Control Circuit and Switching Power Supply

Abstract

This application is applicable to the field of switching power supply technology, and provides a control circuit and a switching power supply. The control circuit includes a first feedback module, a second feedback module, a first switching module, a second switching module, a pull-down module, a first current biasing module, a second current biasing module, and a control module. The pull-down module is electrically connected to the first switching module, the second switching module, and the first current biasing module respectively. The control module is electrically connected to the first feedback module, the second feedback module, and the second switching module respectively. The second switching module is electrically connected to the second current biasing module. The first feedback module and the first switching module are both used to be electrically connected to the source electrode of the isolation switch tube. The pull-down module is used to be electrically connected to the gate electrode of the isolation switch tube. The second feedback module is used to be electrically connected to the drain electrode of the isolation switch tube. The control circuit provided by the embodiments of this application can avoid generating a large peak current during the turn-on process of the isolation switch tube, thereby protecting the isolation switch tube from being damaged.

Description

Technical Field

[0001] This application belongs to the technical field of switching power supplies, and particularly relates to a control circuit and a switching power supply. Background Art

[0002] The short-circuit protection scheme of existing switching power supply chips (such as boost switching power supply chips) usually uses an isolated MOS (Metal-Oxide-Semiconductor) transistor to achieve isolation between input and output. By controlling the conduction and cutoff of the isolated MOS transistor, the voltage difference between input and output is detected after the power supply starts up normally to achieve short-circuit protection. However, during the turn-on process of the isolated MOS transistor, a large peak current will be generated, which is extremely likely to cause damage to the isolated MOS transistor. Summary of the Invention

[0003] The embodiments of this application provide a control circuit and a switching power supply, which can solve the problem that in the existing control circuit, a large peak current will be generated during the turn-on process of the isolated MOS transistor, which is extremely likely to cause damage to the isolated MOS transistor.

[0004] In a first aspect, the embodiments of this application provide a control circuit, including a first feedback module, a second feedback module, a first switching module, a second switching module, a pull-down module, a first current biasing module, a second current biasing module, and a control module. The pull-down module is electrically connected to the first switching module, the second switching module, and the first current biasing module respectively. The control module is electrically connected to the first feedback module, the second feedback module, and the second switching module respectively. The second switching module is electrically connected to the second current biasing module. The first feedback module and the first switching module are both used to be electrically connected to the source electrode of the isolated switch transistor. The pull-down module is used to be electrically connected to the gate electrode of the isolated switch transistor. The second feedback module is used to be electrically connected to the drain electrode of the isolated switch transistor;

[0005] When the control circuit is powered on, the first switch module is controlled to conduct. The pull-down module is used to determine a first drive current transmitted to the gate of the isolation switch tube according to a first current output by the first current biasing module, and the first drive current is used to limit the output current of the isolation switch tube. The first feedback module is used to output a first feedback voltage to the control module according to a first voltage, the second feedback module is used to output a second feedback voltage to the control module according to an output voltage, the control module is used to output a control signal to the second switch module according to the first feedback voltage and the second feedback voltage, the second switch module is used to conduct according to the control signal, and the pull-down module is further used to determine a second drive current transmitted to the gate of the isolation switch tube according to the first current and a second current output by the second current biasing module, and the second drive current is used to indicate that the isolation switch tube is fully opened.

[0006] In a possible implementation manner of the first aspect, the first feedback module includes a first resistor and a second resistor. The first end of the first resistor is used to be electrically connected to the source electrode of the isolation switch tube, the second end of the first resistor is respectively electrically connected to the first end of the second resistor and the control module, and the second end of the second resistor is grounded.

[0007] In a possible implementation manner of the first aspect, the second feedback module includes a third resistor and a fourth resistor. The first end of the third resistor is used to be electrically connected to the drain electrode of the isolation switch tube, the second end of the third resistor is respectively electrically connected to the first end of the fourth resistor and the control module, and the second end of the fourth resistor is grounded.

