A series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit

Abstract

The present invention discloses a series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit, which belongs to the field of power electronics technology and includes: n short-circuit protection sub-circuits, wherein the short-circuit protection sub-circuits include: a short-circuit detection circuit for detecting whether a SiC MOSFET is short-circuited; an overcurrent suppression circuit for reducing the voltage between the G and S poles of the short-circuited SiC MOSFET when the short-circuit detection circuit detects that the SiC MOSFET is short-circuited, and at the same time, according to the voltage division state of the SiC MOSFET adjacent to the short-circuited SiC MOSFET, further reducing the voltage between the G and S poles of the short-circuited SiC MOSFET to balance the short-circuit transient voltage distribution; an overvoltage suppression circuit, which is activated when the voltage of the short-circuited SiC MOSFET exceeds the average voltage value of all series-connected SiC MOSFETs, suppresses the voltage rise rate between the D and S poles of the short-circuited SiC MOSFET, and realizes overvoltage suppression. The present invention can be integrated into a traditional series-connected SiC MOSFET drive circuit as an additional circuit for short-circuit protection, extending the short-circuit withstand time of each series-connected SiC MOSFET and improving reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics and relates to a series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit. Background Art

[0002] Directly connecting SiC MOSFETs in series is one of the key methods for addressing the insufficient withstand voltage rating of a single device and reducing converter costs. When a short-circuit occurs in a series SiC MOSFET module, due to the varying volt-ampere characteristics of the individual SiC MOSFETs in the module, some will initially enter saturation at the same short-circuit current. These SiC MOSFETs entering saturation have higher on-resistance than the other SiC MOSFETs in series, and will also experience a higher voltage divider within the entire series module. Therefore, unlike a single SiC MOSFET in a short-circuit condition at rated voltage, a series SiC MOSFET module will experience a higher short-circuit voltage for some SiC MOSFETs, resulting in greater transient losses and reduced short-circuit withstand time and safety. Summary of the Invention

[0003] In order to solve the above problems, the technical solution adopted by the present invention is: a series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit, comprising:

[0004] n short-circuit protection sub-circuits,

[0005] n short-circuit protection sub-circuits are respectively connected to n SiC MOSFETs connected in series, one by one, where n ≥ 2; the short-circuit protection sub-circuits include:

[0006] A short-circuit detection circuit is used to detect whether a short circuit occurs in the SiC MOSFET;

[0007] an overcurrent suppression circuit for reducing the voltage between the G and S poles of the short-circuited SiC MOSFET when the short-circuit detection circuit detects that the SiC MOSFET is short-circuited, and further reducing the voltage between the G and S poles of the short-circuited SiC MOSFET according to the voltage division state of the SiC MOSFET adjacent to the short-circuited SiC MOSFET to balance the short-circuit transient voltage distribution;

[0008] The overvoltage suppression circuit is activated when the voltage applied to the short-circuited SiC MOSFET exceeds the average voltage of all series-connected SiC MOSFETs. It suppresses the rate of voltage rise between the D and S poles of the short-circuited SiC MOSFET, thus achieving overvoltage suppression.

[0009] Furthermore: the short circuit detection circuit includes a second resistor R B , capacitor C A And comparator U, second resistor R B With capacitor C A A low-pass filter is formed to detect when the voltage across the parasitic inductance L between the K and S poles of the SiC MOSFET rises to the threshold value V due to the rapid change of current. ref When , the comparator U outputs a short-circuit alarm signal and activates the overcurrent suppression circuit.

[0010] Furthermore: the overcurrent suppression circuit includes a gate drive resistor R G , the first diode D A , the first N-channel MOSFET Q A , the second N-channel MOSFET Q B , the first resistor R A , the third resistor R C ;

[0011] When the short-circuit protection subcircuit turns on the first N-channel MOSFET Q A When the gate drive resistor R G With the first resistor R A The voltage divider circuit is formed to quickly reduce the voltage between the G and S poles of the short-circuited SiC MOSFET to suppress the short-circuit current; at the same time, the second N-channel MOSFET Q B Turn off the third resistor R C When the next SiC MOSFET connected in series with the short-circuited SiC MOSFET is over-voltage, the third resistor R C The voltage drop across the short-circuited SiC MOSFET will further reduce the voltage between the G and S poles, increasing its own on-resistance to balance the voltage distribution.

