阅读说明：本技术 用于优化碳化硅mosfet开关特性的驱动电路及方法 (Drive circuit and method for optimizing silicon carbide MOSFET switching characteristics ) 是由 梁帅 孙鹏 赵志斌 于 2021-08-23 设计创作，主要内容包括：用于优化碳化硅MOSFET开关特性的驱动电路及方法,包括输入单元、隔离单元、驱动单元、电感单元、连接单元和保护单元,所述输入单元的电压信号和脉冲信号经过隔离单元的隔离和电平转换后输入到驱动单元；所述驱动单元通过接收脉冲信号完成对电压信号的切换,经连接单元向碳化硅MOSFET施加正负驱动电压；所述电感单元采用带螺纹的软磁铁氧体,通过旋转改变软磁铁氧体在线圈中的位置,改变线圈的磁导率,进而改变线圈的电感值,最终实现驱动回路总寄生电感值的调整。(The driving circuit and the method for optimizing the switching characteristics of the silicon carbide MOSFET comprise an input unit, an isolation unit, a driving unit, an inductance unit, a connecting unit and a protection unit, wherein a voltage signal and a pulse signal of the input unit are input to the driving unit after being isolated by the isolation unit and subjected to level conversion; the driving unit completes the switching of voltage signals by receiving pulse signals and applies positive and negative driving voltages to the silicon carbide MOSFET through the connecting unit; the inductance unit adopts soft magnetic ferrite with threads, the position of the soft magnetic ferrite in the coil is changed through rotation, the magnetic conductivity of the coil is changed, the inductance value of the coil is further changed, and finally the adjustment of the total parasitic inductance value of the driving circuit is achieved.)

1. The driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET comprises an input unit, an isolation unit, a driving unit, an inductance unit, a connecting unit and a protection unit, wherein a voltage signal and a pulse signal of the input unit are input to the driving unit after being isolated by the isolation unit and subjected to level conversion; the driving unit completes the switching of voltage signals by receiving pulse signals and applies positive and negative driving voltages to the silicon carbide MOSFET through the connecting unit; it is characterized in that: the inductance unit adopts soft magnetic ferrite with threads, the position of the soft magnetic ferrite in the coil is changed through rotation, the magnetic conductivity of the coil is changed, the inductance value of the coil is further changed, and finally the adjustment of the total parasitic inductance value of the driving circuit is achieved.

2. The drive circuit for optimizing switching characteristics of a silicon carbide MOSFET of claim 1, wherein: the input unit comprises a 5V voltage input and a pulse input; the 5V voltage input adopts a constant voltage source power supply; the pulse signal is generated by a pulse signal generator, and the pulse time and the pulse interval can be manually input.

3. The drive circuit for optimizing switching characteristics of a silicon carbide MOSFET of claim 1, wherein: the isolation unit comprises a power supply module and an optical fiber module; the power supply module realizes level conversion on one hand, converts 5V input voltage into positive and negative switching voltage required by the silicon carbide MOSFET, and can realize voltage isolation by adopting an optical coupling isolation technology on the other hand; the optical fiber module realizes signal isolation to avoid signal noise interference, the pulse signal generator converts the electric signal into an optical signal, and the optical signal is converted into the electric signal again at the optical fiber receiver after being conducted through the optical fiber in the optical fiber module, and the electric signal is specifically represented as a high level and a low level output by the optical fiber receiver.

4. The drive circuit for optimizing switching characteristics of a silicon carbide MOSFET of claim 1, wherein: the driving unit comprises a driving chip and a driving resistor; the output end of the power supply module is connected with the voltage input end of the driving chip, the output end of the optical fiber receiver in the optical fiber module is connected with the control input end of the driving chip, and the driving chip is controlled to output positive driving voltage or negative driving voltage through the high and low level output by the optical fiber receiver.

5. The drive circuit for optimizing switching characteristics of a silicon carbide MOSFET of claim 4, wherein: the driving resistor is selected to be 3.3 ohm/0.5 watt, so that the fast switching speed is ensured, and the switching loss problem is considered while overshoot of the voltage of a source electrode and a drain electrode of the device is inhibited.

