Temperature protection circuit

Abstract

The utility model provides a temperature protection circuit. The temperature protection circuit comprises an instrument amplifier sub-circuit, a subtraction operation amplification sub-circuit, a cold junction compensation sub-circuit and a hysteresis comparator sub-circuit, the forward input end and the reverse input end of the instrument amplifier sub-circuit are used for receiving first voltage converted by the thermocouple; the subtraction operation amplification sub-circuit comprises a first operational amplifier, the output end of the instrument amplifier sub-circuit is connected with the reverse input end of the first operational amplifier, and the output end of the cold junction compensation sub-circuit is connected with the positive input end of the first operational amplifier; the hysteresis comparator sub-circuit comprises a second operational amplifier, the output end of the subtraction operation amplification sub-circuit is connected with the reverse input end of the second operational amplifier, the output end of the second operational amplifier is used for being connected with a switch, and the switch can switch the switch state according to an output signal of the second operational amplifier. According to the utility model, no extra space is occupied, and the set values of the protection temperature and the recovery temperature can be adjusted as required, thereby being more flexible.

Description

Technical Field

[0001] The utility model relates to the technical field of temperature protection, in particular to a temperature protection circuit. Background Art

[0002] In some scenarios involving heating, such as during aging tests, in order to prevent the temperature of the fixture from exceeding the tolerance temperature due to abnormal operation of the heating system, thereby damaging the device under test or causing a fire, an independent overheating protection system needs to be added outside the heating system to prevent accidents. Currently, common overheating protection systems usually use a bimetallic temperature switch in series in the driving circuit of the heating system. This solution is low in cost and can effectively prevent abnormalities caused by overheating of the heating system. However, this solution has the following problems:

[0003] Limited by its implementation principle, the difference between its protection temperature and recovery temperature can only be around 55°C, which cannot meet the application scenarios of integrated circuit aging test. Usually, our test temperature span is in the range of 80-150°C, while the maximum safe temperature allowed by the test device is usually 170°C. When using this solution, the aging fixture cannot be compatible with tests at multiple temperature points;

[0004] This type of protection switch is large in size and requires additional space on the aging fixture for installation. The fixture is large in size and cannot be miniaturized;

[0005] The installation position and installation reliability of this type of protection switch will directly affect the performance of the temperature protection switch, and the consistency between batches is difficult to control.

[0006] There is currently no simple and effective solution to the above defects. Utility Model Content

[0007] The purpose of the utility model is to provide a temperature protection circuit, which can be directly designed on an independent temperature control module without taking up additional space, and the set values ​​of the protection temperature and the recovery temperature can be adjusted as needed, which is more flexible.

[0008] To achieve the above-mentioned purpose, the utility model provides a temperature protection circuit, including an instrument amplifier subcircuit, a subtraction operational amplifier subcircuit, a cold end compensation subcircuit and a hysteresis comparator subcircuit; the instrument amplifier subcircuit includes an instrument amplifier, and the positive input terminal and the reverse input terminal of the instrument amplifier are used to receive a first voltage converted by a thermocouple; the subtraction operational amplifier subcircuit includes a first operational amplifier, the output terminal of the instrument amplifier subcircuit is connected to the reverse input terminal of the first operational amplifier, and the output terminal of the cold end compensation subcircuit is connected to the positive input terminal of the first operational amplifier; the hysteresis comparator subcircuit includes a second operational amplifier, the output terminal of the subtraction operational amplifier subcircuit is connected to the reverse input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is used to be connected to a switch, and the switch can switch the switch state according to the logic level output by the second operational amplifier.

[0009] Optionally, the cold-end compensation subcircuit can output a second voltage, and the instrument amplifier includes a gain configuration resistor R3, and the gain configuration resistor R3 is used to amplify the first voltage by a preset multiple to form and output a first amplified voltage, and make the ratio of the first amplified voltage to the second voltage within a preset ratio.

[0010] Optionally, the instrument amplifier is connected to a bias voltage divider module, and the bias voltage divider module is used to increase the voltage output by the instrument amplifier.

[0011] Optionally, the cold-end compensation subcircuit includes a temperature compensation diode D1 and a voltage output module, the temperature compensation diode D1 is connected in parallel with the voltage output module, and the output end of the voltage output module is connected to the forward input end of the first operational amplifier.

