Low-temperature self-heating device and vehicle

Abstract

The utility model provides a low-temperature self-heating device and a vehicle. The low-temperature self-heating device comprises a heating unit and a heating control circuit. The heating control circuit comprises a first switch unit, a heating trigger unit and a temperature detection unit, a first connecting end of the first switch unit is electrically connected with a first power supply end used for providing first voltage, and a second connecting end of the first switch unit is electrically connected with the heating unit; the heating trigger unit is electrically connected with the temperature detection unit and the control end of the first switch unit. The temperature detection unit is used for detecting the temperature of the circuit board and outputting a voltage signal corresponding to the detected temperature value to the heating trigger unit. When the temperature detection unit outputs a voltage signal corresponding to a temperature value lower than a preset low-temperature threshold value, the heating trigger unit outputs a conduction signal to the control end of the first switch unit so as to trigger the first switch unit to conduct electric connection between the first power supply end and the heating unit, and therefore the heating unit is powered on to heat the circuit board.

Description

Technical Field

[0001] The utility model relates to the technical field of circuit boards, in particular to a low-temperature self-heating device and a vehicle. Background Art

[0002] In PCB (Printed Circuit Board), some electronic components cannot work normally in low temperature environment (for example, below -40 degrees), and their application range is very limited. Therefore, it is particularly important to design a device for heating PCB. Utility Model Content

[0003] In order to solve the above technical problems or at least partially solve the above technical problems, the present disclosure provides a low-temperature self-heating device and a vehicle.

[0004] To achieve the above-mentioned purpose, the first aspect of the utility model provides a low-temperature self-heating device, which is used to heat a circuit board, and the low-temperature self-heating device includes a heating unit and a heating control circuit. The heating control circuit includes a first switch unit, a heating trigger unit and a temperature detection unit, wherein the first switch unit includes a first connection end, a second connection end and a control end, the first connection end of the first switch unit is electrically connected to a first power supply end for providing a first voltage, the second connection end of the first switch unit is electrically connected to the heating unit, and the heating trigger unit is electrically connected to the temperature detection unit and the control end of the first switch unit; the temperature detection unit is used to detect the temperature of the circuit board and output a voltage signal corresponding to the detected temperature value to the heating trigger unit; when the temperature detection unit outputs a voltage signal corresponding to a temperature value lower than a preset low temperature threshold, the heating trigger unit outputs a conduction signal to the control end of the first switch unit to trigger the first switch unit to conduct the electrical connection between the first power supply end and the heating unit, so that the heating unit receives the first voltage provided by the first power supply end and powers on, thereby heating the circuit board.

[0005] The low-temperature self-heating device provided by the utility model detects the temperature of the circuit board through a temperature detection unit and outputs a voltage signal, and responds to the voltage signal corresponding to the temperature value lower than the preset low-temperature threshold value through a heating trigger unit, drives the first switch unit to conduct so that the heating unit is electrically heated. It is not necessary to set up a controller to automatically control the heating unit to heat the circuit board when the temperature of the circuit board is lower than the preset low-temperature threshold value. The circuit structure is simple and the reliability is high.

[0006] In some embodiments, the heating trigger unit includes a second switch unit, the second switch unit includes a first connection end, a second connection end and a control end, the first connection end of the second switch unit is used to receive a first level signal, the second connection end of the second switch unit is electrically connected to the control end of the first switch unit, the control end of the second switch unit is electrically connected to the temperature detection unit, and the second switch unit is turned on in response to a voltage signal corresponding to a temperature value lower than a preset low temperature threshold output by the temperature detection unit, so that the first level signal received by the first connection end is output to the control end of the first switch unit; wherein the turn-on signal is the first level signal.

[0007] In some embodiments, the temperature detection unit includes a first resistor and a second resistor connected in series between a second power supply terminal and ground, and a connection node between the first resistor and the second resistor is electrically connected to the control terminal of the second switch unit; wherein the first resistor is a thermistor, and the resistance value of the thermistor changes according to the change of the temperature of the circuit board, so that the voltage signal received by the control terminal of the second switch unit changes accordingly.

