Temperature compensation circuit for a MEMS pressure sensor

Abstract

The utility model discloses a kind of temperature compensation circuit of MEMS pressure sensor, it is related to sensor field, the temperature compensation circuit of this MEMS pressure sensor includes: zero point drift compensation module, for compensating the zero point temperature drift of work piece by Wheatstone bridge, output two voltage signals to follow amplification module;Follow amplification module, for obtaining the difference of two voltage signals after two voltage signals, as first signal;The output end of zero point drift compensation module is connected with the input end of follow amplification module;Compared with prior art, the beneficial effects of the utility model are: the utility model compensates the zero point temperature drift, sensitivity temperature drift of work piece, so that MEMS pressure sensor precision is extremely high, and can reliably work in wide temperature range;Strong transplantability can be adapted to various circuit design and match various MCU models.

Description

Technical Field

[0001] This utility model relates to the field of sensors, specifically a temperature compensation circuit for a MEMS pressure sensor. Background Technology

[0002] MEMS (Micro Electro Mechanical Systems) pressure sensors, with their advantages of small size, high accuracy, low power consumption, and controllable cost, have been widely adopted in various fields such as consumer electronics, industrial control, automotive electronics, and healthcare. The demand for miniaturized and low-power sensors in consumer electronics has driven the widespread adoption of MEMS pressure sensors, such as altimeters (which use changes in air pressure to calculate altitude and assist GPS positioning), smartwatches for health monitoring (which detect changes in air pressure to determine the user's breathing rate, with chest rise and fall causing air pressure fluctuations), robotic vacuum cleaners (which detect the air pressure difference between the robot and the ground to determine if it is in areas such as stairs, preventing falls), and smart humidifiers / dehumidifiers (which monitor water pressure in the tank or ambient air pressure to control humidification / dehumidification intensity).

[0003] As products demand increasingly higher accuracy in air pressure detection, and some products operate over a wide temperature range, MEMS pressure sensors are required to maintain high accuracy and precision over a broad temperature range.

[0004] Piezoresistive MEMS is the most common type of MEMS sensor. Its temperature error mainly comes from two aspects (zero-point temperature drift and sensitivity temperature drift). This manifests as the sensor's output signal drifting with increasing temperature when there is no pressure (the temperature coefficient of zero-point drift is positive upward and negative downward), affecting the accuracy and precision of the MEMS pressure sensor, which needs to be improved. Utility Model Content

[0005] The purpose of this invention is to provide a temperature compensation circuit for a MEMS pressure sensor to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A temperature compensation circuit for a MEMS pressure sensor includes:

[0008] The zero-point drift compensation module is used to compensate for the zero-point temperature drift of the working chip (specifically resistor R1) through a Wheatstone bridge, and outputs two voltage signals to the follower amplifier module.

[0009] The follow-up amplification module is used to acquire two voltage signals and amplify the difference between the two voltage signals as the first signal;

[0010] The output of the zero-point drift compensation module is connected to the input of the follower amplifier module.

[0011] As a further improvement of this invention, the temperature compensation circuit of the MEMS pressure sensor further includes:

[0012] The temperature detection module is used to detect the temperature at the working plate, obtain the temperature signal, and output it to the main control module;

[0013] Temperature table reading module, used to store temperature-K value table data;

[0014] The main control module is used to receive the first signal and the temperature signal, read the temperature-K value table data, correct the first signal based on the temperature signal and the temperature-K value table data, obtain the second signal, and complete the sensitivity temperature drift compensation based on the first signal.

[0015] The output of the temperature detection module is connected to the first input of the main control module, the output of the temperature table reading module is connected to the second input of the main control module, and the third input of the main control module is connected to the output of the follower amplification module.

[0016] As a further embodiment of this utility model: the zero-point drift compensation module includes resistors R1, R2, R3, and R4. Resistor R1 is a working piece, and resistor R2 is a compensation piece. The working piece is attached to the test piece to sense mechanical strain and temperature changes. The compensation piece is attached to a position with the same material as the test piece, in the same temperature environment, but not subjected to mechanical stress. One end of resistor R1 is grounded, and the other end of resistor R1 is connected to one end of resistor R2 and one end of resistor R5. The other end of resistor R2 is connected to a 5V voltage. One end of resistor R3 is connected to one end of resistor R4 and one end of resistor R6. The other end of resistor R4 is grounded. The other end of resistor R5 is connected to one end of capacitor C1 and the input terminal of the follower amplification module. The other end of capacitor C1 is grounded. The other end of resistor R6 is connected to one end of capacitor C2 and the input terminal of the follower amplification module. The other end of capacitor C2 is grounded.

