Control circuit for a switching converter and switching converter

Abstract

This application discloses a control circuit and a switching converter for a switching converter. The control circuit includes an on-time control circuit and an on-time adjustment circuit. The on-time control circuit controls the on-time of the main power switch transistor based on the input and output voltages of the switching converter. The on-time adjustment circuit is connected to the on-time control circuit and obtains an on-time adjustment signal based on the output voltage. When the load power of the switching converter is less than a power threshold, the on-time control circuit receives the on-time adjustment signal to reduce the on-time of the main power switch transistor within one switching cycle. By adding an on-time adjustment circuit to the control circuit, this invention reduces the output voltage ripple by decreasing the on-time of the main power switch transistor based on the output voltage when the load power of the circuit decreases.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and in particular to the control circuit of a switching converter and the switching converter itself. Background Technology

[0002] Traditional DC-DC converters operate in PWM mode under heavy loads, but switch to PFM mode for light loads to achieve high efficiency. Current technology typically maintains the same on-time as PWM mode in PFM mode, adjusting the off-time according to the load size—that is, the off-time increases as the load lightens. However, if the on-time remains the same as in PWM mode after switching to PFM, the energy delivered to the output during each on-time is larger, resulting in higher ripple voltage at light loads. Summary of the Invention

[0003] This invention provides a control circuit and a switching converter for a switching converter, which at least solves the problem of large ripple voltage in the output voltage when operating in light load mode.

[0004] In a first aspect, embodiments of the present invention provide a control circuit for a switching converter, the switching converter including a main power switch transistor, an on-time control circuit, and an on-time adjustment circuit.

[0005] The on-time control circuit controls the on-time of the main power switch based on the input and output voltages of the switching converter.

[0006] The conduction time adjustment circuit is connected to the conduction time control circuit, and the conduction time adjustment circuit obtains the conduction time adjustment signal based on the output voltage.

[0007] When the load power of the switching converter is less than the power threshold, the on-time control circuit receives the on-time adjustment signal to reduce the on-time of the main power switch in one switching cycle.

[0008] Preferably, the control circuit further includes an error amplifier circuit, which obtains an error amplification signal based on the output voltage feedback signal of the switching converter and the reference voltage signal.

[0009] Preferably, when the inductor current of the switching converter is less than the current threshold, or the error amplification signal is less than the first voltage threshold, or the output voltage is greater than the second voltage threshold, it indicates that the load power of the switching converter is less than the power threshold.

[0010] Preferably, the conduction time adjustment circuit obtains the conduction time adjustment signal based on an error signal generated by the output voltage and a preset third voltage threshold.

[0011] Preferably, when the output voltage is greater than the third voltage threshold, the conduction time adjustment circuit outputs the conduction time adjustment signal.

[0012] Preferably, the conduction time adjustment circuit obtains the conduction time adjustment signal based on the error signal generated by the error amplification signal and the preset fourth voltage threshold.

[0013] Preferably, when the error amplification signal is less than the fourth voltage threshold, the conduction time adjustment circuit outputs the conduction time adjustment signal.

[0014] Preferably, the conduction time adjustment circuit includes a current generation circuit and a current conversion circuit.

[0015] The current generating circuit receives the error signal to generate a first current signal that is proportional to the error signal.

[0016] The current conversion circuit receives the first current signal to obtain a second current signal that is proportional to the first current signal.

[0017] The second current signal is transmitted to the conduction time control circuit as the conduction time adjustment signal.

[0018] Preferably, the control circuit further includes a first comparator and a latch.

[0019] The first comparator receives the error amplification signal and the inductor current signal of the switching converter to control the turn-off time of the main power switch based on the comparison result.

[0020] The set terminal of the latch is connected to the output terminal of the first comparator, and the reset terminal is connected to the output terminal of the conduction time control circuit, so as to control the on / off state of the main power switch according to the output signals of both.

[0021] Preferably, the conduction time control circuit includes a charging / discharging circuit and a comparator circuit.

[0022] The charging and discharging circuit receives a first charging current proportional to the output voltage to charge the charging capacitor and obtain a charging voltage signal.

[0023] The comparator circuit compares the charging voltage signal and the second voltage signal to obtain a comparison signal. The second voltage signal is obtained by dividing the difference between the output voltage and the input voltage.

