An IGBT junction temperature detection system and detection method based on turn-off delay time

Abstract

The present invention discloses a junction temperature measurement system and method based on IGBT turn-off delay time. The system includes an IGBT module to be measured, which is respectively connected to an IGBT control unit, a voltage V eE The invention relates to a collection unit, a collector current collection unit and a collector-emitter voltage collection unit. The method is as follows: the offline data of the IGBT turn-off delay time, the collector current and the junction temperature are calibrated by an offline test method, and then fitting is performed; the emitter current and the turn-off delay time of the IGBT are measured online, and the relationship between the IGBT junction temperature and the turn-off delay time and the collector current obtained by fitting is combined to realize the online detection of the IGBT junction temperature. The invention linearizes the relationship between the IGBT turn-off delay time and the junction temperature, and establishes a function model of its slope and intercept with respect to the forward conduction current of the IGBT. The time-to-digital conversion technology is used to convert the time signal into a digital signal; only the induced voltage and the emitter current on the emitter parasitic inductance need to be collected, which has the advantages of simple modeling, easy measurement and high precision.

Description

Technical Field

[0001] The invention relates to a junction temperature detection system and a detection method, which are applied to the technical field of power electronic device performance measurement. Background Art

[0002] In recent years, with the development of social economy, power conversion technology has been widely used in the fields of new energy generation, power transmission, transportation, etc. As the most widely used power device in high-power power electronic converters, IGBT needs to face more complex working conditions. The high safety requirements of the system have made the reliability of power devices one of the research hotspots. Improving the reliability of IGBT is of great significance to ensure the safe operation of high-power power electronic systems. Studies have shown that 31% of power electronic converter failures are caused by the failure of power electronic devices; among them, 60% of power electronic device failures are caused by overtemperature; and, for every 10°C increase in the junction temperature of power electronic devices, the probability of device failure doubles. Excessive junction temperature can cause many problems. When the junction temperature is high, the voltage resistance of the device decreases, which easily causes the device to fail due to overvoltage breakdown; when the junction temperature is high, the thermal stress between the materials inside the device increases, which easily causes the solder layer to loosen and the bonding wire to break, thereby causing the device to fail. Therefore, it is very important to detect the junction temperature during the operation of the IGBT to improve the reliability of the IGBT.

[0003] Currently, there are three main types of IGBT junction temperature measurement systems.

[0004] The first type of system uses the principle of direct measurement, using the temperature of thermistors, thermocouples or diodes embedded in the IGBT module to infer the temperature of the IGBT chip. This is because the temperature of the chip and thermistor are not exactly the same, and thermistors have a long response time to temperature and poor dynamic performance.

[0005] The second type of system is non-contact and uses thermal imaging technology to measure the IGBT junction temperature. This method can achieve higher accuracy, but it requires destroying the IGBT packaging structure, which is destructive and only suitable for laboratory measurements.

[0006] The third type of system uses the device's own thermally sensitive electrical parameters to measure junction temperature. Typical thermally sensitive electrical parameters include the saturation voltage drop of the IGBT, the voltage drop rate when the IGBT is turned on, the current drop rate when the IGBT is turned off, the peak value of the Miller platform voltage, the peak value of the IGBT gate current when it is turned on, the turn-on delay time, and the turn-off delay time. The methods based on measuring the saturation voltage drop of the IGBT are divided into large current injection method and small current injection method. Both methods inject a specific current value into the IGBT during the interval when the system stops running, and infer the junction temperature based on the relationship between the saturation voltage drop and the junction temperature. They are not suitable for online measurement; the IGBT junction temperature measurement system based on the measurement of the gate signal or the turn-on delay time results in low sensitivity and poor accuracy of the measurement results. Studies have shown that the relationship between the turn-off delay time and the junction temperature of the IGBT is the most linear, and the sensitivity is also the highest.

