An igbt module junction temperature monitoring device and method with thermistor

Abstract

The application provides an IGBT module junction temperature monitoring device and method with a thermistor. The IGBT module junction temperature monitoring device comprises a resistance voltage division subcircuit, a voltage comparison subcircuit, a voltage / current conversion subcircuit, a current / voltage conversion subcircuit and a signal processor. The voltage comparison subcircuit comprises a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a first diode and a second diode. When the thermistor is a negative temperature coefficient thermistor, the thermistor is located between an input end of the resistance voltage division subcircuit and an output end of the resistance voltage division subcircuit in the resistance voltage division subcircuit. When the thermistor is a positive temperature coefficient thermistor, the thermistor is located between a ground end of the resistance voltage division subcircuit and the output end of the resistance voltage division subcircuit in the resistance voltage division subcircuit.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of IGBT module junction temperature monitoring device and method, especially in the field of continuous casting, in the frequency conversion power supply for electromagnetic stirring, the junction temperature monitoring device and detection method of IGBT module with thermistor (especially negative temperature coefficient thermistor) in it. BACKGROUND

[0002] In the field of continuous casting, the junction temperature of IGBT module in the frequency conversion power supply for electromagnetic stirring needs to be monitored to ensure production safety.

[0003] In the prior art, the junction temperature is generally converted into resistance value by the NTC thermistor (negative temperature coefficient thermistor) built in the IGBT module. That is, the NTC thermistor converts the junction temperature of the IGBT module into resistance value, and then converts the resistance value into other electrical signals and transmits them to the main control board of the electromagnetic stirring system (i.e. the control board that controls the whole electromagnetic stirring system). When the junction temperature is monitored to be greater than a certain set value, the main control board is used to stop the frequency conversion power supply for electromagnetic stirring in time. The IGBT module that constitutes the inverter circuit in the large-capacity frequency conversion power supply for electromagnetic stirring (i.e. the power supply of the electromagnetic stirring system) generally has a certain physical structural distance from the main control board of the electromagnetic stirring system (also as the control end of the power supply of the electromagnetic stirring system). The cable for long-distance transmission of signals may be disconnected. When the frequency conversion power supply is working, if the main control board monitors that the electrical signal is 0 (for example, 0V or 0mA), it cannot be judged whether the actual electrical signal transmitted by the cable is 0 or the cable has been disconnected. If the main control board receives a signal of 0 due to the disconnection of the cable and mistakenly judges that the actual electrical signal transmitted by the cable is 0, the main control board cannot monitor the junction temperature of the IGBT module in the frequency conversion power supply in time.

[0004] In addition, with the continuous expansion of continuous casting steel, especially silicon steel, automobile plate steel and stainless steel, and the continuous development of domestic forging wind power, high-speed train wheels, petrochemical and engineering machinery, the market demand for larger section, more reliable quality and higher product performance is increasingly urgent, which requires the center of electromagnetic stirring to have a larger magnetic field strength. Larger magnetic field strength requires the electromagnetic stirring frequency power supply to be able to output larger current capacity. The maximum demand current size of the largest 1400mm diameter ultra-large square billet electromagnetic stirrer in a domestic steel plant has reached 1600A effective value. Therefore, the excessive output current of the electromagnetic stirring power supply will cause great electromagnetic interference to the junction temperature remote collection system of the IGBT module in the electromagnetic stirring frequency power supply. Moreover, the IGBT module in the large-capacity electromagnetic stirring frequency power supply is generally physically distant from the main control board of the electromagnetic stirring system, so that in the process of long-distance signal transmission, the signal is also easily affected by the strong magnetic field and electric field interference of the large current and high voltage output by the electromagnetic stirring frequency power supply, greatly affecting the monitoring accuracy of the IGBT module junction temperature (which may make the monitoring accuracy greater than 5°C).

[0005] For the processing of the resistance value of the NTC thermistor, the prior art generally adopts the following three forms:

[0006] (1) Voltage source excitation. In the voltage source excitation form, the resistance value of the thermistor is converted into a voltage signal, which is then transmitted to the main control board of the electromagnetic stirring system through a long-distance transmission line. The real-time resistance value of the NTC thermistor is calculated by the voltage drop on the thermistor, and the IGBT module junction temperature is calculated according to the resistance value. This form is only suitable for cases where the IGBT module constituting the inverter circuit in the electromagnetic stirring frequency power supply is close to the main control board of the electromagnetic stirring system. When the electromagnetic stirring frequency power supply is far away from the main control board of the electromagnetic stirring system, due to strong electromagnetic interference and the voltage drop caused by the transmission wire itself, the voltage signal received by the main control board is significantly different from the initial transmitted voltage signal, making it impossible to effectively monitor the junction temperature.

[0007] (2) Current source excitation. In the current source excitation form, the current signal flowing through the thermistor is detected, and then the current signal is transmitted to the main control board of the electromagnetic stirring system through a long-distance transmission line. The resistance value of the NTC thermistor in real time is calculated through the current flowing through the thermistor and the constant voltage applied to the thermistor. The size of the IGBT module junction temperature is calculated according to the resistance value. However, the junction temperature monitoring of the IGBT module generally requires a temperature range of at least -20°C-110°C. When the temperature is below 0°C, the resistance of the NTC thermistor of the IGBT module is very large, and even can reach tens of KΩ, resulting in a very small current flowing through the NTC thermistor at this time. When the temperature is greater than 0°C and the temperature is relatively high, the resistance of the thermistor is very small, resulting in a very large current flowing through the NTC thermistor at this time. When the main control board of the electromagnetic stirring system processes the current signal transmitted over a long distance, the current signal is often converted into a voltage signal again through a sampling resistor, so that the voltage signal processing circuit not only needs to have a very large voltage input range, but also needs to have a high voltage detection accuracy, thereby greatly increasing the circuit complexity and cost of the junction temperature monitoring device.

[0008] (3) In the patent application CN 109855758 A, the resistance value analog signal of the collected NTC thermistor is first converted into a frequency signal by the sending end processor (i.e. voltage-to-frequency conversion), and then the frequency size of the sending end is identified by the input capture of the receiving end processor. Finally, the core junction temperature of the IGBT is calculated according to the pre-constructed formula. This method requires two independent and isolated high-performance processors to work simultaneously, and also requires the use of optical fiber medium to transmit signals. The cost of the optical fiber medium and hardware such as the sending end, optical fiber transmission cable and receiving end needs to be considered. The system is complex and the cost is very high. Moreover, with the increase of the sampling number of the IGBT module junction temperature, the voltage-to-frequency conversion will occupy a large amount of resources of the processor of the main control board, which will interfere with the overall control of the electromagnetic stirring system. SUMMARY

[0009] The problem to be solved by the present application is that in the prior art, when the junction temperature of the IGBT module with a thermistor in the frequency conversion power supply for electromagnetic stirring is monitored, if the signal received by the main control board is 0 due to the disconnection of the cable, it will be misjudged that the actual electrical signal transmitted by the cable is 0, resulting in the inability to monitor the junction temperature of the IGBT module in the frequency conversion power supply in a timely manner. A junction temperature monitoring device for an IGBT module with a thermistor is provided.

[0010] To solve the above technical problems, the technical scheme adopted by the present application is: a junction temperature monitoring device for an IGBT module with a thermistor, comprising at least one resistor connected in series with the thermistor, the at least one resistor and the thermistor forming a resistance voltage dividing subcircuit, the input end of the resistance voltage dividing subcircuit being electrically connected with the output end of a first power supply:

[0011] The IGBT module junction temperature monitoring device further comprises a voltage comparison sub-circuit, a voltage / current conversion sub-circuit, a current / voltage conversion sub-circuit and a signal processor connected in sequence.

[0012] The correspondence between the resistance value of the thermistor and the theoretical value of the voltage signal collected by the signal processor is determined according to the actual circuit of the IGBT module junction temperature monitoring device and is known. According to the voltage signal collected by the signal processor, the correspondence between the resistance value of the thermistor and the theoretical value of the voltage signal collected by the signal processor, and the relationship between the resistance value of the thermistor and the ambient temperature (i.e. the junction temperature) of the thermistor, the junction temperature or the temperature range of the junction temperature can be obtained.

[0013] The voltage comparison sub-circuit comprises a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a first diode and a second diode.

[0014] One input end, the other input end and the output end of the first operational amplifier are electrically connected with a reference voltage supply end, one end of the first resistor and the anode of the first diode, respectively, and the voltage of the reference voltage supply end is greater than 0.

