Current injection type SiC MOSFET parallel current-sharing driving circuit

Abstract

The invention discloses a current injection type SiC MOSFET parallel current-sharing driving circuit, which detects the voltage difference between two ends of a current sampling resistor through an isolation amplifier and a differential amplification circuit, indirectly measures the current value of each parallel branch, and determines the current difference value of the parallel branches through the differential amplification circuit. And when the current of the SiC MOSFET parallel circuit is unbalanced, a control signal is output to the forward current injection circuit or the reverse current injection circuit. Through a forward current injection circuit and a reverse current injection circuit, forward current or reverse current is injected into a grid electrode under the action of a control signal, the change rate of grid-source voltage is changed, the switching-on and switching-off speed of SiC MOSFETs is dynamically adjusted, the phenomenon of non-uniform parallel current of the SiC MOSFETs caused by inconsistent device parameters or asymmetric circuit layout in the circuit is effectively inhibited, and the switching-on and switching-off speed of the SiC MOSFETs is improved. The active current sharing circuit has the advantages of being good in adjusting performance and high in response speed.

Description

Technical Field

[0001] The invention relates to a SiC MOSFET parallel drive circuit. Background Art

[0002] Thanks to the higher saturation velocity, thermal conductivity and breakdown field strength of SiC materials, SiC MOSFET has the advantages of high voltage resistance, high temperature resistance and low loss, and has gradually been used in electric vehicles, new energy and other fields.

[0003] Affected by factors such as process and cost, the current carrying capacity of a single SiC MOSFET is low. Therefore, in high-current applications, multiple discrete devices are usually required to be connected in parallel. Due to inconsistent device parameters and asymmetric circuit parasitic parameters, the problem of unbalanced current in each branch will occur when SiC MOSFET is connected in parallel. Unbalanced current will lead to uneven distribution of device losses, which in turn affects its heat distribution and ultimately leads to uneven device life. In order to prevent the problem of uneven current from causing irreversible damage to the device, it is often necessary to reserve a larger current margin in the industry. This approach does not fully utilize the current capacity of the device, so it requires greater cost to implement.

[0004] The existing layout optimization scheme is difficult to achieve complete symmetry when multiple devices are connected in parallel; device screening cannot ensure that device parameters are completely consistent; the number of coupled inductors required for current sharing schemes increases with the number of devices connected in parallel, and the total volume also increases exponentially, reducing the system power density. At the same time, this approach worsens the voltage overshoot when the device is turned off. Therefore, it is necessary to propose a new parallel current sharing method to improve the problem of uneven current sharing of parallel devices, ensure uniform distribution of device losses, and improve system reliability. Summary of the invention

[0005] Purpose of the invention: In view of the above-mentioned prior art, a current injection type SiC MOSFET parallel current equalization driving circuit is proposed to improve the uneven current problem of SiC MOSFET parallel circuit, ensure uniform distribution of device losses, and improve system reliability.

[0006] Technical solution: A current injection type SiC MOSFET parallel current sharing drive circuit, comprising parallel SiCMOSFET M 1 and SiC MOSFET M 2 , further comprising a current sampling circuit, a current difference feedback circuit, a forward current injection circuit, and a reverse current injection circuit; the SiC MOSFET M 1 and SiC MOSFET M 2The current sampling circuit uses an isolation amplifier and a differential amplifier circuit to respectively detect the voltage difference between the two ends of the current sampling resistor, thereby indirectly measuring the SiC MOSFET M 1 Branch and SiC MOSFET M 2 The current difference feedback circuit measures the current difference of the two parallel branches by using the voltage difference between the two current sampling resistors and the differential amplifier circuit, and outputs a control signal to the forward current injection circuit or the reverse current injection circuit when the current of the SiC MOSFET parallel circuit is unbalanced; the forward current injection circuit is used to inject the current into the SiC MOSFET M 2 The circuit injects a forward current into the gate, changes the rate of change of the gate-source voltage under the control signal, and dynamically adjusts the SiC MOSFET M 2 The turn-on and turn-off speeds are reduced, thereby suppressing the uneven current flow in the parallel circuit; the reverse current injection circuit is used to inject the reverse current into the SiC MOSFET M 2 The circuit injects reverse current into the gate, changes the rate of change of the gate-source voltage under the control signal, and dynamically adjusts the SiC MOSFET M 2 The turn-on and turn-off speeds are reduced, thereby suppressing the uneven current in the parallel circuit.

