SiCMOSFET isolation drive circuit, high step-down ratio flyback power supply and drive control method

Abstract

The invention relates to the technical field of thermal power plants, in particular to a SiC MOSFET isolation driving circuit, a high step-down ratio flyback power supply and a driving control method, and the circuit comprises a power amplification circuit module which is used for amplifying a PMW control signal; a blocking circuit module; the input winding of the transformer is connected with the blocking circuit module, and the output side of the transformer is provided with a plurality of independent windings; the level transfer circuit module comprises a capacitor and a diode, is connected with an output winding of the transformer, and is used for storing negative level energy and superposing the negative level energy with a positive level; the charging circuit module and the discharging circuit module comprise a charging branch and a discharging branch, and are used for adjusting the turn-on time and the turn-off time of the SiC MOSFETs; and the energy discharge circuit module is connected in parallel with a capacitor in the blocking circuit module and a capacitor in the level transfer circuit module, and is used for quickly releasing stored energy after PMW (Pulse Width Modulation) wave sealing, thoroughly solving the potential safety hazard of PWM wave sealing misconduction, ensuring the voltage-sharing performance through multi-path driving and high consistency, comprehensively improving the adaptability to high-frequency and high-voltage scenes, and enhancing the system-level safety.

Description

Technical Field

[0001] This invention relates to the field of power electronic drive technology, and in particular to a SiC MOSFET isolated drive circuit, a high buck ratio flyback power supply, and a drive control method. Background Technology

[0002] With the development of power electronics technology, the single-unit power of photovoltaic and energy storage modules is gradually increasing. To meet the development needs of high power and high capacity, the system bus voltage is also gradually increasing, with the commonly used voltage level being 1500V and the highest being 2000V. The auxiliary power supply is an important component of the module, providing power to the control system. Typically, the auxiliary power supply input voltage is taken from the bus, and the output voltage is 24V. Traditional single-transistor flyback power supply topologies suffer from excessive voltage stress on devices, making device selection difficult. Therefore, flyback power supply topologies suitable for high step-down ratios have been developed. Multiple power units are connected in series on the input side to meet the high step-down ratio requirement. The series connection of multiple power units brings new challenges to the switching transistor drive. Consistency of multi-path drive and smooth waveform without backlash are important conditions for ensuring reliable power supply operation. Most existing SiC MOSFET drive circuits integrate sampling and protection circuits, are fully functional, and are suitable for driving high-power SiC modules, while some single-transistor drive circuits have shortcomings. Summary of the Invention

[0003] In view of the above-mentioned problems, such as the fact that existing SiC MOSFET driving circuits mostly integrate sampling and protection circuits, are fully functional and suitable for driving high-power SiC modules, while some single-transistor driving circuits have shortcomings, this invention is proposed.

[0004] Therefore, the purpose of this invention is to provide a SiC MOSFET isolated drive circuit, a high buck ratio flyback power supply, and a drive control method.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a SiC MOSFET isolation drive circuit, comprising,

[0006] Power amplifier circuit module, used to amplify PWM control signals;

[0007] The DC blocking circuit module includes capacitor C2, which filters out the DC component;

[0008] Transformer T2 has an input winding (N1) connected to the DC blocking circuit module, and its output side has multiple independent windings (N21-N2n, n=2~4).

[0009] The level shifting circuit module includes capacitors C11-C1n and diodes D11-D1n, which are connected to the output winding of the transformer to store negative level energy and superimpose it with positive level energy.

[0010] The charging circuit module and the discharging circuit module include a charging branch and a discharging branch. The charging branch includes diodes D21-D2n and resistors R21-R2n. The discharging branch includes diodes D31-D3n, resistors R31-R3n / R41-R4n and PMOS transistors S1-Sn.

[0011] The turn-on and turn-off times of the SiC MOSFET are adjusted through the charging and discharging branches; and,

[0012] The energy discharge circuit module includes discharge resistors R3 and R11-R1n, capacitor C2 connected in parallel in the DC blocking circuit module and capacitors C11-C1n in the level transfer circuit module, for rapidly releasing stored energy after PWM blocking.