6. The drive circuit for optimizing switching characteristics of a silicon carbide MOSFET of claim 1, wherein: the protection unit is composed of Schottky diodes; the anode of the Schottky diode is connected with the input end of the connecting unit, and the cathode of the Schottky diode is connected with the positive voltage output end of the power supply module.

7. Drive circuit PCB board structure for optimizing switching characteristics of silicon carbide MOSFETs comprising a drive circuit for optimizing switching characteristics of silicon carbide MOSFETs according to any of claims 1 to 6, characterized in that: the PCB structure of the driving circuit adopts a double-sided design; the front surface of the PCB board of the driving circuit comprises an optical fiber receiver, a driving chip, a driving resistor, a wiring terminal and an SMA connector; the power module, the adjustable inductor and the protection unit are arranged on the reverse side of the PCB; in the isolation unit, the power module and the optical fiber receiver in the optical fiber module are connected with the input end of the driving chip, the driving resistor is connected with the output end of the driving chip, the power module, the optical fiber receiver and the driving resistor are tightly connected around the driving chip, the wiring distance is reduced, the input and output wiring of the driving chip are parallel, and the mutual inductance is increased to reduce the total parasitic inductance; the driving resistor, the adjustable inductor and the SMA connector are closely connected and adopt a copper-clad design, so that the wiring distance is short and the parasitic inductance is small.

8. A method of designing a PCB panel of a driving circuit for optimizing switching characteristics of a silicon carbide MOSFET, comprising the driving circuit for optimizing switching characteristics of a silicon carbide MOSFET according to any one of claims 1 to 6, characterized in that: the method comprises the following steps:

step 1: the power supply module is adopted to realize isolation;

step 2: the PCB layout of the driving circuit is optimized, and parasitic inductance introduced by the wiring layout is reduced;

and step 3: the total parasitic inductance of the driving circuit is adjusted by the adjustable inductance and the copper-clad design;

and 4, step 4: the switching characteristics of the silicon carbide MOSFET are optimized by adjusting the total parasitic inductance of the driving circuit.

9. The design method according to claim 8, wherein: the step 2 further comprises: the driving circuit PCB and the power circuit PCB are connected by an SMA connector, and because the SMA connector adopts a coaxial structure and current paths are opposite, the parasitic inductance of the circuit is reduced due to mutual inductance of the conducting wires.

10. Use of a driver circuit according to any of claims 1 to 6 for optimizing the switching characteristics of silicon carbide MOSFETs in driver circuit PCB board design.

Technical Field

The present invention relates to a driving circuit, and more particularly, to a driving circuit, a method and an application thereof for optimizing the switching characteristics of a silicon carbide MOSFET.

Background

With the vigorous development of the application field of power electronic devices such as electric automobiles and photovoltaic inverters, the power electronic devices are gradually developed towards high frequency and high power density. Silicon carbide power devices are increasingly widely used in the field of power electronics applications due to their superior electrical properties, such as wide bandgap, high breakdown field strength, high saturation drift velocity, and high thermal conductivity. Compared with the silicon MOSFET or silicon IGBT of the same grade, the silicon carbide MOSFET has the advantages of high switching speed, high voltage withstanding grade, good thermal stability and the like, and can stably work in severe environments such as high temperature, high radiation and the like.

The fast switching transient process makes the silicon carbide MOSFET particularly sensitive to parasitic inductance, resulting in large overshoot of the turn-off drain-source voltage and overshoot of the turn-on drain current of the silicon carbide MOSFET during switching. On the one hand, the large voltage and current overshoot can cause electromagnetic interference problems, and threatens the safe operation of the device. On the other hand, the device is used in a derating way, and the device cost is increased. The driving circuit can directly control the on and off of the silicon carbide MOSFET device, so that the switching speed of the device can be changed directly by designing the driving circuit of the silicon carbide MOSFET, and the optimization of the switching process is further realized. At present, two driving circuit design methods are mainly used for solving the problem of large voltage and current overshoot in the switching process of the silicon carbide MOSFET.

