Device for monitoring igbt junction temperature

Abstract

The application discloses an IGBT junction temperature monitoring device, comprising: a collector-emitter voltage acquisition module, a filtering module, an AD conversion module and a controller, wherein the first output end and the second output end of the collector-emitter voltage acquisition module are electrically connected with the collector and the emitter of the IGBT to be measured one by one, the third output end of the collector-emitter voltage acquisition module is electrically connected with the input end of the filtering module, the output end of the filtering module is electrically connected with the input end of the AD conversion module, and the output end of the AD conversion module is electrically connected with the voltage input end of the controller; the collector-emitter voltage acquisition module is used for providing a constant current source, so that the IGBT to be measured and the constant current source form a loop, the voltage between the collector and the emitter of the IGBT to be measured in the loop is collected, and the controller determines the junction temperature of the IGBT to be measured according to the received voltage signal, the preset voltage threshold and the driving signal of the IGBT to be measured. The application obtains the junction temperature with relatively high accuracy, does not need to damage the packaging structure of the IGBT, and realizes real-time monitoring of the junction temperature of the IGBT.

Description

Technical Field

[0001] This invention belongs to the field of power electronic device testing technology, specifically relating to a monitoring device for IGBT junction temperature. Background Technology

[0002] As the core component of power electronic systems, the operational reliability of power semiconductor devices is directly related to the stability of the entire system, and junction temperature is a key indicator for evaluating the health status and lifespan of power devices.

[0003] Currently, methods for measuring junction temperature in power devices can be mainly categorized into four types: optical measurement, physical contact, thermal network modeling, and temperature-sensitive electrical parameter methods. While optical and physical contact methods can provide some temperature data, they often require damaging the physical packaging structure of the power device, failing to meet the non-destructive requirements for online junction temperature monitoring in actual power electronic equipment operation. The thermal network modeling method, recommended by device manufacturers for online prediction, uses a thermal impedance network provided in the datasheet combined with actual operating conditions to predict junction temperature fluctuations, calculating the internal temperature state of the power device without disassembling it. However, because thermal network model parameters are usually set based on worst-case operating conditions, and some parameters drift with device aging, the prediction accuracy decreases as the thermal network model makes predictions without parameter drift, and the calculated results often do not perfectly match the measured results. Although the temperature-sensitive electrical parameter method utilizes the sensitive relationship between the device's internal electrical parameters and temperature, offering advantages such as no need to change the packaging structure and fast response speed, it currently cannot achieve online measurement of the junction temperature of power devices.

[0004] Therefore, there is a need for an online measurement method for the junction temperature of power devices that has high measurement accuracy and does not damage the packaging structure of the power devices. Summary of the Invention

[0005] In view of this, the present invention provides an IGBT junction temperature monitoring device, the main purpose of which is to solve the problem that existing IGBT junction temperature monitoring devices cannot achieve online measurement with high accuracy and without damaging the packaging structure of power devices.

[0006] To address the aforementioned problems, this application provides an IGBT junction temperature monitoring device, comprising: a collector-emitter voltage acquisition module, a filtering module, an AD conversion module, and a controller, wherein... The first output terminal of the collector-emitter voltage acquisition module is electrically connected to the collector of the IGBT under test, the second output terminal of the collector-emitter voltage acquisition module is electrically connected to the emitter of the IGBT under test, the third output terminal of the collector-emitter voltage acquisition module is electrically connected to the input terminal of the filter module, the output terminal of the filter module is electrically connected to the input terminal of the AD conversion module, the output terminal of the AD conversion module is electrically connected to the voltage input terminal of the controller, and the drive signal input terminal of the controller is electrically connected to the drive signal providing terminal of the IGBT under test. The collector-emitter voltage acquisition module provides a constant current source, forming a loop between the IGBT under test and the constant current source. It acquires the voltage between the collector and emitter of the IGBT under test in the loop. The filtering module filters the voltage signal output by the collector-emitter voltage acquisition module. The AD conversion module converts the filtered signal from an analog signal to a digital signal and transmits it to the controller. The controller determines the junction temperature of the IGBT under test based on the received voltage signal, a preset voltage threshold, and the drive signal of the IGBT under test.

[0007] In one embodiment of the present invention, optionally, the collector-emitter voltage acquisition module includes a clamping circuit and an arithmetic circuit, wherein the first output terminal of the clamping circuit is electrically connected to the collector of the IGBT under test, the second output terminal of the clamping circuit is electrically connected to the emitter of the IGBT under test, the third output terminal of the clamping circuit is electrically connected to the input terminal of the arithmetic circuit, and the output terminal of the arithmetic circuit is electrically connected to the input terminal of the filtering module.