[0008] In some embodiments, the first switch unit is a PMOS field effect transistor, and the source, drain and gate of the PMOS field effect transistor correspond one-to-one to the first connection end, the second connection end and the control end of the first switch unit; the second switch unit is an NMOS field effect transistor, and the source, drain and gate of the NMOS field effect transistor correspond one-to-one to the first connection end, the second connection end and the control end of the second switch unit.

[0009] In some embodiments, the first resistor is a thermistor with a negative temperature coefficient, the first resistor is electrically connected between the control terminal of the second switch unit and ground, and the second resistor is electrically connected between the second power supply terminal and the control terminal of the second switch unit.

[0010] In some embodiments, the temperature detection unit further includes a diode, and the diode is used to achieve unidirectional conduction from the second power supply end to the control end of the second switch unit.

[0011] In some embodiments, the low-temperature self-heating device also includes a protection unit electrically connected between the first power supply terminal and the first connection end of the first switch unit, and the protection unit is used to limit the current output from the first power supply terminal to the heating unit to below a first preset current threshold when there is a short circuit fault in the heating main circuit; wherein the heating main circuit is a circuit from the first power supply terminal to the ground through the first switch unit and the heating unit.

[0012] In some embodiments, the protection unit is a positive temperature coefficient thermistor.

[0013] In some embodiments, the low-temperature self-heating device also includes a power supply unit electrically connected to the first power supply terminal and the second power supply terminal, the power supply unit being used to output the first voltage with a constant voltage value to the first power supply terminal, and to output a second voltage with a constant voltage value to the second power supply terminal when the low-temperature self-heating device is in the on state, and to stop outputting voltage to the second power supply terminal when the low-temperature self-heating device is in the off state.

[0014] In some embodiments, the low-temperature self-heating device also includes the circuit board, which includes a surface device layer and a heating layer isolated from each other, the heating control circuit is arranged on the surface device layer of the circuit board, and the heating unit is arranged on the heating layer of the circuit board.

[0015] In some embodiments, the heating unit includes a first heating resistor and a second heating resistor connected in parallel between the second connection end of the first switch unit and the ground and isolated from each other. The first heating resistor and the second heating resistor are both in a mosquito coil-shaped spiral and are nested with each other.

[0016] In some embodiments, the low-temperature self-heating device further includes a current limiting unit connected in series between the second connection end of the first switch unit and the heating unit, and the current limiting unit is used to limit the current flowing through the heating unit to below a second preset current threshold.

[0017] In some embodiments, the current limiting unit includes a first current limiting resistor and a second current limiting resistor, the first current limiting resistor and the first heating resistor are connected in series between the second connection end of the first switch unit and the ground, and the second current limiting resistor and the second heating resistor are connected in series between the second connection end of the first switch unit and the ground.

[0018] The second aspect of the utility model further provides a vehicle, the vehicle comprising the low-temperature self-heating device described in the first aspect.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a low-temperature self-heating device provided by an embodiment of the utility model;

[0021] Figure 2 yes Figure 1 A schematic diagram of the circuit structure of the heating control circuit;

[0022] Figure 3It is a temperature-resistance characteristic curve diagram of a negative temperature coefficient thermistor provided by an embodiment of the utility model;

[0023] Figure 4 yes Figure 1 A schematic diagram of the structure of the circuit board in FIG.

[0024] Figure 5 yes Figure 2 Schematic diagram of the structure of the first heating resistor wire and the second heating resistor wire.