[0013] As a preferred embodiment of the SiC MOSFET isolation drive circuit of the present invention, the energy discharge circuit includes a primary-side discharge resistor R3 connected in parallel across the DC blocking capacitor C2, and secondary-side discharge resistors R11-R1n connected in parallel across each level transfer capacitor C11-C1n.

[0014] As a preferred embodiment of the SiC MOSFET isolated drive circuit of the present invention, the discharge circuit module includes a series PMOS transistor (S1-Sn) and a discharge resistor (R31-R3n / R41-R4n), the gate of the PMOS transistor is connected to the output terminal of the level transfer circuit module, and the source is connected to the gate of the SiC MOSFET.

[0015] As a preferred embodiment of the SiC MOSFET isolation drive circuit of the present invention, the level transfer circuit module stores the negative half-cycle energy of the transformer through capacitors (C11-C1n), and superimposes the energy with the positive level of the transformer during the positive half-cycle and outputs it to the gate of the SiC MOSFET.

[0016] As a preferred embodiment of the SiC MOSFET isolation drive circuit of the present invention, a damping resistor R2 is provided between the power amplifier circuit module and the DC blocking circuit module to adjust the circuit damping characteristics and suppress the oscillation amplitude.

[0017] As a preferred embodiment of the SiC MOSFET isolation drive circuit of the present invention, wherein: the resistance value of the charging resistor (R21-R2n) in the charging circuit module and the discharging circuit module adjusts the turn-on time of the SiC MOSFET, and the resistance value of the discharging resistor (R31-R3n / R41-R4n) adjusts the turn-off time of the SiC MOSFET.

[0018] A high buck ratio flyback power supply includes a SiC MOSFET isolated drive circuit, wherein,

[0019] The input side has n power units (n = 2 to 4) connected in series. Each unit includes a SiC MOSFET switch (Q1-Qn), a transformer primary winding (N11-N1n), an RCD snubber circuit (C21-C2n, R11-R1n, D11-D1n), and voltage equalization capacitors (C1-Cn). The output of the multi-channel isolation drive circuit drives the SiC MOSFET of each power unit respectively.

[0020] As a preferred embodiment of the high step-down ratio flyback power supply of the present invention, the RCD absorption circuit of each power unit is composed of capacitors (C21-C2n), resistors (R11-R1n) and diodes (D11-D1n), and is used to absorb the leakage inductance energy of the transformer.

[0021] A drive control method includes a SiC MOSFET isolated drive circuit, comprising the following steps:

[0022] The PMW signal is amplified by power and then converted into an alternating square wave by a transformer.

[0023] The negative half-cycle energy is stored through a level transfer circuit and superimposed onto the driving voltage during the positive half-cycle.

[0024] During PMW blocking, the energy of the energy storage capacitor is released within ≤10μs through the bleed resistors (R3, R11-R1n), causing the gate voltage to drop below the SiC MOSFET turn-on threshold.

[0025] As a preferred embodiment of the SiC MOSFET isolated drive circuit, high buck ratio flyback power supply, and drive control method of the present invention, wherein: the discharge action keeps the gate voltage ≤2V after the blocking operation.

[0026] The advantages of this invention are: It completely eliminates the safety hazard of PWM blocking-induced turn-on: By adding an energy discharge branch (discharge resistors R3, R11-R1n) to the drive circuit, and taking advantage of the energy storage characteristics of the DC blocking capacitor (C2) and the level transfer capacitors (C11-C1n), the typical turn-on threshold voltage of the SiC MOSFET is reduced. This design eliminates the risk of erroneous turn-on of the switching transistor caused by residual energy in the energy storage element at its source, ensuring the reliability of the high-voltage system.

[0027] High consistency of multi-channel drive ensures voltage equalization performance: The single transformer multi-winding output structure (T2 secondary winding N21-N2n) is adopted. By utilizing the natural synchronization characteristics of magnetic coupling, the strict alignment of multi-channel drive signals is achieved, ensuring that the switching action of the series power units (such as 2 to 4 units) on the input side is highly synchronized, thus solving the voltage equalization problem of high buck ratio flyback power supplies.

