CN106100297B - Driving circuit based on silicon carbide MOSFET - Google Patents

Abstract

The invention relates to a driving circuit based on silicon carbide MOSFET. The turn-on and turn-off loops of the drive circuit go through different loops, including: four capacitors C _{a1_H} , C _{a2_H} , C _{a1_L} and C _{a2_L} , the function of capacitors C _{a2_H} and C _{a2_L} is to reduce the common source on the package pin The influence of parasitic inductance L _S2H and L _S2L ; the function of capacitance C _{a1_H} and C _{a1_L} is to provide a lower impedance loop for the charge and discharge current of junction capacitance C _GDH and C _GDL inside the silicon carbide MOSFET package when crosstalk occurs. The invention can be used to suppress the crosstalk problem in converters with bridge arm structures such as three-phase bridge inverters, full-bridge DC-DC converters, etc., and suppress the crosstalk problem without increasing the complexity of the driving circuit The resulting silicon carbide MOSFET gate-source voltage spike improves the reliability of silicon carbide MOSFET-based power electronic devices.

Description

Driver circuit based on silicon carbide MOSFET

technical field

The invention belongs to the technical field of power electronic circuits, and relates to a drive circuit based on a silicon carbide MOSFET with low turn-off gate loop impedance.

Background technique

As shown in Figure 1, capacitors C _{a_H} and C _{a_L} are added to the traditional SiC MOSFET-based drive circuit to build a low-impedance branch and suppress gate-source voltage spikes caused by crosstalk problems, but adding capacitors C _{a_H} and C _{a_L} is equivalent to increasing the gate-source junction capacitance C _GSH and C _GSL , which will affect the switching speed. Figure 2 shows a way to add auxiliary switch tubes S _{a_H} and S _{a_L} and capacitors C _{a_H} and C _{a_L} to a traditional silicon carbide MOSFET-based drive circuit, which can suppress the gate-source voltage spike caused by the crosstalk problem, and at the same time avoid only Adding capacitors C _{a_H} and C _{a_L} affects the switching speed of SiC MOSFETs. FIG. 3 is the driving signal corresponding to the switching tube in FIG. 2 .

The working principle of the prior art solution shown in Fig. 2 is as follows:

(t ₀ ˜t ₁ ): the capacitors C _{a_H} and C _{a_L} are precharged. Through the body diodes of the auxiliary switch transistors S _{a_H} and S _{a_L} and the gate resistors R _{g_H} and R _{g_L} , the voltages of the capacitors C _{a_H} and C _{a_L} are -V _{SS_H} and -V _{SS_L} .

(t ₁ ˜t ₂ ): the auxiliary switch tubes S _{a_H} and S _{a_L} are still in the cut-off state. At time _t2 , the lower transistor _Q2 of the bridge arm starts to conduct.

(t ₂ ～t ₃ ): the lower switch Q ₂ of the bridge arm is turned on. At this moment, the switch tube S _{1_L} is in the on state, and at the same time the switch tube S _{2_L} and the auxiliary switch tube S _{a_L} are in the off state. At the same time, the auxiliary switch tube S _{a_H} is turned on, and the capacitor C _{a_H} is connected in parallel to the two ends of the capacitor C _GSH of the upper tube Q ₁ of the bridge arm, providing a low impedance branch for the capacitor C _GDH during the switching process. The gate impedance of the transistor _Q1 on the bridge arm is greatly reduced, so the forward voltage peak of the gate and source is also reduced correspondingly, and the crosstalk problem caused by the turn-on moment is suppressed.

(t ₃ ～t ₄ ): The lower switch Q ₂ of the bridge arm is completely turned on. The capacitors C _{a_H} and C _GSH are electrically charged through the gate resistors R _{g_H} and -V _{SS_H} until the voltage on the capacitors C _{a_H} and C _GSH drops to -V _{SS_H} .

(t ₄ ～t ₅ ): the lower switch Q ₂ of the bridge arm is turned off. During this process, the switch tube S _{1_L} is turned off, and the switch tube S _{2_L} is turned on. At the same time, the auxiliary switching transistor S _{a_H} is in the conduction phase, and the capacitor C _{a_H} is connected in parallel to both ends of the capacitor C _GSH of the transistor Q ₂ on the bridge arm. The gate impedance of the transistor _Q2 on the bridge arm is small, so it can effectively suppress the negative voltage spike of the gate-source.

(t ₅ ˜t ₆ ): the lower tube Q ₂ of the bridge arm is completely turned off. The auxiliary switch S _{a_H} is turned off, and the connection between the capacitor C _{a_H} and C _GSH is disconnected. Capacitor C _GSH charges until its voltage rises to -V _{SS_H} .

