Heating control circuit for PTC heater

Abstract

The utility model discloses a heating control circuit used for a PTC heater. The heating control circuit comprises a control unit, a current acquisition circuit, a drive circuit and a short circuit self-locking circuit. The control unit outputs a pulse signal to adjust the heating power of the PTC heater; the current acquisition circuit acquires an electric signal of the IGBT device; the control unit stops outputting the pulse signal according to the electric signal and enables the driving circuit to stop outputting the driving signal; the short-circuit self-locking circuit triggers self-locking according to the electric signal or an abnormal operation signal output by the driving circuit, outputs a short-circuit self-locking signal to the driving circuit and outputs a short-circuit fault signal to the control unit; the control unit stops outputting the pulse signal according to the short-circuit fault signal; and the driving circuit enables the IGBT device to stop working according to the short-circuit self-locking signal, directly monitors an electric signal of the IGBT device, enables the IGBT device to stop working according to the electric signal, and outputs an abnormal operation signal to the short-circuit self-locking circuit. By using the structure, graded short-circuit protection is realized.

Description

Technical Field

[0001] This utility model relates to the technical field of automotive parts, and in particular to a heating control circuit for a PTC heater. Background Technology

[0002] New energy vehicles are the future trend of automobile development. Currently, PTC heaters are used for in-vehicle heating or battery heating in new energy vehicles on the market. However, in actual applications, PTC heaters may have problems such as working environment pollution or leakage in the structure, which can cause short circuits at the high-voltage end of the PTC heater and damage to IGBT devices.

[0003] Currently, short-circuit protection for PTC heaters typically employs two methods: microcontroller-based detection and hardware circuit voltage comparison. Microcontroller-based detection provides protection within milliseconds, while hardware circuit voltage comparison provides protection within approximately 0.1 milliseconds, showing a different response time. However, in more serious issues such as leakage, the maximum current that the IGBT device in the drive circuit can withstand is exceeded, requiring immediate disconnection of the IGBT. Ideally, the protection action time for IGBTs should be less than 10 microseconds, but currently, the optimal protection time is only around 0.1 milliseconds. This means that the IGBT device may be damaged before it is disconnected, reducing its reliability. Utility Model Content

[0004] This invention provides a heating control circuit for a PTC heater, which collects the electrical signal of the IGBT device and quickly cuts off the IGBT device according to the level of the electrical signal, thereby preventing damage to the IGBT device and improving the reliability of the IGBT device.

[0005] This utility model provides a heating control circuit for a PTC heater, including a control unit, a current acquisition circuit, a drive circuit, and a short-circuit self-locking circuit; the control unit is electrically connected to the current acquisition circuit, the drive circuit, and the short-circuit self-locking circuit respectively; the short-circuit self-locking circuit is electrically connected to the current acquisition circuit and the drive circuit respectively; the current acquisition circuit and the drive circuit are also electrically connected to the IGBT device respectively; and the IGBT device is electrically connected to the PTC heater.

[0006] The control unit is used to output pulse signals to the drive circuit; the drive circuit is used to convert the pulse signals into drive signals, and adjust the heating power of the PTC heater through the IGBT device.

[0007] The current acquisition circuit is used to acquire the electrical signals of the IGBT device in real time;

[0008] The control unit is also used to acquire electrical signals and stop outputting pulse signals to the drive circuit according to the electrical signals;

[0009] The short-circuit self-locking circuit is used to acquire electrical signals and abnormal operation signals output by the drive circuit. Based on the electrical signals or abnormal operation signals, the short-circuit self-locking circuit is triggered to self-lock, and a short-circuit self-locking signal is output to the drive circuit, as well as a short-circuit fault signal is output to the control unit.

[0010] The control unit is also used to stop outputting pulse signals to the drive circuit based on a short-circuit fault signal;

[0011] The drive circuit is also used to monitor the electrical signals of the IGBT device, and to stop the IGBT device from working based on the electrical signals, and output an abnormal operation signal to the short-circuit self-locking circuit; or to stop the IGBT device from working based on the short-circuit self-locking signal.

[0012] Optionally, the circuit may also include a signal conversion circuit;

[0013] The signal conversion circuit is electrically connected between the current acquisition circuit and the control unit. The signal conversion circuit is used to perform analog-to-digital conversion on electrical signals.

[0014] Optionally, the current acquisition circuit includes a differential operational amplifier circuit, an RC filter circuit, a sampling resistor, and a second capacitor;

[0015] The sampling resistor and the second capacitor are both connected in parallel between the first and second input terminals of the differential operational amplifier circuit. The first input terminal of the differential operational amplifier circuit is electrically connected to the electrical signal output terminal of the IGBT device, and the second input terminal is electrically connected to the first power supply voltage terminal. The output terminal of the differential operational amplifier circuit is electrically connected to the electrical signal input terminal of the control unit and the electrical signal input terminal of the short-circuit self-locking circuit through an RC filter circuit.

[0016] Optionally, the differential operational amplifier circuit includes a first operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor;

[0017] The second and third resistors are connected in series between the electrical signal output terminal of the IGBT device and the positive input terminal of the first operational amplifier; the fifth and sixth resistors are connected in series between the first power supply voltage terminal and the negative input terminal of the first operational amplifier; the first terminal of the second capacitor is electrically connected to the series connection point of the second and third resistors, and the second terminal is electrically connected to the series connection point of the fifth and sixth resistors; the first terminal of the fourth resistor is electrically connected between the first terminal of the third resistor and the positive input terminal, and the second terminal is electrically connected to the ground terminal; the first terminal of the seventh resistor is electrically connected to the negative input terminal, and the second terminal is electrically connected to the output terminal of the first operational amplifier.

[0018] Optionally, the short-circuit self-locking circuit includes a second operational amplifier, a threshold voltage unit, and a first diode;

[0019] The positive input terminal of the second operational amplifier is electrically connected to the electrical signal output terminal of the current acquisition circuit and the operation abnormal signal output terminal of the drive circuit. The negative input terminal of the second operational amplifier is electrically connected to the output terminal of the threshold voltage unit. The first diode is connected in series between the output terminal and the positive input terminal of the second operational amplifier. The output terminal of the second operational amplifier is also electrically connected to the short-circuit self-locking signal output terminal and the short-circuit fault signal output terminal.

