Online detection device and method for IGBT collector current based on gate current

Abstract

This invention relates to the field of power electronics technology, specifically to an online detection device and method for IGBT collector current based on gate current. The detection method includes: a drive Miller plateau detection module processing the IGBT gate drive waveform to extract the Miller plateau region; an IGBT drive current integration module extracting the voltage across the IGBT gate drive resistor, integrating the voltage waveform during the Miller plateau period, and using the integration result to characterize the gate current during the Miller plateau period; measuring the integrator output voltage and collector current under three different load currents, and performing second-order polynomial fitting within a DSP to fit a function of the collector current with respect to the integrator output voltage. This fitting result allows for online measurement of the collector current via the gate current. This method avoids the use of high-voltage, high-power devices, is easy to integrate, has low detection costs, and is easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and specifically relates to an online detection device and method for IGBT collector current based on gate current. Background Technology

[0002] Insulated-gate bipolar transistors (IGBTs) are characterized by high power capacity, low saturation voltage, and high switching frequency, making them widely used in high-voltage and high-power electronic converters and one of the most promising power semiconductor switching devices. However, IGBTs are among the most vulnerable components in a system. In high-power power electronic converters, IGBTs typically operate under high voltage and high current conditions. Hard short circuits with shot-through in the bridge arm, soft short circuits with short circuits on the load side, and latch-up failures caused by excessive collector current can all lead to IGBT failure. If faults are not detected, located, repaired, and protected in a timely and accurate manner, permanent damage to the IGBT devices can easily occur, resulting in equipment failure and a significant reduction in system reliability. Some industry surveys show that 39% of system failures in power electronic converters can be attributed to IGBT device failures and damage, and IGBT and driver failures account for more than 50% of system failures.

[0003] Therefore, precise current measurement is a crucial function that modern high-voltage, high-current power systems must possess. Accurate measurement of the current in the IGBT collector is essential for output regulation and safety.

[0004] Traditional IGBT collector current sensing methods typically employ an external series resistor, i.e., a small resistor is inserted between the IGBT emitter and ground. This method is popular due to its low cost and small size. However, the significant power loss from the series resistor reduces system efficiency. Furthermore, any voltage drop across the sensing resistor during the IGBT's on-state reduces the actual gate-emitter voltage and increases the on-state voltage drop. This method also has lower accuracy and lacks isolation circuitry.

[0005] Another common method for detecting IGBT collector current is to embed a sensing structure within the IGBT, namely the current mirror method. This method measures the IGBT current by sensing the emitter series resistor and the IGBT itself. Since the IGBT module has multiple symmetrically arranged current units, a built-in current detection circuit is designed to proportionally measure the current value of one unit. The total current flowing through the entire IGBT can then be calculated using a scaling factor M. This method has relatively poor accuracy and noise immunity, and is mostly used for overcurrent detection. Furthermore, adding a current mirror detection module to the IGBT module increases manufacturing complexity, thereby raising costs.

[0006] Currently, various current sensors, such as Hall effect sensors, Rogowski coils, current transformers, and tunnel magnetoresistance (TMR), are widely used for IGBT current sensing. Current sensors can directly sense current and have built-in isolation, making them more promising than the aforementioned methods that lack isolation. However, current sensors are typically expensive, bulky, and have low power density, making them difficult to integrate. Summary of the Invention

[0007] To address the problems existing in the background technology, the present invention provides an online detection device and method for indirectly detecting the collector current of an IGBT using only a low gate voltage signal.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a universal online detection device for IGBT collector current based on gate current, the detection device comprising at least an IGBT main circuit, an IGBT driving module, a Miller platform detection module, a gate current integration module, and a digital signal processing module (DSP); the DSP is connected to the IGBT driving module, the Miller platform detection module, and the gate current integration module respectively, and the IGBT driving module is connected to the Miller platform detection module and the gate current integration module respectively; the IGBT main circuit includes a first IGBT, a second IGBT, and an inductor, wherein the second IGBT is the IGBT under test; the IGBT driving module includes a driving module and a gate driving resistor;

[0009] The IGBT driver module is used to drive the second IGBT and is connected to the Miller platform detection module and the gate current integration module through the gate drive resistor to detect the collector current of the second IGBT.

[0010] The Miller platform detection module is connected to the gate of the second IGBT and is used to detect the Miller platform of the gate drive voltage of the second IGBT. The Miller platform detection result is output to the digital signal processing module DSP for processing.

[0011] The gate current integration module is connected across the drive resistor and controlled by the Miller platform signal output by the digital signal processing module DSP. It is used to integrate the voltage across the gate resistor to extract the gate current. The extraction result is sent to the digital signal processing module DSP to calculate the collector current.

