IGBT junction temperature on-line monitoring circuit system based on grid peak current

Abstract

The invention discloses an IGBT junction temperature on-line monitoring circuit system based on grid peak current, and the system comprises an IGBT grid driver which is used for controlling a to-be-detected IGBT to charge and discharge; the grid signal processing circuit is used for converting the grid peak current of the IGBT to be detected into a narrow pulse voltage signal, performing amplitude processing on the narrow pulse voltage signal, and outputting the narrow pulse voltage signal after the amplitude processing; the two-stage narrow pulse peak holding circuit is used for holding the narrow pulse voltage signal after amplitude processing; and the acquisition and processing circuit is used for acquiring the signal output by the two-stage narrow pulse peak holding circuit to obtain an acquisition voltage, acquiring the frequency of the driving input signal, selecting a junction temperature calibration formula according to the acquired frequency, and calculating the junction temperature of the IGBT to be measured according to the acquisition voltage and the selected junction temperature calibration formula. The junction temperature monitoring circuit is high in monitoring precision, simple in circuit structure and few in influence factors during junction temperature monitoring.

Description

Technical Field

[0001] The invention belongs to the technical field of power device state monitoring, and in particular relates to an IGBT junction temperature online monitoring circuit system based on gate peak current. Background Art

[0002] Insulated-Gate Bipolar Transistor (IGBT) has become an indispensable and important component in modern power electronic equipment due to its high efficiency, high withstand voltage and good thermal stability. Its wide range of application backgrounds covers many fields such as industry, renewable energy, power transmission and electric transportation, which has promoted the continuous innovation and development of power electronic technology. Online monitoring of junction temperature can provide necessary data support for power electronic systems, realize IGBT health status assessment, early warning of potential failures, and reduce sudden downtime. It can not only improve the safety and reliability of equipment, but also help to extend its service life and improve operating efficiency. Traditionally, the junction temperature is estimated by using an electrothermal model combined with analytical calculations from a data sheet.

[0003] However, these techniques are often prone to errors and have difficulty in reliably measuring junction temperature during converter operation. Physical measurement methods such as infrared cameras or optical fibers are extremely limited and difficult to directly measure chip junction temperature. Therefore, electrical methods are considered to be beneficial for real-time measurement of power electronic device junction temperature. Using Temperature Sensitive Electrical Parameters (TSEP), such as on-state voltage drop or threshold voltage, online monitoring of junction temperature can be achieved on standard power modules without modifying their structure. However, electrical temperature measurement in power electronic converters using TSEP has not been well developed. Issues worth noting about the use of TSEP include the need to compensate for operating conditions other than temperature (such as load current), and the need for complex measurement circuits.

[0004] In other words, the existing IGBT junction temperature online monitoring technology has low monitoring accuracy, complex measurement circuits, and many influencing factors. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides an IGBT junction temperature online monitoring circuit system based on gate peak current.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solutions: The present invention provides an IGBT junction temperature online monitoring circuit system based on gate peak current, comprising: an IGBT gate driver, a gate signal processing circuit, a two-stage narrow pulse peak holding circuit and a collection and processing circuit; The IGBT gate driver is connected to the output end of the driving input signal, the gate signal processing circuit and the IGBT to be tested respectively, the output end of the driving input signal is used to output the driving input signal, and the IGBT gate driver is used to provide driving capability for the IGBT to be tested, so as to control the IGBT to be tested to charge and discharge; The gate signal processing circuit is also connected to the two-stage narrow pulse peak holding circuit, and is used to convert the gate peak current of the IGBT to be tested into a narrow pulse voltage signal, perform amplitude processing, and output the amplitude processed narrow pulse voltage signal; The two-stage narrow pulse peak holding circuit is also connected to the IGBT to be tested and the acquisition and processing circuit respectively, wherein the two-stage narrow pulse peak holding circuit includes a triode, and the two-stage narrow pulse peak holding circuit is used to hold the narrow pulse voltage signal after the amplitude processing; The acquisition and processing circuit is also connected to the output end of the drive input signal, and is used to acquire the signal output by the two-stage narrow pulse peak holding circuit to obtain an acquisition voltage, and to acquire the frequency of the drive input signal, and select a junction temperature calibration formula according to the acquired frequency, and calculate the junction temperature of the IGBT to be tested according to the acquisition voltage and the selected junction temperature calibration formula.

