Soft start circuit

Abstract

Embodiments of the present disclosure provide a soft-start circuit. The circuit includes a soft-start module and a resistance proportional sampling module. The soft-start module is configured to generate a first current signal and provide the first current signal to the resistance proportional sampling module via a first node; the resistance proportional sampling module is configured to generate a current shunt signal of the first current signal and provide the current shunt signal to a charging capacitor in the soft-start module via a second node. Embodiments of the present invention are applicable to improvements in soft-start circuits.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to the technical field of integrated circuits, and in particular to a soft start circuit. Background Art

[0002] During the operation of a switching power supply chip, in order to prevent a large current spike from occurring in the power tube of the chip at the initial start-up, a soft start circuit is generally added to the chip to ensure that the current can gradually increase smoothly and slowly to the target value.

[0003] However, the soft start circuit generally requires a large charging capacitor and an extremely small charging current. If a large capacitor is integrated on the chip, the chip area will be significantly increased, thereby increasing the chip cost. Summary of the Invention

[0004] The purpose of the embodiments of the present disclosure is to provide a soft start circuit, which uses a resistance ratio sampling and amplification technology to achieve a smaller charging capacitor in the soft start circuit, reduce chip area, and lower costs.

[0005] To achieve the above objectives, a first aspect of an embodiment of the present disclosure provides a soft-start circuit, comprising: a soft-start module and a resistance proportional sampling module. The soft-start module is configured to generate a first current signal and provide the first current signal to the resistance proportional sampling module via a first node; the resistance proportional sampling module is configured to generate a current shunt signal of the first current signal and provide the current shunt signal to a charging capacitor in the soft-start module via a second node.

[0006] In some embodiments of the present disclosure, the soft start module includes: a constant current source, a transistor, a voltage comparator, an inverter, and a charging capacitor. The first terminal of the constant current source is coupled to the first voltage terminal, and the second terminal of the constant current source is coupled to the first node; the control terminal of the transistor is coupled to the output terminal of the inverter, the first terminal of the transistor is coupled to the first voltage terminal, and the second terminal of the transistor is coupled to the first node; the positive input terminal of the voltage comparator is coupled to the second node, the negative input terminal of the voltage comparator is coupled to the third voltage terminal, and the output terminal of the voltage comparator is coupled to the output terminal of the soft start circuit; the input terminal of the inverter is coupled to the output terminal of the voltage comparator; the first terminal of the charging capacitor is coupled to the second node, and the second terminal of the charging capacitor is coupled to the second voltage terminal.

[0007] In some embodiments of the present disclosure, the resistance ratio sampling module includes: a first resistor, a second resistor, and an operational amplifier. The first end of the first resistor is coupled to the first node, and the second end of the first resistor is coupled to the second node; the first end of the second resistor is coupled to the first node, and the second end of the second resistor is coupled to the inverting input of the operational amplifier; the non-inverting input of the operational amplifier is coupled to the second node, and the output of the operational amplifier is coupled to the inverting input of the operational amplifier.

[0008] In some embodiments of the present disclosure, the transistor is a PMOS transistor.

[0009] In some embodiments of the present disclosure, the first current signal is sampled by the first resistor and the operational amplifier, and the first current signal is shunted by the operational amplifier and the second resistor to obtain the current shunting signal.

[0010] In some embodiments of the present disclosure, the power supply of the operational amplifier is coupled to the first voltage terminal and the second voltage terminal respectively.

[0011] In some embodiments of the present disclosure, the current shunt signal is obtained by: The current shunt signal Is is obtained, wherein R1 is the resistance of the first resistor, R2 is the resistance of the second resistor, and I1 is the first current signal.

[0012] In some embodiments of the present disclosure, the capacitance of the charging capacitor is obtained by: Get the capacitance C of the charging capacitor ss , wherein V3 is the input voltage of the third voltage terminal, and t is the start-up time of the soft start circuit.

[0013] In some embodiments of the present disclosure, a resistance ratio of the first resistor to the second resistor is greater than or equal to 10.

