CN113315353B - SiC MOSFET parallel driving circuit with gate-source impedance dynamically adjusted and active current sharing - Google Patents

SiC MOSFET parallel driving circuit with gate-source impedance dynamically adjusted and active current sharing Download PDF

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CN113315353B
CN113315353B CN202110701356.8A CN202110701356A CN113315353B CN 113315353 B CN113315353 B CN 113315353B CN 202110701356 A CN202110701356 A CN 202110701356A CN 113315353 B CN113315353 B CN 113315353B
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sic mosfet
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resistance
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CN113315353A (en
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张雷
秦岭
任磊
桑顺
黄杰杰
姚子豪
吴典
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Nantong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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Abstract

The invention discloses a SiCMOS parallel driving circuit for dynamically adjusting gate-source impedance and actively equalizing current, which indirectly measures current by measuring voltage drop of a shunt; the differential amplification isolation circuit is adopted to realize the isolation and differential amplification of the measurement signal; performing current difference processing and signal feedback by using a current difference feedback circuit; an NPN triode, a resistor and a capacitor are adopted to form a gate-source low-impedance circuit, and the dynamic adjustment of the impedance of the driving loop is realized by combining a feedback signal. The invention can effectively inhibit the phenomenon of parallel non-uniform current of the SiCMOS MOSFET caused by the reasons of inconsistent device parameters, larger stray inductance and the like in the circuit, achieves the aim of active current sharing, and has the characteristics of good regulation performance, strong real-time performance, low cost and the like.

Description

SiC MOSFET parallel driving circuit with gate-source impedance dynamically adjusted and active current sharing
Technical Field
The invention relates to a SiC MOSFET parallel driving circuit.
Background
With the development of power electronics technology, in recent years, new materials are beginning to be applied to power devices, of which SiC MOSFETs are typically used as representative. Compared with the traditional Si power device, the SiC MOSFET has the advantages of high switching frequency, low switching loss, low on-state resistance, strong pressure resistance, strong temperature resistance and the like, and can adapt to application occasions with high voltage level and high power density.
Although SiC MOSFETs are widely used for their excellent performance, single SiC MOSFETs have limited current capability compared to IGBT power devices due to limitations in production processes and manufacturing costs. In actual industrial production, a mode of connecting a plurality of SiC MOSFET single tubes in parallel is often needed to achieve the purpose of improving the current grade. Due to device parameter difference, power circuit parasitic parameter difference, driving circuit parameter difference and the like, the problem of unbalanced current of each branch circuit can occur when SiC MOSFET is connected in parallel, the problems include unbalanced dynamic current and unbalanced static current after conduction caused in the switching process, damage can be caused to the SiC MOSFET device, and the damage is mainly reflected in loss difference, current stress difference and the like, so that a single device is damaged due to the fact that the single device is in a state of loss and overlarge stress for a long time, and even the safe operation of the whole system is influenced.
The traditional method adopts measures such as coupling inductance and the like for current sharing, although the method is simple and has good effect, the voltage overshoot, the sacrifice opening current rising speed and the like of the system are increased, meanwhile, the coupling inductance increases the system volume, reduces the power density and inhibits the exertion of the advantages of the SiC MOSFET. Therefore, a new parallel current sharing method is needed to be provided, so that the current imbalance phenomenon of the SiC MOSFET parallel circuit is suppressed, the current stress and the loss of the SiC MOSFET power device are consistent, the durability of the SiC MOSFET is improved, and the safety and the stability of the circuit are ensured.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the prior art, the SiC MOSFET parallel driving circuit with the gate-source impedance dynamically adjusted and actively equalized current is provided, so that the phenomenon of unbalanced current of the SiC MOSFET parallel circuit is inhibited, and the current stress and the loss of a SiC MOSFET power device are consistent.
The technical scheme is as follows: a SiC MOSFET parallel drive circuit with gate-source impedance dynamically adjusted and active current sharing comprises a SiC MOSFET M1、SiC MOSFETM2The circuit comprises a current acquisition circuit, a differential amplification isolation circuit, a current difference value feedback circuit, a gate source low impedance circuit and a SiC MOSFET basic driving circuit;
the current collecting circuit comprises a current divider R100And R101Respectively for series connection in SiC MOSFET M1Branch and SiC MOSFET M2A branch circuit;
the differential amplification isolation circuit and the current difference valueFeedback circuit connected to measure potential difference across the shunt to indirectly measure the SiC MOSFET M1Branch and SiC MOSFET M2When the current of the branch circuit is unbalanced, the current of the SiC MOSFET parallel circuit outputs a control signal to the gate-source low-impedance circuit;
the gate-source low impedance circuit comprises a SiC MOSFET M1Gate-source low-impedance auxiliary circuit of branch circuit and SiC MOSFET M2The gate-source low-impedance auxiliary circuits of the branches are SiC MOSFET M1And SiC MOSFET M2The grid electrode of the silicon controlled rectifier provides a low impedance loop, the change rate of the grid source voltage and the steady state value of the grid source voltage are changed under the action of the control signal, and the switching speed of the SiC MOSFET is dynamically adjusted, so that the phenomenon of non-uniform current is suppressed.