[0008] In a possible implementation manner of the first aspect, the first switch module includes a first switch. The first end of the first switch is used to be electrically connected to the source electrode of the isolation switch tube, the second end of the first switch is electrically connected to the pull-down module, and the control end of the first switch is used to receive a switch control signal.

[0009] In a possible implementation manner of the first aspect, the second switch module includes a second switch. The first end of the second switch is respectively electrically connected to the pull-down module and the first current biasing module, the second end of the second switch is electrically connected to the second current biasing module, the control end of the second switch is electrically connected to the control module, and the first end of the second switch is used to be electrically connected to the gate of the isolation switch tube.

[0010] In a possible implementation of the first aspect, the pull-down module includes a first switching transistor. The gate of the first switching transistor is electrically connected to the drain of the first switching transistor, the second switching module, and the first current biasing module respectively. The source of the first switching transistor is electrically connected to the first switching module. The gate of the first switching transistor is used to be electrically connected to the gate of the isolation switching transistor.

[0011] In a possible implementation of the first aspect, the first current biasing module includes a first current source. The first end of the first current source is electrically connected to the second switching module and the pull-down module respectively. The second end of the first current source is grounded. The first end of the first current source is used to be electrically connected to the gate of the isolation switching transistor.

[0012] In a possible implementation of the first aspect, the second current biasing module includes a second current source. The first end of the second current source is electrically connected to the second switching module. The second end of the second current source is grounded.

[0013] In a possible implementation of the first aspect, the control module includes a multiplexer and a soft start unit. The multiplexer is electrically connected to the soft start unit, the first feedback module, the second feedback module, and the second switching module respectively. The soft start unit is used to output a soft start voltage to the multiplexer.

[0014] In a second aspect, an embodiment of the present application provides a switching power supply, including the control circuit according to any one of the first aspect.

[0015] The beneficial effects of the embodiments of the present application compared with the prior art are:

[0016] The control circuit provided by the embodiment of the present application includes a first feedback module, a second feedback module, a first switch module, a second switch module, a pull-down module, a first current biasing module, a second current biasing module, and a control module. When the control circuit is powered on, the first switch module is first controlled to conduct, entering the pre-charge stage. In this stage, the pull-down module can determine a first driving current transmitted to the gate of the isolation switch tube according to the first current, that is, provide a pull-down current for the isolation switch tube. At this time, the isolation switch tube is controlled by a small current and cannot be fully opened, and the output current is limited. Then, the control module determines whether the output voltage is in a normal state by detecting the first feedback voltage and the second feedback voltage. If the control module determines that the output voltage is in a short-circuit state, at this time, the control module does not control the second switch module to conduct, so the current transmitted to the gate of the isolation switch tube is still the first driving current, that is, the isolation switch tube is still controlled by a small current and cannot be fully opened. If the control module determines that the output voltage is in a normal state, at this time, the control module controls the second switch module to conduct, so that a connection is established between the second current biasing module and the gate of the isolation switch tube. At this time, the current transmitted to the gate of the isolation switch tube is a second driving current determined by the pull-down module according to the first current and the second current. At this time, the isolation switch tube is controlled by a large current and the isolation switch tube is fully opened. It can be seen that during the process of controlling the isolation switch tube to turn on, the control circuit provided by the embodiment of the present application first uses a small current to control the isolation switch tube to limit the output current of the isolation switch tube. If the control module determines that the output voltage is in a short-circuit state, the isolation switch tube is still controlled by a small current. Only when the control module determines that the output voltage is normal, a large current is used to control the isolation switch tube to fully open it. This can avoid a large peak current from being generated during the opening process of the isolation switch tube, thereby protecting the isolation switch tube from being damaged. Brief Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 is a typical application schematic diagram of a switching power supply circuit;

[0019] Figure 2 is a principle block diagram of the control circuit provided by an embodiment of the present application;

[0020] Figure 3 is a circuit connection schematic diagram of the control circuit provided by an embodiment of the present application.

