Series SiC MOSFET short circuit transient overvoltage and overcurrent suppression circuit

Abstract

The invention discloses a series SiC MOSFET short circuit transient overvoltage and overcurrent suppression circuit, and belongs to the technical field of power electronics, the series SiC MOSFET short circuit transient overvoltage and overcurrent suppression circuit comprises n short circuit protection sub-circuits, and each short circuit protection sub-circuit comprises a short circuit detection circuit used for detecting whether a SiC MOSFET is short-circuited or not; the over-current suppression circuit is used for reducing the voltage between the G pole and the S pole 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 pole and the S pole of the short-circuited SiC MOSFET according to the voltage division state of the SiC MOSFET adjacent to the short-circuited SiC MOSFET so as to balance short-circuit transient voltage distribution; and the overvoltage suppression circuit is activated when the voltage borne by the SiC MOSFETs in short circuit exceeds the average voltage value of all the SiC MOSFETs connected in series, the rising rate of the voltage between the D electrode and the S electrode of the SiC MOSFETs in short circuit is suppressed, and overvoltage suppression is achieved. The circuit can be integrated in a traditional series SiC MOSFET drive circuit to serve as an additional circuit for short circuit protection, the short circuit tolerance time of the series SiC MOSFETs is prolonged, and the reliability is improved.

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 over - voltage and over - current suppression circuit. Background Art

[0002] The direct series application of SiC MOSFETs is one of the important methods to solve the problem of insufficient withstand voltage rating of a single device and reduce the cost of converters. When a short - circuit fault occurs in a series SiC MOSFET module, due to the different volt - ampere characteristics of each SiC MOSFET in the series module, some SiC MOSFETs will work in the saturation state first under the same short - circuit current. These SiC MOSFETs that enter the saturation working region have a higher on - resistance relative to other series SiC MOSFETs and will also bear a higher voltage division in the entire series module. Therefore, different from the short - circuit state of a single SiC MOSFET under the rated voltage, in the short - circuit state of a series SiC MOSFET module, some SiC MOSFETs will bear a higher short - circuit voltage, the short - circuit transient loss is also greater, and the short - circuit withstand time and safety of the device are lower. Summary of the Invention

[0003] To solve the above problems, the technical solution adopted by the present invention is: a series SiC MOSFET short - circuit transient over - voltage and over - current suppression circuit, comprising: n short - circuit protection sub - circuits, The n short - circuit protection sub - circuits are respectively connected to n series - connected SiC MOSFETs in one - to - one correspondence, where n≥2; the short - circuit protection sub - circuit includes: A short - circuit detection circuit for detecting whether a short - circuit occurs in the SiC MOSFET; An over - current suppression circuit for reducing the voltage between the G - pole and S - pole of the short - circuited SiC MOSFET when the short - circuit detection circuit detects a short - circuit in the SiC MOSFET, and further reducing the voltage between the G - pole and S - pole 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; An over - voltage suppression circuit, which is activated when the voltage borne by the short - circuited SiC MOSFET exceeds the average voltage value of all series SiC MOSFETs, and suppresses the rising rate of the voltage between the D - pole and S - pole of the short - circuited SiC MOSFET to achieve over - voltage suppression.

[0004] Further: the short - circuit detection circuit includes a second resistor R B and a capacitor C A and a comparator U, the second resistor R B and the capacitor CA A low-pass filter is formed to compare the voltage across the parasitic inductance L between the K and S poles of the SiC MOSFET. When the voltage rises to the threshold V due to a rapid change in current ref the comparator U outputs a short-circuit alarm signal to activate the overcurrent suppression circuit.

[0005] Furthermore, the overcurrent suppression circuit includes a gate drive resistor R G , a first diode D A , a first N-channel MOSFET Q A , a second N-channel MOSFET Q B , a first resistor R A , a third resistor R C ; When the short-circuit protection sub-circuit turns on the first N-channel MOSFET Q A , the gate drive resistor R G and the first resistor R A form a voltage-dividing circuit 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 turns off to insert the third resistor R C into the drive loop. When the next series-connected SiC MOSFET adjacent to the short-circuited SiC MOSFET is over-voltage, the voltage drop across the third resistor R C will further reduce the voltage between the G and S poles of the short-circuited SiC MOSFET and increase its own on-resistance to balance the voltage distribution; The first diode D A is used to separate the overcurrent suppression circuit from the drive circuit during the off period of the SiC MOSFET.

