Negative voltage driving circuit for silicon carbide mosfet, switching power converter and device

Abstract

The application relates to the technical field of semiconductors, and provides a negative voltage driving circuit suitable for a silicon carbide MOSFET, a switching power supply converter and equipment, wherein the circuit comprises: a control module configured to generate a first control signal, a second control signal and a third control signal in response to a PWM control signal; a switching module comprising a first switch tube, a second switch tube and a third switch tube; when the PWM control signal is a first level, the first and third switch tubes are turned on, the second switch tube is turned off, a negative feedback voltage charges a capacitor, negative charges are stored in the capacitor, and a turn-off voltage is equal to the negative feedback voltage; when the PWM control signal is a second level, the first and third switch tubes are turned off, the second switch tube is turned on, and the voltage stored on the capacitor is output to a driving module as a turn-off voltage for turning off the silicon carbide MOSFET. The multiplexing feedback winding voltage effectively suppresses the false triggering of the silicon carbide MOSFET during turn-off without the need for an additional independent negative voltage generation circuit.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a negative voltage drive circuit, switching power converter, and device suitable for silicon carbide MOSFETs. Background Technology

[0002] Silicon carbide (SiC) MOSFETs, as representative devices of third-generation wide-bandgap semiconductors, are widely used in applications requiring high power density and high efficiency, such as new energy vehicles, industrial power supplies, and photovoltaic inverters, due to their excellent characteristics such as high temperature resistance, high voltage resistance, fast switching speed, and low on-resistance. Compared with traditional silicon (Si)-based MOSFETs, SiC MOSFETs can operate at higher switching frequencies, which helps to reduce the size of passive components in the system and improve power density. However, their inherently low gate threshold voltage (Vth) and small gate-source charge (Qgs) product also result in relatively weak gate immunity, especially in the off state, where they are prone to false turn-on due to voltage noise or crosstalk in the circuit, affecting the reliability and safety of the system.

[0003] To suppress false triggering of silicon carbide MOSFETs during the turn-off phase, existing technologies typically employ two approaches: First, increasing the gate drive resistance or adding an additional parallel gate capacitor to slow down the voltage change rate during switching, thereby enhancing anti-interference capabilities. However, this method directly sacrifices the high-frequency switching performance of the silicon carbide MOSFET, increasing switching losses, which contradicts its original purpose. Second, designing an independent negative voltage turn-off circuit applies a negative voltage (negative Vgs) to the gate during turn-off to increase the voltage margin in the turn-off state. While this method effectively improves turn-off reliability, it requires an additional negative voltage generation circuit (such as a charge pump), increasing system complexity, cost, and layout area, and potentially introducing new noise sources and power consumption. Summary of the Invention

[0004] In view of this, embodiments of this application provide a negative voltage drive circuit, a switching power converter, and an apparatus suitable for silicon carbide MOSFETs to address the technical deficiencies existing in the prior art.

[0005] In a first aspect, embodiments of this application provide a negative voltage driving circuit suitable for silicon carbide MOSFETs, including: a control module, a switching module, a capacitor, and a driving module;

[0006] The control module is configured to generate a first control signal, a second control signal, and a third control signal in response to a PWM control signal.

[0007] The switching module includes a first switching transistor, a second switching transistor, and a third switching transistor;

[0008] The first control terminal of the first switch receives the first control signal, the first path terminal is connected to the negative feedback voltage node, and the second path terminal is connected to the first node.

[0009] The second control terminal of the second switch receives the second control signal, the third path terminal is connected to the first node, and the fourth path terminal is connected to the reference ground.

[0010] The third control terminal of the third switch receives the third control signal, the fifth path terminal is connected to the first node, and the sixth path terminal is connected to the first terminal of the capacitor.

[0011] The second terminal of the capacitor is connected to a reference ground.

[0012] The input terminal of the driving module is connected to the first terminal of the capacitor to obtain the turn-off voltage, and the output terminal of the driving module is connected to the gate of the silicon carbide MOSFET.

