Over-temperature protection circuit, PCB and over-temperature protection device
By designing an overtemperature protection circuit including reference voltage unit, comparison unit, sampling voltage unit, thermally resistant oscillation unit and signal enhancement unit, the problem of chip overtemperature under high power output is solved, the stability and reliability of the chip are improved, and the safety risks caused by equipment overheating are prevented.
Patent Information
- Application Number
- CN202411767234.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-04
- Publication Date
- 2025-03-28
AI Technical Summary
Under high power output conditions, the temperature of the circuit chip increases, resulting in a decrease in driving capacity and an increase in the risk of failure, and the existing technology is difficult to effectively solve the problem of overtemperature protection.
An over-temperature protection circuit is designed, including a reference voltage unit, a comparison unit, a sampling voltage unit, a thermally anti-oscillation unit and a signal enhancement unit. By comparing the temperature and threshold values in real time, the temperature control signal is output to realize the chip's working cut-off or restart.
Improves the stability and reliability of the chip when working, prevents overheating from damaging the equipment, extends the service life of the equipment, and prevents fires or safety accidents in applicable scenarios.
Smart Images
Figure CN119726575A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of over-temperature protection, and in particular to an over-temperature protection circuit, a PCB board and an over-temperature protection device. Background Art
[0002] Under high power output conditions, that is, when the output of the circuit is at a larger power level, the entire circuit will experience a significant increase in power consumption during operation, resulting in an increase in the chip temperature during operation; therefore, designing an effective over-temperature protection mechanism is crucial for the stable operation of the chip in the circuit.
[0003] According to current research results, for every 1 degree Celsius increase in the chip's operating temperature, the MOS tube's driving capability will decrease by approximately 4%, and the risk of circuit failure will increase accordingly; in addition, key components such as transistors and capacitors are extremely sensitive to temperature changes. The extreme temperature conditions in the actual working environment, whether too high or too low, will seriously affect the chip's working performance and even cause chip damage.
[0004] It can be seen that the existing technology still needs to be improved and enhanced. Summary of the invention
[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide an over-temperature protection circuit, which can output a temperature control signal in time when the temperature is over or when the temperature is normal to realize chip operation cut-off or chip operation restart, thereby improving the stability and reliability of the chip during operation.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions: An over-temperature protection circuit comprises a reference voltage unit, a comparison unit, a sampling voltage unit, an anti-thermal oscillation unit and a signal enhancement unit; the reference voltage unit is used to generate a reference voltage signal, the sampling voltage unit is used to generate a sampling voltage signal, the output ends of the reference voltage unit and the sampling voltage unit are respectively connected to a first input end and a second input end of the comparison unit; the output end of the comparison unit is connected to an input end of the signal enhancement unit through the anti-thermal oscillation unit, and the signal enhancement unit is used to output a temperature control signal.
[0007] In the over-temperature protection circuit, the reference voltage unit includes a bias voltage unit and a first filter unit, and a signal output end of the bias voltage unit is connected to the first input end of the comparison unit through the first filter unit.
[0008] In the over-temperature protection circuit, the first filtering unit includes a first transistor Q1, a first resistor R1 and an eighteenth field effect transistor M18, the signal output end of the bias voltage unit is connected to the base and collector of the first transistor Q1 and one end of the first resistor R1, the other end of the first resistor R1 is respectively connected to the first input end of the comparison unit and the gate of the eighteenth field effect transistor M18; the emitter of the first transistor Q1 and the source and drain of the eighteenth field effect transistor M18 are respectively grounded.
[0009] In the over-temperature protection circuit, the sampling voltage unit includes a bias current unit and a second filter unit, and a signal output end of the bias current unit is connected to the second input end of the comparison unit through the second filter unit.
[0010] In the over-temperature protection circuit, the second filtering unit includes a second resistor R2 and a nineteenth field effect transistor M19, the signal output end of the bias current unit is connected to one end of the second resistor R2, and the other end of the second resistor R2 is respectively connected to the second input end of the comparison unit and the gate of the nineteenth field effect transistor M19; the source and drain of the nineteenth field effect transistor M19 are respectively grounded.
