CN112229530A - 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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CN112229530A
CN112229530A CN202011062518.XA CN202011062518A CN112229530A CN 112229530 A CN112229530 A CN 112229530A CN 202011062518 A CN202011062518 A CN 202011062518A CN 112229530 A CN112229530 A CN 112229530A
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junction temperature
current
mosfet
tested
operational amplifier
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CN112229530B (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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Abstract

An on-line monitoring system and an on-line monitoring method for junction temperature of SiC-based MOSFET are disclosed, wherein the on-line monitoring system for junction temperature of 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 obtaining unit, a second test junction temperature obtaining 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 junction temperature testing precision and can be used for on-line monitoring of 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 online monitoring system and an online monitoring method for junction temperature of a SiC-based MOSFET.
Background
Silicon carbide (SiC) material is a third-generation semiconductor material, and has the characteristics of large forbidden bandwidth, low dielectric constant, high breakdown voltage, high thermal conductivity, low electronic drift velocity and the like, and is very stable in thermal, chemical and mechanical aspects. A power switch module made of SiC material, such as a metal oxide semiconductor Field Effect Transistor (MOSFET for short), has significant advantages of low switching loss, high withstand voltage, high operating temperature, and the like, compared to a power switch module made of Si material, and is predicted to be a substitute for a Si-based Insulated Gate Bipolar Transistor (IGBT for short).
Junction temperature is an important parameter characterizing the operating and health of semiconductor devices. At present, the SiC substrate on the manufacturing level is complex in production and processing and generally has defects, and the processing technology of the SiC chip is not perfect; practical technologies such as a basic model and a driving technology of an application-level SiC device are not complete, and particularly when the junction temperature of a SiC MOSFET chip is high, carrier scattering is enhanced, mobility is reduced, the large-current conduction capability of the chip is remarkably reduced, and the stability and reliability of the device are affected by capturing and releasing of carriers on a high-temperature gate interface. Under the condition, the SiC MOSFET is subjected to junction temperature on-line monitoring, so that the current carrying capacity of the chip can be further improved, the power density of equipment is improved, and the reliability of the equipment is enhanced. The measurement of the junction temperature of the SiC MOSFET is the basis of life prediction, reliability evaluation, the active heat management technology of the converter and over-temperature protection.
However, in the prior art, the junction temperature monitoring technology for the SiC-based MOSFET has no comparative system and deep related research, the testing precision is low, and online monitoring cannot be performed.
Disclosure of Invention
The invention aims to solve the technical problems that the junction temperature test precision of the SiC-based MOSFET is low and online monitoring cannot be realized in the prior art.
In order to solve the above technical problems, the present invention provides an online monitoring system and an online monitoring method 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 MOSFET to be tested in the forward direction 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 first conduction current and junction temperature of 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 a turn-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 data in the first mapping relation to obtain a first functional relation, and the first functional relation takes the first conduction saturation voltage drop and the first conduction current as independent variables and takes 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, and the second functional relation takes the second conduction saturation voltage drop as an independent variable and takes the junction temperature of the MOSFET to be tested as a dependent variable; the work sampling module, the work sampling module is suitable for when the MOSFET that awaits measuring is in the characteristic sampling state real-time acquisition third and switches on saturation voltage drop and third and switches on electric current, the characteristic sampling state includes: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and the grid electrode of the MOSFET to be tested is in a conducting state; the second current calibration module is also suitable for performing an off-line test on the MOSFET to be tested after the working sampling module obtains the third conduction saturation voltage drop and the third conduction current, and obtaining fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and a turn-off state by reversely injecting the second current into the MOSFET to be tested; the first test junction temperature obtaining unit is suitable for obtaining a first test junction temperature, and the first test junction temperature is a junction temperature value of the MOSFET to be tested corresponding to the data of the third conduction saturation voltage drop and the third conduction current in a first functional relation at the moment that the working equipment module stops working; the second test junction temperature obtaining unit is suitable for obtaining corresponding junction temperature sampling values of the MOSFET to be tested in the second function relation according to fourth conduction saturation voltage drop data at different moments, and obtaining second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling values of the MOSFET to be tested; and the comparison and correction module is suitable for comparing the difference between the first test junction temperature and the second test junction temperature and correcting the first mapping relation 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 smaller than a threshold value.
Optionally, 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 anode 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 the first source drain of the MOSFET to be tested and the first operational amplifier module, the cathode of the constant voltage source is connected with the second source drain 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 acquiring a first conduction saturation voltage drop, and the first current sensor is suitable for testing and acquiring a first conduction current; 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 or the second source drain 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, and a first analog signal isolation unit, an input end of the first initial operational amplifier unit is connected to the second end, 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.
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, 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 at an output end of the second proportional amplifier is smaller than a voltage signal at 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 bleed-off circuit, an auxiliary switch, a first current sensor, a first operational amplifier module and a first switch, which are connected in parallel with the constant current source, 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 of the MOSFET to be tested, a negative connection end of the constant current source is suitable for being connected with a second source/drain 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 and obtaining a first conduction current; and the second current calibration module comprises a second operational amplifier module and a second switch, and the second operational amplifier module is connected with the second source drain 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, 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, a voltage signal of the output end of the second proportional amplifier is smaller than a voltage signal 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, an anode input end of the first current-voltage conversion operational amplifier is connected to a forward connection end of the first diode and a reverse connection end of the second diode, a forward connection end of the second diode is connected to a cathode input end of the first current-voltage conversion operational amplifier and the first bias current source, a reverse connection end of the first diode serves as an input end of the first initial operational amplifier unit, and an output end of the first current-voltage conversion operational amplifier serves as an 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, an anode input end of the second current-voltage conversion operational amplifier is connected to a forward connection end of the third diode and a reverse connection end of the fourth diode, a forward connection end of the fourth diode is connected to a cathode input end of the second current-voltage conversion operational amplifier and the second bias current source, a reverse connection end of the third diode is used as an input end of the second initial operational amplifier unit, and an output end of the second current-voltage conversion operational amplifier is used as an output end of the second initial operational amplifier unit.