[0008] In one embodiment of the present invention, optionally, the clamping circuit includes a constant current source, a clamping unit, and a voltage-bearing unit, wherein the positive output terminal of the constant current source is electrically connected to the negative input terminal of the operational circuit and the input terminal of the voltage-bearing unit, respectively; the first output terminal of the voltage-bearing unit is electrically connected to the positive input terminal of the operational circuit and the first terminal of the clamping unit, respectively; the second output terminal of the voltage-bearing unit is electrically connected to the collector of the IGBT under test; and the second terminal of the clamping unit is electrically connected to the emitter of the IGBT under test and the negative output terminal of the constant current source, respectively.

[0009] In one embodiment of the present invention, optionally, the voltage-bearing unit includes a first voltage-bearing diode, a second voltage-bearing diode, and a third voltage-bearing diode, wherein the anode of the first voltage-bearing diode is electrically connected to the positive output terminal of the constant current source, the cathode of the first voltage-bearing diode is electrically connected to the anode of the third voltage-bearing diode, the input terminal of the clamping unit, and the positive input terminal of the operational circuit, the cathode of the third voltage-bearing diode is electrically connected to the anode of the second voltage-bearing diode, and the cathode of the second voltage-bearing diode is electrically connected to the collector of the IGBT under test.

[0010] In one embodiment of the present invention, optionally, when there are multiple third voltage-bearing diodes, the multiple third voltage-bearing diodes are cascaded, the anode of the first-stage third voltage-bearing diode is electrically connected to the cathode of the first voltage-bearing diode, the input terminal of the clamping unit and the positive input terminal of the operational circuit, and the cathode of the last-stage third voltage-bearing diode is electrically connected to the anode of the second voltage-bearing diode.

[0011] In one embodiment of the present invention, optionally, the clamping unit includes a first clamping diode and a second clamping diode, wherein the cathode of the first clamping diode is electrically connected to the cathode of the first voltage-bearing diode, the anode of the third voltage-bearing diode and the positive input terminal of the operational circuit, the anode of the first clamping diode is electrically connected to the anode of the second clamping diode, and the cathode of the second clamping diode is electrically connected to the emitter of the IGBT under test and the negative output terminal of the constant current source.

[0012] In one embodiment of the present invention, optionally, the operational circuit includes an operational amplifier, a first resistor, and a second resistor, wherein a first terminal of the first resistor is electrically connected to the positive output terminal of the constant current source and the positive terminal of the first voltage-bearing diode, a second terminal of the first resistor is electrically connected to the negative input terminal of the operational amplifier and the first terminal of the second resistor, a positive input terminal of the operational amplifier is electrically connected to the negative terminal of the third voltage-bearing diode and the negative terminal of the first clamping diode, and an output terminal of the operational amplifier is electrically connected to the input terminal of the filter module and the second terminal of the second resistor.

[0013] In one embodiment of the present invention, optionally, the filtering module includes an RC filter circuit and a voltage follower, the input terminal of the RC filter circuit is electrically connected to the output terminal of the operational circuit, the output terminal of the RC filter circuit is electrically connected to the positive input terminal of the voltage follower, and the output terminal of the voltage follower is electrically connected to the input terminal of the AD conversion module.

[0014] In one embodiment of the present invention, optionally, the controller is used to compare the acquired voltage. If the acquired voltage is less than a preset voltage threshold, the controller obtains the IGBT drive signal from the drive signal providing terminal of the IGBT under test, determines the IGBT's on-time and off-time based on the drive signal, takes the voltage acquired during the IGBT's on-time as the voltage between the IGBT's collector and emitter, searches for the IGBT junction temperature corresponding to the IGBT under test in a preset IGBT junction temperature-voltage relationship curve based on the voltage between the IGBT's collector and emitter, takes the voltage acquired during the IGBT's off-time as the voltage of the IGBT's freewheeling diode, and searches for the IGBT junction temperature corresponding to the freewheeling diode in a preset freewheeling diode junction temperature-voltage relationship curve based on the voltage of the freewheeling diode.

[0015] In one embodiment of the present invention, the controller is optionally configured to confirm that the IGBT under test is in a turned-off state if the collected voltage is much greater than a preset voltage threshold.