[0012] The digital signal processing module (DSP) is connected to the output of the Miller platform detection module, the input of the IGBT drive module, and the analog switch control and integration module output of the gate current integration module. It is used to process the Miller platform drive signal of the IGBT drive module, provide the drive signal of the IGBT drive module, control the integration of the gate current during the Miller platform, and acquire the differential voltage output of the gate current integration module by the ADC. After obtaining the output voltage of the gate current integration module, the collector current is calculated by the internal second-order polynomial regression function to realize the collector current detection.

[0013] In the aforementioned general online detection device for IGBT collector current based on gate current, the gate of the first IGBT is connected to the emitter of the first IGBT, and the collector of the first IGBT is connected to a DC power supply V. DD The emitter of the first IGBT is connected to the collector of the second IGBT, the gate of the second IGBT is connected to the gate drive resistor, the emitter of the second IGBT is grounded, and the inductor is connected in parallel between the emitter and collector of the first IGBT.

[0014] In the above-mentioned general online detection device for IGBT collector current based on gate current, the Miller platform detection module includes a bandpass filter, an amplifier, and a high-speed comparator;

[0015] The bandpass filter includes a high-pass filter and a low-pass filter. The high-pass filter is connected to the gate of the second IGBT driving module and is used to extract the slope characteristics of the gate driving voltage of the second IGBT. The low-pass filter is used to filter out the high-frequency noise contained in the output of the high-pass filter.

[0016] The amplifier includes an operational amplifier circuit, and its input terminal is connected to the output terminal of a bandpass filter to amplify the output of the bandpass filter.

[0017] The input of the high-speed comparator is connected to the output of the amplifier and a 1.8V reference voltage. The output of the high-speed comparator is connected to a digital signal processing module (DSP) to convert the amplifier's output and the reference voltage into pulses containing only high and low levels.

[0018] In the above-mentioned general online detection device for IGBT collector current based on gate current, the gate current integration module includes a buffer, an analog switch, and an RC fully differential integrator.

[0019] The buffer is connected across the gate drive resistor to isolate the voltage across the gate drive resistor from the analog switch and the RC fully differential integrator.

[0020] One end of the analog switch is connected to the output of the buffer, and the other end is connected to the input of the RC fully differential integrator. It is controlled by the Miller plateau signal output by the digital signal processing module DSP to connect the voltage across the gate drive resistor during the Miller plateau to the RC fully differential integrator.

[0021] The RC fully differential integrator is connected to the output of the analog switch. During the Miller plateau, the analog switch is turned on, feeding the voltage across the gate drive resistor into the RC fully differential integrator. The integrator processes the differential signal V... IN_DIFF Integrate and output the differential integral signal V. OUT_DIFF .

[0022] A general online detection method for IGBT collector current based on gate current is proposed. When the Miller plateau region of the gate voltage of the IGBT drive module is detected, the voltage across the gate drive resistor is integrated to obtain the integrated output value of the gate current during the Miller plateau period. The integrator output value and collector current value under three different collector currents are measured. A second-order polynomial function of collector current with respect to integrator output value is formed inside the digital signal processing module (DSP). The collector current is detected by using the second-order polynomial function and the integrator output value.

[0023] In the above-mentioned general online detection method for IGBT collector current based on gate current, the specific steps of the method include:

[0024] Step 1: The Miller plateau detection module processes the gate drive waveform of the IGBT under test and extracts the Miller plateau region from the gate drive waveform of the IGBT under test.

[0025] Step 2: The gate current integration module of the IGBT under test extracts the voltage across the gate drive resistor, integrates the voltage waveform during the Miller plateau, and the integration result characterizes the gate current during the Miller plateau.

[0026] Step 3: Measure the integrator output voltage and collector current under three different load currents. Perform second-order polynomial fitting inside the digital signal processing module (DSP) to fit the function of collector current with respect to integrator output voltage. Use the fitting result to realize online measurement of collector current through gate current.

[0027] In the above-mentioned general online detection method for IGBT collector current based on gate current, the collector current and gate current of the second IGBT under test satisfy the following relationship during the Miller plateau:

[0028] Transient of the second IGBT turn-on:

[0029]

[0030] Second IGBT turn-off transient:

[0031]

[0032] Among them I C R is the collector current of the second IGBT under test. G(ON) and R G(OFF) It is the gate resistor for turning on and off, G m For the transconductance of the second IGBT under test, I G V represents the gate current during the Miller plateau of the second IGBT under test. DRIVE V is the driving voltage of the second IGBT under test. TH It is the threshold voltage of the second IGBT under test.

[0033] In the above-mentioned general online detection method for IGBT collector current based on gate current, the voltage across the gate drive resistor is integrated to obtain the integrated output value of the gate current during the Miller plateau, including:

[0034] During the Miller platform operation, the analog switch is turned on, feeding the voltage across the gate drive resistor into the RC fully differential integrator. The RC fully differential integrator processes the differential signal V. IN_DIFF Integrate and output the differential integral signal V. OUT_DIFF The relationship between the input and output of the RC fully differential integrator is as follows:

[0035]

[0036] Where RC represents the resistance and capacitance values ​​in the fully differential integrator, and t miller For the fixed Miller plateau duration controlled by the digital signal processing module DSP, I G R is the gate current of the IGBT to be measured. G This is the gate resistor.

