A method for suppressing crosstalk in SiC MOSFET bridge arms with negative voltage turn-off function

Abstract

The application discloses a SiC MOSFET bridge arm crosstalk suppression method with a negative voltage off function, and belongs to the technical field of power electronics and electrical engineering. The method is characterized in that an auxiliary triode circuit with a discharge function is connected in parallel between the gate and the source of the SiC MOSFET. The driving negative voltage on the voltage division capacitor is lifted to about 0V before the off transient state of the SiC MOSFET arrives, thereby relieving the problem of negative crosstalk deterioration caused by the negative voltage off of the SiC MOSFET. At the same time, the voltage division capacitor is used to provide the driving negative voltage for the SiC MOSFET without an additional isolated negative voltage source. The voltage on the voltage division capacitor is discharged through the triode discharge circuit, so that the negative crosstalk voltage peak starts to drop on the basis of zero voltage instead of negative voltage. An auxiliary MOS tube is used in series with an auxiliary capacitor. When the main power tube is normally turned on and off, the auxiliary capacitor is disconnected from the gate and the source of the circuit, thereby relieving the problems of increased turn-on time and increased switching loss caused by the increase of the equivalent capacitance between the gate and the source, and better suppressing the bridge arm crosstalk problem.

Description

Technical Field

[0001] This invention relates to the fields of power electronics and electrical engineering, and in particular to a method for suppressing crosstalk in SiC MOSFET bridge arms with negative voltage turn-off function. Background Technology

[0002] Compared to traditional Si-based devices, SiC MOSFETs offer higher voltage tolerance and higher switching speeds than Si IGBTs, making them ideal for high-voltage, high-frequency applications. However, higher voltage and switching frequency mean larger dv / dt and di / dt, making SiC MOSFETs more sensitive to parasitic parameters of the circuit than Si MOSFETs. This can lead to problems such as bridge arm shoot-through or breakdown. Therefore, traditional Si MOSFET drive circuits are often unsuitable for SiC MOSFETs, requiring a redesign of the drive circuit specifically tailored to the characteristics of SiC MOSFETs.

[0003] Currently, existing suppression schemes both domestically and internationally can be broadly categorized into two types: altering the drive circuit impedance and actively controlling the gate voltage. The former can specifically reduce the voltage change rate dv / dt during the Miller plateau period, or provide a path for the induced current, thus reducing the equivalent impedance of the drive circuit. However, this method increases the charging and discharging time of the gate-source capacitance of the switching transistor, sacrificing its fast switching speed advantage, and consequently leading to greater switching losses and a decrease in switching frequency. The latter is equivalent to increasing the relative turn-on threshold voltage of the SiC MOSFET, but this method also reduces the relative negative voltage tolerance of the SiC MOSFET, resulting in an increase in the negative crosstalk voltage amplitude and a certain degree of deterioration of the negative crosstalk. From a safety perspective, the value of the gate drive negative voltage is limited by the device's negative voltage tolerance; when the device's negative voltage tolerance is low, the range of selectable negative voltages is very limited.

[0004] Therefore, in order to fully leverage the advantages of SiC MOSFETs in fast switching speed, it is necessary to continue researching a SiC MOSFET drive circuit design method that has bridge arm crosstalk suppression function, mitigates negative crosstalk degradation, and minimizes the sacrifice of switching speed.

[0005] Regarding crosstalk suppression methods using parallel capacitance between the gate and source, besides the theoretically analyzed issue of reduced switching speed and increased switching losses due to the series capacitance, the threshold voltage of SiC MOSFETs is relatively low, sometimes as low as 1-2V. While this suppression measure does suppress positive crosstalk during turn-on, there is still a risk of the switching transistor being mistakenly turned on due to oscillation exceeding the threshold voltage. Therefore, in practical applications, a negative voltage turn-off is generally used in addition to this crosstalk suppression measure to reduce the harm caused by positive crosstalk and make the entire system safer and more reliable. However, this will correspondingly lead to a deterioration of negative crosstalk.