[0007] The existing method of extracting the IGBT turn-off delay time collects the IGBT gate voltage and collector-emitter voltage signals, compares them with the threshold value, and obtains the start and end points of the turn-off delay. This method has many detection quantities, and the external circuit requires a very high bandwidth. In addition, when offline calibrating the relationship between the IGBT turn-off delay time and the collector current, it is necessary to measure the linear relationship between the junction temperature and the turn-off delay time under a specific collector current.

[0008] The purpose of the present invention is to overcome the shortcomings of the existing IGBT junction temperature detection method, linearize the relationship between the IGBT turn-off delay time and the junction temperature, and establish a functional model of its slope and intercept with respect to the IGBT collector current. And use the time-to-digital conversion technology to convert the time signal into a digital signal. The method only needs to collect the induced voltage and emitter current on the emitter parasitic inductance, and has the advantages of simple modeling, easy measurement, and high accuracy. Summary of the invention

[0009] In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide an IGBT junction temperature detection system and detection method based on the shutdown delay time, which uses the induced voltage on the IGBT emitter parasitic inductance to extract the IGBT's shutdown delay time, and measures the IGBT junction temperature online based on the relationship between the IGBT shutdown delay time and the IGBT's collector current.

[0010] In order to achieve the above invention purpose, the present invention adopts the following technical solution:

[0011] An IGBT junction temperature detection system based on shutdown delay time includes an IGBT module to be tested, wherein the IGBT module to be tested is respectively connected to an IGBT control unit, a voltage V eE A collection unit, a collector current collection unit and a collector-emitter voltage collection unit;

[0012] The IGBT module to be tested, as a test object, provides a test port;

[0013] The voltage V eE The acquisition unit is used to collect the potential difference V between the auxiliary emitter e and the emitter E of the IGBT module to be tested. eE ;

[0014] The collector current acquisition unit is used to acquire the collector current i of the IGBT module to be tested. c ;

[0015] The collector-emitter voltage acquisition unit is used to acquire the potential difference V between the collector C and the emitter E of the IGBT module to be tested. CE ;

[0016] The voltage V eE The acquisition unit is connected to a delay time measurement unit via a starting time base comparator and an end time base comparator;

[0017] The starting time base comparator and the end time base comparator are based on V eE The start and end pulse signals of the turn-off delay phase of the IGBT module to be tested are respectively obtained;

[0018] The delay time measurement unit is used to measure the turn-off delay time of the IGBT module to be tested according to the start and end information of the turn-off delay phase;

[0019] The IGBT control unit is used to control the on and off of the IGBT module to be tested, and to control the operation of the collector current acquisition unit, the collector-emitter voltage acquisition unit, and the delay time measurement unit;

[0020] The collector-emitter voltage acquisition unit, the collector current acquisition unit, and the delay time measurement unit are connected to a junction temperature calculation unit for data processing and calculation of the junction temperature of the IGBT module to be measured.

[0021] Preferably, the IGBT control unit is connected to the IGBT module to be tested, and is connected to the collector current acquisition unit, the collector-emitter voltage acquisition unit and the delay time calculation unit. The collector current acquisition unit and the collector-emitter voltage acquisition unit respectively acquire the emitter current of the IGBT module to be tested and the collector-emitter voltage of the IGBT module to be tested; the voltage V eE The acquisition unit acquires the voltage of the emitter and the auxiliary emitter of the IGBT module to be tested, and is connected to the starting time base comparator and the end time base comparator; the delay time measurement unit receives the output of the starting time base comparator and the end time base comparator; the junction temperature calculation unit receives the signals of the collector current acquisition unit, the collector-emitter voltage acquisition unit and the output of the delay time measurement unit.

[0022] Preferably, the voltage V eE The acquisition unit includes a voltage attenuation circuit, a voltage follower and a signal offset circuit which are connected in sequence.

[0023] Preferably, the collector current acquisition unit comprises a current sensor, a shaping circuit and a signal output which are connected in sequence.

[0024] Preferably, the collector-emitter voltage acquisition unit comprises a voltage sensor, a shaping circuit and a signal output which are connected in sequence.

[0025] Preferably, the turn-off delay time calculation unit is implemented by a time-to-digital converter chip.