[0037] In the above-described general online detection method for IGBT collector current based on gate current, the second-order polynomial function expression of the collector current with respect to the integrator output value is as follows:

[0038]

[0039] The integrator output and collector current values ​​were measured under three different collector currents, and denoted as I. C1 V OUT_DIFF1 I C2 V OUT_DIFF2 I C3 V OUT_DIFF3 The measured values ​​are input into the digital signal processing module (DSP), where the system of three linear equations is solved using the principal component elimination method with back substitution.

[0040]

[0041] Solve for the three coefficients a, b, and c to form a second-order polynomial function of the collector current with respect to the integrator output value.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. Based on gate current and collector current (I G and I C The unique Miller plateau relationship between the gate and collector currents allows for indirect acquisition of collector current through the gate current. This enables collector current detection on the low-voltage side of the drive, eliminating the drawbacks of high cost, large device size, reduced main circuit efficiency, low accuracy, and susceptibility to DC voltage when implementing collector current detection on the high-voltage side.

[0044] 2. Gate current and collector current (I G and I C The unique Miller plateau relationship between the IGBTs is very stable, exists in every IGBT, and does not change with the applied DC voltage, but is only related to temperature and IGBT process.

[0045] 3. This invention extracts the gate current by integrating the gate current during the Miller plateau, which has the advantages of suppressing high-frequency noise and amplifying the gate current. The gate current extraction is achieved through an integrator, which can amplify the gate current and suppress noise of the gate current during the Miller plateau, making the extracted gate current accurate and thus ensuring high precision of the collector current.

[0046] 4. This measurement method only needs to measure three sets of data on the integrator digital quantity and collector current under different load currents to form a function of the collector current with respect to the integrator digital quantity. Therefore, it can quickly realize online detection of collector current for any IGBT, eliminating the disadvantage of other collector current detection methods that require pre-measuring a large amount of data for data fitting.

[0047] 5. This extraction method only requires extracting the voltage across the gate resistor of the IGBT. The acquisition is simple and easy to implement, and it has built-in isolation, so it will not affect the IGBT main circuit or the drive circuit.

[0048] 6. The components used in the extraction circuit of this invention are all easy-to-integrate components, such as operational amplifiers, resistors and capacitors. Therefore, this extraction circuit is easy to integrate and can be integrated into a driving circuit or fabricated into an IC chip.

[0049] 7. This invention overcomes the limitations of detecting V during the Miller platform. GE To achieve current sensing, the parasitic inductance on the emitter side of the IGBT will be affected, leading to inaccurate measurement results. GThis problem will not exist, and it has the advantage of high accuracy. Attached Figure Description

[0050] Figure 1 A simplified IGBT model diagram for an embodiment of the present invention;

[0051] Figure 2 This is a graph showing the relationship between the collector current and gate current of an IGBT according to an embodiment of the present invention.

[0052] Figure 3 This is a circuit block diagram of a method for detecting collector current based on gate current and collector current according to an embodiment of the present invention;

[0053] Figure 4 This is a waveform diagram of a key node in the Miller platform extraction circuit of an embodiment of the present invention;

[0054] Figure 5 This is a waveform diagram of a key node in the gate current extraction circuit of an embodiment of the present invention;

[0055] Figure 6 This is a flowchart of the DSP second-order polynomial fitting process according to an embodiment of the present invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0057] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0058] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0059] This embodiment provides a method for indirectly detecting the collector current of an IGBT using only a low gate voltage signal. This addresses the problems of existing technologies that require high-voltage devices, resulting in high cost, difficulty in integration, and large size when detecting the collector current of an IGBT.

[0060] This method is based on gate current and collector current (I G and I C The unique Miller plateau relationship between them can be measured by measuring the Miller plateau period I. G To indirectly obtain I C It also allows for cycle-by-cycle measurement of I during the on and off transients. CThis relationship exists in all IGBTs and is universally applicable. This relationship can be expressed through I / O under three sets of actual operating conditions. G and I C The data is obtained by solving a system of three linear equations in the DSP. Based on this relationship, the I during the Miller plateau can be measured. G The value of the collector current I is calculated. C This eliminates the hassle of pre-measuring large amounts of data for data fitting, providing a new approach for IGBT collector current detection.

[0061] This embodiment is achieved through the following technical solution: a universal online detection device for IGBT collector current based on gate current, comprising at least:

[0062] IGBT driver module, Miller platform detection module, gate current integration module, and digital signal processing module (DSP).