Adding auxiliary switch tubes S _{a_H} and S _{a_L} to the drive circuit shown in Figure 2 requires additional control signals to control the opening and closing of the auxiliary switch tubes. The disadvantages are mainly reflected in the following aspects:

1) The auxiliary switching tube requires additional control signals, which increases the complexity of the control;

2) Affect the layout of the drive circuit: Due to the existence of auxiliary switch tubes and capacitors, the area of the drive loop increases, which will affect the switching characteristics of the switch tube in the high-frequency circuit.

When silicon carbide MOSFETs are used in high-frequency bridge circuits, crosstalk problems will occur, causing positive or negative peaks in the gate-source voltage of silicon carbide MOSFETs, as shown in Figure 4. The crosstalk problem has a great impact on the reliability of power electronic devices. The positive peak of the gate-source voltage will cause false conduction of the silicon carbide MOSFET, resulting in a short circuit of the bridge arm; and the negative peak of the gate-source voltage will cause the gate of the silicon carbide MOSFET to fail. source breakdown. The factors that form the crosstalk problem are mainly caused by the parasitic parameters of the circuit, such as the junction capacitance C _GD (that is, C _GDH and C _GDL in Figures 1 and 2) and C _GS (that is, C _GSH in Figures 1 and 2) of the silicon carbide MOSFET. and C _GSL ), common-source parasitic inductance (exists in both the drive circuit loop and the main power loop). Whether there is a common-source parasitic inductance in the driving circuit determines different crosstalk phenomena. Moreover, none of the existing technical solutions considers the influence of the cosource parasitic inductance in the device package, and does not take suppression measures for its influence on the crosstalk problem.

To sum up, when the existing technology solves the crosstalk problem, it is necessary to add an auxiliary circuit to the drive circuit, and the auxiliary switch tube in the auxiliary circuit needs an additional control signal, and the control signal requires a certain accuracy, which will increase the cost of digital control. difficulty. Moreover, after the auxiliary circuit is added to the driving circuit, the layout of the original driving circuit will be affected, so that the loop area of the driving circuit will increase. In high-frequency circuits, the increase in the loop area of the drive circuit will affect the switching characteristics of the switch tube. In addition, none of the existing technical solutions considers the influence of the parasitic inductance in the device package—the common source parasitic inductance, and does not take suppression measures for its influence on the crosstalk problem.

Contents of the invention

Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a driving circuit based on silicon carbide MOSFET, which is used to suppress the current transformer with bridge arm structure such as three-phase bridge inverter, full bridge DC-DC Crosstalk problems in converters, etc. When a crosstalk problem occurs, a low-impedance branch is provided in the drive circuit to reduce gate-to-source voltage variations. On the premise of not increasing the complexity of the driving circuit, the invention suppresses the gate-source voltage peak of the silicon carbide MOSFET caused by the crosstalk problem, and improves the reliability of the power electronic device based on the silicon carbide MOSFET.

For achieving above object, the technical scheme that the present invention takes is:

A driving circuit based on a silicon carbide MOSFET, the silicon carbide MOSFET includes a bridge arm upper transistor _Q1 and a bridge arm lower transistor _Q2 ; the inductance L _S2H and the inductance L _S2L are respectively the common points of the package pins of _Q1 and _Q2 source parasitic inductance;

The driving circuit of the transistor Q ₁ on the bridge arm includes a voltage source V _{GS_H} , a switch tube S _{1_H} , an on-gate resistor R _{on_H} , a voltage source -V _{SS_H} , a switch tube S _{2_H} and an off-gate resistor R _{off_H} ;

The anode of the voltage source V _{GS_H} is connected to the drain of the switching tube S _{1_H} , the source of the switching tube S _{1_H} is connected to one end of the on-gate resistor R _{on_H} , and the other end of the on-gate resistor R _{on_H} is connected to The gate connection of _Q1 on the bridge arm;

The negative pole of the voltage source V _{GS_H} is connected to the positive pole of the voltage source -V _{SS_H} , the negative pole of the voltage source -V _{SS_H} is connected to the source of the switching tube S _{2_H} , and the drain of the switching tube S _{2_H} is connected to the shutdown gate One end of the pole resistor R _{off_H} is connected, the other end of the turn-off gate resistor R _{off_H} is connected to the gate of the transistor _Q1 on the bridge arm, and one end of the inductance L _S2H is connected to the source of the transistor _Q1 on the bridge arm , the other end is connected to the anode of the voltage source -V _{SS_H} ;

The driving circuit of the lower tube Q ₂ of the bridge arm includes a voltage source V _{GS_L} , a switch tube S _{1_L} , an on-gate resistor R _{on_L} , a voltage source -V _{SS_L} , a switch tube S _{2_L} and an off-gate resistor R _{off_L} ;