[0007] Compared with the prior art, the present invention has the following beneficial effects: The IGBT junction temperature online monitoring circuit system based on gate peak current provided by the present invention is integrated with an IGBT gate driver, drives the IGBT to be tested to charge and discharge through the IGBT gate driver, converts the gate peak current of the IGBT to be tested into a narrow pulse voltage signal through a gate signal processing circuit, converts the narrow pulse voltage signal into a square wave signal through a two-stage narrow pulse peak holding circuit including a triode, performs voltage acquisition and frequency measurement of the driving input signal through an acquisition and processing circuit, selects a corresponding junction temperature calibration formula according to the measured frequency, converts the acquired voltage value into the junction temperature of the IGBT to be tested through the junction temperature calibration formula, realizes the measurement of the IGBT to be tested, simplifies the circuit structure, and, since only the voltage and frequency need to be acquired, the influencing factors during junction temperature monitoring are reduced; in addition, since the two-stage narrow pulse peak holding circuit includes a triode, the charging current inside the two-stage narrow pulse peak holding circuit can be greatly increased, thereby increasing the bandwidth of the two-stage narrow pulse peak holding circuit, improving the holding accuracy of the two-stage narrow pulse peak holding circuit, and further improving the acquired voltage accuracy, and finally improving the accuracy of junction temperature measurement. In summary, the IGBT junction temperature online monitoring circuit system based on gate peak current provided by the present invention has high monitoring accuracy, simple circuit structure, and few influencing factors during junction temperature monitoring.

[0008] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a structural schematic diagram of an IGBT junction temperature online monitoring circuit system based on gate peak current provided by an embodiment of the present invention; Figure 2 It is a circuit connection diagram of an IGBT junction temperature online monitoring circuit system based on gate peak current provided by an embodiment of the present invention; Figure 3 is a schematic diagram of an RLC second-order network obtained by mathematically modeling a gate loop of an IGBT to be tested provided by an embodiment of the present invention; Figure 4 is a circuit structure diagram of a gate signal processing circuit provided by an embodiment of the present invention; Figure 5 The invention is a schematic diagram of a circuit structure of a two-stage narrow pulse peak holding circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0010] 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.

[0011] The embodiment of the present invention provides an IGBT junction temperature online monitoring circuit system based on gate peak current, such as Figure 1 As shown, the circuit system includes: an IGBT gate driver, a gate signal processing circuit, a two-stage narrow pulse peak holding circuit and an acquisition and processing circuit. The IGBT gate driver is respectively connected to the output end of the drive input signal, the gate signal processing circuit and the IGBT to be tested, the output end of the drive input signal is used to output the drive input signal PWM, and the IGBT gate driver is used to provide driving capability for the IGBT to be tested to control the IGBT to be tested to charge and discharge. The gate signal processing circuit is also connected to the two-stage narrow pulse peak holding circuit, the gate signal processing circuit is used to convert the gate peak current of the IGBT to be tested into a narrow pulse voltage signal and then perform amplitude processing, and output the narrow pulse voltage signal after amplitude processing. The two-stage narrow pulse peak holding circuit is also respectively connected to the IGBT to be tested and the acquisition and processing circuit, wherein the two-stage narrow pulse peak holding circuit includes a triode, and the two-stage narrow pulse peak holding circuit is used to hold the narrow pulse voltage signal after amplitude processing. The acquisition and processing circuit is also connected to the output end of the driving input signal. The acquisition and processing circuit is used to acquire the signal output by the two-stage narrow pulse peak holding circuit to obtain the acquisition voltage, and the frequency of the acquisition driving input signal. The junction temperature calibration formula is selected according to the acquired frequency, and the junction temperature of the IGBT to be tested is calculated according to the acquisition voltage and the selected junction temperature calibration formula.

