A self-driven synchronous rectification protection circuit

Abstract

The application provides a self-driven synchronous rectification protection circuit, which comprises a power circuit, a synchronous rectification circuit and a protection circuit. The power circuit provides power VF1 and VF2 for the synchronous rectification circuit and provides driving for the protection circuit, and outputs power V0 and a driving square wave. The input end of the synchronous rectification circuit is connected with two output powers VF1 and VF2 of the power circuit, and the output end is used as the driving of the secondary square wave of the power circuit, so as to rectify the power circuit. The driving of the protection circuit is the same as the driving of the primary square wave of the power circuit, and the output of the protection circuit is used as the driving of the secondary square wave of the power circuit, so as to ensure that the output of the power circuit will not drop in the voltage rising process and will not generate negative voltage in the voltage descending process. The application can prevent the power supply from dropping in the starting rising process and can prevent the output current from returning to the power supply in the shutdown process.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, specifically relating to a self-driven synchronous rectification protection circuit. Background Technology

[0002] Since there is no driver chip, the drive waveform comes from the transformer. The self-driven synchronous rectifier circuit is usually uncontrolled when the switching power supply is started and turned off. When the power is turned on, the power supply rise process drops, and when the power is turned off, the output current flows back, causing the synchronous rectifier MOSFET to burn out. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a self-driven synchronous rectification protection circuit. The solution of this invention can solve the problems existing in the prior art.

[0004] The technical solution of this invention:

[0005] A self-driven synchronous rectification protection circuit includes a power circuit, a synchronous rectification circuit, and a protection circuit. The power circuit provides power VF1 and VF2 to the synchronous rectification circuit and drives the protection circuit, outputting power V0 and a driving square wave. The input terminal of the synchronous rectification circuit is connected to the two output powers VF1 and VF2 of the power circuit, and its output terminal serves as the driver for the secondary square wave of the power circuit, rectifying the power circuit and preventing negative voltage from appearing in the output power of the power circuit. The driving of the protection circuit is the same as the driving of the primary square wave of the power circuit. The output of the protection circuit serves as the driver for the secondary square wave of the power circuit, ensuring that the output of the power circuit does not drop during voltage rise and does not generate negative voltage during voltage drop.

[0006] Furthermore, the power circuit includes driver one, driver two, MOSFET one, MOSFET two, capacitor seven, transformer, MOSFET three, and MOSFET four. Driver one provides drive for MOSFET three, and driver two provides drive for MOSFET four. MOSFET four and capacitor seven are connected in series and then in parallel with MOSFET three, located on one side of the transformer, providing power and a square wave to the circuit on the other side of the transformer. The circuit on the other side of the transformer is a circuit in parallel with MOSFET one and MOSFET two, outputting power V0 at one end of MOSFET two and grounding at the other end, generating output powers Vf1 and Vf2 as inputs to the synchronous rectification circuit.

[0007] Furthermore, the synchronous rectification circuit includes capacitors 8, 9, 10, and 11, resistors 1, 4, and 5, MOSFET 5, and MOSFET 6. Capacitors 8 and 10 are connected in parallel, with one end connected to the input power Vf1 and the other end connected to pin 1 of MOSFET 5. The input power Vf2, after passing through resistor 5, drives MOSFET 5 and is connected to pin 2 of MOSFET 5. Resistor 1, capacitor 9, and pin 2 of MOSFET 6 are connected to pin 1 of MOSFET 5. The other end of resistor 1, the other end of capacitor 9, and pin 3 of MOSFET 6, along with resistors 4 and 11, are connected to pin 3 of MOSFET 5. Pin 1 of MOSFET 5 is connected to the other end of resistor 4, the other end of capacitor 11, and pin 1 of MOSFET 6. Power Vd1 is output from pin 2 of MOSFET 6, and power Vd2 is output from pin 1 of MOSFET 6.

