Switching converter and its control circuit

Abstract

The present invention discloses a switching converter and its control circuit. The control circuit includes: an error amplifier that obtains an error amplified signal based on a first feedback signal of the DC output voltage and a reference voltage; a soft start control circuit that compares the first feedback signal with a reference signal related to the reference voltage and outputs a soft start output signal or an error amplified signal according to the comparison result; a PWM comparator that compares a superimposed signal of a second feedback signal of the DC output voltage and a ripple signal with the error amplified signal or the soft start output signal to obtain a pulse width modulation signal; a logic and drive circuit that converts the pulse width modulation signal into a switch control signal to control the conduction state of at least one switch tube. Among them, the soft start control circuit is used to provide the soft start output signal to the PWM comparator when the first feedback signal is lower than the reference signal related to the reference voltage, so as to achieve soft start control with a constant slope for the superimposed signal.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and particularly to a switching converter and its control circuit. Background Art

[0002] With the demand for power electronic products and the development of semiconductor technology, power management chips are more widely used in portable computers, mobile phones, personal digital assistants, and other portable or non-portable electronic devices. A switching converter uses a power switch tube to control the power transmission from the input end to the output end, and thus can provide a constant output voltage and / or output current at the output end. During the startup process of the switching converter, due to reasons such as the load and the output capacitor, a large current from the power supply to the output will be generated, so a soft-start control circuit is required to control the startup process of the switching converter.

[0003] Figure 1 A schematic circuit diagram of a switching converter according to the prior art is shown. The switching converter 100 includes a main power circuit and a control circuit. The main power circuit includes a switch tube M and a diode D1 connected in series between the input end and the ground end. An inductor Lx is connected between the intermediate node of the switch tube M and the diode D1 and the output end. An output capacitor Cout is connected between the output end and the ground end. The input end of the switching converter 100 receives a DC input voltage Vin, and the output end provides a DC output voltage Vout. The control circuit of the switching converter 100 is used to provide a switching control signal to the switch tube M.

[0004] In the control circuit of the switching converter 100, a feedback circuit 130 generates a feedback signal FB according to the output voltage Vout. An error amplifier 110 generates an error amplification signal according to the feedback signal FB and the signal provided by the soft-start control circuit 140. A PWM comparator generates a pulse-width modulation signal PWM according to the error amplification signal Vea and a ramp signal Vramp to control the conduction state of the switch tube M. Among them, the soft-start control circuit 140 is as Figure 2 shown. The soft-start output signal generation unit 142 includes a current source Iss and a soft-start capacitor Css connected in series between the operating voltage Vdd and the ground. The intermediate node of the current source Iss and the soft-start capacitor Css outputs a soft-start output signal Vss. One end of a first switch K1 receives a reference voltage Vref, and the other end is connected to the non-inverting input terminal of the error amplifier 110. One end of a second switch K2 receives the soft-start output signal Vss, and the other end is connected to the non-inverting input terminal of the error amplifier 110. A comparator 141 controls the conduction states of the first switch K1 and the second switch K2 according to the reference voltage Vref and the soft-start output signal Vss. An inverter INV1 is also connected between the output terminal of the comparator 141 and the first switch K1.

[0005] During the startup phase of the switching converter 100, the current source Iss charges the soft-start capacitor Css to generate a soft-start output signal Vss that rises from 0. At this time, the soft-start output signal Vss is less than the reference voltage Vref. The comparator 141 controls the first switch K1 to turn off and the second switch K2 to turn on. The soft-start output signal Vss enters the non-inverting input terminal of the error amplifier 110, and the rising speed of the feedback signal FB is controlled through loop negative feedback. When the soft-start output signal Vss is greater than the reference voltage Vref, the comparator 141 controls the first switch K1 to turn on and the second switch K2 to turn off. The reference voltage Vref enters the non-inverting input terminal of the error amplifier 110, and the feedback voltage FB is stabilized at the reference voltage Vref, thus completing the soft start.