[0013] When the PWM control signal is at the first level, the first control signal and the third control signal control the first switch and the third switch to be turned on, and the second control signal controls the second switch to be turned off, so that the capacitor is charged with negative feedback voltage, and the turn-off voltage is equal to the negative feedback voltage.

[0014] When the PWM control signal is at the second level, the first control signal and the third control signal control the first switch and the third switch to turn off, the second control signal controls the second switch to turn on, and the voltage stored on the capacitor is output to the drive module as the turn-off voltage to turn off the silicon carbide MOSFET.

[0015] In one possible implementation, the first switch and the third switch form a series circuit, with one end of the series circuit connected to the negative feedback voltage node and the other end connected to the first terminal of the capacitor.

[0016] In one possible implementation, a discharge prevention module is also included, with one end connected to the first node and the other end connected to the first terminal of the capacitor, for preventing the capacitor from discharging through the switching module when the second switch is turned on.

[0017] In one possible implementation, the anti-discharge module includes a diode, the anode of which is connected to a first terminal of the capacitor, and the cathode of which is connected to the first node.

[0018] In one possible implementation, the control module includes an inverter, the input of which receives the PWM control signal and the output of which outputs the second control signal; the first control signal and the third control signal are the PWM control signal.

[0019] In one possible implementation, the first switch, the second switch, and the third switch are all N-type MOSFETs.

[0020] In one possible implementation, the negative feedback voltage originates from the feedback network of the primary side of the transformer in a switching power converter containing the silicon carbide MOSFET, and the negative feedback voltage is negative when the silicon carbide MOSFET is turned on.

[0021] In one possible implementation, the drive module is further configured to receive a turn-on voltage, and when the PWM control signal is at a first level, the drive module outputs the turn-on voltage to the gate of the silicon carbide MOSFET.

[0022] Secondly, embodiments of this application also provide a switching power converter, including a transformer, a main power switching transistor, a feedback network, and the negative voltage drive circuit provided in the first aspect;

[0023] The main power switch is the silicon carbide MOSFET, with its drain connected to the primary winding of the transformer and its source connected to the current sensing resistor.

[0024] The feedback network is used to sample the voltage associated with the primary winding of the transformer and generate the negative feedback voltage.

[0025] Thirdly, embodiments of this application also provide an electronic device, including the switching power converter provided in the second aspect.

[0026] The technical solution provided in this application uses a control module to precisely control a switching module consisting of three switching transistors based on a PWM control signal, utilizing the existing negative feedback voltage node on the primary side of the system as a negative voltage source. When the silicon carbide MOSFET needs to be turned on (PWM at the first level), the first and third switching transistors are controlled to turn on, charging the capacitor with the negative feedback voltage and storing it as a negative turn-off voltage. When it needs to be turned off (PWM at the second level), the second switching transistor is controlled to turn on, outputting the negative voltage stored in the capacitor as the turn-off voltage to the drive module, which applies it to the gate of the silicon carbide MOSFET to achieve negative voltage turn-off. This solution directly obtains and reuses the negative voltage resource from the system, eliminating the need for an additional independent negative voltage generation circuit. While effectively suppressing false triggering of the silicon carbide MOSFET turn-off, it avoids the problems of decreased switching speed and increased conduction losses caused by increasing gate resistance or capacitance. Attached Figure Description

[0027] Figure 1 This is a simplified structural diagram of a negative voltage drive circuit for silicon carbide MOSFETs provided in one embodiment of this application;

[0028] Figure 2 This is a detailed structural diagram of a negative voltage drive circuit suitable for silicon carbide MOSFETs provided in one embodiment of this application;

[0029] Figure 3 This is a waveform timing diagram of a key signal of a negative voltage drive circuit provided in one embodiment of this application;

[0030] Figure 4 This is a schematic diagram of a switching power converter provided in one embodiment of this application. Detailed Implementation

[0031] Many specific details are set forth in the following description to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below.

