Multi-point temperature monitoring and over-temperature protection circuit

Abstract

The utility model discloses a multi-point temperature monitoring and over-temperature protection circuit, which relates to the technical field of temperature monitoring and comprises a temperature sampling unit used for collecting temperature sampling signals and transmitting the temperature sampling signals to a multiplexer, and the multiplexer selectively reads the temperature sampling signals and outputs real-time temperature; the over-temperature detection unit is used for comparing the real-time temperature output by the multiplexer with a preset temperature threshold value and generating a comparison result; the micro-control unit is used for monitoring the real-time temperature read by the multiplexer, receiving a comparison result of the over-temperature detection unit and generating a control signal when the temperature exceeds a preset temperature threshold value; and the over-temperature protection unit is used for receiving the control signal generated by the micro-control unit to dissipate heat or turn off the equipment. The multi-point temperature monitoring and over-temperature protection circuit has the advantages that temperature monitoring and over-temperature protection are performed on a plurality of key points, fewer sampling channels of the micro-control unit are occupied, fewer comparators are used, and the design cost and the size of the multi-point temperature monitoring and over-temperature protection circuit are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of temperature monitoring, in particular to a multi-point temperature monitoring and over-temperature protection circuit. Background Art

[0002] During the operation of the circuit, due to the internal resistance of the components, the current flowing through the resistor generates heat, and the circuit board is often placed inside the product, so the heat continues to accumulate. If the normal operating temperature range of the components is exceeded, it may cause damage to the components or even cause accidents such as fire. Therefore, the temperature must be monitored and heat dissipation protection must be performed when the temperature exceeds the limit.

[0003] The existing multi-point temperature monitoring and over-temperature protection units do not have a modular design. The existing temperature monitoring circuit is usually a temperature sensor that transmits the collected electrical signal to the MCU through the MCU sampling channel for conversion and processing. The existing over-temperature protection unit is usually a temperature sensor matched with a comparator connected to it. This comparator is used to compare the temperature at the sampling location with the preset temperature to determine whether it is over-temperature. For multi-point temperature collection and over-temperature protection, it is necessary to occupy multiple MCU ADC (analog-to-digital converter) sampling channels and multiple comparators, which not only expands the volume but also increases the cost.

[0004] Therefore, a multi-point temperature monitoring and over-temperature protection circuit is needed to solve the above problems. Utility Model Content

[0005] In view of the above problems or problems existing in the prior art, the present utility model is proposed.

[0006] Therefore, the purpose of the present invention is to provide a multi-point temperature monitoring and over-temperature protection circuit, which aims to solve the problem of complicated steps in the prior art for determining whether the temperature of multiple points is over-temperature.

[0007] In order to solve the above technical problems, the utility model provides the following technical solutions: a multi-point temperature monitoring and over-temperature protection circuit, which includes a temperature sampling unit, the temperature sampling unit collects multiple temperature sampling signals and transmits them to a multiplexer, and the multiplexer transmits one of the temperature sampling signals to an over-temperature detection unit and a micro-control unit respectively;

[0008] The micro control unit receives a comparison signal generated by the over-temperature detection unit;

[0009] The over-temperature protection unit receives the control signal generated by the micro control unit.

[0010] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the temperature sampling unit includes a first resistor, a thermistor and a first capacitor, the thermistor is connected in parallel with the first capacitor, the thermistor is connected in series with the first resistor, one end of the first resistor is connected to a 3.3V power supply, and the thermistor and the first capacitor are grounded at one end away from the first resistor.

[0011] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: a temperature sampling signal is output between the thermistor and the first resistor to a multiplexer.

[0012] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the input end of the multiplexer is connected to n temperature sampling units, wherein n is a natural number greater than or equal to 1.

[0013] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the VDD pin of the multiplexer output terminal is connected to the power supply VCC, and the INH pin, A0 pin, A1 pin, A2 pin and Z pin are connected to the micro control unit;

[0014] The Z pin of the multiplexer is also connected to the over-temperature detection unit.

