A temperature protection circuit

Abstract

The application relates to the technical field of power supply circuits and discloses a temperature protection circuit which comprises a heat-sensitive unit, a voltage acquisition unit, a control processing unit and an alarm prompting unit. The heat-sensitive unit monitors the temperature of a target device in real time and outputs a corresponding electric signal, and the voltage acquisition unit acquires the electric signal and converts the electric signal into a voltage signal. The control processing unit comprises a timing pulse trigger subunit, a delay subunit, a heat source subunit and a comparison subunit. The timing pulse trigger subunit generates a periodic signal to start detection. The heat source subunit applies a preset heating amount to the device under the triggering of the heat source subunit. The delay subunit controls the heating duration. The comparison subunit compares the voltage signal after heating with a reference voltage signal to judge the deviation between the actual and reference temperature rise values. The alarm prompting unit sends an alarm signal when the deviation exceeds a preset range, can accurately identify the temperature abnormality of the device and improves the protection reliability.

Description

Technical Field

[0001] This application relates to the technical field of power supply circuits, and in particular to a temperature protection circuit. Background Technology

[0002] With the popularization of LED lighting technology, LED drivers, as the core components that ensure the stable operation of LEDs, provide stable operating current for LEDs and avoid current fluctuations that could lead to accelerated light decay or burnout of LEDs. Their performance directly determines the luminous efficiency and lifespan of LEDs.

[0003] During operation, LED drivers generate heat from internal power semiconductor devices (such as MOSFETs and rectifier bridges) due to power loss. This heat is particularly pronounced under high loads, prolonged operation, or in poorly ventilated environments, causing the driver temperature to rise continuously. If the temperature exceeds a safe threshold, it can accelerate the aging of internal components, cause output current drift, and even lead to driver circuit burnout and LED light source damage. In severe cases, overheating can pose safety hazards. Therefore, LED drivers must be equipped with temperature protection functions to monitor the temperature in real time and trigger protective actions to ensure equipment safety.

[0004] Current temperature protection solutions for LED drivers mostly rely on a single thermistor (such as an NTC thermistor or PTC thermistor) for temperature monitoring and protection. While this solution is simple and low-cost, it has significant drawbacks: when a single thermistor fails due to aging, impact, or circuit malfunction, not only does the temperature protection function completely fail, failing to protect against overheating risks in the LED driver, but it also cannot report the abnormal state of the thermistor damage to external equipment or users, making it difficult for staff to detect faults in a timely manner. Utility Model Content

[0005] To indicate the operating status of the thermistor in a temperature protection circuit, this application provides a temperature protection circuit employing the following technical solution:

[0006] A temperature protection circuit includes a thermistor, a voltage acquisition unit, a control processing unit, and an alarm indication unit;

[0007] The thermal unit is used to monitor the temperature of the target device in real time and output an electrical signal corresponding to the temperature;

[0008] The input terminal of the voltage acquisition unit is electrically connected to the output terminal of the thermistor unit, and is used to acquire the electrical signal output by the thermistor unit and convert it into a voltage signal;

[0009] The control processing unit includes a timing pulse trigger subunit, a delay subunit, a heat source subunit, and a comparison subunit. The input terminal of the control processing unit is electrically connected to the output terminal of the voltage acquisition unit, wherein:

[0010] The timing pulse triggering subunit is used to generate periodic trigger signals to periodically initiate the temperature detection process of the target device;

[0011] The heat source subunit is used to apply a preset heating amount to the target device under the triggering of the timing pulse triggering subunit;

[0012] The delay subunit is associated with the heat source subunit and is used to control the heating duration of the heat source subunit so that the target device completes heating within a preset time.

[0013] The first input terminal of the comparison subunit receives the voltage signal output by the voltage acquisition unit after heating, and the second input terminal is connected to the reference voltage signal for comparing the actual temperature rise value with the reference temperature rise value.

[0014] The input terminal of the alarm notification unit is electrically connected to the output terminal of the comparison subunit. When the comparison subunit determines that the deviation between the actual temperature rise value and the reference temperature rise value exceeds a preset range, the alarm notification unit is triggered to issue an alarm signal.

