Soft start circuit, control circuit and control chip

Abstract

The utility model relates to a soft start circuit, a control circuit and a control chip. The soft start circuit comprises a current mirror circuit, a soft start capacitor and a voltage output circuit. The current mirror circuit is connected with the first current source, and outputs charging current after mirroring the starting current output by the first current source under the action of an externally input starting signal; the soft start capacitor outputs a target voltage after charging for a target time according to the charging current; the voltage output circuit outputs the starting voltage under the action of the target voltage, the starting signal and the external power supply voltage. According to the soft start circuit, the starting current output by the first current source is mirrored through the current mirror circuit, so that the time for charging the soft start capacitor to the target voltage is the target time, and the charging time is prolonged compared with that of directly charging the soft start capacitor to the target voltage; that is to say, the soft start circuit can obtain larger equivalent capacitance, the overall area of the control circuit is saved, and the cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of analog chips, and in particular to a soft start circuit, a control circuit and a control chip. Background Art

[0002] In various analog chips, in order to prevent the surge current generated by the instantaneous voltage rise during the startup process from damaging the chip, or for other circuit functions, it is necessary to make a certain voltage rise slowly and at a certain slope. The soft start circuit is a circuit that realizes this function. The currently widely used soft start circuits can be roughly divided into two categories: one is a structure controlled by digital signals. For example, a trigger can be used to generate a digital signal with several bits and a step-up shape to control the on and off of a series of current mirrors, and then the output voltage is controlled by controlling the current, so that the voltage rises in a step-like manner within a certain period of time; the other is a structure controlled by analog signals with capacitor charging and discharging as the core. For example, a small current can be used to charge a large capacitor to obtain a slowly rising voltage. According to the formula Q=I·t=C·U, a 10nA current is used to charge a 10pF capacitor, and the time taken for the voltage across the capacitor to rise to 5V is 5ms, so a voltage that rises at a slope within a certain period of time can be obtained.

[0003] At present, the structure controlled by digital signals is essentially to make the voltage change multiple times within a certain period of time, so a large number of triggers and current mirrors are needed to minimize the step size of each voltage change and achieve a slow change of voltage. This will mainly lead to two problems: first, the circuit structure is more complicated, and the power consumption of current-to-voltage conversion is also larger; second, too many current mirrors cause large offsets, resulting in poor output voltage accuracy. The soft-start circuit with capacitor charging and discharging as the core often needs to use larger capacitors to slow down the speed of voltage rise, which occupies a larger area and requires higher costs. Utility Model Content

[0004] Based on this, it is necessary to provide a soft start circuit, a control circuit and a control chip to address the above technical problems.

[0005] In a first aspect, the present application provides a soft start circuit, comprising:

[0006] a current mirror circuit, connected to a first current source, and under the action of an externally inputted start-up signal, mirroring a start-up current outputted by the first current source to output a charging current;

[0007] a soft start capacitor connected to the current mirror circuit and configured to output a target voltage after charging for a target time according to the charging current;

[0008] The voltage output circuit is connected to the soft start capacitor and is used to output a start voltage under the action of the target voltage, the start signal and the external power supply voltage.

[0009] The above-mentioned soft start circuit mirrors the starting current output by the first current source through a current mirror circuit so that the time for the soft start capacitor to charge to the target voltage is the target time. Compared with directly charging the soft start capacitor to the target voltage, the charging time is extended. That is, the soft start circuit of the present application can obtain a larger equivalent capacitance, saving the overall area of ​​the control circuit and reducing the cost.

[0010] In one embodiment, the voltage output circuit includes:

[0011] A first MOSFET tube, wherein the gate of the first MOSFET tube is used to receive the start signal input from the outside, and the source of the first MOSFET tube is used to connect to the equivalent ground terminal;

[0012] A second MOSFET tube, the gate of the second MOSFET tube is connected to the current mirror circuit and the soft start capacitor, the source of the second MOSFET tube is connected to the drain of the first MOSFET tube, the drain of the second MOSFET tube is used to access the external power supply voltage, and the second MOSFET tube is used to output the starting voltage under the action of the external power supply voltage and the target voltage when the drain of the first MOSFET tube is turned on by the equivalent ground terminal.

