CN219041625U

CN219041625U - Slow start circuit

Info

Publication number: CN219041625U
Application number: CN202223303316.7U
Authority: CN
Inventors: 邵占丰; 越兴隆
Original assignee: Hangzhou Optimax Technology Co ltd
Current assignee: Hangzhou Optimax Technology Co ltd
Priority date: 2022-12-09
Filing date: 2022-12-09
Publication date: 2023-05-16
Anticipated expiration: 2032-12-09

Abstract

The application relates to a slow start circuit, including field effect transistor and first electric capacity, still include: the circuit comprises an operational amplifier, a voltage stabilizing diode, an NPN triode, a PNP triode, a second capacitor and a first resistor; the negative input end of the operational amplifier is connected with the power input end, the positive input end inputs the threshold voltage, and the output end is connected with the cathode of the voltage stabilizing diode; the anode of the voltage stabilizing diode is connected with the base electrode of the NPN type triode and the collector electrode of the PNP type triode, and the base electrode of the PNP type triode is connected with the collector electrode of the NPN type triode; the collector of the NPN triode and the emitter of the PNP triode are connected with the positive electrode of the first capacitor, the emitter of the NPN triode and the collector of the PNP triode are connected with the negative electrode of the first capacitor, the first resistor is connected with the second capacitor in series and then connected between the positive input end of the power supply and the drain electrode of the field effect tube, and the positive electrode of the second capacitor is connected with the grid electrode of the field effect tube. Through the application, the safety of the slow start circuit is improved.

Description

Slow start circuit

Technical Field

The application relates to the field of starting circuits, in particular to a slow starting circuit.

Background

Most of the electronic systems now need to support a Hot plug function, namely Hot plug (Hot Swap), which means that units such as modules, boards and the like are plugged into or pulled out of the system without shutting down the power supply of the system, so that the normal operation of the system is not affected, and the reliability, the quick maintainability, the redundancy, the timely recovery capability to disasters and the like of the system are improved. However, the hot plug also has a certain influence on the system, and the influence mainly comprises two aspects: firstly, when hot plug, the mechanical contact of the connector bounces at the moment of contact, so that power supply oscillation is caused, the oscillation process can cause system power supply fall, error code is caused, or the system is restarted, and the connector can be triggered to fire, so that fire is caused. The method is to delay the energizing time of the connector, not energize the connector within tens of milliseconds of connector shaking, and energize the connector after the insertion is stable, namely, the shaking prevention delay. Secondly, the power supply input ports of the modules, the boards and other units are provided with large-capacity energy storage capacitors so as to maintain the working stability of the power supply input ports, and when in hot plug, the large impact current can occur in the system due to the charging effect of the large-capacity energy storage capacitors of the system, and when the capacitors are charged, the current is exponentially reduced, so that the impact current is very large when the capacitors are just started to be charged. This surge current may burn the equipment power fuse, so the surge current must be controlled during hot plug.

In order to prevent power oscillation and impact current generated by hot plug, a slow start circuit is arranged at a power input port to realize anti-shake delayed power-on, so that the influence of hot plug on a system is overcome.

In the conventional slow start mode of a field effect transistor (MOSFET), the MOSFET is generally connected in series with a power input end, and a capacitor with a certain capacity is connected in parallel with a gate source electrode of the MOSFET. However, under the condition that the power input end is repeatedly powered off and electrified, the energy storage capacitor discharges slowly, and the grid-source electrode capacitor of the MOSFET can be always charged, so that the MOSFET can not be always turned off; if the power is applied when the MOSFET is in a semi-open and semi-closed state, the MOSFET can generate great impact current and transient stress, and even burn out the power supply of the equipment in severe cases, thereby leading to the failure of the slow start circuit.

Aiming at the problem that the slow start circuit is invalid due to frequent hot plug in the related technology, no effective solution is proposed at present.

Disclosure of Invention

In this embodiment, a slow start circuit is provided to solve the problem that in the related art, frequent hot plug causes the slow start circuit to fail.

In a first aspect, in this embodiment, there is provided a soft start circuit, including a field effect transistor and a first capacitor connected to a power input end, where the power input end includes a power positive input end and a power negative input end, a gate of the field effect transistor is connected to the power positive input end, a drain and a source of the field effect transistor are connected to the power negative input end, and the first capacitor is connected between the gate and the source of the field effect transistor, and the soft start circuit further includes: the circuit comprises an operational amplifier, a voltage stabilizing diode, an NPN triode, a PNP triode, a second capacitor and a first resistor;

the negative electrode input end of the operational amplifier is connected with the power supply input end, the positive electrode input end of the operational amplifier inputs threshold voltage, and the output end of the operational amplifier is connected with the cathode of the zener diode;

the anode of the voltage stabilizing diode and the collector of the PNP triode are connected with the base electrode of the NPN triode, and the base electrode of the PNP triode is connected with the collector of the NPN triode;

the collector of the NPN triode and the emitter of the PNP triode are connected with the positive electrode of the first capacitor, and the emitter of the NPN triode and the collector of the PNP triode are connected with the negative electrode of the first capacitor;

The first end of the first resistor is connected with the positive input end of the power supply, the second end of the first resistor is connected with the positive electrode of the second capacitor, the positive electrode of the second capacitor is connected with the grid electrode of the field effect tube, and the negative electrode of the second capacitor is connected with the drain electrode of the field effect tube.