[0015] By adopting the above technical solution, on the one hand, with the cooperation of the timed pulse trigger subunit and the heat source subunit, the target equipment can be actively heated and detected periodically. Combined with the delay subunit, the heating time can be precisely controlled, avoiding the lag of traditional passive monitoring. On the other hand, by comparing the actual temperature rise value after heating with the reference temperature rise value by the comparison subunit, it can not only identify the target equipment overheating in time, but also quickly detect the abnormal monitoring caused by the aging or failure of the thermal unit, and then issue an alarm signal simultaneously through the alarm prompt unit.

[0016] Optionally, the heat source subunit includes an electric heating wire or a heat-conducting component that is attached to the heat dissipation concentration area of ​​the target device;

[0017] The electric heating wire achieves active heating of the target device through controlled conduction;

[0018] The heat-conducting component forms a local heat source by conducting the heat generated by the operation of the target device itself, so as to apply a preset heating amount to a specific area of ​​the target device.

[0019] By adopting the above technical solutions, the electric heating wire can provide a stable and controllable active heating amount through controlled conduction, ensuring that heating conditions can still be accurately simulated when the target equipment is under low load and generates less heat, thus guaranteeing the effectiveness of the testing process. Meanwhile, the heat-conducting component that is attached to the heat dissipation concentration area can use the heat generated by the equipment itself to form a local heat source, reducing additional energy consumption while better matching the actual heating state of the equipment and improving the realism of the heating simulation.

[0020] Optionally, the timing pulse triggering subunit includes a 555 timer or a manual switch. The output of the 555 timer is connected to the input of the heat source subunit through an optocoupler to output a periodic pulse signal and start the heating of the heat source subunit. Alternatively, one end of the manual switch is connected to a DC power supply, and the other end is connected to the input of the heat source subunit through an optocoupler.

[0021] By adopting the above technical solutions, a longer trigger cycle can be used to reduce unnecessary detection energy consumption during the low load or initial operation phase of the equipment. When the equipment enters high load operation, heat dissipation pressure increases, or monitoring needs to be strengthened, the trigger cycle can be gradually shortened through manual operation or semi-automatic control, which can improve the density and timeliness of temperature detection.

[0022] Optionally, the delay subunit includes an RC delay circuit or a 555 timer; the RC delay circuit includes a capacitor and a resistor connected in series, with the end of the resistor away from the capacitor grounded, and the end of the capacitor away from the resistor electrically connected to the input terminal of the heat source subunit; or, the output terminal of the 555 timer is electrically connected to the input terminal of the heat source subunit to output a delay signal for controlling the heating duration of the heat source subunit.

[0023] By adopting the above technical solution, the RC delay circuit can adjust the charging and discharging time by adjusting the resistance value or capacitance value to achieve the delay duration adjustment; the 555 timer can output a delay signal of fixed duration by setting the parameters of the peripheral components to control the heating duration of the heat source subunit.

[0024] Optionally, the output terminal of the voltage acquisition unit is connected to the input terminal of the inverting amplifier, the output terminal of the inverting amplifier is connected to the input terminal of the inverter, the output terminal of the inverter is connected to the input terminal of the comparator subunit, and the output terminal of the inverter is grounded through a filter capacitor.

[0025] Optionally, the comparison subunit adopts a single threshold comparison circuit, including a voltage comparator. The power supply Vcc is connected to ground after being connected in series with resistors R4 and R5. The connection point of R4 and R5 is the output point of the reference voltage Vref, which is connected to the inverting input terminal of the voltage comparator. The Vcc pin of the voltage comparator is connected to the power supply Vcc, and the GND pin is grounded. The temperature and voltage signal after heating acquired by the voltage acquisition unit is filtered and connected to the non-inverting input terminal of the voltage comparator. The other end of the filter capacitor C1 is grounded. The output terminal of the voltage comparator is connected to the power supply Vcc through the pull-up resistor R6, and the output terminal is also connected to the alarm indication unit.

[0026] By adopting the above technical solution, the single threshold comparison circuit has a simple structure. It can quickly determine the overheating state of the target device with only one voltage comparator and can quickly trigger an alarm when the actual temperature rise exceeds the safety threshold.

[0027] Optionally, the comparison subunit adopts a dual threshold window comparison circuit, including two voltage comparators. One voltage comparator has its non-inverting input terminal connected to the lower limit reference voltage threshold signal and its inverting input terminal receiving the voltage signal output by the voltage acquisition unit after heating. The other voltage comparator has its non-inverting input terminal receiving the voltage signal and its inverting input terminal connected to the upper limit reference voltage threshold signal. When the voltage signal is lower than the lower limit reference voltage threshold signal or higher than the upper limit reference voltage threshold signal, a trigger signal is output to the alarm indication unit.

