On-line monitoring system of power device junction temperature based on dynamic threshold voltage

Abstract

The present invention discloses an online monitoring system for junction temperature of a power device based on dynamic threshold voltage, comprising: a power device to be tested, a temperature control unit, a gate drive circuit, a working condition sampling unit, a junction temperature monitoring unit, a junction temperature evaluation unit and a control unit. The present invention establishes an online monitoring system for junction temperature of a power device, extracts dynamic threshold voltages under different DC bus voltages and working junction temperatures, establishes an offline reference database, and monitors the dynamic threshold voltage of the device when it is turned on during the actual operation of the power device to be tested, thereby performing online junction temperature calculation, thereby providing a basis for life prediction of the power device when it is working, and has higher real-time performance and portability compared with the existing SiC MOSFET working junction temperature monitoring technology.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic devices, and in particular relates to an online monitoring system for junction temperature of a power device based on dynamic threshold voltage. Background Art

[0002] In recent years, with the continuous development of power electronic systems, SiC (Silicon Carbide) MOSFET has become an ideal choice for applications in harsh working conditions and high-power power electronic systems. With the promotion and application of SiC devices, their health management and reliability assessment have also received more and more attention. Among various failure factors, device failures caused by thermal stress account for as much as 55%. The number of temperature cycle cycles experienced by power devices before failure is mainly determined by factors such as junction temperature swing, maximum junction temperature, average junction temperature, minimum case temperature and module cycle conduction time. Therefore, the precise extraction and detection of the junction temperature of SiC MOSFET devices is the basis for their loss calculation, life prediction, health management and reliability assessment.

[0003] In the related technology, the junction temperature monitoring methods of SiC MOSFET devices mainly include: physical contact method, optical non-contact method and thermal resistance network model prediction method. Among them, the physical contact method places temperature measuring elements such as thermistors or thermocouples inside the device to be tested to obtain its internal temperature information. The response speed of this method is generally around seconds, and the response time is relatively long. It is only suitable for average temperature detection of heat sinks or substrates, and cannot reflect the dynamic changes of junction temperature of the device to be tested in real time; the optical non-contact method is mainly based on the characterization parameters of light-temperature coupling effects such as cold light, Raman effect, refractive index, reflectance, laser deflection, etc., and uses the relationship between the temperature of the device to be tested and infrared radiation to achieve junction temperature monitoring. However, this method can only measure unpackaged exposed chips. For modules with packaged structures, the module package needs to be opened, and the maximum sampling rate of the test instrument is limited, which cannot meet the requirements of real-time monitoring of dynamic junction temperature; the thermal resistance network model prediction method, that is, measuring the temperature of the SiC MOSFET module substrate, based on the real-time loss of the device to be tested and the transient thermal impedance network model, reversely infers the chip junction temperature and its change trend through simulation calculation or offline table lookup; because aging factors will affect the thermal resistance network model and the loss model of the device to be tested, it is difficult to accurately calculate in real time, and the thermal resistance network model prediction method is not suitable for online monitoring of the working junction temperature of SiC MOSFET. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides an online monitoring system for junction temperature of a power device based on dynamic threshold voltage. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] The present invention provides a power device junction temperature online monitoring system based on dynamic threshold voltage, comprising: a power device to be tested, a temperature control unit, a gate drive circuit, a working condition sampling unit, a junction temperature monitoring unit, a junction temperature evaluation unit and a control unit; wherein,

[0006] The temperature control unit is used to adjust the ambient temperature of the power device to be tested to a preset temperature;

[0007] The gate driving circuit is connected to the gate of the power device to be tested and is used to switch the off state and the on state of the power device to be tested;

[0008] The operating condition sampling unit is used to collect the DC bus voltage during the transient process when the power device to be tested switches from the off state to the on state;

[0009] The junction temperature monitoring unit is used to obtain the DC bus voltage and the dynamic threshold voltage when the device under test is turned on, and determine the operating junction temperature of the power device under test according to the DC bus voltage and the dynamic threshold voltage;

[0010] The junction temperature evaluation unit is used to generate a warning signal and send the warning signal to the control circuit when the operating junction temperature exceeds a preset threshold;

[0011] The control circuit is used to use the gate drive circuit to shut down the power device to be tested after receiving the early warning signal.

[0012] In one embodiment of the present invention, the junction temperature monitoring unit includes: an isolation module, a comparison module, a sampling and holding module and a junction temperature calculation module; wherein,

[0013] The isolation module is used to isolate and convert the gate voltage signal and the drain voltage signal of the power device to be tested;

[0014] The comparison module is used to measure the moment of the dynamic threshold voltage according to the reference voltage;

[0015] The sampling and holding module is used to capture the gate voltage of the power device to be tested during the opening process according to the time and maintain the dynamic threshold voltage;

[0016] The junction temperature calculation module is used to determine the operating junction temperature of the power device to be tested according to the DC bus voltage and the dynamic threshold voltage.