In some of these embodiments, the slow start circuit further comprises:

the first voltage dividing resistor, the second voltage dividing resistor and the third capacitor;

the first voltage dividing resistor and the second voltage dividing resistor are connected in series between the positive power input end and the negative power input end;

the negative electrode input end of the operational amplifier is connected between the first voltage dividing resistor and the second voltage dividing resistor;

the third capacitor is connected between the negative input end of the operational amplifier and the negative input end of the power supply.

In some of these embodiments, the slow start circuit further comprises:

the three-terminal voltage stabilizer, the second resistor, the first regulating resistor and the second regulating resistor;

the A pole of the three-terminal voltage stabilizer is connected with the positive input end of the power supply through the second resistor, the K pole of the three-terminal voltage stabilizer is connected with the negative input end of the power supply, the A pole of the three-terminal voltage stabilizer is connected with the power supply end of the operational amplifier, the first regulating resistor is connected between the reference source and the A pole of the three-terminal voltage stabilizer, and the second regulating resistor is connected between the reference source and the K pole of the three-terminal voltage stabilizer.

In some of these embodiments, the slow start circuit further comprises:

a third voltage dividing resistor, a fourth voltage dividing resistor and a fourth capacitor;

the positive electrode input end of the operational amplifier is connected with the A electrode of the three-terminal voltage stabilizer through the third voltage dividing resistor, the positive electrode input end of the operational amplifier is connected with the negative power input end through the fourth voltage dividing resistor, and the fourth capacitor is connected between the positive electrode input end of the operational amplifier and the negative power input end.

In some of these embodiments, the slow start circuit further comprises:

and the pull-up resistor is connected between the A pole of the three-terminal voltage stabilizer and the output end of the operational amplifier.

In some of these embodiments, the slow start circuit further comprises: a third resistor and a fourth resistor;

the first end of the third resistor is connected with the positive electrode of the second capacitor, the second end of the third resistor is connected with the grid electrode of the field effect tube, the first end of the fourth resistor is connected with the negative electrode of the second capacitor, and the second end of the fourth resistor is connected with the drain electrode of the field effect tube.

In some of these embodiments, the slow start circuit further comprises: and the cathode of the clamping diode is connected with the first end of the third resistor, and the anode of the clamping diode is connected with the source electrode of the field effect transistor.

In some of these embodiments, the slow start circuit further comprises: a fifth resistor and a sixth resistor;

the first end of the fifth resistor is connected with the emitter of the PNP triode, and the second end of the fifth resistor is connected with the anode of the first capacitor;

the first end of the sixth resistor is connected with the base electrode of the NPN triode and the collector electrode of the PNP triode, and the second end of the sixth resistor is connected with the negative input end of the power supply.

In some of these embodiments, the slow start circuit further comprises: and the first end of the seventh resistor is connected with the positive input end of the power supply, and the second end of the seventh resistor is connected with the first end of the fifth resistor.

In some of these embodiments, the slow start circuit further comprises: and the eighth resistor is connected between the grid electrode and the source electrode of the field effect transistor.

Compared with the prior art, the slow starting circuit provided in the embodiment forms a discharge trigger circuit through the operational amplifier, forms a discharge circuit through the combination of the voltage-stabilizing diode, the NPN triode and the PNP triode, determines the voltage of the power input end and the threshold voltage through the discharge trigger circuit when the power input end is powered off, and when the voltage of the power input end is smaller than the threshold voltage, the discharge trigger circuit sends a trigger signal to trigger the discharge circuit to start, and further, the discharge circuit controls the first capacitor to be locked in a discharge state, so that the field effect transistor is turned off immediately, the situation that the power module is electrified again to generate larger impact current in the slow turning-off process of the MOSFET can be effectively avoided, the power equipment is burnt out, the safety of the slow starting circuit is further improved, and the current change rate control module is formed through the combination of the second capacitor and the first resistor, so that the current limiting effect of the slow starting circuit is effectively improved, and the safety of the slow starting circuit is improved when the power supply and the power input end are conducted.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the other features, objects, and advantages of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:

fig. 1 is a schematic diagram of a slow start circuit according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a second slow start circuit according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a third slow start circuit according to an embodiment of the present disclosure;

fig. 4 is a schematic diagram of a fourth slow start circuit according to an embodiment of the present disclosure;

fig. 5 is a schematic diagram of a fifth slow start circuit according to an embodiment of the present application;

FIG. 6 is a schematic diagram of a sixth slow start circuit according to an embodiment of the present disclosure;

fig. 7 is a schematic diagram comparing the impact current of the embodiment of the present application with the prior art.

Detailed Description

For a clearer understanding of the objects, technical solutions and advantages of the present application, the present application is described and illustrated below with reference to the accompanying drawings and examples.