[0006] This patent proposes a SiC MOSFET bridge arm crosstalk suppression method with negative voltage turn-off function to address problems such as crosstalk degradation caused by SiC MOSFET bridge arm crosstalk and negative voltage turn-off suppression methods. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a SiC MOSFET bridge arm crosstalk suppression method with negative voltage turn-off functionality. This method involves connecting an auxiliary transistor circuit with a discharge function in parallel between the gate and source of the power transistor. Before negative crosstalk occurs, the driving negative voltage on the voltage divider capacitor is raised to approximately 0V. Furthermore, by using an auxiliary MOSFET connected in series with an auxiliary capacitor, the auxiliary capacitor is disconnected from the gate-source of the circuit during the main power transistor's turn-on and turn-off operations. This alleviates, to some extent, the problems caused by the increased turn-on time and switching losses due to the increased equivalent capacitance between the gate and source, thus better suppressing bridge arm crosstalk. This effectively solves the problems of SiC MOSFET bridge arm crosstalk and the deterioration of negative crosstalk caused by negative voltage turn-off suppression methods.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for suppressing crosstalk in SiC MOSFET bridge arms with negative voltage turn-off function is disclosed. The method adds a transistor discharge circuit to solve the problem caused by negative voltage turn-off. During normal turn-on and turn-off, the auxiliary power transistor disconnects the capacitor from the circuit, which does not affect the normal operation of the main transistor. During the turn-on transient, the capacitor voltage divider provides a negative voltage to the disturbed transistor to alleviate the harm caused by positive crosstalk. During normal turn-on, the discharge circuit raises the capacitor voltage to zero to prepare for the reduction of negative crosstalk during the turn-off transient.

[0010] The driving circuit used in the method includes a SiC MOSFET negative voltage turn-off circuit considering parasitic parameters, a SiC MOSFET negative voltage discharge circuit, and a SiC MOSFET crosstalk current shunt circuit; the upper transistor S... H The gate of the voltage divider is connected to the voltage divider circuit, which consists of C. 1H R1H D H Branch and C 2H R 2H S 3H C is formed by connecting branches in parallel. 1H R 1H D H The branch line is connected to the upper pipe S. H Between the driver chip and the gate, diode D H The direction is consistent with the direction of the drive current flowing to the gate of the driver chip. The crosstalk current shunt circuit is composed of C. 2H R 2H S 3H Composition, S 3H For auxiliary power transistors; SiC MOSFET transistor negative voltage discharge route transistor T H Pull-down resistor R 3H R 4H Composition: The emitter of the transistor and the capacitor C 1H Connected, collector through resistor R 4H With capacitor C 2H Connected, with the base connected through a pull-down resistor R 3H When connected, when the driver chip provides a positive voltage, the forward voltage drop of the diode causes the base voltage of the transistor to be greater than the emitter voltage, and the transistor is in a reverse cutoff state. At the same time as the lower transistor is turned on, the driving voltage of the upper transistor is reduced to zero. At this time, the base voltage is much smaller than the emitter voltage, and the transistor begins to conduct in the forward direction. The auxiliary circuit of the lower transistor is the same as that of the upper transistor.

[0011] Furthermore, the auxiliary power transistor S 3H S 3L There are two basic requirements for the selection of [the component / component]: firstly, the on-resistance R... DS(on) The requirements are small size and short switching time to keep up with the switching speed of the main switching transistor. Therefore, a low-power transistor is considered. Low-power transistors have high input impedance, low drive power, and are easy to drive; they have very fast switching speeds, reaching several ns to tens of ns, making them suitable for high-frequency circuits; they have simple structure, small size, are easy to integrate and manufacture, and have good stability.

[0012] Furthermore, the equivalent model of SiC MOSFET is derived from the gate-drain capacitance C. GD Gate-source capacitance C GS Drain-source capacitance C DS Composition, R G This is the gate drive resistor. The RCD voltage divider circuit is connected between the gate and source of the device and the driver chip. This circuit consists of capacitors C1 and C2 and resistors R1 and R2. The voltage division between capacitors C1 and C2 can be achieved by the ratio of R1 and R2.

