A voltage conversion circuit and control circuit and control method thereof

Abstract

The present invention discloses a control circuit of a voltage conversion circuit and a control method thereof. When the voltage conversion circuit operates in an ultra-light load state, the control circuit increases the value of a feedback adjustment signal in a control loop, thereby reducing the switching frequency of the voltage conversion circuit in the ultra-light load state, thereby reducing the loss of the voltage conversion circuit related to the switching frequency in the ultra-light load state, and improving the light load efficiency of the voltage conversion circuit.

Description

Technical Field

[0001] The present invention relates to an electronic circuit, in particular to a control circuit in a voltage conversion circuit. Background Art

[0002] Figure 1 The existing voltage conversion circuit 10 is shown, including a feedback circuit 101, an error amplifier circuit 102, a switch control circuit 103 and a power circuit 104. The feedback circuit 101 receives the output voltage Vout of the switch circuit 10, and generates a feedback voltage Vfb proportional to the output voltage Vout based on the output voltage Vout. The error amplifier circuit 102 compares the feedback voltage Vfb with the reference voltage Vref to obtain a feedback adjustment signal Vcomp between the two. The feedback adjustment signal Vcomp represents the error between the target output voltage and the actual output voltage. The switch control circuit 103 receives the feedback adjustment signal Vcomp, and generates a switch control signal G1 based on the feedback adjustment signal Vcomp to control the conduction and disconnection of the power switch in the power circuit 104, thereby controlling the output power Pout of the voltage conversion circuit 10.

[0003] Figure 2 The figure shows the relationship between the feedback adjustment signal Vcomp and the output power Pout of the existing voltage conversion circuit 10. Generally speaking, the feedback adjustment signal Vcomp reflects the size of the output power Pout, that is, the larger the output power Pout, the larger the feedback adjustment signal Vcomp. In some applications, in order to improve the light load efficiency of the voltage conversion circuit 10, the voltage conversion circuit 10 determines the load state according to the output power Pout, and when the load is light, the circuit is operated in the hiccup mode (Burst mode). Summary of the invention

[0004] The object of the present invention is to adjust the value of a feedback adjustment signal in a voltage conversion circuit under an ultra-light load mode, thereby further improving the light load efficiency of the voltage conversion circuit.

[0005] A control circuit of a voltage conversion circuit according to an embodiment of the present invention includes: a feedback adjustment signal generating circuit, receiving a feedback voltage representing an output voltage of the voltage conversion circuit, and outputting a feedback adjustment signal based on the feedback voltage; a hysteresis comparison circuit, receiving an output power signal, an ultra-light load entry power threshold, and an ultra-light load exit power threshold of the voltage conversion circuit, and outputting a selection signal based on a comparison between the output power signal and the ultra-light load entry power threshold and the ultra-light load exit power threshold; a selection circuit, receiving a feedback adjustment signal, an ultra-light load feedback characterization value, and a selection signal, and outputting a feedback adjustment signal or an ultra-light load feedback characterization value as a selected feedback adjustment signal based on the selection signal; and a switch control circuit, receiving a selected feedback adjustment signal, and outputting a switch control signal based on the selected feedback adjustment signal; wherein the ultra-light load exit power threshold is greater than the ultra-light load entry power threshold, and the ultra-light load feedback characterization value is greater than the feedback adjustment signal when the output power signal is equal to the ultra-light load exit power threshold.

[0006] In one embodiment, the output power signal of the voltage conversion circuit is replaced by a feedback adjustment signal, the ultra-light load entry power threshold and the ultra-light load exit power threshold are respectively replaced by an ultra-light load entry feedback threshold and an ultra-light load exit feedback threshold, and the ultra-light load entry feedback threshold is less than the ultra-light load exit feedback threshold; and the hysteresis comparison circuit receives the feedback adjustment signal, the ultra-light load entry feedback threshold and the ultra-light load exit feedback threshold, and outputs a selection signal based on a comparison of the feedback adjustment signal with the ultra-light load entry feedback threshold and the ultra-light load exit feedback threshold.

