A motor overheat protection circuit

Abstract

Embodiments of the present invention relate to the field of electronic technology, and more particularly to a motor overheating protection circuit. Embodiments of the present invention provide a motor overheating protection circuit, comprising a temperature detection circuit, a reference signal circuit, a comparison circuit, a switch circuit, and a control unit; the comparison circuit has a first input connected to the temperature detection circuit, a second input connected to the reference signal circuit, and an output connected to a first end of the switch circuit; the temperature detection circuit is used to detect the motor temperature and output a corresponding temperature detection signal; the comparison circuit is used to output a first control signal based on the temperature detection signal and the reference signal; the switch circuit has a second end connected to a first end of the control unit, a third end connected to the motor, and a fourth end connected to a first power supply; the switch circuit is used to start or shut down the motor based on the first control signal and a second control signal from the control unit; the circuit is controlled by a hardware circuit, does not require software protection, and has low safety certification difficulty.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electronic technology, and in particular to a motor overheating protection circuit. Background Art

[0002] Blenders, a small appliance, rely on a high-speed AC motor to drive a sharp blade. They have the highest safety requirements among small appliances, meeting both safety standards for preventing electric shock and motor temperature rise to prevent fires caused by overheating. There are many reasons for blender motor overheating, including motor overload, mismatched selection, cooling failures, and premature insulation aging due to lack of monitoring and necessary maintenance. Motors generate losses during operation, which reduce their efficiency while also causing them to heat up and increase the temperature of their windings. Excessively high temperatures accelerate the aging of the winding insulation, sharply reducing the insulation performance and significantly shortening the motor's service life. They can even lead to fires and electric shock hazards.

[0003] To this end, NTC thermistors are usually installed on the motor body or motor windings, connected to the microcontroller on the control board, and controlled by the microcontroller. However, this method requires software protection. Due to the high cost and long cycle of software certification, its safety certification is difficult. Summary of the Invention

[0004] The main technical problem solved by the embodiments of the present invention is to provide a motor overheat protection circuit, which adopts hardware circuit control, does not require software to participate in protection, and has low difficulty in safety certification.

[0005] In order to solve the above technical problems, a technical solution adopted in an embodiment of the present invention is: providing a motor overheating protection circuit, including: a temperature detection circuit, a reference signal circuit, a comparison circuit, a switching circuit and a control unit; the output end of the temperature detection circuit is connected to the first input end of the comparison circuit, and the temperature detection circuit is used to detect the current temperature of the motor and output a corresponding temperature detection signal; the output end of the reference signal circuit is connected to the second input end of the comparison circuit, and the reference signal circuit is used to output a reference signal; the output end of the comparison circuit is connected to the first end of the switching circuit, and the comparison circuit is used to output a first control signal according to the temperature detection signal and the reference signal; the second end of the switching circuit is connected to the first end of the control unit, the third end of the switching circuit is connected to the motor, and the fourth end of the switching circuit is connected to the first power supply, and the switching circuit is used to start or shut down the motor according to the first control signal and the second control signal of the control unit.

[0006] In some embodiments, the switching circuit includes a first switching unit and a second switching unit; the first end of the first switching unit is connected to the output end of the comparison circuit, the second end of the first switching unit is connected to the first end of the second switching unit, and the first switching unit is used to control the second switching unit to open or close according to the first control signal; the first end of the second switching unit is also connected to the first end of the control unit, the second end of the second switching unit is connected to the motor, the third end of the second switching unit is connected to the first power supply, and the second switch unit is used to start or shut down the motor according to the first control signal and the second control signal.

[0007] In some embodiments, the first switching unit includes a first NPN transistor and a first resistor; the base of the first NPN transistor is connected to the output end of the comparison circuit, the collector of the first NPN transistor is connected to the first end of the second switching unit, and the emitter of the first NPN transistor is grounded; one end of the first resistor is connected to the base of the first NPN transistor, and the other end of the first resistor is connected to the emitter of the first NPN transistor.

