A reverse-connection protected DC input soft-start circuit and method with a protection shutdown function

Abstract

The present invention discloses an anti-reverse connection DC input soft-start circuit and method with a protection shutdown function. The circuit includes an anti-reverse connection circuit, a direct-through bypass, a protection circuit, a drive control circuit, and an anti-inrush current soft-start circuit. The anti-reverse connection circuit is disconnected when the input voltage is reversely connected. The anti-inrush current soft-start circuit is connected in parallel with the direct-through bypass. When the input voltage is normal, the anti-inrush current soft-start circuit pre-charges the energy storage device at the DC input port, and when the energy storage device is charged to a preset value, it drives the DC bypass to conduct so that the subsequent circuit is normally powered. When the protection circuit detects a fault, it controls the drive of the direct-through bypass and the anti-inrush current soft-start circuit to be turned off through the control circuit, so that the input voltage is disconnected from the subsequent circuit. When faults such as over-voltage, under-voltage, over-current, and over-heat occur and protection shutdown is required, the present invention can control the soft-start circuit and the direct-through bypass to be disconnected simultaneously, thereby disconnecting the main circuit and improving the reliability of the device.

Description

Technical Field

[0001] The present invention belongs to the field of electronic technology, and particularly relates to an anti-reverse connection DC input soft-start circuit and method with a protection shutdown function. Background Art

[0002] Generally, capacitors with different capacities are used at the DC input port of the power supply of electronic devices. When voltage is suddenly applied or the device is powered on, a large inrush current will be generated, which has a certain impact on the front-end power supply device, the selection of the fuse at the input end of the electronic device, and the reliability of the components. Each version of the airborne equipment environmental conditions and test standard RTCA / DO-160 has clear limit requirements for the peak value of the inrush current generated when voltage is suddenly applied to the device. In order to overcome this inrush current, an appropriate anti-reverse connection and soft-start protection circuit needs to be equipped at the DC input end of the power supply of the electronic device.

[0003] Currently, in the existing DC power input anti-reverse connection and soft-start protection circuits, two MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) Q1 and Q2 are usually used to implement the anti-reverse connection and soft-start functions. As Figure 1 shown, among them, Q2 plays the role of anti-reverse connection. When just powered on, it conducts through its internal diode. After normal power-on, R4, R5, and ZD2 generate a positive voltage drop for the GS pole of Q2, and the tube turns on, reducing the loss caused by the forward voltage drop of its internal diode. Q1 plays the role of soft start. R2 slowly charges C1, and the GS pole voltage of Q1 rises slowly, acting as a variable resistor to limit the input current. When overvoltage or undervoltage occurs, the over / under voltage protection circuit drives the optocoupler OC1, making the secondary side CE of the optocoupler conduct, pulling down the GS pole voltage of Q1, playing the role of over / under voltage protection shutdown, and protecting the DC input of the subsequent DC input converter from being damaged by high voltage or not working in an unstable undervoltage state. However, since it works in the linear region of the MOSFET, usually the above solution needs to use MOSFET packages with larger rated voltage and rated current, and the cost performance is relatively low. Moreover, if the capacitance of C2 is large and the input voltage is large, this MOSFET is extremely prone to excessive short-term loss, and the heat cannot be dissipated in time, exceeding its safe operating area and causing damage or reducing its lifespan.

[0004] In order to solve the problem that the MOSFET in the above-mentioned prior art is extremely prone to excessive short-term loss and is likely to be damaged or have its lifespan reduced, the industry adopts Figure 2In the proposed solution where R1 and Q1 are connected in parallel, the capacitance value of C1 is increased. Before Q1 conducts, resistor R1 pre-charges C2. When C2 is charged to a certain value, Q1 is turned on, which not only reduces the short-term loss when Q1 conducts but also short-circuits resistor R1 during operation to provide a normal working current path. However, when over-voltage or under-voltage protection occurs, resistor R1 cannot break the circuit, and thus cannot fully protect the subsequent circuit.