[0063] The IGBT driver module is used to drive the IGBTs whose current needs to be measured and provides a gate drive resistor so that the Miller platform detection module and the gate current integration module can be connected to perform collector current detection.

[0064] The Miller platform detection module is connected to the gate of the IGBT and is used to detect the Miller platform of the IGBT gate drive voltage. The Miller platform detection result is output to the digital signal processing module DSP for processing.

[0065] The gate current integration module is connected across the drive resistor and is controlled by the Miller platform signal output by the digital signal processing module (DSP). It is used to integrate the voltage across the gate resistor, that is, to integrate and extract the gate current. The extraction result is sent to the DSP to calculate the collector current.

[0066] The digital signal processing module (DSP) is connected to the output of the Miller platform detection module, the input of the IGBT drive module, and the analog switch control and integration module output of the gate current integration module. It is used to process the IGBT drive Miller platform signal, provide the IGBT drive signal, control the integration of the gate current during the Miller platform, and acquire the differential voltage output of the gate current integration module by the ADC. After obtaining the output voltage of the gate current integration module, the collector current can be calculated by the internal second-order polynomial regression function to realize the collector current detection.

[0067] During the Miller plateau period of the IGBT under test, the collector current and gate current satisfy the following relationship:

[0068] During the transient activation:

[0069]

[0070] During the shutdown transient:

[0071]

[0072] Among them I C R is the collector current of the IGBT device under test. G(ON) and R G(OFF) It is the gate resistor for turning on and off, G m For the transconductance of IGBT, I G V represents the gate current during the Miller plateau of the IGBT under test. DRIVE V is the driving voltage of the IGBT under test. TH It is the threshold voltage of the IGBT under test.

[0073] The Miller platform detection module includes: a bandpass filter, an amplifier, and a high-speed comparator;

[0074] A bandpass filter consists of a high-pass filter and a low-pass filter. The high-pass filter is connected to the gate of the IGBT to extract the slope characteristics of the IGBT gate drive voltage, and the low-pass filter is used to filter out high-frequency noise contained in the output of the high-pass filter.

[0075] The amplifier is composed of an operational amplifier circuit and is connected to the output of the bandpass filter to amplify the output of the bandpass filter;

[0076] A high-speed comparator is connected to the amplifier output and a 1.8V reference voltage. It compares the amplifier output with the reference voltage and converts the amplifier output into pulses containing only high and low levels that can be recognized by the digital signal processing module (DSP).

[0077] The output of the Miller platform detection module is connected to the digital signal processing module (DSP) to realize Miller platform detection.

[0078] After the Miller platform detection module sends the signal to the digital signal processing module (DSP), the DSP captures the falling edge of the first pulse through the eCAP module, outputs a high level, and then delays it by t using the DSP's internal timer. miller The output is low to achieve Miller platform detection, and the transformed waveform is used to control the opening and closing of the analog switch.

[0079] The gate current integration module includes: a buffer, an analog switch, and an RC fully differential integrator;

[0080] The buffer is connected across the driving resistor to isolate the voltage across the driving resistor from the analog switch and the RC fully differential integrator, thus preventing the subsequent integration from affecting the driving voltage.

[0081] An analog switch is connected to the output of the buffer and the input of the RC fully differential integrator. Controlled by the Miller plateau signal output by the DSP, the voltage across the gate resistor during the Miller plateau is connected to the RC fully differential integrator.

[0082] The RC fully differential integrator is connected to the output of the analog switch. During the Miller plateau, the analog switch is turned on, feeding the voltage across the gate resistor into the RC fully differential integrator. The integrator processes the differential signal V... IN_DIFF Integrate and output the differential integral signal V. OUT_DIFF The relationship between the input and output of an RC fully differential integrator is as follows:

[0083]

[0084] Where RC represents the resistance and capacitance in the fully differential integrator, t miller For the duration of the fixed Miller plateau controlled by the DSP, I G R is the gate current of the IGBT. G This is the gate resistor.

[0085] The input and output of an RC fully differential integrator are proportional.

[0086] From the input-output integrator relationship of the total differential integrator, it can be seen that RC, t miller R G Since it is a constant, the gate current I G With the integrator output V OUT_DIFF Proportional.

[0087] This embodiment also provides a general online detection method for IGBT collector current based on gate current, which includes at least:

[0088] When the Miller plateau region of the gate voltage is detected, the voltage across the drive resistor is integrated to obtain the integrated output value of the gate current during the Miller plateau. The integrator output value and collector current value under three different collector currents are measured. A second-order polynomial function of the collector current with respect to the integrator output value is formed inside the digital signal processing module (DSP). The collector current can then be detected using this function and the integrator output value.