[0032] The terminology used in one or more embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of one or more embodiments of this application. The singular forms “a” and “the” as used in one or more embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in one or more embodiments of this application refers to and includes any or all possible combinations of one or more associated listed items.

[0033] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this application, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this application, and similarly, second may also be referred to as first. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0034] To facilitate understanding of the technical solutions provided in the embodiments of this application, the following explanations are provided for the nouns and terms involved in one or more embodiments of this application.

[0035] 1. Silicon carbide MOSFET, namely, silicon carbide metal oxide semiconductor field-effect transistor.

[0036] 2. Negative voltage drive refers to applying a voltage lower than the source potential (usually reference ground) to the gate of a power device (such as a MOSFET) when it is necessary to turn off the power device. This is called a negative gate-source voltage (i.e., Vgs < 0).

[0037] 3. Gate charge (Qgs) refers to the amount of charge injected to bring the gate-source voltage of a MOSFET to the threshold value. Qgs is an important component of the total gate charge, specifically referring to the charging charge of the gate-source capacitance.

[0038] 4. Primary-side negative feedback voltage (VFB): In isolated switching power supplies, this is a feedback signal reflecting the output voltage state, sampled from the primary side of the transformer via an auxiliary winding or optocoupler. In certain topologies (such as flyback), this voltage is negative when the main switch is turned on.

[0039] 5. Reference Ground (GND): A common zero-potential reference point defined in the circuit. The voltages of all other nodes are relative to the potential difference at this point. It is different from grounding.

[0040] 6. PWM control signal: A digital signal that controls the switching state or power output of a circuit by adjusting the pulse width. A high level usually represents "on", and a low level represents "off".

[0041] This application provides a negative voltage drive circuit suitable for silicon carbide MOSFETs. This application also relates to a switching power converter and an electronic device, which will be described in detail in the following embodiments.

[0042] Figure 1 A simplified structural diagram of a negative voltage drive circuit for silicon carbide MOSFETs provided in one embodiment of this application.

[0043] Reference Figure 1 As shown, the negative pressure drive circuit may include a control module 10, a switch module 20, a capacitor 30, and a drive module 40.

[0044] In some embodiments, refer to Figure 1 As shown, the switching module 20 may include a first switching transistor, a second switching transistor, and a third switching transistor.

[0045] In some embodiments, refer to Figure 1As shown, the control module 10 is configured to generate a first control signal, a second control signal, and a third control signal in response to a PWM control signal. The first control terminal of the first switch receives the first control signal, its first path terminal N1 is connected to the negative feedback voltage node, and its second path terminal N2 is connected to the first node D1. The second control terminal of the second switch receives the second control signal, its third path terminal N3 is connected to the first node D1, and its fourth path terminal N4 is connected to the reference ground GND. The third control terminal of the third switch receives the third control signal, its fifth path terminal N5 is connected to the first node D1, thereby receiving the signals output from the second path terminal N2 and the fourth path terminal, and its sixth path terminal N6 is connected to the first terminal S1 of a capacitor. The second terminal of the capacitor is connected to S2 and then to the reference ground GND. The input terminal of the drive module 40 is connected to the first terminal S1 of the capacitor 30 to obtain the turn-off voltage, and its output terminal is connected to the gate of the silicon carbide MOSFET.

[0046] Among them, the negative feedback voltage node can generate the primary-side negative feedback voltage, namely VFB.