[0017] In one embodiment of the present invention, V probe node;

[0018] The isolation module includes: a high-voltage capacitor C1, a diode D1 and a differential amplifier AMP1; wherein the anode of D1 is connected to the drain of the power device to be tested, the cathode is connected to one end of C1, and the other end of C1 is connected to V probe Node; the in-phase input terminal of AMP1 is connected to the gate of the power device to be tested, the inverting input terminal is connected to the Kelvin source of the power device to be tested, and the output terminal is connected to the sampling and holding module.

[0019] In one embodiment of the present invention, it further comprises: a reference voltage signal terminal and a power supply voltage signal terminal;

[0020] The comparison module includes: a voltage follower, a resistor R1, a diode D2, an NMOS tube, a PMOS tube, a resistor R2, a resistor R3 and inverters: A1, A2, A3; wherein,

[0021] The non-inverting input terminal of the voltage follower is connected to the reference voltage signal terminal, the inverting input terminal is connected to the output terminal, and the output terminal of the voltage follower is connected to the V probe Node, the anode of D2 is grounded, the cathode of D2 and the gate of the NMOS tube are connected to V probe Node, the source of the NMOS tube is grounded, and the drain is connected to the power supply voltage signal terminal V through R3. DD , the input of A1 is connected to the drain of the NMOS tube, the output is connected to the input of A2, and the gate of the PMOS tube is connected to V probe Node, source and power supply voltage signal terminal V DD The drain is grounded through R2, and the input end of A3 is connected to the drain of the PMOS tube.

[0022] In one embodiment of the present invention, it also includes a PWM control signal terminal;

[0023] The sampling and holding module includes: an OR gate, a D trigger, an n-channel JFET field effect transistor and a capacitor C2; wherein,

[0024] The output end of A2 is connected to the first input end of the OR gate, the output end of A3 is connected to the second input end of the OR gate, the output end of the OR gate is connected to the CLK end of the D flip-flop, the data D input end of the D flip-flop is connected to the PWM control signal end, the output The end is connected to the gate of the n-channel JFET field effect transistor, the source of the JFET field effect transistor is connected to the output end of AMP1, and the drain is grounded through C2.

[0025] In one embodiment of the present invention, the junction temperature calculation module includes a field programmable gate array FPGA.

[0026] In one embodiment of the present invention, the preset temperature is 25-175°C.

[0027] In one embodiment of the present invention, the power device to be tested is a SiC MOSFET.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention provides an online monitoring system for junction temperature of a power device based on dynamic threshold voltage, comprising: a power device to be tested, a temperature control unit, a gate drive circuit, a working condition sampling unit, a junction temperature monitoring unit, a junction temperature evaluation unit and a control unit. The system performs online monitoring on the dynamic threshold voltage of the power device to be tested at the moment of switching on, and can evaluate the junction temperature of the power device to be tested online during the operation of the power electronic device, which can not only ensure that the chip junction temperature of the power device is within a safe and controllable working range, but also provide a basis for measures such as over-temperature protection and derating cooling when the power equipment is in long-term service.

[0030] 2. The online monitoring system provided by the present invention utilizes dynamic threshold voltage to obtain junction temperature information. As a temperature-sensitive electrical parameter, dynamic threshold voltage has the advantage of being independent of load current changes and is easier to calibrate junction temperature.

[0031] 3. The present invention can obtain the junction temperature information of the power device under test only by monitoring the dynamic threshold voltage signal of the power device under test. The junction temperature monitoring unit does not affect the normal operation of the power device under test in the converter. Therefore, the system provides an accurate, real-time, non-invasive solution, which is convenient for engineering integration application.

[0032] 4. The power device junction temperature online monitoring system based on dynamic threshold voltage provided by the present invention is suitable for gate-controlled power devices, and has the advantages of low cost, fast response, simple circuit structure, etc., and can provide a basis for evaluating the health status and life of power devices.

