Temperature compensation circuit for a silicon piezoresistive pressure sensor

Abstract

The application provides a silicon piezoresistive pressure sensor temperature compensation circuit, which comprises an adjustable voltage reference chip, a power supply end Vi, an output end Vo, an adjustable voltage pin ADJ and a ground end GND; the power supply end Vi is connected with a power supply, the output end Vo is connected with a power supply end of a Wheatstone bridge, and the ground end GND is grounded; an adjusting circuit is connected with the adjustable voltage reference chip, and the adjusting circuit comprises a diode D1, a resistor R1 and a resistor R f The anode of the diode D1 is connected with the adjustable voltage pin ADJ of the adjustable voltage reference chip, and the cathode is connected with the ground end GND of the adjustable voltage reference chip through the resistor R1; the two ends of the resistor R f The adjustable voltage pin ADJ and the output end Vo of the adjustable voltage reference chip are connected with the two ends of the resistor R respectively; that is, the sensitivity temperature drift of the pressure sensitive core body can be compensated by adjusting the ratio of the resistor Rf and the resistor R1, so that the sensitivity temperature drift of the pressure sensitive core body is compensated to a qualified range.

Description

TECHNICAL FIELD

[0001] The present application relates to a silicon piezoresistive pressure sensor, in particular to a temperature compensation circuit of a silicon piezoresistive pressure sensor. BACKGROUND

[0002] At present, the existing pressure sensor temperature compensation methods on the market mainly include analog compensation and digital compensation, and the digital compensation is mainly completed by a signal conditioning chip; and the analog compensation is mainly completed by an NTC and an adjusting circuit. Since the NTC has an exponential monotone decreasing trend with temperature, and after the NTC is combined with the adjusting circuit to form a resistance network, a linear monotone decreasing resistance network needs to be obtained, and it is difficult to compensate the sensitivity of a pressure sensitive core body which has a fold line type with temperature to a qualified range. SUMMARY

[0003] In view of this, the technical problem to be solved by the present application is to provide a temperature compensation circuit of a silicon piezoresistive pressure sensor, which is composed of a diode and an adjustable voltage reference chip to form a temperature control voltage source, so that the output voltage of the adjustable voltage reference chip changes linearly with temperature, thereby compensating the sensitivity temperature drift of the pressure sensitive core body to a qualified range.

[0004] To achieve the above-mentioned purpose, the technical scheme adopted by the embodiment of the present application is as follows: a temperature compensation circuit of a silicon piezoresistive pressure sensor, the internal structure of a pressure sensitive core body of the silicon piezoresistive pressure sensor is equivalent to a Wheatstone bridge composed of four bridge arm resistors Ra, Rb, Rc and Rd, wherein Rb and Rd increase with the increase of input pressure, Ra and Rc decrease with the increase of input pressure, S+ and S- are output terminals of the Wheatstone bridge, and the compensation circuit comprises:

[0005] an adjustable voltage reference chip having a power supply end Vi, an output end Vo, an adjustable voltage pin ADJ and a ground end GND; the power supply end Vi is connected to a power supply, the output end Vo is connected to a power supply end of the Wheatstone bridge, and the ground end GND is grounded;

[0006] an adjusting circuit composed of a diode D1, a resistor R1 and a resistor R f The anode of the diode D1 is connected to the adjustable voltage pin ADJ of the adjustable voltage reference chip, and the cathode is connected to the ground end GND of the adjustable voltage reference chip through the resistor R1. The two ends of the resistor R f are connected to the adjustable voltage pin ADJ and the output end Vo of the adjustable voltage reference chip, respectively.

[0007] Vo = V ADJ + R f *(V ADJ -V D1 ) / R1.

[0008] The voltage at the output terminal Vo of the adjustable voltage reference chip increases with temperature by means of diode D1, and the sensitivity temperature drift of the pressure-sensitive core is compensated by adjusting the ratio of resistor Rf to resistor R1.

[0009] Furthermore, embodiments of the present invention also include a voltage divider resistor R. t The voltage divider resistor R t One end is connected to the output terminal Vo of the adjustable voltage reference chip, and the other end is connected between the bridge arm resistors Ra and Rb of the Wheatstone bridge.