[0007] Furthermore, the current sampling circuit includes an isolation amplifier U 1 and U 2 、Operational amplifier U 3 and U 4 , current sampling resistor R 3 and R 4 , resistor R 5 ~R 12 ; Current sampling resistor R 3 and R 4 are connected in series with SiC MOSFET M 1 Branch and SiC MOSFET M 2 Branch; isolation amplifier U 1 The positive input terminal is connected to the current sampling resistor R 3 The current input terminal is connected to the current sampling resistor R 3 Current output terminal; resistor R 5 One end is connected to the isolation amplifier U 1 The positive output terminal of the amplifier is connected to the other end of the operational amplifier U 3 The positive input terminal and resistor R 7 One end of the resistor R 7 The other end is connected to the reference ground; the resistor R 6 One end is connected to the isolation amplifier U 1 The negative output terminal of the amplifier is connected to the other end of the operational amplifier U3 Negative input terminal and resistor R 8 One end of the resistor R 8 The other end is connected to the operational amplifier U 3 Output end of isolation amplifier U 2 The positive input terminal is connected to the current sampling resistor R 4 The current input terminal is connected to the current sampling resistor R 4 Current output terminal; resistor R 9 One end is connected to the isolation amplifier U 2 The positive output terminal of the amplifier is connected to the other end of the operational amplifier U 4 The positive input terminal and resistor R 11 One end of the resistor R 11 The other end is connected to the reference ground; the resistor R 10 One end is connected to the isolation amplifier U 2 The negative output terminal of the amplifier is connected to the other end of the operational amplifier U 4 Negative input terminal and resistor R 12 One end of the resistor R 12 The other end is connected to the operational amplifier U 4 The output terminal.

[0008] Furthermore, the current difference feedback circuit includes an operational amplifier U 5 and U 6 , resistor R 13 ~R 20 ; Resistance R 13 One end is connected to the operational amplifier U 3 The output terminal and resistor R 18 One end of the circuit is connected to the operational amplifier U 5 The positive input terminal and resistor R 15 One end of the resistor R 15 The other end is connected to the reference ground; the resistor R 14 One end is connected to the operational amplifier U 4 The output terminal and resistor R 17 One end of the circuit is connected to the operational amplifier U 5 Negative input terminal and resistor R 16 One end of the resistor R 16 The other end is connected to the operational amplifier U 5 The output terminal; resistor R 17 The other end is connected to the operational amplifier U 6 The positive input terminal and resistor R 19 One end of the resistor R 19 The other end is connected to the reference ground; the resistor R 18 The other end is connected to the operational amplifier U 6 Negative input terminal and resistor R 20 One end of the resistor R 20 The other end is connected to the operational amplifier U6 The output terminal.

[0009] Furthermore, the forward current injection circuit includes a power supply V CC 、NPN transistor T 1 、PNP transistor T 2 , resistor R 21 、Diode D 2 ;NPN transistor T 1 The base of the operational amplifier U 5 The output terminal and the PNP transistor T 2 The base of NPN transistor T 1 The collector is connected to the power supply V CC , NPN transistor T 1 The emitter of the PNP transistor T 2 The emitter and resistor R 21 One end of the PNP transistor T 2 The collector of the resistor R 21 The other end is connected to diode D 2 Anode of diode D 2 The cathode of SiC MOSFET M 2 of the gate.