[0011] In the over-temperature protection circuit, the comparison unit includes a ninth field effect transistor M9, a tenth field effect transistor M10, an eleventh field effect transistor M11 and a voltage difference limiting portion; the source of the ninth field effect transistor M9 is used to connect to an external power supply device, the gate of the ninth field effect transistor M9 is connected to the bias voltage portion, and the drain of the ninth field effect transistor M9 is respectively connected to the source of the tenth field effect transistor M10 and the source of the eleventh field effect transistor M11; the other end of the first resistor R1 is connected to the gate of the tenth field effect transistor M10, the other end of the second resistor R2 is connected to the gate of the eleventh field effect transistor M11, the drain of the tenth field effect transistor M10 and the drain of the eleventh field effect transistor M11 are respectively connected to the voltage difference limiting portion, and the drain of the eleventh field effect transistor M11 is also connected to the input end of the thermal oscillation prevention unit.
[0012] In the over-temperature protection circuit, the anti-thermal oscillation unit includes a non-inverting amplifier and a positive feedback unit, the input end of the non-inverting amplifier is connected to the output end of the comparison unit, the output end of the non-inverting amplifier is connected to one end of the positive feedback unit, and the other end of the positive feedback unit is connected to the input end of the signal enhancement unit.
[0013] In the over-temperature protection circuit, the signal enhancement unit includes a first amplifier, a second amplifier and a third amplifier with the same structure, the input end of the first amplifier is connected to the output end of the anti-thermal oscillation unit, the output end of the first amplifier is connected to the input end of the second amplifier, the output end of the second amplifier is connected to the input end of the third amplifier, and the output end of the third amplifier is used to output a temperature control signal.
[0014] The present application also discloses a PCB board, on which any of the above-mentioned over-temperature protection circuits is printed.
[0015] The present application also discloses an over-temperature protection device, which uses any of the above-mentioned over-temperature protection circuits to achieve working control.
[0016] Beneficial effects: The present invention provides an over-temperature protection circuit, which compares the real-time temperature with the shutdown temperature threshold and the startup temperature threshold through a comparison unit, and can output a temperature control signal in time when the temperature is over or when the temperature is normal to realize the operation cut-off or operation restart of the chip, thereby improving the stability and reliability of the chip when it is working; further, by setting an anti-thermal oscillation unit, thermal oscillation phenomena can be prevented at the moment of opening and closing, and the influence of ripple on the circuit signal can be reduced, and by setting a signal enhancement unit, the gain of the circuit can be improved, the influence of signal distortion and noise interference on the output temperature control signal can be reduced, and the accuracy and reliability of the temperature control signal at the output end can be improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 A circuit block diagram of the over-temperature protection circuit provided by the present invention; Figure 2 This is a circuit schematic diagram of the over-temperature protection circuit provided by the present invention.
[0018] Explanation of main component symbols: 1-reference voltage unit, 11-bias voltage unit, 12-first filtering unit, 2-comparison unit, 3-sampling voltage unit, 31-bias current unit, 32-second filtering unit, 4-anti-thermal oscillation unit, 41-non-inverting amplifier unit, 42-positive feedback unit, 5-signal enhancement unit, 51-first amplifier unit, 52-second amplifier unit, 53-third amplifier unit. DETAILED DESCRIPTION
[0019] The present invention provides an over-temperature protection circuit, a PCB board and an over-temperature protection device. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples.
[0020] In the description of the present invention, it should be understood that the terms "installation", "connection" and the like should be understood in a broad sense, and a person skilled in the art can understand the specific meanings of the above terms in the present invention according to specific circumstances.
[0021] See also Figure 1 and Figure 2 The present invention provides an over-temperature protection circuit, comprising a reference voltage unit 1, a comparison unit 2, a sampling voltage unit 3, an anti-thermal oscillation unit 4 and a signal enhancement unit 5; the reference voltage unit 1 is used to generate a reference voltage signal, the sampling voltage unit 3 is used to generate a sampling voltage signal, the output ends of the reference voltage unit 1 and the sampling voltage unit 3 are respectively connected to the first input end and the second input end of the comparison unit 2; the output end of the comparison unit 2 is connected to the input end of the signal enhancement unit 5 through the anti-thermal oscillation unit 4, and the signal enhancement unit 5 is used to output a temperature control signal.