[0008] In some embodiments, the second switching unit includes a relay, a second NPN transistor and a second resistor; the base of the second NPN transistor is respectively connected to the first end of the control unit and the collector of the first NPN transistor, the emitter of the second NPN transistor is grounded, and the collector of the second NPN transistor is connected to the first end of the coil of the relay; one end of the second resistor is connected to the base of the second NPN transistor, and the other end of the second resistor is connected to the emitter of the second NPN transistor; the second end of the coil of the relay is connected to the second power supply, the first end of the switch of the relay is connected to the motor, and the second end of the switch of the relay is connected to the first power supply.

[0009] In some embodiments, the temperature detection circuit includes a third resistor and a thermistor; the first end of the third resistor is connected to a third power supply, the second end of the third resistor is respectively connected to the first end of the thermistor and the first input end of the comparison circuit, and the second end of the thermistor is grounded.

[0010] In some embodiments, the reference signal circuit includes a first reference resistor and a second reference resistor; the first end of the first reference resistor is connected to a third power supply, the second end of the first reference resistor is respectively connected to the first end of the second reference resistor and the second input end of the comparison circuit, and the second end of the second reference resistor is grounded.

[0011] In some embodiments, the comparison circuit includes a comparator; the negative input of the comparator is connected to the output of the temperature detection circuit, the positive input of the comparator is connected to the output of the reference signal circuit, and the output of the comparator is connected to the first end of the switching circuit.

[0012] In some embodiments, the comparison circuit further includes a positive feedback circuit; one end of the positive feedback circuit is connected to the positive input end of the comparator, and the other end of the positive feedback circuit is connected to the output end of the comparator.

[0013] In some embodiments, the positive feedback circuit includes a fourth resistor and a first diode; one end of the fourth resistor is connected to the positive input end of the comparator, the other end of the fourth resistor is connected to the cathode of the first diode, and the anode of the first diode is connected to the output end of the comparator.

[0014] In some embodiments, the motor overheat protection circuit also includes an emitter follower; one end of the emitter follower is connected to the output end of the temperature detection circuit, and the other end of the emitter follower is connected to the second end of the control unit, and the emitter follower is used to input the temperature detection signal into the control unit.

[0015] Compared with the prior art, the beneficial effects of the present invention are: different from the prior art, the embodiment of the present invention provides a motor overheating protection circuit, which includes a temperature detection circuit, a reference signal circuit, a comparison circuit, a switching circuit and a control unit; the first input end of the comparison circuit is connected to the temperature detection circuit, the second input end is connected to the reference signal circuit, and the output end is connected to the first end of the switching circuit. The temperature detection circuit is used to detect the motor temperature and output a corresponding temperature detection signal. The comparison circuit is used to output a first control signal according to the temperature detection signal and the reference signal; the second end of the switching circuit is connected to the first end of the control unit, the third end is connected to the motor, and the fourth end is connected to the first power supply. The switching circuit is used to start or shut down the motor according to the first control signal and the second control signal of the control unit; in this circuit, the control unit can start the motor by outputting the second control signal to the switching circuit. When the motor overheats, the comparison circuit will output the first control signal to shut down the motor according to the temperature detection signal and the reference signal, thereby realizing overheating control through a pure hardware circuit, without the need for software to participate in protection, and the difficulty of safety certification is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] One or more embodiments are exemplarily described by pictures in the corresponding drawings. These exemplified descriptions do not constitute limitations on the embodiments. Elements / modules and steps with the same reference numerals in the drawings are represented as similar elements / modules and steps. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation.

[0017] Figure 1 This is a schematic structural block diagram of a motor overheat protection circuit provided by an embodiment of the present invention;

[0018] Figure 2 This is a schematic structural block diagram of another motor overheat protection circuit provided by an embodiment of the present invention;

[0019] Figure 3 The present invention provides a circuit diagram of a motor overheat protection circuit. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0021] For ease of understanding of the present application, the present application will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those generally understood by those skilled in the art in the field of the present application. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more related listed items.