[0012] Optionally, the cold-end compensation subcircuit further includes a voltage divider module, which is used to divide the voltage across the temperature compensation diode D1 and input the divided voltage to the forward input terminal of the first operational amplifier.

[0013] Optionally, the voltage output module includes a resistor R9, and the voltage divider module includes a resistor R12 and a resistor R17; one end of the resistor R12 is close to the power supply and is connected to the input end of the temperature compensation diode D1 at the same time, the other end of the resistor R12 is connected to the input end of the resistor R9 and is connected to one end of the resistor R17 at the same time, the other end of the resistor R17 is grounded and is connected to the output end of the temperature compensation diode D1 at the same time, and the output end of the resistor R9 is connected to the first operational amplifier.

[0014] Optionally, the voltage output module includes a resistor R9, and the voltage divider module includes a resistor R13 and a filter capacitor C1; the resistor R13 and the filter capacitor C1 are connected in parallel, one end of the resistor R13 and the filter capacitor C1 are connected to the output end of the resistor R9 and the positive input end of the first operational amplifier at the same time, and the other ends of the resistor R13 and the filter capacitor C1 are grounded; the output end of the resistor R9 is connected to the first operational amplifier, and the input end of the resistor R9 is close to the power supply.

[0015] Optionally, the voltage output module includes a resistor R9, a resistor R2 is provided between the output end of the instrumentation amplifier sub-circuit and the inverting input end of the first operational amplifier, and the resistance value of the resistor R2 is equal to that of the resistor R9.

[0016] Optionally, the hysteresis comparator sub-circuit also includes a resistor R14, a resistor R15, a resistor R16 and a resistor R18; one end of the resistor R14 is connected to a power supply, the other end of the resistor R14 is connected to one end of the resistor R18 and simultaneously connected to one end of R15, the other end of R18 is grounded, the other end of R15 is connected to the positive input terminal of the second operational amplifier and simultaneously connected to one end of the resistor R16, and the other end of the resistor R16 is connected to the output terminal of the second operational amplifier.

[0017] Optionally, the hysteresis comparator sub-circuit further includes a resistor R4, one end of the resistor R4 is connected to a power supply, and the other end of the resistor R4 is connected to an output end of the second operational amplifier.

[0018] The temperature protection circuit provided by the utility model has the following beneficial effects:

[0019] The utility model provides a temperature protection circuit, comprising an instrument amplifier subcircuit, a subtraction operational amplifier subcircuit, a cold end compensation subcircuit and a hysteresis comparator subcircuit; the positive input terminal and the reverse input terminal of the instrument amplifier subcircuit are used to receive a first voltage converted by a thermocouple; the subtraction operational amplifier subcircuit comprises a first operational amplifier, the output terminal of the instrument amplifier subcircuit is connected to the reverse input terminal of the first operational amplifier, and the output terminal of the cold end compensation subcircuit is connected to the positive input terminal of the first operational amplifier; the hysteresis comparator subcircuit comprises a second operational amplifier, the output terminal of the subtraction operational amplifier subcircuit is connected to the reverse input terminal of the second operational amplifier, the output terminal of the second operational amplifier is used to be connected to a switch, and the switch can switch a switch state according to an output signal of the second operational amplifier. With such an arrangement, the utility model provides a temperature protection switch solution based on integrated circuit control. The output signal of the temperature sensor thermocouple is amplified several times by an instrument amplifier with high input impedance, the temperature coefficient of the thermocouple and the temperature coefficient of the cold-end compensation subcircuit are unified, and after the cold-end temperature compensation, it is amplified several times by a subtraction amplifier subcircuit and output to a suitable voltage range, and finally compared with the hysteresis comparator subcircuit to generate a temperature abnormality protection signal to control the switch switching. The advantages of this solution are as follows: 1) High reliability: The external temperature switch needs to be fixed by a structure and filled with thermal conductive materials. After long-term use, the ceramic shell of the temperature switch will break, or it will be separated from the heating block and fail to provide protection. The built-in temperature switch directly reuses the temperature sensor signal. The sensor is built into the heating block, so there is no fitting problem and no risk of the temperature switch shell breaking. 2) Miniaturization and reduced module structure complexity: The built-in temperature sensor does not require additional fixed structures or external interconnection power lines. The volume is much smaller than that of the ceramic temperature switch, and an ultra-thin and miniaturized structural design can be achieved. 3) High flexibility and customizable temperature switch parameters: Users can adjust the temperature switch parameters by changing several resistor devices. 4) High precision: The error temperature accuracy of the built-in temperature switch is much higher than that of traditional ceramic temperature switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The overall principle diagram of the temperature protection circuit provided by one embodiment of the utility model;