[0021] In the figure, 10 is a control circuit; 101 is a first feedback module; 102 is a second feedback module; 103 is a first switch module; 104 is a second switch module; 105 is a pull-down module; 106 is a first current bias module; 107 is a second current bias module; 108 is a control module. Detailed implementation manners

[0022] In the following description, specific details such as specific system architectures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0023] It should be understood that when used in the specification of the present application and the appended claims, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0024] It should also be understood that the term "and / or" as used in the specification of the present application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0025] As used in the specification of the present application and the appended claims, the term "if" can be interpreted as "when", "once", "in response to determining", or "in response to detecting" according to the context. Similarly, the phrase "if determined" or "if [the described condition or event] is detected" can be interpreted as meaning "once determined", "in response to determining", "once [the described condition or event] is detected", or "in response to detecting [the described condition or event]" according to the context.

[0026] In addition, in the description of the specification of the present application and the appended claims, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0027] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that a specific feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of this application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification do not necessarily all refer to the same embodiment, but rather mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "comprising", "including", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0028] The short - circuit protection scheme of existing switching - power - supply chips usually uses an isolated MOS transistor to achieve isolation between input and output. By controlling the on - off of the isolated MOS transistor, the voltage difference between input and output is detected after the power supply starts up normally to achieve short - circuit protection. However, during the turn - on process of the isolated MOS transistor, a large peak current will be generated, which is very likely to cause damage to the isolated MOS transistor.

[0029] Based on the above problems, the control circuit provided in the embodiments of the present application includes a first feedback module, a second feedback module, a first switching module, a second switching module, a pull-down module, a first current biasing module, a second current biasing module, and a control module. When the control circuit is powered on, the first switching module is first controlled to conduct, entering the pre-charging stage. In this stage, the pull-down module can determine a first drive current transmitted to the gate of the isolation switch tube according to the first current, that is, provide a pull-down current for the isolation switch tube. At this time, the isolation switch tube is controlled by a small current and cannot be fully opened, and the output current is limited. Then, the control module determines whether the output voltage is in a normal state by detecting the first feedback voltage and the second feedback voltage. If the control module determines that the output voltage is in a short-circuit state, at this time, the control module will not control the second switching module to conduct, so the current transmitted to the gate of the isolation switch tube is still the first drive current, that is, the isolation switch tube is still controlled by a small current and cannot be fully opened. If the control module determines that the output voltage is in a normal state, at this time, the control module controls the second switching module to conduct, so that a connection is established between the second current biasing module and the gate of the isolation switch tube. At this time, the current transmitted to the gate of the isolation switch tube is a second drive current determined by the pull-down module according to the first current and the second current. At this time, the isolation switch tube is controlled by a large current and the isolation switch tube is fully opened. It can be seen that in the process of controlling the isolation switch tube to turn on, the control circuit provided in the embodiments of the present application first controls the isolation switch tube with a small current to limit the output current of the isolation switch tube. If the control module determines that the output voltage is in a short-circuit state, the isolation switch tube is still controlled by a small current. Only when the control module determines that the output voltage is normal, the isolation switch tube is controlled by a large current to fully open the isolation switch tube. This can avoid a large peak current from being generated during the opening process of the isolation switch tube, thereby protecting the isolation switch tube from being damaged.

[0030] It should be noted that Figure 1 For the switching power supply circuit applicable to the control circuit provided in the embodiments of the present application, the isolation switch tube described in the present application is Figure 1 the isolation MOS tube Q2 shown in the figure, VIN is the input voltage, Ci is the input capacitor, L1 is the boost inductor, D1 is the isolation freewheeling diode, Co is the output voltage of the boost converter, Q0 is the power switch, VOUT is the output voltage, and Cout is the output capacitor. Among them, Figure 1 Q0 in the figure is an NMOS tube, and Q2 is a PMOS tube.

[0031] In order to illustrate the technical solutions described in the present application, the following will be described through specific embodiments.

