, when the number of piezoresistive sensing elements includes multiple, the pressure detection means is respectively connected to the second ends of each piezoresistive sensing element (1301,..., 130N), so as to obtain multiple pressure sensing signals (Vout1,..., VoutN), and the pressure values received by the sensing parts of the corresponding probe heads can be obtained according to each pressure sensing signal (Vout1,..., VoutN).

[0076] The beneficial effects of this embodiment can be referred to the beneficial effects of the above-mentioned pressure sensing circuit embodiments, which will not be elaborated here.

[0077] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied to other related technical fields, shall be included in the patent protection scope of the present application by the same token.

Claims

1. A pressure sensing circuit with temperature compensation, characterized in that, Applied to a pressure detection device, the pressure detection device includes a probe head, and the pressure sensing circuit includes: A reference sensing element, which is arranged outside the sensing part of the probe head; A pressure supply module, which is respectively connected to the first end and the second end of the reference sensing element, and is used to provide a constant voltage to the reference sensing element to generate a loop current flowing through the reference sensing element; A piezoresistive sensing element, which is arranged in the sensing part of the probe head. The resistance value of the piezoresistive sensing element is used to characterize the pressure value received by the sensing part. The first end of the piezoresistive sensing element is used to receive an external voltage; A current mirror module, which is respectively connected to the second end of the piezoresistive sensing element, the second end of the reference sensing element and the pressure supply module, and is used to mirror the loop current to the conduction path of the piezoresistive sensing element, so as to transfer the influence of temperature on the resistance value change of the reference sensing element to the current flowing through the piezoresistive sensing element, and generate a pressure sensing signal at the second end of the piezoresistive sensing element based on the current flowing through the piezoresistive sensing element; Wherein, the reference sensing element and the piezoresistive sensing element are in the same ambient temperature, and the change of the resistance value of the reference sensing element with the rise of the ambient temperature is positively correlated with the change of the resistance value of the piezoresistive sensing element with the rise of the ambient temperature; The current mirror module includes an input-side switching tube, a first pull-down resistor, at least one output-side switching tube and at least one second pull-down resistor; the first connection end and the control end of the input-side switching tube are commonly connected, and are respectively connected to the control end of each output-side switching tube, the second end of the reference sensing element and the pressure supply module; the second connection end of the input-side switching tube is connected to the first end of the first pull-down resistor, and the second end of the first pull-down resistor is connected to the ground end; the first connection end of each output-side switching tube is respectively connected to the second end of each piezoresistive sensing element; the second connection end of each output-side switching tube is respectively connected to the first end of each second pull-down resistor, and the second end of each second pull-down resistor is respectively connected to the ground end; the first pull-down resistor and each second pull-down resistor have the same resistance value.

2. The pressure sensing circuit according to claim 1, characterized in that The number of the probe heads and the piezoresistive sensing elements are respectively multiple, and each piezoresistive sensing element is respectively arranged in the sensing part of each probe head in a one-to-one correspondence manner.

3. The pressure sensing circuit according to claim 1, characterized in that, The pressure supply module includes: A power supply unit, which is used to output a power supply voltage; A voltage holding unit, which is respectively connected to the first end and the second end of the reference sensing element, the power supply unit and the current mirror module, and is used to generate and output the constant voltage to the reference sensing element according to the power supply voltage, and keep the voltage drop of the reference sensing element equal to the constant voltage; The voltage holding unit includes a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, an operational amplifier U1, an operational amplifier U2, and a switching transistor Q1; a first end of the resistor R11 is connected to the power supply unit, and a second end of the resistor R11 is respectively connected to a non-inverting terminal of the operational amplifier U1 and a first end of the resistor R12; an inverting terminal of the operational amplifier U1 is respectively connected to a first end of the resistor R13 and a first end of the resistor R14, and an output terminal of the operational amplifier U1 is connected to a first end of the resistor R15; a second end of the resistor R15 is connected to a control terminal of the switching transistor Q1; a first connection end of the switching transistor Q1 is used to receive an input voltage; a second end of the resistor R13 is connected to the ground terminal; a second end of the resistor R14 is respectively connected to a second connection end of the switching transistor Q1 and a first end of the reference sensing element; a second end of the resistor R12 is respectively connected to an inverting terminal and an output terminal of the operational amplifier U2; a non-inverting terminal of the operational amplifier U2 is respectively connected to a second end of the reference sensing element and the current mirror module; wherein, the resistor R11 and the resistor R12 have equal resistance values; the resistor R13 and the resistor R14 have equal resistance values.

4. The pressure sensing circuit according to claim 3, wherein The constant voltage is equal to the power supply voltage.

5. The pressure sensing circuit according to claim 1, wherein The resistance value of the reference sensing element changes with the temperature rise of the ambient temperature in the same way as the resistance value of the piezoresistive sensing element changes with the temperature rise of the ambient temperature.

6. The pressure sensing circuit according to claim 1, wherein Both the piezoresistive sensing element and the reference sensing element are strain sensors.

7. A pressure detection device, characterized in that, Comprising: A pressure detection device; And the pressure sensing circuit with temperature compensation according to any one of claims 1 to 6.

8. The pressure detection device according to claim 7, wherein, The pressure detection device is further connected to a second end of the piezoresistive sensing element, and is used for collecting the pressure sensing signal and obtaining the pressure value received by the sensing part according to the pressure sensing signal.

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