[0007] A voltage conversion circuit according to an embodiment of the present invention includes the aforementioned control circuit and a feedback circuit that receives an output voltage of the voltage conversion circuit and outputs a feedback voltage based on the output voltage.

[0008] A control method for a voltage conversion circuit according to an embodiment of the present invention includes: generating a feedback adjustment signal based on the output voltage of the voltage conversion circuit; comparing the output power signal of the voltage conversion circuit with an ultra-light load entry power threshold and an ultra-light load exit power threshold, and when the output power signal is less than the ultra-light load entry power threshold, adjusting the switch control signal based on the ultra-light load feedback characterization value, thereby controlling the on-off of the power circuit of the voltage conversion circuit; when the output power signal is greater than the ultra-light load exit power threshold, adjusting the switch control signal based on the feedback adjustment signal, thereby controlling the on-off of the power circuit of the voltage conversion circuit; wherein the ultra-light load exit power threshold is greater than the ultra-light load entry power threshold, and the ultra-light load feedback characterization value is greater than the feedback adjustment signal corresponding to when the output power signal is equal to the ultra-light load exit power threshold.

[0009] In one embodiment, comparing the output power signal of the voltage conversion circuit with an ultra-light load entry power threshold and an ultra-light load exit power threshold includes: using a feedback adjustment signal to characterize the output power signal, and simultaneously using an ultra-light load entry feedback threshold to characterize the ultra-light load entry power threshold, and using an ultra-light load exit feedback threshold to characterize the ultra-light load exit power threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 An existing voltage conversion circuit 10 is shown;

[0011] Figure 2 A schematic diagram showing the relationship between the feedback adjustment signal Vcomp and the output power Pout of the existing voltage conversion circuit 10;

[0012] Figure 3 A schematic diagram showing the relationship between the feedback adjustment signal Vcomp and the output power Pout of the voltage conversion circuit according to an embodiment of the present invention;

[0013] Figure 4 FIG. 4 is a schematic diagram showing a circuit structure of a voltage conversion circuit 40 according to an embodiment of the present invention;

[0014] Figure 5 FIG. 5 shows a schematic diagram of a circuit structure of a voltage conversion circuit 50 according to an embodiment of the present invention;

[0015] Figure 6 FIG. 6 is a flow chart of a control method 60 for a voltage conversion circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not have to be used to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, materials or methods are not specifically described.

[0017] Throughout the specification, references to "one embodiment", "an embodiment", "an example" or "an example" mean that a particular feature, structure or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment", "in an embodiment", "an example" or "an example" that appear in various places throughout the specification do not necessarily refer to the same embodiment or example. In addition, particular features, structures or characteristics may be combined in one or more embodiments or examples in any appropriate combination and / or sub-combination. In addition, it should be understood by those of ordinary skill in the art that the drawings provided herein are for illustrative purposes and that the drawings are not necessarily drawn to scale. It should be understood that when an element is said to be "connected to" or "coupled to" another element, it may be directly connected or coupled to another element or there may be an intermediate element. In contrast, when an element is said to be "directly connected to" or "directly coupled to" another element, there is no intermediate element. The same reference numerals indicate the same element. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0018] Figure 3 A schematic diagram showing the relationship between the feedback adjustment signal Vcomp and the output power Pout of the voltage conversion circuit according to an embodiment of the present invention is shown. In an embodiment of the present invention, when the output power Pout of the voltage conversion circuit decreases to the ultra-light load power threshold P1, the voltage conversion circuit enters the ultra-light load mode, at which time, the preset ultra-light load feedback characterization value Vcomp_con is used to replace the feedback adjustment signal Vcomp characterizing the output power Pout to adjust the switch control signal G1. When the output power Pout of the voltage conversion circuit increases to the ultra-light load exit power threshold P2, the voltage conversion circuit exits the ultra-light load mode, at which time, the feedback adjustment signal Vcomp characterizing the output power Pout is used to adjust the switch control signal G1. In one embodiment, the ultra-light load entry power threshold P1 is less than the ultra-light load exit power threshold P2.

[0019] In one embodiment, the ultra-light load mode is a hiccup mode, i.e., a Burst mode. In this mode, the power circuit is turned on once every certain period of time to provide energy to the load.