[0005] To address the problems existing in the above solution where R1 and Q1 are connected in parallel, a P-channel MOSFET Q3 is added to the main path, as Figure 3 shown. When over-voltage or under-voltage protection or over-current protection occurs, Q3 is turned off, achieving disconnection protection well. Equivalently, Q3 can be a variable N-channel MOSFET, connected in series to the loop of Q1 and Q2. However, as the main circuit path switch, Q3 must be selected with the same voltage and current specifications as Q1 and Q2, which undoubtedly increases the cost, the area of the circuit board, and the volume of the device. Summary of the Invention

[0006] To solve the problems existing in the above-mentioned prior art, the present invention provides an anti-reverse connection DC input soft-start circuit with a protection shutdown function.

[0007] The present invention is realized through the following technical solutions:

[0008] An anti-reverse connection DC input soft-start circuit with a protection shutdown function includes an anti-reverse connection circuit, a direct-through bypass, a protection circuit, a drive control circuit, and an anti-surge current soft-start circuit;

[0009] The anti-reverse connection circuit disconnects under the condition of reverse connection of the input voltage, so that the input voltage is disconnected from the subsequent circuit;

[0010] The anti-surge current soft-start circuit is connected in parallel with the direct-through bypass. Under the condition of normal input voltage, the anti-surge current soft-start circuit pre-charges the energy storage device at the DC input port, and when the energy storage device is charged to a preset value, drives the DC bypass to conduct to supply power to the subsequent circuit normally;

[0011] When the protection circuit detects a fault, it controls the drive of the direct-through bypass and the anti-surge current soft-start circuit to be turned off through the drive control circuit, so that the input voltage is disconnected from the subsequent circuit.

[0012] The present invention can, on the premise of ensuring the anti-reverse connection and soft-start functions, control the soft-start circuit and the direct-through bypass to be disconnected simultaneously when faults such as over-voltage, under-voltage, over-current, and overheat occur and protection shutdown is required, thereby disconnecting the main circuit and protecting the circuit from further damage and dangerous accidents, improving the reliability of the device.

[0013] As a preferred embodiment, the reverse connection prevention circuit of the present invention includes MOSFET Q2, zener diode ZD2, resistor R4 and resistor R5;

[0014] The direct connection bypass includes MOSFET Q1, resistor R2, resistor R3, resistor R6, capacitor C1, zener diode ZD1 and diode D1;

[0015] The inrush current soft start circuit includes MOSFET Q4 and resistor R1;

[0016] Among them, one end of resistor R4 is connected to the input voltage, the other end of resistor R4 is connected to one end of resistor R5, and the other end of resistor R5 is connected to the source electrode of Q2; the drain electrode of Q2 is grounded, the gate electrode of Q2 is connected to the common connection end of resistor R4 and resistor R5, and the source electrode of Q2 is connected to the source electrode of Q1; zener diode ZD2 is connected in parallel between the gate electrode and the source electrode of Q2;

[0017] The source electrode of Q1 is connected to the source electrode of Q4, the gate electrode of Q1 is connected to the gate electrode of Q4, one end of resistor R2 and one end of resistor R3 through resistor R6, and the drain electrode of Q4 is connected to the drain electrode of Q1 and the energy storage device through resistor R1;

[0018] Capacitor C1 is connected in parallel between the gate electrode and the source electrode of Q1;

[0019] The other end of resistor R2 is connected to the input voltage, and the other end of resistor R3 is connected to the source electrode of Q1;

[0020] Zener diode ZD1 is connected in parallel across resistor R3, and diode D1 is connected in parallel across resistor R6.

[0021] As a preferred embodiment, the direct connection bypass of the present invention further includes diode D3;

[0022] The diode D3 is connected in series between resistor R2 and resistor R3.

[0023] As a preferred embodiment, the direct connection bypass of the present invention further includes resistor R8;

[0024] The resistor R8 is connected in series with diode D1 and then connected in parallel across resistor R6.

[0025] As a preferred embodiment, the resistor R2 of the present invention can be designed with equivalent series-parallel connection according to the magnitude of the input voltage.

[0026] As a preferred embodiment, the reverse connection prevention circuit of the present invention further includes diode D2;

[0027] The diode D2 is connected in series between resistor R4 and resistor R5.

[0028] As a preferred embodiment, the resistor R4 of the present invention can be designed with series-parallel equivalence according to the magnitude of the input voltage.