[0016] This invention provides an IGBT junction temperature monitoring device. The IGBT under test is connected in the main circuit, and the collector and emitter of the IGBT under test are respectively connected to the first and second output terminals of a collector-emitter voltage acquisition module. The collector-emitter voltage acquisition module provides a constant current source, so that the IGBT under test and the constant current source form a loop. The collector-emitter voltage acquisition module acquires the voltage between the collector and emitter of the IGBT under test in the loop, and transmits it to the controller through an AD conversion module. The controller obtains the drive signal of the IGBT under test from the drive signal providing module of the IGBT under test. Based on the drive signal of the IGBT under test and the voltage between the collector and emitter of the IGBT under test acquired by the AD conversion module, the junction temperature of the IGBT under test is determined, resulting in a junction temperature with relatively high accuracy. This does not require damage to the IGBT's packaging structure and enables real-time monitoring of the IGBT's junction temperature.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1This is a structural block diagram of an IGBT junction temperature monitoring device, which is an exemplary embodiment of the present invention.

[0019] Figure 2 This is a circuit connection diagram of the collector-emitter voltage acquisition module of an IGBT junction temperature monitoring device, which is an exemplary embodiment of the present invention.

[0020] Figure 3 This is a circuit connection diagram of an IGBT junction temperature monitoring device according to an exemplary embodiment of the present invention, when the IGBT under test is in the on-state.

[0021] Figure 4 This is a circuit connection diagram of an IGBT junction temperature monitoring device according to an exemplary embodiment of the present invention, when the IGBT under test is turned off.

[0022] Figure 5 This is a circuit connection diagram of an IGBT junction temperature monitoring device according to an exemplary embodiment of the present invention, when the IGBT under test is in diode freewheeling mode.

[0023] in, The following are the labels: 1-Collider voltage acquisition module; 2-Filtering module; 3-AD conversion module; 4-Controller; 5-Drive signal supply terminal for the IGBT under test; 11-Clamping circuit; 12-Operational circuit; 111-Voltage bearing unit; 112-Clamping unit; Q1-IGBT under test; Ia-Constant current source; Va-First voltage; Vb-Second voltage; D1-First voltage bearing diode; D2-Second voltage bearing diode; D3-First clamping diode; D4-Second clamping diode; D5-Third voltage bearing diode; Dn-Third voltage bearing diode; R1-First resistor; R2-Second resistor; U1-Operational amplifier. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0026] The following is combined with Figures 1 to 5 A device for monitoring IGBT junction temperature is described according to some embodiments of the present invention.

[0027] In one embodiment, such as Figure 1 As shown, an IGBT junction temperature monitoring device includes: a collector-emitter voltage acquisition module 1, a filter module 2, an AD conversion module 3, and a controller 4, wherein... The first output terminal of the collector-emitter voltage acquisition module 1 is electrically connected to the collector of the IGBT Q1 under test, the second output terminal of the collector-emitter voltage acquisition module 1 is electrically connected to the emitter of the IGBT Q1 under test, the third output terminal of the collector-emitter voltage acquisition module 1 is electrically connected to the input terminal of the filter module 2, the output terminal of the filter module 2 is electrically connected to the input terminal of the AD conversion module 3, the output terminal of the AD conversion module 3 is electrically connected to the voltage input terminal of the controller 4, and the drive signal input terminal of the controller 4 is electrically connected to the drive signal providing terminal of the IGBT Q1 under test. The collector-emitter voltage acquisition module 1 is used to provide a constant current source so that the IGBT Q1 under test forms a loop with the constant current source and acquires the voltage between the collector and emitter of the IGBT Q1 under test in the loop. The filter module 2 is used to filter the voltage signal output by the collector-emitter voltage acquisition module 1. The AD conversion module 3 is used to convert the filtered signal from an analog signal to a digital signal and transmit it to the controller 4. The controller 4 determines the junction temperature of the IGBT Q1 under test based on the received voltage signal, the preset voltage threshold and the drive signal of the IGBT Q1 under test.

[0028] Specifically, the IGBT under test is connected in the main circuit. The IGBT operates normally in the main circuit, and its collector and emitter each have connection ports. The first and second output terminals of the collector-emitter voltage acquisition module are connected to these connection ports, respectively. When the constant current source in the collector-emitter voltage acquisition module outputs a small current, the module and the IGBT form a loop. The collector-emitter voltage acquisition module acquires the voltage between the collector and emitter of the IGBT. The acquired voltage is then filtered by a filtering module to remove high-frequency noise and interference pulses, thus outputting a stable and clean voltage signal and improving monitoring accuracy.

[0029] The filtered signal is input to the AD conversion module, which converts the filtered signal from analog to digital and transmits it to the controller. The controller acquires the signal collected by the AD conversion module and obtains the drive signal of the IGBT under test from the drive signal provider terminal. Based on the drive signal, the controller determines the conduction time of the IGBT and determines the junction temperature corresponding to the voltage between the collector and emitter of the IGBT under test based on the conduction time.

