Temperature compensation circuit for piezoresistive Wheatstone bridge feedback output and MEMS micromirror

Abstract

The invention discloses a temperature compensation circuit for piezoresistive Wheatstone bridge feedback output and an MEMS micromirror, the temperature compensation circuit is provided with a third resistor, the symmetry axis position of an output curve is changed, the symmetry axis curve is close to the environment temperature, the output voltage output is stable, and the stability of the temperature compensation circuit is improved. In addition, the power consumption, noise and heat loss of the MEMS micromirror can be reduced, and the precision of the MEMS micromirror is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS micromirrors, and in particular to a temperature compensation circuit for piezoresistive Wheatstone bridge feedback output and a MEMS micromirror. Background Art

[0002] MEMS micromirrors offer numerous advantages and are currently widely used. However, they also suffer from low resolution and accuracy. In related technologies, Wheatstone bridges are often used as feedback sensors to improve the accuracy of MEMS micromirrors.

[0003] However, the performance of the Wheatstone bridge is affected by temperature fluctuations. Current methods for compensating for the temperature effects of the Wheatstone bridge often struggle to meet required compensation requirements, resulting in poor feedback from the Wheatstone bridge and ultimately impacting the accuracy of the MEMS micromirror. Therefore, improving the compensation effect of the Wheatstone bridge has become a pressing issue for those skilled in the art. Summary of the Invention

[0004] In view of this, the present application provides a temperature compensation circuit and MEMS micromirror for the feedback output of a piezoresistive Wheatstone bridge, the main purpose of which is to solve the technical problem of poor feedback effect of the compensation method when the Wheatstone bridge is affected by temperature.

[0005] In a first aspect, a temperature compensation circuit for a piezoresistive Wheatstone bridge feedback output is provided, comprising a bandgap reference voltage source and a voltage follower; wherein the bandgap reference voltage source comprises a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a fourth PMOS transistor, a fifth PMOS transistor, a sixth PMOS transistor, a first resistor, a second resistor, a third resistor, a first transistor, a second transistor, and a third transistor; and the third resistor is a thermistor;

[0006] The sources of the first PMOS transistor, the second PMOS transistor, and the third PMOS transistor are respectively connected to the power supply VDD; the gates of the first PMOS transistor, the second PMOS transistor, and the third PMOS transistor are connected and connected to a first reference voltage; the drains of the first PMOS transistor, the second PMOS transistor, and the third PMOS transistor are connected to the sources of the fourth PMOS transistor, the fifth PMOS transistor, and the sixth PMOS transistor, and the gates of the fourth PMOS transistor, the fifth PMOS transistor, and the sixth PMOS transistor are connected and connected to a second reference voltage;

[0007] The drain of the fourth PMOS tube is connected to the first transistor, the drain of the fifth PMOS tube is connected to one end of the first resistor, and the other end of the first resistor is connected to the second transistor; the drain of the sixth PMOS tube is connected to one end of the third resistor, and the other end of the third resistor is connected to the third transistor. The drain of the sixth PMOS tube is also connected to the output end, and the output end is connected to the voltage follower.

[0008] In some embodiments, the voltage follower includes a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a seventh PMOS transistor, an eighth PMOS transistor, a ninth PMOS transistor, and a tenth PMOS transistor;

[0009] The gate of the first NMOS transistor is connected to the output end, and the drain of the first NMOS transistor is connected to the drain of the seventh PMOS transistor; the sources of the seventh PMOS transistor and the eighth PMOS transistor are connected to the power supply VDD; the drain of the eighth PMOS transistor is connected to the drain of the second NMOS transistor, and outputs a voltage to the gate of the tenth PMOS transistor; the first NMOS transistor and the second NMOS transistor are respectively connected to the ninth PMOS transistor, and the gate of the ninth PMOS transistor is connected to the third reference voltage; the third NMOS transistor is connected to the tenth PMOS transistor, and the gate of the third NMOS transistor is connected to the fourth reference voltage.