Furthermore, the differential amplification isolation circuit comprises an optical coupling isolation amplifier U1And U2Operational amplifier U3And U4Resistance R5～R12；
Optical coupling isolation amplifier U1Is connected with the shunt R100Current input terminal and negative input terminal of the current divider R100A current output terminal of (a); optical coupling isolation amplifier U1Is connected with the resistor R5One end of (3), the negative output end is connected with a resistor R7One end of (a); resistance R5The other end of the first switch is connected with an operational amplifier U3Positive input terminal and resistor R6One terminal of (1), resistance R6The other end of the first switch is connected with a reference ground; resistance R7The other end of the first switch is connected with an operational amplifier U3Negative input terminal and resistor R8One end of (a); resistance R8The other end of the first switch is connected with an operational amplifier U3An output terminal of (a);
optical coupling isolation amplifier U2Is connected with the shunt R101Current input terminal and negative input terminal of the current divider R101A current output terminal of (a); optical coupling isolation amplifier U2Is connected with the resistor R9One end of (3), the negative output end is connected with a resistor R11One end of (a); resistance R9The other end of the first switch is connected with an operational amplifier U4Positive input terminal and resistor R10ToTerminal, resistance R10The other end of the first switch is connected with a reference ground; resistance R11The other end of the first switch is connected with an operational amplifier U4Negative input terminal and resistor R12One end of (a); resistance R12The other end of the first switch is connected with an operational amplifier U4To the output terminal of (a).
Further, the current difference feedback circuit comprises an operational amplifier U5And U6Resistance R13～R20；
Resistance R15One end of is connected with an operational amplifier U3Output terminal and resistor R17One end of (a); resistance R15The other end of the first switch is connected with an operational amplifier U5Positive input terminal and resistor R16One terminal of (1), resistance R16The other end of the first switch is connected with a reference ground; resistance R13One end of is connected with an operational amplifier U4Output terminal and resistor R19One terminal of (1), resistance R13The other end of the first switch is connected with an operational amplifier U5Negative input terminal and resistor R14One terminal of (1), resistance R14The other end of the first switch is connected with an operational amplifier U5An output terminal of (a); resistance R19The other end of the first switch is connected with an operational amplifier U6Positive input terminal and resistor R20One terminal of (1), resistance R20The other end of the first switch is connected with a reference ground; resistance R17The other end of the first switch is connected with an operational amplifier U6Negative input terminal and resistor R18One terminal of (1), resistance R18The other end of the first switch is connected with an operational amplifier U6To the output terminal of (a).
Further, the SiC MOSFET basic driving circuit comprises a power supply voltage source V1Power supply voltage source V2Switch tube S1Switch tube S2Turn on the driving resistor RonTurn off the driving resistor RoffA Schottky diode D; supply voltage source V1Anode and switch tube S1Is connected to a supply voltage source V1And SiC MOSFET M1And SiC MOSFET M2Is connected with the source electrode of the switching tube S1Source and turn-on driving resistor RonAnd turn-off driving resistor RoffIs connected to turn on the driving resistor RonAnd the other end of the SiC MOSFET M1And SiC MOSFET M2Is connected with the anode of the Schottky diode D, the cathode of the Schottky diode D is connected with the turn-off driving resistor RoffThe other ends of the two are connected; supply voltage source V2Negative electrode of (2) and switching tube S2Is connected to a supply voltage source V2Positive electrode and SiC MOSFET M1And SiC MOSFET M2And a supply voltage source V1The negative electrodes are connected; the switch tube S2Drain electrode of and switch tube S1Are connected.
Further, said M1The gate-source low impedance auxiliary circuit of the branch circuit comprises a capacitor C1Resistance R1Resistance R3NPN triode Q1(ii) a The M is2The gate-source low impedance auxiliary circuit of the branch circuit comprises a capacitor C2Resistance R2Resistance R4NPN triode Q2；
Triode Q1Emitter-connected SiC MOSFET M1Source electrode of (2), triode Q1Base electrode connecting resistance R3One terminal of (1), resistance R3The other end of the first switch is connected with an operational amplifier U5An output terminal of (a); capacitor C1One end of which is connected with a triode Q1The other end of the collector is connected with a SiC MOSFET M1A gate electrode of (1); resistance R1Connected in parallel to a capacitor C1Both ends of (a);
triode Q2Emitter-connected SiC MOSFET M2Source electrode of (2), triode Q2Base electrode connecting resistance R4One terminal of (1), resistance R4The other end of the first switch is connected with an operational amplifier U6An output terminal of (a); capacitor C2One end of which is connected with a triode Q2The other end of the collector is connected with a SiC MOSFET M2A gate electrode of (1); resistance R2Connected in parallel to a capacitor C2At both ends of the same.
