A driving circuit and a switching power supply

Abstract

This invention discloses a driving circuit and a switching power supply. The driving circuit includes: a primary winding and a first output circuit connected thereto; a secondary winding and a second output circuit connected thereto; one end of the primary winding and one end of the secondary winding are opposite terminals; both the first and second output circuits include: a first charge storage unit, a first diode, a first MOSFET, a voltage limiting circuit, and a negative voltage module. One end of the negative voltage module and the drain of the first MOSFET are simultaneously connected to one end of the corresponding secondary winding, and the other end of the negative voltage module is connected to the gate of the driven switching transistor. The first end of the voltage limiting circuit and the cathode of the first diode are simultaneously connected to the other end of the corresponding secondary winding, and the second end of the voltage limiting circuit is simultaneously connected to one end of the first charge storage unit and the gate of the first MOSFET. The anode of the first diode, the other end of the first charge storage unit, and the source of the first MOSFET are connected together to connect to the source of the driven switching transistor. This invention provides a low-cost and stable SiC driving circuit solution.

Description

Technical Field

[0001] This invention belongs to the field of power electronics, and specifically relates to a drive circuit and a switching power supply. Background Technology

[0002] With the development of power electronics technology, SiC MOSFETs have been widely used in many fields such as car charging, photovoltaic power generation, rail transportation, and data centers due to their advantages such as high voltage withstand, fast switching speed, and low reverse recovery. However, SiCMOS transistors have a low gate drive voltage threshold, making them susceptible to interference, and require stable negative voltage turn-off during application. Using an integrated negative voltage isolation driver IC is costly, has limited drive capability, and for half-bridge topologies, additional power supply costs are required.

[0003] like Figure 1 The diagram shown is a schematic of a conventional transformer drive scheme, which includes a transformer isolation drive and a negative voltage module. When the drive signal is turned off, a negative voltage circuit is formed through a transistor. This transformer isolation drive scheme is a low-cost scheme, but the negative voltage value exceeds the withstand voltage limit of the SiC MOSFET, and it is difficult to achieve negative voltage turn-off during the dead time, resulting in low reliability.

[0004] Figure 2 This existing transformer drive improvement scheme also has shortcomings, including duty cycle loss, large drive current, and slow switching speed. Specifically: due to the transistor's tailing effect, although it can maintain a negative voltage drive signal during the dead time, it also exhibits a loss of drive duty cycle because the transistor cannot be turned off in time when the drive voltage rises. In addition, during high-frequency drive, when the transformer drive voltage changes from low to high, the transistor's tailing effect causes the current loop formed by the transformer T1 winding S1-transistor Qa-diode Da1 to generate additional drive current. The transistor's tailing effect leads to a large drive current, which is a huge burden on the transformer's preceding drive circuit, thus slowing down the switching speed.

[0005] Patent CN 116388534 A proposes an isolated SiC drive circuit. In this circuit, the secondary side of the drive transformer forms a loop through two resistors, which leads to a large drive current and increases the burden on the front-end. Furthermore, when the circuit is turned off, it relies on the gate voltage of the drive switch u1 to turn on the discharge switch Q1, thus forming a discharge loop. When the gate voltage of the drive switch u1 drops below the threshold (i.e., after u1 is turned off), the discharge switch is also turned off. Therefore, it is impossible to provide a negative voltage to the drive switch during the dead time, resulting in insufficient ability to maintain a negative voltage during the dead time, which leads to large switching losses. In addition, the gate stress of the NPN MOS used to maintain the negative voltage in this scheme is the same as that of the SiC MOS (SiC can reach a maximum of 22V), which puts great pressure on the selection of this MOS.

[0006] Therefore, there is an urgent need to provide a low-cost and stable SiC driving circuit solution that can fully utilize the excellent performance of SiC while bringing higher economic benefits. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a solution that at least partially solves one of the technical problems existing in the prior art.

[0008] As a first aspect of the present invention, the technical solution of the provided driving circuit embodiment is as follows:

[0009] A driving circuit includes: a transformer core; a primary winding wound around the transformer core for inputting a driving signal source; a first secondary winding wound around the transformer core and a first output circuit connected thereto; a second secondary winding wound around the transformer core and a second output circuit connected thereto; one end of the first secondary winding and one end of the second secondary winding are opposite ends to each other.