[0047] In some embodiments, when the PWM control signal received by the control module 10 is at a first level, the first and third control signals control the first and third switching transistors to turn on, and the second control signal controls the second switching transistor to turn off. The negative feedback voltage node charges the capacitor 30, making the turn-off voltage equal to VFB. Specifically, when the PWM control signal is at a first level (high level), the control module 10 responds to this logic, and its internal logic circuit (e.g., a combination of a direct path and an inverter) generates a first control signal (high level), a third control signal (high level), and a complementary second control signal (low level), all in phase with the PWM. The first and third control signals act on the control terminals (gates) of the first and third switching transistors, respectively, driving them into a deep conduction state; while the second control signal controls the second switching transistor to remain reliably off. At this time, VFB introduced from the primary side of the system, which itself is a negative potential during the main power transistor conduction phase of the switching power supply, is applied to the first terminal of the capacitor 30 through the low-resistance path formed by the already conducted first and third switching transistors, charging the capacitor 30. This establishes a stable voltage difference equal to VFB across capacitor 30. At this point, VGL is pulled down to a negative voltage equal to VFB, meaning VGL is established and temporarily stored in capacitor 30. Through this control method, the negative voltage drive circuit of this application intercepts and stores an existing VFB that naturally exists within the system at a specific time period, converting it into a negative bias voltage that can be directly used in the subsequent turn-off phase. This avoids the complexity and cost of adding an independent negative voltage power supply or charge pump circuit to obtain negative voltage in traditional solutions, and also avoids the inevitable decrease in switching speed and increase in switching losses caused by increasing the gate resistance or capacitance to enhance noise immunity. Thus, without sacrificing the high-frequency performance of the silicon carbide MOSFET, reliable negative voltage turn-off preparation is achieved with a minimally simplistic circuit.

[0048] In some embodiments, when the PWM control signal received by the control module 10 is at the second level, the first and third control signals control the first and third switching transistors to turn off, and the second control signal controls the second switching transistor to turn on. The voltage stored on the capacitor is output as the turn-off voltage to the drive module 40 to turn off the silicon carbide MOSFET. Specifically, when the PWM control signal switches to the second level (low level), the internal logic of the control module 10 synchronously flips, and its output first and third control signals become low, while the second control signal jumps to a high level. This transition directly causes the control terminal voltages of the first and third switching transistors to be pulled low, and they quickly switch from the on state to the off state, thereby completely cutting off the connection between the negative feedback voltage node and the capacitor 30, and releasing the clamping of the second terminal of the capacitor to the reference ground; at the same time, the high level of the second control signal drives the second switching transistor to enter the saturation conduction state. At this time, the capacitor 30 cannot discharge because its two ends are physically isolated, and the negative voltage stored on it in the first stage is completely maintained. The negative voltage is directly applied to the first terminal of the capacitor and serves as VGL. Through the established potential reference pointing to ground established by the already turned-on second switch, it is stably output to the drive module 40. The drive module 40 then applies this negative voltage to the gate of the silicon carbide MOSFET, rapidly pulling its gate-source voltage (Vgs) down from the positive voltage to this negative voltage value, thereby achieving efficient negative voltage turn-off. This control method, through precise timing control of the three switch states, allows the circuit to seamlessly and losslessly reuse the temporarily stored negative voltage resources as an effective turn-off driving force at critical moments. This not only ensures the high reliability of the silicon carbide MOSFET in the turn-off state and completely eliminates the risk of mis-turn-on due to interference, but also avoids the forced reduction in switching speed and the resulting additional switching losses in traditional methods, as the entire turn-off action directly utilizes the stored charge energy without relying on increasing the gate resistance or capacitance to delay the turn-off process. This improves the system's anti-interference capability and turn-off reliability while maintaining the inherent high-frequency, high-efficiency operating characteristics of the silicon carbide MOSFET.

[0049] Figure 2 This is a detailed structural diagram of a negative voltage drive circuit for silicon carbide MOSFETs provided in one embodiment of this application.

[0050] in, Figure 2 The negative voltage drive circuit shown is in Figure 1 The circuit structure shown is a refined version with additional components.

[0051] Reference Figure 2As shown, the circuit uses transformer T1 and primary power supply VDD as the main body of power conversion. After the negative feedback voltage node is led out, it is connected to a switching module composed of three N-type MOSFETs: the first switching transistor MN1, the second switching transistor MN2, and the third switching transistor MN3. MN1 is directly controlled by the PWM signal, and MN3 is controlled by the signal inverted by inverter I1. The two work together to conduct during the high level of PWM, charging the storage capacitor Cvgl through the negative feedback voltage node. When PWM is low, MN1 and MN3 are turned off, and MN2 is turned on. At this time, the VCTRL voltage is set to 0, the diode D1 prevents the capacitor charge from flowing back, and the negative voltage stored in the capacitor Cvgl is output as VGL to the driver module. The driver receives VGH and VGL at the same time, generates the corresponding PWMSW signal according to the PWM state, and outputs the corresponding level to the gate of the silicon carbide MOSFET, thereby controlling its on and off. Finally, the current is detected at the output through the sampling resistor, i.e., the current sensing resistor RCS, forming a complete negative voltage turn-off drive and power control loop.

