Driving circuit for switching power supply MOSFET

Abstract

A drive circuit for a switching power supply MOSFET comprises a power supply unit, a triangular wave generation circuit unit, a push-pull drive circuit unit, a buck circuit unit, a soft start circuit unit with an adjustable duty ratio, a bootstrap capacitor power-on start circuit unit and a sampling protection circuit unit. The sampling protection circuit unit comprises an IDS overcurrent protection circuit unit and a VGS overvoltage protection circuit unit; the output end of the push-pull driving circuit unit is connected with a to-be-driven MOS tube Q12 through the bootstrap capacitor power-on starting circuit unit, the triangular wave generation circuit unit is connected with the input end of the push-pull driving circuit unit through the soft starting circuit unit, and the input end and the output end of the buck circuit unit are both connected with the bootstrap capacitor power-on starting circuit unit. And the buck circuit outputs power. The invention has the characteristics of good maintainability, low cost, small temperature rise and the like.

Description

Technical Field

[0001] The present invention relates to the field of switching power supplies, and particularly to a driving circuit for a MOSFET in a switching power supply. Background Art

[0002] In current switching power supply designs, driving circuits often adopt integrated circuit designs. However, due to the defects of integrated circuits themselves, there are many problems in such driving circuits designed with integrated circuits as follows: I. Poor stability 1) The manufacturing process of integrated circuits has extremely high requirements for technology. During the manufacturing process of integrated circuits, fluctuations in process parameters may cause changes in the performance and characteristics of integrated circuits. For example, the size and threshold voltage of transistors may not be consistent with the design values. Therefore, for a driving circuit designed with an integrated circuit, the theoretically achievable performance and the actually achievable performance often deviate, resulting in a decrease in overall performance, an increase in power consumption, or abnormal functions, affecting the reliability of the entire circuit; 2) Impurities, particles, or other physical defects may be introduced during the manufacturing process, affecting the performance and reliability of integrated circuits. For example, in a driving circuit designed with an integrated circuit, impurities during the manufacturing process may increase the leakage current of transistors, and may even cause short-circuit or open-circuit faults, resulting in failures of the driving circuit during use, reducing the lifespan and reliability of the switching power supply.

[0003] 3) During the packaging process, due to packaging problems, it may cause failures of integrated circuits during use, reducing the reliability and lifespan of products. For example, in the packaging process of a driving circuit designed with an integrated circuit, poor wire bonding may cause problems in signal transmission of the driving circuit, or defects in the packaging material may allow moisture to invade, affecting the stability of the chip and reducing the performance and reliability of the switching power supply.

[0004] 4) Integrated circuits may be affected by external electromagnetic interference, resulting in signal distortion, misoperation, or abnormal functions. For example, a driving circuit designed with an integrated circuit may be interfered by electromagnetic radiation from other electronic devices, resulting in the abnormal operation of the switching power supply and affecting the performance and reliability of the system.

[0005] 5) Electrostatic discharge may damage integrated circuits. For example, during the manufacturing, transportation, and installation processes of a driving circuit designed with an integrated circuit, electrostatic discharge may cause breakdown of transistors in the driving circuit, short-circuit or open-circuit faults of the circuit, thereby affecting the stability of the switching power supply.

[0006] II. Large temperature rise High temperatures may cause an increase in leakage current and a shortening of the lifespan of transistors in integrated circuits, while low temperatures may affect the startup and performance of integrated circuit chips. For example, in a drive circuit designed with an integrated circuit, due to the concentration of the circuit, it is very easy for the temperature to rise, increasing the leakage current of the transistors in the drive circuit, shortening the service life of the switching power supply, and affecting the stability of the switching power supply.

[0007] III. Poor maintainability Integrated circuits are usually encapsulated in small chip packages, making it extremely difficult to directly access and operate the internal circuits. When a drive circuit designed with an integrated circuit fails, professional equipment and advanced technical means are required to identify the damaged components and replace them to restore the normal operation of the switching power supply. Without the technical support of expensive professional equipment, ordinary technicians usually have to spend a high price to purchase a new integrated circuit directly and replace the entire integrated circuit chip that needs to be repaired to fix the switching power supply.

[0008] Therefore, how to design the drive circuit of the switching power supply to balance the relationship between the volume and performance of the drive circuit of the switching power supply, reduce the impact of temperature on the drive circuit of the switching power supply, and improve the stability of each stage of the drive circuit of the switching power supply (including the manufacturing stage, transportation stage, use stage, etc.), while maximizing the maintainability of the drive circuit of the switching power supply and reducing costs, has always been an urgent problem for technicians in this field. Summary of the Invention

[0009] The object of the present invention is to provide a drive circuit for a switching power supply MOSFET in response to the deficiencies of the prior art, which can optimize parameters for different switching power supplies, has good stability, low maintenance costs, strong portability, a simple structure, and low manufacturing costs.

[0010] The object of the present invention is achieved by the following solution: A drive circuit for a switching power supply MOSFET includes a power supply providing unit, a triangular wave generating circuit unit, a push-pull drive circuit unit, a buck circuit unit, a soft start circuit unit with adjustable duty cycle, a bootstrap capacitor power-on start circuit unit, and a sampling protection circuit unit. The sampling protection circuit unit includes an IDS overcurrent protection circuit unit and a VGS overvoltage protection circuit unit; The output end of the push-pull drive circuit unit is connected to the bootstrap capacitor power-on start circuit unit, the triangular wave generating circuit unit is connected to the input end of the push-pull drive circuit unit through the soft start circuit unit, and both the input end and the output end of the buck circuit unit are connected to the bootstrap capacitor power-on start circuit unit to supply power from the buck circuit output; The power supply providing unit is used to provide power for each functional unit.