[0014] A second aspect of an embodiment of the present disclosure provides a soft start circuit, comprising: a constant current source, a transistor, a voltage comparator, an inverter, a charging capacitor, a first resistor, a second resistor, and an operational amplifier. The first terminal of the constant current source is coupled to the first voltage terminal, and the second terminal of the constant current source is coupled to the first node; the control terminal of the transistor is coupled to the output terminal of the inverter, the first terminal of the transistor is coupled to the first voltage terminal, and the second terminal of the transistor is coupled to the first node; the positive input terminal of the voltage comparator is coupled to the second node, the negative input terminal of the voltage comparator is coupled to the third voltage terminal, and the output terminal of the voltage comparator is coupled to the output terminal of the soft start circuit; the input terminal of the inverter is coupled to the output terminal of the voltage comparator; the first terminal of the charging capacitor is coupled to the second node, and the second terminal of the charging capacitor is coupled to the second voltage terminal; the first terminal of the first resistor is coupled to the first node, and the second terminal of the first resistor is coupled to the second node; the first terminal of the second resistor is coupled to the first node, and the second terminal of the second resistor is coupled to the inverting input terminal of the operational amplifier; the positive input terminal of the operational amplifier is coupled to the second node, and the output terminal of the operational amplifier is coupled to the inverting input terminal of the operational amplifier; the power supply of the operational amplifier is coupled to the first voltage terminal and the second voltage terminal, respectively.

[0015] Through the above technical solution, the resistance ratio sampling and amplification technology is adopted, thereby achieving a smaller charging capacitor in the soft start circuit, reducing the chip area and lowering the cost.

[0016] Other features and advantages of the embodiments of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the embodiments of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present disclosure, but do not constitute a limitation of the embodiments of the present disclosure. In the accompanying drawings:

[0018] Figure 1 is an exemplary circuit diagram of a soft start circuit;

[0019] Figure 2 is a schematic block diagram of a soft start circuit according to an embodiment of the present disclosure;

[0020] Figure 3 is an exemplary circuit diagram of a soft start circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work also fall within the scope of protection of the present disclosure.

[0022] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal manner unless otherwise explicitly defined herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that the parts are joined together either directly or through one or more intermediate components.

[0023] In all embodiments of the present disclosure, since the source and drain of the field effect transistor are symmetrical, and the conduction current between the source and drain of the N-type field effect transistor and the P-type field effect transistor is in opposite directions, in the embodiments of the present disclosure, the controlled middle end of the field effect transistor is referred to as the control electrode, and the other two ends of the field effect transistor are referred to as the first electrode and the second electrode, respectively. In addition, terms such as "first" and "second" are only used to distinguish one component (or a portion of a component) from another component (or another portion of a component).

[0024] Figure 1 FIG. 1 shows an exemplary circuit diagram of a soft start circuit 100. Figure 1 In the example, the constant current source Iss generates a constant current I C , charging capacitor Css, when the voltage SS_REF of charging capacitor Css (i.e. the voltage of the positive input terminal of voltage comparator COMP) rises to the reference voltage V of the negative input terminal of voltage comparator COMP BG When the voltage comparator COMP flips and outputs a high level, SS_Done becomes high, the soft start ends, and the soft start start time t ss The relationship between the charging capacitor Css is shown in the following formula (1):

[0025]

[0026] Formula (1) shows that the capacitance of the charging capacitor in the soft-start circuit is proportional to the charging current. The smaller the charging current, the smaller the capacitance of the charging capacitor, and thus the smaller the area of ​​the charging capacitor. Therefore, in the embodiment of the present disclosure, the resistor ratio sampling and amplification technology is adopted to achieve a smaller charging capacitor in the soft-start circuit, reducing the chip area and lowering the cost.

[0027] Figure 2 FIG. 2 shows a schematic block diagram of a soft start circuit 200 according to an embodiment of the present disclosure. Figure 2 As shown, the soft start circuit 200 may include: a soft start module 210 and a resistance ratio sampling module 220 .

[0028] The soft-start module 210 can be coupled to the resistance proportional sampling module 220, a first voltage terminal V1, a second voltage terminal V2, a third voltage terminal V3, and an output terminal OUT of the soft-start circuit. The soft-start module 210 is configured to generate a first current signal I1 and provide the first current signal I1 to the resistance proportional sampling module 220 via a first node N1.

[0029] The resistance proportional sampling module 220 can be coupled to the soft-start module 210, the first voltage terminal V1, and the second voltage terminal V2. The resistance proportional sampling module 220 is configured to generate a current shunt signal Is of the first current signal I1 and provide the current shunt signal Is to a charging capacitor in the soft-start module 210 via a second node N2.

[0030] According to the embodiment of the present disclosure, the soft start circuit effectively shunts the charging current through the resistance proportional sampling module, thereby achieving a smaller charging capacitor and saving circuit area.