[0028] By adopting the above technical solution, the dual threshold window comparison circuit can simultaneously monitor the actual temperature rise value as too low or too high. It can trigger an alarm when the target device is overheated (exceeding the upper threshold) and provide timely warning when the thermal unit is damaged, causing the monitored value to be abnormally low (below the lower threshold).

[0029] Optionally, the thermal unit includes two thermal elements located close to each other but not overlapping. The two thermal elements are electrically connected to the two input terminals of the voltage acquisition unit, respectively. The two output terminals of the voltage acquisition unit are electrically connected to the two input terminals of a differential amplifier. The output terminal of the differential amplifier is electrically connected to the input terminal of a comparator. The other input terminal of the comparator is connected to a differential reference voltage. The output terminal of the comparator is electrically connected to the input terminal of an abnormal alarm unit. When the deviation between the actual voltage signal difference and the differential reference voltage exceeds a preset range, the abnormal alarm unit is triggered to issue an alarm signal.

[0030] By adopting the above technical solution, the close-range setting of dual thermistors can ensure the monitoring of the temperature in the same area. By comparing the signals, abnormalities such as aging and damage of a single thermistor can be quickly identified, avoiding the protection blind spot caused by the failure of a traditional single thermistor. At the same time, the monitoring function for exceeding temperature limits is retained. Attached Figure Description

[0031] Figure 1 This is a block diagram of a temperature protection circuit.

[0032] Figure 2 This is a temperature protection circuit diagram, in which the comparison subunit includes a comparator.

[0033] Figure 3 This is another temperature protection circuit diagram, in which the comparator subunit includes two comparators.

[0034] Figure 4 This is a circuit diagram of two thermistors. Detailed Implementation

[0035] The embodiments of this application are described in detail below, and examples of the embodiments are shown in the accompanying drawings.

[0036] This application discloses a temperature protection circuit, referring to... Figure 1 It includes a thermal sensing unit, a voltage acquisition unit, a control processing unit, and an alarm display unit.

[0037] The thermistor unit is responsible for real-time monitoring of the target device temperature and outputting an electrical signal that matches the temperature; the input terminal of the voltage acquisition unit is electrically connected to the output terminal of the thermistor unit, and can acquire the electrical signal and convert it into a voltage signal.

[0038] The control processing unit includes a timing pulse trigger subunit, a delay subunit, a heat source subunit, and a comparison subunit. Its input terminals are electrically connected to the output terminals of the voltage acquisition unit. The timing pulse trigger subunit generates a periodic trigger signal to periodically start the temperature detection process of the target device. Under the action of the trigger signal, the heat source subunit applies a preset heating amount to the target device. The delay subunit is linked with the heat source subunit to ensure that the target device completes heating within a preset time by controlling the heating duration. The first input terminal of the comparison subunit receives the voltage signal output by the voltage acquisition unit after heating, and the second input terminal is connected to the reference voltage signal to compare the actual temperature rise value with the reference temperature rise value.

[0039] The input terminal of the alarm notification unit is electrically connected to the output terminal of the comparison subunit. When the comparison subunit determines that the deviation between the two exceeds the preset range, it will trigger the alarm notification unit to output an alarm signal.

[0040] On the one hand, the circuit achieves periodic active heating detection of the target device through the coordination of the timing pulse trigger subunit and the heat source subunit, and with the delay subunit for precise temperature control, it solves the problem of lag in traditional passive monitoring. On the other hand, relying on the comparison function of the comparison subunit, it can not only identify the overheating of the target device itself in a timely manner, but also quickly detect the monitoring abnormalities caused by aging or failure of the thermal unit, and then the alarm prompt unit will issue an alarm signal simultaneously.

[0041] Reference Figure 2 The heat source subunit includes an electric heating wire or a heat-conducting component that is attached to the heat dissipation concentration area of ​​the target device;

[0042] Implementation method 1: The electric heating wire RS achieves active heating of the target device through controlled conduction.

[0043] Implementation Method 2: The heat-conducting component forms a local heat source by conducting the heat generated by the operation of the target device itself, so as to apply a preset heating amount to a specific area of ​​the target device.

