An overheat protection circuit and an electric appliance

Abstract

The application provides an overheat protection circuit and an electric device. The overheat protection circuit comprises a temperature acquisition module and a switching module. The switching module comprises a first resistor, a second resistor, a first triode and a switching element. The temperature acquisition module is used for acquiring a current temperature of a load circuit. If the current temperature is less than a preset temperature threshold, a high level is output to a base of the first triode. If the current temperature is greater than or equal to the preset temperature threshold, a low level is output to the base of the first triode. The switching element is used for keeping a conduction state when the base of the first triode is loaded with the high level and keeping a disconnection state when the base of the first triode is loaded with the low level. When the base of the first triode is loaded with the low level, the first triode is in a cut-off state. At this time, a voltage difference between a first electrode and a second electrode of the switching element is almost 0, which fails to meet a conduction voltage difference, and the switching element keeps the disconnection state. Therefore, a power supply circuit of the load circuit is cut off, and the load circuit is protected.

Description

Technical Field

[0001] This application relates to the field of circuits, and more specifically, to an overheat protection circuit and electrical equipment. Background Technology

[0002] With social development and scientific progress, electrical energy is widely used in various fields. In these applications, the main components include circuits or circuit boards. However, the use of electrical energy also presents some safety hazards; for example, prolonged operation of circuits may lead to overheating, potentially damaging components. To prevent overheating, existing technology provides an overheat protection circuit.

[0003] In existing overheat protection circuits, the on / off state of a relay is controlled by a thermistor, thereby switching the circuit's conduction state. This approach has the following drawbacks: near the temperature critical point, the circuit's conduction state repeatedly changes, causing repeated circuit restarts; the relay triggering device has a short lifespan, large size, and high power consumption, making it unsuitable for designs with limitations on circuit board height and area. Summary of the Invention

[0004] The purpose of this application is to provide an overheat protection circuit and electrical equipment to at least partially improve the above-mentioned problems.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0006] In a first aspect, embodiments of this application provide an overheat protection circuit, the overheat protection circuit including a temperature acquisition module and a switching module, the switching module including a first resistor, a second resistor, a first transistor and a switching element;

[0007] The output terminal of the temperature acquisition module is connected to the base of the first transistor, one end of the second resistor is connected to the emitter of the first transistor, one end of the first resistor and the first terminal of the switching element are both connected to the positive terminal of the power supply, the other end of the first resistor and the second terminal of the switching element are both connected to the collector of the first transistor, the third terminal of the switching element is connected to the input terminal of the load circuit, and the output terminal of the load circuit and the other end of the second resistor are both connected to the negative terminal of the power supply.

[0008] The temperature acquisition module is used to acquire the current temperature of the load circuit. If the current temperature is less than a preset temperature threshold, it outputs a high level to the base of the first transistor. If the current temperature is greater than or equal to the preset temperature threshold, it outputs a low level to the base of the first transistor.

[0009] The switching element is used to remain in a conducting state when a high level is applied to the base of the first transistor, and to remain in a disconnected state when a low level is applied to the base of the first transistor.

[0010] Optionally, the temperature acquisition module includes a third resistor, a fourth potentiometer, a fifth resistor, a sixth thermistor, a first Zener diode, a second transistor, and an operational amplifier;

[0011] One end of the third resistor and the collector of the second transistor are both connected to the positive terminal of the power supply. The other end of the third resistor and the base of the second transistor are both connected to the negative terminal of the first Zener diode. The positive terminal of the first Zener diode is connected to the negative terminal of the power supply. The emitter of the second transistor is connected to the positive terminal of the operational amplifier, and the negative terminal of the operational amplifier is connected to the negative terminal of the power supply.

[0012] The two fixed terminals of the fourth potentiometer are respectively connected to the emitter of the second transistor and the negative terminal of the power supply; the sliding terminal of the fourth potentiometer is connected to the inverting input terminal of the operational amplifier.

[0013] One end of the fifth resistor is connected to the emitter of the second transistor, the other end of the fifth resistor is connected to one end of the sixth thermistor, the other end of the sixth thermistor is connected to the negative terminal of the power supply, and the non-inverting input terminal of the operational amplifier is connected between the fifth resistor and the sixth thermistor.

[0014] The output of the operational amplifier is connected to the base of the first transistor.

[0015] Optionally, the temperature acquisition module further includes a seventh resistor, one end of which is connected to the output of the operational amplifier, and the other end of which is connected between the fifth resistor and the sixth thermistor.

