Monitoring circuit suitable for various temperature sensors

Abstract

The invention relates to a monitoring circuit suitable for various temperature sensors. The invention is applied to a temperature sensor, and the temperature sensor comprises a temperature measurement resistor, and comprises a voltage division module which is used for providing a stable voltage source to the temperature measurement resistor; the output end of the constant current source module is connected with the temperature measuring resistor, and the constant current source module is used for providing constant current for the temperature measuring resistor; the operational amplifier module is connected with the temperature measuring resistor and used for amplifying the voltage difference signals at the two ends of the temperature measuring resistor to obtain a voltage difference value at the two ends of the temperature measuring resistor; the data processing module comprises an ADC module and a control module which are connected; the differential pressure value is subjected to analog-to-digital conversion through the ADC module to obtain a digital signal, and the control module obtains temperature data of the measured position according to the digital signal and the temperature characteristic of the corresponding temperature measuring resistor. According to the invention, on the premise of ensuring the measurement precision, adaptation to various temperature sensors can be realized with less adjustment and lower cost, and the circuit cost is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile electronics and hardware circuit design, and in particular to a monitoring circuit suitable for a variety of temperature sensors. Background Art

[0002] At present, the temperature measurement circuits used in most cars are mainly based on RTD (resistance temperature detector) or thermistor. In order to ensure the measurement accuracy, an expensive voltage regulator is often used in conjunction with an operational amplifier to form a constant current source through a platinum resistor, and then the voltage difference across the detection resistor is amplified to obtain the measured temperature value. If a traditional thermistor is to be used on this basis, it is necessary to increase investment in the selection of the resistor and the matching of the voltage regulator, which is often difficult to effectively reduce costs and also increases the complexity of the design.

[0003] In addition, the existing temperature measurement circuit uses a constant current source module formed by a voltage regulator, an operational amplifier and a fixed resistor to obtain the temperature signal through the resistance change of the temperature measuring resistor, and after being collected by the ADC (analog-to-digital converter), the CPU (central processing unit) calculates the corresponding temperature value. However, the existing temperature measurement circuit has problems such as complex circuit structure of the constant current source module, limited selection of temperature measuring resistors and poor anti-interference ability. Summary of the invention

[0004] To this end, the present invention provides a monitoring circuit suitable for a variety of temperature sensors. Under the premise of ensuring measurement accuracy, it can adapt to a variety of temperature sensors with fewer adjustments and lower costs, effectively reducing circuit costs and meeting the requirements of the new energy vehicle industry for different temperature measurement needs.

[0005] In order to solve the above technical problems, the present invention provides a monitoring circuit applicable to a variety of temperature sensors, which is applied to the temperature sensor, wherein the temperature sensor includes a temperature measuring resistor, including: A voltage divider module, used for providing a stable voltage source to the temperature measuring resistor; A constant current source module, whose output end is connected to the temperature measuring resistor, and is used to provide a constant current to the temperature measuring resistor; An operational amplifier module, connected to the temperature measuring resistor, for amplifying the pressure difference signal across the temperature measuring resistor to obtain the pressure difference value across the temperature measuring resistor; The data processing module includes a connected ADC module and a control module; wherein the pressure difference value is converted into a digital signal by the ADC module, and the control module obtains the temperature data of the measured position according to the digital signal and the temperature characteristics of the corresponding temperature measuring resistor.

[0006] In one embodiment of the present invention, the voltage dividing module includes a power supply DC1, a voltage dividing resistor R1, a capacitor C1 and a voltage stabilizing diode D01; The power supply DC1, the voltage dividing resistor R1 and the positive electrode of the voltage zener diode D01 are connected in sequence, and the negative electrode of the voltage zener diode D01 is connected to the temperature measuring resistor; One end of the capacitor C1 is connected between the power supply DC1 and the voltage dividing resistor R1 , and the other end is grounded.

[0007] In one embodiment of the present invention, the constant current source module includes a power supply DC2, a voltage stabilizing source chip U1, a transistor Q1, a resistor R2 and a resistor R3; Among them, the reference end of the voltage stabilizing source chip U1 is grounded through the resistor R3; The power source DC2 is connected to the cathode terminal of the voltage stabilizing source chip U1 through the resistor R2; The anode terminal of the voltage stabilizing source chip U1 is grounded; The emitter of transistor Q1 is connected between the reference end of voltage stabilizing source chip U1 and resistor R3; The base of transistor Q1 is connected between resistor R2 and the cathode terminal of voltage stabilizing source chip U1; One end of the temperature measuring resistor is connected to the cathode of the voltage stabilizing diode D01; The other end of the temperature measuring resistor is connected to the collector of transistor Q1.