[0044] The electric heating wire can provide a stable and controllable active heating amount through controlled conduction, ensuring that heating conditions can still be accurately simulated when the target equipment is under low load and generates less heat, thus guaranteeing the effectiveness of the testing process. Meanwhile, the heat-conducting component that is attached to the heat dissipation concentration area can use the heat generated by the equipment itself to form a local heat source, reducing additional energy consumption while more closely matching the actual heating state of the equipment and improving the realism of the heating simulation.

[0045] Reference Figure 2 and Figure 3 The timing pulse trigger subunit includes a 555 timer or a manual switch S. The output of the 555 timer is connected to the input of the heat source subunit via an optocoupler, specifically to one end of the heating wire RS, with the other end grounded. The 555 timer outputs a periodic pulse signal to activate the heating of the heat source subunit, triggering it weekly or bi-weekly to detect the thermistor. Alternatively, one end of the manual switch S is connected to a DC power supply, and the other end is connected to the input of the heat source subunit via an optocoupler. This allows for manual closing and periodic detection.

[0046] During the low-load or initial operation phase of the equipment, a longer trigger cycle can be used to reduce unnecessary detection energy consumption; while when the equipment enters high-load operation, heat dissipation pressure increases, or monitoring needs to be strengthened, the trigger cycle can be gradually shortened through manual operation or semi-automatic control, which can improve the density and timeliness of temperature detection.

[0047] The delay subunit includes an RC delay circuit or a 555 timer. The RC delay circuit includes a capacitor C1 and a resistor R8 connected in series. The end of the resistor R8 away from the capacitor C1 is grounded, and the end of the capacitor C1 away from the resistor R8 is electrically connected to the input terminal of the heat source subunit. Alternatively, the output terminal of the 555 timer is electrically connected to the input terminal of the heat source subunit to output a delay signal, which is used to control the heating duration of the heat source subunit.

[0048] The RC delay circuit adjusts the charging and discharging time by changing the resistance or capacitance value to achieve the delay duration adjustment; the 555 timer outputs a delay signal of fixed duration by setting the parameters of the external components, which is used to control the heating duration of the heat source subunit.

[0049] The output of the voltage acquisition unit is connected to the input of the inverting amplifier U1, the output of the inverting amplifier U1 is connected to the input of the inverter, the output of the inverter is connected to the input of the comparator subunit, and the output of the inverter is grounded through the filter capacitor C2.

[0050] Reference Figure 2The comparison subunit adopts a single threshold comparison circuit, including a voltage comparator U2. The power supply Vcc is connected to ground after being connected in series with resistors R4 and R5. The connection point of R4 and R5 is the output point of the reference voltage Vref, which is connected to the inverting input terminal of the voltage comparator U2. The Vcc pin of the voltage comparator U2 is connected to the power supply Vcc, and the GND pin is grounded. The temperature voltage signal after heating acquired by the voltage acquisition unit is filtered and connected to the non-inverting input terminal of the voltage comparator U2. The other end of the filter capacitor C1 is grounded. The output terminal of the voltage comparator U2 is connected to the power supply Vcc through the pull-up resistor R6, and the output terminal is also connected to the alarm indication unit.

[0051] The single threshold comparison circuit has a simple structure and can quickly determine the overheating state of the target device using only a voltage comparator. It can quickly trigger an alarm when the actual temperature rise exceeds the safety threshold.

[0052] The alarm unit includes a transistor Q1, a resistor R7, and an LED. The output of the voltage comparator U2 is electrically connected to the base of the NPN transistor Q1. The emitter of the transistor Q1 is electrically connected to the positive terminal of the LED. The negative terminal of the LED is grounded. The collector of the transistor Q1 is electrically connected to the power supply VCC through the resistor R7.

[0053] One end of capacitor C1 is connected to the heating wire RS, which is then connected to the gate (G) of the NMOS transistor. The drain (D) of the NMOS transistor is connected to the power supply Vcc, and the source (S) of the NMOS transistor is connected to the positive terminal of relay KM1. The negative terminal of KM1 is grounded through resistor R9. The normally open switch controlled by KM1 is connected in series between the power supply terminal of voltage comparator U2 and the power supply Vcc to control whether the comparator subunit is working.

[0054] After the heating wire RS is energized for a certain period, capacitor C1 in the RC delay circuit gradually charges. When the voltage reaches the trigger voltage of the NMOS transistor, the relay activates, K1 closes, and the comparator subunit can then operate, performing the comparison operation on the processed data collected by the thermistor. When the delayed heating ends, capacitor C1 in the RC delay circuit discharges. When the voltage at the gate (G) of the NMOS transistor is insufficient to turn it on, the comparison operation of the comparator subunit ends.