[0013] Let's analyze the specific steps of turning the upper transistor off and the lower transistor on and off: Before the lower transistor is turned on, there is no current in the drive circuit of the upper transistor. Through the positive voltage of the upper transistor's drive, the power module provides voltage V. GG For auxiliary capacitor C 1H C 2H Pre-charging is performed, where R 1H and R 2H There are two large resistors, C 1H C 2H A preset negative voltage is provided to ensure sufficient negative voltage before positive crosstalk occurs when the lower transistor is turned on. The emitter of the transistor and capacitor C... 1H Connected, collector through resistor R 4H With capacitor C 2H The base of the transistor is connected to ground via a pull-down resistor R3. A diode D is connected between the base and emitter of the transistor. H Its direction is the same as the direction of the current flow in the drive circuit when it is on. When the driver chip provides a positive voltage, the forward voltage drop of the diode causes the base voltage of the transistor to be greater than the emitter voltage, and the transistor is in the reverse cutoff state. Therefore, the positive drive voltage only passes through the voltage divider capacitor C. 1H and C 2H In the branch circuit, the auxiliary power transistor is also in the conducting state. At this time, the capacitor divides the voltage, causing C to... 1H The voltage across the capacitor is the required negative voltage, preparing for the positive crosstalk voltage when the lower transistor turns on. After stabilization, the capacitor voltage dividers are as follows:

[0014]

[0015] Furthermore, when the lower transistor begins to turn on, the auxiliary power transistor removes the voltage divider capacitor from the circuit, which has no impact on the normal turn-on of the lower transistor. Simultaneously with the turn-on of the lower transistor, the drive voltage of the upper transistor is reduced to zero due to the pull-down resistor R. 3H The presence of [a specific voltage source] causes the base voltage of the transistor to drop to zero within a very short time. At this point, the base voltage is much smaller than the emitter voltage, and the transistor begins forward conduction. During the transient turn-on of the lower transistor, the drain-source capacitance of the lower transistor decreases, while the drain-source current of the upper transistor increases, supplying power to the output capacitor C of the upper transistor. oss_H Charging, in its gate-drain capacitance C GD The upper induced displacement current i GD The current flows through the drive circuit of the upper transistor, is shunt between the two branches of the gate, and a portion of it is distributed across the gate-source capacitance C. GS A positive crosstalk voltage with the upper polarity positive and the lower polarity negative is generated at both ends. Part of it flows through the external drive circuit and into the voltage divider capacitor C. 1H The upward direction is from right to left, therefore diode D H When in reverse cutoff state, capacitor C 1H The charge on the transistor will only pass through the resistor R. 4HThe branch circuit discharges the pre-stored negative charge, and the auxiliary power transistor S of the upper transistor... 3H The auxiliary capacitor C is turned on along with the transient turn-on of the lower transistor. 2H Integrating it between the gate and source of the upper transistor also provides a low-impedance loop for crosstalk induced current, mitigating the harm caused by positive crosstalk during the turn-on transient period.

[0016] Meanwhile, during the turn-on transient, the capacitance C can be basically considered to be... 1H The voltage across the capacitor is the pre-stored negative driving voltage from the first stage. Therefore, when positive crosstalk occurs, the capacitor C... 1H The charge on the capacitor C hasn't had time to dissipate, and there's enough negative voltage on it to mitigate positive crosstalk. 1H The charge on the transistor begins to discharge through the transistor branch; simply remove capacitor C before turning it off. 1H The charge stored on the transistor is complete, and the time from the turn-on transient to the turn-on steady state is sufficient to raise the charge on the voltage divider capacitor to 0V. Therefore, the switching speed of the transistor has no effect on this method.