[0017] As a further embodiment of this utility model: the follower amplification module includes amplifier U3-A, amplifier U3-B, and amplifier U3-C. The non-inverting input of amplifier U3-A is connected to the output of the zero-drift compensation module. The non-inverting input of amplifier U3-B is connected to the output of the zero-drift compensation module. The inverting input of amplifier U3-A is connected to the output of amplifier U3-A and one end of resistor R7. The inverting input of amplifier U3-B is connected to the output of amplifier U3-B and one end of resistor R8. The other end of resistor R7 is connected to one end of capacitor C3, one end of resistor R9, and the non-inverting input of amplifier U3-C. The other end of resistor R9 is grounded. The other end of resistor R8 is connected to one end of resistor R10, the other end of capacitor C3, and the inverting input of amplifier U3-C. The output of amplifier U3-C is connected to the other end of resistor R10 and one end of resistor R11. The other end of resistor R11 is connected to the positive terminal of diode D1 and one end of capacitor C4. The negative terminal of diode D1 is connected to a 5V voltage. The other end of capacitor C4 is grounded.

[0018] As a further embodiment of this utility model: the temperature detection module includes a resistor R12 and a temperature sensor TH1. One end of the resistor R12 is connected to a 5V voltage, and the other end of the resistor R12 is connected to one end of the temperature sensor TH1 and one end of the resistor R13. The other end of the temperature sensor TH1 is grounded, and the other end of the resistor R13 is connected to one end of the capacitor C5 and the first input terminal of the main control module. The other end of the capacitor C5 is grounded.

[0019] As a further embodiment of this utility model: the temperature table reading module includes a chip U2, which is an EEPROM (Read-Only Memory). Pin 8 of chip U2 is connected to a 5V voltage, one end of resistor R16, one end of resistor R17, and one end of resistor R18. Pin 5 of chip U2 is connected to one end of resistor R21, and the other end of resistor R21 is connected to the other end of resistor R16 and the second input terminal of the main control module. Pin 6 of chip U2 is connected to one end of resistor R20, and the other end of resistor R20 is connected to the other end of resistor R17 and the second input terminal of the main control module. Pin 7 of chip U2 is connected to one end of resistor R19, and the other end of resistor R19 is connected to the other end of resistor R18 and the second input terminal of the main control module.

[0020] As a further improvement of this utility model: the main control module includes chip U1, chip U1 is an MCU, one AD port (pin 1) of chip U1 is connected to the output of the temperature detection module, three IIC communication ports (pins 6, 7 and 8) of chip U1 are connected to the output of the temperature table reading module, another AD port (pin 10) of chip U1 is connected to the output of the follower amplification module, and two UART communication ports (pins 4 and 5) of chip U1 are connected to the third and fourth terminals of interface CN1 through resistors R14 and R15 respectively.

[0021] Compared with the prior art, the beneficial effects of this utility model are: this utility model compensates for the zero-point temperature drift and sensitivity temperature drift of the working plate, making the MEMS pressure sensor extremely accurate and able to work reliably in a wide temperature range; it is highly portable and can be adapted to various circuit designs and matched with various MCU models. Attached Figure Description

[0022] Figure 1 This is a circuit diagram of a temperature compensation circuit for a MEMS pressure sensor. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0024] Please see Figure 1 A temperature compensation circuit for a MEMS pressure sensor, comprising:

[0025] The zero-point drift compensation module is used to compensate for the zero-point temperature drift of the working chip (specifically resistor R1) through a Wheatstone bridge, and outputs two voltage signals to the follower amplifier module.

[0026] The follow-up amplification module is used to acquire two voltage signals and amplify the difference between the two voltage signals as the first signal;

[0027] The output of the zero-point drift compensation module is connected to the input of the follower amplifier module.

[0028] In this embodiment: Please refer to Figure 1 The temperature compensation circuit of the MEMS pressure sensor further includes:

[0029] The temperature detection module is used to detect the temperature at the working plate, obtain the temperature signal, and output it to the main control module;

[0030] Temperature table reading module, used to store temperature-K value table data;

[0031] The main control module is used to receive the first signal and the temperature signal, read the temperature-K value table data, correct the first signal based on the temperature signal and the temperature-K value table data, obtain the second signal, and complete the sensitivity temperature drift compensation based on the first signal.

[0032] The output of the temperature detection module is connected to the first input of the main control module, the output of the temperature table reading module is connected to the second input of the main control module, and the third input of the main control module is connected to the output of the follower amplification module.