For a conventional driving circuit, a large resistance driving method is generally adopted. Patent [1 ]: publication No.: CN103944549A, the title of the invention, "a high reliability MOSFET driving circuit", discloses a MOSFET driving circuit. In the on-off stage of the driving circuit, different driving resistors are selected through different driving loops, and then the on-off speed of the device is adjusted. When the small resistor is selected for driving, the switching-on and switching-off speeds of the device are increased due to the small driving resistor, so that the overshoot of the switching-off drain-source voltage or the overshoot of the switching-on drain current of the silicon carbide MOSFET is increased; when a large resistor is selected for driving, the turn-on and turn-off speeds are reduced, overshoot of turn-off drain-source voltage or overshoot of turn-on drain current of the device is reduced, but due to the increase of turn-on and turn-off time, the rise and fall time of the drain-source voltage and the drain current is prolonged, and further the turn-on and turn-off loss of the device is increased linearly.

The active driving circuit can realize better switching characteristics than the traditional driving circuit by changing driving parameters in the switching process, and reduce overshoot of the voltage of a turn-off drain-source electrode and overshoot of a turn-on drain current while reducing switching loss. The currently common active driving circuit mainly includes: a variable driving resistance driving circuit, a variable driving voltage driving circuit, a variable driving current driving circuit, and the like. Patent [2 ]: publication No.: CN106059552A, inventive name: a driving circuit for realizing dynamic switching of a driving circuit at each stage of a MOSFET switch is disclosed in "a driving circuit based on dynamic characteristics of a MOSFET switch", and patent [3 ]: publication No.: CN110112893A, inventive name: the 'a drive circuit of a silicon carbide semiconductor field effect transistor' discloses a grid shunt circuit which can realize high switching speed and low voltage spike by regulating and controlling drive current. However, such a method requires an additional detection circuit and a feedback circuit, and the circuit design is very complicated and costly. Patent [4 ]: publication No.: CN 103293383A discloses a test circuit for series resistance of power MOSFET devices, which includes a pulse generator, a phase display, a voltage waveform digitizer, a current waveform digitizer, an adjustable inductor, a first gating switch and a second gating switch; the signal end of the pulse generator is electrically connected with the fixed end of the first gating switch through a series current waveform digital converter and an adjustable inductor; two selection ends of the first gating switch are respectively and electrically connected with the grid electrode and the drain electrode; two selection ends of the second gating switch are respectively and electrically connected with the source electrode and the drain electrode; one end of the voltage waveform digital converter is electrically connected with the adjustable inductor; one end of the voltage input end of the phase display is electrically connected with the adjustable inductor, and the other end of the voltage input end of the phase display is grounded; the phase display current input end is electrically connected with the adjustable inductor. Furthermore, such as the prior art: CN 103592517A, CN 108092419A, CN207602108U and the like, wherein the inductance comprises an adjustable inductance, the common mode adjustment inductance adopts soft magnetic ferrite with threads, an adjustable inductance module is connected in series with two ends of a socket of a resonance coil, an inductance adjusting knob changes the inductance size by controlling the position of an iron core of the soft magnetic ferrite in the adjustable inductance, and the inductance adjustable range is 2.1-6.8 uH; the following steps are repeated: although CN 106298165A, CN 109917192A, CN 102543361A also relates to an adjustable inductor, the function and function of the adjustable inductor in the above prior art are not to improve the problems of drain-source voltage overshoot and drain current overshoot of the silicon carbide MOSFET during switching, and those skilled in the art have no motivation or suggestion to apply the adjustable inductor in the driving circuit to improve the switching characteristics of the silicon carbide MOSFET based on the above prior art.

Disclosure of Invention

Aiming at the problems existing in the existing design method of the drive circuit, the invention provides the drive circuit for optimizing the switching characteristics of the silicon carbide MOSFET so as to solve the technical problems. The technical scheme is as follows:

the driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET comprises an input unit, an isolation unit, a driving unit, an inductance unit, a connecting unit and a protection unit, wherein a voltage signal and a pulse signal of the input unit are input to the driving unit after being isolated by the isolation unit and subjected to level conversion; the driving unit completes the switching of voltage signals by receiving pulse signals and applies positive and negative driving voltages to the silicon carbide MOSFET through the connecting unit; the inductance unit adopts soft magnetic ferrite with threads, the magnetic conductivity of the coil is changed by rotating the position of the soft magnetic ferrite in the coil, and then the inductance value of the coil is changed, and finally the adjustment of the total parasitic inductance value of the driving loop is realized. The switching characteristic of the silicon carbide MOSFET is improved, and overshoot of the turn-off drain-source voltage and overshoot of the turn-on drain current of the device are effectively inhibited.