[0052] In some embodiments, the first and third switching transistors form a series circuit, with one end connected to the negative feedback voltage node and the other end connected to the first terminal of a capacitor. Specifically, the first path terminal of the first switching transistor is connected to the negative feedback voltage node, and the fifth path terminal of the third switching transistor is connected to the first terminal of the capacitor Cvgl, thus forming an electrical series structure. This connection method provides a low-impedance series path when both the first and third switching transistors are driven to conduct by their respective control signals during the first level (high level) of the PWM control signal. This allows for efficient and rapid charging of the capacitor Cvgl by the negative feedback voltage node, ensuring that VGL can quickly establish and equalize with VFB.

[0053] In some embodiments, the negative voltage drive circuit may further include an anti-discharge module, one end of which is connected to the first node and the other end of which is connected to the first terminal of the capacitor, for preventing the capacitor from discharging through the control module when the second switch is turned on. In one embodiment, the anti-discharge module may include... Figure 2The diode D1 shown has its anode connected to the first terminal of the capacitor and its cathode connected to the first node. The core of this anti-discharge module lies in the unidirectional conductive device, diode D1, connected in series between the first terminal of the capacitor and the first node. Specifically, the anode of diode D1 is directly connected to the first terminal of capacitor Cvgl, while its cathode is connected to the first node. This connection constitutes a crucial one-way valve. Specifically, when the potential at the first terminal of capacitor Cvgl is higher than the potential at the input terminal of the drive module, the diode conducts in the forward direction, allowing current to flow to the drive module; conversely, it is reverse-biased and cut off the current. When the circuit is in the off-state (i.e., PWM is at the second level, and the second switch is on), the conducting second switch pulls the potential at the first terminal of the capacitor up to near the reference ground. At this time, the input terminal of the drive module may present a different potential due to internal circuitry or load characteristics. Diode D1 is then reliably reverse-biased and cut off because the anode potential is not higher than the cathode potential. This method blocks the potential discharge loop formed by the negative voltage stored on the capacitor through the switching transistor, ensuring that during the turn-off phase, the negative voltage stored in the capacitor can be completely and stably maintained and used entirely for the drive module to turn off the silicon carbide MOSFET, thereby improving the stability and reliability of the turn-off negative voltage and avoiding the risk of weakened turn-off force or failure due to charge loss.

[0054] In some embodiments, the control module may include Figure 2 The inverter I1 shown receives a PWM control signal at its input and outputs a second control signal; the first and third control signals are also PWM control signals. Specifically, the input of inverter I1 directly receives the external PWM control signal, and its output directly outputs a second control signal with a logic level completely opposite to it; simultaneously, the first and third control signals are directly taken from the original PWM control signal itself (or its signal driven by a non-inverting buffer). Based on this connection architecture and the corresponding control logic, when the PWM is high (first level), the first and third control signals are synchronously high, driving the corresponding switching transistors to turn on, while the second control signal output by the inverter is low, ensuring that the relevant switching transistors are turned off; when the PWM turns low (second level), the control logic synchronously and complementaryly flips. The beneficial effect is that, with only a basic inverter unit, two sets of strictly complementary control signals required to drive the switching module (three switching transistors) can be reliably constructed. This greatly simplifies the structure of the control logic circuit, reduces the design and implementation complexity, and ensures the inherent strict synchronization and complementarity between the signals. It avoids the risk that the switching transistors may be turned on simultaneously due to timing deviations or race conditions of the control signals, thereby improving the timing accuracy and operational reliability of the entire negative voltage drive circuit.