[0012] Here, the junction temperature calibration formula corresponding to the driving input signal PWM of different frequencies can be obtained by theoretically measuring the junction temperature of the IGBT and curve fitting. The present invention does not limit the specific frequency of the driving input signal PWM and the specific junction temperature calibration formula.

[0013] Figure 2 FIG. 1 is a circuit connection diagram of an IGBT junction temperature online monitoring circuit system based on gate peak current provided by the present invention. For example, Figure 2 As shown, the IGBT gate driver may include a gate driver chip and an external gate resistor. The input end of the gate driver chip is connected to the output end of the drive input signal PWM, and the output end of the gate driver chip is also connected to the external gate resistor One end of the gate signal processing circuit is connected to the first input end of the external gate resistor The other end is connected to the second input end of the gate signal processing circuit and the gate G of the IGBT to be tested.

[0014] Here, after the gate driver chip receives the PWM signal, it outputs high and low levels to the IGBT to be tested, so that the gate-emitter parasitic capacitance of the IGBT to be tested The charge and discharge are performed to control the on and off of the IGBT to be tested. At the moment when the gate drive chip switches the level, the charge and discharge current of the IGBT to be tested reaches the maximum value.

[0015] Figure 3 The figure is a schematic diagram of an RLC second-order network obtained by mathematically modeling the gate loop of the IGBT to be tested, where R in RLC represents resistance, L represents inductance, and C represents capacitance. Figure 3 As shown, is the external gate resistor, is the gate internal resistance of the IGBT to be tested, is the gate parasitic inductance, is the gate-emitter parasitic capacitance, is the gate voltage, Gate Driver is the IGBT gate driver. Then the gate peak current of the IGBT to be measured is It can be expressed as the following formula: ; ; ; By detecting the external gate resistance of the IGBT under test during turn-on or turn-off The peak voltage on both sides is proportional to the gate peak current, that is, the gate peak current of the IGBT to be tested can be measured. Therefore, by monitoring the change of the gate peak current of the IGBT to be tested in real time, the change of the junction temperature of the IGBT to be tested can be obtained.

[0016] In some embodiments, the gate signal processing circuit includes: a voltage follower and a differential amplifier circuit. The first input terminal of the voltage follower is connected to the external gate resistor The second input terminal of the voltage follower is connected to the external gate resistor The other end of the voltage follower is used to collect the external gate resistance The first input terminal of the differential amplifier circuit is connected to the first output terminal of the voltage follower, the second input terminal of the differential amplifier circuit is connected to the second output terminal of the voltage follower, and the output terminal of the differential amplifier circuit is connected to the two-stage narrow pulse peak holding circuit. The differential amplifier circuit is used to connect the external gate resistor The differential voltage on both sides is converted into a single-ended output and a negative bias voltage is added to obtain a narrow pulse voltage signal after amplitude processing and output.

[0017] For example, Figure 4 A circuit structure diagram of a gate signal processing circuit.

[0018] like Figure 4 As shown, the voltage follower includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, an operational amplifier U1 and an operational amplifier U2, wherein one end of R1 is simultaneously connected to one end of the external gate resistor and one end of R4, the other end of R4 is grounded, the other end of R1 is connected to the positive input end of U1, the negative input end of U1 is connected to the output end of U1, and the output end of U1 serves as the first output end of the voltage follower, one end of R2 is connected to the other end of the external gate resistor The other end of R2 is connected to one end of R3 and the positive input end of U2 at the same time, the other end of R3 is grounded, the negative input end of U2 is connected to the output end of U2, and the output end of U2 serves as the second output end of the voltage follower.