[0013] In one embodiment, the voltage output circuit further includes:

[0014] A first trigger unit, wherein an input terminal of the first trigger unit is connected to a source of the first MOSFET tube, and the first trigger unit is configured with a trigger voltage, and is used to output a trigger signal when a difference between the start voltage and the trigger voltage is a preset value;

[0015] A switch unit, wherein the controlled end of the switch unit is connected to the output end of the first trigger unit, the first end of the switch unit is connected to the source of the second MOSFET tube, the second end of the switch unit is used to connect to the equivalent ground end, and the third end of the switch unit is used to access the external power supply voltage. The switch unit is used to disconnect the connection between the source of the second MOSFET tube and the equivalent ground end, and to connect the connection between the source of the second MOSFET tube and the external power supply voltage when receiving the trigger signal, and output the external power supply voltage as the starting voltage.

[0016] In one embodiment, the current mirror circuit comprises:

[0017] A starting unit, wherein the first end of the starting unit is used to connect to the equivalent ground end, the controlled end of the starting unit is used to access the starting signal, and the starting unit is used to conduct the connection between the third end of the starting unit and the equivalent ground end under the action of the starting signal, so as to output the signal accessed by the equivalent ground end as a control signal;

[0018] a first current mirror unit, the first current mirror unit being connected to the soft start capacitor and the start unit, and being used to connect to the first current source and output the first current under the action of the control signal and the start current;

[0019] a second current mirror unit, connected to the first current mirror unit and the soft-start capacitor, and configured to output the second current under the action of the control signal, the start-up current and the first current, wherein the second current is used as the charging current to charge the soft-start capacitor;

[0020] The sum of the first current and the second current is equal to the starting current.

[0021] In one embodiment, the first current mirror unit includes a third MOSFET tube; the second current mirror unit includes a fourth MOSFET tube; the ratio of the width to length ratio of the first current mirror unit to the second current mirror unit is the ratio of the width to length ratio of the third MOSFET tube to the fourth MOSFET tube x:1, where x is greater than 1; or,

[0022] The first current mirror unit includes multiple MOSFET tubes connected in series or in parallel, and the width-to-length ratio of the first current mirror unit is the first total width-to-length ratio of the multiple MOSFET tubes connected in series or in parallel in the first current mirror unit; the second current mirror unit includes one or more MOSFET tubes connected in series or in parallel, and the width-to-length ratio of the second current mirror unit is the second total width-to-length ratio of the multiple MOSFET tubes connected in series or in parallel in the second current mirror unit; the ratio of the width-to-length ratios of the first current mirror unit and the second current mirror unit is the ratio of the first total width-to-length ratio to the second total width-to-length ratio x:1, where x is greater than 1.

[0023] In one embodiment, the startup unit comprises:

[0024] a fifth MOSFET tube, wherein the gate of the fifth MOSFET tube is used to access the start signal, the drain of the fifth MOSFET tube is connected to the first current mirror unit and the second current mirror unit, and the source of the fifth MOSFET tube is used to connect to the equivalent ground terminal;

[0025] A sixth MOSFET tube, wherein the gate of the sixth MOSFET tube is used to access the start signal, the drain of the sixth MOSFET tube is connected to the first current mirror, and the source of the sixth MOSFET tube is used to connect to the equivalent ground terminal.

[0026] In a second aspect, the present application further provides a control circuit, comprising:

[0027] Such as the soft start circuit mentioned above;

[0028] A first current source, connected to the soft start circuit, for outputting a start current;

[0029] The second trigger unit is connected to the soft start circuit and is used to output a start signal.

[0030] The above-mentioned control circuit uses the current mirror circuit in the soft-start circuit to mirror the starting current output by the first current source so that the time for the soft-start capacitor to charge to the target voltage is the target time. Compared with directly charging the soft-start capacitor to the target voltage, the charging time is extended. That is, the soft-start circuit of the present application can obtain a larger equivalent capacitance and avoid the use of a large capacitor, thereby saving the overall area of ​​the circuit and reducing costs.

[0031] In one embodiment, the second trigger unit is further configured to output a first enable signal and a second enable signal; and the control circuit further comprises:

[0032] a control unit connected to the second trigger unit and the first current source, configured to pull down the soft start capacitor in the soft start circuit to make the target voltage at a low level when receiving the first enable signal, and control the first current mirror in the soft start circuit to output the start current when receiving the second enable signal;

[0033] The second trigger unit outputs the first enable signal earlier than the second enable signal.