[0055] Reference Figure 3In other embodiments, the comparison subunit employs a dual-threshold window comparison circuit, including two voltage comparators U21 and U22. The non-inverting input of voltage comparator U21 is connected to the lower limit reference voltage threshold signal URL, and the inverting input receives the voltage signal output by the voltage acquisition unit after heating. The non-inverting input of voltage comparator U22 receives the voltage signal, and the inverting input is connected to the upper limit reference voltage threshold signal URH. When the voltage signal is lower than the lower limit reference voltage threshold signal URH or higher than the upper limit reference voltage threshold signal URL, a trigger signal is output to the alarm indication unit. The alarm indication unit is the same as the alarm circuit of the aforementioned transistor Q1.

[0056] The dual threshold window comparison circuit can simultaneously monitor both excessively low and excessively high actual temperature values. It can trigger an alarm when the target device is overheated (exceeding the upper threshold) and provide timely warnings when the thermal unit is damaged, causing the monitored value to be abnormally low (below the lower threshold).

[0057] Reference Figure 4 The thermal unit includes two thermal elements RT1 and RT2 located close to each other but not overlapping. The two thermal elements RT1 and RT2 are electrically connected to the two input terminals of the voltage acquisition unit, respectively. The two output terminals of the voltage acquisition unit are electrically connected to the two input terminals of the differential amplifier. The output terminal of the differential amplifier is electrically connected to the input terminal of the comparator. The other input terminal of the comparator is connected to the differential reference voltage. The output terminal of the comparator is electrically connected to the input terminal of the abnormal alarm unit. When the deviation between the actual voltage signal difference and the differential reference voltage exceeds a preset range, the abnormal alarm unit is triggered to issue an alarm signal.

[0058] The abnormal alarm unit includes a transistor Q3, a resistor R11, and an LED. The output of the comparator is electrically connected to the base of the NPN transistor Q3. At the same time, the output of the comparator is also electrically connected to the power supply VCC through a pull-up resistor R10. The emitter of the transistor Q3 is electrically connected to the positive terminal of the LED, the negative terminal of the LED is grounded, and the collector of the transistor Q3 is electrically connected to the power supply VCC through a resistor R11.

[0059] The close proximity of the dual thermistors ensures monitoring of the temperature in the same area. By comparing the signals, abnormalities such as aging or damage of a single thermistor can be quickly identified, avoiding the protection blind spots caused by the failure of a traditional single thermistor. At the same time, the monitoring function for exceeding temperature limits is retained.

[0060] In other embodiments, the thermistor unit also includes an alternating switching circuit connected to the two thermistors; the alternating switching circuit is implemented using a resonant circuit. The alternating switching circuit is electrically connected to a timing pulse trigger subunit and is used to alternately conduct the path between one of the thermistors and the voltage acquisition unit under the trigger of a timing pulse signal, allowing the two thermistors to alternately participate in temperature monitoring. When the comparison subunit determines that the signal of the currently operating thermistor is normal, the alternating switching mode is maintained. When any thermistor is determined to be abnormal, the circuit switches to a single normal thermistor continuously operating and triggers an alarm. Specifically, the circuit can be implemented using two thermistor acquisition circuits. In both acquisition circuits, the outputs of the two comparators are connected to alarm units. If the LEDs of the alarm units are both off, it indicates that they are both normal; if one LED is on, it indicates an abnormality. In this case, the on / off status of the LED can be monitored using an optocoupler, thereby using the abnormal signal as a switching signal to control the operation of the optocoupler output. A relay can be set at the optocoupler-isolated output, for example, to short-circuit control the acquisition circuit where the thermistor RT2 is located.

