Switching converter and its control circuit

Abstract

This application discloses a switching converter and its control circuit. The circuit includes a hysteresis control circuit, logic and drive circuits, a light-load mode detection circuit, and an output monitoring circuit. The light-load mode detection circuit provides a high-level light-load indication signal at the load end of the switching converter to control the switching converter to operate in light-load mode. This shuts down the hysteresis control circuit and other modules of the system, while simultaneously enabling the output monitoring circuit. In this mode, most of the operating circuits in the switching converter are shut down, and only the output of the switching converter is monitored by the output monitoring circuit. The quiescent current of the entire converter decreases accordingly, thereby ensuring that the chip can operate normally and maintain low power consumption under light-load conditions.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and more specifically, to a switching converter and its control circuit. Background Technology

[0002] With the increasing demand for power electronic products and the development of semiconductor technology, power management chips are being used more widely in portable computers, mobile phones, personal digital assistants, and other portable or non-portable electronic devices. Switching converters use power switches to control the transfer of electrical energy from the input to the output, thus providing a constant output voltage and / or output current. In switching converters, the ripple-based constant on-time control method, evolved from hysteresis mode, has advantages such as constant system frequency, good light-load efficiency, fast transient response, and ease of implementation, and has therefore been widely used in recent years.

[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 switching transistors MD1 and MD2 connected in series between the input terminal and ground. An inductor Lx is connected between the intermediate node of switching transistors MD1 and MD2 and the output terminal. An output capacitor Cout is connected between the output terminal and ground. The input terminal of the switching converter 100 receives a DC input voltage Vin, and the output terminal provides a DC output voltage Vout. The control circuit of the switching converter 100 provides switching control signals to the switching transistors MD1 and MD2.

[0004] In the control circuit of the switching converter 100, the on-time control circuit 110 sets a fixed on-time Ton for the switching period Tsw, thereby generating a reset signal. The minimum off-time control circuit 120 sets a minimum off-time Toff_min (or maximum switching frequency) corresponding to a predetermined output voltage and a predetermined load. The error amplifier EA obtains an error signal Vcomp based on the feedback signal FB of the DC output voltage Vout and the reference voltage Vref. The PWM comparator 131 compares the error signal Vcomp with the feedback signal FB to obtain an intermediate signal. The two inputs of the NAND gate 132 receive the intermediate signal output by the comparator and the minimum off-time Toff_min, respectively, and the output provides a set signal. The RS flip-flop 140 generates a pulse width modulation signal PWM based on the reset signal and the set signal. The drive circuit 150 converts the pulse width modulation signal PWM into a switching control signal to control the conduction state of the switching transistors MD1 and MD2.

[0005] The power consumption of a switching converter generally consists of three parts: conduction loss, switching loss, and static losses of the internal analog circuitry. Conduction loss is mainly the energy consumed by current flowing through the on-resistance of the power transistor, increasing with the chip's load current. Switching loss is the dynamic loss generated during each duty cycle due to the charging and discharging of the power transistor's gate capacitance. Static losses are the energy consumed by the internal analog circuitry during operation; both switching and static losses are independent of the chip's load current. Therefore, under heavy load, conduction loss is the primary loss, while under light load, switching and static losses constitute the main losses of the switching converter. Since the standby efficiency and standby time of portable devices largely depend on the power consumption of the switching converter under light load, the design of low-power and high-efficiency switching converters has become one of the key research focuses for current portable devices. Summary of the Invention

[0006] In view of the above problems, the purpose of this invention is to provide a low-power and high-efficiency switching converter and its control circuit, which can reduce the static current of the switching converter under light load, and ensure that the chip can work normally and maintain low power consumption under light load.

[0007] According to one aspect of the present invention, a control circuit for a switching converter is provided. The switching converter uses at least one switching transistor to control the power transfer from the input terminal to the output terminal, thereby generating a DC output voltage based on a DC input voltage. The control circuit includes: a hysteresis control circuit for generating a pulse width modulation (PWM) signal based on a first feedback signal of the DC output voltage, a second feedback signal of the DC output voltage, and a superimposed signal of a ripple signal; a logic and drive circuit for converting the PWM signal into a switching control signal to control the conduction state of the at least one switching transistor; a light load mode detection circuit for detecting the switching node voltage of the switching converter to determine whether the load terminal of the switching converter is in a light load state, and providing a light load indication signal characterizing the determination result; the light load mode detection circuit is used to provide a logic high-level light load indication signal to turn off the hysteresis control circuit when the load terminal is in a light load state, thereby controlling the switching converter to operate in a light load mode; and an output monitoring circuit for monitoring the first feedback signal when the switching converter is operating in the light load mode, and providing a wake-up signal to the logic and drive circuit when the first feedback signal is less than a preset reference voltage, thereby controlling the switching converter to operate in a normal mode.