[0008] In one embodiment of the present invention, it further includes a capacitor C2 and a capacitor C3; One end of capacitor C2 is connected between the cathode of voltage stabilizing diode D01 and one end of temperature measuring resistor; The other end of the capacitor C2 is respectively connected to the collector of the transistor Q1 and the other end of the temperature measuring resistor and one end of the capacitor C3, and the other end of the capacitor C3 is grounded.

[0009] In one embodiment of the present invention, the operational amplifier module includes an operational amplifier U47, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; The output end of the A channel of the operational amplifier U47 is connected to the resistor R5, the resistor R4 and one end of the temperature measuring resistor in sequence; The inverting input terminal of the A channel output terminal of the operational amplifier U47 is connected between the resistor R5 and the resistor R4; The negative power supply terminal of the operational amplifier U47 is grounded; The other end of the temperature measuring resistor is connected to resistor R6 and resistor R7 in sequence, and resistor R7 is grounded; The A channel output terminal and the non-inverting input terminal of the operational amplifier U47 are connected between the resistor R6 and the resistor R7; The B channel non-inverting input terminal of the operational amplifier U47 is connected to the A channel output terminal of the operational amplifier U47; The inverting input terminal of the B channel of the operational amplifier U47 is connected to the input terminal of the ADC module through resistors R8 and R9 in sequence; The B channel output terminal of the operational amplifier U47 is connected between the resistor R8 and the resistor R9; The positive power supply of operational amplifier U47 is connected to voltage VCC.

[0010] In one embodiment of the present invention, a capacitor C5 is further included, and the capacitor C5 is connected in parallel across the resistor R5.

[0011] In one embodiment of the present invention, a capacitor C6 is further included, and the voltage VCC is grounded through the capacitor C6.

[0012] In one embodiment of the present invention, the temperature measuring resistor includes PT100, PT1000 or NTC.

[0013] The above technical solution of the present invention has the following advantages compared with the prior art: The monitoring circuit suitable for various temperature sensors described in the present invention can provide a more stable current to pass through the temperature measuring resistor by using a better constant current source module, has a stronger anti-interference ability, and is not easily affected by the interference caused by voltage source fluctuations to affect the detection result; the optimized constant current source and voltage divider part in the monitoring circuit can better adapt to various types of temperature measuring resistors, making the circuit more unified and reducing the cost in the repeated development process; the monitoring circuit adopts a negative feedback amplification and voltage follower two-stage operational amplifier circuit to ensure the accuracy and stability of the ADC sampling signal.

[0014] The monitoring circuit of the present invention can support various types of temperature sensors, including different types of temperature measuring resistors such as PT100, PT1000, and NTC. This design has good versatility and can adapt to different types of temperature sensors without making a lot of modifications to the circuit. It is more adaptable and is particularly suitable for scenarios such as new energy vehicles that require high-precision multi-point temperature monitoring.

[0015] The monitoring circuit of the present invention adopts an optimized voltage divider module and a constant current source module, so that the circuit structure is relatively simple. The constant current source is realized by combining a voltage stabilizer chip with a triode, avoiding expensive constant current source chips, thereby reducing development costs. In addition, the circuit structure is streamlined, reducing the number and complexity of components, and further reducing manufacturing and maintenance costs while ensuring accuracy.

[0016] The constant current source module of the present invention provides a constant current to the temperature measuring resistor, so that the temperature measurement will not be affected by the fluctuation of the external power supply. In addition, the operational amplifier module adopts a secondary amplification and voltage follower structure, which ensures the accuracy of the output signal, reduces signal distortion, and ultimately improves the accuracy of temperature measurement, meeting the requirements for higher accuracy of temperature monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0018] Figure 1 It is a structural diagram of a monitoring circuit applicable to various temperature sensors of the present invention.

[0019] Figure 2 It is a structural diagram of the circuit composed of the voltage divider module and the constant current source module.