[0006] However, the switching converter 100 of the prior art adopts a fixed-time soft-start method, and the expressions for the voltage rising slope and the current rising slope are as follows:

[0007] Kvout = Vout / tss (Equation 1)

[0008] Kiout = Vout / (tss * Rload) (Equation 2)

[0009] Among them, Kvout represents the startup slope of the output voltage Vout, Kiout represents the startup slope of the output current, tss represents the set soft-start time. For example, the soft-start time tss is fixed as the time required for the value of the soft-start output signal Vss to rise to the reference voltage Vref, and Rload represents the load.

[0010] It can be easily known from Equation 1 and Equation 2 that when the soft-start time tss is fixed, the rising slope of the output voltage Vout is related to the value of the output voltage Vout, and the rising slope of the output current Iout is related to the output voltage Vout and the load Rload. In different application scenarios, the output voltage Vout and the load Rload are also different, thus bringing different startup stresses to the power supply, and it is impossible to achieve an ideal soft-start effect. If the tss is adjusted by an external capacitor to adjust power supply stress, noise and other indicators, not only are the parameters numerous, making the design work more complicated, but also the pins of the added external capacitor are not conducive to chip miniaturization, and it is also vulnerable to external noise interference, affecting the stability of the switching converter.

[0011] Therefore, an improved switching converter and its control circuit are expected, which can adopt a soft start with a fixed slope of the output voltage Vout, thereby simplifying the startup design of the switching converter. Summary of the Invention

[0012] In view of the above problems, the purpose of the present invention is to provide a switching converter and its control circuit, which can achieve a soft start with a fixed slope of the output voltage, thereby simplifying the startup design of the switching converter.

[0013] According to one aspect of the present invention, there is provided a control circuit for a switching converter. The switching converter uses at least one switching transistor to control the power transmission from the input terminal to the output terminal, so as to generate a DC output voltage according to a DC input voltage. Wherein, the control circuit includes: an error amplifier for obtaining an error amplification signal according to a first feedback signal of the DC output voltage and a reference voltage; a soft start control circuit for comparing the first feedback signal with a reference signal related to the reference voltage and outputting a soft start output signal or the error amplification signal according to the comparison result; a PWM comparator for comparing a superimposed signal of a second feedback signal of the DC output voltage and a ripple signal with the error amplification signal or the soft start output signal to obtain a pulse width modulation signal; and a logic and drive circuit for converting the pulse width modulation signal into a switching control signal to control the conduction state of the at least one switching transistor. Wherein, the soft start control circuit is used to provide the soft start output signal to the PWM comparator when the first feedback signal is lower than the reference signal related to the reference voltage, so as to realize soft start control with a constant slope for the superimposed signal.

[0014] Optionally, when the first feedback signal is lower than the reference signal, the soft start control circuit provides the soft start output signal to the PWM comparator. When the first feedback signal is higher than the reference signal, the soft start control circuit provides the error amplification signal to the PWM comparator.

[0015] Optionally, the soft start control circuit includes: a first switch, one end of which receives the error amplification signal and the other end of which is connected to the non-inverting input terminal of the PWM comparator; a second switch, one end of which receives the soft start output signal and the other end of which is connected to the non-inverting input terminal of the PWM comparator; a hysteresis comparator for controlling the conduction and turn-off of the first switch and the second switch according to the first feedback signal and the reference signal; and a soft start signal generation unit for generating the soft start output signal.

[0016] Optionally, the soft start signal generation unit includes: a current source and a soft start capacitor connected in series between the operating voltage and the ground, and a middle node between the current source and the soft start capacitor outputs the soft start output signal.

[0017] Optionally, the ratio of the reference signal to the reference voltage is a predetermined value.

[0018] Optionally, the control circuit further includes: a conduction time control circuit for generating a conduction time signal; and an OR gate, the first input terminal of which receives the pulse width modulation signal, the second input terminal of which is connected to the conduction time control circuit to receive the conduction time signal, and the output terminal of which provides a conduction time control signal; wherein, the logic and drive circuit controls the conduction and cutoff of the at least one switching transistor according to the conduction time control signal.

[0019] Optionally, the control circuit further includes: a ripple compensation circuit for generating the ripple signal.

[0020] Optionally, the control circuit further includes: a compensation resistor and a compensation capacitor connected in sequence between the output terminal of the error amplifier and the ground; and a first capacitor, the first terminal of which is connected to the output terminal of the error amplifier and the second terminal of which is grounded.