The anode of the voltage source V _{GS_L} is connected to the drain of the switching transistor S _{1_L} , the source of the switching transistor S _{1_L} is connected to one end of the on-gate resistor R _{on_L} , and the other end of the on-gate resistor R _{on_L} is connected to The gate connection of the lower transistor _Q2 of the bridge arm;

The negative pole of the voltage source V _{GS_L} is connected to the positive pole of the voltage source -V _{SS_L} , the negative pole of the voltage source -V _{SS_L} is connected to the source of the switching transistor S _{2_L} , and the drain of the switching transistor S _{2_L} is connected to the shutdown gate One end of the pole resistor R _{off_L} is connected, the other end of the turn-off gate resistor R _{off_L} is connected to the gate of the lower transistor _Q2 of the bridge arm, and one end of the inductance L _S2L is connected to the source of the lower transistor _Q2 of the bridge arm , the other end is connected to the anode of the voltage source -V _{SS_L} ;

It is characterized by:

The turn-on and turn-off loops of the silicon carbide MOSFET drive circuit go through different loops, and also include: four capacitors C _{a1_H} , C _{a2_H} , C _{a1_L} and C _{a2_L} ,

The function of the capacitor C _{a2_H} is to reduce the influence of the common-source parasitic inductance L _S2H on the package pin, one end of the capacitor C _{a2_H} is connected to the source of the upper transistor _Q1 of the bridge arm, and the other end is used to provide a shutdown Negative Voltage Source - Negative connection of V _{SS_H} ;

The function of the capacitor C _{a2_L} is to reduce the influence of the common-source parasitic inductance L _S2L on the package pin. One end of the capacitor C _{a2_L} is connected to the source of the lower transistor Q ₂ of the bridge arm, and the other end is connected to the source for providing shutdown Negative Voltage Source - Negative connection of V _{SS_L} ;

The function of the capacitor C _{a1_H} is to provide a lower impedance loop for the charging and discharging current of the gate-drain junction capacitance C _GDH inside the silicon carbide MOSFET package when crosstalk occurs in _Q1 . The capacitor C _{a1_H} is connected to the off gate resistor R _{off_H} in parallel;

The function of the capacitor C _{a1_L} is to provide a lower impedance loop for the charging and discharging current of the gate-drain junction capacitance C _GDL inside the silicon carbide MOSFET package when crosstalk occurs in _Q2 . The capacitor C _{a1_L} and the turn-off gate resistor R _{off_L} in parallel.

In the above driving circuit,

The open circuit of the driving circuit of Q ₁ passes through the voltage source V _{GS_H} , the switch tube S _{1_H} and the open gate resistance R _{on_H} ;

The turn-off loop of the driving circuit of Q ₁ passes through the voltage source -V _{SS_H} , the switch tube S _{2_H} and the turn-off gate resistance R _{off_H} ;

The open circuit of the driving circuit of Q ₂ passes through the voltage source V _{GS_L} , the switch tube S _{1_L} and the open gate resistance R _{on_L} ;

The turn-off loop of the driving circuit of Q ₂ passes through the voltage source -V _{SS_L} , the switch tube S _{2_L} and the turn-off gate resistor R _{off_L} .

In the above driving circuit,

In the driving circuit of Q ₁ , the driving signals of the switching tube S _{1_H} and the switching tube S _{2_H} are complementary;

In the driving circuit of _Q2 , the driving signals of the switching tube _{S1_L} and the switching tube _{S2_L} are complementary.

In the above driving circuit,

The package of Q ₁ includes gate-source junction capacitance C _GSH , gate-drain junction capacitance C _GDH and drain-source junction capacitance C _DSH ;

The package of Q ₂ includes gate-source junction capacitance C _GSL , gate-drain junction capacitance C _GDL and drain-source junction capacitance C _DSL ;

The common-source parasitic inductances of the internal connection lines of the packages of Q ₁ and Q ₂ are inductance L _S1H and inductance L _S1L respectively;

The internal gate resistors of _Q1 and _Q2 are resistors R _G1H and R _G1L , respectively.

In the above driving circuit,

When crosstalk occurs in Q ₁ , the capacitance C _{a1_H} is large enough, so that most of the junction capacitance C _GDH change current will flow through the capacitance C _{a1_H} instead of the junction capacitance C _GSH , and the voltage spike on the gate and source of Q ₁ will be reduced;

When crosstalk occurs in Q ₂ , the capacitance C _{a1_L} is large enough, so that most of the changing current of the junction capacitance C _GDL will flow through the capacitance C _{a1_L} instead of the junction capacitance C _GSL , and the voltage spike on the gate-source of Q ₂ will be reduced.