[0010] In some embodiments, the temperature compensation circuit further includes a first feedback element, wherein the first feedback element is connected to the power supply VDD, and the first feedback element is further connected to a second NMOS transistor.

[0011] In some embodiments, the first feedback element includes a PMOS transistor, and a drain of the PMOS transistor is connected to the power supply VDD.

[0012] In some embodiments, the first feedback element is a first capacitor.

[0013] In some embodiments, the temperature compensation circuit further includes a second feedback element connected to the tenth PMOS transistor.

[0014] In some embodiments, the second feedback element is a second capacitor.

[0015] In some embodiments, the second capacitor is a Miller compensation capacitor.

[0016] In some embodiments, the first transistor, the second transistor, and the third transistor are all PNP transistors.

[0017] In a second aspect, a MEMS micromirror is provided, comprising the temperature compensation circuit.

[0018] In the above embodiment, a temperature compensation circuit and a MEMS micromirror for the feedback output of a piezoresistive Wheatstone bridge are provided. Since a third resistor is provided in the temperature compensation circuit, the position of the symmetry axis of the output curve is changed, so that the symmetry axis curve is brought closer to the ambient temperature, thereby stabilizing the output voltage. At the same time, the circuit area is small, and the power consumption, noise and heat loss of the MEMS micromirror can be reduced, thereby improving the accuracy of the MEMS micromirror.

[0019] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 The following is a schematic structural diagram of a temperature compensation circuit for a piezoresistive Wheatstone bridge feedback output according to some embodiments;

[0022] Figure 2 A schematic diagram exemplarily shows a curve showing the relationship between output voltage and temperature according to some embodiments. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0024] In modern optical applications, beam steering technology is a vital link. By changing the phase of the light beam, the beam angle is changed, allowing the device to scan a certain field of view and analyze the scanned target. This technology has the advantages of a large market, long distance and high efficiency. The key indicators of the beam steering system include the horizontal and vertical scanning field of view (the horizontal and vertical steering angle range of the emitted light beam), the detection field of view (the observable effective distance), the resolution (the minimum angular interval for distinguishing two objects) and the two-dimensional imaging frame rate (the number of times a point cloud image is generated per second).

[0025] To address the issues of narrow field of view and low imaging frame rates, MEMS mirrors are widely used. MEMS mirrors are key components in micro-electro-mechanical systems (MEMS), precisely controlling and adjusting the direction of incident light. Compared to traditional steering methods such as DMDs (digital micromirror devices), MEMS mirrors offer advantages such as autofocus, miniaturization, and a large rotation angle.

[0026] In the field of projection display, MEMS micromirrors have played a positive role in promoting the development of the technology. Their autofocus function can make projected images clearer, enhancing the viewing experience. Furthermore, the miniaturization of MEMS micromirrors makes the devices lighter and more portable.

[0027] MEMS mirrors also play an important role in the field of AR glasses. They not only provide a wide field of view and high-resolution display, but also reduce the weight of the glasses and enhance the user experience due to their miniaturized design.

[0028] In the field of 3D scanning, MEMS micromirrors can achieve large rotation angles, which is crucial for 3D scanning that requires precise measurement and modeling.

[0029] In summary, MEMS micromirrors offer numerous advantages. First, their autofocus function provides clearer images; second, their compact design makes them portable and space-saving; and finally, their wide-angle operation improves work efficiency. Compared to other technologies like DMD, MEMS micromirrors undoubtedly demonstrate superior performance and application prospects. However, MEMS micromirrors also face challenges with accuracy.

[0030] In related technologies, MEMS micromirrors often use a Wheatstone bridge as a feedback sensor, but its performance is affected by temperature changes. To address this issue, two methods can be used: hardware compensation and software compensation.

[0031] Hardware compensation mainly includes series-parallel resistor circuit, double Wheatstone bridge offset compensation and variable gain amplifier compensation.