[0021] According to another aspect of the present invention, there is provided a switching converter, including: a main power circuit that uses at least one switching transistor to control the power transmission from the input terminal to the output terminal, so as to generate a DC output voltage according to a DC input voltage; and a control circuit according to any one of the above, for generating a switching control signal to control the conduction state of the at least one switching transistor.

[0022] Optionally, the main power circuit adopts any one of the following topologies: a floating ground type Buck power circuit, a grounded type Buck power circuit, a flyback power circuit, a Buck-boost type power circuit, a Boost type power circuit.

[0023] In the switching converter and its control circuit according to the embodiment of the present invention, the soft start control circuit provides a soft start output signal to the PWM comparator during the start-up phase to perform soft start control on the superimposed signal of the second feedback signal and the ripple signal. Since the DC component in the superimposed signal comes from the second feedback signal, the ratio of this DC component to the output voltage is a fixed value. Therefore, by performing soft start control of loop negative feedback on this DC component, soft start control of the output voltage can be achieved, so that the output voltage can start at a constant slope during the start-up phase of the switching converter, solving the problem that the soft start time in the switching converter of the prior art changes with the change of the output voltage, making it easier to predict soft start indicators such as soft start current and noise, and capable of simplifying the start-up design of the switching converter. Description of the Drawings

[0024] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features and advantages of the present invention will become clearer. In the drawings:

[0025] Figure 1 A schematic circuit diagram of a switching converter according to the prior art is shown;

[0026] Figure 2 shows Figure 1 the circuit structure diagram of the soft start control circuit;

[0027] Figure 3 shows the schematic circuit diagram of the switching converter according to an embodiment of the present invention;

[0028] Figure 4 shows Figure 3 the circuit structure diagram of the soft start control circuit;

[0029] Figure 5 and Figure 6 shows the soft start simulation diagram of the switching converter according to an embodiment of the present invention. Detailed implementation manners

[0030] The various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the respective drawings, the same elements or modules are denoted by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0031] It should be understood that in the following description, "circuit" may include a single or a combination of multiple hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by the programmable circuits. When an element or circuit is referred to as "connected to" another element or when an element or circuit is referred to as "connected between" two nodes, it can be directly coupled or connected to another element or there may be intermediate elements, and the connection between the elements can be physical, logical, or a combination thereof. In contrast, when an element is referred to as "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between the two.

[0032] Meanwhile, in this patent specification and claims, certain terms are used to refer to specific components. Those of ordinary skill in the art should understand that hardware manufacturers may use different terms to refer to the same component. This patent specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of the components as the criterion for distinction.

[0033] In this application, the switching transistor is a transistor that operates in a switching mode to provide a current path and includes one selected from bipolar transistors or field effect transistors. The first end and the second end of the switching transistor are respectively the high potential end and the low potential end on the current path, and the control end is used to receive a driving signal to control the conduction and turn-off of the switching transistor. Many specific details of the present invention are described below, such as the structure, material, size, processing technology, and technique of the device, so as to understand the present invention more clearly. However, as those skilled in the art can understand, the present invention can be implemented without following these specific details.

[0034] In addition, it should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0035] The present invention can be presented in various forms, and some examples will be described below.

[0036] Figure 3 A schematic circuit diagram showing a switching converter according to an embodiment of the present invention is shown. The switching converter 200 employs a Buck topology and includes a main power circuit and a control circuit. The main power circuit includes switching transistors MD1 and MD2 connected in series between the input terminal and the ground terminal. Switching transistor MD1 is also referred to as the "main switching transistor", and switching transistor MD2 is also referred to as the "synchronous switching transistor". In some embodiments, a rectifier diode can also be used to replace switching transistor MD2 in the figure. Inductor Lx is connected between the intermediate node of switching transistors MD1 and MD2 and the output terminal, output capacitor Cout is connected between the output terminal and the ground terminal, resistor Resr is the equivalent series resistance of output capacitor Cout, and load Rload is connected in parallel across output capacitor Cout. The input terminal of switching converter 200 receives a DC input voltage Vin, and the output terminal provides a DC output voltage Vout. A voltage-dividing network composed of resistors R1 and R2 is used to obtain a first feedback signal FB1 of DC output voltage Vout. A voltage-dividing network composed of resistors R3 and R4 is used to obtain a second feedback signal FB2 of DC output voltage Vout, and the voltage-dividing ratio m = R4 / (R3 + R4).