[0008] Optionally, the control circuit further includes: an on-time control circuit for generating a first on-time, wherein the logic and drive circuit controls the switching converter to operate in a hysteresis control mode or an adaptive on-time control mode based on a comparison result of the on-time of the pulse width modulation signal and the first on-time.

[0009] Optionally, the control circuit further includes a minimum turn-off time control circuit for generating a minimum turn-off time, wherein the turn-off time determined by the pulse width modulation signal is greater than the minimum turn-off time.

[0010] Optionally, the control circuit further includes a ripple compensation circuit for generating the ripple signal.

[0011] Optionally, the logic and driving circuit are configured to: control the switching converter to operate in an adaptive on-time control mode when the on-time of the pulse width modulation signal is less than the first on-time, and control the switching converter to operate in a hysteresis control mode when the on-time of the pulse width modulation signal is greater than the first on-time.

[0012] Optionally, the first conduction time is the minimum conduction time of the at least one switching transistor in the hysteresis control mode.

[0013] Optionally, the hysteresis control circuit includes: an error amplifier, whose inverting input and non-inverting input respectively receive the first feedback signal and the first reference voltage, and whose output is used to provide an error signal; and a hysteresis comparator, whose inverting input and non-inverting input respectively receive the superimposed signal and the error signal, and whose output is used to provide the pulse width modulation signal, wherein the power supply terminals of the error amplifier and the hysteresis comparator are connected to the light load indication signal, and when the light load indication signal is at a logic high level, the error amplifier and the hysteresis comparator are turned off.

[0014] Optionally, the hysteresis control circuit further includes: a compensation resistor and a compensation capacitor connected in sequence between the output terminal of the error amplifier and ground; and a first capacitor, with its first end connected to the output terminal of the error amplifier and its second end grounded.

[0015] Optionally, the hysteresis control circuit further includes: a first transistor, with a first terminal connected to the second feedback signal and a second terminal connected to the output terminal of the error amplifier, and a control terminal receiving the light load indication signal, wherein when the light load indication signal is at a logic high level, the first transistor is turned on to short-circuit the output terminal of the error amplifier with the second feedback signal.

[0016] Optionally, the light load mode detection circuit includes: a zero-crossing comparator, with its non-inverting input receiving the switching node voltage, its inverting input receiving a reference ground voltage, and its output providing a zero-crossing indication signal; and a judgment unit, with its input connected to the output of the zero-crossing comparator to receive the zero-crossing indication signal, the judgment unit being used to output a logic high-level light load indication signal when the high-level time of the zero-crossing indication signal is greater than a preset time.

[0017] Optionally, the output monitoring circuit includes: a first comparator, whose inverting input and non-inverting input respectively receive the first error signal and the reference voltage, and whose output is used to provide a comparison signal between the two; and an AND gate, whose first input receives the light load indication signal, whose second input is connected to the output of the first comparator to receive the comparison signal, and whose output is used to provide the wake-up signal.

[0018] Optionally, the hysteresis comparator is configured to adaptively adjust its hysteresis voltage according to the DC output voltage to stabilize the switching frequency.

[0019] Optionally, the hysteresis voltage is equal to the product of the DC output voltage and a proportionality coefficient.

[0020] According to another aspect of the present invention, a switching converter is provided, comprising: a main power circuit that uses at least one switching transistor to control the transfer of electrical energy from the input terminal to the output terminal, thereby generating a DC output voltage based on a DC input voltage; and the aforementioned control circuit for generating a switching control signal to control the conduction state of the at least one switching transistor.

[0021] Optionally, the main power circuit adopts a topology selected from any of the following: floating Buck power circuit, ground Buck power circuit, flyback power circuit, Buck-boost power circuit, and Boost power circuit.

