Flyback switching power supply circuit based on primary side and secondary side MOS tube conduction detection

Abstract

The invention relates to the technical field of switching power supplies, in particular to a flyback switching power supply circuit based on primary and secondary side MOS tube conduction detection, which comprises a primary side control circuit, a power conversion circuit, a synchronous rectification control circuit, a primary and secondary side MOS tube detection circuit, a self-locking circuit and an output circuit, wherein the primary and secondary side MOS tube detection circuit is used for detecting whether a primary side MOS tube and a secondary side MOS tube are conducted at the same time and providing self-locking driving voltage; and the self-locking circuit is used for pulling the starting voltage of the primary side control circuit and the synchronous rectification control circuit to a low level when detecting that the primary side MOS tube and the secondary side MOS tube are switched on simultaneously, so that the power conversion circuit stops working until the input voltage is switched off. The flyback switching power supply solves the problem of circuit damage caused by simultaneous conduction of the primary side MOS tube and the secondary side MOS tube in the existing flyback switching power supply.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a flyback switching power supply circuit based on primary and secondary MOSFET conduction detection. Background Technology

[0002] In the field of flyback switching power supplies, synchronous rectification technology replaces traditional diodes with low-resistance MOSFETs, significantly reducing conduction losses in low-voltage, high-current scenarios, and has become a key technology path for improving power supply efficiency.

[0003] However, the risk of common operation of the primary and secondary MOSFETs introduced by this technology has become a core technical bottleneck: when the primary MOSFET is turned on, if the secondary synchronous rectifier is turned on by mistake due to timing deviation or abnormal drive, a short circuit path will be formed in the transformer winding, causing serious consequences such as short circuit current surge, voltage spike and deterioration of electromagnetic interference, which directly threatens the reliability of the power system and limits the potential for high-frequency applications.

[0004] Existing protection solutions have significant limitations: fixed dead-time control is difficult to adapt to dynamic operating conditions, demagnetization detection technology is limited by detection delays of tens of nanoseconds, hardware interlocking circuits increase system complexity and cost, and overcurrent protection mechanisms, as a post-event intervention method, cannot prevent device stress damage; especially in high-frequency (such as GaN device applications) and wide input voltage scenarios, the effects of parasitic parameters are aggravated, and the dynamic range of secondary-side reflected voltage is expanded, causing traditional fixed threshold detection to fail. Existing technologies cannot meet the requirements of real-time protection and efficiency optimization. Summary of the Invention

[0005] To address the shortcomings of existing methods, this invention monitors the conduction status of the primary and secondary power transistors in real time, thus solving the circuit damage problem caused by the simultaneous conduction of the primary and secondary MOSFETs in existing flyback switching power supplies.

[0006] The technical solution adopted in this invention is: a flyback switching power supply circuit based on primary and secondary MOSFET conduction detection, comprising: a primary-side control circuit, a power conversion circuit, a synchronous rectification control circuit, a primary and secondary MOSFET detection circuit, a self-locking circuit, and an output circuit; wherein, The primary and secondary MOSFET detection circuit is used to detect whether the primary and secondary MOSFETs are turned on simultaneously and to provide a self-locking drive voltage. The self-locking circuit is used to detect when the primary-side MOSFET and the secondary-side MOSFET are simultaneously turned on. It pulls the start-up voltage of the primary-side control circuit and the synchronous rectification control circuit to a low level, thereby stopping the power conversion circuit from working until the input voltage is disconnected.

[0007] In a preferred embodiment of the present invention, the primary and secondary side MOSFET detection circuit includes: transistors Q10 to Q15, resistors R26 to R32, and diode D5; the left end of R29 is connected to the primary side control circuit; the right end of R29 is connected to the emitter of Q12, the base of Q12 is connected to the collector of Q13, and the collector of Q12 is connected to the upper end of R31, the base of Q11, the base of Q15, and the self-locking circuit; the base of Q13 is connected to the right end of R30, and the left end of R30 is connected to the synchronous rectification control circuit. The collector of Q11 is connected to the emitter of Q10, the left end of R28, and the negative terminal of D5; the collector of Q10 is connected to the left end of R29 and the primary-side control circuit; the base of Q10 is connected to the right end of R26; the positive terminal of D5 is connected to the left end of R27, and the right end of R27 is connected to the right end of R28 and the primary-side control circuit; the collector of Q15 is connected to the emitter of Q14 and the synchronous rectification control circuit; the base of Q14 is connected to the right end of R32, and the collector of Q14 is connected to the left end of R30 and the synchronous rectification control circuit.

