CN112229530B - SiC-based MOSFET junction temperature online monitoring system and online monitoring method - Google Patents

SiC-based MOSFET junction temperature online monitoring system and online monitoring method Download PDF

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CN112229530B
CN112229530B CN202011062518.XA CN202011062518A CN112229530B CN 112229530 B CN112229530 B CN 112229530B CN 202011062518 A CN202011062518 A CN 202011062518A CN 112229530 B CN112229530 B CN 112229530B
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current
mosfet
junction temperature
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operational amplifier
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CN112229530A (en
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郑丹
宁圃奇
范涛
温旭辉
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Institute of Electrical Engineering of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/01—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using semiconducting elements having PN junctions
    • G01K7/015—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using semiconducting elements having PN junctions using microstructures, e.g. made of silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10—Measuring as part of the manufacturing process
    • H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/20—Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Of Individual Semiconductor Devices (AREA)

Abstract

An on-line monitoring system and an on-line monitoring method for junction temperature of a SiC-based MOSFET, wherein the on-line monitoring system for junction temperature of the SiC-based MOSFET comprises: the device comprises a current calibration module, a first data fitting module, a second data fitting module, a working sampling module, a first test junction temperature acquisition unit, a second test junction temperature acquisition unit and a comparison and correction module, wherein the current calibration module comprises a first current calibration module and a second current calibration module. The SiC-based MOSFET junction temperature on-line monitoring system can improve the accuracy of testing junction temperature and can be used for on-line monitoring junction temperature.

Description

SiC-based MOSFET junction temperature online monitoring system and online monitoring method
Technical Field
The invention relates to the field of semiconductor testing, in particular to an on-line monitoring system and an on-line monitoring method for junction temperature of a SiC-based MOSFET.
Background
Silicon carbide (SiC) materials are third-generation semiconductor materials, and have the characteristics of large forbidden bandwidth, low dielectric constant, high breakdown voltage, high thermal conductivity, low electron drift velocity and the like, and are very stable in thermal, chemical and mechanical aspects. Compared with a power switch module made of Si material, the power switch module made of SiC material, such as a metal oxide semiconductor field effect transistor (meta loxide semiconductor Field Effect Transistor, MOSFET for short), has the remarkable advantages of low switching loss, high voltage resistance, high working temperature and the like, and is predicted to be a substitute of a Si-based insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT for short).
Junction temperature is an important parameter that characterizes the operating state and health of semiconductor devices. At present, the production and processing of the SiC substrate at the manufacturing level are complex, defects exist generally, and the processing technology of the SiC chip is not perfect; the practical technologies such as a basic model and a driving technology of an SiC device at an application level are incomplete, particularly when the junction temperature of a SiC MOSFET chip is high, the carrier scattering is enhanced, the mobility is reduced, the large-current conduction capacity of the chip is obviously reduced, and the carrier capture and release of a high-temperature gate interface can influence the stability and the reliability of the device. Under the condition, junction temperature on-line monitoring is carried out on the SiC MOSFET, so that the current carrying capacity of the chip can be further improved, the power density of the device is improved, and the reliability of the device is enhanced. The measurement of the junction temperature of the SiC MOSFET is the basis of life prediction, reliability evaluation, active heat management technology of the converter and over-temperature protection.
However, the junction temperature monitoring technology of the SiC-based MOSFET in the prior art has no comparison system and deep related research, has lower test precision and cannot be monitored on line.
Disclosure of Invention
The invention aims to solve the technical problems that the junction temperature test of the SiC-based MOSFET in the prior art is low in precision and cannot be monitored on line.
In order to solve the technical problems, the invention provides an on-line monitoring system and an on-line monitoring method for junction temperature of a SiC-based MOSFET, comprising the following steps: the current calibration module comprises a first current calibration module and a second current calibration module; the first current calibration module is suitable for injecting current into the forward direction of the MOSFET to be tested, and acquiring a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a junction temperature of the first conduction current and the MOSFET to be tested; the second current calibration module is suitable for reversely injecting a second current into the MOSFET to be tested, and acquiring a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and an off-state and the junction temperature of the MOSFET to be tested, wherein the first conduction current is larger than the second current; the first data fitting module is suitable for fitting the data in the first mapping relation to obtain a first functional relation, wherein the first functional relation takes a first conduction saturation voltage drop and a first conduction current as independent variables and the junction temperature of the MOSFET to be tested as a dependent variable; the second data fitting module is suitable for fitting data in a second mapping relation to obtain a second functional relation, wherein the second functional relation takes a second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET to be tested as a dependent variable; the work sampling module is suitable for acquiring a third conduction saturation voltage drop and a third conduction current in real time when the MOSFET to be tested is in a characteristic sampling state, and the characteristic sampling state comprises: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and a grid electrode of the MOSFET to be tested is in a conducting state; the second current calibration module is further adapted to perform off-line test on the MOSFET to be tested after the working sampling module obtains a third conduction saturation voltage drop and a third conduction current, and obtain a fourth conduction saturation voltage drop of the MOSFET to be tested at different moments in an off-line state and an off-state by reversely injecting the second current into the MOSFET to be tested; the first test junction temperature acquisition unit is suitable for acquiring a first test junction temperature, wherein the first test junction temperature is a junction temperature value of a MOSFET to be tested corresponding to data of a third conduction saturation voltage drop and a third conduction current in a first functional relation at the moment when the working equipment module stops working; the second test junction temperature acquisition unit is suitable for acquiring a junction temperature sampling value of a corresponding MOSFET to be tested in the second functional relation according to data of fourth conduction saturation voltage drops at different moments, and acquiring a second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling value of the MOSFET to be tested; the comparison and correction module is suitable for comparing the difference value between the first test junction temperature and the second test junction temperature and correcting the first mapping relation according to the difference value between the first test junction temperature and the second test junction temperature until the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value.
Optionally, the first current calibration module and the second current calibration module are independent from each other; the first current calibration module comprises a constant voltage source, a first capacitor, a load unit, a first current sensor and a first operational amplifier module, wherein the first capacitor is connected with the constant voltage source in parallel, the positive electrode of the constant voltage source is connected with the first end of the load unit, the second end of the load unit is suitable for being connected with a first source drain electrode of a MOSFET to be tested and the first operational amplifier module, the negative electrode of the constant voltage source is connected with a second source drain electrode of the MOSFET to be tested, the first operational amplifier module is suitable for converting a current signal in the MOSFET to be tested into a voltage signal, the output end of the first operational amplifier module is suitable for obtaining a first conduction saturation voltage drop, and the first current sensor is suitable for obtaining a first conduction current in a test mode; the second current calibration module comprises a second operational amplifier module, the output end of the second operational amplifier module is suitable for obtaining a second conduction saturation voltage drop, and the input end of the second operational amplifier module is connected with the first source drain electrode or the second source drain electrode of the MOSFET to be tested.
Optionally, the first operational amplifier module includes a first initial operational amplifier unit, a first low pass filter, a first proportional amplifier, a first analog signal isolation unit, the input end of the first initial operational amplifier unit is connected with the second end, the input end of the first low pass filter is connected with the output end of the first initial operational amplifier unit, the input end of the first proportional amplifier is connected with the output end of the first low pass filter, the voltage signal of the output end of the first proportional amplifier is smaller than the voltage signal of the input end of the first proportional amplifier, the input end of the first analog signal isolation unit is connected with the output end of the first proportional amplifier, and the output end of the first analog signal isolation unit is suitable for obtaining the first conduction saturation voltage drop.
Optionally, the second operational amplifier module includes a second initial operational amplifier unit, a second low-pass filter, a second proportional amplifier, and a second analog signal isolation unit, where an input end of the second initial operational amplifier unit is connected to the first source drain or the second source drain, an input end of the second low-pass filter is connected to an output end of the second initial operational amplifier unit, an input end of the second proportional amplifier is connected to an output end of the second low-pass filter, an input end of the second analog signal isolation unit is connected to an output end of the second proportional amplifier, a voltage signal of an output end of the second proportional amplifier is smaller than a voltage signal of an input end of the second proportional amplifier, and an output end of the second analog signal isolation unit is adapted to obtain a second conduction saturation voltage drop.
Optionally, the first current calibration module includes a constant current source, a first bleeder circuit connected in parallel with the constant current source, an auxiliary switch, a first current sensor, a first operational amplifier module and a first switch, wherein a positive connection end of the constant current source is connected with one end of the auxiliary switch, the other end of the auxiliary switch is suitable for being connected with a first source drain electrode of a MOSFET to be tested, a negative connection end of the constant current source is suitable for being connected with a second source drain electrode of the MOSFET to be tested, an input end of the first operational amplifier module is connected with the other end of the auxiliary switch through the first switch, the first operational amplifier module is suitable for converting a current signal in the MOSFET to be tested into a voltage signal, an output end of the first operational amplifier module is suitable for obtaining a first conduction saturation voltage drop, and the first current sensor is suitable for testing to obtain a first conduction current; the second current calibration module comprises a second operational amplifier module and a second switch, and the second operational amplifier module is connected with a second source drain electrode of the MOSFET to be tested through the second switch.