[0032] Series-parallel resistor circuits: Temperature drift correction is achieved by adding fixed or adjustable resistors of specific values ​​in series or parallel to the original Wheatstone bridge. However, this method has some disadvantages. First, it requires additional components, and different values ​​of additional components must be selected for different sensor types and specifications. Second, in practical applications, it is difficult to find fixed or adjustable resistors with the same temperature coefficient as the sensor.

[0033] Dual Wheatstone Bridge Compensation: This approach combines two similar but independently operating Wheatstone bridges to form a differential system, mitigating the effects of environmental factors on measurement results. While this method effectively mitigates the effects of environmental factors, it also has drawbacks: requiring two similar bridges increases system complexity and cost; and, if the characteristics of the two bridges are not identical, the compensation effect can be compromised.

[0034] Variable-gain amplifier compensation: This approach compensates for temperature drift by changing the amplifier's gain. However, this approach also has its drawbacks: first, adjustable gain can lead to increased noise levels; second, if the temperature range is large, the amplifier's gain needs to be adjusted frequently.

[0035] Software compensation corrects measurement results during the data processing phase. Typically, mathematical models such as linear or nonlinear fitting are used to model the relationship between sensor output and actual values, and this model is used to correct the measurement results. While software compensation can effectively reduce the impact of environmental factors on measurement results and eliminates the need for additional hardware components, it relies on precise and stable mathematical models and algorithms, making it difficult to achieve satisfactory correction results in some cases.

[0036] The low precision of MEMS piezoelectric micromirrors with piezoresistive feedback is primarily due to their operating principle and drive method. The feedback circuit utilizes a Wheatstone bridge circuit, while the drive method utilizes a piezoelectric drive. Both designs are affected by temperature fluctuations, introducing zero-point drift and sensitivity drift, resulting in nonlinearity and noise in the output signal.

[0037] First, the Wheatstone bridge output is affected by temperature fluctuations. When the ambient temperature changes, physical effects such as thermal expansion or contraction of the material alter the micromirror's structural parameters and internal component characteristics (such as elastic modulus and resistance) to varying degrees, causing deviations in the measurement results. This is known as zero drift.

[0038] Secondly, a similar problem exists in terms of sensitivity. As the ambient temperature rises or falls, the micromirror's ability to perceive input signals (such as light sources) (i.e., sensitivity) will change accordingly, and within a certain range, it will show a nonlinear relationship.

[0039] Furthermore, noise may be a problem during use. If a disturbance signal is suddenly introduced when the system is in a stable state, this may disrupt the system's steady state and generate some unwanted but unavoidable interference information in the measurement results—this is called "noise."

[0040] Furthermore, piezoelectric drives utilize waveform modulation technology within a relatively high range of 10V to 20V. This high-frequency operation easily generates and accumulates significant heat, further increasing the overall system operating temperature. This temperature rise can lead to multiple negative effects, including changes in material physical properties and structural distortion of the device itself.

[0041] In summary, the challenges in precise control of MEMS piezoresistive feedback piezoelectric micromirrors mainly focus on:

[0042] (1) The system is complex and easily affected by external conditions (especially ambient temperature differences);

[0043] (2) Excessive heat generation during high-frequency operation causes degradation of the device's performance;

[0044] (3) The system has obvious nonlinear characteristics and large noise interference.

[0045] These problems need to be solved through multiple aspects such as design optimization, material improvement and control strategy to improve their accuracy and stability in practical applications.

[0046] An embodiment of the present application provides a temperature compensation circuit for a piezoresistive Wheatstone bridge feedback output. In the temperature compensation circuit, a third resistor is provided to change the position of the axis of symmetry of the output curve, so that the axis of symmetry curve approaches the ambient temperature, thereby stabilizing the output voltage. At the same time, the circuit area is small, and the power consumption, noise, and heat loss of the MEMS micromirror can be reduced, thereby improving the accuracy of the MEMS micromirror.

