Soft start circuit and soft start method

Abstract

The application relates to a slow start circuit and a slow start method, wherein the slow start circuit comprises a field effect tube and a first capacitor connected to a power input end, the power input end comprises a power positive input end and a power negative input end, the gate of the field effect tube is connected to the power positive input end, the drain and the source of the field effect tube are connected to the power negative input end, the first capacitor is connected between the gate and the source of the field effect tube, the slow start circuit further comprises a discharge trigger module and a discharge module, wherein: the discharge trigger module is connected with the discharge module and is used for detecting the state of the power input end, and the discharge module is triggered when it is detected that the power input end is powered off; the discharge module is connected in parallel with the first capacitor and is used for being triggered by the discharge trigger module to control the first capacitor to be locked in a discharge state so that the field effect tube is turned off. Through the application, the safety of the slow start circuit is improved, and the problem that the slow start circuit is invalid due to frequent hot plug is solved.

Description

Technical Field

[0001] This application relates to the field of power control technology, and in particular to a soft-start circuit and a soft-start method. Background Technology

[0002] Most electronic systems now require hot-swapping functionality. Hot-swapping, or hot-plugging, refers to inserting or removing modules, boards, or other units into or from a system without shutting down the system power, thus improving system reliability, rapid maintainability, redundancy, and timely disaster recovery capabilities. However, hot-swapping can also have certain impacts on the system, mainly in two aspects: First, during hot-swapping, the mechanical contacts of the connector may bounce at the moment of contact, causing power oscillation. This oscillation can cause power drops, leading to bit errors or system restarts, and may also cause connector arcing, potentially causing a fire. The solution is to delay the connector's power-on time, not energizing the connector during the tens of milliseconds of connector jitter, and then energizing it only after the insertion is stable—this is known as anti-jitter delay. Secondly, modules, boards, and other units have large-capacity energy storage capacitors at their power input ports to maintain operational stability. During hot-swapping, a large inrush current occurs due to the charging effect of these capacitors. As the capacitor charges, the current decreases exponentially, resulting in a very high inrush current at the beginning of charging. This inrush current may burn out the device's power fuse, so it is essential to control the inrush current during hot-swapping.

[0003] To prevent power oscillations and inrush currents caused by hot-plugging, a soft-start circuit is typically installed at the power input port to achieve anti-jitter delay power-on, thereby overcoming the impact of hot-plugging on the system.

[0004] Existing MOSFET (Metal-Oxide-Semiconductor) soft-start methods typically involve connecting a MOSFET in series at the power input and a capacitor in parallel with the MOSFET's gate and source. When power is applied to the input, the MOSFET's gate-source capacitor charges, causing the MOSFET to turn on slowly, thus achieving a soft start. However, with repeated power-off cycles at the input, the energy storage capacitor discharges slowly, continuously charging the MOSFET's gate-source capacitor, preventing the MOSFET from turning off. If power is applied while the MOSFET is in a partially open / closed state, it will generate a large inrush current and instantaneous stress, potentially even burning out the power supply and causing the soft-start circuit to fail.

[0005] There is currently no effective solution to the problem of frequent hot-swapping causing soft-start circuit failure in related technologies. Summary of the Invention

[0006] This embodiment provides a soft-start circuit and a soft-start method to solve the problem of soft-start circuit failure caused by frequent hot-plugging in related technologies.

[0007] In a first aspect, this embodiment provides a soft-start circuit, including a field-effect transistor (FET) and a first capacitor connected to a power input terminal. The power input terminal includes a positive power input terminal and a negative power input terminal. The gate of the FET is connected to the positive power input terminal, and the drain and source of the FET are connected to the negative power input terminal. The first capacitor is connected between the gate and source of the FET. The soft-start circuit further includes a discharge trigger module and a discharge module, wherein:

[0008] The discharge trigger module is connected to the discharge module and is used to detect the status of the power input terminal. When the power input terminal is detected to be de-energized, the discharge module is triggered.

[0009] The discharge module is connected in parallel with the first capacitor and is used to control the first capacitor to lock in the discharge state and turn off the field-effect transistor when triggered by the discharge trigger module.

[0010] In some embodiments, the discharge triggering module includes: a voltage acquisition unit and a comparison unit;

[0011] The voltage acquisition unit is connected between the positive input terminal and the negative input terminal of the power supply, and is used to acquire the voltage at the power input terminal and transmit the voltage at the power input terminal to the comparison unit.

[0012] The comparison unit is connected to the discharge module and is used to compare the voltage at the power input terminal with the threshold voltage. When the voltage at the power input terminal is less than the threshold voltage, the discharge module is triggered.

[0013] The threshold voltage is less than the power supply voltage, and the threshold voltage is set according to the power input terminal power-on operation time.

[0014] In some embodiments, the comparison unit includes a reference voltage source and an operational amplifier; the reference voltage source is connected to the power supply terminal of the operational amplifier to supply power to the operational amplifier.

[0015] The voltage acquisition unit includes a plurality of first voltage divider resistors connected in series between the positive input terminal and the negative input terminal of the power supply, and the negative input terminal of the operational amplifier is connected between the first voltage divider resistors;

[0016] The threshold voltage is input to the positive input terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the discharge module.

[0017] In some embodiments, the reference voltage source includes a three-terminal regulator, wherein the A terminal of the three-terminal regulator is connected to the positive input terminal of the power supply, the K terminal of the three-terminal regulator is connected to the negative input terminal of the power supply, the A terminal of the three-terminal regulator is connected to the power supply terminal of the operational amplifier, a first regulating resistor is connected between the reference source and the A terminal of the three-terminal regulator, and a second regulating resistor is connected between the reference source and the K terminal of the three-terminal regulator.

[0018] In some embodiments, a third voltage divider resistor is connected between the positive input terminal of the operational amplifier and the A terminal of the three-terminal regulator, and a fourth voltage divider resistor is connected between the positive input terminal of the operational amplifier and the negative input terminal of the power supply. The threshold voltage is set by the third and fourth voltage divider resistors.

[0019] In some embodiments, the discharge module includes: an NPN transistor, a Zener diode, and a PNP transistor;

[0020] The collector of the NPN transistor and the emitter of the PNP transistor are connected to the positive terminal of the first capacitor, and the emitter of the NPN transistor is connected to the negative terminal of the first capacitor.