[0012] The first diode D A Used to separate the overcurrent suppression circuit from the driver circuit during SiC MOSFET turn-off.

[0013] Furthermore: the overvoltage suppression circuit includes a buffer capacitor C B , the second diode D B , transient suppression diode Z top and the third diode D C ;

[0014] The third diode D C connected to the overvoltage suppression circuit of the next series-connected SiC MOSFET adjacent to the short-circuited SiC MOSFET;

[0015] Among them, the buffer capacitor CB When the voltage of the sub-SiC MOSFET exceeds the average voltage between the D-pole and S-pole of each series SiC MOSFET unit, the second diode D B Charging to reduce the voltage rise rate, transient suppression diode Z top When the voltage between the D and S electrodes of the short-circuited SiC MOSFET exceeds Z top Reverse breakdown occurs when the voltage is clamped, clamping the voltage between the D-pole and S-pole of the corresponding SiC MOSFET to avoid overvoltage breakdown of the short-circuited SiC MOSFET. The third diode D C During the normal turn-on period of the short-circuited SiC MOSFET, the stored overvoltage energy is released to the snubber capacitor of other series-connected SiC MOSFETs.

[0016] Furthermore, the comparator U is of type TLV3501, and the reference voltage of the comparator U is provided by the voltage reference chip TL432. ref The value is 1.25V.

[0017] Furthermore: the first diode D A The first N-channel MOSFET Q is SS110. A The model used is BSP315PH6327, the second N-channel MOSFET Q B The model is STD10N60M2, the gate drive resistor R G is 5Ω, the first resistor R A is 15Ω, the third resistor R C is 15Ω.

[0018] Furthermore: the buffer capacitor C in the overvoltage suppression circuit B The value of the second diode D is 42nF. B With the third diode D C The models are all SP20D120CTT, transient suppression diode Z top It consists of two BNAK3-430C connected in series.

[0019] The present invention provides a series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit. When a series SiC MOSFET short-circuit fault occurs, each SiC MOSFET series unit reduces its own drive voltage to suppress the short-circuit current. Simultaneously, when any SiC MOSFET first enters the saturation region, the overcurrent suppression circuit of the adjacent SiC MOSFET is activated, balancing the voltage distribution during the short-circuit period while further suppressing the short-circuit current.

[0020] The present invention can be integrated into a conventional series SiC MOSFET drive circuit as an additional short-circuit protection circuit, extending the short-circuit withstand time of each series SiC MOSFET and improving module reliability. When a short-circuit fault occurs, the circuit can suppress the short-circuit current by reducing the drive voltage of the SiC MOSFET operating in the non-saturation region. At the same time, it also has an overvoltage protection function to prevent a single SiC MOSFET from entering the saturation region first and causing excessive voltage division. The present invention does not require the use of additional isolation devices and can be integrated with a commonly used series SiC MOSFET drive circuit. It has the following advantages:

[0021] When a short-circuit fault occurs in a series SiC MOSFET, each series unit reduces its own drive voltage to suppress the short-circuit current. Simultaneously, when any SiC MOSFET first enters the saturation region, it activates the overcurrent suppression circuit of the adjacent SiC MOSFET above it, balancing the voltage distribution during the short-circuit period while further suppressing the short-circuit current. This invention can be integrated into a conventional series SiC MOSFET drive circuit as an additional short-circuit protection circuit, extending the short-circuit withstand time of each series SiC MOSFET and improving module reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 It is a schematic diagram of the composition of the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of three SiC MOSFETs connected in series using the device of the present invention;

[0025] Figure 3 This is a simulation diagram of the short-circuit transient voltage waveform of three series-connected SiC MOSFETs according to the present invention;

[0026] Figure 4 This is a simulation diagram of the transient voltage waveform of three series-connected SiC MOSFETs short-circuited without applying the present invention;

[0027] Figure 5 This is a simulation diagram of the short-circuit transient current waveform of three series-connected SiC MOSFETs using the present invention;

[0028] Figure 6 This is a simulation diagram of the short-circuit transient current waveform of three series-connected SiC MOSFETs without applying the present invention. DETAILED DESCRIPTION

[0029] It should be noted that, unless there is any conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Figure 1 It is a schematic diagram of the composition of the present invention;

[0032] A series SiC MOSFET (silicon carbide MOSFET) short-circuit transient overvoltage and overcurrent suppression circuit, comprising:

[0033] n short-circuit protection sub-circuits,

[0034] The n short-circuit protection sub-circuits are connected one-to-one with the n SiC MOSFETs connected in series, where n ≥ 2. The first SiC MOSFET corresponds to the first short-circuit protection sub-circuit, the second SiC MOSFET corresponds to the second short-circuit protection sub-circuit, and so on.