Has the advantages that: 1. because the internal parameters of the SiC MOSFET can not be completely consistent, the switching speeds of the SiC MOSFET are inconsistent, and the traditional gate-source capacitance compensation method, the coupling inductance method and the like have the defects of loss increase, voltage overshoot increase, system volume increase, low universality and the like. According to the invention, the feedback signal is generated to the triode of the gate-source low-impedance circuit through the current acquisition circuit, the differential amplification isolation circuit and the current difference value feedback circuit, so that a low-impedance loop is provided, thus the switching speed of the SiC MOSFET is dynamically regulated in the switching process, the universality is stronger, and the loss increase problem is avoided.
2. According to the invention, through designing the gate-source low-impedance circuit, the on-state non-uniform current and the off-state non-uniform current of the SiC MOSFET are inhibited, the current-equalizing effect is obvious, compared with the traditional gate-source capacitance compensation, the method can reduce the gate-source equivalent capacitance as much as possible, and the switching speed of the SiC MOSFET is ensured.
3. The invention adopts the NPN triode, the capacitor and the resistor to provide a low impedance loop, inhibits the parallel non-uniform current, generates a signal through a current difference value to control the state of the triode, provides a low impedance loop for the grid current, controls the charging and discharging speed of the grid source of the SiC MOSFET, and has the advantages of fast response, strong feedback, good real-time performance and the like.
Drawings
FIG. 1 is a schematic diagram of the circuit of the present invention;
FIG. 2 is a schematic diagram of a gate-source low impedance circuit;
FIG. 3 is a schematic diagram of a current collection circuit and a differential amplification isolation circuit;
FIG. 4 is a schematic diagram of a current difference feedback circuit;
FIG. 5(a) (b) shows M on and off respectively1The current flow of the gate-source low-impedance auxiliary circuit of the branch circuit is shown in a schematic diagram;
FIG. 6(a) is the ON stage M1A circuit working schematic diagram when the switching-on speed is higher;
FIG. 6(b) is the ON stage M2A circuit working schematic diagram when the switching-on speed is higher;
FIG. 7(a) shows the turn-off phase M1A circuit working schematic diagram when the turn-off speed is higher;
FIG. 7(b) shows the turn-off phase M2A circuit working schematic diagram when the turn-off speed is higher;
FIGS. 8(a) and (b) are M in the absence of current sharing1And M2Drain current switching waveform of (1);
FIGS. 9(a) (b) are diagrams of M in the case of suppression of current imbalance using the present invention1And M2The switching waveform of the drain current in (1).
Detailed Description
The invention is further explained below with reference to the drawings.
As shown in FIG. 1, a SiC MOSFET parallel driving circuit with gate-source impedance dynamically adjusted active current sharing comprises a SiC MOSFET M1、SiC MOSFET M2The circuit comprises a current acquisition circuit, a differential amplification isolation circuit, a current difference value feedback circuit, a gate source low impedance circuit and a SiC MOSFET basic driving circuit. The current collecting circuit comprises a current divider R100And R101Respectively for series connection in SiC MOSFET M1Branch and SiC MOSFET M2And (4) branching. The differential amplification isolation circuit is connected with the current difference value feedback circuit and is used for measuring the potential difference on the current divider to indirectly measure the SiC MOSFET M1Branch and SiC MOSFET M2And when the current of the branch circuit is unbalanced, the current of the SiC MOSFET parallel circuit outputs a control signal to the gate-source low-impedance circuit. The gate-source low impedance circuit comprises a SiC MOSFET M1Gate-source low-impedance auxiliary circuit of branch circuit and SiC MOSFET M2The gate-source low-impedance auxiliary circuits of the branches are SiC MOSFET M1And SiC MOSFET M2The grid electrode of the silicon controlled rectifier provides a low-impedance loop, the change rate of the grid source voltage and the steady-state value of the grid source voltage are changed under the action of the control signal, and the switching speed of the SiC MOSFET is dynamically adjusted, so that the phenomenon of non-uniform current is suppressed.