[0020] In one embodiment, the voltage conversion circuit includes three working modes, namely, a continuous switching mode, a skip switching mode and a hiccup mode. In the continuous switching mode, the voltage conversion circuit controls the on and off of the power circuit according to the load. In the skip switching mode, the voltage conversion circuit inserts an idle period after each N consecutive switching cycles, that is, the duration of the power circuit being turned off. The hiccup mode is similar to the skip switching mode, except that the idle period inserted in the hiccup mode is longer. The conduction of the power circuit means that the power circuit forms a path between the input and output of the voltage conversion circuit, and the shutdown means that there is no path between the input and output of the voltage conversion circuit.

[0021] In some embodiments, the voltage conversion circuit includes two operating modes, namely, a continuous switching mode and a hiccup mode. In some embodiments, the voltage conversion circuit includes two operating modes, namely, a skip switching mode and a hiccup mode.

[0022] In one embodiment, the output power Pout of the voltage conversion circuit in the hiccup mode is calculated as follows:

[0023]

[0024] Where T burst is the duration of the Burst cycle of the voltage conversion circuit, that is, when the voltage conversion circuit operates in the hiccup mode, the sum of each pulse duration and the idle duration, N is the number of pulses in each Burst cycle when the voltage conversion circuit operates in the hiccup mode, that is, the number of times the power circuit is turned on, and Vcompi is the value of the feedback adjustment signal Vcomp detected at each pulse in the hiccup mode.

[0025] In one embodiment, the output power Pout of the voltage conversion circuit in the continuous switching mode is calculated as follows:

[0026]

[0027] Where T switch It is the switching cycle length when the voltage conversion circuit works in continuous switching mode.

[0028] It should be understood that the working mode of the voltage conversion circuit is selected according to the needs of the application, and is usually determined according to the weight of the load, that is, the size of the output power Pout. The weight of the load is a relative concept, and ordinary technicians in this field can determine the weight threshold of the load according to the needs of the application, that is, the value of the ultra-light load power threshold P1 and the ultra-light load exit power threshold P2 are selected according to the needs of the application.

[0029] exist Figure 3When the output power Pout is less than the ultra-light load power threshold P1, the voltage conversion circuit enters the first working mode, i.e., the hiccup mode, and when the output power Pout is greater than the ultra-light load power threshold P2, the voltage conversion circuit enters the second working mode. The second working mode can be a continuous switching mode or a skipping switching mode.

[0030] In one embodiment, the ultra-light load feedback characterization value Vcomp_con is a constant, and its value is greater than the feedback adjustment signal Vcomp when the output power Pout is equal to the exit ultra-light load power threshold P2. The larger the ultra-light load feedback characterization value Vcomp_con is, the higher the efficiency of the voltage conversion circuit is, and the larger the output voltage ripple is. Conversely, the lower the efficiency of the voltage conversion circuit is, the smaller the output voltage ripple is. In some embodiments, the ultra-light load feedback characterization value Vcomp_con can also be a variable value related to the feedback voltage Vfb characterizing the output voltage Vout, and its value is greater than the feedback adjustment signal Vcomp when the output power Pout is equal to the exit ultra-light load power threshold P2. For example, the value of Vcomp_con can be Vfb×A+B, where A and B are constants and can be selected according to specific parameters of the application.

[0031] It should be understood that the output power Pout of the voltage conversion circuit is the power provided to its load. In the specific circuit of the embodiment of the present invention, the output power Pout of the voltage conversion circuit is expressed as an output power signal Po. The output power signal Po can be calculated by generating a digital circuit using a digital description language such as Verilog or VHDL according to the above formulas (1) and (2), or other applicable calculation methods. In addition, the output power signal Po can represent the output power Pout in any signal form such as voltage or current, and can also be the same or proportional to the output power Pout calculated by the above formulas (1) and (2), or any other known signal relationship form that can reflect the output power Pout. When the output power signal Po is proportional to the output power Pout, the ultra-light load entry power threshold P1 and the ultra-light load exit power threshold P2 are also adjusted proportionally accordingly. It should be understood that the ultra-light load power threshold P1 and the ultra-light load power threshold P2 are used to distinguish the load state of the voltage conversion circuit so as to determine the working mode corresponding to the load state. The signal form and value can correspond to the output power Pout, or correspond to the output power signal Po that characterizes the output power Pout.