[0020] Figure 3 It is a circuit structure diagram of the operational amplifier module of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0022] In the present invention, "several" means one or more, "multiple" means more than two, "greater than", "less than", "exceed" and the like are understood to exclude the number itself; "above", "below", "within" and the like are understood to include the number itself. In the description of the present invention, if there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0023] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected or electrically connected or able to communicate with each other; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0024] Reference Figure 1 As shown, a monitoring circuit applicable to a variety of temperature sensors of the present invention is applied to a temperature sensor, wherein the temperature sensor includes a temperature measuring resistor, including: A voltage divider module, used for providing a stable voltage source to the temperature measuring resistor; A constant current source module, whose output end is connected to the temperature measuring resistor, is used to provide a constant current to the temperature measuring resistor; the constant current passes through the temperature measuring resistor and forms a voltage difference at both ends of the temperature measuring resistor; An operational amplifier module, connected to the temperature measuring resistor, for amplifying the pressure difference signal across the temperature measuring resistor to obtain the pressure difference value across the temperature measuring resistor; The data processing module includes a connected ADC module and a control module CPU (control chip); wherein the pressure difference value is converted into a digital signal by the ADC module, and the control module obtains the temperature data of the measured position according to the digital signal and the temperature characteristics of the corresponding temperature measuring resistor.

[0025] It can be understood that the signal ADC_IN obtained after the operational amplifier is converted by the ADC module, and the obtained digital signal is transmitted for data processing and comparison according to the temperature characteristics of the selected temperature measuring resistor and the amplification factor of the operational amplifier circuit, and finally the temperature data of the measured position can be obtained.

[0026] In one embodiment, referring to Figure 2 As shown, the voltage dividing module includes a power supply DC1, a voltage dividing resistor R1, a capacitor C1 and a voltage stabilizing diode D01; Among them, the power supply DC1, the voltage dividing resistor R1 and the positive electrode of the voltage zener diode D01 are connected in sequence, and the negative electrode of the voltage zener diode D01 is connected to the temperature measuring resistor; One end of the capacitor C1 is connected between the power supply DC1 and the voltage dividing resistor R1 , and the other end is grounded.

[0027] It should be noted that the power supply voltage divider circuit composed of power supply DC1, voltage divider resistor R1 and voltage stabilizing diode DO1 ensures that the temperature measuring resistor can obtain sufficient voltage division in this circuit system. The power supply DC1 must be selected to be higher than the voltage required within the resistance range of the constant current source module and the temperature measuring resistor for normal operation. At the same time, the conduction voltage drop of the voltage divider resistor R1 and the voltage stabilizing diode DO1 also needs to be considered.

[0028] Reference Figure 2 As shown, the constant current source module includes a power supply DC2, a voltage stabilizing source chip U1, a transistor Q1, a resistor R2 and a resistor R3; one end of the temperature measuring resistor is connected to the RTD_1 node, and the other end is connected to the RTD_3 node; Among them, the reference end (pin 2) of the voltage stabilizing source chip U1 is grounded through the resistor R3; The power source DC2 is connected to the cathode terminal of the voltage stabilizing source chip U1 through the resistor R2; The anode terminal (pin 3) of the voltage regulator chip U1 is grounded; The emitter of transistor Q1 is connected between the reference end of voltage stabilizing source chip U1 and resistor R3; The base of transistor Q1 is connected between resistor R2 and the cathode end (pin 1) of voltage regulator chip U1; One end of the temperature measuring resistor is connected to the cathode of the voltage stabilizing diode D01; The other end of the temperature measuring resistor is connected to the collector of transistor Q1.

[0029] In one embodiment, it further includes a capacitor C2 and a capacitor C3; One end of capacitor C2 is connected between the cathode of voltage stabilizing diode D01 and one end of temperature measuring resistor; The other end of the capacitor C2 is respectively connected to the collector of the transistor Q1 and the other end of the temperature measuring resistor and one end of the capacitor C3, and the other end of the capacitor C3 is grounded.

[0030] It should be noted that capacitors C1 , C2 and C3 are filter capacitors, the purpose of which is to filter the signals of each link to reduce possible interference or fluctuation.

[0031] In addition, the voltage divider resistors R1, R2, and R3 can be selected according to the actual system conditions and constant current source module parameters to match appropriate voltage divider resistors.

[0032] The temperature measuring resistor can be PT100, PT1000, NTC, etc. You can also choose a suitable temperature measuring resistor for matching according to the actual design requirements, such as RTD, PTC, NTC and other types, and also choose the temperature measuring range of the corresponding type of temperature measuring resistor to be in the appropriate range of the application.