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a power device junction temperature online monitoring system based on dynamic threshold voltage provided by an embodiment of the present invention;

[0035] Figure 2 It is a partial circuit diagram of a power device junction temperature online monitoring system based on dynamic threshold voltage provided by an embodiment of the present invention;

[0036] Figure 3 It is a waveform diagram of a turn-on process of a power device to be tested provided by an embodiment of the present invention;

[0037] Figure 4 This is a control timing diagram of a SiC MOSFET dynamic threshold voltage measurement circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0039] There is a close connection between the working state of SiC MOSFET and its working junction temperature. This is because SiC physical parameters such as carrier concentration and carrier lifetime increase with the increase of junction temperature, and carrier mobility decreases with the increase of temperature. The electrical characteristics of SiC MOSFET depend on the above-mentioned semiconductor physical parameters. This electrical parameter that changes with the junction temperature is called TSEP (Temperature Sensitive Electrical Parameter). The temperature sensitive electrical parameters of SiC MOSFET provide the possibility for monitoring the working junction temperature of SiC MOSFET.

[0040] At present, the research on junction temperature monitoring mainly focuses on the temperature characteristics and offline correction of temperature-sensitive electrical parameters, and less on the online measurement of junction temperature under actual working conditions and the junction temperature extraction of SiC devices. SiC devices have low temperature dependence due to their wide bandgap and low intrinsic carrier concentration. Compared with Si-based devices with the same electrical parameters, the static and dynamic characteristics of SiC MOSFET show great differences from Si devices, so it is difficult to achieve the transplantation of some traditional temperature-sensitive electrical parameter measurement technologies from Si IGBT to SiC MOSFET devices. It can be seen that how to monitor the junction temperature of SiC MOSFET devices in real time has become an urgent problem to be solved by technicians in this field.

[0041] In view of this, an embodiment of the present invention provides an online monitoring system for junction temperature of a power device based on dynamic threshold voltage.

[0042] Figure 1 A schematic diagram of the structure of an online monitoring system for junction temperature of a power device based on dynamic threshold voltage provided by an embodiment of the present invention. Figure 1 The embodiment of the present invention provides an online monitoring system for junction temperature of a power device based on dynamic threshold voltage, comprising: a power device to be tested 10, a temperature control unit 20, a gate drive circuit 30, a working condition sampling unit 40, a junction temperature monitoring unit 50, a junction temperature evaluation unit 60 and a control circuit 70; wherein,

[0043] The temperature control unit 20 is used to adjust the ambient temperature of the power device 10 to a preset temperature;

[0044] The gate driving circuit 30 is connected to the gate of the power device 10 to be tested, and is used to switch the off state and the on state of the power device 10 to be tested;

[0045] The operating condition sampling unit 40 is used to collect the DC bus voltage during the transient process when the power device 10 to be tested switches from the off state to the on state;

[0046] The junction temperature monitoring unit 50 is used to obtain the DC bus voltage and the dynamic threshold voltage when the device under test is turned on, and determine the operating junction temperature of the power device under test 10 according to the DC bus voltage and the dynamic threshold voltage;

[0047] The junction temperature evaluation unit 60 is used to generate a warning signal and send the warning signal to the control circuit 70 when the operating junction temperature exceeds a preset threshold;

[0048] The control circuit 70 is used to shut down the power device 10 under test by using the gate driving circuit 30 after receiving the warning signal.

[0049] In this embodiment, the online monitoring system for junction temperature of power devices based on dynamic threshold voltage includes: a power device to be tested 10, a temperature control unit 20, a gate drive circuit 30, a working condition sampling unit 40, a junction temperature monitoring unit 50, a junction temperature evaluation unit 60 and a control circuit 70. Specifically, the temperature control unit 20 is used to adjust the ambient temperature of the power device to be tested 10 to a preset temperature, the working condition sampling unit 40 is connected to the drain and the power source of the power device to be tested 10 to collect the DC bus voltage when the power device to be tested 10 is switched from the off state to the on state, the input of the junction temperature monitoring unit 50 includes: the voltage drop signal between the gate and the Kelvin source of the power device to be tested 10, and the voltage drop signal between the drain and the power source of the power device to be tested 10, after the junction temperature monitoring unit 50 obtains the DC bus voltage and the dynamic threshold voltage when the device to be tested is turned on, the working junction temperature T of the power device to be tested 10 is calculated by looking up the table or the function model. j Further, the output end of the junction temperature monitoring unit 50 is connected to the junction temperature evaluation unit 60, and the junction temperature evaluation unit 60 obtains the working junction temperature T of the power device 10 to be tested. j Compared with the preset threshold, when the operating junction temperature T j When the preset threshold is exceeded, an early warning signal is generated; Figure 1As shown, the output end of the junction temperature evaluation unit 60 is connected to the control circuit 70, the control circuit 70 is connected to the gate drive circuit, and the gate drive circuit is connected to the gate of the power device to be tested 10. Since the gate drive circuit can provide a switching control signal for the gate of the power device to be tested 10 to switch the off state and the on state of the power device to be tested 10, after receiving the early warning signal, the control circuit 70 can use the gate drive circuit to shut down the power device to be tested 10, thereby effectively avoiding the power device to be tested 10 from completely failing due to excessively high working junction temperature.