[0008] In a preferred embodiment of the present invention, the primary-side control circuit controls the on and off states of the primary-side MOS transistor.

[0009] In a preferred embodiment of the present invention, the synchronous rectification circuit is used to control the on and off states of the secondary-side MOSFET.

[0010] In a preferred embodiment of the present invention, the power conversion circuit is used to convert the input voltage into a stable output voltage.

[0011] In a preferred embodiment of the present invention, the output circuit is used to provide voltage and current to the load.

[0012] In a preferred embodiment of the present invention, a voltage feedback circuit is further included for adjusting the magnitude of the output voltage.

[0013] As a preferred embodiment of the present invention, it further includes: an AC / DC conversion circuit for converting AC power to DC power.

[0014] In a preferred embodiment of the present invention, a voltage regulator circuit is further included for outputting a 5V voltage.

[0015] The beneficial effects of this invention are: 1. Compared with traditional flyback switching power supplies, the primary and secondary MOSFET detection circuit of this invention has a simple structure. When the primary and secondary MOSFETs are detected to be conducting simultaneously, the circuit can quickly disconnect the chips of the primary control circuit and the synchronous rectification control circuit, and perform self-locking control in a timely manner to effectively prevent damage to the circuit components. 2. Design two self-locking circuits to achieve immediate protection for the two switching power supplies on the primary and secondary sides. When the primary and secondary MOSFETs are simultaneously turned on in the circuit, the self-locking circuit can be activated immediately to pull the start pins of the primary control chip and / or synchronous rectifier chip low to a low level, thereby cutting off the power output and protecting the components and load in the circuit to avoid damage. 3. In terms of power supply design, this invention differs significantly from traditional flyback switching power supplies. The driving voltage of some transistors in this invention comes from a voltage regulator circuit. This design enables the power supply to stably output rated voltage and / or rated current, providing reliable power support for the entire circuit. Compared with traditional power supply designs, the voltage output of this invention is more stable and less affected by external factors, improving the overall performance and reliability of the circuit. Attached Figure Description

[0016] Figure 1 This is the logic block diagram of the flyback switching power supply circuit based on the conduction detection of primary and secondary MOSFETs of the present invention; Figure 2 This is a circuit diagram of a flyback switching power supply for primary and secondary side MOSFET conduction detection according to the present invention. Figure 3 This is a circuit diagram of the primary and secondary MOS transistor detection circuit of the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. The drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0018] Existing flyback switching power supplies present significant challenges in protection circuit detection, especially under special conditions such as light load, capacitive load, or short circuit. Therefore, there is an urgent need for a highly integrated circuit with rapid response and self-locking function that can balance real-time performance and reliability while being easy to implement, in order to meet protection requirements under complex operating conditions, and at the same time maintain the structural advantages and cost-effectiveness of flyback topologies.

[0019] Traditional synchronous rectification flyback switching power supplies, while combining the advantages of synchronous rectification technology and flyback topology, have characteristics such as high efficiency and low cost; however, the primary and secondary MOSFETs may conduct simultaneously due to overlapping drive signals or timing errors, resulting in a low-impedance short circuit path in the secondary circuit, which can cause instantaneous overcurrent and burn out the devices. Therefore, in order to ensure the stable operation of the power supply and the safety of the load, additional protection circuits need to be designed.

[0020] Traditional flyback switching power supplies can refer to the patent titled "A Self-Locking Flyback Switching Power Supply Circuit with Overcurrent and Overvoltage Protection". Figure 2As shown, traditional flyback switching power supply designs lack detection circuits for the primary and secondary MOSFETs. When both the primary and secondary MOSFETs are turned on simultaneously, traditional flyback switching power supplies cannot protect the circuit, leading to damage to the secondary circuit. Furthermore, the transformer cannot store energy; the energy is consumed by the short circuit path instead of being transferred to the load, resulting in a significant decrease in transformer efficiency.

