Switching converter and its control circuit

Abstract

The present application discloses a switching converter and a control circuit thereof, wherein the control circuit includes a first error amplifier, a logic and driving circuit, and a reference voltage generating circuit. The reference voltage generating circuit generates a reference voltage by intermittently sampling and holding a DC input voltage. The reference voltage generating circuit is only turned on for a period of time in each clock cycle, and the reference voltage is maintained stable through a holding stage during the remaining time of the clock cycle, which not only ensures the stability of the DC output voltage, but also achieves extremely low static power consumption, which is beneficial to improving the efficiency of the switching converter under light load conditions and realizing an ultra-low power switching converter.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and more specifically, to a switching converter and a control circuit thereof. 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. Switching converters in switching power supplies are widely used due to their high conversion efficiency, large output current, small quiescent current, and wide output load range. In portable devices, the efficiency of the switching converter under light load largely determines the standby time of the portable product system. Therefore, in recent years, the design of low-power, high-efficiency switching converters has become one of the research hotspots of portable devices.

[0003] The power consumption of a switching converter generally consists of three parts: conduction loss, switching loss, and static loss of the analog circuit inside the chip. Among them, the conduction loss is mainly the energy consumed by the current flowing through the on-resistance of the power tube, which increases with the increase of the chip load current. The switching loss is the dynamic loss generated by the charging and discharging of the gate capacitance of the driving power tube in each working cycle. The static loss is the consumption of the analog circuit inside the chip during operation. Both the switching loss and the static loss are independent of the chip load current. Therefore, when the chip is heavily loaded, the conduction loss is the main loss, while when it is lightly loaded, the switching loss and the static loss constitute the main loss of the converter. Since the efficiency of portable devices in standby mode mainly depends on the power consumption of the switching converter under light load, improving the efficiency of the switching converter under light load can effectively extend the battery life of portable devices.

[0004] like Figure 1 FIG. 2 shows a circuit diagram of a switching converter according to the prior art. Figure 1 As shown, the switching converter 100 includes a main circuit and a control circuit integrated in the same integrated circuit chip. The control circuit includes an error amplifier EA, a reference voltage source 110, a logic and drive circuit 120, a current limiting protection circuit 130, a current backflow protection circuit 140, and a light load mode control circuit 150. The main circuit includes discrete components such as a switch tube Q1, a switch tube Q2, an inductor Lx, an output capacitor Cout, and resistors R1 and R2.

[0005] like Figure 1As shown, the light load mode control circuit 150 determines whether the load end of the switching converter 100 is in a light load state by detecting the load current of the converter. When the switching converter 100 is working in a light load state, the light load mode control circuit 150 outputs a sleep signal Sleep of a logic high level, that is, the sleep signal Sleep is valid, and controls the switching converter 100 to enter a sleep state. At this time, most of the working circuits in the switching converter 100 are turned off, such as the current limiting protection circuit 130 and the current backfeed protection circuit 140 stop working, and the static current of the entire converter is reduced accordingly to ensure that the chip can work normally and maintain low power consumption when in a light load state. However, the switching converter 100 of the prior art requires the reference voltage source 110 and the resistor feedback network to remain turned on in a light load state to ensure the stability of the DC output voltage Vout, so the static losses of these two parts are not reduced, which reduces the efficiency of the entire switching converter in a light load state, and cannot achieve an ultra-low power switching converter. Summary of the invention

[0006] In view of the above problems, an object of the present invention is to provide an ultra-low power consumption switching converter and a control circuit thereof, which are helpful to improve the efficiency of the switching converter under light load state.

[0007] According to one aspect of an embodiment of the present invention, a control circuit of a switching converter is provided, wherein the switching converter comprises a first switching tube and a second switching tube connected in series, wherein the first switching tube and the second switching tube are used to control the transmission of electric energy from an input end to an output end so as to convert a DC input voltage into a DC output voltage, wherein the control circuit comprises: a first error amplifier, used to compare the DC output voltage with a reference voltage to obtain an error signal; a logic and drive circuit, used to generate a pulse width modulation signal according to the error signal and convert the pulse width modulation signal into a switch control signal; and a reference voltage generating circuit, used to intermittently sample and hold the DC input voltage so as to generate the reference voltage.