[0050] Figure 2 FIG. 1 is a partial circuit diagram of a power device junction temperature online monitoring system based on dynamic threshold voltage provided by an embodiment of the present invention. Figure 2 As shown, in this embodiment, the power device 10 to be tested is a SiC MOSFET.

[0051] In this embodiment, the junction temperature monitoring unit 50 includes: an isolation module 501, a comparison module 502, a sampling and holding module 503 and a junction temperature calculation module 504; wherein,

[0052] The isolation module 501 is used to isolate and convert the gate voltage signal and the drain voltage signal of the power device 10 to be tested;

[0053] A comparison module 502, configured to measure a moment of a dynamic threshold voltage according to a reference voltage;

[0054] The sampling and holding module 503 is used to capture the gate voltage of the power device 10 to be tested during the turn-on process according to the time and maintain the dynamic threshold voltage;

[0055] The junction temperature calculation module 504 is used to determine the operating junction temperature of the power device 10 to be tested according to the DC bus voltage and the dynamic threshold voltage.

[0056] It should be understood that the turn-on process of the power device 10 to be tested can be divided into four stages. In this embodiment, the dynamic threshold voltage V th Through the analysis of the opening delay stage, that is, Figure 3 Please refer to the time period t0 to t1 shown in the figure. Figure 3 In the turn-on delay phase, the external drive circuit starts to charge the gate-source capacitance Cgs and the gate-drain capacitance Cgd, V GS It gradually rises and has not yet reached the 10 threshold voltage V of the power device under test. GS,th The device is still in the off state, and the drain current I D is zero, the drain-source voltage V DS is the blocking voltage V ds, at this time the power device 10 to be tested is in the cut-off region. In the current rising stage during the time period t1 to t2, the gate-source voltage V GS Greater than the threshold voltage V GS,th , drain current I D Start with V GS After t1, the drain-source voltage V ds By blocking voltage V DC The gate voltage V of the power device 10 to be tested begins to decrease at time t1. GS Rising to the threshold voltage V GS,th At the moment when the online junction temperature monitoring system collects the dynamic threshold voltage V of the temperature-sensitive electrical parameter th moment.

[0057] For example, the device threshold voltage V GS,th It can be expressed as:

[0058]

[0059] Among them, V FB indicates that the flat band voltage is independent of temperature, k is the Boltzmann constant, ψ B is the Fermi potential, which represents the intermediate energy level E of the semiconductor bandgap i The potential difference between the Fermi level and the surface is expressed as:

[0060]

[0061] In the formula, ψ B It is related to the doping concentration and temperature of the semiconductor. As the junction temperature increases, the intrinsic carrier concentration (n i ) is increased by the temperature prefactor (kT) and the ionization concentration N of the acceptor caused by the temperature increase. A The increase in temperature offsets part of the Fermi level, but the increase in temperature makes the Fermi level gradually approach the midline of the bandgap, thus forming the surface potential (2ψ B ) will decrease accordingly, so the Fermi potential ψ B It decreases with increasing temperature. It can be seen that the threshold voltage V th It is a function of temperature and decreases with increasing junction temperature, and has a negative temperature coefficient.

[0062] The inventors found during the research that as the working junction temperature of the power device 10 under test increases, the threshold voltage decreases accordingly. Therefore, the dynamic threshold voltage V th The information is used to analyze the operating junction temperature of the SiC MOSFET60 device and realize the health status monitoring of the power device.

[0063] In addition, the junction temperature calculation module 504 stores the DC bus voltage V under various operating conditions. dc , the dynamic threshold voltage when the SiC MOSFET device is turned on, and the data table or function model of the working junction temperature of the SiC MOSFET device, and then the DC bus voltage V during the transient process of the SiC MOSFET60 device switching from the off state to the on state can be calculated. dc 、Dynamic threshold voltage V of SiC MOSFET60 device th , the operating junction temperature T of the SiCMOSFET60 device is calculated by looking up the table or function model j .

[0064] Please continue to see Figure 2 The above-mentioned power device junction temperature online monitoring system based on dynamic threshold voltage also includes V probe node;

[0065] The isolation module 501 includes: a high voltage capacitor C1, a diode D1 and a differential amplifier AMP1; wherein the anode of D1 is connected to the drain of the power device 10 to be tested, the cathode is connected to one end of C1, and the other end of C1 is connected to V probe AMP1's in-phase input terminal is connected to the gate of the power device to be tested 10, its inverting input terminal is connected to the Kelvin source of the power device to be tested 10, and its output terminal is connected to the sample and hold module 503.