[0021] The cathode of the Zener diode is connected to the output terminal of the discharge trigger module. The base of the NPN transistor is connected to the anode of the Zener diode and the collector of the PNP transistor. The base of the PNP transistor is connected to the collector of the NPN transistor.

[0022] In some embodiments, the soft-start circuit further includes: a first resistor and a second resistor;

[0023] The first end of the first resistor is connected to the positive input terminal of the power supply, and the second end of the first resistor is connected to the emitter of the PNP transistor. The first resistor is used to provide the conduction current for the PNP transistor.

[0024] The first end of the second resistor is connected to the base of the NPN transistor and the collector of the PNP transistor, and the second end of the second resistor is connected to the negative input terminal of the power supply. The second resistor is used to provide conduction current for the NPN transistor.

[0025] In some embodiments, the soft-start circuit further includes a third resistor and a fourth resistor;

[0026] The first end of the third resistor is connected to the positive input terminal of the power supply, the second end of the third resistor is connected to the gate of the field-effect transistor, the first end of the fourth resistor is connected to the positive input terminal of the power supply, and the second end of the fourth resistor is connected to the drain of the field-effect transistor.

[0027] In some embodiments, the soft-start circuit further includes a clamping diode, the cathode of which is connected to a first terminal of the third resistor, and the anode of which is connected to the source of the field-effect transistor. The clamping diode is used to limit the potential between the gate and source of the field-effect transistor.

[0028] Secondly, this embodiment provides a soft-start method, which is applied to the soft-start circuit described in any of the first aspects above. The soft-start circuit includes a field-effect transistor (FET) and a first capacitor connected to a power input terminal. The power input terminal includes a positive power input terminal and a negative power input terminal. The gate of the FET is connected to the positive power input terminal, and the drain and source of the FET are connected to the negative power input terminal. The first capacitor is connected between the gate and source of the FET. The soft-start circuit further includes a discharge trigger module and a discharge module. The soft-start method includes:

[0029] The discharge trigger module detects the status of the power input terminal, and triggers the discharge module when it detects that the power input terminal is de-energized.

[0030] The discharge module is triggered by the discharge trigger module to control the first capacitor to lock in the discharge state, thereby turning off the field-effect transistor.

[0031] Compared with related technologies, the soft-start circuit provided in this embodiment connects a discharge trigger module to a discharge module to detect the state of the power input terminal. Upon detecting a power outage at the power input terminal, the discharge module is triggered. The discharge module is connected in parallel with a first capacitor and is controlled by the discharge trigger module to lock the first capacitor in a discharge state, thus turning off the MOSFET. This effectively avoids the generation of a larger inrush current during the slow turn-off process of the MOSFET, preventing the power supply equipment from burning out, thereby improving the safety of the soft-start circuit.

[0032] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0033] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 This is a schematic diagram of a soft-start circuit structure provided in an embodiment of this application;

[0035] Figure 2 This is a schematic diagram of the second type of soft-start circuit structure provided in the embodiments of this application;

[0036] Figure 3 This is a schematic diagram of a third type of soft-start circuit structure provided in an embodiment of this application;

[0037] Figure 4 This is a schematic diagram of the fourth soft-start circuit structure provided in the embodiments of this application;

[0038] Figure 5 This is a schematic diagram of the fifth type of soft-start circuit provided in the embodiments of this application;

[0039] Figure 6 This is a schematic diagram of an embodiment of a soft-start circuit provided in this application.

[0040] Figure 7 This is a schematic diagram comparing the inrush current of the embodiments of this application with that of the prior art. Detailed Implementation

[0041] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0042] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these,” used in this application, do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to such processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled,” used in this application, are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0043] Most electronic systems now require hot-swapping functionality. Hot-swapping, or hot-plugging, refers to inserting or removing modules, boards, or other units into or from a system without shutting down the system power, thus improving system reliability, rapid maintainability, redundancy, and timely disaster recovery capabilities. However, hot-swapping can also have certain impacts on the system, mainly in two aspects: First, during hot-swapping, the mechanical contacts of the connector may bounce at the moment of contact, causing power oscillation. This oscillation can cause power drops, leading to bit errors or system restarts, and may also cause connector arcing, potentially causing a fire. The solution is to delay the connector's power-on time, not energizing the connector during the tens of milliseconds of connector jitter, and then energizing it only after the insertion is stable—this is known as anti-jitter delay. Secondly, modules, boards, and other units have large-capacity energy storage capacitors at their power input ports to maintain operational stability. During hot-swapping, a large inrush current occurs due to the charging effect of these capacitors. As the capacitor charges, the current decreases exponentially, resulting in a very high inrush current at the beginning of charging. This inrush current may burn out the device's power fuse, so it is essential to control the inrush current during hot-swapping.

[0044] To prevent power oscillations and inrush currents caused by hot-plugging, a soft-start circuit is typically installed at the power input port to achieve anti-jitter delay power-on, thereby overcoming the impact of hot-plugging on the system.

[0045] Existing MOSFET (Metal-Oxide-Semiconductor) soft-start methods typically involve connecting a MOSFET in series at the power input and a capacitor in parallel with the MOSFET's gate and source. When power is applied to the input, the MOSFET's gate-source capacitor charges, causing the MOSFET to turn on slowly, thus achieving a soft start. However, with repeated power-off cycles at the input, the energy storage capacitor discharges slowly, continuously charging the MOSFET's gate-source capacitor, preventing the MOSFET from turning off. If power is applied while the MOSFET is in a partially open / closed state, it will generate a large inrush current and instantaneous stress, potentially even burning out the power supply and causing the soft-start circuit to fail.

[0046] Therefore, improving the safety of soft-start circuits is a problem that needs to be solved.

[0047] This embodiment provides a soft-start circuit. Figure 1 This is a schematic diagram of a soft-start circuit structure provided in an embodiment of this application, such as... Figure 1 As shown, the soft-start circuit includes a field-effect transistor 110 and a first capacitor 120 connected to the power input terminal. The power input terminal includes a positive power input terminal and a negative power input terminal. The gate of the field-effect transistor 110 is connected to the positive power input terminal, and the source of the field-effect transistor 110 is connected to the negative power input terminal. The first capacitor 120 is connected between the gate and the source of the field-effect transistor 110. An energy storage capacitor 130 and a load 160 are connected between the positive power input terminal and the drain of the field-effect transistor 110. The energy storage capacitor 130 and the load 160 are connected in parallel. That is, the soft-start circuit is connected between the power input terminal and the energy storage capacitor 130. The energy storage capacitor 130 and the load 160 are powered on and off by turning the field-effect transistor 110 on and off. The field-effect transistor 110 can be a MOSFET.