[0006] Furthermore, the over-voltage suppression circuit includes a buffer capacitor C B , a second diode D B , a transient suppression diode Z top and a third diode D C ; The third diode D C is connected to the over-voltage suppression circuit of the next series-connected SiC MOSFET adjacent to the short-circuited SiC MOSFET; Among them, the buffer capacitor C B charges through the second diode D B when the voltage borne by the sub-SiC MOSFET exceeds the average voltage between the D and S poles of each series-connected SiC MOSFET unit to reduce the voltage rise rate. The transient suppression diode Z topWhen the voltage between the D and S poles of a short - circuited SiC MOSFET exceeds Z top the clamping voltage, it breaks down reversely. Clamp the voltage between the D and S poles of the corresponding SiC MOSFET to avoid over - voltage breakdown of the short - circuited SiC MOSFET. The third diode D C During the normal turn - on period of the short - circuited SiC MOSFET, release the stored over - voltage energy to the buffer capacitors of other series - connected SiC MOSFETs.

[0007] Furthermore: The model of the comparator U is TLV3501. The reference voltage of the comparator U is provided by the voltage reference chip TL432, and V ref takes a value of 1.25V.

[0008] Furthermore: The first diode D A adopts the model SS110. The first N - channel MOSFET Q A adopts the model BSP315PH6327. The second N - channel MOSFET Q B has the model STD10N60M2. The gate - drive resistor R G is 5Ω. The first resistor R A is 15Ω. The third resistor R C is 15Ω.

[0009] Furthermore: In the over - voltage suppression circuit, the value of the buffer capacitor C B is 42nF. The models of the second diode D B and the third diode D C are both SP20D120CTT. The transient suppression diode Z top is composed of two series - connected BNAK3 - 430C.

[0010] A series - connected SiC MOSFET short - circuit transient over - voltage and over - current suppression circuit provided by the present invention. When a short - circuit fault occurs in the series - connected SiC MOSFETs, each SiC MOSFET series unit will reduce its own drive voltage to suppress the short - circuit current. At the same time, when any one SiC MOSFET first enters the saturation region, the over - current suppression circuit of the previous SiC MOSFET adjacent to it will be activated to balance the voltage distribution during the short - circuit and further suppress the short - circuit current.

[0011] The present invention can be integrated into a traditional series SiC MOSFET drive circuit as an additional circuit for short-circuit protection, extending the short-circuit withstand time of each series SiC MOSFET and improving the reliability of the module. 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 having too high a voltage drop. The present invention does not require additional isolation devices and can be integrated with common series SiC MOSFET drive circuits. It has the following advantages: When a short-circuit fault occurs in the series SiC MOSFET, each series unit will reduce its own drive voltage to suppress the short-circuit current. At the same time, when any one SiC MOSFET enters the saturation region first, the overcurrent suppression circuit of the upper SiC MOSFET adjacent to it will be activated to balance the voltage distribution during the short circuit and further suppress the short-circuit current. The present invention can be integrated into a traditional series SiC MOSFET drive circuit as an additional circuit for short-circuit protection, extending the short-circuit withstand time of each series SiC MOSFET and improving the reliability of the module. Brief Description of the Drawings

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0013] Figure 1 It is a schematic diagram of the composition of the present invention; Figure 2 It is a schematic diagram of the series structure of three SiC MOSFETs applying the device of the present invention; Figure 3 It is a simulation diagram of the short-circuit transient voltage waveform of three series SiC MOSFETs applying the present invention; Figure 4 It is a simulation diagram of the short-circuit transient voltage waveform of three series SiC MOSFETs without applying the present invention; Figure 5 It is a simulation diagram of the short-circuit transient current waveform of three series SiC MOSFETs applying the present invention; Figure 6 It is a simulation diagram of the short-circuit transient current waveform of three series SiC MOSFETs without applying the present invention. Detailed Embodiments