[0032] Figure 4 FIG. 4 is a schematic diagram showing a circuit structure of a voltage conversion circuit 40 according to an embodiment of the present invention. Figure 4As shown, the voltage conversion circuit 40 includes a control circuit 400 and a power circuit 406. The control circuit 400 includes: a feedback adjustment signal generating circuit 402, which receives a feedback voltage Vfb and outputs a feedback adjustment signal Vcomp based on the feedback voltage Vfb; a hysteresis comparison circuit 403, which receives an output power signal Po, an ultra-light load power threshold P1 for entering an ultra-light load, and an ultra-light load power threshold P2 for exiting an ultra-light load, and outputs a selection signal S1 based on a comparison between the output power signal Po and the ultra-light load power threshold P1 for entering an ultra-light load, and the ultra-light load power threshold P2 for exiting an ultra-light load; a selection circuit 404, which receives a feedback adjustment signal Vcomp, an ultra-light load feedback characterization value Vcomp_con, and a selection signal S1, and outputs a feedback adjustment signal Vcomp or an ultra-light load feedback characterization value Vcomp_con as a selected feedback adjustment signal Vadj based on the selection signal S1; and a switch control circuit 405, which receives a selected feedback adjustment signal Vadj, and outputs a switch control signal G1 based on the selected feedback adjustment signal Vadj.

[0033] The power circuit 406 includes at least one main power switch. The switch control signal G1 is used to control the main power switch in the power circuit 406. The power circuit 406 may include any existing switch topology, such as BUCK, BOOST, BUCK-BOOST and FLYBACK. The power circuit 406 may also include a power drive circuit. Taking the BUCK circuit as an example, the switch control signal G1 is used to control the pull-up power switch and the pull-down power switch of the BUCK circuit to be turned on and off alternately after the power is amplified by the power drive circuit. When the pull-up power switch of the BUCK circuit is turned on and the pull-down power switch is turned off, the input and output of the voltage conversion circuit form a path through the pull-up power switch, and the power circuit 406 is in the on state at this time, otherwise the power circuit 406 is in the off state.

[0034] In one embodiment, the voltage conversion circuit 40 further includes a feedback circuit 401, which receives the output voltage Vout and outputs a feedback voltage Vfb representing the output voltage Vout based on the output voltage Vout. In one embodiment, the feedback circuit 401 includes a resistor voltage divider network, and the feedback voltage Vfb is proportional to the output voltage Vout. In other embodiments, the feedback circuit 401 may also include a resistor-capacitor network or a TL431 device, etc. The feedback circuit 401 may be integrated with the control circuit 400 in the same module or the same chip, or may be a discrete component.

[0035] In one embodiment, the feedback adjustment signal generating circuit 402 includes an error amplifier that receives a feedback voltage Vfb and a reference voltage Vref (not shown in the figure), and amplifies the error between the feedback voltage Vfb and the reference voltage Vref to obtain a feedback adjustment signal Vcomp.

[0036] In some embodiments, the feedback adjustment signal generating circuit 402 includes other calculation circuits. In one embodiment, the feedback adjustment signal Vcomp is linearly related to the feedback voltage Vfb, that is, Vcomp=K1×Vfb+K2, wherein K1 and K2 are constants, and K1 is greater than 0. In one embodiment, the feedback adjustment signal Vcomp is related to the feedback voltage Vfb as follows: Vcomp=Vfb-K3, wherein K3 is a constant greater than 0. A person of ordinary skill in the art may select the values ​​of K1, K2, and K3 according to the system application parameters. The feedback adjustment signal generating circuit 402 may be implemented by a traditional analog circuit, or may be implemented by a digital circuit using a digital description language such as VHDL, Verilog, etc.