[0015] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the over-temperature detection unit includes a comparator, the inverting input terminal of the comparator is connected to the Z pin of the multiplexer through a fourth resistor, the non-inverting input terminal of the comparator is connected to the 3V reference voltage through a second resistor, and the non-inverting input terminal and output terminal of the comparator are connected in parallel with a third resistor.

[0016] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the output end of the comparator outputs an over-temperature protection signal, and a fifth resistor is connected between the output end of the comparator and the positive power supply pin;

[0017] The lead of the comparator outputting the over-temperature protection signal is grounded via a second capacitor;

[0018] The positive power supply pin of the comparator is connected to a 3.3V power supply, and the negative power supply pin is grounded.

[0019] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the IO1, IO2 and IO3 pins of the microcontroller unit are connected to the A0, A1 and A2 pins of the multiplexer in sequence, the IO4 pin is connected to the INH pin of the multiplexer, the ADC1 pin is connected to the Z pin of the multiplexer, the VDD pin is connected to the power supply VCC, the VSS pin is grounded, the IO5 pin is connected to the over-temperature protection unit, and the IO6 pin is connected to the output end of the comparator.

[0020] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the over-temperature protection unit includes a transistor, a PMOS tube and a fan, the base of the transistor is connected to the IO5 pin of the micro control unit through a sixth resistor, the collector of the transistor is connected to the gate of the PMOS tube through a seventh resistor, and the drain of the PMOS tube is connected to the fan;

[0021] The emitter of the transistor is grounded, and a third capacitor is connected between the base and the emitter of the transistor.

[0022] As a preferred solution of the multi-point temperature monitoring and over-temperature protection circuit of the utility model, wherein: the source of the PMOS tube is connected to a 12V power supply, the drain of the PMOS tube is connected to pin 1 of a fan, and pin 2 of the fan is grounded;

[0023] An eighth resistor is also connected between the source and the gate of the PMOS tube.

[0024] The beneficial effects of the utility model: the utility model can realize temperature monitoring and over-temperature protection for multiple key points while occupying fewer ADC1 sampling channels of the MCU and using fewer comparators, which can reduce the design cost and volume of multi-point temperature monitoring and over-temperature protection circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is the overall schematic diagram of the multi-point temperature monitoring and over-temperature protection circuit.

[0027] Figure 2 This is the circuit connection diagram of the temperature sampling unit of the multi-point temperature monitoring and over-temperature protection circuit.

[0028] Figure 3This is a connection diagram of the multiplexer for multi-point temperature monitoring and over-temperature protection circuits.

[0029] Figure 4 The circuit connection diagram of the over-temperature detection unit of the multi-point temperature monitoring and over-temperature protection circuit.

[0030] Figure 5 It is a connection diagram of the microcontroller unit of the multi-point temperature monitoring and over-temperature protection circuit.

[0031] Figure 6 The circuit connection diagram of the over-temperature protection unit of the multi-point temperature monitoring and over-temperature protection circuit.

[0032] In the figure: 100, temperature sampling unit; R1, first resistor; RT1, thermistor; C1, first capacitor; U1, multiplexer; 200, over-temperature detection unit; U2, comparator; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; C2, second capacitor; MCU, microcontroller unit; 300, over-temperature protection unit; BJT1, transistor; R6, sixth resistor; R7, seventh resistor; C3, third capacitor; G1, PMOS tube; R8, eighth resistor; G2, fan. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] Example 1

[0037] Reference Figure 1~Figure 3, which is the first embodiment of the utility model, and this embodiment provides a multi-point temperature monitoring and over-temperature protection circuit, which includes a temperature sampling unit 100, and the temperature sampling unit 100 is used to collect the real-time temperature around the device with large power and serious heat generation, collect multiple temperature signals, and transmit the temperature sampling signals to the multiplexer U1, and the multiplexer U1 is used to select the reading of the sampled temperature, and the output end of the multiplexer U1 is connected to the over-temperature detection unit 200 and the microcontroller unit MCU.