[0034] In one embodiment, it also includes:

[0035] A power supply is connected to the voltage output circuit and is used to output an external power supply voltage.

[0036] In a third aspect, the present application also provides a control chip, including the soft start circuit as described above or the control circuit as described above.

[0037] The above-mentioned control chip mirrors the starting current output by the first current source through the current mirror circuit in the soft start circuit or the control circuit so that the time for the soft start capacitor to charge to the target voltage is the target time. Compared with directly charging the soft start capacitor to the target voltage, the charging time is extended. That is, the soft start circuit or the control circuit of the present application can obtain a larger equivalent capacitance, saving the overall area of ​​the control chip and reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the structure of a soft start circuit in an embodiment of the present application;

[0039] Figure 2 A circuit structure for charging the soft-start capacitor without using the soft-start circuit in the embodiment of the present application;

[0040] Figure 3 This is one of the structural schematic diagrams of a voltage output circuit in an embodiment of the present application;

[0041] Figure 4 This is a second structural diagram of a voltage output circuit in an embodiment of the present application;

[0042] Figure 5 is a schematic structural diagram of a current mirror circuit in an embodiment of the present application;

[0043] Figure 6 Schematic diagram of the structure of a control circuit in one embodiment of the present application.

[0044] Description of Figure Numbers:

[0045] Control circuit: 10; soft start circuit: 100; current mirror circuit: 110; start unit: 111; first current mirror unit: 112; second current mirror unit: 113; soft start capacitor: 120; voltage output circuit: 130; voltage output module: 131; first trigger unit: 132; switch unit: 133; first current source: 200; second trigger unit: 300. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0047] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0048] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0049] In one embodiment, a soft start circuit 100 is provided. Figure 1 The structural schematic diagram of the soft start circuit 100 shown in the figure, the soft start circuit 100 in this embodiment includes a current mirror circuit 110, a soft start capacitor 120 and a voltage output circuit 130, the current mirror circuit 110 is used to connect the first current source 200, and under the action of the external input start signal, the start current output by the first current source 200 is mirrored and then outputs the charging current; the soft start capacitor 120 is connected to the current mirror circuit 110, and is used to output the target voltage after charging for the target time according to the charging current; the voltage output circuit 130 is connected to the soft start capacitor 120, and is used to output the start voltage Vsoftstart under the action of the target voltage, the start signal and the external power supply voltage VDD.

[0050] The above-mentioned current mirror circuit 110 includes a plurality of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) of the same type, and the external input start signal is a signal for controlling the conduction or shutdown of some MOSFETs in the current mirror circuit 110. The current mirror circuit 110 performs mirror processing on the start signal output by the first current source 200 to charge the soft start capacitor 120, thereby obtaining a slowly rising target voltage until the target voltage is close to the external power supply voltage VDD after a target time, wherein the target time is related to the ability of the current mirror circuit 110 to perform mirror processing on the start current.

[0051] Exemplarily, the starting current is I1, and the charging current is I2. If the current mirror circuit 110 performs mirror processing on the starting current I1, the charging current I2=k*I1, k is a positive number, and k<1, then correspondingly, compared with not using the soft start circuit 100 in this embodiment to charge the soft start capacitor 120, the time it takes for the output voltage of the soft start capacitor 120 to reach the target voltage is extended by 1 / k times. The circuit structure in which the soft start circuit 100 in this embodiment is not used to charge the soft start capacitor 120 can be as follows: Figure 2 As shown, it includes a soft start capacitor 120, a MOSFET tube M1, a current source I and a voltage output module 131. The current source I directly charges the soft start capacitor 120. At this time, the current charging the soft start capacitor is increased by 1 / k times compared with the charging current I2 in this embodiment, which is equivalent to reducing the capacitance by k times.