[0010] The first output circuit and the second output circuit have the same structure, both including:

[0011] The system comprises a first charge storage unit, a first diode, a first MOSFET, a voltage limiting circuit, and a negative voltage module. One end of the negative voltage module and the drain of the first MOSFET are simultaneously connected to one end of the corresponding secondary winding. The other end of the negative voltage module is used to connect to the gate of the driven switching transistor. The first end of the voltage limiting circuit and the cathode of the first diode are simultaneously connected to the other end of the corresponding secondary winding. The second end of the voltage limiting circuit is simultaneously connected to one end of the first charge storage unit and the gate of the first MOSFET. The anode of the first diode, the other end of the first charge storage unit, and the source of the first MOSFET are connected together to connect to the source of the driven switching transistor.

[0012] Each output circuit forms a discharge circuit to the gate capacitance of the corresponding driven switch through the conduction of the corresponding first MOS transistor, and generates a negative voltage drive signal to the corresponding driven switch during the non-conducting time.

[0013] At the moment the drive signal source is turned off, the negative voltage module of each output circuit, as well as the corresponding secondary winding, voltage limiting circuit, and first charge storage unit, form a first discharge circuit for the gate capacitance of the corresponding driven switch. At the same time, the voltage limiting circuit stabilizes the drive voltage of the corresponding first MOS transistor and rapidly charges the corresponding first charge storage unit. The charge stored in the corresponding first charge storage unit maintains the charge required for the corresponding first MOS transistor to conduct during the drive dead time.

[0014] Preferably, the first charge storage unit is a capacitor.

[0015] Preferably, the voltage limiting circuit includes a Zener diode and a resistor. The cathode of the Zener diode is connected to the first terminal of the voltage limiting circuit, the anode of the Zener diode is connected to one terminal of the resistor, and the other terminal of the resistor is connected to the second terminal of the voltage limiting circuit.

[0016] Preferably, the voltage limiting circuit includes two resistors, one of which has its first end connected to the first and second ends of the voltage limiting circuit, and the other resistor has its first end connected to the second end of the voltage limiting circuit. The other resistor has its second end connected to the junction point of the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.

[0017] Preferably, the negative pressure module includes a capacitor and a resistor, with one end of the capacitor connected to one end of the negative pressure module and the other end connected to one end of the resistor, and the other end of the resistor connected to the other end of the negative pressure module.

[0018] Furthermore, the negative voltage module also includes a Zener diode, with the cathode of the Zener diode connected to one end of the negative voltage module and the anode connected to the other end of the capacitor.

[0019] Furthermore, the negative voltage module also includes a diode, with the cathode of the diode connected to one end of the negative voltage module and the anode connected to the other end of the resistor.

[0020] Furthermore, the driving circuit also includes a resistor, one end of which is connected to the connection point of the other end of the negative voltage module, the other end of which is connected to the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.

[0021] Furthermore, the driving circuit also includes two Zener diodes, one of which has its cathode connected to the other end of the negative voltage module and its anode connected to the anode of the other Zener diode, and the other Zener diode has its cathode connected to the junction of the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.

[0022] Furthermore, the selection of the first MOSFET satisfies the requirement that the first MOSFET operates in the variable resistance region during the dead time between the high-level and low-level switching of the input drive signal source.

[0023] As a second aspect of the present invention, the technical solution of the provided switching power supply embodiment is as follows:

[0024] A switching power supply, wherein the switching power supply adopts a half-bridge topology, characterized in that: the switching power supply includes the driving circuit described in any one of the first aspects above.

[0025] The driving circuit of this invention includes two complementary output circuits. The specific working principle will be analyzed in detail with reference to specific embodiments. The beneficial effects of this invention are as follows:

[0026] 1. When the input drive signal source of the drive circuit in this embodiment of the invention is switched to a low level, the voltage across the first winding is zero, the voltage across the corresponding first charge storage unit rises and the corresponding first MOS transistor is stably turned on through the corresponding voltage limiting circuit, which can provide a stable and reliable negative voltage drive signal for the corresponding driven switch transistor within the dead time, thus achieving high reliability.

[0027] 2. When the input drive signal source of the drive circuit in the embodiment of the present invention is switched to a low level, the voltage across the first winding is zero. Through the stable conduction of the corresponding first MOS transistor, the negative voltage module provides a negative drive voltage to the corresponding driven switching transistor, thereby achieving fast switching speed, reducing switching losses, and meeting the requirements of high-frequency design.