Optionally, the working 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 bleeder switch, 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, 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 that 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 acquiring a third conduction saturation voltage drop; the current release switch is suitable for being opened when the MOSFET to be tested is turned off and releasing the current in the third initial operational amplifier unit; the second current sensor is suitable for testing and obtaining a third conducting 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, an anode input end of the third current-voltage conversion operational amplifier is connected to a positive connection end of the fifth diode, a negative connection end of the sixth diode, a positive connection end of the seventh diode, and a current bleeder switch, a positive connection end of the sixth diode is connected to a 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 a 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 an output end of the third current-voltage conversion operational amplifier, and a reverse connection end of the fifth diode is used as an 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 comparison and correction module includes a comparison unit and a correction unit, the comparison 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, and the correction unit is adapted to correct the test environment of the MOSFET to be tested and correct the first mapping relationship based on the corrected test environment when the difference between the first test junction temperature and the second test junction temperature is greater than the threshold, until the difference between the first test junction temperature and the second test junction temperature is less than the threshold.
Optionally, the method further includes: a first correction function relationship, the first correction function relationship being a first function relationship determined when a difference between the first test junction temperature and the second test junction temperature is less than a threshold; and the working online test module is suitable for acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET online.
The invention also provides a SiC-based MOSFET junction temperature on-line monitoring method, and the SiC-based MOSFET junction temperature on-line monitoring system adopted by the invention comprises the following steps: a first current calibration module is adopted to inject current into the MOSFET to be tested in a forward direction, and a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a first conduction current and junction temperature of the MOSFET to be tested is obtained; a second current is injected into the MOSFET to be tested in a reverse direction by adopting a second current calibration module, and a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a turn-off state and the junction temperature of the MOSFET to be tested is obtained, wherein the second current is smaller than the first conduction current; 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 takes the junction temperature of the MOSFET to be tested as a dependent variable; fitting the data in the second mapping relation by using 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 takes the junction temperature of the MOSFET to be tested as a dependent variable; adopt the work sampling module acquires third and switches on saturation voltage drop and third and switches on electric current when the MOSFET that awaits measuring is in the characteristic sampling state in real time, the characteristic sampling state includes: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and the grid electrode of the MOSFET to be tested is in a conducting state; after the third conduction saturation voltage drop and the third conduction current are obtained, a second current calibration module is adopted to carry out off-line test on the MOSFET to be tested, second current is reversely injected into the MOSFET to be tested, and fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and a turn-off state are obtained; acquiring a first test junction temperature by using a first test junction temperature acquisition unit, wherein the first test junction temperature is a junction temperature value of the MOSFET to be tested corresponding to the data of the third conduction saturation voltage drop and the third conduction current in a first function relation at the moment that the working equipment module stops working; acquiring a junction temperature sampling value of the corresponding MOSFET to be tested in the second functional relation according to fourth conduction saturation voltage drop data at different moments by using 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 between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation 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 smaller than a threshold value.
Optionally, in the process that the first current calibration module injects a current to the MOSFET to be tested in the forward direction, the MOSFET to be tested is suitable for being placed on the heating platform, 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 that the second current calibration module reversely injects the second current into the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on the 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 includes a comparison unit and a correction unit; comparing, with the comparison unit, whether a difference between the first tested junction temperature and the second tested junction temperature is greater than a threshold; and when the difference between the first test junction temperature and the second test junction temperature is larger than the threshold, correcting the test environment of the MOSFET to be tested by using the correction unit, and correcting 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 smaller than the threshold.
Optionally, the method further includes: when the difference value between the first test junction temperature and the second test junction temperature is smaller than a threshold value, acquiring a first correction function relation; adopting a working online test module to acquire the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET online; and inputting the on-line acquired conduction saturation voltage drop and the on-line acquired conduction current into the first correction function relation, and outputting the junction temperature of the SiC-based MOSFET.
The technical scheme of the invention has the following advantages:
the SiC-based MOSFET junction temperature on-line monitoring method provided by the technical scheme of the invention adopts a first test junction temperature obtaining unit to obtain 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 function relation at the moment when a working equipment module stops working, and adopts a second test junction temperature obtaining unit to obtain a junction temperature sampling value of the corresponding MOSFET to be tested in a second function relation according to data of a 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 MOSFET to be tested; the sampling comparison and correction module compares the difference between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation 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 smaller than a threshold value. The first test junction temperature and the second test junction temperature can be compared with each other, and after multiple cycles, the difference value between the first test junction temperature and the second test junction temperature is finally smaller than the threshold value, at the moment, a corrected first function relation and a first correction function relation can be obtained, the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET obtained through online test can obtain the junction temperature of the SiC-based MOSFET according to the first correction function relation, the test 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 used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a system for online monitoring junction temperature of a SiC-based MOSFET according to an embodiment of the present invention;
fig. 2 is a specific structure of a first current calibration module according to an embodiment of the present invention;
FIG. 3 is a specific structure of a second current calibration module according to an embodiment of the present invention;
fig. 4 is a specific structure of a voltage sampling module according to an embodiment of the present invention;
FIG. 5 shows an embodiment of a second current sensor;
FIG. 6 is a block diagram of a current calibration module according to another embodiment of the present invention;
fig. 7 is a method for monitoring junction temperature of a SiC-based MOSFET in an online manner according to another embodiment of the present invention;
fig. 8 is a graph of junction temperature versus time.
Detailed Description
As described in the background, the junction temperature test of the SiC-based MOSFET in the prior art has low accuracy.
The traditional power semiconductor chip junction temperature detection method is mainly based on S iIGBT research and comprises four major types of physical contact method, optical non-contact measurement method, model prediction method and thermal inductance parameter method (TSEPs) extraction method.
The physical contact method generally places a thermistor or a thermocouple on the power module substrate to measure the temperature, but the temperature difference between the temperature of the power module substrate and the internal junction temperature of the power chip is large (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 solution requires a peripheral circuit of a load and a special custom chip, which is not common to most power modules on the market.
The optical non-contact measurement method needs uncovering and sol treatment on the power module, can reduce the voltage tolerance of the power module, and when an infrared thermal imager is used for measurement, black paint needs to be coated on the upper surface of the power module to enhance the radiation coefficient. In addition, the response time of the temperature-sensitive optical fiber and the infrared thermal imager is in millisecond level, and the response is too slow compared with the on-off period of the power module, so that the temperature-sensitive optical fiber and the infrared thermal imager are not suitable for junction temperature on-line monitoring.