[0052] In this embodiment, the voltage output circuit 130 mentioned above may also include a plurality of MOSFET tubes, wherein the start signal is used to control the MOSFET tubes in part of the voltage output circuit 130 to be turned on or off, thereby controlling the output of the start voltage Vsoftstart. In some embodiments, the voltage output circuit 130 may also include other control circuits for realizing the control of the output conditions of the start voltage Vsoftstart. Exemplarily, a voltage detection circuit is provided, which is connected to the soft start capacitor 120, and is used to detect the magnitude of the target voltage. When the target voltage reaches a preset voltage, a corresponding control signal is output to control the connection between the access terminal of the external power supply voltage VDD and the output terminal of the voltage output circuit 130, thereby outputting the external power supply voltage VDD as the start voltage Vsoftstart. Not limited to this.

[0053] The soft start circuit 100 in the present embodiment avoids using a digital signal control structure, and the start current output by the first current source 200 is mirrored by the current mirror circuit 110 so that the time for the soft start capacitor 120 to charge to the target voltage is the target time. Compared with directly charging the soft start capacitor 120 to the target voltage, the charging time is extended. That is, the soft start circuit 100 in the present embodiment adopts a current multiplication technology, which can obtain a larger equivalent capacitance and avoid the use of a large capacitor, thereby saving the overall area of ​​the circuit and reducing the cost.

[0054] In one embodiment, Figure 3One of the structural schematic diagrams of the voltage output circuit 130 shown in FIG. 1 , the voltage output circuit 130 in this embodiment includes a first MOSFET tube M2 and a second MOSFET tube M3. The gate of the first MOSFET tube M2 is used to access the start signal input from the outside, and the source of the first MOSFET tube M2 is used to connect to the equivalent ground terminal GND; the gate of the second MOSFET tube M3 is connected to the current mirror circuit 110 and the soft start capacitor 120, the source of the second MOSFET tube M3 is connected to the drain of the first MOSFET tube M2, and the drain of the second MOSFET tube M3 is used to access the external power supply voltage VDD. The second MOSFET tube M3 is used to output the start voltage Vsoftstart under the action of the external power supply voltage VDD and the target voltage when the drain of the first MOSFET tube M2 is connected to the equivalent ground terminal GND.

[0055] In this embodiment, the voltage output circuit 130 includes a first MOSFET tube M2 and a second MOSFET tube M3, which can directly output the target voltage as the starting voltage Vsoftstart. When the target voltage gradually rises and approaches the external power supply voltage VDD, the starting voltage Vsoftstart also gradually rises and approaches the external power supply voltage VDD accordingly. Therefore, at this time, the soft start circuit 100 in this embodiment can output a starting voltage Vsoftstart that slowly rises and approaches the external power supply voltage VDD.

[0056] In one embodiment, Figure 4 The second structural schematic diagram of the voltage output circuit 130 shown in FIG. 1 is a schematic diagram of the voltage output circuit 130. The voltage output circuit 130 in this embodiment further includes a first trigger unit 132 and a switch unit 133. The input end of the first trigger unit 132 is connected to the source of the first MOSFET tube M2. The first trigger unit 132 is configured with a trigger voltage and is used to output a trigger signal when the difference between the start voltage Vsoftstart and the trigger voltage is a preset value; the controlled end of the switch unit 133 is connected to the output end of the first trigger unit 132, the first end of the switch unit 133 is connected to the source of the second MOSFET tube M3, the second end of the switch unit 133 is used to connect to the equivalent ground terminal GND, and the third end of the switch unit 133 is used to connect to the external power supply voltage VDD. The switch unit 133 is used to disconnect the connection between the source of the second MOSFET tube M3 and the equivalent ground terminal GND when receiving the trigger signal, and to connect the connection between the source of the second MOSFET tube M3 and the external power supply voltage VDD, and output the external power supply voltage VDD as the start voltage Vsoftstart.