[0017] Furthermore, when the lower transistor begins to turn off, its auxiliary power transistor remains off, disconnecting the auxiliary capacitor from the gate-source of the lower transistor, similar to the turn-on transient. Before the lower transistor reaches the turn-off transient, the voltage across the voltage divider capacitor has risen to approximately 0V, preparing to mitigate the negative crosstalk voltage during the lower transistor's turn-off transient. During the lower transistor's turn-off transient, the drain-source capacitance of the lower transistor increases, while the drain-source current of the upper transistor decreases, similarly affecting the output capacitor C of the upper transistor. oss_H Charging, in its gate-drain capacitance C GD A displacement current i is induced on the upper part, which is opposite to the direction of the turn-on period. GD This current also flows through the drive circuit of the upper transistor, and is shunt between the two branches of the gate. A portion of it is distributed across the gate-source capacitance C. GS Crosstalk voltages with negative at the top and positive at the bottom are generated at both ends. Part of this voltage flows through the external drive circuit and into the voltage divider capacitor C. 1H The direction of upward movement is from left to right, therefore diode D H When the transistor is in forward conduction mode, the base voltage is greater than the collector voltage; when it is in reverse cutoff mode, the transistor is in reverse cutoff mode. Furthermore, the auxiliary power transistor S of the upper transistor... 3H The circuit remains open; the auxiliary capacitor C will be used. 2H The parallel connection between the gate and source of the upper transistor also provides a low-impedance loop for the reverse crosstalk induced current. The negative crosstalk voltage spike starts to decrease from 0V instead of starting to decrease from a negative voltage, which alleviates the harm caused by negative crosstalk during the turn-off transient.

[0018] Compared with the prior art, the technical solution adopted in this invention has the following technical effects:

[0019] (1) By using an RC voltage divider circuit, negative voltage shutdown can be achieved when the external driver chip only provides positive voltage. Compared with the traditional negative voltage shutdown circuit, it is not necessary to add an additional negative voltage source.

[0020] (2) To address the problem of worsening negative crosstalk in the traditional negative voltage turn-off suppression method for bridge arm crosstalk, a discharge circuit of transistor and diode is used to turn off the transistor by utilizing the voltage drop of the diode. This discharges the charge on the voltage divider capacitor that provides negative voltage for positive crosstalk during turn-on, raising its voltage to 0V, so that the negative crosstalk voltage spike begins to decrease from zero voltage rather than negative voltage.

[0021] (3) To address the problem of slowing down the normal turn-on speed of the switching transistor caused by the traditional RCD negative voltage turn-off circuit, a small power auxiliary power transistor is used to remove the auxiliary capacitor from the gate-source of the circuit when the switching transistor is normally turned on, so that the auxiliary circuit does not affect the normal turn-on of the main power transistor. Attached Figure Description

[0022] Figure 1 This is a circuit diagram of a SiC MOSFET bridge arm crosstalk suppression method with negative voltage turn-off function in this invention.

[0023] Figure 2 This is a schematic diagram of the gate-source and drain-source voltage waveforms when the lower transistor of the bridge arm circuit is turned on and off in this invention.

[0024] Figure 3 This is a timing diagram of the switching of the power transistors in the bridge arm circuit and auxiliary circuit of this invention.

[0025] Figure 4 This is a schematic diagram of the current loop for pre-charging the voltage divider capacitor in the auxiliary circuit of the upper transistor before the lower transistor is turned on.

[0026] Figure 5 This is a schematic diagram showing the flow direction of crosstalk induced current and voltage divider capacitor discharge current in the drive circuit of the upper transistor during the transient state of the lower transistor being turned on.

[0027] Figure 6 This is a schematic diagram showing the flow direction of crosstalk induced current in the drive circuit of the upper transistor during the transient state of the lower transistor being turned off. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to this specific embodiment.

[0029] In the following detailed description of the invention, certain specific details are described in detail. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0030] A method for suppressing crosstalk in SiC MOSFET bridge arms with negative voltage turn-off function is disclosed. The method adds a transistor discharge circuit to solve the problem caused by negative voltage turn-off. During normal turn-on and turn-off, the auxiliary power transistor disconnects the capacitor from the circuit, which does not affect the normal operation of the main transistor. During the turn-on transient, the capacitor voltage divider provides a negative voltage to the disturbed transistor to alleviate the harm caused by positive crosstalk. During normal turn-on, the discharge circuit raises the capacitor voltage to zero to prepare for the reduction of negative crosstalk during the turn-off transient.