[0089] The process includes the following steps: A: The Miller plateau detection module processes the gate drive waveform of the IGBT under test and extracts the Miller plateau region from the waveform; B: The gate current integration module extracts the voltage across the gate drive resistor and integrates the voltage waveform during the Miller plateau period. The integration result represents the gate current during the Miller plateau period; C: The integrator output voltage and collector current under three different load currents are measured. A second-order polynomial fitting is performed inside the digital signal processing module (DSP) to fit the function of collector current with respect to integrator output voltage. The collector current can be measured online by the gate current based on the fitting result.

[0090] The digital signal processing module (DSP) internally generates a second-order polynomial function of the collector current with respect to the integrator output value.

[0091] The second-order polynomial function expression of the collector current with respect to the integrator output value is as follows:

[0092]

[0093] The integrator output and collector current values ​​were measured under three different collector currents, and denoted as I. C1 V OUT_DIFF1 I C2 V OUT_DIFF2 I C3 V OUT_DIFF3 The measured values ​​are input into the DSP, and the three linear equations are solved by the principal component elimination method through back substitution. The three coefficients a, b, and c are then solved, forming a second-order polynomial function of the collector current with respect to the integrator output value.

[0094] Miller Platform Period I G and I C The derivation process of the relationship is as follows:

[0095] like Figure 1 The diagram shows a simplified model of an IGBT, which is a MOSFET driving a PNP type BJT. In this IGBT, the electron current I flowing through the MOSFET is... n This is used as the base drive current of the BJT. Therefore, the hole current I flowing through the BJT is... p for:

[0096]

[0097] Where β PNP α represents the common-emitter AC current amplification factor of the BJT; PNP This is the common-base AC current amplification factor of the BJT. The emitter current I of the IGBT... E This can be obtained by adding the electron current and the hole current:

[0098]

[0099] Because the MOS gate structure has a high input impedance, the gate current I... G It is zero in steady state. Even during switching, the gate current during charging and discharging is much smaller than the emitter current. Therefore, I E Approximately equal to I C Electron current I n It is actually the drain current of the MOSFET. Therefore, I C and I D The following can be associated:

[0100]

[0101] Assume a voltage source at V DRIVE The signal switches between ground and I, and the switched signal is applied to the gate of the IGBT. During the turn-on process, the gate current I of the IGBT (which is also a MOSFET) is... G and the drain current I of the MOSFET D It can be represented as:

[0102]

[0103]

[0104] Where V GE V is the gate-emitter voltage of the IGBT. TH This is the turn-on and turn-off threshold voltage of the IGBT.

[0105] Combining formulas (18) and (19), we can obtain:

[0106]

[0107] Substituting formula (17) into formula (20), we get I C and I G Relationship:

[0108]

[0109] Where g m It is the transconductance of the MOSFET, and its transconductance G of the IGBT. m The relationship is as follows:

[0110]

[0111] During the launch of the Miller platform, I C It can be determined by the following formula:

[0112]

[0113] During the shutdown of the Miller platform, I C It can be determined by the following formula:

[0114]

[0115] Where R G(ON) and R G(OFF) It is the gate resistor for turning on and off, V TH R is the threshold voltage of the IGBT. G V DRIVE and V TH It is usually a constant. The G of IGBT m From the device datasheet I C With V GE The conversion curve provides the information. Therefore, the gate current I... G and collector current I C There is indeed a relationship between them, such as Figure 2 As shown. This is a unique relationship resulting from the IGBT structure, which is only affected by temperature and process variations.

[0116] like Figure 3 As shown, a universal online detection device for IGBT collector current based on gate current includes at least:

[0117] IGBT main circuit, IGBT drive module, Miller platform detection module, gate current integration module, digital signal processing module (DSP);

[0118] The IGBT main circuit includes a half-bridge structure formed by the second IGBT at the lower end of the IGBT under test and the first IGBT at the upper end. An inductor is connected in parallel with the first IGBT to form a clamping inductor load. The IGBT drive module includes a drive module and a gate resistor R. G .

[0119] The gate of the first IGBT is connected to the emitter of the first IGBT, and the collector is connected to the DC power supply V. DD The emitter is connected to the collector of the second IGBT, and the gate of the second IGBT under test is connected to the gate resistor R. G The emitter is grounded, and the inductor L is connected in parallel between the collector and emitter of the first IGBT. The IGBT main circuit is not limited to this embodiment and can be any circuit topology that includes the IGBT under test.

[0120] like Figure 3 As shown, the IGBT drive module is connected to the PWM wave output by the digital signal processing module DSP and the gate of the second IGBT under test, providing a drive signal for the second IGBT.

[0121] The boost converter is connected to the PWM wave output by the digital signal processing module (DSP) and the gate resistor R. G It is used to boost the 3.3V PWM output from the digital signal processing module (DSP) to a 15V PWM wave.

[0122] Gate resistance R G It is connected to the output of the drive boost section, the gate of the second IGBT, the input of the Miller platform extraction module, and the input of the gate current integration module.