[0015] One input end, the other input end and the output end of the second operational amplifier are electrically connected with the output end of the resistance voltage dividing sub-circuit, one end of the second resistor and the anode of the second diode, respectively.

[0016] The other end of the first resistor, the cathode of the first diode, the other end of the second resistor and the cathode of the second diode are electrically connected with each other, thereby forming an output end of the voltage comparison sub-circuit.

[0017] When the thermistor is a negative temperature coefficient thermistor, the thermistor is located between the input end of the resistance voltage dividing sub-circuit and the output end of the resistance voltage dividing sub-circuit in the resistance voltage dividing sub-circuit.

[0018] When the thermistor is a positive temperature coefficient thermistor, the thermistor is located between the ground end of the resistance voltage dividing sub-circuit and the output end of the resistance voltage dividing sub-circuit in the resistance voltage dividing sub-circuit.

[0019] According to the above technical solution:

[0020] When the thermistor is a negative temperature coefficient thermistor: if the junction temperature is less than a certain preset value, the thermistor has a large resistance, so that the resistance voltage division between the ground end of the resistance voltage division sub-circuit and the output end of the resistance voltage division sub-circuit is small, so that the voltage at one input end of the second operational amplifier is small and less than the voltage at the reference voltage supply end, so that the first diode is in a conductive state, the first operational amplifier works normally, and the current flowing through the first resistor is extremely small, that is, the output at the output end of the voltage comparison sub-circuit is the voltage value at the reference voltage supply end, while the second diode is in a cut-off state, and the current flowing through the second resistor is large, that is, the output end of the second operational amplifier is 0V; if the junction temperature is greater than the preset value, the resistance proportion of the thermistor in the resistance voltage division sub-circuit makes the voltage at one input end of the second operational amplifier (i.e. the output voltage of the resistance voltage division sub-circuit) greater than the voltage at the reference voltage supply end, so that the second diode is in a conductive state, the second operational amplifier works normally, and the current flowing through the second resistor is extremely small, that is, the output at the output end of the voltage comparison sub-circuit is the voltage value at the output end of the resistance voltage division sub-circuit, while the first diode is in a cut-off state, and the current flowing through the first resistor is large, that is, the output end of the first operational amplifier is 0V; if the junction temperature is equal to the preset value, the resistance proportion of the thermistor in the resistance voltage division sub-circuit makes the voltage at one input end of the second operational amplifier (i.e. the output voltage of the resistance voltage division sub-circuit) equal to the voltage at the reference voltage supply end, so that the first diode and the second diode are both in a conductive state, the first operational amplifier and the second operational amplifier both work normally, that is, the output at the output end of the voltage comparison sub-circuit is the voltage value at the output end of the resistance voltage division sub-circuit (i.e. the voltage at the reference voltage supply end).

[0021] When the thermistor is a positive temperature coefficient thermistor: if the junction temperature is less than a certain preset value, the thermistor has a small resistance, so that the thermistor voltage division between the ground end of the resistance voltage division subcircuit and the output end of the resistance voltage division subcircuit is small, so that the voltage at one input end of the second operational amplifier is small and less than the voltage at the reference voltage supply end, so that the first diode is in a conductive state, the first operational amplifier works normally, and the current flowing through the first resistor is extremely small, that is, the output at the output end of the voltage comparison subcircuit is the voltage value at the reference voltage supply end, and at this time the second diode is in a cut-off state, and the current flowing through the second resistor is large, that is, the output end of the second operational amplifier is 0V; if the junction temperature is greater than the preset value, the proportion of the resistance value of the thermistor in the resistance voltage division subcircuit makes the voltage at one input end of the second operational amplifier (i.e. the output voltage of the resistance voltage division subcircuit) greater than the voltage at the reference voltage supply end, so that the second diode is in a conductive state, the second operational amplifier works normally, and the current flowing through the second resistor is extremely small, that is, the output at the output end of the voltage comparison subcircuit is the voltage value at the output end of the resistance voltage division subcircuit, and at this time the first diode is in a cut-off state, and the current flowing through the first resistor is large, that is, the output end of the first operational amplifier is 0V; if the junction temperature is equal to the preset value, the proportion of the resistance value of the thermistor in the resistance voltage division subcircuit makes the voltage at one input end of the second operational amplifier (i.e. the output voltage of the resistance voltage division subcircuit) equal to the voltage at the reference voltage supply end, so that the first diode and the second diode are both in a conductive state, and the first operational amplifier and the second operational amplifier both work normally, that is, the output at the output end of the voltage comparison subcircuit is the voltage value at the output end of the resistance voltage division subcircuit (i.e. the voltage at the reference voltage supply end).

[0022] Since the voltage at the reference voltage supply end is greater than 0, the output at the output end of the voltage comparison subcircuit is at least greater than 0V, so that the subsequent transmitted signal is not 0V or 0mA, so that when the current signal is transmitted from the voltage / current conversion subcircuit to the current / voltage conversion subcircuit, if the current / voltage conversion subcircuit receives a 0mA signal, the signal input end of the signal processor will receive a 0V signal (if the signal processor directly receives a voltage signal), so that it can be determined that the cable is disconnected, so that the situation that the main control board receives a 0 signal due to the disconnection of the cable is misjudged as the actual electrical signal transmitted by the cable being 0 can be avoided, and safety is ensured.

[0023] In the above technical solution, the relationship between the output current of the voltage / current conversion subcircuit and the input voltage, and the relationship between the output voltage of the current / voltage conversion subcircuit and the input current are both linear relationships.

[0024] In the application, the correspondence between the resistance value of the thermistor and the theoretical value of the signal (voltage signal or digital signal) collected by the signal processor is determined, so that the junction temperature value or the temperature range to which the junction temperature belongs can be obtained according to the electric signal.

[0025] In the technical solution, the voltage / current conversion sub-circuit comprises a third operational amplifier, a third resistor, a fourth resistor and an NMOS tube.

[0026] One input end and an output end of the third operational amplifier are correspondingly electrically connected with an output end of the voltage comparison sub-circuit and one end of the third resistor, respectively.

[0027] The gate of the NMOS tube is electrically connected with the other end of the third resistor, the source of the NMOS tube, the other input end of the third operational amplifier and one end of the fourth resistor are mutually electrically connected, and the other end of the fourth resistor is grounded.

[0028] The drain of the NMOS tube is the output end of the voltage / current conversion sub-circuit.

[0029] In the application, the voltage is converted into current, so that the current signal can be transmitted through a long-distance cable, and the signal can be transmitted from the position of the IGBT module of the frequency conversion power supply for electromagnetic stirring to the position of the main control board of the electromagnetic stirring system. Through the long-distance cable transmission of the current signal, the voltage drop caused by the long-distance cable transmission of the current signal can be avoided, and the influence of the magnetic field and the electric field interference on the transmitted electric signal can be reduced as much as possible.

[0030] In the technical solution, the current / voltage conversion sub-circuit is electrically connected with the signal processor through the voltage processing sub-circuit; the current / voltage conversion sub-circuit comprises a sampling resistor. The voltage between the two ends of the sampling resistor is the output voltage of the current / voltage conversion sub-circuit. The input end of the voltage processing sub-circuit, one end of the sampling resistor and the output end of the second power supply are electrically connected, the other end of the sampling resistor, the drain of the NMOS tube and the reference ground of the third power supply are mutually electrically connected, and the reference ground of the second power supply is electrically connected with the reference ground of the first power supply.

[0031] The power supply end on the input side of the voltage processing sub-circuit and the ground end on the input side are correspondingly electrically connected with the output end of the third power supply and the reference ground of the third power supply, respectively; the third power supply and the second power supply are different power supplies, and the reference ground of the second power supply and the reference ground of the third power supply are independent of each other (i.e., the second power supply and the third power supply do not share the ground); and the voltage processing sub-circuit is an optically isolated voltage amplification sub-circuit or an A / D converter.

[0032] In the application, the optically isolated voltage amplification sub-circuit in the form of optical isolation improves the anti-electromagnetic interference capability of the IGBT module junction temperature monitoring device.

[0033] In a preferred embodiment, the IGBT module constitutes an inverter circuit of an electromagnetic stirring system power supply, the first power supply, the second power supply, the resistance voltage division sub-circuit, the voltage comparison sub-circuit, and the voltage / current conversion sub-circuit are arranged close to the IGBT module, and the current / voltage conversion sub-circuit, the voltage processing sub-circuit, and the signal processor are arranged close to or on a main control panel of the electromagnetic stirring system.