[0031] The driving circuit used in the method is as follows: Figure 1 As shown, it includes a SiC MOSFET negative voltage turn-off circuit considering parasitic parameters, a SiC MOSFET negative voltage discharge circuit, and a SiC MOSFET crosstalk current shunt circuit; the upper transistor S... H The gate of the voltage divider is connected to the voltage divider circuit, which consists of C. 1H R 1H D H Branch and C 2H R 2H S 3H C is formed by connecting branches in parallel. 1H R 1H D H The branch line is connected to the upper pipe S. H Between the driver chip and the gate, diode D H The direction is consistent with the direction of the drive current flowing to the gate of the driver chip. The crosstalk current shunt circuit is composed of C. 2H R 2H S 3H Composition, S 3H For auxiliary power transistors; SiC MOSFET transistor negative voltage discharge route transistor T H Pull-down resistor R 3H R 4H Composition: The emitter of the transistor and the capacitor C 1H Connected, collector through resistor R 4H With capacitor C 2H Connected, with the base connected through a pull-down resistor R 3H When connected, when the driver chip provides a positive voltage, the forward voltage drop of the diode causes the base voltage of the transistor to be greater than the emitter voltage, and the transistor is in a reverse cutoff state. At the same time as the lower transistor is turned on, the driving voltage of the upper transistor is reduced to zero. At this time, the base voltage is much smaller than the emitter voltage, and the transistor begins to conduct in the forward direction. The auxiliary circuit of the lower transistor is the same as that of the upper transistor.

[0032] Furthermore, the auxiliary power transistor S 3H S 3L There are two basic requirements for the selection of [the component / component]: firstly, the on-resistance R...DS(on) The requirements are small size and short switching time to keep up with the switching speed of the main switching transistor. Therefore, a low-power transistor is considered. Low-power transistors have high input impedance, low drive power, and are easy to drive; they have very fast switching speeds, reaching several ns to tens of ns, making them suitable for high-frequency circuits; they have simple structure, small size, are easy to integrate and manufacture, and have good stability.

[0033] Furthermore, the equivalent model of SiC MOSFET is derived from the gate-drain capacitance C. GD Gate-source capacitance C GS Drain-source capacitance C DS Composition, R G This is the gate drive resistor. The RCD voltage divider circuit is connected between the gate and source of the device and the driver chip. This circuit consists of capacitors C1 and C2 and resistors R1 and R2. The voltage division between capacitors C1 and C2 can be achieved by the ratio of R1 and R2.

[0034] The following analysis focuses on turning the upper transistor off and the lower transistor on and off: Before the lower transistor is turned on, there is no current in the drive circuit of the upper transistor. Through the positive voltage of the upper transistor's drive, the power module provides voltage V. GG For auxiliary capacitor C 1H C 2H Pre-charging is performed, where R 1H and R 2H There are two large resistors, C 1H C 2H A preset negative voltage is provided to ensure sufficient negative voltage before positive crosstalk occurs when the lower transistor is turned on. The emitter of the transistor and capacitor C... 1H Connected, collector through resistor R 4H With capacitor C 2H The base of the transistor is connected to ground via a pull-down resistor R3. A diode D is connected between the base and emitter of the transistor. H Its direction is the same as the direction of the current flow in the drive circuit when it is on. When the driver chip provides a positive voltage, the forward voltage drop of the diode causes the base voltage of the transistor to be greater than the emitter voltage, and the transistor is in the reverse cutoff state. Therefore, the positive drive voltage only passes through the voltage divider capacitor C. 1H and C 2H In the branch circuit, the auxiliary power transistor is also in the conducting state. At this time, the capacitor divides the voltage, causing C to... 1H The voltage across the capacitor is the required negative voltage, preparing for the positive crosstalk voltage when the lower transistor turns on. After stabilization, the capacitor voltage dividers are as follows:

[0035]