[0030] Compared with the prior art, the IGBT junction temperature monitoring device provided in this application connects the IGBT under test to the main circuit. The collector and emitter of the IGBT under test are connected to the first and second output terminals of a collector-emitter voltage acquisition module, respectively. The collector-emitter voltage acquisition module provides a constant current source, forming a loop between the IGBT under test and the constant current source. The collector-emitter voltage acquisition module acquires the voltage between the collector and emitter of the IGBT under test in the loop, and transmits it to the controller through a filtering module and an AD conversion module. The controller obtains the drive signal of the IGBT under test from the drive signal providing module of the IGBT under test, and determines the junction temperature of the IGBT under test based on the drive signal and the voltage between the collector and emitter of the IGBT under test. This provides a junction temperature with relatively high accuracy, without damaging the IGBT's packaging structure, and achieves real-time monitoring of the IGBT's junction temperature.

[0031] In one embodiment, such as Figure 2 As shown, the collector-emitter voltage acquisition module includes a clamping circuit 11 and an arithmetic circuit 12. The first output terminal of the clamping circuit 11 is electrically connected to the collector of the IGBT Q1 under test, the second output terminal of the clamping circuit 11 is electrically connected to the emitter of the IGBT Q1 under test, the third output terminal of the clamping circuit 11 is electrically connected to the input terminal of the arithmetic circuit 12, and the output terminal of the arithmetic circuit 12 is electrically connected to the input terminal of the filter module 2.

[0032] Specifically, the two outputs of the clamping circuit are connected to the collector and emitter of the IGBT under test, respectively, to track and acquire the collector-emitter saturation voltage drop when the IGBT is turned on in real time. The clamping circuit transmits the collector-emitter saturation voltage drop signal when the IGBT is turned on to the arithmetic circuit through the third output. The arithmetic circuit amplifies the signal as necessary, converting it into a low-voltage analog signal suitable for back-end processing, so that subsequent circuits can process it.

[0033] When the IGBT is turned off, a high voltage will appear between the collector and emitter. At this time, the clamping circuit will clamp the high voltage to a stable value to prevent the high voltage surge from damaging the subsequent operation circuit, thus realizing the measurement of the collector-emitter voltage of the IGBT when it is turned on.

[0034] In one embodiment, such as Figure 2As shown, the clamping circuit 11 includes a constant current source Ia, a clamping unit 112, and a pressure bearing unit 111. The positive output terminal of the constant current source Ia is electrically connected to the negative input terminal of the operational circuit 12 and the input terminal of the pressure bearing unit 111, respectively. The first output terminal of the pressure bearing unit 111 is electrically connected to the positive input terminal of the operational circuit 12 and the first terminal of the clamping unit 112, respectively. The second output terminal of the pressure bearing unit 111 is electrically connected to the collector of the IGBT Q1 under test. The second terminal of the clamping unit 112 is electrically connected to the emitter of the IGBT Q1 under test and the negative output terminal of the constant current source Ia, respectively.

[0035] Specifically, the constant current source provides a stable bias current for the entire clamping circuit, ensuring the accuracy of signal extraction. The current from the constant current source flows through the voltage-bearing unit and the IGBT under test. When the IGBT under test is turned on, its collector-emitter voltage drop is extracted by the voltage-bearing unit and transmitted to the input terminal of the operational circuit. When the IGBT under test is turned off, the clamping unit clamps the collector-emitter voltage drop of the IGBT under test to a stable value to ensure that the voltage does not exceed the tolerance range of the operational circuit, thereby achieving safe and accurate collector-emitter voltage sampling.

[0036] In one embodiment, such as Figure 2 As shown, the voltage-bearing unit 111 includes a first voltage-bearing diode D1, a second voltage-bearing diode D2, and a third voltage-bearing diode D5. The anode of the first voltage-bearing diode D1 is electrically connected to the positive output terminal of the constant current source Ia. The cathode of the first voltage-bearing diode D1 is electrically connected to the anode of the third voltage-bearing diode D5, the input terminal of the clamping unit 112, and the positive input terminal of the operational circuit 12, respectively. The cathode of the third voltage-bearing diode D5 is electrically connected to the anode of the second voltage-bearing diode D2. The cathode of the second voltage-bearing diode D2 is electrically connected to the collector of the IGBT Q1 under test.

[0037] Specifically, the voltage-bearing diode is an ultra-fast recovery diode, and its impedance decreases as the conduction current increases. The first, second, and third voltage-bearing diodes are all high-voltage fast-switching diodes, and the clamping unit includes a Zener diode that performs the clamping function.