[0014] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0015] To make the objectives, 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 with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation on the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0016] Figure 1 Schematic diagram of the composition of the present invention; A series SiC MOSFET (silicon carbide MOSFET) short-circuit transient overvoltage and overcurrent suppression circuit, comprising: n short-circuit protection sub-circuits, The n short-circuit protection sub-circuits are respectively connected in one-to-one correspondence with n serially connected SiC MOSFETs, 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; The short-circuit protection sub-circuit includes: A short-circuit detection circuit for detecting whether the SiC MOSFET has a short circuit; An overcurrent suppression circuit for, when the short-circuit detection circuit detects that the SiC MOSFET has a short circuit, reducing the voltage between the G pole and the S pole of the short-circuited SiC MOSFET, 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 pole and the S pole of the short-circuited SiC MOSFET to balance the short-circuit transient voltage distribution; For example, when the second SiC MOSFET has a short circuit, according to the voltage division state of the adjacent third SiC MOSFET, further reducing the voltage between the G pole and the S pole of the short-circuited second SiC MOSFET to balance the short-circuit transient voltage distribution; For example, when the first SiC MOSFET has a short circuit, according to the voltage division state of the adjacent second SiC MOSFET, further reducing the voltage between the G pole and the S pole of the short-circuited first SiC MOSFET to balance the short-circuit transient voltage distribution; Overvoltage suppression circuit: It is activated when the voltage borne by the short-circuited SiC MOSFET exceeds the average voltage value of all series-connected SiC MOSFETs, and suppresses the rising rate of the voltage between the D and S poles of the short-circuited SiC MOSFET to achieve overvoltage suppression.

[0017] Each SiC MOSFET in the series-connected SiC MOSFETs has a corresponding short-circuit detection circuit, overcurrent suppression circuit, and overvoltage suppression circuit; when all short-circuit detection circuits of all SiC MOSFETs detect a short circuit, all overcurrent suppression circuits will be activated. Of course, each short-circuit detection circuit activates its corresponding overcurrent suppression circuit, and all "overvoltage suppression circuits" will not be all activated during a short circuit.

[0018] The short-circuit detection circuit includes a second resistor R B and a capacitor C A and a comparator U. The second resistor RB and the capacitor C A form a low-pass filter, which is used to output a short-circuit alarm signal by the comparator U when the voltage across the parasitic inductor L between the K and S poles of the SiC MOSFET rises to the threshold V ref due to a rapid change in current, and activate the overcurrent suppression circuit.

[0019] The overcurrent suppression circuit includes a gate drive resistor R G a first diode D A a first N-channel MOSFET Q A a second N-channel MOSFET Q B a first resistor R A a third resistor R C ; When the short-circuit protection sub-circuit turns on the first N-channel MOSFET Q A , the gate drive resistor R G and the first resistor R A form a voltage-dividing circuit 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 turns off to connect the third resistor R C in series in the drive loop. When the next series-connected SiC MOSFET adjacent to the short-circuited SiC MOSFET is overvoltage, the voltage drop across the third resistor R C will further reduce the voltage between the G and S poles of the short-circuited SiC MOSFET, and increase its own on-resistance to balance the voltage distribution; The first diode D A is used to separate the overcurrent suppression circuit from the drive circuit during the off period of the SiC MOSFET.

[0020] The overvoltage suppression circuit includes a buffer capacitor C B , a second diode D B , a transient suppression diode Z top , and a third diode D C ; The third diode DC is connected to the overvoltage suppression circuit of the next series SiC MOSFET adjacent to the short - circuited SiC MOSFET; Among them, when the voltage borne by the sub - SiC MOSFET exceeds the average voltage between the D - pole and S - pole of the series SiC MOSFET unit, the buffer capacitor C B is charged through the second diode D B to reduce the voltage rising speed. When the voltage between the D - pole and S - pole of the short - circuited SiC MOSFET exceeds the Z top clamping voltage, the transient suppression diode Z top breaks down reversely, clamping the voltage between the D - pole and S - pole of the corresponding SiC MOSFET to prevent the short - circuited SiC MOSFET from overvoltage breakdown. During the normal turn - on of the short - circuited SiCMOSFET, the third diode D C releases the stored overvoltage energy to the buffer capacitors of other series SiC MOSFETs.