[0008] Optionally, the reference voltage generating circuit includes a first switch, a second switch, a storage capacitor and a voltage stabilizing module, wherein the first end of the first switch is connected to the DC input voltage, and the second end is connected to the input end of the voltage stabilizing module, the first end of the second switch is connected to the output end of the voltage stabilizing module, and the second end is connected to the first end of the storage capacitor, and the second end of the storage capacitor is grounded, wherein the intermediate node between the second switch and the storage capacitor is used to output the reference voltage.

[0009] Optionally, when the first switch and the second switch are turned on, the voltage stabilizing module charges the storage capacitor according to the DC input voltage to generate the reference voltage, and when the first switch and the second switch are turned off, the storage capacitor maintains the stability of the reference voltage.

[0010] Optionally, in each clock cycle, the turn-on time of the first switch and the second switch is equal to 1 / N of the clock cycle, where N is an integer greater than 2.

[0011] Optionally, the reference voltage generating circuit further includes a timing control module for controlling the on and off of the first switch and the second switch.

[0012] Optionally, the voltage stabilization module is implemented by a low voltage drop linear regulator.

[0013] Optionally, the voltage stabilizing module includes: a transistor, a first end of the transistor connected to the second end of the first switch, and a second end connected to the first end of the second switch; a first feedback resistor and a second feedback resistor, connected sequentially between the second end of the transistor and ground; a second error amplifier, a non-phase input terminal connected to the middle node of the first feedback resistor and the second feedback resistor, an inverting input terminal for receiving a reference voltage, and an output terminal connected to the control terminal of the transistor.

[0014] Optionally, the reference voltage generating circuit further includes a bandgap reference voltage source for providing the reference voltage.

[0015] Optionally, the control circuit also includes: a current limiting protection circuit, which obtains a sampling current by detecting the current flowing through the first switch tube, and turns off the first switch tube when the sampling current is greater than a set current value; a current backflow protection circuit, which is used to turn off the second switch tube when the inductor current of the switching converter is less than or equal to zero to prevent current backflow in the inductor; and a light load mode control circuit, which determines whether the load end of the switching converter is in a light load state by detecting the inductor current, wherein the current limiting protection circuit and the current backflow protection circuit are suitable for stopping working when the load end of the switching converter is in a light load state.

[0016] According to another aspect of an embodiment of the present invention, a switching converter is provided, comprising: a main circuit, comprising a first switching tube and a second switching tube connected in series, the first switching tube and the second switching tube being used to control the transmission of electric energy from an input end to an output end, thereby generating a DC output voltage according to a DC input voltage; and the control circuit.

[0017] In the switching converter and its control circuit in the embodiment of the present invention, the reference voltage generating circuit generates a reference voltage by intermittently sampling and holding the DC input voltage. The reference voltage generating circuit is only turned on for a period of time in each clock cycle, and the stability of the reference voltage is maintained through a holding stage in the remaining time of the clock cycle. This not only ensures the stability of the DC output voltage, but also reduces the static loss of the reference voltage generating circuit, which is beneficial to improving the efficiency of the switching converter under light load conditions and realizing an ultra-low power switching converter.

[0018] In a further embodiment, the error amplifier in the switching converter directly compares the DC output voltage with the reference voltage. Compared with the switching converter in the prior art, the feedback network at the output end is omitted, which is beneficial to improving the response speed of the switching converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0020] Figure 1 A circuit diagram of a switching converter according to the prior art is shown;

[0021] Figure 2 A circuit diagram of a switching converter according to an embodiment of the present invention is shown;

[0022] Figure 3 Show Figure 2 A circuit diagram of a reference voltage generating circuit in FIG.

