Slow start circuit

Abstract

The utility model relates to a slow start circuit used for supplying power to a capacitive load, and the slow start circuit comprises a switch unit which is used for connecting a power supply to the slow start circuit when the switch unit is closed; the voltage dividing unit is used for dividing power supply voltage provided by the power supply; the delay unit is used for outputting a first voltage to the second end of the selection unit when the power supply is connected to the slow start circuit, and the first voltage is a voltage slowly rising from zero to a first preset voltage; the driving unit is used for providing a second voltage for the selection unit; the selection unit is used for selectively connecting the current limiting unit to the slow start circuit or the short circuit current limiting unit according to the first voltage and the second voltage; the first end of the current limiting unit is connected with the power ground, and the second end is connected with the load ground. In the embodiment of the utility model, the slow start circuit supplies power to the capacitive load through the current limiting unit at the moment of being connected with the power supply, so that the capacitive load can be supplied with power at low current and low voltage, and the capacitive load is prevented from being damaged.

Description

Technical Field

[0001] The utility model relates to the field of circuits, and particularly relates to a soft-start circuit. Background Art

[0002] A capacitive load generally refers to a load with capacitance parameters. Usually, a capacitive load can be considered as a combination of a capacitor and a load.

[0003] Because a capacitor is easily broken down under high voltage and / or high current, a capacitive load is also likely to be damaged under high voltage and / or high current conditions. In a general circuit, power is supplied by an external power source. At the moment when the power source is turned on, high voltage and / or high current are extremely likely to be generated in the circuit. If there is a capacitive load in this circuit, at the moment when the power source is turned on, the instantaneous large current in the circuit and / or the rapid rise of the voltage on the capacitive load are likely to cause damage to the capacitive load.

[0004] In the prior art, there is no way to solve the problem that the capacitive load in the circuit is easily damaged. Summary of the Utility Model

[0005] In order to solve the above technical problems or at least partially solve the above technical problems, the utility model provides a soft-start circuit.

[0006] In a first aspect, a soft-start circuit is provided. The soft-start circuit is used to supply power to a capacitive load. The second end of the capacitive load is connected to the load ground. The soft-start circuit includes:

[0007] A switch unit, the first end of which is connected to a power source, and the second end of which is connected to the first end of the capacitive load, and is used to connect the power source to the soft-start circuit when it is closed;

[0008] A voltage-dividing unit, the first end of which is connected to the second end of the switch unit, and the third end of which is connected to the power source ground, and is used to divide the power voltage provided by the power source;

[0009] A delay unit, the first end of which is connected to the second end of the voltage-dividing unit, the second end of which is connected to the power source ground, and the third end of which is connected to the second end of the selection unit, and is used to output a first voltage to the second end of the selection unit when the power source is connected to the soft-start circuit. The first voltage is a voltage that slowly rises from zero to a first preset voltage;

[0010] A driving unit, the first end of which is connected to the second end of the switch unit, the second end of which is connected to the power source ground, and the third end of which is connected to the first end of the selection unit, and is used to provide a second voltage to the selection unit;

[0011] The selection unit has its third terminal connected to the first terminal of the current-limiting unit, its fourth terminal connected to the second terminal of the current-limiting unit, and its fifth terminal connected to the power ground, and is configured to selectively connect the current-limiting unit to the soft-start circuit or short-circuit the current-limiting unit according to the first voltage and the second voltage;

[0012] The current-limiting unit has its first terminal connected to the power ground and its second terminal connected to the load ground.

[0013] Optionally, the soft-start circuit includes an instantaneous power supply state, and the instantaneous power supply state is as follows:

[0014] From the switch unit being turned on to being turned off, the voltage applied to the soft-start circuit rises from zero to the power supply voltage. The selection unit connects the current-limiting unit to the soft-start circuit, and the power supply, the switch unit, the capacitive load, and the current-limiting unit form a first current loop to supply power to the capacitive load.