[0025] The following are the descriptions of the reference numerals:

[0026] Low temperature self-heating device 100

[0027] Circuit board 10

[0028] Heating unit 20

[0029] Heating control circuit 30

[0030] The first switch unit 31

[0031] Heating trigger unit 32

[0032] Temperature detection unit 33

[0033] The second switch unit 321

[0034] The first resistor R1

[0035] Second resistors R21, R22

[0036] PMOS field effect tube Q1 NMOS field effect tube Q2

[0037] Diode D1

[0038] Protection unit 34

[0039] Current limiting unit 35

[0040] First power supply terminal 1

[0041] Second power supply terminal 2

[0042] Surface device layer 11

[0043] Heating layer 12

[0044] The first heating resistor 21

[0045] The second heating resistor 22

[0046] The first current limiting resistor R6

[0047] The second current limiting resistor R7

[0048] The third resistor R3

[0049] The fourth resistor R4

[0050] Positive temperature coefficient thermistor R5

[0051] The first capacitor C1

[0052] The second capacitor C2

[0053] The following specific implementation manner will illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0055] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0056] See also Figure 1 The utility model provides a low-temperature self-heating device 100 , which is used to heat a circuit board 10 . The low-temperature self-heating device 100 includes a heating unit 20 and a heating control circuit 30 .

[0057] The heating control circuit 30 includes a first switch unit 31, a heating trigger unit 32 and a temperature detection unit 33. The first switch unit 31 includes a first connection end, a second connection end and a control end. The first connection end of the first switch unit 31 is electrically connected to the first power supply end 1 for providing a first voltage, the second connection end of the first switch unit 31 is electrically connected to the heating unit 20, and the heating trigger unit 32 is electrically connected to the temperature detection unit 33 and the control end of the first switch unit 31. The temperature detection unit 33 is used to detect the temperature of the circuit board 10 and output a voltage signal corresponding to the detected temperature value to the heating trigger unit 32. When the temperature detection unit 33 outputs a voltage signal corresponding to a temperature value lower than a preset low temperature threshold, the heating trigger unit 32 outputs a conduction signal to the control end of the first switch unit 31 to trigger the first switch unit 31 to conduct the electrical connection between the first power supply end 1 and the heating unit 20, so that the heating unit 20 receives the first voltage provided by the first power supply end 1 and powers on, thereby heating the circuit board 10.

[0058] Among them, the heating trigger unit 32 outputs a conduction signal to the control end of the first switch unit 31 when the temperature detection unit 33 outputs a voltage signal corresponding to a temperature value lower than a preset low temperature threshold, which means that the heating trigger unit 32 outputs a conduction signal to the control end of the first switch unit 31 when the temperature value corresponding to the voltage signal output by the temperature detection unit 33 is lower than the preset low temperature threshold.

[0059] The low-temperature self-heating device 100 provided by the utility model detects the temperature of the circuit board 10 through the temperature detection unit 33 and outputs a voltage signal. The heating trigger unit 32 responds to the voltage signal corresponding to the temperature value lower than the preset low-temperature threshold, drives the first switch unit 31 to be turned on so that the heating unit 20 is electrically heated. There is no need to set up a controller to automatically control the heating unit 20 to heat the circuit board 10 when the temperature of the circuit board 10 is lower than the preset low-temperature threshold. The circuit structure is simple and the reliability is high.

[0060] In some embodiments, the heating trigger unit 32 includes a second switch unit 321, the second switch unit 321 includes a first connection end, a second connection end and a control end, the first connection end of the second switch unit 321 is used to receive a first level signal, the second connection end of the second switch unit 321 is electrically connected to the control end of the first switch unit 31, the control end of the second switch unit 321 is electrically connected to the temperature detection unit 33, and the second switch unit 321 is turned on in response to a voltage signal corresponding to a temperature value lower than a preset low temperature threshold output by the temperature detection unit 33, so that the first level signal received by the first connection end is output to the control end of the first switch unit 31. The conduction signal is the first level signal.

[0061] Among them, the second switch unit 321 is turned on in response to the voltage signal corresponding to the temperature value lower than the preset low temperature threshold output by the temperature detection unit 33, which means that the second switch unit 321 is turned on when the temperature value corresponding to the voltage signal output by the temperature detection unit 33 is lower than the preset low temperature threshold, and is turned off when the temperature value corresponding to the voltage signal output by the temperature detection unit 33 is higher than the preset low temperature threshold.