[0010] Furthermore, the reverse current injection circuit includes a power supply V CC 、NPN transistor T 3 、PNP transistor T 4 、NPN transistor T 5 、NPN transistor T 6 , resistor R 22 、Diode D 3 ;NPN transistor T 3 The base of the operational amplifier U 6 The output terminal and the PNP transistor T 4 The base of NPN transistor T 3 The collector is connected to the power supply V CC , NPN transistor T 3 The emitter of the PNP transistor T 4 The emitter and resistor R 22 One end of the PNP transistor T 4 The collector of NPN transistor T is connected to the reference ground; 5 And NPN transistor T 6 Form a mirror current source; resistor R 22 The other end is connected to the NPN transistor T 5 The collector and base of NPN transistor T 5 The base of the NPN transistor T 6The base of NPN transistor T 5 The emitter of the NPN transistor T 6 The emitter and reference ground of NPN transistor T 6 The collector of the diode D 3 The cathode of diode D 3 The anode of SiC MOSFET M 2 of the gate.

[0011] Beneficial effects: Due to inconsistent device parameters and differences in circuit parasitic inductance, the problem of unbalanced current in each branch will occur when SiC MOSFET is connected in parallel. Device screening cannot ensure that the device parameters are completely consistent; the existing layout optimization scheme cannot completely eliminate the difference in circuit parasitic inductance when multiple devices are connected in parallel; the coupled inductor method has the disadvantages of worsening voltage overshoot and increasing system volume. The present invention determines the current difference of the parallel branches by detecting the voltage difference across the current sampling resistor and using a differential amplifier circuit. When the parallel branch current of SiC MOSFET is unbalanced, a forward current or a reverse current is injected into the gate to change the rate of change of the gate-source voltage, dynamically adjust the opening and closing speed of the SiC MOSFET, and suppress the uneven current phenomenon of the parallel circuit. The present invention can effectively suppress the uneven current phenomenon of SiC MOSFET in parallel due to inconsistent device parameters or asymmetric circuit layout in the circuit, achieve the purpose of active current sharing, and has the characteristics of good adjustment performance and fast response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of a circuit of the present invention;

[0013] Figure 2 is a schematic diagram of a current sampling circuit;

[0014] Figure 3 Schematic diagram of current difference feedback circuit;

[0015] Figure 4 (a) and (b) are schematic diagrams of the forward current injection circuit and the reverse current injection circuit respectively;

[0016] Figure 5 (a) and (b) are respectively the case when there is no current sharing measure. 1 The drain current i d1 With M 2 The drain current i d2 The switching waveform of

[0017] Figure 6 (a) and (b) are the cases where the present invention is used to suppress uneven flow. 1 The drain current i d1 With M 2 The drain current id2 The switching waveform. DETAILED DESCRIPTION

[0018] The present invention will be further explained below in conjunction with the accompanying drawings.

[0019] like Figure 1 As shown, a current injection type SiC MOSFET parallel current sharing driving circuit includes SiC MOSFET M 1 、SiC MOSFET M 2 , current sampling circuit, current difference feedback circuit, forward current injection circuit, reverse current injection circuit. By detecting the voltage difference across the current sampling resistor, the current difference of the parallel branch is determined using the differential amplifier circuit. When the current of the SiC MOSFET parallel circuit is unbalanced, a forward current or a reverse current is injected into the gate to change the rate of change of the gate-source voltage, dynamically adjust the turn-on and turn-off speed of the SiC MOSFET, and suppress the uneven current phenomenon of the parallel circuit.

[0020] like Figure 1 As shown, the DC power supply V DC The positive pole of the diode D 1 The cathode and one end of the inductor L, the DC power supply V DC The cathode of diode D is connected to the reference ground; 1 The anode is connected to the current sampling resistor R 3 and R 4 The other end of the inductor L is connected to the diode D 1 Anode; drive signal V P One end of the drive resistor R 1 and R 2 One end of the drive resistor R 1 The other end is connected to SiC MOSFET M 1 The gate of the drive resistor R 2 The other end is connected to SiC MOSFET M 2 Gate of SiC MOSFETM 1 The drain is connected to the current sampling resistor R 3 The current output terminal of SiC MOSFET M 1 The source of SiC MOSFET M is connected to the reference ground; 2 The drain is connected to the current sampling resistor R 4 The current output terminal of SiC MOSFET M 2 The source is connected to the reference ground.