[0015] Optionally, the soft-start circuit further includes a delayed power supply state, and the delayed power supply state is as follows:

[0016] The power supply supplies power to the delay unit through the voltage-dividing unit, and the power supply also supplies power to the driving unit. The voltage output from the third terminal of the delay unit rises slowly from zero to the first preset voltage, and the driving unit outputs the second voltage.

[0017] Optionally, the soft-start circuit further includes a stable power supply state, and the stable power supply state is as follows:

[0018] The first terminal of the selection unit is connected to the second voltage, and the voltage connected to the second terminal is equal to the first preset voltage. The selection unit shorts the current-limiting unit,

[0019] The power supply forms a second current loop through the switch unit, the capacitive load, and the selection unit to supply power to the capacitive load.

[0020] Optionally, the voltage-dividing unit includes:

[0021] A third resistor, with its first terminal connected to the second terminal of the switch unit and its second terminal connected to the first terminal of the delay unit;

[0022] A fourth resistor, with its first terminal connected to the second terminal of the third resistor and its second terminal connected to the power ground.

[0023] Optionally, the delay unit includes:

[0024] A fifth resistor, with its first terminal connected to the second terminal of the third resistor;

[0025] The first capacitor, with its first terminal connected to the second terminal of the fifth resistor and its second terminal connected to the power ground.

[0026] Optionally, the driving unit includes:

[0027] The first resistor, with its first terminal connected to the first terminal of the voltage dividing unit;

[0028] The second resistor, with its first terminal connected to the second terminal of the first resistor;

[0029] The voltage stabilizing diode, with its positive electrode connected to the power ground;

[0030] The first triode, with its collector connected to the second terminal of the first resistor, its base connected to the negative electrode of the voltage stabilizing diode, and its emitter connected to the first terminal of the selection unit;

[0031] The second capacitor, with its first terminal connected to the emitter of the first triode and its second terminal connected to the positive electrode of the voltage stabilizing diode.

[0032] Optionally, the selection unit includes:

[0033] The sixth resistor, with its first terminal connected to the third terminal of the driving unit,

[0034] The second triode, with its emitter connected to the first terminal of the sixth resistor and its base connected to the second terminal of the sixth resistor;

[0035] The seventh resistor, with its first terminal connected to the base of the second triode;

[0036] The fourth triode, with its base connected to the third terminal of the delay unit, its collector connected to the second terminal of the seventh resistor, and its emitter connected to the power ground;

[0037] The eighth resistor, with its first terminal connected to the collector of the second triode;

[0038] The ninth resistor, with its first terminal connected to the second terminal of the eighth resistor;

[0039] The third MOS transistor, with its gate connected to the second terminal of the eighth resistor, its source connected to the second terminal of the ninth resistor, and its drain connected to the load ground.

[0040] Optionally, the current limiting unit includes:

[0041] The tenth resistor, with its first terminal connected to the power ground and its second terminal connected to the load ground.

[0042] Optionally, the first triode is an NPN triode, the second triode is a PNP triode, the third MOS transistor is an N-channel MOS transistor, and the fourth triode is an NPN triode.

