High-precision temperature sensor circuit

Abstract

The utility model provides a high-precision temperature sensor circuit. The high-precision temperature sensor circuit comprises a first constant current source circuit of which the output end is connected with the first end of a temperature sensing element, a second constant current source circuit of which the output end is connected with the second end of the temperature sensing element, and a subtraction circuit of which the output end is connected with the second end of the temperature sensing element, the inverting input end of the subtraction circuit is connected with the first end of the temperature sensing element, the non-inverting input end of the subtraction circuit is connected with the second end of the temperature sensing element, and the output end of the subtraction circuit is the output end of the high-precision temperature sensor. The detection precision of the temperature sensor can be improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of temperature sensors, and in particular to a high-precision temperature sensor circuit. Background Art

[0002] A temperature sensor is a device that can sense temperature and convert it into an electrical signal. It contains a temperature sensing element. The resistance of the temperature sensing element changes with the temperature. Therefore, the temperature change can be obtained by designing a detection circuit to detect the change in the resistance of the temperature sensing element. If the lead between the temperature sensing element and the detection circuit is too long, the line impedance is too large, which will affect the resistance detection accuracy of the temperature sensing element. Utility Model Content

[0003] The disclosed embodiments provide a high-precision temperature sensor circuit to solve the problem of poor detection accuracy of existing temperature sensors.

[0004] The present disclosure provides a high-precision temperature sensor circuit, comprising:

[0005] a first constant current source circuit, wherein an output end of the first constant current source circuit is connected to a first end of a temperature sensing element,

[0006] a second constant current source circuit, wherein the output end of the second constant current source circuit is connected to the second end of the temperature sensing element,

[0007] A subtraction circuit, wherein the inverting input terminal of the subtraction circuit is connected to the first terminal of the temperature sensing element, the non-inverting input terminal of the subtraction circuit is connected to the second terminal of the temperature sensing element, and the output terminal of the subtraction circuit is the output terminal of the high-precision temperature sensor.

[0008] In an exemplary embodiment of the present disclosure, the first constant current source circuit includes an operational amplifier U5, a switch tube Q2 and a first current limiting resistor.

[0009] The non-inverting input terminal of the operational amplifier U5 is connected to the first reference voltage, the output terminal of the operational amplifier U5 is connected to the control terminal of the switch tube Q2, the first terminal of the switch tube Q2 is the output terminal of the first constant current source circuit, the second terminal of the switch tube Q2 is grounded through a first current limiting resistor, and the second terminal of the switch tube Q2 is feedback connected to the inverting input terminal of the operational amplifier U5.

[0010] In an exemplary embodiment of the present disclosure, a voltage stabilizing module U6 is further included, wherein a reference electrode of the voltage stabilizing module U6 is connected to a first power supply via a resistor R15, an anode of the voltage stabilizing module U6 is grounded, a cathode of the voltage stabilizing module U6 is connected to the reference electrode of the voltage stabilizing module U6, and the cathode of the voltage stabilizing module U6 outputs a first reference voltage.

[0011] In an exemplary embodiment of the present disclosure, an amplification circuit is provided between the first end of the temperature sensing element and the inverting input end of the subtraction circuit.

[0012] In an exemplary embodiment of the present disclosure, the output end of the subtraction circuit is connected to the input end of the voltage-current conversion circuit, and the output end of the voltage-current conversion circuit is the output end of the high-precision temperature sensor.

[0013] In an exemplary embodiment of the present disclosure, the voltage-current conversion circuit includes an operational amplifier U3, a switch tube Q1, a resistor R12, a resistor R14, a resistor R11 and a terminal H1.

[0014] The non-inverting input terminal of the operational amplifier U3 is connected to the output terminal of the subtraction circuit, the inverting input terminal of the operational amplifier U3 is grounded, the output terminal of the operational amplifier U3 is connected to the control terminal of the switch tube Q1, the first terminal of the switch tube Q1 is connected to the second power supply, the second terminal of the switch tube Q1 is connected to the first terminal of the resistor R12, the second terminal of the resistor R12 is feedback connected to the inverting input terminal of the operational amplifier U3, and the second terminal of the resistor R12 is grounded.

[0015] The second end of the resistor R12 is connected to the first end of the resistor R14, and the second end of the resistor R14 is connected to the in-phase input end of the operational amplifier U3 through the resistor R13 and the resistor R11 in sequence.

[0016] The first end of the terminal H1 is connected to the third power supply, the second end of the terminal H1 is connected to the second end of the resistor R14, and the first end and the second end of the terminal H1 are output ends of the voltage-current conversion circuit.