[0021] like Figure 1 , Figure 2 As shown, the current sampling circuit includes an isolation amplifier U 1and U 2 、Operational amplifier U 3 and U 4 , current sampling resistor R 3 and R 4 , resistor R 5 ~R 12 . Current sampling resistor R 3 and R 4 are connected in series with SiC MOSFET M 1 Branch and SiC MOSFET M 2 Branch; isolation amplifier U 1 The positive input terminal is connected to the current sampling resistor R 3 The current input terminal is connected to the current sampling resistor R 3 Current output terminal; resistor R 5 One end is connected to the isolation amplifier U 1 The positive output terminal of the amplifier is connected to the other end of the operational amplifier U 3 The positive input terminal and resistor R 7 One end of the resistor R 7 The other end is connected to the reference ground; the resistor R 6 One end is connected to the isolation amplifier U 1 The negative output terminal of the amplifier is connected to the other end of the operational amplifier U 3 Negative input terminal and resistor R 8 One end of the resistor R 8 The other end is connected to the operational amplifier U 3 Output end of isolation amplifier U 2 The positive input terminal is connected to the current sampling resistor R 4 The current input terminal is connected to the current sampling resistor R 4 Current output terminal; resistor R 9 One end is connected to the isolation amplifier U 2 The positive output terminal of the amplifier is connected to the other end of the operational amplifier U 4 The positive input terminal and resistor R 11 One end of the resistor R 11 The other end is connected to the reference ground; the resistor R 10 One end is connected to the isolation amplifier U 2 The negative output terminal of the amplifier is connected to the other end of the operational amplifier U 4 Negative input terminal and resistor R 12 One end of the resistor R 12 The other end is connected to the operational amplifier U 4 The output terminal.

[0022] like Figure 1 , Figure 3 As shown, the current difference feedback circuit includes an operational amplifier U 5 and U 6 , resistor R13 ~R 20 . Resistance R 13 One end is connected to the operational amplifier U 3 The output terminal and resistor R 18 One end of the circuit is connected to the operational amplifier U 5 The positive input terminal and resistor R 15 One end of the resistor R 15 The other end is connected to the reference ground; the resistor R 14 One end is connected to the operational amplifier U 4 The output terminal and resistor R 17 One end of the circuit is connected to the operational amplifier U 5 Negative input terminal and resistor R 16 One end of the resistor R 16 The other end is connected to the operational amplifier U 5 The output terminal; resistor R 17 The other end is connected to the operational amplifier U 6 The positive input terminal and resistor R 19 One end of the resistor R 19 The other end is connected to the reference ground; the resistor R 18 The other end is connected to the operational amplifier U 6 Negative input terminal and resistor R 20 One end of the resistor R 20 The other end is connected to the operational amplifier U 6 The output terminal.

[0023] like Figure 1 , Figure 4 As shown in (a), the forward current injection circuit includes a power supply V CC 、NPN transistor T 1 、PNP transistor T 2 , resistor R 21 、Diode D 2 . NPN transistor T 1 The base of the operational amplifier U 5 The output terminal and the PNP transistor T 2 The base of NPN transistor T 1 The collector is connected to the power supply V CC , NPN transistor T 1 The emitter of the PNP transistor T 2 The emitter and resistor R 21 One end of the PNP transistor T 2 The collector of the resistor R 21 The other end is connected to diode D 2 Anode of diode D 2 The cathode of SiC MOSFET M 2 of the gate.

[0024] like Figure 1 , Figure 4 As shown in (b), the reverse current injection circuit includes a power supply V CC 、NPN transistor T 3 、PNP transistor T 4 、NPN transistor T 5 、NPN transistor T 6 , resistor R 22 、Diode D 3 . NPN transistor T 3 The base of the operational amplifier U 6 The output terminal and the PNP transistor T 4 The base of NPN transistor T 3 The collector is connected to the power supply V CC , NPN transistor T 3 The emitter of the PNP transistor T 4 The emitter and resistor R 22 One end of the PNP transistor T 4 The collector of NPN transistor T is connected to the reference ground; 5 And NPN transistor T 6 Form a mirror current source; resistor R 22 The other end is connected to the NPN transistor T 5 The collector and base of NPN transistor T 5 The base of the NPN transistor T 6 The base of NPN transistor T 5 The emitter of the NPN transistor T 6 The emitter and reference ground of NPN transistor T 6 The collector of the diode D 3 The cathode of diode D 3 The anode of SiC MOSFET M 2 of the gate.