[0024] When the load power of the switching converter is less than the power threshold, the on-time adjustment signal is used as a second charging current to charge the charging capacitor.

[0025] The on-time of the main power switch and the discharge of the charging capacitor are controlled according to the comparison signal.

[0026] Preferably, the comparison circuit is a second comparator, the charging voltage signal is transmitted to the positive input terminal of the second comparator, and the second voltage signal is transmitted to the negative input terminal of the second comparator.

[0027] When the main power switch is turned on, the charging voltage signal begins to rise, and the time it takes for the charging voltage signal to rise to the second voltage signal is the turn-on time.

[0028] Secondly, embodiments of the present invention provide a switching converter, including a DC-DC conversion circuit and a control circuit for the switching converter described in any of the above embodiments, wherein the DC-DC conversion circuit is any one of a buck converter circuit, a boost converter circuit, or a buck-boost converter circuit.

[0029] Compared to related technologies, the control circuit and switching converter of the switching converter provided in this embodiment of the invention, by adding a conduction time adjustment circuit to the control circuit, allows the conduction time adjustment circuit to generate a corresponding conduction time adjustment signal based on the output voltage when the load power of the DC-DC conversion circuit is less than a certain value. Then, the conduction time control circuit reduces the conduction time of the main power switch based on the conduction time adjustment signal. Reducing the conduction time of the main power switch lowers the peak value of the output voltage, thereby achieving a smaller output voltage ripple under light load mode compared to existing technologies. Furthermore, the conduction time adjustment circuit of this invention is composed of simple electronic components, thus saving hardware costs. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 This is a circuit schematic diagram of the control circuit of a switching converter according to an embodiment of the present invention;

[0032] Figure 2 This is a circuit diagram of a conduction time control circuit and a conduction time adjustment circuit according to an embodiment of the present invention;

[0033] Figure 3This is a circuit diagram of a conduction time control circuit and a conduction time adjustment circuit according to another embodiment of the present invention;

[0034] Figure 4(a) is a waveform diagram of the control circuit of a switching converter according to an embodiment of the present invention;

[0035] Figure 4(b) is a waveform diagram of the operation of a prior art switching converter. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention. Furthermore, it is understood that although the efforts made in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the invention.

[0037] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention may be combined with other embodiments without conflict.

[0038] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," "an," "the," and similar words used in this invention do not indicate quantity limitation and may indicate singular or plural. The terms "comprising," "including," "having," and any variations thereof used in this invention are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms "connected," "linked," "coupled," and similar words used in this invention are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "A plurality" in this invention means two or more. "And / or" describes the relationship between related objects, indicating that three relationships may exist; for example, "A and / or B" can represent: A alone, A and B simultaneously, and B alone. The terms "first," "second," and "third" used in this invention are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0039] This invention provides a control circuit for a switching converter, mainly used in switching converters. For a detailed circuit diagram, please refer to [reference needed]. Figure 1 This embodiment uses a boost converter as an example to illustrate the control circuit of the present invention, such as... Figure 1 As shown, the power stage circuit includes a main power switch Q1 and a freewheeling switch Q2, and the control circuit includes a feedback circuit, an error amplifier circuit, an adjustment circuit U2, a first comparator circuit, a latch U4, and a signal control circuit U5.

[0040] The boost converter includes a boost-type DC-DC converter circuit, an error amplifier circuit including an error amplifier U1, and a first comparator circuit including a first comparator U3. The input of the feedback circuit is connected to the output of the DC-DC converter circuit to obtain the output voltage V of the DC-DC converter circuit. OUT The output of the feedback circuit is connected to the negative input of the error amplifier U1. Specifically, the feedback circuit includes a first feedback resistor R. F1 Second feedback resistor R F2 Among them, the first feedback resistor R F1 The first terminal is connected to the output terminal of the DC-DC converter circuit, and the first feedback resistor R F1 The second terminal is connected to the second feedback resistor R. F2 The first terminal, the second feedback resistor R F2 The second terminal is connected to the ground terminal; the first feedback resistor RF1 Second feedback resistor R F2 The connection point between them serves as the output terminal of the feedback circuit, and the output voltage V of the DC-DC converter circuit is affected by two feedback resistors. OUT After voltage division, the output voltage feedback signal is obtained, i.e. Figure 1 The feedback voltage V in FB The feedback voltage V FB It is connected to the negative input terminal of error amplifier U1.