[0038] When the IGBT under test is in the ON state, taking advantage of the characteristic that the reverse resistance is very large and the leakage current is very small when the reverse voltage of the Zener diode is lower than the reverse breakdown voltage (its leakage current is in the μA range), the current flowing through the second and third Zener diodes can be approximately equal to the current flowing through the first Zener diode. Furthermore, since the conduction characteristics, external environment, and junction temperature of the first, second, and third Zener diodes are the same, then V... D1 =V D2 =……=V D5 At this time, the current flow direction of the monitoring circuit for the collector-emitter port electrical parameters of the IGBT under test is as follows: Figure 3 As shown.

[0039] When there is only one third voltage-bearing diode in the circuit, and the first resistor R1 is equal to the second resistor R2, then the output voltage V of the operational amplifier is... ce1-mea Approximately equal to the voltage drop V between the collector and emitter of the IGBT under test. ce1 Based on the principle that the current at the negative input node of an operational amplifier is equal, the following formula is obtained:

[0040]

[0041] Among them, V ce1-mea This is the output voltage of the operational amplifier. For example... Figure 3 As shown, V a The first voltage is the voltage at the positive output terminal of the constant current source, V. b The second voltage is the voltage at the positive input terminal of the operational circuit. Since the emitter of the IGBT under test is connected to the negative terminal of the constant current source, the voltage between the collector and emitter of the IGBT under test is equal to the collector voltage. The collector voltage is equal to the voltage at the positive input terminal of the operational circuit minus the voltages of the second and third voltage-bearing diodes. The voltage of the first voltage-bearing diode is the voltage V output from the positive terminal of the constant current source. a With the positive input terminal V of the operational amplifier b The difference, i.e., V D1 =V a -V b When only the first and second voltage-bearing diodes are present, and the third voltage-bearing diode is not present, the voltage between the collector and emitter of the IGBT under test is: ; Therefore, the voltage Vce1 between the collector and emitter of the IGBT under test is equal to the output voltage Vce1-mea of ​​the operational amplifier. Thus, by acquiring the output voltage of the operational amplifier, the voltage between the collector and emitter of the IGBT under test can be obtained.

[0042] In one embodiment, such as Figure 2 As shown, the clamping unit 112 includes a first clamping diode D3 and a second clamping diode D4. The cathode of the first clamping diode D3 is electrically connected to the cathode of the first voltage-bearing diode D1, the anode of the third voltage-bearing diode D5, and the positive input terminal of the operational circuit 12, respectively. The anode of the first clamping diode D3 is electrically connected to the anode of the second clamping diode D4, and the cathode of the second clamping diode D4 is electrically connected to the emitter of the IGBT Q1 under test and the negative output terminal of the constant current source Ia, respectively.

[0043] Specifically, the first clamping diode and the second clamping diode are Zener diodes. When the reverse voltage applied across the Zener diode reaches its nominal Zener voltage, the diode will undergo controllable reverse breakdown. At this time, even if the current flowing through it changes significantly, the voltage across it remains almost unchanged and stabilizes at a certain value.

[0044] When the IGBT under test is in the off state, the second voltage-bearing diode and the second clamping diode isolate the main circuit voltage, preventing main circuit current from flowing into the monitoring circuit. The first clamping diode and the second clamping diode implement the voltage regulation clamping function. The first clamping diode and the second clamping diode clamp the voltage at the non-inverting input terminal of the operational amplifier to a stable value, thus achieving the voltage regulation clamping function. The current from the constant current source forms a closed loop through the first voltage-bearing diode, the first clamping diode, the second clamping diode, and the constant current source. The current flow direction of the monitoring circuit for the collector-emitter port electrical parameters of the IGBT under test is as follows: Figure 4 As shown.

[0045] The first clamping diode and the second clamping diode will clamp the voltage V at the non-inverting input of the operational amplifier. b The diode is clamped to a stable value to prevent interference from the turn-off voltage within its withstand voltage range, and is determined by the following formula:

[0046]

[0047]

[0048]

[0049] Among them, V z1 V is the voltage of the first clamping diode. z2 This is the voltage of the second clamping diode. V a V b Substitute V ce1-mea The formula is obtained. ,and Therefore, the output voltage is clamped to a stable value: .

[0050] The Zener diode can regulate voltages of 3V, 5V, 6V, etc. Therefore, when the IGBT under test is in the off state, the voltage between the collector and the transmitter is relatively large, and the AD conversion module collects a relatively large voltage value. The controller determines whether the IGBT under test is in the off state or the on state based on the comparison between the voltage value and the preset voltage threshold.