[0026] A method for detecting IGBT junction temperature based on turn-off delay time is implemented by using an IGBT junction temperature detection system based on turn-off delay time of the present invention. The control operation process of the control unit includes the following steps:

[0027] 1) Establishing a data model: setting the operating conditions under the condition of not exceeding the maximum operating voltage, maximum operating current and maximum operating junction temperature of the IGBT module; for any operating condition, it corresponds to a set of data on the DC bus voltage, the collector current of the IGBT module and the operating junction temperature of the IGBT module, collecting the voltage signal between the power emitter and the auxiliary emitter of the IGBT module under the operating condition, and extracting the time difference between the two amplitudes of the voltage signal in the transient process of the IGBT module switching from the on state to the blocking state, which is the turn-off delay time;

[0028] 2) Fix the bus voltage and collector current, change the junction temperature of the IGBT module and collect the IGBT turn-off delay time, model the relationship between the turn-off delay time and the junction temperature, and obtain the rate of change and intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module under the conditions of specific bus voltage and specific collector current; repeat this step under different collector current conditions, and then establish a correlation function model of the slope of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module under a specific bus voltage, and a correlation function model of the intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module;

[0029] 3) Before the driving circuit controls the IGBT module to switch from the on state to the blocking state, the collector current of the IGBT module is collected; when the driving circuit controls the IGBT module to switch from the on state to the blocking state, the voltage signal between the power emitter and the auxiliary emitter of the IGBT module is collected, and the time difference between the two peak values ​​of the voltage signal is extracted during the transient process of the IGBT module switching from the on state to the blocking state; and then, according to the IGBT module collector current and the shutdown delay time collected during the transient process of the IGBT module switching from the on state to the blocking state, the operating junction temperature of the IGBT module is obtained by calculating the function model or reversely looking up the table.

[0030] Preferably, in the step 2), the correlation function model is composed of rational functions of the turn-off delay time under each DC bus voltage with respect to the collector current of the IGBT module and the operating junction temperature of the IGBT module; for any DC bus voltage, the rational function of the turn-off delay time, the collector current of the IGBT module and the operating junction temperature of the IGBT module under the DC bus voltage is as follows:

[0031]

[0032] Among them, a1, b1, c1, d1, a2, b2, c2, and d2 are constants, which can be obtained by fitting the data after offline calibration. c is the collector current before IGBT is turned off, T j is the junction temperature of the IGBT, t doff is the turn-off delay time of the IGBT, and the slope is The intercept is

[0033] Compared with the prior art, the present invention has the following outstanding substantive features and significant advantages:

[0034] 1. The system of the present invention linearizes the relationship between the IGBT turn-off delay time and the junction temperature, establishes a functional model of its slope and intercept with respect to the IGBT collector current, and uses time-to-digital conversion technology to convert the time signal into a digital signal. The method only needs to collect the dry sound voltage and collector current on the emitter parasitic inductance, and has the advantages of simple modeling, easy measurement, and high accuracy.

[0035] 2. The method of the present invention is simple in process, easy to implement, and has very obvious economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the detection system structure.

[0037] Figure 2 is the voltage V eE Circuit diagram of the acquisition unit.

[0038] Figure 3 Schematic diagram of the current acquisition unit structure.

[0039] Figure 4 This is a schematic diagram of the voltage acquisition unit structure.

[0040] Figure 5 This is a schematic diagram of the control process of the control unit.

[0041] Figure 6 Schematic diagram of the mechanism for generating induced voltage on the emitter parasitic inductance.

[0042] Figure 7 is t under different collector currents doff =f(T j )’s linear relationship graph.

[0043] Figure 8 is t under different collector currents doff =f(T j ) is a graph of the slope of the linear relationship.