[0062] In this way, there is no need to set up a controller. Instead, by setting up a second switch unit 321, when the temperature of the circuit board 10 is lower than the preset low temperature threshold, the first switch unit 31 can be automatically triggered to turn on, so that the heating unit 20 is electrically heated. The circuit structure is simple, the cost is low, and the reliability is high.

[0063] In some embodiments, the temperature detection unit 33 includes a first resistor R1 and a second resistor connected in series between the second power supply terminal 2 and the ground, and a connection node between the first resistor R1 and the second resistor is electrically connected to the control end of the second switch unit 321. The first resistor R1 is a thermistor, and the resistance value of the thermistor changes according to the change of the temperature of the circuit board 10, so that the voltage signal received by the control end of the second switch unit 321 changes accordingly.

[0064] For example, Figure 2As shown, the first resistor R1 is a thermistor with a negative temperature coefficient, the first resistor R1 is electrically connected between the control end of the second switch unit 321 and the ground, and the second resistor is electrically connected between the second power supply terminal 2 and the control end of the second switch unit 321. The first switch unit 31 is a PMOS field effect transistor Q1, and the source, drain and gate of the PMOS field effect transistor Q1 correspond to the first connection end, the second connection end and the control end of the first switch unit 31. The second switch unit 321 is an NMOS field effect transistor Q2, and the source, drain and gate of the NMOS field effect transistor Q2 correspond to the first connection end, the second connection end and the control end of the second switch unit 321. Among them, the source of the NMOS field effect transistor Q2 is grounded, that is, the first level signal is a low level signal. The heating trigger unit 32 also includes a first capacitor C1, the first capacitor C1 and the first resistor R1 are connected in parallel between the gate of the NMOS field effect transistor Q2 and the ground, and are used to filter out low-order harmonics in the voltage signal output by the temperature detection unit 33. The number of the second resistors is 2, namely, a second resistor R21 and a second resistor R22 electrically connected in series. Of course, in other embodiments, the number of the second resistors may be other.

[0065] Furthermore, the heating trigger unit 32 further includes a third resistor R3, a fourth resistor R4 and a second capacitor C2. The third resistor R3 is electrically connected between the gate of the PMOS field effect transistor Q1 and the drain of the NMOS field effect transistor Q2, and the fourth resistor R4 and the second capacitor C2 are connected in parallel between the source and the gate of the PMOS field effect transistor Q1, wherein the fourth resistor R4 and the second capacitor C2 constitute a slow start circuit of the PMOS field effect transistor Q1, and are used to prevent the PMOS field effect transistor Q1 from being damaged by an overshoot current caused by rapid conduction.

[0066] For example, the first resistor R1 is a negative temperature coefficient thermistor of the TDK manufacturer NTCGS163JF103FT8 model, which can operate in a temperature range of -55 to 150 degrees and has good temperature consistency. Figure 3 , Figure 3 The temperature-resistance characteristic curve of the negative temperature coefficient thermistor is as follows: Figure 3As shown, the resistance of the negative temperature coefficient thermistor is 300 KΩ at -40°C and 80 KΩ at -20°C. Among them, the second voltage provided by the second power supply terminal 2 is 9V, R21 = 82 KΩ, R22 = 820 KΩ, R3 = 1 K, R4 = 100 K, C2 = 100 nF. The turn-on threshold Vgsth of the NMOS field effect transistor Q2 is 0.8V, and the preset low temperature threshold is between -40°C and -20°C.

[0067] During operation, when the temperature of the circuit board 10 is -40°C, the gate-source voltage Vgs of the NMOS field effect transistor Q2 is Vgs=(300 / (300 + 820 + 82))*9 = 2.24V > Vgsth = 0.8V. Thus, the NMOS field effect transistor Q2 conducts, causing the gate of the PMOS field effect transistor Q1 to be grounded through the conducting NMOS field effect transistor Q2. As a result, the PMOS field effect transistor Q1 conducts the electrical connection between the first power supply terminal 1 and the heating unit 20, enabling the heating unit 20 to receive the first voltage provided by the first power supply terminal 1 and power on for operation, thereby heating the circuit board 10.