[0022] The present application discloses an over-temperature protection circuit, which compares the real-time temperature with the shutdown temperature threshold and the startup temperature threshold through a comparison unit 2, and can output a temperature control signal in time when the temperature is over or when the temperature is normal to realize the chip operation cut-off or chip operation restart, thereby improving the stability and reliability of the chip during operation, and can effectively prevent the device from being damaged due to overheating, thereby improving the reliability and service life of the device, and for applicable scenarios such as battery charging and electronic equipment heat dissipation, timely cutting off the chip operation when overtemperature occurs can prevent the device from overheating and causing fire or other safety accidents, thereby protecting the safety of equipment and personnel; further, by setting an anti-thermal oscillation unit 4, thermal oscillation phenomena can be prevented at the moment of opening and closing, and the influence of ripple on the circuit signal can be reduced, and by setting a signal enhancement unit 5, the gain of the circuit can be improved, the influence of signal distortion and noise interference on the output temperature control signal can be reduced, and the accuracy and reliability of the temperature control signal at the output end can be improved.
[0023] For further information, see Figure 1 and Figure 2 The reference voltage unit 1 includes a bias voltage unit 11 and a first filter unit 12 , and a signal output end of the bias voltage unit 11 is connected to a first input end of the comparison unit 2 through the first filter unit 12 .
[0024] In this embodiment, the bias voltage signal generated by the bias voltage unit 11 is processed by the first filter unit 12 and then input to the first input terminal of the comparison unit 2, which can effectively reduce noise interference, improve the stability of the output reference voltage signal, enhance the adaptability of the over-temperature protection circuit to environmental changes, and improve the stability and reliability of the over-temperature protection circuit during operation.
[0025] For further information, see Figure 2The first filtering unit 12 includes a first transistor Q1, a first resistor R1 and an eighteenth field effect transistor M18. The signal output end of the bias voltage unit 11 is connected to the base and collector of the first transistor Q1 and one end of the first resistor R1. The other end of the first resistor R1 is respectively connected to the first input end of the comparison unit 2 and the gate of the eighteenth field effect transistor M18; the emitter of the first transistor Q1 and the source and drain of the eighteenth field effect transistor M18 are respectively grounded.
[0026] In this embodiment, the bias voltage signal generated by the bias voltage unit 11 is processed by the first transistor Q1 to generate a reference voltage signal and input to the first input terminal of the comparison unit 2; the bias voltage unit 11 is a current mirror circuit, including a first field effect transistor M1, a second field effect transistor M2, a third field effect transistor M3, a fourth field effect transistor M4, a fifth field effect transistor M5, a sixth field effect transistor M6, a seventh field effect transistor M7 and an eighth field effect transistor M8; the gate of the sixth field effect transistor M6 is connected to the gate of the ninth field effect transistor M9 of the comparison unit 2, and the drain of the eighth field effect transistor M8 is respectively connected to one end of the first resistor R1 and the collector and base of the first transistor Q1.
[0027] For further information, see Figure 1 and Figure 2 The sampling voltage unit 3 includes a bias current unit 31 and a second filter unit 32 , and a signal output end of the bias current unit 31 is connected to a second input end of the comparison unit 2 through the second filter unit 32 .
[0028] In this embodiment, the sampling voltage signal generated by the bias current unit 31 is processed by the second filter unit 32 and then input to the second input terminal of the comparison unit 2, which can effectively reduce noise interference, improve the stability of the output sampling voltage signal, enhance the adaptability of the over-temperature protection circuit to environmental changes, and improve the stability and reliability of the over-temperature protection circuit during operation.
[0029] In this embodiment, the bias current unit 31 includes a current mirror circuit consisting of a twentieth field effect transistor M20, a twenty-first field effect transistor M21, a twenty-second field effect transistor M22, a twenty-third field effect transistor M23 and a twenty-fourth field effect transistor M24, and a third resistor R3; the current mirror circuit is used to generate a saturation current, and generate a sampling voltage signal through the third resistor R3 to be input to the second filtering unit 32; the drain of the twenty-first field effect transistor M21, the source of the twenty-fourth field effect transistor M24 and one end of the third resistor R3 are respectively connected to one end of the second resistor R2; the gate of the twenty-fourth field effect transistor M24 is also connected to the input end of the third amplifier 53.
[0030] For further information, see Figure 2 The second filtering unit 32 includes a second resistor R2 and a nineteenth field effect transistor M19. The signal output end of the bias current unit 31 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is respectively connected to the second input end of the comparison unit 2 and the gate of the nineteenth field effect transistor M19; the source and drain of the nineteenth field effect transistor M19 are respectively grounded.