[0031] Figure 3 FIG. 2 shows an exemplary circuit diagram of a soft start circuit 200 according to an embodiment of the present disclosure. Figure 3As shown, the soft start module 210 may include: a constant current source Iss, a transistor M, a voltage comparator COMP, an inverter D, and a charging capacitor Css. A first terminal of the constant current source Iss is coupled to the first voltage terminal V1, and a second terminal of the constant current source Iss is coupled to the first node N1. In the embodiment of the present disclosure, the specific circuit of the constant current source Iss is not limited, as long as it can output a constant current. The control electrode of the transistor M is coupled to the output terminal of the inverter D, the first electrode of the transistor M is coupled to the first voltage terminal V1, and the second electrode of the transistor M is coupled to the first node N1. The transistor M is a PMOS transistor. The positive input terminal of the voltage comparator COMP is coupled to the second node N2, the negative input terminal of the voltage comparator COMP is coupled to the third voltage terminal V3, and the output terminal of the voltage comparator COMP is coupled to the output terminal OUT of the soft start circuit. The input terminal of the inverter D is coupled to the output terminal of the voltage comparator COMP. A first terminal of the charging capacitor Css is coupled to the second node N2 , and a second terminal of the charging capacitor Css is coupled to the second voltage terminal V2 .

[0032] The resistance proportional sampling module 220 may include: a first resistor R1, a second resistor R2, and an operational amplifier AMP. A first end of the first resistor R1 is coupled to the first node N1, and a second end of the first resistor R1 is coupled to the second node N2. A first end of the second resistor R2 is coupled to the first node N1, and a second end of the second resistor R2 is coupled to the inverting input of the operational amplifier AMP. A positive input of the operational amplifier AMP is coupled to the second node N2, and an output of the operational amplifier AMP is coupled to the inverting input of the operational amplifier AMP. Power supplies of the operational amplifier AMP are coupled to a first voltage terminal V1 and a second voltage terminal V2, respectively.

[0033] exist Figure 3 In the example, the internal power supply Vdd of the switching power supply chip is input from the first voltage terminal V1, the second voltage terminal V2 is grounded, and the third voltage terminal inputs a fixed power supply, for example, the voltage of the fixed power supply is 1.2V. The output of the output terminal OUT can provide a signal for the subsequent circuit. It should be understood by those skilled in the art that based on the above inventive concept, Figure 3 The variation of the circuit shown should also fall within the scope of protection of the present disclosure. In this variation, the above-mentioned transistor and voltage terminal may also have the same Figure 3 Examples of different setups are shown.

[0034] The following combination Figure 3 The working process of the over-temperature protection circuit 200 according to the embodiment of the present disclosure is explained with an example.

[0035] The constant current source Iss can generate a constant first current signal I1 and provide the first current signal I1 to the resistance proportional sampling module 220. In this way, the first current signal I1 is sampled by the first resistor R1 and the operational amplifier AMP, and then the first current signal I1 is accurately divided by the operational amplifier AMP and the second resistor R2 that form negative feedback, thereby obtaining the current division signal Is for charging the charging capacitor.

[0036] exist Figure 3 In the example of , the current shunt signal Is can be obtained by the following formula (2):

[0037]

[0038] Thus in this disclosure Figure 3 In the example, the charging capacitor C ss The capacitance value is obtained by the following formula (3):

[0039]

[0040] Wherein, V3 is the input voltage of the third voltage terminal, and t is the start-up time of the soft start circuit.

[0041] By comparing the capacitance formula (1) of the charging capacitor in the soft start circuit of the related art with the capacitance formula (3) of the charging capacitor in the soft start circuit of the embodiment of the present disclosure, it can be seen that under the same startup time, first current signal and input voltage of the third voltage terminal, the capacitance of the charging capacitor in the embodiment of the present disclosure is reduced by (1+R1 / R2) times compared to the original capacitance, greatly reducing the area of ​​the charging capacitor, thereby saving circuit area and cost. In the embodiment of the present disclosure, the resistance ratio of the first resistor to the second resistor is greater than or equal to 10. For example, when the multiple of R1 / R2 is 19, if the capacitance of the original charging capacitor is 1nF, the capacitance of the charging capacitor in the embodiment of the present disclosure is reduced by 20 times to 50pF.