[0033] It can be understood that a constant current source module is formed by a circuit including transistor Q1, resistor R2 and resistor R3, which ensures that the current passing through the temperature measuring resistor is constant. For example, if the resistance value of resistor R3 is 2.5K, the constant current source module will output a current of 1mA. If it needs to be configured to other rated currents, it is only necessary to change the resistance value of resistor R3.

[0034] Therefore, the resistance of the temperature measuring resistor changes with the change of the temperature at the measured position. The constant current source module ensures that the current passing through the temperature measuring resistor will not be affected by other factors such as temperature, thereby stably and accurately reflecting the voltage difference across the temperature measuring resistor for subsequent amplification and A\D conversion.

[0035] Optionally, the voltage stabilizer chip U1 adopts a TL431BQDBZ voltage stabilizer chip.

[0036] In one embodiment, referring to Figure 3 As shown, the operational amplifier module includes an operational amplifier U47, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; The A channel output terminal (OUTA) of the operational amplifier U47 is connected to the resistor R5, the resistor R4 and one end of the temperature measuring resistor in sequence; The inverting input terminal (-INA) of the A channel output terminal of the operational amplifier U47 is connected between the resistor R5 and the resistor R4; The negative power supply terminal (V-) of the operational amplifier U47 is grounded; The other end of the temperature measuring resistor is connected to resistor R6 and resistor R7 in sequence, and resistor R7 is grounded; The A channel output terminal non-inverting input terminal (+INA) of the operational amplifier U47 is connected between the resistor R6 and the resistor R7; The B channel non-inverting input terminal (+INB) of the operational amplifier U47 is connected to the A channel output terminal of the operational amplifier U47; The inverting input terminal (-INB) of the B channel of the operational amplifier U47 is connected to the input terminal of the ADC module through resistors R8 and R9 in sequence; The B channel output terminal (OUTB) of the operational amplifier U47 is connected between the resistor R8 and the resistor R9; The positive power supply (V+) of operational amplifier U47 is connected to voltage VCC.

[0037] Optionally, the operational amplifier U47 uses an IC_OPA2376 chip.

[0038] It should be noted that the operational amplifier part adopts a structure of one-stage amplification and one-stage following. The gain of the amplification part is determined by the resistance values ​​of resistors R4, R5, R6, and R7. Appropriate resistance values ​​can be selected for matching according to actual needs; the following part is protected by current limiting resistors. The two-stage operational amplifier module is based on the operational amplifier chip, in which the amplification factor of the first-stage operational amplifier is determined by resistors R4, R5, R6, and R7, and the current limiting protection of the second-stage voltage follower circuit is provided by resistors R8 and R9. The selection of all resistance parameters can be adjusted according to the actual ADC accuracy and detection range requirements to ensure the best system performance.

[0039] Specifically, the device further includes a capacitor C5, which is connected in parallel to both ends of the resistor R5; and a capacitor C6, through which the voltage VCC is grounded.

[0040] The voltage regulator chip (such as TL431) provides a stable reference voltage and outputs a constant current through transistor Q1. The current of the constant current source can be adjusted by adjusting the value of resistor R3 to meet the needs of different types of temperature measuring resistors. Since the current is constant, when the resistance of the temperature measuring resistor changes with temperature, the voltage across the resistor will change accordingly.

[0041] During the temperature measurement process, the resistance of the temperature measuring resistor changes with the temperature, so the voltage difference formed at both ends of the temperature measuring resistor by the constant current provided by the constant current source also changes with the temperature. This voltage difference directly reflects the temperature change and becomes the basic signal of the temperature data.

[0042] The voltage signal across the temperature measuring resistor is amplified by the operational amplifier module to enhance the detectability of the signal.

[0043] The amplified voltage signal is transmitted to the ADC module in the data processing module, which converts the analog voltage signal into a digital signal and transmits the digital signal to the control module. The control module calculates the actual temperature data based on the temperature characteristic curve of the temperature measuring resistor (such as the resistance-temperature relationship of PT100) and the amplification factor.

[0044] The control module calculates based on the digitized voltage data and the characteristic curve of the sensor, converts the voltage value into the corresponding temperature data, and completes the accurate measurement of the temperature. The final temperature data can be used for display, recording or other temperature control systems.