[0047] The embodiment of the present application provides a schematic structural diagram of a temperature compensation circuit for a piezoresistive Wheatstone bridge feedback output, as shown in FIG. Figure 1 As shown, the temperature compensation circuit includes a bandgap reference voltage source 1 and a voltage follower 2; the bandgap reference voltage source 1 includes a first PMOS transistor M1, a second PMOS transistor M2, a third PMOS transistor M3, a fourth PMOS transistor M4, a fifth PMOS transistor M5, a sixth PMOS transistor M6, a first resistor R1, a second resistor R2, a third resistor R3, a first transistor Q1, a second transistor Q2 and a third transistor Q3; the third resistor R3 is a thermistor;

[0048] The sources of the first PMOS transistor M1, the second PMOS transistor M2, and the third PMOS transistor M3 are respectively connected to the power supply VDD; the gates of the first PMOS transistor M1, the second PMOS transistor M2, and the third PMOS transistor M3 are connected and connected to the first reference voltage V1; the drains of the first PMOS transistor M1, the second PMOS transistor M2, and the third PMOS transistor M3 are connected to the sources of the fourth PMOS transistor, the fifth PMOS transistor, and the sixth PMOS transistor, and the gates of the fourth PMOS transistor, the fifth PMOS transistor, and the sixth PMOS transistor are connected and connected to the second reference voltage V2;

[0049] The drain of the fourth PMOS transistor M4 is connected to the first transistor Q1, the drain of the fifth PMOS transistor M5 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the second transistor Q2; the drain of the sixth PMOS transistor M6 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is connected to the third transistor Q3. The drain of the sixth PMOS transistor M6 is also connected to the output end, and the output end is connected to the voltage follower 2.

[0050] The following is an analysis of the principle by which the temperature compensation circuit in the embodiment of the present application can achieve temperature compensation:

[0051] The piezoresistive Wheatstone bridge includes semiconductor materials, which are inherently temperature-sensitive. The resistance of the embedded piezoresistor is affected not only by pressure but also by the ambient temperature. However, ambient temperature is a difficult factor to control, so errors are bound to occur in the sensor output.

[0052] There are two mechanisms for the temperature drift of embedded piezoresistors:

[0053] Zero temperature drift:

[0054] Due to process mismatches during manufacturing, the resistor values ​​in the four arms of a Wheatstone bridge are not exactly equal, resulting in a zero-position output. When the temperature changes, the resistance values ​​of the four resistors change together, causing the zero-position output to vary. A common solution is to add a compensation resistor in series with the bridge to eliminate the zero-position output and a negative temperature coefficient thermistor in parallel to compensate for temperature drift in the zero-position output.

[0055] Sensitivity temperature drift:

[0056] When the temperature rises, the lattice scattering inside the semiconductor becomes more significant, and the electrons in the valence band are more likely to gain energy and jump to the conduction band, which changes the carrier mobility. Therefore, the resistance values ​​of the four bridge arm resistors will also change. Let the change be ΔR tIn addition, since the piezoresistance coefficient changes with temperature, the resistance change caused by pressure will also change. Let the change be ΔR r , then the Wheatstone bridge feedback output becomes:

[0057]

[0058] V out is the output voltage of the embedded piezoresistive bridge;

[0059] V ref is the supply voltage of the piezoresistive voltage;

[0060] R is the resistance of the piezoresistive bridge;

[0061] ΔR r The resistance change caused by pressure change;

[0062] ΔR t The change in resistance due to temperature change.

[0063] Due to the full-bridge Wheatstone bridge structure, the ΔR in the numerator of the output expression r are offset, generally, ΔR t If R is much smaller than R, the sensitivity temperature drift caused by the change of semiconductor resistivity with temperature can be approximately ignored, and the output expression is approximately:

[0064]

[0065] Simplify formula (1) and ignore ΔR in the denominator t , and we get formula (2).

[0066] Therefore, the sensitivity temperature drift is mainly caused by the change of piezoresistive coefficient with temperature.