The invention also discloses a design method of the drive circuit PCB for optimizing the switching characteristics of the silicon carbide MOSFET.

The invention also discloses a method for designing the drive circuit PCB for optimizing the switching characteristics of the silicon carbide MOSFET, which is applied to the design of the drive circuit PCB.

Advantageous effects

The invention can effectively reduce the drain-source voltage overshoot and the drain current overshoot of the silicon carbide MOSFET in the switching process, and compared with other driving circuit design methods, the driving circuit provided by the invention has the following advantages:

(1) the driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET has higher effectiveness. The driving circuit can effectively solve the problems of overshoot of the turn-off drain-source voltage and overshoot of the turn-on drain current caused by the transient process of the rapid switch of the silicon carbide MOSFET, and also solves the problems of switching loss of devices without causing the additional problems of high switching loss and the like.

(2) The driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET has stronger practicability. The drive circuit introduces the adjustable inductance on the basis of the traditional drive circuit, has no additional circuit, and has simple design and lower cost.

(3) The driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET has wider applicability. When the driving circuit provided by the invention is applied, the driving PCB is connected with the power circuit PCB through the SMA connector, the use is simple and convenient, and the driving circuit is suitable for different power circuit layouts. The driving circuit adopts the power supply module to realize positive and negative voltage driving voltage, can select power supply modules with different output voltages under the same package, and is suitable for power semiconductor devices with various models and different driving voltage standards.

The driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET has higher effectiveness, practicability and wider applicability. The driving circuit provided by the invention can improve the drain-source voltage overshoot and the drain current overshoot of the silicon carbide MOSFET in the switching process, gives consideration to the switching loss of the device, can be used for guiding the design of the driving circuit related to the silicon carbide MOSFET, and has important significance for improving the economy and the reliability of the silicon carbide MOSFET in application.

Drawings

FIG. 1 is a schematic diagram of a driving circuit according to the present invention;

FIG. 2 is a diagram of an adjustable inductor;

FIG. 3a is a schematic diagram of the front side of a PCB driving board of the driving circuit of the present invention;

FIG. 3b is a schematic diagram of the reverse side of the PCB driver board of the driving circuit of the present invention;

FIG. 4 is a gate-source voltage waveform of the device with or without the protection unit of the driving circuit of the present invention;

FIG. 5a is a graph comparing the turn-off drain-source voltage of the driving circuit of the present invention with that of a conventional circuit silicon carbide MOSFET;

FIG. 5b is a graph comparing the on-drain current of the SiC MOSFET of the present invention driver circuit with that of a conventional circuit.

Detailed Description

The driving circuit provided by the invention comprises an input unit, an isolation unit, a driving unit, an inductance unit, a connecting unit and a protection unit, and a driving schematic diagram is shown in figure 1. The voltage signal and the pulse signal of the input unit are input to the driving unit after being isolated by the isolation unit and subjected to level conversion. The driving unit completes the switching of voltage signals by receiving pulse signals and is connected with the inductance unit through the output resistor Rg, and the output end of the inductance unit is connected with the input end of the connecting unit so as to apply positive and negative driving voltage to the silicon carbide MOSFET in the power circuit.

The input unit comprises a 5V voltage input and a pulse input. The 5V voltage input adopts a constant voltage source power supply; the pulse signal is generated by a pulse signal generator, and the pulse time and the pulse interval can be manually input.