Optionally, the first operational amplifier module includes a first initial operational amplifier unit, a first low-pass filter, a first proportional amplifier, and a first analog signal isolation unit, where an input end of the first initial operational amplifier unit is connected to the first switch, an input end of the first low-pass filter is connected to an output end of the first initial operational amplifier unit, an input end of the first proportional amplifier is connected to an output end of the first low-pass filter, a voltage signal of an output end of the first proportional amplifier is smaller than a voltage signal of an input end of the first proportional amplifier, an input end of the first analog signal isolation unit is connected to an output end of the first proportional amplifier, and an output end of the first analog signal isolation unit is adapted to obtain a first conduction saturation voltage drop; the second operational amplifier module comprises a second initial operational amplifier unit, a second low-pass filter, a second proportional amplifier and a second analog signal isolation unit, wherein the input end of the second initial operational amplifier unit is connected with a second switch, the input end of the second low-pass filter is connected with the output end of the second initial operational amplifier unit, the input end of the second proportional amplifier is connected with the output end of the second low-pass filter, the input end of the second analog signal isolation unit is connected with the output end of the second proportional amplifier, the voltage signal of the output end of the second proportional amplifier is smaller than that of the input end of the second proportional amplifier, and the output end of the second analog signal isolation unit is suitable for obtaining a second conduction saturation voltage drop.
Optionally, the first initial operational amplifier unit includes a first current-voltage conversion operational amplifier, a first diode, a second diode and a first bias current source, the positive input end of the first current-voltage conversion operational amplifier is connected with the positive connection end of the first diode and the reverse connection end of the second diode, the positive connection end of the second diode is connected with the negative input end of the first current-voltage conversion operational amplifier and the first bias current source, the reverse connection end of the first diode is used as the input end of the first initial operational amplifier unit, and the output end of the first current-voltage conversion operational amplifier is used as the output end of the first initial operational amplifier unit.
Optionally, the second initial operational amplifier unit includes a second current-voltage conversion operational amplifier, a third diode, a fourth diode and a second bias current source, the positive input end of the second current-voltage conversion operational amplifier is connected with the positive connection end of the third diode and the reverse connection end of the fourth diode, the positive connection end of the fourth diode is connected with the negative input end of the second current-voltage conversion operational amplifier and the second bias current source, the reverse connection end of the third diode is used as the input end of the second initial operational amplifier unit, and the output end of the second current-voltage conversion operational amplifier is used as the output end of the second initial operational amplifier unit.
Optionally, the operation sampling module includes a voltage sampling module and a second current sensor; the voltage sampling module comprises a third initial operational amplifier unit, a third low-pass filter, a third proportional amplifier, a third analog signal isolation unit and a current release switch, wherein the input end of the third initial operational amplifier unit is connected with a first source drain electrode of a MOSFET to be tested, the input end of the third low-pass filter is connected with the output end of the third initial operational amplifier unit, the input end of the third proportional amplifier is connected with the output end of the third low-pass filter, the voltage signal of the output end of the third proportional amplifier is smaller than the voltage signal of the input end of the third proportional amplifier, the input end of the third analog signal isolation unit is connected with the output end of the third proportional amplifier, and the output end of the third analog signal isolation unit is suitable for obtaining a third conduction saturation voltage drop; the current release switch is suitable for opening and releasing the current in the third initial operational amplifier unit when the MOSFET to be tested is turned off; the second current sensor is adapted to test for a third conduction current.
Optionally, the third initial operational amplifier unit includes a third current-voltage conversion operational amplifier, a third bias current source, a fifth diode, a sixth diode, a seventh diode, a first resistor and a second resistor, the positive input end of the third current-voltage conversion operational amplifier is connected to the positive connection end of the fifth diode, the negative connection end of the sixth diode, the positive connection end of the seventh diode and a current release switch, the positive connection end of the sixth diode is connected to the negative connection end of the seventh diode, one end of the first resistor and the third bias current source, the other end of the first resistor is connected to the negative input end of the third current-voltage conversion operational amplifier and one end of the second resistor, the other end of the second resistor is connected to the output end of the third current-voltage conversion operational amplifier, the reverse connection end of the fifth diode is used as the input end of the third initial operational amplifier unit, and the output end of the third current-voltage conversion operational amplifier is used as the output end of the third initial operational amplifier unit.
Optionally, the comparing and correcting module includes a comparing unit and a correcting unit, the comparing unit is adapted to compare whether a difference between the first test junction temperature and the second test junction temperature is greater than a threshold value, and the correcting unit is adapted to correct the test environment of the MOSFET to be tested when the difference between the first test junction temperature and the second test junction temperature is greater than the threshold value, and correct the first mapping relation based on the corrected test environment until the difference between the first test junction temperature and the second test junction temperature is less than the threshold value.
Optionally, the method further comprises: a first modified functional relationship, the first modified functional relationship being a first functional relationship determined when a difference between the first test junction and the second test junction temperature is less than a threshold; and the working on-line testing module is suitable for acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET on line.
The invention also provides an on-line monitoring method for the junction temperature of the SiC-based MOSFET, which comprises the following steps: adopting a first current calibration module to forward inject current into the MOSFET to be tested, and obtaining a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a junction temperature of the MOSFET to be tested; reversely injecting a second current into the MOSFET to be tested by adopting a second current calibration module, and acquiring a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and an off-state and the junction temperature of the MOSFET to be tested, wherein the second current is smaller than the first conduction current; fitting data in a first mapping relation by adopting a first data fitting module to obtain a first functional relation, wherein the first functional relation takes a first conduction saturation voltage drop and a first conduction current as independent variables and the junction temperature of a MOSFET to be tested as a dependent variable; fitting the data in the second mapping relation by adopting a second data fitting module to obtain a second functional relation, wherein the second functional relation takes a second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET to be tested as an independent variable; the working sampling module is adopted to acquire a third conduction saturation voltage drop and a third conduction current in real time when the MOSFET to be detected is in a characteristic sampling state, and the characteristic sampling state comprises: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and a grid electrode of the MOSFET to be tested is in a conducting state; after obtaining the third conduction saturation voltage drop and the third conduction current, adopting a second current calibration module to perform off-line test on the MOSFET to be tested, reversely injecting the second current into the MOSFET to be tested, and obtaining fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and an off-state; acquiring a first test junction temperature by adopting a first test junction temperature acquisition unit, wherein the first test junction temperature is a junction temperature value of a MOSFET to be tested corresponding to data of a third conduction saturation voltage drop and a third conduction current in a first functional relation at the moment when the working equipment module stops working; acquiring a junction temperature sampling value of a corresponding MOSFET to be tested in the second functional relation according to data of fourth conduction saturation voltage drops at different moments by adopting a second test junction temperature acquisition unit, and acquiring a second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling value of the MOSFET to be tested; the sampling comparison and correction module compares the difference value between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation according to the difference value between the first test junction temperature and the second test junction temperature until the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value.
Optionally, in the process that the first current calibration module injects current into the forward direction of the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on a heating platform, and the junction temperature of the MOSFET to be tested in the first mapping relation is calibrated by the temperature of the heating platform; and in the process of reversely injecting the second current into the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on a heating platform, and the junction temperature of the MOSFET to be tested in the second mapping relation is calibrated by the temperature of the heating platform.
Optionally, the comparison and correction module comprises a comparison unit and a correction unit; comparing whether the difference between the first test junction temperature and the second test junction temperature is greater than a threshold value by adopting the comparison unit; and when the difference value between the first test junction temperature and the second test junction temperature is larger than the threshold value, adopting the correction unit to correct the test environment of the MOSFET to be tested, and correcting the first mapping relation based on the corrected test environment until the difference value between the first test junction temperature and the second test junction temperature is smaller than the threshold value.
Optionally, the method further comprises: when the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value, obtaining a first correction function relation; acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET on line by adopting an on-line working test module; and inputting the on-saturation voltage drop and the on-current obtained on line into a first correction function relation, and outputting the junction temperature of the SiC-based MOSFET.
The technical scheme of the invention has the following advantages:
according to the SiC-based MOSFET junction temperature on-line monitoring method provided by the technical scheme of the invention, a first test junction temperature acquisition unit is adopted to acquire a first test junction temperature, wherein the first test junction temperature is a junction temperature value of a MOSFET to be tested corresponding to data of a third conduction saturation voltage drop and a third conduction current in a first functional relation at the moment when a working equipment module stops working, a second test junction temperature acquisition unit is adopted to acquire a corresponding junction temperature sampling value of the MOSFET to be tested in the second functional relation according to data of a fourth conduction saturation voltage drop at different moments, and a second test junction temperature at the moment when the working equipment module stops working is acquired according to the junction temperature sampling value of the MOSFET to be tested; the sampling comparison and correction module compares the difference value between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation according to the difference value between the first test junction temperature and the second test junction temperature until the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value. The first test junction temperature and the second test junction temperature can be mutually compared, the difference value of the first test junction temperature and the second test junction temperature is finally enabled to be smaller than a threshold value through multiple times of circulation, a corrected first function relation and a first correction function relation can be obtained at the moment, the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET obtained through online test can be used for obtaining the junction temperature of the SiC-based MOSFET according to the first correction function relation, the testing precision of the junction temperature of the SiC-based MOSFET is improved, and the method can be used for online test.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a diagram of an on-line monitoring system for junction temperature of a SiC-based MOSFET according to an embodiment of the present invention;
FIG. 2 is a schematic diagram showing a specific structure of a first current calibration module according to an embodiment of the present invention;
FIG. 3 is a schematic diagram showing a specific structure of a second current calibration module according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a voltage sampling module according to an embodiment of the present invention;
FIG. 5 is a schematic diagram showing a specific structure of a second current sensor according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a current calibration module according to another embodiment of the present invention;
FIG. 7 is a schematic diagram of an on-line monitoring method for junction temperature of a SiC-based MOSFET according to another embodiment of the present invention;
FIG. 8 is a graph showing junction temperature versus time.