[0067] If in N-type silicon semiconductor <100> Surface-oriented diffusion doping in thin films <110> The piezoresistance coefficient of a P-type resistor with a crystal orientation is approximately:

[0068] π l =-π t =π 44 / twenty three)

[0069] π l : longitudinal piezoresistive coefficient; π t : lateral piezoresistive coefficient; π 44 : Piezoresistive coefficient along the crystal axis.

[0070] Substituting the above formula into the resistance change is:

[0071]

[0072] where π 44 : piezoresistive coefficient in the crystal axis direction;

[0073] σ x : The stress in the transverse direction of the resistor is proportional to the pressure on the silicon film;

[0074] σ y : The longitudinal stress of the resistor is proportional to the pressure of the silicon film.

[0075] The output voltage and output voltage sensitivity are obtained from equations (2), (3) and (4):

[0076]

[0077] V out : Output voltage of the embedded piezoresistive bridge;

[0078] π 44 : Piezoresistive coefficient in the crystal axis direction;

[0079] σ x : The stress in the transverse direction of the resistor is proportional to the pressure on the silicon film;

[0080] σ y : The longitudinal stress of the resistor is proportional to the pressure of the silicon film.

[0081] V ref : Supply voltage of the piezoresistive voltage.

[0082]

[0083] S: output voltage sensitivity;

[0084] P: External pressure value.

[0085] The output voltage sensitivity temperature coefficient can be expressed as:

[0086]

[0087] because It is a negative value, so the output voltage sensitivity temperature coefficient is also negative, that is, under a certain applied stress, the output voltage decreases as the temperature rises.

[0088] Sensitivity temperature drift has a great impact on the sensor output, causing the sensor output to change with a negative temperature coefficient. Figure 2 A schematic diagram exemplarily shows a curve showing the relationship between output voltage and temperature according to some embodiments.

[0089] Then, providing a voltage with a positive temperature coefficient to a piezoresistive bridge with a negative temperature coefficient can compensate for the temperature drift to a certain extent.

[0090] The MEMS voltage output curve is given by Figure 2 It can be obtained that the output voltage and temperature show a first-order monotonically decreasing relationship. Suppose the relationship between the output curve and temperature is:

[0091] V out =V0-k(T-T0) (8)

[0092] Equation (8) is the fitting of the output voltage curve. out is the output voltage, V0 is the voltage value at T0; k is the coefficient, T: temperature; T0 is the selected operating temperature.

[0093] In summary: the temperature drift of the output voltage is introduced by the temperature drift of the piezoresistive sensitivity.

[0094] Because the output voltage is theoretically:

[0095] V out =S 压阻 ·F·V ref , where F = Γ 结构 ·S 压电 ·V 驱动 ·f;

[0096] S 压阻 is the piezoresistive sensitivity, which indicates the output voltage generated under unit stress;

[0097] F represents the stress pressure of the embedded piezoresistor, which is generated by the flipping of the MEMS micromirror;

[0098] V ref Represents the supply voltage of the Wheatstone bridge.

[0099] Γ 结构 Indicates the stress effect introduced by the MEMS micromirror structure;

[0100] S 压电 is the piezoelectric sensitivity, which indicates how much stress is generated under unit voltage drive;

[0101] V 驱动 is the amplitude of the driving voltage; f is the frequency of the driving signal.

[0102] It is obtained from the simulation software comsol that F is almost insensitive to T, that is, changes in the external temperature T basically do not change the stress F.

[0103] From formula (8), we can get:

[0104]

[0105] V out Taking the derivative with respect to temperature, we get the coefficient k.

[0106] Ignore Vref Sensitivity to temperature, V out Sensitivity to temperature is determined by S 压阻 Introduction, that is, the sensitivity drift of the embedded piezoresistor occurs.

[0107] get

[0108]

[0109] The derivative of piezoresistive sensitivity with respect to temperature is set as a,

[0110] a: derivative of piezoresistive sensitivity with respect to temperature

[0111] S 压阻 =a0-a(T-T0) (11)

[0112] By integrating formula (10), we can infer formula (11):

[0113] a0: Sensitivity at temperature T0.