[0035] The short-circuit protection subcircuit comprises:

[0036] A short-circuit detection circuit is used to detect whether a short circuit occurs in the SiC MOSFET;

[0037] an overcurrent suppression circuit for reducing the voltage between the G and S poles of the short-circuited SiC MOSFET when the short-circuit detection circuit detects that the SiC MOSFET is short-circuited, and further reducing the voltage between the G and S poles of the short-circuited SiC MOSFET according to the voltage division state of the SiC MOSFET adjacent to the short-circuited SiC MOSFET to balance the short-circuit transient voltage distribution;

[0038] If the second SiC MOSFET is short-circuited, the voltage between the G and S poles of the second SiC MOSFET that is short-circuited is further reduced according to the voltage division state of the adjacent third SiC MOSFET to balance the short-circuit transient voltage distribution;

[0039] For example, when the first SiC MOSFET is short-circuited, the voltage between the G and S poles of the first SiC MOSFET is further reduced according to the voltage division state of the adjacent second SiC MOSFET to balance the short-circuit transient voltage distribution.

[0040] Overvoltage suppression circuit: Activated when the voltage applied to the short-circuited SiC MOSFET exceeds the average voltage of all series-connected SiC MOSFETs, it suppresses the voltage rise rate between the D and S poles of the short-circuited SiC MOSFET, achieving overvoltage suppression.

[0041] Each SiC MOSFET in a series connection has its own corresponding short-circuit detection circuit, overcurrent suppression circuit, and overvoltage suppression circuit. When all the SiC MOSFETs' short-circuit detection circuits detect a short circuit, all overcurrent suppression circuits are activated. However, each short-circuit detection circuit activates its own corresponding overcurrent suppression circuit; not all overvoltage suppression circuits are activated during a short circuit.

[0042] The short circuit detection circuit includes a second resistor R B , capacitor C A and comparator U, second resistor RB and capacitor C A A low-pass filter is formed to detect when the voltage across the parasitic inductance L between the K and S poles of the SiC MOSFET rises to the threshold value V due to the rapid change of current. ref When , the comparator U outputs a short-circuit alarm signal and activates the overcurrent suppression circuit.

[0043] The overcurrent suppression circuit includes a gate drive resistor R G , the first diode D A , the first N-channel MOSFET Q A , the second N-channel MOSFET Q B , the first resistor R A , the third resistor R C ;

[0044] When the short-circuit protection subcircuit turns on the first N-channel MOSFET Q A When the gate drive resistor R G With the first resistor R A The voltage divider circuit is formed to quickly reduce the voltage between the G and S poles of the short-circuited SiC MOSFET to suppress the short-circuit current; at the same time, the second N-channel MOSFET Q B Turn off the third resistor R C When the next SiC MOSFET connected in series with the short-circuited SiC MOSFET is over-voltage, the third resistor R CThe voltage drop across the short-circuited SiC MOSFET will further reduce the voltage between the G and S poles, increasing its own on-resistance to balance the voltage distribution.

[0045] The first diode D A Used to separate the overcurrent suppression circuit from the driver circuit during SiC MOSFET turn-off.

[0046] The overvoltage suppression circuit includes a buffer capacitor C B , the second diode D B , transient suppression diode Z top and the third diode D C ;

[0047] The third diode DC is connected to the overvoltage suppression circuit of the next series-connected SiC MOSFET adjacent to the short-circuited SiC MOSFET;

[0048] Among them, the buffer capacitor C B When the voltage of the sub-SiC MOSFET exceeds the average voltage between the D-pole and S-pole of the series SiC MOSFET unit, the second diode D B Charging to reduce the voltage rise rate, transient suppression diode Z top When the voltage between the D and S electrodes of the short-circuited SiC MOSFET exceeds Z top Reverse breakdown occurs when the voltage is clamped, clamping the voltage between the D-pole and S-pole of the corresponding SiC MOSFET to avoid overvoltage breakdown of the short-circuited SiC MOSFET. The third diode D C During the normal turn-on period of the short-circuited SiC MOSFET, the stored overvoltage energy is released to the snubber capacitor of other series-connected SiC MOSFETs.