[0020] Optionally, the threshold voltage unit includes a tenth resistor and a fourteenth resistor;

[0021] The tenth and fourteenth resistors are connected in series between the second power supply voltage terminal and the ground terminal, and the connection terminal of the tenth and fourteenth resistors serves as the output terminal of the threshold voltage unit.

[0022] Optionally, the short-circuit self-locking circuit also includes a second diode, a third diode, a fourth diode, a fourth capacitor, a ninth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fifteenth resistor, and a sixteenth resistor;

[0023] The second diode is connected in series between the electrical signal output terminal of the current acquisition circuit and the positive input terminal of the second operational amplifier; the sixteenth resistor and the third diode are connected in series between the output terminal and the positive input terminal of the drive circuit; the fourth diode is connected in series between the series connection point of the sixteenth resistor and the third diode and the ground terminal; the fourth capacitor and the thirteenth resistor are connected in parallel and in series between the positive input terminal and the ground terminal; the ninth resistor is connected in series between the positive input terminal and the self-locking reset terminal; the eleventh resistor is connected in series between the output terminal of the second operational amplifier and the second power supply voltage terminal; the twelfth resistor is connected in series between the output terminal and the short-circuit self-locking signal output terminal; and the fifteenth resistor is connected in series between the output terminal and the short-circuit fault signal output terminal.

[0024] Optionally, the driving circuit includes a driving chip, a second transistor, a third transistor, and a driving signal circuit;

[0025] The pulse signal output terminal of the control unit is electrically connected to the control terminal of the second transistor. The first terminal of the second transistor is grounded, and the second terminal is electrically connected to the INP pin of the driver chip. The short-circuit self-locking signal output terminal of the short-circuit self-locking circuit is electrically connected to the control terminal of the third transistor. The first terminal of the third transistor is grounded, and the second terminal is electrically connected to the control terminal of the second transistor. The DRV pin of the driver chip is electrically connected to the control terminal of the IGBT device through the drive signal circuit. The Desat pin of the driver chip is electrically connected to the first terminal of the IGBT device, and the second terminal of the IGBT device is the electrical signal output terminal. The Fault pin of the driver chip is electrically connected to the operation abnormality signal input terminal of the short-circuit self-locking circuit.

[0026] Optionally, the drive signal circuit includes a twentieth resistor, a twenty-second resistor, a twenty-fifth resistor, and a sixth diode;

[0027] The 20th resistor is connected in series between the DRV pin of the driver chip and the control terminal of the IGBT device; the 22nd resistor and the 6th diode are connected in series and in parallel across the 20th resistor; the first terminal of the 25th resistor is electrically connected to the control terminal of the IGBT device, and the second terminal of the 25th resistor is grounded.

[0028] Optionally, the driving circuit may also include a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twenty-first resistor, a twenty-third resistor, a twenty-fourth resistor, a twenty-sixth resistor, a fifth capacitor, a sixth capacitor, and a fifth diode;

[0029] The 21st resistor is connected in series between the pulse signal input terminal and the control terminal of the second transistor; the 23rd resistor is connected in series between the short-circuit self-locking signal output terminal and the control terminal of the third transistor; the 26th resistor is connected in series between the control terminal and the first terminal of the third transistor; the 24th resistor is connected in series between the control terminal and the first terminal of the second transistor; the 19th resistor is connected in series between the third power supply voltage terminal and the INP pin of the driver chip; the 17th resistor is connected in series between the third power supply voltage terminal and the SEN pin of the driver chip; the 6th capacitor is connected in series between the SEN pin and the ground terminal; the ground terminal is also electrically connected to the KGND pin and the VEE pin of the driver chip; the 18th resistor and the 5th diode are connected in series between the Desat pin of the driver chip and the first terminal of the IGBT device.

[0030] The technical solution of this utility model can acquire the electrical signal of the IGBT device in real time through a current acquisition circuit. The control unit acquires the electrical signal in a polling manner and stops outputting pulse signals to the drive circuit when the electrical signal exceeds a first overcurrent threshold, so that the drive circuit stops outputting drive signals to the IGBT device. The short-circuit self-locking circuit receives the electrical signal in real time and triggers self-locking when the electrical signal exceeds a second overcurrent threshold, and outputs a short-circuit self-locking signal to the drive circuit and a short-circuit fault signal to the control unit. When the drive circuit receives the short-circuit self-locking signal, the IGBT device will stop working. When the control unit receives the short-circuit fault signal, it will stop outputting pulse signals to the drive circuit. The drive circuit can also directly monitor the electrical signal of the IGBT device in real time and stop heating the PTC heater when the electrical signal exceeds a third overcurrent threshold, and output an abnormal operation signal to the short-circuit self-locking circuit. When the short-circuit self-locking circuit receives the abnormal operation signal, it will trigger self-locking and output a short-circuit self-locking signal to the drive circuit. Using the above structure, the heating can be cut off in a timely manner by acquiring the electrical signal of the IGBT device and reacting at different speeds according to the magnitude of the electrical signal; the circuit can also be self-locked by hardware devices to prevent repeated current surges during the PWM control process, thus preventing damage to the IGBT device or the entire PTC heater.

[0031] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of a heating control circuit for a PTC heater provided for an embodiment of this utility model;

[0034] Figure 2 A schematic diagram of the structure of a second heating control circuit for a PTC heater provided in an embodiment of this utility model;

[0035] Figure 3 A schematic diagram of a current acquisition circuit provided in an embodiment of this utility model;

[0036] Figure 4 A schematic diagram of a short-circuit self-locking circuit provided for an embodiment of this utility model;

[0037] Figure 5 This is a schematic diagram of a driving circuit provided in an embodiment of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0039] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this utility model described herein can be implemented in sequences other than those illustrated or described herein.

