CMTI parameter detection circuit for SiCMOSFET driver

Abstract

The invention discloses a CMTI parameter detection circuit for a SiC MOSFET driver, the CMTI parameter detection circuit is connected to a driver driving half-bridge circuit, and the CMTI parameter detection circuit comprises a voltage division circuit, a differentiating circuit and a comparison circuit which are connected in sequence; the voltage division circuit comprises a C1 and a C2, and the C1 and the C2 are connected in series between the drain electrode and the source electrode of the SiC MOSFET; the differentiating circuit is connected to the voltage division circuit through a voltage follower U1 and comprises a C3 and an R1 which are connected in series, and the voltage on the R1 is in direct proportion to the voltage on the C2; the comparison circuit comprises U2 and U3 which are connected in parallel, and when the voltage on the R1 is larger than or smaller than a critical value, the output of the U2 or U3 is changed from a low level to a high level. The detection circuit can be directly applied to the actual working environment for CMTI detection, various actual factors can be fully considered, the detection result is closer to the real situation, the design is more flexible, the detection circuit does not depend on high-consistency devices, and the detection circuit can adapt to the characteristics of different devices.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically to a CMTI parameter detection circuit for a SiC MOSFET driver. Background Technology

[0002] SiC MOSFETs, as a novel type of power device, possess advantages such as high switching speed, low on-resistance, and high temperature resistance, and are widely used in fields such as new energy vehicles. In SiC MOSFET applications, the driver plays a crucial role. The driver needs to provide the SiC MOSFET with appropriate drive voltage and current to ensure its normal switching. However, in practical applications, various factors, such as common-mode interference, may cause driver performance degradation or even damage to the SiC MOSFET. Therefore, detecting the CMTI parameters of the SiC MOSFET driver to improve its anti-interference capability has become an urgent problem to be solved.

[0003] Under current technological conditions, CMTI testing of SiC MOSFET drivers primarily relies on laboratory instruments such as oscilloscopes. The process involves using these instruments to acquire and measure the driver's output signal, and then configuring the drive circuit based on the measured data. However, this testing method has significant technical limitations: First, the laboratory measurement environment differs greatly from real-world application scenarios. Laboratory measurement conditions cannot fully encompass the various complexities of real-world scenarios, while real-world applications involve numerous uncertainties such as electromagnetic interference and temperature variations, which are difficult to fully simulate in a laboratory environment. Second, this testing method places high demands on device consistency. Due to measurement limitations, poor device consistency can lead to drive circuits that are incompatible with different devices, thus affecting the performance and reliability of the SiC MOSFET driver. Summary of the Invention

[0004] The present invention provides a more adaptable and reliable CMTI parameter detection circuit for SiC MOSFET drivers, which can at least solve one of the above-mentioned technical problems.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A CMTI parameter detection circuit for a SiC MOSFET driver is connected to a driver drive half-bridge circuit, which includes a DC power supply, a driver, two SiC MOSFETs, and an output bus capacitor. The driver is connected to and drives the two SiC MOSFETs. The CMTI parameter detection circuit includes a voltage divider circuit, a differentiator circuit, and a comparator circuit connected in sequence. The voltage divider circuit includes voltage divider capacitor C1 and voltage divider capacitor C2, which are connected in series between the drain and source of the SiC MOSFET. The differentiating circuit is connected to the voltage divider circuit via a voltage follower U1, including a DC blocking capacitor C3 and a feedback resistor R1 connected in series. One end of the DC blocking capacitor C3 is connected to the output terminal of the voltage follower U1, and the other end is connected to the feedback resistor R1. The voltage on the feedback resistor R1 is proportional to the voltage on the voltage divider capacitor C2. The comparison circuit includes comparators U2 and U3 connected in parallel. When the voltage on the feedback resistor R1 is greater than or less than a threshold value, the output of comparator U2 or U3 changes from low level to high level.

[0006] Furthermore, the voltage divider circuit is used to reduce the high voltage to be detected, and the voltage after reduction is:

[0007] Among them, V C2 Vbus is the voltage across the voltage divider capacitor C2, i.e., the voltage after step-down, and Vbus is the power supply voltage on the driver, i.e., the high voltage to be detected.