Wherein, the differential amplification isolation circuit comprises an optical coupling isolation amplifier U1And U2Operational amplifier U3And U4Resistance R5～R12. Optical coupling isolation amplifier U1Is connected with the shunt R100Current input terminal and negative input terminal of the current divider R100A current output terminal of (a); optical coupling isolation amplifier U1Is connected with the resistor R5One end of (3), the negative output end is connected with a resistor R7One end of (a); resistance R5The other end of the first switch is connected with an operational amplifier U3Positive input terminal and resistorR6One terminal of (1), resistance R6The other end of the first switch is connected with a reference ground; resistance R7The other end of the first switch is connected with an operational amplifier U3Negative input terminal and resistor R8One end of (a); resistance R8The other end of the first switch is connected with an operational amplifier U3To the output terminal of (a).
Optical coupling isolation amplifier U2Is connected with the shunt R101Current input terminal and negative input terminal of the current divider R101A current output terminal of (a); optical coupling isolation amplifier U2Is connected with the resistor R9One end of (3), the negative output end is connected with a resistor R11One end of (a); resistance R9The other end of the first switch is connected with an operational amplifier U4Positive input terminal and resistor R10One terminal of (1), resistance R10The other end of the first switch is connected with a reference ground; resistance R11The other end of the first switch is connected with an operational amplifier U4Negative input terminal and resistor R12One end of (a); resistance R12The other end of the first switch is connected with an operational amplifier U4To the output terminal of (a).
The current difference feedback circuit comprises an operational amplifier U5And U6Resistance R13～R20. Resistance R15One end of is connected with an operational amplifier U3Output terminal and resistor R17One end of (a); resistance R15The other end of the first switch is connected with an operational amplifier U5Positive input terminal and resistor R16One terminal of (1), resistance R16The other end of the first switch is connected with a reference ground; resistance R13One end of is connected with an operational amplifier U4Output terminal and resistor R19One terminal of (1), resistance R13The other end of the first switch is connected with an operational amplifier U5Negative input terminal and resistor R14One terminal of (1), resistance R14The other end of the first switch is connected with an operational amplifier U5An output terminal of (a); resistance R19The other end of the first switch is connected with an operational amplifier U6Positive input terminal and resistor R20One terminal of (1), resistance R20The other end of the first switch is connected with a reference ground; resistance R17The other end of the first switch is connected with an operational amplifier U6Negative input terminal and resistor R18One terminal of (1), resistance R18The other end of the first switch is connected with an operational amplifier U6To the output terminal of (a).
The SiC MOSFET basic drive circuit comprises a supply voltage source V1Power supply voltage source V2Switch tube S1Switch tube S2Turn on the driving resistor RonTurn off the driving resistor RoffAnd a schottky diode D. Supply voltage source V1Anode and switch tube S1Is connected to a supply voltage source V1And SiC MOSFET M1And SiC MOSFET M2Is connected with the source electrode of the switching tube S1Source and turn-on driving resistor RonAnd turn-off driving resistor RoffIs connected to turn on the driving resistor RonAnd the other end of the SiC MOSFET M1And SiC MOSFET M2Is connected with the anode of the Schottky diode D, the cathode of the Schottky diode D is connected with the turn-off driving resistor RoffThe other ends of the two are connected; supply voltage source V2Negative electrode of (2) and switching tube S2Is connected to a supply voltage source V2Positive electrode and SiC MOSFET M1And SiC MOSFET M2And a supply voltage source V1The negative electrodes are connected; the switch tube S2Drain electrode of and switch tube S1Are connected.
M1The gate-source low impedance auxiliary circuit of the branch circuit comprises a capacitor C1Resistance R1Resistance R3NPN triode Q1；M2The gate-source low impedance auxiliary circuit of the branch circuit comprises a capacitor C2Resistance R2Resistance R4NPN triode Q2. Triode Q1Emitter-connected SiC MOSFET M1Source electrode of (2), triode Q1Base electrode connecting resistance R3One terminal of (1), resistance R3The other end of the first switch is connected with an operational amplifier U5An output terminal of (a); capacitor C1One end of which is connected with a triode Q1The other end of the collector is connected with a SiC MOSFET M1A gate electrode of (1); resistance R1Connected in parallel to a capacitor C1At both ends of the same. Triode Q2Emitter-connected SiC MOSFET M2Source electrode of (2), triode Q2Base electrode connecting resistance R4One terminal of (1), resistance R4The other end of the first switch is connected with an operational amplifier U6An output terminal of (a); capacitor C2One end of which is connected with a triode Q2The other end of the collector is connected with a SiC MOSFET M2A gate electrode of (1); resistance R2Connected in parallel to a capacitor C2At both ends of the same.