[0022] The switching converter and its control circuit in this embodiment of the invention further include a light load mode detection circuit and an output monitoring circuit. The light load mode detection circuit determines whether the load end of the switching converter is in a light load state based on the switching node voltage of the switching converter. When the switching converter is in a light load state, it outputs a light load indication signal at a logic high level, controls the switching converter to enter the light load mode, shuts down the hysteresis control circuit and other modules of the system, and simultaneously turns on the output monitoring circuit. At this time, most of the working circuits in the switching converter are shut down, and the static current of the entire converter is reduced accordingly, ensuring that the chip can work normally and maintain low power consumption in the light load state.

[0023] Optionally, the hysteresis control circuit uses a high DC gain error amplifier, which helps to improve the output accuracy of the switching converter.

[0024] Optionally, the hysteresis comparator in the hysteresis control circuit adopts an adaptive hysteresis voltage architecture, which allows the switching converter to adaptively change the size of the hysteresis window according to the DC output voltage to maintain the relative stability of the switching frequency. This improves the problem of large frequency variation range in the hysteresis control mode and helps to improve the frequency stability and light-load efficiency of the system.

[0025] Optionally, the hysteresis comparator compares the superimposed signal of the ripple signal and the second feedback signal with the error signal to generate a pulse width modulation signal. Since the ripple signal provides an AC signal in phase with the inductor current, it ensures that changes in the DC output voltage can be quickly reflected to the hysteresis comparator to make corresponding switching actions, thereby improving the transient response speed of the switching converter.

[0026] Optionally, the hysteresis control circuit also includes a transistor connected between the output of the error amplifier and the second feedback signal. The transistor is turned on when the light load indicator is at a logic high level, shorting the output of the error amplifier and the second feedback signal. This can maintain the DC operating point voltage of the error signal, thereby enabling the error signal to be quickly established when the switching converter switches from light load mode to normal mode, achieving a smooth switching between the light load mode and normal mode of the switching converter. Attached Figure Description

[0027] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0028] Figure 1 A schematic circuit diagram of a switching converter according to the prior art is shown;

[0029] Figure 2 A schematic circuit diagram of a switching converter according to an embodiment of the present invention is shown;

[0030] Figure 3 A schematic circuit diagram of a hysteresis control circuit for a switching converter according to an embodiment of the present invention is shown.

[0031] Figure 4 A schematic circuit diagram of a light-load mode detection circuit for a switching converter according to an embodiment of the present invention is shown.

[0032] Figure 5 A schematic circuit diagram of the output monitoring circuit of a switching converter according to an embodiment of the present invention is shown. Detailed Implementation

[0033] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale. Furthermore, some well-known parts may not be shown.

[0034] It should be understood that, in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0035] In this application, the switching transistor is a transistor that operates in switching mode to provide a current path, including a bipolar transistor or a field-effect transistor. The first terminal and the second terminal of the switching transistor are respectively the high potential terminal and the low potential terminal on the current path, and the control terminal is used to receive a drive signal to control the switching transistor to turn on and off.

[0036] This invention can be presented in various forms, some of which will be described below.

[0037] Figure 2 A schematic circuit diagram of a switching converter according to an embodiment of the present invention is shown. The switching converter 200 employs a Buck topology and operates in floating ground mode. It 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 ground terminal. An inductor Lx is connected between the intermediate node of switching transistors MD1 and MD2 and the output terminal. An output capacitor Cout is connected between the output terminal and ground terminal. A resistor Resr is the equivalent series resistance of the output capacitor Cout. A load RL is connected in parallel across the output capacitor Cout. The input terminal of the switching converter 200 receives a DC input voltage Vin, and the output terminal provides a DC output voltage Vout. A voltage divider network composed of resistors R1 and R2 is used to obtain a first feedback signal FB1 for the DC output voltage Vout. A voltage divider network composed of resistors R3 and R4 is used to obtain a second feedback signal FB2 for the DC output voltage Vout. A capacitor Cc is connected in parallel across resistor R1.

[0038] The control circuit of the switching converter 200 is used to provide switching control signals to the switching transistors MD1 and MD2. The control circuit of the switching converter 200 includes an on-time control circuit 210, a minimum off-time control circuit 220, a hysteresis control circuit 230, a logic and drive circuit 240, a ripple compensation circuit 250, a light-load mode detection circuit 260, and an output monitoring circuit 270.