[0044] Fig. 9 is t under different collector currents doff =f(T j ) is the intercept plot of the linear relationship. DETAILED DESCRIPTION

[0045] The above scheme is further described below in conjunction with specific implementation examples. The preferred embodiments of the present invention are described in detail as follows:

[0046] Embodiment 1:

[0047] In this embodiment, see Figure 1 , an IGBT junction temperature detection system based on turn-off delay time, comprising an IGBT module 1 to be tested, the IGBT module 1 to be tested is respectively connected to an IGBT control unit 9, a voltage V eE A collection unit 2, a collector current collection unit 3 and a collector-emitter voltage collection unit 4;

[0048] The IGBT module 1 to be tested, as a test object, provides a test port;

[0049] The voltage V eE The acquisition unit 2 is used to acquire the potential difference V between the auxiliary emitter e and the emitter E of the IGBT module 1 to be tested. eE ;

[0050] The collector current acquisition unit 3 is used to acquire the collector current i of the IGBT module 1 to be tested. c ;

[0051] The collector-emitter voltage acquisition unit 4 is used to acquire the potential difference V between the collector C and the emitter E of the IGBT module 1 to be tested. CE ;

[0052] The voltage V eE The acquisition unit 2 is connected to a delay time measurement unit 7 via a starting time base comparator 5 and an end time base comparator 6;

[0053] The starting time base comparator 5 and the end time base comparator 6 are based on V eE The start and end pulse signals of the turn-off delay phase of the IGBT module 1 to be tested are respectively obtained;

[0054] The delay time measuring unit 7 is used to measure the turn-off delay time of the IGBT module 1 to be tested according to the start and end information of the turn-off delay phase;

[0055] The IGBT control unit 9 is used to control the on and off of the IGBT module 1 to be tested, and control the operation of the collector current acquisition unit 3, the collector-emitter voltage acquisition unit 4, and the delay time measurement unit 7;

[0056] The collector-emitter voltage acquisition unit 4 , the collector current acquisition unit 3 , and the delay time measurement unit 7 are connected to a junction temperature calculation unit 8 for data processing and calculating the junction temperature of the IGBT module 1 to be measured.

[0057] Embodiment 2:

[0058] This embodiment is basically the same as the first embodiment, except that:

[0059] In this embodiment, see Figure 2-Figure 9 , the voltage V eE The acquisition unit 2 includes a voltage attenuation circuit 2-1, a voltage follower 2-2 and a signal offset circuit 2-3 connected in sequence. The collector current acquisition unit 3 includes a current sensor 3-1, a shaping circuit 3-2 and a signal output 3-3 connected in sequence. The collector-emitter voltage acquisition unit 4 includes a voltage sensor 4-1, a shaping circuit 4-2 and a signal output 4-3 connected in sequence. The turn-off delay time calculation unit 7 is implemented by a time-to-digital converter chip.

[0060] Embodiment three:

[0061] This embodiment is basically the same as the above embodiment, with the following features:

[0062] In this embodiment, see Figure 5 , a method for detecting IGBT junction temperature based on turn-off delay time, using the IGBT junction temperature detection system based on turn-off delay time described in embodiment 1 to operate, and the control operation process of the control unit includes the following steps:

[0063] 1) Establish data model:

[0064] The operating condition is set under the condition that the maximum operating voltage, the maximum operating current and the maximum operating junction temperature of the IGBT module are not exceeded; for any operating condition, it corresponds to a set of data on the DC bus voltage, the collector current of the IGBT module and the operating junction temperature of the IGBT module, and the voltage signal between the power emitter and the auxiliary emitter of the IGBT module under the operating condition is collected, and the time difference between the two amplitudes of the voltage signal is extracted during the transient process of the IGBT module switching from the on state to the blocking state, which is the turn-off delay time;

[0065] 2) Fix the bus voltage and collector current, change the junction temperature of the IGBT module and collect the IGBT turn-off delay time, model the relationship between the turn-off delay time and the junction temperature, and obtain the rate of change and intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module under the conditions of specific bus voltage and specific collector current; repeat this step under different collector current conditions, and then establish a correlation function model of the slope of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module under a specific bus voltage, and a correlation function model of the intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module;

[0066] 3) Before the driving circuit controls the IGBT module to switch from the on state to the blocking state, the collector current of the IGBT module is collected; when the driving circuit controls the IGBT module to switch from the on state to the blocking state, the voltage signal between the power emitter and the auxiliary emitter of the IGBT module is collected, and the time difference between the two peak values ​​of the voltage signal is extracted during the transient process of the IGBT module switching from the on state to the blocking state; and then, according to the IGBT module collector current and the shutdown delay time collected during the transient process of the IGBT module switching from the on state to the blocking state, the operating junction temperature of the IGBT module is obtained by calculating the function model or reversely looking up the table.