[0040] In one embodiment, Figure 1 This utility model provides a schematic diagram of a heating control circuit for a PTC heater. This embodiment is applicable to situations where a short circuit in the PTC heater causes damage to the IGBT device, providing short-circuit protection. Figure 1 As shown, the circuit includes: a control unit 1, a current acquisition circuit 2, a drive circuit 3, and a short-circuit self-locking circuit 4; the control unit 1 is electrically connected to the current acquisition circuit 2, the drive circuit 3, and the short-circuit self-locking circuit 4 respectively; the short-circuit self-locking circuit 4 is electrically connected to the current acquisition circuit 2 and the drive circuit 3 respectively; the current acquisition circuit 2 and the drive circuit 3 are also electrically connected to the IGBT device 5 respectively; the IGBT device 5 is electrically connected to the PTC heater 6; the control unit 1 is used to output pulse signals to the drive circuit 3; the drive circuit 3 is used to convert the pulse signals into drive signals, and adjust the heating power of the PTC heater 6 through the IGBT device 5; the current acquisition circuit 2 is used to acquire the current of the IGBT device in real time. The control unit 1 is also used to acquire electrical signals and stop outputting pulse signals to the drive circuit 3 according to the electrical signals; the short-circuit self-locking circuit 4 is used to acquire electrical signals and the abnormal operation signal output by the drive circuit 3, and trigger the short-circuit self-locking circuit 4 to self-lock according to the electrical signals or the abnormal operation signal, and output a short-circuit self-locking signal to the drive circuit 3, and output a short-circuit fault signal to the control unit 1; the control unit 1 is also used to stop outputting pulse signals to the drive circuit 3 according to the short-circuit fault signal; the drive circuit 3 is used to monitor the electrical signals of the IGBT device 5, and output an abnormal operation signal to the short-circuit self-locking circuit 4 according to the electrical signals; or stop the IGBT device 5 from working according to the short-circuit self-locking signal.

[0041] The current acquisition circuit 2 is used to acquire the electrical signal of the IGBT device 5 in real time during operation. This electrical signal reflects the magnitude of the current flowing through the IGBT device 5 or the voltage across the IGBT device 5. A larger electrical signal value indicates a larger current flowing through the IGBT device 5 and a larger voltage across the IGBT device 5 during acquisition. It is understood that when the current or voltage across the IGBT device 5 exceeds its normal operating range, it indicates that the PTC heater 6 may be short-circuited. In this case, the acquired electrical signal will also exceed a preset threshold, which can be referred to as the overcurrent threshold in this application. Different overcurrent thresholds correspond to different current or voltage conditions experienced by the IGBT device 5. In this application, the electrical signal can be in the form of a current signal or a voltage signal; the essence remains unchanged. The threshold comparison step in the circuit can use the appropriate form for comparison, which can be determined based on the components used in the actual circuit and is not limited here.

[0042] The drive circuit 3 provides drive capability to the IGBT device 5, enabling it to operate. Once the IGBT device 5 is operational, it controls the PTC heater 6 to begin heating. The short-circuit self-locking circuit 4 is a protection circuit whose main function is to quickly lock itself in the event of a short circuit, protecting the components in the circuit from damage. The short-circuit self-locking circuit 4 does not automatically recover after the short-circuit fault is removed; external intervention is required for it to resume normal operation. The IGBT device 5 is a three-terminal semiconductor switching device that combines the characteristics of a MOSFET and a bipolar transistor, featuring high input impedance, low on-state voltage drop, high-speed switching characteristics, and low on-state losses. The IGBT device 5 uses voltage control to turn on and off. When the voltage drop between the gate and emitter is greater than zero, the IGBT device 5 conducts, and current flows between the collector and emitter. When the voltage drop between the gate and emitter drops to zero or a negative value, the IGBT device 5 turns off, cutting off the current. The PTC heater 6 is a heating device made using a thermistor material with a positive temperature coefficient. Control unit 1 is the core control unit of this circuit. It is used to output pulse signals and send the pulse signals to drive circuit 3. Drive circuit 3 will output drive signals to IGBT device 5 to make IGBT device 5 work, thereby making PTC heater 6 heat up. When the duty cycle of the pulse signal output by control unit 1 changes, the heating power output to PTC heater 6 will change, thereby realizing the adjustment of the heating power of PTC heater 6.

[0043] Specifically, by electrically connecting the control unit 1 to the current acquisition circuit 2, the drive circuit 3, and the short-circuit self-locking circuit 4, and the short-circuit self-locking circuit 4 to both the current acquisition circuit 2 and the drive circuit 3, and by electrically connecting the IGBT device 5 to the current acquisition circuit 2, the drive circuit 3, and the PTC heater 6, the pulse signal output by the control unit 1 can be sent to the drive circuit 3. Upon receiving the pulse signal, the drive circuit 3 outputs a drive signal to the IGBT device 5 to start it working. Once the IGBT device 5 is working, it controls the PTC heater 6 to heat the device. During normal operation, the IGBT device 5 generates a certain amount of electrical signal. The current acquisition circuit 2 can acquire the electrical signal of the IGBT device 5 in real time, and both the control unit 1 and the short-circuit self-locking circuit 4 can obtain the electrical signal acquired by the current acquisition circuit 2.

[0044] More specifically, control unit 1 can acquire the electrical signal output by current acquisition circuit 2 through polling or other methods at preset intervals. The preset interval can be 5s or 10s, etc., and can be determined according to actual conditions; no restriction is placed here. After acquiring the electrical signal, control unit 1 will determine whether the electrical signal exceeds a preset first overcurrent threshold. The first overcurrent threshold can be a range of electrical signals slightly higher than the rated current of IGBT device 5, and can be determined according to actual conditions; no restriction is placed here. If the electrical signal is greater than the first preset overcurrent threshold, it indicates that the current flowing through IGBT device 5 is too large, and IGBT device 5 may have at least a minor fault such as a soft short circuit. The cause of this phenomenon may be poor wire contact, etc. Furthermore, prolonged operation in this state will damage IGBT device 5; therefore, it is necessary to control IGBT device 5 to stop working. In this embodiment, upon detecting an electrical signal exceeding the first overcurrent threshold, the control unit 1 immediately stops outputting pulse signals to the drive circuit 3, causing the drive circuit 3 to stop outputting drive signals to the IGBT device 5, thus ensuring that the PTC heater 6 stops heating. Otherwise, it indicates that the IGBT device 5 is operating within its rated current, and therefore the control unit 1 can continue outputting pulse signals to ensure that the PTC heater 6 heats up normally. In this embodiment, the action time from when the control unit 1 determines that the electrical signal of the IGBT device 5 exceeds the first preset overcurrent threshold to when it stops outputting pulse signals is approximately 10ms. The protection function implemented by the control unit 1 in conjunction with the current acquisition circuit 2 can be understood as the first level of protection for the IGBT device 5 and the PTC heater 6 in this case.

