CN214045432U - Soft start circuit and power supply circuit - Google Patents

Abstract

The utility model discloses a soft start circuit and power supply circuit. The soft start circuit is arranged between the negative electrode of the direct current bus capacitor and the negative electrode terminal of the direct current source; after starting, controlling whether the direct current source is conducted with the direct current bus capacitor according to the current input by the direct current bus capacitor in the constant current module; one end of the soft start circuit is also connected with the filtering protection module and used for controlling the conduction between the direct current source and the direct current bus capacitor according to the voltage output by the filtering protection module at the starting moment. Through the utility model discloses, can be when the electric current of the input of direct current bus-bar electric capacity is too big, break off between control direct current source and the direct current bus-bar electric capacity, only realize the soft start through soft start circuit, circuit structure is simple, need not complicated control procedure, has improved control efficiency.

Description

Soft start circuit and power supply circuit

Technical Field

The utility model relates to an electron electric power technical field particularly, relates to a soft start circuit and power supply circuit.

Background

In the prior art, a power supply circuit is generally used for supplying power to a load, and with the increasing requirements on circuit integration and miniaturization of the load (such as an LED lamp), in the technical scheme of the prior art, the size of a starting current is suppressed by a relay charging circuit or a thermistor, so that the circuit is complex and has a large volume; the thermistor always has loss after being started, is sensitive to temperature, and is used for switching on and off a lamp at high temperature, so that the current inhibition effect of the thermistor is weakened, and circuit devices cannot be effectively protected. The soft start can be realized by using a chip control switch device, but a chip control circuit and a control program are required, so that the design of a power supply circuit of a load becomes complicated.

Aiming at the problems that the power circuit required by the soft start function in the prior art is complex in design and difficult to realize, an effective solution is not provided at present.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides an in provide a soft start circuit and power supply circuit to solve among the prior art the required power supply circuit design of soft start function complicacy, the problem of difficult realization.

In order to solve the technical problem, the utility model provides a soft start circuit, which is applied to a power circuit, wherein the power circuit comprises a filtering protection module and a constant current module, the filtering protection module is connected with a direct current source, the constant current module comprises a direct current bus capacitor, and the soft start circuit is arranged between the negative electrode of the direct current bus capacitor and the negative electrode terminal of the direct current source; after starting, controlling whether the direct current source is conducted with the direct current bus capacitor according to the current input by the direct current bus capacitor in the constant current module;

one end of the soft start circuit is also connected with the filtering protection module and used for controlling the conduction between the direct current source and the direct current bus capacitor according to the voltage output by the filtering protection module at the starting moment.

Further, the soft start circuit includes a soft start chip, which includes:

the first pin is connected with the positive terminal of the direct current source through a filter capacitor and a charging resistor in the filter protection module and used for inputting a voltage signal at the starting moment so as to control the conduction between the fourth pin and the fifth pin; the fourth pin is connected with a first end of a sampling resistor, and a second end of the sampling resistor is connected with a negative terminal of the direct current source; the fifth pin is connected with the negative electrode of the direct current bus capacitor;

the second pin and the third pin are respectively connected to two ends of the sampling resistor and used for detecting voltages at two ends of the sampling resistor; the voltage at two ends of the sampling resistor is in direct proportion to the current input by the direct current bus capacitor;

and the soft start chip is used for controlling the connection and disconnection between the fourth pin and the fifth pin according to the voltages at two ends of the sampling resistor after starting, so as to control whether the direct current source is connected with the direct current bus capacitor.

Further, the soft start chip further includes:

the first switch is arranged between the fourth pin and the fifth pin, and the control end of the first switch is connected with the first pin; the on-off of the fourth pin and the fifth pin is controlled through the on-off of the fourth pin and the fifth pin;

the detection unit is arranged between the second pin and the third pin and used for detecting the voltage at two ends of the sampling resistor;

the second switch is arranged between the second pin and the first pin and is used for being switched on when the voltage at two ends of the sampling resistor is greater than a first preset value so as to control the first switch to be switched off; when the voltage at the two ends of the sampling resistor is smaller than a second preset value, the sampling resistor is turned off, and the first switch is further controlled to be turned on; wherein the second preset value is smaller than the first preset value.

Further, the soft start chip further includes:

and the first unidirectional element is connected between the second pin and the first pin, is connected with the second switch in series and is used for controlling the current to flow from the first pin to the second pin.