[0036] Furthermore, such as Figure 2The diagram shows the gate-source and drain-source voltage waveforms of the lower transistor in the bridge arm circuit during turn-on and turn-off in this invention. The [t0~t1] stage is before the lower transistor turns on. During this stage, the gate-source voltage of the lower transistor is a preset negative voltage value. This negative voltage does not require an external isolation negative voltage source; it can be provided by the voltage divider capacitor in the auxiliary circuit. At this time, the gate-source voltage of the upper transistor is also a preset negative voltage, and the drain-source voltage is zero. [t1~t3] is the turn-on transient stage. At time t1, the lower transistor begins to turn on, and the gate-source voltage of the lower transistor begins to rise. At time t2, the gate-source voltage of the lower transistor reaches the Miller plateau voltage, and the drain-source voltage of the lower transistor begins to decrease. The drain-source voltage of the upper transistor begins to rise. A positive crosstalk voltage is generated during the Miller plateau stage. This voltage rises from the preset negative voltage. During this stage, a low-impedance loop supplies the flow of crosstalk induced current, alleviating the bridge arm shoot-through problem caused by the positive crosstalk during the turn-on transient period. [t3~t5] represents the steady-state turn-on process. During this process, the gate-source voltage of the lower transistor and the drain-source voltage of the upper transistor remain unchanged. However, due to the presence of the transistor's discharge circuit, the charge on the voltage divider capacitor C1 of the upper transistor gradually dissipates, and its gate-source voltage gradually rises from a negative voltage. At time t4, when the lower transistor begins to turn on, the auxiliary power transistor of the lower transistor removes the voltage divider capacitor from the circuit, having no impact on the normal turn-on of the lower transistor. Simultaneously with the turn-on of the lower transistor, the drive voltage of the upper transistor is reduced to zero due to the pull-down resistor R. 3H The presence of [a specific element] causes the base voltage of the transistor to drop to zero within a very short time. At this point, the base voltage is much smaller than the emitter voltage, and the transistor begins forward conduction. During the turn-on transient of the lower transistor, its drain-source capacitance decreases, while the drain-source current of the upper transistor increases, supplying power to the output capacitor C of the upper transistor. oss_H Charging, in its gate-drain capacitance C GD The upper induced displacement current i GD The current flows through the drive circuit of the upper transistor, is shunt between the two branches of the gate, and a portion of it is distributed across the gate-source capacitance C. GS A positive crosstalk voltage with the upper polarity positive and the lower polarity negative is generated at both ends. Part of it flows through the external drive circuit and into the voltage divider capacitor C. 1H The upward direction is from right to left, therefore diode D H When in reverse cutoff state, capacitor C 1H The charge on the transistor will only pass through the resistor R. 4H The branch circuit discharges the pre-stored negative charge, and the auxiliary power transistor S of the upper transistor... 3H The auxiliary capacitor C is turned on along with the transient turn-on of the lower transistor. 2H Integrating it between the gate and source of the upper transistor also provides a low-impedance loop for crosstalk induced current, mitigating the harm caused by positive crosstalk during the turn-on transient period.

[0037] Furthermore, such as Figure 3The diagram shows the switching timing of the upper and lower power transistors in the bridge arm circuit of this invention. Taking the turn-on phase of the lower transistor as an example, i.e., the [t1~t5] phase, at time t1, the lower transistor begins to turn on, while the upper transistor remains off. At this time, the auxiliary power transistor of the lower transistor remains off, while the auxiliary power transistor of the upper transistor turns on transiently along with the turn-on of the lower transistor, turning on the auxiliary capacitor C of the upper transistor. 2H The auxiliary power transistor is connected between the gate and source of the upper transistor to provide a low-impedance loop for the crosstalk current caused by the turn-on transient of the lower transistor, thus mitigating the impact of forward crosstalk on the power transistor during the turn-on of the lower transistor. During the normal turn-on phase of the lower transistor, the auxiliary power transistor of the upper transistor is always on, and the auxiliary capacitor C... 2H It is always connected between the gate and source of the upper transistor, but it does not affect the normal switching of the lower transistor. At time t5, the lower transistor begins to turn off. At this time, the auxiliary power transistor of the upper transistor does not turn off with the lower transistor, but leaves sufficient margin to provide a path for the crosstalk current during the turn-off period before turning it off. The turn-on period of the upper transistor begins after time t8, and the analysis is similar to that of the upper transistor turn-on.

[0038] Furthermore, such as Figure 4 The diagram shown is an equivalent circuit diagram of the pre-charging of the upper transistor before the lower transistor is turned on in this invention. Before the lower transistor is turned on, the upper transistor is pre-charged by the driver chip via D. 2H C 1H S 3H C 2H Branch to auxiliary capacitor C 1H C 2H Pre-charge C 1H The voltage on the tube is charged to the negative voltage required to drive the power transistor, in preparation for the upcoming positive crosstalk.