[0031] For further information, see Figure 2 The comparison unit 2 includes a ninth field effect transistor M9, a tenth field effect transistor M10, an eleventh field effect transistor M11 and a voltage difference limiting part; the source of the ninth field effect transistor M9 is used to connect to an external power supply device, the gate of the ninth field effect transistor M9 is connected to the bias voltage part 11, and the drain of the ninth field effect transistor M9 is respectively connected to the source of the tenth field effect transistor M10 and the source of the eleventh field effect transistor M11; the other end of the first resistor R1 is connected to the gate of the tenth field effect transistor M10, the other end of the second resistor R2 is connected to the gate of the eleventh field effect transistor M11, the drain of the tenth field effect transistor M10 and the drain of the eleventh field effect transistor M11 are respectively connected to the voltage difference limiting part, and the drain of the eleventh field effect transistor M11 is also connected to the input end of the thermal oscillation prevention unit 4.
[0032] In this example, see Figure 2 The voltage difference limiting unit includes a twelfth field effect transistor M12, a thirteenth field effect transistor M13, a fourteenth field effect transistor M14, a fifteenth field effect transistor M15, a sixteenth field effect transistor M16 and a seventeenth field effect transistor M17; the drain of the tenth field effect transistor M10 is connected to the drain of the thirteenth field effect transistor M13, and the drain of the eleventh field effect transistor M11 is connected to the drain of the fifteenth field effect transistor M15; the voltage difference limiting unit is used to process and adjust the voltage signals from the tenth field effect transistor M10 and the eleventh field effect transistor M11 to ensure that these signals are within a safe and stable range and prevent circuit failure or instability caused by excessive voltage difference.
[0033] The comparison unit 2 disclosed in the present application has the following working modes: When the chip initially starts working, it is at room temperature. At this time, the sampling voltage signal is greater than the reference voltage signal, the eleventh field effect tube M11 is turned on so that the voltage on the first resistor R1 is zero, and the output temperature control signal is high level; as the operating temperature of the chip increases, since the transistor has a negative temperature coefficient, the sampling voltage signal gradually decreases as the operating temperature increases. When the sampling voltage signal is consistent with the reference voltage signal, the threshold point of the shutdown temperature can be calculated based on the sampling voltage value, the reference voltage value, the BE voltage of the first transistor Q1, and the resistance value of the second resistor R2; when the sampling voltage signal is lower than the reference voltage signal, the eleventh field effect tube M11 is turned off and the output temperature control signal is low level. At this time, the chip will automatically stop working, that is, the timely shutdown function when overtemperature is realized; As the chip stops working, the working temperature of the chip will continue to decrease, the reference voltage signal will gradually decrease as the temperature drops, and the sampling voltage signal will gradually increase as the temperature rises. When the reference voltage signal is consistent with the sampling voltage signal, the threshold point of the start-up temperature can be calculated according to the sampling voltage value, the reference voltage value, the BE voltage of the first transistor Q1, the resistance value of the first resistor R1, and the resistance value of the second resistor R2. When the sampling voltage signal is greater than the reference voltage signal, the first field effect tube M11 is turned on and the output temperature control signal is high. At this time, the chip automatically resumes the working state, that is, the automatic restart function when the temperature is normal is realized, and the stability and continuity of the circuit during operation are improved; From the foregoing, it can be seen that the temperature hysteresis can be calculated by the threshold point of the shutdown temperature and the threshold point of the startup temperature. In the actual working process, the threshold point of the shutdown temperature can be adjusted by adjusting the resistance of the second resistor R2, and the temperature hysteresis can be adjusted by adjusting the resistance of the first resistor R1 to achieve the adjustment of the threshold point of the startup temperature. The shutdown temperature threshold and the startup temperature threshold can be adjusted according to the actual application scenario of the over-temperature protection circuit to adapt to different temperature environments and working conditions, thereby improving the flexibility of the over-temperature protection circuit during operation and expanding its scope of application.
[0034] For further information, see Figure 1 and Figure 2 The anti-thermal oscillation unit 4 includes a non-inverting amplifier 41 and a positive feedback unit 42. The input end of the non-inverting amplifier 41 is connected to the output end of the comparison unit 2, the output end of the non-inverting amplifier 41 is connected to one end of the positive feedback unit 42, and the other end of the positive feedback unit 42 is connected to the input end of the signal enhancement unit 5.