[0022] It should be noted that, unless they conflict, the various features of the embodiments of the present invention may be combined with each other and are all within the scope of protection of this application. Furthermore, although the functional modules are divided in the device schematic, in some cases, the module division may be different from that in the device. Furthermore, the terms "first," "second," and the like used herein do not limit the order of data or execution; they are merely used to distinguish between identical or similar items with substantially the same functions and effects.

[0023] The present invention provides a motor overheat protection circuit. Figure 1The motor overheat protection circuit 100 includes: a temperature detection circuit 10, a reference signal circuit 20, a comparison circuit 30, a switch circuit 40 and a control unit 50; wherein, the output end of the temperature detection circuit 10 is connected to the first input end of the comparison circuit 30, and the temperature detection circuit 10 is used to detect the current temperature of the motor 200 and output a corresponding temperature detection signal; the output end of the reference signal circuit 20 is connected to the second input end of the comparison circuit 30, and the reference signal circuit 20 is used to output a reference signal; the output end of the comparison circuit 30 is connected to the first end of the switch circuit 40, and the comparison circuit 30 is used to output a first control signal according to the temperature detection signal and the reference signal; the second end of the switch circuit 40 is connected to the first end of the control unit 50, the third end of the switch circuit 40 is connected to the motor 200, and the fourth end of the switch circuit 40 is connected to the first power supply 300, and the switch circuit 40 is used to start or shut down the motor 200 according to the first control signal and the second control signal of the control unit 50.

[0024] In the motor overheat protection circuit 100, the user can first set the reference signal circuit 20 according to the temperature threshold at which the motor needs to trigger protection, so that the reference signal circuit 20 can output a reference signal corresponding to the temperature threshold. Then, the control unit 50 outputs a second control signal to close the switch circuit 40, thereby starting the motor 200. Then, the temperature detection circuit 10 detects the current temperature of the motor 200 and outputs a corresponding temperature detection signal to the comparison circuit 30. The comparison circuit 30 compares the temperature detection signal with the reference signal and outputs a first control signal. When the current temperature of the motor 200 is lower than the preset temperature threshold, the temperature detection signal is higher than the reference signal, and the comparison circuit 30 outputs the first control signal to keep the switch circuit 40 in the started state. When the current temperature of the motor 200 is higher than the preset temperature threshold, the temperature detection signal is lower than the reference signal, and the comparison circuit 30 outputs the first control signal to open the switch circuit 40, shutting down the motor 200. As can be seen, the design structure is simple. After the motor is started, the circuit uses pure hardware circuit control to implement the motor overheat protection process, without the need for software to participate in the protection circuit, which reduces the difficulty of safety certification.

[0025] In some of these examples, see Figure 2The switch circuit 40 includes a first switch unit 41 and a second switch unit 42. A first end of the first switch unit 41 is connected to the output end of the comparison circuit 30, and a second end of the first switch unit 41 is connected to a first end of the second switch unit 42. The first switch unit 41 is configured to control the second switch unit 42 to open or close according to a first control signal. The first end of the second switch unit 42 is also connected to a first end of the control unit 50, a second end of the second switch unit 42 is connected to the motor 200, and a third end of the second switch unit 42 is connected to the first power supply 300. The second switch unit 42 is configured to start or stop the motor 200 according to the first and second control signals. In this case, the second switch unit 42 can not only be closed or opened according to the first control signal of the control unit 50, thereby achieving normal power on and off of the motor 200, but the closing or opening of the second switch unit 42 is also controlled by the first switch unit 41, thereby achieving overheat protection for the motor.