[0043] In the embodiment of the present utility model, the soft-start circuit is used to supply power to a capacitive load. The second end of the capacitive load is connected to the load ground. The soft-start circuit includes: a switch unit, the first end of which is connected to a power supply, and the second end of which is connected to the first end of the capacitive load, and is used to connect the power supply to the soft-start circuit when it is closed; a voltage-dividing unit, the first end of which is connected to the second end of the switch unit, and the third end of which is connected to the power supply ground, and is used to divide the power supply voltage provided by the power supply; a delay unit, the first end of which is connected to the second end of the voltage-dividing unit, the second end of which is connected to the power supply ground, and the third end of which is connected to the second end of the selection unit, and is used to output a first voltage to the second end of the selection unit when the power supply is connected to the soft-start circuit, and the first voltage is a voltage that slowly rises from zero to a first preset voltage; a driving unit, the first end of which is connected to the second end of the switch unit, the second end of which is connected to the power supply ground, and the third end of which is connected to the first end of the selection unit, and is used to provide a second voltage to the selection unit; the selection unit, the third end of which is connected to the first end of the current-limiting unit, the fourth end of which is connected to the second end of the current-limiting unit, and the fifth end of which is connected to the power supply ground, and is used to selectively connect the current-limiting unit to the soft-start circuit or short-circuit the current-limiting unit according to the first voltage and the second voltage; the current-limiting unit, the first end of which is connected to the power supply ground, and the second end of which is connected to the load ground. When the soft-start circuit is connected to the power supply instantaneously, it supplies power to the capacitive load through the current-limiting unit, and can supply power to the capacitive load with a small current and a low voltage, avoiding damage to the capacitive load. After a period of time after the power supply 110 is connected, the voltage provided by the soft-start circuit to the capacitive load 180 slowly rises until it reaches a large voltage / large current, so that the capacitive load can work normally. Description of the Drawings

[0044] The drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present utility model, and are used together with the specification to explain the principles of the present utility model.

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0046] Figure 1 The structural block diagram of the soft-start circuit according to the embodiment of the present utility model is shown;

[0047] Figure 2 The circuit schematic diagram of the soft-start circuit according to the embodiment of the present utility model is shown. Detailed Embodiments

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0049] Figure 1 The following shows a structural block diagram of the soft-start circuit according to an embodiment of the present utility model. Figure 2 The following shows a circuit schematic diagram of the soft-start circuit according to an embodiment of the present utility model.

[0050] Reference Figure 1 、 Figure 2 As shown in

[0051] a soft-start circuit is provided according to an embodiment of the present utility model. The soft-start circuit is used to supply power to a capacitive load 180. The second end of the capacitive load 180 is connected to a load ground GND2. The soft-start circuit includes:

[0052] a switch unit 120, with its first end connected to a power supply 110 and its second end connected to the first end of the capacitive load 180, for connecting the power supply 110 to the soft-start circuit when it is closed;

[0053] a voltage-dividing unit 130, with its first end connected to the second end of the switch unit 120 and its third end connected to a power supply ground GND1, for dividing the power supply voltage provided by the power supply 110;

[0054] a delay unit 140, with its first end connected to the second end of the voltage-dividing unit 130, its second end connected to the power supply ground GND1, and its third end connected to the second end of a selection unit 160, for outputting a first voltage to the second end of the selection unit 160 when the power supply 110 is connected to the soft-start circuit. The first voltage is a voltage that slowly rises from zero to a first preset voltage;

[0055] a driving unit 150, with its first end connected to the second end of the switch unit 120, its second end connected to the power supply ground GND1, and its third end connected to the first end of the selection unit 160, for providing a second voltage to the selection unit 160;

[0056] the selection unit 160, with its third end connected to the first end of a current-limiting unit 170, its fourth end connected to the second end of the current-limiting unit 170, and its fifth end connected to the power supply ground GND1, for selectively connecting the current-limiting unit 170 to the soft-start circuit or short-circuiting the current-limiting unit 170 according to the first voltage and the second voltage;

[0056] The current limiting unit 170 has its first end connected to the power ground GND1 and its second end connected to the load ground GND2.

[0057] In an embodiment of the present invention, when the soft start circuit is connected to the power supply 110 instantaneously, it supplies power to the capacitive load 180 through the current limiting unit 170, and can supply power to the capacitive load 180 with a small current and a low voltage, avoiding damage to the capacitive load 180. After a period of time after the power supply 110 is connected, the voltage provided by the soft start circuit to the capacitive load 180 rises slowly until it reaches a large voltage / large current, enabling the capacitive load 180 to work normally.

[0058] In an embodiment of the present invention, the soft start circuit includes three states, namely, an instantaneous power supply state, a delayed power supply state, and a stable power supply state.