[0068] When the heating unit 20 heats the temperature of the circuit board 10 to -20°C, the gate-source voltage Vgs of the NMOS field effect transistor Q2 is Vgs=(80 / (80 + 820 + 82))*9 = 0.73V < Vgsth = 0.8V. Thus, the NMOS field effect transistor Q2 turns off, and the gate of the PMOS field effect transistor Q1 receives the first voltage provided by the first power supply terminal 1 through the fourth resistor R4. As a result, the PMOS field effect transistor Q1 disconnects the electrical connection between the first power supply terminal 1 and the heating unit 20, causing the heating unit 20 to stop heating.

[0069] It should be noted that in other embodiments, the first level signal can also be a high level signal. At this time, the second switch unit 321 can use a PMOS field effect transistor, the first switch unit 31 can use an NMOS field effect transistor, the first resistor R1 can be a positive temperature coefficient thermistor, and is electrically connected between the first power supply terminal 1 and the control terminal of the second switch unit 321, and the second resistor is electrically connected between the control terminal of the second switch unit 321 and the ground.

[0070] In some embodiments, the temperature detection unit 33 further includes a diode D1. The diode D1 is used to achieve the one-way conduction from the second power supply terminal 2 to the control terminal of the second switch unit 321, thereby preventing the second power supply terminal 2 from inputting a negative voltage to the gate of the NMOS field effect transistor Q2 and causing damage to the NMOS field effect transistor Q2. Specifically, as Figure 2As shown, the anode of the diode D1 is electrically connected to the second power supply terminal 2, and the cathode of the diode D1 is electrically connected to the second resistor.

[0071] In some embodiments, the low-temperature self-heating device 100 further includes a protection unit 34 electrically connected between the first power supply terminal 1 and the first connection terminal of the first switch unit 31, and the protection unit 34 is used to limit the current output from the first power supply terminal 1 to the heating unit 20 to below a first preset current threshold when there is a short circuit fault in the heating main circuit. The heating main circuit is a circuit from the first power supply terminal 1 to the ground through the first switch unit 31 and the heating unit 20.

[0072] For example, Figure 2 As shown, the protection unit 34 can adopt a positive temperature coefficient thermistor R5 of Junyao Electronics model SMD1812P200TF / 16. The holding current Ihold of the positive temperature coefficient thermistor R5 is 2A, the protection action current is 3.5A, and the dissipated power is 1W. When the heating unit 20 or the PMOS field effect tube Q1 is short-circuited to the ground, the temperature of the positive temperature coefficient thermistor R5 rises, so that the equivalent impedance increases rapidly, which is equivalent to opening the main heating circuit, thereby limiting the short-circuit current to the mA level. In this way, other devices can be protected from short-circuit current shocks. Furthermore, the positive temperature coefficient thermistor R5 has a self-recovery function, that is, when the short-circuit fault is relieved, the positive temperature coefficient thermistor R5 can restore the normal impedance value.

[0073] In some embodiments, the low-temperature self-heating device 100 also includes a power supply unit (not shown in the figure) electrically connected to the first power supply terminal 1 and the second power supply terminal 2, and the power supply unit is used to output the first voltage with a constant voltage value to the first power supply terminal 1, and output the second voltage with a constant voltage value to the second power supply terminal 2 when the low-temperature self-heating device 100 is in the turned-on state, and stop outputting voltage to the second power supply terminal 2 when the low-temperature self-heating device 100 is in the turned-off state.

[0074] In this way, when the low-temperature self-heating device 100 is in the shutdown state, the heating trigger unit 32 stops working, which can reduce leakage loss.

[0075] See also Figure 4 In some embodiments, the low-temperature self-heating device 100 includes the circuit board 10, the circuit board 10 includes a surface device layer 11 and a heating layer 12 isolated from each other, the heating control circuit 30 is arranged on the surface device layer 11 of the circuit board 10, and the heating unit 20 is arranged on the heating layer 12 of the circuit board 10.