[0026] In some of these examples, see Figure 3 The first switch unit 41 includes a first NPN transistor Q1 and a first resistor R1; wherein the base of the first NPN transistor Q1 is connected to the output of the comparison circuit 30, the collector of the first NPN transistor Q1 is connected to the first end of the second switch unit 42, and the emitter of the first NPN transistor Q1 is grounded; one end of the first resistor R1 is connected to the base of the first NPN transistor Q1, and the other end of the first resistor R1 is connected to the emitter of the first NPN transistor Q1. In order to limit the current of the first control signal, the base of the first NPN transistor Q1 is also connected to the output of the comparison circuit 30 via a current-limiting resistor Rp1. In practical applications, the first switch unit 41 can use other transistors, or MOS transistors, or any other suitable switch units, and there is no need to stick to the limitations of this embodiment.

[0027] In some embodiments, the second switch unit 42 includes a relay RY1, a second NPN transistor Q2, and a second resistor R2. The base of the second NPN transistor Q2 is connected to the first terminal of the control unit 50 and the collector of the first NPN transistor Q1, respectively. The emitter of the second NPN transistor Q2 is grounded, and the collector of the second NPN transistor Q2 is connected to the first terminal of the coil of the relay RY1. One terminal of the second resistor R2 is connected to the base of the second NPN transistor Q2, and the other terminal of the second resistor R2 is connected to the emitter of the second NPN transistor Q2. The second terminal of the coil of the relay RY1 is connected to a second power supply VDD, which is used to power the relay RY1. The first terminal of the switch of the relay RY1 is connected to the motor 200, and the second terminal of the switch of the relay RY1 is connected to the first power supply 300, which is used to power the motor 200. To limit the current of the second control signal of the control unit 50, the base of the second NPN transistor Q2 is also connected to the first terminal of the control unit 50 via a current-limiting resistor Rp2. In practical applications, the second switch unit 42 may use other transistors, or MOS transistors, or any other suitable switch units, and there is no need to stick to the limitations of this embodiment.

[0028] To protect relay RY1, in some embodiments, second switch unit 42 further includes a Zener diode D2. The cathode of Zener diode D2 is connected to the second power supply VDD, and the anode of Zener diode D2 is connected to the collector of second NPN transistor Q2. Zener diode D2 maintains the voltage across relay RY1 substantially constant, preventing relay RY1 from breakdown due to high current.

[0029] In some of these examples, see Figure 3 The temperature detection circuit 10 includes a third resistor R3 and a thermistor RT1. The first end of the third resistor R3 is connected to a third power source, which is used for powering the motor. The second end of the third resistor R3 is connected to the first end of the thermistor RT1 and the first input end of the comparison circuit 30, respectively. The second end of the thermistor RT1 is grounded. In this case, the temperature detection signal output by the temperature detection circuit 10 is the voltage across the thermistor RT1. In actual applications, the thermistor RT1 is insulated and closely mounted to the motor winding of the motor 200. The thermistor's room temperature resistance and B value can be selected based on the insulation level of the motor winding, which is not limited here.

[0030] In some embodiments, the thermistor RT1 is a negative temperature coefficient thermistor. When the temperature rises, the resistance of the negative temperature coefficient thermistor RT1 decreases, and the voltage of the temperature detection signal output by the temperature detection circuit 10 decreases accordingly. In practical applications, the thermistor RT1 can also be a positive temperature coefficient thermistor, and the circuit can be configured accordingly. This is not necessarily limited to the limitations of this embodiment.

[0031] In some of these examples, please see Figure 3 The reference signal circuit 20 includes a first reference resistor Rf1 and a second reference resistor Rf2; the first end of the first reference resistor Rf1 is connected to a third power supply, the second end of the first reference resistor Rf1 is connected to the first end of the second reference resistor Rf2 and the second input end of the comparison circuit 30, respectively, and the second end of the second reference resistor Rf2 is grounded. At this time, the reference signal output by the reference signal circuit 20 is the voltage across the resistor Rf2. During design, the temperature detection circuit 10 can be set to obtain the temperature detection signal value output by the temperature detection circuit 10 at the temperature threshold. The reference signal value of the reference signal circuit 20 can be set based on the temperature detection signal value, and the resistance values ​​of the first reference resistor Rf1 and the second reference resistor Rf2 can be set accordingly. It can be seen that the resistance values ​​of the two resistors have a corresponding relationship with the set temperature threshold. In actual application, the resistance ratio of the first reference resistor Rf1 and the second reference resistor Rf2 can be adjusted according to the insulation level of the motor winding to set the temperature protection threshold of the motor 200. At the same time, the number and connection method of the voltage divider resistors in the reference signal circuit 20 can be set according to actual needs and are not limited to the limitations of this embodiment.