[0025] To analyze the working principle of the circuit, the following definitions are made: The turn-on voltage of SiC MOSFET is V GG , the shutdown voltage is V EE , the driving resistance is R 1 and R 2 , M 1 The drain current is i d1 , M 2 The drain current is i d2 , M 1 The gate current at turn-on is i g1 , M 2 The gate current at turn-on is i g2 , M 1The gate current at turn-off is i ga , M 2 The gate current at turn-off is i gb , M 1 The gate-source capacitance is C gs1 , M 2 The gate-source capacitance is C gs2 , M 1 The gate-drain capacitance is C gd1 , M 2 The gate-drain capacitance is C gd2 , the output of the current difference feedback circuit is V O1 and V O2 .

[0026] The current sampling circuit uses an isolation amplifier and a differential amplifier circuit to detect the voltage difference across the current sampling resistor and indirectly measure the SiC MOSFET M 1 Branch and SiC MOSFET M 2 The current in the branch.

[0027] The current difference feedback circuit measures the current difference of the two parallel branches through the voltage difference across the current sampling resistor using the differential amplifier circuit. When the current of the SiC MOSFET parallel circuit is unbalanced, the control signal is output to the forward current injection circuit or the reverse current injection circuit.

[0028] like Figure 4 (a) shows a forward current injection circuit. When the current in the SiC MOSFET parallel circuit is unbalanced during the turn-on and turn-off phases, the SiC MOSFET M 2 The gate injects forward current, changes the rate of change of the gate-source voltage, and dynamically adjusts the SiCMOSFET M 2 The opening and closing speed of the circuit can be reduced, thereby suppressing the uneven current in the parallel circuit. Figure 4 (b) shows a reverse current injection circuit. When the current in the SiC MOSFET parallel circuit is unbalanced during the turn-on and turn-off phases, the reverse current injection circuit is injected into the SiC MOSFET M. 2 The gate injects reverse current, changes the rate of change of the gate-source voltage, and dynamically adjusts the SiC MOSFET M 2 The turn-on and turn-off speeds are reduced, thereby suppressing the uneven current in the parallel circuit.

[0029] When the SiC MOSFET is turned on and off, the drain current flows through the current sampling resistor R 3 and R 4 , so a voltage drop will occur on the sampling resistor, and the current difference can be determined by the differential amplifier circuit. Figure 1 Medium R 3 =R 4 , R 5=R 6 =R 9 =R 10 , R 13 =R 14 =R 17 =R 18 , R 15 =R 16 =R 19 =R 20 , isolation amplifier U 1 and U 2 The magnification is A V , then the output of the current difference feedback circuit is:

[0030]

[0031] 1. During the opening process of the SiC MOSFET parallel circuit, assuming that M 1 The opening speed is greater than M 2 opening speed.

[0032] At this time d1 >i d2 , the forward current injection circuit to M 2 Gate injected forward current I a , the injected forward current value is:

[0033]

[0034] Among them, V BE,T1 For transistor T 1 The threshold voltage of M 2 Gate drive current i g2 Get bigger, M 2 The gate-source voltage rises faster, M 2 The opening speed is faster, the parallel M 1 With M 2 The drain current in the circuit tends to balance.

[0035] 2. During the opening process of the SiC MOSFET parallel circuit, assuming that M 2 The opening speed is greater than M 1 opening speed.

[0036] At this time d2 >i d1 , the reverse current injection circuit to M 2 Gate injection reverse current I b , the injected reverse current value is:

[0037]

[0038] Among them, V BE,T3 For transistor T3 The threshold voltage of M 2 Gate drive current i g2 Get smaller, M 2 The gate-source voltage rises slower, M 2 The opening speed is slowed down, and the parallel M 1 With M 2 The drain current in the circuit tends to balance.