[0123] like Figure 3 As shown, the Miller plateau detection module is connected to the gate of the second IGBT under test. It is used to detect the Miller plateau region of the gate drive voltage of the second IGBT under test and outputs the feedback signal to the digital signal processing module DSP to generate the Miller plateau region detection waveform.

[0124] The Miller platform detection module includes a bandpass filter, an amplifier, and a high-speed comparator.

[0125] The input terminal of the bandpass filter is connected to the gate of the second IGBT, and the gate waveform of the second IGBT is as follows. Figure 4 V GE As shown, the output is connected to the amplifier's input. The bandpass filter consists of a high-pass filter and a low-pass filter. The high-pass filter is connected to the gate of the second IGBT to extract the slope characteristics of the second IGBT gate drive voltage. The low-pass filter is used to filter out high-frequency noise contained in the high-pass filter output. The output waveform is shown in the figure. Figure 4 V RC As shown.

[0126] The amplifier's input is connected to the output of the bandpass filter, and its output is connected to the input of a high-speed comparator. The amplifier, composed of an operational amplifier circuit, amplifies the output of the bandpass filter; the output waveform is as follows. Figure 4 V AMP As shown.

[0127] The high-speed comparator's input is connected to the amplifier's output and a 1.8V reference voltage, while its output is connected to a digital signal processing (DSP) module. This comparator compares the amplifier's output with the 1.8V reference voltage, converting the amplifier's output into pulses containing only high and low levels that the DSP can recognize. The output waveform is shown below. Figure 4 V FEEDBACK As shown.

[0128] like Figure 3 As shown, the input terminal of the gate current integration module is connected to the gate resistor R. G Both ends are also connected to the Miller platform detection signal V provided by the digital signal processing module DSP. SWThe gate current during the Miller plateau is used to obtain the differential voltage V characterizing the gate current. OUT_DIFF The output is sent to the digital signal processing module (DSP) for collector current calculation.

[0129] The gate current integration module includes: a buffer, an analog switch, and an RC fully differential integrator.

[0130] The buffer input is connected to both ends of the gate drive resistor to isolate the voltage across the gate drive resistor from the analog switch and the RC fully differential integrator, thus preventing the subsequent integrator circuit from affecting the drive voltage.

[0131] One end of the analog switch is connected to the output of the buffer, and the other end is connected to the input of the RC fully differential integrator. The Miller plateau signal V is output by the digital signal processing module DSP. SW The control enables the voltage across the gate drive resistor during the Miller plateau to be connected to the RC fully differential integrator.

[0132] The RC fully differential integrator is connected to the output of the analog switch. During the Miller plateau, the analog switch is turned on, feeding the gate drive resistor voltage into the RC fully differential integrator. The integrator processes the differential signal V... IN_DIFF Integrate and output the differential integral signal V. OUT_DIFF The output waveform is as follows Figure 5 V OUT_DIFF As shown. The relationship between the output of the RC fully differential integrator and the gate current is:

[0133]

[0134] Where RC represents the resistance and capacitance values ​​in the fully differential integrator, and t miller For the duration of the fixed Miller plateau controlled by the DSP, I G R is the gate current of the second IGBT. G This is the gate resistor.

[0135] like Figure 3 As shown, the digital signal processing module (DSP) is connected to the output of the Miller platform detection module, the input of the drive module, the analog switch control terminal of the gate current integration module, and the output of the gate current integration module.

[0136] The digital signal processing module (DSP) is connected to the output of the Miller platform detection module. The DSP captures the falling edge of the first pulse through the eCAP module, outputs a high level, and then delays it by t using the DSP's internal timer. miller The output is low to achieve Miller platform detection. The transformed waveform is shown below. Figure 4 V SWUsed to control the opening and closing of analog switches.

[0137] The digital signal processing module (DSP) is connected to the input of the driver module to provide the PWM signal for driving the IGBT.

[0138] The digital signal processing module (DSP) is connected to the control terminal of the analog switch of the gate current integration module. It is used to control the closing of the analog switch during the Miller plateau, so that the gate current during the Miller plateau is input into the RC fully differential integrator.

[0139] The digital signal processing module (DSP) is connected to the output of the gate current integrator module. The DSP's internal ADC outputs V. OUT_DIFF By sampling and substituting the sampled value into the second-order polynomial function of the collector current of the second IGBT under test with respect to the integrator output value, the collector current of the second IGBT under test can be obtained, thus realizing the IGBT collector current detection.

[0140] like Figure 6 As shown, the digital signal processing module (DSP) internally forms a second-order polynomial function of the collector current with respect to the integrator output value.

[0141] The second-order polynomial function expression of the collector current with respect to the integrator output value is as follows:

[0142]

[0143] The process of forming the function expression is shown in Figure 6 The integrator output and collector current values ​​were measured under three different collector currents, and denoted as I. C1 V OUT_DIFF1 I C2 V OUT_DIFF2 I C3 V OUT_DIFF3 The measured values ​​are input into the digital signal processing module (DSP), where the system of three linear equations is solved using the principal component elimination method with back substitution.