[0114] a: derivative of piezoresistive sensitivity with respect to temperature

[0115] T0: Selected operating temperature

[0116] In summary: the temperature drift of the output voltage is introduced by the temperature drift of the piezoresistive sensitivity.

[0117] Because the output voltage is theoretically:

[0118] V out =S 压阻 ·F·V ref ;

[0119] where F = Γ 结构 ·S 压电 ·V 驱动 ·f

[0120] S 压阻 is the piezoresistive sensitivity, which indicates the output voltage generated under unit stress;

[0121] F represents the stress pressure of the embedded piezoresistor,

[0122] V ref Represents the supply voltage of the Wheatstone bridge.

[0123] Γ 结构 Indicates the stress effect introduced by the MEMS micromirror structure;

[0124] S 压电 is the piezoelectric sensitivity, which indicates how much stress is generated under unit voltage drive;

[0125] V 驱动is the amplitude of the driving voltage; f is the frequency of the driving signal.

[0126] S 压阻 The temperature shows a first-order monotonically decreasing relationship. Then, a first-order monotonically increasing supply voltage can be input to the Wheatstone bridge to compensate for the overall output V out Sensitivity to temperature.

[0127] Consider providing a voltage Vref with a positive temperature coefficient to achieve temperature compensation.

[0128] V ref =V0+b(T-T0) (12)

[0129] V0: supply voltage at T0 temperature;

[0130] b: Vref temperature coefficient.

[0131] Equation (12) assumes the form of the supply voltage, which is exactly the bandgap reference voltage Output format.

[0132] The temperature coefficient can be modified by modifying the parameter b (third resistor R3 / first resistor R1 ).

[0133] S 压阻 ·V ref =a0V0+a0b(T-T0)-aV0(T-T0)-ab(T-T0) 2 (13)

[0134] Equation (13) is the product of the piezoresistive sensitivity with a negative temperature coefficient and the supply voltage with a positive temperature coefficient.

[0135] V0: supply voltage at T0 temperature;

[0136] a0: sensitivity at temperature T0;

[0137] b:V ref The coefficient of temperature.

[0138] It can be seen that the output voltage V out It has a second-order relationship with temperature T.

[0139] Then when the temperature T-T0 is on the symmetry axis of the curve When the output voltage is at a certain temperature range, the sensitivity of the output voltage to temperature is very small, that is, within this temperature range,

[0140] And V in formula (12) ref =V0+b(T-T0) can be generated by a Bandgap voltage source.

[0141] The first PMOS transistor, the second PMOS transistor, the third PMOS transistor, the fourth PMOS transistor, the fifth PMOS transistor, the sixth PMOS transistor, the first resistor, the second resistor, the third resistor, the first transistor, the second transistor and the third transistor together constitute a bandgap reference voltage source, and the output voltage is:

[0142]

[0143] Voltage It is a reference voltage that is independent of temperature. It is a PTAT voltage. As the temperature rises, the voltage output increases. The output voltage format satisfies formula (12):

[0144] V ref =V0+b(T-T0) (12)

[0145] The ambient temperature is sensed by the thermistor. As the third resistor R3 changes, the coefficient b in formula (12) changes, thereby changing formula (13)

[0146] S 压阻 ·V ref =a0V0+a0b(T-T0)-aV0(T-T0)-ab(T-T0) 2 (13)

[0147] The position of the symmetry axis of the output voltage, because the derivative of the output with respect to temperature is 0 in the vicinity of the symmetry axis, that is, The temperature compensation effect can be achieved. That is, the change in ambient temperature causes the third resistor R3 to change, changing the position of the symmetric axis of the output curve so that the position of the symmetric axis is closer to the ambient temperature, thereby making the output voltage stable under this temperature condition and achieving temperature compensation.