Detailed Description
As described in the background art, the junction temperature test of the SiC-based MOSFET in the prior art is low in accuracy.
The detection method for the junction temperature of the traditional power semiconductor chip is mainly based on the study of the SiIGBT and comprises four major types of physical contact method, optical non-contact measurement method, model prediction method and thermal-sensitive electrical parameter method (Therma lSensitive Electrica lParameters, TSEPs) extraction method.
In the physical contact method, a thermistor or a thermocouple is usually placed on a power module substrate to measure the temperature, but the temperature of the power module substrate and the junction temperature inside a power chip have large temperature difference (can reach more than 60K). The current advanced technology is to integrate a temperature sensor, usually a thermal diode or a thermal resistor, on the upper surface of a power chip, and this scheme needs a peripheral circuit of a load, and a special custom chip, which is not universal for most power modules in the market.
The optical non-contact measurement method needs to perform uncapping and sol treatment on the power module, so that the voltage tolerance capability of the power module can be reduced, and when the infrared thermal imaging instrument is used for measurement, black paint needs to be coated on the upper surface of the power module to enhance the emissivity. In addition, the response time of the temperature-sensitive optical fiber and the infrared thermal imager is in millisecond level, and compared with the switching period response of the power module, the temperature-sensitive optical fiber and the infrared thermal imager are too slow to be suitable for on-line monitoring of junction temperature.
The model prediction method is used for completing the prediction of junction temperature by establishing an accurate power device loss model and a thermal-electric coupling model. The building of the model cannot take account of individual differences and aging differences of the chip, and also cannot reflect some fault conditions in the operation of equipment, and redundant design is usually required and is usually only used for off-line junction temperature prediction.
The thermal sensitive electrical parameter method uses the chip itself as a temperature sensor, and reflects the change of the average junction temperature of the chip by measuring the change of the temperature sensitive electrical parameter, so that the non-invasive measurement of the measured power module can be realized, and the method is theoretically the most suitable method for on-line junction temperature monitoring. By monitoring different heat-sensitive parameters, the heat-sensitive electrical parameter method is roughly divided into a small-current saturated conduction voltage drop method, a large-current saturated conduction voltage drop method and the like.
The small current saturated conduction voltage drop method is based on the fact that the conduction saturated voltage drop of the IGBT under the small current and the junction temperature are in a negative linear relation, is recommended by industry association to be used for thermal resistance testing and off-line junction temperature testing of the IGBT module, and is also an accuracy verification method for on-line monitoring data of the IGBT junction temperature to be reliable. However, due to the characteristics of the SiC material, the small-current voltage drop method applied to the channel is not stable enough, and the small-current conduction voltage drop of the SiC MOSFET cannot be used as a junction temperature monitoring parameter, and cannot be used as a verification method for on-line junction temperature monitoring.
High-current saturated conduction voltage drop method and saturated conduction voltage drop V based on IGBT CE And current I flowing through the channel C Relative relation with junction temperature Tj by detecting V in real time CE And I C And calculating to obtain the real-time junction temperature. The high-current saturated conduction voltage drop method can reflect the junction temperature of the chip in principle, does not influence the normal operation of the equipment in the working state, and is very suitable for being used as a method for on-line monitoring of the junction temperature.
However, since the power module is in a switching state when in operation, when the power module is turned off, V CE For bus voltage, in generalUp to several hundred volts; when the power module is on, V CE Is saturated conduction voltage drop, and is only about 0-3V; and the on-off time changes along with PWM pulse modulation, so that the on-saturation voltage drop in the on-process is not easy to accurately detect. Simultaneously saturated conduction voltage drop V CE Junction temperature Tj and on-state current I C And a driving voltage V GE The method has the advantages that the influence of multiple factors is achieved, one-to-one sampling calibration is needed, the synchronization problem, the bandwidth problem and the interference problem are needed to be considered in the sampling process, and the engineering application is quite complex. In addition, because the junction temperature monitoring difficulty is high, different detection methods are lack of mutual comparison verification, and especially for SiC MOSFETs, the traditional off-line junction temperature measurement method based on small current injection cannot be applied, and other methods must be selected for verification.
At present, the IGBT-based on-saturation voltage drop method is only remained in a laboratory principle verification stage, and no calibration, detection and verification method of the system exists. For the SiC MOSFET, the manufacturing process and the application technology are far immature, the related thermoelectric mechanism model is not established, and a comparison system and intensive related research are not available for the on-line monitoring technology of the junction temperature of the SiC MOSFET.
On this basis, the embodiment of the invention provides an on-line junction temperature monitoring system of a SiC-based MOSFET, referring to FIG. 1, comprising:
the current calibration module B comprises a first current calibration module 110 and a second current calibration module 120; the first current calibration module 110 is adapted to forward inject current into the MOSFET to be tested, and obtain a first mapping relationship between a first conduction saturation voltage drop of the MOSFET10 to be tested (refer to fig. 2 and 6) and a first conduction current and a junction temperature of the MOSFET10 to be tested in an offline state; the second current calibration module 120 is adapted to reversely inject a second current into the MOSFET10 to be tested (refer to fig. 3 and 6), and obtain a second mapping relationship between a second conduction saturation voltage drop of the MOSFET10 to be tested in an off-line state and an off-state and a junction temperature of the MOSFET10 to be tested, wherein the first conduction current is greater than the second current;
The first data fitting module 200 is adapted to fit the data in the first mapping relationship to obtain a first functional relationship, where the first functional relationship uses a first conduction saturation voltage drop and a first conduction current as independent variables and uses a junction temperature of the MOSFET10 to be tested as a dependent variable;
the second data fitting module 300 is adapted to fit the data in the second mapping relationship to obtain a second functional relationship, where the second functional relationship uses the second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET10 to be measured as a dependent variable;
the operation sampling module 400, the operation sampling module 400 is adapted to obtain the third conduction saturation voltage drop and the third conduction current in real time when the MOSFET10 to be tested is in a characteristic sampling state, and the characteristic sampling state includes: the MOSFET10 to be tested is a working element of a working equipment module, the working equipment module is in a working state, and a grid electrode of the MOSFET10 to be tested is in a conducting state;
the second current calibration module 120 is further adapted to perform offline testing on the MOSFET10 to be tested after the operation sampling module obtains the third conduction saturation voltage drop and the third conduction current, and obtain the fourth conduction saturation voltage drop of the MOSFET10 to be tested at different moments in the offline state and the off state by reversely injecting the second current into the MOSFET10 to be tested;
The first test junction temperature obtaining unit 500, where the first test junction temperature obtaining unit 500 is adapted to obtain a first test junction temperature, where the first test junction temperature is a junction temperature value of the MOSFET10 to be tested corresponding to data of the third conduction saturation voltage drop and the third conduction current in the first functional relationship at a time when the working equipment module stops working;
a second test junction temperature obtaining unit 600, adapted to obtain a junction temperature sampling value of the corresponding MOSFET10 to be tested in the second functional relationship according to the data of the fourth conduction saturation voltage drop at different moments, and obtain a second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling value of the MOSFET10 to be tested;
the comparison and correction module 700 is adapted to compare the difference between the first test junction temperature and the second test junction temperature, and correct the first mapping relationship according to the difference between the first test junction temperature and the second test junction temperature until the difference between the first test junction temperature and the second test junction temperature is less than a threshold value.
The MOSFET10 is a planar MOSFET, or the MOSFET10 is a fin field effect transistor.
The working equipment module comprises a current transformer. It should be noted that, in other embodiments, the working device module may also select other modules.
In this embodiment, the first current calibration module 110 and the second current calibration module 120 are independent from each other.
In this embodiment, referring to fig. 2, a specific structure of the first current calibration module 110 is shown, where the first current calibration module 110 includes: the constant voltage source 1101, a first capacitor 1102, a load unit 1103, a first current sensor 1104, and a first operational amplifier module Y1, where the first capacitor 1102 is connected in parallel with the constant voltage source 1101, the positive electrode of the constant voltage source 1101 is connected with a first end of the load unit 1103, a second end of the load unit 1103 is adapted to be connected with a first source drain of the MOSFET10 to be tested and the first operational amplifier module Y1, the negative electrode of the constant voltage source 1101 is adapted to be connected with a second source drain of the MOSFET10 to be tested, the first operational amplifier module Y1 is adapted to convert a current signal in the MOSFET10 to be tested into a voltage signal, and the output end of the first operational amplifier module Y1 is adapted to obtain a first conduction saturation voltage drop V DS1 The first current sensor 1104 is adapted to obtain a first on-current I by testing D1 。
The load unit 1103 includes: a load resistor and an additional transistor, one end of the load resistor being a first end of the load unit 1103 and the other end of the load resistor being a second end of the load unit 1103. The load resistor is connected in parallel with the additional transistor.
The constant voltage source 1101 is an adjustable constant voltage source.