[0028] The adaptability to high-frequency and high-voltage scenarios has been comprehensively improved: the level transfer circuit module (C11-C1n and D11-D1n) stores the energy of the transformer's negative half-cycle and superimposes it onto the positive half-cycle, driving the output voltage to +15V (meeting the optimal driving requirements of SiC MOSFETs), while also supporting high-frequency switching; the charging and discharging resistors are independently adjustable (charging resistors R21-R2n control the turn-on speed, and discharging resistors R31-R3n / R41-R4n control the turn-off speed), adapting to SiC MOSFETs with different gate charges, and achieving a switching time adjustment accuracy of ±5ns; the discrete device solution reduces costs and size compared to traditional integrated driver chips, and avoids the control logic burden caused by complex switching capacitors or active drive circuits.

[0029] System-level safety enhancement: Damping resistor R2 forces the circuit to operate in an overdamped state, suppressing voltage oscillations during transformer transmission and preventing the gate overshoot voltage from exceeding the SiC MOSFET's withstand voltage limit (±20V); RCD absorption circuit (C21-C2n / R11-R1n / D11-D1n) efficiently absorbs transformer leakage inductance energy. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the overall structure of a SiC MOSFET isolated drive circuit, a high buck ratio flyback power supply, and a drive control method.

[0032] Figure 2 This is a topology diagram of a SiC MOSFET isolated drive circuit, a high buck ratio flyback power supply, and a drive control method.

[0033] Figure 3 This is a schematic diagram of an isolated drive circuit in a SiC MOSFET isolated drive circuit, a high buck ratio flyback power supply, and a drive control method. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0037] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include the three-dimensional spatial dimensions of length, width, and depth.

[0038] Example

[0039] Reference Figure 1 - Figure 3 This invention provides an embodiment of a SiC MOSFET isolated drive circuit, a high buck ratio flyback power supply, and a drive control method. The application includes a power amplifier circuit module for amplifying the PWM control signal; a DC blocking circuit module, including capacitor C2, to filter out the DC component; a transformer T2, with its input winding (N1) connected to the DC blocking circuit module and multiple independent windings (N21-N2n, n = 2-4) on the output side; a level shifting circuit module, including capacitors C11-C1n and diodes D11-D1n, connected to the transformer output winding, storing negative level energy and superimposing it with positive level energy; a charging circuit module and a discharging circuit module, including a charging branch and a discharging branch. The charging branch includes diodes D21-D2n and resistors R21-R2n, and the discharging branch includes diodes D31-D3n, resistors R31-R3n / R41-R4n, and PMOS transistors S1-Sn. The SiC MOSFET is adjusted through the charging and discharging branches. MOSFET turn-on and turn-off times; energy discharge circuit module, including discharge resistors R3, R11-R1n, capacitor C2 connected in parallel in the DC blocking circuit module and capacitors C11-C1n in the level transfer circuit module, used for rapid release of stored energy after MOSFET blocking.

[0040] The energy discharge circuit includes a primary discharge resistor R3 connected in parallel across the DC blocking capacitor C2, and secondary discharge resistors R11-R1n connected in parallel across each level transfer capacitor C11-C1n.

[0041] The discharge circuit module includes a series PMOS transistor (S1-Sn) and a discharge resistor (R31-R3n / R41-R4n). The gate of the PMOS transistor is connected to the output terminal of the level transfer circuit module, and the source is connected to the gate of the SiC MOSFET.

[0042] The level transfer circuit module stores the energy of the transformer during the negative half-cycle through capacitors (C11-C1n), and then superimposes this energy with the positive level of the transformer during the positive half-cycle and outputs it to the gate of the SiC MOSFET.

[0043] A damping resistor R2 is provided between the power amplifier circuit module and the DC blocking circuit module to adjust the circuit damping characteristics and suppress the oscillation amplitude.

[0044] In the charging circuit module and the discharging circuit module, the resistance value of the charging resistor (R21-R2n) adjusts the turn-on time of the SiC MOSFET, and the resistance value of the discharging resistor (R31-R3n / R41-R4n) adjusts the turn-off time of the SiC MOSFET.