[0035] In this example, see Figure 2The non-inverting amplifier 41 includes a twenty-fifth field effect transistor M25, a twenty-sixth field effect transistor M26, a twenty-seventh field effect transistor M27 and a twenty-eighth field effect transistor M28; the positive feedback unit 42 includes a twenty-ninth field effect transistor M29 and a thirtieth field effect transistor M30; the gate of the twenty-fifth field effect transistor M25, the gate of the twenty-sixth field effect transistor M26, the gate of the twenty-seventh field effect transistor M27 and the gate of the twenty-eighth field effect transistor M28 are respectively connected to the drain of the eleventh field effect transistor M11; the source of the twenty-fifth field effect transistor M25 and the source of the twenty-sixth field effect transistor M28 are connected to the drain of the eleventh field effect transistor M11; The drain of the transistor M26 is respectively connected to the drain of the twenty-ninth field effect transistor M29, the source of the twenty-sixth field effect transistor M26 and the drain of the twenty-seventh field effect transistor M27 are respectively connected to the gate of the twenty-ninth field effect transistor M29 and the thirtieth field effect transistor M30, the source of the twenty-seventh field effect transistor M27 and the drain of the twenty-eighth field effect transistor M28 are respectively connected to the source of the thirtieth field effect transistor M30, and the gate of the twenty-ninth field effect transistor M29 and the gate of the thirtieth field effect transistor M30 are also connected to the input end of the signal enhancement unit 5.
[0036] In this embodiment, the anti-thermal oscillation unit 4 is a Schmitt circuit, which has two stable states and can switch between the two states according to the level change of the input signal. When the input signal changes between two threshold levels, the output signal will jump from a low level to a high level, or from a high level to a low level, thereby realizing the signal shaping and de-jittering functions; in the Schmitt circuit, the output of the non-inverting amplifier 41 is partially or completely fed back to its input end to form a closed loop; the function of the positive feedback part 42 is to feed back part or all of the output signal to the input end of the non-inverting amplifier 41 without changing the phase, thereby enhancing the signal in the circuit. When this feedback reaches a certain condition, the circuit will generate self-oscillation and output a stable periodic signal.
[0037] For further information, see Figure 1 and Figure 2 The signal enhancement unit 5 includes a first amplifier 51, a second amplifier 52 and a third amplifier 53 with the same structure. The input end of the first amplifier is connected to the output end of the thermal oscillation protection unit 4, the output end of the first amplifier is connected to the input end of the second amplifier 52, the output end of the second amplifier 52 is connected to the input end of the third amplifier 53, and the output end of the third amplifier 53 is used to output a temperature control signal.
[0038] In this embodiment, the first amplifier unit includes a thirty-first field effect transistor M31 and a thirty-second field effect transistor M32, the second amplifier unit 52 includes a thirty-third field effect transistor M33 and a thirty-fourth field effect transistor M34, and the third amplifier unit 53 includes a thirty-fifth field effect transistor M35 and a thirty-sixth field effect transistor M36; the gates of the thirty-first field effect transistor M31 and the thirty-second field effect transistor M32 are respectively connected to the output end of the positive feedback unit 42, the drain of the thirty-first field effect transistor M31 and the drain of the thirty-second field effect transistor M32 are respectively connected to the gate of the thirty-third field effect transistor M33 and the gate of the thirty-fourth field effect transistor M34; the drain of the thirty-third field effect transistor M33 and the drain of the thirty-fourth field effect transistor M34 are respectively connected to the gate of the thirty-fifth field effect transistor M35 and the gate of the thirty-sixth field effect transistor M36; the drain of the thirty-fifth field effect transistor M35 and the drain of the thirty-sixth field effect transistor M36 are used to output a temperature control signal.
[0039] In this embodiment, the first amplifier, the second amplifier 52 and the third amplifier 53 constitute a cascade driver. Cascading refers to connecting multiple circuit units, such as field effect transistors, in a certain order so that the output of the previous circuit unit becomes the input of the next circuit unit, thereby realizing step-by-step amplification or processing of the signal. The cascade method can significantly improve the gain and performance of the circuit to obtain a stronger output signal.