[0059] In an embodiment of the present invention, the working state refers to different states when the power supply 110 supplies power to the capacitive load 180 through the soft start circuit, that is, the state after the power supply 110 is connected to the soft start circuit.

[0060] In an embodiment of the present invention, when the switch unit 120 is closed and the power supply 110 is connected to the soft start circuit, it will successively go through the instantaneous power supply state, the delayed power supply state, and the stable working state.

[0061] In an embodiment of the present invention, the soft start circuit includes an instantaneous power supply state, and the instantaneous power supply state is as follows:

[0062] When the switch unit 120 is turned from on to off, the voltage connected to the soft start circuit rises from zero to the power supply voltage, the selection unit 160 connects the current limiting unit 170 to the soft start circuit, and the power supply 110, the switch unit 120, the capacitive load 180, and the current limiting unit 170 form a first current loop to supply power to the capacitive load 180.

[0063] In an embodiment of the present invention, the soft start circuit further includes a delayed power supply state, and the delayed power supply state is as follows:

[0064] The power supply 110 supplies power to the delay unit 140 through the voltage dividing unit 130, the power supply 110 also supplies power to the driving unit, the voltage output from the third end of the delay unit 140 rises slowly from zero to the first preset voltage, and the driving unit 150 outputs the second voltage.

[0065] In an embodiment of the present invention, the soft start circuit further includes a stable power supply state, and the stable power supply state is as follows:

[0066] The first end of the selection unit 160 is connected to the second voltage, and when the voltage at the second end reaches the first preset voltage, the selection unit 160 shorts the current limiting unit 170.

[0067] The power supply 110 forms a second current loop through the switch unit 120, the capacitive load 180, and the selection unit 160 to supply power to the capacitive load 180.

[0068] In the embodiment of the present invention, the instantaneous power supply state is the moment when the switch unit 120 closes to connect the power supply 110 to the soft start circuit. At this time, the power supply 110, the switch unit 120, the capacitive load 180, and the current limiting unit 170 form a first current loop, and the current provided to the capacitive load 180 is a smaller current / lower voltage, thereby avoiding damage to the capacitive load 180 caused by instantaneous large current / high voltage.

[0069] After the power supply 110 is connected to the soft start circuit, it changes from the instantaneous power supply state to the delayed power supply state. At this time, the voltage output by the delay unit 140 slowly rises from zero to the first preset voltage, and the drive unit 150 outputs the second voltage. At this time, the current / voltage provided to the capacitive load 180 still passes through the current limiting unit 170.

[0070] When the voltage output by the delay unit 140 reaches the first preset voltage, the soft start circuit enters the stable power supply state, and the current limiting unit 170 is shorted. At this time, the power supply 110, the switch unit 120, the capacitive load 180, and the selection unit 160 form a second current loop. Since the resistance of the selection unit 160 can be very small, the current provided to the capacitive load 180 at this time is a larger current / voltage, so that the capacitive load 180 can work normally under large current / voltage.

[0071] Figure 2 The following shows the circuit diagram of the soft start circuit according to the embodiment of the present invention, as Figure 2 shown, in the embodiment of the present invention, the voltage dividing unit 130 includes:

[0072] A third resistor R3, the first end is connected to the second end of the switch unit 120, and the second end is connected to the first end of the delay unit 140;

[0073] A fourth resistor R4, the first end is connected to the second end of the third resistor R3, and the second end is connected to the power supply ground GND1.

[0074] In the embodiment of the present invention, the delay unit 140 includes:

[0075] A fifth resistor R5, the first end is connected to the second end of the third resistor R3;

[0076] The first capacitor C1 has its first terminal connected to the second terminal of the fifth resistor R5 and its second terminal connected to the power ground GND1.