[0033] In this embodiment: Please refer to Figure 1 The zero-point drift compensation module includes resistors R1, R2, R3, and R4. Resistor R1 is the working piece, and resistor R2 is the compensation piece. The working piece is attached to the test piece to sense mechanical strain and temperature changes. The compensation piece is attached to a position with the same material as the test piece, in the same temperature environment, but without mechanical stress. One end of resistor R1 is grounded, and the other end of resistor R1 is connected to one end of resistor R2 and one end of resistor R5. The other end of resistor R2 is connected to a 5V voltage. One end of resistor R3 is connected to one end of resistor R4 and one end of resistor R6. The other end of resistor R4 is grounded. The other end of resistor R5 is connected to one end of capacitor C1 and the input terminal of the follower amplifier module. The other end of capacitor C1 is grounded. The other end of resistor R6 is connected to one end of capacitor C2 and the input terminal of the follower amplifier module. The other end of capacitor C2 is grounded.

[0034] Strain gauge resistors R1 and R2, and resistors R3 and R4 form a Wheatstone bridge. Resistor R1 acts as the working strain gauge, bearing mechanical pressure, while resistor R2 acts as a compensating strain gauge, compensating for the zero-point temperature drift of resistor R1. Resistor R3 is 1 kΩ, and resistor R4 is 990 Ω. This ensures that even without mechanical pressure on resistor R1, the input voltage at the non-inverting input of amplifier U3-A is greater than that at the non-inverting input of amplifier U3-B. When the working strain gauge bears mechanical pressure, the resistance of resistor R1 increases, making the input voltage at the non-inverting input of amplifier U3-A even greater than that of amplifier U3-B. It is important to note that resistors R1 and R2 must be from the same batch and installed close together, and their temperatures must be the same.

[0035] In this embodiment: Please refer to Figure 1The following amplification module includes amplifiers U3-A, U3-B, and U3-C. The non-inverting input of amplifier U3-A is connected to the output of the zero-drift compensation module. The non-inverting input of amplifier U3-B is connected to the output of the zero-drift compensation module. The inverting input of amplifier U3-A is connected to the output of amplifier U3-A and one end of resistor R7. The inverting input of amplifier U3-B is connected to the output of amplifier U3-B and one end of resistor R8. The other end of resistor R7 is connected to one end of capacitor C3, one end of resistor R9, and the non-inverting input of amplifier U3-C. The other end of resistor R9 is grounded. The other end of resistor R8 is connected to one end of resistor R10, the other end of capacitor C3, and the inverting input of amplifier U3-C. The output of amplifier U3-C is connected to the other end of resistor R10 and one end of resistor R11. The other end of resistor R11 is connected to the positive terminal of diode D1 and one end of capacitor C4. The negative terminal of diode D1 is connected to a 5V voltage. The other end of capacitor C4 is grounded.

[0036] The voltage follower, composed of amplifiers U3-A and U3-B, resistors R5 and R6, and capacitors C1 and C2, utilizes the infinite input impedance of the sampling voltage follower to minimize the current flowing out of the Wheatstone bridge, thereby reducing the impact of the measurement on the bridge voltage difference to the greatest extent.

[0037] Amplifier U3-A, resistors R7 to R11, capacitors C3 and C4, and diode D1 form an amplification circuit for the differential signal output of the bridge circuit. The differential signal is amplified by 10 times through resistor configuration. Diode D1 is used for voltage clamping to prevent excessively high voltage output from damaging the MCU (chip U1).

[0038] In this embodiment: Please refer to Figure 1 The temperature detection module includes a resistor R12 and a temperature sensor TH1. One end of the resistor R12 is connected to a 5V voltage, and the other end of the resistor R12 is connected to one end of the temperature sensor TH1 and one end of the resistor R13. The other end of the temperature sensor TH1 is grounded, and the other end of the resistor R13 is connected to one end of the capacitor C5 and the first input terminal of the main control module. The other end of the capacitor C5 is grounded.

[0039] The high-precision NTC sensor TH1, resistor R13, and capacitor C5 form a temperature detection circuit. Note that the temperature sensor TH1 must be very close to resistors R1 and R2 to ensure that the temperature monitored is at resistor R1.