[0028] 3. In the driving circuit of this embodiment, a first charge storage unit is provided in the discharge circuit of the gate capacitor of each driven switch. The switching speed can be adjusted by adjusting the magnitude of the charge storage power supply of the first charge storage unit or the impedance of the discharge circuit.

[0029] 4. The driving circuit of this embodiment does not add an extra current loop, thus maintaining low driving loss and strong driving capability;

[0030] 5. The driving circuit of this embodiment of the invention uses transformer isolation driving, which does not require additional power supply and has low cost. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a conventional transformer drive scheme.

[0032] Figure 2 An improvement scheme for existing transformer drives;

[0033] Figure 3 This is a circuit diagram of a first specific embodiment of the driving circuit of the present invention;

[0034] Figure 4 for Figure 3 Waveform diagram of the drive circuit;

[0035] Figure 5 This is a second specific implementation circuit diagram of the driving circuit of the present invention. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] It should be understood that in the specification, claims, and drawings, when a step is described as continuing into another step, the step may directly continue into that other step or be continued into that other step through a third step; when an element / unit is described as "continuing" into another element / unit, the element / unit may be "directly connected" to that other element / unit or "connected" to that other element / unit through a third element / unit.

[0040] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions thereof will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0041] The inventive concept of this application is to set up two complementary output circuits in the driving circuit. Each output circuit is connected to a transformer secondary winding. Each output circuit includes a negative voltage module, a negative voltage clamping MOSFET (i.e., the first MOSFET), a negative voltage clamping diode (i.e., the first diode), a voltage limiting circuit, and a charge storage unit (i.e., the first charge storage unit). Each output circuit forms a fast discharge circuit for the gate capacitance of the corresponding driven switch through the conduction of the corresponding negative voltage clamping MOSFET, and forms a negative voltage driving signal for the corresponding driven switch during the non-conducting time. When the driving signal source is turned off, the negative voltage module, the corresponding secondary winding, the voltage limiting circuit, and the first charge storage unit of each output circuit form a first discharge circuit for the gate capacitance of the corresponding driven switch. The voltage limiting circuit stabilizes the driving voltage of the negative voltage clamping MOSFET and rapidly charges the first charge storage unit. The charge stored in the first charge storage unit maintains the charge required for the negative voltage clamping MOSFET to conduct during the driving dead time.

[0042] Based on the above inventive concept, the present invention provides a driving circuit, including: a transformer core; a primary winding for inputting a driving signal source; a first primary winding and a first output circuit connected thereto; a second secondary winding and a second output circuit connected thereto; one end of the first secondary winding and one end of the second secondary winding are opposite ends to each other;

[0043] The first output circuit and the second output circuit have the same structure, both including:

[0044] The system comprises a first charge storage unit, a first diode, a first MOSFET, a voltage limiting circuit, and a negative voltage module. One end of the negative voltage module and the drain of the first MOSFET are simultaneously connected to one end of the corresponding secondary winding. The other end of the negative voltage module is used to connect to the gate of the driven switch. The first end of the voltage limiting circuit and the cathode of the first diode are simultaneously connected to the other end of the corresponding secondary winding. The second end of the voltage limiting circuit is simultaneously connected to one end of the first charge storage unit and the gate of the first MOSFET. The anode of the first diode, the other end of the first charge storage unit, and the source of the first MOSFET are connected together to connect to the source of the driven switch.

[0045] Each output circuit forms a fast discharge circuit for the gate capacitance of the corresponding driven switch through the conduction of the corresponding first MOS transistor, and generates a negative voltage drive signal for the corresponding driven switch during the non-conducting time.

[0046] At the moment the drive signal source is turned off, the negative voltage module of each output circuit, as well as the corresponding secondary winding, voltage limiting circuit, and first charge storage unit, form a first discharge circuit for the gate capacitance of the corresponding driven switch. At the same time, the voltage limiting circuit stabilizes the drive voltage of the corresponding first MOS transistor and rapidly charges the corresponding first charge storage unit. The charge stored in the corresponding first charge storage unit maintains the charge required for the corresponding first MOS transistor to conduct during the drive dead time.