[0045] The short-circuit self-locking circuit 4 can receive the electrical signal of the IGBT device 5 collected by the current acquisition circuit 2 in real time. The electrical signal affects the working state of the short-circuit self-locking circuit 4. The range of electrical signals corresponding to four times the rated current of the IGBT device 5 can be used as the second overcurrent threshold, which can be determined according to the actual situation and is not limited here. When the electrical signal exceeds the second overcurrent threshold, it indicates that the IGBT device 5 may have at least a hard short circuit or other fault. In order to avoid damage to the IGBT device 5, heating needs to be stopped with a faster response speed than the first-level protection. If the electrical signal collected by the current acquisition circuit 2 exceeds the second overcurrent threshold, it will trigger the short-circuit self-locking circuit 4 to self-lock, outputting a short-circuit self-locking signal to the drive circuit 3 and outputting a short-circuit fault signal to the control unit 1. When the drive circuit 3 receives the short-circuit self-locking signal, it will cause the IGBT device to stop working. In this embodiment, the action time from obtaining the electrical signal collected by the current acquisition circuit 2 from the short-circuit self-locking circuit 4 to this point is about 100us. Specifically, after the drive circuit 3 receives the short-circuit self-locking signal, it will cause the pulse signal output by the control unit 1 to the drive circuit 3 to be grounded and stop generating the drive signal. Upon receiving a short-circuit fault signal, control unit 1 immediately stops outputting pulse signals to drive circuit 3. Therefore, the time required for the short-circuit self-locking circuit 4 to trigger self-locking and protect IGBT device 5 and PTC heater 6 is less than the time required for the first level of protection. The protection function achieved by combining short-circuit self-locking circuit 4 with current acquisition circuit 2 can be understood as the second level of protection for IGBT device 5 and PTC heater 6 in this case.

[0046] Furthermore, since the drive circuit 3 and the IGBT device 5 are electrically connected, the drive circuit 3 can also monitor the electrical signal of the IGBT device 5. A third overcurrent threshold can be defined as an electrical signal range ten times the rated current of the IGBT device 5, which can be determined based on actual conditions and is not limited here. When the electrical signal exceeds the third overcurrent threshold, it indicates that the IGBT device 5 has experienced a relatively serious short-circuit fault, such as leakage, requiring a faster response speed than the second-level protection to stop heating. If the drive circuit 3 detects that the electrical signal of the IGBT device 5 is greater than the third overcurrent threshold, it stops outputting drive signals to the IGBT device 5. In this embodiment, the action time from the drive circuit 3 detecting the fault to stopping heating is less than 10µs. After detecting the fault, the drive circuit 3 also outputs an abnormal operation signal to the short-circuit self-locking circuit 4. Upon receiving the abnormal operation signal, the short-circuit self-locking circuit 4 also triggers self-locking, performing subsequent actions in the second-level protection. Therefore, the time for the drive circuit 3 to monitor the IGBT device 5 for protection is less than the time required for the second-level protection. The protection function implemented by the drive circuit 3 in combination with the short-circuit self-locking circuit 4 can be understood as the third level of protection for the IGBT device 5 and the PTC heater 6 in this case.

[0047] It should be noted that in the second-level protection, the time for the self-locking triggered by the short-circuit self-locking circuit 4 is shorter than the time for the control unit 1 to stop outputting pulse signals in the first-level protection. Similarly, in the third-level protection, the time for the drive circuit 3 to disconnect the IGBT device 5 is shorter than the time for the short-circuit self-locking circuit 4 to trigger the self-locking in the second-level protection. In other words, the time required for the drive circuit 3 to disconnect the IGBT device 5 is the shortest, while the time required for the control unit 1 to stop outputting pulse signals is the longest. Essentially, the difference in time is due to the fact that the drive circuit 3 is closest to the IGBT device 5, resulting in the shortest transmission path when monitoring the electrical signal of the IGBT device 5, the fewest components required for the response, and the fastest response time. Conversely, the control unit 1 is farther from the IGBT device 5, and its response still requires passing through the drive circuit 3, thus delaying the response and requiring a longer time. The reason why the self-locking time of the short-circuit self-locking circuit 4 is less than the time of stopping the output of the pulse signal by the control unit 1 is essentially because the control unit 1 obtains the electrical signal of the current acquisition circuit 2 by polling, while the short-circuit self-locking circuit 4 obtains it in real time. Therefore, when the electrical signal exceeds the overcurrent threshold, the short-circuit self-locking circuit 4 will output the short-circuit fault signal to the control unit 1 more quickly, so that the control unit 1 stops outputting the pulse signal.

[0048] The technical solution of this utility model embodiment can acquire the electrical signal of the IGBT device in real time through a current acquisition circuit. The control unit acquires the electrical signal in a polling manner and stops outputting pulse signals to the drive circuit when the electrical signal is greater than a first overcurrent threshold, so that the drive circuit stops outputting drive signals to the IGBT device. The short-circuit self-locking circuit receives the electrical signal in real time and triggers self-locking when the electrical signal is greater than a second overcurrent threshold, outputting a short-circuit self-locking signal to the drive circuit and a short-circuit fault signal to the control unit. When the drive circuit receives the short-circuit self-locking signal, the IGBT device will stop working. The control unit will stop outputting pulse signals to the drive circuit according to the short-circuit fault signal. The drive circuit can also directly monitor the electrical signal of the IGBT device in real time and stop the IGBT device when the electrical signal is greater than a third overcurrent threshold, outputting an abnormal operation signal to the short-circuit self-locking circuit. When the short-circuit self-locking circuit receives the abnormal operation signal, it will trigger self-locking and simultaneously output a short-circuit self-locking signal to the drive circuit. Using the above structure, the heating can be cut off in a timely manner according to the magnitude of the electrical signal by acquiring the electrical signal of the IGBT device and reacting at different speeds. It can also form a circuit self-locking through hardware devices to prevent repeated current surges during the PWM control process, thus preventing damage to the IGBT device or the entire PTC heater.