To analyze the circuit operating principle, the following definitions are made: the turn-on voltage of the SiC MOSFET is Vgs(on)Off voltage of Vgs(off)The on drive resistance is RonThe turn-off drive resistance is Roff，M1Has a gate current of ig1，M2Has a gate current of ig2，M1The gate-source capacitance of Cgs1，M2The gate-source capacitance of Cgs2，M1The gate-drain capacitance of Cgd1，M2The gate-drain capacitance of Cgd2，Q1Has a base voltage of Vbe1，Q2Has a base voltage of Vbe2，Q1Collector current of ic1，Q2Collector current of ic2。
As shown in fig. 2, the gate-source low-impedance circuit is used, when the current of the parallel circuit of the SiC MOSFET is unbalanced, the current collection circuit and the differential amplification isolation circuit generate control signals, so as to adjust the gate-source impedance of the SiC MOSFET in real time and control the switching speed of the SiC MOSFET, thereby realizing dynamic current sharing.
Fig. 3 is a schematic diagram of the current collecting circuit and the differential amplifying and isolating circuit of the SiC MOSFET parallel circuit. The circuit measures the potential difference across the shunt to indirectly measure the branch current id1And id2. Meanwhile, a high-voltage high-speed optical coupler isolator is adopted to realize the isolation of the measurement signal, and the interference of the measurement signal is suppressed through a differential signal.
Fig. 4 is a schematic diagram of the current difference feedback circuit. The circuit forms a difference circuit through an operational amplifier, and realizes the processing of the current difference value of the SiC MOSFET parallel circuit and the feedback of a control signal.
FIG. 5(a) and FIG. 5(b) are M at the time of ON and OFF, respectively1The current of the branch gate-source low impedance auxiliary circuit flows to the schematic diagram.
(1) During the turn-on of the SiC MOSFET parallel circuit, assume M1Has a turn-on speed of more than M2The turn-on speed of (c).
If the current difference of the parallel branches is extremely small and can be ignored, Q1And Q2All cut off, assay M1The gate-source low impedance auxiliary circuit of the branch can be obtained as follows:
Figure BDA0003130084410000061
Figure BDA0003130084410000062
because the drain-source voltage is kept unchanged in the rising process of the drain current in the turn-on stage of the SiC MOSFET, the leakage-source voltage can be obtained
Figure BDA0003130084410000063
And Cgs1>>Cgd1So that Cgd1The miller current in (1) is negligible and can be found as follows:
Figure BDA0003130084410000064
the following equations (1) and (3) show that:
Figure BDA0003130084410000071
similarly, analyze M2The gate-source low-impedance auxiliary circuit of the branch can obtain:
Figure BDA0003130084410000072
at this time M1And M2The driving voltage is not adjusted, and the expressions are consistent.
If the parallel branches have current difference,M1has a drain current greater than M2But not so much, Q1Start to conduct, Q2Cut-off, analysis M as shown in FIG. 5(a)1The gate-source low impedance auxiliary circuit of the branch circuit obtains the following formula:
Figure BDA0003130084410000073
wherein, the triode collector current
Figure BDA0003130084410000074
In the same way, Cgd1The miller current in (1) can be ignored, and can obtain:
Figure BDA0003130084410000075
the following equations (1) and (7) show that:
Figure BDA0003130084410000076
at this time M2The voltage expression on the gate-source capacitance is still shown as (5). M1The gate-source voltage decreases and the drain current decreases. M2The grid source voltage and the drain current of the transistor are constant, and M is connected in parallel1And M2The drain current in (1) tends to be balanced.
③ when in parallel branch, M1Has a drain current greater than M2Drain current of (2) and uneven flow rate is severe, Q1Saturated, Q2Remaining at cut-off, analysis M1Low impedance auxiliary circuit of gate source of branch circuit, at this time Q1Neglecting the on-state equivalent impedance of (A), the following formula is obtained:
Figure BDA0003130084410000077
Figure BDA0003130084410000078
in the same way, Cgd1The miller current in (1) can be ignored, and can obtain:
Figure BDA0003130084410000079
from (1), (10) and (11):
Figure BDA00031300844100000710
at this time M2The voltage expression on the gate-source capacitance is still shown as (5). M1The gate-source voltage decreases and the drain current decreases. M2The grid source voltage and the drain current of the transistor are constant, and M is connected in parallel1And M2The drain current in (1) tends to be balanced.
When M is2Has a turn-on speed of more than M1Of turn-on speed, i.e. M2Has a drain current greater than M1The drain current in (2) is the same as the above analysis.
(2) During the turn-off of the SiC MOSFET parallel circuit, assume M1Turn-off speed of less than M2The turn-off speed of.