[0037] In one embodiment, the hysteresis comparison circuit 403 includes a hysteresis comparator, receives the output power signal Po, the ultra-light load power threshold P1 and the ultra-light load power threshold P2, and outputs the selection signal S1. When the output power signal Po is less than the ultra-light load power threshold P1, the selection signal S1 has a first level, indicating that the voltage conversion circuit 40 works in the first working mode, and when the output power signal Po is greater than the ultra-light load power threshold P2, the selection signal S1 has a second level, indicating that the voltage conversion circuit 40 works in the second working mode. In one embodiment, the first level is a high level and the second level is a low level. It should be understood that the level form of the selection signal S1 can be selected according to application needs, or it can also be applicable to distinguish different states of the selection signal by other states of the signal, such as rising edge and falling edge. In one embodiment, the ultra-light load power threshold P1 is less than the ultra-light load power threshold P2.

[0038] In one embodiment, the selection circuit 404 includes a multiplexer, which receives the feedback adjustment signal Vcomp, the ultra-light load feedback characterization value Vcomp_con and the selection signal S1. When the selection signal S1 indicates that the output power signal Po is less than the ultra-light load power threshold P1, the selection signal S1 selects the output ultra-light load feedback characterization value Vcomp_con as the selected feedback adjustment signal Vadj, and provides it to the switch control circuit 405. When the selection signal S1 indicates that the output power signal Po is greater than the ultra-light load exit power threshold P2, the selection signal selects the output feedback adjustment signal Vcomp as the selected feedback adjustment signal Vadj, and provides it to the switch control circuit 405.

[0039] In one embodiment, the switch control circuit 405 includes any circuit that generates the switch control signal G1 based on the feedback adjustment signal Vcomp, such as a PWM control circuit, a PFM control circuit, or a PWM / PFM control circuit. The switch control circuit 405 may also adopt any control mode, such as a voltage control mode, a peak current control mode, an average current control mode, etc. Any switch control circuit that generates the switch control signal G1 based on the feedback adjustment signal Vcomp may be used in the present invention.

[0040] Figure 5 FIG. 4 shows a schematic diagram of a circuit structure of a voltage conversion circuit 50 according to an embodiment of the present invention. Figure 5 As shown, the voltage conversion circuit 50 includes a control circuit 500 and a power circuit 406. The control circuit 500 includes: a feedback adjustment signal generating circuit 402, receiving a feedback voltage Vfb, and outputting a feedback adjustment signal Vcomp based on the feedback voltage Vfb; a hysteresis comparison circuit 503, receiving the feedback adjustment signal Vcomp, a super light load feedback threshold VL and an exit super light load feedback threshold VH, and outputting a selection signal S1 based on a comparison between the feedback adjustment signal Vcomp and the super light load feedback threshold VL and the exit super light load feedback threshold VH; a selection circuit 404, receiving the feedback adjustment signal Vcomp, a super light load feedback characterization value Vcomp_con and a selection signal S1, and outputting a feedback adjustment signal Vcomp or a super light load feedback characterization value Vcomp_con as a selected feedback adjustment signal Vadj based on the selection signal S1; and a switch control circuit 405, receiving the selected feedback adjustment signal Vadj, and outputting a switch control signal G1 based on the selected feedback adjustment signal Vadj.

[0041] In one embodiment, the hysteresis comparison circuit 503 includes a hysteresis comparator, receives a feedback adjustment signal Vcomp, a super light load feedback threshold VL, and an exit super light load feedback threshold VH, and outputs a selection signal S1. When the feedback adjustment signal Vcomp is less than the entry super light load feedback threshold VL, the selection signal S1 has a first level, indicating that the voltage conversion circuit 50 operates in the first operating mode, and when the feedback adjustment signal Vcomp is greater than the exit super light load feedback threshold VH, the selection signal S1 has a second level, indicating that the voltage conversion circuit 50 operates in the second operating mode. In one embodiment, the entry super light load feedback threshold VL is less than the exit super light load feedback threshold VH.