[0049] In another alternative embodiment, Figure 2 A schematic diagram of the structure of a second heating control circuit for a PTC heater provided in an embodiment of this utility model is shown below. Figure 2As shown, the heating control circuit also includes a signal conversion circuit 7; the signal conversion circuit 7 is electrically connected between the current acquisition circuit 2 and the control unit 1, and is used to perform analog-to-digital conversion on the electrical signal.

[0050] The signal conversion circuit 7 converts the electrical signal collected by the current acquisition circuit 2 into an analog-to-digital signal and sends it to the control unit 1. The control unit 1 then compares the converted electrical signal with the first overcurrent threshold. If the overcurrent threshold is exceeded, the control unit stops outputting pulse signals to the drive circuit 3 to prevent damage to the IGBT device 5.

[0051] In another alternative embodiment, Figure 3 This is a schematic diagram of a current acquisition circuit provided in an embodiment of the present invention, with reference to... Figure 3 As shown, the current acquisition circuit 2 includes a differential operational amplifier circuit 21, an RC filter circuit 22, a sampling resistor R1, and a second capacitor C2. The sampling resistor R1 and the second capacitor C2 are both connected in parallel between the first input terminal and the second input terminal of the differential operational amplifier circuit 21. The first input terminal of the differential operational amplifier circuit 21 is electrically connected to the electrical signal output terminal IGBT_E of the IGBT device 5, and the second input terminal is electrically connected to the first power supply voltage terminal DC-. The output terminal of the differential operational amplifier circuit 21 is electrically connected to the electrical signal input terminal of the control unit 1 and the electrical signal input terminal I_PTC of the short-circuit self-locking circuit through the RC filter circuit 22.

[0052] Optional, continue to refer to Figure 3 The differential operational amplifier circuit 21 includes a first operational amplifier U1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7. The second resistor R2 and the third resistor R3 are connected in series between the electrical signal output terminal IGBT_E of the IGBT device 5 and the positive input terminal of the first operational amplifier U1. The fifth resistor R5 and the sixth resistor R6 are connected in series between the first power supply voltage terminal DC- and the negative input terminal of the first operational amplifier U1. The first terminal of the second capacitor C2 is electrically connected to the series connection point of the second resistor R2 and the third resistor R3, and the second terminal is electrically connected to the series connection point of the fifth resistor R5 and the sixth resistor R6. The first terminal of the fourth resistor R4 is electrically connected between the first terminal of the third resistor R3 and the positive input terminal, and the second terminal is electrically connected to the ground terminal DGND. The first terminal of the seventh resistor R7 is electrically connected to the negative input terminal, and the second terminal is electrically connected to the output terminal of the first operational amplifier U1.

[0053] The differential operational amplifier circuit 21 amplifies the electrical signal output from the current acquisition circuit 2. The differential operational amplifier circuit 21 includes a first operational amplifier U1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7. The first operational amplifier U1 has a high amplification factor. The second resistor R2, third resistor R3, fourth resistor R4, fifth resistor R5, and sixth resistor R6 are all voltage divider resistors. The seventh resistor R7 is a feedback resistor, typically connected in parallel between the negative input and output terminals of the first operational amplifier U1, which can reduce output offset voltage and improve the accuracy and stability of the analog voltage signal. The RC filter circuit 22 includes an eighth resistor R8 and a third capacitor C3, used to filter the electrical signal. It has a simple structure and strong anti-interference capability. The sampling resistor R1 converts the current signal output from the current acquisition circuit 2 into a voltage signal. The second capacitor C2 is a filter capacitor with a relatively large capacitance and a small resistance value, enabling good switching performance for high-frequency signals and serving as a filter. The first capacitor C1 is used to power and filter the first operational amplifier U1. The first power supply voltage terminal DC- is used to power the current acquisition circuit 2. The ground terminal DGND is the ground voltage.

[0054] Specifically, when an electrical signal is input to the current acquisition circuit 2 through the electrical signal output terminal IGBT_E, a voltage U will be generated across the sampling resistor R1 when the signal passes through the sampling resistor R1. R1 The generated voltage passes through a differential operational amplifier circuit 21 composed of a first operational amplifier U1 and resistors R2, R3, R4, R5, R6, and R7. Resistors R2, R3, R4, R5, R6, and R7 in the differential operational amplifier circuit 21 adjust the amplification factor, thereby increasing the voltage U. R1 The voltage is amplified by i times. After passing through the RC filter circuit 22 formed by the eighth resistor R8 and the third capacitor C3, the output voltage signal I_PTC corresponding to the input of IGBT_E is generated. The generated voltage signal is input to the control unit 1 and the short-circuit self-locking circuit 4.

[0055] In another alternative embodiment, Figure 4 This is a schematic diagram of a short-circuit self-locking circuit provided in an embodiment of the present invention, with reference to... Figure 4As shown, the short-circuit self-locking circuit 4 includes a second operational amplifier U2, a threshold voltage unit 41, and a first diode D1. The positive input terminal of the second operational amplifier U2 is electrically connected to the electrical signal output terminal I_PTC of the current acquisition circuit 2 and the operation abnormal signal output terminal DRIVER_FAULT_1 of the drive circuit 3. The negative input terminal of the second operational amplifier U2 is electrically connected to the output terminal of the threshold voltage unit 41. The first diode D1 is connected in series between the output terminal and the positive input terminal of the second operational amplifier U2. The output terminal of the second operational amplifier is also electrically connected to the short-circuit self-locking signal output terminal and the short-circuit fault signal output terminal.

[0056] Optional, continue to refer to Figure 4 The threshold voltage unit 41 includes a tenth resistor R10 and a fourteenth resistor R14; the tenth resistor R10 and the fourteenth resistor R14 are connected in series between the second power supply voltage terminal VDD1 and the ground terminal DGND, and the connection terminal of the tenth resistor R10 and the fourteenth resistor R14 serves as the output terminal of the threshold voltage unit 41.