[0051] In one embodiment, when the IGBT under test is in reverse diode freewheeling mode, the measurement circuit current flows from the current source through the first voltage-bearing diode, the second voltage-bearing diode, and the equivalent inductance of other IGBTs in the main circuit, and then back to the current source to form a closed loop. At this time, the voltage V between the collector and emitter of the IGBT under test is... ce1 The value is negative, representing the voltage drop V across the diode connected in reverse parallel to the IGBT under test. f The current flow direction of the monitoring circuit for the collector-emitter port electrical parameters of the IGBT under test is as follows: Figure 5 As shown.

[0052] V a - V b = V b - (- V f )

[0053] get: V f =- V f_mea。

[0054] Among them, V f-mea The output voltage of the operational amplifier is given. When the IGBT under test is in diode freewheeling mode, the junction temperature of the freewheeling diode is analyzed.

[0055] In one embodiment, when there are multiple third voltage-bearing diodes, the multiple third voltage-bearing diodes are cascaded. The anode of the first-stage third voltage-bearing diode is electrically connected to the cathode of the first voltage-bearing diode, the input terminal of the clamping unit, and the positive input terminal of the operational circuit. The cathode of the last-stage third voltage-bearing diode is electrically connected to the anode of the second voltage-bearing diode.

[0056] Specifically, when there are multiple third voltage-bearing diodes, except for the first and last third voltage-bearing diodes, the anode of each third voltage-bearing diode is connected to the cathode of the preceding third voltage-bearing diode, the anode of the first third voltage-bearing diode is connected to the cathode of the first voltage-bearing diode, and the cathode of the last third voltage-bearing diode is connected to the anode of the second voltage-bearing diode. The number of third voltage-bearing diodes used is set as needed. Accordingly, when using n third voltage-bearing diodes, the resistance value of the second resistor connected to the operational amplifier is n times the resistance value of the first resistor.

[0057] When there are n third voltage-bearing diodes, R1 = R2 / n is set so that the output voltage V of the operational amplifier is... ce1-mea Approximately equal to the voltage drop V across the collector-emitter terminals of the IGBT under test.ce1 : ; The output voltage V of the operational amplifier ce1-mea :

[0058] ; Therefore, when there are n third voltage-bearing diodes, and R1 = R2 / n is set, the output voltage Vce1-mea of ​​the operational amplifier is approximately equal to the voltage drop Vce1 across the collector-emitter terminals of the IGBT under test.

[0059] In one embodiment, such as Figure 2 As shown, the operational circuit 12 includes an operational amplifier U1, a first resistor R1, and a second resistor R2. The first end of the first resistor R1 is electrically connected to the positive output terminal of the constant current source Ia and the positive terminal of the first voltage-bearing diode D1, respectively. The second end of the first resistor R1 is electrically connected to the negative input terminal of the operational amplifier U1 and the first end of the second resistor R2, respectively. The positive input terminal of the operational amplifier U1 is electrically connected to the negative terminal of the third voltage-bearing diode D5 and the negative terminal of the first clamping diode D3, respectively. The output terminal of the operational amplifier U1 is electrically connected to the input terminal of the filter module 2 and the second end of the second resistor R2, respectively.

[0060] Specifically, the operational circuit includes an operational amplifier, a first resistor, and a second resistor. The positive input terminal of the operational amplifier is connected to the cathode of the third voltage-bearing diode and the cathode of the first clamping diode. The negative input terminal of the operational amplifier is connected to the anode of the first voltage-bearing diode through the first resistor. Simultaneously, the output terminal of the operational amplifier is connected to the negative input terminal through the second resistor. The voltage between the collector and emitter of the IGBT under test is amplified and output as a clean, usable voltage signal.

[0061] In a real-time example, such as Figure 2 As shown, the filter module 2 includes an RC filter circuit and a voltage follower. The input terminal of the RC filter circuit is electrically connected to the output terminal of the operational amplifier, the output terminal of the RC filter circuit is electrically connected to the positive input terminal of the voltage follower, and the output terminal of the voltage follower is electrically connected to the input terminal of the AD conversion module.

[0062] Specifically, the filter circuit uses a first-order active filter circuit, including an RC filter and a voltage follower. The RC filter is composed of a series resistor and a parallel capacitor. The RC filter is connected to the positive input terminal of the voltage follower, and the output terminal of the voltage follower is connected to the negative input terminal.

[0063] A first-order active low-pass filter is a signal conditioning circuit that combines a passive RC network with an operational amplifier. As the simplest filter circuit, its core function is to allow low-frequency signals to pass through while suppressing high-frequency interference. Compared to passive filters, active filter circuits, by introducing operational amplifiers, can achieve signal gain, improve input and output impedance characteristics, and avoid signal amplitude attenuation, making them particularly suitable for weak signal processing and high-precision systems.