[0039] 3. During the shutdown process of the SiC MOSFET parallel circuit, assuming that M 1 The shut-off speed is greater than M 2 The shut-off speed.

[0040] At this time d2 >i d1 , the reverse current injection circuit to M 2 Gate injection reverse current I b . Flows through the driving resistor R 2 The current is:

[0041] i off =i gb -I b (4)

[0042] M 2 The gate-source voltage is:

[0043]

[0044] I b Make the driving resistor R 2 The pressure drop is reduced, M 2 The gate-source voltage drops faster, M 2 The turn-off speed becomes faster, and the parallel M 1 With M 2 The drain current in the circuit tends to balance.

[0045] 4. During the shutdown process of the SiC MOSFET parallel circuit, assuming that M 2 The shut-off speed is greater than M 1 The shut-off speed.

[0046] At this time d1 >i d2 , the forward current injection circuit to M 2 Gate injected forward current I a . Flows through the driving resistor R 2 The current is:

[0047] i off =i gb +I a (6)

[0048] M2 The gate-source voltage is:

[0049]

[0050] I a Make the driving resistor R 2 The pressure drop of M 2 The gate-source voltage drops slower, M 2 The turn-off speed is slowed down, and the parallel M 1 With M 2 The drain current in the circuit tends to balance.

[0051] Figure 5 (a) and (b) show the M when there is no current sharing measure. 1 The drain current i d1 With M 2 The drain current i d2 The switching waveform, Figure 6 (a) and (b) show the effect of suppressing uneven flow by using the present invention. 1 The drain current i d1 With M 2 The drain current i d2 The switching waveform of Figure 5 (a) and Figure 6 (a) Comparison of turn-on current and Figure 5 (b) and Figure 6 From the comparison of the turn-off current (b), it can be found that the current injection type SiC MOSFET parallel drive circuit proposed in the present invention has an obvious current sharing effect.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A current injection type SiC MOSFET parallel current sharing driving circuit, comprising a SiC MOSFET M1 and a SiC MOSFET M2 connected in parallel, characterized in that: It also includes a current sampling circuit, a current difference feedback circuit, a forward current injection circuit, and a reverse current injection circuit; For the current sampling resistors connected in series to the SiC MOSFET M1 and the SiC MOSFET M2, respectively, the current sampling circuit uses an isolation amplifier and a differential amplifier circuit to respectively detect the voltage difference across the current sampling resistors, thereby indirectly measuring the current of the SiC MOSFET M1 branch and the SiC MOSFET M2 branch; The current difference feedback circuit measures the current difference of the two parallel branches by using the voltage difference between the two current sampling resistors and the differential amplifier circuit, and outputs a control signal to the forward current injection circuit or the reverse current injection circuit when the current of the SiC MOSFET parallel circuit is unbalanced; The forward current injection circuit is a circuit for injecting a forward current into the gate of the SiC MOSFET M2. Under the action of the control signal, the change rate of the gate-source voltage is changed, and the turn-on and turn-off speeds of the SiC MOSFET M2 are dynamically adjusted, thereby suppressing the uneven current phenomenon of the parallel circuit. The reverse current injection circuit is a circuit for injecting reverse current into the gate of SiC MOSFET M2. Under the action of the control signal, the change rate of the gate-source voltage is changed, and the turn-on and turn-off speeds of SiC MOSFET M2 are dynamically adjusted, thereby suppressing the uneven current phenomenon of the parallel circuit.