[0040] The present application also discloses a PCB board, on which any of the above-mentioned over-temperature protection circuits is printed.
[0041] The present application also discloses an over-temperature protection device, which uses any of the above-mentioned over-temperature protection circuits to achieve working control.
[0042] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the present invention.
Claims
1. An over-temperature protection circuit, characterized in that: It includes a reference voltage unit, a comparison unit, a sampling voltage unit, an anti-thermal oscillation unit and a signal enhancement unit; the reference voltage unit is used to generate a reference voltage signal, the sampling voltage unit is used to generate a sampling voltage signal, the output ends of the reference voltage unit and the sampling voltage unit are respectively connected to the first input end and the second input end of the comparison unit; the output end of the comparison unit is connected to the input end of the signal enhancement unit through the anti-thermal oscillation unit, and the signal enhancement unit is used to output a temperature control signal.
2. An over-temperature protection circuit according to claim 1, characterized in that: The reference voltage unit includes a bias voltage unit and a first filter unit, and a signal output terminal of the bias voltage unit is connected to a first input terminal of the comparison unit through the first filter unit.
3. An over-temperature protection circuit according to claim 2, characterized in that: The first filtering unit includes a first transistor Q1, a first resistor R1 and an eighteenth field effect transistor M18. The signal output end of the bias voltage unit is connected to the base and collector of the first transistor Q1 and one end of the first resistor R1. The other end of the first resistor R1 is respectively connected to the first input end of the comparison unit and the gate of the eighteenth field effect transistor M18; the emitter of the first transistor Q1 and the source and drain of the eighteenth field effect transistor M18 are respectively grounded.
4. An over-temperature protection circuit according to claim 3, characterized in that: The sampling voltage unit includes a bias current unit and a second filter unit, and a signal output terminal of the bias current unit is connected to a second input terminal of the comparison unit through the second filter unit.
5. An over-temperature protection circuit according to claim 4, characterized in that: The second filtering unit includes a second resistor R2 and a nineteenth field effect transistor M19, the signal output end of the bias current unit is connected to one end of the second resistor R2, and the other end of the second resistor R2 is respectively connected to the second input end of the comparison unit and the gate of the nineteenth field effect transistor M19; the source and drain of the nineteenth field effect transistor M19 are respectively grounded.
6. An over-temperature protection circuit according to claim 5, characterized in that: The comparison unit includes a ninth field effect transistor M9, a tenth field effect transistor M10, an eleventh field effect transistor M11 and a voltage difference limiting portion; the source of the ninth field effect transistor M9 is used to connect to an external power supply device, the gate of the ninth field effect transistor M9 is connected to the bias voltage portion, and the drain of the ninth field effect transistor M9 is respectively connected to the source of the tenth field effect transistor M10 and the source of the eleventh field effect transistor M11; the other end of the first resistor R1 is connected to the gate of the tenth field effect transistor M10, the other end of the second resistor R2 is connected to the gate of the eleventh field effect transistor M11, the drain of the tenth field effect transistor M10 and the drain of the eleventh field effect transistor M11 are respectively connected to the voltage difference limiting portion, and the drain of the eleventh field effect transistor M11 is also connected to the input end of the thermal oscillation prevention unit.
7. The over-temperature protection circuit according to claim 1, characterized in that: The anti-thermal oscillation unit includes a non-inverting amplifier and a positive feedback unit, the input end of the non-inverting amplifier is connected to the output end of the comparison unit, the output end of the non-inverting amplifier is connected to one end of the positive feedback unit, and the other end of the positive feedback unit is connected to the input end of the signal enhancement unit.
8. The over-temperature protection circuit according to claim 1, characterized in that: The signal enhancement unit includes a first amplifier, a second amplifier and a third amplifier with the same structure. The input end of the first amplifier is connected to the output end of the thermal oscillation protection unit, the output end of the first amplifier is connected to the input end of the second amplifier, the output end of the second amplifier is connected to the input end of the third amplifier, and the output end of the third amplifier is used to output a temperature control signal.
9. A PCB board, characterized in that: The PCB board is printed with the over-temperature protection circuit as described in any one of claims 1 to 8.
10. An over-temperature protection device, characterized in that: The over-temperature protection device uses the over-temperature protection circuit described in any one of claims 1-8 to achieve working control.