[0011] Preferably, the bootstrap capacitor power-on startup circuit unit includes a PNP transistor Q10, an NPN transistor Q14, and a bootstrap capacitor C11. The positive electrode of the bootstrap capacitor C11 is connected to the +30V voltage of the power supply unit through a third resistor R25, and the negative electrode of the bootstrap capacitor C11 is connected to GND1; The positive electrode of the bootstrap capacitor C11 is connected to the emitter of the PNP transistor Q10. The base of the NPN transistor Q14 is connected to the collector of the PNP transistor Q10 through a fourth resistor R30, and the collector of the NPN transistor Q14 is connected to the base of the PNP transistor Q10 through a fifth resistor R26; A first voltage stabilizing diode D6 is also provided. The negative electrode of the first voltage stabilizing diode D6 is connected to the collector of the NPN transistor Q14, and the first voltage stabilizing diode D6 is connected to the emitter of the NPN transistor Q14, and the emitter of the NPN transistor Q14 is connected to GND1.

[0012] Preferably, the push-pull drive circuit unit includes an NPN transistor Q11, a PNP transistor Q13. The collector of the NPN transistor Q11 is connected to the collector of the PNP transistor Q10. The emitter of the PNP transistor Q13 is connected to the emitter of the NPN transistor Q11. The base of the NPN transistor Q11 is connected to the base of the PNP transistor Q13. The collector of the PNP transistor Q13 is connected to GND1, and a sixth resistor R31 is provided. One end of the sixth resistor R31 is connected to the base of the PNP transistor Q13, and the other end is connected to the collector of the PNP transistor Q13; The drain of the MOS transistor Q12 is connected to the +30V voltage of the power supply unit. The source of the MOS transistor Q12 is connected to the ground through a first resistor R33. The gate of the MOS transistor Q12 is connected to the emitter of the NPN transistor Q11 through a startup resistor R29, and the gate of the MOS transistor Q12 is connected to the ground through a second resistor R32 to provide a gate discharge circuit.

[0013] Preferably, the triangular wave generation circuit unit includes a hysteresis comparator OPM2A, a first capacitor C9, and a second capacitor C10. One end of the first capacitor C9 is connected to the +12V- voltage of the power supply unit, and the other end is connected to GND1. The VCC+ port of the hysteresis comparator OPM2A is connected to the +30V voltage of the power supply unit, and the VCC- port of the hysteresis comparator OPM2A is connected to GND1; It further includes an eighth resistor R20, a ninth resistor R21, a tenth resistor R27, and an eleventh resistor R28. The +12V- voltage of the power supply providing unit is connected to one end of the tenth resistor R27 through the ninth resistor R21, and the other end of the tenth resistor R27 is connected to GND1, forming a positive feedback circuit; The output end of the hysteresis comparator OPM2A is connected to the +12V- voltage of the power supply providing unit through a seventh resistor R22. The non-inverting input end of the hysteresis comparator OPM2A is connected to the end where the ninth resistor R21 and the tenth resistor R27 are connected in series. The inverting input end of the hysteresis comparator OPM2A is connected to GND1 through a second capacitor C10. And an eighth resistor R20 is connected between the output end of the hysteresis comparator OPM2A and the non-inverting input end of the hysteresis comparator OPM2A, and an eleventh resistor R28 is connected between the output end of the hysteresis comparator OPM2A and the inverting input end of the hysteresis comparator OPM2A.

[0014] Preferably, the soft start circuit unit includes a variable resistor, a PNP type triode Q9, and a third capacitor C8. The emitter of the PNP type triode Q9 is connected to the +12V- voltage of the power supply providing unit through a twelfth resistor R19, and both ends of the third capacitor (C8) are respectively connected to the emitter and the collector of the PNP type triode (Q9). The collector of the PNP type triode Q9 is connected to GND1. The base of the PNP type triode Q9 is connected to the +12V- voltage of the power supply providing unit through a variable resistor, and the base of the PNP type triode Q9 is connected to GND1 through a thirteenth resistor R23.

[0015] Preferably, the VGS overvoltage protection circuit unit includes an NPN type triode Q15, a second zener diode D8, and a fourteenth resistor R35. The collector of the NPN type triode Q15 is connected to the base of the PNP type triode Q9. The base of the NPN type triode Q15 is connected in series with the positive electrode of the second zener diode D8 through a fourteenth resistor R35. The negative electrode of the second zener diode D8 is connected to the output end of the push-pull drive circuit unit. The emitter of the NPN type triode Q15 is connected to GND1.

[0016] Preferably, the IDS overcurrent protection circuit unit includes an NPN type triode Q16, a fourth capacitor C14, and a fifteenth resistor R36. The collector of the NPN type triode Q16 is connected to the collector of the PNP type triode Q10 through a sixteenth resistor R24. The base of the NPN type triode Q16 is connected to the source of the MOS transistor Q12 through the fifteenth resistor R36. The emitter of the NPN type triode Q16 is connected to GND1, and both ends of the fourth capacitor C14 are respectively connected to the base and the emitter of the NPN type triode Q16.