[0008] Furthermore, after voltage division by the voltage divider circuit, the voltage slope across the voltage divider capacitor C2 decreases proportionally, as expressed by:

[0009] Furthermore, the voltage follower U1 is connected in parallel to the voltage divider circuit, and its input is the voltage on the voltage divider capacitor C2, which is used to collect the voltage across the SiC MOSFET after being divided by the voltage divider circuit.

[0010] Furthermore, the voltage across the feedback resistor R1 is proportional to the dv / dt across the voltage divider capacitor C2, and the dv / dt across the voltage divider capacitor C2 is proportional to the dv / dt across the SiC MOSFET. The dv / dt across the SiC MOSFET is equal to the current CMTI of the driver. Therefore, it can be deduced that the voltage across the feedback resistor R1 reflects the current CMTI of the driver.

[0011] Furthermore, one end of the feedback resistor R1 is grounded, and the other end is connected to two diodes D1 and D2. The output of the differentiating circuit is the output of the feedback resistor R1 connected to the two diodes D1 and D2. When the dv / dt across the SiC MOSFET is positive, the output of the differentiating circuit is a positive voltage, and the diode D1 is turned on. When the dv / dt across the SiC MOSFET is negative, the output of the differentiating circuit is a negative voltage, and the diode D2 is turned on.

[0012] Furthermore, the input terminal of one of the comparators U2 or U3 is connected to the diode D1 or D2, and the input terminal of the other is connected to a reference voltage, the theoretical value of which is:

[0013] In the formula, CMTI is the maximum value of CMTI on the drive core specification datasheet.

[0014] Furthermore, it also includes a logic OR gate U4, which is connected to the comparison circuit to perform a logical conversion on the outputs of the comparator U2 and the comparator U3, and to give the converted output to the enable signal of the driver. When the measured dv / dt value at the source and drain of the SiC MOSFET is greater than the threshold, the driver is directly turned off.

[0015] The beneficial effects of this invention are reflected in: 1. In view of the problem that existing technologies cannot simulate the complex situations such as electromagnetic interference and temperature changes in real-world scenarios when measuring CMTI in experimental environments, the detection circuit of the present invention can be directly applied to CMTI detection in actual working environments, and can fully consider various practical factors, so that the detection results are closer to the real situation.

[0016] 2. In view of the problem of high requirements for device consistency in the prior art, the detection circuit design of the present invention is more flexible, does not rely on highly consistent devices, and can adapt to the characteristics of different devices. Even in the case of poor device consistency, it can accurately detect the CMTI of SiC MOSFET driver, avoiding the problem of mismatch of drive circuit due to device differences, thereby ensuring the performance and reliability of driver in practical applications. Attached Figure Description

[0017] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0018] Figure 1This is a block diagram of a CMTI system where the driver drives a half-bridge circuit.

[0019] Figure 2 This is a schematic diagram of a half-bridge circuit structure consisting of two MOSFETs driven by a driver according to an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the connection structure between the CMTI parameter detection circuit and the driver driving half-bridge circuit in an embodiment of the present invention.

[0021] Figure 4 This is a structural block diagram of a computer device according to an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, "multiple" refers to two or more. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] The key technical terms used in this application are defined as follows: SiC MOSFET: This stands for Silicon Carbide Metal-Oxide Semiconductor Field-Effect Transistor. In power electronics, it offers advantages such as high switching speed, low on-resistance, and high temperature resistance. High switching speed increases power density, low on-resistance reduces losses, and high temperature resistance reduces heat dissipation requirements, making it widely used in fields such as new energy vehicles.

[0025] Driver: The driver is used to control and drive SiC MOSFETs. It provides appropriate drive voltage and current to ensure normal switching, and can also realize switch control to regulate output power. Some drivers also have protection functions to improve system reliability and safety.