[0047] Since one end of the first stage winding and one end of the second stage winding are opposite to each other, the first driving voltage provided by the first output circuit and the second driving voltage provided by the second output circuit are symmetrical and complementary driving signals. Taking the first driving voltage provided by the first output circuit as an example, the specific explanation is as follows:

[0048] When the input drive signal source is high, the first primary winding, the corresponding negative voltage module, the gate capacitor of the corresponding driven switch and the corresponding first diode constitute the first drive circuit to provide the first drive voltage.

[0049] When the input drive signal source switches to a low level, the voltage across the primary winding is zero. The gate capacitor of the corresponding driven switch, the corresponding negative voltage module, the primary winding, the corresponding voltage limiting circuit, and the corresponding first charge storage unit form a first loop. The gate capacitor of the corresponding driven switch discharges, and the corresponding first charge storage unit charges, causing the voltage across the first charge storage unit to rise and stably turn on the corresponding first MOS transistor through the corresponding voltage limiting circuit. This allows the corresponding negative voltage module to provide a negative drive voltage to the corresponding driven switch.

[0050] It should be noted that in practical applications, by controlling the emission time of the drive signal source input to the primary winding, a dead zone can be created between the two complementary drive signals, thereby preventing the two switching transistors in the half-bridge circuit from burning out due to simultaneous conduction.

[0051] Figure 3 This is a circuit diagram of a first specific embodiment of the driving circuit of the present invention, wherein:

[0052] The primary winding is P1, the first secondary winding is S1, the second secondary winding is S2, the driven switch connected to the first output circuit is Sa1, and the driven switch connected to the second output circuit is Sa2.

[0053] The first charge storage unit in the first output circuit is a capacitor Ca0, the first diode is Da1, and the first MOSFET is Sa0; the voltage limiting circuit in the first output circuit includes a Zener diode Da0 and a Zener diode Ra0; the negative voltage module in the first output circuit includes a capacitor Ca1, a resistor Ra1, a Zener diode Da2, and a diode Da3.

[0054] The first charge storage unit in the second output circuit is capacitor Cb0, the first diode is Db1, and the first MOSFET is Sb0; the voltage limiting circuit in the second output circuit includes Zener diodes Db0 and Rb0; the negative voltage module in the second output circuit includes capacitor Cb1, resistor Rb1, Zener diode Db2, and diode Db3.

[0055] Figure 4 for Figure 3 The waveform diagram of the driving circuit shows that PWMSa1 is the first driving voltage of 120kHz output by the first output circuit, and PWMSa0 is the driving voltage of the negative clamp MOSFET Sa0 in the first output circuit.

[0056] The following combination Figure 4 Waveform diagram Figure 3 A detailed analysis of the circuit's operating principle during one duty cycle is provided.

[0057] In the first stage, when the secondary winding S1 of the transformer is under positive drive voltage, the secondary winding S1, together with the negative voltage module, the gate capacitor of the switching transistor Sa1, and the negative voltage clamping diode Da1, forms the first drive circuit and outputs the first drive voltage V0 required by the switching transistor Sa1. The first drive voltage V0 is the voltage across the secondary winding S1 minus the voltage across the negative voltage module. Its advantage is that there are no resistive devices in the drive circuit, the loss is small, and the driving capability requirement of the transformer primary side can be reduced.

[0058] It should be noted that capacitor Ca1 will be charged in the first one or two cycles before the drive circuit starts working. In the subsequent normal operation, it is assumed that the voltage across capacitor Ca1 is a stable voltage, and the current during the charging and discharging process is relatively small. The driving process hardly consumes the charge in capacitor Ca1, so its discharge process does not need to be considered.

[0059] In the second stage, when the positive drive voltage of the transformer secondary winding S1 turns to 0, this is the dead time. The voltage across the transformer secondary winding S1 is zero. The gate capacitor of the switch Sa1, the negative voltage module, the transformer secondary side S1, the Zener diode Da0, the current limiting resistor Ra0, and the Zener capacitor Ca0 form the first discharge circuit for the gate capacitor of the switch Sa1 at the moment when the drive voltage of the switch Sa1 is turned off, and rapidly charge the Zener capacitor Ca0. The charge stored in the Zener capacitor Ca0 maintains the charge required for the negative voltage clamp MOSFET Sa0 to conduct during the drive dead time. The Zener diode Da0 and the current limiting resistor Ra0 stabilize the drive voltage of the negative voltage clamp MOSFET Sa0.