[0017] Preferably, the buck circuit unit includes a Schottky diode, an inductor L2, an electrolytic capacitor C13, a fifth capacitor C12, and an output load current-limiting resistor R34. The Schottky diode includes a first Schottky diode D5 and a second Schottky diode D7. The negative electrode of the first Schottky diode D5 is connected to the positive electrode of the boost capacitor C11. The positive electrode of the first Schottky diode D5 is connected to GND1 through the electrolytic capacitor C13, and the positive electrode of the first Schottky diode D5 is connected to the +12V voltage of the power supply unit. The output load current-limiting resistor R34 and the fifth capacitor C12 are both connected in parallel with the electrolytic capacitor C13; The positive electrode of the first Schottky diode D5 is connected to the negative electrode of the second Schottky diode D7 through the inductor L2, and the negative electrode of the second Schottky diode D7 is connected to the negative electrode of the boost capacitor C11. The positive electrode of the second Schottky diode D7 is connected to GND1.

[0018] Preferably, it further includes a PWM wave generation circuit. The PWM wave generation circuit includes OPM2B. The non-inverting input terminal of OPM2B is connected to the emitter of the PNP-type triode Q9. The inverting input terminal of OPM2B is connected to the inverting input terminal of the hysteresis comparator OPM2A. The output terminal of OPM2B is connected to the input terminal of the push-pull drive circuit unit.

[0019] The present invention has the following beneficial effects: It includes a power supply unit, a triangular wave generation circuit unit, a push-pull drive circuit unit, a buck circuit unit, a soft start circuit unit with adjustable duty cycle, a boost capacitor power-on start circuit unit, and a sampling protection circuit unit. The sampling protection circuit unit includes an IDS overcurrent protection circuit unit and a VGS overvoltage protection circuit unit; The output terminal of the push-pull drive circuit unit is connected to the boost capacitor power-on start circuit unit. The triangular wave generation circuit unit is connected to the input terminal of the push-pull drive circuit unit through the soft start circuit unit. The input terminal and the output terminal of the buck circuit unit are both connected to the boost capacitor power-on start circuit unit to supply power to the output of the buck circuit; The power supply unit is used to supply power to each functional unit.

[0020] Preferably, the boost capacitor power-on start circuit unit includes a PNP-type triode Q10, an NPN-type triode Q14, and a boost capacitor C11. The positive electrode of the boost capacitor C11 is connected to the +30V voltage of the power supply unit through the third resistor R25 to charge the boost capacitor C11 by the power supply unit. The negative electrode of the boost capacitor C11 is connected to GND1.

[0021] The positive electrode of the bootstrap capacitor C11 is connected to the emitter of the PNP transistor Q10. The base of the NPN transistor Q14 is connected to the collector of the PNP transistor Q10 through the fourth resistor R30. The collector of the NPN transistor Q14 is connected to the base of the PNP transistor Q10 through the fifth resistor R26. A first voltage stabilizing diode D6 is further provided. The negative electrode of the first voltage stabilizing diode D6 is connected to the collector of the NPN transistor Q14, and the first voltage stabilizing diode D6 is connected to the emitter of the NPN transistor Q14, and the emitter of the NPN transistor Q14 is connected to GND1.

[0022] By connecting the first voltage stabilizing diode D6 in parallel with the NPN transistor Q14, when the bootstrap capacitor C11 supplies power to the subsequent drive circuit, it is possible to prevent the discharge speed of the bootstrap capacitor C11 from being too fast due to a large load, resulting in too small a voltage of the bootstrap capacitor C11, causing the VCE of the NPN transistor Q10 to stop conducting, and thus the entire system cannot operate normally.

[0023] When the +30V voltage of the power supply unit charges the bootstrap capacitor C11 to a certain voltage, the first voltage stabilizing diode D6 starts to be broken down and starts to stabilize the voltage. At this time, the VCE of the PNP transistor Q10 starts to conduct, and the bootstrap capacitor C11 starts to supply power to the subsequent drive circuit. By connecting the NPN transistor Q14 in parallel with the first voltage stabilizing diode D6, when the VCE of the PNP transistor Q10 conducts, the NPN transistor Q14 also starts to conduct and shorts the first voltage stabilizing diode D6. At this time, the first voltage stabilizing diode D6 no longer stabilizes the voltage, and the +30V voltage of the power supply unit charges the bootstrap capacitor C11, preventing the electricity on the bootstrap capacitor C11 from being absorbed quickly due to a large load, so that when the voltage of the bootstrap capacitor C11 is less than 12V, the VCE of the PNP transistor Q10 stops conducting, causing the system to stop operating.

[0024] Preferably, the push-pull drive circuit unit includes an NPN transistor Q11 and a PNP transistor Q13. The collector of the NPN transistor Q11 is connected to the collector of the PNP transistor Q10. The emitter of the PNP transistor Q13 is connected to the emitter of the NPN transistor Q11. The base of the NPN transistor Q11 is connected to the base of the PNP transistor Q13. The collector of the PNP transistor Q13 is connected to GND1, and a sixth resistor R31 is provided. One end of the sixth resistor R31 is connected to the base of the PNP transistor Q13, and the other end is connected to the collector of the PNP transistor Q13. The drain of the MOS transistor Q12 is connected to the +30V voltage of the power supply unit. The source of the MOS transistor Q12 is connected to the ground through the first resistor R33. The gate of the MOS transistor Q12 is connected to the emitter of the NPN transistor Q11 through a startup resistor R29, and the gate of the MOS transistor Q12 is connected to the ground through a second resistor R32 to provide a gate discharge circuit.