The first operational amplifier module Y1 includes a first initial operational amplifier unit Y11, a first low-pass filter Y12, a first proportional amplifier Y13, and a first analog signal isolation unit Y14, where an input end of the first initial operational amplifier unit Y11 is connected to a second end, and the first low-pass filter Y12The input end of the filter Y12 is connected with the output end of the first initial operational amplifier unit Y11, the input end of the first proportional amplifier Y13 is connected with the output end of the first low-pass filter Y12, the voltage signal of the output end of the first proportional amplifier Y13 is smaller than that of the input end of the first proportional amplifier Y13, the input end of the first analog signal isolation unit Y14 is connected with the output end of the first proportional amplifier Y13, and the output end of the first analog signal isolation unit Y14 is suitable for obtaining a first conduction saturation voltage drop V DS1 。
In a specific embodiment, the first initial operational amplifier unit Y11 includes a first current-voltage conversion operational amplifier Y111, a first diode Y112, a second diode Y113, and a first bias current source Y114, where an anode input terminal of the first current-voltage conversion operational amplifier Y111 is connected to a forward connection terminal of the first diode Y112 and a reverse connection terminal of the second diode Y113, a forward connection terminal of the second diode Y113 is connected to a cathode input terminal of the first current-voltage conversion operational amplifier Y111 and the first bias current source Y114, and a reverse connection terminal of the first diode Y112 is used as an input terminal of the first initial operational amplifier unit Y11, and an output terminal of the first current-voltage conversion operational amplifier Y111 is used as an output terminal of the first initial operational amplifier unit Y11.
In this embodiment, the constant voltage source 1101 is adapted to inject a forward current, specifically a large forward current, on the order of 100 a to thousands of a, specifically, in one embodiment, 100 a to 1000 a, into the MOSFET10 under test.
In a specific embodiment, the first low-pass filter Y12 includes a third resistor Y121, a fourth resistor Y122, a second capacitor Y123, a first operational amplifier Y124, and a third capacitor Y125, where one end of the third resistor Y121 is connected to the output end of the first initial operational amplifier Y11, specifically, one end of the third resistor Y121 is connected to the output end of the first current-voltage conversion operational amplifier Y111, the other end of the third resistor Y121 is connected to one end of the fourth resistor Y122 and one end of the second capacitor Y123, the other end of the fourth resistor Y122 is connected to the positive input end of the first operational amplifier Y124 and one end of the third capacitor Y125, the other end of the third capacitor Y125 is grounded, the other end of the second capacitor Y123 is connected to the negative input end of the first operational amplifier Y124, and the negative input end of the first operational amplifier Y124 is connected to the output end of the first operational amplifier Y124.
The first proportional amplifier Y13 is used to adjust the input signal to a suitable level.
The first analog signal isolation unit Y14 realizes an analog signal isolation function and is used for isolating strong electric interference and ensuring safe operation of equipment and personnel safety. The isolation method of the first analog signal isolation unit Y14 may be selected from high-resistance isolation, optocoupler isolation, magnetic isolation, or capacitive isolation.
In this embodiment, when the first current calibration module 110 calibrates the MOSFET10 to be tested, the second source/drain of the MOSFET10 to be tested is grounded, and the MOSFET10 to be tested is turned on.
In this embodiment, the second current calibration module 120, referring to fig. 3, includes: the output end of the second operational amplifier module Y2 is suitable for obtaining a second conduction saturation voltage drop V DS2 The input end of the second operational amplifier module Y2 is connected with the first source drain electrode or the second source drain electrode of the MOSFET10 to be tested.
In this embodiment, referring to fig. 3, the input end of the second operational amplifier module Y2 is connected to the second source/drain of the MOSFET10 to be tested, and when the second current calibration module 120 calibrates the MOSFET10 to be tested, the first source/drain of the MOSFET10 to be tested is grounded, and the voltage is applied to the gate of the MOSFET10 to be tested to turn off the MOSFET10 to be tested.
In a specific embodiment, referring to fig. 3, the second operational amplifier module Y2 includes a second initial operational amplifier unit Y21, a second low-pass filter Y22, a second proportional amplifier Y23, and a second analog signal isolation unit Y24, where an input end of the second initial operational amplifier unit Y21 is connected to the first source drain or the second source drain, in this embodiment, an input end of the second initial operational amplifier unit Y21 is connected to the second source drain, an input end of the second low-pass filter Y22 is connected to an output end of the second initial operational amplifier unit Y21, an input end of the second proportional amplifier Y23 is connected to an output end of the second low-pass filter Y22, an input end of the second analog signal isolation unit Y24 is connected to an output end of the second proportional amplifier Y23, and a voltage signal of an output end of the second proportional amplifier Y23 is smaller than a voltage signal of an input end of the second proportional amplifier Y23, and an output end of the second analog signal isolation unit Y24 is adapted to obtain a second saturation voltage drop.
In a specific embodiment, the second initial operational amplifier unit Y21 includes a second current-voltage conversion operational amplifier Y211, a third diode Y212, a fourth diode Y213, and a second bias current source Y214, where a positive input terminal of the second current-voltage conversion operational amplifier Y211 is connected to a positive connection terminal of the third diode Y212 and a negative connection terminal of the fourth diode Y213, a positive connection terminal of the fourth diode Y213 is connected to a negative input terminal of the second current-voltage conversion operational amplifier Y211 and the second bias current source Y214, a negative connection terminal of the third diode Y212 is used as an input terminal of the second initial operational amplifier unit Y21, and an output terminal of the second current-voltage conversion operational amplifier Y211 is used as an output terminal of the second initial operational amplifier unit Y21.
In a specific embodiment, the second low-pass filter Y22 includes a fifth resistor Y221, a sixth resistor Y222, a fourth capacitor Y223, a second operational amplifier Y224, and a fifth capacitor Y225, where one end of the fifth resistor Y221 is connected to the output end of the second initial operational amplifier Y21, specifically, one end of the fifth resistor Y221 is connected to the output end of the second current-voltage conversion operational amplifier Y211, the other end of the fifth resistor Y221 is connected to one end of the sixth resistor Y222 and one end of the fourth capacitor Y223, the other end of the sixth resistor Y222 is connected to the positive input end of the second operational amplifier Y224 and one end of the fifth capacitor Y225, the other end of the fifth capacitor Y225 is grounded, the other end of the fourth capacitor Y223 is connected to the negative input end of the second operational amplifier Y224, and the negative input end of the second operational amplifier Y224 is connected to the output end of the second operational amplifier Y224.
The second proportional amplifier Y23 is used to adjust the input signal to a suitable level.
The second analog signal isolation unit Y24 realizes an analog signal isolation function and is used for isolating strong electric interference and ensuring safe operation of equipment and personnel safety. The method of the second analog signal isolation unit Y24 may select high-resistance isolation, optocoupler isolation, magnetic isolation, or capacitive isolation. In this embodiment, the second bias current source Y214 is adapted to inject a reverse current, specifically a reverse small current, on the order of 5mA-100mA, into the MOSFET10 under test.
A first data fitting module 200, where the first data fitting module 200 is adapted to fit the data in the first mapping relationship to obtain a first functional relationship, where the first functional relationship is represented by a first on saturation voltage drop V DS1 And a first on-current I D1 The junction temperature Tj of the MOSFET to be measured is taken as a dependent variable.
The first functional relationship that the first data fitting module 200 fits to may be a polynomial or a trigonometric function.
A second data fitting module 300, wherein the second data fitting module 300 is adapted to fit the data in the second mapping relationship to obtain a second functional relationship, and the second functional relationship is represented by a second conduction saturation voltage drop V DS2 The junction temperature Tj1 of the MOSFET to be measured is used as a dependent variable.
The second functional relationship that the second data fitting module 300 fits to may be a polynomial or a trigonometric function.
The operation sampling module 400 includes a voltage sampling module 410 and a current sampling module 420, the current sampling module 420 including a second current sensor.
Referring to fig. 4, the voltage sampling module 410 includes a third initial operational amplifier unit Y41, a third low-pass filter Y42, a third proportional amplifier Y43, a third analog signal isolation unit Y44, and a current release switch Y45, where an input end of the third initial operational amplifier unit Y41 is connected to a first source drain of the MOSFET10 to be tested, an input end of the third low-pass filter Y42 is connected to an output end of the third initial operational amplifier unit Y41, an input end of the third proportional amplifier Y43 is connected to an output end of the third low-pass filter Y42, a voltage signal of the output end of the third proportional amplifier Y43 is smaller than a voltage signal of the input end of the third proportional amplifier Y43, and an input end of the third analog signal isolation unit Y44 is connected to the third proportional amplifierThe output end of the amplifier Y43 is connected, and the output end of the third analog signal isolation unit Y44 is suitable for obtaining a third conduction saturation voltage drop V DS3 The current bleed switch Y45 is adapted to open and bleed the current in the third initial operational amplifier unit Y41 when the MOSFET10 to be tested is turned off.
The second current sensor is suitable for obtaining a third conduction current I through testing D3 。
The third initial operational amplifier unit Y41 includes a third current-voltage conversion operational amplifier Y411, a third bias current source Y412, a fifth diode Y413, a sixth diode Y414, a seventh diode Y415, a first resistor Y416, and a second resistor Y417, where the positive input terminal of the third current-voltage conversion operational amplifier Y411 is connected to the positive connection terminal of the fifth diode Y413, the negative connection terminal of the sixth diode Y414, the positive connection terminal of the seventh diode Y415, and a current bleed switch Y45, the positive connection terminal of the sixth diode Y414 is connected to the negative connection terminal of the seventh diode Y415, one end of the first resistor Y416, and the third bias current source Y412, the other end of the first resistor Y416 is connected to the negative input terminal of the third current-voltage conversion operational amplifier Y411, and one end of the second resistor Y417, the other end of the second resistor Y417 is connected to the output terminal of the third current-voltage conversion operational amplifier Y411, and the positive connection terminal of the sixth diode Y414 is connected to the negative connection terminal of the third initial operational amplifier unit Y415 as the output terminal of the third operational amplifier unit Y41.