[0016] Optionally, the temperature acquisition module further includes a first capacitor, the two terminals of which are respectively connected to the two terminals of the first Zener diode.

[0017] Optionally, the temperature acquisition module further includes a second capacitor, the two terminals of which are respectively connected to the emitter of the second transistor and the negative terminal of the power supply.

[0018] Optionally, the switching module further includes a second Zener diode, the negative terminal of which is connected to the first terminal of the switching element, and the positive terminal of which is connected to the second terminal of the switching element.

[0019] Optionally, the switching module further includes an eighth resistor, the two ends of which are respectively connected to the output terminal of the temperature acquisition module and the base of the first transistor.

[0020] Optionally, the switching element is a PMOS transistor, with the source of the PMOS transistor being the first terminal of the switching element, the gate of the PMOS transistor being the second terminal of the switching element, and the drain of the PMOS transistor being the third terminal of the switching element.

[0021] Secondly, embodiments of this application provide an electrical device, which includes the overheat protection circuit described above.

[0022] Compared to existing technologies, the overheat protection circuit and electrical equipment provided in this application include a temperature acquisition module and a switching module. The switching module includes a first resistor, a second resistor, a first transistor, and a switching element. The temperature acquisition module acquires the current temperature of the load circuit. If the current temperature is less than a preset temperature threshold, it outputs a high level to the base of the first transistor; if the current temperature is greater than or equal to the preset temperature threshold, it outputs a low level to the base of the first transistor. The switching element remains in a conducting state when a high level is applied to the base of the first transistor and remains in a disconnected state when a low level is applied to the base of the first transistor. When the base of the first transistor is low, the first transistor is in a cutoff state. At this time, the voltage difference between the first and second terminals of the switching element is almost zero, failing to meet the conduction voltage difference requirement, and the switching element remains in a disconnected state. This disconnects the power supply to the load circuit, protecting the load circuit.

[0023] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a connection diagram of the overheat protection circuit provided in an embodiment of this application;

[0026] Figure 2 This is one of the connection diagrams of the overheat protection circuit provided in the embodiments of this application;

[0027] Figure 3 This is one of the connection diagrams of the overheat protection circuit provided in the embodiments of this application;

[0028] Figure 4 This is one of the connection diagrams for the overheat protection circuit provided in the embodiments of this application.

[0029] In the diagram: 10 - Temperature acquisition module; 20 - Switch module; 30 - Load circuit; 201 - Switch element. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0032] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0034] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of this application is usually placed in. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0035] In the description of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0036] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] Please refer to Figure 1 , Figure 1 This is a connection diagram of an overheat protection circuit provided in an embodiment of this application. Figure 1 As shown, resistor R9 is a negative temperature coefficient thermistor (NTC). At room temperature, an NTC has a very high resistance, which gradually decreases as the temperature rises. At room temperature, the resistance of resistor R10 should be much smaller than that of resistor R9. Resistor R10 is used to ensure that the third transistor Q3 is in the off state at room temperature. Specifically, at room temperature, the voltage output by the power supply is mainly applied across resistor R9. The voltage drop across resistor R10 is relatively small, and the base-emitter voltage Ube of the third transistor Q3 is less than 0.7V (for silicon transistors). At this time, the third transistor Q3 is in the off state, the normally closed relay K2 remains closed, and the circuit operates normally. When the ambient temperature around the thermistor R9 rises, the resistance of resistor R9 also decreases. At this time, the voltage drop across R10 gradually increases. When the base-emitter voltage Ube of the third transistor Q3 reaches the transistor's conduction threshold, the third transistor Q3 switches to the conducting state, and the normally closed relay K2 switches to the open state. In other words, it disconnects the protected circuit (load circuit) when an overheating event occurs. The function of C3 is to filter, and a small-value ceramic capacitor is generally used to avoid interference causing Q3 to turn on falsely.

[0038] Through extensive practical experience, the inventor discovered that Figure 1The overheat protection circuit shown has the following defects: ① Near the temperature critical point, the third transistor Q3 will repeatedly conduct, at which time the normally closed relay K2 will repeatedly open and close, causing the circuit to repeatedly restart; ② The normally closed relay K2, the triggering device, has a short lifespan, large size, and high power consumption, which is not conducive to the design of circuit boards with limited height and area requirements; ③ The temperature trigger point is not adjustable, and the selection of the third transistor Q3 and the normally closed relay K2 is limited by the input voltage; ④ When the temperature is near the critical point, the third transistor Q3 may be in a semi-conducting state. At this time, the heat power on the third transistor Q3 is large, which may burn out the third transistor Q3 in severe cases.