[0025] The push-pull drive circuit unit is used to amplify the PWM wave signal and input the signal to the MOSFET gate level to turn on and off the gate level.

[0026] Preferably, the triangular wave generation circuit unit includes a hysteresis comparator OPM2A, a first capacitor C9, and a second capacitor C10. One end of the first capacitor C9 is connected to the +12V- voltage of the power supply unit, and the other end is connected to GND1. The VCC+ port of the hysteresis comparator OPM2A is connected to the +30V voltage of the power supply unit, and the VCC- port of the hysteresis comparator OPM2A is connected to GND1; It also includes an eighth resistor R20, a ninth resistor R21, a tenth resistor R27, and an eleventh resistor R28. The +12V- voltage of the power supply unit is connected to one end of the tenth resistor R27 through the ninth resistor R21, and the other end of the tenth resistor R27 is connected to GND1 to form a positive feedback circuit; The output end of the hysteresis comparator OPM2A is connected to the +12V- voltage of the power supply unit through a seventh resistor R22. The non-inverting input end of the hysteresis comparator OPM2A is connected to the end where the ninth resistor R21 and the tenth resistor R27 are connected in series. The inverting input end of the hysteresis comparator OPM2A is connected to GND1 through the second capacitor C10. An eighth resistor R20 is connected between the output end of the hysteresis comparator OPM2A and the non-inverting input end of the hysteresis comparator OPM2A, and an eleventh resistor R28 is connected between the output end of the hysteresis comparator OPM2A and the inverting input end of the hysteresis comparator OPM2A.

[0027] Preferably, the soft start circuit unit includes a variable resistor, a PNP transistor Q9, and a third capacitor C8. The emitter of the PNP transistor Q9 is connected to the +12V- voltage of the power supply unit through a twelfth resistor R19, and both ends of the third capacitor (C8) are respectively connected to the emitter and the collector of the PNP transistor (Q9). The collector of the PNP transistor Q9 is connected to GND1. The base of the PNP transistor Q9 is connected to the +12V- voltage of the power supply unit through a variable resistor, and the base of the PNP transistor Q9 is connected to GND1 through a thirteenth resistor R23.

[0028] Upon power-on, the power-on startup time can be adjusted according to the RC charging delay to avoid damage to circuit components caused by instantaneous large current surges or excessive voltages.

[0029] Preferably, the VGS overvoltage protection circuit unit includes an NPN transistor Q15, a second zener diode D8, and a fourteenth resistor R35. The collector of the NPN transistor Q15 is connected to the base of the PNP transistor Q9. The base of the NPN transistor Q15 is connected in series with the anode of the second zener diode D8 through the fourteenth resistor R35. The cathode of the second zener diode D8 is connected to the output terminal of the push-pull drive circuit unit. The emitter of the NPN transistor Q15 is connected to GND1.

[0030] When VGS overvoltage occurs in the circuit, the VGS overvoltage protection circuit unit adjusts the duty cycle to make the buck circuit unit have no output.

[0031] Preferably, the IDS overcurrent protection circuit unit includes an NPN transistor Q16, a fourth capacitor C14, and a fifteenth resistor R36. The collector of the NPN transistor Q16 is connected to the collector of the PNP transistor Q10 through a sixteenth resistor R24. The base of the NPN transistor Q16 is connected to the source of the MOS transistor Q12 through the fifteenth resistor R36. The emitter of the NPN transistor Q16 is connected to GND1, and both ends of the fourth capacitor C14 are respectively connected to the base and emitter of the NPN transistor Q16.

[0032] When IDS overcurrent occurs, the IDS overcurrent protection circuit unit pulls down the push-pull drive circuit unit, stops outputting the PWM wave, and turns off the MOSFET.

[0033] Preferably, the buck circuit unit includes a Schottky diode, an inductor L2, an electrolytic capacitor C13, a fifth capacitor C12, and an output load current limiting resistor R34. The Schottky diode includes a first Schottky diode D5 and a second Schottky diode D7. The cathode of the first Schottky diode D5 is connected to the anode of the bootstrap capacitor C11. The anode of the first Schottky diode D5 is connected to GND1 through the electrolytic capacitor C13, and the anode of the first Schottky diode D5 is connected to the +12V voltage of the power supply unit. The output load current limiting resistor R34 and the fifth capacitor C12 are both connected in parallel with the electrolytic capacitor C13; The anode of the first Schottky diode D5 is connected to the cathode of the second Schottky diode D7 through the inductor L2, and the cathode of the second Schottky diode D7 is connected to the cathode of the bootstrap capacitor C11. The anode of the second Schottky diode D7 is connected to GND1.

[0034] The buck circuit can maintain the relative stability of the output voltage and continuously supply power to the boost capacitor C11.