Further, the soft start chip further includes:

and the voltage stabilizing unit is arranged between the grid electrode and the source electrode of the first switch and is used for stabilizing the voltage between the grid electrode and the source electrode of the first switch.

Further, the soft start circuit further comprises: a first end of the inductor is connected with the negative electrode of the direct current bus capacitor, and a second end of the inductor is connected with the fifth pin;

the soft start chip further comprises: a sixth pin, a first end of which is connected with the fifth pin, and a second end of which is connected between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor;

the inductor, the fifth pin, the sixth pin and the direct current bus capacitor form a closed loop, and the closed loop is used for maintaining the voltage at two ends of the direct current bus capacitor when the direct current source stops supplying power to the direct current bus capacitor.

Further, the soft start chip further includes:

a second unidirectional element, the anode of which is connected with the fifth pin, and the cathode of which is connected with the sixth pin; for controlling current flow from the fifth pin to the sixth pin.

Further, the soft start chip further includes:

and the seventh pin is connected between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor and used for inputting a voltage signal so as to control the first switch to maintain a conducting state after the start is completed.

Further, the soft start circuit further comprises:

and the voltage limiting resistor is arranged between a line led out between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor and the seventh pin and is used for limiting the voltage input by the seventh pin.

The utility model also provides a power supply circuit, including filtering protection module and constant current module, its characterized in that still includes above-mentioned soft start circuit.

By applying the technical scheme of the utility model, a soft start circuit is arranged between the negative pole of the DC bus capacitor and the negative pole terminal of the DC source; after starting, controlling whether the direct current source is conducted with the direct current bus capacitor or not according to the current input by the direct current bus capacitor in the constant current module; one end of the soft start circuit is also connected with the filtering protection module and used for controlling the direct current source to be conducted with the direct current bus capacitor according to the voltage output by the filtering protection module at the starting moment, so that the direct current source and the direct current bus capacitor can be controlled to be disconnected when the input current of the direct current bus capacitor is too large, the soft start is realized only through the soft start circuit, the circuit structure is simple, a complex control program is not needed, and the control efficiency is improved.

Drawings

Fig. 1 is a block diagram of a power circuit and a soft start circuit according to an embodiment of the present invention;

fig. 2 is a block diagram of a soft start circuit according to another embodiment of the present invention;

fig. 3 is a block diagram of a soft start chip according to an embodiment of the present invention;

fig. 4 is a block diagram of a power circuit according to an embodiment of the present invention;

fig. 5 is a comparison graph of the starting current waveform of the conventional starting circuit and the starting current waveform of the soft start circuit according to the embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the embodiments of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be understood that although the terms first, second, etc. may be used to describe the switches in the embodiments of the present invention, the switches should not be limited to these terms. These terms are only used to distinguish between different switches. For example, a first switch may also be referred to as a second switch, and similarly, a second switch may also be referred to as a first switch, without departing from the scope of embodiments of the present invention.

The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.

The following describes in detail alternative embodiments of the present invention with reference to the accompanying drawings.

Example 1

The present embodiment provides a soft start circuit, which is applied to a power circuit, fig. 1 is a structural diagram of a power circuit and a soft start circuit according to an embodiment of the present invention, fig. 1 is a structural diagram of a soft start circuit and a power circuit according to an embodiment of the present invention, as shown in fig. 1, the power circuit includes a filter protection module 10 and a constant current module 30, the filter protection module 10 includes a charging resistor R1, a filter capacitor C1 and a FUSE1, the filter capacitor C1 is connected to a dc source through the charging resistor R1 and the FUSE1, the constant current module 30 includes a dc bus capacitor C2 therein, the positive electrode of the dc bus capacitor C2 is connected to the positive electrode terminal of the dc source through the FUSE1, the negative electrode is connected to the negative electrode of the dc source, the constant current module 30 further includes a half-bridge resonant circuit composed of a switching tube Q2, a switching tube Q3, a second inductor L2, a transformer T1, and a third capacitor C3, and realizing high-efficiency isolation conversion. The output of the rectifying circuit is composed of diodes D3, D4 and a fourth capacitor C4, and the rectifying circuit outputs voltage to the LED light source module 40 through a positive terminal V0 +. The LED light source module 40 includes two parallel LED lamp beads, and may further include a resistor R4 connected in parallel at two ends of the LED lamp beads.