The model prediction method completes the prediction of the junction temperature by establishing an accurate power device loss model and a thermal-electric coupling model. The establishment of the model cannot take account of individual differences and aging differences of chips, and cannot reflect some fault conditions in the operation of equipment, and the model usually needs to be designed redundantly and is usually only used for off-line junction temperature prediction.
The thermosensitive electrical parameter method uses the chip as a temperature sensor, reflects the change of the average junction temperature of the chip by measuring the change of the temperature sensitive electrical parameter, can realize non-invasive measurement of the power module to be measured, and is theoretically the most suitable method for online monitoring of the junction temperature. By monitoring different thermal sensitive parameters, thermal sensitive electrical parameter methods are roughly classified into a small current saturation conduction voltage drop method, a large current saturation conduction voltage drop method and the like.
A small current saturation conduction voltage drop method is recommended by industry associations to be used for thermal resistance testing and off-line junction temperature testing of IGBT modules based on the fact that the conduction saturation voltage drop of the IGBT under small current and junction temperature are in a negative linear relation, and is also an accuracy verification method for the reliability of IGBT junction temperature on-line monitoring data. However, due to the characteristics of the SiC material, the method of applying the small current drop through the channel is not stable enough, and the small current conduction drop of the SiC MOSFET cannot be used as a junction temperature monitoring parameter, nor a verification method for online junction temperature monitoring.
High current saturation conduction voltage drop method, saturation conduction voltage drop V based on IGBTCEWith the current I flowing through the channelCWith junction temperature Tj, by detecting V in real timeCEAnd ICAnd calculating to obtain the real-time junction temperature. The large-current saturation 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 junction temperature on-line monitoring method.
But due to workThe power module is in a switch switching state when working, and V is in a switch-off state when the power module is switched offCEBus voltages, typically up to several hundred volts; when the power module is on, VCEThe saturated conduction voltage drop is only about 0-3V; and the on-off time is changed along with the PWM pulse modulation, and it is not easy to accurately detect the on-saturation voltage drop in the on-process. Simultaneous saturation conduction voltage drop VCETemperature Tj of junction and current I in on stateCAnd a driving voltage VGEAnd the influence of multiple factors is needed, sampling calibration is needed one by one, the problems of synchronization, bandwidth and interference need to be considered in the sampling process, and the engineering application is very complex. In addition, because the junction temperature monitoring difficulty is high, different detection methods are lacked to verify the junction temperature in a mutual comparison mode, particularly for the SiC MOSFET, the traditional off-line junction temperature measurement method based on small current injection cannot be applied, and other methods must be selected to verify the junction temperature.
At present, the turn-on saturation voltage drop method based on the IGBT only stays in the laboratory principle verification stage, and there is no systematic calibration, detection and verification method. However, as the manufacturing process and application technology of the SiC MOSFET are far immature, a relevant thermoelectric mechanism model is not established, and as for the on-line monitoring technology of the junction temperature, no comparative system and deep relevant research are available.
On this basis, an embodiment of the present invention provides an online junction temperature monitoring system for a SiC-based MOSFET, and with reference to fig. 1, the system includes:
a current calibration module B, which comprises a first current calibration module 110 and a second current calibration module 120; the first current calibration module 110 is adapted to inject a current into the MOSFET to be tested in a forward direction, 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) in an offline state and a first conduction current and a junction temperature of the MOSFET10 to be tested; 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 the junction temperature of the MOSFET10 to be tested, where the first conduction current is greater than the second current;
a first data fitting module 200, where the first data fitting module 200 is adapted to fit data in the first mapping relationship to obtain a first functional relationship, where the first functional relationship takes the first conduction saturation voltage drop and the first conduction current as independent variables, and takes the junction temperature of the MOSFET10 to be tested as a dependent variable;
a second data fitting module 300, where the second data fitting module 300 is adapted to fit data in the second mapping relationship to obtain a second functional relationship, where the second functional relationship takes the second conduction saturation voltage drop as an independent variable and the junction temperature of the MOSFET10 to be tested as a dependent variable;
a working sampling module 400, wherein the working sampling module 400 is adapted to obtain a third conduction saturation voltage drop and a 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 the working equipment module, the working equipment module is in a working state, and the grid of the MOSFET10 to be tested is in a conducting state;
the second current calibration module 120 is further adapted to perform an offline test on the MOSFET10 to be tested after the working sampling module obtains the third conduction saturation voltage drop and the third conduction current, reversely inject the second current into the MOSFET10 to be tested, and obtain a fourth conduction saturation voltage drop of the MOSFET10 to be tested at different times in an offline state and in an off state;
a 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 a first functional relationship at a time when the working equipment module stops working;
a second test junction temperature obtaining unit 600, adapted to obtain junction temperature sampling values of the corresponding MOSFET10 to be tested in the second function relation according to fourth conduction saturation voltage drop data at different times, and obtain a second test junction temperature at a time when the working equipment module stops working according to the junction temperature sampling values of the MOSFET10 to be tested;
a comparison and correction module 700, wherein the comparison and correction module 700 is adapted to compare a difference between the first tested junction temperature and the second tested junction temperature, and correct the first mapping relationship according to the difference between the first tested junction temperature and the second tested junction temperature until the difference between the first tested junction temperature and the second tested 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, other modules may be selected as the working device module.
In this embodiment, the first current calibration module 110 and the second current calibration module 120 are independent of each other.
In this embodiment, referring to fig. 2, a specific structure of a first current calibration module 110 is shown, where the first current calibration module 110 includes: constant voltage source 1101, first electric capacity 1102, load unit 1103, first current sensor 1104, first operational amplifier module Y1, first electric capacity 1102 with constant voltage source 1101 parallel connection, the positive pole of constant voltage source 1101 with the first end of load unit 1103 is connected, the second end of load unit 1103 is suitable for being connected with the first source drain and the first operational amplifier module Y1 of MOSFET10 that awaits measuring, the negative pole of constant voltage source 1101 is suitable for being connected with the second source drain of MOSFET10 that awaits measuring, first operational amplifier module Y1 is suitable for with the current signal in the MOSFET10 that awaits measuring converts voltage signal into, the output of first operational amplifier module Y1 is suitable for obtaining first conduction saturation voltage drop VDS1The first current sensor 1104 is adapted to test for obtaining a first on-current ID1。
The load unit 1103 includes: a load resistor and an additional transistor, wherein one end of the load resistor is used as a first end of the load unit 1103, and the other end of the load resistor is used as a second end of the load unit 1103. The load resistor and the additional transistor are connected in parallel.