[0039] To overcome the above problems, embodiments of this application provide an overheat protection circuit. For example... Figure 2 As shown, the overheat protection circuit includes a temperature acquisition module 10 and a switching module 20. The switching module 20 includes a first resistor R1, a second resistor R2, a first transistor Q1, and a switching element 201.

[0040] The output terminal of the temperature acquisition module 10 is connected to the base of the first transistor Q1. One end of the second resistor R2 is connected to the emitter of the first transistor Q1. One end of the first resistor R1 and the first terminal of the switching element 201 are both connected to the positive terminal of the power supply. The other end of the first resistor R1 and the second terminal of the switching element 201 are both connected to the collector of the first transistor Q1. The third terminal of the switching element 201 is connected to the input terminal of the load circuit 30. The output terminal of the load circuit 30 and the other end of the second resistor R2 are both connected to the negative terminal of the power supply.

[0041] The temperature acquisition module 10 is used to acquire the current temperature of the load circuit 30. If the current temperature is less than the preset temperature threshold, it outputs a high level to the base of the first transistor Q1. If the current temperature is greater than or equal to the preset temperature threshold, it outputs a low level to the base of the first transistor Q1.

[0042] The switching element 201 is used to maintain the conducting state when the base of the first transistor Q1 is loaded with a high level, and to maintain the disconnected state when the base of the first transistor Q1 is loaded with a low level.

[0043] Specifically, when a high level is applied to the base of the first transistor Q1, Q1 conducts, and current flows from the first resistor R1 through the second resistor R2 back to the negative terminal of the power supply. The voltage difference between the first and second terminals of the switching element 201 meets the conduction voltage difference requirement, and the switching element 201 remains on. Conversely, if the current temperature is greater than or equal to a preset temperature threshold, a low level is output to the base of the first transistor Q1. When a low level is applied to the base of the first transistor Q1, Q1 is in the off state. At this time, the voltage difference between the first and second terminals of the switching element 201 is almost zero, failing to meet the conduction voltage difference requirement, and the switching element 201 remains off.

[0044] In summary, the overheat protection circuit provided in this application includes a temperature acquisition module and a switching module. The switching module includes a first resistor, a second resistor, a first transistor, and a switching element. The temperature acquisition module acquires the current temperature of the load circuit. If the current temperature is less than a preset temperature threshold, it outputs a high level to the base of the first transistor; if the current temperature is greater than or equal to the preset temperature threshold, it outputs a low level to the base of the first transistor. The switching element remains in a conducting state when a high level is applied to the base of the first transistor and remains in a disconnected state when a low level is applied to the base of the first transistor. When the base of the first transistor is low, the first transistor is in a cutoff state. At this time, the voltage difference between the first and second terminals of the switching element is almost zero, failing to meet the conduction voltage difference requirement, and the switching element remains in a disconnected state. This disconnects the power supply to the load circuit, protecting the load circuit.

[0045] exist Figure 2 Based on this, regarding the structure of the temperature acquisition module 10, this application embodiment also provides a possible implementation method, please refer to... Figure 3 The temperature acquisition module 10 includes a third resistor R3, a fourth potentiometer R4, a fifth resistor R5, a sixth thermistor R6, a first Zener diode D1, a second transistor Q2, and an operational amplifier OP.

[0046] One end of the third resistor R3 and the collector of the second transistor Q2 are both connected to the positive terminal of the power supply. The other end of the third resistor R3 and the base of the second transistor Q2 are both connected to the negative terminal of the first Zener diode D1. The anode of the first Zener diode D1 is connected to the negative terminal of the power supply. The emitter of the second transistor Q2 is connected to the positive terminal of the operational amplifier OP. The negative terminal of the operational amplifier OP is connected to the negative terminal of the power supply.

[0047] Optionally, the power input is divided by the third resistor R3 and the first Zener diode D1 to provide a bias voltage for the second transistor Q2. The second transistor Q2 is turned on. At this time, the emitter voltage of the second transistor Q2 is equal to the voltage of the first Zener diode D1 minus one diode voltage drop. Changing the Zener value of the first Zener diode D1 can change the output voltage of this part, thereby protecting the operational amplifier.

[0048] The two fixed terminals of the fourth potentiometer R4 are connected to the emitter of the second transistor Q2 and the negative terminal of the power supply, respectively; the sliding terminal of the fourth potentiometer R4 is connected to the inverting input terminal of the operational amplifier OP.