In the above driving circuit,

When the current changes sharply, the common-source parasitic inductance L _S2H induces a voltage drop and stores energy. At this time, the voltage and energy on the capacitor C _{a2_H} also change accordingly. When the capacitor C _{a2_H} is large enough, the common-source parasitic inductance L _S2H and The driving circuit _Q1 is decoupled, and the influence of the common source parasitic inductance L _S2H is reduced;

When the current changes sharply, the common-source parasitic inductance L _S2L induces a voltage drop and stores energy. At this time, the voltage and energy on the capacitor C _{a2_L} also change accordingly. When the capacitor C _{a2_L} is large enough, the common-source parasitic inductance L _S2L and The driving circuit _Q2 is decoupled, and the influence of the common source parasitic inductance L _S2L is reduced.

The beneficial effect of the driver circuit based on silicon carbide MOSFET described in the present invention is as follows:

Figure 5 shows an existing drive circuit, which is characterized in that the drive circuit loops for turning on and off the silicon carbide MOSFET pass through different loops. For example, when silicon carbide MOSFET Q ₁ is turned on, its driving circuit passes through voltage source V _{GS_H} , switch tube S _{1_H} and turn-on gate resistor R _{on_H} ; when silicon carbide MOSFET Q ₁ is turned off, its driving circuit passes through -V _{SS_H} , S _{2_H} and R _{off_H} . The present invention adds four capacitors C _{a1_H} , C _{a2_H} , C _{a1_L} and C _{a2_L} on the basis of the driving circuit shown in FIG. 5 , as shown in FIG. 6 . The driving circuit of the present invention can not only reduce the influence of common source parasitic inductance, but also suppress the problem of crosstalk, and does not need an auxiliary switching tube, does not affect the normal switching speed of the silicon carbide MOSFET, does not affect the layout of the driving circuit, and has a simple structure and is easy to implement ,details as follows:

1. The structure of the drive circuit with low turn-off gate loop impedance: the feature of this drive circuit is that it does not require additional active devices, and it does not affect the normal switching speed of silicon carbide MOSFETs under the premise of suppressing crosstalk. , and does not affect the layout of the driving circuit, the structure is simple and easy to implement.

2. The connection method of capacitors C _{a2_H} and C _{a2_L} : the function of capacitors C _{a2_H} and C _{a2_L} is to reduce the influence of common source parasitic inductance L _S2H and L _S2L on the package pins, capacitors C _{a2_H} and C _{a2_L} need to be connected in parallel Source parasitic inductance and the voltage source -V _{SS_H} or -V _{SS_L} used to provide the negative voltage for shutdown.

3. The connection method of capacitors C _{a1_H} and C _{a1_L} : the function of capacitors C _{a1_H} and C _{a1_L} is to provide a lower impedance loop for the charging and discharging current of junction capacitors C _GDH and C _GDL inside the silicon carbide MOSFET package when crosstalk occurs . The capacitors C _{a1_H} and C _{a1_L} are equivalent to the capacitors C _{a_H} and C _{a_L} in Figure 1, but in order to avoid adding auxiliary switch tubes, the capacitors C _{a1_H} and C _{a1_L} are connected in parallel to the turn-off gate resistors R _{off_H} and R _{off_L} , and then use the switch Transistors S _{2_H} and S _{2_L} are controlled which do not affect the SiC MOSFET switching speed.

Description of drawings

The present invention has following accompanying drawing:

Fig. 1 is the driving circuit of prior art scheme;

Fig. 2 is the improved driving circuit based on prior art scheme

Fig. 3 is the driving signal corresponding to the switching tube of the driving circuit in Fig. 2;

Figure 4 shows the positive and negative voltage spikes caused by the crosstalk problem;

Fig. 5 is existing driving circuit;

Fig. 6 is the improved driving circuit diagram proposed by the present invention based on the driving circuit of Fig. 5;

Fig. 7 is the signal logic of the switches S _{1_H} , S _{2_H} , S _{1_L} and S _{2_L} in the driving circuit of the present invention;

Fig. 8 is the equivalent circuit diagram of four stages of one switching period of the drive circuit of the present invention; wherein, (a) is the equivalent circuit diagram of t ₁ -t ₂ moment; (b) is the equivalent circuit diagram of t ₂ -t ₃ moment ; (c) is the equivalent circuit diagram of t ₃ -t ₄ moment; (d) is the equivalent circuit diagram of t ₄ -t ₅ moment;

FIG. 9 is an equivalent circuit for calculating the capacitance Ca1_H.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Example 1

1. The driving circuit of the present invention (as shown in FIG. 6 ).

Since the crosstalk problem occurs at the moment of switching, it is considered that the load current I _o and the input voltage V _DC are constant. The drive circuit shown in Figure 6 is based on the existing drive circuit shown in Figure 5 with four capacitors C _{a1_H} , C _{a2_H} , C _{a1_L} and C _{a2_L} added, as follows:

In the drive circuit of Q ₁ , the S _{1_H} and S _{2_H} drive signals are complementary, and in the drive circuit of Q ₂ , the S _{1_L} and S _{2_L} drive signals are complementary;

The capacitance C _GSH , the capacitance C _GDH , and the capacitance C _DSH are respectively the internal gate-source junction capacitance, gate-drain junction capacitance, and drain-source junction capacitance of the silicon carbide MOSFET Q ₁ package;

The capacitance C _GSL , the capacitance C _GDL , and the capacitance C _DSL are respectively the internal gate-source junction capacitance, gate-drain junction capacitance, and drain-source junction capacitance of the silicon carbide MOSFET Q ₂ package;

The inductance L _S1H and the inductance L _S1L are the common-source parasitic inductances of the internal connection lines of the packages of the silicon carbide MOSFETs Q ₁ and Q ₂ , respectively;

The inductance L _S2H and the inductance L _S2L are the common-source parasitic inductance of the package pins of the silicon carbide MOSFETs Q ₁ and Q ₂ , respectively;

Resistance R _G1H and resistance R _G1L are the internal gate resistances of silicon carbide MOSFET Q ₁ and Q ₂ respectively;

The resistance R _{on_H} and the resistance R _{off_H} are the turn-on gate resistance and the turn-off gate resistance of the silicon carbide MOSFET Q ₁ , respectively;

The resistance R _{on_L} and the resistance R _{off_L} are the on-gate resistance and the off-gate resistance of the silicon carbide MOSFET Q ₂ , respectively.

2. Working principle of drive circuit

As shown in Figure 7, one switching cycle of the drive circuit of the present invention is divided into four stages: (t ₁ ~ t ₂ ), (t ₂ ~ t ₃ ), (t ₃ ~ t ₄ ) and (t ₄ ~ t ₅ ), the equivalent circuit diagram of each stage is shown in Figure 8, and the specific analysis is as follows:

Before time t ₁ , it is assumed that the circuit is in a steady state. The drive circuits S _{2_H} and S _{2_L} are turned on, both Q ₁ and Q ₂ are in the off state, and the body diode D ₁ of Q ₁ acts as a freewheeling diode for freewheeling.

(t ₁ ~ t ₂ ): The switch tube S _{2_H} in the drive circuit of Q ₁ is still on, the switch tube S _{2_L} in the drive circuit of Q ₂ is off, and the switch tube S _{1_L} is on. The equivalent circuit at this stage is shown in Figure 8 (a) shown. During this phase, _Q2 enters the conduction state, while _Q1 is always in the off state. Since S _{2_L} in the driving circuit of Q ₂ is in the off state at this stage, the capacitor C _{a1_L} is not connected in the turn-on loop, which will not affect the turn-on speed of Q ₂ . During the turn-on process of Q ₂ , when Q ₂ commutates with the body diode D ₁ of Q ₁ , the current changes rapidly, and voltage drops will occur on the common-source parasitic inductances L _S1H , L _S2H , L _S1L , and L _S2L . Since the common-source parasitic inductance L _S1H and L _S1L are used as the parasitic inductance on the internal link line of the silicon carbide MOSFET package, the inductance value is small, and the influence caused by it is ignored. In the driving circuit of Q ₂ , the capacitor C _{a2_L} forms a loop with the common source parasitic inductance L _S2L and the voltage source -V _{SS_L} . If the capacitance C _{a2_L} is large enough, the influence of the voltage drop on the common source parasitic inductance L _S2L is reduced. Similarly, in the driving loop of _Q1 , the capacitor C _{a2_H} reduces the influence of the common source parasitic inductance L _S2H . When the drain-source voltages of Q ₁ and Q ₂ change simultaneously during the turn-on process of Q ₂ , the junction capacitances C _GDH , C _DSH and C _GDL , C _DSL are charged and discharged. During this process, the charging current of the junction capacitance C _GDH of Q ₁ will flow through the junction capacitance C _GSH branch and the drive circuit. If the capacitance C _{a1_H} is large enough, most of the junction capacitance C _GDH charging current will flow through the capacitance C _{a1_H} . In summary, the voltage spike on the gate and source of _Q1 will be reduced, and the crosstalk problem can be suppressed.