[0026] CMTI: CMTI is a metric for measuring the noise immunity of a SiC MOSFET driver, representing its ability to operate normally under common-mode interference. The unit is typically kilovolts per microsecond. A higher CMTI value ensures stable operation of the system in harsh electromagnetic environments and influences the system's noise immunity design.

[0027] See Figures 2-3 This invention provides a CMTI parameter detection circuit for a SiC MOSFET driver. The CMTI parameter detection circuit is connected to a driver drive half-bridge circuit, which includes a driver and two SiC MOSFETs. The driver is connected to and drives the two SiC MOSFETs. The CMTI parameter detection circuit includes a voltage divider circuit, a differentiator circuit, and a comparator circuit connected in sequence. The voltage divider circuit includes voltage divider capacitor C1 and voltage divider capacitor C2, which are connected in series between the drain and source of the SiC MOSFET. The differentiating circuit is connected to the voltage divider circuit via a voltage follower U1, including a DC blocking capacitor C3 and a feedback resistor R1 connected in series. One end of the DC blocking capacitor C3 is connected to the output terminal of the voltage follower U1, and the other end is connected to the feedback resistor R1. The voltage on the feedback resistor R1 is proportional to the voltage on the voltage divider capacitor C2. The comparison circuit includes comparators U2 and U3 connected in parallel. When the voltage on the feedback resistor R1 is greater than or less than a threshold value, the output of comparator U2 or U3 changes from low level to high level.

[0028] The CMTI (Common Mode Transient Immunity) metric of SiC drivers is closely related to the turn-on speed of the MOSFET. CMTI refers to the minimum rise or fall time (dv / dt, kV / µs or V / ns) required for a transient to pass through the isolation layer and disrupt the driver's output state. In simpler terms, it can be understood as the rate of voltage change between the primary and secondary grounds of the driver. Figure 1 As shown. When the driver drives two SiC MOSFETs... Figure 1When the circuit structure in the circuit (this circuit structure is called a half-bridge, which is a widely used structure in power electronics) is in use, the CMTI characterizing the driver is equal to the dv / dt characterizing the switching speed of the SiC MOSFET. Therefore, the greater conduction speed of the SiC MOSFET means that the driver is subjected to greater common-mode noise (this noise is the aforementioned dv / dt (CMTI)). When this value approaches the rated value (i.e. the threshold) indicated by the chip manufacturer, the chip will be at risk of going out of control.

[0029] Generally, the turn-on speed of a SiC MOSFET is reduced by adjusting its drive resistor and capacitor, thereby lowering common-mode noise. However, when the device is in an outdoor environment and encounters surges, the common-mode noise may far exceed the measured value under normal conditions, and in severe cases, it may even damage the device. Therefore, to address the above problems, this invention proposes the following technical solution: This invention achieves effective monitoring of actual common-mode noise (dv / dt) by accurately detecting the turn-on speed of SiC MOSFETs. Once this parameter exceeds a predetermined threshold range, the device is rapidly shut down, providing reliable protection. This invention effectively solves the drawback of existing technologies that do not detect CMTI, greatly improving the stability and reliability of equipment in complex environments and bringing a new breakthrough to the development of related fields.

[0030] In this embodiment, the voltage divider circuit is used to reduce the high voltage to be detected, and the voltage after reduction is:

[0031] Among them, V C2 Vbus is the voltage across the voltage divider capacitor C2, i.e., the voltage after step-down, and Vbus is the power supply voltage on the driver, i.e., the high voltage to be detected.

[0032] In this embodiment, after voltage division by the voltage divider circuit, the voltage slope across the voltage divider capacitor C2 decreases proportionally, as expressed by:

[0033] Since the voltage being detected is generally high, it cannot be used directly for detection. The voltage divider circuit, which consists of two voltage divider capacitors, ensures that the voltage obtained is easy to operate and process.

[0034] In this embodiment, the voltage follower U1 is connected in parallel to the voltage divider circuit, and its input is the voltage on the voltage divider capacitor C2, which is used to collect the voltage across the SiC MOSFET after being divided by the voltage divider circuit.