[0077] In an embodiment of the present invention, the driving unit 150 includes:

[0078] The first resistor R1 has its first terminal connected to the first terminal of the voltage dividing unit 130;

[0079] The second resistor R2 has its first terminal connected to the second terminal of the first resistor R1;

[0080] The voltage stabilizing diode ZD has its positive electrode connected to the power ground GND1;

[0081] The first triode Q1 has its collector C connected to the second terminal of the first resistor R1, its base B connected to the negative electrode of the voltage stabilizing diode ZD, and its emitter E connected to the first terminal of the selection unit 160;

[0082] The second capacitor C2 has its first terminal connected to the emitter E of the first triode Q1 and its second terminal connected to the positive electrode of the voltage stabilizing diode ZD.

[0083] In an embodiment of the present invention, the selection unit 160 includes:

[0084] The sixth resistor R6 has its first terminal connected to the third terminal of the driving unit 150,

[0085] The second triode Q2 has its emitter E connected to the first terminal of the sixth resistor R6 and its base B connected to the second terminal of the sixth resistor R6;

[0086] The seventh resistor R7 has its first terminal connected to the base B of the second triode Q2;

[0087] The fourth triode Q4 has its base B connected to the third terminal of the delay unit 140, its collector C connected to the second terminal of the seventh resistor R7, and its emitter E connected to the power ground GND1;

[0088] The eighth resistor R8 has its first terminal connected to the collector C of the second triode Q2;

[0089] The ninth resistor R9 has its first terminal connected to the second terminal of the eighth resistor R8;

[0090] The third MOS transistor Q3 has its gate G connected to the second terminal of the eighth resistor R8, its source S connected to the second terminal of the ninth resistor R9, and its drain D connected to the load ground GND2.

[0091] In an embodiment of the present invention, the current limiting unit 170 includes:

[0092] The tenth resistor R10 has its first end connected to the power supply ground GND1 and its second end connected to the load ground GND2.

[0093] In the embodiment of the present utility model, the first triode Q1 is an NPN triode, the second triode Q2 is a PNP triode, the third MOS transistor Q3 is an N-channel MOS transistor, and the fourth triode Q4 is an NPN triode.

[0094] In the embodiment of the present utility model, the switch unit 120 includes a switch S1. At the moment when the switch S1 is closed, neither the driving unit 150 nor the delay unit 140 outputs voltage. The power supply 110, the switch S1, the capacitive load 180, the tenth resistor R10, and the power supply ground GND1 form a first current loop, and the power supply 110 directly supplies power to the capacitive load 180. Since the internal resistance of the capacitive load 180 is relatively low, or the resistance value of the tenth resistor R10 is set to be relatively large at the same time, the current flowing through the capacitive load 180 can be a small current or a micro current, avoiding damage to the capacitive load 180. This state can be called the instantaneous power supply state.

[0095] After the switch S1 is closed, the soft-start circuit enters the delayed power supply state.

[0096] In the delayed power supply state, the power supply 110 supplies power to the driving unit 150 and the voltage dividing unit 130.

[0097] When the power supply 110 supplies power to the voltage dividing unit 130, at this time, after the power supply voltage is divided by the third resistor R3 and the fourth resistor R4, the voltage output at the second end of the third resistor R3 charges the first capacitor C1 through the fifth resistor R5. The first capacitor C1 causes the voltage provided to the base B of the fourth triode Q4 to slowly rise from zero to a first preset voltage.

[0098] The first preset voltage is equal to the turn-on voltage of the fourth triode Q4. In the delayed power supply state, the voltage input to the base B of the fourth triode Q4 has not reached the turn-on voltage, so the fourth triode Q4 is not turned on.

[0099] In the delayed power supply state, the power supply 110 supplies power to the driving unit 150. At this time, after the power supply voltage is divided by the first resistor R1 and the second resistor R2 and passes through the voltage stabilizing diode ZD, the voltage applied to the base B of the first triode Q1 is the second voltage. The power supply voltage is greater than the second voltage, so the first triode Q1 is turned on. The voltage output from the emitter E of the first triode Q1 will be slightly less than the second voltage, but through the filtering and reverse charging of the second capacitor C2, etc., the voltage output at the first end of the second capacitor C2 is the second voltage, and the second voltage is provided to the first end of the selection unit 160, that is, the second voltage is provided to the emitter E of the second triode Q2.