[0021] Figure 2 A circuit diagram of a temperature protection circuit provided in one embodiment of the utility model;

[0022] Figure 3 A diagram showing simulation results of a temperature protection circuit provided by an embodiment of the utility model;

[0023] The accompanying drawings are denoted as follows:

[0024] 01-Instrumentation amplifier subcircuit; 011-Instrumentation amplifier; 02-Subtraction operational amplifier subcircuit; 021-First operational amplifier; 03-Cold end compensation subcircuit; 04-Hysteresis comparison subcircuit; 041-Second operational amplifier;

[0025] 05-Logic level change line; 06-Temperature change line. DETAILED DESCRIPTION

[0026] In order to make the purpose, advantages and features of the utility model clearer, the utility model is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the utility model. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0027] It should be understood that when an element or layer is referred to as "on...", "connected to" other elements or layers, it can be directly on other elements or layers, connected to other elements or layers, or can include intervening elements or layers. On the contrary, when an element is referred to as "directly on...", "directly connected to" other elements or layers, intervening elements or layers are not included. Although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teaching of the present invention, the first element, component, region, layer or part discussed below can be expressed as a second element, component, region, layer or part. Spatial relationship terms such as "under...", "below", "below", "above...", "above", "above", etc., can be used here for the convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, the spatial relationship terms are intended to include different orientations of the devices in use and operation. For example, if the device in the accompanying drawings is turned over, then, the elements or features described as "under...", "below", "below" will be oriented to be "on" other elements or features. The device can be oriented in other ways (rotated 90 degrees or other orientations) and the spatial descriptors used here are interpreted accordingly. The purpose of the terms used here is only to describe specific embodiments and is not intended to be a limitation of the utility model. When used here, the singular forms of "one", "one" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the term "include" is used to determine the inclusion of features, steps, operations, elements and / or parts, but does not exclude the inclusion or addition of one or more other features, steps, operations, elements, parts and / or groups. When used here, the term "and / or" includes any and all combinations of the relevant listed items.

[0028] The purpose of the utility model is to provide a temperature protection circuit, which can be directly designed on an independent temperature control module without taking up additional space, and the set values ​​of the protection temperature and the recovery temperature can be adjusted as needed, which is more flexible.

[0029] Please refer to Figure 1 and Figure 2 , Figure 1 The overall principle diagram of the temperature protection circuit provided by one embodiment of the utility model; Figure 2 The circuit diagram of the temperature protection circuit provided by one embodiment of the utility model is shown in FIG. Figure 1 and Figure 2As shown, in order to achieve the above-mentioned purpose, the utility model provides a temperature protection circuit, including an instrument amplifier subcircuit 01, a subtraction amplifier subcircuit 02, a cold end compensation subcircuit 03 and a hysteresis comparator subcircuit 04;

[0030] The instrument amplifier subcircuit 01 includes an instrument amplifier 011, and the positive input terminal and the reverse input terminal of the instrument amplifier 011 are used to receive the first voltage converted by the thermocouple;

[0031] The subtraction operational amplifier subcircuit 02 includes a first operational amplifier 021, the output end of the instrument amplifier subcircuit 01 is connected to the reverse input end of the first operational amplifier 021, and the output end of the cold end compensation subcircuit 03 is connected to the positive input end of the first operational amplifier 021;

[0032] The hysteresis comparator subcircuit 04 includes a second operational amplifier 041, the output end of the subtraction operational amplifier subcircuit 02 is connected to the inverting input end of the second operational amplifier 041, and the output end of the second operational amplifier 041 is used to connect to a switch, and the switch can switch the switch state according to the logic level output by the second operational amplifier 041.

[0033] With such an arrangement, the utility model provides a temperature protection switch solution based on integrated circuit control, in which the output signal of the temperature sensor thermocouple is amplified several times by an instrument amplifier with high input impedance, the temperature coefficient of the thermocouple and the temperature coefficient of the cold-end compensation subcircuit are unified, and after the cold-end temperature compensation, it is amplified several times by a subtraction amplifier subcircuit and output to a suitable voltage range, and finally compared with the hysteresis comparator subcircuit to generate a temperature abnormality protection signal to control the switch switching.