The constant voltage source 1101 is an adjustable constant voltage source.
The first operational amplifier module Y1 comprises a first initial operational amplifier unit Y11, a first low pass filter Y12, a first proportional amplifier Y13 and a first operational amplifierAn analog signal isolation unit Y14, wherein an input end of the first initial operational amplifier unit Y11 is connected to the second end, an input end of the first low-pass filter Y12 is connected to an output end of the first initial operational amplifier unit Y11, an input end of the first proportional amplifier Y13 is connected to an output end of the first low-pass filter Y12, a voltage signal of an output end of the first proportional amplifier Y13 is smaller than a voltage signal of an input end of the first proportional amplifier Y13, an input end of the first analog signal isolation unit Y14 is connected to an output end of the first proportional amplifier Y13, and an output end of the first analog signal isolation unit Y14 is adapted to obtain a first conduction saturation voltage drop VDS1。
In a specific embodiment, the first initial operational amplifier unit Y11 includes a first current-to-voltage conversion operational amplifier Y111, a first diode Y112, a second diode Y113, and a first bias current source Y114, an anode input terminal of the first current-to-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-to-voltage conversion operational amplifier Y111 and the first bias current source Y114, a reverse connection terminal of the first diode Y112 serves as an input terminal of the first initial operational amplifier unit Y11, and an output terminal of the first current-to-voltage conversion operational amplifier Y111 serves 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, into the MOSFET10 under test, in the order of 100 a to up to ka, specifically, in one embodiment, 100 a to 1000 a.
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, one end of the third resistor Y121 is connected to the output end of the first initial operational amplifier unit Y11, and specifically, one end of the third resistor Y121 is connected to the output end of the first current-to-voltage conversion 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 terminal 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 the appropriate magnitude.
The first analog signal isolation unit Y14 realizes the analog signal isolation function and is used for isolating strong electric interference and ensuring the safe operation of equipment and the safety of personnel. The method for isolating the first analog signal isolation unit Y14 can select high-resistance isolation, optical coupling isolation, magnetic isolation or capacitance 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 and the output end of the second operational amplifier module Y2 are suitable for obtaining a second conduction saturation voltage drop VDS2The input end of the second operational amplifier module Y2 is connected to the first source/drain electrode or the second source/drain electrode of the MOSFET10 to be tested.
In this embodiment, referring to fig. 3, an input end of the second operational amplifier module Y2 is connected to a second source/drain of the MOSFET10 to be tested, when the second current calibration module 120 calibrates the MOSFET10 to be tested, a first source/drain of the MOSFET10 to be tested is grounded, and a voltage is applied to a 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, an input end of the second initial operational amplifier unit Y21 is connected to the first source/drain or the second source/drain, specifically, 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, a voltage signal at an output end of the second proportional amplifier Y23 is smaller than a voltage signal at an input end of the second proportional amplifier Y23, the output terminal of the second analog signal isolation unit Y24 is adapted to obtain a second conduction saturation voltage drop.
In a specific embodiment, the second initial operational amplifier unit Y21 includes a second current-to-voltage conversion operational amplifier Y211, a third diode Y212, a fourth diode Y213, and a second bias current source Y214, an anode input terminal of the second current-to-voltage conversion operational amplifier Y211 is connected to the forward connection terminal of the third diode Y212 and the reverse connection terminal of the fourth diode Y213, a forward connection terminal of the fourth diode Y213 is connected to the cathode input terminal of the second current-to-voltage conversion operational amplifier Y211 and the second bias current source Y214, a reverse connection terminal of the third diode Y212 serves as the input terminal of the second initial operational amplifier unit Y21, and an output terminal of the second current-to-voltage conversion operational amplifier Y211 serves as the 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, one end of the fifth resistor Y221 is connected to the output end of the second initial operational amplifier unit Y21, and specifically, one end of the fifth resistor Y221 is connected to the output end of the second current-to-voltage conversion opamp 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 terminal 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 the appropriate magnitude.
The second analog signal isolation unit Y24 realizes the analog signal isolation function, is used for isolating strong current interference, and ensures the safe operation of equipment and the safety of personnel. The method for isolating the second analog signal isolation unit Y24 can select high-resistance isolation, optical coupling isolation, magnetic isolation or capacitance isolation. In this embodiment, the second bias current source Y214 is adapted to inject a reverse current, specifically a reverse small current, into the MOSFET10 to be tested, and the magnitude of the reverse small current is 5mA to 100 mA.
A first data fitting module 200, said first data fitting module 200 being adapted to fit data in said first mapping relationship to obtain a first functional relationship, said first functional relationship being a first conduction saturation voltage drop VDS1And a first on-current ID1Is independent variable and takes the junction temperature Tj of the MOSFET to be tested as dependent variable.
The first functional relationship to be fitted by the first data fitting module 200 may be a polynomial or trigonometric function.
A second data fitting module 300, said second data fitting module 300 being adapted to fit data in the second mapping relationship to obtain a second functional relationship, said second functional relationship being a second conduction saturation voltage drop VDS2Is independent variable and takes the junction temperature Tj1 of the MOSFET to be tested as dependent variable.
The second functional relationship to be fitted by the second data fitting module 300 may be a polynomial or trigonometric function.
The duty sampling module 400 includes a voltage sampling module 410 and a current sampling module 420, and the current sampling module 420 includes 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 bleeder switch Y45, an input end of the third initial operational amplifier unit Y41 is connected to a first source-drain electrode 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, and a voltage signal at an output end of the third proportional amplifier Y43 is smaller than a third ratioThe voltage signal of the input end of the amplifier Y43 is sampled, the input end of the third analog signal isolation unit Y44 is connected with the output end of the third proportional amplifier Y43, and the output end of the third analog signal isolation unit Y44 is suitable for obtaining a third conduction saturation voltage drop VDS3The current bleeder 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 testing and acquiring a third breakover current ID3。
The third initial operational amplifier unit Y41 includes a third current-voltage converting 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, an anode input terminal of the third current-voltage converting operational amplifier Y411 is connected to a positive connection terminal of the fifth diode Y413, a negative connection terminal of the sixth diode Y414, a positive connection terminal of the seventh diode Y415, and a current bleeder switch Y45, a positive connection terminal of the sixth diode Y414 is connected to a negative connection terminal of the seventh diode Y415, one end of the first resistor Y416, and the third bias current source Y412, another end of the first resistor Y416 is connected to a cathode input terminal of the third current-voltage converting operational amplifier Y411 and one end of the second resistor Y417, another end of the second resistor Y417 is connected to an output terminal of the third current-voltage converting operational amplifier Y411, the reverse connection end of the fifth diode Y413 serves as the input end of the third initial operational amplifier unit Y41, and the output end of the third current-voltage conversion operational amplifier Y411 serves as the output end of the third initial 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 unit 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, 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 the appropriate magnitude.