[0066] In this embodiment, the isolation module 501 may include a high voltage capacitor C1, a diode D1 and a differential amplifier AMP1; Figure 2 As shown, the anode of the diode D1 is connected to the drain of the power device 10 to be tested, the cathode is connected to one end of the high-voltage capacitor C1, and the other end of the high-voltage capacitor C1 is connected to V probe The node, high-voltage capacitor C1 and diode D1 ensure that the online monitoring of junction temperature based on the dynamic threshold voltage will not affect the normal switching process of the power device under test 10. DS Furthermore, the non-inverting input terminal of the differential amplifier AMP1 is connected to the gate of the power device 10 to be tested, and the inverting input terminal is connected to the Kelvin source of the power device 10 to be tested, so as to ensure that the junction temperature monitoring unit 50 is isolated from the gate drive circuit 30 to avoid affecting the V gs .

[0067] Please continue to see Figure 2 The above junction temperature online monitoring system also includes a reference voltage signal terminal V ref and the power supply voltage signal terminal V DD ;

[0068] The comparison module 502 includes: a voltage follower, a resistor R1, a diode D2, an NMOS transistor, a PMOS transistor, a resistor R2, a resistor R3 and inverters: A1, A2, A3; wherein,

[0069] The non-inverting input terminal of the voltage follower is connected to the reference voltage signal terminal, the inverting input terminal is connected to the output terminal, and the output terminal of the voltage follower is connected to V probe Node, the anode of D2 is grounded, the cathode of D2 and the gate of the NMOS tube are connected to V probe Node, the source of the NMOS tube is grounded, and the drain is connected to the power supply voltage signal terminal V through R3. DD , the input of A1 is connected to the drain of the NMOS tube, the output is connected to the input of A2, and the gate of the PMOS tube is connected to V probe Node, source and power supply voltage signal terminal V DD The drain is grounded through R2, and the input end of A3 is connected to the drain of the PMOS tube.

[0070] In this embodiment, the comparison module 502 includes: a voltage follower, a resistor R1, a diode D2, an NMOS tube, a PMOS tube, a resistor R2, a resistor R3 and three inverters: A1, A2, and A3; wherein the non-inverting input terminal of the voltage follower is connected to the reference voltage signal terminal, the inverting input terminal is connected to the output terminal, and the output terminal of the voltage follower is connected to V through the resistor R1. probe When the power device 10 to be tested switches from the off state to the on state, the voltage V DS Starts to decrease, V probe The node voltage starts to drop from the reference voltage, and V probe The node voltage is determined by the reference voltage V ref The moment when the gate voltage starts to decrease is t1, which is the moment when the gate voltage V gs Rising to the dynamic threshold voltage V th moment.

[0071] like Figure 2 As shown, the anode of diode D2 is grounded and the cathode is connected to V probe node to prevent V probe The node voltage drops below -0.7V; the threshold voltage of the NMOS tube is less than and close to the reference voltage provided by the reference voltage signal terminal, and the gate of the NMOS tube is connected to V probe The node, the source is grounded, and the drain is connected to the power supply voltage signal terminal V through resistor R3. DD , the drain of the NMOS tube is connected in series with the inverter A1 and the inverter A2. When the power device 10 to be tested switches from the off state to the on state, V probeThe node voltage starts to drop from the reference voltage. When the gate voltage of the NMOS tube is lower than the threshold voltage, the NMOS tube is turned off and a pulse signal S1 is generated. The PMOS tube is similar to the NMOS tube. The absolute value of the threshold voltage of the PMOS tube is less than and close to V DD -V ref , whose gate is connected to V probe The node is connected, the source is connected to the power supply voltage signal terminal, and the drain is grounded through the resistor R2. In addition, the drain of the PMOS tube is also connected to the inverter A3. When the SiC MOSFET switches from the on state to the off state, V probe The node voltage starts to rise from the reference voltage, and when it reaches a certain value, the PMOS tube is turned off, generating a pulse signal S2 to control the release of the voltage value held by the sampling and holding module 503, so as to monitor the junction temperature in the next switching cycle.

[0072] like Figure 2 As shown, the above-mentioned junction temperature online monitoring system also includes a PWM control signal terminal;

[0073] The sampling and holding module 503 includes: an OR gate, a D flip-flop, an n-channel JFET field effect transistor and a capacitor C2; wherein,

[0074] The output of A2 is connected to the first input of the OR gate, the output of A3 is connected to the second input of the OR gate, and the output of the OR gate is connected to the CLK terminal of the D flip-flop. The data D input of the D flip-flop is connected to the PWM control signal terminal. The end is connected to the gate of the n-channel JFET field effect transistor, the source of the JFET field effect transistor is connected to the output end of AMP1, and the drain is grounded through C2.