[0048] It should be noted that the first capacitor in the embodiments of this application can be a single capacitor or multiple capacitors connected in parallel, and there is no limitation here.

[0049] The soft-start circuit also includes a discharge trigger module 140 and a discharge module 150, wherein: the discharge trigger module 140 is connected to the discharge module 150 and is used to detect the state of the power input terminal. When the power input terminal is detected to be de-energized, the discharge module 150 is triggered; the discharge module 150 is connected in parallel with the first capacitor 120 and is used to be triggered by the discharge trigger module 140 to control the first capacitor 120 to lock in the discharge state so that the field-effect transistor 110 is turned off.

[0050] For example, the power input terminal is used to connect to a power source. The power input terminal includes a positive power input terminal and a negative power input terminal, i.e., the positive power input terminal is connected to the positive terminal of the power source, and the negative power input terminal is connected to the negative terminal of the power source. The discharge trigger module 140 is connected to both the power input terminal and the discharge module 150, and is used to detect the connection status between the power source and the power input terminal. When the power input terminal is connected to the power source, the discharge trigger module 140 will not trigger the discharge module 150, and the power source charges the first capacitor 120, causing the field-effect transistor 110 to turn on slowly, thereby realizing the soft-start current limiting function. When the power source is detected to be disconnected from the power input terminal, the discharge trigger module 140 triggers the discharge module 150.

[0051] Furthermore, the discharge module 150, triggered by the discharge trigger module 140, controls the first capacitor 120 to be locked in the discharge state, causing the field-effect transistor 110 to be quickly turned off, thereby ensuring that the field-effect transistor 110 is completely turned off before the next power-on. The first capacitor 120 is locked in the discharge state, that is, the first capacitor 120 is always in the discharge state until the charge is completely discharged, thereby ensuring that the field-effect transistor 110 is completely turned off, and avoiding the situation where the first capacitor 120 is recharged while the field-effect transistor 110 is in a half-open and half-closed state, causing the field-effect transistor 110 to remain in a non-turn-off state.

[0052] In the above implementation process, when the power input terminal is de-energized by the discharge trigger module, the discharge module is triggered, thereby controlling the first capacitor to lock in the discharge state, so that the field-effect transistor is immediately turned off. This can effectively avoid the problem of the device's power field-effect transistor being damaged by rapid and repeated hot plugging and unplugging, thus improving the safety of the soft start circuit.

[0053] In some embodiments, the discharge triggering module includes a voltage acquisition unit and a comparison unit.

[0054] The voltage acquisition unit is connected between the positive input terminal and the negative input terminal of the power supply. It is used to acquire the voltage at the power input terminal and transmit the voltage at the power input terminal to the comparison unit.

[0055] The comparison unit, connected to the discharge module, is used to compare the voltage at the power input terminal with the threshold voltage. When the voltage at the power input terminal is less than the threshold voltage, the discharge module is triggered.

[0056] The threshold voltage is less than the power supply voltage and is set according to the power-on action time of the power input terminal.

[0057] For example, Figure 2 This is a schematic diagram of the second type of soft-start circuit structure provided in the embodiments of this application, as shown below. Figure 2As shown, the discharge trigger module 140 may include a voltage acquisition unit 142 and a comparison unit 141. Specifically, the voltage acquisition unit 142 is connected between the positive and negative ports of the power input terminal and is connected to the comparison unit 141 to acquire the voltage of the power input terminal and transmit the voltage of the power input terminal to the comparison unit 141.

[0058] Furthermore, a threshold voltage can be set in the comparison unit 141. The comparison unit 141 compares the acquired voltage at the power input terminal with the threshold voltage. When the voltage at the power input terminal is less than the threshold voltage, the discharge module 150 is triggered. The threshold voltage is less than the power supply voltage and is set according to the power-on time of the power input terminal. When the power input terminal is powered on, the voltage at the power input terminal is the power supply voltage. When the power input terminal is powered off, the energy storage capacitor 130 begins to discharge, so the voltage at the power input terminal will start to drop from the power supply voltage. Because the voltage at the power input terminal fluctuates due to the load 160, if the threshold voltage is set to the power supply voltage, the voltage drop caused by voltage fluctuations when the power input terminal is powered on will cause the discharge trigger module 140 to trigger the discharge module 150, turning off the field-effect transistor 110. Therefore, to improve anti-interference, the threshold voltage must be less than the power supply voltage. At the same time, to improve detection sensitivity, the threshold voltage cannot be set too low. Therefore, the threshold voltage setting is linked to the power-on action time of the power input terminal. The threshold voltage is set according to the power input terminal power-on action time in the usage scenario to ensure that the discharge module 150 is triggered before the next power-on. The power input terminal power-on action time refers to the action time when the power input terminal connects to the power supply, which can be obtained through the action or reaction time of the power-on switch component, statistics, or experience. For example, if the usage scenario involves frequent manual switching on and off of the power switch, and the manual power-on action cycle generally requires at least 20ms, then the power input terminal power-on action time can be set to 20ms.

[0059] Furthermore, after the discharge module 150 is triggered, the control field-effect transistor 110 is immediately turned off.

[0060] Specifically, under DC power supply excitation, the general expression for the solution of the differential equation of a first-order linear circuit is:

[0061] f(t)=f(∞)+[f(0 + )-f(∞)]e -t / τ (1)

[0062] Where f(t) represents the voltage function in the first-order response circuit, f(0 +Let f(∞) represent the initial value, f(∞) represent the steady-state value, and τ represent the time constant. If this expression is applied to the soft-start circuit in this application, when the power input is de-energized, the energy storage capacitor 130 begins to discharge. The energy storage capacitor 130, along with the load 160, the discharge trigger module 140, the discharge module 150, and the field-effect transistor 110, constitute a discharge circuit, which can be equivalent to the aforementioned first-order linear circuit. Then f(0) represents the initial value, f(∞) represents the steady-state value, and τ represents the time constant. + Since f(∞) = power supply voltage and f(∞) = 0, the following relationship exists:

[0063] Capacitor discharge voltage = 0 + power supply voltage * -t / τ (2)

[0064] Where t represents the discharge time, and the time constant τ satisfies the following relationship:

[0065] τ=RC (3)

[0066] Where R is equivalent to the equivalent impedance of the load 160, and C represents the capacitance of the energy storage capacitor 130.