If the current difference of the parallel branches is extremely small and can be ignored, Q1And Q2All cut off, assay M1The gate-source low impedance auxiliary circuit of the branch can be obtained as follows:
Figure BDA0003130084410000081
Figure BDA0003130084410000082
because the drain-source voltage is reduced in the process of the drain current reduction in the turn-off stage of the SiC MOSFETRemain unchanged and can obtain
Figure BDA0003130084410000083
And Cgs1>>Cgd1So that Cgd1The miller current in (1) is negligible and can be found as follows:
Figure BDA0003130084410000084
the following equations (13) and (15) show that:
Figure BDA0003130084410000085
similarly, analyze M2The gate-source low-impedance auxiliary circuit of the branch can obtain:
Figure BDA0003130084410000086
at this time M1And M2The driving voltage is not adjusted, and the expressions are consistent.
② if there is current difference in the parallel branch, M1Has a drain current greater than M2But not so much, Q1Start to conduct, Q2Cut-off, analysis M as shown in FIG. 5(b)1The gate-source low impedance auxiliary circuit of the branch circuit obtains the following formula:
Figure BDA0003130084410000087
wherein, the triode collector current
Figure BDA0003130084410000088
In the same way, Cgd1Negligible, we can get:
Figure BDA0003130084410000089
the following equations (13) and (19) show that:
Figure BDA00031300844100000810
at this time M2The voltage expression on the gate-source capacitance is still shown as (17). M1The gate-source voltage decreases and the drain current decreases. M2The grid source voltage and the drain current of the transistor are constant, and M is connected in parallel1And M2The drain current in (1) tends to be balanced.
③ when in parallel branch, M1Has a drain current greater than M2Drain current of (2) and uneven flow rate is severe, Q1Saturated, Q2Remaining at cut-off, analysis M1Low impedance auxiliary circuit of gate source of branch circuit, at this time Q1Neglecting the on-state equivalent impedance of (A), the following formula is obtained:
Figure BDA0003130084410000091
Figure BDA0003130084410000092
in the same way, Cgd1Negligible, we can get:
Figure BDA0003130084410000093
from (13), (22) and (23):
Figure BDA0003130084410000094
at this time M2The voltage expression on the gate-source capacitance is still shown as (17). M1The gate-source voltage of (1) is reduced and the drain current thereof is reduced。M2The grid source voltage and the drain current of the transistor are constant, and M is connected in parallel1And M2The drain current in (1) tends to be balanced.
When M is2Turn-off speed of less than M1Of turn-on speed, i.e. M2Has a drain current greater than M1The drain current in (2) is the same as the above analysis.
From equations (8) (20) we can derive: the grid-source low-impedance circuit provides a low-impedance loop for the grid-source electrode, the change rate of grid-source voltage and the steady-state value of the grid-source voltage can be changed, the charging and discharging speed of a grid-source capacitor is adjusted by controlling the grid-source voltage, the speed of a switching tube is balanced, and the phenomenon of non-uniform current is restrained. The formulas (4) and (12) are derived from the limit conditions of the cut-off and saturation of the triode of the grid-source low-impedance circuit in the switching-on process; equations (16) and (24) are derived for the limit conditions for triode cut-off and saturation of the gate-source low impedance circuit during turn-off.
The invention mainly aims at the uneven current suppression during the switching of the SiC MOSFET, and in order to better explain the working principle of the driving circuit, M is assumed1Switching speed ratio M2The switching speed of (2) is fast. The following forward current difference is id1-id2The negative current difference is id2-id1。
The opening process:
the first state: m1And M2At the beginning of the switch-on, M1And M2The difference of the drain current is very small and can be ignored, and the triode Q1And Q2Off, the gate-source low impedance circuit does not function.
And a second state: m1And M2Continue to turn on due to M1And M2There is a disparity in the switching speed, M1And M2The branch circuit has a forward current difference value, and the current acquisition circuit, the differential amplification isolation circuit and the current difference value feedback circuit can generate control signals with corresponding strength according to the magnitude of the current difference value. As shown in FIG. 6(a), M1Drain current id1To M2Drain current id2Rise fast and there is a forward current difference, Q1From the off-state to the amplifying state (even ifWill saturate), Q2Still off. The gate-source low impedance circuit provides a low impedance path for the gate current through resistor R1Part of the gate current is discharged, and the gate current simultaneously gives the capacitor C1And junction capacitance Cgs1Charging to reduce junction capacitance Cgs1Charging current of, decrease M1The forward current difference is reduced.
And a third state: due to the access of the gate-source impedance dynamic regulation circuit, M is caused2Drain current id2To M1Drain current id1Rising quickly, a negative current difference is created. As shown in FIG. 6(b), Q is now present1Cutoff, Q2Changing from the off state to the amplifying state (even saturating), and lowering M2The turn-on speed of (c).