[0040] In this embodiment: Please refer to Figure 1The temperature reading module includes chip U2, which is an EEPROM (Read-Only Memory). Pin 8 of chip U2 is connected to a 5V voltage, one end of resistor R16, one end of resistor R17, and one end of resistor R18. Pin 5 of chip U2 is connected to one end of resistor R21, and the other end of resistor R21 is connected to the other end of resistor R16 and the second input terminal of the main control module. Pin 6 of chip U2 is connected to one end of resistor R20, and the other end of resistor R20 is connected to the other end of resistor R17 and the second input terminal of the main control module. Pin 7 of chip U2 is connected to one end of resistor R19, and the other end of resistor R19 is connected to the other end of resistor R18 and the second input terminal of the main control module.

[0041] Chip U2 and resistors R16 to R21 form an EEPROM read / write circuit. Chip U2 stores temperature-K value table data.

[0042] Table 1, Temperature-K Values ​​Table:

[0043]

[0044] In practical applications, the temperature resolution of the table above can be improved to 0.1℃.

[0045] In this embodiment: Please refer to Figure 1 The main control module includes chip U1, which is an MCU. One AD port (pin 1) of chip U1 is connected to the output of the temperature detection module. The three IIC communication ports (pins 6, 7, and 8) of chip U1 are connected to the output of the temperature table reading module. Another AD port (pin 10) of chip U1 is connected to the output of the follower amplifier module. The two UART communication ports (pins 4 and 5) of chip U1 are connected to the third and fourth terminals of interface CN1 through resistors R14 and R15, respectively.

[0046] MCUs use established formulas to perform data processing, which is a conventional technique and does not involve any innovation in methodology.

[0047] Compensation for the temperature coefficient of sensitivity is primarily achieved through software. This software compensation requires acquiring temperature data from the TH1 temperature sensor and then correcting the sensitivity based on this data. The sensitivity is adjusted using actual temperature-K value table data.

[0048] The relationship between the resistance change of a resistance strain gauge and the applied strain (a direct manifestation of stress) can be described by the basic formula: ΔR / R0=K·ε, where:

[0049] ΔR / R0: The relative change in strain gauge resistance (dimensionless);

[0050] R0: The initial resistance of the strain gauge when it is not under stress;

[0051] ΔR: The change in resistance after being subjected to force (ΔR = R - R0);

[0052] K: Sensitivity coefficient (as detailed above, it is related to the strain gauge type);

[0053] ε: The strain sensed by the strain gauge (ε = ΔL / L, i.e., the relative change in length of the measured object, dimensionless, often expressed as "micro-strain", 1με = 10). -6 ).

[0054] Chip U1 has a built-in basic formula ΔR / R0=K·ε, which is used to obtain the second signal based on the first signal, the temperature signal, and the temperature-K value table data.

[0055] Interface CN1 and resistors R14 and R15 form an external serial communication circuit to enable communication between chip U1 and the outside world.

[0056] In chip U1: MCU AN0 function pin: AD port, reads the voltage difference output by the bridge.

[0057] MCU AN1 function pin: AD port, reads the voltage on the NTC.

[0058] MCU SCL / SDA function pins: IIC communication port, used for real-time reading of the EEPROM temperature-K value table.

[0059] MCU RXD0 / TXD0 function pins: UART communication port, used for communication with external devices.

[0060] Chip U1 is an MCU, and any MCU model can be used as long as it has the corresponding functional pins (interfaces, ports) mentioned above.

[0061] The working principle of this utility model is as follows: The zero-point drift compensation module is used to compensate for the zero-point temperature drift of the working piece (specifically resistor R1) through a Wheatstone bridge, and outputs two voltage signals to the follower amplification module; the follower amplification module is used to acquire the two voltage signals and amplify the difference between the two voltage signals as the first signal; the temperature detection module is used to detect the temperature at the working piece, obtain the temperature signal, and output it to the main control module; the temperature table reading module is used to store temperature-K value table data; the main control module is used to receive the first signal and the temperature signal, read the temperature-K value table data, correct the first signal based on the temperature signal and the temperature-K value table data, obtain the second signal, and complete the sensitivity temperature drift compensation based on the first signal.

[0062] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0063] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A temperature compensation circuit for a MEMS pressure sensor, characterized by, The temperature compensation circuit of the MEMS pressure sensor includes: The zero-point drift compensation module is used to compensate for the zero-point temperature drift of the working plate through a Wheatstone bridge, and outputs two voltage signals to the follower amplifier module. The follow-up amplification module is used to acquire two voltage signals and amplify the difference between the two voltage signals as the first signal; The output of the zero-point drift compensation module is connected to the input of the follower amplifier module.