2. A current injection type SiC MOSFET parallel current sharing driving circuit according to claim 1, characterized in that: The current sampling circuit includes isolation amplifiers U1 and U2, operational amplifiers U3 and U4, and current sampling resistors R 3 and R 4. Resistance R 5~ R 12 ; Current sampling resistor R 3 and R 4 are connected in series to the SiC MOSFET M1 branch and the SiC MOSFET M2 branch respectively; the positive input terminal of the isolation amplifier U1 is connected to the current sampling resistor R 3 current input terminal, the negative input terminal is connected to the current sampling resistor R 3 current output terminal; resistance R 5 One end is connected to the positive output of the isolation amplifier U1, and the other end is connected to the positive input of the operational amplifier U3 and the resistor R 7, one end of the resistor R 7The other end is connected to the reference ground; the resistor R 6 One end is connected to the negative output terminal of the isolation amplifier U1, and the other end is connected to the negative input terminal of the operational amplifier U3 and the resistor R One end of 8; resistor R 8The other end is connected to the output of the operational amplifier U3; the positive input of the isolation amplifier U2 is connected to the current sampling resistor R 4 current input terminal, the negative input terminal is connected to the current sampling resistor R 4 current output terminal; resistance R 9 One end is connected to the positive output of the isolation amplifier U2, and the other end is connected to the positive input of the operational amplifier U4 and the resistor R 11 One end of the resistor R 11 The other end is connected to the reference ground; the resistor R 10 One end is connected to the negative output of the isolation amplifier U2, and the other end is connected to the negative input of the operational amplifier U4 and the resistor R 12 one end of a resistor R 12 The other end is connected to the output end of the operational amplifier U4.

3. A current injection type SiC MOSFET parallel current sharing driving circuit according to claim 2, characterized in that: The current difference feedback circuit includes operational amplifiers U5 and U6, resistors R 13 ~ R 20 ;resistance R 13 One end is connected to the output of operational amplifier U3 and resistor R 18 One end of the resistor is connected to the positive input of the operational amplifier U5 and the other end R 15 One end of the resistor R 15 The other end is connected to the reference ground; the resistor R 14 One end is connected to the output of operational amplifier U4 and resistor R 17 One end of the resistor is connected to the negative input terminal of the operational amplifier U5 and the other end is connected to the negative input terminal of the operational amplifier U5 and the resistor R 16 one end of a resistor R 16 The other end is connected to the output of operational amplifier U5; R 17 The other end is connected to the positive input of operational amplifier U6 and resistor R 19 One end of the resistor R 19 The other end is connected to the reference ground; the resistor R 18 The other end is connected to the negative input terminal of operational amplifier U6 and resistor R 20 one end of a resistor R 20 The other end is connected to the output end of the operational amplifier U6.

4. A current injection type SiC MOSFET parallel current sharing driving circuit according to claim 3, characterized in that: The forward current injection circuit includes a power supply V CC 、NPN transistor T 1. PNP transistor T 2. Resistance R 21 , diode D2; NPN transistor T The base of 1 is connected to the output of operational amplifier U5 and the PNP transistor T 2 base, NPN transistor T The collector of 1 is connected to the power supply V CC , NPN transistor T The emitter of 1 is connected to the PNP transistor T 2 emitter and resistor R 21 One end of the PNP transistor T The collector of 2 is connected to the reference ground; the resistor R 21 The other end is connected to the anode of the diode D2; the cathode of the diode D2 is connected to the gate of the SiC MOSFET M2.

5. A current injection type SiC MOSFET parallel current sharing driving circuit according to claim 3, characterized in that: The reverse current injection circuit includes a power supply V CC 、NPN transistor T 3. PNP transistor T 4. NPN transistor T 5. NPN transistor T 6. Resistance R 22 , diode D3; NPN transistor T The base of 3 is connected to the output of operational amplifier U6 and the PNP transistor T 4 base, NPN transistor T The collector of 3 is connected to the power supply V CC , NPN transistor T The emitter of 3 is connected to the PNP transistor T 4 emitter and resistor R 22 One end of the PNP transistor T The collector of 4 is connected to the reference ground; NPN transistor T 5 and NPN transistor T 6 constitutes a mirror current source; resistance R 22 The other end is connected to the NPN transistor T 5 collector and base; NPN transistor T The base of 5 is connected to the NPN transistor T 6 base, NPN transistor T The emitter of 5 is connected to the NPN transistor T 6's emitter and reference ground; NPN transistor T The collector of 6 is connected to the cathode of the diode D3; the anode of the diode D3 is connected to the gate of the SiC MOSFET M2.

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