[0067] Embodiment 4:

[0068] This embodiment is basically the same as the above embodiment, with the following features:

[0069] In this embodiment, in step 2), the correlation function model is composed of rational functions of the turn-off delay time under each DC bus voltage with respect to the collector current of the IGBT module and the operating junction temperature of the IGBT module; for any DC bus voltage, the rational functions of the turn-off delay time, the collector current of the IGBT module and the operating junction temperature of the IGBT module under the DC bus voltage are as follows:

[0070]

[0071] Among them, a1, b1, c1, d1, a2, b2, c2, and d2 are constants, which can be obtained by fitting the data after offline calibration. c is the collector current before IGBT is turned off, T j is the junction temperature of the IGBT, t doff is the turn-off delay time of the IGBT, and the slope is The intercept is

[0072] Embodiment five:

[0073] This embodiment is basically the same as the above embodiment, with the following features:

[0074] In this embodiment, if Figure 1 As shown, an IGBT junction temperature detection system based on turn-off delay time includes:

[0075] The IGBT module to be tested is used as a test object and provides a test port;

[0076] Voltage V eE The acquisition unit 2 is used to acquire the potential difference VeE between the auxiliary emitter e and the emitter E of the IGBT module 1 to be tested;

[0077] The collector current acquisition unit 3 is used to acquire the collector current ic of the IGBT module 1 to be tested;

[0078] The collector-emitter voltage acquisition unit 4 is used to acquire the potential difference VCE between the collector C and the emitter E of the IGBT module 1 to be tested;

[0079] The start time base comparator 5 and the end time base comparator 6 respectively obtain the start and end pulse signals of the turn-off delay phase of the IGBT module 1 to be tested according to VeE.

[0080] The delay time measuring unit 7 is used to measure the turn-off delay time of the IGBT module 1 to be tested according to the start and end information of the turn-off delay phase;

[0081] An IGBT control unit 9, used to control the on and off of the IGBT module 1 to be tested, and to control the operation of the collector current acquisition unit 3, the collector-emitter voltage acquisition unit 4, and the delay time measurement unit 7;

[0082] The junction temperature calculation unit 8 is used for data processing and calculating the junction temperature of the IGBT module 1 to be tested;

[0083] The IGBT control unit 9 is connected to the IGBT module to be tested, and is connected to the collector current acquisition unit 3, the collector-emitter voltage acquisition unit 4 and the delay time calculation unit 7. The collector current acquisition unit 3 and the collector-emitter voltage acquisition unit 4 respectively acquire the emitter current of the IGBT module to be tested and the collector-emitter voltage of the IGBT module to be tested; the voltage VeE acquisition unit 2 acquires the voltage of the emitter and the auxiliary emitter of the IGBT module to be tested, and is connected to the starting time base comparator 5 and the end time base comparator 6; the delay time measurement unit 7 receives the output of the starting time base comparator 5 and the end time base comparator 6; the junction temperature calculation unit 8 receives the signals of the collector current acquisition unit 3, the collector-emitter voltage acquisition unit 4 and the output of the delay time measurement unit 7;

[0084] like Figure 2 As shown, the voltage VeE acquisition unit 2, the voltage V eE The acquisition unit 2 includes a voltage attenuation circuit 2-1, a voltage follower 2-2 and a signal shift circuit 2-3 connected in sequence; Figure 3 As shown, the collector current acquisition unit 3 includes a current sensor 3-1, a shaping circuit 3-2 and a signal output 3-3 connected in sequence; Figure 4 As shown, the collector-emitter voltage acquisition unit 4 includes a voltage sensor 4-1, a shaping circuit 4-2 and a signal output 4-3 connected in sequence; Figure 5 As shown, the starting time base comparator unit 5 includes a voltage reference circuit 5-1 and a high-speed comparator 5-2 connected in sequence; Figure 6 As shown, the end point time base comparator unit 6 includes a voltage reference circuit 6-1 and a high-speed comparator 6-2; Figure 7 As shown, the turn-off delay time calculation unit 7 can be implemented by a time-to-digital converter chip.