[0057] Among them, the above-mentioned first trigger unit 132 can be any circuit or component that can judge the voltage value of the target voltage and output a corresponding trigger signal based on the judgment result, such as a Schmitt trigger. The above-mentioned switch unit 133 can be any component that can be used as a controlled switch, such as a MOSFET tube, a BJT (Bipolar Junction Transistor) switch, an SCR (Silicon Controlled Rectifier), a GTO (Gate-Turn-Off Thyristor), an IGBT (Insulated Gate Bipolar Transistor), etc. This embodiment is attached Figure 4 , the switch unit 133 includes a MOSFET tube M4, a MOSFET tube M5 and a second current source I_load, wherein the types of the MOSFET tube M4 and the MOSFET tube M5 are different, and the second current source I_load can provide a stable current for the MOSFET tube M5, thereby improving the circuit stability. Specifically, when the start voltage Vsoftstart rises slowly, the corresponding input terminal voltage of the first trigger unit 132 also rises accordingly. It can be understood that the input terminal voltage of the first trigger unit 132 is equal to the start voltage Vsoftstart in value, and the change rate is about ΔV=I*Δt / (C*k), wherein C is the capacitance value of the soft start capacitor 120. That is, when the difference between the start voltage Vsoftstart and the trigger low voltage configured in the first trigger unit 132 is a preset value, a trigger signal is output, and the trigger signal can control the MOSFET tube M5 to be turned off, and control the MOSFET tube M4 to be turned on, so that the voltage value of the start voltage Vsoftstart is quickly pulled up to the external power supply voltage VDD, that is, at this time, the power supply output circuit outputs the external power supply voltage VDD as the start voltage Vsoftstart.

[0058] In one embodiment, Figure 5 The structural schematic diagram of the current mirror circuit 110 shown in the figure, the current mirror circuit 110 in this embodiment includes a startup unit 111, a first current mirror unit 112 and a second current mirror unit 113, the first current mirror unit 112 is connected to the soft-start capacitor 120 and the startup unit, and is used to connect the first current source 200, and output a first current under the action of a control signal and a startup current; the second current mirror unit is connected to the first current mirror and the soft-start capacitor 120, and is used to output a second current under the action of a control signal, a startup current and the first current, and the second current is used as a charging current to charge the soft-start capacitor 120; wherein the sum of the first current and the second current is equal to the startup current.

[0059] The start-up unit may be any circuit structure capable of starting the first and second current mirror units. Figure 5 The structure of the start-up unit includes a MOSFET tube M6 and a MOSFET tube M7. The gate of the MOSFET tube M6 is used to access the start-up signal, the drain of the MOSFET tube M6 is connected to the first current mirror unit 112 and the second current mirror unit 113, and the source of the MOSFET tube M6 is used to connect to the equivalent ground terminal GND; the gate of the MOSFET tube M7 is used to access the start-up signal, the drain of the MOSFET tube M7 is connected to the first current mirror, and the source of the MOSFET tube M7 is used to connect to the equivalent ground terminal GND.

[0060] The first current mirror unit 112 and the second current mirror unit 113 may include one or more MOSFET tubes. Figure 5 It shows a structure in which the first current mirror unit 112 includes a third MOSFET tube M8; the second current mirror unit 113 includes a fourth MOSFET tube M9; the ratio of the width to length ratio of the first current mirror unit 112 to the second current mirror unit 113 is the ratio of the width to length ratio of the third MOSFET tube M8 to the fourth MOSFET tube M9, x:1, x is greater than 1, and illustratively, x:1 can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0061] It can be understood that, in other embodiments, the first current mirror unit 112 may also include multiple MOSFET tubes connected in series or in parallel, and the width-to-length ratio of the first current mirror unit 112 is the first total width-to-length ratio of the multiple MOSFET tubes connected in series or in parallel in the first current mirror unit 112; the second current mirror unit 113 may also include one or more MOSFET tubes connected in series or in parallel, and the width-to-length ratio of the second current mirror unit 113 is the second total width-to-length ratio of the multiple MOSFET tubes connected in series or in parallel in the second current mirror unit 113; at this time, the ratio of the width-to-length ratios of the first current mirror unit 112 and the second current mirror unit 113 is the ratio of the first total width-to-length ratio to the second total width-to-length ratio x:1, where x is greater than 1. By way of example, x:1 can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and the like.

[0062] Specifically, assuming that the startup current is I1, the absolute value of the first current flowing through the first current mirror unit 112 is I3, and the absolute value of the second current flowing through the second current mirror unit 113 is I4. Since the ratio of the width to length of the first current mirror unit 112 to the second current mirror unit 113 is x:1, I3=I4. According to the characteristics of the capacitor, after the current mirror circuit 110 is turned on by the startup signal, the absolute value I4 of the second current flowing through the second current mirror unit 112 will be equal to the absolute value of the charging current I2 for charging the soft start capacitor 120. Therefore, I4=I2=I1-I3. Combining the above two equivalent relationships, I2=I1 / 1+x, that is, the charging current at this time is I1 / 1+x. Therefore, the current mirror circuit 110 can reduce the starting current I1 by a preset multiple, thereby extending the time it takes to charge the voltage of the soft-start capacitor 120 to the target voltage. That is, the soft-start circuit 100 is used as a circuit with an equivalent capacitor larger than the soft-start capacitor 120, saving the overall area of ​​the large capacitor and reducing the circuit cost.