[0045] Specifically, according to the appendix Figure 1 As can be seen, the power amplifier circuit module amplifies the signal output by the PWM controller, and then passes it through a DC blocking capacitor and a transformer to the level transfer circuit module. The alternating signal passed through the transformer is converted back to zero level and high level. The converted signal controls the turn-on and turn-off of the SiC MOSFET through the charging / discharging circuit. Since the drive circuit contains energy storage elements such as capacitors and transformers, the drive output signal cannot remain at zero level after the PWM signal is blocked. If the gate voltage is greater than the minimum turn-on threshold voltage of the SiC MOSFET, there is a risk of the switching transistor being falsely turned on. Therefore, an energy discharge circuit is added to the circuit to ensure that the energy in the energy storage element is quickly discharged after the PWM signal is blocked, so that the drive output voltage is less than the minimum turn-on threshold voltage of the SiC MOSFET, ensuring that the drive circuit meets the drive requirements of the switching transistor.

[0046] Furthermore, the power amplifier circuit module employs a push-pull circuit to amplify the signal output from the PWM controller, driving the isolation transformer. A DC blocking capacitor prevents the transformer from generating DC bias, which could lead to magnetic saturation. The transformer converts the PWM output into an alternating square wave signal. As the duty cycle increases, the absolute value of the transformer's negative level increases. The level transfer circuit module stores the negative level energy from the transformer and, during the turn-on period, superimposes it with the positive level to increase the drive level of the output circuit. The level transfer circuit module is connected to the charging and discharging circuit modules to drive the SiC... MOSFFT consists of a charging circuit module for turning on the switching transistor, adjusting the turn-on time by regulating the driving resistor value; a discharging circuit module for accelerating the turn-off of the switching transistor, adjusting the turn-off time by regulating the discharging resistor value; and an energy discharge circuit for providing an energy discharge path to the energy storage element after PWM blocking, rapidly releasing energy and preventing energy from being transferred to the gate of the switching transistor, which would cause the gate voltage to rise. If the voltage exceeds the minimum gate turn-on voltage, the switching transistor may mis-turn on, leading to device damage. For multiple power units connected in series on the input side (commonly 2 to 4 power units connected in series), only a winding needs to be added to the output side of the drive transformer to drive multiple power transistors. This drive circuit has a simple structure, low cost, and is easy to implement and promote.

[0047] Preferably, a high buck ratio flyback power supply includes n power units (n = 2 to 4) connected in series on the input side. Each unit includes a SiC MOSFET switch (Q1-Qn), a transformer primary winding (N11-N1n), an RCD snubber circuit (C21-C2n, R11-R1n, D11-D1n), voltage equalization capacitors (C1-Cn), and the output of a multi-channel isolation drive circuit to drive the SiC MOSFET of each power unit respectively.

[0048] The RCD absorption circuit of each power unit consists of capacitors (C21-C2n), resistors (R11-R1n), and diodes (D11-D1n), and is used to absorb the leakage inductance energy of the transformer.

[0049] Preferably, the drive control method includes the following steps:

[0050] The PMW signal is amplified by power and then converted into an alternating square wave by a transformer.

[0051] The negative half-cycle energy is stored through a level transfer circuit and superimposed onto the driving voltage during the positive half-cycle.

[0052] During PMW blocking, the energy of the energy storage capacitor is released within ≤10μs through the bleed resistors (R3, R11-R1n), causing the gate voltage to drop below the SiC MOSFET turn-on threshold.

[0053] The discharge action keeps the gate voltage ≤2V after the ripple is blocked.