The third analog signal isolation unit Y44 realizes the analog signal isolation function, and is used for isolating strong current interference and ensuring the safe operation of equipment and the safety of personnel. The isolation method of the third analog signal isolation unit Y44 can select high-resistance isolation, optical coupling isolation, magnetic isolation or capacitance isolation.
The current bleeder switch Y45 is a MOS switch. One source drain electrode of the current release switch Y45 is grounded, and the other source drain electrode of the current release switch Y45 is connected with the forward connection end of the third current-voltage conversion operational amplifier Y411.
When the working sampling module 400 samples the MOSFET10 to be tested, the MOSFET10 to be tested is used as a working element of the working equipment module, the working equipment 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 (PWM) signal of the working equipment module. The grid of the current bleeder switch Y45 is composed of
Figure BDA0002712788200000151
Driving, that is, a level signal applied to the gate of the MOSFET10 to be tested is opposite to a level signal applied to the gate of the current bleeder switch Y45, when the gate of the MOSFET10 to be tested applies a high level, the gate of the current bleeder switch Y45 applies a low level, and when the gate of the MOSFET10 to be tested applies a low level, the gate of the current bleeder switch Y45 applies a high level.
Referring to fig. 5, the second current sensor includes a first hall sampling unit 4203, a fourth initial operational amplifier unit 4201, and a fourth low-pass filter 4202, 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 a MOSFET10 to be tested, two voltage output ends of the first hall sampling unit are respectively 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 a third on-current.
The first hall sampling unit 4203 includes a first magnetic core, the first magnetic core is of an annular structure and has a notch, a first hall element is placed at the notch of the first magnetic core, a first guide rod is arranged in the first magnetic core, the first magnetic core surrounds the first guide rod, specifically, the first guide rod is suitable for being electrically connected with a first source drain or a 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 constant voltage.
In this embodiment, the structure of the fourth low-pass filter 4202 is the same as the structure of the third low-pass filter Y42, 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 third conduction saturation voltage drop of the MOSFET10 to be tested sampled by the working sampling module 400 is synchronized with the signal of the third conduction current.
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, a current input end of the second hall sampling unit is adapted to be electrically connected to a first source/drain or a second source/drain 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 op-amp unit refers to the fourth initial op-amp unit 4201.
In this embodiment, the structure of the fifth low-pass filter is the same as the structure of the first low-pass filter Y12, 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 sampled by the MOSFET10 to be tested with the signal of the first conduction current.
In the process that the first current calibration module 110 injects the current into the MOSFET10 to be tested in the forward direction, the MOSFET10 to be tested is suitable for being placed on the heating platform, and the junction temperature of the MOSFET10 to be tested in the first mapping relation is calibrated by the temperature of the heating platform.
In the process that the second current calibration module 120 reversely injects the second current into the MOSFET10 to be tested, the MOSFET10 to be tested is suitable for being placed on the heating platform, and the junction temperature of the MOSFET10 to be tested in the second mapping relation 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, the comparison unit 710 is adapted to compare whether a difference between the first test junction temperature and the second test junction temperature is greater than a threshold, and the correction unit 720 is adapted to correct the test environment of the MOSFET10 to be tested and correct the first mapping relation based on the corrected test environment when the difference between the first test junction temperature and the second test junction temperature is greater than the threshold, until the difference between the first test junction temperature and the second test junction temperature is less than the threshold.
The test environment of the MOSFET10 to be tested includes the deviation range of the driving voltage of the MOSFET to be tested in actual work and in the calibration process, the upper limit of the current conduction pulse, and the temperature accuracy of the heating platform.
In actual work and in a calibration process, the driving voltage VGS of the MOSFET10 to be tested needs to be within a certain deviation range, and the smaller the deviation range, the better; in actual operation and during calibration, the current conducting pulse needs to be small enough, usually 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 correction function relationship, the first correction function relationship being a first function relationship determined when a difference between the first test junction temperature and the second test junction temperature is less than a threshold; and the working online test module is suitable for acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET online.
Another embodiment of the present invention further provides an online SiC-based MOSFET junction temperature monitoring system, where the difference between the SiC-based MOSFET junction temperature monitoring system of the present embodiment and the SiC-based MOSFET junction temperature monitoring system of the previous embodiment is: 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 to 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, a forward connection terminal of the constant current source 8001 is connected to one end of the auxiliary switch 8003, the other end of the auxiliary switch 8003 is adapted to be connected to a first source-drain electrode of the MOSFET10 to be tested, the negative connecting end of the constant current source 8001 is suitable for being connected with the second source drain electrode of the MOSFET10 to be tested, the input end of the first operational amplifier module Y1 is connected to the other end of the auxiliary switch 8003 through a first switch 8005, the first operational amplifier module Y1 is adapted to convert a current signal in the MOSFET10 to be tested into a voltage signal, the output end of the first operational amplifier module Y1 is adapted to obtain a first conduction saturation voltage drop, and the first current sensor 8004 is adapted to test and obtain a first conduction current.
The first current sensor 8004 of the present embodiment refers to the contents of the foregoing embodiments, and is not described in detail.
The specific structure of the first operational amplifier module Y1 refers to the first operational amplifier module Y1 of the previous embodiment. The input end of a first initial operational amplifier unit in the first operational amplifier module is connected with a first switch 8005.