[0034] The advantages of this solution are as follows:

[0035] 1) High reliability: The external temperature switch needs to be fixed by structure and filled with thermal conductive materials. After long-term use, the ceramic shell of the temperature switch may break, or it may be separated from the heating block and fail to provide protection. The built-in temperature switch directly reuses the temperature sensor signal. The sensor is built into the heating block, so there is no problem of fitting and no risk of the temperature switch shell breaking.

[0036] 2) Miniaturization and reduced module structure complexity: Built-in temperature sensor, no need to add additional fixed structure, no external interconnection power line, the volume is much smaller than the ceramic temperature switch, and ultra-thin and miniaturized structural design can be achieved;

[0037] 3) High flexibility, customizable temperature switch parameters: users can adjust the temperature switch parameters by changing several resistor components;

[0038] 4) High precision: The built-in temperature switch has a much higher error temperature accuracy than traditional ceramic temperature switches.

[0039] Further, the cold-end compensation subcircuit 03 can output a second voltage, and the instrument amplifier 011 includes a gain configuration resistor R3, which is used to amplify the first voltage by a preset multiple to form and output a first amplified voltage, and make the ratio of the first amplified voltage to the second voltage within a preset ratio. In an exemplary embodiment, the gain configuration resistor R3 is set to 750Ω, so that the amplification multiple of the instrument amplifier 011 is 66.6, so that the coefficient of the cold-end compensation subcircuit 03 is consistent with the voltage caused by the change of the cold-end temperature of the thermocouple, and after the subtraction operation amplifier subcircuit 02, the cold-end temperature compensation is realized.

[0040] Furthermore, the instrument amplifier 011 is connected to a bias voltage divider module, and the bias voltage divider module is used to increase the voltage output by the instrument amplifier so that the first voltage is converted and output and amplified by a preset multiple to a reasonable voltage range. Figure 2 In an exemplary embodiment, the bias voltage divider module includes a resistor R8 and a resistor R11. Figure 2 The 3.3V voltage is divided by R8=4.75KΩ and R11=150Ω, and the series voltage division is used for the bias voltage of the instrument amplifier 011. The voltage at the division point is about 103.1mV. At this time, the output voltage range of the instrument amplifier 011 is positively biased to 103.1mV, reducing the zero point offset.

[0041] Furthermore, the cold-end compensation subcircuit 03 includes a temperature compensation diode D1 and a voltage output module, the temperature compensation diode D1 is connected in parallel with the voltage output module, and the output end of the voltage output module is connected to the positive input end of the first operational amplifier 021. The cold-end compensation subcircuit 03 may also include a voltage divider module, which is used to divide the voltage across the temperature compensation diode D1 and input the divided voltage to the positive input end of the first operational amplifier.

[0042] For details, please refer to Figure 2 .like Figure 2 As shown, the voltage output module includes a resistor R9, and the voltage dividing module includes a resistor R12 and a resistor R17;

[0043] One end of the resistor R12 is close to the power supply and connected to the input end of the temperature compensation diode D1, the other end of the resistor R12 is connected to the input end of the resistor R9 and connected to one end of the resistor R17, the other end of the resistor R17 is grounded and connected to the output end of the temperature compensation diode D1, and the output end of the resistor R9 is connected to the first operational amplifier;

[0044] The resistance values ​​of the resistor R12 and the resistor R17 can be reasonably configured according to the actual application scenario to achieve the required voltage division ratio. In an exemplary embodiment, the resistance value of the resistor R12 can be 0, and the resistor R17 can be opened or closed in the circuit.

[0045] When the R17 is in an open state, the temperature compensation diode D1 is directly connected in parallel with the resistor R12 and the resistor R9. When the R17 is in a closed state, the temperature compensation diode D1 is connected in parallel with the resistor R9 and the resistor R17, respectively. In this way, different voltage division modes of the temperature compensation diode D1 are realized in different states to cope with different temperature compensation scenarios.