[0049] The comparator U is of TLV3501 type, and the reference voltage of the comparator U is provided by the voltage reference chip TL432, with a value of Vref of 1.25V.

[0050] The first diode D A The first N-channel MOSFET Q is SS110. A The model used is BSP315PH6327, the second N-channel MOSFET Q B The model is STD10N60M2, the gate drive resistor R G is 5Ω, the first resistor R A is 15Ω, the third resistor R C is 15Ω.

[0051] The buffer capacitor C in the overvoltage suppression circuit BThe value of the second diode D is 42nF. B With the third diode D C The models are all SP20D120CTT, transient suppression diode Z top It consists of two BNAK3-430C connected in series.

[0052] like Figure 2 As shown, the circuit of the present invention is applied to three series SiC MOSFETs. When a short circuit fault occurs in the series SiC MOSFETs, Figure 2 In this example, T1, T2, and T3 are three SiC MOSFETs connected in series, forming a SiC MOSFET series module. Here, each SiC MOSFET has its own corresponding short-circuit detection circuit, overcurrent suppression circuit, and overvoltage suppression circuit. Because the three SiC MOSFETs are connected in series, when a short-circuit fault occurs, the short-circuit detection circuits of all SiC MOSFETs will detect the short-circuit fault, thereby activating all overcurrent suppression circuits.

[0053] After the overcurrent suppression circuit is activated, it will be further affected by the voltage between the D-pole and S-pole of the adjacent SiC MOSFET. Figure 2 In a short circuit, the overcurrent suppression circuits of all three SiC MOSFETs, T1 through T3, activate. However, if the voltage between the D and S poles of T2 increases, this further reduces the voltage between the G and S poles of T1. Similarly, if the voltage between the D and S poles of T3 increases, this further reduces the voltage between the G and S poles of T2. However, only T3 affects T2, and only T2 affects T1. The order of activation cannot be changed due to the circuit structure.

[0054] The rapidly rising short-circuit current will generate an induced voltage across the parasitic inductance between the K-pole and S-pole of each series-connected SiC MOSFET. When the induced voltage exceeds the protection threshold V ref When the N-channel MOSFET Q 1A , Q 2A and Q 3A All series SiC MOSFETs are turned on and the driving voltage of each series SiC MOSFET is reduced. As the driving voltage decreases, the equivalent resistance of the series SiC MOSFET increases, and the short-circuit current is initially suppressed. At the same time, due to the Q 1A With Q 2A Turn on, N-channel MOSFET Q 1B With Q 2B It will then turn off, and the resistor R 1C With R 2C Connected to the SiC MOSFET drive circuit.

[0055] If the SiC MOSFET T3 at the bottom of the series module enters the saturation region first due to its own switching characteristics, the voltage across it will exceed the average withstand voltage, and part of the short-circuit current will flow through the resistor R 2C , diode D 3B To the buffer capacitor C 3B Charging. Resistor R 2C The voltage drop across the terminals is added to the gate drive voltage of the adjacent SiC MOSFET T2 in series, reducing it. This reduced drive voltage further increases T2's on-resistance. This increased on-resistance increases the voltage T2 withstands during a short-circuit transient, thereby relatively reducing the voltage across T3, which enters its saturation region first, thereby achieving its overvoltage suppression function.

[0056] Similarly, if the SiC MOSFET T2 in the middle enters the saturation region first during a short circuit, the short-circuit current flows through the resistor R 1C The resulting pressure drop will increase the pressure on T1, thus suppressing the overvoltage on T2.

[0057] If the SiC MOSFET (T1) at the top enters the saturation region first, the transient suppression diode Z top When the voltage on T1 exceeds the clamping value, it will break down, consuming part of the short-circuit energy to protect T1.