Unless defined otherwise, technical or scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms "a," "an," "the," "these," and the like in this application are not intended to be limiting in number, but rather are singular or plural. The terms "comprising," "including," "having," and any variations thereof, as used in the present application, are intended to cover a non-exclusive inclusion; for example, a process, method, and system, article, or apparatus that comprises a list of steps or modules (units) is not limited to the list of steps or modules (units), but may include other steps or modules (units) not listed or inherent to such process, method, article, or apparatus. The terms "connected," "coupled," and the like in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Reference to "a plurality" in this application means two or more. "and/or" describes an association relationship of an association object, meaning that there may be three relationships, e.g., "a and/or B" may mean: a exists alone, A and B exist together, and B exists alone. Typically, the character "/" indicates that the associated object is an "or" relationship. The terms "first," "second," "third," and the like, as referred to in this application, merely distinguish similar objects and do not represent a particular ordering of objects.

Therefore, how to improve the security of the slow start circuit is a problem to be solved.

In this embodiment, a slow start circuit is provided, and fig. 1 is a schematic structural diagram of the slow start circuit provided in this embodiment, as shown in fig. 1, where the slow start circuit includes: the field effect transistor 110 and the first capacitor C1 are connected to the power input end, the power input end comprises a power positive input end and a power negative input end, the grid electrode of the field effect transistor 110 is connected to the power positive input end, the source electrode of the field effect transistor 110 is connected to the power negative input end, and the first capacitor C1 is connected between the grid electrode and the source electrode of the field effect transistor 110.

The power input end is used for being connected with a power supply, when the power supply is connected with the power input end, namely the power supply is electrified, the power supply charges the first capacitor C1, so that the field effect tube 110 is slowly opened, and the soft start current limiting function is realized.

The slow start circuit further includes: the load 120 and the energy storage capacitor 130 are connected between the positive input end of the power supply and the drain electrode of the field effect tube 110, the energy storage capacitor 130 and the load 120 are connected in parallel, namely, a slow start circuit is connected between the input end of the power supply and the energy storage capacitor 130, and the power on and power off of the energy storage capacitor 130 and the load 120 are realized through the turn-off and the turn-on of the field effect tube 110, wherein the field effect tube 110 can be a mos tube.

It should be noted that, in the embodiment of the present application, the first capacitor may be one capacitor, or may be a plurality of capacitors connected in parallel, which is not limited herein.

The slow start circuit further includes: the circuit comprises an operational amplifier U2B, a zener diode D1, an NPN triode Q1, a PNP triode Q2, a second capacitor C2 and a first resistor R5.

The negative input end of the operational amplifier U2B is connected with the power input end, the positive input end of the operational amplifier U2B inputs the threshold voltage, and the output end of the operational amplifier U2B is connected with the cathode of the zener diode D1.

For example, when the power supply is disconnected from the power supply input end, that is, when the power supply is disconnected, the first capacitor C1 is discharged, and the negative input end of the operational amplifier U2B is connected to the power supply input end, so that the operational amplifier U2B obtains the voltage of the power supply input end, the positive input end of the operational amplifier U2B is used for inputting the set threshold voltage, so that the operational amplifier U2B is convenient for comparing the voltage of the power supply input end with the threshold voltage, and outputs a comparison result, further, when the voltage of the power supply input end is less than the threshold voltage, the operational amplifier U2B outputs a trigger signal, and further, the zener diode D1 is turned on by the trigger signal, so that the first capacitor 120 is always in a discharging state until the amount of charge is discharged, thereby ensuring that the fet 110 is completely turned off, and avoiding the situation that the first capacitor C1 is charged in the half-open half-closed state of the fet 110 so that the fet 110 is not always turned off.

The threshold voltage is smaller than the power supply voltage, and the threshold voltage is set according to the electric operation time on the power supply input terminal.

When the power input terminal is in a power-on state, the voltage of the power input terminal is the power voltage, and when the power input terminal is powered off, the energy storage capacitor 130 starts to discharge, so that the voltage of the power input terminal will drop from the power voltage. Since the voltage at the power input terminal is affected by the load 120 and fluctuates, if the threshold voltage is set to the power supply voltage, the first capacitor C1 is discharged due to a drop caused by the voltage fluctuation when the power input terminal is in the power-on state, and the fet 110 is turned off. Therefore, to improve the tamper resistance, the threshold voltage needs to be smaller than the power supply voltage. Meanwhile, in order to improve the detection sensitivity, the threshold voltage cannot be set too low. Therefore, the setting of the threshold voltage is related to the power-on time of the power input terminal, and the threshold voltage is set according to the power-on time of the power input terminal in the use scene, so that the operational amplifier U2B can be ensured to output the trigger signal before the next power-on. The electric action time on the power input end refers to action time of the power input end connected with the power supply, and can be obtained through action or reaction time, statistics or experience of the power-on switch component. For example, if the use scenario is that the power-on switch is manually turned on and off frequently, the action period of power-on of the power-on switch is manually turned on generally at least 20ms, and then the value of the power-on action time of the power input end may be 20ms.