The second current calibration module comprises 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 previous embodiment. And the input end of a 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 online junction temperature monitoring method for a SiC-based MOSFET, which is suitable for using the above online junction temperature monitoring system for a SiC-based MOSFET, and with reference to fig. 7, includes the following steps:
s01: a first current calibration module is adopted to inject current into the MOSFET to be tested in a forward direction, and a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a first conduction current and junction temperature of the MOSFET to be tested is obtained;
s02: a second current is reversely injected into the MOSFET to be tested by adopting a second current calibration module, and a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a turn-off state and the junction temperature of the MOSFET to be tested is obtained;
s03: 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 takes the junction temperature of the MOSFET to be tested as a dependent variable;
s04: fitting the data in the second mapping relation by using 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 takes the junction temperature of the MOSFET to be tested as a dependent variable;
s05: adopt the work sampling module acquires third and switches on saturation voltage drop and third and switches on electric current when the MOSFET that awaits measuring is in the characteristic sampling state in real time, the characteristic sampling state includes: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and the grid electrode of the MOSFET to be tested is in a conducting state;
s06: after the third conduction saturation voltage drop and the third conduction current are obtained, a second current calibration module is adopted to carry out off-line test on the MOSFET to be tested, second current is reversely injected into the MOSFET to be tested, and fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and a turn-off state are obtained;
s07: acquiring a first test junction temperature by using a first test junction temperature acquisition unit, wherein the first test junction temperature is a junction temperature value of the MOSFET to be tested corresponding to the data of the third conduction saturation voltage drop and the third conduction current in a first function relation at the moment that the working equipment module stops working;
s08: acquiring a junction temperature sampling value of the corresponding MOSFET to be tested in the second functional relation according to fourth conduction saturation voltage drop data at different moments by using 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 between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation 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 smaller than a threshold value.
In the process that the first current calibration module injects current to the MOSFET to be tested in the forward direction, the MOSFET to be tested is suitable for being placed on the 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 that the second current calibration module reversely injects the second current into the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on the 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 for calibrating the MOSFET to be tested, it is specific, the second end of the load unit 1103 is connected with 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 with 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, one applied to the gate of the MOSFET10 to be testedThe time of the periodic pulse signal is less than or equal to 100 microseconds, so that the phenomenon that the interior of the MOSFET10 to be tested generates heat due to overlarge conducting current caused by overlong time is avoided. When the first current calibration module of fig. 2 is used to calibrate the MOSFET10 to be tested, the first on-current I of the MOSFET 10T to be testedD1The voltage of the constant voltage source 1101 and the load unit 1103 are jointly determined, and under the condition of fixing the load unit 1103, the voltage amplitude of the constant voltage source 1101 is adjusted, so that a group of first conduction currents I can be obtainedD1And a first conduction saturation voltage drop VDS1By adjusting the temperature of the heating stage, junction temperatures T of different MOSFETs 10 to be tested can be obtainedjFirst on-state current ID1And a first conduction saturation voltage drop VDS1To obtain a first conduction saturation voltage drop V of the MOSFET10 under test in an off-line stateDS1And a first conduction current ID1And junction temperature of the MOSFET10 under test.
When the first current calibration module of fig. 6 is used for calibrating the MOSFET10 to be tested, specifically, the negative connection end of the constant current source 8001 is connected to the second source drain of the MOSFET10 to be tested, the input end of the first operational amplifier module Y1 is connected to the other end of the auxiliary switch 8003 through the first switch 8005, 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 of one period is applied to the gate of the MOSFET10 to be tested, the time of the pulse signal of one period is less than or equal to 100 microseconds, so as to prevent the time from causing the inside of the MOSFET10 to be tested to generate heat due to overlarge conducting current.
When the first current calibration module of fig. 6 is used to calibrate the MOSFET10 to be tested, the first on-current I of the MOSFET to be testedD1The constant current source 8001 determines that the auxiliary switch 8003 and the first switch 8005 are turned on, the second switch 8006 is turned off, the constant current source 8001 injects large current to the MOSFET10 to be tested in the forward direction, and then a group of first conduction currents I can be obtainedD1And a first conduction saturation voltage drop VDS1Is mapped toBy adjusting the temperature of the heating stage, junction temperatures T of different MOSFETs 10 to be tested can be obtainedjFirst on-state current ID1And a first conduction saturation voltage drop VDS1To obtain a first mapping relationship between the first conduction saturation voltage drop of the MOSFET10 under test in the offline state and the first conduction current and the junction temperature of the MOSFET10 under test.
When the second current calibration module of fig. 3 is used for calibrating 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, a 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 predetermined temperature by the heating platform, a small current is reversely injected into the body diode of the MOSFET10 to be tested by the second bias current source Y214, and the junction temperature T10 of different MOSFETs 10 to be tested can be obtained by adjusting the temperature of the heating platformjSecond conduction saturation voltage drop V at 1DS2To obtain a second conduction saturation voltage drop V of the MOSFET10 under test in an off-line state and an off-stateDS2Junction temperature T with MOSFET to be testedj1, in the second mapping relationship.
When the second current calibration module of fig. 6 is used for calibrating 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, a voltage is applied to the gate of the MOSFET10 to be tested to turn off the MOSFET10 to be tested, 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 bleeds current from 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, and the junction temperature T of the MOSFET10 to be tested can be obtained by adjusting the temperature of the heating platformjSecond conduction saturation voltage drop V at 1DS2To obtain a second conduction saturation voltage drop of the MOSFET10 under test in an off-line state and an off-stateVDS2Junction temperature T with MOSFET to be testedj1, in the second mapping relationship.
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 takes the junction temperature of the MOSFET to be tested as a dependent variable.
In a specific embodiment, the first functional relationship is fit using a binary second-order polynomial as:
Figure BDA0002712788200000201
A1、A2、A3、A4、A5、A6is the coefficient of 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 takes the junction temperature of the MOSFET to be tested as a dependent variable.
In a specific embodiment, the second functional relationship is fitted using a unary first order polynomial: t isj1＝A7+A8*VDS2
A7、A8Is the coefficient of each polynomial in the second functional relationship.
Adopt the work sampling module acquires third and switches on saturation voltage drop and third and switches on electric current when the MOSFET that awaits measuring is in the characteristic sampling state in real time, the characteristic sampling state includes: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and the 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 gate of the MOSFET to be tested is driven by a Pulse Width Modulation (PWM) signal of the working equipment module, the PWM signal is applied to turn on the MOSFET to be tested, and at this time, the current discharging switch Y45 is turned off,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 the output end of the third analog signal isolation unit Y44 obtains a third conduction saturation voltage drop VDS3Simultaneously, a second current sensor is adopted to obtain a third conduction current ID3。
It should be noted that after the real-time sampling by the working sampling module is completed, the MOSFET to be tested is turned off, the current leakage switch Y45 is turned on at this time, the current in the third bias current source Y412 is leaked out, and the output of the third initial operational amplifier unit Y41 is 0V at this time.