As shown in fig. 1, the soft start circuit 20 is provided between the negative electrode of the dc bus capacitor C2 in the constant current module 30 and the negative electrode terminal of the dc source; the constant current module is used for controlling whether the direct current source is conducted with the direct current bus capacitor or not according to the current input by the direct current bus capacitor in the constant current module after starting;

one end of the soft start circuit 20 is further connected to the filtering protection module 10, and is configured to control conduction between the dc source and the dc bus capacitor according to the voltage output by the filtering protection module at the start time.

With the soft start circuit of the embodiment, the soft start circuit is arranged between the negative electrode of the direct current bus capacitor and the negative electrode terminal of the direct current source; after starting, controlling whether the direct current source is conducted with the direct current bus capacitor or not according to the current input by the direct current bus capacitor in the constant current module; one end of the soft start circuit is also connected with the filtering protection module and used for controlling the direct current source to be conducted with the direct current bus capacitor according to the voltage output by the filtering protection module at the starting moment, so that the direct current source and the direct current bus capacitor can be controlled to be disconnected when the input current of the direct current bus capacitor is too large, the soft start is realized only through the soft start circuit, the circuit structure is simple, a complex control program is not needed, and the control efficiency is improved.

Example 2

This embodiment provides another kind of soft start circuit, fig. 2 is a structure diagram of a soft start circuit according to another embodiment of the present invention, in order to specifically realize the soft start function, as shown in fig. 2, the soft start circuit includes a soft start chip IC, which includes: the first pin IN1 is connected with the positive terminal of the direct current source through a filter capacitor C1 and a charging resistor R1 IN the filter protection module, and is used for inputting a voltage signal at the starting moment so as to control the conduction between the fourth pin DC 2-and the fifth pin DC 1-; the fourth pin DC 2-is connected with the first end of the sampling resistor R2, and the second end of the sampling resistor R2 is connected with the negative terminal of the direct current source; a fifth pin DC 1-is connected with the negative electrode of the direct current bus capacitor C2; a second pin ISEN1 and a third pin ISEN2 which are respectively connected to two ends of the sampling resistor R2 and used for detecting the voltage at two ends of the sampling resistor R2; the voltage at two ends of the sampling resistor R2 is in direct proportion to the current input by the direct current bus capacitor; and the soft start chip IC is used for controlling the connection and disconnection between the fourth pin DC 2-and the fifth pin DC 1-according to the voltage at two ends of the sampling resistor R2 after starting, and further controlling whether the direct current source is connected with the direct current bus capacitor or not.

Fig. 3 is a structural diagram of a soft start chip according to the embodiment of the present invention, in order to control the on/off between the fourth pin DC 2-and the fifth pin DC 1-according to the voltage at the two ends of the sampling resistor R2, as shown in fig. 3, the soft start chip IC further includes:

a first switch Q1, arranged between the fourth pin DC 2-and the fifth pin DC 1-and having its control terminal connected to the first pin IN 1; the switching device is used for controlling the switching between the fourth pin DC 2-and the fifth pin DC 1-through self switching;

a detection unit 201, disposed between the second pin ISEN1 and the third pin ISEN2, for detecting a voltage across the sampling resistor R2;

the second switch K is arranged between the second pin ISEN1 and the first pin IN1 and is used for being switched on when the voltage at two ends of the sampling resistor R2 is larger than a first preset value so as to control the first switch Q1 to be switched off; when the voltage at the two ends of the sampling resistor R2 is smaller than a second preset value, the sampling resistor R2 is turned off, and the first switch Q1 is further controlled to be turned on; the second preset value is smaller than the first preset value, and the specific values of the second preset value and the first preset value need to be determined according to the maximum current allowed to pass through the direct-current bus capacitor and the resistance value of the sampling resistor R2. The second switch K is repeatedly turned on and off to control the first switch Q1 to be repeatedly turned on and off, thereby controlling the current flowing into the dc bus capacitor, i.e., controlling the starting current.

IN order to prevent the current from flowing from the second pin ISEN1 to the first pin IN1, the soft-start chip IC further includes: a first unidirectional element D1 connected between the second pin ISEN1 and the first pin IN1 is connected IN series with the second switch K for controlling current flow from the first pin IN1 to the second pin ISEN 1.