[0039] The conduction time control circuit 210 sets the first conduction time Ton1 of the switching period Tsw. Further, the first conduction time Ton1 is set as follows:

[0040] Ton1 = Vout / Vin * Tsw

[0041] Where Vout represents the DC output voltage value, Vin represents the DC input voltage value, and Tsw represents the switching cycle of the switching converter, which can ensure the consistency of the operating frequency of the switching converter.

[0042] The minimum off-time control circuit 220 is used to set the minimum off-time Toff_min (or maximum switching frequency) corresponding to the predetermined output voltage and predetermined load.

[0043] Ripple compensation circuit 260 is connected to inductor Lx to provide ripple signal Ripple. Hysteresis control circuit 230 is used to generate pulse width modulation signal PWM based on the superposition signal Vramp of first feedback signal FB1, second feedback signal FB2 and ripple signal Ripple.

[0044] The logic and drive circuit 240 is used to implement the logic control function of the system and to generate a switch control signal based on the pulse width modulation signal PWM, the first on time Ton1 and the minimum off time Toff_min to control the on state of the switching transistors MD1 and MD2.

[0045] Furthermore, the logic and drive circuit 250 controls the switching converter 200 to operate in either a hysteresis control mode or an adaptive on-time control mode based on the comparison result between the on-time Ton determined by the pulse width modulation signal (PWM) and the first on-time Ton1. When the on-time Ton determined by the PWM is greater than the first on-time Ton1, the switching converter 200 operates in hysteresis control mode, and the off-time of the switch MD1 is determined by the PWM; when the on-time Ton determined by the PWM is less than the first on-time Ton1, the switching converter 200 operates in adaptive on-time control mode, and the off-time of the switch MD1 is determined by the first on-time Ton1.

[0046] Furthermore, the first conduction time Ton1 is set as the minimum conduction time of the switch MD1 in the hysteresis control mode. When the conduction time Ton determined by the pulse width modulation signal PWM is less than the first conduction time Ton1, the conduction time of the switch MD1 is limited to the first conduction time Ton1. Since the first conduction time Ton1 is adaptive to a fixed frequency, it can ensure that the system operates in a pseudo-fixed frequency state, retaining the advantages of fast transient response and high efficiency under light load in the hysteresis control mode. At the same time, it improves the problem of large frequency variation range in the hysteresis control mode, which is conducive to improving the frequency stability and efficiency under light load of the system.

[0047] The light-load mode detection circuit 260 determines whether the load side of the switching converter 200 is in a light-load state by detecting the switching node voltage Vsw of the converter. For example, when the switching node voltage Vsw is greater than zero for a preset time, the light-load mode detection circuit 260 determines that the switching converter 200 is in a light-load state, outputs a light-load indication signal PSM at a logic high level, controls the switching converter 200 to enter the light-load mode, shuts down the hysteresis control circuit 230 and other modules of the system, and simultaneously turns on the output monitoring circuit 270. At this time, most of the working circuits in the switching converter 200 are shut down, and the static current of the entire converter decreases accordingly to ensure that the chip can work normally and maintain low power consumption in the light-load state.

[0048] The input terminal of the output monitoring circuit 270 receives the first feedback signal FB1 and the light load indication signal PSM. The output monitoring circuit 270 is used to monitor the first feedback signal FB1 when the light load indication signal PSM is at a logic high level, and to provide a wake-up signal Wake to the logic and drive circuit 240 when the first feedback signal FB1 is less than a preset reference voltage. The logic and drive circuit 240 turns on the switching transistor MD1 according to the wake-up signal Wake, and turns on the hysteresis control circuit 230 and other modules of the system to ensure that the system can work normally.

[0049] Figure 3 A schematic circuit diagram of a hysteresis control circuit for a switching converter according to an embodiment of the present invention is shown. Figure 3 As shown, the hysteresis control circuit 230 includes an error amplifier EA and a hysteresis comparator 231. The inverting input of the error amplifier EA receives a first feedback signal FB1, and the non-inverting input receives a reference voltage Vref. The error amplifier EA compares the first feedback signal FB1 with the reference voltage Vref to obtain an error signal Vcomp. The inverting input of the hysteresis comparator 231 receives a superimposed signal Vramp of a second feedback signal FB2 and a ripple signal Ripple. The hysteresis comparator 231 compares the superimposed signal Vramp with the error signal Vcomp to generate the pulse width modulation signal PWM. The power supply terminals of the error amplifier EA and the hysteresis comparator 231 are connected to the light load indication signal PSM. When the light load indication signal PSM is at a logic high level, the error amplifier EA and the hysteresis comparator 231 are turned off.