The output end of the input unit is connected with the input end of the isolation unit. The isolation unit comprises a power supply module, an optical fiber and an optical fiber receiver. On one hand, the power module can realize DC/DC voltage conversion, and convert the module input voltage into positive and negative switching voltages required by the silicon carbide MOSFET. The non-isolated circuit mainly comprises a BUCK voltage reduction circuit, a BOOST voltage boosting circuit and a BUCK-BOOST voltage boosting circuit. The isolated circuit mainly comprises a forward circuit, a flyback circuit, a half-bridge circuit, a full-bridge circuit and a push-pull circuit. Generally, a power module adopts a non-isolated circuit and optical coupling isolation combination mode. The optical coupler is a conversion device, and the principle is that through the conversion process from electricity to light and then to electricity, the front stage and the rear stage can be separated through the conversion, so that the protection effect is achieved. The optocoupler generally encapsulates the light emitting diode and the phototriode together, with the light emitting diode being the input and the phototriode being the output. The optical coupler has the advantages that signals are transmitted in a single direction, the input end and the output end are completely electrically isolated, output signals have no influence on the input end, the anti-interference capability is high, the work is stable, no contact is made, the service life is long, and the transmission efficiency is high. The power supply module can be equivalent to a voltage source end of the driving loop, and parasitic inductance of the driving loop can be calculated from an output end of the power supply module, so that parasitic inductance introduced by a lead wire connected with the driving board and a constant-voltage driving source does not need to be considered. The optical fiber module can realize signal isolation and effectively avoid signal noise interference. The pulse signal generator converts the electrical signal into an optical signal, and after the optical signal is transmitted through the optical fiber in the optical fiber module, the optical signal is converted into the electrical signal again at the optical fiber receiver, specifically, the electrical signal is represented as a high level and a low level output by the optical fiber receiver.

The output end of the isolation unit is connected with the input end of the driving unit. The driving unit comprises a driving chip and a driving resistor. The output end of the power supply module is connected with the voltage input end of the driving chip, the output end of the optical fiber receiver is connected with the control input end of the driving chip, and the driving chip is controlled to output positive driving voltage or negative driving voltage through the high and low levels output by the optical fiber receiver. The driving resistor in the driving circuit provided by the invention can select a small resistor (such as 3.3 ohm/0.5 watt), so that the high switching speed is ensured, and the switching loss problem is considered while overshoot of the voltage of the source electrode and the drain electrode of the device is inhibited.

One end of the inductance unit is connected with the output end of the driving unit, and the other end of the inductance unit is connected with the input end of the protection unit and the connecting unit. The inductance unit is composed of an adjustable inductance, and the adjustable inductance comprises four parts, namely a base, a framework, a coil and a soft magnetic ferrite with threads. The structure diagram of the adjustable inductor is shown in fig. 2, the base is used for fixing the adjustable inductor, the framework is located on the base, the coil is spirally wound on the surface of the framework, and the soft magnetic ferrite with threads is located in the framework. The inner surface of the framework is provided with threads, the depth of the soft magnetic ferrite in the framework can be changed by rotating the soft magnetic ferrite, and further the magnetic conductivity of the coil is changed, so that the inductance value of the coil is changed, and finally the adjustment of the total parasitic inductance of the driving circuit is realized. Adjust inductance value through the degree of depth of manual regulation magnetic core in the skeleton, compare in other adjustable inductance structures such as saturated inductor and switch inductor, possess the less characteristics of volume on the one hand, be favorable to reducing drive circuit PCB board size and walk line length, accord with drive circuit design requirement. On the other hand can realize the setting of required inductance value completely through manual regulation, and manual regulation is more simple and convenient than automatically regulated, need not set up extra circuit, and the cost is lower. The length, width and height of the adjustable inductor are 7mm x 12mm, the length of the magnetic core is 8mm, and the number of turns of the coil is 6.5T. The method comprises the steps of extracting the variable range of the adjustable inductor by using an impedance analyzer, respectively connecting the measuring terminals of the impedance analyzer with two ends of the adjustable inductor, and respectively measuring and recording the changing depth of the rotating soft magnetic ferrite, wherein the measuring method of the impedance analyzer is an automatic balance bridge method, and is the optimal selection scheme below the frequency of 110MHz when the measuring precision and the operation portability are considered. When the magnetic core is completely screwed out of the framework, the inductance value of the adjustable inductor is 30 nH; when the magnetic core is completely screwed into the framework, the inductance value of the adjustable inductor is 200 nH; the change of the inductance value of the adjustable inductor is approximately in direct proportion to the screwing depth of the magnetic core into the framework. By rotating the soft magnetic ferrite, the variable range of the inductance value of the adjustable inductor from 50nH to 200nH can be realized, and the requirement of a driving circuit is met.

The PCB of the driving circuit is connected with the PCB of the power circuit through the SMA connector, the SMA connector is of a coaxial structure, current paths are opposite, the parasitic inductance of the circuit is reduced due to mutual inductance of wires, and a coupled inductor series calculation formula is shown in a formula (1).