[0049] One end of the fifth resistor R5 is connected to the emitter of the second transistor Q2, and the other end of the fifth resistor R5 is connected to one end of the sixth thermistor R6. The other end of the sixth thermistor R6 is connected to the negative terminal of the power supply. The non-inverting input of the operational amplifier OP is connected between the fifth resistor R5 and the sixth thermistor R6.

[0050] The output of the operational amplifier OP is connected to the base of the first transistor Q1.

[0051] Optionally, the sixth thermistor R6 is a negative temperature coefficient thermistor (NTC), whose resistance decreases as temperature increases. The fourth potentiometer R4 is used to adjust the temperature threshold. A potentiometer is a type of variable resistor. It typically consists of a resistive element and a rotating or sliding system, where a moving contact moves along the resistive element to obtain a partial voltage output. The function of a potentiometer is to adjust the magnitude of voltage (including DC voltage and signal voltage) and current.

[0052] By moving the slider of the fourth potentiometer R4, the level of the inverting input of the operational amplifier OP is adjusted, thereby regulating the temperature threshold.

[0053] When the voltage level at the non-inverting input of operational amplifier OP is higher than that at the inverting input, it indicates that the resistance of the sixth thermistor R6 is large, resulting in a larger voltage drop. At this time, the temperature of the load circuit 30 is low, and operational amplifier OP outputs a high level. When the temperature of the load circuit 30 rises, the resistance of the sixth thermistor R6 decreases until the voltage level at the non-inverting input of operational amplifier OP falls below that at the inverting input, at which point operational amplifier OP outputs a low level.

[0054] Alternatively, please continue to refer to Figure 3 Regarding how to avoid repeated circuit startup, this application embodiment also provides a possible implementation method: the temperature acquisition module 10 further includes a seventh resistor R7, one end of the seventh resistor R7 is connected to the output terminal of the operational amplifier OP, and the other end of the seventh resistor R7 is connected between the fifth resistor R5 and the sixth thermistor R6.

[0055] Specifically, when the resistance of the sixth thermistor R6 changes, the output level of the operational amplifier OP remains unchanged when its temperature varies within a certain range of the set temperature point. This range is called the "dead zone" of the hysteresis amplifier. Adjusting the resistance of the seventh resistor R7 can adjust the range of the dead zone; the smaller the resistance of the seventh resistor R7, the wider the dead zone range.

[0056] When the temperature is at or below room temperature, the NTC exhibits high impedance. At this time, the voltage at the non-inverting input of the operational amplifier (OP) is greater than the voltage at the inverting input, and the OP outputs a high level. For a rail-to-rail op-amp, the circuit is equivalent to R7 and R5 connected in parallel and then in series with R6. The voltage across R6 is greater than the voltage across R6 in a typical voltage comparator circuit. Therefore, to make the output of the OP transition from high to low, R6 needs to have a lower resistance than that of a typical voltage comparator. This results in a dead zone to the left of the set temperature point. As the temperature rises, the NTC resistance decreases, and the voltage drop across the NTC decreases. When the voltage at the non-inverting input of the OP is lower than the voltage at the inverting input, the op-amp outputs a low level, and the first transistor Q1 is turned off. For rail-to-rail op-amps, the circuit is equivalent to R6 and R7 connected in parallel and then in series with R5. The voltage across R6 is less than the voltage across R6 in a typical voltage comparator circuit of the same type. Therefore, to make the op-amp switch, R6 needs to have a higher switching resistance than a typical voltage comparator. As a result, there is a dead zone for triggering to the right of the set temperature point.

[0057] exist Figure 3 Based on this, regarding how to eliminate interference and noise, embodiments of this application also provide a possible implementation method, please refer to... Figure 4 The temperature acquisition module 10 also includes a first capacitor C1, the two terminals of which are respectively connected to the two terminals of the first Zener diode D1.

[0058] The first capacitor C1 is used to filter out noise interference from the first Zener diode D1.

[0059] Optionally, the temperature acquisition module 10 also includes a second capacitor C2, the two terminals of which are connected to the emitter of the second transistor Q2 and the negative terminal of the power supply, respectively.

[0060] The second capacitor C2 is used to reduce the output impedance of the power supply.

[0061] Alternatively, please continue to refer to Figure 4 Regarding how to protect the switch module 20, this application embodiment also provides a possible implementation method, in which the switch module 20 further includes a second Zener diode D2 and an eighth resistor R8.

[0062] The negative terminal of the second Zener diode D2 is connected to the first terminal of the switching element 201, and the positive terminal of the second Zener diode D2 is connected to the second terminal of the switching element 201.