[0038] The over-temperature detection unit 200 is used to compare the collected temperature with the preset temperature threshold, and input the comparison result into the microcontroller unit MCU. The microcontroller unit MCU is used to monitor the real-time temperature of multiple points received by the multiplexer, and perform over-temperature protection when the temperature exceeds the preset temperature threshold.

[0039] The over-temperature protection unit 300 is used to perform protective measures such as heat dissipation or device shutdown when the sampled temperature is higher than a threshold value. That is, the over-temperature protection unit 300 receives a control signal from the microcontroller unit MCU and executes protective measures.

[0040] It should be noted that multiple temperature sampling units 100 can be set up, and they are arranged at points where the power of components is large and the heat is serious. The output end of the temperature sampling unit 100 transmits the collected real-time temperature to the input end of the multiplexer, and the input port of the multiplexer U1 is connected according to the number of temperature sampling units 100. For example, if there are n points that need to be monitored, that is, the output ends of n temperature sampling units 100 are connected to n input ports of the multiplexer, where n is a natural number greater than or equal to 1.

[0041] The multiplexer U1 adopts the CD4051 chip, including 8 bidirectional analog switches, one side of each switch is connected to an independent input / output, and the other side is connected to a common input / output. By reading the real-time temperature of each point, and transmitting the real-time temperature to the over-temperature detection unit 200 for temperature comparison and receiving real-time monitoring from the micro-control unit MCU, the micro-control unit MCU selects the channel of the multiplexer U1, transmits it to the micro-control unit MCU for processing and calculating the actual temperature of the sampling point, and compares the information transmitted to the over-temperature detection unit 200 with the preset temperature threshold to determine whether it is over-temperature, and transmits the judgment result to the micro-control unit MCU, and the micro-control unit MCU drives the over-temperature protection unit to cool down by rotating the fan.

[0042] In summary, this design can monitor the temperature at multiple locations of devices with high power and severe heat generation. The real-time temperature can be read through the multiplexer to determine whether heat dissipation is required at each point.

[0043] Example 2

[0044] Reference Figure 1~Figure 4, which is the second embodiment of the utility model, the multi-point temperature monitoring and over-temperature protection circuit includes a temperature sampling unit 100 , a multiplexer U1 and an over-temperature detection unit 200 .

[0045] like Figure 2 As shown, the temperature sampling unit 100 includes a first resistor R1, a thermistor RT1 and a first capacitor C1. One end of the first resistor R1 is connected to a power supply 3.3V, and the other end is connected in series with the thermistor RT1. The other end of the thermistor RT1 is grounded. The first capacitor C1 is connected in parallel to both ends of the thermistor RT1 to filter out high-frequency noise. The resistance of the thermistor RT1 decreases as the temperature increases. The real-time temperature is reflected by collecting the voltage of the thermistor RT1 to the ground, and the collected voltage is transmitted to the multiplexer U1 and the over-temperature detection unit 200.

[0046] The thermistor RT1 is a resistor model that is already publicly used in the market, such as PT100, NTC, etc., and will not be described in detail here.

[0047] like Figure 3 As shown, the connection mode of each port of the multiplexer U1 is as follows: Y0-Y7 are respectively connected to the temperature sampling signal 1-temperature sampling signal 8 sampled at multiple points by the temperature sampling unit 100, and the sampling of each point can refer to Figure 2 The sampling circuit is designed as shown, the VDD pin is connected to the power supply VCC, the INH pin is the channel enable pin, each channel is turned on when the level is low, and each channel is turned off when the level is high, which is connected to the IO4 pin of the microcontroller unit MCU, A0, A1 and A2 are channel selection pins, which are connected to the IO1, IO2 and IO3 pins of the microcontroller unit MCU in turn, and high and low levels are input through different pins of A0, A1 and A2 to select different sampling channels. The Z pin is an output pin, which is connected to an ADC analog-to-digital converter sampling channel of the overtemperature detection unit 200 and the microcontroller unit MCU. The VEE pin is the negative power supply of the analog switch, and the VSS pin is the power ground, both of which are connected to the ground.

