Switching converter and average current sampling circuit thereof

Abstract

The invention discloses a switching converter and an average current sampling circuit thereof, and the circuit employs a current detection module to detect the drain-source voltage of a low-side switching tube, so as to generate a sampling current which is proportional to the switching tube current of the low-side switching tube. The sampling current is converted into the sampling voltage through the current-voltage conversion module and the sampling holding module, and finally the average current signal is obtained through the current output module according to the sampling voltage, so that the accurate sampling of the average current of the switching converter is realized. According to the average current sampling circuit, a sampling resistor connected in series at the output end of the switching converter is omitted, so that the power loss of the circuit can be reduced, the utilization rate of energy is improved, and the average current sampling circuit is particularly suitable for application scenes with strict efficiency requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and more particularly to a switching converter and an average current sampling circuit thereof. Background Art

[0002] A switching converter is a power supply that uses a switching tube to control the charging and discharging process of an energy storage element to provide power, and maintains a stable output voltage and / or output current by controlling the on-time ratio of the switching tube. Due to its ease of forming modular and miniaturized integrated circuits, it has been widely used in various charging power supplies for mobile phones, tablet computers, and portable media players.

[0003] Advances in semiconductor technology and the exponential increase in device power consumption are placing higher demands on existing charging power supplies, requiring them to deliver higher power and smaller size. The power of traditional single-phase power supplies is limited by the current capacity and heat dissipation capabilities of a single inductor and switching components. Multiphase power supply technology, however, breaks through the single-phase power bottleneck by distributing the total power across multiple phases through parallel connections. Multiphase power supplies also allow for the use of smaller inductors, and combined with high-frequency switching, can significantly reduce the size of power modules.

[0004] In a multiphase power system, current sharing is crucial for ensuring balanced current distribution across all phases. If current sharing fails, single-phase power transistors may become continuously overloaded, ultimately overheating and short-circuiting, leading to system downtime. Furthermore, if current sharing is not achieved within each phase's switching converter, inductor saturation may occur, reducing conversion efficiency. Current sharing requires sampling the average current of each phase's switching converter. Existing technologies typically implement this function using methods such as resistor sampling, DCR sampling, and MOSFET sampling.

[0005] like Figure 1 Figure 2 shows the schematic diagram of a resistor sampling circuit. A sampling resistor, Rs, is connected in series with the output of each phase of the switching converter. The voltage drop across the sampling resistor, Rs, is detected and processed in the current sensing circuit to obtain the average current, Iavg, of the switching converter. This resistor sampling method requires additional external components for current sampling. Furthermore, the need to connect a resistor in series with the power transmission path of the switching converter results in power loss, reducing conversion efficiency.

[0006] like Figure 2Figure 2 shows the schematic diagram of a DCR sampling circuit. The DCR sampling circuit consists of a sampling resistor, Rs, and a sampling capacitor, Cs. Rs and Cs are connected in series and then in parallel with an inductor, L (RL represents the DC resistance of the inductor). The basic principle is that when the time constants of the Rs, Cs, and L branches are perfectly matched (Cs*Rs=L / RL), the voltage signal Vsen across Cs is equal to IL multiplied by RL. This DCR sampling circuit, due to the mismatch in the sampling circuit time constant, requires compensation and adjustment, often struggling to balance stability and dynamic response speed, and can also lead to low sampling accuracy.

[0007] like Figure 3 Figure 2 shows the schematic diagram of a MOSFET sampling circuit. Current detection is performed through a sampling resistor at the source of the MOS tube. This mode is usually used for power supplies controlled in valley mode. The presence of the sampling resistor causes inconsistencies in the three-terminal operating conditions of the MOS tube and the power tube, resulting in poor sampling accuracy.

[0008] Therefore, how to improve the sampling accuracy of the sampling circuit while reducing power loss has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0009] In view of the above problems, an object of the present invention is to provide a switching converter and an average current sampling circuit thereof, which have the advantages of high sampling accuracy and low power loss.

[0010] According to one aspect of the present invention, an average current sampling circuit for a switching converter is provided. The switching converter includes a high-side switch tube, a low-side switch tube and an inductor. The high-side switch tube and the low-side switch tube are used to control the charging and discharging of the inductor to control the switching converter to achieve power transmission. The average current sampling circuit includes: a current detection module, which is used to detect the drain-source voltage of the low-side switch tube under the control of a low-side control signal to generate a sampling current proportional to the switching tube current of the low-side switch tube; a current-voltage conversion module, which is used to convert the sampling current into a voltage signal; a sampling and holding module, which is used to sample and hold the voltage signal according to the low-side control signal to generate a sampling voltage; and a current output module, which is used to generate an average current signal according to the sampling voltage.

[0011] Optionally, the sampling and holding module is used to sample the voltage signal when the low-side switch tube is turned on, and to hold the voltage signal when the low-side switch tube is turned off.

[0012] Optionally, the current detection module includes: a first operational amplifier, whose positive input terminal is connected to a reference ground voltage; a first transistor, whose first terminal is used to output the sampled current, a control terminal is connected to the output terminal of the first operational amplifier, and a second terminal is connected to the negative input terminal of the first operational amplifier; a first resistor, whose first terminal is connected to the negative input terminal of the first operational amplifier and the second terminal of the first transistor; and a set of switches, wherein the set of switches is used to selectively connect the second terminal of the first resistor to the switch node or the reference ground voltage according to the low-side control signal. Optionally, the set of switches is used to connect the second terminal of the first resistor to the switch node when the low-side switch tube is turned on, and to connect the second terminal of the first resistor to the reference ground voltage when the low-side switch tube is turned off.