[0144]

[0145] The values ​​of the three coefficients a, b, and c can then be solved, forming a second-order polynomial function of the collector current with respect to the integrator output value.

[0146] like Figures 3-6 As shown in the figure, this embodiment provides a general online detection method for IGBT collector current based on gate current, including:

[0147] The Miller plateau region of the IGBT gate voltage is detected. When the Miller plateau region of the gate voltage is detected, the voltage across the drive resistor is integrated to obtain the integrated output value of the gate current during the Miller plateau period. The integrator output value and collector current value under three different collector currents are measured. A second-order polynomial function of the collector current with respect to the integrator output value is formed inside the digital signal processing module (DSP). Subsequently, the collector current can be detected by using this function and the integrator output value.

[0148] Specifically, the gate voltage of the IGBT under test is connected to the input terminal of the Miller platform detection module, and a bandpass filter filters the gate voltage signal to obtain V. RC It is then connected to an amplifier for amplification to obtain the amplified voltage V. AMP Connect it to a high-speed comparator, and the high-speed comparator will convert V... AMP Comparing it with a 1.8V voltage, a pulse voltage V containing only high and low levels is obtained. FEEDBACK The digital signal processing module (DSP) processes V. FEEDBACK The Miller plateau region signal V is obtained through processing. SW In the Miller plateau region signal control gate current integration module, the analog switch is closed, and the voltage across the gate resistor is fed into the RC fully differential integrator through a buffer and the analog switch. The fully differential integrator integrates the gate current during the Miller plateau period to obtain the characterization value V of the gate current. OUT_DIFF The collector current of the IGBT under test is changed, and the integrator output value and collector current value under three different collector currents are measured. The three sets of data are sent to the digital signal processing module (DSP). The DSP solves a system of three linear equations using the principal component elimination method with back substitution, forming a second-order polynomial function of the collector current with respect to the integrator output value. Subsequently, the collector current can be detected using this second-order polynomial function and the integrator output value.

[0149] The collector current detection method of this embodiment can also be further applied to load current detection of other semiconductor devices, such as MOSFETs and SiC IGBTs. The collector current function of the digital signal processing module (DSP) in this embodiment, with respect to the integrator output value, can be fitted as a third-, fourth-, and higher-order polynomial function. This embodiment can also be applied to overcurrent detection of semiconductor devices such as IGBTs. The digital signal processing module (DSP) in the collector current detection method of this embodiment can be replaced with various controllers such as STM32 and FPGA.

[0150] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A universal online detection device for IGBT collector current based on gate current, characterized in that, The detection device includes at least an IGBT main circuit, an IGBT drive module, a Miller platform detection module, a gate current integration module, and a digital signal processing module (DSP). The digital signal processing module (DSP) is connected to the IGBT drive module, the Miller platform detection module, and the gate current integration module, respectively. The IGBT drive module is connected to the Miller platform detection module and the gate current integration module, respectively. The IGBT main circuit includes a first IGBT, a second IGBT, and an inductor. The second IGBT is the IGBT under test. The IGBT drive module includes a drive module and a gate drive resistor. The IGBT driver module is used to drive the second IGBT and is connected to the Miller platform detection module and the gate current integration module through the gate drive resistor to detect the collector current of the second IGBT. The Miller platform detection module is connected to the gate of the second IGBT and is used to detect the Miller platform of the gate drive voltage of the second IGBT. The Miller platform detection result is output to the digital signal processing module DSP for processing. The gate current integration module is connected across the drive resistor and controlled by the Miller platform signal output by the digital signal processing module DSP. It is used to integrate the voltage across the gate resistor to extract the gate current. The extraction result is sent to the digital signal processing module DSP to calculate the collector current. The digital signal processing module (DSP) is connected to the output of the Miller platform detection module, the input of the IGBT drive module, and the analog switch control and integration module output of the gate current integration module. It is used to process the Miller platform drive signal of the IGBT drive module, provide the drive signal of the IGBT drive module, control the integration of the gate current during the Miller platform, and acquire the differential voltage output of the gate current integration module by the ADC. After obtaining the output voltage of the gate current integration module, the collector current is calculated by the internal second-order polynomial regression function to realize the collector current detection.

2. The universal online detection device for IGBT collector current based on gate current according to claim 1, characterized in that, The gate of the first IGBT is connected to the emitter of the first IGBT, and the collector of the first IGBT is connected to the DC power supply V. DD The emitter of the first IGBT is connected to the collector of the second IGBT, the gate of the second IGBT is connected to the gate drive resistor, the emitter of the second IGBT is grounded, and the inductor is connected in parallel between the emitter and collector of the first IGBT.