L′＝L₁+L₂-2M (1)

Wherein L is₁And L₂The self-inductance values of the two inductors are respectively, and M is a mutual inductance value.

Meanwhile, the SMA connector can be applied to different power circuit PCB boards with corresponding SMA interfaces. The calculation formula of the PCB routing inductance is shown as formula (2).

Wherein l is the trace length and W is the trace width.

The calculation formula of the PCB via hole inductance is shown as formula (3).

Wherein h is the via depth and d is the via diameter.

It can be seen that in the process of PCB wiring, it should be ensured that the PCB board wiring is shorter and thicker as much as possible and via holes are reduced, and parasitic inductance introduced by the wiring is controlled.

The PCB of the driving circuit adopts a double-sided design, has small size of only 50mm x 40mm x 2mm, ensures compact layout, enables components to be close to each other as far as possible, reduces the routing distance and increases the routing width properly. The schematic diagram of the object is shown in figures 3a and 3 b. The front surface of the PCB board of the driving circuit comprises an optical fiber receiver, a driving chip, a driving resistor, a wiring terminal and an SMA connector. The power module with larger volume and the adjustable inductor are arranged on the reverse side of the PCB, so that the design size is reduced to the maximum extent. In the isolation unit, the power module and the optical fiber receiver in the optical fiber module are connected with the input end of the driving chip, the driving resistor is connected with the output end of the driving chip, the three are tightly connected around the driving chip, the wiring distance is reduced, the input and output wiring of the driving chip is parallel, and the mutual inductance is increased to reduce the total parasitic inductance. The driving resistor Rg, the adjustable inductor and the SMA connector are closely connected and adopt a copper-clad design, so that the wiring distance is short, and the parasitic inductance is small.

Because the drive circuit divide into the multistage and be not convenient for connect impedance analyzer's measurement terminal, divide drive circuit current path into a plurality of path sections, be power module to drive core segment (length 3mm, wide 2mm) respectively, drive chip to drive resistance section (1.5mm, 1mm), drive resistance to adjustable inductance section (length 2.5mm, wide 2mm), adjustable inductance to device grid section (length 2mm, wide 2mm), device common source convergent point to drive chip segment (length 5mm, wide 2mm), drive chip to power module section (length 3mm, wide 2 mm). The PCB design drawing of the driving circuit is led into ANSYS Q3D software, Q3D is a quasi-static 2D/3D electromagnetic field simulation tool, a circuit theory is adopted, a circuit equation set is established for voltage and current to solve, an RLC circuit equivalent model of each path section of the driving circuit is built, self parasitic inductance values and mutual parasitic inductance values of the driving circuit are extracted, and the inductance values of each section of the driving current path are added to obtain the original parasitic inductance value of the driving circuit. The total parasitic inductance of the PCB of the driving circuit is 11nH, which is reduced by at least 60% compared with the common design.

The protection unit is composed of a schottky diode. The anode of the Schottky diode is connected with the input end of the connecting unit, and the cathode of the Schottky diode is connected with the positive voltage output end of the power supply module. The schottky diode is a low-power consumption and ultra-high speed semiconductor device, and has the most remarkable characteristics that the reverse recovery time is extremely short and the forward conduction voltage drop is only about 0.4V. When the grid voltage of the device exceeds the positive voltage output of the power supply module, the Schottky diode is conducted in the forward direction rapidly to form a current path, the current of the driving circuit flows back to the power supply module through the protection unit path, the phenomenon that the gate-source capacitance of the device is charged continuously is avoided, and therefore overshoot of the grid-source voltage of the silicon carbide MOSFET is restrained. The waveform of the gate-source voltage of the device with or without the protection unit is shown in fig. 4, and when the protection unit is not added, the gate-source voltage of the silicon carbide MOSFET overshoots over 25V safe working voltage, so that the normal operation of the device is potentially damaged. And after the protection unit is added, the grid-source voltage of the device is controlled below the safe working voltage of 25V. By adding the protection unit, overshoot of the grid-source voltage of the silicon carbide MOSFET is effectively inhibited, and reliable operation of the silicon carbide MOSFET is guaranteed.