[0100] In the delayed power supply state, the voltage at the base B of the fourth triode Q4 does not reach the turn-on voltage of the fourth triode Q4, so the fourth triode Q4 is not turned on. The voltage at the base B of the second triode Q2 is a high voltage. At this time, the voltage on the emitter E of the second diode is the second voltage, which is also a high voltage, and the second triode Q2 is not turned on. The non-conduction of the second triode Q2 makes the gate G of the third MOS transistor Q3 a low voltage, and the third MOS transistor Q3 is not turned on.

[0101] In one embodiment of the present invention, the first preset voltage can be the turn-on voltage of 0.6V at the base B of the fourth triode Q4, and the second voltage can be 12V.

[0102] After the voltage at the base B of the fourth triode Q4 rises to the first preset voltage, the soft-start circuit enters the stable power supply state.

[0103] In the stable power supply state, when the voltage at the base B of the fourth triode Q4 is the first preset voltage, reaching the turn-on voltage of the fourth triode Q4, the collector C of the fourth triode Q4 is a high voltage, so the fourth triode Q4 is turned on. After the fourth triode Q4 is turned on, the collector C of the fourth triode Q4 is a low voltage, that is, the base B of the second triode Q2 is a low voltage. At this time, the emitter E of the second triode Q2 is still a high voltage, and the second triode Q2 is turned on. After the second triode Q2 is turned on, the second voltage passes through the eighth resistor R8 and the ninth resistor R9, making the gate G of the third MOS transistor Q3 a high voltage, and the third MOS transistor Q3 is turned on. After the third MOS transistor Q3 is turned on, the tenth resistor R10 connected between the drain D and the source S of the third MOS transistor Q3 is short-circuited. At this time, the second end of the capacitive load 180 is directly connected to the power supply ground GND1 through the drain D and the source S of the third MOS transistor Q3.

[0104] After the third MOS transistor Q3 is turned on, the power supply 110, the switch S1, the capacitive load 180, the drain D and the source S of the third MOS transistor Q3 in the selection unit 160, and the power supply ground GND1 form a second current loop, and the power supply 110 supplies power to the capacitive load 180. The resistance of the third MOS transistor Q3 itself is very small, which is equivalent to only the equivalent resistance of the capacitive load 180 in the second current loop, and the current in the second current loop is a large current.

[0105] In the embodiment of the present invention, when the soft-start circuit is connected to the power supply 110, it supplies power to the capacitive load 180 through the current limiting unit 170, and can supply power with a small current and a low voltage to avoid damage to the capacitive load 180. After a period of time after the power supply 110 is connected, the voltage provided by the soft-start circuit to the capacitive load 180 rises slowly until a large voltage / large current, so that the capacitive load 180 can work normally.

[0106] It should be noted that in this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0107] The above are only specific embodiments of the present utility model, enabling those skilled in the art to understand or implement the present utility model. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to these embodiments shown herein, but rather will conform to the widest scope consistent with the principles and novel features of the present utility model disclosed herein.

Claims

1. A slow-start circuit, characterized in that: The slow-start circuit is used to supply power to a capacitive load, a second terminal of the capacitive load is connected to a load ground, and the slow-start circuit comprises: A switch unit, a first end of which is connected to a power source, and a second end of which is connected to a first end of the capacitive load, for connecting the power source to the slow-start circuit when turned off; A voltage dividing unit, a first end of which is connected to the second end of the switch unit and a third end of which is connected to a power ground, and is used to divide the power voltage provided by the power supply; A delay unit, a first end of which is connected to the second end of the voltage dividing unit, a second end of which is connected to the power ground, and a third end of which is connected to the second end of the selection unit, and is used to output a first voltage to the second end of the selection unit when the power supply is connected to the slow-start circuit, wherein the first voltage is a voltage that slowly rises from zero to a first preset voltage; a driving unit, a first end of which is connected to the second end of the switch unit, a second end of which is connected to the power ground, and a third end of which is connected to the first end of the selection unit, and is used to provide a second voltage to the selection unit; The selection unit has a third end connected to the first end of the current limiting unit, a fourth end connected to the second end of the current limiting unit, and a fifth end connected to the power ground, and is used to selectively connect the current limiting unit to the slow-start circuit or short-circuit the current limiting unit according to the first voltage and the second voltage; The current limiting unit has a first terminal connected to the power ground and a second terminal connected to the load ground.

