Varistor driving circuit for inhibiting overshoot of SiC MOSFET
Technical Field
The invention belongs to the technical field of power electronics and electricians, relates to a driving circuit suitable for a SiC MOSFET, and particularly relates to a variable resistance driving circuit for inhibiting overshoot of the SiC MOSFET.
Background
Compared with silicon (Si) -based power devices, SiC MOSFETs have faster switching frequencies, lower on-resistances, and are more suitable for high-frequency, high-voltage, and high-temperature applications. Such as electric vehicles, photovoltaic inverters, and wind power generation. However, the existence of the internal parasitic inductance causes excessive current, voltage overshoot and oscillation, which not only increases the switching loss of the device and aggravates electromagnetic interference, but also may cause device malfunction, reduces reliability, and even damages the device, and how to suppress the current and voltage overshoot becomes one of the main problems in SiC MOSFET research.
The conventional driving method for solving the problem of current and voltage overshoot of the SiC MOSFET driving circuit in the literature can be classified into variable resistance type, variable current type and variable voltage type driving according to the adjustment mode, wherein the variable resistance type driving controls the switching process waveform by changing the driving resistance at different switching stages, and similarly, the variable current type driving and the variable voltage type driving improve the switching process waveform by changing the driving current and the driving voltage respectively. The control method can be divided into analog control and digital control, the digital control can realize flexible self-adaptive control, but digital-to-analog conversion and analog-to-digital conversion devices are needed in the process, so that delay is greatly increased, the SiC MOSFET (metal oxide semiconductor field effect transistor) extremely short switching time is difficult to correspond, and the analog control can realize the suppression of the overshoot of the switching process under the condition of introducing the delay as little as possible, so that the analog control has important practical value for realizing the overshoot suppression of the switching process. The patent proposes an objective to propose a variable resistance driving circuit which has a simple circuit structure and can suppress overshoot of a SiC MOSFET by an analog circuit.
Disclosure of Invention
The invention aims to provide a variable resistance driving circuit for inhibiting overshoot of a SiC MOSFET, which can effectively inhibit overshoot of current and voltage generated in a switching process under the condition of fully keeping the advantages of high switching speed and low loss of the SiC MOSFET.
The invention adopts the following technical scheme for realizing the purpose:
a resistance-variable driving circuit for inhibiting overshoot of a SiC MOSFET (metal oxide semiconductor field effect transistor) comprises the SiC MOSFET and is characterized by further comprising a totem-pole structure circuit, a turn-on driving circuit, a turn-off driving circuit and a voltage feedback signal conditioning circuit, wherein the totem-pole structure circuit, the turn-on driving circuit, the turn-off driving circuit and the voltage feedback signal conditioning circuit are arranged between a positive power supply source and a negative power supply source, the output end of the totem-pole structure circuit is respectively connected with the input end of the turn-on driving circuit and the input end of the voltage feedback signal conditioning circuit, the output end of the turn-on driving circuit and the output end of the turn-off driving circuit and the input end of the voltage feedback signal conditioning circuit are connected with a grid electrode of the SiC MOSFET, the turn-on driving circuit and the turn-off driving circuit are used for changing the driving resistance of the SiC MOSFET, and the voltage feedback signal conditioning circuit is used for judging that the SiC MOSFET is in a corresponding stage in a switching stage and outputting a control signal to change the driving resistance so as to realize overshoot inhibition.
Preferably, the totem-pole structure circuit comprises a first switching control tube Q1_onAnd a first turn-off control tube Q1_offFirst on control tube Q1_onDrain and forward power supplyU G,onConnected to one another, a first open control tube Q1_onSource and first turn-off control tube Q1_offA source connected to the on/off drive circuit, a first off control transistor Q1_offDrain and negative power supplyU G,offConnected to one another, a first open control tube Q1_onAnd a first turn-off control tube Q1_offThe gates each receive a given PWM signal.