[0032] Figure 2 The principle block diagram of the control circuit 10 provided in an embodiment of the present application is shown. Refer to Figure 2As shown, the control circuit 10 includes a first feedback module 101, a second feedback module 102, a first switch module 103, a second switch module 104, a pull-down module 105, a first current bias module 106, a second current bias module 107, and a control module 108. The pull-down module 105 is electrically connected to the first switch module 103, the second switch module 104, and the first current bias module 106 respectively. The control module 108 is electrically connected to the first feedback module 101, the second feedback module 102, and the second switch module 104 respectively. The second switch module 104 is electrically connected to the second current bias module 107. Both the first feedback module 101 and the first switch module 103 are used to be electrically connected to the source of the isolation switch tube Q2. The pull-down module 105 is used to be electrically connected to the gate of the isolation switch tube Q2. The second feedback module 102 is used to be electrically connected to the drain of the isolation switch tube Q2.

[0033] Specifically, when the control circuit 10 is powered on, first, the first switch module 103 is controlled to conduct, entering the pre-charge stage. In this stage, the pull-down module 105 can determine the first drive current transmitted to the gate of the isolation switch tube Q2 according to the first current, that is, provide a pull-down current for the isolation switch tube Q2. At this time, the isolation switch tube Q2 is controlled by a small current and cannot be fully opened, and the output current is limited. Then, the control module 108 determines whether the output voltage VOUT is in a normal state by detecting the first feedback voltage FB1 and the second feedback voltage FB2. If the control module 108 determines that the output voltage VOUT is in a short-circuit state, at this time, the control module 108 will not control the second switch module 104 to conduct. Therefore, the current transmitted to the gate of the isolation switch tube Q2 is still the first drive current, that is, the isolation switch tube Q2 is still controlled by a small current and cannot be fully opened. If the control module 108 determines that the output voltage VOUT is in a normal state, at this time, the control module 108 controls the second switch module 104 to conduct, so that a connection is established between the second current bias module 107 and the gate of the isolation switch tube Q2. At this time, the current transmitted to the gate of the isolation switch tube Q2 is the second drive current determined by the pull-down module 105 according to the first current and the second current. At this time, the isolation switch tube Q2 is controlled by a large current and the isolation switch tube Q2 is fully opened. It can be seen that in the process of controlling the isolation switch tube Q2 to turn on, the control circuit 10 provided by the embodiment of the present application first controls the isolation switch tube Q2 with a small current to limit the output current of the isolation switch tube Q2. If the control module 108 determines that the output voltage VOUT is in a short-circuit state, the isolation switch tube Q2 is still controlled by a small current. Only when the control module 108 determines that the output voltage VOUT is normal, then the isolation switch tube Q2 is controlled by a large current to make the isolation switch tube Q2 fully opened. This can avoid generating a large peak current during the opening process of the isolation switch tube Q2, thereby protecting the isolation switch tube Q2 from being damaged.

[0034] It should be noted that when the output voltage VOUT is in a short - circuit state, the output voltage VOUT cannot reach the preset voltage, and the control module 108 will not control the second switch module 104 to conduct. At this time, the current of the gate of the isolation switch tube Q2 is the first driving current, that is, the isolation switch tube Q2 is controlled by a small current, and the output current of the isolation switch tube Q2 is limited, which can ensure that the isolation switch tube Q2 will not be damaged during long - term operation, thereby realizing the short - circuit start - up protection of the switching power supply. In addition, when the output voltage VOUT is in a normal state, the output voltage VOUT will reach the preset voltage. The control module 108 knows that the output voltage VOUT is in a normal state according to the first feedback voltage FB1 and the second feedback voltage FB2, and then controls the second switch module 104 to conduct, so that a connection is established between the second current biasing module 107 and the gate of the isolation switch tube Q2. At this time, the current of the gate of the isolation switch tube Q2 is the second driving current, that is, the isolation switch tube Q2 is controlled by a large current, and the isolation switch tube Q2 is fully opened. Since the output voltage VOUT is equal to the first voltage Vo at this time, no large peak current will be generated when the isolation switch tube Q2 is fully opened, which can effectively reduce the input peak current at the moment when the isolation switch tube Q2 is fully turned on.