[0041] In this embodiment of the invention, the error amplifier U1 is based on the output voltage feedback signal V from the switching converter. FB and reference voltage signal V REF_1 In order to obtain the error amplification signal, the error amplification signal can be understood as the compensation signal after the error signal has been compensated.

[0042] like Figure 1 As shown, the positive input terminal of the first comparator U3 is connected to the output terminal of the error amplifier U1, and receives the error amplification signal V output by the error amplifier U1. comp1 The negative input terminal of the first comparator U3 receives the inductor current I, which characterizes the DC-DC converter circuit. L The signal is received by the first comparator U3, whose output is connected to the set terminal S of the latch U4. The first comparator U3 receives the error amplification signal V. Comp1 and the inductor current signal I characterizing the switching converter L The signal is used to control the turn-off time of the main power switch based on the comparison result.

[0043] refer to Figure 1 It can be seen that the first input terminal of the adjustment circuit U2 is connected to the output terminal of the error amplifier, and the error amplification signal V is input. comp1 The second input terminal is connected to the input terminal of the DC-DC converter circuit, and the input voltage V of the DC-DC converter circuit is connected to it. IN The third input terminal of the regulating circuit U2 is connected to the output terminal of the DC-DC converter circuit, and the output voltage V of the DC-DC converter circuit is connected to it. OUTThe output of the regulating circuit U2 is connected to the reset terminal R of the latch U4. The set terminal S of the latch U4 is connected to the output of the first comparator U3, and the reset terminal R is connected to the output of the regulating circuit U2, so as to control the on / off state of the main power switch based on the output signals of both. The control circuit of this embodiment also includes a signal control circuit U5. The output of the latch U4 is connected to the input of the signal control circuit U5, and the output of the signal control circuit U5 is connected to the control terminal of the switch in the DC-DC converter circuit. The first output terminal S1 of the signal control circuit U5 is connected to the freewheeling switch Q2, and the second output terminal S2 of the signal control circuit U5 is connected to the main power switch Q1. The latch U4 and the signal control circuit U5 control the on and off state of the two switches based on the signals received from the set terminal S and the reset terminal R of the latch.

[0044] In this embodiment of the invention, when the load power of the switching converter is less than a preset power threshold (i.e., the load is light), the control circuit of the invention operates in PFM mode, and the adjustment circuit U2 adjusts according to the error amplification signal V. comp1 Output a corresponding adjustment signal to reduce the on-time T of the main power switch. ON Alternatively, the regulating circuit U2 outputs a corresponding regulating signal based on the output signal to reduce the on-time T of the main power switch. ON In this embodiment, multiple criteria can be set for determining the load power. For example, if the inductor current of the switching converter is less than a current threshold, or the error amplification signal is less than a first voltage threshold, or the output voltage of the switching converter is greater than a second voltage threshold, then the load power of the switching converter is less than a power threshold. The current threshold, the first voltage threshold, and the second voltage threshold can all be preset.

[0045] In a preferred embodiment of the present invention, the adjustment circuit U2 includes an on-time control circuit and an on-time adjustment circuit, specifically as follows: Figure 2 As shown, the conduction time control circuit U7 is based on the input voltage V of the switching converter. IN and output voltage V OUTThe on-time of the main power switch Q1 is controlled. The output of the on-time adjustment circuit U6 is connected to the input of the on-time control circuit U7. The on-time adjustment circuit U6 obtains the on-time adjustment signal based on the output voltage. Specifically, the on-time adjustment circuit obtains the on-time adjustment signal based on the error signal generated by the output voltage and a preset third voltage threshold. When the output voltage is greater than the third voltage threshold, the on-time adjustment circuit outputs the on-time adjustment signal. Here, the third voltage threshold can be equal to the second voltage threshold. That is, when the output voltage reaches the second voltage threshold, the on-time adjustment circuit outputs the on-time adjustment signal. At the same time, the on-time control circuit U7 receives the on-time adjustment signal to reduce the on-time of the main power switch Q1 within one switching cycle.