[0029] As a preferred embodiment, the drive control circuit of the present invention includes an optocoupler OC1 and a resistor R7;

[0030] The input end of the optocoupler OC1 is connected through the resistor R7 and a protection circuit;

[0031] The collector C of the photosensitive triode of the optocoupler OC1 is connected to the common connection end of the gate of Q4, the resistor R6 and the resistor R3;

[0032] The emitter E of the photosensitive triode of the optocoupler OC1 is connected to the source of Q4 and the source of Q1.

[0033] As a preferred embodiment, the optocoupler OC1 of the present invention can be replaced by a magnetic isolation device, a triode, a comparator or a relay.

[0034] On the other hand, the present invention proposes a working method of the anti-reverse connection DC input soft-start circuit as described in the present invention, including:

[0035] After power-on and startup, if there is a fault, the protection circuit controls the drive of Q1 and Q4 to turn off through the drive control circuit, and the fault voltage is disconnected from the subsequent circuit; if the input is reverse-connected, Q2 is cut off, and the input voltage is disconnected from the subsequent circuit;

[0036] If there is no fault or reverse connection and the input voltage is within the normal range, the input voltage charges the energy storage device through the resistor R1, so as to achieve the function of soft start; during the power-on process, the body diode of Q2 conducts first, and the input voltage drives Q2 to conduct through the resistor R4, the resistor R5 and the zener diode ZD2, reducing the conduction loss;

[0037] During the soft-start process, the input voltage charges the capacitor C1 through the resistor R2 and the resistor R6. When the voltage of the capacitor C1 reaches the preset value, Q1 conducts;

[0038] After Q1 conducts, the subsequent circuit can be normally turned on and powered;

[0039] If a fault occurs during normal operation, the protection circuit turns on and off Q1 and Q4 by controlling the drive control circuit. When Q1 is turned off, the voltage of the capacitor C1 discharges through the diode D1.

[0040] The present invention has the following advantages and beneficial effects:

[0041] The present invention can, on the premise of ensuring the functions of anti-reverse connection and soft start, timely disconnect the input short circuit when faults such as overvoltage, overcurrent and overheating occur, protect the subsequent circuit from being damaged, and improve the reliability of the equipment.

[0042] In the present invention, a MOSFET is connected in series on the slow start resistor branch. The MOSFET can be selected to have a smaller current specification than the MOSFET on the main circuit, which reduces the cost and has a relatively small impact on the circuit board area. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0044] Figure 1 is the circuit schematic diagram of the prior art 1.

[0045] Figure 2 is the circuit schematic diagram of the prior art 2.

[0046] Figure 3 is the circuit schematic diagram of the prior art 3.

[0047] Figure 4 is the circuit principle block diagram of the embodiment of the present invention.

[0048] Figure 5 is the circuit schematic diagram of the embodiment of the present invention.

[0049] Figure 6 is the circuit operation flowchart of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] In the following, the term "comprise" or "may comprise" that can be used in various embodiments of the present invention indicates the presence of the functions, operations, or elements of the present invention, and does not limit the addition of one or more functions, operations, or elements. In addition, as used in various embodiments of the present invention, the terms "comprise", "have" and their cognates are only intended to represent specific features, numbers, steps, operations, elements, components, or combinations of the foregoing items, and should not be construed as precluding the existence or addition of the possibility of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing items.

[0051] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the recited words. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0052] Expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0053] It should be noted that: if it is described that one constituent element is "connected" to another constituent element, the first constituent element may be directly connected to the second constituent element, and a third constituent element may be "connected" between the first constituent element and the second constituent element. Conversely, when one constituent element is "directly connected" to another constituent element, it can be understood that there is no third constituent element between the first constituent element and the second constituent element.

[0054] The terms used in the various embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as those defined in a commonly used dictionary) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the present invention.

[0055] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments and drawings. The illustrative embodiments and descriptions thereof of the present invention are only for explaining the present invention and do not serve as a limitation to the present invention.