[0061] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A temperature protection circuit, characterized in that, It includes a thermal sensing unit, a voltage acquisition unit, a control processing unit, and an alarm display unit; The thermal unit is used to monitor the temperature of the target device in real time and output an electrical signal corresponding to the temperature; The input terminal of the voltage acquisition unit is electrically connected to the output terminal of the thermistor unit, and is used to acquire the electrical signal output by the thermistor unit and convert it into a voltage signal; The control processing unit includes a timing pulse trigger subunit, a delay subunit, a heat source subunit, and a comparison subunit. The input terminal of the control processing unit is electrically connected to the output terminal of the voltage acquisition unit, wherein: The timing pulse triggering subunit is used to generate periodic trigger signals to periodically initiate the temperature detection process of the target device; The heat source subunit is used to apply a preset heating amount to the target device under the triggering of the timing pulse triggering subunit; The delay subunit is associated with the heat source subunit and is used to control the heating duration of the heat source subunit so that the target device completes heating within a preset time. The first input terminal of the comparison subunit receives the voltage signal output by the voltage acquisition unit after heating, and the second input terminal is connected to the reference voltage signal for comparing the actual temperature rise value with the reference temperature rise value. The input terminal of the alarm notification unit is electrically connected to the output terminal of the comparison subunit. When the comparison subunit determines that the deviation between the actual temperature rise value and the reference temperature rise value exceeds a preset range, the alarm notification unit is triggered to issue an alarm signal.

2. The temperature protection circuit according to claim 1, characterized in that, The heat source subunit includes an electric heating wire or a heat-conducting component that is attached to the heat dissipation concentration area of ​​the target device; The electric heating wire achieves active heating of the target device through controlled conduction; The heat-conducting component forms a local heat source by conducting the heat generated by the operation of the target device itself, so as to apply a preset heating amount to a specific area of ​​the target device.

3. The temperature protection circuit according to claim 2, characterized in that, The timing pulse triggering subunit includes a 555 timer or a manual switch. The output of the 555 timer is connected to the input of the heat source subunit through an optocoupler to output a periodic pulse signal and start the heating of the heat source subunit. Alternatively, one end of the manual switch is connected to a DC power supply, and the other end is connected to the input of the heat source subunit through an optocoupler.

4. The temperature protection circuit according to claim 3, characterized in that, The delay subunit includes an RC delay circuit or a 555 timer; the RC delay circuit includes a capacitor and a resistor connected in series, with the end of the resistor away from the capacitor grounded, and the end of the capacitor away from the resistor electrically connected to the input terminal of the heat source subunit; or, the output terminal of the 555 timer is electrically connected to the input terminal of the heat source subunit to output a delay signal for controlling the heating duration of the heat source subunit.

5. The temperature protection circuit according to claim 1, characterized in that, The output of the voltage acquisition unit is connected to the input of the inverting amplifier, the output of the inverting amplifier is connected to the input of the inverter, the output of the inverter is connected to the input of the comparator subunit, and the output of the inverter is grounded through a filter capacitor.

6. The temperature protection circuit according to claim 5, characterized in that, The comparison subunit adopts a single threshold comparison circuit, including a voltage comparator. The power supply Vcc is connected to ground after being connected in series with resistors R4 and R5. The connection point of R4 and R5 is the output point of the reference voltage Vref, which is connected to the inverting input terminal of the voltage comparator. The Vcc pin of the voltage comparator is connected to the power supply Vcc, and the GND pin is grounded. The output of the voltage acquisition unit, after acquiring the temperature and voltage signal after heating, is connected to the non-inverting input terminal of the voltage comparator. The output terminal of the voltage comparator is connected to the power supply Vcc through the pull-up resistor R6, and the output terminal is also connected to the alarm indication unit.

7. The temperature protection circuit according to claim 5, characterized in that, The comparison subunit employs a dual-threshold window comparison circuit, comprising two voltage comparators. One voltage comparator has its non-inverting input connected to a lower limit reference voltage threshold signal and its inverting input receiving the voltage signal output by the voltage acquisition unit after heating. The other voltage comparator has its non-inverting input receiving the voltage signal and its inverting input connected to an upper limit reference voltage threshold signal. When the voltage signal is lower than the lower limit reference voltage threshold signal or higher than the upper limit reference voltage threshold signal, a trigger signal is output to the alarm indication unit.

8. The temperature protection circuit according to claim 1, characterized in that, The thermal unit includes two thermal elements located close to each other but not overlapping. The two thermal elements are electrically connected to the two input terminals of the voltage acquisition unit, respectively. The two output terminals of the voltage acquisition unit are electrically connected to the two input terminals of a differential amplifier. The output terminal of the differential amplifier is electrically connected to the input terminal of a comparator. The other input terminal of the comparator is connected to a differential reference voltage. The output terminal of the comparator is electrically connected to the input terminal of an abnormal alarm unit. When the deviation between the actual voltage signal difference and the differential reference voltage exceeds a preset range, the abnormal alarm unit is triggered to issue an alarm signal.

Images