[0046] Specifically, the conduction time adjustment circuit further includes a current generation circuit and a current conversion circuit. The current generation circuit receives the error signal to generate a first current signal that is proportional to the error signal. The current conversion circuit receives the first current signal to obtain a second current signal that is proportional to the first current signal. The second current signal is transmitted to the conduction time control circuit as a conduction time adjustment signal.

[0047] Specifically, the current generating circuit includes a second error amplifier U9, which outputs a voltage feedback signal V. FB With the third voltage threshold V REF_3 A comparison is made to generate a second error signal V. comp2 The input terminal of the current conversion circuit is connected to the output terminal of the second error amplifier U9, converting the second error signal V... comp2 The conversion yields the on-time adjustment signal; the input of the on-time control circuit U7 is connected to the output of the on-time adjustment circuit U6, and the on-time control circuit U7 adjusts the on-time of the main power switch Q1 according to the on-time adjustment signal.

[0048] In this embodiment, the current generation circuit is based on the second error signal V. comp2 Generate and the second error signal V comp2 A first current signal I_Gm is directly proportional to the first current signal, and the first current signal I_Gm is sent to the current conversion circuit. The current conversion circuit receives the first current signal I_Gm and converts the first current signal I_Gm to obtain a second current signal I_TON that has a certain proportional coefficient to the first current signal. The current conversion circuit transmits the second current signal I_TON as a conduction time adjustment signal to the conduction time control circuit U7. In this embodiment, the proportional coefficient can be set according to the circuit needs and is a positive number greater than zero.

[0049] More specifically, the current conversion circuit can be a mirror current source connected between the output terminal and ground terminal of the error amplifier. Based on the error signal output by the second error amplifier U9, it outputs a first current signal I_Gm. The mirror current source is also connected between the input terminal and ground terminal of the on-time control circuit U7, converting the first current signal I_Gm into a second current signal I_TON, which is then output as the on-time adjustment signal. According to the working principle of the error amplifier, when the output voltage is greater than the third voltage threshold, the current direction of the first current signal is upward, flowing into the interior of the error amplifier. At this time, the on-time adjustment circuit outputs the on-time adjustment signal. When the output voltage is less than the third voltage threshold, the current direction of the first current signal is downward, flowing out to the internal output terminal of the error amplifier. At this time, the on-time adjustment circuit stops outputting the on-time adjustment signal.

[0050] For the on-time control circuit U7, refer to Figure 2 The circuit includes a first resistor R1, a charging capacitor C, and an electronic switch K; the comparator circuit includes a second resistor R2, a third resistor R3, and a second comparator U8. In this embodiment, the electronic switch K is generally a MOSFET. When the voltage reached by the charging capacitor C reaches the value at the negative input of the second comparator U8, the second comparator U8 outputs a comparison signal to control the on-time of the main power switch Q1, and simultaneously closes the electronic switch K, thus releasing the voltage of the charging capacitor C. The specific connection relationship is as follows: Figure 2 As shown, the first end of the first resistor R1 is connected to the input terminal of the DC-DC converter circuit, the second end of the first resistor R1 is connected to the first end of the charging capacitor C, and the second end of the charging capacitor C is connected to the ground terminal; the connection point between the first resistor R1 and the charging capacitor C serves as the input terminal of the conduction time control circuit U7; the first end of the electronic switch K is connected to the connection point between the first resistor R1 and the charging capacitor C, the second end of the electronic switch K is connected to the second end of the charging capacitor C, and the third end of the electronic switch K is connected to the output terminal of the second comparator U8; the first end of the second resistor R2 is connected to the input-output voltage difference signal V of the DC-DC converter circuit. OUT -V IN The second end of the second resistor R2 is connected to the first end of the third resistor R3, and the second end of the third resistor R3 is connected to the ground terminal. The positive input terminal of the second comparator U8 is connected to the connection point between the first resistor R1 and the charging capacitor C, and the negative input terminal of the second comparator U8 is connected to the connection point between the second resistor R2 and the third resistor R3. The output terminal of the second comparator U8 is connected to the reset terminal R of the latch U4. When the comparison signal output by the second comparator U8 is in a high-level active state, the reset terminal signal is active, controlling the main power switch to turn off, thereby controlling the conduction time of the main power switch.