[0035] In this embodiment, the voltage across the feedback resistor R1 is proportional to the dv / dt across the voltage divider capacitor C2, and the dv / dt across the voltage divider capacitor C2 is proportional to the dv / dt across the SiC MOSFET. The dv / dt across the SiC MOSFET is equal to the current CMTI of the driver. Therefore, it can be deduced that the voltage across the feedback resistor R1 reflects the current CMTI of the driver.

[0036] In this embodiment, one end of the feedback resistor R1 is grounded, and the other end is connected to two diodes D1 and D2. The output of the differentiating circuit is the output of the feedback resistor R1 connected to the two diodes D1 and D2. When the dv / dt across the SiC MOSFET is positive, the output of the differentiating circuit is a positive voltage, and the diode D1 is turned on. When the dv / dt across the SiC MOSFET is negative, the output of the differentiating circuit is a negative voltage, and the diode D2 is turned on.

[0037] In this embodiment, the input terminal of one of the comparators U2 or U3 is connected to the diode D1 or D2, and the input terminal of the other is connected to a reference voltage, the theoretical value of which is:

[0038] In the formula, CMTI is the maximum value of CMTI on the drive core specification datasheet.

[0039] Taking the NSI6602B-DSPNR driver chip from Nanochip Microelectronics as an example, its datasheet specifies a typical value of 150kV / us and a minimum value of 100kV / us. The driver chip specification sheet (datasheet) is a document provided by the device supplier detailing all relevant parameters of the device, used for device selection and related design in R&D.

[0040] In this embodiment, a logic OR gate U4 is also included. The logic OR gate U4 is connected to the comparator circuit and is used to logically convert the outputs of comparators U2 and U3. The converted output is then given to the enable signal of the driver. When the measured dv / dt value across the source and drain of the SiC MOSFET is greater than a threshold, the measured dv / dt characterizes the turn-on speed of the SiC MOSFET and also the CMTI of the driver at this time. This value is compared with the value indicated in the datasheet to determine if the driver has a spacetime risk. If so, the driver is directly shut down to protect the machine. Generally, the threshold is set to 100V / ns, determined by the driver's datasheet. The CMTI of drivers used in silicon carbide is generally between 100-120V / ns; only the maximum value needs to be considered.

[0041] See Figure 4 The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor causes the processor to implement the CMTI parameter detection circuit for SiC MOSFET driver as described above.

[0042] It should be noted that those skilled in the art will understand that all or part of the steps implemented in the embodiments of the present invention can be implemented entirely or partially by software, hardware, firmware, or any combination thereof. When implemented in hardware, it can be implemented entirely or partially by purchasing standard parts or modifications. When implemented in software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid state disks (SSDs)).

[0043] In summary, this invention provides a CMTI parameter detection circuit for SiC MOSFET drivers, which can be directly applied to CMTI detection in actual working environments. It can fully consider various practical factors and make the detection results closer to the real situation.

[0044] Specifically, in existing technologies, a CMTI value is typically measured in an experimental environment. By adjusting the switching speed of the driver (by adjusting parameters such as the drive resistor and capacitor), this CMTI value is made to be less than the maximum value on the datasheet. However, in real-world scenarios, external electromagnetic interference and temperature changes, among other factors, can affect the switching speed of SiC MOSFETs. As a result, the CMTI value measured in the experimental environment may meet the requirements, but in more complex external environments, the CMTI value may be larger than that measured in the experimental environment. This could potentially exceed the specification and cause the device to malfunction.

[0045] Meanwhile, addressing the issue of high device consistency requirements in existing technologies, the detection circuit design of this invention is more flexible, does not rely on highly consistent devices, and can adapt to the characteristics of different devices. Even in cases of poor device consistency, it can accurately detect the CMTI of the SiC MOSFET driver, avoiding the problem of mismatch in the drive circuit due to device differences, thereby ensuring the performance and reliability of the driver in practical applications.