[0042] exist Figure 5 In an embodiment, the feedback adjustment signal Vcomp is used to characterize the output power Pout of the voltage conversion circuit. The ultra-light load feedback threshold VL corresponds to the value of Vcomp when the output power Pout is equal to the ultra-light load power threshold P1, and the ultra-light load exit feedback threshold VH corresponds to the value of Vcomp when the output power Pout is equal to the ultra-light load exit power threshold P2. It should be understood that in other embodiments, other parameters of the voltage conversion circuit, such as load current, switching frequency, etc., can also be used to characterize the output power Pout to determine the working mode of the voltage conversion circuit.

[0043] Figure 6 FIG. 6 is a flow chart of a control method 60 for a voltage conversion circuit according to an embodiment of the present invention. The control method 60 includes:

[0044] Step 601: Generate a feedback adjustment signal Vcomp based on the output voltage Vout of the voltage conversion circuit;

[0045] Step 602: compare the output power signal Po of the voltage conversion circuit with the ultra-light load power threshold P1 and the ultra-light load exit power threshold P2. When the output power signal Po is less than the ultra-light load power threshold P1, jump to step 603. When the output power signal Po is greater than the ultra-light load exit power threshold P2, jump to step 604.

[0046] Step 603: adjusting the switch control signal G1 based on the ultra-light load feedback characterization value Vcomp_con, thereby controlling the on and off of the power circuit of the voltage conversion circuit; and

[0047] Step 604: adjusting the switch control signal G1 based on the feedback adjustment signal Vcomp, thereby controlling the on and off of the power circuit of the voltage conversion circuit;

[0048] Among them, the exit ultra-light load power threshold P2 is greater than the entry ultra-light load power threshold P1, and the value of the super-conversion feedback characterization value Vcomp_con is greater than the feedback adjustment signal Vcomp when the output power signal Po is equal to the entry ultra-light load power threshold P1, and is greater than the feedback adjustment signal Vcomp when the output power signal Po is equal to the exit ultra-light load power threshold P2.

[0049] In one embodiment, the ultra-light load feedback characterization value Vcomp_con is a constant value.

[0050] In one embodiment, the ultra-light load feedback characterization value Vcomp_con is linearly related to a feedback voltage Vfb characterizing the output voltage Vout of the voltage conversion circuit.

[0051] In one embodiment, the feedback adjustment signal Vcomp represents the output power signal Po of the voltage conversion circuit. In step 602, the feedback adjustment signal Vcomp is compared with the ultra-light load feedback threshold VL and the ultra-light load exit feedback threshold VH. When the feedback adjustment signal Vcomp is less than the ultra-light load feedback threshold VL, the process jumps to step 603. When the feedback adjustment signal Vcomp is greater than the ultra-light load exit feedback threshold VH, the process jumps to step 604. The ultra-light load entry feedback threshold VL corresponds to the value of Vcomp when the output power signal Po is equal to the ultra-light load entry power threshold P1, and the ultra-light load exit feedback threshold VH corresponds to the value of Vcomp when the output power signal Po is equal to the ultra-light load exit power threshold P2.

[0052] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A control circuit for a voltage conversion circuit, comprising: A feedback adjustment signal generating circuit receives a feedback voltage representing an output voltage of the voltage conversion circuit, and outputs a feedback adjustment signal based on the feedback voltage; A hysteresis comparison circuit receives an output power signal of the voltage conversion circuit, an ultra-light load entry power threshold, and an ultra-light load exit power threshold, and outputs a selection signal based on a comparison between the output power signal and the ultra-light load entry power threshold and the ultra-light load exit power threshold; A selection circuit receives a feedback adjustment signal, an ultra-light load feedback characterization value, and a selection signal, and based on the selection signal, outputs a feedback adjustment signal or an ultra-light load feedback characterization value as a selected feedback adjustment signal, wherein when the selection signal represents that the output power signal is less than an ultra-light load power threshold, the ultra-light load feedback characterization value is selected as the selected feedback adjustment signal, and when the selection signal represents that the output power signal is greater than an ultra-light load power threshold, the feedback adjustment signal is selected as the selected feedback adjustment signal; as well as a switch control circuit that receives a selected feedback adjustment signal and outputs a switch control signal based on the selected feedback adjustment signal; The ultra-light load exit power threshold is greater than the ultra-light load entry power threshold, and the ultra-light load feedback characterization value is greater than the feedback adjustment signal when the output power signal is equal to the ultra-light load exit power threshold.