[0035] Exemplarily, the preset voltage can be set by the designer himself. For example, the preset voltage can be 90% of the first voltage Vo. Only when the output voltage VOUT reaches 90% of the first voltage Vo, the control module 108 determines that the output voltage VOUT is in a normal state, and then controls the second switch module 104 to conduct, so that the isolation switch tube Q2 is controlled by the second driving current.

[0036] It should be noted that the first feedback module 101, the second feedback module 102, the first switch module 103, the second switch module 104, the pull - down module 105, the first current biasing module 106, the second current biasing module 107 and the control module 108 provided in the control circuit 10 of the present application embodiment are all arranged inside the chip. Therefore, the first switch module 103 can receive the switch control signal inside the chip. When the control circuit 10 is powered on, that is, when there is an input voltage VIN, the control logic module inside the chip will output a switch control signal to control the first switch module 103 to conduct.

[0037] It should be noted that the direction of the first current is the same as that of the second current, the direction of the first driving current is the same as that of the second driving current, and the second driving current is greater than the first driving current. When the isolation switch tube Q2 is controlled by the first driving current with a small value, the isolation switch tube Q2 cannot be fully opened, and the output current is limited. When the isolation switch tube Q2 is controlled by the second driving current with a large value, the isolation switch tube Q2 is fully opened.

[0038] In an embodiment of the present application, such as Figure 3As shown, the first feedback module 101 includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 is used to be electrically connected to the source electrode of the isolation switch tube Q2. The second end of the first resistor R1 is respectively electrically connected to the first end of the second resistor R2 and the control module 108, and the second end of the second resistor R2 is grounded.

[0039] Specifically, the first resistor R1 and the second resistor R2 are used to divide the first voltage Vo and transmit the first feedback voltage FB1 obtained after voltage division to the control module 108, so that the control module 108 can know the first voltage Vo through the first feedback voltage FB1.

[0040] It should be noted that the resistance values of the first resistor R1 and the second resistor R2 are not limited here. For example, the resistance values of the first resistor R1 and the second resistor R2 can both be fixed resistance values or variable resistance values. In addition, in addition to using one first resistor R1 and one second resistor R2, designers can also use other quantities of the first resistor R1 and the second resistor R2. For example, the first resistor R1 can be in series-parallel connection with 2, 3, etc., and the second resistor R2 can be in series-parallel connection with 2, 3, etc. This application Figure 3 Only shows the circuit structure in which the first feedback module 101 includes a first resistor R1 with a fixed resistance value and a second resistor R2 with a fixed resistance value in series. Resistors with different quantities, different types or different connection relationships can be used to replace the first resistor R1 and the second resistor R2, and their basic working principles are similar, so no more details will be described here.

[0041] It should be noted that only one circuit structure of the first feedback module 101 is shown in the embodiments provided in this application, which does not mean that only this one circuit structure can achieve the function of the first feedback module 101. Other circuit structures that can achieve this function can also be replaced, and are not limited thereto.

[0042] In an embodiment of this application, as Figure 3 shown, the second feedback module 102 includes a third resistor R3 and a fourth resistor R4. The first end of the third resistor R3 is used to be electrically connected to the drain electrode of the isolation switch tube Q2. The second end of the third resistor R3 is respectively electrically connected to the first end of the fourth resistor R4 and the control module 108, and the second end of the fourth resistor R4 is grounded.

[0043] Specifically, the third resistor R3 and the fourth resistor R4 are used to divide the output voltage VOUT and transmit the second feedback voltage FB2 obtained after voltage division to the control module 108, so that the control module 108 can know the output voltage VOUT through the second feedback voltage FB2.