[0010] Furthermore, the compensation circuit also includes fixed resistors R2, R3, R4, and R5; the first end of R2 is connected to the output terminal S+ of the Wheatstone bridge, and the second end is grounded; the first end of R3 is connected to the output terminal S- of the Wheatstone bridge, and the second end is grounded; R4 is connected in series with the Wheatstone bridge, with its first end connected to one end of the bridge arm resistor Rd, and the second end grounded; R5 is connected in series with the Wheatstone bridge, with its first end connected to one end of the bridge arm resistor Rc, and the second end grounded; R2 and R3 are used to compensate for the zero-point temperature drift of the pressure sensor, increasing R4 increases the output zero point of the pressure sensor, and increasing R5 decreases the output zero point of the pressure sensor.

[0011] The advantages of this invention are as follows: The temperature compensation circuit of the silicon piezoresistive pressure sensor uses diodes and an adjustable voltage reference chip for compensation, simplifying the compensation calculation and fully utilizing the characteristics of the adjustable voltage reference chip. Sensitivity compensation does not require the use of operational amplifiers, and the compensation circuit can be used without operational amplifiers when no additional amplification circuit is needed for the output. The zero-point temperature drift and zero-point compensation circuits are simple, and the output is flexible and versatile. [Attached Image Description]

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0013] Figure 1 This is a schematic diagram of the temperature compensation circuit for the silicon piezoresistive pressure sensor of the present invention.

[0014] Figure 2 This is a schematic diagram illustrating the compensation principle for sensitivity temperature drift in an embodiment of the present invention.

[0015] Figure 3 This is a schematic diagram of the compensation effect curve for sensitivity temperature drift of the present invention.

Detailed Implementation Methods

[0016] The embodiment of the present application provides a silicon piezoresistive pressure sensor temperature compensation circuit, a temperature control voltage reference source is composed of a linear PTC and an adjustable voltage reference chip, and the output voltage of the voltage reference chip is linearly changed with temperature through improvement and innovation of the peripheral circuit of the adjustable voltage reference chip, so that the sensitivity temperature drift of the pressure sensitive core is compensated, and the zero point and the zero point temperature drift are adjusted through series and parallel resistors on the Wheatstone bridge.

[0017] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0018] Please refer to Figure 1 The internal structure of the pressure sensitive core of the silicon piezoresistive pressure sensor is equivalent to a Wheatstone bridge composed of four bridge arm resistors Ra, Rb, Rc and Rd, wherein Rb and Rd increase with the increase of the input pressure, Ra and Rc decrease with the increase of the input pressure, and S+ and S- are output ends of the Wheatstone bridge, and the compensation circuit comprises:

[0019] An adjustable voltage reference chip has a power supply end Vi, an output end Vo, an adjustable voltage pin ADJ and a ground end GND; the power supply end Vi is connected with a power supply, the output end Vo is connected with a power supply end of the Wheatstone bridge, and the ground end GND is grounded;

[0020] An adjusting circuit is composed of a diode D1, a resistor R1 and a resistor R f The anode of the diode D1 is connected with the adjustable voltage pin ADJ of the adjustable voltage reference chip, and the cathode is connected with the ground end GND of the adjustable voltage reference chip through the resistor R1; the two ends of the resistor R f are connected with the adjustable voltage pin ADJ and the output end Vo of the adjustable voltage reference chip respectively;

[0021] Then Vo=V ADJ +R f *(V ADJ -V D1 ) / R1;

[0022] The voltage of the output end Vo of the adjustable voltage reference chip is increased with the increase of temperature through the diode D1, and the sensitivity temperature drift of the pressure sensitive core is compensated by adjusting the ratio of the resistor R f and the resistor R1.

[0023] As Figure 2 shown, the adjusting circuit R1, R f, D1 and an adjustable voltage reference chip constitute a temperature-controlled voltage reference circuit, and provide a temperature-controlled voltage reference with a linear change in voltage with temperature, which is used to compensate for the temperature drift of the sensitivity of the pressure sensor. ADJ = 1.33V, Vo = V ADJ + R f *(V ADJ -V D1 ) / R1 = 1.33 + R F *(1.33-V D1 ) / R1, by adjusting the ratio of R f and R1, the output voltage of the voltage reference circuit can be adjusted. D1 is a diode, according to the temperature characteristics of the conduction voltage drop of the diode, the conduction voltage drop decreases with the increase of temperature, which can make the output voltage Vo of the voltage reference circuit increase with the increase of temperature. By adjusting the ratio of R f and R1, the temperature drift of the sensitivity of the pressure sensor can be compensated.