Specifically, under the condition of direct current power supply excitation, a general expression of a first-order linear circuit differential equation solution is as follows:

f(t)＝f(∞)+[f(0 ₊ )-f(∞)] _e ^-t/τ (1)

wherein f (t) represents a voltage function in the first-order response circuit, f (0) ₊ ) The initial value, f (+_j), represents the steady state value, τ represents the time constant, and t represents the time from power down to re-power up.

If the expression is applied to the slow start circuit in the present application, when the power input terminal is powered off, the energy storage capacitor 130 starts to discharge, and the slow start circuit forms a discharge loop, which can be equivalently the first-order linear circuit, f (0 ₊ ) =a power supply voltage, f (++) a) of (c) and (d) 0, namely, the following relationship exists:

capacitor discharge voltage=0+supply voltage e ^-t/τ (2)

Wherein t represents discharge time, and the time constant τ satisfies the following relationship:

τ＝RC (3)

where R corresponds to the equivalent impedance of the load 160, and C represents the capacitance of the storage capacitor 130.

Then, substituting the relation (3) into the relation (2) yields the following relation:

capacitor discharge voltage = supply voltage e ^-t/RC (4)

In a specific usage scenario, the power supply voltage in the relation (4), the equivalent impedance R of the load 160, and the capacitance C of the energy storage capacitor 130 are all known values, so the relation between the discharge time and the capacitor discharge voltage can be obtained directly by using the relation (4). Because the shortest time for the next power-on is the power-on time immediately after the power input end is powered off, namely the power-on time of the power input end. In order to ensure that the fet 110 is turned off during the power-off period, it is necessary to ensure that the operational amplifier U2B outputs a trigger signal before the next power-on, that is, the threshold voltage should be set to be the corresponding capacitor discharge voltage when t in the relation (4) is the power-on operation time of the power input terminal, so that the threshold voltage can be set according to the power-on operation time of the power input terminal.

The anode of the zener diode D1 and the collector of the PNP triode Q2 are connected with the base of the NPN triode Q1, and the base of the PNP triode Q2 is connected with the collector of the NPN triode Q1.

The collector of the NPN triode Q1 and the emitter of the PNP triode Q2 are connected with the positive electrode of the first capacitor C1, and the emitter of the NPN triode Q1 and the collector of the PNP triode Q2 are connected with the negative electrode of the first capacitor C1.

For example, when an interlock circuit is formed by the NPN type triode Q1 and the PNP type triode Q2, the NPN type triode Q1 is turned on after the zener diode D1 is turned on, and the NPN type triode Q1 and the PNP type triode Q2 are latched, so that the voltage of the first capacitor C1 is rapidly discharged, and further, when the power supply is turned off, the field effect transistor 110 is rapidly turned off.

For example, when the slow start circuit is applied in a manual plug scene, the power input end is connected with a 48V direct current power supply, the equivalent impedance R of the load 120 is 100deg.C, the capacitance value C of the energy storage capacitor 130 is 880 μf, according to the relation (4), the discharge time t is set to the lower limit of 20ms of the manual plug action time, the calculated capacitor discharge voltage is 38V, the lower limit of the threshold voltage is set to 38V, when the power input end starts to be powered off, the voltage of the power input end starts to drop to 38V for 20ms, when the voltage of the power input end is lower than 38V, the operational amplifier U2B outputs a trigger signal, so that the zener diode D1 is turned on, the NPN transistor Q1 generates base current, and further, the NPN transistor Q1 is triggered by the base current, so that the first capacitor C1 is discharged through the turned on NPN transistor Q1, further, the first capacitor C1 cannot be powered by the field effect transistor 110, the immediate turn-off of the field effect transistor 110 is realized, and when the voltage of the turned on input end is lower than 38V, the PNP transistor Q1 is turned on, the PNP transistor Q2 is turned on, the PNP transistor Q1 is turned off, the state is continuously controlled, and the PNP transistor Q1 is turned on, the state is completed, and the PNP transistor Q1 is turned on, the state is continuously turned on, and the state is completed.

Even if the power input end is powered on manually immediately, the time is more than 20ms, and when the power input end is powered on, the first capacitor C1 is discharged to the emptying charge quantity, and the field effect tube 110 is in a turn-off state, so that the field effect tube 110 can be restarted. Of course, the threshold voltage may be set to any value between greater than 38V and less than 48V, but the voltage fluctuation at the power supply input terminal needs to be taken into consideration. The higher the threshold voltage setting, the faster the fet 110 is turned off since the power input is powered down.

The first end of the first resistor R5 is connected to the positive input terminal of the power supply, the second end of the first resistor R5 is connected to the positive electrode of the second capacitor C2, the positive electrode of the second capacitor C2 is connected to the gate of the field effect transistor 110, and the negative electrode of the second capacitor C2 is connected to the drain of the field effect transistor 110. The current change rate control module is formed through the second capacitor C2 and the first resistor R5, so that when the power supply is conducted with the power supply input end, the change rate of the power-on current is controlled, the current limiting effect of the slow starting circuit is effectively improved, and the safety of the slow starting circuit is further improved.