[0008] Furthermore, the protection circuit includes diode 1, diode 2, capacitor 12, transistor 2, transistor 3, transistor 4, capacitor 12, capacitor 13, resistor 2, resistor 3, resistor 6, and an optocoupler. The driver 1 is connected to the anode of diode 1, the cathode of diode 1 is connected to resistor 3, the other end of resistor 3 is connected to the anode of the optocoupler's diode, the base of transistor 4, and capacitor 12, the other end of capacitor 12 is connected to the emitter of transistor 4, and the cathode of the optocoupler's diode is connected to... The collector of transistor four is connected, the collector of the optocoupler transistor is connected to the positive terminal of diode two and resistor two, the emitter of the optocoupler transistor is connected to resistor six, capacitor thirteen and the base of transistor three, the other end of resistor six, the other end of capacitor thirteen, the emitter of transistor three and the emitter of transistor two are connected, the negative terminal of diode two, the other end of resistor two and the base of transistor two are connected, the collector of transistor two is connected to power Vd1, and the positive terminal of diode two is connected to power V0.

[0009] The beneficial effects of this invention compared to the prior art are as follows:

[0010] (1) When the present invention is powered on, Vd1 is delayed to start. MOS transistors 1 and 2 are rectified by diodes during the startup process. After startup, they enter synchronous rectification to ensure that the output power will not drop during the rise of the output voltage. The Vd1 drive waveform voltage is not directly given as a square wave, but rises with resistor 3 and capacitor 12 to ensure that MOS transistors 1 and 2 will not cause output drop when they enter synchronous rectification from diode rectification.

[0011] (2) When the present invention is turned off, since the base of transistor 2 changes with the output power of the power circuit, before the output power of the power circuit is turned off to 0, transistor 2 will gradually reduce the output power to 0, so that MOS transistor 2 will gradually enter the diode rectification state from the synchronous rectification state, and will definitely enter the diode rectification state before the output power is 0, so that the output power of the power circuit will not be negative. Attached Figure Description

[0012] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0013] Figure 1 (a)(b)(c) show schematic diagrams of a self-driven synchronous rectification protection circuit according to an embodiment of the present invention. Detailed Implementation

[0014] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0016] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0017] like Figure 1 As shown, according to an embodiment of the present invention, a self-driven synchronous rectification protection device is provided, including a power circuit, a synchronous rectification circuit, and a protection circuit. The power circuit provides power VF1 and VF2 to the synchronous rectification circuit and provides drive for the protection circuit, outputting power V0 and a drive square wave. The input terminal of the synchronous rectification circuit is connected to the two output powers VF1 and VF2 of the power circuit, and the output terminal serves as the drive for the secondary square wave of the power circuit, rectifying the power circuit and preventing negative voltage from appearing in the output power of the power circuit. The drive of the protection circuit is the same as the drive of the primary square wave of the power circuit. The output of the protection circuit serves as the drive for the secondary square wave of the power circuit, ensuring that the output of the power circuit will not drop during voltage rise and will not generate negative voltage during voltage drop.

[0018] Further in one embodiment, such as Figure 1 As shown in (a), the power circuit includes a driver VG1, a driver VG2, a MOSFET Q1, a MOSFET Q2, a capacitor C7, a transformer T1, a MOSFET Q3, and a MOSFET Q4. Driver VG1 drives the MOSFET Q3, and driver VG2 drives the MOSFET Q4, generating the primary drive square wave of the power circuit. The MOSFET Q4 and capacitor C7 are connected in series and then in parallel with the MOSFET Q3, located on one side of the transformer, providing power and square waves to the circuit on the other side of the transformer. The circuit on the other side of the transformer is a circuit in parallel with the MOSFET Q1 and MOSFET Q2, outputting power V0 at one end of MOSFET Q2 and grounding the other end, generating output power Vf1 and Vf2 as inputs to the synchronous rectification circuit.