[0037] The control circuit of switching converter 200 is used to provide switching control signals to switching transistors MD1 and MD2. The control circuit of switching converter 200 includes an error amplifier 210, a PWM comparator 220, a logic and drive circuit 230, a soft start control circuit 240, a ripple compensation circuit 250, a conduction time control circuit 260, and an OR gate 270.

[0038] The ripple compensation circuit 250 is used to provide a ripple signal Ripple. In a feasible embodiment, the ripple compensation circuit 250 is connected to the inductor Lx to provide the ripple signal Ripple. The on-time control circuit 260 is used to generate an on-time signal Ton, so as to control the time conduction mode of the switching converter 200, for example, to make the switching converter 200 operate in a constant on-time control mode (COT, Constant On-Time) or an adaptive on-time control mode (AHPCOT, Adaptive Hysteresis and Pseudo Constant On-Time). The error amplifier 210 is used to obtain an error amplified signal Vea according to the first feedback signal FB1 and the reference voltage Vref. The PWM comparator 220 is used to compare the superimposed signal Vramp of the second feedback signal FB2 and the ripple signal Ripple with the error amplified signal Vea or the soft start output signal Vss to obtain a pulse width modulation signal PWM. One input terminal of the OR gate 270 receives the pulse width modulation signal PWM, the other input terminal receives the on-time signal Ton, and the output terminal provides an on-time control signal. Then the logic and drive circuit 230 is configured to convert the on-time control signal into a switch control signal to control the conduction states of the switching transistors MD1 and MD2.

[0039] In the above embodiment, since the DC component in the superimposed signal Vramp comes from the second feedback signal FB2, the ratio of this DC component to the output voltage Vout is a fixed value. The PWM comparator 220 realizes the soft start control of the output voltage Vout by performing soft start control of loop negative feedback on this DC component.

[0040] Optionally, the soft start control circuit 240 compares the first feedback signal FB1 with a reference signal Vref1 related to the reference voltage Vref, and provides the error amplified signal Vea or the soft start output signal Vss to the PWM comparator 220 according to the comparison result. For example, when the first feedback signal FB1 is lower than the reference signal Vref1, the soft start control circuit 240 provides the soft start output signal Vss to the PWM comparator 220 to realize the soft start control with a constant slope of the DC component in the superimposed signal Vramp. Wherein, the ratio of the reference signal Vref1 to the reference voltage Vref is a predetermined value. Optionally, the value of the reference signal Vref1 is equal to 0.95 times the reference voltage Vref.

[0041] See Figure 4 , Figure 4 shows Figure 3 the circuit structure diagram of the soft start control circuit in. The soft start control circuit 240 includes a first switch K1, a second switch K2, a hysteresis comparator 241, and a soft start signal generation unit 242.

[0042] The soft start signal generation unit 242 includes a current source Iss and a soft start capacitor Css connected in series between the operating voltage Vdd and the ground. Among them, the intermediate node of the current source Iss and the soft start capacitor Css outputs a soft start output signal Vss.

[0043] One end of the first switch K1 receives the error amplification signal Vea, and the other end is connected to the non-inverting input terminal of the PWM comparator 220. One end of the second switch K2 receives the soft start control signal Vss, and the other end is connected to the non-inverting input terminal of the PWM comparator 220. The hysteresis comparator 241 controls the on-off states of the first switch K1 and the second switch K2 according to the comparison result between the first feedback signal FB1 and the reference signal Vref1. An inverter INV2 is also connected between the output terminal of the hysteresis comparator 241 and the first switch K1.

[0044] When the first feedback signal FB1 is less than the reference signal Vref1, the hysteresis comparator 241 controls the first switch K1 to turn off and the second switch K2 to turn on, and provides the soft start output signal Vss to the non-inverting input terminal of the PWM comparator 220. When the first feedback signal FB1 is greater than the reference signal Vref1, the hysteresis comparator 241 controls the first switch K1 to turn on and the second switch K2 to turn off, and provides the error amplification signal Vea to the non-inverting input terminal of the PWM comparator 220.