[0044] It should be noted that the resistance values of the third resistor R3 and the fourth resistor R4 are not limited herein. For example, the resistance values of the third resistor R3 and the fourth resistor R4 can both be fixed resistance values or variable resistance values. In addition, in addition to using one third resistor R3 and one fourth resistor R4, designers can also use other numbers of third resistors R3 and fourth resistors R4. For example, the third resistor R3 can be connected in series and parallel with 2, 3, etc., and the fourth resistor R4 can be connected in series and parallel with 2, 3, etc. This application Figure 3 only shows the circuit structure in which the second feedback module 102 includes a third resistor R3 with a fixed resistance value and a fourth resistor R4 with a fixed resistance value connected in series. Resistors with different numbers, different types or different connection relationships can be used to replace the third resistor R3 and the fourth resistor R4, and their basic working principles are similar, so no more details will be described here.

[0045] It should be noted that only one circuit structure of the second feedback module 102 is shown in the embodiments provided in this application, which does not mean that only this one circuit structure can realize the function of the second feedback module 102. Other circuit structures that can realize this function can also be replaced, and are not limited thereto.

[0046] In an embodiment of this application, as Figure 3 shown, the first switch module 103 includes a first switch SW1. The first end of the first switch SW1 is used to be electrically connected to the source electrode of the isolation switch tube Q2, the second end of the first switch SW1 is connected to the pull-down module 105, and the control end of the first switch SW1 is used to receive a switch control signal.

[0047] Specifically, the control end of the first switch SW1 is used to receive the switch control signal inside the chip and conduct and cut off according to the switch control signal. When the first switch SW1 is in the conducting state, the first switch SW1, the pull-down module 105 and the first current biasing module 106 form a loop, thereby determining the first driving current transmitted to the gate of the isolation switch tube Q2.

[0048] Exemplarily, the first switch SW1 can be replaced by a triode, a MOS tube or other switching devices, as long as it can realize the functions in this application, and it is not limited herein.

[0049] In an embodiment of this application, as Figure 3 shown, the second switch module 104 includes a first switch SW2. The first end of the first switch SW2 is electrically connected to the pull-down module 105 and the first current biasing module 106 respectively, the second end of the first switch SW2 is connected to the second current biasing module 107, the control end of the first switch SW2 is connected to the control module 108, and the first end of the first switch SW2 is used to be electrically connected to the gate of the isolation switch tube Q2.

[0050] Specifically, the control terminal of the first switch SW2 is used to receive the control signal output by the control module 108 and conduct according to the control signal. When the first switch SW2 is in the conducting state, the second current biasing module 107 is connected to the circuit, and the first switch SW1, the pull-down module 105, the first switch SW2, and the second current biasing module 107 form another loop, thereby determining the second driving current transmitted to the gate of the isolation switch tube Q2.

[0051] Exemplarily, the first switch SW2 can be replaced by a triode, a MOS transistor, or other switching devices as long as it can implement the functions in this application, and no limitation is made here.

[0052] In an embodiment of the present application, as Figure 3 shown, the pull-down module 105 includes a first switching tube Q1. The gate of the first switching tube Q1 is electrically connected to the drain of the first switching tube Q1, the second switching module 104, and the first current biasing module 106 respectively. The source of the first switching tube Q1 is electrically connected to the first switching module 103, and the gate of the first switching tube Q1 is used to be electrically connected to the gate of the isolation switch tube Q2.

[0053] Specifically, when the first switch SW1 conducts, the first switching tube Q1 forms a mirror image with the isolation switch tube Q2 to provide a pull-down current for the isolation switch tube Q2, thereby controlling the conduction degree of the isolation switch tube Q2. When only the first switch SW1 conducts, the first switching tube Q1 is used to determine the first driving current according to the first current, so that the isolation switch tube Q2 is not fully opened, and the output current of the isolation switch tube Q2 is limited. When both the first switch SW1 and the first switch SW2 conduct, the first switching tube Q1 is used to determine the second driving current according to the first current and the second current, so that the isolation switch tube Q2 is fully opened.