[0076] The surface device layer 11 and the heating layer 12 may be isolated by an insulating layer.

[0077] In this way, by disposing the heating unit 20 on the heating layer 12 of the circuit board 10 , the heating efficiency of the heating unit 20 can be improved.

[0078] See also Figure 5 In some embodiments, the heating unit 20 includes a first heating resistor 21 and a second heating resistor 22 connected in parallel between the second connection end of the first switch unit 31 and the ground and isolated from each other. The first heating resistor 21 and the second heating resistor 22 are both in the shape of a mosquito coil-shaped spiral and are nested with each other.

[0079] Exemplarily, the first heating resistance wire 21 and the second heating resistance wire 22 are both made of copper, and the thickness is 1oZ (35um), the line width is 40mil (1mm), the winding length is 4m, and the resistance value is 2Ω. Of course, in other embodiments, the first heating resistance wire 21 and the second heating resistance wire 22 can also be made of other materials, such as aluminum, iron, and the size parameters can also be other parameters.

[0080] Thus, the first heating resistance wire 21 and the second heating resistance wire 22 are arranged in a mutually nested spiral shape, which can not only improve the resistance wire space utilization and heating efficiency, but also improve the heating uniformity. In addition, this nested design can also improve the reliability of the heating unit 20, that is, when one of the first heating resistance wire 21 and the second heating resistance wire 22 is damaged and disconnected, the other one can be used as a backup.

[0081] In some embodiments, the low-temperature self-heating device 100 also includes a current limiting unit 35 connected in series between the second connection end of the first switch unit 31 and the heating unit 20, and the current limiting unit 35 is used to limit the current flowing through the heating unit 20 to below a second preset current threshold.

[0082] In this way, the first heating resistance wire 21 and the second heating resistance wire 22 can be prevented from receiving a large current and being burned out, thereby improving the reliability of the heating unit 20 .

[0083] For example, Figure 2 As shown, the current limiting unit 35 includes a first current limiting resistor R6 and a second current limiting resistor R7, the first current limiting resistor R6 and the first heating resistor 21 are connected in series between the second connection end of the first switch unit 31 and the ground, and the second current limiting resistor R7 and the second heating resistor 22 are connected in series between the second connection end of the first switch unit 31 and the ground.

[0084] Based on the same concept, the utility model also provides a vehicle, which includes the low-temperature self-heating device 100 described in any of the above embodiments.

[0085] Illustratively, the vehicle may be a hybrid vehicle, or a non-hybrid vehicle or an electric vehicle.

[0086] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A low-temperature self-heating device for heating a circuit board. It is characterized in that The low-temperature self-heating device comprises: a heating unit; and A heating control circuit includes a first switch unit, a heating trigger unit and a temperature detection unit, wherein the first switch unit includes a first connection end, a second connection end and a control end, the first connection end of the first switch unit is electrically connected to a first power supply end for providing a first voltage, the second connection end of the first switch unit is electrically connected to the heating unit, and the heating trigger unit is electrically connected to the temperature detection unit and the control end of the first switch unit; the temperature detection unit is used to detect the temperature of the circuit board and output a voltage signal corresponding to the detected temperature value to the heating trigger unit; when the temperature detection unit outputs a voltage signal corresponding to a temperature value lower than a preset low temperature threshold, the heating trigger unit outputs a conduction signal to the control end of the first switch unit to trigger the first switch unit to conduct the electrical connection between the first power supply end and the heating unit, so that the heating unit receives the first voltage provided by the first power supply end and powers on, thereby heating the circuit board.

2. The low temperature self-heating device according to claim 1, It is characterized in that The heating trigger unit includes a second switch unit, which includes a first connection end, a second connection end and a control end. The first connection end of the second switch unit is used to receive a first level signal, the second connection end of the second switch unit is electrically connected to the control end of the first switch unit, and the control end of the second switch unit is electrically connected to the temperature detection unit. The second switch unit is turned on in response to a voltage signal corresponding to a temperature value lower than a preset low temperature threshold output by the temperature detection unit, so that the first level signal received by the first connection end is output to the control end of the first switch unit; wherein the turn-on signal is the first level signal.