[0021] The model of the comparator U is TLV3501. The reference voltage of the comparator U is provided by the voltage reference chip TL432, and the value of Vref is 1.25V.

[0022] The first diode D A adopts the model SS110. The first N - channel MOSFET Q A adopts the model BSP315PH6327. The second N - channel MOSFET Q B has the model STD10N60M2. The gate - driving resistor R G is 5Ω, the first resistor R A is 15Ω, and the third resistor R C is 15Ω.

[0023] In the overvoltage suppression circuit, the value of the buffer capacitor C B is 42nF. The models of the second diode D B and the third diode D C are both SP20D120CTT. The transient suppression diode Z top is composed of two series - connected BNAK3 - 430C.

[0024] Such as Figure 2As shown, the circuit of the present invention is applied to three series-connected SiC MOSFETs. When a short-circuit fault occurs in the series-connected SiC MOSFETs, Figure 2 In Figure 2 , T1, T2, and T3 are three sequentially series-connected SiC MOSFETs, which form a series module of SiC MOSFETs. Here, it can be said that each SiC MOSFET has its own corresponding short-circuit detection circuit, overcurrent suppression circuit, and overvoltage suppression circuit. Since 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, and then activate all overcurrent suppression circuits.

[0025] After the overcurrent suppression circuit is activated, it will be further affected by the voltage between the D pole and the S pole of the adjacent SiC MOSFET. As Figure 2 shown in Figure 2 , when a short circuit occurs, the overcurrent suppression circuits of the three SiC MOSFETs from T1 to T3 will all be activated. However, if the voltage between the D pole and the S pole of T2 is high, it will further reduce the voltage between the G pole and the S pole of T1. Similarly, if the voltage between the D pole and the S pole of T3 is high, it will further reduce the voltage between the G pole and the S pole of T2. But only T3 can affect T2, and T2 can affect T1. The sequence is affected by the circuit structure and cannot be changed.

[0026] The rapidly rising short-circuit current will generate an induced voltage across the parasitic inductance at both ends of the K pole and the S pole of each series-connected SiC MOSFET. When the induced voltage exceeds the protection threshold V ref , the N-channel MOSFETs Q 1A , Q 2A , and Q 3A will all turn on and reduce the driving voltage of each series-connected SiC MOSFET. As the driving voltage decreases, the equivalent resistance of the series-connected SiC MOSFET also increases, and the short-circuit current is initially suppressed. At the same time, since Q 1A and Q 2A are turned on, the N-channel MOSFETs Q 1B and Q 2B will turn off accordingly, and then the resistors R 1C and R 2C will be connected into the driving circuit of the SiC MOSFET.

[0027] If the SiC MOSFET T3 at the bottom of the series module enters the saturation region first due to its own switching characteristics at this time, the voltage across it will exceed the average bearing voltage, and part of the short-circuit current will pass through the resistor R 2C , the diode D 3B and charge the buffer capacitor C 3B . The resistor R 2CThe voltage drop across both ends will be superimposed on the gate drive voltage of the adjacent previous SiC MOSFET T2 in series and reduce it. The on-resistance of T2 will further increase due to the reduction of the drive voltage. The increase in the on-resistance causes the voltage across T2 to rise during the short-circuit transient, thereby relatively reducing the voltage across T3 that enters the saturation region first, realizing its overvoltage suppression function.

[0028] Similarly, if the middle SiC MOSFET T2 enters the saturation region first during a short circuit, the short-circuit current flows through the resistor R 1C The resulting voltage drop will cause the voltage across T1 to increase, realizing overvoltage suppression of T2.

[0029] If the top SiC MOSFET (T1) enters the saturation region first, the transient suppression diode Z top will break down when the voltage across T1 exceeds the clamping value, consuming part of the short-circuit energy to protect T1.