[0050] In this embodiment, the hysteresis control circuit 230 employs a high DC gain error amplifier EA, which is beneficial for improving the output accuracy of the switching converter. Furthermore, the hysteresis comparator 231 in the hysteresis control circuit 230 adopts an adaptive hysteresis voltage architecture. The hysteresis voltage Vhys = K% × Vout of the hysteresis comparator 231 allows the switching converter to adaptively change the size of the hysteresis window according to the DC output voltage, maintaining relative stability of the switching frequency. This improves the problem of large frequency variation range in the hysteresis control mode, and is beneficial for improving the frequency stability and light-load efficiency of the system. Moreover, the ripple signal Ripple provides an AC signal in phase with the inductor current. The hysteresis comparator 231 compares the superimposed signal Vramp with the error signal Vcomp, and directly controls the on and off of the switching transistor based on the comparison result. This ensures that changes in the DC output voltage Vout can be quickly reflected to the hysteresis comparator to make corresponding switching actions, giving the switching converter 200 excellent transient response.

[0051] Furthermore, the hysteresis control circuit 230 also includes a compensation network and a capacitor Ce. The compensation network is connected between the output of the error amplifier EA and ground. The compensation network includes a compensation resistor Rea and a compensation capacitor Cea. The first end of the capacitor Ce is connected to the output of the error amplifier EA, and the second end is grounded.

[0052] Furthermore, the hysteresis control circuit 230 also includes a transistor M1 connected between the output of the error amplifier EA and the second feedback signal FB2. The control terminal of the transistor M1 receives the light load indication signal PSM. The transistor M1 is implemented, for example, using an NMOS transistor. When the light load indication signal PSM is at a logic high level, the transistor M1 is turned on, shorting the output of the error amplifier EA and the second feedback signal FB2, maintaining the DC operating point voltage of the error signal Vcomp. This allows the error signal Vcomp to be quickly established when the switching converter 200 switches from light load mode to normal mode, achieving a smooth switching between the light load mode and normal mode of the switching converter.

[0053] Figure 4 A schematic circuit diagram of a light-load mode detection circuit for a switching converter according to an embodiment of the present invention is shown. Figure 4As shown, the light-load mode detection circuit 260 includes a zero-crossing comparator 261 and a judgment unit 262. The non-inverting input of the zero-crossing comparator 261 receives the switching node voltage Vsw, and the inverting input receives a zero-crossing reference value. The zero-crossing comparator 261 provides a zero-crossing indication signal ZCD based on the switching node voltage Vsw and the zero-crossing reference value. This zero-crossing indication signal ZCD characterizes whether the inductor current flowing through the inductor Lx has decreased to 0. The zero-crossing reference value is, for example, a reference ground voltage. When the switching node voltage Vsw is greater than the reference ground voltage, the zero-crossing comparator 261 outputs a logic high-level zero-crossing indication signal ZCD to indicate that the inductor current has crossed zero; when the switching node voltage Vsw is less than or equal to the reference ground voltage, the zero-crossing comparator 261 outputs a logic low-level zero-crossing indication signal ZCD to indicate that the inductor current has not crossed zero.

[0054] The judgment unit 262 is used to determine whether the load terminal of the switching converter 200 is in a light load state based on the received zero-crossing indication signal ZCD. For example, when the high-level time of the zero-crossing indication signal ZCD is greater than a preset time, the judgment unit 262 outputs a logic high-level light load indication signal PSM to indicate that the load terminal of the switching converter 200 is in a light load state.