2. The control circuit according to claim 1, wherein: The output power signal of the voltage conversion circuit is replaced by a feedback adjustment signal, the ultra-light load entry power threshold and the ultra-light load exit power threshold are replaced by an ultra-light load entry feedback threshold and an ultra-light load exit feedback threshold, respectively, and the ultra-light load entry feedback threshold is less than the ultra-light load exit feedback threshold; and The hysteresis comparison circuit receives a feedback adjustment signal, an ultra-light load entry feedback threshold and an ultra-light load exit feedback threshold, and outputs a selection signal based on a comparison between the feedback adjustment signal and the ultra-light load entry feedback threshold and the ultra-light load exit feedback threshold. 3 . The control circuit as claimed in claim 1 , wherein the feedback adjustment signal generating circuit comprises an error amplifier. 4 . The control circuit of claim 1 , wherein the feedback adjustment signal has a linear relationship with a feedback voltage representing an output voltage of the voltage conversion circuit. 5 . The control circuit as claimed in claim 1 , wherein the feedback adjustment signal is greater than a feedback voltage representing an output voltage of the voltage conversion circuit, and a difference between the feedback adjustment signal and the feedback voltage is a constant.

6. The control circuit of claim 1, wherein the selection circuit comprises a multiplexer. 7 . The control circuit as claimed in claim 1 , wherein the ultra-light load feedback characteristic value is a constant. 8 . The control circuit of claim 1 , wherein the ultra-light load feedback characterization value has a linear relationship with a feedback voltage characterizing an output voltage of the voltage conversion circuit.

9. A voltage conversion circuit, comprising the control circuit according to any one of claims 1 to 8, further comprising: The feedback circuit receives the output voltage of the voltage conversion circuit and outputs a feedback voltage based on the output voltage.

10. The voltage conversion circuit of claim 9, further comprising a power circuit, the power circuit comprising at least one main power switch. 11 . The voltage conversion circuit according to claim 9 , further comprising a power circuit, wherein the power circuit has a BUCK topology. 12 . The voltage conversion circuit of claim 9 , further comprising a power circuit, wherein the power circuit has a BOOST topology. 13 . The voltage conversion circuit according to claim 9 , further comprising a power circuit, wherein the power circuit has a FLYBACK topology. 14 . The voltage conversion circuit of claim 9 , further comprising a power circuit, wherein the power circuit has a BUCK-BOOST topology.

15. A control method for a voltage conversion circuit, comprising: generating a feedback adjustment signal based on an output voltage of the voltage conversion circuit; The output power signal of the voltage conversion circuit is compared with the ultra-light load entry power threshold and the ultra-light load exit power threshold. When the output power signal is less than the ultra-light load entry power threshold, the switch control signal is adjusted based on the ultra-light load feedback characterization value to control the on-off of the power circuit of the voltage conversion circuit. When the output power signal is greater than the ultra-light load exit power threshold, the switch control signal is adjusted based on the feedback adjustment signal to control the on-off of the power circuit of the voltage conversion circuit. Among them, the exit ultra-light load power threshold is greater than the entry ultra-light load power threshold, and the ultra-light load feedback characterization value is greater than the corresponding feedback adjustment signal when the output power signal is equal to the exit ultra-light load power threshold.

16. The control method of the voltage conversion circuit according to claim 15, wherein comparing the output power signal of the voltage conversion circuit with an ultra-light load entry power threshold and an ultra-light load exit power threshold comprises: The feedback adjustment signal is used to characterize the output power signal, while the ultra-light load entry feedback threshold is used to characterize the ultra-light load entry power threshold, and the ultra-light load exit feedback threshold is used to characterize the ultra-light load exit power threshold. 17 . The control method of the voltage conversion circuit as claimed in claim 15 , wherein the ultra-light load feedback characteristic value is a constant. 18 . The control method of the voltage conversion circuit according to claim 15 , wherein the ultra-light load feedback characterization value is linearly related to a feedback voltage characterizing the output voltage of the voltage conversion circuit.

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