[0148] In some embodiments, the voltage follower 2 includes a first NMOS transistor M7, a second NMOS transistor M8, a third NMOS transistor M13, a seventh PMOS transistor M9, an eighth PMOS transistor M10, a ninth PMOS transistor M11, and a tenth PMOS transistor M12;

[0149] The gate of the first NMOS transistor M7 is connected to the output end, and the drain of the first NMOS transistor M7 is connected to the drain of the seventh PMOS transistor M9; the sources of the seventh PMOS transistor M9 and the eighth PMOS transistor are connected to the power supply VDD; the drain of the eighth PMOS transistor is connected to the drain of the second NMOS transistor M10, and outputs a voltage to the gate of the tenth PMOS transistor M12; the first NMOS transistor M7 and the second NMOS transistor M8 are respectively connected to the ninth PMOS transistor M11, and the gate of the ninth PMOS transistor M11 is connected to the third reference voltage V3; the third NMOS transistor M13 is connected to the tenth PMOS transistor M12, and the gate of the third NMOS transistor M13 is connected to the fourth reference voltage V4.

[0150] In the embodiment of the present application, the temperature-varying voltage generated by the bandgap reference voltage source is connected to a voltage follower for output, and the voltage follower can improve the load capacity of the circuit.

[0151] In some embodiments, the temperature compensation circuit further includes a first feedback element, wherein the first feedback element is connected to the power supply VDD, and the first feedback element is further connected to a second NMOS transistor.

[0152] In the embodiment of the present application, a first feedback element is added to the temperature compensation circuit to provide feedback and improve circuit stability. In the embodiment of the present application, in addition to the output end of the bandgap reference voltage source being used as one input of the voltage follower, the other input is fed back by the first feedback element.

[0153] In some embodiments, refer again to Figure 1 The first feedback element includes a PMOS transistor M14, the drain of which is connected to the power supply VDD. In the embodiment of the present application, the PMOS transistor can improve circuit stability. In addition, when the first feedback element serves as an input of a voltage follower and the first feedback element includes the PMOS transistor M14, the other input of the voltage follower is fed back by the source of the PMOS transistor M14.

[0154] In some embodiments, the first feedback element is a first capacitor. In the embodiment of the present application, the first capacitor can improve the stability of the circuit.

[0155] In some embodiments, the temperature compensation circuit further includes a second feedback element connected to the tenth PMOS transistor. In the embodiment of the present application, the second feedback element is added to the temperature compensation circuit to provide feedback and improve circuit stability.

[0156] In some embodiments, refer again to Figure 1The second feedback element is a second capacitor C1. The second capacitor C1 is connected to the tenth PMOS transistor M12.

[0157] In some embodiments, the second capacitor is a Miller compensation capacitor. Miller compensation capacitors are used to improve circuit stability and reliability. They achieve this by compensating for phase shifts caused by inductive components in the circuit. Phase shift refers to the phase difference between two waveforms at the same point in time. Miller compensation capacitors reduce this phase shift by adding appropriate capacitance to the circuit.

[0158] In some embodiments, the first transistor, the second transistor, and the third transistor are all PNP transistors.

[0159] An embodiment of the present application also provides a MEMS micromirror, comprising the temperature compensation circuit.

[0160] In order to improve the accuracy of the MEMS micromirror, the MEMS micromirror provided in the embodiment of the present application may include a temperature compensation circuit. Since a third resistor is provided in the temperature compensation circuit, the position of the symmetry axis of the output curve is changed, so that the symmetry axis curve is closer to the ambient temperature, thereby stabilizing the output voltage. This can reduce the power consumption, noise and heat loss of the MEMS micromirror and improve the accuracy of the MEMS micromirror.

[0161] In the above embodiment, a temperature compensation circuit and a MEMS micromirror for the feedback output of a piezoresistive Wheatstone bridge are provided. Since a third resistor is provided in the temperature compensation circuit, the position of the symmetry axis of the output curve is changed, so that the symmetry axis curve is brought closer to the ambient temperature, thereby stabilizing the output voltage. At the same time, the circuit area is small, and the power consumption, noise and heat loss of the MEMS micromirror can be reduced, thereby improving the accuracy of the MEMS micromirror.