And a fourth state: at Q1(or Q)2) After cut-off, the capacitance C1(or C)2) Through a resistance R1(or R)2) Discharging, and preparing for detecting the existence of the current difference again and connecting the grid source low-impedance circuit. And repeatedly adjusting the charging speed of the junction capacitor of the parallel SiC MOSFET in real time to enable the parallel branches to be uniform in current.
And (3) a turn-off process:
the first state: m1And M2Start of shutdown, M1And M2Has very small difference of drain current, and the triode Q1、Q2Off, the gate-source low impedance circuit does not function.
And a second state: when M is1And M2Continue to turn off due to M1And M2There is a disparity in the switching speed, M1And M2And a negative current difference value appears in the branch, and the current acquisition circuit, the differential amplification isolation circuit and the current difference value feedback circuit can generate control signals with corresponding strength according to the magnitude of the current difference value. As shown in FIG. 7(a), M1Drain current id1To M2Drain current id2Fast fall and negative current difference, Q2From off-state to amplified state (and even saturated), Q1Still off. The gate-source low impedance circuit provides a low impedance path for gate currentResistance R2Accelerated junction capacitance Cgs2Speed of discharge, junction capacitance Cgs2Simultaneous discharge to grid supply and capacitor C2Accelerate M2The turn-off speed of (2) reduces the negative current difference.
And a third state: due to the access of the gate-source low impedance circuit, M is caused2Drain current id2To M1Drain current id1The drop is fast, resulting in a forward current difference. As shown in FIG. 7(b), Q is now present2Cutoff, Q1Change from the cut-off state to the amplification state (even saturation), and accelerate M1The turn-off speed of.
And a fourth state: at Q1(or Q)2) After cut-off, the capacitance C1(or C)2) Through a resistance R1(or R)2) Discharging, and preparing for detecting the existence of the current difference again and connecting the grid source low-impedance circuit. And repeatedly adjusting the discharge speed of the junction capacitor of the parallel SiC MOSFET in real time to enable the parallel branches to be uniform in current.
FIG. 8(a) (b) shows M without current sharing1And M2FIG. 9(a) (b) shows M when the current is suppressed by the present invention1And M2The switching waveform of the drain current in (1). From the comparison between the on-currents of fig. 8(a) and fig. 9(a) and the off-currents of fig. 8(b) and fig. 9(b), it can be found that the SiC MOSFET parallel driving circuit with dynamically adjusted gate-source impedance and actively current sharing provided by the invention has a significant current sharing effect.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (2)

1. A SiC MOSFET parallel driving circuit with gate-source impedance dynamically adjusted and active current sharing is characterized by comprising a SiC MOSFET M1、SiC MOSFET M2Current acquisition circuit, differential amplification isolation circuit, current difference value feedback circuit, gate source low-impedance circuit and SiCA MOSFET basic driving circuit;
the current collecting circuit comprises a current dividerR 100AndR 101respectively for series connection in SiC MOSFET M1Branch and SiC MOSFET M2A branch circuit;
the differential amplification isolation circuit is connected with the current difference value feedback circuit and is used for measuring the potential difference on the current divider to indirectly measure the SiC MOSFET M1Branch and SiC MOSFET M2When the current of the branch circuit is unbalanced, the current of the SiC MOSFET parallel circuit outputs a control signal to the gate-source low-impedance circuit;
the gate-source low impedance circuit comprises a SiC MOSFET M1Gate-source low-impedance auxiliary circuit of branch circuit and SiC MOSFET M2The gate-source low-impedance auxiliary circuits of the branches are SiC MOSFET M1And SiC MOSFET M2The grid electrode of the silicon controlled rectifier provides a low impedance loop, the change rate of the grid source voltage and the steady state value of the grid source voltage are changed under the action of the control signal, and the switching speed of the SiC MOSFET is dynamically adjusted, so that the phenomenon of non-uniform current is suppressed;
the differential amplification isolation circuit comprises an optical coupling isolation amplifier U1And U2Operational amplifier U3And U4Resistance, and a method for manufacturing the sameR 5~R 12；
Optical coupling isolation amplifier U1The positive input end of the shunt is connected with the shuntR 100Current input terminal and negative input terminal of the current dividerR 100A current output terminal of (a); optical coupling isolation amplifier U1Positive output end of the resistorR 5One end of (3), negative output end of (3) is connected with a resistorR 7One end of (a); resistance (RC)R 5The other end of the first switch is connected with an operational amplifier U3Positive input terminal and resistorR 6One end of (1), a resistorR 6The other end of the first switch is connected with a reference ground; resistance (RC)R 7The other end of the first switch is connected with an operational amplifier U3Negative input terminal and resistorR 8One end of (a); resistance (RC)R 8The other end of the first switch is connected with an operational amplifier U3An output terminal of (a);