[0035] Preferably, it further includes a PWM wave generation circuit. The PWM wave generation circuit includes OPM2B. The non-inverting input terminal of OPM2B is connected to the emitter of the PNP type triode Q9. The inverting input terminal of OPM2B is connected to the inverting input terminal of the hysteresis comparator OPM2A. The output terminal of OPM2B is connected to the input terminal of the push-pull drive circuit unit.

[0036] The advantages of the present invention are as follows: ① For the drive circuit adopted by the present invention, when a single component fails, only the single component needs to be repaired or replaced, and there is no need to replace and repair the entire circuit. Moreover, no professional instruments and high professional knowledge are required, and ordinary technicians can simply repair the present invention, greatly reducing the maintenance cost.

[0037] ② The manufacturing process requirements for the drive circuit adopted by the present invention are relatively low, and it is not affected by electromagnetic interference, making the stability of the circuit better.

[0038] ③ Since the drive circuit adopted by the present invention has a low degree of circuit concentration, the temperature rise of a single component during use will not cause the overall circuit to generate temperature rise, improving the stability and reliability of the circuit.

[0039] ④ The drive circuit adopted by the present invention adds an overcurrent protection circuit, which can prevent the subsequent load from being too large and causing the power supply circuit function to fail, improving the safety and reliability of the circuit.

[0040] ⑤ In the switching power supply system, as a key power switching component, the MOSFET is in a high-frequency on-off alternating cycle. Such frequent switching actions will generate a large amount of heat accumulation, which will have a great negative impact on the reliability of the entire circuit and the Layout layout; compared with the full-bridge structure, the drive circuit adopted by the present invention reduces one MOSFET, effectively enhancing the circuit reliability and facilitating the Layout layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a circuit diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] Such as Figures 1 to 2As shown in the figure, a drive circuit for a switching power supply MOSFET includes a power supply unit, a triangular wave generation circuit unit, a push-pull drive circuit unit, a buck circuit unit, a soft start circuit unit with adjustable duty cycle, a bootstrap capacitor power-on start circuit unit, and a sampling protection circuit unit. The sampling protection circuit unit includes an IDS overcurrent protection circuit unit and a VGS overvoltage protection circuit unit; The output end of the push-pull drive circuit unit is connected to the bootstrap capacitor power-on start circuit unit. The triangular wave generation circuit unit is connected to the input end of the push-pull drive circuit unit through the soft start circuit unit. The input end and the output end of the buck circuit unit are both connected to the bootstrap capacitor power-on start circuit unit to supply power from the buck circuit output; The power supply unit is used to supply power to each functional unit.

[0043] The bootstrap capacitor power-on start circuit unit includes a PNP transistor Q10, an NPN transistor Q14, and a bootstrap capacitor C11. The positive electrode of the bootstrap capacitor C11 is connected to the +30V voltage of the power supply unit through a third resistor R25, and the negative electrode of the bootstrap capacitor C11 is connected to GND1; The positive electrode of the bootstrap capacitor C11 is connected to the emitter of the PNP transistor Q10. The base of the NPN transistor Q14 is connected to the collector of the PNP transistor Q10 through a fourth resistor R30. The collector of the NPN transistor Q14 is connected to the base of the PNP transistor Q10 through a fifth resistor R26; A first zener diode D6 is also provided. The negative electrode of the first zener diode D6 is connected to the collector of the NPN transistor Q14, and the first zener diode D6 is connected to the emitter of the NPN transistor Q14, and the emitter of the NPN transistor Q14 is connected to GND1 In this embodiment, when power is turned on, the +30V voltage terminal of the power supply unit charges the bootstrap capacitor C11 through a third resistor R25 with a resistance value of 20K.

[0044] When the bootstrap capacitor C11 is charged to 12.6V, the first zener diode D6 is broken down and starts to regulate the voltage. At this time, current passes through the base of the PNP transistor Q10, the VCE of the PNP transistor Q10 starts to conduct, and the bootstrap capacitor C11 starts to supply power to other circuit functional units.

[0045] When the bootstrap capacitor C11 starts to supply power to other circuit functional units, due to the large load, the power absorption of the bootstrap capacitor C11 is very fast. When the voltage of the bootstrap capacitor C11 is less than 12V, the PNP transistor Q10 stops conducting, and the system will stop running. In this embodiment, by connecting the NPN transistor Q14 in parallel with the first zener diode D6, when the PNP transistor Q10 conducts, the NPN transistor Q14 also conducts, and the first zener diode D6 is short-circuited, so that the first zener diode D6 no longer stabilizes the voltage. At this time, the +30V voltage terminal of the power supply providing unit continuously charges the bootstrap capacitor C11, enabling the bootstrap capacitor C11 to continuously discharge externally.

[0046] In this embodiment, when the MOS transistor Q12 conducts, the voltage of the bootstrap capacitor C11 is lifted, and GND1 is not 0V.