[0051] In this embodiment, the charging and discharging circuit receives a first charging current proportional to the output voltage to charge the charging capacitor C to obtain a charging voltage signal. The comparison circuit compares the charging voltage signal and a second voltage signal to obtain a comparison signal. The second voltage signal is the output voltage V. OUT and input voltage V IN The difference is obtained by voltage division. When the load power of the switching converter is less than the power threshold, the on-time adjustment signal (i.e., the second current signal I_TON) is used as the second charging current to charge the charging capacitor C, and the on-time T of the main power switch is controlled according to the comparison signal. ON And the discharge of the charging capacitor C.

[0052] In a preferred embodiment of the present invention, the comparison circuit is a second comparator U8. The charging voltage signal is transmitted to the positive input terminal of the second comparator U8, and the second voltage signal is transmitted to the negative input terminal of the second comparator U8. When the main power switch Q1 is turned on, the charging voltage signal begins to rise, and the time it takes for the charging voltage signal to rise to the second voltage signal is the on-time T. ON Furthermore, the comparison signal output by the second comparator U8 becomes high, controlling the switch K to conduct and causing the charging capacitor to discharge.

[0053] When the circuit operates in PFM mode, the regulating circuit U2 reduces the on-time of the main power switch based on the error signal, thereby avoiding the problem that the on-time in PFM mode is the same as that in PWM mode, which would lead to excessive output voltage in light load mode. Since the on-time of the main power switch in each switching cycle is reduced, the peak value of the output voltage of the switching converter is reduced, thereby reducing the voltage ripple of the switching converter output.

[0054] In another embodiment of the invention, reference is made to... Figure 3 The control circuit in this embodiment also includes a third error amplifier U10. The negative input terminal of the third error amplifier U10 is connected to a fourth voltage threshold V. comp_r The positive input terminal is connected to the output terminal of the first error amplifier U1 to obtain the error amplification signal V. comp1 The output of the third error amplifier U10 is connected to the input of the conduction time adjustment circuit. In this embodiment, when the error amplification signal V... comp1 Less than the fourth voltage threshold V comp_r At that time, the third error amplifier U10 generates the third error signal V. comp3 The conduction time adjustment circuit adjusts the conduction time based on the third error signal V. comp3 A conduction time adjustment signal is generated. Here, the fourth voltage threshold can be equal to the first voltage threshold, i.e., the third error signal V. comp3When the voltage is less than the first voltage threshold, the conduction time adjustment circuit outputs the conduction time adjustment signal. At the same time, the conduction time control circuit U7 receives the conduction time adjustment signal to reduce the conduction time of the main power switch Q1 within one switching cycle.

[0055] More specifically, the current generating circuit uses the third error signal V output by the third error amplifier U10. comp3 A first current signal I_Gm is generated; the mirror current source converts the first current signal I_Gm into a second current signal I_TON, which is then output as the conduction time adjustment signal. When the error amplification signal is greater than the fourth voltage threshold, the current direction of the first current signal is upward, and the conduction time adjustment circuit outputs the conduction time adjustment signal; when the error amplification signal is less than the fourth voltage threshold, the current direction of the first current signal is downward, and the conduction time adjustment circuit stops outputting the conduction time adjustment signal.

[0056] It should be noted that a specific example of the conduction time control circuit in this embodiment can be found in [reference needed]. Figure 2 The examples described in the embodiments and optional implementations will not be repeated here.

[0057] Referring to the working waveform diagram in Figure 4(a), for Figure 1 and Figure 2 The operation of the control circuit is explained in detail. Specifically, when the load on the DC-DC converter circuit is heavy, i.e., the load power exceeds the power threshold, the circuit operates in PWM mode, and the DC-DC circuit is in the CCM (Continuous Current Mode) stage. At this time, switches Q1 and Q2 alternately conduct within one switching cycle, so the current in the circuit is continuous. When the load power is less than the power threshold, the control circuit enters PFM control mode, and the DC-DC converter circuit enters the DCM (Discontinuous Current Mode) stage. At this time, switches Q1 and Q2 alternately conduct in Burst ON mode and are off in Burst OFF mode within one switching cycle. Specifically, before time t1, the control circuit operates in PWM mode; after time t1, the load on the DC-DC converter circuit is light, and the control circuit enters PFM operating mode, and the DC-DC converter circuit is in the DCM (Discontinuous Current Mode) stage. At this time, the output voltage VOUT_PFM of the DC-DC converter circuit is higher than the output voltage VOUT_PWM in PWM operating mode. During times t1-t2 and t3-t4, the control circuit operates in Burst ON mode, at which time the switching transistors Q1 and Q2 are turned on alternately, and the output voltage of the DC-DC converter circuit is still on an upward trend; during times t2-t3, the control circuit operates in Burst OFF mode, at which time both switching transistors Q1 and Q2 are turned off, and the output voltage of the DC-DC converter circuit decreases.