The third low-pass filter Y42 includes a seventh resistor Y421, an eighth resistor Y422, a sixth capacitor Y423, a third operational amplifier Y424, and a seventh capacitor Y425, where one end of the seventh resistor Y421 is connected to the output end of the third initial operational amplifier Y41, specifically, one end of the seventh resistor Y421 is connected to the output end of the third current-voltage conversion operational amplifier Y411, the other end of the seventh resistor Y421 is connected to one end of the eighth resistor Y422 and one end of the sixth capacitor Y423, the other end of the eighth resistor Y422 is connected to the positive input end of the third operational amplifier Y424 and one end of the seventh capacitor Y425, the other end of the seventh capacitor Y425 is grounded, and the other end of the sixth capacitor Y423 is connected to the negative input end of the third operational amplifier Y424, and the negative input end of the third operational amplifier Y424 is connected to the output end of the third operational amplifier Y424.
The third proportional amplifier Y43 is used to adjust the input signal to a suitable level.
The third analog signal isolation unit Y44 realizes an analog signal isolation function and is used for isolating strong electric interference and ensuring safe operation of equipment and personnel safety. The isolation method of the third analog signal isolation unit Y44 may be selected from high-resistance isolation, optocoupler isolation, magnetic isolation, or capacitive isolation.
The current drain switch Y45 is a MOS switch. One source drain electrode of the current drain switch Y45 is grounded, and the other source drain electrode of the current drain switch Y45 is connected to the forward connection end of the third current-voltage conversion operational amplifier Y411.
When the work sampling module 400 samples the MOSFET10 to be tested, the MOSFET10 to be tested is used as a working element of the working device module, the working device module is in a working state, and the gate of the MOSFET10 to be tested is in a conducting state, specifically, the gate of the MOSFET10 to be tested is driven by a pulse width modulation signal (Pulse width modulation, abbreviated as PWM) of the working device module. The grid electrode of the current release switch Y45 is formed byThe driving, that is, the level signal applied by the gate of the MOSFET10 to be tested is opposite to the level signal applied by the gate of the current drain switch Y45, when the gate of the MOSFET10 to be tested is applied at a high level, the gate of the current drain switch Y45 is applied at a low level, and when the gate of the MOSFET10 to be tested is applied at a low level, the gate of the current drain switch Y45 is applied at a high level.
The second current sensor, referring to fig. 5, includes a first hall sampling unit 4203, a fourth initial operational amplifier unit 4201, and a fourth low-pass filter 4202, wherein a current input end of the first hall sampling unit is adapted to be electrically connected to a first source drain or a second source drain of the MOSFET10 to be measured, two voltage output ends of the first hall sampling unit are electrically connected to a first input end and a second input end of the fourth initial operational amplifier unit 4201, an output end of the fourth initial operational amplifier unit 4201 is connected to an input end of the fourth low-pass filter 4202, and an output end of the fourth low-pass filter 4202 is adapted to output a signal of the third on current.
The first hall sampling unit 4203 includes a first magnetic core, the first magnetic core is in an annular structure and has a notch, the notch of the first magnetic core is provided with a first guide rod, the first magnetic core surrounds the first guide rod, specifically, the first guide rod is suitable for being electrically connected with the first source drain or the second source drain of the MOSFET10 to be tested, and one end of the first guide rod is used as a current input end of the first hall sampling unit.
The fourth initial operational amplifier unit 4201 is adapted to output the differential voltage output by the first hall sampling unit 4203 as a single-ended fixed voltage.
In the present embodiment, the structure of the fourth low-pass filter 4202 is identical to that of the third low-pass filter Y42 described above, and will not be described in detail.
In this embodiment, the fourth low-pass filter 4202 is used to adjust the delay of the second current sensor, so that the operation sampling module 400 synchronizes the signal of the third conduction saturation voltage drop and the third conduction current to be tested for sampling the MOSFET 10.
In this embodiment, the first current sensor includes a second hall sampling unit, a fifth initial operational amplifier unit and a fifth low-pass filter, where a current input end of the second hall sampling unit is adapted to be electrically connected to a first source drain electrode or a second source drain electrode of the MOSFET10 to be tested, two voltage output ends of the second hall sampling unit are respectively electrically connected to a first input end and a second input end of the fifth initial operational amplifier unit, an output end of the fifth initial operational amplifier unit is connected to an input end of the fifth low-pass filter, and an output end of the fifth low-pass filter is adapted to output a signal of the first on current.
The second hall sampling unit refers to the first hall sampling unit.
The fifth initial operational amplifier unit refers to the fourth initial operational amplifier unit 4201.
In this embodiment, the structure of the fifth low-pass filter is identical to that of the first low-pass filter Y12 described above, and will not be described in detail.
In this embodiment, the fifth low-pass filter is used to adjust the delay of the first current sensor, so that the first current calibration module synchronizes the first conduction saturation voltage drop of the MOSFET10 to be tested and the signal of the first conduction current.
The first current calibration module 110 is adapted to place the MOSFET10 to be tested on the heating platform during the process of forward injecting current into the MOSFET10 to be tested, and the junction temperature of the MOSFET10 to be tested in the first mapping relationship is calibrated by the temperature of the heating platform.
The second current calibration module 120 is adapted to place the MOSFET10 to be tested on the heating platform during the process of reversely injecting the second current into the MOSFET10 to be tested, and the junction temperature of the MOSFET10 to be tested in the second mapping relationship is calibrated by the temperature of the heating platform.
The comparison and correction module 700 includes a comparison unit 710 and a correction unit 720, wherein the comparison unit 710 is adapted to compare whether the difference between the first test junction temperature and the second test junction temperature is greater than a threshold value, and the correction unit 720 is adapted to correct the test environment of the MOSFET10 to be tested when the difference between the first test junction temperature and the second test junction temperature is greater than the threshold value and correct the first mapping relationship based on the corrected test environment until the difference between the first test junction temperature and the second test junction temperature is less than the threshold value.
The test environment of the MOSFET10 to be tested includes the deviation range of the driving voltage of the MOSFET to be tested, the upper limit of the current conducting pulse, and the temperature accuracy of the heating platform in the actual operation and the calibration process.
In actual operation and in the calibration process, the driving voltage VGS of the MOSFET10 to be measured needs to be within a certain deviation range, and the smaller the deviation range is, the better the deviation range is; in actual operation and during calibration, the current conduction pulse needs to be small enough, typically about tens of microseconds to two hundred microseconds, so that the self-heating problem of the MOSFET10 to be tested can be ignored.
The SiC-based MOSFET junction temperature on-line monitoring system further comprises: a first modified functional relationship, the first modified functional relationship being a first functional relationship determined when a difference between the first test junction and the second test junction temperature is less than a threshold; and the working on-line testing module is suitable for acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET on line.
The junction temperature monitoring system of the SiC-based MOSFET of the present embodiment is different from the junction temperature monitoring system of the SiC-based MOSFET of the previous embodiment in that: the current calibration modules are different.
Specifically, referring to fig. 6, the current calibration module of the present embodiment includes a first current calibration module and a second current calibration module.
The first current calibration module comprises a constant current source 8001, a first bleeder circuit 8002 connected in parallel with the constant current source 8001, an auxiliary switch 8003, a first current sensor 8004, a first operational amplifier module Y1 and a first switch 8005, wherein a positive connection end of the constant current source 8001 is connected with one end of the auxiliary switch 8003, the other end of the auxiliary switch 8003 is suitable for being connected with a first source drain electrode of a MOSFET10 to be tested, a negative connection end of the constant current source 8001 is suitable for being connected with a second source drain electrode of the MOSFET10 to be tested, an input end of the first operational amplifier module Y1 is connected with the other end of the auxiliary switch 8003 through the first switch 8005, the first operational amplifier module Y1 is suitable for converting a current signal in the MOSFET10 to be tested into a voltage signal, and an output end of the first operational amplifier module Y1 is suitable for obtaining a first conduction saturation voltage drop, and the first current sensor 8004 is suitable for being tested to obtain a first conduction current.
The first current sensor 8004 of this embodiment refers to the content of the foregoing embodiment and will not be described in detail.
The specific structure of the first operational amplifier module Y1 refers to the first operational amplifier module Y1 of the foregoing embodiment. The input end of the first initial operational amplifier unit in the first operational amplifier module is connected with a first switch 8005.
The second current calibration module includes a second operational amplifier module Y2 and a second switch 8006, and the second operational amplifier module Y2 is connected with a second source drain of the MOSFET10 to be tested through the second switch 8006. The specific structure of the second operational amplifier module Y2 refers to the second operational amplifier module Y2 of the foregoing embodiment. The input end of the second initial operational amplifier unit in the second operational amplifier module is connected with a second switch 8006.