[0030] Figure 3 is the simulation diagram of the short-circuit transient voltage waveform of three series-connected SiC MOSFETs applying the present invention; Figure 4 is the simulation diagram of the short-circuit transient voltage waveform of three series-connected SiC MOSFETs without applying the present invention; Figure 5 is the simulation diagram of the short-circuit transient current waveform of three series-connected SiC MOSFETs applying the present invention; Figure 6 is the simulation diagram of the short-circuit transient current waveform of three series-connected SiC MOSFETs without applying the present invention.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A series SiC MOSFET short - circuit transient over - voltage and over - current suppression circuit, characterized in that: Including: n short - circuit protection sub - circuits, The n short - circuit protection sub - circuits are respectively connected in one - to - one correspondence with n series - connected SiC MOSFETs, where n≥2; The short - circuit protection sub - circuit includes: A short - circuit detection circuit for detecting whether the SiC MOSFET has a short - circuit; An over - current suppression circuit for reducing the voltage between the G - pole and S - pole of the short - circuited SiC MOSFET when the short - circuit detection circuit detects a short - circuit of the SiC MOSFET, and further reducing the voltage between the G - pole and S - pole 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; An over - voltage suppression circuit, which is activated when the voltage borne by the short - circuited SiC MOSFET exceeds the average voltage value of all series - connected SiC MOSFETs, and suppresses the rising rate of the voltage between the D - pole and S - pole of the short - circuited SiC MOSFET to achieve over - voltage suppression; The overcurrent suppression circuit includes a gate drive resistor R G , a first diode D A , a first N-channel MOSFET Q A , a second N-channel MOSFET Q B , a first resistor R A , a third resistor R C ; When the short - circuit protection sub - circuit turns on the first N - channel MOSFET Q A , the gate - driving resistor R G and the first resistor R A form a voltage - dividing circuit to quickly reduce the voltage between the G - pole and S - pole of the short - circuited SiC MOSFET to suppress the short - circuit current; meanwhile, the second N - channel MOSFET Q B turns off and the third resistor R C is connected in series into the driving loop. When the next series - connected SiC MOSFET adjacent to the short - circuited SiC MOSFET has over - voltage, the voltage drop across the third resistor R C will further reduce the voltage between the G - pole and S - pole of the short - circuited SiC MOSFET, increase 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 turn-off of the SiC MOSFET; The overvoltage suppression circuit includes a buffer capacitor C B , a second diode D B , a transient suppression diode Z top , and a third diode D C ; The third diode D C is connected to the overvoltage suppression circuit of the next series SiC MOSFET adjacent to the short-circuited SiC MOSFET; Among them, buffer capacitor C B When the voltage borne by the sub-SiC MOSFET exceeds the average voltage between the D and S poles of the series SiC MOSFET unit, it is charged through the second diode D B to reduce the voltage rising speed. The transient suppression diode Z top breaks down reversely when the voltage between the D and S poles of the short-circuited SiC MOSFET exceeds the clamping voltage of the transient suppression diode Z top to clamp the voltage between the D and S poles of the corresponding SiC MOSFET to avoid overvoltage breakdown of the short-circuited SiC MOSFET. The third diode D C releases the stored overvoltage energy to the buffer capacitors of other series SiC MOSFETs during the normal turn-on of the short-circuited SiC MOSFET.

2. The series SiC MOSFET short - circuit transient over - voltage and over - current suppression circuit according to claim 1, characterized in that: The short - circuit detection circuit includes a second resistor R B , a capacitor C A , and a comparator U. The second resistor R B and the capacitor C A form a low - pass filter, which is used to output a short - circuit alarm signal by the comparator U and activate the over - current suppression circuit when the voltage across the parasitic inductor L between the K - pole and S - pole of the SiC MOSFET rises to the threshold V ref due to the rapid change of the current.

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

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

5. The series SiC MOSFET short - circuit transient over - voltage and over - current suppression circuit according to claim 1, characterized in that: The buffer capacitor C in the overvoltage suppression circuit B has a value of 42 nF. The second diode D B and the third diode D C are both of the model SP20D120CTT. The transient suppression diode Z top is composed of two series-connected BNAK3-430C.

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