[0057] Optional, continue to refer to Figure 4 The short-circuit self-locking circuit 4 also includes a second diode D2, a third diode D3, a fourth diode D4, a fourth capacitor C4, a ninth resistor R9, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fifteenth resistor R15, and a sixteenth resistor R16; the second diode D2 is connected in series between the electrical signal output terminal I_PTC of the current acquisition circuit 2 and the positive input terminal of the second operational amplifier U2; the sixteenth resistor R16 and the third diode D3 are connected in series between the output terminal and the positive input terminal of the drive circuit 3; the fourth diode D4 is connected in series between the tenth resistor R9 and the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, the fifteenth resistor R15, and the sixteenth resistor R16; The sixth resistor R16 and the third diode D3 are connected in series between the connection point and the ground terminal DGND; the fourth capacitor C4 and the thirteenth resistor R13 are connected in parallel and in series between the positive input terminal and the ground terminal DGND; the ninth resistor R9 is connected in series between the positive input terminal and the self-locking reset terminal SCP_RST; the eleventh resistor R11 is connected in series between the output terminal of the second operational amplifier U2 and the second power supply voltage terminal VDD1; the twelfth resistor R12 is connected in series between the output terminal and the short-circuit self-locking signal output terminal; the fifteenth resistor R15 is connected in series between the output terminal and the short-circuit fault signal output terminal.

[0058] The second operational amplifier U2 has a high amplification factor. The threshold voltage unit 41 is a reference voltage used to determine whether the input voltage signal exceeds the reference voltage, which can be a second preset overcurrent threshold. The threshold voltage unit 41 includes a tenth resistor R10, a fourteenth resistor R14, a second power supply voltage terminal VDD1, and a ground terminal DGND. The tenth resistor R10 and the fourteenth resistor R14 are both voltage divider resistors. The second power supply voltage terminal VDD1 supplies power to the second operational amplifier U2 and the threshold voltage unit 41. The ground terminal DGND is the ground voltage. The first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 are all Zener diodes used to stabilize the voltage. The fourth capacitor C4 is a filter capacitor with a relatively large capacitance and a small resistance value, enabling good switching performance for high-frequency signals and serving as a filter. The ninth resistor R9, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, the fifteenth resistor R15, and the sixteenth resistor R16 are all used for current limiting.

[0059] Specifically, the tenth resistor R10 and the fourteenth resistor R14 form a voltage divider and are connected to the negative input terminal of the second operational amplifier U2 to provide a short-circuit protection threshold for the short-circuit self-locking circuit 4 to generate a reference voltage. The second diode D2 and the third diode D3 are two input terminals of different signals connected to the positive input terminal of the second operational amplifier U2. One of the input terminals connected to the second diode D2 is the voltage signal output by the current acquisition circuit 2, and the other of the input terminal connected to the third diode D3 is the operation abnormal signal output by the driver chip U3. The two signals form an OR logic, that is, either signal input can be used for normal operation. The second operational amplifier U2 compares the signal at the positive input terminal with the reference voltage signal at the negative input terminal. When the voltage signal at the positive input terminal is greater than the voltage signal at the negative input terminal, it indicates that the voltage signal of the IGBT device 5 exceeds the preset overcurrent threshold, which triggers the short-circuit self-locking circuit 4 to self-lock. At this time, the output terminal 5 of the second operational amplifier U2 will output a high level of 5V. The 5V high-level voltage is transmitted to the positive input terminal of the second operational amplifier U2 through the first diode D1, thereby forming a fault self-lock. At the same time, the high-level signal output will output a short-circuit self-locking signal SCP to the drive circuit 3 after passing through the twelfth resistor R12, and the high-level signal will output a high-level 5V short-circuit fault signal SCP_DET to the control unit 1 after passing through the fifteenth resistor R15.

[0060] Optional, please continue to refer to Figure 4 The short-circuit self-locking circuit 4 can also directly output a signal FAULT_1 between the sixteenth resistor R16 and the third diode D3 to the control unit 1 to stop the output of the drive signal. Its function and effect are similar to the short-circuit fault signal SCP_DET, and it should be regarded as one of the embodiments of the third level of protection in this case.

[0061] In another alternative embodiment, Figure 5 This is a schematic diagram of a driving circuit provided in an embodiment of the present invention, with reference to... Figure 5 As shown, the drive circuit 3 includes a drive chip U3, a second transistor Q2, a third transistor Q3, and a drive signal circuit 31; the pulse signal output terminal IGBT_PWM1 of the control unit 1 is electrically connected to the control terminal of the second transistor Q2, the first terminal of the second transistor Q2 is grounded, and the second terminal is electrically connected to the INP pin of the drive chip U3; the short-circuit self-locking signal output terminal of the short-circuit self-locking circuit 4 is electrically connected to the control terminal of the third transistor Q3; the first terminal of the third transistor Q3 is grounded, and the second terminal is electrically connected to the control terminal of the second transistor Q2; the DRV pin of the drive chip U3 is electrically connected to the control terminal of the IGBT device 5 through the drive signal circuit 31, the Desat pin of the drive chip U3 is electrically connected to the first terminal of the IGBT device 5, and the second terminal of the IGBT device 5 is the electrical signal output terminal IGBT_E; the Fault pin of the drive chip U3 is electrically connected to the DRIVER_FAULT_1, the abnormal operation signal input terminal of the short-circuit self-locking circuit 4.

[0062] Optional, continue to refer to Figure 5 As shown, the drive signal circuit 31 includes a twentieth resistor R20, a twenty-second resistor R22, a twenty-fifth resistor R25, and a sixth diode D6; the twentieth resistor R20 is connected in series between the DRV pin of the drive chip U3 and the control terminal of the IGBT device 5; the twenty-second resistor R22 and the sixth diode D6 are connected in series and in parallel across the twentieth resistor R20; the first terminal of the twenty-fifth resistor R25 is electrically connected to the control terminal of the IGBT device 5, and the second terminal of the twenty-fifth resistor R25 is grounded.