[0055] Figure 5 A schematic circuit diagram of the output monitoring circuit of a switching converter according to an embodiment of the present invention is shown. Figure 5 As shown, the output detection circuit 270 includes a comparator 271 and an AND gate 272. The inverting input of comparator 271 receives a first feedback signal FB1, and the non-inverting input receives a reference voltage Vref. Comparator 271 compares the first feedback signal FB1 with the reference voltage Vref to obtain a comparison signal. One input of AND gate 272 receives a light load indication signal PSM, and the other input is connected to the output of comparator 271 to receive the comparison signal. The output is used to output the wake-up signal Wake. When the switching converter 200 is in light load mode, comparator 271 compares the first feedback signal FB1 with the reference voltage Vref, and outputs a logic high-level comparison signal when the first feedback signal FB1 is less than the reference voltage Vref. AND gate 272 outputs a logic high-level wake-up signal Wake based on the logic high-level comparison signal and the logic high-level light load indication signal PSM, indicating that the logic and drive circuit 240 turns on the switching transistor MD1 and starts other modules of the system, ensuring the system can operate normally.

[0056] In summary, in the switching converter and its control circuit of this embodiment, the control circuit further includes a light-load mode detection circuit and an output monitoring circuit. The light-load mode detection circuit determines whether the load end of the switching converter is in a light-load state based on the switching node voltage of the switching converter, and outputs a light-load indication signal at a logic high level when the switching converter is in a light-load state, controlling the switching converter to enter the light-load mode, shutting down the hysteresis control circuit and other modules of the system, and simultaneously turning on the output monitoring circuit. At this time, most of the working circuits in the switching converter are shut down, and the static current of the entire converter is reduced accordingly, ensuring that the chip can work normally and maintain low power consumption in the light-load state.

[0057] In an optional embodiment, the hysteresis control circuit employs a high DC gain error amplifier, which is beneficial for improving the output accuracy of the switching converter.

[0058] In an optional embodiment, the hysteresis comparator in the hysteresis control circuit adopts an adaptive hysteresis voltage architecture, which enables the switching converter to adaptively change the size of the hysteresis window according to the DC output voltage to maintain the relative stability of the switching frequency. This improves the problem of large frequency variation range in the hysteresis control mode and helps to improve the frequency stability and light-load efficiency of the system.

[0059] In an optional embodiment, the hysteresis comparator compares the superimposed signal of the ripple signal and the second feedback signal with the error signal to generate a pulse width modulation signal. Since the ripple signal provides an AC signal in phase with the inductor current, it ensures that changes in the DC output voltage can be quickly reflected to the hysteresis comparator to make corresponding switching actions, thereby improving the transient response speed of the switching converter.

[0060] In an optional embodiment, the hysteresis control circuit further includes a transistor connected between the output of the error amplifier and the second feedback signal. The transistor is turned on when the light load indicator is at a logic high level, shorting the output of the error amplifier and the second feedback signal. This maintains the DC operating point voltage of the error signal, thereby enabling the error signal to be quickly established when the switching converter switches from light load mode to normal mode, achieving a smooth switching between the light load mode and normal mode of the switching converter.

[0061] In the above embodiments, although combined Figure 2 A buck converter topology has been described. However, it is understood that the control circuit 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, floating-ground Buck power circuits, ground-ground Buck power circuits, flyback power circuits, Buck-boost power circuits, and Boost power circuits.

[0062] In the above description, well-known structural elements and steps have not been described in detail. However, those skilled in the art should understand that the corresponding structural elements and steps can be implemented through various technical means. Furthermore, in order to form the same structural elements, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0063] As described above, these embodiments of the present invention do not exhaustively describe all details, nor do they limit the invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The scope of protection of this invention should be determined by the scope defined in the claims of this invention.

Claims

1. A control circuit for a switching converter, wherein the switching converter uses at least one switching transistor to control the transfer of electrical energy from the input terminal to the output terminal, thereby generating a DC output voltage based on the DC input voltage, wherein, The control circuit includes: A hysteresis control circuit is used to generate a pulse width modulation signal based on the first feedback signal of the DC output voltage, the second feedback signal of the DC output voltage, and the superposition signal of the ripple signal. The logic and driving circuitry converts the pulse width modulation signal into a switching control signal to control the conduction state of at least one switching transistor. A light-load mode detection circuit detects the switching node voltage of the switching converter to determine whether the load terminal of the switching converter is in a light-load state, and provides a light-load indication signal characterizing the determination result. The light-load mode detection circuit provides a logic high-level light-load indication signal when the load terminal is in a light-load state to disable the hysteresis control circuit, thereby controlling the switching converter to operate in light-load mode; and An output monitoring circuit is configured to monitor the first feedback signal when the switching converter is operating in the light load mode, and to provide a wake-up signal to the logic and drive circuit when the first feedback signal is less than a preset reference voltage, so as to control the switching converter to operate in the normal mode.