[0085] like Figure 8 As shown, the control process of the control unit includes the following steps:

[0086] Establish a data model: set the operating conditions under the condition that the maximum operating voltage, maximum operating current and maximum operating junction temperature of the IGBT module are not exceeded; for any operating condition, it corresponds to a set of data about the DC bus voltage, the collector current of the IGBT module and the operating junction temperature of the IGBT module, collect the voltage signal between the power emitter and the auxiliary emitter of the IGBT module under the operating condition, and extract the time difference between the two amplitudes of the voltage signal during the transient process of the IGBT module switching from the on state to the blocking state, which is the turn-off delay time; fix the bus voltage and the collector current, change The junction temperature of the IGBT module is changed and the turn-off delay time of the IGBT is collected. The relationship between the turn-off delay time and the junction temperature is modeled, and the rate of change and the intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module under the conditions of specific bus voltage and specific collector current are obtained; under different collector current conditions, this step is repeated to establish a correlation function model between the slope of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module, and a correlation function model between the intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module under a specific bus voltage.

[0087] Extract junction temperature online: before the drive circuit controls the IGBT module to switch from the on state to the blocking state, collect the collector current of the IGBT module; when the drive circuit controls the IGBT module to switch from the on state to the blocking state, collect the voltage signal between the power emitter and the auxiliary emitter of the IGBT module, and extract the time difference between the two peak values ​​of the voltage signal during the transient process of the IGBT module switching from the on state to the blocking state; and then, based on the IGBT module collector current and the shutdown delay time collected during the transient process of the IGBT module switching from the on state to the blocking state, obtain the operating junction temperature of the IGBT module through function model calculation or table lookup.

[0088] like Figure 8 As shown in Figure 1, when the IGBT is turned off, the voltage induced on the emitter parasitic inductance is caused by the sudden change of i at the beginning of the turn-off. g In L ek It can be seen from the induction that at the moment when the IGBT starts to turn off, that is, the end moment of the turn-off delay, the collector current i c In L kE It can be sensed on

[0089] like Fig. 9 The IGBT turn-off delay time t doff It is linearly positively correlated with the junction temperature.

[0090] The slope and intercept under different collector currents are as follows: Figure 8 and Fig. 9As shown, we can use rational functions and Fitting.

[0091] The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention of the present invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention of the present invention and do not deviate from the technical principles and inventive concepts of the IGBT junction temperature detection system and detection method based on the shutdown delay time of the present invention, they all belong to the protection scope of the present invention.

Claims

1. An IGBT junction temperature detection system based on turn-off delay time, comprising an IGBT module to be tested (1), characterized in that: The IGBT module (1) to be tested is respectively connected to an IGBT control unit (9), a voltage V eE A collection unit (2), a collector current collection unit (3) and a collector-emitter voltage collection unit (4); The IGBT module (1) to be tested is used as a test object and provides a test port; The voltage V eE A collection unit (2) is used to collect the potential difference V between the auxiliary emitter e and the power emitter E of the IGBT module (1) to be tested. eE ; The collector current acquisition unit (3) is used to acquire the collector current i of the IGBT module (1) to be tested. c ; The collector-emitter voltage acquisition unit (4) is used to acquire the potential difference V between the collector C and the power emitter E of the IGBT module (1) to be tested. CE ; The voltage V eE The acquisition unit (2) is connected to a delay time measurement unit (7) via a starting time base comparator (5) and an end time base comparator (6); The starting time base comparator (5) and the end time base comparator (6) are configured according to V eE respectively obtaining the start and end pulse signals of the turn-off delay phase of the IGBT module (1) to be tested; The delay time measurement unit (7) is used to measure the turn-off delay time of the IGBT module (1) to be tested according to the start and end information of the turn-off delay phase; The IGBT control unit (9) is used to control the on and off of the IGBT module (1) to be tested, and to control the operation of the collector current acquisition unit (3), the collector-emitter voltage acquisition unit (4), and the delay time measurement unit (7); The collector-emitter voltage acquisition unit (4), the collector current acquisition unit (3), and the delay time measurement unit (7) are connected to a junction temperature calculation unit (8) for data processing and calculating the junction temperature of the IGBT module (1) to be tested; The voltage V eE The acquisition unit (2) comprises a voltage attenuation circuit (2-1), a voltage follower (2-2) and a signal offset circuit (2-3) which are connected in sequence.