[0054] Specifically, in order to meet the application requirements of high-voltage input and low-voltage output, according to the attached... Figure 2 It can be seen that the input side consists of multiple flyback power units connected in series, with the input voltage taken from the DC bus. The first power unit comprises capacitors C11 and C21, resistor R11, diode D11, transformer T1 winding N11, switch Q1, and current transformer TA1. Capacitor C21, resistor C11, and diode D11 form an RCD snubber circuit, which absorbs the leakage inductance energy of winding N11. The second power unit comprises capacitors C12 and C22, resistor R12, diode D12, transformer T1 winding N12, switch Q2, and current transformer TA2. The second power unit consists of an RCD snubber circuit composed of capacitor C22, resistor C12, and diode D12, which absorbs leakage inductance energy from winding N12. The nth power unit consists of capacitors C1n and C2n, resistor R1n, diode D1n, transformer T1 winding N1n, switching transistor Qn, and current transformer TAn. In this nth power unit, capacitor C2n, resistor C1n, and diode D1n form an RCD snubber circuit, which absorbs leakage inductance energy from winding N1n. Depending on component selection requirements and drive design complexity, the input-side power units typically consist of 2 to 4 groups. Capacitors C1, C2, ..., Cn (n = 2 to 4) are voltage-equalizing capacitors to ensure balanced input voltage across all power units. Current sampling signals Ics1, Ics2, ..., Icsn (n = 2 to 4) are used for peak current mode control. PWM1, PWM2, ..., PWMn (n = 2 to 4) drive signals come from the drive circuit and are used to drive the corresponding SiC MOSFETs in the power units. Resistor R1, capacitor C1, diode D1, transformer T1 winding N21, and electrolytic capacitor C2 form the main output circuit, which supplies power to the module's overall control system. Resistor R1 and capacitor C1 form an RC snubber circuit, which suppresses voltage spikes from diode D1. Diode D2, transformer T1 winding N21, and electrolytic capacitor C2 form the auxiliary power supply circuit, which supplies power to the chip control circuit after the power supply starts up, ensuring normal operation of the power supply.

[0055] Furthermore, for an input-side series-type flyback power supply topology, the drive power supplies for each power unit need to be electrically isolated, as shown in the attached diagram. Figure 3 As shown, the drive signal output by the PWM controller is connected to the power amplifier circuit through an RC low-pass filter composed of resistor R1 and capacitor C1. The power amplifier circuit is composed of NMOS transistors and PMOS transistors. Resistor R2 is a damping resistor. Adjusting the resistance value makes the circuit work in an overdamped state.

[0056] Among them, capacitor C2 is a DC blocking capacitor to prevent the DC component in the circuit from causing DC bias magnetization in the transformer; resistor R3 is a bleeder resistor, used to quickly release the energy in capacitor C2 when the PWM is blocked. The transformer T2 winding N1 is the input winding, and windings N21, N22, ..., N2n (n takes 2 to 4) are the output windings; resistors R11, R21, R31, R41, R51, diodes D11, D21, D31, capacitor C11, transformer T2 winding N21 and PMOS transistor S1 constitute the first driving unit.

[0057] In this circuit, capacitor C11 and diode D11 form a level transfer circuit, storing the negative energy of the transformer in the capacitor, which is then superimposed with the positive level to drive the switching transistor. Diode D21 and resistor R12 form a charging circuit, which charges the gate capacitor and turns on the switching transistor Q1 when the drive output is high. Diode D31, resistors R31 and R41, and PMOS transistor S1 form a discharge circuit, which discharges the gate capacitor and turns off the switching transistor Q1 when the drive output is low. Resistors R11, R12, ..., R1n (n takes 2 to 4) are bleeder resistors, used to quickly release the energy in capacitors C11, C12, ..., C1n (n takes 2 to 4). Resistors R12, R22, R32, R42, R52, diodes D12, D22, D32, capacitor C12, transformer T2 winding N22, and PMOS transistor S2 form the second driving unit.

[0058] Among them, capacitor C12 and diode D12 form a level transfer circuit, which stores the negative level energy of the transformer in the capacitor and superimposes it with the positive level to drive the switching transistor; diode D22 and resistor R22 form a charging circuit, which charges the gate capacitor when the drive output is high, and turns on the switching transistor Q2; diode D32, resistors R32, R42 and PMOS transistor S2 form a discharge circuit, which discharges the gate capacitor when the drive output is low, and turns off the switching transistor Q2; resistors R1n, R2n, R3n, R4n, R5n, diodes D1n, D2n, D3n, capacitor C1n, transformer T2 winding N2n and PMOS transistor Sn form the nth driving unit.