In the implementation process, when the power supply is powered off, the voltage of the power supply input end is obtained and compared with the threshold voltage through the operational amplifier, when the voltage of the power supply input end is smaller than the threshold voltage, the operational amplifier outputs a trigger signal, so that the trigger signal triggers the voltage stabilizing diode to conduct, and further, the NPN type triode is conducted through the conducted voltage stabilizing diode, so that the first capacitor can rapidly discharge through the conducted NPN type triode, an interlocking circuit is formed through the NPN type triode and the PNP type triode, the continuous discharge of the first capacitor is ensured, after the first capacitor rapidly discharges to zero, the first capacitor cannot supply power to the field effect transistor, the rapid turn-off of the field effect transistor is realized, the problem that the field effect transistor of the equipment is damaged due to rapid repeated hot plug is effectively avoided, the current limiting effect on the power supply is effectively improved due to the fact that the second capacitor and the first resistor are combined, and the current limiting effect on the power supply is effectively improved.

In some embodiments, fig. 2 is a schematic structural diagram of a second slow start circuit provided in the embodiments of the present application, where, as shown in fig. 2, the slow start circuit further includes: three-terminal voltage stabilizer U1, second resistance R12, first regulating resistor R1 and second regulating resistor R2; the A pole of the three-terminal voltage regulator U1 is connected with a positive input end of a power supply through a second resistor R12, the K pole of the three-terminal voltage regulator U1 is connected with a negative input end of the power supply, the A pole of the three-terminal voltage regulator U1 is connected with a power supply end of an operational amplifier U2B, a first regulating resistor R1 is connected between a reference source and the A pole of the three-terminal voltage regulator U1, and a second regulating resistor R2 is connected between the reference source and the K pole of the three-terminal voltage regulator U1.

Illustratively, the a pole of the three-terminal voltage regulator U1 is connected to the positive power input terminal through the second resistor R12, the K pole of the three-terminal voltage regulator U1 is connected to the negative power input terminal, and the a pole of the three-terminal voltage regulator U1 is connected to the power terminal of the operational amplifier U2B, so as to supply power to the operational amplifier U2B through the three-terminal voltage regulator U1. The second resistor R12 provides an on-current for the three-terminal regulator U1. The power supply end of the operational amplifier U2B can be one or positive and negative, when the power supply end of the operational amplifier U2B is provided with the positive and negative two, the A pole of the three-terminal voltage regulator U1 is connected with the positive power supply end of the operational amplifier U2B, and the negative power supply end of the operational amplifier U2B is connected with the negative power supply input end. The negative power supply end of the operational amplifier U2B may be connected to the negative power supply input end through a seventh capacitor C7, so as to keep the operational amplifier U2B stably powered.

The three-terminal voltage regulator comprises a reference source and an A pole of a three-terminal voltage regulator U1, wherein a first regulating resistor R1 is connected between the reference source and the A pole of the three-terminal voltage regulator U1, and a second regulating resistor R2 is connected between the reference source and the K pole of the three-terminal voltage regulator U1, so that the output voltage of the A pole of the three-terminal voltage regulator U1 is regulated through the first regulating resistor R1 and the second regulating resistor R2, and the A pole of the three-terminal voltage regulator U1 outputs stable voltage, and further supplies power for an operational amplifier U2B through the stable voltage.

It should be noted that the second resistor in the embodiment of the present application may be one resistor or a plurality of resistors connected in series, which is not limited herein.

In some of these embodiments, the slow start circuit further comprises: the first voltage dividing resistor, the second voltage dividing resistor and the third capacitor.

The first voltage dividing resistor and the second voltage dividing resistor are connected in series between the positive power input end and the negative power input end.

The negative input end of the operational amplifier is connected between the first voltage dividing resistor and the second voltage dividing resistor.

The first capacitor is connected between the negative input end of the operational amplifier and the negative input end of the power supply.

For example, fig. 3 is a schematic diagram of a third slow start circuit provided in the embodiment of the present application, as shown in fig. 3, a first voltage dividing resistor R6 and a second voltage dividing resistor R7 are connected in series between a positive power input end and a negative power input end, a negative input end of an operational amplifier U2B is connected between the first voltage dividing resistor R6 and the second voltage dividing resistor R7, an anode of a third capacitor C3 is connected with the negative input end of the operational amplifier U2B, and a cathode of the third capacitor C3 is connected with the negative power input end. The voltage of the power input end is obtained through the first voltage dividing resistor R6, the second voltage dividing resistor R7 and the third capacitor C3, and the voltage of the power input end is transmitted to the negative electrode input end of the operational amplifier U2B, so that the operational amplifier can conveniently obtain the voltage of the power input end.

In the implementation process, the voltage of the power input end is obtained through the first voltage dividing resistor, the second voltage dividing resistor and the third capacitor, and the voltage of the power input end is transmitted to the negative electrode input end of the operational amplifier, so that the operational amplifier can compare the voltage of the power input end with the threshold voltage conveniently.

In some of these embodiments, the slow start circuit further comprises: and the negative input end of the operational amplifier is connected between the first voltage dividing resistor and the second voltage dividing resistor through the fifth voltage dividing resistor. The positive pole of the third capacitor is connected with the first end of the fifth voltage dividing resistor, and the negative pole of the third capacitor is connected with the negative input end of the power supply.