[0017] In an exemplary embodiment of the present disclosure, a power supply circuit is further included, wherein the power supply circuit includes a voltage stabilizing module U9, a diode D1 and a diode D2.

[0018] The input end of the voltage stabilizing module U9 is connected to the second power supply, the output end of the voltage stabilizing module U9 outputs the fourth power supply, and the output of the voltage stabilizing module outputs the fifth power supply via the diode D1 and the diode D2 in sequence.

[0019] The working principle and beneficial effects of the high-precision temperature sensor circuit provided by the embodiment of the present disclosure are as follows:

[0020] In the disclosed embodiment, the output current of the first constant current source circuit is added to the first end of the temperature sensing element, and the output current of the second constant current source circuit is added to the second end of the temperature sensing element, so as to generate a potential difference between the two ends of the temperature sensing element. The potential difference is calculated by a subtraction circuit to obtain the voltage between the two ends of the temperature sensing element. Therefore, the change in temperature can be obtained by detecting the change in the output voltage of the subtraction circuit, thereby avoiding the influence of line impedance and facilitating accurate temperature measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 is a schematic diagram of a high-precision temperature sensor circuit provided by an embodiment of the present disclosure;

[0023] Figure 2 is a schematic diagram of a power supply circuit provided by an embodiment of the present disclosure;

[0024] Figure 3 It is a schematic diagram of the interface circuit of the temperature sensing element provided in the embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] In order to enable people in the technical field to better understand the present solution, the technical solution in the embodiment of the present solution will be clearly described below in conjunction with the drawings in the embodiment of the present solution. Obviously, the described embodiment is an embodiment of a part of the present solution, not all of the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present solution.

[0026] The term "including" and any other variations in the specification and claims of this solution and the above drawings mean "including but not limited to", and is intended to cover non-exclusive inclusions and is not limited to the examples listed in the text. In addition, the terms "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0027] The following is a detailed description of the implementation of the present disclosure in conjunction with the specific drawings:

[0028] Figure 1 A circuit schematic diagram of a high-precision temperature sensor circuit provided by an embodiment of the present disclosure. Figure 1 , the high-precision temperature sensor circuit includes:

[0029] a first constant current source circuit, wherein an output end of the first constant current source circuit is connected to a first end of the temperature sensing element,

[0030] A second constant current source circuit, wherein the output end of the second constant current source circuit is connected to the second end of the temperature sensing element,

[0031] The subtraction circuit has an inverting input terminal connected to a first terminal of the temperature sensing element, a non-inverting input terminal connected to a second terminal of the temperature sensing element, and an output terminal of the subtraction circuit is an output terminal of the high-precision temperature sensor.

[0032] In the disclosed embodiment, the output current of the first constant current source circuit is added to the first end of the temperature sensing element, and the output current of the second constant current source circuit is added to the second end of the temperature sensing element, so as to generate a potential difference between the two ends of the temperature sensing element. The potential difference is calculated by a subtraction circuit to obtain the voltage between the two ends of the temperature sensing element. Therefore, the change in temperature can be obtained by detecting the change in the output voltage of the subtraction circuit, thereby avoiding the influence of line impedance and facilitating accurate temperature measurement.

[0033] It should be noted that the temperature sensing element in this embodiment can be a currently commonly used thermocouple, thermistor or other temperature sensitive element, and no limitation is made here.

[0034] In an exemplary embodiment of the present disclosure, the first constant current source circuit includes an operational amplifier U5, a switch tube Q2 and a first current limiting resistor.

[0035] The non-inverting input terminal of the operational amplifier U5 is connected to the first reference voltage, the output terminal of the operational amplifier U5 is connected to the control terminal of the switch tube Q2, the first terminal of the switch tube Q2 is the output terminal of the first constant current source circuit, the second terminal of the switch tube Q2 is grounded through the first current limiting resistor, and the second terminal of the switch tube Q2 is feedback connected to the inverting input terminal of the operational amplifier U5.

[0036] Reference Figure 1 and Figure 3In this embodiment, the operational amplifier U5, the switch tube Q2 and the first current limiting resistors R16 and R17 form a first constant current source circuit, which can absorb a constant current at the second end of the switch tube Q2. The working principle is as follows: Since the voltage at the in-phase input end of the operational amplifier U5 is constant at the first reference voltage +2.5V, according to the "virtual short" of the operational amplifier, the inverting input end of U5 is also +2.5V, and the upper end of R16 is connected to the inverting input end of the operational amplifier U5, so the upper end of R16 is also constant at +2.5V, so the size of R16 and R17 determines the size of the constant current source current. Since the inverting input end of U5 cannot provide current, this constant current can only be provided by the second end (source) of the switch tube Q2, then the current at the first end (drain) of Q2 is connected to the +6V power supply through the temperature sensing element and R23, thereby realizing the constant current in the temperature sensing element.