[0055] In some embodiments, the negative feedback voltage node originates from the feedback network of the primary winding of the transformer in a switching power converter containing a silicon carbide MOSFET. When the silicon carbide MOSFET is turned on, the negative feedback voltage node is negative. Specifically, this negative feedback voltage node itself presents a negative potential during a specific phase of normal operation of the switching power supply (i.e., when the main power transistor is turned on), eliminating the need for an additional independent negative voltage generation circuit (such as a charge pump or auxiliary winding), thus significantly simplifying the system architecture and reducing overall cost and board area. Simultaneously, since this negative voltage is directly taken from the internal operating node of the system, its voltage amplitude and timing are naturally synchronized with the main power loop, avoiding noise, loss, or timing mismatch issues that may arise from introducing additional circuitry, thereby improving system integration and operational reliability. Without adding any dedicated negative voltage source, the drive requirement for negative voltage turn-off of the silicon carbide MOSFET is efficiently and economically resolved.

[0056] In some embodiments, the drive module 40 is further configured to receive a turn-on voltage, and when the control signal PWM is at the first level, the drive circuit outputs the turn-on voltage to the gate of the silicon carbide MOSFET.

[0057] The aforementioned turn-on voltage is VGH.

[0058] In one embodiment, the drive module 40 is configured with dual power supply voltage input interfaces, one receiving VGL generated by the negative voltage drive circuit and the other receiving VGH from the system power supply. Internally, it includes a circuit that directly or indirectly controls the output selection via a PWM control signal. Specifically, when the PWM control signal is at a first level (high level), the output selection circuit switches the output of the drive circuit to the VGH channel, thereby applying VGH to the gate of the silicon carbide MOSFET, turning it on. Simultaneously, the high level of the PWM also triggers the negative voltage generation circuit to charge the capacitor in preparation for negative voltage. Without adding an additional independent drive chip or complex external circuitry, this method achieves both highly reliable turn-off using the generated negative voltage and efficient turn-on using a standard positive voltage, thus providing a complete drive method for silicon carbide MOSFETs with high responsivity and high integration.

[0059] The following provides a detailed description of the negative voltage drive circuit for silicon carbide MOSFETs provided in the embodiments of this application through a complete example.

[0060] Reference Figure 2As shown, the circuit may include a control module, a switching module (containing NMOS transistors MN1, MN2, and MN3), a capacitor Cvgl, a diode D1, and a driver module. The control module includes an inverter I1, whose input receives the system PWM signal and whose output serves as the second control signal; the PWM signal itself is directly used as the first and third control signals. The source of MN1 is connected to VFB generated by the auxiliary winding of the transformer, and its drain, along with the drain of MN2, the source of MN3, and the positive terminal of capacitor Cvgl, is connected to VGL; the source of MN2, the drain of MN3, and the negative terminal of Cvgl are connected to the reference ground. VGL is connected to the negative voltage input of the driver chip via diode D1 (anode connected to VGL), and the positive voltage input of the driver chip is connected to 16~18V (VGH), with the output connected to the gate of a silicon carbide MOSFET.

[0061] Combination Figure 2 and Figure 3 As shown, when the PWM signal jumps to a high level (at time t1), the first and third control signals simultaneously go high, driving MN1 and MN3 to conduct; the second control signal is inverted to low by inverter I1, causing MN2 to turn off. At this time, due to the conduction of the silicon carbide MOSFET, the current in transformer T1 rises, and the VFB induced by the auxiliary winding becomes negative (approximately -1V as shown in the waveform). This negative voltage charges Cvgl through the conducting MN1, while MN3 clamps the negative terminal of Cvgl to ground, causing VGL (the voltage across Cvgl) to be quickly pulled down to -1V, equal to VFB (as shown in the waveform, VGL immediately follows VFB as it decreases). During this stage, the PWM signal controls the drive module to output a 16~18V drive signal to the gate of the silicon carbide MOSFET, making it fully conduct. When the PWM signal jumps to a low level (at time t2), the first and third control signals go low, MN1 and MN3 immediately turn off, cutting off the path of the negative feedback voltage node and releasing Cvgl from ground clamping; simultaneously, the second control signal goes high, driving MN2 to conduct. The conduction of MN2 pulls the VGL node potential up to near ground. Since the capacitor voltage cannot change abruptly, the positive terminal of Cvgl (VGL) maintains a negative voltage of -1V (VGL maintains a stable -1V plateau after t2 in the waveform). At this time, the PWM signal controls the drive module to turn off the silicon carbide MOSFET using the aforementioned negative voltage, thereby achieving reliable negative voltage turn-off. This negative voltage persists throughout the entire PWM low-level period, effectively suppressing turn-off oscillations and false triggering.