[0019] Further in one embodiment, such as Figure 1As shown in (b), the synchronous rectification circuit includes capacitors C8, C9, C10, C11, R1, R4, R5, MOSFET Q5, and MOSFET Q6. C8 and C10 are connected in parallel, with one end connected to the input power Vf1 and the other end connected to pin 1 of MOSFET Q5. The input power Vf2, after passing through resistor R5, drives MOSFET Q5 and is connected to pin 2 of MOSFET Q5. Resistors R1 and C9, C10, and C11... Pin 2 of MOSFET Q6 (C9) is connected to pin 1 of MOSFET Q5 (Q5). The other end of resistor R1, the other end of capacitor C9, pin 3 of MOSFET Q6, resistor R4, capacitor C11, and pin 3 of MOSFET Q5 are connected. Pin 1 of MOSFET Q5 is connected to the other end of resistor R4, the other end of capacitor C11, and pin 1 of MOSFET Q6. Power Vd1 is output from pin 2 of MOSFET Q6, and power Vd2 is output from pin 1 of MOSFET Q6. The design of MOSFETs Q5 and Q6, along with the capacitors, prevents negative voltages in power outputs Vd1 and Vd2, thus ensuring the stability of the drive square wave and the overall power output of the power circuit.

[0020] Further in one embodiment, such as Figure 1 As shown in (c), the protection circuit includes diode P1, diode P2, capacitor C12, transistors V2, V3, and V4, capacitors C12 and C13, resistors R2, R3, and R6, and optocoupler IC1. Driver VG1 is connected to the anode of diode P1, and the cathode of diode P1 is connected to resistor R3. The other end of resistor R3 is connected to the anode of diode P1, the base of transistor V4, and capacitor C12. The other end of capacitor C12 is connected to the emitter of transistor V4. The negative terminal of diode 1 is connected to the collector of transistor 4V4. The collector of optocoupler IC1 is connected to the positive terminal of diode 2P2 and resistor 2R2. The emitter of optocoupler IC1 is connected to resistor 6R6, capacitor 13C13 and the base of transistor 3V3. The other end of resistor 6R6, the other end of capacitor 13C13, the emitter of transistor 3V3 and the emitter of transistor 2V2 are connected. The negative terminal of diode 2V2, the other end of resistor 2R2 and the base of transistor 2V2 are connected. The collector of transistor 2V2 is connected to power Vd1. The positive terminal of diode 2V2 is connected to power V0.

[0021] In the protection circuit, R3, C12, and V4 are signal delay devices. Adjusting the values ​​of R3 and C12 adjusts the turn-on time of V4 and the current flowing through it, which is used to control the turn-on time and rise rate of the synchronous rectifier drive Vd1. IC1 is used to transmit the current signal. R6 is used to discharge C13 and reduce the charging speed of C13. C13 is used to filter V3 and delay the turn-on time of V3. V2 is used to ensure that the control signal Vd1 is consistent with the shutdown when the circuit is turned off. R2 is used to turn on V2 and turn off the synchronous rectifier drive Vd1.

[0022] The circuit works as follows:

[0023] When the power is turned on, VG1 immediately generates a drive, Q3 switch generates a square wave, the transformer transmits the square wave to Vo / GND for output power and Vf1, Vf2 for generating synchronous rectification drive of Q1, Q2.

[0024] When VG1 is generated, since R3, C12, and V4 will not turn on immediately, IC1 has no current. However, the power circuit is working at this time, and Vo output is the set value. Then R2 drives V2 to turn on, and Vd1 is pulled low. At this time, the synchronous rectifier MOSFET Q2 does not work.

[0025] When the set time is reached, V4 turns on, and the current on the diode side of IC1 increases from 0 to (VG1-V1) / R3; the time is approximately 5 / (R3×C12);

[0026] As the current on the IC1 diode side increases, the optocoupler transistor coupled photocurrent increases from 0 to CTR×(VG1-V1) / R3.

[0027] Assuming the current amplification factor of V3 is β, in one embodiment, β is selected as 80-160, then V2 is gradually turned on, and the driving voltage of Vd1 gradually increases at the corresponding rate.

[0028] When the power is turned off, the base voltage of V2 drops rapidly with Vo, and Vd1 follows suit, causing the drive to turn off before the power-off process is complete.

[0029] In summary, the self-driven synchronous rectification protection device provided by this invention has at least the following advantages compared to the prior art:

[0030] (1) When the present invention is powered on, Vd1 is delayed to start. MOS transistors 1 and 2 are rectified by diodes during the startup process. After startup, they enter synchronous rectification to ensure that the output power will not drop during the rise of the output voltage. The Vd1 drive waveform voltage is not directly given as a square wave, but rises with resistor 3 and capacitor 12 to ensure that MOS transistors 1 and 2 will not cause output drop when they enter synchronous rectification from diode rectification.