[0162] Those skilled in the art will understand that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily required to implement the present application. Those skilled in the art will understand that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the implementation scenario description, or can be changed accordingly and located in one or more devices different from the implementation scenario. The modules of the above-mentioned implementation scenario can be combined into one module, or can be further split into multiple sub-modules.

[0163] The serial numbers of the above application are for descriptive purposes only and do not represent the advantages or disadvantages of the implementation scenarios. The above disclosure only discloses several specific implementation scenarios of the present application, but the present application is not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present application.

Claims

1. A temperature compensation circuit for a piezoresistive Wheatstone bridge feedback output, characterized in that: The invention comprises a bandgap reference voltage source and a voltage follower; wherein the bandgap reference voltage source comprises a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a fourth PMOS transistor, a fifth PMOS transistor, a sixth PMOS transistor, a first resistor, a second resistor, a third resistor, a first triode, a second triode and a third triode; and the third resistor is a thermistor; The sources of the first PMOS transistor, the second PMOS transistor, and the third PMOS transistor are respectively connected to the power supply VDD; the gates of the first PMOS transistor, the second PMOS transistor, and the third PMOS transistor are connected and connected to a first reference voltage; the drains of the first PMOS transistor, the second PMOS transistor, and the third PMOS transistor are connected to the sources of the fourth PMOS transistor, the fifth PMOS transistor, and the sixth PMOS transistor, and the gates of the fourth PMOS transistor, the fifth PMOS transistor, and the sixth PMOS transistor are connected and connected to a second reference voltage; The drain of the fourth PMOS tube is connected to the first transistor, the drain of the fifth PMOS tube is connected to one end of the first resistor, and the other end of the first resistor is connected to the second transistor; the drain of the sixth PMOS tube is connected to one end of the third resistor, and the other end of the third resistor is connected to the third transistor. The drain of the sixth PMOS tube is also connected to the output end, and the output end is connected to the voltage follower.

2. The temperature compensation circuit according to claim 1, wherein: The voltage follower includes a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a seventh PMOS transistor, an eighth PMOS transistor, a ninth PMOS transistor and a tenth PMOS transistor; The gate of the first NMOS transistor is connected to the output end, and the drain of the first NMOS transistor is connected to the drain of the seventh PMOS transistor; the sources of the seventh PMOS transistor and the eighth PMOS transistor are connected to the power supply VDD; the drain of the eighth PMOS transistor is connected to the drain of the second NMOS transistor, and outputs a voltage to the gate of the tenth PMOS transistor; the first NMOS transistor and the second NMOS transistor are respectively connected to the ninth PMOS transistor, and the gate of the ninth PMOS transistor is connected to the third reference voltage; the third NMOS transistor is connected to the tenth PMOS transistor, and the gate of the third NMOS transistor is connected to the fourth reference voltage.

3. The temperature compensation circuit according to claim 1, wherein: The device further includes a first feedback element, wherein the first feedback element is connected to the power supply VDD and is further connected to a second NMOS transistor.

4. The temperature compensation circuit according to claim 3, wherein: The first feedback element includes a PMOS transistor, and a drain of the PMOS transistor is connected to the power supply VDD.

5. The temperature compensation circuit according to claim 3, wherein: The first feedback element is a first capacitor.

6. The temperature compensation circuit according to claim 1, wherein: The device further includes a second feedback element connected to the tenth PMOS transistor.

7. The temperature compensation circuit according to claim 1, wherein: The second feedback element is a second capacitor.

8. The temperature compensation circuit according to claim 7, wherein: The second capacitor is a Miller compensation capacitor.

9. The temperature compensation circuit according to claim 1, wherein: The first transistor, the second transistor and the third transistor are all PNP transistors.

10. A MEMS micromirror, characterized in that: The temperature compensation circuit comprises the temperature compensation circuit according to any one of claims 1 to 9.

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