[0062] Figure 4 This is a schematic diagram of a switching power converter provided in one embodiment of this application.

[0063] Reference Figure 4As shown, the switching power converter may include a transformer 401, a main power switch 402, a feedback network 403, and a negative voltage drive circuit 404. The negative voltage drive circuit 404 may be a negative voltage drive circuit suitable for silicon carbide MOSFETs provided in any embodiment of this application.

[0064] In some embodiments, the main power switch 402 is a silicon carbide MOSFET, with its drain connected to the primary winding of the transformer 401 and its source connected to a current sensing resistor; the feedback network 403 is used to sample the voltage related to the primary winding of the transformer 401 and generate VFB.

[0065] In one embodiment, the system uses a transformer 401 as the core for energy transmission and isolation. One end of its primary winding is connected to the input voltage, and the other end is connected in series with a silicon carbide MOSFET (402) serving as the main power switch, connected to a reference ground, forming the main power loop. The feedback network 403 generates a VFB (voltage free circuit) reflecting the system's operating state in real time by directly sampling the primary winding voltage or indirectly coupling the auxiliary winding voltage. The negative voltage drive circuit 404 described in this application serves as a dedicated drive unit. Its negative feedback voltage node input is connected to the output of the feedback network 403, its drive output is directly connected to the gate of the silicon carbide MOSFET 402, and its control terminal receives the system's PWM control signal. During operation, the VFB naturally generated by the feedback network 403 during the conduction of the main power switch 402 is captured, stored, and converted into the negative voltage drive signal required for the turn-off phase by the negative voltage drive circuit 404, thereby achieving reliable negative voltage turn-off control of the silicon carbide MOSFET 402. This architecture seamlessly embeds the negative voltage drive circuit into a standard switching power supply topology, creating a highly integrated and fully functional power supply solution. It not only achieves the advantages of "no additional negative pressure source, no sacrifice in response speed, and reliable shutdown", but also realizes the native optimization matching of drive and power circuit at the system level: the VFB provided by the feedback network is naturally synchronized with the main switch state, ensuring the timeliness and accuracy of negative pressure sampling; while the dedicated drive circuit ensures the decisiveness and anti-interference of the shutdown action.

[0066] This application also provides an electronic device, which may include... Figure 4 The switching power converter shown is an example of an electronic device that integrates... Figure 4The switching power converter shown provides a core power supply solution for various high-power applications. For example, in an on-board charger for a new energy vehicle, this converter, serving as a pre-stage PFC or LLC resonant power stage, features a built-in negative voltage drive circuit that ensures stable operation of the main power silicon carbide MOSFETs at switching frequencies up to hundreds of kHz, effectively suppressing switching noise interference and thus improving overall efficiency and reliability. In a high-density server power supply for a data center, this converter, with its high efficiency and compact design, can achieve higher power density while maintaining the preset conversion efficiency. Its reliable negative voltage shutdown mechanism significantly reduces the risk of downtime due to power transistor mis-triggering. Furthermore, this solution is also suitable for industrial motor drives, photovoltaic energy storage converters, and other equipment, providing them with a high-efficiency and robust power core.