[0031] (2) When the present invention is turned off, since the base of transistor 2 changes with the output power of the power circuit, before the output power of the power circuit is turned off to 0, transistor 2 will gradually reduce the output power to 0, so that MOS transistor 2 will gradually enter the diode rectification state from the synchronous rectification state, and will definitely enter the diode rectification state before the output power is 0, so that the output power of the power circuit will not be negative.

[0032] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-driven synchronous rectification protection circuit, characterized in that, The system includes a power circuit, a synchronous rectification circuit, and a protection circuit. The power circuit provides power VF1 and VF2 to the synchronous rectification circuit and drives the protection circuit. It outputs power V0 and a driving square wave. The input terminal of the synchronous rectification circuit is connected to the two output powers VF1 and VF2 of the power circuit. The output terminal drives the secondary square wave of the power circuit to rectify the power circuit and prevent negative voltage from appearing in the output power of the power circuit. The driving of the protection circuit is the same as the driving of the primary square wave of the power circuit. The output of the protection circuit drives the secondary square wave of the power circuit, ensuring that the output of the power circuit will not drop during voltage rise and will not generate negative voltage during voltage drop. The power circuit includes driver 1, driver 2, MOSFET 1, MOSFET 2, capacitor 7, transformer, MOSFET 3, and MOSFET 4. Driver 1 provides drive for MOSFET 3, and driver 2 provides drive for MOSFET 4. MOSFET 4 and capacitor 7 are connected in series and then in parallel with MOSFET 3, located on one side of the transformer, providing power and a square wave to the circuit on the other side of the transformer. The circuit on the other side of the transformer is a circuit in parallel with MOSFET 1 and MOSFET 2, outputting power V0 at one end of MOSFET 2 and grounding at the other end, generating output powers Vf1 and Vf2 as inputs to the synchronous rectification circuit. The synchronous rectification circuit includes capacitors 8, 9, 10, and 11, resistors 1, 4, and 5, MOSFET 5, and MOSFET 6. Capacitors 8 and 10 are connected in parallel, with one end connected to the input power Vf1 and the other end connected to pin 1 of MOSFET 5. The input power Vf2, after passing through resistor 5, drives MOSFET 5 and is connected to pin 2 of MOSFET 5. Resistor 1, capacitor 9, and pin 2 of MOSFET 6 are connected to pin 1 of MOSFET 5. The other end of resistor 1, the other end of capacitor 9, and pin 3 of MOSFET 6, along with resistors 4 and 11, are connected to pin 3 of MOSFET 5. Pin 1 of MOSFET 5 is connected to the other end of resistor 4, the other end of capacitor 11, and pin 1 of MOSFET 6. Power Vd1 is output from pin 2 of MOSFET 6, and power Vd2 is output from pin 1 of MOSFET 6. The protection circuit includes diode 1, diode 2, capacitor 12, transistor 2, transistor 3, transistor 4, capacitor 12, capacitor 13, resistor 2, resistor 3, resistor 6, and an optocoupler. The driver 1 is connected to the anode of diode 1, the cathode of diode 1 is connected to resistor 3, the other end of resistor 3 is connected to the anode of the optocoupler's diode, the base of transistor 4, and capacitor 12, the other end of capacitor 12 is connected to the emitter of transistor 4, and the cathode of the optocoupler's diode is connected to... The collector of transistor four is connected, the collector of the optocoupler transistor is connected to the positive terminal of diode two and resistor two, the emitter of the optocoupler transistor is connected to resistor six, capacitor thirteen and the base of transistor three, the other end of resistor six, the other end of capacitor thirteen, the emitter of transistor three and the emitter of transistor two are connected, the negative terminal of diode two, the other end of resistor two and the base of transistor two are connected, the collector of transistor two is connected to power Vd1, and the positive terminal of diode two is connected to power V0.

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