According to the driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET, on the basis of the design of reducing the original parasitic inductance, the soft magnetic ferrite with the threads is adopted, the magnetic conductivity of the coil is changed by rotating the position of the soft magnetic ferrite in the coil, the inductance value of the coil is further changed, and finally the large-range adjustment of the total parasitic inductance value of the driving circuit is realized. By adjusting the total parasitic inductance of the driving loop, the optimization of the switching characteristic of the silicon carbide MOSFET can be realized. Fig. 5 shows a voltage-current pair of a driving circuit (the total parasitic inductance of the driving circuit can be adjusted in a wide range, for example, 105 nH) and a conventional driving circuit (the total parasitic inductance of the driving circuit is fixed to 30nH) in a double-pulse experiment. The overshoot of the turn-off drain-source voltage of the traditional driving circuit is 160V, while the overshoot of the turn-off drain-source voltage of the driving circuit provided by the invention is 90V, which is reduced by 43%. The overshoot of the drain current of the conventional driving circuit is 3A, while the overshoot of the drain current of the driving circuit proposed by the present invention is 2A, which is reduced by 33%. Compared with the traditional drive circuit, the drive circuit provided by the invention has lower overshoot of the turn-off drain-source voltage and the turn-on drain current.

The driving circuit adopts the power supply module, thereby realizing electrical isolation and avoiding parasitic inductance introduced by a connecting wire of the constant voltage driving source and the driving PCB. The PCB design of the driving circuit ensures that the wiring is shorter and thicker and the through holes are reduced as far as possible, the size of the PCB of the driving circuit is 50mm x 40mm x 2mm, the total wiring length of the PCB of the driving circuit is about 17mm, the width of the PCB of the driving circuit is about 2mm, and the wiring of the opposite current path is close to the mutual inductance effect of the opposite driving current path, so that the mutual inductance effect of the opposite driving current path is fully utilized. The driving circuit PCB and the power circuit PCB are connected by an SMA coaxial connector, and due to the mutual inductance effect of the coaxial structure, parasitic inductance introduced by the SMA coaxial connector is approximately ignored. The total parasitic inductance of the PCB board of the finally extracted driving loop is 11nH, which is reduced by at least 60% compared with the common design.

The inductance unit adjusts the total parasitic inductance of the driving loop; the inductance unit adopts soft magnetic ferrite with threads, the magnetic conductivity of the coil is changed by rotating the position of the soft magnetic ferrite in the coil, and then the inductance value of the coil is changed, and finally the adjustment of the total parasitic inductance value of the driving loop is realized. The switching characteristic of the silicon carbide MOSFET can be improved, and overshoot of the turn-off drain-source voltage and overshoot of the turn-on drain current of the device can be effectively inhibited. In addition, the protection unit can effectively inhibit the gate-source voltage overshoot of the silicon carbide MOSFET caused by the gate inductance change of the driving loop, and the gate-source protection function of the device is realized.

The invention provides a driving circuit for optimizing the switching characteristics of a silicon carbide MOSFET (metal oxide semiconductor field effect transistor), which can effectively inhibit drain-source voltage overshoot and drain current overshoot of a device in the switching process. In addition, the method has the advantages of considering switching loss, introducing no high loss and other accessory problems to the circuit and the like.

The driving circuit for optimizing the switching characteristic of the silicon carbide MOSFET has higher practicability. After the drive circuit is optimally designed through power isolation, routing layout, SMA connection and the like, the large-range adjustment of the total parasitic inductance of the drive circuit is realized through the simple adjustable inductance, and further, the optimization of the switch characteristic of the silicon carbide MOSFET is realized. The driving circuit is applied, a complex monitoring and feedback circuit is not required to be designed, the operation is simple, more electronic components are not required, and the cost is lower.

In addition, the driving circuit for optimizing the switching characteristics of the silicon carbide MOSFET has wider applicability. When the driving circuit provided by the invention is applied, the driving circuit PCB is connected with the power circuit PCB through the SMA connector, so that the driving circuit PCB is simple and convenient to use and is suitable for different power circuit layouts. In addition, the driving circuit adopts the power supply module to realize positive and negative voltage driving voltage, can select power supply modules with different output voltages under the same package, and is suitable for power semiconductor devices with various models and different driving voltage standards.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.