[0021] like Figure 1 , 2 As shown, the flyback switching power supply circuit based on primary and secondary MOSFET conduction detection includes: a primary-side control circuit, a power conversion circuit, an AC / DC conversion circuit, a synchronous rectification control circuit, a voltage feedback circuit, a primary and secondary MOSFET detection circuit, a self-locking circuit, and an output circuit; wherein, AC-DC converter circuits convert alternating current (AC) to direct current (DC). The primary-side control circuit is used to control the on and off states of the primary-side MOSFETs; Power conversion circuits are used to convert input voltage into a stable output voltage; The synchronous rectification circuit is used to control the on and off states of the secondary-side MOSFETs; The voltage feedback circuit is used to adjust the magnitude of the output voltage; The primary and secondary MOSFET detection circuit is used to detect whether the primary and secondary MOSFETs are turned on simultaneously and provides a self-locking drive voltage DRV3. The self-locking circuit is used to detect when the primary-side MOSFET and the secondary-side MOSFET are simultaneously turned on, and pulls the start-up voltage of the primary-side control circuit and the synchronous rectification control circuit to a low level, thereby stopping the power conversion circuit from working until the input voltage is disconnected; The output circuit is used to provide output voltage and output current to the load.

[0022] This invention detects the conduction status of the primary and secondary MOSFETs. When both the primary and secondary MOSFETs are conducting simultaneously, a self-locking circuit pulls the chip start-up pins of the primary control circuit and the synchronous rectification control circuit to a low level, thereby protecting the circuit. This invention controls the on / off state of the primary-side MOSFET Q4. When Q4 is on, the electrical energy provided by the input circuit is converted into magnetic field energy in the primary winding of the transformer T2 of the power conversion circuit and stored. When Q4 is off, the magnetic field energy in the primary winding decays rapidly and generates an induced electromotive force in the secondary winding, thereby transferring energy to the secondary side. After processing by the output circuit, the energy is supplied to the load.

[0023] The AC / DC conversion circuit includes: AC input terminal P1, fuse F1, thermistor NTC1, adjustable resistor TR1, capacitors C4 and C3, common mode inductor T1, rectifier bridge BD1, and polarized capacitor EC1; P1 is connected to 220V AC power, the two ends of F1 and NTC1 are connected to the two ends of TR1, TR1 is connected in parallel with C4, the two ends of C4 are connected to pins 1 and 3 of T1, the two ends of T1 are connected in parallel with C3, the two ends of C3 are connected to pins 1 and 2 of BD1, the third pin of BD1 is connected to the upper end of EC1, and the lower end of EC1 is connected to pin 4 of BD1 and GND.

[0024] The primary-side control circuit includes: primary-side control chip U3, MOSFET Q4, resistors R2, R4, R12, R18, R21, R22, polarized capacitor EC2 and capacitor C8. U3 has a startup pin VDD, a drive pin GATE, an overcurrent detection pin CS, a feedback pin FB, and an overheat protection pin PRT. The upper end of the starting resistor R2 is connected to the input voltage, and the lower end of R2 is connected to the upper end of the starting resistor R4. The lower end of R4 is connected to the VDD pin of U3. The source of Q4 is connected to the common terminal of R12, R18 and R22. The left end of R18 is connected to the fourth pin of U3 and the upper end of C8. The upper end of EC2 is connected to the lower end of R4 and the fifth pin of U3. The upper end of R21 is connected to the third pin of U3. The lower ends of R21, EC2, C8 and R22 are grounded.

[0025] The power conversion circuit includes: resistors R3 and R7, diodes D2 and D3, capacitor C6, and transformer T2. The upper end of the parallel connection between R3 and C6 is connected to the first pin of T2, and the lower end of the parallel connection between R3 and C6 is connected to the negative terminal of D2. The positive terminal of D2 is connected to the second pin of T2 and the drain of Q4. The third pin of T2 is connected to the positive terminals of R7 and D3 in sequence. The negative terminal of D3 is connected to the lower end of R4 and the fifth pin of U3. The fourth pin of T2 is connected to GND.