Correspondingly, another embodiment of the present invention further provides an on-line monitoring method for junction temperature of a SiC-based MOSFET, which is suitable for using the on-line monitoring system for junction temperature of a SiC-based MOSFET, and referring to fig. 7, the method includes the following steps:
s01: adopting a first current calibration module to forward inject current into the MOSFET to be tested, and obtaining a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a junction temperature of the MOSFET to be tested;
s02: reversely injecting a second current into the MOSFET to be tested by adopting a second current calibration module, and acquiring a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and an off-state and the junction temperature of the MOSFET to be tested;
s03: fitting data in a first mapping relation by adopting a first data fitting module to obtain a first functional relation, wherein the first functional relation takes a first conduction saturation voltage drop and a first conduction current as independent variables and the junction temperature of a MOSFET to be tested as a dependent variable;
S04: fitting the data in the second mapping relation by adopting a second data fitting module to obtain a second functional relation, wherein the second functional relation takes a second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET to be tested as an independent variable;
s05: the working sampling module is adopted to acquire a third conduction saturation voltage drop and a third conduction current in real time when the MOSFET to be detected is in a characteristic sampling state, and the characteristic sampling state comprises: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and a grid electrode of the MOSFET to be tested is in a conducting state;
s06: after obtaining the third conduction saturation voltage drop and the third conduction current, adopting a second current calibration module to perform off-line test on the MOSFET to be tested, reversely injecting the second current into the MOSFET to be tested, and obtaining fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and an off-state;
s07: acquiring a first test junction temperature by adopting a first test junction temperature acquisition unit, wherein the first test junction temperature is a junction temperature value of a MOSFET to be tested corresponding to data of a third conduction saturation voltage drop and a third conduction current in a first functional relation at the moment when the working equipment module stops working;
S08: acquiring a junction temperature sampling value of a corresponding MOSFET to be tested in the second functional relation according to data of fourth conduction saturation voltage drops at different moments by adopting a second test junction temperature acquisition unit, and acquiring a second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling value of the MOSFET to be tested;
s09: the sampling comparison and correction module compares the difference value between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation according to the difference value between the first test junction temperature and the second test junction temperature until the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value.
And in the process of forward current injection of the MOSFET to be detected by the first current calibration module, the MOSFET to be detected is suitable for being placed on a heating platform, and the junction temperature of the MOSFET to be detected in the first mapping relation is calibrated by the temperature of the heating platform.
And in the process of reversely injecting the second current into the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on a heating platform, and the junction temperature of the MOSFET to be tested in the second mapping relation is calibrated by the temperature of the heating platform.
When the first current calibration module of fig. 2 is used to calibrate the MOSFET to be tested, specifically, the second end of the load unit 1103 is connected to the first source drain of the MOSFET10 to be tested and the first operational amplifier module Y1, the negative electrode of the constant voltage source 1101 is connected to the second source drain of the MOSFET10 to be tested, the MOSFET10 to be tested is placed on the heating platform, specifically, the chip corresponding to the MOSFET10 to be tested is placed on the heating platform, the MOSFET10 to be tested is heated to a predetermined temperature by the heating platform, the gate of the MOSFET10 to be tested is turned on, specifically, a pulse signal with a period is applied to the gate of the MOSFET10 to be tested, and the time of the pulse signal with a period is less than or equal to 100 microseconds to prevent the excessive time from causing the MOSFET to be tested The inside of the MOSFET10 heats up due to the excessive on-current. When the first current calibration module of fig. 2 is used for calibrating the MOSFET10 to be tested, the first on current I of the MOSFET 10T to be tested D1 Is determined by the voltage of the constant voltage source 1101 and the load unit 1103, and in the case of a fixed load unit 1103, the voltage amplitude of the constant voltage source 1101 is adjusted to obtain a set of first on-current I D1 And a first conduction saturation voltage drop V DS1 By adjusting the temperature of the heating stage, the junction temperature T of the MOSFETs 10 to be measured can be obtained j First on-current I D1 And a first conduction saturation voltage drop V DS1 To obtain the first conduction saturation voltage drop V of the MOSFET10 under test in the off-line state DS1 With a first conduction current I D1 And the junction temperature of the MOSFET10 under test.
When the first current calibration module of fig. 6 is adopted to calibrate the MOSFET10 to be tested, specifically, the negative connection end of the constant current source 8001 is connected with the second source drain of the MOSFET10 to be tested, the input end of the first operational amplifier module Y1 is connected with the other end of the auxiliary switch 8003 through the first switch 8005, the MOSFET10 to be tested is placed on a heating platform, specifically, a chip corresponding to the MOSFET10 to be tested is placed on the heating platform, the MOSFET10 to be tested is heated to a predetermined temperature by the heating platform, the gate of the MOSFET10 to be tested is turned on, specifically, a pulse signal of a period is applied to the gate of the MOSFET10 to be tested, and the time of the pulse signal of a period is less than or equal to 100 microseconds to prevent the inside of the MOSFET10 to be tested from heating due to overlarge conduction current.
When the first current calibration module of fig. 6 is used for calibrating the MOSFET10 to be tested, the first conduction current I of the MOSFET to be tested D1 The auxiliary switch 8003 and the first switch 8005 are opened and the second switch 8006 is closed, and the constant current source 8001 positively injects a large current into the MOSFET10 to be tested, thereby obtaining a group of first on-current I D1 And a first conduction saturation voltage drop V DS1 By adjusting the temperature of the heating stage, the junction temperature T of the MOSFETs 10 to be measured can be obtained j First conduction electricityStream I D1 And a first conduction saturation voltage drop V DS1 And thus a first mapping relationship between the first conduction saturation voltage drop and the first conduction current of the MOSFET10 to be tested in the off-line state and the junction temperature of the MOSFET10 to be tested is obtained.
When the second current calibration module shown in fig. 3 is adopted to calibrate the MOSFET to be tested, specifically, the input end of the second operational amplifier module Y2 is connected with the second source drain of the MOSFET10 to be tested, the first source drain of the MOSFET10 to be tested is grounded, the voltage is applied to the gate of the MOSFET10 to be tested to turn off the MOSFET10 to be tested, the MOSFET to be tested is placed on the heating platform, specifically, the chip corresponding to the MOSFET10 to be tested is placed on the heating platform, the MOSFET10 to be tested is heated to a preset temperature by the heating platform, the second bias current source Y214 reversely injects small current into the body diode of the MOSFET10 to be tested, and the junction temperature T of different MOSFETs 10 to be tested can be obtained by adjusting the temperature of the heating platform j Second conduction saturation voltage drop V under 1 DS2 Thereby obtaining the second conduction saturation voltage drop V of the MOSFET10 under test in the off-line state and the off-state DS2 Junction temperature T with MOSFET to be tested j A second mapping relationship between 1.
When the second current calibration module shown in fig. 6 is adopted to calibrate the MOSFET10 to be tested, the second operational amplifier module Y2 is connected with the second source drain of the MOSFET10 to be tested through the second switch 8006, the voltage applied to the gate of the MOSFET10 to be tested makes the MOSFET10 to be tested turn off, the MOSFET10 to be tested is placed on the heating platform, the first switch 8005 and the auxiliary switch 8003 are turned off, the first bleeder circuit 80021 bleeder the current in the constant current source 8001, the current in the constant current source 8001 is prevented from being injected into the MOSFET10 to be tested, the second switch 8006 is turned on, the second bias current source Y214 reversely injects small current into the body diode of the MOSFET10 to be tested, the temperature of the heating platform is adjusted, and the junction temperature T of different MOSFETs 10 to be tested can be obtained j Second conduction saturation voltage drop V under 1 DS2 Thereby obtaining the second conduction saturation voltage drop V of the MOSFET10 under test in the off-line state and the off-state DS2 Junction temperature T with MOSFET to be tested j A second mapping relationship between 1.
And fitting the data in the first mapping relation by adopting a first data fitting module to obtain a first functional relation, wherein the first functional relation takes the first conduction saturation voltage drop and the first conduction current as independent variables and the junction temperature of the MOSFET to be tested as dependent variables.
In a specific embodiment, the first functional relationship is fitted using a binary second order polynomial:
A 1 、A 2 、A 3 、A 4 、A 5 、A 6 coefficients for each polynomial in the first functional relationship.
And fitting the data in the second mapping relation by adopting a second data fitting module to obtain a second functional relation, wherein the second functional relation takes the second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET to be tested as an independent variable.
In a specific embodiment, the second functional relationship employs a unitary first order polynomial fit: t (T) j 1＝A 7 +A 8 *V DS2
A 7 、A 8 Coefficients for each polynomial in the second functional relationship.
The working sampling module is adopted to acquire a third conduction saturation voltage drop and a third conduction current in real time when the MOSFET to be detected is in a characteristic sampling state, and the characteristic sampling state comprises: the MOSFET to be tested is a working element of the working device module, the working device module is in a working state, and a gate of the MOSFET to be tested is in a conducting state, specifically, the voltage sampling module 410 is used for sampling a third conducting saturation voltage drop, and the second current sensor is used for sampling a third conducting current. Specifically, when the working equipment module is in a working state, the grid electrode of the MOSFET to be tested is driven by a pulse width modulation signal (Pulse width modulation, abbreviated as PWM) of the working equipment module, the pulse width modulation signal is applied to enable the MOSFET to be tested to be conducted, a current release switch Y45 is turned off at the moment, when the MOSFET to be tested is conducted, a third bias current source Y412 is adopted to inject bias current into the MOSFET to be tested, and a third analog signal is isolated The output end of the separation unit Y44 obtains a third conduction saturation voltage drop V DS3 Simultaneously, a second current sensor is adopted to obtain a third conduction current I D3 。
It should be noted that after the real-time sampling of the working sampling module is completed, the MOSFET to be tested is turned off, at this time, the current bleeder switch Y45 is turned on, and the current in the third bias current source Y412 is bleeder, at this time, the output of the third initial operational amplifier unit Y41 is 0V.