[0045] When the switch converter 200 starts, the current source Iss charges the soft start capacitor Css to generate a soft start output signal Vss starting from 0, and its slope Kss = Iss / Css. The first feedback signal FB1 is less than the reference signal Vref1, and the hysteresis comparator 241 controls the first switch K1 to turn off and the second switch K2 to turn on, and provides the soft start output signal Vss to the PWM comparator 220. The increase in the output voltage Vout enables the second feedback signal FB2 to follow the soft start output signal Vss, so as to achieve a soft start control with a constant slope for the second feedback signal FB2, and thus achieve a soft start control with a constant slope for the output voltage Vout.

[0046] The slope of the output voltage Vout is:

[0047] Kvout = Kss / m = Iss / (Css*m)

[0048] Where m = R4 / (R3 + R4).

[0049] It can be seen that the slope Kvout of the output voltage Vout is determined by the parameters inside the chip of the switch converter 100, so the slope Kvout is a fixed value.

[0050] Furthermore, in the design and application of the switching converter 200, adopting a soft-start control with a fixed slope of the output voltage Vout makes it easier to predict soft-start indicators such as soft-start current and noise, and can simplify the start-up design of the switching converter 200.

[0051] When the first feedback signal FB1 is greater than the reference signal Vref1, the hysteresis comparator 241 controls the first switch K1 to close, the second switch K2 to conduct, and locks this state. The soft-start control circuit 240 provides the error amplification signal Vea to the PWM comparator 220, and the switching converter 200 enters the normal operating state.

[0052] In a feasible embodiment, the control circuit of the switching converter 200 further includes a compensation network and a capacitor Ce. The compensation network is connected between the output terminal of the error amplifier 210 and the ground. The compensation network includes a compensation resistor Rea and a compensation capacitor Cea. The first terminal of the capacitor Ce is connected to the output terminal of the error amplifier 210, and the second terminal is grounded.

[0053] Figure 5 and Figure 6 respectively show the soft-start stage simulation diagrams of the switching converter according to the embodiments of the present invention. Figure 5 In [a certain situation], the input voltage Vin is set to 3.3V, the output voltage Vout is set to 1.2V, and the load Rload is 1.2Ω. Among them, the coordinates of x1 are (222.3502, 0.4026495), and the coordinates of x2 are (327.4952, 0.9195981). Then, the slope of the output voltage Vout is 4.91653.

[0054] In Figure 6 In [another situation], the input voltage Vin is set to 5.5V, the output voltage Vout is set to 4.0V, and the load Rload is 4.0Ω. Among them, the coordinates of x3 are (532.0683, 1.60374), and the coordinates of x4 are (780.6815, 2.851822). Then, the slope of the output voltage Vout is 5.020177.

[0055] It can be seen that in the case of different output voltages Vout and loads Rload, the switching converter and its control circuit have performed soft-start control at the set slope.

[0056] In summary, in the switching converter and its control circuit according to the embodiments of the present invention, during the startup phase, the soft-start control circuit provides a soft-start output signal to the PWM comparator to perform soft-start control on the superimposed signal of the second feedback signal and the ripple signal. Since the DC component in the superimposed signal comes from the second feedback signal, the ratio of this DC component to the output voltage is a constant value. Therefore, by performing soft-start control of loop negative feedback on this DC component, soft-start control of the output voltage can be achieved, enabling the output voltage to start with a constant slope during the startup phase of the switching converter, solving the problem in the prior art that the soft-start time in a switching converter varies with the change of the output voltage, making it easier to predict soft-start indicators such as soft-start current and noise, and being able to simplify the startup design of the switching converter.

[0057] In the above embodiments, although a buck-type topology switching converter is described in combination with Figure 3 it can be understood that the control circuit according to the embodiments of the present invention can also be used in switching converters with other topologies. The structure of the main power circuit includes, but is not limited to, topologies such as a floating-ground Buck power circuit, a grounded Buck power circuit, a flyback power circuit, a Buck-boost power circuit, and a Boost power circuit.