[0037] The circuit structure of the second constant current source circuit is the same as that of the first constant current source circuit, and will not be described here. The first constant current source circuit and the second constant current source circuit are respectively used for a shunt branch at the double-wire end of the temperature sensing element and another branch at the single-wire end, and are used to offset the error caused by the lead line resistance to the temperature sensing element, thereby improving the measurement accuracy.

[0038] In an exemplary embodiment of the present disclosure, a voltage stabilizing module U6 is also included, a reference electrode of the voltage stabilizing module U6 is connected to the first power supply through a resistor R15, an anode of the voltage stabilizing module U6 is grounded, a cathode of the voltage stabilizing module U6 is connected to the reference electrode of the voltage stabilizing module U6, and the cathode of the voltage stabilizing module U6 outputs a first reference voltage.

[0039] In this embodiment, the specific model of the voltage stabilizing module U6 is TL431. The voltage stabilizing module U6 outputs a constant +2.5V voltage as the first reference voltage, which is beneficial to improving the accuracy of the first constant current source circuit or the second constant current source circuit.

[0040] In an exemplary embodiment of the present disclosure, an amplification circuit is provided between the first end of the temperature sensing element and the inverting input end of the subtraction circuit.

[0041] In this embodiment, an amplifier circuit is provided between the first end of the temperature sensing element and the inverting input end of the subtraction circuit to condition the voltage signal at the first end of the temperature sensing element, thereby further amplifying the voltage signal at both ends of the temperature sensing element.

[0042] In an exemplary embodiment of the present disclosure, the output end of the subtraction circuit is connected to the input end of the voltage-current conversion circuit, and the output end of the voltage-current conversion circuit is the output end of the high-precision temperature sensor.

[0043] In this embodiment, a voltage-current conversion circuit is provided at the output end of the subtraction circuit, which can convert the voltage signal output by the subtraction circuit into a current signal, so as to facilitate long-distance transmission.

[0044] In an exemplary embodiment of the present disclosure, the voltage-current conversion circuit includes an operational amplifier U3, a switch tube Q1, a resistor R12, a resistor R14, a resistor R11 and a terminal H1.

[0045] The non-inverting input terminal of the operational amplifier U3 is connected to the output terminal of the subtraction circuit, the inverting input terminal of the operational amplifier U3 is grounded, the output terminal of the operational amplifier U3 is connected to the control terminal of the switch tube Q1, the first terminal of the switch tube Q1 is connected to the second power supply, the second terminal of the switch tube Q1 is connected to the first terminal of the resistor R12, the second terminal of the resistor R12 is feedback connected to the inverting input terminal of the operational amplifier U3, and the second terminal of the resistor R12 is grounded.

[0046] The second end of the resistor R12 is connected to the first end of the resistor R14, and the second end of the resistor R14 is connected to the non-inverting input end of the operational amplifier U3 through the resistor R13 and the resistor R11 in sequence.

[0047] A first end of the terminal H1 is connected to the third power source, a second end of the terminal H1 is connected to the second end of the resistor R14, and the first end and the second end of the terminal H1 are output ends of the voltage-current conversion circuit.

[0048] In this embodiment, the voltage at the output end of the subtraction circuit is denoted as Ui. According to the "virtual short" principle of the operational amplifier, the in-phase input and the inverting input of the operational amplifier U3 are both grounded, and the current in the resistor R7 is equal to Ui / R7. This current flows through the resistors R11 and R13, forming a voltage Added to the non-inverting input terminal of the operational amplifier U3. Due to the "virtual short" of the operational amplifier, the voltage at the inverting input terminal of the operational amplifier U3 is equal to the voltage at the non-inverting input terminal, so that the voltage U' is added to the resistor R14 and converted into a current signal.

[0049] Among them, according to the "virtual disconnection" principle of the operational amplifier, the current of resistor R14 can only be provided by resistor R12, the current is proportional to the voltage U', and the voltage U' is proportional to the voltage Ui, so the current of resistor R14 is proportional to kUi / R14 (k is a constant), thereby realizing the conversion of voltage Ui to current.