Preferably, the upper end of the turn-on driving circuit is connected with the output end of the totem-pole structure circuit, and the first turn-on control tube Q1_onThe source electrode of the transistor is connected with a second turn-on control tube Q2_onAnd a third open control tube Q3_onDrain electrode and first on-resistanceR 1_onOne end; second opening control tube Q2_onIs connected with a second on-resistanceR 2_onAnd a gate receiving a second amplifier AMP2Output signal ofS 2(ii) a Third on-off control tube Q3_onThe source electrode is connected with a third on-off resistorR 3_onAnd a gate receiving a first amplifier AMP1Output signal ofS 1First, a,The other ends of the second and third on-resistances are connected with an on-diode D1_onIs connected to turn on the diode D1_onThe cathode of the switch-on driving circuit is the output end of the switch-on driving circuit and is connected with the grid electrode of the SiC MOSFET.
Preferably, the upper end of the turn-off drive circuit is connected with the output end of the totem-pole structure circuit, and the first turn-off control tube Q1_offIs connected with a second turn-off control tube Q2_offAnd a third turn-off control tube Q3_offDrain electrode and first on-resistanceR 1_offOne end, second turn-off control tube Q2_offIs connected with a second turn-off resistorR 2_offAnd a gate receiving a second amplifier AMP2Output signal ofS 2Third turn off control tube Q3_offIs connected with a third off-resistanceR 3_offAnd a gate receiving a first amplifier AMP1Output signal ofS 1The other end of the turn-off resistor is connected with a turn-off diode D1_offIs connected to turn off the diode D1_offIs connected to the gate of the SiC MOSFET.
Preferably, the first sampling resistor of the voltage feedback signal conditioning circuitR 4One end of the sampling resistor is connected with the grid of the SiC MOSFET, and the other end of the sampling resistor is connected with the second sampling resistorR 5Second sampling resistorR 5The other end is grounded, and a sampling voltage signal is arranged at a first sampling resistorR 4And a second sampling resistorR 5And a first comparator CAMP1Negative input terminal, second comparator CAMP2Positive input terminal and third comparator CAMP3Negative input end connected to the first comparator CAMP1The positive input end is connected with a first reference voltageU 1_refThe output end is connected with a first OR logic gate OR1First input terminal, second comparator CAMP2The negative input end is connected with a second reference voltageU 2_refThe output end is connected with a first OR logic gate OR1And a second OR logic gate OR2First input terminal of (1), third comparator CAMP3The positive input end is connected with a third reference voltageU 3_refThe output end is connected with a second OR logic gate OR2Second input ofAn input terminal, a first OR logic gate OR1The output end is connected with the first amplifier AMP1Positive input terminal, second OR logic gate OR2Connected to a second amplifier AMP2Positive input terminal, first amplifier AMP1Output signalS 1To the third open control tube Q3_onAnd a third turn-off control tube Q3_offA gate of the second amplifier AMP2Output signalS 2To the second opening control tube Q2_onA second turn-off control tube Q2_offA gate electrode of (1).
The invention also discloses a control method of the variable resistance drive circuit for inhibiting the overshoot of the SiC MOSFET, and when the SiC MOSFET is switched on, the sampling circuit controls the grid source voltageU GSSampling and setting three reference voltagesU 1_ref、U 2_refAndU 3_refcomparing, judging whether the parallel resistor is controlled in the non-current overshoot regionR 1_on、R 2_onAndR 3_onto accelerate the turn-on speed, reduce the turn-on time to reduce the turn-on loss, control the parallel resistance in the current overshoot regionR 1_on、R 2_onAndR 3_onto suppress current overshoot. When the SiC MOSFET is turned off, the sampling circuit is used for sampling the gate-source voltageU GSSampling and setting three reference voltagesU 1_ref、U 2_refAndU 3_refcomparing, judging whether the parallel resistor is controlled in the non-voltage overshoot regionR 1_off、R 2_offAndR 3_offto accelerate the turn-off speed, shorten the turn-off time to reduce the turn-off loss, and control the parallel resistor in the voltage overshoot regionR 1_off、R 2_offAndR 3_offto inhibit voltage overshoot.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
(1) when the SiC MOSFET is switched on, the number of the parallel resistors is increased at a non-current overshoot corresponding stage, the switching-on time is shortened, and the number of the parallel resistors is reduced at a current overshoot corresponding stage to inhibit the switching-on current overshoot.
(2) When the SiC MOSFET is switched off, the number of the parallel resistors is increased at a non-voltage overshoot corresponding stage, the switching-off time is shortened, and the number of the parallel resistors is reduced at a voltage overshoot corresponding stage to inhibit the switching-off voltage overshoot.