[0075] Specifically, the sampling and holding module 503 includes an OR gate 102, a D flip-flop 101, an n-channel JFET field effect transistor and a capacitor C2. Figure 2 As shown, the output end of A2 is connected to the first input end of the OR gate, and the output end of A3 is connected to the second input end of the OR gate. That is, the two inputs of the OR gate 102 are the pulse signals S1 and S2, and the output end of the OR gate 102 is connected to the CLK end of the D flip-flop 101. The data input end D of the D flip-flop 101 is connected to the PWM control signal end and the output end Connected to the gate of the n-channel JFET field effect transistor, the source of the JFET field effect transistor is connected to the output of the amplifier AMP1, and the drain is connected to one end of the capacitor C2. The voltage on the capacitor C2 is the dynamic threshold voltage V th , which is output to the junction temperature calculation module 504 as a temperature-sensitive electrical parameter for junction temperature monitoring.

[0076] Optionally, the junction temperature calculation module 504 includes a field programmable gate array FPGA.

[0077] It can be seen that the online junction temperature monitoring unit 50 extracts the dynamic threshold voltage V th As the key characteristic parameter, the initial state calibration and real-time online monitoring are performed, and the dynamic threshold voltage V is monitored during the switching process of the power device 10 under test. th The health status and reliability of the device can be evaluated by observing the changes in the temperature of the device, and the power electronic device can be prevented from malfunctioning due to overheating. In addition, the present invention can realize online status monitoring of the key characteristic parameters of the power device 10 to be tested without affecting the normal operation of the device and the converter device and being unaffected by the external load and device package degradation, thus solving the problem of difficulty in online evaluation of the junction temperature of the working process of SiC MOSFET and Si IGBT devices in the prior art, and is easy to be integrated with the driver.

[0078] Figure 4 This is a control timing diagram of a dynamic threshold voltage measurement circuit of a power device to be tested provided by an embodiment of the present invention. It should be noted that: Figure 2 The circuit shown is composed of an FPGA and a dynamic threshold voltage measurement circuit. In other words, in addition to the FPGA used for storage and calculation, Figure 2 The remaining part is the dynamic threshold voltage measurement circuit of the power device to be tested. Figure 1 , Figure 3 and Figure 4 When the control circuit 70 sends a PWM control signal to the gate drive circuit, the power device 10 to be tested switches from the off state to the on state. From time t0, the gate voltage V gs Gradually increases, to the moment t1, the voltage V DS starts to decrease; affected by the decrease in drain voltage, V probe The node voltage also starts to drop from the reference voltage, and the gate of the NMOS tube is connected to V probe When the gate voltage of the NMOS tube is lower than the threshold voltage, the NMOS tube is turned off, and the first pulse signal S1 is generated through the inverters A1 and A2. During the NMOS tube is turned off, the S1 signal remains at a high level until the power device 10 to be tested is fully turned on, that is, the voltage across the drain and source V DS When V is zero, probe The node voltage returns to the reference voltage, the NMOS tube is turned on, the S1 signal changes from high level to low level, and the third pulse signal S3 obtained after passing through the OR gate 102 is high level. At this time, the PWM control signal connected to the data input D terminal of the D flip-flop 101 is high level, and the S3 signal connected to the clock CLK terminal of the D flip-flop 101 jumps from low level to high level at this time, and the D flip-flop 101 outputs The terminal jumps from high level to low level; please continue to refer to Figure 3 and Figure 4 , D flip-flop 101 output The terminal is connected to the gate of the JFET, and the source voltage of the JFET is the gate and Kelvin source voltage difference of the power device 10 to be tested collected by the differential amplifier AMP1, that is, the voltage signal V gs Before time t1, the JFET is in the on state, and the voltage signal V gs The capacitor C2 is charged to generate a fourth pulse signal S4 and sent to the junction temperature calculation module 504 to perform initial junction temperature calibration or table lookup to calculate the real-time junction temperature; the voltage signal V of the power device 10 to be tested at time t1 gs Rising to the threshold voltage V th , and the JFET gate voltage changes from a high level to a low level. Therefore, when the JFET gate-source voltage increases in a negative direction to the JFET pinch-off voltage, the JFET is turned off, and the voltage signal V gs The capacitor C2 is no longer charged, and the voltage on C2 is maintained at the dynamic threshold voltage V of the power device 10 to be tested. th When the power device 10 to be tested is turned off, see Figure 4 At time t4, the voltage signal V gs Falling, voltage signal V DS Rising, at this time due to the effect of high voltage capacitor C1, V probe The node voltage will generate an upward spike from the reference voltage, so the PMOS tube is turned off, and the second pulse signal S2 is generated through the inverter A3. Similar to the turn-on process, the third pulse signal S3 is obtained through the logic OR of the OR gate 102, and S3 is high. At this time, the PWM control signal connected to the data input D terminal of the D flip-flop 101 is low, and the S3 signal connected to the clock CLK terminal of the D flip-flop 101 jumps from a low level to a high level at this time, so the D flip-flop 101 outputs The terminal flips from low level to high level, at which time the JFET is turned on again, the capacitor C2 is discharged, and the output pulse signal S4 is released to enable junction temperature monitoring in the next switching cycle.