[0034] Through the above arrangement, when the electromagnetic stirring system power supply is far away from the main control panel of the electromagnetic stirring system, the output current of the voltage / current conversion sub-circuit is transmitted to the current / voltage conversion sub-circuit through a long-distance cable, so that the transmitted current signal is less affected by electromagnetic interference and cable voltage drop.

[0035] In a preferred embodiment, the second power supply is the same as the first power supply. Through the above arrangement, the number of power supplies is reduced, and the circuit structure is simplified.

[0036] In a preferred embodiment, the A / D converter and the signal processor are independently arranged, or the A / D converter is integrated in the signal processor.

[0037] In the above technical solution, the optical isolation voltage amplification sub-circuit comprises a linear optocoupler, a fourth operational amplifier, a fifth resistor, a sixth resistor, and a seventh resistor.

[0038] The input end of the linear optocoupler is an input end of the optical isolation voltage amplification sub-circuit, and the input side of the linear optocoupler is an input side of the optical isolation voltage amplification sub-circuit. The input end of the linear optocoupler, one end of the sampling resistor, and the output end of the second power supply are electrically connected to each other.

[0039] The positive output end and the negative output end of the linear optocoupler are respectively electrically connected to one end of the fifth resistor and one end of the sixth resistor. One input end of the fourth operational amplifier is electrically connected to the other end of the fifth resistor, and the other input end of the fourth operational amplifier, the other end of the sixth resistor, and one end of the seventh resistor are electrically connected to each other. The other end of the seventh resistor is electrically connected to the output end of the fourth operational amplifier, thereby constituting an output end of the optical isolation voltage amplification sub-circuit.

[0040] The power supply end of the input side of the linear optocoupler is electrically connected to the output end of the third power supply, and the ground end of the input side of the linear optocoupler is electrically connected to the reference ground of the third power supply. The power supply end of the output side of the linear optocoupler and the power supply end of the fourth operational amplifier are electrically connected to the output end of the fourth power supply, and the ground end of the output side of the linear optocoupler and the ground end of the fourth operational amplifier are electrically connected to the reference ground of the fourth power supply.

[0041] The second power supply, the third power supply and the fourth power supply are different power supplies, and the reference ground of the second power supply, the reference ground of the third power supply and the reference ground of the fourth power supply are independent of each other (that is, the second power supply, the third power supply and the fourth power supply are all independently grounded).

[0042] In the application, the linear optocoupler in the form of optical isolation is used to convert the voltage signal into a differential output signal, and the single-ended output signal is obtained after the differential output signal is amplified (for example, 1:1 amplification) by the fourth operational amplifier. The use of the linear optocoupler improves the anti-electromagnetic interference capability of the IGBT module junction temperature monitoring device, and the use of the differential amplification structure greatly improves the anti-common-mode interference capability.

[0043] In the above technical solution, the relationship between the output voltage and the input voltage of the optical isolation voltage amplification sub-circuit is a linear relationship; preferably, the ratio of the output voltage to the input voltage of the optical isolation voltage amplification sub-circuit is 1:1.

[0044] Through the above setting, the correspondence between the resistance value of the thermistor and the theoretical value of the signal collected by the signal processor is determined.

[0045] In the above technical solution, the IGBT module junction temperature monitoring device further comprises an eighth resistor and a ninth resistor, and the eighth resistor, the ninth resistor and the thermistor are connected in series to form the resistance voltage dividing sub-circuit.

[0046] When the thermistor is a negative temperature coefficient thermistor, one end of the thermistor is the input end of the resistance voltage dividing sub-circuit, the other end of the thermistor is electrically connected to the reference ground of the first power supply through the eighth resistor and the ninth resistor in turn, and the connection end of the eighth resistor and the ninth resistor is the output end of the resistance voltage dividing sub-circuit.

[0047] When the thermistor is a positive temperature coefficient thermistor, one end of the eighth resistor is the input end of the resistance voltage dividing sub-circuit, the other end of the eighth resistor is electrically connected to the reference ground of the first power supply through the ninth resistor and the thermistor in turn, and the connection end of the eighth resistor and the ninth resistor is the output end of the resistance voltage dividing sub-circuit.

[0048] In the above technical solution, when the ambient temperature value (i.e. the junction temperature) of the thermistor is less than Ta, the voltage at the output end of the resistance voltage dividing sub-circuit is less than the voltage at the reference voltage supply end, and when the ambient temperature value of the thermistor (R3) is greater than or equal to Ta, the voltage at the output end of the resistance voltage dividing sub-circuit is greater than or equal to the voltage at the reference voltage supply end, wherein [Ta, Tb] is a preset monitoring temperature range; or

[0049] When the temperature value of the environment where the thermistor is located is less than or equal to Ta, the voltage at the output end of the resistance voltage dividing sub-circuit is less than or equal to the voltage at the reference voltage supply end; when the temperature value of the environment where the thermistor (R3) is located is greater than Ta, the voltage at the output end of the resistance voltage dividing sub-circuit is greater than the voltage at the reference voltage supply end, wherein [Ta, Tb] is a preset monitoring temperature range.

[0050] Preferably, the voltage at the reference voltage supply end is 2.5 V.

[0051] In the technical solution, each power supply is an isolated power supply. By using the isolated power supply, the anti-electromagnetic interference capability of the IGBT module junction temperature monitoring device is improved.

[0052] The application further provides a junction temperature monitoring method using the IGBT module junction temperature monitoring device, the junction temperature monitoring method comprising: obtaining the junction temperature Tj of the IGBT module or the temperature range to which the junction temperature Tj belongs according to the correspondence between the temperature value of the environment where the thermistor is located and the resistance value of the thermistor, the correspondence between the resistance value of the thermistor and the theoretical value of the signal collected by the signal processor, and the signal Ux actually collected by the signal processor; the signal collected by the signal processor is a voltage signal or a digital signal.

[0053] When the signal processor integrates an A / D conversion module, the signal collected by the signal processor is a voltage signal collected by the A / D conversion module. If the signal processor does not integrate an A / D conversion module or uses an external A / D conversion circuit or chip, the signal received by the signal processor is a digital signal.

[0054] In the technical solution, the correspondence between the theoretical value of the signal collected by the signal processor and the temperature value of the environment where the thermistor is located is that the temperature values Ta, Ta+△T, Ta+2△T, …, Ta+n△T, Tb are respectively in one-to-one correspondence with the theoretical values Ua, Uc(1), Uc(2), …, Uc(n), Ub of the collected signals;

[0055] wherein △T is a preset temperature increment, 0.5°C≤△T≤2°C; [Ta, Tb] is a preset monitoring temperature range; Tb=Ta+(n+1)△T or Ta+n△T<Tb<Ta+(n+1)△T;

[0056] The step of obtaining the junction temperature Tj of the IGBT module or the temperature range to which the junction temperature Tj belongs according to the correspondence between the temperature value of the environment where the thermistor is located and the resistance value of the thermistor, the correspondence between the resistance value of the thermistor and the theoretical value of the signal collected by the signal processor, and the signal Ux actually collected by the signal processor comprises:

[0057] If Ux=Ua, it is judged that Tj≤Ta;

[0058] If Ux > Ub, it is judged that Tj > Tb;

[0059] If Ua < Ux ≤ Uc (1), it is judged that Ta < Tj ≤ Ta + △T or Tj = Ta;

[0060] If Uc (n) < Ux ≤ Ub, it is judged that Ta + n△T < Ux ≤ Tb or Tj = Tb.

[0061] 1. The scheme requires less types and quantities of components, and can use general electronic components, so the hardware cost is low;

[0062] 2. The scheme has lower performance processing capacity requirements for the signal processor (i.e. the processor of the main control board, such as MCU), and occupies less resources of the signal processor;

[0063] 3. The sampling conversion end of the thermistor and the sampling end of the signal processor are electrically isolated in a linear isolation optical coupling light isolation mode and an isolated power supply isolation mode, which greatly improves the electromagnetic interference ability of the IGBT module junction temperature monitoring device with a thermistor. In addition, the differential amplification structure can also greatly improve the ability to resist common mode interference;

[0064] 4. The scheme takes advantage of the characteristics of the large resistance value of the thermistor at low temperature and the strong anti-electromagnetic interference ability of the current source when transmitting signals, and avoids the characteristics of the voltage source that is not suitable for strong electromagnetic interference and the characteristics of the current source that is not suitable for the large resistance value of the thermistor at low temperature. The application meets the demand of long-distance signal transmission while ensuring the accuracy of the large-capacity IGBT module junction temperature monitoring device and the anti-electromagnetic interference ability of the device;

[0065] 5. In the scheme, the minimum transmission circuit signal is greater than 0mA when transmitting at a long distance, avoiding the defect that the current signal may be broken in the electrical transmission process and misjudged as 0mA. BRIEF DESCRIPTION OF DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0067] Figure 1 is a structure block diagram of the IGBT module junction temperature monitoring device of embodiment 1 of the present application.