[0060] In the third stage, when the voltage of the stabilizing capacitor Ca0 reaches the conduction threshold Vth of the negative voltage clamping MOSFET Sa0, the first output circuit forms a rapid discharge circuit for the gate capacitor of the switching transistor Sa1 through the conduction of the negative voltage clamping MOSFET Sa0. Furthermore, due to the presence of capacitor Ca1... Figure 3 With a voltage that is positive on the left and negative on the right, the negative voltage clamping MOSFET Sa0 will generate a negative voltage drive signal V1 for Sa1 during the dead time after it is turned on. The advantage of this negative voltage control scheme is that the charge stored in the Zener capacitor Ca0 keeps the negative voltage clamping MOSFET Sa0 on during the dead time, providing a reliable negative voltage with high reliability.

[0061] Furthermore, the selection of the first MOSFET satisfies the requirement that the negative voltage clamp MOSFET Sa0 operates in the variable resistance region during the dead time between the high and low level switching of the input drive signal source, in order to avoid current spikes in the discharge circuit.

[0062] In the fourth stage, when the secondary winding S1 connected to the first output circuit is in negative conduction voltage, the secondary winding S1, together with the Zener diode Da0, the current limiting resistor Ra0, and the Zener capacitor Ca0, provides driving charge for the negative voltage clamping MOSFET Sa0. The negative voltage clamping MOSFET Sa0 is fully turned on and forms a second discharge circuit with the gate capacitor of the negative voltage module to the switching transistor Sa1, forming a stable negative voltage driving voltage V2.

[0063] Figure 3 The Zener diode Da0, current-limiting resistor Ra0, and Zener capacitor Ca0 constitute the driving circuit for the negative voltage clamp MOSFET Sa0. This circuit stabilizes the turn-on of the negative voltage clamp MOSFET Sa0 while filtering out false turn-on caused by high-frequency noise. It also provides adjustable driving voltage for the selection of the negative voltage clamp MOSFET.

[0064] In practice, the driving voltage change rate can be adjusted by adjusting the voltage limit value of the Zener diode Da0, the capacitance value of the Zener capacitor Ca0, or the resistance value of the current limiting resistor Ra0, so as to improve the driving speed of the switching transistor Sa1.

[0065] In addition, it should be noted that, Figure 3 In the circuit, Da2 is a Zener diode used to form a stable negative voltage drive signal V1; Da3 is a discharge diode that provides a discharge circuit for the gate capacitor of the switching transistor Sa1, enabling the rapid discharge of the gate capacitor of the switching transistor Sa1; Ra2 is an anti-static resistor for the switching transistor Sa1; a pair of Zener diodes connected in reverse series between the gate and source of the switching transistor Sa1 are overshoot protection devices to prevent damage to the switching transistor Sa1 due to excessively high or low drive voltage.

[0066] Figure 5 This is a second specific implementation circuit diagram of the driving circuit of the present invention, and... Figure 3 The difference lies in the following: the voltage limiting circuit includes a first voltage divider resistor Ra01 / Rb01 and a second voltage divider resistor Ra02 / Rb02 connected in series. The first end of the first voltage divider resistor is connected to the first end of the voltage limiting circuit, and the second end of the second voltage divider resistor is also connected to the second end of the voltage limiting circuit. The second end of the second voltage divider resistor is connected to the connection point of the anode of the first diode in the corresponding output circuit, the other end of the first charge storage unit, and the source of the first MOSFET. The second voltage divider resistor is used to provide a suitable driving voltage for the negative voltage clamp MOSFET Sa0, and the first voltage divider resistor Ra01 is used for current limiting. The first voltage divider resistor and the voltage regulator capacitor Ca0 also form an RC filter circuit to filter out high-frequency noise interference and prevent the corresponding first MOSFET from being turned on incorrectly. The second voltage divider resistor Ra02 and the voltage regulator capacitor Ca0 also form a discharge circuit, which must ensure that the voltage regulator capacitor Ca0 can provide sufficient charge during the dead time to keep the negative voltage clamp MOSFET Sa0 on.

[0067] This invention also provides a switching power supply, which adopts a half-bridge topology and includes any of the aforementioned driving circuits.