(3) The analog circuit is used as a conditioning control circuit to reduce time delay and realize more accurate control, and the driving resistance is reduced in a non-overshoot area to shorten the switching time and reduce the switching loss.
Drawings
Fig. 1 is a diagram of a configuration of a turn-on driving circuit according to an embodiment of the present invention.
Fig. 2 is a block diagram of a shutdown driving circuit according to an embodiment of the present invention.
FIG. 3 is a diagram of a voltage feedback signal conditioning circuit according to an embodiment of the present invention.
Fig. 4 is a circuit diagram of an embodiment of the present invention.
FIG. 5 is a waveform timing diagram of the comparator and the switches according to one embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 4, the present invention relates to a varistor driving circuit for suppressing overshoot of a SiC MOSFET and a control method thereof, wherein a driving circuit connected to a gate of the SiC MOSFET includes a totem-pole structure circuit between a positive power supply and a negative power supply, a turn-on driving circuit, a turn-off driving circuit, and a voltage feedback signal conditioning circuit. The output end of the on driving circuit, the output end of the off driving circuit and the input end of the voltage feedback signal conditioning circuit are connected with the grid of the SiC MOSFET. The totem-pole structure circuit comprises a first on control tube and a first off control tube, the on drive circuit comprises a first on resistor, a second on control tube, a second on resistor, a third on control tube and a third on resistor, the off drive circuit comprises a first off resistor, a second off control tube, a second off resistor, a third off control tube and a third off resistor, and the voltage feedback signal conditioning circuit comprises a first sampling resistor, a second sampling resistor, a first comparator, a second comparator, a third comparator, a first OR logic gate, a second OR logic gate, a first amplifier and a second amplifier.
As shown in FIG. 1, the turn-on driving circuit of the present invention comprises a first turn-on control transistor Q1,onThe drain electrode of the positive power supply is connected with a positive power supplyU G,onA gate receiving a given PWM signal and a source connected to a second turn-on control transistor Q2_onAnd a third open control tube Q3_onDrain electrode and first on-resistanceR 1_onOne end; second opening control tube Q2_onIs connected with a second on-resistanceR 2_onAnd a gate receiving a second amplifier AMP2Output signal ofS 2And a third opening control tube Q3_onThe source electrode is connected with a third on-off resistorR 3_onAnd a gate receiving a first amplifier AMP1Output signal ofS 1First, second and third on/off resistorsR 1_on、R 2_on、R 3_onAnd the other end of the same is connected with a turn-on diode D1_onIs connected to turn on the diode D1_onIs connected to the gate of the SiC MOSFET.
As shown in FIG. 2, the turn-off driving circuit of the present invention has a structure symmetrical to that of the turn-on driving circuit, and includes a first turn-off control transistor Q1_offIts grid electrode receives given PWM signal and its drain electrode is connected with negative power supplyU G,offThe source of the second switch-off control tube Q is connected with the source of the first switch-off control tube Q2_offAnd a third turn-off control tube Q3_offAnd a first off-resistanceR 1_offOne end of (a); second turn-off control tube Q2_offIs connected with a second turn-off resistorR 2_offAnd a gate receiving a second amplifier AMP2Output signal ofS 2Third turn off control tube Q3_offIs connected with a third off-resistanceR 3_offAnd a gate receiving a first amplifier AMP1Output signal ofS 1First, second and third off-resistancesR 1_off、R 2_off、R 3_offAnd the other end of the diode D is connected with a turn-off diode D1_offIs connected to turn off the diode D1_offIs connected to the gate of the SiC MOSFET.
Wherein, the first, the second and the third open control tubes Q1,on、 Q2_on、Q3_onAre N-channel MOSFET, and the first, second and third turn-off control tubes Q1_off、Q2_off、Q3_offAre all P-channel MOSFETs.