Illustratively, the first voltage dividing resistor R6 and the second voltage dividing resistor R7 are connected in series between the positive input terminal and the negative input terminal of the power supply, the first terminal of the fifth voltage dividing resistor R8 is connected between the first voltage dividing resistor R6 and the second voltage dividing resistor R7, and the second terminal of the fifth voltage dividing resistor R8 is connected to the negative input terminal of the operational amplifier U2B. The positive pole of the third capacitor C3 is connected with the first end of the fifth voltage dividing resistor R8, and the negative pole of the third capacitor C3 is connected with the negative input end of the power supply.

In some of these embodiments,

The slow start circuit further includes: a third voltage dividing resistor, a fourth voltage dividing resistor and a fourth capacitor; the positive electrode input end of the operational amplifier is connected with the A electrode of the three-terminal voltage stabilizer through a third voltage dividing resistor, the positive electrode input end of the operational amplifier is connected with the negative input end of the power supply through a fourth voltage dividing resistor, and a fourth capacitor is connected between the positive electrode input end of the operational amplifier and the negative input end of the power supply.

Fig. 4 is a schematic diagram of a fourth slow start circuit according to the embodiment of the present application, as shown in fig. 4, a fourth capacitor C4 is connected to the positive input end and the negative input end of the operational amplifier U2B, the positive input end of the operational amplifier U2B is connected to the a pole of the three-terminal voltage regulator U1 through a third voltage dividing resistor R3, and the positive input end of the operational amplifier U2B is connected to the negative input end of the power supply through a fourth voltage dividing resistor R4. Thereby realizing the setting and acquisition of the threshold voltage in the operational amplifier U2B through the fourth capacitor C4, the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4

In some of these embodiments, the slow start circuit further comprises: and the pull-up resistor is connected between the A pole of the three-terminal voltage stabilizer and the output end of the operational amplifier.

Illustratively, a pull-up resistor R11 is connected between the a pole of the three-terminal voltage regulator U1 and the output terminal of the operational amplifier U2B, so that the operational amplifier U2B outputs a stable conduction current of the zener diode D1, and when the voltage of the power input terminal is smaller than the threshold voltage, the operational amplifier U2B outputs a high-level signal, so that the high-level signal triggers the zener diode D1 to be conducted, and when the voltage of the power input terminal is smaller than the threshold voltage, the zener diode D1 is effectively conducted.

In some of these embodiments, the slow start circuit further comprises: a third resistor and a fourth resistor.

The third resistor and the fourth resistor form an oscillating circuit, and the oscillating circuit is used for controlling self-oscillation of the field effect transistor.

Illustratively, the slow start circuit may further comprise: and a clamping diode D2, wherein the cathode of the clamping diode D2 is connected with the first end of the third resistor R9, and the anode of the clamping diode D2 is connected with the source electrode of the field effect transistor 110, so that the clamping diode D2 limits the potential between the gate electrode and the source electrode of the field effect transistor 110, and the gate electrode and the source electrode of the field effect transistor 110 are prevented from being broken down by high voltage.

In the implementation process, the cathode of the clamping diode is connected with the first end of the second resistor, and the anode of the clamping diode is connected with the source electrode of the field effect transistor, so that the grid electrode and the source electrode of the field effect transistor can be effectively prevented from being broken down by high voltage.

Specifically, fig. 5 is a schematic diagram of a fifth slow start circuit structure provided in the embodiment of the present application, as shown in fig. 5, a first end of a third resistor R9 is connected to an anode of a second capacitor C2, a second end of the third resistor R9 is connected to a gate of a field effect transistor 110, a first end of a fourth resistor R10 is connected to a cathode of the second capacitor C2, and a second end of the fourth resistor R10 is connected to a drain of the field effect transistor 110. The first end of the first resistor R5 is connected with the positive input end of the power supply, and the positive electrode of the second capacitor C2 is connected with the second end of the first resistor R5. The second capacitor C2 and the first resistor R5 form a current change rate control circuit, and when the power supply is electrified, the current change rate during electrification is controlled, so that the damage of impact current generated in the moment of the power supply electrification to the power supply is effectively avoided, and the current limiting effect of the slow start circuit is effectively improved. The third resistor R9 and the fourth resistor R10 form an oscillating circuit, so that self-oscillation of the field effect transistor can be effectively controlled, and the potential between the grid electrode and the source electrode of the field effect transistor is limited through the clamping diode D2, so that the grid electrode and the source electrode of the field effect transistor are prevented from being broken down by high voltage.

Specifically, the resistance of the first resistor R5 may be between 100K and 200K ohms, the resistance of the third resistor R9 may be between 10 and 50 ohms, the resistance of the fourth resistor R10 may be between 2K ohms, and the value of the second capacitor C2 may be between 10nF and 100 nF.

In some of these embodiments, the slow start circuit further comprises: a fifth resistor and a sixth resistor.

The first end of the fifth resistor is connected with the emitter of the PNP triode, and the second end of the fifth resistor is connected with the anode of the first capacitor.