[0068] Figure 2is a circuit schematic diagram of a part of circuit structure of the IGBT module junction temperature monitoring device of the embodiment 1 of the present application;

[0069] Figure 3 is a circuit schematic diagram of another part of circuit structure of the IGBT module junction temperature monitoring device of the embodiment 1 of the present application;

[0070] Figure 4 is a linear optical coupling input signal and output signal comparison relationship diagram of the embodiment 1 of the present application;

[0071] Figure 5-1 、 Figure 5-2 、 Figure 5-3 、 Figure 5-4 are respectively circuit principle diagrams of the first power supply, the third power supply, the fourth power supply and the fifth power supply of the embodiment 1 of the present application, wherein the second power supply can adopt the same circuit structure as the first power supply;

[0072] Figure 6 is a part of circuit structure schematic diagram of the embodiment 2 of the present application;

[0073] Figure 7 is a circuit schematic diagram of another part of circuit structure of the IGBT module junction temperature monitoring device of the embodiment 3 of the present application (i.e. replacing the circuit structure in the Figure 3 of the embodiment 1). DETAILED DESCRIPTION

[0074] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0075] Embodiment 1: Negative temperature coefficient thermistor

[0076] Considering that the frequency conversion power supply for electromagnetic stirring itself has a physical structure of long-distance transmission of NTC thermistor acquisition signals, the acquisition circuit of the main control board will be interfered by the strong magnetic field and high voltage electric field of the output current of the high-power electromagnetic stirring frequency conversion power supply, in order to ensure the sampling accuracy and avoid the limitations of high NTC thermistor resistance, long-distance transmission signals being easily interfered by electromagnetic interference, high system cost and complex structure, the present application discloses a NTC thermistor junction temperature detection device and method suitable for a large-capacity IGBT of a frequency conversion power supply for electromagnetic stirring.

[0077] As Figures 1-4 、 Figures 5-1 to 5-4As shown, the embodiment 1 provides an IGBT module junction temperature monitoring device with a thermistor, comprising at least one resistor connected in series with the thermistor R3, the at least one resistor and the thermistor R3 forming a resistance voltage dividing subcircuit 1, and an input end of the resistance voltage dividing subcircuit 1 being electrically connected with an output end of a first power supply (24V).

[0078] The IGBT module junction temperature monitoring device further comprises a voltage comparison subcircuit 2, a voltage / current conversion subcircuit 3 and a current / voltage conversion subcircuit 4 connected in sequence.

[0079] An output end of the current / voltage conversion subcircuit 4 is electrically connected with a signal input end I1 of a signal processor U6, and a corresponding relationship between a resistance value of the thermistor R3 and a theoretical value of a signal collected by the signal input end I1 is determined according to an actual circuit of the IGBT module junction temperature monitoring device and is known.

[0080] The voltage comparison subcircuit 2 comprises a first operational amplifier U1, a second operational amplifier U2, a first resistor R2, a second resistor R6, a first diode D1 and a second diode D2.

[0081] The same-phase input end, the opposite-phase input end and the output end of the first operational amplifier U1 are electrically connected with a reference voltage supply end, one end of the first resistor R2 and the positive electrode of the first diode D1, respectively, and the voltage of the reference voltage supply end is greater than 0.

[0082] The same-phase input end, the opposite-phase input end and the output end of the second operational amplifier U2 are electrically connected with the output end of the resistance voltage dividing subcircuit 1, one end of the second resistor R6 and the positive electrode of the second diode D2, respectively.

[0083] The other end of the first resistor R2, the negative electrode of the first diode D1, the other end of the second resistor R6 and the negative electrode of the second diode D2 are electrically connected with each other, thereby forming an output end of the voltage comparison subcircuit 2.

[0084] In the embodiment 1, the voltage comparison subcircuit 2 compares the voltage of the same-phase input end of the second operational amplifier U2 with the voltage of the same-phase input end of the first operational amplifier U1, and outputs the voltage of the same-phase input end of the second operational amplifier U2 or the voltage of the same-phase input end of the first operational amplifier U1.

[0085] In the embodiment 1, the thermistor R3 is a negative temperature coefficient thermistor, and the thermistor is located between the input end of the resistance voltage dividing subcircuit 1 and the output end of the resistance voltage dividing subcircuit 1 in the resistance voltage dividing subcircuit 1.

[0086] The IGBT module junction temperature monitoring device further comprises a voltage stabilizing tube W1 for providing a reference voltage (2.5V in this embodiment) to the reference voltage supply end. The cathode of the voltage stabilizing tube W1 forms the reference voltage supply end, and the anode of the voltage stabilizing tube W1 is electrically connected with the reference ground DGND of the first power supply.

[0087] The relationship between the output current of the voltage / current conversion sub-circuit 3 and the input voltage and the relationship between the output voltage of the current / voltage conversion sub-circuit 4 and the input current are linear relationships.

[0088] The voltage / current conversion sub-circuit 3 comprises a third operational amplifier U3, a third resistor R7, a fourth resistor R8, and an NMOS tube Q1.

[0089] The non-inverting input terminal of the third operational amplifier U3 and the output terminal thereof are respectively electrically connected with the output terminal of the voltage comparison sub-circuit 2 and one end of the third resistor R7.

[0090] The gate of the NMOS tube Q1 is electrically connected with the other end of the third resistor R7, the source of the NMOS tube Q1, the inverting input terminal of the third operational amplifier U3, and one end of the fourth resistor R8 are mutually electrically connected, and the other end of the fourth resistor R8 is grounded.

[0091] The drain of the NMOS tube Q1 is the output terminal of the voltage / current conversion sub-circuit 3.

[0092] The current / voltage conversion sub-circuit 4 is electrically connected with the signal input terminal I1 of the signal processor U6 through the voltage processing sub-circuit. The current / voltage conversion sub-circuit 4 comprises a sampling resistor R9, and the voltage between the two ends of the sampling resistor R9 is the output voltage of the current / voltage conversion sub-circuit 4.

[0093] In this embodiment, the second power supply is the same as the first power supply. The input terminal of the voltage processing sub-circuit, one end of the sampling resistor R9, and the output terminal of the second power supply (which is the same as the first power supply 24V in this embodiment) are mutually electrically connected, and the other end of the sampling resistor R9, the drain of the NMOS tube Q1, and the reference ground GND1 of the third power supply are mutually electrically connected.

[0094] The power supply end on the input side of the voltage processing sub-circuit and the ground end on the input side are respectively electrically connected with the output terminal 5V1 of the third power supply and the reference ground GND1 of the third power supply, the third power supply is different from the second power supply, and the reference ground DGND of the second power supply and the reference ground GND1 of the third power supply are mutually independent (i.e., not common ground).

[0095] In this embodiment, the voltage processing sub-circuit is the optical isolation voltage amplification sub-circuit 5. The signal processor U6 can be a single-chip microcomputer, a DSP, etc. The signal processor U6 can be powered by the fifth power supply. The power supply end of the fifth power supply is 3.3V, and the ground end is GND. In this embodiment 1, the signal processor U6 integrates an A / D conversion module, that is, the signal processor can directly receive a voltage signal.

[0096] The IGBT module constitutes an inverter circuit of an electromagnetic stirring system power supply. The first power supply, the second power supply, the resistance voltage division sub-circuit 1, the voltage comparison sub-circuit 2, and the voltage / current conversion sub-circuit 3 are arranged close to the IGBT module. That is, the first power supply, the second power supply, the resistance voltage division sub-circuit 1, the voltage comparison sub-circuit 2, and the voltage / current conversion sub-circuit 3 are far away from the main control panel of the electromagnetic stirring system, and close to the IGBT module.