[0046] The voltage divider module may also include a resistor R13 and a filter capacitor C1; the resistor R13 and the filter capacitor C1 are connected in parallel, one end of the resistor R13 and the filter capacitor C1 are connected to the output end of the resistor R9 and the positive input end of the first operational amplifier, and the other ends of the resistor R13 and the filter capacitor C1 are grounded; the output end of the resistor R9 is connected to the first operational amplifier, and the input end of the resistor R9 is close to the power supply. In an exemplary embodiment, the capacitance value of the filter capacitor C1 is set to 100nF to prevent the interference voltage signal from overshooting and possibly causing the temperature switch to be falsely triggered.

[0047] Preferably, a resistor R2 is provided between the output end of the instrumentation amplifier subcircuit and the reverse input end of the first operational amplifier, and the resistance value of the resistor R2 is equal to that of the resistor R9. In this case, the resistor R2 and the resistor R9 also serve as matching resistors for the positive and negative input ends. It should be understood that according to Figure 2 In the design, the resistor R2 and the resistor R1 serve as gain adjustment resistors and together constitute a component of the subtraction amplifier subcircuit. In an exemplary embodiment, the resistance ratio of the resistor R1 and the resistor R2 can be set to 5. With this setting, the input voltage differential value can be amplified to two-thirds of the operating voltage range of the operational amplifier, thereby improving the temperature resolution capability without exceeding the operating range of the operational amplifier.

[0048] Specifically, the hysteresis comparator subcircuit 04 also includes a resistor R14, a resistor R15, a resistor R16 and a resistor R18; one end of the resistor R14 is connected to the power supply, the other end of the resistor R14 is connected to one end of the resistor R18 and to one end of the resistor R15 at the same time, the other end of the resistor R18 is grounded, the other end of the resistor R15 is connected to the positive input end of the second operational amplifier and to one end of the resistor R16 at the same time, and the other end of the resistor R16 is connected to the output end of the second operational amplifier. The resistors R14, R15, R16 and R18 work together to set the high and low output levels of the hysteresis comparator. We can preset the opening action temperature and the restoration closing temperature of the switch, and use the relationship to obtain the ratio of the resistors R14, R15, R16 and R18, so as to set the resistance values ​​of the resistors R14, R15, R16 and R18. The relationship is as follows:

[0049]

[0050]

[0051] in:

[0052] T 动作 Indicates the disconnection action temperature; T 恢复 Indicates recovery closing temperature

[0053] In an exemplary embodiment, the recovery closing temperature is set as: T 恢复 =93.2℃, disconnection temperature T 动作 =165.7℃, so as to obtain the ratio of each resistance by calculation, and then perform specific resistance value matching, for example: R14=36KΩ, R18=2KΩ, R15=82KΩ, R16=196KΩ.

[0054] Furthermore, the hysteresis comparator subcircuit 04 further includes a resistor R4, one end of which is connected to the power supply, and the other end of which is connected to the output end of the second operational amplifier 041. The resistor R4 is an output pull-up resistor to ensure that it can quickly switch to a high level.

[0055] It should be understood that Figure 2 The resistor R5 is a current limiting resistor. In an exemplary embodiment, R5=20KΩ is set to limit the current of the diode to less than 0.165mA to prevent the diode from heating due to excessive current in the forward channel. The resistor R6 is an op amp output current limiting resistor to prevent the capacitive load from causing the op amp to oscillate. The resistor R7 is an op amp input current limiting resistor. The resistor R10 is a series resistor used to protect the circuit itself from short circuit.

[0056] Please refer to Figure 3 , Figure 3 This is a simulation result diagram of a temperature protection circuit provided by an embodiment of the utility model. Figure 3 As shown, according to the logic level change line 05 and the temperature change line 06 shown in the practical results, the temperature protection circuit provided by the utility model can output different logic levels when the temperature changes, so that the switch is disconnected when the temperature is too high and restored when the temperature drops.

[0057] It should also be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the above disclosed technical content can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

[0058] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are merely used to distinguish between the various components, elements, steps, etc. in the specification, and are not used to indicate the logical relationship or sequential relationship between the various components, elements, steps, etc.

[0059] It should also be recognized that the terms described herein are only used to describe specific embodiments and are not used to limit the scope of the utility model. It must be noted that the singular forms "one" and "a kind" used herein and in the appended claims include plural references unless the context clearly indicates the opposite meaning. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or", not a logical "exclusive or" definition, unless the context clearly indicates the opposite meaning. In addition, the implementation of the embodiments of the utility model may include performing the selected tasks manually, automatically, or in combination.