[0048] It should be noted that the multiplexer U1 selects the channel according to the instruction of the microcontroller unit MCU. Specifically, A0, A1 and A2 of the multiplexer are channel selection pins, which are connected to the IO1, IO2 and IO3 pins of the microcontroller unit MCU in sequence. High and low levels are input through different pins A0, A1 and A2. For example, if the three pins output a low level 000, the first channel is selected accordingly. If the three pins output two low levels and one high level 001, the second channel is selected, and so on... Eight sampling signals can be read through binary. The microcontroller unit MCU can actively select to read a certain channel according to the staff's own needs, or it can loop through each channel.

[0049] like Figure 4As shown, the overtemperature detection unit 200 includes: a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a second capacitor C2 and a comparator U2, wherein one end of the second resistor R2 is connected to a 3V reference voltage, and the other end is connected to the in-phase input end of the comparator U2, for controlling the voltage to be within a suitable range. The in-phase input end and the output end of the comparator U2 are connected in parallel with the third resistor R3. The inverting input end of the comparator U2 is connected to the Z pin of the multiplexer U1 through the fourth resistor R4, and the read temperature sampling signal is transmitted to the inverting input end of the comparator U2 through the Z pin of the multiplexer U1 through the fourth resistor R4, and is compared with the preset temperature threshold. One end of the fifth resistor R5 is connected to a 3.3V power supply, and the other end is connected to the output end of the comparator U2, which acts as a pull-up resistor to ensure that when the input voltage of the in-phase input end of the comparator U2 is greater than the voltage of the inverting input end, the output end of the comparator U2 outputs a high level. One end of the second capacitor C2 is connected to the output end of the comparator U2, and the other end is grounded, which plays a role in filtering out high-frequency noise. The 8th pin of the comparator U2 is connected to the 3.3V power supply, and the 4th pin is grounded.

[0050] Comparator U2 and surrounding resistors form a hysteresis comparator. The threshold value of the output voltage of comparator U2 from low to high is UT-=R3 / (R2+R3)*3=2.9, and the threshold value of the output voltage of comparator U2 from high to low is UT+= R3 / (R2+R3)*3+R2 / (R2+R3)*3.3=3. When the voltage at the reverse input terminal of the comparator is lower than 2.9V, the output terminal of comparator U2 is high level; when the voltage at the reverse input terminal of comparator U2 is higher than 3V, the output terminal of comparator U2 is low level.

[0051] In summary, this design collects the temperature of each point through the temperature sampling unit 100, and transmits it to the over-temperature detection unit 200 for comparison to determine whether over-temperature protection is required.

[0052] Example 3

[0053] Reference Figure 1 to Figure 6 , which is the third embodiment of the utility model, which is different from the previous two embodiments in that: it also includes a micro control unit MCU using each port connection method: IO1, IO2 and IO3 pins are connected to the channel selection pins A0, A1 and A2 of the multiplexer U1, the IO4 pin is connected to the multiplexer channel enable pin INH, the ADC1 pin is connected to the multiplexer U1 output pin Z, the VDD pin is connected to the power supply VCC, the VSS pin is grounded, the IO5 pin is connected to the over-temperature protection unit 300, and the IO6 pin is connected to the output end of the comparator U2 of the over-temperature detection unit 200.