Setting the working sampling module to stop sampling at the moment T1, and stopping working the working equipment module, wherein the moment T1 corresponds to V DS3 (T1) and I D3 (T1), V DS3 (T1) and I D3 (T1) bringing the junction temperature value of the MOSFET to be tested into the first functional relation, and calculating the junction temperature value of the MOSFET to be tested as a first test junction temperature Tb1.
After the working equipment module stops working, the MOSFET10 to be tested is tested offline by adopting a second current calibration module, and a second current is reversely injected into the MOSFET10 to be tested, and fourth conduction saturation voltage drops V of the MOSFET10 to be tested at different moments under the offline state and the off state are obtained DS4 。
Suppose that V is tested at time T2 DS4 (T2) obtaining V in the T3 etching test DS4 (T3) obtaining V in the T4 etching test DS4 (T4). Will V DS4 (T2)、V DS4 (T3) and V DS4 And (T4) respectively carrying out second functional relations to respectively obtain junction temperature sampling values Tj (T2), tj (T3) and Tj (T4) of the MOSFETs to be tested.
Referring to fig. 8, fig. 8 shows the relationship between the junction temperature change Δt of the MOSFET10 to be tested and the time T after the operation device module stops operating, wherein the horizontal axis in fig. 8 shows the time T in seconds, and the vertical axis shows the junction temperature of the MOSFET10 to be tested, and the time T shows the duration from the time T1. According to Δt=k (T) 1/2 According to the relation of the junction temperature sampling values Tj (T2), tj (T3), tj (T4) with DeltaT=k (T) 1/2 In the relation of (2), the value of k is obtained, and the junction temperature at the time of reversely pushing out T1 is taken as the second test junction temperature Tb2.
The comparison and correction module comprises a comparison unit and a correction unit.
Comparing whether the difference between the first test junction temperature Tb1 and the second test junction temperature Tb2 is larger than a threshold value by adopting the comparison unit; when the difference between the first test junction temperature Tb1 and the second test junction temperature Tb2 is greater than the threshold, the correction unit is used to correct the test environment of the MOSFET10 to be tested, and the first mapping relationship is corrected based on the corrected test environment until the difference between the first test junction temperature and the second test junction temperature is less than the threshold.
The SiC-based MOSFET junction temperature on-line monitoring method further comprises the following steps: when the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value, obtaining a first correction function relation; acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET on line by adopting an on-line working test module; and inputting the on-saturation voltage drop and the on-current obtained on line into a first correction function relation, and outputting the junction temperature of the SiC-based MOSFET.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims (16)

1. An on-line monitoring system for junction temperature of a SiC-based MOSFET, comprising:
the current calibration module comprises a first current calibration module and a second current calibration module; the first current calibration module is suitable for injecting current into the forward direction of the MOSFET to be tested, and acquiring a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a junction temperature of the first conduction current and the MOSFET to be tested; the second current calibration module is suitable for reversely injecting a second current into the MOSFET to be tested, and acquiring a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and an off-state and the junction temperature of the MOSFET to be tested, wherein the first conduction current is larger than the second current;
The first data fitting module is suitable for fitting the data in the first mapping relation to obtain a first functional relation, wherein the first functional relation takes a first conduction saturation voltage drop and a first conduction current as independent variables and the junction temperature of the MOSFET to be tested as a dependent variable;
the second data fitting module is suitable for fitting data in a second mapping relation to obtain a second functional relation, wherein the second functional relation takes a second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET to be tested as a dependent variable;
the work sampling module is suitable for acquiring a third conduction saturation voltage drop and a third conduction current in real time when the MOSFET to be tested is in a characteristic sampling state, and the characteristic sampling state comprises: the MOSFET to be tested is a working element of a working equipment module, the working equipment module comprises a converter, the working equipment module is in a working state, and a grid electrode of the MOSFET to be tested is in a conducting state; the working sampling module comprises a voltage sampling module and a second current sensor, the voltage sampling module is suitable for testing and obtaining a third conduction saturation voltage drop, and the second current sensor is suitable for testing and obtaining a third conduction current; the voltage sampling module comprises a third initial operational amplifier unit and a third low-pass filter, wherein the input end of the third initial operational amplifier unit is connected with the first source drain electrode of the MOSFET to be tested, and the input end of the third low-pass filter is connected with the output end of the third initial operational amplifier unit; the second current sensor comprises a first Hall sampling unit, a fourth initial operational amplifier unit and a fourth low-pass filter, wherein the current input end of the first Hall sampling unit is suitable for being electrically connected with a first source drain electrode or a second source drain electrode of a MOSFET to be tested, two voltage output ends of the first Hall sampling unit are respectively and electrically connected with the first input end and the second input end of the fourth initial operational amplifier unit, the output end of the fourth initial operational amplifier unit is connected with the input end of the fourth low-pass filter, and the output end of the fourth low-pass filter is suitable for outputting a signal of a third conducting current; the structure of the fourth low-pass filter is consistent with that of the third low-pass filter, and the fourth low-pass filter is used for adjusting the delay of the second current sensor so that the working sampling module synchronizes the signal of the third conduction saturation voltage drop and the third conduction current sampled by the MOSFET to be tested; the second current calibration module is further adapted to perform off-line test on the MOSFET to be tested after the working sampling module obtains a third conduction saturation voltage drop and a third conduction current, and obtain a fourth conduction saturation voltage drop of the MOSFET to be tested at different moments in an off-line state and an off-state by reversely injecting the second current into the MOSFET to be tested;
The first test junction temperature acquisition unit is suitable for acquiring a first test junction temperature, wherein the first test junction temperature is a junction temperature value of a MOSFET to be tested corresponding to data of a third conduction saturation voltage drop and a third conduction current in a first functional relation at the moment when the working equipment module stops working;
the second test junction temperature acquisition unit is suitable for acquiring a junction temperature sampling value of a corresponding MOSFET to be tested in the second functional relation according to data of fourth conduction saturation voltage drops at different moments, and acquiring a second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling value of the MOSFET to be tested;
the comparison and correction module is suitable for comparing the difference value between the first test junction temperature and the second test junction temperature and correcting the first mapping relation according to the difference value between the first test junction temperature and the second test junction temperature until the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value.
2. The SiC-based MOSFET junction temperature online monitoring system of claim 1, wherein the first current calibration module and the second current calibration module are independent of each other;
The first current calibration module comprises a constant voltage source, a first capacitor, a load unit, a first current sensor and a first operational amplifier module, wherein the first capacitor is connected with the constant voltage source in parallel, the positive electrode of the constant voltage source is connected with the first end of the load unit, the second end of the load unit is suitable for being connected with a first source drain electrode of a MOSFET to be tested and the first operational amplifier module, the negative electrode of the constant voltage source is connected with a second source drain electrode of the MOSFET to be tested, the first operational amplifier module is suitable for converting a current signal in the MOSFET to be tested into a voltage signal, the output end of the first operational amplifier module is suitable for obtaining a first conduction saturation voltage drop, and the first current sensor is suitable for obtaining a first conduction current in a test mode;
the second current calibration module comprises a second operational amplifier module, the output end of the second operational amplifier module is suitable for obtaining a second conduction saturation voltage drop, and the input end of the second operational amplifier module is connected with the first source drain electrode or the second source drain electrode of the MOSFET to be tested.
3. The SiC-based MOSFET junction temperature online monitoring system of claim 2, wherein the first operational amplifier module includes a first initial operational amplifier unit, a first low-pass filter, a first proportional amplifier, and a first analog signal isolation unit, an input of the first initial operational amplifier unit is connected to the second end, an input of the first low-pass filter is connected to an output of the first initial operational amplifier unit, an input of the first proportional amplifier is connected to an output of the first low-pass filter, a voltage signal of an output of the first proportional amplifier is smaller than a voltage signal of an input of the first proportional amplifier, an input of the first analog signal isolation unit is connected to an output of the first proportional amplifier, and an output of the first analog signal isolation unit is adapted to obtain a first on saturation voltage drop.
4. The SiC-based MOSFET junction temperature online monitoring system according to claim 2, wherein the second operational amplifier module includes a second initial operational amplifier unit, a second low-pass filter, a second proportional amplifier, and a second analog signal isolation unit, an input end of the second initial operational amplifier unit is connected to the first source drain or the second source drain, an input end of the second low-pass filter is connected to an output end of the second initial operational amplifier unit, an input end of the second proportional amplifier is connected to an output end of the second low-pass filter, an input end of the second analog signal isolation unit is connected to an output end of the second proportional amplifier, a voltage signal of an output end of the second proportional amplifier is smaller than a voltage signal of an input end of the second proportional amplifier, and an output end of the second analog signal isolation unit is adapted to obtain a second conduction saturation voltage drop.