The working sampling module stops sampling at the time of T1, the working equipment module stops working, and the time of T1 corresponds to VDS3(T1) and ID3(T1), mixing VDS3(T1) and ID3(T1) substituting the first function relation, and calculating the junction temperature value of the MOSFET to be tested as a first test junction temperature Tb 1.
After the working equipment module stops working, the second current calibration module is adopted to carry out offline test on the MOSFET10 to be tested, second current is reversely injected into the MOSFET10 to be tested, and fourth conduction saturation voltage drop V of the MOSFET10 to be tested at different moments in an offline state and an off state is obtainedDS4。
Suppose that V is tested at time T2DS4(T2), test at T3 to obtain VDS4(T3), test at T4 to obtain VDS4(T4). Will VDS4(T2)、VDS4(T3) and VDS4(T4) are respectively brought into the second functional relation to respectively obtain junction temperature sampling values Tj (T2), Tj (T3) and Tj (T4) of the MOSFET to be tested.
Referring to fig. 8, fig. 8 is a relationship between a junction temperature change Δ T of the MOSFET10 to be tested and time T after the operation device module stops operating, where the horizontal axis in fig. 8 is time T in seconds, the vertical axis is the junction temperature of the MOSFET10 to be tested, and the time T represents the time duration from the time T1. According to Δ T ═ k (T)1/2According to the relation of the junction temperature sampling values Tj (T2), Tj (T3) and Tj (T4), the relation is substituted into delta T (k) (T)1/2In the relationship of (1), the value of k is obtained, and the junction temperature at T1 is deduced back as the second tested junction temperature Tb 2.
The comparison and correction module comprises a comparison unit and a correction unit.
Comparing whether the difference value between the first tested junction temperature Tb1 and the second tested junction temperature Tb2 is larger than a threshold value or not by using 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, acquiring a first correction function relation; adopting a working online test module to acquire the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET online; and inputting the on-line acquired conduction saturation voltage drop and the on-line acquired conduction current into the first correction function relation, and outputting the junction temperature of the SiC-based MOSFET.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (16)

1. An on-line junction temperature monitoring system for a SiC-based MOSFET is characterized by 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 MOSFET to be tested in the forward direction 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 first conduction current and junction temperature of 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 a turn-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 data in the first mapping relation to obtain a first functional relation, and the first functional relation takes the first conduction saturation voltage drop and the first conduction current as independent variables and takes 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, and the second functional relation takes the second conduction saturation voltage drop as an independent variable and takes the junction temperature of the MOSFET to be tested as a dependent variable;
the work sampling module, the work sampling module is suitable for when the MOSFET that awaits measuring is in the characteristic sampling state real-time acquisition third and switches on saturation voltage drop and third and switches on electric current, the characteristic sampling state includes: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and the grid electrode of the MOSFET to be tested is in a conducting state;
the second current calibration module is also suitable for performing an off-line test on the MOSFET to be tested after the working sampling module obtains the third conduction saturation voltage drop and the third conduction current, and obtaining fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and a turn-off state by reversely injecting the second current into the MOSFET to be tested;
the first test junction temperature obtaining unit is suitable for obtaining a first test junction temperature, and the first test junction temperature is a junction temperature value of the MOSFET to be tested corresponding to the data of the third conduction saturation voltage drop and the third conduction current in a first functional relation at the moment that the working equipment module stops working;
the second test junction temperature obtaining unit is suitable for obtaining corresponding junction temperature sampling values of the MOSFET to be tested in the second function relation according to fourth conduction saturation voltage drop data at different moments, and obtaining second test junction temperature at the moment when the working equipment module stops working according to the junction temperature sampling values of the MOSFET to be tested;
and the comparison and correction module is suitable for comparing the difference between the first test junction temperature and the second test junction temperature and correcting the first mapping relation 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 smaller than a threshold value.
2. The SiC-based MOSFET junction temperature on-line monitoring system of claim 1, wherein 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 anode 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 the first source drain of the MOSFET to be tested and the first operational amplifier module, the cathode of the constant voltage source is connected with the second source drain 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 acquiring a first conduction saturation voltage drop, and the first current sensor is suitable for testing and acquiring a first conduction current;
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 or the second source drain of the MOSFET to be tested.
3. The system for monitoring the junction temperature of the SiC-based MOSFET on line as recited in claim 2, 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, wherein an input end of the first initial operational amplifier unit is connected to the second end, 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 the first conduction saturation voltage drop.
4. The system for on-line monitoring of junction temperature of the SiC-based MOSFET of claim 2, wherein 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 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 at an output end of the second proportional amplifier is smaller than a voltage signal at an input end of the second proportional amplifier, and an output end of the second analog signal isolation unit is adapted to obtain the second conduction saturation voltage drop.
5. The SiC-based MOSFET junction temperature on-line monitoring system of claim 1, characterized in that the first current calibration module comprises a constant current source, a first bleeder circuit, an auxiliary switch, a first current sensor, a first operational amplifier module and a first switch which are connected with the constant current source in parallel, the positive connecting 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 the MOSFET to be tested, the negative connecting end of the constant current source is suitable for being connected with the second source drain electrode of the MOSFET to be tested, the input end of the first operational amplifier module is connected with the other end of the auxiliary switch through a first switch, 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 testing and obtaining a first conduction current;
and the second current calibration module comprises a second operational amplifier module and a second switch, and the second operational amplifier module is connected with the second source drain of the MOSFET to be tested through the second switch.