[0054] like Figure 6As shown, the over-temperature protection unit 300 includes: a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a third capacitor C3, a PMOS tube G1, a transistor BJT1, and a fan G2. The base of the transistor BJT1 is connected to the IO5 pin of the microcontroller unit MCU through the voltage regulation of the sixth resistor R6, and is used to receive the control signal of the microcontroller unit MCU. The emitter of the transistor BJT1 is grounded, and the base and emitter of the transistor BJT1 are connected in parallel with the third capacitor C3. The third capacitor C3 plays a role in filtering high-frequency interference and ensuring the stability of the circuit. The collector of the transistor BJT1 is connected to the seventh resistor R7. The gate of the PMOS tube G1 is connected to the collector of the transistor BJT1 through the seventh resistor R7, and the source of the PMOS tube G1 is connected to a 12V power supply. The source and drain of the PMOS tube G1 are connected in parallel with the eighth resistor R8, and the drain of the PMOS tube G1 is connected to the power supply end of the fan G2. Pin 1 of the fan G2 is connected to the drain of the PMOS tube G1, and pin 2 is grounded.

[0055] When the IO5 pin of the microcontroller unit MCU is high level output, the transistor BJT1 is turned on. The gate voltage of the PMOS tube G1 is 12*R7 / (R7+R8)=6, which is less than the source voltage. The PMOS tube G1 is also turned on, and the 1 pin of the fan G2 is connected to 12V, and the fan works. When IO5 is low level output, the transistor BJT1 is turned off, the PMOS tube G1 is also turned off, and the fan is turned off without power supply signal.

[0056] During operation, the temperature sampling unit 100 is arranged at the point where temperature collection is required, and the temperature information collected by each sampling circuit is connected to the multiplexer U1. The multiplexer U1 channel is selected by the microcontroller MCU, that is, the temperature information of different points is selected and transmitted to the over-temperature detection unit 200 and the ADC analog-to-digital converter sampling channel of the microcontroller MCU. The information transmitted to the sampling channel of the microcontroller MCU is processed by the microcontroller MCU to calculate the actual temperature of the sampling point, and the information transmitted to the over-temperature detection unit 200 is compared with the preset value to determine whether it is over-temperature, and the judgment result is transmitted to the microcontroller MCU. If it is over-temperature, the corresponding IO pin of the microcontroller MCU outputs a high level and transmits it to the over-temperature protection unit 300, thereby driving the rotation of the fan G2 in the corresponding area to achieve the purpose of cooling. When the temperature is less than a certain value, the over-temperature detection unit 200 determines that it is not over-temperature. After the result of judging that it is not over-temperature is transmitted to the microcontroller MCU, the corresponding IO port of the microcontroller MCU is set to a low level. After the low-level signal is transmitted to the over-temperature protection unit 300, the fan G2 is turned off.

[0057] In summary, through the above working process, multi-point temperature monitoring and over-temperature protection are realized, occupying fewer ADC sampling channels of the microcontroller unit MCU and using fewer comparators, reducing the design cost and volume of the multi-point temperature monitoring and over-temperature protection circuit.

[0058] Importantly, it should be noted that the construction and arrangement of the present application shown in a number of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, changes in orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature or number or position of the discrete element may be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present utility model. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and is not only structurally equivalent but also an equivalent structure. Without departing from the scope of the present invention, other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the present invention is not limited to a specific embodiment, but extends to various modifications that still fall within the scope of the appended claims.

[0059] Additionally, in order to provide a concise description of example embodiments, all features of an actual embodiment may not be described (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention).

[0060] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A multi-point temperature monitoring and over-temperature protection circuit, characterized in that: include, A temperature sampling unit (100), the temperature sampling unit (100) collecting multiple temperature sampling signals and transmitting them to a multiplexer (U1), the multiplexer (U1) transmitting one of the temperature sampling signals to an over-temperature detection unit (200) and a micro control unit (MCU) respectively; The micro control unit (MCU) receives a comparison signal generated by the over-temperature detection unit (200); An over-temperature protection unit (300) receives a control signal generated by the micro control unit (MCU).