[0058] It should be noted that those of ordinary skill in the art can understand that the terms "during", "when", and "when... is" used herein in relation to circuit operation are not strict terms indicating an action that occurs immediately at the start of a startup action, but there may be some small but reasonable one or more delays between them and the reaction action initiated by the startup action, such as various transmission delays. The terms "about" or "substantially" used herein mean that an element value has a parameter that is expected to be close to the stated value or position. However, as is well known in the art, there are always small deviations such that the value or position is difficult to be strictly the stated value. It has been appropriately determined in the art that a deviation of at least ten percent (10%) (for semiconductor doping concentration, at least twenty percent (20%)) is a reasonable deviation from the accurately described ideal target. When used in combination with signal states, the actual voltage value or logical state of a signal (e.g., "1" or "0") depends on whether positive logic or negative logic is used.

[0059] As described above with reference to the embodiments of the present invention, these embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the above description. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and its modifications. The protection scope of the present invention shall be subject to the scope defined by the claims of the present invention and their equivalents.

Claims

1. A control circuit for a switching converter, the switching converter using at least one switching transistor to control the power transfer from the input terminal to the output terminal, so as to generate a DC output voltage according to a DC input voltage, wherein, The control circuit includes: an error amplifier for obtaining an error amplified signal based on a first feedback signal of the DC output voltage and a reference voltage; a soft start control circuit for comparing the first feedback signal with a reference signal related to the reference voltage and outputting a soft start output signal or the error amplified signal according to a comparison result; a PWM comparator for comparing a superimposed signal of a second feedback signal of the DC output voltage and a ripple signal with the error amplified signal or the soft start output signal to obtain a pulse width modulation signal; and a logic and drive circuit for converting the pulse width modulation signal into a switch control signal to control an on / off state of the at least one switching transistor, wherein the soft start control circuit is configured to provide the soft start output signal to the PWM comparator when the first feedback signal is lower than the reference signal related to the reference voltage, so as to implement soft start control with a constant slope for the superimposed signal, and the soft start control circuit is further configured to provide the error amplified signal to the PWM comparator when the first feedback signal is higher than the reference signal.

2. The control circuit of the switching converter according to claim 1, wherein the soft start control circuit includes: a first switch having one end receiving the error amplified signal and the other end connected to the non-inverting input terminal of the PWM comparator; a second switch having one end receiving the soft start output signal and the other end connected to the non-inverting input terminal of the PWM comparator; a hysteresis comparator for controlling conduction and cutoff of the first switch and the second switch according to the first feedback signal and the reference signal; and a soft start signal generation unit for generating the soft start output signal.

3. The control circuit according to claim 2, wherein the soft start signal generation unit includes: a current source and a soft start capacitor connected in series between a working voltage and ground, wherein an intermediate node between the current source and the soft start capacitor outputs the soft start output signal.

4. The control circuit of the switching converter according to claim 1, wherein a ratio of the reference signal to the reference voltage is a predetermined value.

5. The control circuit of the switching converter according to claim 1, further including: a conduction time control circuit for generating a conduction time signal; and an OR gate having a first input terminal receiving the pulse width modulation signal, a second input terminal connected to the conduction time control circuit to receive the conduction time signal, and an output terminal providing a conduction time control signal; wherein the logic and drive circuit controls the on / off state of the at least one switching transistor according to the conduction time control signal.

6. The control circuit according to claim 1, further including: a ripple compensation circuit for generating the ripple signal.

7. The control circuit according to claim 1, further including: a compensation resistor and a compensation capacitor connected in series between an output terminal of the error amplifier and ground; and a first capacitor having a first end connected to the output terminal of the error amplifier and a second end grounded.

8. A switching converter includes: The main power circuit uses at least one switching transistor to control the power transmission from the input end to the output end, so as to generate a DC output voltage according to the DC input voltage; and The control circuit according to any one of claims 1-7, which is used to generate a switching control signal to control the on-state of the at least one switching transistor.

9. The switching converter according to claim 8, wherein the main power circuit adopts a topology structure selected from any one of the following: floating ground type Buck power circuit, grounded type Buck power circuit, flyback power circuit, Buck-boost type power circuit, Boost type power circuit.

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