[0067] Substituting relation (3) into relation (2) yields the following relation:

[0068] Capacitor discharge voltage = power supply voltage * -t / RC (4)

[0069] In specific application scenarios, the power supply voltage, the equivalent impedance R of the load 160, and the capacitance C of the energy storage capacitor 130 in equation (4) are all known values. Therefore, the relationship between the discharge time and the capacitor discharge voltage can be directly obtained using equation (4). Since the shortest time for the next power-on is immediately after the power input terminal is de-energized, i.e., the power input terminal power-on action time. To ensure that the field-effect transistor 110 is turned off during the power-off period, it is necessary to ensure that the discharge module 150 can be triggered before the next power-on. That is, the threshold voltage should be set to a minimum of t, where t in equation (4) is the capacitor discharge voltage corresponding to the power input terminal power-on action time. Therefore, the threshold voltage can be set according to the power input terminal power-on action time.

[0070] For example, when the soft-start circuit of this application is applied to a manual plug-in / plug-out scenario, the power input terminal is connected to a 48V DC power supply, the equivalent impedance R of the load 160 is 100Ω, and the capacitance C of the energy storage capacitor 130 is 880μF. According to the relationship (4), the discharge time t is set to the lower limit of the manual plug-in / plug-out action time of 20ms. The calculated capacitor discharge voltage is 38V. Therefore, the lower limit of the threshold voltage is set to 38V. When the power input terminal is de-energized, the voltage at the power input terminal begins to drop. The time to drop to 38V is 20ms. When the voltage at the power input terminal is lower than 38V, the comparison unit 141 immediately triggers the discharge module 150, and the discharge module 150 immediately turns off the field-effect transistor 110. Even if the power input terminal is manually powered on immediately after being disconnected, the time will be more than 20ms. When the power input terminal is powered on, the discharge trigger module 140 has already triggered the discharge module 150 to turn off the field-effect transistor 110, so that the field-effect transistor 110 can restart soft-start. Of course, the threshold voltage can also be set to any value between 38V and 48V, but voltage fluctuations at the power input terminal need to be taken into account. The higher the threshold voltage is set, the faster the MOSFET 110 will be turned off after the power input terminal is disconnected.

[0071] In the above implementation process, the voltage at the power input terminal is obtained by the voltage acquisition unit and the capacitor voltage is transmitted to the comparison unit. Further, the comparison unit compares the voltage at the power input terminal with the threshold voltage. When the voltage at the power input terminal is less than the threshold voltage, the discharge module is triggered, so that the discharge module can control the field-effect transistor to be turned off immediately before the next power-on.

[0072] In some of these embodiments, the comparison unit includes a reference voltage source and an operational amplifier.

[0073] The reference voltage source is connected to the power supply terminal of the operational amplifier to provide power to the operational amplifier.

[0074] The voltage acquisition unit includes multiple first voltage divider resistors connected in series between the positive input terminal and the negative input terminal of the power supply, and the negative input terminal of the operational amplifier is connected between the multiple first voltage divider resistors.

[0075] The threshold voltage is input to the positive input terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the discharge module.

[0076] For example, such as Figure 2 As shown, the discharge trigger module 140 may include a voltage acquisition unit 142 and a comparison unit 141.

[0077] The comparison unit 141 includes a reference voltage source 10 and an operational amplifier 20. The reference voltage source 10 is connected to the power supply terminal of the operational amplifier 20 and is used to provide power to the operational amplifier 20.

[0078] The voltage acquisition unit 142 includes two first voltage divider resistors R1 and R2 connected in series between the positive input terminal and the negative input terminal of the power supply, and the negative input terminal of the operational amplifier 20 is connected between the first voltage divider resistors R1 and R2.

[0079] It should be noted that the multiple first voltage divider resistors in this application embodiment are only illustrated by resistors R1 and R2. In actual applications, the multiple first voltage divider resistors can also be 3 resistors or 4 resistors. The resistance value of each resistor can be the same or different, and there is no limitation here.

[0080] The threshold voltage is input to the positive input terminal of the operational amplifier 20, and the output terminal of the operational amplifier 20 is connected to the discharge module 150. When the voltage at the power input terminal is less than the threshold voltage, the operational amplifier 20 outputs a high-level signal, which triggers the discharge module 150 to start, and then the discharge module 150 controls the field-effect transistor to turn off immediately.

[0081] In the above implementation process, the voltage at the power input terminal is obtained through multiple first voltage divider resistors. This facilitates the operational amplifier to compare the voltage at the power input terminal with the threshold voltage, thereby outputting a trigger signal when the voltage at the power input terminal is less than the threshold voltage. Furthermore, the operational amplifier is powered by a reference voltage source, which facilitates the normal operation of the operational amplifier.

[0082] In some embodiments, the reference voltage source includes a three-terminal regulator, with the A terminal of the three-terminal regulator connected to the positive input terminal of the power supply and the K terminal of the three-terminal regulator connected to the negative input terminal of the power supply. A first regulating resistor is connected between the reference source and the A terminal of the three-terminal regulator, and a second regulating resistor is connected between the reference source and the K terminal of the three-terminal regulator.

[0083] For example, the reference voltage source 10 may include a three-terminal regulator, with the A terminal of the three-terminal regulator connected to the positive input terminal of the power supply, the K terminal of the three-terminal regulator connected to the negative input terminal of the power supply, the A terminal of the three-terminal regulator connected to the power supply terminal of the operational amplifier 20, a first regulating resistor connected between the reference source of the three-terminal regulator and the A terminal, and a second regulating resistor connected between the reference source of the three-terminal regulator and the K terminal.

[0084] In the above implementation process, the three-terminal regulator is connected between the positive and negative terminals of the power supply, so that the power supply can power the three-terminal regulator, which in turn can power the operational amplifier. Furthermore, a first regulating resistor is connected between the reference source and the A terminal of the three-terminal regulator, and a second regulating resistor is connected between the reference source and the K terminal of the three-terminal regulator, so that the voltage input from the three-terminal regulator to the operational amplifier can be adaptively adjusted.