[0054] Exemplarily, designers can select the type of the first switching tube Q1 according to the actual situation, that is, all can adopt fully controlled power devices such as metal-oxide field-effect transistors or insulated-gate bipolar transistors. For example, the first switching tube Q1 can be selected as a PMOS transistor.

[0055] In an embodiment of the present application, as Figure 3 shown, the first current biasing module 106 includes a first current source I1. The first end of the first current source I1 is electrically connected to the second switching module 104 and the pull-down module 105 respectively. The second end of the first current source I1 is grounded, and the first end of the first current source I1 is used to be electrically connected to the gate of the isolation switch tube Q2.

[0056] Specifically, the first current source I1 is used to provide a constant first current. When the first switch SW1 conducts, the first current source I1 is connected to the circuit, thereby determining the first driving current transmitted to the gate of the isolation switch tube Q2.

[0057] In one embodiment of the present application, as Figure 3 shown, the second current bias module 107 includes a second current source I2. The first end of the second current source I2 is electrically connected to the second switch module 104, and the second end of the second current source I2 is grounded.

[0058] Specifically, the second current source I2 is used to provide a constant second current. When the first switch SW2 is turned on, the second current source I2 is connected to the current, thereby determining the second drive current transmitted to the gate of the isolation switch tube Q2.

[0059] In one embodiment of the present application, as Figure 3 shown, the control module 108 includes a multiplexer MUX and a soft start unit. The multiplexer MUX is electrically connected to the soft start unit, the first feedback module 101, the second feedback module 102, and the second switch module 104 respectively. The soft start unit is used to output a soft start voltage VSST to the multiplexer MUX.

[0060] Specifically, the multiplexer MUX can receive the first feedback voltage FB1 output by the first feedback module 101, the second feedback voltage FB2 output by the second feedback module 102, and the soft start voltage VSST output by the soft start unit, and can also receive the reference voltage VREF output by the reference module. The multiplexer MUX can know the first voltage Vo according to the first feedback voltage FB1, and know the output voltage VOUT according to the second feedback voltage FB2. When it is determined that the output voltage VOUT reaches 90% of the first voltage Vo, the multiplexer MUX determines that the output voltage VOUT is in a normal state. At this time, the control logic module in the chip controls the soft start unit to start working, and the soft start unit outputs a soft start voltage VSST to the multiplexer MUX. When the multiplexer MUX detects that the soft start voltage VSST reaches the threshold voltage, it determines that the pre-charging is completed, and the multiplexer MUX outputs a control signal to the first switch SW2 to turn on the first switch SW2, connect the second current source I2 to the circuit, increase the current of the gate of the isolation switch tube Q2, and completely open the isolation switch tube Q2.

[0061] Exemplarily, the threshold voltage can be set to 50% of the second feedback voltage FB2, that is, when the soft start voltage VSST slowly rises to 50% of the second feedback voltage FB2, the multiplexer MUX determines that the pre-charging is completed and controls the first switch SW2 to turn on.

[0062] It should be noted that only one circuit structure of the control module 108 is shown in the embodiments provided in the present application, which does not mean that only this one circuit structure can implement the function of the control module 108. Other circuit structures that can implement this function can also be replaced, and are not limited thereto.

[0063] The present application also discloses a control chip, in which the above-mentioned control circuit 10 is provided. By arranging the control circuit 10 in the control chip, the modules in the control circuit 10 can be controlled through the control logic of the chip, which can effectively reduce the input peak current at the moment when the isolation switch tube Q2 is fully turned on, and ensure that the isolation switch tube Q2 will not be damaged during the turning-on process.

[0064] The present application also discloses a switching power supply, including the above-mentioned control circuit 10. By adopting the above-mentioned control circuit 10 in the switching power supply, the reliability and service life of the switching power supply can be improved.

[0065] Since the processing and functions implemented by the switching power supply in this embodiment basically correspond to the embodiments, principles, and examples of the foregoing control circuit, for the details not described in the description of this embodiment, reference can be made to the relevant descriptions in the foregoing embodiments and will not be elaborated here.