[0032] In some of these examples, see Figure 3 The comparison circuit 30 includes a comparator U1; a negative input terminal of the comparator U1 is connected to the output terminal of the temperature detection circuit 10, a positive input terminal of the comparator U1 is connected to the output terminal of the reference signal circuit 20, and an output terminal of the comparator U1 is connected to the first terminal of the switch circuit 40. The comparator U1 can be used to compare the input voltages of the two input terminals. Specifically, when the voltage of the positive input terminal of the comparator U1 is higher than the negative input terminal of the comparator U1, the voltage comparator output is a high level; when the voltage of the positive input terminal of the comparator U1 is lower than the negative input terminal of the comparator U1, the voltage comparator output is a low level.

[0033] In some embodiments, the comparison circuit 30 further includes a positive feedback circuit; one end of the positive feedback circuit is connected to the positive input of the comparator U1, and the other end of the positive feedback circuit is connected to the output of the comparator U1. By introducing the positive feedback circuit, after the comparator U1 switches to a high level, the voltage value of the reference signal output by the reference signal circuit 20 increases, thereby changing the switching value of the comparator U1. When the motor cools down, the comparator U1 can still maintain a high-level output. In this way, the protection circuit can only be released when the user turns off the power to the machine when the motor is cooled. Specifically, the positive feedback circuit includes a fourth resistor R3 and a first diode D1; wherein one end of the fourth resistor R4 is connected to the positive input of the comparator U1, the other end of the fourth resistor R4 is connected to the cathode of the first diode D1, and the anode of the first diode D1 is connected to the output of the comparator U1. In actual applications, the positive feedback circuit can be configured according to actual needs and is not limited here.

[0034] In some embodiments, the motor overheat protection circuit 100 further includes an emitter follower; the emitter follower is used to input the temperature detection signal to the control unit, which can then enable the control unit to set other functions based on the temperature detection signal, such as letting the user know the current temperature of the motor in real time. One end of the emitter follower is connected to the output end of the temperature detection circuit 10, and the other end of the emitter follower is connected to the second end of the control unit 50. For details, please refer to Figure 3 The emitter follower can be an operational amplifier U2, wherein the negative input terminal and the output terminal of the operational amplifier U2 are directly connected to form an emitter follower. At the same time, the positive input terminal of the operational amplifier U2 is connected to the output terminal of the temperature detection circuit 10 through the resistor Rp4, and the output terminal of the operational amplifier U2 is connected to the second terminal of the control unit 50 through the filter circuit, wherein the filter circuit is composed of the resistor Rp5 and the capacitor C3 to form an RC filter circuit. Since the input impedance of the operational amplifier U2 is infinite, the voltage at the positive input terminal of the operational amplifier U2 is equal to the voltage of the temperature detection signal output by the temperature detection circuit 10, and the negative input terminal of the operational amplifier U2 is short-circuited to the output terminal of the operational amplifier U2 to form an emitter follower, so that the voltage at the output terminal of the operational amplifier U2 is equal to the voltage at the positive input terminal of the operational amplifier U2. In this way, the control unit 50 can identify the temperature of the motor 200 based on the voltage at the output terminal of the operational amplifier U2, which can then allow the user to more conveniently know the current temperature of the motor 200, or the control unit 50 can set other controls based on the temperature.