6. The system for monitoring the junction temperature of the SiC-based MOSFET on line as recited in 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, wherein an input end of the first initial operational amplifier unit is connected with the first switch, an input end of the first low pass filter is connected with an output end of the first initial operational amplifier unit, an input end of the first proportional amplifier is connected with 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 with 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, a voltage signal of the output end of the second proportional amplifier is smaller than a voltage signal 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 system for monitoring the junction temperature of the SiC-based MOSFET as claimed in claim 3 or 6, wherein the first initial operational amplifier unit comprises a first current-voltage conversion operational amplifier, a first diode, a second diode and a first bias current source, wherein the positive input terminal of the first current-voltage conversion operational amplifier is connected with the positive connection terminal of the first diode and the reverse connection terminal of the second diode, the positive connection terminal of the second diode is connected with the negative input terminal of the first current-voltage conversion operational amplifier and the first bias current source, the reverse connection terminal of the first diode is used as the input terminal of the first initial operational amplifier unit, and the output terminal of the first current-voltage conversion operational amplifier is used as the output terminal of the first initial operational amplifier unit.
8. The system for monitoring the junction temperature of the SiC-based MOSFET on-line as recited in claim 4 or 6, wherein the second initial operational amplifier unit comprises a second current-to-voltage conversion operational amplifier, a third diode, a fourth diode and a second bias current source, wherein the positive input terminal of the second current-to-voltage conversion operational amplifier is connected with the positive connection terminal of the third diode and the reverse connection terminal of the fourth diode, the positive connection terminal of the fourth diode is connected with the negative input terminal of the second current-to-voltage conversion operational amplifier and the second bias current source, the reverse 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-to-voltage conversion operational amplifier is used as the output terminal of the second initial operational amplifier unit.
9. The SiC-based MOSFET junction temperature on-line monitoring system of claim 1, wherein the working sampling module comprises 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 bleeder switch, 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, 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 that 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 acquiring a third conduction saturation voltage drop; the current release switch is suitable for being opened when the MOSFET to be tested is turned off and releasing the current in the third initial operational amplifier unit; the second current sensor is suitable for testing and obtaining a third conducting current.
10. The system for on-line monitoring of junction temperature of SiC-based MOSFET as claimed in claim 9, wherein the third initial operational amplifier unit comprises 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, wherein an anode input terminal of the third current-to-voltage conversion operational amplifier is connected to a positive connection terminal of the fifth diode, a negative connection terminal of the sixth diode, a positive connection terminal of the seventh diode, and a current bleeder switch, a positive connection terminal of the sixth diode is connected to a negative connection terminal 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 a cathode input terminal of the third current-to-voltage conversion operational amplifier and one end of the second resistor, and the other end of the second resistor is connected to an output terminal of the third current-to-voltage conversion operational amplifier, and 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.
11. The SiC-based MOSFET junction temperature online monitoring system of claim 1, wherein the comparison and correction module comprises a comparison unit and a correction unit, the comparison 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, and the correction unit is adapted to correct the test environment of the MOSFET to be tested and correct the first mapping relationship based on the corrected test environment when the difference between the first test junction temperature and the second test junction temperature is greater than the threshold until the difference between the first test junction temperature and the second test junction temperature is less than the threshold.
12. The SiC-based MOSFET junction temperature on-line monitoring system of claim 1, further comprising:
a first correction function relationship, the first correction function relationship being a first function relationship determined when a difference between the first test junction temperature and the second test junction temperature is less than a threshold;
and the working online test module is suitable for acquiring the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET online.
13. An on-line monitoring method for junction temperature of a SiC-based MOSFET, which adopts the on-line monitoring system for junction temperature of the SiC-based MOSFET as claimed in any one of claims 1 to 12, is characterized by comprising the following steps:
a first current calibration module is adopted to inject current into the MOSFET to be tested in a forward direction, and a first mapping relation between a first conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a first conduction current and junction temperature of the MOSFET to be tested is obtained;
a second current is injected into the MOSFET to be tested in a reverse direction by adopting a second current calibration module, and a second mapping relation between a second conduction saturation voltage drop of the MOSFET to be tested in an off-line state and a turn-off state and the junction temperature of the MOSFET to be tested is obtained, wherein the second current is smaller than the first conduction current;
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 takes the junction temperature of the MOSFET to be tested as a dependent variable;
fitting the data in the second mapping relation by using 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 takes the junction temperature of the MOSFET to be tested as a dependent variable;
adopt the work sampling module acquires third and switches on saturation voltage drop and third and switches on electric current when the MOSFET that awaits measuring is in the characteristic sampling state in real time, the characteristic sampling state includes: the MOSFET to be tested is a working element of the working equipment module, the working equipment module is in a working state, and the grid electrode of the MOSFET to be tested is in a conducting state;
after the third conduction saturation voltage drop and the third conduction current are obtained, a second current calibration module is adopted to carry out off-line test on the MOSFET to be tested, second current is reversely injected into the MOSFET to be tested, and fourth conduction saturation voltage drops of the MOSFET to be tested at different moments in an off-line state and a turn-off state are obtained;
acquiring a first test junction temperature by using a first test junction temperature acquisition unit, wherein the first test junction temperature is a junction temperature value of the MOSFET to be tested corresponding to the data of the third conduction saturation voltage drop and the third conduction current in a first function relation at the moment that the working equipment module stops working;
acquiring a junction temperature sampling value of the corresponding MOSFET to be tested in the second functional relation according to fourth conduction saturation voltage drop data at different moments by using 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 between the first test junction temperature and the second test junction temperature, and corrects the first mapping relation 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 smaller than a threshold value.
14. The SiC-based MOSFET junction temperature online monitoring method according to claim 13, wherein in the process of injecting the current into the MOSFET to be tested in the forward direction by the first current calibration module, the MOSFET to be tested is adapted to be placed on a heating platform, 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 that the second current calibration module reversely injects the second current into the MOSFET to be tested, the MOSFET to be tested is suitable for being placed on the 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 SiC-based MOSFET junction temperature online monitoring method of claim 13, wherein the comparison and correction module comprises a comparison unit and a correction unit; comparing, with the comparison unit, whether a difference between the first tested junction temperature and the second tested junction temperature is greater than a threshold; and when the difference between the first test junction temperature and the second test junction temperature is larger than the threshold, correcting the test environment of the MOSFET to be tested by using the correction unit, and correcting 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 smaller than the threshold.
16. The SiC-based MOSFET junction temperature on-line monitoring method according to 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, acquiring a first correction function relation; adopting a working online test module to acquire the conduction saturation voltage drop and the conduction current of the SiC-based MOSFET online; and inputting the on-line acquired conduction saturation voltage drop and the on-line acquired conduction current into the first correction function relation, and outputting the junction temperature of the SiC-based MOSFET.
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