[0023] Figure 4 Show Figure 3 Schematic waveform diagram of the reference voltage generating circuit in . DETAILED DESCRIPTION

[0024] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0025] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuit, a programmable circuit, a state machine circuit and / or an element that can store instructions executed by a programmable circuit. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0026] In the present application, a switch tube is a transistor that works in a switching mode to provide a current path, including one selected from a bipolar transistor or a field effect transistor. The first end and the second end of the switch tube are respectively the high potential end and the low potential end on the current path, and the control end is used to receive a drive signal to control the on and off of the switch tube. MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) includes a first end, a second end and a control end. In the on state of the MOSFET, the current flows from the first end to the second end. The first end, the second end and the control end of the P-type MOSFET are the source, the drain and the gate, respectively, and the first end, the second end and the control end of the N-type MOSFET are the drain, the source and the gate, respectively.

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Figure 2 FIG. 2 shows a circuit diagram of a switching converter according to an embodiment of the present invention. Figure 2 As shown, switching converter 200 includes a main circuit and a control circuit integrated in the same integrated circuit chip.

[0029] The main circuit of the switching converter 200 includes a switch tube Q1 and a switch tube Q2 connected in series between an input terminal and a ground terminal, an inductor Lx connected between an intermediate node of the switch tube Q1 and the switch tube Q2 and an output terminal, and an output capacitor Cout connected between the output terminal and the ground terminal. The input terminal of the main circuit receives a DC input voltage Vin, and the output terminal provides a DC output voltage Vout. The switch tube Q1 and the switch tube Q2 are, for example, respectively referred to as a high-side switch tube and a low-side switch tube. The control circuit of the switching converter 200 is used to provide a switch control signal to the switch tube Q1 and the switch tube Q2. The switch control signal is a drive signal generated according to a pulse width modulation signal. The switch tube Q1, for example, uses a P-type MOSFET, and the switch tube Q2, for example, uses an N-type MOSFET. In each switching cycle, the switch tube Q1 and the switch tube Q2 are alternately turned on and off, so that the inductor Lx alternately stores and supplies electrical energy. When the switch tube Q1 is turned on and the switch tube Q2 is turned off, the inductor Lx starts to store electric energy. When the switch tube Q1 is turned off and the switch tube Q2 is turned on, the inductor Lx starts to supply electric energy to the output capacitor Cout, so that the DC output voltage Vout is stable.

[0030] In other embodiments of the present invention, the switch tube Q1 and the switch tube Q2 may also be other types of transistors, such as NPN Darlington transistors, NPN bipolar transistors, PNP bipolar transistors, etc.

[0031] The control circuit includes an error amplifier EA1 , a reference voltage generating circuit 210 , a logic and driving circuit 220 , a current limiting protection circuit 230 , a current backfeed protection circuit 240 and a light load mode control circuit 250 .

[0032] The error amplifier EA1 compares the DC output voltage Vout with the reference voltage VREF to generate an error signal Verr.

[0033] The reference voltage generating circuit 210 is used to generate a reference voltage VREF inside the chip. Furthermore, the reference voltage generating circuit 210 is used to intermittently sample and hold according to the DC input voltage Vin to generate the reference voltage VREF. In each clock cycle, the reference voltage generating circuit 210 is only turned on for a period of time, and the reference voltage VREF is maintained stable through the holding stage during the remaining time of the clock cycle, which not only ensures the stability of the DC output voltage Vout, but also reduces the static loss of the reference voltage generating circuit 210, which is conducive to improving the light load efficiency of the switching converter 200.

[0034] The logic and drive circuit 220 is used to implement the logic control function of the system, and is used to generate a pulse width modulation signal according to the error signal Verr and the clock signal OSC, and convert the pulse width modulation signal into a switch control signal to control the conduction state of the switch tube Q1 and the switch tube Q2. For example, the logic and drive circuit 220 outputs the control signal PD for the switch control of the switch tube Q1 to the control end of the switch tube Q1, and outputs the control signal ND for the switch control of the switch tube Q2 to the control end of the switch tube Q2.