[0063] The second Zener diode D2 is used to prevent overvoltage damage to the switching element 201.

[0064] The two ends of the eighth resistor R8 are connected to the output terminal of the temperature acquisition module 10 and the base of the first transistor Q1, respectively.

[0065] The eighth resistor, R8, is used to prevent overcurrent.

[0066] Optionally, the switching element 201 is a PMOS transistor, with the source of the PMOS transistor being the first terminal of the switching element 201, the gate of the PMOS transistor being the second terminal of the switching element 201, and the drain of the PMOS transistor being the third terminal of the switching element 201.

[0067] Optionally, the transistors provided in the embodiments of this application are all NPN transistors. It should be noted that the transistors in the embodiments of this application can be replaced by NMOS transistors.

[0068] This application also provides an electrical device that includes the overheat protection circuit described above.

[0069] It should be noted that the electrical equipment provided in this embodiment can achieve the technical effects corresponding to the overheat protection circuit described above. For the sake of brevity, any parts not mentioned in this embodiment can be referred to the corresponding content in the above embodiments.

[0070] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0071] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. An overheat protection circuit, characterized in that, The overheat protection circuit includes a temperature acquisition module and a switching module. The switching module includes a first resistor, a second resistor, a first transistor, and a switching element. The output terminal of the temperature acquisition module is connected to the base of the first transistor, one end of the second resistor is connected to the emitter of the first transistor, one end of the first resistor and the first terminal of the switching element are both connected to the positive terminal of the power supply, the other end of the first resistor and the second terminal of the switching element are both connected to the collector of the first transistor, the third terminal of the switching element is connected to the input terminal of the load circuit, and the output terminal of the load circuit and the other end of the second resistor are both connected to the negative terminal of the power supply. The temperature acquisition module is used to acquire the current temperature of the load circuit. If the current temperature is less than a preset temperature threshold, it outputs a high level to the base of the first transistor. If the current temperature is greater than or equal to the preset temperature threshold, it outputs a low level to the base of the first transistor. The switching element is used to remain in the on state when the base of the first transistor is loaded with a high level, and to remain in the off state when the base of the first transistor is loaded with a low level. The temperature acquisition module includes a third resistor, a fourth potentiometer, a fifth resistor, a sixth thermistor, a first Zener diode, a second transistor, and an operational amplifier. One end of the third resistor and the collector of the second transistor are both connected to the positive terminal of the power supply. The other end of the third resistor and the base of the second transistor are both connected to the negative terminal of the first Zener diode. The positive terminal of the first Zener diode is connected to the negative terminal of the power supply. The emitter of the second transistor is connected to the positive terminal of the operational amplifier, and the negative terminal of the operational amplifier is connected to the negative terminal of the power supply. The two fixed terminals of the fourth potentiometer are respectively connected to the emitter of the second transistor and the negative terminal of the power supply; the sliding terminal of the fourth potentiometer is connected to the inverting input terminal of the operational amplifier. One end of the fifth resistor is connected to the emitter of the second transistor, the other end of the fifth resistor is connected to one end of the sixth thermistor, the other end of the sixth thermistor is connected to the negative terminal of the power supply, and the non-inverting input terminal of the operational amplifier is connected between the fifth resistor and the sixth thermistor. The output terminal of the operational amplifier is connected to the base of the first transistor; The temperature acquisition module also includes a seventh resistor, one end of which is connected to the output of the operational amplifier, and the other end of which is connected between the fifth resistor and the sixth thermistor. The temperature acquisition module also includes a first capacitor, the two terminals of which are respectively connected to the two terminals of the first Zener diode; The temperature acquisition module also includes a second capacitor, the two terminals of which are respectively connected to the emitter of the second transistor and the negative terminal of the power supply.

2. The overheat protection circuit as described in claim 1, characterized in that, The switching module further includes a second Zener diode, the negative terminal of which is connected to the first terminal of the switching element, and the positive terminal of which is connected to the second terminal of the switching element.

3. The overheat protection circuit as described in claim 1, characterized in that, The switching module also includes an eighth resistor, the two ends of which are connected to the output terminal of the temperature acquisition module and the base of the first transistor, respectively.

4. The overheat protection circuit as described in claim 1, characterized in that, The switching element is a PMOS transistor, with the source of the PMOS transistor being the first terminal of the switching element, the gate of the PMOS transistor being the second terminal of the switching element, and the drain of the PMOS transistor being the third terminal of the switching element.

5. An electrical appliance, characterized in that, The electrical equipment includes an overheat protection circuit as described in any one of claims 1-4.

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