[0068] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention. For those skilled in the art, several equivalent substitutions, improvements, and modifications can be made without departing from the spirit and scope of the present invention. These equivalent substitutions, improvements, and modifications should also be considered within the protection scope of the present invention. Further details will not be provided here, and the protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A drive circuit characterized by comprising: The application relates to a driving circuit for driving a plurality of switches, comprising: a transformer primary winding for inputting a driving signal source; a first secondary winding and a first output circuit connected thereto; and a second secondary winding and a second output circuit connected thereto; one end of the first secondary winding and one end of the second secondary winding are mutually named ends; the first output circuit and the second output circuit have the same structure and each comprise: a first charge storage unit, a first diode, a first MOS tube, a voltage limiting circuit and a negative voltage module, one end of the negative voltage module and the drain of the first MOS tube are connected to one end of the corresponding secondary winding, the other end of the negative voltage module is used for connecting the gate of the driven switch tube, the first end of the voltage limiting circuit and the cathode of the first diode are connected to the other end of the corresponding secondary winding, the second end of the voltage limiting circuit is connected to the first charge storage unit and the gate of the first MOS tube, the anode of the first diode, the other end of the first charge storage unit and the source of the first MOS tube are connected together and used for connecting the source of the driven switch tube; each output circuit forms a discharge loop for the gate capacitor of the corresponding driven switch tube through the conduction of the corresponding first MOS tube, and forms a negative voltage driving signal for the corresponding driven switch tube in the non-conduction time of the corresponding driven switch tube; the negative voltage module of each output circuit, the corresponding secondary winding, the voltage limiting circuit and the first charge storage unit form a first discharge loop for the gate capacitor of the corresponding driven switch tube at the turn-off moment of the driving signal source, the voltage limiting circuit stabilizes the driving voltage of the corresponding first MOS tube, and the corresponding first charge storage unit is rapidly charged, and the charge stored in the corresponding first charge storage unit maintains the conduction of the corresponding first MOS tube in the driving dead time.

2. The drive circuit of claim 1, wherein: The first charge storage unit is a capacitor.

3. The drive circuit of claim 1, wherein: The voltage limiting circuit comprises a voltage stabilizing diode and a resistor, the cathode of the voltage stabilizing diode is connected to the first end of the voltage limiting circuit, the anode of the voltage stabilizing diode is connected to one end of the resistor, and the other end of the resistor is connected to the second end of the voltage limiting circuit.

4. The drive circuit of claim 1, wherein: The voltage limiting circuit comprises two resistors, one end of one of the resistors is connected to the first end of the voltage limiting circuit, the second end of the voltage limiting circuit and the first end of the other resistor are connected together, and the second end of the other resistor is connected to the connection point of the anode of the first diode, the other end of the first charge storage unit and the source of the first MOS tube.

5. The drive circuit of claim 1, wherein: The negative voltage module comprises a capacitor and a resistor, one end of the capacitor is connected to one end of the negative voltage module, the other end of the capacitor is connected to one end of the resistor, and the other end of the resistor is connected to the other end of the negative voltage module.

6. The drive circuit of claim 5, wherein: The negative voltage module further comprises a voltage stabilizing diode, the cathode of the voltage stabilizing diode is connected to one end of the negative voltage module, and the anode of the voltage stabilizing diode is connected to the other end of the capacitor.

7. The drive circuit according to claim 5 or 6, characterized in that: The negative voltage module further comprises a diode, the cathode of the diode is connected to one end of the negative voltage module, and the anode of the diode is connected to the other end of the resistor.

8. The drive circuit of claim 1, wherein: The driving circuit further comprises a resistor, one end of the resistor is connected to the other end of the negative voltage module, and the other end of the resistor is connected to the connection point of the anode of the first diode, the other end of the first charge storage unit and the source of the first MOS tube.

9. The drive circuit according to claim 1 or 8, characterized in that: The driving circuit further comprises two voltage stabilizing diodes, one of which has its cathode connected to the other end of the negative voltage module, and its anode connected to the anode of the other voltage stabilizing diode, and the other voltage stabilizing diode has its cathode connected to the anode of the first diode, the connection point of the other end of the first charge storage unit and the source of the first MOS transistor.

10. The drive circuit of claim 1, wherein: The first MOS transistor is selected to satisfy the condition that the first MOS transistor works in the variable resistance region during the dead time of the input driving signal source between the high level and the low level switching.

11. A switched mode power supply employing a half bridge topology characterised in that: The switching power supply comprises the driving circuit according to any one of claims 1 to 10.

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