[0097] As shown in Figure 2 , Figure 3 , the output end of the second power supply (in this embodiment, the first power supply) is also arranged close to the IGBT module. For this embodiment, when the IGBT module in the inverter circuit of the electromagnetic stirring system power supply is far away from the position where the main control panel of the electromagnetic stirring system is located, two long-distance cables (i.e., the first cable and the second cable) are arranged. That is, at the position where the main control panel of the electromagnetic stirring system is located, one end of the sampling resistor R9 is electrically connected with the input end of the linear optocoupler U4, and the other end of the sampling resistor R9 and the reference ground of the third power supply (outputting +5V1) are electrically connected with each other. The first cable connects the output end of the second power supply (in this embodiment, the first power supply) with one end of the sampling resistor R9 (i.e., the input end of the linear optocoupler U4), and the second cable connects the drain of the NMOS tube Q1 with the other end of the sampling resistor R9 (i.e., the reference ground of the third power supply).

[0098] The first cable and the second cable transmit current signals. Although the long-distance cables cause a voltage drop on the cables when transmitting current signals, the linear optocoupler U4 measures the voltage difference between the two ends of the sampling resistor R9, and the R9 is arranged close to the linear optocoupler U4, so it will not be disturbed by the voltage drop of the cables, and the transmission of the current signals can reduce the influence of electromagnetic interference on the transmitted electrical signals as much as possible.

[0099] The current / voltage conversion sub-circuit 4, the voltage processing sub-circuit, and the signal processor U6 are arranged close to or at the main control panel of the electromagnetic stirring system. The power supply of the electromagnetic stirring system can be a variable frequency power supply, which is a prior art in the field of electromagnetic stirring.

[0100] The optical isolation voltage amplification sub-circuit 5 includes a linear optocoupler U4, a fourth operational amplifier U5, a fifth resistor R10, a sixth resistor R11, and a seventh resistor R13.

[0101] The input end of the linear optocoupler U4 is connected to the input end of the optical isolation voltage amplification sub-circuit 5, and the input end of the linear optocoupler U4, one end of the sampling resistor R9 and the output end of the second power supply are electrically connected to each other.

[0102] The positive output end and the negative output end of the linear optocoupler U4 are respectively connected to one end of the fifth resistor R10 and one end of the sixth resistor R11; the same-phase input end of the fourth operational amplifier U5 is electrically connected to the other end of the fifth resistor R10, the opposite-phase input end of the fourth operational amplifier U5, the other end of the sixth resistor R11 and one end of the seventh resistor R13 are electrically connected to each other; the other end of the seventh resistor R13 is connected to the output end of the fourth operational amplifier U5, thereby forming the output end of the optical isolation voltage amplification sub-circuit 5.

[0103] The power supply end of the input side of the linear optocoupler U4 is electrically connected to the output end 5V1 of the third power supply, and the grounding end of the input side of the linear optocoupler U4 is electrically connected to the reference ground GND1 of the third power supply; the power supply end of the output side of the linear optocoupler U4 and the power supply end of the fourth operational amplifier U5 are electrically connected to the output end 5V of the fourth power supply; and the grounding end of the output side of the linear optocoupler U4 and the grounding end of the fourth operational amplifier U5 are electrically connected to the reference ground GND of the fourth power supply.

[0104] The second power supply, the third power supply and the fourth power supply are different power supplies, and the reference ground DGND of the second power supply, the reference ground GND1 of the third power supply and the reference ground GND of the fourth power supply are independently set (i.e., not common ground).

[0105] The output voltage of the optical isolation voltage amplification sub-circuit 5 has a linear relationship with the input voltage; preferably, the ratio of the output voltage of the optical isolation voltage amplification sub-circuit 5 to the input voltage is 1:1.

[0106] The IGBT module junction temperature monitoring device further comprises an eighth resistor R4 and a ninth resistor R5, and the eighth resistor R4, the ninth resistor R5 and the thermistor R3 are connected in series to form the resistance voltage division sub-circuit 1.

[0107] One end of the thermistor R3 is the input end of the resistance voltage division sub-circuit 1, the other end of the thermistor R3 is sequentially connected to the reference ground of the first power supply through the eighth resistor R4 and the ninth resistor R5, and the connection end of the eighth resistor R4 and the ninth resistor R5 is the output end of the resistance voltage division sub-circuit 1.

[0108] When the ambient temperature value of the thermistor R3 is less than Ta, the output end voltage of the resistance voltage division sub-circuit 1 is less than the voltage of the reference voltage power supply end; when the ambient temperature value of the thermistor R3 is greater than or equal to Ta, the output end voltage of the resistance voltage division sub-circuit 1 is greater than or equal to the voltage of the reference voltage power supply end, wherein [Ta, Tb] is a preset monitoring temperature range; or

[0109] When the ambient temperature value at which the thermistor R3 is located is less than or equal to Ta, the output end voltage of the resistance voltage dividing sub-circuit 1 is less than or equal to the voltage of the reference voltage supply end, and when the ambient temperature value at which the thermistor R3 is located is greater than Ta, the output end voltage of the resistance voltage dividing sub-circuit 1 is greater than the voltage of the reference voltage supply end, wherein [Ta, Tb] is a preset monitoring temperature range.

[0110] The application further provides a junction temperature monitoring method using the IGBT module junction temperature monitoring device, and the junction temperature monitoring method comprises the following steps: obtaining the junction temperature Tj of the IGBT module 10 according to the corresponding relationship between the ambient temperature value at which the thermistor R3 is located and the resistance value of the thermistor R3, the corresponding relationship between the resistance value of the thermistor R3 and the theoretical value of the signal collected by the signal input end I1, and the signal Ux actually collected by the signal input end I1.

[0111] The corresponding relationship between the theoretical value of the signal collected by the signal input end I1 and the ambient temperature value at which the thermistor R3 is located is that the temperature values Ta, Ta+△T, Ta+2△T, …, Ta+n△T, Tb are respectively in one-to-one correspondence with the theoretical values Ua, Uc(1), Uc(2), …, Uc(n), Ub of the collected signal;

[0112] Wherein, △T is a preset temperature increment, 0.5°C≤△T≤2°C; [Ta, Tb] is a preset monitoring temperature range; Tb=Ta+(n+1)△T or Ta+n△T<Tb<Ta+(n+1)△T;

[0113] The step of obtaining the junction temperature Tj of the IGBT module 10 or the temperature range to which the junction temperature Tj belongs according to the corresponding relationship between the ambient temperature value at which the thermistor R3 is located and the resistance value of the thermistor R3, the corresponding relationship between the resistance value of the thermistor R3 and the theoretical value of the signal collected by the signal input end I1, and the signal Ux actually collected by the signal input end I1 comprises:

[0114] If Ux=Ua, it is judged that Tj≤Ta;

[0115] If Ux>Ub, it is judged that Tj>Tb;

[0116] If Ua<Ux≤Uc(1), it is judged that Ta<Tj≤Ta+△T or Tj=Ta;

[0117] If Uc(n)<Ux≤Ub, it is judged that Ta+n△T<Ux≤Tb or Tj=Tb.

[0118] The following further details the scheme of the embodiment 1 of the application:

[0119] The application proposes a system composed of resistance voltage division principle of voltage source, plug and play driving NTC resistance sampling circuit, V-I conversion circuit, current source remote transmission, I-V conversion circuit, linear isolation differential amplification and analog-digital conversion acquisition circuit of core processor MCU. The principle diagram of the system is shown below Figure 1 The detailed circuit diagram is shown below Figure 2 、 Figure 3 The A1 point and the A2 point of Figure 2 correspond to the same points as the A1 point and the A2 point in Figure 3 .

[0120] The left side of the dashed line is the sampling conversion end of the NTC thermistor, which is composed of the plug and play voltage source NTC thermistor sampling processing circuit and the current source conversion processing circuit of the voltage source driven NTC thermistor. The resistance R1, the resistance R2, the thermistor R3, the resistance R4, the resistance R5, the resistance R6, the chip capacitor C1, C2 and C3, the voltage stabilizing tube W1, the Schottky diode D1 and D2, and the operational amplifier U1 and U2 are the plug and play voltage source NTC thermistor sampling processing circuit of the voltage source driven NTC thermistor. The operational amplifier U3, the resistance R7, the resistance R8, the MOS tube Q1 and the chip capacitor C4 are the current source conversion processing circuit. This part of the circuit is designed and installed near the internal NTC thermistor of the IGBT, and the closer to the NTC thermistor of the IGBT, the better (i.e. near the IGBT module). The resistance R1 is 10KΩ, the resistance R2 is 2KΩ, the resistance R4 is 3925Ω, the resistance R5 is 4480Ω, the resistance R6 and R7 are 2KΩ, the resistance R8 is 625Ω, all of which are 2512 packaging and have a precision of ±0.1%, the thermistor R3 is the negative temperature system thermistor packaged in the IGBT, the voltage stabilizing tube W1 is the TL432AQDBZR of TI company, and the operational amplifier U1, U2 and U3 are all OPA171AIDBVT of TI company. The MOS tube Q1 is N-channel enhancement mode MOS tube 2N7002. The diode D1 and D2 are SS16 Schottky diodes of Welsun company.