[0058] After the load power drops to a certain value at time t1, the control circuit switches the switching converter to PFM operating mode. At this time, the main power switch Q1 is turned on, and the current I in the inductor L increases. L The output voltage V of the DC-DC converter circuit rises linearly. OUT_PFM The voltage increases, at which point the error amplifier U1 will output the feedback voltage V from the feedback circuit in real time. FB With reference voltage V REF_1 When the feedback voltage is less than the reference voltage, the first comparator U3 compares the sampled signal representing the inductor current of the DC-DC converter circuit with the error amplification signal V output by the error amplifier U1 in real time. comp1 Comparison is performed when the sampled signal is less than the error amplification signal V. comp1 When the first comparator outputs a high level, the signal control circuit U5 controls the main power switch Q1 to turn on and the freewheeling switch Q2 to turn off. After that, the inductor current increases linearly, and this cycle continues until the feedback voltage is greater than the reference voltage.

[0059] When the switching converter is in PFM operating mode, the error amplification signal V output by the error amplifier circuit U1 is... comp1 The input is given to the on-time adjustment circuit U6, which generates a second current signal I_TON (i.e., the on-time adjustment signal) proportional to the output voltage. This second current signal, along with the first charging current, charges the charging capacitor C. Because a current signal is added to the charging capacitor C, the capacitor charges rapidly and reaches the preset voltage value. At this point, the voltage at the positive input terminal of the second comparator U8 is greater than that at the negative input terminal, so the second comparator U8 outputs a comparison signal that turns off the main power switch Q1. This invention shortens the capacitor's charging time through the current signal output by the on-time adjustment circuit U6, thus shortening the on-time T of the main power switch in one switching cycle. ON This avoids the DC-DC converter circuit supplying too much energy to the output, causing the output voltage to rise continuously, thus achieving the effect of reducing output voltage ripple in light load mode.

[0060] Figure 4(b) shows the working waveform of the existing PWM-PFM dual-mode control circuit. Compared with the working waveform of 4(a), it can be seen that the output voltage V of the DC-DC converter circuit of the control circuit using the technical solution of this invention is higher. OUT The ripples are relatively small.

[0061] In one embodiment of the present invention, a switching converter is provided, specifically referring to... Figure 1This includes a DC-DC converter circuit and the control circuit of the switching converter described in any of the above embodiments. The DC-DC converter circuit is a boost converter circuit, including an inductor L, a main power switch Q1, and a freewheeling switch Q2. The first terminal of the inductor L serves as the input terminal of the DC-DC converter circuit, connected to the input voltage V. IN The second terminal of inductor L is connected to the source of freewheeling switch Q2 and the drain of main power switch Q1, respectively. The drain of freewheeling switch Q2 serves as the output terminal of the DC-DC converter circuit, outputting voltage V. OUT The drain of the main power switch Q1 is connected to ground, and the gates of the freewheeling switch Q2 and the main power switch Q1 are connected to the output of the light-load low-ripple control circuit. The transformer in this embodiment can achieve the function of step-up voltage.

[0062] In another embodiment of the present invention, a switching converter is provided, including a DC-DC converter circuit and a control circuit for the switching converter described in any of the above embodiments. The DC-DC converter circuit is a buck converter circuit, including an inductor, a main power switch, and a freewheeling switch. The gates of the main power switch and the freewheeling switch are connected to the output terminal of a new light-load, low-ripple control circuit. The source of the main power switch serves as the input terminal of the DC-DC converter circuit, receiving the input voltage. The drain of the main power switch is connected to the drain of the freewheeling switch and a first terminal of the inductor, respectively. The source of the freewheeling switch is connected to ground. The second terminal of the inductor serves as the output terminal of the DC-DC converter circuit, outputting the voltage. The converter in this embodiment can achieve the function of buck conversion.