[0066] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A control circuit, characterized in that, It includes a first feedback module, a second feedback module, a first switch module, a second switch module, a pull-down module, a first current biasing module, a second current biasing module and a control module. The pull-down module is electrically connected to the first switch module, the second switch module and the first current biasing module respectively. The control module is electrically connected to the first feedback module, the second feedback module and the second switch module respectively. The second switch module is electrically connected to the second current biasing module. The first feedback module and the first switch module are both used to be electrically connected to the source electrode of the isolation switch tube. The pull-down module is used to be electrically connected to the gate electrode of the isolation switch tube. The second feedback module is used to be electrically connected to the drain electrode of the isolation switch tube; When the control circuit is powered on, the first switch module is controlled to conduct. The pull-down module is used to determine the first drive current transmitted to the gate electrode of the isolation switch tube according to the first current output by the first current biasing module. The first drive current is used to limit the output current of the isolation switch tube. The first feedback module is used to output a first feedback voltage to the control module according to the first voltage. The second feedback module is used to output a second feedback voltage to the control module according to the output voltage. The control module is used to output a control signal to the second switch module according to the first feedback voltage and the second feedback voltage. The second switch module is used to conduct according to the control signal. The pull-down module is also used to determine the second drive current transmitted to the gate electrode of the isolation switch tube according to the first current and the second current output by the second current biasing module. The second drive current is used to indicate that the isolation switch tube is fully opened.

2. The control circuit according to claim 1, wherein The first feedback module includes a first resistor and a second resistor. The first end of the first resistor is used to be electrically connected to the source electrode of the isolation switch tube. The second end of the first resistor is electrically connected to the first end of the second resistor and the control module respectively. The second end of the second resistor is grounded.

3. The control circuit according to claim 1, wherein The second feedback module includes a third resistor and a fourth resistor. The first end of the third resistor is used to be electrically connected to the drain electrode of the isolation switch tube. The second end of the third resistor is electrically connected to the first end of the fourth resistor and the control module respectively. The second end of the fourth resistor is grounded.

4. The control circuit according to claim 1, wherein The first switch module includes a first switch. The first end of the first switch is used to be electrically connected to the source electrode of the isolation switch tube. The second end of the first switch is electrically connected to the pull-down module. The control end of the first switch is used to receive a switch control signal.

5. The control circuit according to claim 1, characterized in that The second switch module includes a second switch. The first end of the second switch is electrically connected to the pull-down module and the first current biasing module respectively. The second end of the second switch is electrically connected to the second current biasing module. The control end of the second switch is electrically connected to the control module. The first end of the second switch is used to be electrically connected to the gate electrode of the isolation switch tube.

6. The control circuit according to claim 1, wherein The pull-down module includes a first switching transistor. The gate of the first switching transistor is electrically connected to the drain of the first switching transistor, the second switching module, and the first current biasing module respectively. The source of the first switching transistor is electrically connected to the first switching module. The gate of the first switching transistor is used to be electrically connected to the gate of the isolation switching transistor.

7. The control circuit according to claim 1, wherein The first current biasing module includes a first current source. The first terminal of the first current source is electrically connected to the second switching module and the pull-down module respectively. The second terminal of the first current source is grounded. The first terminal of the first current source is used to be electrically connected to the gate of the isolation switching transistor.

8. The control circuit according to claim 1, characterized in that, The second current biasing module includes a second current source. The first terminal of the second current source is electrically connected to the second switching module. The second terminal of the second current source is grounded.

9. The control circuit according to claim 1, wherein The control module includes a multiplexer and a soft start unit. The multiplexer is electrically connected to the soft start unit, the first feedback module, the second feedback module, and the second switching module respectively. The soft start unit is used to output a soft start voltage to the multiplexer.

10. A switching power supply, characterized in that, Comprising the control circuit according to any one of claims 1-9.

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