(t ₂ ~ t ₃ ): The switch tube S _{2_H} in the drive circuit of Q ₁ is still in the cut-off state, the switch tube S _{1_L} in the drive circuit of Q ₂ is turned off, and the switch tube S _{2_L} is turned on. The equivalent circuit at this stage is shown in Figure 8 (b) shown. During this phase, _Q2 enters the off state, and _Q1 remains in the off state. In the driving circuit of Q ₂ , S _{2_L} is turned on, and the capacitor C _{a1_L} and the turn-off resistor R _{off_L} are connected into the turn-off circuit. Because the capacitance C _{a1_L} is relatively large, the influence on the turn-off speed of Q ₂ is negligible, and the turn-off speed of Q ₂ The speed is mainly regulated by the _off resistor Roff_L. During the turn-off process of Q ₂ , when the drain-source voltage of Q ₁ and Q ₂ changes simultaneously, the discharge current of the junction capacitance C _GDH of Q ₁ will flow through the junction capacitance C _GSH branch and the drive circuit, due to the capacitance C _{a1_H} The impedance of the loop where it is located is small, so most of the charging current of the capacitor C _GDH flows through C _{a1_H} . When Q ₂ is turned off, when Q ₂ and body diode D ₁ of Q ₁ commutate, the current changes sharply, and voltage drops will occur on the common source parasitic inductance L _S1H , L _S2H , L _S1L , and L _S2L , and due to The influence of capacitors C _{a2_H} and C _{a2_L} , and the influence of common source parasitic inductance L _S2H and L _S1H on the crosstalk problem are reduced.

(t ₃ ~ t ₄ ): The switch tube S _{1_L} in the driving circuit of Q ₂ is still in the cut-off state, the switch tube S _{2_H} in the driving circuit of Q ₁ is turned off, and the switch tube S _{1_H} is turned on. The equivalent circuit at this stage is shown in Figure 8 (c) shown. In this phase, _Q1 enters the on state, and _Q2 has been in the off state. Since the load current flows into the midpoint of the bridge arm, during the turn-on process of _Q1 , _Q1 commutates with its body diode _D1 , the drain-source voltage of _Q1 and _Q2 basically does not change, and there is basically no voltage on the common source parasitic inductance and junction capacitance The current varies, so there are no crosstalk issues.

(t ₄ ～t ₅ ): The switch tube S _{1_L} in the drive circuit of Q ₂ is still in the cut-off state, the switch tube S _{1_H} in the drive circuit of Q ₁ is turned off, and the switch tube S _{2_H} is turned on. The equivalent circuit at this stage is shown in Figure 8 (d) shown. During this phase, _Q1 enters the off state, and _Q2 remains off all the time. The turn-off process of Q ₁ is similar to its turn-on process, Q ₁ commutates with its body diode D ₁ , the drain-source voltage of Q ₁ and Q ₂ basically does not change, and there is basically no voltage and current change on the source parasitic inductance and junction capacitance, so there will be no There is a crosstalk problem.

3. Parameter calculation of the drive circuit

Calculation of parameters in _Q1 drive circuit:

1) Calculation of capacitance C _{a2_H}

The function of the capacitor C _{a2_H} is to reduce the influence of the common source parasitic inductance L _S2H on the package pin. When the current changes sharply, the common-source parasitic inductance L _S2H induces a voltage drop and stores energy, and the voltage and energy on the capacitor C _{a2_H} also change accordingly; when the capacitor C _{a2_H} is large enough, the common-source parasitic inductance L _S2H and The driving circuit of Q ₁ is decoupled, and the influence of the common source parasitic inductance L _S2H is reduced.

Set the capacitance C _{a2_H} voltage variation Δv _{Ca2_H} < ΔV _{Ca2_H} (ΔV _{Ca2_H} is the set value), then the capacitor C _{a2_H} needs to meet the conditions shown in formula (1):

In formula (1), I _peak is the maximum value of the current variation on the common source inductance.

2) Calculation of capacitance C _{a1_H}

When Q ₁ has a crosstalk problem, the capacitance C _{a1_H} is large enough, and most of the current changing in the junction capacitance C _GDH will flow through the capacitance C _{a1_H} instead of the junction capacitance C _GSH , and the voltage spike on the gate-source of Q ₁ will be reduced.

Figure 9 is a simplified equivalent circuit when _Q1 has crosstalk problems. Assuming that the voltage change rate κ of the drain-source voltage v _DSH of Q ₁ is constant at the moment of switching, κ=κ ₁ when Q ₂ is turned on, and κ=κ ₂ when Q ₂ is turned off, the equations (2) and (3) respectively give The positive-going peak value v _GSH(+) of the gate-source voltage of Q ₁ when Q ₂ is turned on, and the negative-going peak value v _GSH(-) of the gate-source voltage of Q ₁ when Q ₂ is turned off. In order to ensure the reliability of the power electronic device, the positive peak value v _GSH(+) of the gate-source voltage of Q ₁ needs to be less than the threshold voltage V _th of the silicon carbide MOSFET, and the negative peak value v _GSH(-) needs to be greater than the negative gate-source voltage. to the safe voltage V _{GS_MAX(-)} , as shown in formula (4). According to formulas (2) and (3), it can be seen that the negative voltage V _{SS_H} also has an impact on the peak value of the gate-source voltage of Q ₁ , and the range of V _{SS_H} needs to be selected according to formula (5).