[0056] Embodiment

[0057] The existing protection circuits for reverse connection prevention and soft start of DC power input cannot ensure that, on the premise of reverse connection prevention and soft start functions, when faults such as overvoltage, overcurrent, and overheating occur, the input short circuit can be timely disconnected to prevent the subsequent circuit from being damaged, or the volume and cost of the device are increased. Based on this, this embodiment provides a reverse connection prevention DC input soft start circuit with a protection shutdown function. In this embodiment, a switching device is arranged on the soft start circuit. When faults such as over- and under-voltage, overcurrent, and overheating occur and protection shutdown is required, the soft start circuit and the direct-through bypass can be disconnected simultaneously, thereby disconnecting the main circuit to protect the circuit from further damage and dangerous accidents; at the same time, the switching device does not need to be selected with the same specifications as the switch in the main circuit, reducing the cost and having a small impact on the device volume.

[0058] Specifically, as Figure 4 shown, the circuit proposed in this embodiment specifically includes modules such as a lightning and surge voltage protection circuit, a reverse connection prevention circuit, a surge current soft start circuit, a direct-through bypass, energy storage devices (such as capacitors), a protection circuit, and a drive control circuit.

[0059] Among them, the lightning and surge voltage protection circuit is arranged at the input port, the energy storage element is connected in parallel at the front end of the DC input converter, the reverse connection prevention circuit and the direct-through bypass are connected in the main circuit of the DC input of the device power supply, the surge current soft start circuit is connected in parallel with the direct-through bypass, and the surge current soft start circuit pre-charges the energy storage device at the DC input port when the input voltage is normal, and when the energy storage device is charged to a preset value, it drives the DC bypass to conduct to supply power to the subsequent circuit normally.

[0060] The protection circuit is used to monitor the input voltage. When faults such as overvoltage, undervoltage, overcurrent, and overheating occur, it controls the disconnection of the drive of the direct-through bypass and the surge current soft start circuit through the drive control circuit to ensure that the subsequent circuit is not damaged and improve the reliability of the device.

[0061] As Figure 5 shown, in the embodiment of the present invention, the reverse connection prevention circuit is mainly composed of devices such as MOSFET Q2, zener diode ZD2, resistor R4, and resistor R5. Among them, one end of resistor R4 is connected to the output end of the lightning and surge voltage protection circuit, the other end of resistor R4 is connected to one end of resistor R5 and the base of Q2, resistor R5 and ZD2 are connected in parallel between the gate and source of Q2, and the drain of Q2 is grounded.

[0062] As an optional implementation manner, the reverse connection prevention circuit may further include diode D2, and diode D2 is connected in series between resistor R4 and resistor R5.

[0063] As an optional implementation manner, resistor R4 can be designed with series and parallel equivalents according to the magnitude of the input voltage.

[0064] In the embodiment of the present invention, the direct bypass mainly consists of devices such as MOSFET Q1, resistor R2, resistor R3, resistor R6, capacitor C1, zener diode ZD1, diode D1, etc. Among them, the source of Q1 is connected to the source of Q2, and the drain of Q1 is connected to one end of the energy storage element and the inrush current soft-start circuit; one end of resistor R2 is connected to the output end of the lightning and surge voltage protection circuit, and the other end of resistor R2 is connected to one end of resistor R3, one end of resistor R6, and the positive electrode of zener diode ZD1; the other end of resistor R3 is connected to the source of Q1; the other end of resistor R6 is connected to one end of capacitor C1 and the gate of Q1; capacitor C1 is connected in parallel between the gate and source of Q1; the negative electrode of zener diode ZD1 is connected to the source of Q1, and diode D1 is connected in parallel across resistor R6.

[0065] As an alternative embodiment, the direct bypass further includes diode D3, and diode D3 is connected in series between resistor R2 and resistor R3.

[0066] As an alternative embodiment, the direct bypass further includes resistor R8, and resistor R8 is connected in series with diode D1 and then connected in parallel across resistor R6.

[0067] As an alternative embodiment, resistor R2 can be designed with series-parallel equivalence according to the magnitude of the input voltage.

[0068] In the embodiment of the present invention, the drive control circuit mainly consists of optocoupler OC1 and resistor R7. Among them, the input end of optocoupler OC1 is connected to the protection circuit through resistor R7, the collector C of the photosensitive triode of optocoupler OC1 is connected to the gate of Q1 through resistor R6, and the emitter E of the photosensitive triode is connected to the inrush current soft-start circuit.

[0069] As an alternative embodiment, the drive control circuit can also use magnetic isolation devices, triodes, comparators, or relays and other devices to replace optocoupler OC1.