[0050] In an exemplary embodiment of the present disclosure, a power supply circuit is also included, such as Figure 2 As shown, the power supply circuit includes a voltage stabilizing module U9, a diode D1 and a diode D2.

[0051] The input end of the voltage stabilizing module U9 is connected to the second power supply, the output end of the voltage stabilizing module U9 outputs the fourth power supply, and the output of the voltage stabilizing module outputs the fifth power supply via the diode D1 and the diode D2 in sequence.

[0052] Reference Figure 2 In this embodiment, the voltage of the second power supply is converted to the voltage of the fourth power supply +6V after passing through the voltage stabilizing module U9, and the voltage of the fourth power supply is then stepped down by two diodes D1 and D2 to obtain the fifth power supply +5V. The circuit structure is simple and the cost is low. A variety of power supply voltages can meet the various power supply requirements of circuit components.

[0053] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A high-precision temperature sensor circuit, characterized in that: include: a first constant current source circuit, wherein an output end of the first constant current source circuit is connected to a first end of a temperature sensing element, a second constant current source circuit, wherein the output end of the second constant current source circuit is connected to the second end of the temperature sensing element, A subtraction circuit, wherein the inverting input terminal of the subtraction circuit is connected to the first terminal of the temperature sensing element, the non-inverting input terminal of the subtraction circuit is connected to the second terminal of the temperature sensing element, and the output terminal of the subtraction circuit is the output terminal of the high-precision temperature sensor.

2. The high-precision temperature sensor circuit according to claim 1, characterized in that: The first constant current source circuit includes an operational amplifier U5, a switch tube Q2 and a first current limiting resistor. The non-inverting input terminal of the operational amplifier U5 is connected to the first reference voltage, the output terminal of the operational amplifier U5 is connected to the control terminal of the switch tube Q2, the first terminal of the switch tube Q2 is the output terminal of the first constant current source circuit, the second terminal of the switch tube Q2 is grounded through a first current limiting resistor, and the second terminal of the switch tube Q2 is feedback connected to the inverting input terminal of the operational amplifier U5.

3. The high-precision temperature sensor circuit according to claim 1, characterized in that: It also includes a voltage stabilizing module U6, the reference electrode of the voltage stabilizing module U6 is connected to the first power supply through a resistor R15, the anode of the voltage stabilizing module U6 is grounded, the cathode of the voltage stabilizing module U6 is connected to the reference electrode of the voltage stabilizing module U6, and the cathode of the voltage stabilizing module U6 outputs a first reference voltage.

4. The high-precision temperature sensor circuit according to claim 1, characterized in that: An amplifier circuit is arranged between the first end of the temperature sensing element and the inverting input end of the subtraction circuit.

5. The high-precision temperature sensor circuit according to claim 1, characterized in that: The output end of the subtraction circuit is connected to the input end of the voltage-current conversion circuit, and the output end of the voltage-current conversion circuit is the output end of the high-precision temperature sensor.

6. The high-precision temperature sensor circuit according to claim 5, characterized in that: The voltage-current conversion circuit includes an operational amplifier U3, a switch tube Q1, a resistor R12, a resistor R14, a resistor R11 and a terminal H1. The non-inverting input terminal of the operational amplifier U3 is connected to the output terminal of the subtraction circuit, the inverting input terminal of the operational amplifier U3 is grounded, the output terminal of the operational amplifier U3 is connected to the control terminal of the switch tube Q1, the first terminal of the switch tube Q1 is connected to the second power supply, the second terminal of the switch tube Q1 is connected to the first terminal of the resistor R12, the second terminal of the resistor R12 is feedback connected to the inverting input terminal of the operational amplifier U3, and the second terminal of the resistor R12 is grounded. The second end of the resistor R12 is connected to the first end of the resistor R14, and the second end of the resistor R14 is connected to the in-phase input end of the operational amplifier U3 through the resistor R13 and the resistor R11 in sequence. The first end of the terminal H1 is connected to the third power supply, the second end of the terminal H1 is connected to the second end of the resistor R14, and the first end and the second end of the terminal H1 are output ends of the voltage-current conversion circuit.

7. The high-precision temperature sensor circuit according to claim 1, characterized in that: It also includes a power supply circuit, which includes a voltage stabilizing module U9, a diode D1 and a diode D2. The input end of the voltage stabilizing module U9 is connected to the second power supply, the output end of the voltage stabilizing module U9 outputs the fourth power supply, and the output of the voltage stabilizing module outputs the fifth power supply via the diode D1 and the diode D2 in sequence.

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