[0085] In some embodiments, a third voltage divider resistor is connected between the positive input terminal of the operational amplifier and the A terminal of the three-terminal regulator, and a fourth voltage divider resistor is connected between the positive input terminal of the operational amplifier and the negative input terminal of the power supply. The threshold voltage is set by the third and fourth voltage divider resistors.

[0086] For example, Figure 3 This is a schematic diagram of the third soft-start circuit structure provided in the embodiments of this application, as shown below. Figure 3 As shown, the reference voltage source may include a three-terminal regulator U1. The A terminal of the three-terminal regulator U1 is connected to the positive input terminal of the power supply, the K terminal of the three-terminal regulator is connected to the negative input terminal of the power supply, the A terminal of the three-terminal regulator is connected to the power supply terminal of the operational amplifier 20, a first regulating resistor R3 is connected between the reference source and the A terminal of the three-terminal regulator U1, a second regulating resistor R4 is connected between the reference source and the K terminal of the three-terminal regulator U1, and the A terminal of the three-terminal regulator U1 is connected to the output terminal of the operational amplifier.

[0087] Furthermore, a third voltage divider resistor R5 is connected between the positive input terminal of the operational amplifier 20 and the A terminal of the three-terminal regulator, and a fourth voltage divider resistor R6 is connected between the positive input terminal of the operational amplifier 20 and the negative input terminal of the power supply. The threshold voltage is set by the third voltage divider resistor R5 and the fourth voltage divider resistor R6.

[0088] In the above implementation process, the threshold voltage is obtained from the power supply provided by the three-terminal regulator U1 through the third and fourth voltage divider resistors, and the threshold voltage is connected to the positive input terminal of the operational amplifier, thereby realizing the setting of the threshold voltage.

[0089] In some embodiments, the discharge module includes an NPN transistor, a Zener diode, and a PNP transistor.

[0090] The collector of the NPN transistor and the emitter of the PNP transistor are connected to the positive terminal of the first capacitor, and the emitter of the NPN transistor is connected to the negative terminal of the first capacitor.

[0091] The cathode of the Zener diode is connected to the output terminal of the discharge trigger module. The base of the NPN transistor is connected to the anode of the Zener diode and the collector of the PNP transistor. The base of the PNP transistor is connected to the collector of the NPN transistor.

[0092] For example, Figure 4 This is a schematic diagram of the fourth soft-start circuit structure provided in the embodiments of this application, as shown below. Figure 4 As shown, the discharge module includes: an NPN transistor Q1, a Zener diode D1, and a PNP transistor Q2.

[0093] The collector of NPN transistor Q1 and the emitter of PNP transistor Q2 are connected to the positive terminal of the first capacitor, and the emitter of NPN transistor Q1 is connected to the negative terminal of the first capacitor.

[0094] The cathode of Zener diode D1 is connected to the output terminal of the discharge trigger module. The base of NPN transistor Q1 and the collector of PNP transistor Q2 are connected to the anode of Zener diode D1. The base of PNP transistor Q2 is connected to the collector of NPN transistor Q1.

[0095] When the power input terminal is powered on, the operational amplifier 20 outputs a low-level signal. At this time, the Zener diode D1 is disconnected, so the discharge module 150 cannot be turned on. In addition, the power input terminal charges the first capacitor C1, thereby supplying power to the field-effect transistor 110 through the first capacitor C1, so that the field-effect transistor 110 is slowly turned on.

[0096] When the power input is de-energized and the power input voltage is less than the threshold voltage, the current is increased through the pull-up resistor R7, and the operational amplifier 20 outputs a high-level signal. This high-level signal then turns on the Zener diode D1, triggering the discharge module to start. Specifically, the high-level signal causes the NPN transistor Q1 to generate a base current. This base current then triggers the NPN transistor Q1 to conduct, causing the first capacitor C1 to discharge instantaneously through the conducting NPN transistor Q1. This prevents the first capacitor C1 from supplying power to the field-effect transistor 110, thus enabling the field-effect transistor 110 to discharge. The NPN transistor Q1 is immediately turned off, and the conducting NPN transistor Q1 pulls down the base voltage of the PNP transistor Q2, forcing the PNP transistor Q2 to conduct. After the PNP transistor Q2 is turned on, the energy storage capacitor 130 continuously provides conduction current to the base of the NPN transistor Q1 through the PNP transistor Q2, so that the NPN transistor Q1 and the PNP transistor Q2 enter a cyclic conduction latching state. The NPN transistor Q1 remains in the conducting state and is no longer controlled by the Zener diode D1. Then the first capacitor C1 continues to discharge until the first capacitor C1 is completely discharged, thus completing the rapid turn-off of the field-effect transistor 110.

[0097] In the above implementation process, a high-level signal is transmitted through a Zener diode, which in turn turns on the NPN transistor. This causes the voltage of the first capacitor to discharge instantaneously through the turned-on NPN transistor, thereby achieving immediate turn-off of the field-effect transistor. Furthermore, an interlocking unit is formed by the NPN transistor and the PNP transistor. When the voltage at the power input terminal is less than the threshold voltage, the Zener diode triggers the interlocking unit to turn on, causing the voltage of the first capacitor to discharge through the turned-on interlocking unit, thus blocking the power supply to the field-effect transistor and achieving rapid turn-off of the field-effect transistor.

[0098] Understandably, resistors are provided between the NPN transistor Q1 and the negative input terminal of the power supply, and between the energy storage capacitor 130 and the emitter of the PNP transistor Q2 to provide conduction current.

[0099] In some embodiments, the soft-start circuit further includes a first resistor and a second resistor.

[0100] The first end of the first resistor is connected to the positive input terminal of the power supply, and the second end of the first resistor is connected to the emitter of the PNP transistor.

[0101] The first end of the second resistor is connected to the base of the NPN transistor and the collector of the PNP transistor, and the second end of the second resistor is connected to the negative input terminal of the power supply.

[0102] For example, a first resistor is provided between the positive input terminal of the power supply and the emitter of the PNP transistor Q2. When the power supply is turned off, the conducting NPN transistor Q1 pulls down the base voltage of the PNP transistor Q2, thereby forcing the energy storage capacitor 130 to provide conduction current to the PNP transistor through the first resistor, thereby turning on the PNP transistor Q2.