[0067] The foregoing has described specific embodiments of this application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0068] The computer instructions include computer program code, which may be in the form of source code, object code, executable file, or certain intermediate forms. The computer-readable medium may include any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium may be appropriately added to or subtracted according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media may not include electrical carrier signals and telecommunication signals.

[0069] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of this application are not limited to the described order of actions, because according to the embodiments of this application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the embodiments of this application.

[0070] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0071] The preferred embodiments disclosed above are merely illustrative of this application. The optional embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the embodiments of this application. These embodiments are selected and specifically described in this application to better explain the principles and practical applications of the embodiments of this application, thereby enabling those skilled in the art to better understand and utilize this application. This application is limited only by the claims and their full scope and equivalents.

Claims

1. A negative voltage drive circuit suitable for silicon carbide MOSFETs, characterized in that, include: Control module, switch module, capacitor and drive module; The control module is configured to generate a first control signal, a second control signal, and a third control signal in response to a PWM control signal. The switching module includes a first switching transistor, a second switching transistor, and a third switching transistor; The first control terminal of the first switch receives the first control signal, the first path terminal is connected to the negative feedback voltage node, and the second path terminal is connected to the first node. The second control terminal of the second switch receives the second control signal, the third path terminal is connected to the first node, and the fourth path terminal is connected to the reference ground. The third control terminal of the third switch receives the third control signal, the fifth path terminal is connected to the first node, and the sixth path terminal is connected to the first terminal of the capacitor. The second terminal of the capacitor is connected to a reference ground. The input terminal of the driving module is connected to the first terminal of the capacitor to obtain the turn-off voltage, and the output terminal of the driving module is connected to the gate of the silicon carbide MOSFET. When the PWM control signal is at the first level, the first control signal and the third control signal control the first switch and the third switch to be turned on, and the second control signal controls the second switch to be turned off, so that the capacitor is charged with negative feedback voltage, and the turn-off voltage is equal to the negative feedback voltage. When the PWM control signal is at the second level, the first control signal and the third control signal control the first switch and the third switch to turn off, the second control signal controls the second switch to turn on, and the voltage stored on the capacitor is output to the drive module as the turn-off voltage to turn off the silicon carbide MOSFET. It also includes an anti-discharge module, one end of which is connected to the first node and the other end of which is connected to the first terminal of the capacitor, used to prevent the capacitor from discharging through the switching module when the second switch is turned on; The anti-discharge module includes a diode, the anode of which is connected to the first terminal of the capacitor, and the cathode of which is connected to the first node.

2. The negative voltage driving circuit according to claim 1, characterized in that, The first switch and the third switch form a series circuit. One end of the series circuit is connected to the negative feedback voltage node, and the other end is connected to the first terminal of the capacitor.

3. The negative voltage driving circuit according to claim 1, characterized in that, The control module includes an inverter, the input of which receives the PWM control signal and the output of which outputs the second control signal; the first control signal and the third control signal are the PWM control signal.

4. The negative voltage driving circuit according to claim 1, characterized in that, The first switch, the second switch, and the third switch are all N-type MOSFETs.

5. The negative voltage driving circuit according to claim 1, characterized in that, The negative feedback voltage comes from the feedback network of the primary side of the transformer in the switching power converter containing the silicon carbide MOSFET. When the silicon carbide MOSFET is turned on, the negative feedback voltage is negative.

6. The negative voltage driving circuit according to claim 1, characterized in that, The drive module is also configured to receive a turn-on voltage, and when the PWM control signal is at the first level, the drive module outputs the turn-on voltage to the gate of the silicon carbide MOSFET.

7. A switching power supply converter, characterized in that, Includes a transformer, a main power switch, a feedback network, and a negative voltage drive circuit as described in any one of claims 1 to 6; The main power switch is the silicon carbide MOSFET, with its drain connected to the primary winding of the transformer and its source connected to the current sensing resistor. The feedback network is used to sample the voltage associated with the primary winding of the transformer and generate the negative feedback voltage.

8. An electronic device, characterized in that, The device body and the switching power converter as described in claim 7.

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