[0079] When using the power device junction temperature online monitoring system based on dynamic threshold voltage provided by the present invention for monitoring, firstly, the ambient temperature of the device under test is set to a first preset temperature such as 25°C by using the temperature control unit, and at the same time, a DC voltage source output is set to V dc A first preset voltage V1;

[0080] (1) At time t0, the gate drive circuit outputs a PWM control signal to turn on the power device under test, and the DC voltage source V dcThe load inductor L is charged through the power device to be tested; the working condition sampling unit collects the DC bus voltage V after the power device to be tested is turned on. dc The junction temperature monitoring unit extracts the dynamic threshold voltage V from the power device to be tested at the time t1. th , the DC bus voltage V collected by the operating condition sampling unit dc , the ambient temperature set by the temperature control unit and the dynamic threshold voltage V extracted by the junction temperature monitoring unit th One-to-one correspondence is recorded in the FPGA lookup table of the junction temperature monitoring unit.

[0081] (2) Using the temperature control unit, the ambient temperature of the power device to be tested is set to the second preset temperature, while keeping the first preset voltage unchanged. The temperature control unit is adjusted to set the ambient temperature of the SiC MOSFET 60, starting from a certain temperature and gradually increasing to a maximum set temperature at a certain temperature interval. For example, the temperature interval step is 25° C., and the maximum set temperature does not exceed the maximum operating temperature allowed by the power device to be tested. Then, step (1) is repeated to obtain the dynamic threshold voltage V of the power device to be tested. th The corresponding relationship with its rated temperature is stored in the FPGA lookup table of the junction temperature monitoring unit.

[0082] (3) Change the first rated voltage and set the DC power supply V dc , so that the voltage starts from a certain voltage value and gradually increases to the maximum test voltage at a certain voltage interval. The maximum test voltage does not exceed the maximum operating voltage allowed by the power device to be tested. Repeat the above steps (1) to (2) to obtain the dynamic threshold voltage V of the power device to be tested at different voltages and different operating junction temperatures. th .

[0083] According to the above steps, the dynamic threshold voltage V of the power device to be tested under different voltages and different operating junction temperatures can be established in the FPGA. th In the actual operation of the power device under test, the junction temperature monitoring unit monitors the dynamic threshold voltage V at the moment of opening in each switching cycle of the power device under test. th Real-time monitoring is performed, and then the DC bus voltage V is measured during the transient process of the power device under test switching from the off state to the on state. dc and the dynamic threshold voltage V th By referring to the information in the database, the working junction temperature T of the power device to be tested can be obtained by using a lookup table or a function model or a neural network model. j .

[0084] It can be seen from the above embodiments that the beneficial effects of the present invention are:

[0085] 1. The present invention provides an online monitoring system for junction temperature of a power device based on dynamic threshold voltage, comprising: a power device to be tested, a temperature control unit, a gate drive circuit, a working condition sampling unit, a junction temperature monitoring unit, a junction temperature evaluation unit and a control circuit. The system performs online monitoring on the dynamic threshold voltage of the power device to be tested at the moment of switching on, and can evaluate the junction temperature of the power device to be tested online during the operation of the power electronic device, which can not only ensure that the chip junction temperature of the power device is within a safe and controllable working range, but also provide a basis for measures such as over-temperature protection and derating cooling when the power equipment is in long-term service.

[0086] 2. The online monitoring system provided by the present invention utilizes dynamic threshold voltage to obtain junction temperature information. As a temperature-sensitive electrical parameter, dynamic threshold voltage has the advantage of being independent of load current changes, making it easier to calibrate junction temperature.

[0087] 3. The present invention can obtain the junction temperature information of the power device under test only by monitoring the dynamic threshold voltage signal of the power device under test. The junction temperature monitoring unit does not affect the normal operation of the power device under test in the converter. Therefore, the system provides an accurate, real-time, non-invasive solution, which is convenient for engineering integration application.

[0088] 4. The power device junction temperature online monitoring system based on dynamic threshold voltage provided by the present invention is suitable for gate-controlled power devices, and has the advantages of low cost, fast response, simple circuit structure, etc., and can provide a basis for evaluating the health status and life of power devices.