[0035] The current limiting protection circuit 230 is used to limit the current of the switch tube Q1 and provide short circuit protection. In one embodiment, the current limiting protection circuit 230 compares the current flowing through the switch tube Q1 with the current limiting threshold. When the current is greater than the current limiting threshold, the current limiting protection circuit 230 outputs a current limiting protection signal LIM to the logic and drive circuit 220, so that the logic and drive circuit 220 stops operating. When the logic and drive circuit 220 stops operating, the control signal PD is at a high level, the switch tube Q1 is disconnected, and the output current is stopped from being supplied to the output terminal, thereby reducing the risk of damage to the chip and the subsequent load when the output terminal of the chip is short-circuited.

[0036] The current backfeed protection circuit 240 is used to detect whether the inductor current drops to zero during the inductor freewheeling stage. When the current of the switch tube Q2 drops close to zero, the current backfeed protection circuit 240 outputs a backfeed protection signal REV. The logic and drive circuit 220 outputs a control signal ND of a low level according to the backfeed protection signal REV, turns off the switch tube Q2, and prevents the current in the inductor from backflowing.

[0037] The light load mode control circuit 250 determines whether the load end of the switching converter 200 is in a light load state by detecting the load current of the converter. For example, the light load mode control circuit 250 determines whether the load end of the switching converter 200 is in a light load state by detecting the DC output voltage Vout and the error signal Verr. When the switching converter 200 is operating in a light load state, the light load mode control circuit 250 outputs a sleep signal Sleep at a logic high level, that is, the sleep signal Sleep is valid, and controls the switching converter 200 to enter a sleep state. At this time, most of the working circuits in the switching converter 200 are turned off, such as the current limiting protection circuit 230 and the current backfeed protection circuit 240 stop working, and the current in the error amplifier EA1 is reduced, and the quiescent current of the entire converter is reduced accordingly, so as to ensure that the chip can work normally and maintain low power consumption when in a light load state.

[0038] In the switching converter 200 of the present embodiment, the reference voltage generating circuit 210 generates the reference voltage VREF by intermittently sampling and holding the DC input voltage Vin. The reference voltage generating circuit 210 is only turned on for a period of time in each clock cycle, and the stability of the reference voltage VREF is maintained through a holding stage during the remaining time of the clock cycle. This not only ensures the stability of the DC output voltage Vout, but also reduces the static loss of the reference voltage generating circuit 210, thereby helping to improve the efficiency of the switching converter 200 under light load conditions and realize an ultra-low power switching converter.

[0039] Figure 3 Show Figure 2 The circuit diagram of the reference voltage generating circuit in FIG. Figure 3 As shown, the reference voltage generating circuit 210 includes a bandgap reference voltage source 211 , a voltage stabilizing module 212 , a timing control module 213 , a switch K1 , a switch K2 , and a storage capacitor C1 .

[0040] The bandgap reference voltage source 211 is used to generate a bandgap reference voltage inside the chip, for example, to provide a reference voltage of 0.85V, 0.8V, or 0.3V, as a reference for the voltage stabilizing module 212. The first end of the switch K1 is connected to the DC input voltage Vin, and the second end is connected to the input end of the voltage stabilizing module 212. The first end of the switch K2 is connected to the output end of the voltage stabilizing module 212, and the second end is connected to the first end of the storage capacitor C1. The second end of the storage capacitor C1 is grounded, and the intermediate node between the switch K2 and the storage capacitor C1 is used to output the reference voltage VREF. The timing control module 213 is used to control the on and off of the switch K1 and the switch K2. In the case where the switch K1 and the switch K2 are turned on, the voltage stabilizing module 212 charges the storage capacitor C1 according to the DC input voltage Vin and the reference voltage Vb, and the voltage at the first end of the storage capacitor C1 increases, thereby generating the reference voltage VREF. In the case where the switch K1 and the switch K2 are turned off, the stability of the reference voltage VREF is maintained by the holding state of the storage capacitor C1.