2. The temperature compensation circuit for the MEMS pressure sensor according to claim 1, characterized in that, The temperature compensation circuit of the MEMS pressure sensor also includes: The temperature detection module is used to detect the temperature at the working plate, obtain the temperature signal, and output it to the main control module; Temperature table reading module, used to store temperature-K value table data; The main control module is used to receive the first signal and the temperature signal, read the temperature-K value table data, correct the first signal based on the temperature signal and the temperature-K value table data, obtain the second signal, and complete the sensitivity temperature drift compensation based on the first signal. The output of the temperature detection module is connected to the first input of the main control module, the output of the temperature table reading module is connected to the second input of the main control module, and the third input of the main control module is connected to the output of the follower amplification module.

3. The temperature compensation circuit for the MEMS pressure sensor according to claim 1 or 2, characterized in that, The zero-point drift compensation module includes resistors R1, R2, R3, and R4. Resistor R1 is the working piece, and resistor R2 is the compensation piece. The working piece is attached to the test piece to sense mechanical strain and temperature changes. The compensation piece is attached to a position with the same material as the test piece, in the same temperature environment, but without mechanical stress. One end of resistor R1 is grounded, and the other end of resistor R1 is connected to one end of resistor R2 and one end of resistor R5. The other end of resistor R2 is connected to a 5V voltage. One end of resistor R3 is connected to one end of resistor R4 and one end of resistor R6. The other end of resistor R4 is grounded. The other end of resistor R5 is connected to one end of capacitor C1 and the input terminal of the follower amplifier module. The other end of capacitor C1 is grounded. The other end of resistor R6 is connected to one end of capacitor C2 and the input terminal of the follower amplifier module. The other end of capacitor C2 is grounded.

4. The temperature compensation circuit for the MEMS pressure sensor according to claim 1 or 2, characterized in that, The follower amplification module includes amplifiers U3-A, U3-B, and U3-C. The non-inverting input of amplifier U3-A is connected to the output of the zero-drift compensation module. The non-inverting input of amplifier U3-B is connected to the output of the zero-drift compensation module. The inverting input of amplifier U3-A is connected to the output of amplifier U3-A and one end of resistor R7. The inverting input of amplifier U3-B is connected to the output of amplifier U3-B and one end of resistor R8. The other end of resistor R7 is connected to one end of capacitor C3, one end of resistor R9, and the non-inverting input of amplifier U3-C. The other end of resistor R9 is grounded. The other end of resistor R8 is connected to one end of resistor R10, the other end of capacitor C3, and the inverting input of amplifier U3-C. The output of amplifier U3-C is connected to the other end of resistor R10 and one end of resistor R11. The other end of resistor R11 is connected to the positive terminal of diode D1 and one end of capacitor C4. The negative terminal of diode D1 is connected to a 5V voltage. The other end of capacitor C4 is grounded.

5. The temperature compensation circuit for the MEMS pressure sensor according to claim 2, characterized in that, The temperature detection module includes a resistor R12 and a temperature sensor TH1. One end of the resistor R12 is connected to a 5V voltage, and the other end of the resistor R12 is connected to one end of the temperature sensor TH1 and one end of the resistor R13. The other end of the temperature sensor TH1 is grounded, and the other end of the resistor R13 is connected to one end of the capacitor C5 and the first input terminal of the main control module. The other end of the capacitor C5 is grounded.

6. The temperature compensation circuit for the MEMS pressure sensor according to claim 2, characterized in that, The temperature table reading module includes chip U2, which is an EEPROM. Pin 8 of chip U2 is connected to a 5V voltage, one end of resistor R16, one end of resistor R17, and one end of resistor R18. Pin 5 of chip U2 is connected to one end of resistor R21, and the other end of resistor R21 is connected to the other end of resistor R16 and the second input terminal of the main control module. Pin 6 of chip U2 is connected to one end of resistor R20, and the other end of resistor R20 is connected to the other end of resistor R17 and the second input terminal of the main control module. Pin 7 of chip U2 is connected to one end of resistor R19, and the other end of resistor R19 is connected to the other end of resistor R18 and the second input terminal of the main control module.

7. The temperature compensation circuit for the MEMS pressure sensor according to claim 2, characterized in that, The main control module includes chip U1, which is an MCU. One AD port of chip U1 is connected to the output of the temperature detection module. Three IIC communication ports of chip U1 are connected to the output of the temperature table reading module. Another AD port of chip U1 is connected to the output of the follower amplifier module. Two UART communication ports of chip U1 are connected to the third and fourth terminals of interface CN1 through resistors R14 and R15, respectively.

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