[0063] In one embodiment, a control circuit is provided, such as Figure 6 As shown in the structural schematic diagram of the control circuit, the control circuit in this embodiment includes the soft start circuit 100, the first current source 200 and the second trigger unit 300 in any of the above embodiments, the first current source 200 is connected to the soft start circuit 100 for outputting a starting current; the second trigger unit 300 is connected to the soft start circuit 100 for outputting a starting signal.

[0064] In the present embodiment, the control circuit performs mirror processing on the starting current output by the first current source 200 through the current mirror circuit 110 in the soft start circuit 100 so that the time for the soft start capacitor 120 to charge to the target voltage is the target time. Compared with directly charging the soft start capacitor 120 to the target voltage, the charging time is extended. That is, the soft start circuit 100 of the present application can obtain a larger equivalent capacitance, saving the overall area of ​​the control circuit and reducing the cost.

[0065] In one embodiment, the second trigger unit is further used to output a first enable signal and a second enable signal; the control circuit further includes a control unit. The control unit is connected to the second trigger unit and the first current source, and is used to pull down the soft start capacitor in the soft start circuit to make the target voltage low when receiving the first enable signal, and control the first current mirror in the soft start circuit to output a start current when receiving the second enable signal; wherein the second trigger unit outputs the first enable signal earlier than outputting the second enable signal.

[0066] In this embodiment, the control unit can be a switch tube and a pull-down tube, which is used to pull down the target voltage when receiving the first enable signal. At the same time, the control unit can control the first current mirror to start outputting the startup circuit when receiving the second enable signal, thereby realizing the switch control of the first current source. The second trigger unit outputs the first enable signal earlier than the second enable signal, thereby ensuring that the target voltage is at a low level in the initial state.

[0067] In one embodiment, the control circuit further includes a power supply connected to the voltage output circuit and configured to output an external power supply voltage to the voltage output circuit.

[0068] In one embodiment, a control chip is provided. The control chip in this embodiment includes the soft start circuit in any of the above embodiments or the control circuit in any of the above embodiments.

[0069] In the present embodiment, the above-mentioned control chip performs mirror processing on the starting current output by the first current source through the soft start circuit or the current mirror circuit in the control circuit so that the time for the soft start capacitor to charge to the target voltage is the target time. Compared with directly charging the soft start capacitor to the target voltage, the charging time is extended. That is, a larger equivalent capacitance can be obtained through the soft start circuit or the control circuit of the present application, thereby saving the overall area of ​​the control chip and reducing the cost.

[0070] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the application. It should be noted that, for a person of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A soft start circuit, characterized in that: include: a current mirror circuit, connected to a first current source, and under the action of an externally inputted start-up signal, mirroring a start-up current outputted by the first current source to output a charging current; a soft start capacitor connected to the current mirror circuit and configured to output a target voltage after charging for a target time according to the charging current; The voltage output circuit is connected to the soft start capacitor and is used to output a start voltage under the action of the target voltage, the start signal and the external power supply voltage.

2. The soft start circuit according to claim 1, characterized in that: The voltage output circuit comprises: A first MOSFET tube, wherein the gate of the first MOSFET tube is used to receive the start signal input from the outside, and the source of the first MOSFET tube is used to connect to the equivalent ground terminal; A second MOSFET tube, the gate of the second MOSFET tube is connected to the current mirror circuit and the soft start capacitor, the source of the second MOSFET tube is connected to the drain of the first MOSFET tube, the drain of the second MOSFET tube is used to access the external power supply voltage, and the second MOSFET tube is used to output the starting voltage under the action of the external power supply voltage and the target voltage when the drain of the first MOSFET tube is turned on by the equivalent ground terminal.