[0024] As shown in Figure 1 , the compensation circuit further comprises fixed resistors R2, R3, R4 and R5; the first end of R2 is connected to the output end S+ of the Wheatstone bridge, and the second end is connected to the ground; the first end of R3 is connected to the output end S- of the Wheatstone bridge, and the second end is connected to the ground; R4 is connected in series on the Wheatstone bridge, the first end is connected to one end of the bridge arm resistor Rd, and the second end is connected to the ground; R5 is connected in series on the Wheatstone bridge, the first end is connected to one end of the bridge arm resistor Rc, and the second end is connected to the ground; R2 and R3 are used to compensate for the zero point temperature drift of the pressure sensor; R4 and R5 are used to adjust the zero point of the pressure sensor, increasing R4 increases the output zero point of the pressure sensor; increasing R5 decreases the output zero point of the pressure sensor.

[0025] The embodiment of the application further comprises a voltage dividing resistor R t , one end of the voltage dividing resistor R t is connected to the output end Vo of the adjustable voltage reference chip, and the other end is connected between the bridge arm resistors Ra and Rb of the Wheatstone bridge. Considering that the output adjustment capability of the temperature-controlled voltage reference circuit is limited, a voltage dividing resistor Rt is added between the temperature-controlled voltage reference circuit and the Wheatstone bridge, to increase the flexibility of the output of the voltage reference circuit.

[0026] The output ends S+ and S- of the Wheatstone bridge can also be connected to an amplification circuit. Thus, the compensation circuit and the amplification circuit of the pressure sensor are separated, and the output can meet various output requirements.

[0027] The following takes the compensation process of a pressure core as an example:

[0028] Table 1 Output characteristics of the pressure core under 1V power supply without compensation

[0029]

[0030] From Table 1, it can be seen that the output sensitivity gradually decreases with the increase of temperature, and the output sensitivity is positively correlated with the supply voltage. By adjusting the supply voltage, the output of the pressure core at different temperatures can be constant. The target supply voltage of the pressure core at different temperatures can be calculated from the above table, and the calculation formula is:

[0031] Supply voltage = target sensitivity ÷ 1V supply sensitivity

[0032] Table 2 Target supply voltage of pressure core at different temperatures

[0033]

[0034] The target supply voltage of the pressure core at different temperatures is calculated as shown in Table 2 above, so it is necessary to select appropriate R f and R1 ratio, and the ratio of R t and Rb (Rb is the resistance value of the Wheatstone bridge, which increases linearly with the increase of temperature) can make Vo meet the above supply voltage requirement at different temperatures.

[0035] The voltage drop of diode D1 at different temperatures is shown in the second column of Table 3.

[0036] The resistance value of R f is 2550Ω, and the resistance value of R1 is 1000Ω. According to the formula Vo = V ADJ + R f *(V ADJ -V D1 ) / R1 = 1.33 + R F *(1.33-V D1 ) / R1, Vo can be calculated as shown in the sixth column of Table 3.

[0037] The resistance value of R t is 451Ω, and according to the formula V 目标 = Vo*R b / (R t +R b ), the target supply voltage can be calculated as shown in the ninth column of Table 3:

[0038] Table 3

[0039]

[0040] The target supply voltage and the calculated supply voltage are basically the same, and the error meets the accuracy requirement. The output comparison at different temperatures is shown in Figure 3 .

[0041] After compensation, the above resistance value is adjusted according to the test results to further improve the compensation accuracy. Selecting appropriate resistance values of R2, R3, R4 and R5 can compensate the zero point and zero point temperature drift of the pressure core. Here, R2=1.3MΩ, R3 is not connected to the resistance, R4=24.4Ω, and R5=0Ω, which can compensate the zero point and zero point temperature drift to the qualified range.

[0042] Table 4 below is the output accuracy error under different temperature and pressure conditions after compensation. The full temperature compensation accuracy can reach within 2%.