[0047] The triangular wave generating circuit unit includes a hysteresis comparator OPM2A, a first capacitor C9, and a second capacitor C10. One end of the first capacitor C9 is connected to the +12V- voltage of the power supply providing unit, and the other end is connected to GND1. The VCC+ port of the hysteresis comparator OPM2A is connected to the +30V voltage of the power supply providing unit, and the VCC- port of the hysteresis comparator OPM2A is connected to GND1; It further includes an eighth resistor R20, a ninth resistor R21, a tenth resistor R27, and an eleventh resistor R28. The +12V- voltage of the power supply providing unit is connected to one end of the tenth resistor R27 through the ninth resistor R21, and the other end of the tenth resistor R27 is connected to GND1, forming a positive feedback circuit; The output terminal of the hysteresis comparator OPM2A is connected to the +12V- voltage of the power supply providing unit through a seventh resistor R22. The non-inverting input terminal of the hysteresis comparator OPM2A is connected to the end where the ninth resistor R21 and the tenth resistor R27 are connected in series. The inverting input terminal of the hysteresis comparator OPM2A is connected to GND1 through the second capacitor C10. An eighth resistor R20 is connected between the output terminal and the non-inverting input terminal of the hysteresis comparator OPM2A, and an eleventh resistor R28 is connected between the output terminal and the inverting input terminal of the hysteresis comparator OPM2A.

[0048] The soft start circuit unit includes a variable resistor, a PNP transistor Q9, and a third capacitor C8. The emitter of the PNP transistor Q9 is connected to the +12V- voltage of the power supply unit through a twelfth resistor R19, and both ends of the third capacitor (C8) are respectively connected to the emitter and collector of the PNP transistor (Q9). The collector of the PNP transistor Q9 is connected to GND1. The base of the PNP transistor Q9 is connected to the +12V- voltage of the power supply unit through a variable resistor, and the base of the PNP transistor Q9 is connected to GND1 through a thirteenth resistor R23.

[0049] In this embodiment, the +12V- voltage terminal of the power supply unit charges the third capacitor C8. When the third capacitor C8 is charged to 8V, the PNP transistor Q9 starts to conduct. At this time, the third capacitor C8 discharges to the ground through the PNP transistor Q9. The PNP transistor Q9 uses emitter voltage follower output, so that the voltage of the third capacitor C8 is stabilized at 8V.

[0050] When power is on, due to the charging delay of the third capacitor C8, the power-on startup time can be adjusted; when power is off, the PNP transistor Q9 conducts, and the power-off speed is fast.

[0051] It further includes a PWM wave generation circuit. The PWM wave generation circuit includes an OPM2B. The non-inverting input terminal of the OPM2B is connected to the emitter of the PNP transistor Q9. The inverting input terminal of the OPM2B is connected to the inverting input terminal of the hysteresis comparator OPM2A. The output terminal of the OPM2B is connected to the input terminal of the push-pull drive circuit unit.

[0052] In this embodiment, a triangular wave and a straight wave are input to a comparator to compare and output a PWM wave. When the straight wave is higher than the triangular wave, the comparator outputs in open-drain mode, and the output pull-up is high; when the straight wave is lower than the triangular wave, the output pull-down is low, forming a PWM wave. The duty cycle can be adjusted by adjusting the height of the straight wave.

[0053] The push-pull drive circuit unit includes an NPN transistor Q11 and a PNP transistor Q13. The collector of the NPN transistor Q11 is connected to the collector of the PNP transistor Q10. The emitter of the PNP transistor Q13 is connected to the emitter of the NPN transistor Q11. The base of the NPN transistor Q11 is connected to the base of the PNP transistor Q13. The collector of the PNP transistor Q13 is connected to GND1, and a sixth resistor R31 is provided. One end of the sixth resistor R31 is connected to the base of the PNP transistor Q13, and the other end is connected to the collector of the PNP transistor Q13; The drain of the MOS transistor Q12 is connected to the +30V voltage of the power supply unit. The source of the MOS transistor Q12 is connected to the ground through a first resistor R33. The gate of the MOS transistor Q12 is connected to the emitter of an NPN transistor Q11 through a starting resistor R29, and the gate of the MOS transistor Q12 is connected to the ground through a second resistor R32 to provide a gate discharge circuit.

[0054] In this embodiment, after the PWM wave signal is amplified by the push-pull amplifier circuit, it is input to the MOSFET gate level to turn on and off the gate level. When the PWM wave signal at the input end of the push-pull circuit unit is at a high level, the NPN transistor Q11 is turned on, and the +12V voltage terminal of the power supply unit is pulled up, and the output is high; when the PWM wave signal at the input end of the push-pull circuit unit is at a low level, the PNP transistor Q13 is turned on, pulled down to the ground, and the output is low.

[0055] The buck circuit unit includes a Schottky diode, an inductor L2, an electrolytic capacitor C13, a fifth capacitor C12, and an output load current limiting resistor R34. The Schottky diode includes a first Schottky diode D5 and a second Schottky diode D7. The negative pole of the first Schottky diode D5 is connected to the positive pole of the bootstrap capacitor C11. The positive pole of the first Schottky diode D5 is connected to GND1 through the electrolytic capacitor C13, and the positive pole of the first Schottky diode D5 is connected to the +12V voltage of the power supply unit. The output load current limiting resistor R34 and the fifth capacitor C12 are both connected in parallel with the electrolytic capacitor C13; The positive pole of the first Schottky diode D5 is connected to the negative pole of the second Schottky diode D7 through an inductor L2, and the negative pole of the second Schottky diode D7 is connected to the negative pole of the bootstrap capacitor C11. The positive pole of the second Schottky diode D7 is connected to GND1.

[0056] In this embodiment, when the bootstrap capacitor C11 discharges externally to about 0.3V and the PWM wave signal runs normally, the buck circuit unit starts to work normally. By charging and discharging the inductor L2, the voltage of the electrolytic capacitor C13 is maintained at +12V and output to the load.