[0089] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0090] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0091] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0092] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A power device junction temperature online monitoring system based on dynamic threshold voltage, characterized in that: include: A power device to be tested, a temperature control unit, a gate drive circuit, a working condition sampling unit, a junction temperature monitoring unit, a junction temperature evaluation unit and a control circuit; wherein, The temperature control unit is used to adjust the ambient temperature of the power device to be tested to a preset temperature; The gate driving circuit is connected to the gate of the power device to be tested and is used to switch the off state and the on state of the power device to be tested; The operating condition sampling unit is used to collect the DC bus voltage during the transient process when the power device to be tested switches from the off state to the on state; The junction temperature monitoring unit is used to obtain the DC bus voltage and the dynamic threshold voltage when the power device to be tested is turned on, and determine the operating junction temperature of the power device to be tested according to the DC bus voltage and the dynamic threshold voltage; The junction temperature evaluation unit is used to generate a warning signal and send the warning signal to the control circuit when the operating junction temperature exceeds a preset threshold; The control circuit is used to shut down the power device to be tested by using the gate drive circuit after receiving the warning signal; wherein, The junction temperature monitoring unit includes: an isolation module, a comparison module, a sampling and holding module, a junction temperature calculation module, V probe node, a reference voltage signal terminal, a power supply voltage signal terminal and a PWM control signal terminal; wherein the isolation module is used to isolate and convert the gate voltage signal and the drain voltage signal of the power device to be tested; the comparison module is used to measure the moment of the dynamic threshold voltage according to the reference voltage; the sampling and holding module is used to capture the gate voltage of the power device to be tested during the opening process according to the moment and maintain the dynamic threshold voltage; the junction temperature calculation module is used to determine the working junction temperature of the power device to be tested according to the DC bus voltage and the dynamic threshold voltage; wherein, The isolation module includes: a high-voltage capacitor C1, a diode D1 and a differential amplifier AMP1; wherein the anode of D1 is connected to the drain of the power device to be tested, the cathode is connected to one end of C1, and the other end of C1 is connected to V probe Node; the in-phase input terminal of AMP1 is connected to the gate of the power device to be tested, the inverting input terminal is connected to the Kelvin source of the power device to be tested, and the output terminal is connected to the sampling and holding module; The comparison module includes: a voltage follower, a resistor R1, a diode D2, an NMOS tube, a PMOS tube, a resistor R2, a resistor R3 and inverters: A1, A2, A3; wherein the in-phase input terminal of the voltage follower is connected to the reference voltage signal terminal, the inverting input terminal is connected to the output terminal, and the output terminal of the voltage follower is connected to the reference voltage signal terminal through R1. V probe The anode of D2 is grounded, the cathode of D2 and the gate of the NMOS tube are connected to V probe Node, the source of the NMOS tube is grounded, and the drain is connected to the power supply voltage signal terminal V through R3. DD The input of A1 is connected to the drain of the NMOS tube, the output is connected to the input of A2, and the gate of the PMOS tube is connected to V probe Node, source and power supply voltage signal terminal V DD The drain is grounded through R2, and the input end of A3 is connected to the drain of the PMOS tube; The sampling and holding module includes: an OR gate, a D flip-flop, an n-channel JFET field effect transistor and a capacitor C2; wherein the output end of A2 is connected to the first input end of the OR gate, the output end of A3 is connected to the second input end of the OR gate, the output end of the OR gate is connected to the CLK end of the D flip-flop, the data D input end of the D flip-flop is connected to the PWM control signal end, the output end of A4 is connected to the second input end of the OR gate, the output end of the OR gate is connected to the CLK end of the D flip-flop, the data D input end of the D flip-flop is connected to the PWM control signal end, the output end of A5 is connected to the second input end of the OR gate, the output end of A6 is connected to the CLK end of the D flip-flop, the data D input end of the D flip-flop is connected to the PWM control signal end, the output end of A7 is connected to the CLK end of The end is connected to the gate of the n-channel JFET field effect transistor, the source of the n-channel JFET field effect transistor is connected to the output end of AMP1, and the drain is grounded through C2.

2. The online monitoring system for junction temperature of a power device based on dynamic threshold voltage according to claim 1, characterized in that: The junction temperature calculation module includes a field programmable gate array FPGA.

3. The online monitoring system for junction temperature of a power device based on dynamic threshold voltage according to claim 1, characterized in that: The preset temperature is 25~175℃.

4. The online monitoring system for junction temperature of a power device based on dynamic threshold voltage according to claim 1, characterized in that: The power device to be tested is SiC MOSFET.

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