[0121] The working principle of the circuit of the sampling conversion end of the NTC thermistor is as follows: the same direction input end of the operational amplifier U1 is constant 2.5V input voltage. Assuming that the IGBT module junction temperature is -20℃, at this time, the resistance value of the negative temperature coefficient NTC thermistor R3 is 34.6KΩ (which can be known from Table 1), and the formula calculation voltage V U2+= (R5 / (R5 + R4 + R3)) * 24V = (4480 / 4480 + 3925 + 34600) * 24V = 2.5V. When the junction temperature is less than or equal to -20℃, the resistance of resistor R3 is greater than 34.6KΩ, and the voltage at the same input terminal of operational amplifier U2 is calculated by the formula U2+ <2.5V, analyzed Figure 2 The circuit shown in the normal output of operational amplifier U1 (operational amplifier U2 abnormal output). According to the virtual break virtual short principle of operational amplifier, the cathode of Schottky diode D1 is constant V D1- = 2.5V, so the same input terminal of operational amplifier U3 is constant 2.5V, and according to the virtual break virtual short principle of operational amplifier, the source of NMOS tube Q1 is constant 2.5V. At this time, the current I R8 = 2.5 / 625Ω = 4mA. The gate current of MOS switch Q1 is almost 0mA when it is working normally, so the drain of switch Q1 is also 4mA at this time. That is, when the junction temperature of IGBT module is -20℃ or lower than -20℃, Figure 2 The dashed line left of the constant output 4mA current source signal, which ensures that there is a minimum constant of 4mA on the long distance transmission circuit to avoid the defect that it is difficult to judge whether the 0mA signal is 0mA or the cable is disconnected when transmitting long distance. When the internal junction temperature of IGBT rises more than -20℃, the resistance of negative temperature coefficient NTC thermistor R3 is less than 34.6KΩ, and the voltage at the same input terminal of operational amplifier U2 is calculated by the formula U2+ = (R5 / (R5 + R4 + R3)) * 24V is greater than 2.5V. Analyzed Figure 2 The circuit shown in the normal output of operational amplifier U2 (operational amplifier U1 abnormal output), according to the virtual break virtual short principle of operational amplifier, the cathode of Schottky diode D2 is constant V D2- = (R5 / (R5 + R4 + R3)) * 24V > 2.5V, and the source voltage of NMOS tube Q1 is also greater than 2.5V at this time. At this time, the current I R8 = V D2- / 625Ω (V D2- > 2.5V at this time) is greater than 4mA. By consulting NTC thermistor temperature resistance table 1, when the internal junction temperature of IGBT is 140℃, the resistance of NTC thermistor of IGBT is approximately 196Ω, and V U2+ = (R5 / (R5 + R4 + R3)) * 24V = 12.5V, the current source I R8 = 12.5 / 625Ω ≈ 20mA of resistor R8 at this time. Therefore, the circuit on the left of the dashed line converts the -20℃ ~ 140℃ temperature signal of the core of large capacity IGBT into a 4-20mA current signal.

[0122] Figure 2 、 Figure 3 The right side of the combined circuit (i.e. the circuit part in Figure 3 ) is the NTC thermistor signal acquisition end, which is integrated on the main control board and consists of resistors R9, R10, R11, R12, R13, chip capacitors C5, C6, C7, linear optocoupler U4, operational amplifier U5, and processor U6. The chip capacitors C5, C6, and C7 are 100000 pF chip decoupling capacitors with a voltage resistance of 50 V. U4 is a linear isolation optocoupler from Anhua High-Tech Company, model ACPL-C87B-500E. +5V1 and GND1 are the supply voltages of the original side of the optocoupler, connected to the 1st pin and the 4th pin of U4, respectively. The 2nd and 3rd pins of U4 are the voltage input terminals of the isolation optocoupler. The input terminal voltage of U4 is the voltage difference signal on the sampling resistor R9. The 8th and 4th pins of U4 are the supply voltages of the secondary side of U4, connected to 5V and GND, respectively. The 7th and 6th pins of U4 are the differential output voltages of the secondary side. The relationship between the input and output of U4 is as shown in the following table. Figure 4 The differential amplification circuit composed of resistors R10, R11, R12, and R13 and operational amplifier U5 has a magnification of 1:1, and the output of the differential amplification circuit is directly sent to the ADC analog-digital conversion interface of the core processor. The magnification formula of the differential amplification circuit is V out =[R12*(R11+R13)*V out+ -R13*(R10+R12)*V out- ] / [R11*(R10+R12)]. Since the resistance values of R10, R11, R12, and R13 are all 10KΩ, the output voltage of operational amplifier U5 is V out =V out+ -V out- (V out+ , V out- are the output voltages of the 7th and 6th pins of U4, respectively); the model of U5 is OPA171AIDBVT, and the model of the core processor U6 is STM32F103ZET6 from ST Company

[0123] The working principle of the NTC thermistor signal acquisition end is as follows: when a current of 4-20 mA flows through resistor R9, a voltage of 0.4-2 V is generated on resistor R9. After the voltage of 0.4-2 V is sent to the input terminal of U4, a differential voltage of 0.4-2 V is generated at the output terminal of U4. After the differential voltage of 0.4-2 V is output by the differential operational amplification circuit, a voltage of 0.4-2 V is directly sent to the ADC analog-digital conversion interface of the processor MCU

[0124] Consider the conversion relationship between NTC thermistor value and actual temperature value: R t = R 25 *exp [B*(1 / (273.15+T)- 1 / 298.15 )](where R t R is the resistance value exhibited by the thermistor at temperature T. 25 The resistance of the NTC thermistor at 25℃ is shown in Table 1 (5KΩ), from which the actual temperature can be calculated. The mathematical functions involved include exponential functions, which ordinary low-end processors lack the capability to calculate. Furthermore, the B values, as shown in Table 1, vary depending on the required resistance value at different temperatures, as indicated in column 5 of Table 1. To ensure that all processors can adapt to the proposed method, this paper employs array lookup combined with five-level interpolation calculations to significantly reduce the performance requirements of the sampling system. At each 5°C integer, this invention calculates the corresponding standard voltage collected by the processor based on the standard resistance values ​​provided in Table 1. For example, when the IGBT operates within a temperature range of 25°C to 30°C, Table 1 shows that at 30°C, the thermistor's resistance is R = 4156Ω. Figure 2 Chinese V D2- = (R5 / R5+R4+R3)*24V=(4480 / 4480+3925+4156)*24V=8.559V, at this time I R8 =8.559 / 625Ω≈13.695mA; when the thermistor is at 25℃, the resistance is R=5000Ω, at this time... Figure 2 Chinese V D2- = (R5 / R5+R4+R3)*24V=(4480 / 4480+3925+5000)*24V=8.020V, at this time I R8=8.020 / 625Ω≈12.833mA; in order to reduce the code resource processor resources as much as possible, in this paper between 25℃~30℃ between the use of intermediate 5 gear average interpolation method in turn 26℃, 27℃, 28℃, 29℃ when the current flowing through the resistance R8 is 13.005mA (12.833+1* (13.695-12.833) / 5), 13.177mA (12.833+2* (13.695-12.833) / 5), 13.350 (12.833+3* (13.695-12.833) / 5), 13.522 (12.833+4* (13.695-12.833) / 5), in the processor (such as MCU) on the main control board calculation only need to carry out simple logic judgment, so that the data processing ability of the processor is greatly reduced, thereby reducing the cost and improving the processing speed.