[0059] Among them, capacitor C1n and diode D1n form a level transfer circuit, which stores the negative level energy of the transformer in the capacitor and superimposes it with the positive half-cycle level to drive the switching transistor; diode D2n and resistor R2n form a charging circuit, which charges the gate capacitor when the drive output is high, and turns on the switching transistor Qn; diode D3n, resistors R3n, R4n and PMOS transistor Sn form a discharge circuit, which discharges the gate capacitor when the drive output is low, and turns off the switching transistor Qn; resistors R51, R52, ..., R5n are the gate protection resistors of the corresponding switching transistors.

[0060] The operation involves using a multi-power unit series topology on the input side to meet the high input voltage requirement and achieve a high step-down ratio. Each power unit is driven by transformer isolation, and its drive circuit has the advantages of electrical isolation, simple structure, and high reliability. The drive circuit inputs the PWM controller's drive signal to the power amplifier circuit via an RC filter. When the controller outputs a high level, switch Q11 is turned on, and the high level is transmitted to the SiC MOSFET gate by transformer T2, turning on the switch. When the controller outputs a low level, switch Q21 is turned on, the energy in the circuit is released, the energy of the SiC MOSFET gate capacitor is discharged by the discharge circuit, the level jumps to zero, and the switch is turned off. Resistor R2 is a damping resistor, and capacitor C2 is a DC blocking capacitor to prevent transformer T2 from generating DC bias magnetism. The working principle of the first drive unit is that capacitor C11 and diode D11 form a level transfer circuit to store the energy of the negative half-cycle, which is superimposed with the high level during the positive half-cycle to drive the SiC MOSFET. The MOSFET has a bleed resistor R11, which is used to quickly discharge the energy in capacitor C11 after the drive is blocked, to prevent the gate voltage from exceeding the minimum turn-on voltage and causing the switch to turn on falsely. Diode D21 and resistor R21 form a charging circuit to charge the gate capacitor. Diode D31, resistors R31 and R41 and switch S1 form a discharging circuit to discharge the gate capacitor. Resistor R51 is the SiC MOSFEFT gate protection resistor. The other drive units work on the same principle as the first drive unit.

[0061] The power amplifier circuit module amplifies the weak signal output by the PWM controller to drive the subsequent transformer and switching transistor. The DC blocking circuit module filters out the DC component in the circuit to prevent the transformer from generating DC bias and causing magnetic saturation. The transformer provides electrical isolation and multi-channel drive output, adapting to high step-down ratio power supply topologies. The level transfer circuit module stores negative level energy, which is superimposed with the positive level during the conduction of Q11 to drive the SiC MOSFET. The charging circuit module and the discharging circuit module are used to adjust the turn-on / turn-off time. The energy discharge current is used to release the energy of the energy storage element in the drive circuit, preventing the switching transistor from being mis-turned due to the lack of energy release path after PWM blocking.

[0062] Among them, the high step-down ratio power supply topology adopts a multi-power unit series topology on the primary side. The switching transistor of each power unit needs to be electrically isolated. It is easy to achieve multi-channel drive output using transformers. The circuit structure is simple and has fewer components, which can better ensure the consistency and reliability of the drive signal.

[0063] The primary side of the drive circuit includes inductors and capacitors. A damping resistor R2 is introduced to adjust the circuit's damping characteristics, preventing the oscillation amplitude from exceeding the maximum allowable gate voltage and ensuring the stability of the drive circuit.

[0064] The drive signal is transformed into an alternating positive and negative level signal after passing through the transformer. The positive level cannot meet the driving requirements of SiCMOSFET. The level transfer circuit stores the negative level energy, which is superimposed on the positive level during the conduction of Q11 to drive the SiCMOSFET.