As shown in FIG. 3, the voltage feedback signal conditioning circuit of the present invention includes a first sampling resistorR 4One end of the sampling resistor is connected with the grid of the SiC MOSFET, and the other end of the sampling resistor is connected with the second sampling resistorR 5Second sampling resistorR 5The other end is grounded, and a sampling voltage signal is arranged at a first sampling resistorR 4And a second sampling resistorR 5And a first comparator CAMP1Negative input terminal, second comparator CAMP2Positive input terminal and third comparator CAMP3Negative input end connected to the first comparator CAMP1The positive input end is connected with a first reference voltageU 1_refThe output end is connected with a first OR logic gate OR1First input terminal, second comparator CAMP2The negative input end is connected with a second reference voltageU 2_refThe output end is connected with a first OR logic gate OR1And a second OR logic gate OR2First input terminal of (1), third comparator CAMP3The positive input end is connected with a third reference voltageU 3_refThe output end is connected with a second OR logic gate OR2A first OR logic gate OR1The output end is connected with the first amplifier AMP1Positive input terminal, second OR logic gate OR2Connected to a second amplifier AMP2Positive input terminal, first amplifier AMP1Output signalS 1To the firstThree-way control tube Q3_onAnd a third turn-off control tube Q3_offA gate of the second amplifier AMP2Output signalS 2To the second opening control tube Q2_onA second turn-off control tube Q2_offA gate electrode of (1). Wherein the first sampling resistorR 4And a second sampling resistorR 5Taking the value as large as possibleR 4、R 5Not less than 10k omega, the sampling voltage is based on the first sampling resistorR 4And a second sampling resistorR 5The ratio of (a) is obtained, and the ratio is adjusted according to the voltage range acceptable by the first, second and third comparators. RG(int)The gate resistance of the SiC MOSFET is obtained according to a specific data manual and is generally 5-10 omega.
The working principle of the invention is as follows:
when the SiC MOSFET is switched on, the sampling circuit samples the grid source voltage, compares the grid source voltage with three given reference voltages, judges that the number of parallel resistors is increased in a non-current overshoot area to accelerate the switching speed, reduces the switching time to reduce the switching loss, and reduces the number of parallel resistors in a current overshoot area to inhibit the current overshoot. When the SiC MOSFET is switched off, the sampling circuit samples the grid-source voltage, compares the grid-source voltage with three given reference voltages, judges that the number of parallel resistors is increased in a non-voltage overshoot area to accelerate the switching-off speed, shortens the switching-off time to reduce the switching-off loss, and reduces the number of parallel resistors in a voltage overshoot area to inhibit the voltage overshoot.
As shown in fig. 5, the reference voltages set by the comparator are all the quasi-reference voltages multiplied by the sampling ratio, and the sampling ratio is the ratio of the sampling resistance to the total resistance, that is, the ratioR 5/(R 4+ R 5). The quasi-reference voltage set by the first comparator is the threshold voltage of the SiC MOSFET, the quasi-reference voltage set by the second comparator is the Miller voltage of the SiC MOSFET, and the quasi-reference voltage set by the third comparator is half of the sum of the threshold voltage of the SiC MOSFET and the Miller voltage of the SiC MOSFET. When a PWM rising edge signal is applied to a first turn-on control tube, the SiC MOSFET enters a turn-on stage, the grid source voltage of the SiC MOSFET is gradually increased, and the grid source voltage of the SiC MOSFET is sampledWhen the value is lower than the value of the threshold voltage multiplied by the sampling proportion or higher than the value of the Miller voltage multiplied by the sampling proportion, the second opening control tube and the third opening control tube are conducted, the three opening resistors are connected in parallel, the opening speed is increased, and the opening time is shortened. When the sampling value of the grid-source voltage is higher than the value of the threshold voltage multiplied by the sampling proportion and lower than the value of the half of the sum of the threshold voltage and the Miller voltage multiplied by the sampling proportion, the second switching-on control tube is conducted, and the second switching-on resistor is connected with the first switching-on resistor in parallel to prepare for overshoot suppression. When the sampling value of the grid source voltage is higher than the value of the half of the sum of the threshold voltage and the Miller voltage multiplied by the sampling proportion and is lower than the value of the Miller voltage multiplied by the sampling proportion, only the first opening resistor is conducted, and the increase and the overshoot of the driving resistor are restrained.
The invention provides a variable resistance driving circuit for inhibiting overshoot of a SiC MOSFET (metal oxide semiconductor field effect transistor) and a control method thereof, and the driving circuit can effectively inhibit current and voltage overshoot generated in the switching process under the condition of keeping the advantages of high switching speed and low loss of the SiC MOSFET.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.