[0103] Connect the first end of the second resistor to the base of NPN transistor Q1 and the collector of PNP transistor Q2, and connect the second end of the second resistor to the negative input terminal of the power supply. After PNP transistor Q2 is turned on, it is connected to the negative input terminal of the power supply through the second resistor. This causes the conducting PNP transistor Q2 to continuously provide conduction current to the base of NPN transistor Q1, causing NPN transistor Q1 and PNP transistor Q2 to enter a cyclic conduction latching state. NPN transistor Q1 remains in the conducting state and is no longer controlled by Zener diode D1, so the first capacitor C1 continues to discharge.

[0104] In the above implementation process, the NPN and PNP transistors are continuously turned on through the first and second resistors, so that the NPN and PNP transistors enter a cyclically turned-on latching state.

[0105] In some embodiments, the soft-start circuit further includes a third resistor and a fourth resistor.

[0106] The first end of the third resistor is connected to the positive input terminal of the power supply, the second end of the third resistor is connected to the gate of the field-effect transistor, the first end of the fourth resistor is connected to the positive input terminal of the power supply, and the second end of the fourth resistor is connected to the drain of the field-effect transistor.

[0107] The third and fourth resistors form an oscillation circuit, which is used to control the self-excited oscillation of the field-effect transistor.

[0108] In some embodiments, the soft-start circuit may further include:

[0109] The current change rate control module is connected between the positive input terminal of the power supply and the drain of the field-effect transistor. It is used to control the rate of change of the current when the power supply is powered on.

[0110] For example, the soft-start circuit may further include a current rate of change control module, which is connected between the positive input terminal of the power supply and the drain of the field-effect transistor. When the power supply is powered on, the current rate of change control module controls the rate of change of the power-on current.

[0111] In the above implementation process, the rate of change of the power-on current during the hot-plugging process is controlled by the current change rate control module, thereby controlling the rising slope and amplitude of the power-on current at the power input terminal, effectively improving the current limiting effect of the soft-start circuit, and thus improving the safety of the soft-start circuit.

[0112] In some embodiments, the current rate of change control module includes a second capacitor and a fifth resistor.

[0113] The first terminal of the fifth resistor is connected to the positive input terminal of the power supply, the positive terminal of the second capacitor is connected to the second terminal of the fifth resistor, and the negative terminal of the second capacitor is connected to the drain of the field-effect transistor.

[0114] In the above implementation process, the current change rate at the power input terminal is controlled by the second capacitor and the fifth resistor, thereby effectively improving the current limiting effect of the soft start circuit.

[0115] For example, Figure 5 This is a schematic diagram of the fifth type of soft-start circuit provided in the embodiments of this application, as shown below. Figure 5 As shown, the soft-start circuit also includes a third resistor R8 and a fourth resistor R9, and the current change rate control module includes a second capacitor C2 and a fifth resistor R10.

[0116] The first end of the third resistor R8 is connected to the positive input terminal of the power supply, and the second end of the third resistor R8 is connected to the gate of the field-effect transistor 110.

[0117] The first terminal of the fifth resistor R10 is connected to the positive input terminal of the power supply. The positive terminal of the second capacitor C2 is connected to the second terminal of the fifth resistor R10. The negative terminal of the second capacitor C2 is connected to the first terminal of the fourth resistor R9. The second terminal of the fourth resistor R9 is connected to the drain of the field-effect transistor 110.

[0118] The third resistor R8 and the fourth resistor R9 form an oscillation circuit, which is used to control the self-excited oscillation of the field-effect transistor.

[0119] Specifically, the resistance value of the fifth resistor R10 can be between 100K and 200K ohms, the resistance value of the third resistor R8 can be between 10 and 50 ohms, the resistance value of the fourth resistor R9 can be 2K ohms, and the value of the second capacitor C2 can be between 10nF and 100nF. It should be noted that in this embodiment, only the above values ​​of resistors and capacitors are used as examples for illustration. In actual applications, the resistance values ​​of capacitors and resistors in the soft-start circuit can be set according to actual needs and are not limited here.

[0120] In the above implementation process, an oscillation circuit is formed by the third resistor and the fourth resistor, which can effectively control the self-excited oscillation of the field-effect transistor and effectively improve the current limiting effect of the soft start circuit.

[0121] In some embodiments, the soft-start circuit further includes a clamping diode, the cathode of which is connected to a first terminal of a third resistor, and the anode of which is connected to the source of a field-effect transistor. The clamping diode is used to limit the potential between the gate and source of the field-effect transistor.

[0122] For example, the soft-start circuit may further include: a clamping diode, the cathode of which is connected to the first end of the third resistor, and the anode of which is connected to the source of the field-effect transistor, thereby limiting the potential between the gate and source of the field-effect transistor and preventing the gate and source of the field-effect transistor from being broken down by high voltage.

[0123] In the above implementation process, the cathode of the clamping diode is connected to the first end of the third resistor, and the anode of the clamping diode is connected to the source of the field-effect transistor, which can effectively protect the gate and source of the field-effect transistor from being broken down by high voltage.

[0124] Figure 6 This is a schematic diagram of an embodiment of a soft-start circuit provided in this application, as shown below. Figure 6As shown, the output of the soft-start circuit is connected to the energy storage capacitor C6 and the load RL1. The two ends of switch S1 are the positive and negative input terminals of the power supply. Series resistors R11 and R12 are connected to the A terminal of the three-terminal regulator U1 to provide current to the three-terminal regulator U1. The number of series resistors R11 and R12 can be adjusted according to specific conditions. One end of R3 is connected to the A terminal of U1 (three-terminal regulator), and the other end is connected to the reference source of U1. One end of R4 is connected to the reference source of the three-terminal regulator U1, and the other end is connected to the K terminal of the three-terminal regulator U1. Pin 8 (positive power supply terminal) of operational amplifier U2B is connected to the A terminal of the three-terminal regulator U1, and pin 4 (negative power supply terminal) of U2B is connected to the anode of D2, i.e., connected to the negative input terminal of the power supply. One end of C4 is connected to pin 8 of U2B, and the other end of C4 is connected to the anode of D2. Resistors R11, R12, R3, R4, and capacitor C4 together form a series of resistors. The three-terminal regulator U1 and R2B work together to ensure a stable power supply for the operational amplifier U2B. Pin 5 of U2B is connected to one end of R6 and C5, and the other end of R6 and C5 is connected to the anode of D2. Pin 6 of U2B is connected to one end of R13, and the other end of R13 is connected to one end of R2 and C8. The other end of R2 and C8 is connected to the anode of D2. One end of R1 is connected to S1, the positive input terminal of the power supply, and the other end of R1 is connected to one end of R13. One end of R5 is connected to the A terminal of the three-terminal regulator U1, and the other end of R5 is connected to pin 5 of U2B. R1, R2, C8, and R13 provide a stable power input voltage for the operational amplifier U2B, and R5, R6, and C5 provide a stable threshold voltage for the operational amplifier U2B. Pin 7 of U2B is connected to one end of R7, and the other end of R7 is connected to the A terminal of the three-terminal regulator U1. R7 provides the conduction current for D1.