[0058] Figure 3 This is a simulation diagram of the short-circuit transient voltage waveform of three series-connected SiC MOSFETs according to the present invention;

[0059] Figure 4 This is a simulation diagram of the transient voltage waveform of three series-connected SiC MOSFETs short-circuited without applying the present invention;

[0060] Figure 5 This is a simulation diagram of the short-circuit transient current waveform of three series-connected SiC MOSFETs using the present invention;

[0061] Figure 6 This is a simulation diagram of the short-circuit transient current waveform of three series-connected SiC MOSFETs without applying the present invention.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit, characterized by: include: n short-circuit protection sub-circuits, The n short-circuit protection sub-circuits are connected one-to-one with the n SiC MOSFETs connected in series, where n ≥ 2; The short-circuit protection subcircuit comprises: A short-circuit detection circuit is used to detect whether a short circuit occurs in the SiC MOSFET; an overcurrent suppression circuit for reducing the voltage between the G and S poles of the short-circuited SiC MOSFET when the short-circuit detection circuit detects that the SiC MOSFET is short-circuited, and further reducing the voltage between the G and S poles of the short-circuited SiC MOSFET according to the voltage division state of the SiC MOSFET adjacent to the short-circuited SiC MOSFET to balance the short-circuit transient voltage distribution; The overvoltage suppression circuit is activated when the voltage on the short-circuited SiC MOSFET exceeds the average voltage of all series-connected SiC MOSFETs. It suppresses the voltage rise rate between the D and S poles of the short-circuited SiC MOSFET, thus achieving overvoltage suppression. The overcurrent suppression circuit includes a gate drive resistor R G , the first diode D A , the first N-channel MOSFET Q A , the second N-channel MOSFET Q B , the first resistor R A , the third resistor R C ; When the short-circuit protection subcircuit turns on the first N-channel MOSFET Q A When the gate drive resistor R G With the first resistor R A The voltage divider circuit is formed to quickly reduce the voltage between the G and S poles of the short-circuited SiC MOSFET to suppress the short-circuit current; at the same time, the second N-channel MOSFET Q B Turn off the third resistor R C When the next SiC MOSFET connected in series with the short-circuited SiC MOSFET is over-voltage, the third resistor R C The voltage drop across the short-circuited SiC MOSFET will further reduce the voltage between the G and S poles, increasing its own on-resistance to balance the voltage distribution. The first diode D A Used to separate the overcurrent suppression circuit from the drive circuit during the SiC MOSFET shutdown period; The overvoltage suppression circuit includes a buffer capacitor C B , the second diode D B , transient suppression diode Z top and the third diode D C ; The third diode D C connected to the overvoltage suppression circuit of the next series-connected SiC MOSFET adjacent to the short-circuited SiC MOSFET; Among them, the buffer capacitor C B When the voltage of the sub-SiC MOSFET exceeds the average voltage between the D-pole and S-pole of the series SiC MOSFET unit, the second diode D B Charging to reduce the voltage rise rate, transient suppression diode Z top When the voltage between the D-pole and S-pole of the short-circuited SiCMOSFET exceeds the transient suppression diode Z top Reverse breakdown occurs when the clamping voltage is applied, clamping the voltage between the D-pole and S-pole of the corresponding SiC MOSFET to avoid overvoltage breakdown of the short-circuited SiC MOSFET. The third diode D C During the normal turn-on period of the short-circuited SiC MOSFET, the stored overvoltage energy is released to the snubber capacitor of other series-connected SiC MOSFETs.

2. The series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit according to claim 1, characterized in that: The short circuit detection circuit includes a second resistor R B , capacitor C A And comparator U, second resistor R B With capacitor C A A low-pass filter is formed to detect when the voltage across the parasitic inductance L between the KS pole and the S pole of the SiC MOSFET rises to the threshold value V due to the rapid change of current. ref When , the comparator U outputs a short-circuit alarm signal and activates the overcurrent suppression circuit.

3. The series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit according to claim 2, characterized in that: The comparator U is of TLV3501 type, and the reference voltage of the comparator U is provided by the voltage reference chip TL432. ref The value is 1.25V.

4. The series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit according to claim 1, characterized in that: The first diode D A The first N-channel MOSFET Q is SS110. A The model used is BSP315PH6327, the second N-channel MOSFET Q B The model is STD10N60M2, the gate drive resistor R G is 5Ω, the first resistor R A is 15Ω, the third resistor R C is 15Ω.

5. The series SiC MOSFET short-circuit transient overvoltage and overcurrent suppression circuit according to claim 1, characterized in that: The buffer capacitor C in the overvoltage suppression circuit B The value of the second diode D is 42nF. B With the third diode D C The models are all SP20D120CTT, transient suppression diode Z top It consists of two BNAK3-430C connected in series.

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