3. The soft start circuit according to claim 2, characterized in that: The voltage output circuit further includes: A first trigger unit, wherein an input terminal of the first trigger unit is connected to a source of the first MOSFET tube, and the first trigger unit is configured with a trigger voltage, and is used to output a trigger signal when a difference between the start voltage and the trigger voltage is a preset value; A switch unit, wherein the controlled end of the switch unit is connected to the output end of the first trigger unit, the first end of the switch unit is connected to the source of the second MOSFET tube, the second end of the switch unit is used to connect to the equivalent ground end, and the third end of the switch unit is used to access the external power supply voltage. The switch unit is used to disconnect the connection between the source of the second MOSFET tube and the equivalent ground end, and to connect the connection between the source of the second MOSFET tube and the external power supply voltage when receiving the trigger signal, and output the external power supply voltage as the starting voltage.

4. The soft start circuit according to claim 1, characterized in that: The current mirror circuit comprises: A starting unit, wherein the first end of the starting unit is used to connect to the equivalent ground end, the controlled end of the starting unit is used to access the starting signal, and the starting unit is used to conduct the connection between the third end of the starting unit and the equivalent ground end under the action of the starting signal, so as to output the signal accessed by the equivalent ground end as a control signal; a first current mirror unit, the first current mirror unit being connected to the soft start capacitor and the start unit, and being used to connect to the first current source and output the first current under the action of the control signal and the start current; a second current mirror unit, connected to the first current mirror unit and the soft-start capacitor, and configured to output the second current under the action of the control signal, the start-up current and the first current, wherein the second current is used as the charging current to charge the soft-start capacitor; The sum of the first current and the second current is equal to the starting current.

5. The soft start circuit according to claim 4, characterized in that: The first current mirror unit includes a third MOSFET tube; the second current mirror unit includes a fourth MOSFET tube; the ratio of the width to length ratio of the first current mirror unit to the second current mirror unit is the ratio of the width to length ratio of the third MOSFET tube to the fourth MOSFET tube x:1, x is greater than 1; or, The first current mirror unit includes multiple MOSFET tubes connected in series or in parallel, and the width-to-length ratio of the first current mirror unit is the first total width-to-length ratio of the multiple MOSFET tubes connected in series or in parallel in the first current mirror unit; the second current mirror unit includes one or more MOSFET tubes connected in series or in parallel, and the width-to-length ratio of the second current mirror unit is the second total width-to-length ratio of the multiple MOSFET tubes connected in series or in parallel in the second current mirror unit; the ratio of the width-to-length ratios of the first current mirror unit and the second current mirror unit is the ratio of the first total width-to-length ratio to the second total width-to-length ratio x:1, where x is greater than 1.

6. The soft start circuit according to claim 4, characterized in that: The startup unit comprises: a fifth MOSFET tube, wherein the gate of the fifth MOSFET tube is used to access the start signal, the drain of the fifth MOSFET tube is connected to the first current mirror unit and the second current mirror unit, and the source of the fifth MOSFET tube is used to connect to the equivalent ground terminal; A sixth MOSFET tube, wherein the gate of the sixth MOSFET tube is used to access the start signal, the drain of the sixth MOSFET tube is connected to the first current mirror, and the source of the sixth MOSFET tube is used to connect to the equivalent ground terminal.

7. A control circuit, characterized in that: include: The soft start circuit according to any one of claims 1 to 6; A first current source, connected to the soft start circuit, for outputting a start current; The second trigger unit is connected to the soft start circuit and is used to output a start signal.

8. The control circuit according to claim 7, characterized in that: The second trigger unit is further configured to output a first enable signal and a second enable signal; and the control circuit further comprises: a control unit connected to the second trigger unit and the first current source, configured to pull down the soft start capacitor in the soft start circuit to make the target voltage at a low level when receiving the first enable signal, and control the first current mirror in the soft start circuit to output the start current when receiving the second enable signal; The second trigger unit outputs the first enable signal earlier than the second enable signal.

9. The control circuit according to claim 7, characterized in that: Also includes: A power supply is connected to the voltage output circuit and is used to output an external power supply voltage.

10. A control chip, characterized in that: It comprises the soft start circuit as claimed in any one of claims 1 to 6 or the control circuit as claimed in any one of claims 7 to 9.

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