2. The multi-point temperature monitoring and over-temperature protection circuit according to claim 1, characterized in that: The temperature sampling unit (100) comprises a first resistor (R1), a thermistor (RT1) and a first capacitor (C1), the thermistor (RT1) and the first capacitor (C1) are connected in parallel, the thermistor (RT1) and the first resistor (R1) are connected in series, one end of the first resistor (R1) is connected to a 3.3V power supply, and one end of the thermistor (RT1) and the first capacitor (C1) away from the first resistor (R1) is grounded.

3. The multi-point temperature monitoring and over-temperature protection circuit according to claim 2, characterized in that: A temperature sampling signal is output between the thermistor (RT1) and the first resistor (R1) to the multiplexer (U1).

4. The multi-point temperature monitoring and over-temperature protection circuit according to claim 3, characterized in that: The input end of the multiplexer (U1) is connected to n temperature sampling units (100), wherein n is a natural number greater than or equal to 1.

5. The multi-point temperature monitoring and over-temperature protection circuit according to claim 4, characterized in that: The output terminal VDD pin of the multiplexer (U1) is connected to the power supply VCC, and the INH pin, A0 pin, A1 pin, A2 pin and Z pin are connected to the micro control unit (MCU); The Z pin of the multiplexer (U1) is also connected to the over-temperature detection unit (200).

6. The multi-point temperature monitoring and over-temperature protection circuit according to claim 5, characterized in that: The over-temperature detection unit (200) comprises a comparator (U2), the inverting input terminal of the comparator (U2) is connected to the Z pin of the multiplexer (U1) via a fourth resistor (R4), the non-inverting input terminal of the comparator (U2) is connected to a 3V reference voltage via a second resistor (R2), and the non-inverting input terminal and output terminal of the comparator (U2) are connected in parallel to a third resistor (R3).

7. The multi-point temperature monitoring and over-temperature protection circuit according to claim 6, characterized in that: The output end of the comparator (U2) outputs an over-temperature protection signal, and a fifth resistor (R5) is bridged between the output end of the comparator (U2) and the positive power supply pin; The lead of the comparator (U2) outputting the over-temperature protection signal is grounded via a second capacitor (C2); The positive power supply pin of the comparator (U2) is connected to a 3.3V power supply, and the negative power supply pin is grounded.

8. The multi-point temperature monitoring and over-temperature protection circuit according to claim 7, characterized in that: The IO1, IO2 and IO3 pins of the microcontroller (MCU) are connected to the A0, A1 and A2 pins of the multiplexer (U1) in sequence, the IO4 pin is connected to the INH pin of the multiplexer (U1), the ADC1 pin is connected to the Z pin of the multiplexer (U1), the VDD pin is connected to the power supply VCC, the VSS pin is grounded, the IO5 pin is connected to the over-temperature protection unit (300), and the IO6 pin is connected to the output end of the comparator (U2).

9. The multi-point temperature monitoring and over-temperature protection circuit according to claim 8, characterized in that: The over-temperature protection unit (300) comprises a transistor (BJT1), a PMOS transistor (G1) and a fan (G2); the base of the transistor (BJT1) is connected to the IO5 pin of the microcontroller unit (MCU) via a sixth resistor (R6); the collector of the transistor (BJT1) is connected to the gate of the PMOS transistor (G1) via a seventh resistor (R7); and the drain of the PMOS transistor (G1) is connected to the fan (G2); The emitter of the transistor (BJT1) is grounded, and a third capacitor (C3) is bridged between the base and the emitter of the transistor (BJT1).

10. The multi-point temperature monitoring and over-temperature protection circuit according to claim 9, characterized in that: The source of the PMOS tube (G1) is connected to a 12V power supply, the drain of the PMOS tube (G1) is connected to pin 1 of a fan (G2), and pin 2 of the fan (G2) is grounded; An eighth resistor (R8) is also bridged between the source and the gate of the PMOS tube (G1).

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