[0041] Further, the voltage stabilizing module 212 is implemented by a low voltage drop linear regulator. For example, the voltage stabilizing module 212 includes: a transistor M1, an error amplifier EA2, and feedback resistors Rf1 and Rf2. The first end of the transistor M1 is connected to the second end of the switch K1, and the second end is connected to the first end of the switch K2. The feedback resistors Rf1 and Rf2 are connected between the second end of the transistor M1 and the ground in sequence. The non-inverting input end of the error amplifier EA2 is connected to the middle node of the feedback resistors Rf1 and Rf2, and the inverting input end is used to receive the reference voltage Vb. The output end is connected to the control end of the transistor M1. The error amplifier EA2 is used to control the control end voltage of the transistor M1 according to the error between the feedback voltage obtained by the feedback resistors Rf1 and Rf2 and the reference voltage Vb, thereby converting the DC input voltage Vin into a stable output voltage, stably charging the storage capacitor C1, and then obtaining the reference voltage VREF (wherein, the reference voltage VREF = Vb*(Rf1+Rf2) / Rf2).

[0042] In this embodiment, the feedback resistor in the voltage stabilizing module 212 is used to replace the resistor in the feedback loop of the switching converter, thereby eliminating the feedback network at the output end, which is beneficial to improving the response speed of the switching converter.

[0043] Figure 4 Show Figure 3 Schematic waveform diagram of the reference voltage generating circuit in . Figure 4In the figure, curves CLK_SH and SH respectively represent the clock signal inside the timing control module 213 and the sampling and holding signal related to the switch K1 and the switch K2. The clock signal CLK_SH is a square wave signal with a period of T. In each clock period T, the sampling and holding signal SH is a pulse signal triggered by the rising edge of the clock signal CLK_SH and lasts for the first time period t1. The sampling and holding signal SH is used to control the on and off of the switch K1 and the switch K2. In the first time period t1, the switch K1 and the switch K2 are turned on, and the voltage stabilizing module obtains the reference voltage VREF according to the DC input voltage Vin. In the second time period t2, the switch K1 and the switch K2 are turned off, and the reference voltage VREF is kept stable by the storage voltage C1. Among them, the first time period t1=T / N, N is an integer greater than 2. It can be seen that compared with the converter in the prior art, the reference voltage generating circuit 210 in the switching converter of this embodiment consumes a quiescent current of Iq / N in each clock cycle T (Iq is the quiescent current consumed by the reference voltage source, resistor R1 and resistor R2 in the switching converter in the prior art), thereby greatly reducing the static loss of the reference voltage generating circuit 210, which is beneficial to improving the efficiency of the switching converter 200 under light load conditions and realizing an ultra-low power consumption switching converter.

[0044] In the above embodiment, although the combination Figure 2 A switching converter with a buck topology is described; however, it can be understood that the reference voltage generating circuit can also be applied to switching converters with other topologies, including but not limited to buck, boost, buck-boost, non-inverting buck-boost, forward, flyback and other topologies.

[0045] To summarize, in the switching converter and its control circuit in the embodiment of the present invention, the reference voltage generating circuit generates a reference voltage by intermittently sampling and holding the DC input voltage. The reference voltage generating circuit is only turned on for a period of time in each clock cycle, and the stability of the reference voltage is maintained through a holding stage in the remaining time of the clock cycle. This not only ensures the stability of the DC output voltage, but also reduces the static loss of the reference voltage generating circuit, which is beneficial to improving the efficiency of the switching converter under light load conditions and realizing an ultra-low power switching converter.

[0046] In a further embodiment, the error amplifier in the switching converter directly compares the DC output voltage with the reference voltage. Compared with the switching converter in the prior art, the feedback network at the output end is omitted, which is beneficial to improving the response speed of the switching converter.