[0125] The specific logic judgment is:

[0126] When 12.833mA R8 ≤13.005mA, 1.283V out ≤1.300V T temp =26℃;

[0127] When 13.005mA R8 ≤13.177mA, 1.300V out ≤1.317V T temp =27℃;

[0128] When 13.177mA R8 ≤13.350mA, 1.317V out ≤1.335V T temp =28℃;

[0129] When 13.350mA R8 ≤13.522mA, 1.335V out ≤1.352V T temp =29℃;

[0130] When 13.522mA R8 ≤13.695mA, 1.352V out ≤1.369V T temp =30℃;

[0131] According to the resistance value corresponding to the classic thermistor of every 5℃ in Table 1, the calculation of all other temperature values between-20℃~25℃ (-20℃~-15℃, …, 20℃~25℃) and 30℃~140℃ (30℃~35℃, …, 135℃~140℃) can be processed in this way, which can greatly reduce the processor's computing task.

[0132] The frequency conversion power supply for electromagnetic stirring is generally installed in a special electrical room beside the continuous casting production line. The electrical room is generally equipped with an industrial air conditioner, and the temperature in the electrical room is kept at about 20℃ all year round. If the frequency conversion power supply for electromagnetic stirring is working, the core junction temperature of the IGBT during the working of the general large-capacity IGBT is about 50~110℃. Only when the forced cooling system fails, the IGBT module junction temperature will rise to 120℃ or even above. Therefore, when the core junction temperature of the IGBT exceeds 120 degrees is detected, the control system of the frequency conversion power supply will immediately shut down or reduce the power to lower the core junction temperature of the IGBT. Therefore, in this paper, the temperature signal of the IGBT module-20℃~140℃ is converted into a 4-20mA current signal, and then the 4-20mA current signal is converted into a 0.4-2V voltage signal through a sampling resistor. The 0.4-2V voltage signal is sent to the ADC of the core processor MCU of the frequency conversion power supply for electromagnetic stirring after being amplified by a 1:1 linear isolation differential amplifier, which is sufficient to meet the normal junction temperature range detection of the frequency conversion power supply for electromagnetic stirring in the electrical room of the steel plant.

[0133] In this embodiment 1:

[0134] The first power supply can be a 24V power supply, and the reference ground of the first power supply is DGND.

[0135] The second power supply can be the same 24V power supply as the first power supply. The second power supply can also be a 36V power supply (not shown in the figure). The first power supply and the second power supply are common. That is, the reference ground of the second power supply is also DGND.

[0136] The third power supply can be a +5V power supply (identified as 5V1 in the figure), and the reference ground of the third power supply is GND1.

[0137] The fourth power supply can be a +5V power supply (identified as 5V in the figure), and the reference ground of the fourth power supply is GND.

[0138] The fifth power supply can be a 3.3V power supply, and the reference ground of the fifth power supply is GND.

[0139] Among them, the first power supply can be converted from a direct current bus voltage (such as a 110V direct current voltage). The third power supply and the fourth power supply can be converted from the first power supply, and the fifth power supply can be converted from the fourth power supply.

[0140] The power supply design for the acquisition circuit can employ four independently isolated power supplies (i.e., the first and second power supplies are identical). The 24V and DGND power supply is obtained from the DC bus voltage via a magnetically isolated switching power supply. The 5V and GND power supply is obtained from the 24V and DGND power supply via a magnetically isolated switching power supply. The 5V1 and GND1 power supply is obtained from the 24V and DGND power supply via a magnetically isolated switching power supply. The 3.3V and GND power supply is obtained from the 5V and GND power supply via a linear power supply. The detailed schematic diagram of the power supply section is as follows: Figure 5-1 , Figure 5-2 , Figure 5-2 , Figure 5-4 As shown.

[0141] The proposed solution was applied to an electromagnetic stirring frequency converter of a certain company for experimental verification, proving its accuracy. The IGBT model used in the experiment was Fuji Electric's 2MBI1400VXB-120P-50, with an effective output current of 800A and an output frequency of 8Hz.

[0142] The table below shows the temperature and resistance correspondence of the NTC negative temperature coefficient inside the IGBT module.

[0143] Table 1. Resistance and Temperature Correspondence of IGBT Internal Negative Temperature Coefficient NTC Thermistors

[0144]

[0145] Example 2: A / D Converter Solution

[0146] Figure 2 , Figure 5-1 , Figure 5-2 , Figure 5-3 , Figure 5-4 , Figure 6 The circuit structure that constitutes Embodiment 2 is as follows. Figure 2 Points A1 and A2 in the diagram are respectively... Figure 6 Points A1 and A2 in the diagram correspond to the same point.

[0147] The difference between Embodiment 3 and Embodiment 1 is that the voltage processing sub-circuit is an A / D converter 6. In this embodiment, the A / D converter 6 and the signal processor U6 are set independently. Alternatively, the A / D converter 6 can also be integrated into the signal processor U6, that is, the A / D converter 6 is the A / D conversion module in the signal processor U6. Other structures of Embodiment 3 can be found in Embodiment 1.

[0148] Example 3: Thermistor with positive temperature coefficient

[0149] Figure 3 , Figure 5-1 , Figure 5-2 ,Figure 5-3 、 Figure 5-4 、 Figure 7 The circuit structure of this embodiment 3 is shown in the following figure.

[0150] The difference between this embodiment 4 and embodiment 1 is that when the thermistor R3 is a positive temperature coefficient thermistor, the thermistor is located between the ground end of the resistance voltage dividing sub-circuit 1 and the output end of the resistance voltage dividing sub-circuit 1.

[0151] In this embodiment, the first power supply 24V is electrically connected to the power supply end DGND of the first power supply in sequence through the eighth resistance R4, the ninth resistance R5 and the thermistor R3 which are connected in series with each other. That is, one end of the eighth resistance R4 connected with the first power supply 24V is the input end of the resistance voltage dividing sub-circuit 1, and the position of the eighth resistance R4 connected with the ninth resistance R5 is the output end of the resistance voltage dividing sub-circuit 1.

[0152] It should be noted that each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same and similar parts between each embodiment can be referred to each other.

[0153] The above detailed description of the embodiments of the present application, but the content is only the preferred embodiments of the present application, can not be considered for limiting the scope of the present application. All equivalent changes and improvements made within the scope of the present application should still belong to the scope of the present patent. After reading the present application, the skilled in the art can modify various equivalent forms of the present application, which fall within the scope defined by the claims attached to the present application. In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

Claims

1. An IGBT module junction temperature monitoring device with a thermistor, comprising at least one resistor connected in series with the thermistor (R3), wherein the at least one resistor and the thermistor (R3) constitute a resistive voltage divider circuit (1), the input terminal of the resistive voltage divider circuit (1) being electrically connected to the output terminal of a first power supply, characterized in that: The IGBT module junction temperature monitoring device also includes a voltage comparison sub-circuit (2), a voltage / current conversion sub-circuit (3), a current / voltage conversion sub-circuit (4), and a signal processor (U6) connected in sequence. The voltage comparator sub-circuit (2) includes a first operational amplifier (U1), a second operational amplifier (U2), a first resistor (R2), a second resistor (R6), a first diode (D1), and a second diode (D2). The first operational amplifier (U1) has one input terminal, the other input terminal, and the output terminal electrically connected to the reference voltage power supply terminal, one end of the first resistor (R2), and the positive terminal of the first diode (D1), respectively. The voltage at the reference voltage power supply terminal is greater than 0. The second operational amplifier (U2) has one input terminal, the other input terminal, and the output terminal connected to the output terminal of the resistor divider circuit (1), one end of the second resistor (R6), and the positive terminal of the second diode (D2), respectively. The other end of the first resistor (R2), the cathode of the first diode (D1), the other end of the second resistor (R6), and the cathode of the second diode (D2) are electrically connected to each other, thereby forming the output terminal of the voltage comparator sub-circuit (2); When the thermistor (R3) is a negative temperature coefficient thermistor, the thermistor is located between the input terminal and the output terminal of the voltage divider circuit (1). When the thermistor (R3) is a positive temperature coefficient thermistor, the thermistor is located between the ground terminal of the resistor voltage divider circuit (1) and the output terminal of the resistor voltage divider circuit (1).

2. The IGBT module junction temperature monitoring device according to claim 1, characterized in that: The relationship between the output current and input voltage of the voltage / current conversion sub-circuit (3) and the relationship between the output voltage and input current of the current / voltage conversion sub-circuit (4) are both linear.