3. The low temperature self-heating device according to claim 2, It is characterized in that The temperature detection unit includes a first resistor and a second resistor connected in series between a second power supply terminal and ground, and a connection node between the first resistor and the second resistor is electrically connected to the control end of the second switch unit; wherein the first resistor is a thermistor, and the resistance value of the thermistor changes according to the change of the temperature of the circuit board, so that the voltage signal received by the control end of the second switch unit changes accordingly.

4. The low temperature self-heating device according to claim 3, It is characterized in that The first switch unit is a PMOS field effect transistor, and the source, drain and gate of the PMOS field effect transistor correspond one-to-one to the first connection end, the second connection end and the control end of the first switch unit; the second switch unit is an NMOS field effect transistor, and the source, drain and gate of the NMOS field effect transistor correspond one-to-one to the first connection end, the second connection end and the control end of the second switch unit.

5. The low temperature self-heating device according to claim 4, It is characterized in that The first resistor is a thermistor with a negative temperature coefficient, the first resistor is electrically connected between the control end of the second switch unit and the ground, and the second resistor is electrically connected between the second power supply end and the control end of the second switch unit.

6. The low temperature self-heating device according to claim 3, It is characterized in that The temperature detection unit further includes a diode, and the diode is used to achieve unidirectional conduction from the second power supply end to the control end of the second switch unit.

7. The low temperature self-heating device according to claim 1, It is characterized in that The low-temperature self-heating device also includes a protection unit electrically connected between the first power supply terminal and the first connection end of the first switch unit, and the protection unit is used to limit the current output from the first power supply terminal to the heating unit to below a first preset current threshold when there is a short circuit fault in the heating main circuit; wherein the heating main circuit is a circuit from the first power supply terminal to the ground through the first switch unit and the heating unit.

8. The low temperature self-heating device according to claim 7, It is characterized in that The protection unit is a positive temperature coefficient thermistor.

9. The low temperature self-heating device according to claim 3, It is characterized in that The low-temperature self-heating device also includes a power supply unit electrically connected to the first power supply terminal and the second power supply terminal, the power supply unit is used to output the first voltage with a constant voltage value to the first power supply terminal, and output the second voltage with a constant voltage value to the second power supply terminal when the low-temperature self-heating device is in the on state, and stop outputting the voltage to the second power supply terminal when the low-temperature self-heating device is in the off state.

10. The low temperature self-heating device according to claim 1, It is characterized in that The low-temperature self-heating device also includes the circuit board, which includes a surface device layer and a heating layer that are isolated from each other. The heating control circuit is arranged on the surface device layer of the circuit board, and the heating unit is arranged on the heating layer of the circuit board.

11. The low temperature self-heating device according to claim 1, It is characterized in that The heating unit comprises a first heating resistor wire and a second heating resistor wire which are connected in parallel between the second connection end of the first switch unit and the ground and isolated from each other. The first heating resistor wire and the second heating resistor wire are both in a mosquito coil-shaped spiral and are nested with each other.

12. The low temperature self-heating device according to claim 11, It is characterized in that The low-temperature self-heating device further includes a current limiting unit connected in series between the second connection end of the first switch unit and the heating unit, and the current limiting unit is used to limit the current flowing through the heating unit to below a second preset current threshold.

13. The low temperature self-heating device according to claim 12, It is characterized in that The current limiting unit includes a first current limiting resistor and a second current limiting resistor, the first current limiting resistor and the first heating resistor are connected in series between the second connection end of the first switch unit and the ground, and the second current limiting resistor and the second heating resistor are connected in series between the second connection end of the first switch unit and the ground.

14. A vehicle, It is characterized in that It comprises a low-temperature self-heating device as claimed in any one of claims 1 to 13.

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