[0064] In one embodiment, the controller compares the acquired voltage. If the acquired voltage is less than a preset voltage threshold, it obtains the IGBT drive signal from the drive signal provider of the IGBT under test, determines the IGBT's on-time and off-time based on the drive signal, uses the voltage acquired during the IGBT's on-time as the voltage between the IGBT's collector and emitter, and searches for the corresponding IGBT junction temperature in a preset IGBT junction temperature-voltage relationship curve based on the voltage between the IGBT's collector and emitter. The controller also uses the voltage acquired during the IGBT's off-time as the voltage of the IGBT's freewheeling diode, and searches for the corresponding IGBT junction temperature in a preset freewheeling diode junction temperature-voltage relationship curve based on the voltage of the freewheeling diode.

[0065] Specifically, the controller monitors the voltage signal acquired by the AD conversion module in real time. This voltage is equal to the voltage between the collector and emitter of the IGBT under test. The IGBT under test exists in both on and off states. When the IGBT under test is in the off state, the acquired voltage value is relatively large. Therefore, when the acquired voltage is greater than the preset voltage threshold, the IGBT under test is determined to be in the off state. Since the IGBT under test is connected in parallel with a freewheeling diode, when the IGBT under test is in the off state, the first voltage-bearing diode, the second voltage-bearing diode, the third voltage-bearing diode, the constant current source, and the equivalent inductance of other IGBTs in the main circuit form a loop. The voltage across the freewheeling diode is equal to the voltage acquired by the collector-emitter voltage acquisition module. When the acquired voltage is less than the preset voltage threshold, the controller obtains the drive signal from the drive signal provider of the IGBT under test. Based on the drive signal, it determines whether the time of voltage acquisition is the IGBT's turn-off or turn-on moment. When the acquired voltage is less than the preset voltage threshold and the IGBT is in the turn-on state, the acquired voltage is the voltage between the collector and emitter of the IGBT. Based on the voltage between the collector and emitter of the IGBT, the controller finds the junction temperature of the IGBT at that voltage from the preset IGBT junction temperature-voltage relationship curve. When the acquired voltage is less than the preset voltage threshold and the IGBT is in the turn-off state, the acquired voltage is the voltage of the freewheeling diode. Based on the voltage of the freewheeling diode, the controller finds the junction temperature of the freewheeling diode at that voltage value from the preset freewheeling diode junction temperature-voltage relationship curve.

[0066] It should be understood that various modifications can be made to the embodiments described herein. Therefore, the above description should not be considered as limiting, but merely as an example of embodiments. Other modifications within the scope and spirit of this application will be apparent to those skilled in the art.

[0067] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the present application and, together with the general description of the present application given above and the detailed description of the embodiments given below, serve to explain the principles of the present application.

[0068] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0069] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application.

[0070] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0071] Specific embodiments of this application are described thereafter with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that could obscure the application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in a variety of substantially any suitable detailed structures.

[0072] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0073] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A device for monitoring the junction temperature of an IGBT, characterized in that, include: The system includes an emitter voltage acquisition module, a filtering module, an AD conversion module, and a controller. The first output terminal of the collector-emitter voltage acquisition module is electrically connected to the collector of the IGBT under test, the second output terminal of the collector-emitter voltage acquisition module is electrically connected to the emitter of the IGBT under test, the third output terminal of the collector-emitter voltage acquisition module is electrically connected to the input terminal of the filter module, the output terminal of the filter module is electrically connected to the input terminal of the AD conversion module, the output terminal of the AD conversion module is electrically connected to the voltage input terminal of the controller, and the drive signal input terminal of the controller is electrically connected to the drive signal providing terminal of the IGBT under test. The collector-emitter voltage acquisition module provides a constant current source, forming a loop between the IGBT under test and the constant current source. It acquires the voltage between the collector and emitter of the IGBT under test in the loop. The filtering module filters the voltage signal output by the collector-emitter voltage acquisition module. The AD conversion module converts the filtered signal from an analog signal to a digital signal and transmits it to the controller. The controller determines the junction temperature of the IGBT under test based on the received voltage signal, a preset voltage threshold, and the drive signal of the IGBT under test.

2. The IGBT junction temperature monitoring device according to claim 1, characterized in that, The collector-emitter voltage acquisition module includes a clamping circuit and a processing circuit. The first output terminal of the clamping circuit is electrically connected to the collector of the IGBT under test, the second output terminal of the clamping circuit is electrically connected to the emitter of the IGBT under test, the third output terminal of the clamping circuit is electrically connected to the input terminal of the processing circuit, and the output terminal of the processing circuit is electrically connected to the input terminal of the filtering module.