[0026] like Figure 3The primary and secondary MOSFET detection circuit includes: transistors Q10 to Q15, resistors R26 to R32, and diode D5; the left end of R29 is the drive signal GATE, connected to pin 6 of U3; the right end of R29 is connected to the emitter of Q12, the base of Q12 is connected to the collector of Q13, the collector of Q12 is connected to the upper end of R31, the base of Q11, the base of Q15, and the common terminal of R8, and the collector of Q12 is the drive signal DRV3; the base of Q13 is connected to the left end of R30, the left end of R30 is connected to the VG pin of U2, and the left end of R30 is the drive signal VG; the emitter of Q13 and the lower end of R31 are connected to GND; the collector of Q11 is connected to the emitter of Q10, the left end of R28, and the common terminal of the negative terminal of D5, Q1... The emitter of Q1 is connected to GND; the collector of Q10 is connected to the left end of R29 and pin 6 of U3, and the collector of Q10 is the drive signal GATE; the base of Q10 is connected to the right end of R26, and the left end of R26 is connected to a 5V voltage; the positive terminal of D5 is connected to the left end of R27, and the right end of R27 is connected to the right end of R28, the gate of Q4, and the upper end of R12, and the right end of R27 is the drive signal DRV1; the emitter of Q15 is connected to GND, and the collector of Q15 is connected to the emitter of Q14 and the gate of Q1, and the collector of Q15 is the drive signal DRV2; the base of Q14 is connected to the right end of R32, and the collector of Q14 is connected to the left end of R30 and pin VG of U2, and the collector of Q14 is the drive signal VG; the left end of R32 is connected to a 5V voltage.

[0027] When the secondary MOSFET driver chip U2 provides the drive voltage GATE, Q13 will turn on, and the base of Q12 connected to it will be pulled low, thus turning on Q12. When the primary MOSFET driver chip U3 also provides the drive voltage GATE, the circuit protection mechanism will be triggered. That is, when both the primary MOSFET driver chip U3 and the secondary MOSFET driver chip U2 generate drive signals, Q11 and Q15 will turn on, grounding DRV1 and DRV2 to 0, so that the drive signals GATE and VG no longer pass through Q4 and Q1, thereby achieving circuit protection.

[0028] In addition, the drive signals of Q10 and Q14 are powered by the voltage regulator chip U1 of the voltage regulator circuit; U1 can provide a stable 5V voltage, and its output voltage is not affected by the voltage signal of the output circuit; thus, even if the output circuit experiences voltage fluctuations or abnormal conditions, the stability and reliability of the entire flyback switching power supply are ensured.

[0029] The voltage regulator circuit includes: a voltage regulator chip U1, capacitors C1 and C2, and diode D1. The positive terminal of D1 is connected to pin 5 of T2, the negative terminal of D1 is connected to the IN pin of U1 and the upper end of C1, the OUT pin of U1 is connected to the upper end of C2, and the lower ends of C2 and C1 are connected to the GND pin of U1 (GND0). U1 outputs a 5V voltage.

[0030] The self-locking circuit includes a self-locking drive circuit, a first self-locking circuit, and a second self-locking circuit; wherein... The self-locking circuit driver circuit includes: resistors R8, R11, R15, and transistor Q3. The right end of R8 is the self-locking drive voltage DRV3. The left end of R8 is connected to the positive terminal of D4. The negative terminal of D4 is connected to the base of Q3. The collector of Q3 is connected to a 5V voltage. The emitter of Q3 is connected to the common terminal of R11 and R15. The lower end of R15 is connected to GND.

[0031] The first self-locking circuit includes: MOSFET Q5, transistors Q6 and Q2, resistors R5, R6, R16, and R17; the gate of Q5 is connected to the left end of R11; the source and drain of Q5 are connected in parallel to the collector and emitter of Q6; R16 and R17 are connected in parallel to the base and emitter of Q6; the upper end of R16 is connected to the collector of Q2; the two ends of the parallel connection of R5 and R6 are connected to the emitter and base of Q2, respectively; the base of Q2 is connected to the collector of Q6; the upper end of R5 is connected to the VCC pin of U2 and the 5th pin of T2. Before the first self-locking circuit is triggered, the voltage across R5 is high, so the startup pin voltage VCC of the synchronous rectifier chip U2 is also high, and U2 is in normal working condition. When the first self-locking circuit is completed, due to the continuous conduction of Q2 and Q6, the voltage across R5 will be pulled to low level, which will also cause the startup pin of U2 to be pulled to low level, and U2 will stop working.