[0019] Continue to refer to the above Figure 4The differential amplifier circuit includes: a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, an operational amplifier U3 and an operational amplifier U4, wherein one end of R5 is connected to the output end of U1 as the first input end of the differential amplifier circuit, the other end of R5 is simultaneously connected to one end of R8 and the negative input end of U3, and the other end of R8 is connected to the output end of U3; one end of R6 is connected to the output end of U2 as the second input end of the differential amplifier circuit, the other end of R6 is simultaneously connected to one end of R7 and the positive input end of U3, and the other end of R7 is grounded; one end of R9 is connected to the output end of U3, the other end of R9 is simultaneously connected to one end of R10 and the positive input end of U4, the other end of R10 is grounded, the negative input end of U4 is simultaneously connected to the reference voltage output end, one end of R11 and one end of R12, and the reference voltage output end is used to output a reference voltage V REF , the other end of R11 is grounded, the other end of R12 is connected to the output end of U4, and the output end of U4 serves as the output end of the differential amplifier circuit, and is used to output the narrow pulse voltage signal after amplitude processing.

[0020] Here, the gate common-mode voltage of the IGBT is very high. Therefore, the present invention first divides the gate common-mode voltage of the IGBT through a voltage follower, which can avoid the influence of the high common-mode voltage of the gate loop and improve the input impedance of the circuit. Thereafter, the processed two-ended signal is converted into a single-ended signal through a differential amplifier circuit and negatively biased. This facilitates the subsequent two-stage narrow pulse peak holding circuit to perform signal processing.

[0021] In some embodiments, the two-stage narrow pulse peak holding circuit includes: a discharge signal generating circuit, a primary circuit and a secondary circuit. The input end of the discharge signal generating circuit is connected to the gate of the IGBT to be tested, and the output end of the discharge signal generating circuit is connected to both the discharge signal input end of the primary circuit and the discharge signal input end of the secondary circuit. The discharge signal generating circuit is used to convert the gate emitter square wave voltage signal of the IGBT to be tested into a narrow pulse width square wave signal, and output the narrow pulse width square wave signal as a discharge signal. The input end of the primary circuit is connected to the output end of the gate signal processing circuit, and the output end of the primary circuit is connected to the input end of the secondary circuit. The primary circuit is used to capture the input amplitude-processed narrow pulse voltage signal, and output the captured amplitude-processed narrow pulse voltage signal to the secondary circuit. The output end of the secondary circuit is connected to the acquisition and processing circuit, and the secondary circuit is used to hold the amplitude-processed narrow pulse voltage signal output by the primary circuit.

[0022] Here, the primary circuit is used to capture the narrow pulse signal after the input amplitude processing. The secondary circuit is similar to the primary circuit in composition. The secondary circuit is used to maintain the pulse signal output by the primary circuit for a long time to facilitate the subsequent acquisition and processing circuit to collect it. The discharge signal generating circuit is used to perform resistance division on the gate-emitter voltage of the IGBT to be tested, and then generate a discharge signal through a differential circuit to keep the capacitors in the primary circuit and the secondary circuit discharged.

[0023] For example, Figure 5 The figure is a circuit structure diagram of a two-stage narrow pulse peak holding circuit.

[0024] like Figure 5 As shown, the primary circuit includes: an operational amplifier U5, an operational amplifier U6, a resistor R13, a resistor R14, a resistor R15, a capacitor C1, a first analog switch S1, a transistor Q1 and a transistor Q2, wherein the positive input end of U5 is used as the input end of the primary circuit, the negative input end of U5 is connected to one end of R13 and the emitter of Q1 at the same time, the other end of R13 is used to access the power supply voltage VEE, the output end of U5 is connected to the base of Q1, the collector of Q1 is connected to one end of R14, and the other end of R14 is used to access the voltage VEE. source voltage VCC; the output end of U5 is also connected to the base of Q2, the collector of Q2 is connected to one end of R15, the other end of R15 is used to access the power supply voltage VCC, the emitter of Q2 is simultaneously connected to one end of C1, the first end of S1 and the positive input end of U6, the other end of C1 and the second end of S1 are both grounded, the control end of S1 is the discharge signal input end of the primary circuit, the discharge signal input end is used to access the discharge signal, the negative input end of U6 is connected to the output end of U6, and the output end of U6 serves as the output end of the primary circuit.