5. The SiC-based MOSFET junction temperature online monitoring system according to claim 1, wherein the first current calibration module includes a constant current source, a first bleeder circuit connected in parallel with the constant current source, an auxiliary switch, a first current sensor, a first operational amplifier module and a first switch, a positive connection end of the constant current source is connected with one end of the auxiliary switch, the other end of the auxiliary switch is adapted to be connected with a first source drain electrode of a MOSFET to be tested, a negative connection end of the constant current source is adapted to be connected with a second source drain electrode of the MOSFET to be tested, an input end of the first operational amplifier module is connected with the other end of the auxiliary switch through the first switch, the first operational amplifier module is adapted to convert a current signal in the MOSFET to be tested into a voltage signal, an output end of the first operational amplifier module is adapted to obtain a first conduction saturation voltage drop, and the first current sensor is adapted to obtain a first conduction current through test;
The second current calibration module comprises a second operational amplifier module and a second switch, and the second operational amplifier module is connected with a second source drain electrode of the MOSFET to be tested through the second switch.
6. The SiC-based MOSFET junction temperature online monitoring system of claim 5, wherein the first operational amplifier module comprises a first initial operational amplifier unit, a first low-pass filter, a first proportional amplifier, and a first analog signal isolation unit, an input end of the first initial operational amplifier unit is connected to the first switch, an input end of the first low-pass filter is connected to an output end of the first initial operational amplifier unit, an input end of the first proportional amplifier is connected to an output end of the first low-pass filter, a voltage signal of an output end of the first proportional amplifier is smaller than a voltage signal of an input end of the first proportional amplifier, an input end of the first analog signal isolation unit is connected to an output end of the first proportional amplifier, and an output end of the first analog signal isolation unit is adapted to obtain a first on saturation voltage drop;
the second operational amplifier module comprises a second initial operational amplifier unit, a second low-pass filter, a second proportional amplifier and a second analog signal isolation unit, wherein the input end of the second initial operational amplifier unit is connected with a second switch, the input end of the second low-pass filter is connected with the output end of the second initial operational amplifier unit, the input end of the second proportional amplifier is connected with the output end of the second low-pass filter, the input end of the second analog signal isolation unit is connected with the output end of the second proportional amplifier, the voltage signal of the output end of the second proportional amplifier is smaller than that of the input end of the second proportional amplifier, and the output end of the second analog signal isolation unit is suitable for obtaining a second conduction saturation voltage drop.
7. The SiC-based MOSFET junction temperature on-line monitoring system according to claim 3 or 6, wherein the first initial operational amplifier unit includes a first current-voltage conversion operational amplifier, a first diode, a second diode, and a first bias current source, an anode input terminal of the first current-voltage conversion operational amplifier is connected to a forward connection terminal of the first diode and a reverse connection terminal of the second diode, a cathode input terminal of the first current-voltage conversion operational amplifier and the first bias current source are connected to a forward connection terminal of the second diode, a reverse connection terminal of the first diode is used as an input terminal of the first initial operational amplifier unit, and an output terminal of the first current-voltage conversion operational amplifier is used as an output terminal of the first initial operational amplifier unit.
8. The SiC-based MOSFET junction temperature on-line monitoring system according to claim 4 or 6, wherein the second initial operational amplifier unit includes a second current-voltage conversion operational amplifier, a third diode, a fourth diode, and a second bias current source, the positive input terminal of the second current-voltage conversion operational amplifier is connected to the positive connection terminal of the third diode and the negative connection terminal of the fourth diode, the positive connection terminal of the fourth diode is connected to the negative input terminal of the second current-voltage conversion operational amplifier and the second bias current source, the negative connection terminal of the third diode is used as the input terminal of the second initial operational amplifier unit, and the output terminal of the second current-voltage conversion operational amplifier is used as the output terminal of the second initial operational amplifier unit.
9. The SiC-based MOSFET junction temperature online monitoring system of claim 1, wherein the voltage sampling module further comprises a third proportional amplifier, a third analog signal isolation unit, and a current bleed switch, the input of the third proportional amplifier is connected to the output of the third low pass filter, the voltage signal at the output of the third proportional amplifier is less than the voltage signal at the input of the third proportional amplifier, the input of the third analog signal isolation unit is connected to the output of the third proportional amplifier, and the output of the third analog signal isolation unit is adapted to obtain a third on-saturation voltage drop; the current bleed switch is adapted to open and bleed current in the third initial operational amplifier unit when the MOSFET under test is turned off.
10. The SiC-based MOSFET junction temperature on-line monitoring system of claim 9, wherein the third initial operational amplifier unit includes a third current-to-voltage conversion operational amplifier, a third bias current source, a fifth diode, a sixth diode, a seventh diode, a first resistor, and a second resistor, the positive input terminal of the third current-to-voltage conversion operational amplifier is connected to the positive connection terminal of the fifth diode, the negative connection terminal of the sixth diode, the positive connection terminal of the seventh diode, and a current bleed switch, the positive connection terminal of the sixth diode is connected to the negative connection terminal of the seventh diode, one end of the first resistor, and a third bias current source, the other end of the first resistor is connected to the negative input terminal of the third current-to-voltage conversion operational amplifier, the other end of the second resistor is connected to the output terminal of the third current-to-voltage conversion operational amplifier, the negative connection terminal of the fifth diode serves as the input terminal of the third initial operational amplifier unit, and the output terminal of the third current-to-voltage conversion operational amplifier serves as the output terminal of the third operational amplifier unit.
11. The SiC-based MOSFET junction temperature online monitoring system of claim 1, wherein the comparison and correction module comprises a comparison unit adapted to compare whether a difference between the first test junction and the second test junction temperature is greater than a threshold value, and a correction unit adapted to correct a test environment of the MOSFET under test when the difference between the first test junction and the second test junction temperature is greater than the threshold value and to correct the first mapping relationship based on the corrected test environment until the difference between the first test junction and the second test junction temperature is less than the threshold value.
12. The SiC-based MOSFET junction temperature online monitoring system of claim 1, further comprising:
a first modified functional relationship, the first modified functional relationship being a first functional relationship determined when a difference between the first test junction and the second test junction temperature is less than a threshold;
and the working on-line testing module is suitable for acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET on line.
13. An on-line monitoring method for junction temperature of a SiC-based MOSFET, using the on-line monitoring system for junction temperature of a SiC-based MOSFET according to any one of claims 1 to 12, comprising:
Adopting a first current calibration module to forward inject current into the MOSFET to be tested, and obtaining a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a junction temperature of the MOSFET to be tested;
reversely injecting a second current into the MOSFET to be tested by adopting a second current calibration module, and acquiring a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and an off-state and the junction temperature of the MOSFET to be tested, wherein the second current is smaller than the first conduction current;
fitting data in a first mapping relation by adopting a first data fitting module to obtain a first functional relation, wherein the first functional relation takes a first conduction saturation voltage drop and a first conduction current as independent variables and the junction temperature of a MOSFET to be tested as a dependent variable;
fitting the data in the second mapping relation by adopting a second data fitting module to obtain a second functional relation, wherein the second functional relation takes a second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET to be tested as an independent variable;
the working sampling module is adopted to acquire a third conduction saturation voltage drop and a third conduction current in real time when the MOSFET to be detected is in a characteristic sampling state, and the characteristic sampling state comprises: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and a grid electrode of the MOSFET to be tested is in a conducting state;
After obtaining the third conduction saturation voltage drop and the third conduction current, adopting a second current calibration module to perform off-line test on the MOSFET to be tested, reversely injecting the second current into the MOSFET to be tested, and obtaining fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and an off-state;
acquiring a first test junction temperature by adopting a first test junction temperature acquisition unit, wherein the first test junction temperature is a junction temperature value of a MOSFET to be tested corresponding to data of a third conduction saturation voltage drop and a third conduction current in a first functional relation at the moment when the working equipment module stops working;
acquiring a junction temperature sampling value of a corresponding MOSFET to be tested in the second functional relation according to data of fourth conduction saturation voltage drops at different moments by adopting a second test junction temperature acquisition unit, and acquiring a second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling value of the MOSFET to be tested;
the sampling comparison and correction module compares the difference value between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation according to the difference value between the first test junction temperature and the second test junction temperature until the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value.
14. The method for on-line monitoring of junction temperature of SiC-based MOSFETs according to claim 13, wherein the MOSFET to be tested is adapted to be placed on a heating platform in a process of forward current injection of the MOSFET to be tested by the first current calibration module, and the junction temperature of the MOSFET to be tested in the first mapping relationship is calibrated by the temperature of the heating platform;
and in the process of reversely injecting the second current into the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on a heating platform, and the junction temperature of the MOSFET to be tested in the second mapping relation is calibrated by the temperature of the heating platform.
15. The method for on-line monitoring of junction temperature of SiC-based MOSFET according to claim 13, wherein the comparing and correcting module includes a comparing unit and a correcting unit; comparing whether the difference between the first test junction temperature and the second test junction temperature is greater than a threshold value by adopting the comparison unit; and when the difference value between the first test junction temperature and the second test junction temperature is larger than the threshold value, adopting the correction unit to correct the test environment of the MOSFET to be tested, and correcting the first mapping relation based on the corrected test environment until the difference value between the first test junction temperature and the second test junction temperature is smaller than the threshold value.
16. The method for on-line monitoring of junction temperature of a SiC-based MOSFET of claim 13, further comprising: when the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value, obtaining a first correction function relation; acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET on line by adopting an on-line working test module; and inputting the on-saturation voltage drop and the on-current obtained on line into a first correction function relation, and outputting the junction temperature of the SiC-based MOSFET.
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