[0057] At the same time, the +12V voltage of the power supply unit is output to the bootstrap capacitor C11 through the first Schottky diode D5. After normal operation, it continuously supplies power to the bootstrap capacitor C11, enabling the bootstrap capacitor C11 to supply power to other circuit function units and making the entire drive circuit system operate normally.

[0058] The VGS overvoltage protection circuit unit includes an NPN transistor Q15, a second zener diode D8, and a fourteenth resistor R35. The collector of the NPN transistor Q15 is connected to the base of the PNP transistor Q9. The base of the NPN transistor Q15 is connected in series with the anode of the second zener diode D8 through the fourteenth resistor R35. The cathode of the second zener diode D8 is connected to the output terminal of the push-pull drive circuit unit. The emitter of the NPN transistor Q15 is connected to GND1.

[0059] In this embodiment, one end of the VGS overvoltage protection circuit unit is connected to the output terminal of the push-pull drive circuit unit, and the other end is connected to the soft start circuit unit. When VGS overvoltage occurs in the circuit, the NPN transistor Q15 pulls down the PNP transistor Q9. At this time, the third capacitor C8 discharges rapidly, adjusting the duty cycle to 0, and the buck circuit unit has no output.

[0060] The IDS overcurrent protection circuit unit includes an NPN transistor Q16, a fourth capacitor C14, and a fifteenth resistor R36. The collector of the NPN transistor Q16 is connected to the collector of the PNP transistor Q10 through a sixteenth resistor R24. The base of the NPN transistor Q16 is connected to the source of the MOS transistor Q12 through the fifteenth resistor R36. The emitter of the NPN transistor Q16 is connected to GND1, and both ends of the fourth capacitor C14 are respectively connected to the base and emitter of the NPN transistor Q16.

[0061] In this embodiment, one end of the IDS overcurrent protection circuit unit is connected to the input terminal of the push-pull drive circuit unit, and the other end is connected to the source of the MOS transistor Q12. When IDS overcurrent occurs, the NPN transistor Q16 directly pulls down the push-pull drive circuit from the hardware. At this time, no PWM wave is output and the MOSFET is turned off.

[0062] The drive circuit in this embodiment adopts the design concept of floating ground, isolating the switching power supply ground from the subsequent load ground, reducing the interference of the switching power supply ground to the subsequent load ground; and cleverly utilizes the charging and discharging characteristics of the bootstrap capacitor C11. For different MOSFETs selected by different switching power supplies, by adjusting the capacitance value of the bootstrap capacitor, the MOSFET turn-on voltage requirements can be met, and the application range is wide and flexible.

[0063] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Those skilled in the art can make modifications to the present invention without departing from the spirit of the present invention, and all such modifications fall within the protection scope of the present invention.

Claims

1. A driving circuit for a switch-mode power supply MOSFET, characterized in that, It includes a power supply unit, a triangular wave generation circuit unit, a push-pull drive circuit unit, a buck circuit unit, a soft start circuit unit with adjustable duty cycle, a bootstrap capacitor power-on start circuit unit, and a sampling protection circuit unit. The sampling protection circuit unit includes an IDS overcurrent protection circuit unit and a VGS overvoltage protection circuit unit; The output end of the push-pull drive circuit unit is connected to the bootstrap capacitor power-on start circuit unit. The triangular wave generation circuit unit is connected to the input end of the push-pull drive circuit unit through the soft start circuit unit. The input end and the output end of the buck circuit unit are both connected to the bootstrap capacitor power-on start circuit unit to supply power from the buck circuit output; The power supply unit is used to provide power for each functional unit.

2. The drive circuit for a switching power supply MOSFET according to claim 1, wherein The bootstrap capacitor power-on start circuit unit includes a PNP transistor (Q10), an NPN transistor (Q14), and a bootstrap capacitor (C11). The positive pole of the bootstrap capacitor (C11) is connected to the +30V voltage of the power supply unit through a third resistor (R25), and the negative pole of the bootstrap capacitor (C11) is connected to GND1; The positive pole of the bootstrap capacitor (C11) is connected to the emitter of the PNP transistor (Q10). The base of the NPN transistor (Q14) is connected to the collector of the PNP transistor (Q10) through a fourth resistor (R30). The collector of the NPN transistor (Q14) is connected to the base of the PNP transistor (Q10) through a fifth resistor (R26); A first zener diode (D6) is also provided. The negative pole of the first zener diode (D6) is connected to the collector of the NPN transistor (Q14), and the first zener diode (D6) is connected to the emitter of the NPN transistor (Q14), and the emitter of the NPN transistor (Q14) is connected to GND1.

3. The driving circuit for a switching power supply MOSFET according to claim 2, characterized in that, The push-pull drive circuit unit includes an NPN transistor (Q11), a PNP transistor (Q13), and a MOS transistor (Q12). The collector of the NPN transistor (Q11) is connected to the collector of the PNP transistor (Q10). The emitter of the PNP transistor (Q13) is connected to the emitter of the NPN transistor (Q11). The base of the NPN transistor (Q11) is connected to the base of the PNP transistor (Q13). The collector of the PNP transistor (Q13) is connected to GND1, and a sixth resistor (R31) is provided. One end of the sixth resistor (R31) is connected to the base of the PNP transistor (Q13), and the other end is connected to the collector of the PNP transistor (Q13); The drain of the MOS transistor (Q12) is connected to the +30V voltage of the power supply unit. The source of the MOS transistor (Q12) is connected to the first resistor (R33) to ground. The gate of the MOS transistor (Q12) is connected to the emitter of the NPN transistor (Q11) through a startup resistor (R29), and the gate of the MOS transistor (Q12) is connected to the second resistor (R32) to ground to provide a gate discharge circuit.