[0039] Furthermore, such as Figure 5 The diagram shows the equivalent circuit diagram of the crosstalk current flow of the upper transistor during the turn-on transient phase of the lower transistor in this invention. During the turn-on transient phase of the lower transistor, the gate-drain capacitance C of the upper transistor... GS_H The induced current generated flows from the drain to the gate, is shunt through the gate, and a portion of the current flows to the device's gate-source capacitance C. GS_H Crosstalk voltage is generated, and part of the current flows through the auxiliary capacitor C. 2H The branch reduces the current flowing through the gate-source capacitance C. GS_H The induced current on it is reduced, which means that C is reduced at this time. GS_H The positive crosstalk voltage on the capacitor. Auxiliary capacitor C 1H The voltage direction on the C is positive on the left and negative on the right. 1H After charging, the charge on it will pass through transistor T. H When the branch circuit is released, the voltage rises accordingly.

[0040] Furthermore, such as Figure 6The diagram shows the equivalent circuit diagram of the crosstalk current flow of the upper transistor during the turn-off transient phase of the lower transistor in this invention. Before the lower transistor reaches the turn-off transient, the voltage across the voltage divider capacitor has risen to approximately 0V, preparing to mitigate the negative crosstalk voltage during the turn-off transient of the lower transistor. During the turn-off transient of the lower transistor, the drain-source capacitance of the lower transistor increases, while the drain-source current of the upper transistor decreases, similarly affecting the output capacitor C of the upper transistor. oss_H Charging, in its gate-drain capacitance C GD_H A displacement current i should be generated in the opposite direction to that during the turn-on period. GD This current also flows through the drive circuit of the upper transistor, and is shunt between the two branches of the gate. A portion of it is distributed across the gate-source capacitance C. GS Crosstalk voltages with negative at the top and positive at the bottom are generated at both ends. Part of this voltage flows through the external drive circuit and into the voltage divider capacitor C. 1H The direction of upward movement is from left to right, therefore diode D H When the transistor is in forward conduction mode, the base voltage is greater than the collector voltage; when it is in reverse cutoff mode, the transistor is in reverse cutoff mode. Furthermore, the auxiliary power transistor S of the upper transistor... 3H The circuit remains open; the auxiliary capacitor C will be used. 2H The parallel connection between the gate and source of the upper transistor also provides a low-impedance loop for the reverse crosstalk induced current. The negative crosstalk voltage spike starts to decrease from 0V instead of starting to decrease from a negative voltage, which alleviates the harm caused by negative crosstalk during the turn-off transient.

[0041] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A SiC MOSFET bridge arm cross-talk suppression method with negative voltage turn-off function, characterized in that, The method employs an auxiliary circuit for the upper transistor, including a SiC MOSFET negative voltage turn-off circuit considering parasitic parameters, a SiC MOSFET negative voltage discharge circuit, and a SiC MOSFET crosstalk current shunt circuit; the upper transistor... S H The gate is connected through the gate resistor. R G_H It is connected to the output terminal of the driver chip and also to a voltage divider circuit, which consists of... C 1H , R 1H , D H branch road and C 2H , R 2H , S 3H Branch road structure, among which C 1H , R 1H , D H One end of the branch is connected to the output of the driver chip, and the other end is connected to the upper transistor. S H gate, diode D H The direction is consistent with the direction of the drive current flowing to the gate of the driver chip; C 1H and R 1H Connected in parallel to the diode D H cathode and S H Between the gates, C 2H , R 2H , S 3H The branch circuit forms a crosstalk current shunt circuit. S 3H As an auxiliary power transistor, its source is connected to the upper transistor. S H Gates connected, S 3H Drain through R 2H Connect the upper pipe S H The source and gate are driven by a control signal. C 2H and R 2H Parallel connection; SiC MOSFET transistor negative voltage discharge route transistor T H pull-down resistor R 3H , R 4H composition, triode T H the emitter is connected to the cathode, and the collector passes through a resistor D H the cathode is connected to the source, and the base passes through a pull-down resistor R 4H the upper tube S H the source is connected to the base, and the base passes through a pull-down resistor R 3H the upper tube S H the source is connected to the base; when the driving chip provides a positive voltage, the conduction voltage drop of the diode causes the base voltage of the triode to be greater than the emitter voltage, the triode is in a reverse-off state, the lower tube is turned on at the same time, the driving voltage of the upper tube is reduced to zero, the base voltage at this time is much smaller than the emitter voltage, and the triode starts to conduct in the forward direction; the auxiliary circuit of the lower tube and the auxiliary circuit of the upper tube have the same structure and working principle; The method utilizes a voltage division circuit to provide a driving negative voltage for a main power tube without an additional isolated negative voltage source, and through parallel connection of an auxiliary triode circuit with a discharge function between the gate and source of the power tube, the driving negative voltage on the voltage division capacitor is raised to about 0V before negative crosstalk occurs, the influence of negative voltage shutdown on the shutdown period is reduced, and through use of an auxiliary MOS tube in series with an auxiliary capacitor, the auxiliary capacitor is disconnected from the gate and source of the circuit when the main power tube is turned on and off, the problem of increased turn-on time and increased switching loss caused by the increase of the equivalent capacitance between the gate and source is alleviated, and the bridge arm crosstalk problem is better inhibited.