[0063] In another embodiment of the present invention, a switching converter is provided, including a DC-DC conversion circuit and a control circuit of the switching converter described in any of the above embodiments, wherein the DC-DC conversion circuit is a buck-boost conversion circuit.

[0064] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0065] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A control circuit for a switching converter, the switching converter comprising a main power switching transistor, characterized in that, Includes a conduction time control circuit and a conduction time adjustment circuit. The on-time control circuit controls the on-time of the main power switch based on the input and output voltages of the switching converter. The output terminal of the conduction time adjustment circuit is connected to the input terminal of the conduction time control circuit. The conduction time adjustment circuit obtains the conduction time adjustment signal based on the output voltage. When the load power of the switching converter is less than the power threshold, the on-time control circuit receives the on-time adjustment signal to reduce the on-time of the main power switch in one switching cycle. The conduction time adjustment circuit includes a current generation circuit and a current conversion circuit. The current generation circuit receives an error signal to generate a first current signal that is proportional to the error signal. The current conversion circuit receives the first current signal to obtain a second current signal that is proportional to the first current signal. The second current signal is transmitted to the conduction time control circuit as the conduction time adjustment signal. The error signal is generated based on the output voltage and the voltage threshold. The conduction time control circuit includes a charging / discharging circuit and a comparison circuit. The charging / discharging circuit receives a first charging current proportional to the output voltage to charge the charging capacitor to obtain a charging voltage signal. The comparison circuit compares the charging voltage signal and a second voltage signal to obtain a comparison signal. The second voltage signal is obtained by voltage division of the difference between the output voltage and the input voltage.

2. The control circuit according to claim 1, characterized in that, The control circuit also includes an error amplifier circuit. The error amplifier circuit obtains the error amplification signal based on the output voltage feedback signal of the switching converter and the reference voltage signal.

3. The control circuit according to claim 2, characterized in that, When the inductor current of the switching converter is less than the current threshold, or the error amplification signal is less than the first voltage threshold, or the output voltage is greater than the second voltage threshold, it indicates that the load power of the switching converter is less than the power threshold.

4. The control circuit according to claim 2, characterized in that, The conduction time adjustment circuit obtains the conduction time adjustment signal based on the error signal generated by the output voltage and the preset third voltage threshold.

5. The control circuit according to claim 4, characterized in that, When the output voltage is greater than the third voltage threshold, the conduction time adjustment circuit outputs the conduction time adjustment signal.

6. The control circuit according to claim 2, characterized in that, The conduction time adjustment circuit obtains the conduction time adjustment signal based on the error signal generated by the error amplification signal and the preset fourth voltage threshold.

7. The control circuit according to claim 6, characterized in that, When the error amplification signal is less than the fourth voltage threshold, the conduction time adjustment circuit outputs the conduction time adjustment signal.

8. The control circuit according to claim 2, characterized in that, The control circuit also includes a first comparator and a latch. The first comparator receives the error amplification signal and the inductor current signal of the switching converter to control the turn-off time of the main power switch based on the comparison result. The set terminal of the latch is connected to the output terminal of the first comparator, and the reset terminal is connected to the output terminal of the conduction time control circuit, so as to control the on / off state of the main power switch according to the output signals of both.

9. The control circuit according to claim 1, characterized in that, When the load power of the switching converter is less than the power threshold, the on-time adjustment signal is used as a second charging current to charge the charging capacitor. The on-time of the main power switch and the discharge of the charging capacitor are controlled according to the comparison signal.

10. The control circuit according to claim 9, characterized in that, The comparison circuit is a second comparator. The charging voltage signal is transmitted to the positive input terminal of the second comparator, and the second voltage signal is transmitted to the negative input terminal of the second comparator. When the main power switch is turned on, the charging voltage signal begins to rise, and the time it takes for the charging voltage signal to rise to the second voltage signal is the turn-on time.

11. A switching converter, characterized in that, Includes a DC-DC converter circuit and a control circuit for the switching converter according to any one of claims 1-10, wherein, The DC-DC converter circuit can be any one of a buck converter circuit, a boost converter circuit, or a buck-boost converter circuit.

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