2. The IGBT junction temperature detection system based on turn-off delay time according to claim 1, characterized in that: The collector current acquisition unit (3) comprises a current sensor (3-1), a shaping circuit (3-2) and a signal output (3-3) which are connected in sequence.

3. The IGBT junction temperature detection system based on turn-off delay time according to claim 1, characterized in that: The collector-emitter voltage acquisition unit (4) comprises a voltage sensor (4-1), a shaping circuit (4-2) and a signal output (4-3) which are connected in sequence.

4. The IGBT junction temperature detection system based on turn-off delay time according to claim 1, characterized in that: The delay time measurement unit (7) is implemented by a time-to-digital converter chip.

5. A method for detecting IGBT junction temperature based on turn-off delay time, which is operated by using the IGBT junction temperature detection system based on turn-off delay time according to claim 1, characterized in that: The control operation flow of the control unit includes the following steps: 1) Establish data model: The operating condition is set under the condition that the maximum operating voltage, the maximum operating current and the maximum operating junction temperature of the IGBT module are not exceeded; for any operating condition, it corresponds to a set of data on the DC bus voltage, the collector current of the IGBT module and the operating junction temperature of the IGBT module, and the voltage signal between the power emitter and the auxiliary emitter of the IGBT module under the operating condition is collected, and the time difference between the two amplitudes of the voltage signal is extracted during the transient process of the IGBT module switching from the on state to the blocking state, which is the turn-off delay time; 2) Fix the bus voltage and collector current, change the junction temperature of the IGBT module and collect the IGBT turn-off delay time, model the relationship between the turn-off delay time and the junction temperature, and obtain the rate of change and intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module under the conditions of specific bus voltage and specific collector current; repeat this step under different collector current conditions, and then establish a correlation function model of the slope of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module under a specific bus voltage, and a correlation function model of the intercept of the turn-off delay time with respect to the operating junction temperature of the IGBT module and the collector current of the IGBT module; 3) Before the driving circuit controls the IGBT module to switch from the on state to the blocking state, the collector current of the IGBT module is collected; when the driving circuit controls the IGBT module to switch from the on state to the blocking state, the voltage signal between the power emitter and the auxiliary emitter of the IGBT module is collected, and the time difference between the two peak values ​​of the voltage signal is extracted during the transient process of the IGBT module switching from the on state to the blocking state; and then, according to the IGBT module collector current and the shutdown delay time collected during the transient process of the IGBT module switching from the on state to the blocking state, the operating junction temperature of the IGBT module is obtained by calculating the function model or reversely looking up the table.

6. The IGBT junction temperature detection method based on turn-off delay time according to claim 5, characterized in that: In the step 2), the correlation function model is composed of rational functions of the turn-off delay time under each DC bus voltage with respect to the collector current of the IGBT module and the operating junction temperature of the IGBT module; for any DC bus voltage, the rational functions of the turn-off delay time, the collector current of the IGBT module and the operating junction temperature of the IGBT module under the DC bus voltage are as follows: Among them, a1, b1, c1, d1, a2, b2, c2, and d2 are constants, which can be obtained by fitting the data after offline calibration. c is the collector current before IGBT is turned off, T j is the junction temperature of the IGBT, t doff is the turn-off delay time of the IGBT, and the slope is The intercept is

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