[0046] Specifically, in existing technologies, a CMTI value is typically measured under experimental conditions. The switching speed of the driver is adjusted (by adjusting parameters such as the drive resistor and capacitor) to make this CMTI value less than the maximum value on the datasheet. Once this CMTI value is determined, subsequent products will use the same parameters (i.e., resistors and capacitors with the same resistance values). However, if the consistency of these resistors and capacitors is not good enough, different machines will have different CMTI values. This could result in some machines having a CMTI that is too high, even exceeding the specification, leading to equipment malfunction. By adding the detection circuit of this invention, excessively high CMTIs can be detected and reported in real time, preventing machine malfunction and damage, and also promptly informing technicians of design deficiencies.

[0047] It should be understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various modifications or changes based on them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A CMTI parameter detection circuit for a SiC MOSFET driver, the CMTI parameter detection circuit being connected to a driver drive half-bridge circuit, the driver drive half-bridge circuit including a driver and two SiC MOSFETs, the driver being connected to and driving the two SiC MOSFETs; Its features are, The CMTI parameter detection circuit includes a voltage divider circuit, a differentiator circuit, and a comparator circuit connected in sequence. The voltage divider circuit includes voltage divider capacitor C1 and voltage divider capacitor C2, which are connected in series between the drain and source of the SiC MOSFET. The differentiating circuit is connected to the voltage divider circuit via a voltage follower U1, including a DC blocking capacitor C3 and a feedback resistor R1 connected in series. One end of the DC blocking capacitor C3 is connected to the output terminal of the voltage follower U1, and the other end is connected to the feedback resistor R1. The voltage on the feedback resistor R1 is proportional to the voltage on the voltage divider capacitor C2. The comparison circuit includes comparators U2 and U3 connected in parallel. When the voltage on the feedback resistor R1 is greater than or less than a threshold value, the output of comparator U2 or U3 changes from low level to high level.

2. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 1, characterized in that, The voltage divider circuit is used to reduce the high voltage to be detected. The voltage after voltage reduction is: 。 3. Among them, V C2 Vbus is the voltage across the voltage divider capacitor C2, i.e., the voltage after step-down, and Vbus is the power supply voltage on the driver, i.e., the high voltage to be detected.

4. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 2, characterized in that, After the voltage is divided by the voltage divider circuit, the voltage slope across the voltage divider capacitor C2 decreases proportionally, as expressed by:

5. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 1, characterized in that, The voltage follower U1 is connected in parallel to the voltage divider circuit, and its input is the voltage on the voltage divider capacitor C2. It is used to collect the voltage across the SiC MOSFET after being divided by the voltage divider circuit.

6. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 4, characterized in that, The voltage across the feedback resistor R1 is proportional to the dv / dt across the voltage divider capacitor C2. The dv / dt across the voltage divider capacitor C2 is proportional to the dv / dt across the SiC MOSFET. The dv / dt across the SiC MOSFET is equal to the current CMTI of the driver. Therefore, the voltage across the feedback resistor R1 reflects the current CMTI of the driver.

7. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 5, characterized in that, One end of the feedback resistor R1 is grounded, and the other end is connected to two diodes D1 and D2. The output of the differentiating circuit is the output of the feedback resistor R1 connected to the two diodes D1 and D2. When the dv / dt across the SiC MOSFET is positive, the output of the differentiating circuit is a positive voltage, and the diode D1 is turned on. When the dv / dt across the SiC MOSFET is negative, the output of the differentiating circuit is a negative voltage, and the diode D2 is turned on.

8. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 6, characterized in that, The input terminal of one of the comparators U2 or U3 is connected to the diode D1 or D2, and the input terminal of the other is connected to a reference voltage, the theoretical value of which is: 。 9. In the formula, CMTI is the maximum value of CMTI on the drive core specification datasheet.

10. The CMTI parameter detection circuit for a SiC MOSFET driver as described in claim 1, characterized in that, It also includes a logic OR gate U4, which is connected to the comparison circuit to perform a logical conversion on the outputs of the comparator U2 and the comparator U3, and to give the converted output to the enable signal of the driver. When the measured dv / dt value at the source and drain of the SiC MOSFET is greater than the threshold, the driver is directly turned off.

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