2. The SiC MOSFET bridge arm cross-talk suppression method with negative voltage turn-off function according to claim 1, characterized in that, The auxiliary power tube S 3H There are two basic requirements for the selection, one is the on-resistance is small, two is the switch time is short, and follow the switch speed of the main switch tube.

3. The SiC MOSFET bridge arm cross-talk suppression method with negative voltage turn-off function according to claim 1, characterized in that, The voltage divider circuit is connected between the gate and source of the device and the driver chip. This circuit consists of a capacitor. C 1H , C 2H and resistance R 1H , R 2H Composition, through R 1H and R 2H The ratio can realize the capacitance C 1H and C 2H The partial pressure.

4. The SiC MOSFET bridge arm cross-talk suppression method with negative voltage turn-off function according to claim 1, characterized in that, Before the lower tube is turned on, there is no current in the auxiliary circuit of the upper tube, and the power module provides voltage to the auxiliary capacitor through the driving positive pressure of the upper tube C 1H 、 C 2H Precharge is performed, wherein R 1H and R 2H Two large resistance resistors are provided, and C 1H 、 C 2H A preset negative voltage is provided, so that sufficient negative voltage is provided before the positive crosstalk of the lower tube is turned on.

5. The SiC MOSFET bridge arm cross-talk suppression method with negative voltage turn-off function according to claim 1, characterized in that, During the turn-on transient of the lower transistor, the induced current generated on the gate-drain capacitance of the upper transistor flows from the drain to the gate. This current is shunt through the gate, with some flowing to the gate-source capacitance to generate crosstalk voltage, and some flowing through the auxiliary capacitor. C 2H The branch circuit reduces the induced current flowing through the gate-source capacitor, which in turn reduces the forward crosstalk voltage on the gate-drain capacitor; auxiliary capacitor C 1H The voltage direction is positive on the left and negative on the right. When the driver chip no longer supplies power... C 1H After charging, the charge on it will pass through the transistor. T H When the branch circuit is released, the voltage rises accordingly.

6. The SiC MOSFET bridge arm cross-talk suppression method with negative voltage turn-off function according to claim 1, characterized in that, Before the lower transistor reaches the turn-off transient, the voltage across the voltage divider capacitor has risen to approximately 0V to prepare for mitigating the negative crosstalk voltage during the turn-off transient. During the turn-off transient, the drain-source capacitance of the lower transistor increases, while the drain-source current of the upper transistor decreases, similarly charging the output capacitor of the upper transistor. This results in a displacement current in its gate-drain capacitance, flowing in the opposite direction to that during the turn-on period. This current also flows through the drive circuit of the upper transistor, being shunt between the two branches at the gate and source. Part of this current generates a crosstalk voltage (negative at the top, positive at the bottom) across the gate-source capacitor, while the other part flows through the external drive circuit and onto the voltage divider capacitor. C 1H The direction of upward movement is from left to right, therefore the diode D H When the transistor is in forward conduction, the base voltage is greater than the collector voltage. When the transistor is in reverse cutoff, the auxiliary power transistor of the upper transistor... S 3H The circuit remains open; the auxiliary capacitor will be used. C 2H It is incorporated into the gate-source space of the upper transistor.

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