[0070] In the embodiment of the present invention, the inrush current soft-start circuit mainly consists of MOSFET Q4 and resistor R1. Among them, the gate of Q4 is connected to the collector C of the photosensitive triode of OC1, the source of Q4 is connected to the emitter E of the photosensitive triode of OC1 and the source of Q1, and the drain of Q4 is connected to one end of resistor R1, and the other end of resistor R1 is connected to the drain of Q1.

[0071] As Figure 6 shown, the working principle of the circuit proposed in the embodiment of the present invention Figure 5 shown is specifically as follows:

[0072] Step 1, after power-on startup, if there are faults such as overvoltage, undervoltage, overcurrent, overheating, etc., the protection circuit controls the drive of Q1 and Q4 to turn off through the optocoupler OC1, disconnecting the faulty voltage from the subsequent circuit. If the input is reverse-connected, Q2 is cut off, also playing the role of protection and disconnection.

[0073] Step 2, if there are no fault conditions in Step 1 and the input voltage is within the normal range, the input voltage charges the C2 capacitor through the resistor R1. Assuming the voltage on the capacitor is 0 and the equivalent series impedance is 0, then according to Ohm's law, the peak value of the instantaneous charging current Ip is the ratio of the input voltage Vin to the resistor R1, that is:

[0074] Ip = Vin / R1

[0075] Thus, the function of soft start is achieved. During the power-on process, the body diode of Q2 conducts first, and the input voltage drives Q2 to conduct through R4, D2, R5, ZD2, reducing the conduction loss. Among them, D2 is an optional non-essential device and can be removed. R4 can be designed equivalently in series or parallel according to the magnitude of the input voltage.

[0076] Step 3, during the soft start process of Step 2, the input voltage Vin charges C1 through R2, D3, R6. Set the charging time so that when C2 is charged to more than 90%, the voltage of C1 just reaches the turn-on threshold Vth of Q1. If the current when Q1 turns on exceeds the standard or the MOSFET selection requirements at this time, increase the rising time of the C1 voltage and wait until C2 is charged to a higher level before conduction. At this time, it can be set according to actual needs. Among them, D3 is an optional non-essential device and can be removed. R2 can be designed equivalently in series or parallel according to the magnitude of the input voltage.

[0077] Step 4, after Q1 is turned on, the subsequent circuit can be normally turned on and powered.

[0078] Step 5, if faults such as input overvoltage, overcurrent, overheating, etc. occur during normal operation, the protection circuit controls the optocoupler OC1 device to turn on and turn off Q1 and Q4. When Q1 is turned off, the voltage of C1 discharges through the diode D1 to achieve the purpose of rapid turn-off. A small resistor R8 can be appropriately connected in series for current limiting to avoid damaging OC1 or the diode D1. R8 is a non-essential device.

[0079] The above-mentioned specific implementation manners further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above is only the specific implementation manners of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A reverse connection protection and turn-off function equipped anti-reverse connection DC input soft start circuit, characterized in that, It includes an anti-reverse connection circuit, a direct-through bypass, a protection circuit, a drive control circuit, and a surge current soft-start circuit; The anti-reverse connection circuit and the direct-through bypass are connected in the main circuit of the DC input terminal of the device power supply; the anti-reverse connection circuit is disconnected when the input voltage is reversely connected, so that the input voltage is disconnected from the subsequent circuit; The surge current soft-start circuit is connected in parallel with the direct-through bypass. When the input voltage is normal, the surge current soft-start circuit pre-charges the energy storage device at the DC input port, and when the energy storage device is charged to a preset value, it drives the direct-through bypass to conduct so that the subsequent circuit is normally powered; When the protection circuit detects a fault, it controls the drive of the direct-through bypass and the surge current soft-start circuit to be turned off through the drive control circuit, so that the input voltage is disconnected from the subsequent circuit; The anti-reverse connection circuit includes MOSFET Q2, zener diode ZD2, resistor R4, and resistor R5; The direct-through bypass includes MOSFET Q1, resistor R2, resistor R3, resistor R6, capacitor C1, zener diode ZD1, and diode D1; The surge current soft-start circuit includes MOSFET Q4 and resistor R1; Wherein, one end of resistor R4 is connected to the input voltage, the other end of resistor R4 is connected to one end of resistor R5, the other end of resistor R5 is connected to the source of MOSFET Q2; the drain of MOSFET Q2 is grounded, the gate of MOSFET Q2 is connected to the common connection end of resistor R4 and resistor R5, and the source of MOSFET Q2 is connected to the source of MOSFET Q1; zener diode ZD2 is connected in parallel between the gate and source of MOSFET Q2; The source of MOSFET Q1 is connected to the source of MOSFET Q4. The gate of MOSFET Q1 is connected to the gate of MOSFET Q4, one end of resistor R2, and one end of resistor R3 through resistor R6. The drain of MOSFET Q4 is connected to the drain of MOSFET Q1 and the energy storage device through resistor R1; Capacitor C1 is connected in parallel between the gate and source of MOSFET Q1; The other end of resistor R2 is connected to the input voltage, and the other end of resistor R3 is connected to the source of MOSFET Q1; Zener diode ZD1 is connected in parallel across resistor R3, and diode D1 is connected in parallel across resistor R6.