4. The driving circuit for a switching power supply MOSFET according to claim 1, wherein The triangular wave generating circuit unit includes a hysteresis comparator OPM2A, a first capacitor (C9), and a second capacitor (C10). One end of the first capacitor (C9) is connected to the +12V- voltage of the power supply unit, and the other end is connected to GND1. The VCC+ port of the hysteresis comparator OPM2A is connected to the +30V voltage of the power supply unit, and the VCC- port of the hysteresis comparator OPM2A is connected to GND1; It further includes an eighth resistor (R20), a ninth resistor (R21), a tenth resistor (R27), and an eleventh resistor (R28). The +12V- voltage of the power supply unit is connected to one end of the tenth resistor (R27) through the ninth resistor (R21), and the other end of the tenth resistor (R27) is connected to GND1, forming a positive feedback circuit; The output end of the hysteresis comparator OPM2A is connected to the +12V- voltage of the power supply unit through a seventh resistor (R22). The non-inverting input end of the hysteresis comparator OPM2A is connected to the end where the ninth resistor (R21) and the tenth resistor (R27) are connected in series. The inverting input end of the hysteresis comparator OPM2A is connected to GND1 through the second capacitor (C10). An eighth resistor (R20) is connected between the output end and the non-inverting input end of the hysteresis comparator OPM2A, and an eleventh resistor (R28) is connected between the output end and the inverting input end of the hysteresis comparator OPM2A.

5. The driving circuit for a switching power supply MOSFET according to claim 1, characterized in that The soft start circuit unit includes a variable resistor, a PNP type triode (Q9), and a third capacitor (C8). The emitter of the PNP type triode (Q9) is connected to the +12V- voltage of the power supply unit through a twelfth resistor (R19). Both ends of the third capacitor (C8) are respectively connected to the emitter and the collector of the PNP type triode (Q9). The collector of the PNP type triode (Q9) is connected to GND1. The base of the PNP type triode (Q9) is connected to the +12V- voltage of the power supply unit through a variable resistor, and the base of the PNP type triode (Q9) is connected to GND1 through a thirteenth resistor (R23).

6. The driving circuit for a switching power supply MOSFET according to claim 5, characterized in that, The VGS overvoltage protection circuit unit includes an NPN type triode (Q15), a second zener diode (D8), and a fourteenth resistor (R35). The collector of the NPN type triode (Q15) is connected to the base of the PNP type triode (Q9). The base of the NPN type triode (Q15) is connected in series with the positive electrode of the second zener diode (D8) through a fourteenth resistor (R35). The negative electrode of the second zener diode (D8) is connected to the output end of the push-pull drive circuit unit. The emitter of the NPN type triode (Q15) is connected to GND1.

7. The driving circuit for a switching power supply MOSFET according to claim 2, wherein The IDS overcurrent protection circuit unit includes an NPN transistor (Q16), a fourth capacitor (C14), and a fifteenth resistor (R36). The collector of the NPN transistor (Q16) is connected to the collector of the PNP transistor (Q10) through a sixteenth resistor (R24). The base of the NPN transistor (Q16) is connected to the source of the MOS transistor (Q12) through the fifteenth resistor (R36). The emitter of the NPN transistor (Q16) is connected to GND1, and both ends of the fourth capacitor (C14) are respectively connected to the base and the emitter of the NPN transistor (Q16).

8. The drive circuit for a switching power supply MOSFET according to claim 2, wherein The buck circuit unit includes a Schottky diode, an inductor (L2), an electrolytic capacitor (C13), a fifth capacitor (C12), and an output load current limiting resistor (R34). The Schottky diode includes a first Schottky diode (D5) and a second Schottky diode (D7). The negative electrode of the first Schottky diode (D5) is connected to the positive electrode of the bootstrap capacitor (C11). The positive electrode of the first Schottky diode (D5) is connected to GND1 through the electrolytic capacitor (C13), and the positive electrode of the first Schottky diode (D5) is connected to the +12V voltage of the power supply unit. The output load current limiting resistor (R34) and the fifth capacitor (C12) are both connected in parallel with the electrolytic capacitor (C13). The positive electrode of the first Schottky diode (D5) is connected to the negative electrode of the second Schottky diode (D7) through an inductor (L2), and the negative electrode of the second Schottky diode (D7) is connected to the negative electrode of the bootstrap capacitor (C11). The positive electrode of the second Schottky diode (D7) is connected to GND1.

9. The drive circuit for a switching power supply MOSFET according to claim 4 or 5, characterized in that, It further includes a PWM wave generation circuit. The PWM wave generation circuit includes OPM2B. The non-inverting input terminal of OPM2B is connected to the emitter of the PNP transistor Q9. The inverting input terminal of OPM2B is connected to the inverting input terminal of the hysteresis comparator OPM2A. The output terminal of OPM2B is connected to the input terminal of the push-pull drive circuit unit.

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