2. The slow-start circuit according to claim 1, characterized in that: The slow-start circuit includes an instantaneous power supply state, and the instantaneous power supply state is: The switch unit is turned from on to off, the voltage connected to the slow-start circuit rises from zero to the power supply voltage, the selection unit connects the current limiting unit to the slow-start circuit, and the power supply, the switch unit, the capacitive load and the current limiting unit form a first current loop to supply power to the capacitive load.

3. The slow-start circuit according to claim 2, characterized in that: The slow-start circuit also includes a delayed power supply state, and the delayed power supply state is: The power supply supplies power to the delay unit through the voltage divider unit, and the power supply also supplies power to the drive unit. The voltage output from the third end of the delay unit slowly rises from zero to the first preset voltage, and the drive unit outputs the second voltage.

4. The slow-start circuit according to claim 3, characterized in that: The slow-start circuit also includes a stable power supply state, which is: The first terminal of the selection unit is connected to the second voltage, the voltage connected to the second terminal is equal to the first preset voltage, and the selection unit short-circuits the current limiting unit. The power supply forms a second current loop through the switch unit, the capacitive load, and the selection unit to supply power to the capacitive load.

5. The slow-start circuit according to claim 1, characterized in that: The voltage dividing unit comprises: a third resistor, a first end of which is connected to the second end of the switch unit, and a second end of which is connected to the first end of the delay unit; A fourth resistor has a first end connected to the second end of the third resistor and a second end connected to the power ground.

6. The slow-start circuit according to claim 5, characterized in that: The delay unit comprises: a fifth resistor, a first end of which is connected to the second end of the third resistor; The first capacitor has a first end connected to the second end of the fifth resistor and a second end connected to the power ground.

7. The slow-start circuit according to claim 6, characterized in that: The driving unit comprises: A first resistor, a first end of which is connected to a first end of the voltage dividing unit; a second resistor, a first end of which is connected to the second end of the first resistor; A voltage regulator tube, the positive electrode of which is connected to the power ground; A first triode, a collector connected to the second end of the first resistor, a base connected to the negative electrode of the voltage regulator tube, and an emitter connected to the first end of the selection unit; A second capacitor has a first end connected to the emitter of the first transistor, and a second end connected to the positive electrode of the voltage regulator.

8. The slow-start circuit according to claim 7, characterized in that: The selection unit comprises: a sixth resistor, a first end of which is connected to the third end of the driving unit, A second triode, an emitter connected to the first end of the sixth resistor, and a base connected to the second end of the sixth resistor; a seventh resistor, a first end of which is connected to the base of the second transistor; a fourth transistor, having a base connected to the third end of the delay unit, a collector connected to the second end of the seventh resistor, and an emitter connected to the power ground; an eighth resistor, a first end of which is connected to the collector of the second triode; a ninth resistor, a first end of which is connected to the second end of the eighth resistor; The third MOS tube has a gate connected to the second end of the eighth resistor, a source connected to the second end of the ninth resistor, and a drain connected to the load ground.

9. The slow-start circuit according to claim 8, characterized in that: The current limiting unit comprises: A tenth resistor has a first end connected to the power ground, and a second end connected to the load ground.

10. The slow-start circuit according to claim 9, characterized in that: The first transistor is an NPN transistor, the second transistor is a PNP transistor, the third MOS transistor is an N-channel MOS transistor, and the fourth transistor is an NPN transistor.

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