[0025] Continue to refer to the above Figure 5The secondary circuit includes: an operational amplifier U7, an operational amplifier U8, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a capacitor C2, a second analog switch S2, a transistor Q3 and a transistor Q4, wherein the positive input terminal of U7 serves as the input terminal of the secondary circuit. The negative input terminal of U7 is connected to one end of R16 and the emitter of Q3 at the same time, and the other end of R16 is used to access the power supply voltage VEE. The output terminal of U7 is connected to the base of Q3, and the collector of Q3 is connected to one end of R17, and the other end of R17 is used to access the power supply voltage VCC. The output terminal of U7 is also connected to the base of Q4, and the collector of Q4 is connected to one end of R18, and the other end of R18 is used to access the power supply voltage VCC. The emitter of Q4 is connected to one end of C2, the first end of S2 and the positive input terminal of U8 at the same time, and the other end of C2 and the second end of S2 are both grounded. The control end of S2 is the discharge signal input terminal of the secondary circuit, and the discharge signal input terminal is used to access the discharge signal. The negative input terminal of U8 is connected to one end of R19 and one end of R20 at the same time, and the other end of R19 is grounded. The other end of R20 is connected to the output terminal of U8, and the output terminal of U8 serves as the output terminal of the secondary circuit.

[0026] Continue to refer to the above Figure 5 The discharge signal generating circuit includes: a resistor R21, a resistor R22, a resistor R23, a diode D1, a diode D2 and a capacitor C3, wherein one end of R21 is connected to one end of R22 and one end of C3 at the same time, the other end of R21 is connected to the gate G of the IGBT to be tested, the other end of R22 is grounded, the other end of C3 is connected to one end of R23, the positive electrode of D1 and the negative electrode of D2 at the same time, the other end of R23 is grounded, the negative electrode of D1 is used to access the power supply voltage VCC, the positive electrode of D2 is grounded, wherein the positive electrode of D1 and the negative electrode of D2 are connected and also serve as the output end of the discharge signal generating circuit to output the discharge signal.

[0027] Continue to refer to the above Figure 5 When the voltage of the signal input to the positive input terminal of U5 rises, Q2 is turned on, and the two-stage narrow pulse peak holding circuit charges the holding capacitor C1 through Q2, and the voltage of C1 is charged to the peak voltage V peak. Q1 is used to compensate for the base-emitter voltage drop of Q2. The two-stage narrow pulse peak holding circuit uses a bipolar junction transistor (BJT, also known as a triode) to replace the diode of the traditional peak holding circuit, which greatly increases the capacitor charging current, increases the bandwidth of the peak holding circuit, and reduces the cost of the high-bandwidth, high-precision peak holding circuit. In this circuit, the capacitance of C1 is small, and C1 is used to capture narrow pulse signals. The capacitance of C2 is large, and C2 is used to hold the signal captured by the first-level circuit. In this circuit, the discharge signal generating circuit specifically converts the gate emitter square wave voltage signal (i.e., gate-emitter square wave voltage signal) of the IGBT to be tested into a narrow pulse width square wave signal (i.e., discharge signal) through a passive differential circuit composed of C3 and R23, thereby obtaining a control signal for maintaining the discharge of capacitors C1 and C2, greatly simplifying the generation of the discharge signal in the peak holding circuit and providing precise timing control.