Δv _GSH(+) -Δv _GSH(-) <V _th -V _{GS_MAX(-)} (4)

V _{GS_MAX(-)} -Δv _GSH(-) <V _{SS_H} <V _th -Δv _GSH(+) (5)

In formula (2)-(3):

Δv _GSH(+) is the positive change of the gate-source voltage of _Q1 ;

Δv _GSH(-) is the negative variation of the gate-source voltage of _Q1 ;

a ₀ =τ _d ;

τ _a = R _{off_H} C _{a1_H} ;

τ _b =(R _G1H +R _{off_H} )(C _GSH +C _GDH );

τ _c =R _G1H R _{off_H} C _{a1_H} (C _GSH +C _GDH );

τ _d = (R _G1H +R _{off_H} )C _GDH ;

Calculation of parameters in _Q2 drive circuit:

3) Calculation method of capacitance C _{a2_L}

The function of the capacitor C _{a2_L} is to reduce the influence of the common source parasitic inductance L _S2L on the package pin. When the current changes sharply, the common-source parasitic inductance L _S2L induces a voltage drop and stores energy, and the voltage and energy on the capacitor C _{a2_L} also change accordingly; when the capacitor C _{a2_L} is large enough, the common-source parasitic inductance L _S2L and The Q ₂ driving circuit is decoupled, and the influence of the common source parasitic inductance L _S2L is reduced. The calculation method of capacitance C _{a2_L} is the same as that of C _{a2_H} .

4) Calculation of capacitance C _{a1_L}

When Q ₂ has a crosstalk problem, the capacitance C _{a1_L} is large enough, most of the junction capacitance C _GDL changing current will flow through the capacitance C _{a1_L} instead of the junction capacitance C _GSL , and the voltage spike on the gate-source of Q ₂ will be reduced. The calculation method of C _{a1_L} is the same as that of C _{a1_H} .

The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims (6)

1. a kind of driving circuit based on silicon carbide MOSFET, the silicon carbide MOSFET includes bridge arm upper tube Q₁With bridge arm down tube Q₂；Inductance L_S2HWith inductance L_S2LRespectively Q₁And Q₂Packaging pin common source parasitic inductance；

The bridge arm upper tube Q₁Driving circuit include voltage source V_{GS_H}, switching tube S_{1_H}, open resistance R_{on_H}, voltage source- V_{SS_H}, switching tube S_{2_H}With shutdown resistance R_{off_H}；

The voltage source V_{GS_H}Anode with switching tube S_{1_H}Drain electrode connection, the switching tube S_{1_H}Source electrode and open grid electricity Hinder R_{on_H}One end connection, it is described to open resistance R_{on_H}The other end and bridge arm upper tube Q₁Grid connection；

The voltage source V_{GS_H}Cathode and voltage source-V_{SS_H}Anode connection, the voltage source-V_{SS_H}Cathode and switching tube S_{2_H}Source electrode connection, the switching tube S_{2_H}Drain electrode and shutdown resistance R_{off_H}One end connection, the shutdown grid is electric Hinder R_{off_H}The other end and bridge arm upper tube Q₁Grid connection, the inductance L_S2HOne end and bridge arm upper tube Q₁Source electrode connection, The other end and the voltage source-V_{SS_H}Anode connection；

The bridge arm down tube Q₂Driving circuit include voltage source V_{GS_L}, switching tube S_{1_L}, open resistance R_{on_L}, voltage source- V_{SS_L}, switching tube S_{2_L}With shutdown resistance R_{off_L}；

The voltage source V_{GS_L}Anode with switching tube S_{1_L}Drain electrode connection, the switching tube S_{1_L}Source electrode and open grid electricity Hinder R_{on_L}One end connection, it is described to open resistance R_{on_L}The other end and bridge arm down tube Q₂Grid connection；

The voltage source V_{GS_L}Cathode and voltage source-V_{SS_L}Anode connection, the voltage source-V_{SS_L}Cathode and switching tube S_{2_L}Source electrode connection, the switching tube S_{2_L}Drain electrode and shutdown resistance R_{off_L}One end connection, the shutdown grid is electric Hinder R_{off_L}The other end and bridge arm down tube Q₂Grid connection, the inductance L_S2LOne end and bridge arm down tube Q₂Source electrode connection, The other end and the voltage source-V_{SS_L}Anode connection；