Claims

1. A temperature protection circuit, characterized in that: It includes an instrumentation amplifier subcircuit, a subtraction operational amplifier subcircuit, a cold-end compensation subcircuit and a hysteresis comparator subcircuit; The instrument amplifier subcircuit includes an instrument amplifier, wherein a positive input terminal and a negative input terminal of the instrument amplifier are used to receive a first voltage converted by the thermocouple; The subtraction operational amplifier subcircuit includes a first operational amplifier, the output end of the instrumentation amplifier subcircuit is connected to the reverse input end of the first operational amplifier, and the output end of the cold end compensation subcircuit is connected to the forward input end of the first operational amplifier; The hysteresis comparator subcircuit includes a second operational amplifier, the output end of the subtraction operational amplifier subcircuit is connected to the inverting input end of the second operational amplifier, the output end of the second operational amplifier is used to connect to a switch, and the switch can switch a switch state according to a logic level output by the second operational amplifier.

2. The temperature protection circuit according to claim 1, characterized in that: The cold-end compensation subcircuit can output a second voltage, and the instrument amplifier includes a gain configuration resistor R3, which is used to amplify the first voltage by a preset multiple to form and output a first amplified voltage, and make the ratio of the first amplified voltage to the second voltage within a preset ratio.

3. The temperature protection circuit according to claim 1, characterized in that: The instrument amplifier is connected to a bias voltage divider module, and the bias voltage divider module is used to increase the voltage output by the instrument amplifier.

4. The temperature protection circuit according to claim 1, characterized in that: The cold-end compensation subcircuit includes a temperature compensation diode D1 and a voltage output module. The temperature compensation diode D1 is connected in parallel with the voltage output module. The output end of the voltage output module is connected to the positive input end of the first operational amplifier.

5. The temperature protection circuit according to claim 4, characterized in that: The cold-end compensation subcircuit further includes a voltage dividing module, which is used to divide the voltage across the temperature compensation diode D1 and input the divided voltage to the positive input terminal of the first operational amplifier.

6. The temperature protection circuit according to claim 5, characterized in that: The voltage output module includes a resistor R9, and the voltage dividing module includes a resistor R12 and a resistor R17; One end of the resistor R12 is close to the power supply and is connected to the input end of the temperature compensation diode D1 at the same time, the other end of the resistor R12 is connected to the input end of the resistor R9 and is connected to one end of the resistor R17 at the same time, the other end of the resistor R17 is grounded and is connected to the output end of the temperature compensation diode D1 at the same time, and the output end of the resistor R9 is connected to the first operational amplifier.

7. The temperature protection circuit according to claim 5, characterized in that: The voltage output module includes a resistor R9, and the voltage dividing module includes a resistor R13 and a filter capacitor C1; The resistor R13 and the filter capacitor C1 are connected in parallel, one end of the resistor R13 and the filter capacitor C1 are connected to the output end of the resistor R9 and the positive input end of the first operational amplifier, and the other end of the resistor R13 and the filter capacitor C1 are grounded; The output end of the resistor R9 is connected to the first operational amplifier, and the input end of the resistor R9 is close to the power supply.

8. The temperature protection circuit according to claim 4, characterized in that: The voltage output module includes a resistor R9, and a resistor R2 is provided between the output end of the instrument amplifier sub-circuit and the inverting input end of the first operational amplifier, and the resistance value of the resistor R2 is equal to that of the resistor R9.

9. The temperature protection circuit according to claim 1, characterized in that: The hysteresis comparator sub-circuit further includes a resistor R14, a resistor R15, a resistor R16 and a resistor R18; One end of the resistor R14 is connected to a power supply, the other end of the resistor R14 is connected to one end of the resistor R18 and to one end of the resistor R15, the other end of the R18 is grounded, the other end of the R15 is connected to the positive input end of the second operational amplifier and to one end of the resistor R16, and the other end of the resistor R16 is connected to the output end of the second operational amplifier.

10. The temperature protection circuit according to claim 1 or 9, characterized in that: The hysteresis comparator sub-circuit further includes a resistor R4, one end of the resistor R4 is connected to a power supply, and the other end of the resistor R4 is connected to an output end of the second operational amplifier.

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