[0065] The drive circuit includes energy storage elements, namely transformer inductance and capacitors C2, C11, C12, ..., C1n (n takes 2 to 4). After PWM blocking, the energy of the energy storage elements needs a fast release circuit. Discharge resistors R3, R11, R12, ..., R1n (n takes 2 to 4) are introduced to discharge the energy storage elements, so as to avoid the lack of energy release circuit, which would cause the gate voltage of the SiC MOSFET to rise and cause the switching transistor to turn on falsely.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A SiC MOSFET isolated drive circuit, characterized in that, include, Power amplifier circuit module, used to amplify PWM control signals; The DC blocking circuit module includes capacitor C2, which filters out the DC component; Transformer T2 has an input winding (N1) connected to the DC blocking circuit module, and its output side has multiple independent windings (N21-N2n, n=2~4). The level shifting circuit module includes capacitors C11-C1n and diodes D11-D1n, which are connected to the output winding of the transformer to store negative level energy and superimpose it with positive level energy. The charging circuit module and the discharging circuit module include a charging branch and a discharging branch. The charging branch includes diodes D21-D2n and resistors R21-R2n. The discharging branch includes diodes D31-D3n, resistors R31-R3n / R41-R4n and PMOS transistors S1-Sn. The turn-on and turn-off times of the SiC MOSFET are adjusted through the charging and discharging branches. as well as, The energy discharge circuit module includes discharge resistors R3 and R11-R1n, capacitor C2 connected in parallel in the DC blocking circuit module and capacitors C11-C1n in the level transfer circuit module, for rapidly releasing stored energy after PWM blocking.

2. The SiC MOSFET isolated drive circuit according to claim 1, characterized in that: The energy discharge circuit includes a primary discharge resistor R3 connected in parallel across the DC blocking capacitor C2, and secondary discharge resistors R11-R1n connected in parallel across each level transfer capacitor C11-C1n.

3. The SiC MOSFET isolated drive circuit according to claim 2, characterized in that: The discharge circuit module includes a series PMOS transistor (S1-Sn) and a discharge resistor (R31-R3n / R41-R4n). The gate of the PMOS transistor is connected to the output terminal of the level transfer circuit module, and the source is connected to the gate of the SiC MOSFET.

4. The SiC MOSFET isolated drive circuit according to claim 3, characterized in that: The level transfer circuit module stores the negative half-cycle energy of the transformer through capacitors (C11-C1n), and superimposes this energy with the positive level of the transformer during the positive half-cycle, outputting it to the gate of the SiC MOSFET.

5. The SiC MOSFET isolated drive circuit according to claim 4, characterized in that: A damping resistor R2 is provided between the power amplifier circuit module and the DC blocking circuit module to adjust the circuit damping characteristics and suppress the oscillation amplitude.

6. The SiC MOSFET isolated drive circuit according to claim 5, characterized in that: The charging circuit module and the discharging circuit module use the charging resistor (R21-R2n) to adjust the turn-on time of the SiC MOSFET, and the discharging resistor (R31-R3n / R41-R4n) to adjust the turn-off time of the SiC MOSFET.

7. A high step-down ratio flyback power supply, characterized in that: Including the SiC MOSFET isolated drive circuit according to any one of claims 1 to 6, and, The input side has n power units (n = 2 to 4) connected in series. Each unit includes a SiC MOSFET switch (Q1-Qn), a transformer primary winding (N11-N1n), an RCD snubber circuit (C21-C2n, R11-R1n, D11-D1n), and voltage equalization capacitors (C1-Cn). The output of the multi-channel isolation drive circuit drives the SiC MOSFET of each power unit respectively.

8. The high buck ratio flyback power supply according to claim 7, characterized in that: The RCD absorption circuit of each power unit consists of capacitors (C21-C2n), resistors (R11-R1n) and diodes (D11-D1n), and is used to absorb the leakage inductance energy of the transformer.

9. A drive control method, characterized in that: The SiC MOSFET isolation drive circuit according to any one of claims 1 to 6 includes the following steps: The PMW signal is amplified by power and then converted into an alternating square wave by a transformer. The negative half-cycle energy is stored through a level transfer circuit and superimposed onto the driving voltage during the positive half-cycle. During PMW blocking, the energy of the energy storage capacitor is released within ≤10μs through the bleed resistors (R3, R11-R1n), causing the gate voltage to drop below the SiC MOSFET turn-on threshold.

10. The SiC MOSFET isolated drive circuit and high buck ratio flyback power supply according to claim 9, characterized in that: The discharge action ensures that the gate voltage remains ≤2V after the ripple is blocked.

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