[0043] Table 4 is the output accuracy error under different temperature and pressure conditions after compensation

[0044] Temperature °C 50 kPa 100 kPa 200 kPa 350 kPa 500 kPa 700 kPa 900 kPa 1200 kPa -45 0.04％ 0.01％ -0.03％ -0.09％ -0.13％ -0.13％ -0.12％ -0.01％ 25 0.11％ -0.02％ -0.14％ -0.39％ -0.55％ -0.76％ -0.97％ -1.17％ 60 0.30％ 0.28％ 0.30％ 0.32％ 0.38％ 0.46％ 0.56％ 0.79％ 120 -0.05％ -0.08％ -0.10％ -0.15％ -0.19％ -0.20％ -0.18％ -0.06％

[0045] The advantages of the present application are that the temperature compensation circuit of the silicon piezoresistive pressure sensor is composed of a diode regulating circuit and an adjustable voltage reference chip to form a temperature-controlled voltage reference source, so that the output voltage of the voltage reference chip changes linearly with temperature, which is used to compensate the sensitivity temperature drift of the pressure sensitive core. The zero point and zero point temperature drift are adjusted by series and parallel resistors on the Wheatstone bridge, so as to compensate the zero point and zero point temperature drift to the qualified range. The adjustable voltage reference chip output voltage is fully utilized, the sensitivity compensation does not need to use an operational amplifier, the sensitivity compensation calculation is simple, and the zero point temperature drift and zero point compensation circuit are also simple and easy to implement.

[0046] Although the specific embodiments of the present application are described above, those skilled in the art should understand that the specific examples described are only illustrative, and are not intended to limit the scope of the present application. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present application should be covered within the scope of the claims of the present application.

Claims

1. A temperature compensation circuit for a silicon piezoresistive pressure sensor, wherein the internal structure of the pressure-sensitive core of the silicon piezoresistive pressure sensor is equivalent to a Wheatstone bridge, consisting of four bridge arm resistors Ra, Rb, Rc, and Rd, wherein Rb and Rd increase with increasing input pressure, and Ra and Rc decrease with increasing input pressure, and S+ and S- are the output terminals of the Wheatstone bridge, characterized in that: The compensation circuit includes: An adjustable voltage reference chip has a power supply terminal Vi, an output terminal Vo, an adjustable voltage pin ADJ, and a ground terminal GND; the power supply terminal Vi is connected to the power supply, the output terminal Vo is connected to the power supply terminal of the Wheatstone bridge, and the ground terminal GND is grounded. The regulating circuit consists of diode D1, resistor R1, and resistor R. f The diode D1 is configured such that its anode is connected to the adjustable voltage pin ADJ of the adjustable voltage reference chip, and its cathode is connected to the ground terminal GND of the adjustable voltage reference chip via resistor R1; the resistor R... f The two ends are respectively connected to the adjustable voltage pin ADJ and the output terminal Vo of the adjustable voltage reference chip; Then Vo = V ADJ + R f *(V ADJ - V D1 ) / R1; The voltage at the output terminal Vo of the adjustable voltage reference chip increases with temperature by means of diode D1, and the sensitivity temperature drift of the pressure-sensitive core is compensated by adjusting the ratio of resistor Rf to resistor R1.

2. The temperature compensation circuit for a silicon piezoresistive pressure sensor as described in claim 1, characterized in that: It also includes the voltage divider resistor R t The voltage divider resistor R t One end is connected to the output terminal Vo of the adjustable voltage reference chip, and the other end is connected between the bridge arm resistors Ra and Rb of the Wheatstone bridge.

3. The temperature compensation circuit for a silicon piezoresistive pressure sensor as described in claim 1, characterized in that: The compensation circuit also includes fixed resistors R2, R3, R4, and R5; the first end of R2 is connected to the output terminal S+ of the Wheatstone bridge, and the second end is grounded; the first end of R3 is connected to the output terminal S- of the Wheatstone bridge, and the second end is grounded; R4 is connected in series with the Wheatstone bridge, the first end is connected to one end of the bridge arm resistor Rd, and the second end is grounded; R5 is connected in series with the Wheatstone bridge, the first end is connected to one end of the bridge arm resistor Rc, and the second end is grounded; R2 and R3 are used to compensate for the zero-point temperature drift of the pressure sensor. Increasing R4 increases the output zero point of the pressure sensor; increasing R5 decreases the output zero point of the pressure sensor.

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