[0063] Optional, continue to refer to Figure 5As shown, the drive circuit 3 also includes a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twenty-first resistor R21, a twenty-third resistor R23, a twenty-fourth resistor R24, a twenty-sixth resistor R26, a fifth capacitor C5, a sixth capacitor C6, and a fifth diode D5; the twenty-first resistor R21 is connected in series between the pulse signal input terminal IGBT_PWM1 and the control terminal of the second transistor Q2; the twenty-third resistor R23 is connected in series between the short-circuit self-locking signal output terminal and the control terminal of the third transistor Q3; and the twenty-sixth resistor R26 is connected in series between the control terminal of the third transistor Q3 and the first terminal. The twenty-fourth resistor R24 ​​is connected in series between the control terminal and the first terminal of the second transistor Q2; the nineteenth resistor R19 is connected in series between the third power supply voltage terminal VDD2 and the INP pin of the driver chip U3; the seventeenth resistor R17 is connected in series between the third power supply voltage terminal VDD2 and the SEN pin of the driver chip U3; the sixth capacitor C6 is connected in series between the SEN pin and the ground terminal DGND; the ground terminal DGND is also electrically connected to the KGND pin and the VEE pin of the driver chip U3; the eighteenth resistor R18 and the fifth diode D5 are connected in series between the Desat pin of the driver chip U3 and the first terminal of the IGBT device 5.

[0064] Among them, the driver chip U3 is the core control chip of the driver circuit 3, used to output abnormal operation signals and drive signals to stop or start the IGBT device 5. The second transistor Q2 and the third transistor Q3 are both semiconductor devices with functions such as detection, rectification, switching, and voltage regulation. Both the second transistor Q2 and the third transistor Q3 can include MOSFETs, etc. The drive signal circuit 31 is used to turn on the IGBT device 5, so that the IGBT device 5 can operate. The drive signal circuit 31 includes the twentieth resistor R20, the twenty-second resistor R22, the twenty-fifth resistor R25, and the sixth diode D6. The twentieth resistor R20, the twenty-second resistor R22, and the twenty-fifth resistor R25 are all voltage divider resistors. The sixth diode D6 is a Zener diode used to stabilize the voltage. The seventeenth resistor R17, the eighteenth resistor R18, the nineteenth resistor R19, the twenty-first resistor R21, the twenty-third resistor R23, the twenty-fourth resistor R24, and the twenty-sixth resistor R26 are all voltage divider resistors. Both capacitors C5 (fifth capacitor) and C6 (sixth capacitor) are filter capacitors, possessing relatively large capacitance and low resistance, enabling them to achieve good switching performance for high-frequency signals and thus serving a filtering function. Diode D5 is a Zener diode.

[0065] Specifically, driver chip U3 provides drive capability for IGBT device 5. When the high-level 5V pulse signal output by control unit 1 is input to the second transistor Q2 through the pulse signal output terminal IGBT_PWM1, the second transistor D2 turns on and starts working, pulling the level of the INP pin of driver chip U3 low to ground. At this time, the DRV pin of driver chip U3 will output a high level of 15V and transmit it to the control terminal of IGBT device 5 through the twentieth resistor R20. After receiving a level higher than 5V, the control terminal of IGBT device 5 will turn on, and IGBT device 5 will start working and generate current. After IGBT device 5 starts working, the current flows through the load connector, i.e., PTC heater 6, and heats PTC heater 6. When a large instantaneous current, such as a current exceeding 10 times the rated current of IGBT device 5, passes through IGBT device 5, the voltage Vce between the first and second terminals of IGBT device 5 will rise instantaneously. Since the Desat pin of driver chip U3 continuously monitors the voltage Vce between the first and second terminals of IGBT device 5, when the voltage Vce rises instantaneously to the third preset overcurrent threshold:

[0066] 1. Driver chip U3 first stops outputting drive signals;

[0067] 2. Simultaneously, the Fault pin of the driver chip U3 will output the operation abnormality signal DRIVER_FAULT_1 and send it to the sixteenth resistor R16 in the short-circuit self-locking circuit 4. After receiving the operation abnormality signal DRIVER_FAULT_1, the short-circuit self-locking circuit 4 will output a 5V high-level short-circuit self-locking signal SCP. After receiving the high-level signal, the third transistor Q3 will turn on, thereby connecting the pulse signal output terminal IGBT_PWM_1 signal to ground. At this time, it can be understood that the control of the pulse signal output terminal IGBT_PWM1 is ignored, and the IGBT device 5 is disconnected.

[0068] 3. When the short-circuit self-locking circuit 4 is triggered, it will also output a short-circuit fault signal to the control unit 1, causing the control unit 1 to immediately stop outputting pulse signals to the drive circuit 3.

[0069] Ultimately, this ensures that the PTC heater 6 completely stops heating in all layers of the heating circuit.

[0070] It should be understood that the various forms of the process shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this utility model can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this utility model can be achieved, and this is not limited herein.

[0071] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A heating control circuit for a PTC heater, characterized in that, It includes a control unit, a current acquisition circuit, a drive circuit, and a short-circuit self-locking circuit; the control unit is electrically connected to the current acquisition circuit, the drive circuit, and the short-circuit self-locking circuit respectively; the short-circuit self-locking circuit is electrically connected to the current acquisition circuit and the drive circuit respectively; the current acquisition circuit and the drive circuit are also electrically connected to the IGBT device respectively; and the IGBT device is electrically connected to the PTC heater. The control unit is used to output pulse signals to the drive circuit; The driving circuit is used to convert the pulse signal into a driving signal, and adjust the heating power of the PTC heater through the IGBT device; The current acquisition circuit is used to acquire the electrical signals of the IGBT device in real time; The control unit is also configured to acquire the electrical signal and stop outputting the pulse signal to the drive circuit according to the electrical signal; The short-circuit self-locking circuit is used to acquire the electrical signal and the operation abnormal signal output by the drive circuit. Based on the electrical signal or the operation abnormal signal, the short-circuit self-locking circuit is triggered to self-lock, and a short-circuit self-locking signal is output to the drive circuit, and a short-circuit fault signal is output to the control unit. The control unit is also configured to stop outputting the pulse signal to the drive circuit based on the short-circuit fault signal; The driving circuit is also used to monitor the electrical signal of the IGBT device, stop the IGBT device from working according to the electrical signal, and output the abnormal operation signal to the short-circuit self-locking circuit; or stop the IGBT device from working according to the short-circuit self-locking signal.