Illustratively, a fifth resistor is connected between the emitter of the PNP transistor Q2 and the anode of the first capacitor to provide on-current to the PNP transistor Q2.

The first end of the sixth resistor is connected with the base electrode of the NPN triode Q1 and the collector electrode of the PNP triode, and the second end of the sixth resistor is connected with the negative input end of the power supply.

The first end of the sixth resistor is connected with the base electrode of the NPN triode and the collector electrode of the PNP triode, and the second end of the sixth resistor is connected with the negative input end of the power supply, so that stable pull-down voltage is provided.

In the implementation process, the fifth resistor is connected between the emitter of the PNP triode and the positive input end of the power supply to provide conduction current for the PNP triode, and stable pull-down voltage is provided through the sixth resistor.

In some of these embodiments, the slow start circuit further comprises: and a fifth capacitor connected in parallel with the sixth resistor.

Illustratively, a fifth capacitor is connected in parallel with the sixth resistor for filtering.

Illustratively, a seventh resistor R15 is added between the positive power supply input and the first end of the fifth resistor R14 to increase the charging current of the first capacitor C1 at power-up.

Illustratively, an eighth resistor R16 is connected between the gate and source of the fet 110 to provide a stable gate pull-down voltage for the fet 110.

Fig. 6 is a schematic diagram of a sixth slow start circuit structure provided in the embodiment of the present application, where an output end of the slow start circuit shown in fig. 6 is connected to an energy storage capacitor C6 and a load RL1, two ends of a switch S1 are positive and negative input ends of a power supply, series resistors R12 and R13 are connected to an a pole of a three-terminal voltage regulator U1 and used for providing current to the three-terminal voltage regulator U1, and the number of the series resistors R12 and R13 can be adjusted according to specific situations; one end of R1 is connected with an A pole of U1 (three-terminal voltage stabilizer), the other end of R2 is connected with a U1 reference source, one end of R2 is connected with a reference source of the three-terminal voltage stabilizer U1, the other end of R2 is connected with a K pole of the three-terminal voltage stabilizer U1, an 8 pin (positive power supply end) of an operational amplifier U2B is connected with an A pole of the three-terminal voltage stabilizer U1, a 4 pin (negative power supply end) of U2B is connected with an anode of D3, namely the anode of D3 is connected with a negative input end of a power supply, one end of C4 is connected with an 8 pin of U2B, and the other end of C4 is connected with resistors R12, R13, R1, R2 and a capacitor C7 in a combined mode so as to ensure that the three-terminal voltage stabilizer U1 provides a stable power supply for the operational amplifier U2B; the 5 pin (positive input end) of the U2B is connected with one ends of R3 and C3, the other ends of R4 and C3 are connected with a D3 anode, the 6 pin (negative input end) of the U2B is connected with one end of R8, the other end of R8 is connected with one ends of R7 and C3, the other ends of R7 and C3 are connected with the anode of D3, one end of R6 is connected with S1, namely the positive input end of a power supply, the other end of R6 is connected with one end of R8, one end of R3 is connected with the A pole of a three-terminal voltage stabilizer U1, the other end of R3 is connected with the 5 pin of U2B, R6, R7, C3 and R8 provide stable power supply input end voltage for the operational amplifier U2B, and R3, R4 and C4 provide stable threshold voltage for the operational amplifier U2B; the 7 pin (output end) of U2B is connected with one end of R11, the other end of R11 is connected with the A pole of the three-terminal voltage stabilizer U1, and R11 provides on-current for D1.

If the power supply voltage is +48v, the three-terminal voltage regulator U1 works, the a pole of the three-terminal voltage regulator U1 outputs a stable +15v voltage [ (1+r1/R2) ×2.5], +15v voltage supplies power to the operational amplifier U2B, and R3 and R4 design thresholds as required to provide threshold voltages for the operational amplifier U2B through R3 and R4.

When the power supply is powered off, the discharging voltage of the power supply input end can be calculated according to the partial pressure of R6 and R7, and when the discharging voltage of the power supply input end is smaller than the threshold voltage, the pin 7 of the U2B outputs a high-level signal (close to the power supply voltage of the U2B), and further, the high level is transmitted to the voltage stabilizing diode D1.

Further, the slow start circuit may include a plurality of first capacitors, and the plurality of first capacitors are connected in parallel, and the slow start circuit shown in fig. 6 may include two first capacitors, respectively C1 and C6.

Specifically, one end of R16 is connected with the anode of D3, the other end of R16 is connected with the anode of C2, and R16 is used for providing pull-down voltage for Q3; one end of C6 is connected with the anode of D3, the other end of C6 is connected with the cathode of the clamping diode D2, one end of C1 is connected with the anode of D3, the other end of C1 is connected with the cathode of the clamping diode D2, and C1 and C6 are connected between the grid electrode and the source electrode of Q3 and used for switching on or off Q3; the emitter of Q1 links to each other with the positive pole of D3, the collector of Q1 links to each other with the negative pole of D2, the base of Q1 links to each other with the collector of Q2, the base of Q2 links to each other with the collector of Q1, the emitter of Q2 links to each other with one end of R14, the other end of R15 is connected S1, the other end of R14 is connected the negative pole of D2, the base of Q1 is connected one end of R17, the other end of R17 is connected the positive pole of D3, R14, R17 is used for providing the conduction current for the latch circuit that Q1 and Q2 constitute, C5 is parallelly connected with R17, C5 is used for filtering, the positive pole of D1 is connected to the base of Q1, the 7 feet of U2B are connected to the negative pole of D1.