[0125] If the power supply voltage is +48V, when the three-terminal regulator U1 is working, the A terminal of the three-terminal regulator U1 outputs a stable +15V voltage [(1+R3 / R4)*2.5]. The +15V voltage supplies power to the operational amplifier U2B. R5 and R6 are designed with threshold values ​​as needed, and provide the threshold voltage to the operational amplifier U2B through R5 and R6.

[0126] When the power is turned off, the discharge voltage at the power input terminal can be calculated based on the voltage division of R1 and R2. When the discharge voltage at the power input terminal is less than the threshold voltage, pin 7 of U2B outputs a high-level signal (close to the power supply voltage of U2B). Furthermore, the high-level signal is transmitted to the Zener diode D1.

[0127] Furthermore, the soft-start circuit may include multiple first capacitors, and the multiple first capacitors are connected in parallel, such as... Figure 6 The soft-start circuit shown may include two first capacitors, namely C1 and C3.

[0128] Specifically, one end of R16 is connected to the anode of D2, and the other end of R16 is connected to the positive terminal of C2. R16 provides a pull-down voltage for Q3. One end of C3 is connected to the anode of D2, and the other end of C3 is connected to the cathode of clamping diode D3. One end of C1 is connected to the anode of D2, and the other end of C1 is connected to the cathode of clamping diode D3. C1 and C3 are connected between the gate and source of Q3 to turn Q3 on or off. The emitter of Q1 is connected to the anode of D2, and the collector of Q1 is connected to the cathode of D3. The base of Q1 is connected to the collector of Q2, and the base of Q2 is connected to the collector of Q1. The emitter of Q2 is connected to one end of R14 and R15. The other end of R15 is connected to S1, and the other end of R14 is connected to the cathode of D3. The base of Q1 is connected to one end of R17, and the other end of R17 is connected to the anode of D2. R14 and R17 are used to provide the conduction current for the latching circuit composed of Q1 and Q2. C7 is connected in parallel with R17 and is used for filtering. The base of Q1 is connected to the anode of D1, and the cathode of D1 is connected to pin 7 of U2B.

[0129] When switch S1 is closed and the power supply is powered on, the power supply voltage charges C1, C2, and C3 through R15, R14, and R10. R15, R14, C1, and C3 can also realize the hot-swap anti-bouncing delay in the soft-start circuit, thus allowing Q3 to slowly turn on. If switch S1 is opened during power-on operation and the power supply is turned off, the energy storage capacitor C6 discharges, and Q1 and Q2 form a trigger latching circuit. When the discharge voltage is less than the threshold voltage, pin 7 of U2B outputs a high level. Furthermore, the Zener diode D1 turns on, thus giving Q1 a certain base current. When the base current reaches a certain level, it triggers Q1 to conduct and latch, and capacitors C1, C2, and C3 discharge rapidly, causing Q3 to turn off quickly, preventing the generation of a large inrush current, and preparing for soft-start current limiting for the next power-on.

[0130] Clamping diode D3 protects the gate-source of MOSFET Q3 from high-voltage breakdown, thus protecting Q3. R10 and C2 control the rise rate of the current. In practical applications, R10 is typically chosen to be around 100K to 200K ohms, and C2 is typically 10nF to 100nF. R8 and R9 prevent self-oscillation of MOSFET Q3. R8 is typically between 10 and 50 ohms, and R9 is typically 2K ohms.

[0131] Figure 7 This is a schematic diagram comparing the inrush current of the embodiments of this application with that of the prior art, as shown below. Figure 7 As shown, if the power supply voltage is +48V, and channel B is the power input voltage, when switch S1 is closed and conducting, the inrush current in the prior art is 5.3A. Figure 7 In channel D of this application embodiment, the loop inrush current is 2A, such as... Figure 7 As can be seen from channel C in this application, the slow-start current limiting effect of this embodiment is relatively good.

[0132] When switch S1 opens and the circuit is broken, the voltage at the power input terminal drops to +28V, and S1 closes and conducts. At this time, the inrush current in the existing design is 61A. Figure 7 In channel D of this application embodiment, the loop inrush current is 2A, such as... Figure 7 Channel C in the middle.

[0133] When switch S1 opens and the circuit is broken, and the voltage at the power input terminal drops to +25V, S1 closes and conducts. At this time, the inrush current in the existing design is greater than 91A. Figure 7 In channel D of this application embodiment, the loop inrush current is 2A, such as... Figure 7 Channel C in the diagram. Therefore, this application effectively improves the drawback of large inrush current after power failure and enhances the current limiting effect of the soft-start circuit.

[0134] This embodiment also provides a soft-start method, which is applied to the soft-start circuit described in any of the above embodiments. The soft-start circuit includes a field-effect transistor (FET) and a first capacitor connected to a power input terminal. The power input terminal includes a positive power input terminal and a negative power input terminal. The gate of the FET is connected to the positive power input terminal, and the drain and source of the FET are connected to the negative power input terminal. The first capacitor is connected between the gate and source of the FET. The circuit also includes a discharge trigger module and a discharge module. The soft-start method includes:

[0135] The discharge trigger module detects the status of the power input terminal. When it detects that the power input terminal is de-energized, it triggers the discharge module.

[0136] The discharge module is triggered by the discharge trigger module, which controls the first capacitor to lock in the discharge state, thus turning off the field-effect transistor.