In order to avoid the failure of the first switch Q1, which may be caused if the driving voltage of the first switch Q1 is too large, the soft-start chip IC further includes: and the voltage stabilizing unit ZD1 is disposed between the gate and the source of the first switch Q, and is used for stabilizing the voltage between the gate and the source of the first switch Q, i.e. limiting the driving voltage of the first switch Q1.

According to the above, when the current of the dc bus capacitor C2 is greater than the first preset value, the dc bus capacitor C2 is controlled to be turned off, and at this time, the dc bus capacitor C2 loses the power supply, so as to maintain the voltage across the dc bus capacitor C2 when the dc source is turned off from the dc bus capacitor C2, the soft-start chip IC shown in fig. 3 further includes: the sixth pin DC +, the first end of which is connected to the fifth pin DC1-, as shown in fig. 2, the soft start circuit further includes: the first end of the inductor L1 is connected with the negative electrode of the direct current bus capacitor C2, the second end of the inductor L1 is connected with the fifth pin DC1-, and the second end of the sixth pin DC + is connected between the positive electrode terminal of the direct current source and the positive electrode of the direct current bus capacitor C2.

The inductor L1, the fifth pin DC1-, the sixth pin DC + and the direct current bus capacitor C2 form a closed loop, and the closed loop is used for maintaining the voltage across the direct current bus capacitor C2 when the direct current source stops supplying power to the direct current bus capacitor C2.

In order to avoid the current flowing from the sixth pin DC + to the fifth pin DC1 —, as shown in fig. 3, the soft-start chip IC further includes: the anode of the second unidirectional element D2 is connected with the fifth pin DC1-, and the cathode of the second unidirectional element D2 is connected with the sixth pin DC +; for controlling the current flowing from the fifth pin DC 1-to the sixth pin DC +.

Since the first pin IN1 is connected to the filter capacitor C1, after the start-up is completed, the bus capacitor inputs dc power, and the filter capacitor C1 has a dc blocking function, so that the first pin IN1 does not input any voltage signal any more, and IN order to control the first switch Q1 to continue conducting, and further control the load to be conducted with the dc power source, as shown IN fig. 2, the soft start chip IC further includes:

and a seventh pin IN2, connected between the positive terminal of the dc source and the positive electrode of the dc bus capacitor C2, for inputting a voltage signal to control the first switch to be turned on after the start-up is completed.

Since the chip pin cannot input an excessive voltage, IN order to limit the voltage input from the seventh pin IN2, as shown IN fig. 2, the soft start circuit further includes: and the voltage limiting resistor R3 is arranged between a line led out between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor C2 and the seventh pin IN2 and is used for limiting the voltage input by the seventh pin IN 2. In the above chip IC, a reserved pin NC may also be included.

Example 3

This embodiment provides a power supply circuit, and fig. 4 is according to the utility model discloses power supply circuit's structure chart, as shown in fig. 4, this power supply circuit includes filtering protection module 10 and constant current module 30, and LED light source module 40 is connected to constant current module 30, still includes soft start circuit 20 for through soft start circuit 30 control starting current, avoid starting current too big.

Example 4

The present embodiment provides another soft start circuit applied to a power supply circuit, as shown in fig. 1 mentioned above, which includes: a filter protection module 10, the soft start circuit 20, a DC/DC constant current module 30 (and the constant current module 30 in the above embodiments), and an LED light source module 40. The current output by the direct current is input to the filtering protection module 10 through the direct current bus, the soft start circuit 20 controls the built-in switching tube to be switched on and off at high frequency by collecting voltage and current signals, the direct current bus capacitor C2 is charged, and the driving current is output to control the LED light source module to be lightened through the post-stage DC/DC constant current module 30, so that the starting process is completed.

The filtering protection module 10 is composed of a charging resistor R1, a filtering capacitor C1 and a FUSE1, and is used for removing faults when a serious short-circuit fault occurs in a rear-stage circuit, so as to avoid influencing the power supply of a direct-current power supply bus.

The DC/DC constant current module 30 includes a half-bridge resonant circuit formed by a switching tube Q2, a switching tube Q3, an inductor L2, a transformer T1, and a third capacitor C3, and realizes efficient isolation conversion. The output of the rectifier circuit is composed of a diode D3, a diode D4 and a fourth capacitor C4, and the rectifier circuit outputs voltage to the LED light source module 40 through the positive terminal V0 +. The LED light source module 40 includes two parallel LED lamp beads, and may further include a resistor R4 connected in parallel at two ends of the LED lamp beads.