When the switch S1 is closed, the power supply is electrified, the power supply voltage charges C1, C2 and C6 through R15, R14 and R5, and hot plug anti-shake delay in a slow starting circuit can be realized through R15, R14, C1 and C6, so that the field effect transistor Q3 is slowly conducted; if the switch S1 is disconnected in the power-on operation process, the power supply is powered off, the energy storage capacitor C6 discharges, Q1 and Q2 form a trigger latch circuit, when the discharge voltage is smaller than the threshold voltage, the 7 pin of the U2B outputs a high level, and further the zener diode D1 is conducted, so that the Q1 has certain base current, the Q1 is triggered to conduct and latch when the base current reaches a certain degree, the C1, C2 and C6 capacitors rapidly discharge, the MOSFET Q3 is rapidly turned off, large impact current is prevented from being generated, and the preparation for slow-start current limiting is made for the next power-on.

The clamp diode D2 may be used to protect the gate-source of the MOSFET transistor Q3 from high voltage breakdown, and serves to protect the MOSFET transistor Q3. R5 and C2 can be used for controlling the rising slope of the power-on current, and in practical application, R5 is generally selected to be about 100K-200K ohms, and C2 takes a value of 10 nF-100 nF. The function of R9 and R10 is to prevent self-oscillation of the MOSFET Q3, the value of R9 is generally between 10 and 50 ohms, and the value of R10 is generally 2 Kohms.

Fig. 7 is a schematic diagram comparing the current surge of the embodiment of the present application with that of the prior art, as shown in fig. 7, if the power voltage is +48v, as shown in the channel B of fig. 7. After the switch S1 is turned on, the loop impact current in the prior art is 5.3A, such as the channel D in fig. 7, and the loop impact current in the embodiment of the present application is 2A, such as the channel C in fig. 7, so that the slow start current limiting effect in the embodiment of the present application is better.

When the switch S1 is opened and disconnected, and the input voltage drops to +28v, the switch S1 is closed and turned on, and the loop surge current in the conventional design is 61A, such as the channel D in fig. 7, and the loop surge current in the embodiment of the present application is 2A, such as the channel C in fig. 7.

When the switch S1 is opened and disconnected, and the input voltage drops to +25v, S1 is closed and turned on, and the loop surge current in the existing design is greater than 91A, such as the channel D in fig. 7, and the loop surge current 2A in the embodiment of the present application, such as the channel C in fig. 7. Therefore, the defect of large impact current existing in power-on after power-off can be effectively overcome, and the current limiting effect of the slow start circuit is improved.

The above-described respective modules may be functional modules or program modules, and may be implemented by software or hardware. For modules implemented in hardware, the various modules described above may be located in the same processor; or the above modules may be located in different processors in any combination.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the patent. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.

Claims

1. The utility model provides a slow start circuit, includes field effect tube and first electric capacity that connects in the power input end, the power input end includes power positive input end and power negative input end, the grid of field effect tube is connected the power positive input end, the drain electrode and the source connection of field effect tube the power negative input end, first electric capacity is connected between the grid and the source of field effect tube, its characterized in that, slow start circuit still includes: the circuit comprises an operational amplifier, a voltage stabilizing diode, an NPN triode, a PNP triode, a second capacitor and a first resistor;

2. The slow start circuit of claim 1, wherein the slow start circuit further comprises: the first voltage dividing resistor, the second voltage dividing resistor and the third capacitor;

3. The slow start circuit of claim 1, wherein the slow start circuit further comprises: the three-terminal voltage stabilizer, the second resistor, the first regulating resistor and the second regulating resistor;

4. A slow start circuit according to claim 3, wherein the slow start circuit further comprises: a third voltage dividing resistor, a fourth voltage dividing resistor and a fourth capacitor;

5. A slow start circuit according to claim 3, wherein the slow start circuit further comprises:

6. The slow start circuit of claim 1, wherein the slow start circuit further comprises: a third resistor and a fourth resistor;

7. The slow start circuit of claim 6, wherein the slow start circuit further comprises: and the cathode of the clamping diode is connected with the first end of the third resistor, and the anode of the clamping diode is connected with the source electrode of the field effect transistor.

8. The slow start circuit of claim 1, wherein the slow start circuit further comprises: a fifth resistor and a sixth resistor;

9. The slow start circuit of claim 8, wherein the slow start circuit further comprises:

and the first end of the seventh resistor is connected with the positive input end of the power supply, and the second end of the seventh resistor is connected with the first end of the fifth resistor.

10. The slow start circuit of claim 9, wherein the slow start circuit further comprises:

and the eighth resistor is connected between the grid electrode and the source electrode of the field effect transistor.