[0045] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A monitoring circuit applicable to a variety of temperature sensors, applied to a temperature sensor, wherein the temperature sensor includes a temperature measuring resistor, characterized in that: include: A voltage divider module, used for providing a stable voltage source to the temperature measuring resistor; A constant current source module, whose output end is connected to the temperature measuring resistor, and is used to provide a constant current to the temperature measuring resistor; An operational amplifier module, connected to the temperature measuring resistor, for amplifying the pressure difference signal across the temperature measuring resistor to obtain the pressure difference value across the temperature measuring resistor; The data processing module includes a connected ADC module and a control module; wherein the pressure difference value is converted into a digital signal by the ADC module, and the control module obtains the temperature data of the measured position according to the digital signal and the temperature characteristics of the corresponding temperature measuring resistor.

2. A monitoring circuit applicable to a variety of temperature sensors according to claim 1, characterized in that: The voltage dividing module includes a power supply DC1, a voltage dividing resistor R1, a capacitor C1 and a voltage stabilizing diode D01; The power supply DC1, the voltage dividing resistor R1 and the positive electrode of the voltage zener diode D01 are connected in sequence, and the negative electrode of the voltage zener diode D01 is connected to the temperature measuring resistor; One end of the capacitor C1 is connected between the power supply DC1 and the voltage dividing resistor R1 , and the other end is grounded.

3. A monitoring circuit applicable to multiple temperature sensors according to claim 2, characterized in that: The constant current source module includes a power supply DC2, a voltage stabilizing source chip U1, a transistor Q1, a resistor R2 and a resistor R3; Among them, the reference end of the voltage stabilizing source chip U1 is grounded through the resistor R3; The power source DC2 is connected to the cathode terminal of the voltage stabilizing source chip U1 through the resistor R2; The anode terminal of the voltage stabilizing source chip U1 is grounded; The emitter of transistor Q1 is connected between the reference end of voltage stabilizing source chip U1 and resistor R3; The base of transistor Q1 is connected between resistor R2 and the cathode terminal of voltage stabilizing source chip U1; One end of the temperature measuring resistor is connected to the cathode of the voltage stabilizing diode D01; The other end of the temperature measuring resistor is connected to the collector of transistor Q1.

4. A monitoring circuit applicable to multiple temperature sensors according to claim 3, characterized in that: Also includes capacitor C2 and capacitor C3; One end of capacitor C2 is connected between the cathode of voltage stabilizing diode D01 and one end of temperature measuring resistor; The other end of the capacitor C2 is respectively connected to the collector of the transistor Q1 and the other end of the temperature measuring resistor and one end of the capacitor C3, and the other end of the capacitor C3 is grounded.

5. The monitoring circuit applicable to various temperature sensors according to claim 1, characterized in that: The operational amplifier module includes an operational amplifier U47, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; The output end of the A channel of the operational amplifier U47 is connected to the resistor R5, the resistor R4 and one end of the temperature measuring resistor in sequence; The inverting input terminal of the A channel output terminal of the operational amplifier U47 is connected between the resistor R5 and the resistor R4; The negative power supply terminal of the operational amplifier U47 is grounded; The other end of the temperature measuring resistor is connected to resistor R6 and resistor R7 in sequence, and resistor R7 is grounded; The A channel output terminal and the non-inverting input terminal of the operational amplifier U47 are connected between the resistor R6 and the resistor R7; The B channel non-inverting input terminal of the operational amplifier U47 is connected to the A channel output terminal of the operational amplifier U47; The inverting input terminal of the B channel of the operational amplifier U47 is connected to the input terminal of the ADC module through resistors R8 and R9 in sequence; The B channel output terminal of the operational amplifier U47 is connected between the resistor R8 and the resistor R9; The positive power supply of operational amplifier U47 is connected to voltage VCC.

6. The monitoring circuit applicable to various temperature sensors according to claim 5, characterized in that: The device further includes a capacitor C5 which is connected in parallel to both ends of the resistor R5.

7. The monitoring circuit applicable to various temperature sensors according to claim 5, characterized in that: A capacitor C6 is also included, and the voltage VCC is grounded via the capacitor C6.

8. The monitoring circuit applicable to various temperature sensors according to claim 1, characterized in that: The temperature measuring resistor includes PT100, PT1000 or NTC.

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