2. The anti-reverse connection DC input soft-start circuit with a protection shutdown function according to claim 1, wherein The direct-through bypass further includes diode D3; Diode D3 is connected in series between resistor R2 and resistor R3.

3. The anti-reverse connection DC input soft start circuit with a protection shutdown function according to claim 1, characterized in that, The direct-through bypass further includes resistor R8; Resistor R8 is connected in series with diode D1 and then connected in parallel across resistor R6.

4. The anti-reverse connection DC input soft-start circuit with a protection shutdown function according to claim 1, characterized in that, Resistor R2 is designed with series-parallel equivalence according to the magnitude of the input voltage.

5. The anti-reverse connection DC input soft-start circuit with a protection shutdown function according to claim 1, characterized in that, The anti-reverse connection circuit further includes diode D2; Diode D2 is connected in series between resistor R4 and resistor R5.

6. The anti-reverse connection DC input soft start circuit with a protection shutdown function according to claim 1, characterized in that, Resistor R4 is designed with series-parallel equivalence according to the magnitude of the input voltage.

7. A reverse connection protection and soft start DC input circuit with a protection shutdown function, characterized in that, The drive control circuit includes optocoupler OC1 and resistor R7; The input end of the optocoupler OC1 is connected to the protection circuit through resistor R7; The collector C of the phototransistor of the optocoupler OC1 is connected to the common connection terminal of the gate of the MOSFET Q4, the resistor R6, and the resistor R3; The emitter E of the phototransistor of the optocoupler OC1 is connected to the source of the MOSFET Q4 and the source of the MOSFET Q1.

8. The anti-reverse connection DC input soft-start circuit with a protection shutdown function according to claim 7, characterized in that, The optocoupler OC1 is replaced by a magnetic isolation device, a triode, a comparator, or a relay.

9. The working method of an anti-reverse connection DC input soft start circuit with a protection shutdown function according to any one of claims 1-8, characterized in that, Including: After power-on startup, if there is a fault, the protection circuit controls the drive to turn off the MOSFET Q1 and the drive of the MOSFET Q4 through the drive control circuit, and the fault voltage is disconnected from the subsequent circuit; If the input is reverse-connected, the MOSFET Q2 is turned off, and the input voltage is disconnected from the subsequent circuit; If there is no fault or reverse connection and the input voltage is within the normal range, the input voltage charges the energy storage device through the resistor R1, so as to achieve the function of soft start; during the power-on process, the body diode of the MOSFET Q2 conducts first, and the input voltage drives the MOSFET Q2 to conduct through the resistor R4, the resistor R5, and the zener diode ZD2, reducing the conduction loss; During the soft start process, the input voltage charges the capacitor C1 through the resistor R2 and the resistor R6. When the voltage of the capacitor C1 reaches the preset value, the MOSFET Q1 conducts; After the MOSFET Q1 conducts, the subsequent circuit is normally turned on and powered; If a fault occurs during normal operation, the protection circuit controls the drive control circuit to turn on and turn off the MOSFET Q1 and the MOSFET Q4. When the MOSFET Q1 is turned off, the voltage of the capacitor C1 discharges through the diode D1.

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