It is characterized in that：

Different circuits is passed through in the circuit that turns on and off of the driving circuit of the silicon carbide MOSFET, further includes：Four capacitances C_{a1_H}、C_{a2_H}、C_{a1_L}And C_{a2_L},

Capacitance C_{a2_H}Effect be reduce packaging pin on common source parasitic inductance L_S2HInfluence, the capacitance C_{a2_H}One end with With bridge arm upper tube Q₁Source electrode connection, the other end with for provides turn off negative pressure voltage source-V_{SS_H}Cathode connection；

Capacitance C_{a2_L}Effect be reduce packaging pin on common source parasitic inductance L_S2LInfluence, the capacitance C_{a2_L}One end with With bridge arm down tube Q₂Source electrode connection, the other end with for provides turn off negative pressure voltage source-V_{SS_L}Cathode connection；

Capacitance C_{a1_H}Effect be in Q₁When crosstalk occurs, for the grid drain junction capacitance C inside silicon carbide MOSFET encapsulation_GDHFill Discharge current provides more low-impedance circuit, the capacitance C_{a1_H}With shutdown resistance R_{off_H}It is in parallel；

Capacitance C_{a1_L}Effect be in Q₂When crosstalk occurs, for the grid drain junction capacitance C inside silicon carbide MOSFET encapsulation_GDLFill Discharge current provides more low-impedance circuit, the capacitance C_{a1_L}With shutdown resistance R_{off_L}It is in parallel.

2. the driving circuit based on silicon carbide MOSFET as described in claim 1, it is characterised in that：

Q₁Driving circuit open circuit pass through voltage source V_{GS_H}, switching tube S_{1_H}With open resistance R_{on_H}；

Q₁Driving circuit turn-off circuit pass through voltage source-V_{SS_H}, switching tube S_{2_H}With shutdown resistance R_{off_H}；

Q₂Driving circuit open circuit pass through voltage source V_{GS_L}, switching tube S_{1_L}With open resistance R_{on_L}；

Q₂Driving circuit turn-off circuit pass through voltage source-V_{SS_L}, switching tube S_{2_L}With shutdown resistance R_{off_L}。

3. the driving circuit based on silicon carbide MOSFET as claimed in claim 1 or 2, it is characterised in that：Q₁Driving circuit in Switching tube S_{1_H}With switching tube S_{2_H}Drive signal is complementary；

Q₂Driving circuit in switching tube S_{1_L}With switching tube S_{2_L}Drive signal is complementary.

4. the driving circuit based on silicon carbide MOSFET as claimed in claim 1 or 2, it is characterised in that：Q₁Encapsulation inside packet Include grid source junction capacitance C_GSH, grid drain junction capacitance C_GDHWith hourglass source electrode junction capacity C_DSH；

Q₂Encapsulation inside include grid source junction capacitance C_GSL, grid drain junction capacitance C_GDLWith hourglass source electrode junction capacity C_DSL；

Q₁And Q₂The common source parasitic inductance of encapsulation internal connection line be respectively inductance L_S1HWith inductance L_S1L；

Q₁And Q₂Internal gate resistance is respectively resistance R_G1HWith resistance R_G1L。

5. the driving circuit based on silicon carbide MOSFET as claimed in claim 4, it is characterised in that：In Q₁When crosstalk occurs, electricity Hold C_{a1_H}It is sufficiently large, make most of junction capacity C_GDHVariable-current will flow through capacitance C_{a1_H}, rather than junction capacity C_GSH, Q₁Grid source Extremely upper due to voltage spikes will reduce；

In Q₂When crosstalk occurs, capacitance C_{a1_L}It is sufficiently large, make most of junction capacity C_GDLVariable-current will flow through capacitance C_{a1_L}, and It is not junction capacity C_GSL, Q₂Due to voltage spikes will reduce on grid source electrode.

6. the driving circuit based on silicon carbide MOSFET as claimed in claim 4, it is characterised in that：When electric current change dramatically When, common source parasitic inductance L_S2HUpper induction generates voltage drop and storage energy, at this time capacitance C_{a2_H}Upper voltage and energy are also therewith Variation, as capacitance C_{a2_H}When sufficiently large, common source parasitic inductance L_S2HWith driving circuit Q₁Decoupling, common source parasitic inductance L_S2HInfluence Reduce；

When electric current change dramatically, common source parasitic inductance L_S2LUpper induction generates voltage drop and storage energy, at this time capacitance C_{a2_L} Upper voltage and energy also change therewith, as capacitance C_{a2_L}When sufficiently large, common source parasitic inductance L_S2LWith driving circuit Q₂Decoupling, common source Parasitic inductance L_S2LInfluence reduce.