[0047] It should be noted that although in this article, the device is described as a certain N-channel or P-channel device, or a certain N-type or P-type doped region, it can be understood by those skilled in the art that complementary devices can also be realized according to the present invention. It can be understood by those skilled in the art that the conductivity type refers to the mechanism by which the conduction occurs, such as conduction by holes or electrons, so the conductivity type does not involve the doping concentration but the doping type, such as P-type or N-type. It can be understood by those skilled in the art that the words "during", "when" and "when..." used in this article in connection with the operation of the circuit are not strict terms indicating the action that occurs immediately when the start-up action begins, but there may be some small but reasonable one or more delays between it and the reaction action initiated by the start-up action, such as various transmission delays, etc. The words "approximately" or "substantially" used in this article mean that the element value has a parameter that is expected to be close to the declared value or position. However, as is well known in the art, there are always slight deviations that make it difficult for the value or position to be strictly the declared value. It has been well established in the art that a deviation of at least ten percent (10%) (or at least twenty percent (20%) for semiconductor doping concentrations) is a reasonable deviation from the exact ideal goal described. When used in conjunction with a signal state, the actual voltage value or logic state (e.g., "1" or "0") of the signal depends on whether positive logic or negative logic is used.

[0048] In addition, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0049] According to the embodiments of the present invention, as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments 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 the modified use based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A control circuit of a switching converter, the switching converter comprising a first switching tube and a second switching tube connected in series, the first switching tube and the second switching tube are used to control the transmission of electric energy from an input end to an output end, so as to convert a DC input voltage into a DC output voltage, wherein: The control circuit comprises: A first error amplifier, used for comparing the DC output voltage with a reference voltage to obtain an error signal; a logic and driving circuit for generating a pulse width modulation signal according to the error signal and converting the pulse width modulation signal into a switch control signal; and A reference voltage generating circuit is used to intermittently sample and hold the DC input voltage to generate the reference voltage. The reference voltage generating circuit includes a first switch, a second switch, a storage capacitor and a voltage stabilizing module, wherein a first end of the first switch is connected to the DC input voltage, and a second end is connected to an input end of the voltage stabilizing module, a first end of the second switch is connected to an output end of the voltage stabilizing module, and a second end is connected to a first end of the storage capacitor, and a second end of the storage capacitor is grounded, wherein an intermediate node between the second switch and the storage capacitor is used to output the reference voltage, When the first switch and the second switch are turned on, the voltage stabilizing module charges the storage capacitor according to the DC input voltage to generate the reference voltage. When the first switch and the second switch are turned off, the storage capacitor maintains the stability of the reference voltage.

2. The control circuit according to claim 1, characterized in that: In each clock cycle, the turn-on time of the first switch and the second switch is equal to 1 / N of the clock cycle, where N is an integer greater than 2.

3. The control circuit according to claim 1, characterized in that: The reference voltage generating circuit further includes a timing control module for controlling the on and off of the first switch and the second switch.

4. The control circuit according to claim 1, characterized in that: The voltage stabilization module is implemented by a low voltage drop linear regulator.

5. The control circuit according to claim 4, characterized in that: The voltage stabilizing module comprises: a transistor, wherein a first end of the transistor is connected to the second end of the first switch, and a second end of the transistor is connected to the first end of the second switch; A first feedback resistor and a second feedback resistor are connected in sequence between the second end of the transistor and the ground; The second error amplifier has a non-phase input terminal connected to the middle node between the first feedback resistor and the second feedback resistor, an inverting input terminal for receiving a reference voltage, and an output terminal connected to the control terminal of the transistor.

6. The control circuit according to claim 5, characterized in that: The reference voltage generating circuit also includes a bandgap reference voltage source for providing the reference voltage.

7. The control circuit according to claim 1, characterized in that: Also includes: A current limiting protection circuit, which detects the current flowing through the first switch tube to obtain a sampling current, and turns off the first switch tube when the sampling current is greater than a set current value; A current backflow protection circuit, used to turn off the second switch tube when the inductor current of the switching converter is less than or equal to zero, so as to prevent the current in the inductor from backflowing; as well as The light load mode control circuit determines whether the load end of the switching converter is in a light load state by detecting the inductor current. The current limiting protection circuit and the current backfeed protection circuit are suitable for stopping working when the load end of the switching converter is in a light load state.

8. A switching converter, characterized in that: include: A main circuit, comprising a first switch tube and a second switch tube connected in series, wherein the first switch tube and the second switch tube are used to control the transmission of electric energy from the input end to the output end, thereby generating a DC output voltage according to a DC input voltage; And a control circuit according to any one of claims 1 to 7.

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