2. The control circuit according to claim 1 further includes: A conduction time control circuit is used to generate a first conduction time. The logic and drive circuit controls the switching converter to operate in either a hysteresis control mode or an adaptive conduction time control mode based on a comparison between the conduction time of the pulse width modulation signal and the first conduction time.

3. The control circuit according to claim 1 further includes: A minimum turn-off time control circuit is used to generate a minimum turn-off time, wherein the turn-off time determined by the pulse width modulation signal is greater than the minimum turn-off time.

4. The control circuit according to claim 1 further includes: A ripple compensation circuit is used to generate the ripple signal.

5. The control circuit according to claim 2, wherein, The logic and driving circuitry are configured as follows: When the conduction time of the pulse width modulation signal is less than the first conduction time, the switching converter is controlled to operate in an adaptive conduction time control mode; when the conduction time of the pulse width modulation signal is greater than the first conduction time, the switching converter is controlled to operate in a hysteresis control mode.

6. The control circuit according to claim 2, wherein, The first conduction time is the minimum conduction time of at least one switching transistor under the hysteresis control mode.

7. The control circuit according to claim 1, wherein, The hysteresis control circuit includes: The error amplifier has an inverting input terminal and a non-inverting input terminal that receive the first feedback signal and the first reference voltage, respectively, and its output terminal is used to provide an error signal. The hysteresis comparator receives the superimposed signal and the error signal at its inverting and non-inverting inputs, respectively, and its output provides the pulse width modulation signal. The power supply terminals of the error amplifier and the hysteresis comparator are connected to the light load indication signal. When the light load indication signal is at a logic high level, the error amplifier and the hysteresis comparator are turned off.

8. The control circuit according to claim 7, wherein, The hysteresis control circuit further includes: The compensation resistor and compensation capacitor are connected sequentially between the output terminal of the error amplifier and ground; and The first capacitor has its first end connected to the output of the error amplifier and its second end grounded.

9. The control circuit according to claim 7, wherein, The hysteresis control circuit further includes: The first transistor has a first terminal connected to the second feedback signal and a second terminal connected to the output terminal of the error amplifier. The control terminal receives the light-load indication signal. When the light load indication signal is at a logic high level, the first transistor is turned on to short-circuit the output of the error amplifier with the second feedback signal.

10. The control circuit according to claim 1, wherein, The light-load mode detection circuit includes: A zero-crossing comparator, with its non-inverting input receiving the switching node voltage, its inverting input receiving the reference ground voltage, and its output providing a zero-crossing indication signal; and The judgment unit has its input terminal connected to the output terminal of the zero-crossing comparator to receive the zero-crossing indication signal. The judgment unit is used to output the light load indication signal with the logic high level when the high level time of the zero-crossing indication signal is greater than a preset time.

11. The control circuit according to claim 1, wherein, The output monitoring circuit includes: A first comparator receives the first feedback signal and the preset reference voltage at its inverting and non-inverting inputs, respectively, and its output provides a comparison signal between the two. The AND gate has a first input terminal that receives the light load indication signal, a second input terminal that is connected to the output terminal of the first comparator to receive the comparison signal, and an output terminal that provides the wake-up signal.

12. The control circuit according to claim 7, wherein, The hysteresis comparator is configured to adaptively adjust its hysteresis voltage according to the DC output voltage to stabilize the switching frequency.

13. The control circuit according to claim 12, wherein, The hysteresis voltage is equal to the product of the DC output voltage and a proportionality coefficient.

14. A switching converter, comprising: The main power circuit uses at least one switching transistor to control the power transfer from the input terminal to the output terminal, thereby generating a DC output voltage based on the DC input voltage. as well as The control circuit according to any one of claims 1-13 is used to generate a switch control signal to control the conduction state of the at least one switch transistor.

15. The switching converter according to claim 14, wherein the main power circuit adopts a topology selected from any of the following: floating Buck power circuit, ground Buck power circuit, flyback power circuit, Buck-boost power circuit, and Boost power circuit.

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