[0035] In order to filter the temperature detection signal and the reference signal, in some embodiments, please continue to refer to Figure 3The temperature detection circuit 10 also includes a first capacitor C1, and the comparison circuit 30 also includes a second capacitor C2; wherein, one end of the first capacitor C1 is connected to the second power supply, and the other end of the first capacitor C1 is connected to the output end of the temperature detection circuit 10; one end of the second capacitor C2 is connected to the positive input end of the comparator U1, and the other end of the second capacitor C2 is grounded. In this way, the first capacitor C1 can be used to filter the temperature detection signal, and the second capacitor C2 can be used to filter the reference signal, so that the motor overheat protection circuit works more stably.

[0036] However, when the motor overheat protection circuit 100 is first powered on, the temperature detection circuit 10 will cause the output temperature detection signal to be unstable due to the charging effect of the first capacitor C1, which will eventually cause the motor overheat protection circuit 100 to malfunction. To prevent the motor overheat protection circuit 100 from being locked at the moment of power-on, the capacity of the second capacitor C2 can be appropriately increased. Specifically, the capacity of the second capacitor C2 can be smaller than the capacity of the first capacitor C1. In this way, when the motor overheat protection circuit 100 is first charged, the voltage across the second capacitor C2 is 0V in the initial state. At this time, the positive input terminal of the comparator U1 is transiently set to 0V, solving the problem of malfunction and preventing the motor overheat protection circuit 100 from being malfunctioning.

[0037] In practical applications, the second power supply and the third power supply are +5V power supplies. The +5V power supplies can be connected by a universal serial bus or by multiple power supplies, which is not limited here.

[0038] The following combination Figure 3 The embodiment shown in the figure illustrates the specific working process of the motor overheat protection circuit provided by the present invention. In particular, the thermistor RT1 is a negative temperature coefficient thermistor, and the thermistor RT1 is insulated and closely mounted to the motor winding of the motor 200.

[0039] First, after the motor overheat protection circuit is powered on, the motor temperature is lower than the preset temperature threshold, the voltage value of the temperature detection signal of the temperature detection circuit 10 is higher than the voltage value of the reference signal of the reference signal circuit 20, the comparator U1 outputs a low level, and the first NPN transistor Q1 is not conducting; then, the control unit 50 first outputs a high-level second control signal to the base of the second NPN transistor Q2. Since the first NPN transistor Q1 is not conducting, at this time, the second NPN transistor Q2 is turned on, turning on the relay RY1 to work, the switch end of the relay RY1 is closed, and the motor is started normally. Similarly, when the control unit 50 outputs a low level, the switch end of the relay RY1 is disconnected, and the motor is shut down normally.

[0040] During motor operation, if improper user operation or other factors cause the motor rotor to stall, causing the motor windings to heat up rapidly, the negative temperature coefficient thermistor RT1 has a very small thermal hysteresis, and its resistance decreases. This reduces the voltage of the temperature detection signal. When the motor winding temperature exceeds a preset temperature threshold, the voltage of the temperature detection signal decreases below the reference signal. At this point, comparator U1 outputs a high level, turning on first NPN transistor Q1, rapidly pulling the base of second NPN transistor Q2 down to 0V. This immediately turns off second NPN transistor Q2, and relay RY1 disconnects the switch terminal, thereby disconnecting the motor power supply and achieving overheat protection. Furthermore, by incorporating a positive feedback circuit consisting of first diode D1 and fourth resistor R4 into comparator U1, the resistance of fourth resistor R4 can be adjusted to ensure that comparator U1 maintains a high level output even after the motor cools down. This protection circuit can only be disabled by the user powering off the machine after the motor has cooled down.

[0041] In summary, the motor overheat protection circuit has a simple structure and is easy to design. At the same time, no software is involved in the protection process, and the protection work is realized through a pure hardware circuit, which reduces the difficulty of energy efficiency certification. The overheat protection is triggered by the comparator. Since the comparator output state has only two states, high and low levels, and the comparator can switch quickly when switching the output state, it can be seen that the circuit is safe and reliable, and the protection accuracy is high. Finally, this circuit is built with conventional components, with low production cost, and can be mass-produced, which is beneficial to manufacturers.