3. The IGBT junction temperature monitoring device according to claim 2, characterized in that, The clamping circuit includes a constant current source, a clamping unit, and a voltage-bearing unit. The positive output terminal of the constant current source is electrically connected to the negative input terminal of the operational circuit and the input terminal of the voltage-bearing unit. The first output terminal of the voltage-bearing unit is electrically connected to the positive input terminal of the operational circuit and the first terminal of the clamping unit. The second output terminal of the voltage-bearing unit is electrically connected to the collector of the IGBT under test. The second terminal of the clamping unit is electrically connected to the emitter of the IGBT under test and the negative output terminal of the constant current source.

4. The IGBT junction temperature monitoring device according to claim 3, characterized in that, The voltage-bearing unit includes a first voltage-bearing diode, a second voltage-bearing diode, and a third voltage-bearing diode. The anode of the first voltage-bearing diode is electrically connected to the positive output terminal of the constant current source. The cathode of the first voltage-bearing diode is electrically connected to the anode of the third voltage-bearing diode, the input terminal of the clamping unit, and the positive input terminal of the operational circuit. The cathode of the third voltage-bearing diode is electrically connected to the anode of the second voltage-bearing diode. The cathode of the second voltage-bearing diode is electrically connected to the collector of the IGBT under test.

5. The IGBT junction temperature monitoring device according to claim 4, characterized in that, When there are multiple third voltage-bearing diodes, the multiple third voltage-bearing diodes are cascaded. The anode of the first-stage third voltage-bearing diode is electrically connected to the cathode of the first voltage-bearing diode, the input terminal of the clamping unit, and the positive input terminal of the operational circuit. The cathode of the last-stage third voltage-bearing diode is electrically connected to the anode of the second voltage-bearing diode.

6. The IGBT junction temperature monitoring device according to claim 4, characterized in that, The clamping unit includes a first clamping diode and a second clamping diode. The cathode of the first clamping diode is electrically connected to the cathode of the first voltage-bearing diode, the anode of the third voltage-bearing diode, and the positive input terminal of the operational circuit. The anode of the first clamping diode is electrically connected to the anode of the second clamping diode. The cathode of the second clamping diode is electrically connected to the emitter of the IGBT under test and the negative output terminal of the constant current source.

7. The IGBT junction temperature monitoring device according to claim 6, characterized in that, The operational circuit includes an operational amplifier, a first resistor, and a second resistor. The first terminal of the first resistor is electrically connected to the positive output terminal of the constant current source and the positive terminal of the first voltage-bearing diode. The second terminal of the first resistor is electrically connected to the negative input terminal of the operational amplifier and the first terminal of the second resistor. The positive input terminal of the operational amplifier is electrically connected to the negative terminal of the third voltage-bearing diode and the negative terminal of the first clamping diode. The output terminal of the operational amplifier is electrically connected to the input terminal of the filter module and the second terminal of the second resistor.

8. The IGBT junction temperature monitoring device according to claim 2, characterized in that, The filtering module includes an RC filter circuit and a voltage follower. The input terminal of the RC filter circuit is electrically connected to the output terminal of the operational circuit, the output terminal of the RC filter circuit is electrically connected to the positive input terminal of the voltage follower, and the output terminal of the voltage follower is electrically connected to the input terminal of the AD conversion module.

9. The IGBT junction temperature monitoring device according to any one of claims 1-8, characterized in that, The controller is used to compare the acquired voltage. If the acquired voltage is less than a preset voltage threshold, the controller obtains the IGBT drive signal from the drive signal provider of the IGBT under test. Based on the drive signal, the controller determines the IGBT's on-time and off-time. The voltage acquired during the IGBT's on-time is taken as the voltage between the IGBT's collector and emitter. Based on the voltage between the IGBT's collector and emitter, the controller searches for the IGBT junction temperature corresponding to the IGBT under test in a preset IGBT junction temperature versus voltage relationship curve. The voltage acquired during the IGBT's off-time is taken as the voltage of the IGBT's freewheeling diode. Based on the voltage of the freewheeling diode, the controller searches for the IGBT junction temperature corresponding to the freewheeling diode in a preset freewheeling diode junction temperature versus voltage relationship curve.

10. The IGBT junction temperature monitoring device according to claim 9, characterized in that, The controller is also used to confirm that the IGBT under test is in a turned-off state if the collected voltage is much greater than a preset voltage threshold.

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