The soft-start circuit includes a soft-start chip IC, as described in fig. 3, the first pin to the seventh pin, the detection unit 201, the second switch K (i.e., the second switch K in the above-mentioned embodiment), a diode D1 (i.e., the first one-way conducting element D1 in the above-mentioned embodiment), a diode D2 (i.e., the second one-way conducting element D2 in the above-mentioned embodiment), a voltage regulator ZD1 (and the voltage regulator unit ZD1 in the above-mentioned embodiment), and a switch Q1 (i.e., the first switch Q1 in the above-mentioned embodiment).

The working principle of the soft start chip IC is as follows:

the first pin IN1 of the soft start chip IC is externally connected with a filter capacitor C1 and a charging resistor R1 for the first time, when the direct current source is turned on, the direct current source charges C1 through the charging resistor R1 to generate a rising edge voltage signal, a switch tube Q1 is controlled to be conducted, a voltage stabilizing tube ZD1 limits the driving voltage value of the switch tube Q1, and the switch tube Q1 is protected; when the driving voltage value Vgs reaches the conduction threshold value of the switching tube Q1, the switching tube Q1 is conducted, at the moment, the direct-current bus capacitor C2, the inductor L1 and the sampling resistor R2 form a loop, the direct-current source charges the direct-current bus capacitor C2, the charging current of the direct-current bus capacitor C2 rises at the moment of electrifying because the capacitor voltage cannot suddenly change, the current peak value can be restrained by utilizing the principle that the current of the inductor L1 cannot suddenly change, the current passes through a fifth pin DC 1-of the soft start chip IC, passes through the switching tube Q1, is output by a fourth pin DC 2-and returns to the cathode of the direct-current source through the current sampling resistor R2.

Voltage signals (U ═ R × I) are generated at two ends of the sampling resistor R2, the second pin ISEN1 and the third pin ISEN2 of the soft-start chip IC collect the voltage signals U at two ends of the sampling resistor R2 and transmit the voltage signals U to the detection module 201, and when the voltage U is higher than the first reference value Von _ ref (i.e., the first preset value in the above embodiment), the second pin ISEN1 and the negative electrode of the dc source are turned on, and the driving voltage Vgs of the switching tube Q1 is pulled low and is turned off. When the switching tube Q1 is turned off, the dc bus C2 continues to flow current through the inductor L1 and the diode D1, and maintains the voltage across the dc bus C2. When the voltage U across the sampling resistor R2 is smaller than the second reference value Voff ref (i.e., the second preset value in the above embodiment), at this time, the detection module 201 controls the second pin ISEN1 to be disconnected from the negative electrode of the dc source, at this time, the dc source charges the C1 through the charging resistor R1, generates a rising edge voltage signal, so that the switching tube driving voltage Vgs rises, and further controls the switching tube Q1, and so on.

The soft start peak current can be changed by calculating and changing the resistance value of the sampling resistor R2 so as to adapt to different product requirements, and the soft start peak current can also be used as an overcurrent protection function of circuit input.

IN the process that the voltage at two ends of the direct current bus capacitor C2 gradually approaches the bus voltage value, the charging current value is gradually reduced each time, when the voltage U at two ends of the sampling resistor R2 is always smaller than the Voff ref value, the detection module 201 controls the second pin ISEN1 to be always kept disconnected from the negative electrode of the direct current source, the voltage of the driving voltage Vgs is kept at a high level through the seventh pin IN2, the switching tube Q1 is controlled to be always connected, and the soft start process is completed.

Fig. 5 is starting current waveform of present starting circuit and according to the utility model discloses the starting current waveform contrast picture of soft starting circuit of embodiment, wherein, fig. 5(a) is the starting current waveform of present starting circuit, and fig. 5(b) is according to the utility model discloses the starting current waveform of soft starting circuit of embodiment, to be the start moment, can know through the contrast, compare with prior art, adopt the utility model discloses a after the soft starting circuit, peak current Imax value lowers a lot, and this maximum current overshoot value can calculate the setting.

After the soft start is completed, the DC bus capacitor C2 capacitor reaches the bus voltage set value, the post-stage DC/DC constant current module is started to drive the load to work, in this embodiment, the load is an LED light source module, and after the soft start is completed, the LED light source module is turned on.