2. The heating control circuit according to claim 1, characterized in that, It also includes signal conversion circuitry; The signal conversion circuit is electrically connected between the current acquisition circuit and the control unit, and the signal conversion circuit is used to perform analog-to-digital conversion on the electrical signal.

3. The heating control circuit according to claim 1, characterized in that, The current acquisition circuit includes a differential operational amplifier circuit, an RC filter circuit, a sampling resistor, and a second capacitor; The sampling resistor and the second capacitor are both connected in parallel between the first input terminal and the second input terminal of the differential operational amplifier circuit. The first input terminal of the differential operational amplifier circuit is electrically connected to the electrical signal output terminal of the IGBT device, and the second input terminal is electrically connected to the first power supply voltage terminal. The output terminal of the differential operational amplifier circuit is electrically connected to the electrical signal input terminal of the control unit and the electrical signal input terminal of the short-circuit self-locking circuit through the RC filter circuit.

4. The heating control circuit according to claim 3, characterized in that, The differential operational amplifier circuit includes a first operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor; The second and third resistors are connected in series between the electrical signal output terminal of the IGBT device and the positive input terminal of the first operational amplifier; the fifth and sixth resistors are connected in series between the first power supply voltage terminal and the negative input terminal of the first operational amplifier; the first terminal of the second capacitor is electrically connected to the series connection point of the second and third resistors, and the second terminal is electrically connected to the series connection point of the fifth and sixth resistors; the first terminal of the fourth resistor is electrically connected between the first terminal of the third resistor and the positive input terminal, and the second terminal is electrically connected to the ground terminal; the first terminal of the seventh resistor is electrically connected to the negative input terminal, and the second terminal is electrically connected to the output terminal of the first operational amplifier.

5. The heating control circuit according to claim 1, characterized in that, The short-circuit self-locking circuit includes a second operational amplifier, a threshold voltage unit, and a first diode; The positive input terminal of the second operational amplifier is electrically connected to the electrical signal output terminal of the current acquisition circuit and the operation abnormal signal output terminal of the driving circuit. The negative input terminal of the second operational amplifier is electrically connected to the output terminal of the threshold voltage unit. The first diode is connected in series between the output terminal and the positive input terminal of the second operational amplifier. The output terminal of the second operational amplifier is also electrically connected to the short-circuit self-locking signal output terminal and the short-circuit fault signal output terminal.

6. The heating control circuit according to claim 5, characterized in that, The threshold voltage unit includes a tenth resistor and a fourteenth resistor; The tenth resistor and the fourteenth resistor are connected in series between the second power supply voltage terminal and the ground terminal, and the connection terminal of the tenth resistor and the fourteenth resistor serves as the output terminal of the threshold voltage unit.

7. The heating control circuit according to claim 6, characterized in that, The short-circuit self-locking circuit also includes a second diode, a third diode, a fourth diode, a fourth capacitor, a ninth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fifteenth resistor, and a sixteenth resistor; The second diode is connected in series between the electrical signal output terminal of the current acquisition circuit and the positive input terminal of the second operational amplifier; the sixteenth resistor and the third diode are connected in series between the output terminal of the drive circuit and the positive input terminal; the fourth diode is connected in series between the series connection point of the sixteenth resistor and the third diode and the ground terminal; the fourth capacitor and the thirteenth resistor are connected in parallel and in series between the positive input terminal and the ground terminal; the ninth resistor is connected in series between the positive input terminal and the self-locking reset terminal; the eleventh resistor is connected in series between the output terminal of the second operational amplifier and the second power supply voltage terminal; the twelfth resistor is connected in series between the output terminal and the short-circuit self-locking signal output terminal; and the fifteenth resistor is connected in series between the output terminal and the short-circuit fault signal output terminal.

8. The heating control circuit according to claim 1, characterized in that, The driving circuit includes a driving chip, a second transistor, a third transistor, and a driving signal circuit; The pulse signal output terminal of the control unit is electrically connected to the control terminal of the second transistor. The first terminal of the second transistor is grounded, and the second terminal is electrically connected to the INP pin of the driver chip. The short-circuit self-locking signal output terminal of the short-circuit self-locking circuit is electrically connected to the control terminal of the third transistor. The first terminal of the third transistor is grounded, and the second terminal is electrically connected to the control terminal of the second transistor. The DRV pin of the driver chip is electrically connected to the control terminal of the IGBT device through the drive signal circuit. The Desat pin of the driver chip is electrically connected to the first terminal of the IGBT device, and the second terminal of the IGBT device is an electrical signal output terminal. The Fault pin of the driver chip is electrically connected to the operation abnormality signal input terminal of the short-circuit self-locking circuit.

9. The heating control circuit according to claim 8, characterized in that, The drive signal circuit includes a twentieth resistor, a twenty-second resistor, a twenty-fifth resistor, and a sixth diode; The twentieth resistor is connected in series between the DRV pin of the driver chip and the control terminal of the IGBT device; the twentieth resistor and the sixth diode are connected in series and in parallel across the twentieth resistor; the first terminal of the twentieth resistor is electrically connected to the control terminal of the IGBT device, and the second terminal of the twentieth resistor is grounded.

10. The heating control circuit according to claim 9, characterized in that, The driving circuit also includes a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twenty-first resistor, a twenty-third resistor, a twenty-fourth resistor, a twenty-sixth resistor, a fifth capacitor, a sixth capacitor, and a fifth diode; The 21st resistor is connected in series between the pulse signal input terminal and the control terminal of the second transistor; the 23rd resistor is connected in series between the short-circuit self-locking signal output terminal and the control terminal of the third transistor; the 26th resistor is connected in series between the control terminal and the first terminal of the third transistor; the 24th resistor is connected in series between the control terminal and the first terminal of the second transistor; the 19th resistor is connected in series between the third power supply voltage terminal and the INP pin of the driver chip; the 17th resistor is connected in series between the third power supply voltage terminal and the SEN pin of the driver chip; the 6th capacitor is connected in series between the SEN pin and the ground terminal; the ground terminal is also electrically connected to the KGND pin and the VEE pin of the driver chip; the 18th resistor and the 5th diode are connected in series between the Desat pin of the driver chip and the first terminal of the IGBT device.

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