[0137] For example, the discharge trigger module detects the state of the power input terminal. When it detects that the power input terminal is de-energized, it acquires the voltage of the power input terminal. When the voltage of the power input terminal is lower than the threshold voltage, it outputs a high-level signal. Furthermore, the high-level signal triggers the discharge module to start, thereby causing the discharge module to control the first capacitor to lock in the discharge state, which in turn causes the field-effect transistor to turn off quickly. This effectively avoids the power module being powered on again during the slow turn-off process of the MOSFET, which would generate a larger inrush current and cause the power supply equipment to burn out. This improves the safety of the soft-start circuit.

[0138] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0139] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0140] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A soft-start circuit, comprising a field-effect transistor (FET) and a first capacitor connected to a power input terminal, wherein the power input terminal includes a positive power input terminal and a negative power input terminal, the gate of the FET is connected to the positive power input terminal, the drain and source of the FET are connected to the negative power input terminal, the first capacitor is connected between the gate and source of the FET, and an energy storage capacitor and a load are connected between the positive power input terminal and the drain of the FET, wherein the energy storage capacitor and the load are connected in parallel, characterized in that... The soft-start circuit further includes a discharge trigger module and a discharge module, wherein: The discharge trigger module is connected to the discharge module and is used to detect the status of the power input terminal. When the power input terminal is detected to be de-energized, the discharge module is triggered. The discharge module is connected in parallel with the first capacitor and is used to control the first capacitor to lock in the discharge state and turn off the field-effect transistor when triggered by the discharge trigger module. The discharge triggering module includes: a voltage acquisition unit and a comparison unit; The voltage acquisition unit is connected between the positive input terminal and the negative input terminal of the power supply, and is used to acquire the voltage at the power input terminal and transmit the voltage at the power input terminal to the comparison unit. The comparison unit is connected to the discharge module and is used to compare the voltage at the power input terminal with the threshold voltage. When the voltage at the power input terminal is less than the threshold voltage, the discharge module is triggered. The threshold voltage is less than the power supply voltage, and the threshold voltage is set according to the power-on action time of the power input terminal; wherein, the threshold voltage is set to a minimum of the voltage value of the power input terminal after the power-on action time has elapsed since the power is first cut off at the power input terminal; The comparison unit includes a reference voltage source and an operational amplifier; the reference voltage source is connected to the power supply terminal of the operational amplifier and is used to power the operational amplifier. The voltage acquisition unit includes a plurality of first voltage divider resistors connected in series between the positive input terminal and the negative input terminal of the power supply, and the negative input terminal of the operational amplifier is connected between the first voltage divider resistors; The threshold voltage is input to the positive input terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the discharge module.

2. The soft-start circuit according to claim 1, characterized in that, The reference voltage source includes a three-terminal regulator. The A terminal of the three-terminal regulator is connected to the positive input terminal of the power supply, the K terminal of the three-terminal regulator is connected to the negative input terminal of the power supply, the A terminal of the three-terminal regulator is connected to the power supply terminal of the operational amplifier, a first regulating resistor is connected between the reference source and the A terminal of the three-terminal regulator, and a second regulating resistor is connected between the reference source and the K terminal of the three-terminal regulator.

3. The soft-start circuit according to claim 2, characterized in that, A third voltage divider resistor is connected between the positive input terminal of the operational amplifier and the A terminal of the three-terminal regulator, and a fourth voltage divider resistor is connected between the positive input terminal of the operational amplifier and the negative input terminal of the power supply. The threshold voltage is set by the third voltage divider resistor and the fourth voltage divider resistor.

4. The soft-start circuit according to claim 1, characterized in that, The discharge module includes: an NPN transistor, a Zener diode, and a PNP transistor; The collector of the NPN transistor and the emitter of the PNP transistor are connected to the positive terminal of the first capacitor, and the emitter of the NPN transistor is connected to the negative terminal of the first capacitor. The cathode of the Zener diode is connected to the output terminal of the discharge trigger module. The base of the NPN transistor is connected to the anode of the Zener diode and the collector of the PNP transistor. The base of the PNP transistor is connected to the collector of the NPN transistor.

5. The soft-start circuit according to claim 4, characterized in that, The soft-start circuit further includes: a first resistor and a second resistor; The first end of the first resistor is connected to the positive input terminal of the power supply, and the second end of the first resistor is connected to the emitter of the PNP transistor. The first end of the second resistor is connected to the base of the NPN transistor and the collector of the PNP transistor, and the second end of the second resistor is connected to the negative input terminal of the power supply.

6. The soft-start circuit according to claim 1, characterized in that, The soft-start circuit also includes: a third resistor, a fourth resistor, a fifth resistor, and a second capacitor; The first end of the third resistor is connected to the positive input terminal of the power supply via the fifth resistor, the second end of the third resistor is connected to the gate of the field-effect transistor, the first end of the fourth resistor is connected to the positive input terminal of the power supply via the second capacitor and the fifth resistor, and the second end of the fourth resistor is connected to the drain of the field-effect transistor.

7. The soft-start circuit according to claim 6, characterized in that, The soft-start circuit further includes a clamping diode, the cathode of which is connected to the first end of the third resistor, and the anode of which is connected to the source of the field-effect transistor. The clamping diode is used to limit the potential between the gate and the source of the field-effect transistor.

8. The soft-start circuit according to claim 1, characterized in that, The soft-start circuit further includes a current change rate control module, connected between the positive input terminal of the power supply and the drain of the field-effect transistor, used to control the rate of change of the power-on current when the power input terminal is powered on.

9. A soft start method, characterized in that, The soft-start method is applied to the soft-start circuit according to any one of claims 1 to 8. The soft-start circuit includes a field-effect transistor (FET) and a first capacitor connected to a power input terminal. The power input terminal includes a positive power input terminal and a negative power input terminal. The gate of the FET is connected to the positive power input terminal, and the drain and source of the FET are connected to the negative power input terminal. The first capacitor is connected between the gate and source of the FET. An energy storage capacitor and a load are connected between the positive power input terminal and the drain of the FET. The energy storage capacitor and the load are connected in parallel. The soft-start circuit further includes a discharge trigger module and a discharge module. The soft-start method includes: The discharge trigger module detects the status of the power input terminal, and triggers the discharge module when it detects that the power input terminal is de-energized. The discharge module is triggered by the discharge trigger module to control the first capacitor to lock in the discharge state, thereby turning off the field-effect transistor.

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