The above-described circuit embodiments are only illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.

Claims (10)

1. A soft start circuit is applied to a power supply circuit, the power supply circuit comprises a filtering protection module and a constant current module, the filtering protection module is connected with a direct current source, the constant current module comprises a direct current bus capacitor, and the soft start circuit is characterized in that,

the soft start circuit is arranged between the negative electrode of the direct current bus capacitor and the negative electrode terminal of the direct current source; after starting, controlling whether the direct current source is conducted with the direct current bus capacitor according to the current input by the direct current bus capacitor in the constant current module;

one end of the soft start circuit is also connected with the filtering protection module and used for controlling the conduction between the direct current source and the direct current bus capacitor according to the voltage output by the filtering protection module at the starting moment.

2. The soft-start circuit of claim 1, wherein the soft-start circuit comprises a soft-start chip, comprising:

the first pin is connected with the positive terminal of the direct current source through a filter capacitor and a charging resistor in the filter protection module and used for inputting a voltage signal at the starting moment so as to control the conduction between the fourth pin and the fifth pin; the fourth pin is connected with a first end of a sampling resistor, and a second end of the sampling resistor is connected with a negative terminal of the direct current source; the fifth pin is connected with the negative electrode of the direct current bus capacitor;

the second pin and the third pin are respectively connected to two ends of the sampling resistor and used for detecting voltages at two ends of the sampling resistor; the voltage at two ends of the sampling resistor is in direct proportion to the current input by the direct current bus capacitor;

and the soft start chip is used for controlling the connection and disconnection between the fourth pin and the fifth pin according to the voltages at two ends of the sampling resistor after starting, so as to control whether the direct current source is connected with the direct current bus capacitor.

3. The soft-start circuit of claim 2, wherein the soft-start chip further comprises:

the first switch is arranged between the fourth pin and the fifth pin, and the control end of the first switch is connected with the first pin; the on-off of the fourth pin and the fifth pin is controlled through the on-off of the fourth pin and the fifth pin;

the detection unit is arranged between the second pin and the third pin and used for detecting the voltage at two ends of the sampling resistor;

the second switch is arranged between the second pin and the first pin and is used for being switched on when the voltage at two ends of the sampling resistor is greater than a first preset value so as to control the first switch to be switched off; when the voltage at the two ends of the sampling resistor is smaller than a second preset value, the sampling resistor is turned off, and the first switch is further controlled to be turned on; wherein the second preset value is smaller than the first preset value.

4. The soft-start circuit of claim 3, wherein the soft-start chip further comprises:

and the first unidirectional element is connected between the second pin and the first pin, is connected with the second switch in series and is used for controlling the current to flow from the first pin to the second pin.

5. The soft-start circuit of claim 3, wherein the soft-start chip further comprises:

and the voltage stabilizing unit is arranged between the grid electrode and the source electrode of the first switch and is used for stabilizing the voltage between the grid electrode and the source electrode of the first switch.

6. The soft-start circuit of claim 2, further comprising: a first end of the inductor is connected with the negative electrode of the direct current bus capacitor, and a second end of the inductor is connected with the fifth pin;

the soft start chip further comprises: a sixth pin, a first end of which is connected with the fifth pin, and a second end of which is connected between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor;

the inductor, the fifth pin, the sixth pin and the direct current bus capacitor form a closed loop, and the closed loop is used for maintaining the voltage at two ends of the direct current bus capacitor when the direct current source stops supplying power to the direct current bus capacitor.

7. The soft-start circuit of claim 6, wherein the soft-start chip further comprises:

a second unidirectional element, the anode of which is connected with the fifth pin, and the cathode of which is connected with the sixth pin; for controlling current flow from the fifth pin to the sixth pin.

8. The soft-start circuit of claim 2, wherein the soft-start chip further comprises:

and the seventh pin is connected between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor and used for inputting a voltage signal so as to control the first switch to maintain a conducting state after the start is completed.

9. The soft-start circuit of claim 8, further comprising:

and the voltage limiting resistor is arranged between a line led out between the positive terminal of the direct current source and the positive electrode of the direct current bus capacitor and the seventh pin and is used for limiting the voltage input by the seventh pin.

10. A power supply circuit comprising a filter protection module and a constant current module, further comprising the soft start circuit of any one of claims 1 to 9.

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