[0042] An embodiment of the present invention provides a motor overheating protection circuit and a motor device, the circuit including a temperature detection circuit, a reference signal circuit, a comparison circuit, a switching circuit and a control unit; the first input end of the comparison circuit is connected to the temperature detection circuit, the second input end is connected to the reference signal circuit, and the output end is connected to the first end of the switching circuit, the temperature detection circuit is used to detect the motor temperature and output a corresponding temperature detection signal, and the comparison circuit is used to output a first control signal based on the temperature detection signal and the reference signal; the second end of the switching circuit is connected to the first end of the control unit, the third end is connected to the motor, and the fourth end is connected to the first power supply, and the switching circuit is used to start or shut down the motor based on the first control signal and the second control signal of the control unit; the circuit is controlled by a hardware circuit, does not require software to participate in protection, and has low difficulty in safety certification.

[0043] It should be noted that the device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A motor overheat protection circuit, characterized in that: include: A temperature detection circuit, a reference signal circuit, a comparison circuit, a switch circuit, an emitter follower and a control unit, wherein the switch circuit includes a first switch unit and a second switch unit; The first switch unit includes a first NPN transistor and a first resistor, and the second switch unit includes a relay, a second NPN transistor and a second resistor; The output end of the temperature detection circuit is connected to the first input end of the comparison circuit, and the temperature detection circuit is used to detect the current temperature of the motor and output a corresponding temperature detection signal; The output end of the reference signal circuit is connected to the second input end of the comparison circuit, and the reference signal circuit is used to output a reference signal; An output end of the comparison circuit is connected to a base of the first NPN transistor and one end of the first resistor, and the comparison circuit is configured to output a first control signal according to the temperature detection signal and the reference signal; The base of the second NPN transistor is respectively connected to the first end of the control unit, the collector of the first NPN transistor and one end of the second resistor, the emitter of the first NPN transistor and the other end of the first resistor are both grounded, the emitter of the second NPN transistor and the other end of the second resistor are both grounded, the collector of the second NPN transistor is connected to the first end of the coil of the relay, the second end of the coil of the relay is connected to the second power supply, the first end of the switch of the relay is connected to the motor, and the second end of the switch of the relay is connected to the first power supply, the first switch unit is used to control the second switch unit to open or close according to the first control signal, and the second switch unit is used to start or stop the motor according to the first control signal and the second control signal of the control unit; One end of the emitter follower is connected to the output end of the temperature detection circuit, and the other end of the emitter follower is connected to the second end of the control unit. The emitter follower is used to input the temperature detection signal to the control unit.

2. The motor overheat protection circuit according to claim 1, characterized in that: The temperature detection circuit includes a third resistor and a thermistor; A first end of the third resistor is connected to a third power supply, a second end of the third resistor is respectively connected to a first end of the thermistor and a first input end of the comparison circuit, and a second end of the thermistor is grounded.

3. The motor overheat protection circuit according to claim 1, characterized in that: The reference signal circuit includes a first reference resistor and a second reference resistor; A first end of the first reference resistor is connected to a third power supply, a second end of the first reference resistor is respectively connected to a first end of the second reference resistor and a second input end of the comparison circuit, and a second end of the second reference resistor is grounded.

4. The motor overheat protection circuit according to claim 1, characterized in that: The comparison circuit includes a comparator; The negative input of the comparator is connected to the output of the temperature detection circuit, the positive input of the comparator is connected to the output of the reference signal circuit, and the output of the comparator is connected to the base of the first NPN transistor and one end of the first resistor.

5. The motor overheat protection circuit according to claim 4, characterized in that: The comparison circuit also includes a positive feedback circuit; One end of the positive feedback circuit is connected to the positive input end of the comparator, and the other end of the positive feedback circuit is connected to the output end of the comparator.

6. The motor overheat protection circuit according to claim 5, characterized in that: The positive feedback circuit includes a fourth resistor and a first diode; One end of the fourth resistor is connected to the positive input end of the comparator, the other end of the fourth resistor is connected to the cathode of the first diode, and the anode of the first diode is connected to the output end of the comparator.

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