[0032] The second self-locking circuit includes: MOSFET Q8, transistors Q7 and Q9, resistors R13, R14, R19, and R20; the gate of Q8 is connected to the left end of R11, the source and drain of Q8 are connected in parallel to the collector and emitter of Q9, R19 and R20 are connected in parallel to the base and emitter of Q9, the upper end of R19 is connected to the collector of Q7, the two ends of R13 and R14 are connected in parallel to the emitter and base of Q7 respectively, the base of Q7 is connected to the collector of Q9; the upper end of R13 is connected to the VDD pin of U3.

[0033] When Q1 and Q4 are both on, i.e., both GATE and VG are high, DRV3 is high, so transistor Q3 will turn on, and the high-level signal will be sent to the gates of Q5 and Q8. Since MOSFETs are voltage-controlled devices, when the gate receives a sufficient high-level signal, the source and drain of Q5 and Q8 will turn on. This conduction state then triggers two self-locking circuit mechanisms, causing U2 and U3 to stop working. Specifically, the conduction of Q5 causes the base voltage of the transistor Q2 connected to it to be pulled low. When the base voltage of transistor Q2 drops to a certain level, Q2 enters saturation, and its collector and emitter... When Q2 is turned on, the voltage signal flows through Q2 and reaches the base of Q6, causing Q6 to also enter saturation, and its collector and emitter are connected. When Q6 is turned on, it will, in turn, maintain the base of Q2 at a low level through the low impedance path between its collector and emitter. This is because the conduction of Q6 pulls down the voltage of the node connected to the base of Q2, thereby ensuring that Q2 continues to conduct. In this way, Q2 will continue to be turned on, and the voltage signal will continue to pass through Q2, ensuring that the base of Q6 is always at a sufficient level to maintain its conduction state. This series of actions completes the self-locking process of the first self-locking circuit.

[0034] Similarly, since the drive signals for MOSFETs Q5 and Q8 come from the same voltage signal, Q5 and Q8 can conduct simultaneously. The gate of Q8 also receives the divided voltage signal, which will turn on and trigger the second self-locking circuit composed of Q7 and Q9. The working principle of this self-locking circuit is similar to that of the first self-locking circuit: the conduction of Q8 causes the base voltage of Q7 to be pulled low, and Q7 enters the saturation state. Subsequently, the voltage signal flows through Q7 to the base of Q9, causing Q9 to also enter the saturation state. The conduction of Q9, in turn, keeps the base of Q7 at a low level, thus completing the self-locking process of the second self-locking circuit. When the second self-locking circuit is completed, the start pin VDD of U3 will also change from the original high level to a low level, and U3 will stop working.

[0035] After the circuit completes its self-locking, the start pins of U2 and U3 are pulled low from high level to low level. Since U2 and U3 do not have sufficient voltage input, they will stop working. The chip's cessation of operation prevents Q1 and Q4 from turning on and off normally. Therefore, the transformer in the power conversion circuit will no longer store or convert energy, and the output circuit will no longer have voltage or current flowing out, thus effectively protecting the output circuit and preventing it from being damaged due to Q4 and Q1 conducting simultaneously.

[0036] The voltage feedback circuit includes: optocoupler sensor U4, resistors R9, R10, R23, R24, R25, capacitors C9, C10, C11, and voltage regulator U5; the upper end of resistor R9 is connected to pin 5 of the secondary winding of T2, and the lower end is connected to the left end of resistor R23 and pin 1 of U4; pin 2 of U4 is connected to pin 1 of U5; pin 2 of U5 is connected to the common terminal of R10 and R25; and pin 3 of U5 is connected to R25. The lower end of R23 is connected to GND0; the right end of R23 is connected to the common terminal of the left end of C9, the left end of R24, and the first pin of U5; the right end of R24 is connected to the left end of C10; the right ends of C9 and C10 are connected to the lower end of R10; the upper end of R10 is connected to the fifth pin of the secondary winding of T2; the fourth pin of U4 is connected to the FB pin of U3 and the upper end of C11; the third pin of U4 is connected to the lower end of C11 and GND.