optical coupling isolation amplifier U2The positive input end of the shunt is connected with the shuntR 101Current input terminal and negative input terminal of the current dividerR 101A current output terminal of (a); optical coupling isolation amplifier U2Positive output end of the resistorR 9One end of (3), negative output end of (3) is connected with a resistorR 11One end of (a); resistance (RC)R 9The other end of the first switch is connected with an operational amplifier U4Positive input terminal and resistorR 10One end of (1), a resistorR 10The other end of the first switch is connected with a reference ground; resistance (RC)R 11The other end of the first switch is connected with an operational amplifier U4Negative input terminal and resistorR 12One end of (a); resistance (RC)R 12The other end of the first switch is connected with an operational amplifier U4An output terminal of (a);
the current difference feedback circuit comprises an operational amplifier U5And U6Resistance, and a method for manufacturing the sameR 13~R 20；
Resistance (RC)R 15One end of is connected with an operational amplifier U3Output terminal and resistorR 17One end of (a); resistance (RC)R 15The other end of the first switch is connected with an operational amplifier U5Positive input terminal and resistorR 16One end of (1), a resistorR 16The other end of the first switch is connected with a reference ground; resistance (RC)R 13One end of is connected with an operational amplifier U4Output terminal and resistorR 19One end of (1), a resistorR 13The other end of the first switch is connected with an operational amplifier U5Negative input terminal and resistorR 14One end of (1), a resistorR 14The other end of the first switch is connected with an operational amplifier U5An output terminal of (a); resistance (RC)R 19The other end of the first switch is connected with an operational amplifier U6Positive input terminal and resistorR 20One end of (1), a resistorR 20The other end of the first switch is connected with a reference ground; resistance (RC)R 17The other end of the first switch is connected with an operational amplifier U6Negative input terminal and resistorR 18One end of (1), a resistorR 18The other end of the first switch is connected with an operational amplifier U6An output terminal of (a);
the M is1Low-impedance auxiliary circuit for branch gate and sourceThe circuit includes a capacitorC 1Resistance, and a method for manufacturing the sameR 1Resistance, and a method for manufacturing the sameR 3NPN triode Q1(ii) a The M is2The gate-source low impedance auxiliary circuit of the branch circuit comprises a capacitorC 2Resistance, and a method for manufacturing the sameR 2Resistance, and a method for manufacturing the sameR 4NPN triode Q2；
Triode Q1Emitter-connected SiC MOSFET M1Source electrode of (2), triode Q1Base electrode connecting resistorR 3One end of (1), a resistorR 3The other end of the first switch is connected with an operational amplifier U5An output terminal of (a); capacitor with a capacitor elementC 1One end of which is connected with a triode Q1The other end of the collector is connected with a SiC MOSFET M1A gate electrode of (1); resistance (RC)R 1Connected in parallel to a capacitorC 1Both ends of (a);
triode Q2Emitter-connected SiC MOSFET M2Source electrode of (2), triode Q2Base electrode connecting resistorR 4One end of (1), a resistorR 4The other end of the first switch is connected with an operational amplifier U6An output terminal of (a); capacitor with a capacitor elementC 2One end of which is connected with a triode Q2The other end of the collector is connected with a SiC MOSFET M2A gate electrode of (1); resistance (RC)R 2Connected in parallel to a capacitorC 2At both ends of the same.
2. The SiC MOSFET parallel drive circuit with dynamically regulated gate-source impedance and active current sharing of claim 1, wherein the SiC MOSFET basic drive circuit comprises a supply voltage sourceV 1Power supply voltage sourceV 2Switch tube S1Switch tube S2Turn on the driving resistorR onTurn off the driving resistorR offSchottky diodeD(ii) a Supply voltage sourceV 1Anode and switch tube S1Is connected to the supply voltage sourceV 1And SiC MOSFET M1And SiC MOSFET M2Is connected with the source electrode of the switching tube S1Source and turn-on driving resistorR onAnd turn-off driving resistorR offIs connected to turn on the driving resistorR onAnd the other end of the SiC MOSFET M1And SiC MOSFET M2Gate and schottky diodeDIs connected with the anode of the Schottky diodeDAnd turn-off driving resistorR offThe other ends of the two are connected; supply voltage sourceV 2Negative electrode of (2) and switching tube S2Is connected with a supply voltage sourceV 2Positive electrode and SiC MOSFET M1And SiC MOSFET M2Source electrode and power supply voltage sourceV 1The negative electrodes are connected; the switch tube S2Drain electrode of and switch tube S1Are connected.
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