3. The IGBT module junction temperature monitoring device according to claim 1, characterized in that: The voltage / current conversion sub-circuit (3) includes a third operational amplifier (U3), a third resistor (R7), a fourth resistor (R8), and an NMOS transistor (Q1). The third operational amplifier (U3) has one input terminal and one output terminal electrically connected to the output terminal of the voltage comparator circuit (2) and one terminal of the third resistor (R7), respectively. The gate of the NMOS transistor (Q1) is electrically connected to the other end of the third resistor (R7). The source of the NMOS transistor (Q1), the other input terminal of the third operational amplifier (U3), and one end of the fourth resistor (R8) are electrically connected to each other. The other end of the fourth resistor (R8) is electrically connected to the reference ground of the first power supply. The drain of the NMOS transistor (Q1) is the output terminal of the voltage / current conversion sub-circuit (3).

4. The IGBT module junction temperature monitoring device according to claim 3, characterized in that: The current / voltage conversion sub-circuit (4) is electrically connected to the signal processor (U6) through the voltage processing sub-circuit; The current / voltage conversion sub-circuit (4) includes a sampling resistor (R9); The input terminal of the voltage processing sub-circuit, one end of the sampling resistor (R9), and the output terminal of the second power supply are electrically connected to each other. The other end of the sampling resistor (R9), the drain of the NMOS transistor (Q1), and the reference ground of the third power supply are electrically connected to each other. The reference ground of the second power supply is electrically connected to the reference ground of the first power supply. The power supply terminal and the ground terminal on the input side of the voltage processing sub-circuit are electrically connected to the output terminal of the third power supply and the reference ground of the third power supply, respectively. The third power supply and the second power supply are different power supplies, and the reference ground of the second power supply and the reference ground of the third power supply are independent of each other. The voltage processing sub-circuit is an optically isolated voltage amplifier sub-circuit (5) or an A / D converter (6). The IGBT module (10) constitutes the inverter circuit of the electromagnetic stirring system power supply. The first power supply, the second power supply, the resistor voltage divider sub-circuit (1), the voltage comparison sub-circuit (2), and the voltage / current conversion sub-circuit (3) are located close to the IGBT module (10). The current / voltage conversion sub-circuit (4), the voltage processing sub-circuit, and the signal processor (U6) are located close to or on the main control board of the electromagnetic stirring system. The second power supply is the same as the first power supply; The A / D converter (6) and the signal processor (U6) are set independently of each other, or the A / D converter (6) is integrated into the signal processor (U6); The output voltage of the optically isolated voltage amplifier sub-circuit (5) is linearly related to the input voltage.

5. The IGBT module junction temperature monitoring device according to claim 4, characterized in that: The optically isolated voltage amplifier sub-circuit (5) includes a linear optocoupler (U4), a fourth operational amplifier (U5), a fifth resistor (R10), a sixth resistor (R11), and a seventh resistor (R13). The input terminal of the linear optocoupler (U4) is the input terminal of the optically isolated voltage amplifier sub-circuit (5), and the input side of the linear optocoupler (U4) is the input side of the optically isolated voltage amplifier sub-circuit (5). The input terminal of the linear optocoupler (U4), one end of the sampling resistor (R9), and the output terminal of the second power supply are electrically connected to each other. The positive and negative output terminals of the linear optocoupler (U4) are electrically connected to one end of the fifth resistor (R10) and one end of the sixth resistor (R11), respectively; one input terminal of the fourth operational amplifier (U5) is electrically connected to the other end of the fifth resistor (R10), and the other input terminal of the fourth operational amplifier (U5), the other end of the sixth resistor (R11), and one end of the seventh resistor (R13) are electrically connected to each other; the other end of the seventh resistor (R13) is connected to the output terminal of the fourth operational amplifier (U5), thereby forming the output terminal of the optically isolated voltage amplifier sub-circuit (5); The power supply terminal on the input side of the linear optocoupler (U4) is electrically connected to the output terminal of the third power supply, the ground terminal on the input side of the linear optocoupler (U4) is electrically connected to the reference ground of the third power supply, the power supply terminal on the output side of the linear optocoupler (U4), the power supply terminal on the fourth operational amplifier (U5) is electrically connected to the output terminal of the fourth power supply, and the ground terminal on the output side of the linear optocoupler (U4), the ground terminal on the fourth operational amplifier (U5) is electrically connected to the reference ground of the fourth power supply. The second power supply, the third power supply, and the fourth power supply are different power supplies, and the reference ground of the second power supply, the reference ground of the third power supply, and the reference ground of the fourth power supply are independent of each other.

6. The IGBT module junction temperature monitoring device according to any one of claims 1-5, characterized in that: The IGBT module junction temperature monitoring device also includes an eighth resistor (R4) and a ninth resistor (R5), which are connected in series to form the resistor voltage divider circuit (1). When the thermistor (R3) is a negative temperature coefficient thermistor, one end of the thermistor (R3) is the input terminal of the voltage divider circuit (1), and the other end of the thermistor (R3) is connected to the reference ground of the first power supply in sequence through the eighth resistor (R4) and the ninth resistor (R5). The connection terminal of the eighth resistor (R4) and the ninth resistor (R5) is the output terminal of the voltage divider circuit (1). When the thermistor (R3) is a positive temperature coefficient thermistor, one end of the eighth resistor (R4) is the input terminal of the resistor voltage divider circuit (1), and the other end of the eighth resistor (R4) is connected to the reference ground of the first power supply in sequence through the ninth resistor (R5) and the thermistor (R3). The connection terminal of the eighth resistor (R4) and the ninth resistor (R5) is the output terminal of the resistor voltage divider circuit (1).

7. The IGBT module junction temperature monitoring device according to any one of claims 1-5, characterized in that: When the ambient temperature of the thermistor (R3) is less than Ta, the output voltage of the voltage divider circuit (1) is less than the voltage of the reference voltage supply terminal. When the ambient temperature of the thermistor (R3) is greater than or equal to Ta, the output voltage of the voltage divider circuit (1) is greater than or equal to the voltage of the reference voltage supply terminal. Here, [Ta, Tb] represents the preset monitoring temperature range. When the ambient temperature of the thermistor (R3) is less than or equal to Ta, the output voltage of the voltage divider circuit (1) is less than or equal to the voltage of the reference voltage supply terminal. When the ambient temperature of the thermistor (R3) is greater than Ta, the output voltage of the voltage divider circuit (1) is greater than the voltage of the reference voltage supply terminal. Here, [Ta,Tb] is the preset monitoring temperature range.

8. The IGBT module junction temperature monitoring device according to any one of claims 1-5, characterized in that: All power supplies are isolated power supplies.

9. A method for monitoring the junction temperature of an IGBT module using the junction temperature monitoring device according to any one of claims 1-8, characterized in that: The junction temperature monitoring method includes: obtaining the junction temperature Tj of the IGBT module (10) or the temperature range to which the junction temperature Tj belongs based on the correspondence between the ambient temperature value of the thermistor (R3) and the resistance value of the thermistor (R3), the correspondence between the resistance value of the thermistor (R3) and the theoretical value of the signal collected by the signal processor (U6), and the signal Ux actually collected by the signal processor (U6); the signal collected by the signal processor (U6) is a voltage signal or a digital signal.

10. The junction temperature monitoring method according to claim 9, characterized in that: The theoretical value of the signal collected by the signal processor (U6) and the ambient temperature value of the thermistor (R3) are as follows: the ambient temperature values ​​Ta, Ta+ΔT, Ta+2ΔT, ..., Ta+nΔT, Tb correspond one-to-one with the theoretical values ​​Ua, Uc(1), Uc(2), ..., Uc(n), Ub of the collected signal, respectively. Where △T is the preset temperature increment, 0.5°C≤△T≤2°C; [Ta,Tb] is the preset monitoring temperature range; Tb=Ta+(n+1)△T or Ta+n△T<Tb<Ta+(n+1)△T; The step of obtaining the junction temperature Tj of the IGBT module (10) or the temperature range to which the junction temperature Tj belongs based on the correspondence between the ambient temperature value of the thermistor (R3) and the resistance value of the thermistor (R3), the correspondence between the resistance value of the thermistor (R3) and the theoretical value of the signal acquired by the signal processor (U6), and the signal Ux actually acquired by the signal processor (U6) includes: If Ux = Ua, then determine if Tj ≤ Ta; If Ux > Ub, then determine if Tj > Tb; If Ua<Ux≤Uc(1), then determine Ta<Tj≤Ta+△T or determine Tj=Ta; If Uc(n) < Ux ≤ Ub, then determine Ta+n△T < Ux ≤ Tb or determine Tj = Tb.

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