3. The universal online detection device for IGBT collector current based on gate current according to claim 2, characterized in that, The Miller platform detection module includes a bandpass filter, an amplifier, and a high-speed comparator; The bandpass filter includes a high-pass filter and a low-pass filter. The high-pass filter is connected to the gate of the second IGBT driving module and is used to extract the slope characteristics of the gate driving voltage of the second IGBT. The low-pass filter is used to filter out the high-frequency noise contained in the output of the high-pass filter. The amplifier includes an operational amplifier circuit, and its input terminal is connected to the output terminal of a bandpass filter to amplify the output of the bandpass filter. The input of the high-speed comparator is connected to the output of the amplifier and a 1.8V reference voltage. The output of the high-speed comparator is connected to a digital signal processing module (DSP) to convert the amplifier's output and the reference voltage into pulses containing only high and low levels.

4. The universal online detection device for IGBT collector current based on gate current according to claim 1, characterized in that, The gate current integration module includes a buffer, an analog switch, and an RC fully differential integrator; The buffer is connected across the gate drive resistor to isolate the voltage across the gate drive resistor from the analog switch and the RC fully differential integrator. One end of the analog switch is connected to the output of the buffer, and the other end is connected to the input of the RC fully differential integrator. It is controlled by the Miller plateau signal output by the digital signal processing module DSP to connect the voltage across the gate drive resistor during the Miller plateau to the RC fully differential integrator. The RC fully differential integrator is connected to the output of the analog switch. During the Miller plateau, the analog switch is turned on, feeding the voltage across the gate drive resistor into the RC fully differential integrator. The integrator processes the differential signal V... IN_DIFF Integrate to output the differential integral signal V OUT_DIFF .

5. The detection method of the universal online detection device for IGBT collector current based on gate current according to any one of claims 1-4, characterized in that, When the Miller plateau region of the gate voltage of the IGBT drive module is detected, the voltage across the gate drive resistor is integrated to obtain the integrated output value of the gate current during the Miller plateau period. The integrator output value and collector current value are measured under three different collector currents. A second-order polynomial function of collector current with respect to integrator output value is formed inside the digital signal processing module (DSP). The collector current is detected by using the second-order polynomial function and the integrator output value.

6. The detection method of the IGBT collector current universal online detection device based on gate current according to claim 5, characterized in that, The specific steps of this method include: Step 1: The Miller plateau detection module processes the gate drive waveform of the IGBT under test and extracts the Miller plateau region from the gate drive waveform of the IGBT under test. Step 2: The gate current integration module of the IGBT under test extracts the voltage across the gate drive resistor, integrates the voltage waveform during the Miller plateau, and the integration result characterizes the gate current during the Miller plateau. Step 3: Measure the integrator output voltage and collector current under three different load currents. Perform second-order polynomial fitting inside the digital signal processing module (DSP) to fit the function of collector current with respect to integrator output voltage. Use the fitting result to realize online measurement of collector current through gate current.

7. The detection method of the IGBT collector current universal online detection device based on gate current according to claim 6, characterized in that, During the Miller plateau period of the second IGBT under test, the collector current and gate current satisfy the following relationship: Transient of the second IGBT being turned on: Second IGBT turn-off transient: Where I C R is the collector current of the second IGBT under test. G(ON) and R G(OFF) It is the gate resistor for turning on and off, G m For the transconductance of the second IGBT under test, I G V represents the gate current during the Miller plateau of the second IGBT under test. DRIVE V is the driving voltage of the second IGBT under test. TH It is the threshold voltage of the second IGBT under test.

8. The detection method of the IGBT collector current universal online detection device based on gate current according to claim 6, characterized in that, Integrating the voltage across the gate drive resistor, the integral output value of the gate current during the Miller plateau includes: During the Miller platform operation, the analog switch is turned on, feeding the voltage across the gate drive resistor into the RC fully differential integrator. The RC fully differential integrator processes the differential signal V. IN_DIFF Integrate and output the differential integral signal V. OUT_DIFF The relationship between the input and output of the RC fully differential integrator is as follows: Where RC represents the resistance and capacitance values ​​in the fully differential integrator, and t miller For the fixed Miller plateau duration controlled by the digital signal processing module DSP, I G R is the gate current of the IGBT to be measured. G This is the gate resistor.

9. The detection method of the IGBT collector current universal online detection device based on gate current according to claim 6, characterized in that, The second-order polynomial function expression of the collector current with respect to the integrator output value is as follows: The integrator output and collector current values ​​were measured under three different collector currents, and denoted as I. C1 V OUT_DIFF1 I C2 V OUT_DIFF2 I C3 V OUT_DIFF3 The measured values ​​are input into the digital signal processing module (DSP), where the system of three linear equations is solved using the principal component elimination method with back substitution. Solve for the three coefficients a, b, and c to form a second-order polynomial function of the collector current with respect to the integrator output value.

Images