[0042] After the constant current source generates a constant first current signal I1, it is sampled and shunted by the resistor proportional sampling module, and the charging capacitor Css is charged through the current shunt signal Is. When the voltage SS_REF of the charging capacitor Css (i.e., the voltage at the positive input terminal of the voltage comparator COMP) rises to the fixed voltage of the third voltage terminal input to the negative input terminal of the voltage comparator COMP, the voltage comparator COMP flips and outputs a high level, so that OUT becomes high, the soft start ends, and then the low level after flipping through the inverter D controls the transistor M to turn on, so that the voltage comparator COMP continues to output a high level, providing a high level signal for the subsequent circuit.

[0043] In summary, the charging capacitor area in the soft start circuit according to the embodiment of the present disclosure is small and can save circuit area.

[0044] The flow charts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the apparatus and method according to multiple embodiments of the present disclosure. In this regard, each box in the flow chart or block diagram can represent a part of a module, program segment or instruction, and the part of the module, program segment or instruction contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in a sequence different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs the specified function or action, or can be implemented by a combination of dedicated hardware and computer instructions.

[0045] Unless the context clearly indicates otherwise, as used herein and in the appended claims, the singular includes the plural, and vice versa. Thus, when referring to the singular, the plural of the corresponding term is generally included. Similarly, the words "include" and "comprising" are to be interpreted as inclusive rather than exclusive. Likewise, the terms "include" and "or" should be interpreted as inclusive unless such interpretation is expressly prohibited herein. Where the term "example" is used herein, particularly when it follows a group of terms, the "example" is merely exemplary and illustrative and should not be considered exclusive or comprehensive.

[0046] Further aspects and scope of adaptability become apparent from the description provided herein. It should be understood that various aspects of the present application can be implemented individually or in combination with one or more other aspects. It should also be understood that the description and specific embodiments herein are intended to be illustrative only and are not intended to limit the scope of the present application.

[0047] Several embodiments of the present disclosure have been described in detail above, but it is obvious that those skilled in the art can make various modifications and variations to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. The scope of protection of the present disclosure is defined by the appended claims.

Claims

1. A soft start circuit, characterized in that: include: Soft start module and resistance proportional sampling module, The soft start module is configured to generate a first current signal and provide the first current signal to the resistance ratio sampling module via a first node; The resistance proportional sampling module is configured to generate a current shunt signal of the first current signal, and provide the current shunt signal to the charging capacitor in the soft start module via the second node. The soft start module includes a constant current source, a transistor, a voltage comparator, an inverter and a charging capacitor. Wherein, the first terminal of the constant current source is coupled to the first voltage terminal, and the second terminal of the constant current source is coupled to the first node; The control electrode of the transistor is coupled to the output terminal of the inverter, the first electrode of the transistor is coupled to the first voltage terminal, and the second electrode of the transistor is coupled to the first node; The positive input terminal of the voltage comparator is coupled to the second node, the negative input terminal of the voltage comparator is coupled to the third voltage terminal, and the output terminal of the voltage comparator is coupled to the output terminal of the soft start circuit; The input terminal of the inverter is coupled to the output terminal of the voltage comparator; The first terminal of the charging capacitor is coupled to the second node, and the second terminal of the charging capacitor is coupled to the second voltage terminal. The resistance ratio sampling module includes: a first resistor, a second resistor and an operational amplifier. Wherein, a first end of the first resistor is coupled to the first node, and a second end of the first resistor is coupled to the second node; A first end of the second resistor is coupled to the first node, and a second end of the second resistor is coupled to the inverting input terminal of the operational amplifier; A non-inverting input terminal of the operational amplifier is coupled to the second node, and an output terminal of the operational amplifier is coupled to an inverting input terminal of the operational amplifier.

2. The soft start circuit according to claim 1, wherein: The transistor is a PMOS transistor.

3. The soft start circuit according to claim 1, wherein: The first current signal is sampled through the first resistor and the operational amplifier, and the first current signal is shunted through the operational amplifier and the second resistor to obtain the current shunting signal.

4. The soft start circuit according to claim 1, wherein: The power supply of the operational amplifier is coupled to the first voltage terminal and the second voltage terminal respectively.

5. The soft start circuit according to claim 1, wherein: The current shunt signal is obtained by: according to The current shunt signal Is is obtained, wherein R1 is the resistance of the first resistor, R2 is the resistance of the second resistor, and I1 is the first current signal.

6. The soft start circuit according to claim 5, characterized in that: The capacitance of the charging capacitor is obtained by: according to Get the capacitance C of the charging capacitor ss , wherein V3 is the input voltage of the third voltage terminal, and t is the start-up time of the soft start circuit.

7. The soft start circuit according to claim 5, characterized in that: in, A resistance ratio of the first resistor to the second resistor is greater than or equal to 10.

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