[0037] When the output voltage of T2 increases, the sampling voltage at pin 2 of U5 increases, leading to increased conductivity of U5 and thus increased current flowing through it. This also increases the current in the LED of U4, resulting in a similar increase in the current in the transistor of U4. Consequently, the voltage at the feedback pin FB of U3 decreases, reducing the duty cycle of the output pin GATE of U3 and thus lowering the output voltage of T2. Conversely, when the output voltage decreases, the sampling voltage of U5 decreases, reducing the current flowing through it. This leads to a decrease in the current in the optocoupler sensor's transistor, causing the voltage at the feedback pin FB of U3 to increase. This, in turn, increases the duty cycle of the output pin GATE of U3, thereby increasing the voltage of the secondary circuit and achieving feedback regulation.

[0038] The synchronous rectification control circuit includes: MOSFET Q1, capacitor C7, and synchronous rectification chip U2. U2 has a startup pin VCC, a drive pin VG, a device bias pin REG, a drain voltage detection pin VD, and a source voltage detection pin VS. The lower end of C7 is connected to the REG pin of U2, and the upper end of C7 is connected to the source of Q1 and the lower ends of C5 and R1. The drain of Q1 is connected to the VD pin of U2 and the 6th pin of T2. The gate of Q1 is connected to the DRV2 pin of the primary and secondary MOSFET detection circuit, and the source of Q1 is connected to the VS pin of U2. The startup pin VCC of U2 is connected to the 5th pin of the secondary winding. The VG pin of U2 is connected to the VG pin of the primary and secondary MOSFET detection circuit.

[0039] The output circuit includes: load resistor R1 and capacitor C5; the upper end of R1 is connected to pin 5 of T2, and the lower end of R1 is connected to the gate of Q1 and the lower end of C5; the upper end of C5 is connected to pin 5 of T2, and the lower end of C5 is connected to GND0.

[0040] In this embodiment, Q2, Q7, and Q12 are PNP transistors, model SS8550; Q3, Q6, Q9, Q10, Q11, Q13, Q14, and Q15 are NPN transistors, model SS8050; and Q1, Q4, Q5, and Q8 are NMOS transistors, model 2N7002.

[0041] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection, characterized in that, include: The circuit consists of a primary-side control circuit, a power conversion circuit, a synchronous rectification control circuit, a primary / secondary-side MOSFET detection circuit, a self-locking circuit, and an output circuit; among which, The primary and secondary MOSFET detection circuit is used to detect whether the primary and secondary MOSFETs are turned on simultaneously and to provide a self-locking drive voltage. The self-locking circuit is used to detect when the primary-side MOSFET and the secondary-side MOSFET are simultaneously turned on. It pulls the start-up voltage of the primary-side control circuit and the synchronous rectification control circuit to a low level, thereby stopping the power conversion circuit from working until the input voltage is disconnected.

2. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, The primary and secondary side MOSFET detection circuit includes: transistors Q10 to Q15, resistors R26 to R32, and diode D5; the left end of R29 is connected to the primary side control circuit; the right end of R29 is connected to the emitter of Q12, the base of Q12 is connected to the collector of Q13, and the collector of Q12 is connected to the upper end of R31, the base of Q11, the base of Q15, and the self-locking circuit; the base of Q13 is connected to the right end of R30, and the left end of R30 is connected to the synchronous rectification control circuit; the collector of Q11... The emitter of Q10, the left end of R28, and the negative terminal of D5 are connected; the collector of Q10 is connected to the left end of R29 and the primary-side control circuit; the base of Q10 is connected to the right end of R26; the positive terminal of D5 is connected to the left end of R27, and the right end of R27 is connected to the right end of R28 and the primary-side control circuit; the collector of Q15 is connected to the emitter of Q14 and the synchronous rectification control circuit; the base of Q14 is connected to the right end of R32, and the collector of Q14 is connected to the left end of R30 and the synchronous rectification control circuit.

3. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, The primary-side control circuit controls the on and off states of the primary-side MOSFET.

4. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, The synchronous rectification circuit is used to control the on and off states of the secondary-side MOSFETs.

5. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, Power conversion circuits are used to convert input voltage into a stable output voltage.

6. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, The output circuit provides voltage and current to the load.

7. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, Also includes: Voltage feedback circuits are used to regulate the magnitude of the output voltage.

8. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, Also includes: AC / DC converter circuits are used to convert AC power to DC power.

9. The flyback switching power supply circuit based on primary and secondary side MOSFET conduction detection according to claim 1, characterized in that, Also includes: The voltage regulator circuit is used to output a 5V voltage.

Images