[0028] Continue to refer to the above Figure 2 , the acquisition and processing circuit includes: an analog-to-digital converter (ADC), a digital isolator and a processor. The ADC is connected to the two-stage narrow pulse peak holding circuit and the digital isolator respectively. The ADC is used to collect the amplitude-processed narrow pulse voltage signal output by the two-stage narrow pulse peak holding circuit according to the acquisition instruction, and send the acquired voltage to the digital isolator. The digital isolator is also connected to the processor. The digital isolator is used to send the acquisition instruction generated by the processor to the ADC, and send the acquisition voltage sent by the ADC to the processor. The processor is also connected to the output end of the drive input signal. The processor is used to generate an acquisition instruction, send the acquisition instruction to the digital isolator, receive the acquisition voltage returned by the digital isolator, and collect the frequency of the drive input signal, and select the junction temperature calibration formula according to the collected frequency. According to the acquisition voltage and the selected junction temperature calibration formula, the junction temperature of the IGBT to be tested is calculated.

[0029] Here, the digital isolator may specifically be a digital isolation chip. By using the digital isolator for isolated communication between the processor and the ADC, it is possible to use the same processor to measure multiple IGBTs, thereby avoiding the situation where multiple processors are used to measure multiple IGBTs one by one, thereby reducing the circuit area.

[0030] It should be noted that 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 technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0031] 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 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 representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features 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 the different embodiments or examples described in this specification.

[0032] In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality of components. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good effects.

[0033] 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. An IGBT junction temperature online monitoring circuit system based on gate peak current, It is characterized in that include: IGBT gate driver, gate signal processing circuit, two-stage narrow pulse peak holding circuit and acquisition and processing circuit; The IGBT gate driver is connected to the output end of the driving input signal, the gate signal processing circuit and the IGBT to be tested respectively, the output end of the driving input signal is used to output the driving input signal, and the IGBT gate driver is used to provide driving capability for the IGBT to be tested, so as to control the IGBT to be tested to charge and discharge; The gate signal processing circuit is also connected to the two-stage narrow pulse peak holding circuit, and is used to convert the gate peak current of the IGBT to be tested into a narrow pulse voltage signal, perform amplitude processing, and output the amplitude processed narrow pulse voltage signal; The two-stage narrow pulse peak holding circuit is also connected to the IGBT to be tested and the acquisition and processing circuit respectively, wherein the two-stage narrow pulse peak holding circuit includes a triode, and the two-stage narrow pulse peak holding circuit is used to hold the narrow pulse voltage signal after the amplitude processing; The acquisition and processing circuit is also connected to the output end of the drive input signal, and is used to acquire the signal output by the two-stage narrow pulse peak holding circuit to obtain an acquisition voltage, and to acquire the frequency of the drive input signal, and select a junction temperature calibration formula according to the acquired frequency, and calculate the junction temperature of the IGBT to be tested according to the acquisition voltage and the selected junction temperature calibration formula.

2. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 1, It is characterized in that The IGBT gate driver comprises: a gate drive chip and an external gate resistor; The input end of the gate drive chip is connected to the output end of the drive input signal, the output end of the gate drive chip is simultaneously connected to one end of the external gate resistor and the first input end of the gate signal processing circuit, and the other end of the external gate resistor is simultaneously connected to the second input end of the gate signal processing circuit and the gate of the IGBT to be tested.

3. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 2, It is characterized in that The gate signal processing circuit includes: a voltage follower and a differential amplifier circuit; The first input terminal of the voltage follower is connected to one end of the external gate resistor, the second input terminal of the voltage follower is connected to the other end of the external gate resistor, and the voltage follower is used to collect the differential voltage on both sides of the external gate resistor; The first input terminal of the differential amplifier circuit is connected to the first output terminal of the voltage follower, the second input terminal of the differential amplifier circuit is connected to the second output terminal of the voltage follower, and the output terminal of the differential amplifier circuit is connected to the two-stage narrow pulse peak holding circuit. The differential amplifier circuit is used to convert the differential voltage on both sides of the external gate resistor into a single-ended output and add a negative bias voltage to obtain the amplitude-processed narrow pulse voltage signal and output it.

4. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 3, It is characterized in that The voltage follower includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, an operational amplifier U1 and an operational amplifier U2; One end of the resistor R1 is connected to one end of the external gate resistor and one end of the resistor R4 at the same time, the other end of the resistor R4 is grounded, the other end of the resistor R1 is connected to the positive input end of the operational amplifier U1, the negative input end of the operational amplifier U1 is connected to the output end of the operational amplifier U1, and the output end of the operational amplifier U1 serves as the first output end of the voltage follower; One end of the resistor R2 is connected to the other end of the external gate resistor, and the other end of the resistor R2 is simultaneously connected to one end of the resistor R3 and the positive input end of the operational amplifier U2, the other end of the resistor R3 is grounded, the negative input end of the operational amplifier U2 is connected to the output end of the operational amplifier U2, and the output end of the operational amplifier U2 serves as the second output end of the voltage follower.

5. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 3, It is characterized in that The differential amplifier circuit includes: a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, an operational amplifier U3 and an operational amplifier U4; One end of the resistor R5 serves as the first input end of the differential amplifier circuit, the other end of the resistor R5 is connected to one end of the resistor R8 and the negative input end of the operational amplifier U3, and the other end of the resistor R8 is connected to the output end of the operational amplifier U3; One end of the resistor R6 serves as the second input end of the differential amplifier circuit, the other end of the resistor R6 is connected to one end of the resistor R7 and the positive input end of the operational amplifier U3, and the other end of the resistor R7 is grounded; One end of the resistor R9 is connected to the output end of the operational amplifier U3, the other end of the resistor R9 is connected to one end of the resistor R10 and the positive input end of the operational amplifier U4, the other end of the resistor R10 is grounded, the negative input end of the operational amplifier U4 is connected to the reference voltage output end, one end of the resistor R11 and one end of the resistor R12, and the reference voltage output end is used to output a reference voltage V REF The other end of the resistor R11 is grounded, and the other end of the resistor R12 is connected to the output end of the operational amplifier U4. The output end of the operational amplifier U4 serves as the output end of the differential amplifier circuit, and is used to output the narrow pulse voltage signal after amplitude processing.

6. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 1, It is characterized in that The two-stage narrow pulse peak holding circuit comprises: a discharge signal generating circuit, a primary circuit and a secondary circuit; The input end of the discharge signal generating circuit is connected to the gate of the IGBT to be tested, and the output end of the discharge signal generating circuit is connected to both the discharge signal input end of the primary circuit and the discharge signal input end of the secondary circuit. The discharge signal generating circuit is used to convert the gate emitter square wave voltage signal of the IGBT to be tested into a narrow pulse width square wave signal, and output the narrow pulse width square wave signal as a discharge signal; The input end of the primary circuit is connected to the output end of the gate signal processing circuit, and the output end of the primary circuit is connected to the input end of the secondary circuit. The primary circuit is used to capture the input narrow pulse voltage signal after amplitude processing, and output the captured narrow pulse voltage signal after amplitude processing to the secondary circuit; The output end of the secondary circuit is connected to the acquisition and processing circuit, and the secondary circuit is used to maintain the amplitude-processed narrow pulse voltage signal output by the primary circuit.

7. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 6, It is characterized in that The first-level circuit includes: an operational amplifier U5, an operational amplifier U6, a resistor R13, a resistor R14, a resistor R15, a capacitor C1, a first analog switch S1, a transistor Q1 and a transistor Q2; The positive input terminal of the operational amplifier U5 serves as the input terminal of the primary circuit, the negative input terminal of the operational amplifier U5 is simultaneously connected to one end of the resistor R13 and the emitter of the transistor Q1, the other end of the resistor R13 is used to access the power supply voltage VEE, the output terminal of the operational amplifier U5 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to one end of the resistor R14, and the other end of the resistor R14 is used to access the power supply voltage VCC; The output end of the operational amplifier U5 is also connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to one end of the resistor R15, the other end of the resistor R15 is used to access the power supply voltage VCC, the emitter of the transistor Q2 is simultaneously connected to one end of the capacitor C1, the first end of the first analog switch S1 and the positive input end of the operational amplifier U6, the other end of the capacitor C1 and the second end of the first analog switch S1 are both grounded, the control end of the first analog switch S1 is the discharge signal input end of the primary circuit, the negative input end of the operational amplifier U6 is connected to the output end of the operational amplifier U6, and the output end of the operational amplifier U6 serves as the output end of the primary circuit.

8. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 6, It is characterized in that The secondary circuit includes: an operational amplifier U7, an operational amplifier U8, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a capacitor C2, a second analog switch S2, a transistor Q3 and a transistor Q4; The positive input terminal of the operational amplifier U7 serves as the input terminal of the secondary circuit, the negative input terminal of the operational amplifier U7 is simultaneously connected to one end of the resistor R16 and the emitter of the transistor Q3, the other end of the resistor R16 is used to access the power supply voltage VEE, the output terminal of the operational amplifier U7 is connected to the base of the transistor Q3, the collector of the transistor Q3 is connected to one end of the resistor R17, and the other end of the resistor R17 is used to access the power supply voltage VCC; The output end of the operational amplifier U7 is also connected to the base of the transistor Q4, the collector of the transistor Q4 is connected to one end of the resistor R18, the other end of the resistor R18 is used to access the power supply voltage VCC, the emitter of the transistor Q4 is simultaneously connected to one end of the capacitor C2, the first end of the second analog switch S2 and the positive input end of the operational amplifier U8, the other end of the capacitor C2 and the second end of the second analog switch S2 are both grounded, the control end of the second analog switch S2 is the discharge signal input end of the secondary circuit, the negative input end of the operational amplifier U8 is simultaneously connected to one end of the resistor R19 and one end of the resistor R20, the other end of the resistor R19 is grounded, the other end of the resistor R20 is connected to the output end of the operational amplifier U8, and the output end of the operational amplifier U8 serves as the output end of the secondary circuit.

9. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 6, It is characterized in that The discharge signal generating circuit comprises: a resistor R21, a resistor R22, a resistor R23, a diode D1, a diode D2 and a capacitor C3; One end of the resistor R21 is simultaneously connected to one end of the resistor R22 and one end of the capacitor C3, the other end of the resistor R21 is connected to the gate of the IGBT to be tested, the other end of the resistor R22 is grounded, the other end of the capacitor C3 is simultaneously connected to one end of the resistor R23, the anode of the diode D1 and the cathode of the diode D2, the other end of the resistor R23 is grounded, the cathode of the diode D1 is used to access the power supply voltage VCC, the anode of the diode D2 is grounded, wherein the anode of the diode D1 and the cathode of the diode D2 are connected and also serve as the output end of the discharge signal generating circuit.

10. The IGBT junction temperature online monitoring circuit system based on gate peak current according to claim 1, It is characterized in that The acquisition and processing circuit includes: ADC, digital isolator and processor; The ADC is connected to the two-stage narrow pulse peak holding circuit and the digital isolator, respectively, and is used to collect the amplitude-processed narrow pulse voltage signal output by the two-stage narrow pulse peak holding circuit according to the collection instruction, and send the obtained collection voltage to the digital isolator; The digital isolator is also connected to the processor, and is used to send the acquisition instruction generated by the processor to the ADC, and send the acquisition voltage sent by the ADC to the processor; The processor is also connected to the output end of the drive input signal, and is used to generate the acquisition instruction, and send the acquisition instruction to the digital isolator, and receive the acquisition voltage returned by the digital isolator, and acquire the frequency of the drive input signal, and select a junction temperature calibration formula according to the acquired frequency, and calculate and obtain the junction temperature of the IGBT to be tested according to the acquisition voltage and the selected junction temperature calibration formula.

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