[0013] Optionally, the current-voltage conversion module includes: a second transistor and a third transistor forming a current mirror, the first ends of the second transistor and the third transistor are connected to the power supply voltage, the control ends of the second transistor and the third transistor are short-circuited with the second end of the second transistor, the second end of the second transistor is used to receive the sampling current, and the second end of the third transistor is used to provide a mirror current of the sampling current; and a second resistor, the first end of which is connected to the second end of the third transistor, and the second end is connected to the reference ground voltage, wherein the common node of the second resistor and the third transistor is used to output the voltage signal.

[0014] Optionally, the sampling and holding module includes: a switch, a first end of the switch is connected to the voltage signal, and a control end is used to receive the low-side control signal; and a filter composed of a third resistor and a first capacitor, the first end of the third resistor is connected to the second end of the switch, the second end of the third resistor is connected to the first end of the first capacitor, and the second end of the first capacitor is connected to the reference ground voltage, wherein the switching state of the switch is consistent with the switching state of the low-side switch tube, so as to obtain the sampling voltage at the intermediate node between the third resistor and the first capacitor.

[0015] Optionally, the current output module includes: a second operational amplifier, whose positive input terminal is used to receive the sampling voltage; a fourth transistor, whose first terminal is used to output the average current signal, whose control terminal is connected to the output terminal of the second operational amplifier, and whose second terminal is connected to the negative input terminal of the second operational amplifier; and a fifth transistor, whose first terminal is connected to the second terminal of the fourth transistor, whose control terminal is connected to the power supply voltage, and whose second terminal is connected to the reference ground voltage.

[0016] Optionally, the fifth transistor and the low-side switch transistor are selected from the same transistor type.

[0017] According to another aspect of the present invention, a switching converter is provided, comprising: a high-side switching tube, a low-side switching tube and an inductor, wherein the high-side switching tube and the low-side switching tube are used to control the charging and discharging of the inductor to control the switching converter to achieve power transmission; and the above-mentioned average current sampling circuit.

[0018] To sum up, the average current sampling circuit provided by the present invention adopts a current detection module to detect the drain-source voltage of the low-side switch tube to generate a sampling current proportional to the switch tube current of the low-side switch tube, and then converts the sampling current into a sampling voltage through the current-voltage conversion module and the sample-and-hold module. Finally, the average current signal is obtained according to the sampling voltage through the current output module, thereby realizing accurate sampling of the average current of the switching converter.

[0019] In addition, the average current sampling circuit of the present invention is different from the traditional MOSFET sampling technology. Since the sampling resistor connected in series at the output end of the switching converter is omitted, the power loss of the circuit can be reduced and the energy utilization rate can be improved. It is particularly suitable for application scenarios with strict efficiency requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0021] Figure 1 It is a schematic diagram of the principle of the resistance sampling circuit in the prior art.

[0022] Figure 2 Schematic diagram of the principle of the DCR sampling circuit in the prior art.

[0023] Figure 3 The figure is a schematic diagram of the principle of a MOSFET sampling circuit in the prior art.

[0024] Figure 4 This is a structural schematic diagram of an average current sampling circuit for a switching converter provided by the present invention.

[0025] Figure 5 This is a circuit diagram of an average current sampling circuit for a switching converter provided by the present invention.

[0026] Figure 6 This is a working waveform diagram of the average current sampling circuit provided by the present invention.

[0027] Figure 7 This is a working waveform diagram of the average current sampling circuit provided by the present invention under different input voltage conditions.

[0028] Figure 8 This is a working waveform diagram of the average current sampling circuit provided by the present invention under different load conditions. DETAILED DESCRIPTION

[0029] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical elements are represented by identical or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0030] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by a programmable circuit. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected" between two nodes, it may be directly coupled or connected to the other element or there may be an intermediate element, and the connection between the elements may 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 the two.

[0031] In the present application, the switch tube is a transistor that works in a switching mode to provide a current path, including one selected from a bipolar transistor or a field effect transistor. The first end and the second end of the switch tube are respectively a high potential end and a low potential end on the current path, and the control end is used to receive a drive signal to control the on and off of the switch tube. MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) includes a first end, a second end and a control end. In the on state of the MOSFET, current flows from the first end to the second end. The first end, the second end and the control end of the P-type MOSFET are the source, the drain and the gate, respectively, and the first end, the second end and the control end of the N-type MOSFET are the drain, the source and the gate, respectively.

[0032] The present invention will be further described below with reference to the accompanying drawings and examples.

[0033] Figure 4 This is a structural schematic diagram of an average current sampling circuit for a switching converter provided by the present invention.

[0034] like Figure 4As shown, the switching converter adopts a buck topology and includes an inductor L, a switch HSD (also known as a high-side switch), a switch LSD (also known as a low-side switch), and an output capacitor Cout. The switching converter receives an input voltage VIN and generates an output voltage VOUT that is less than the input voltage VIN. In this embodiment, the output voltage VOUT is provided to an external load. The high-side switch HSD and the low-side switch LSD are connected in series between the input voltage VIN and ground, with their common terminal forming a switching node SW. A first terminal of the inductor L is connected to the switching node SW, and a second terminal of the inductor L is connected to the output of the switching converter. The output capacitor Cout is disposed between the output of the switching converter 100 and ground to generate the output voltage VOUT across its terminals. It should be understood that in this embodiment, the switch HSD is the main power transistor, the switch LSD is the rectifier, and the switches HSD and M2 can be any type of field-effect transistor, such as a metal-oxide-semiconductor field-effect transistor (MOSFET). Other types of field-effect transistors and / or other types of transistors known to those skilled in the art may also be used without departing from the teachings of the present invention.

[0035] exist Figure 4 In the example, the high-side switch HSD is controlled by the control signal GH, and the low-side switch LSD is controlled by the control signal GL. The output voltage VOUT can be adjusted by adjusting the pulse widths of the control signals GH and GL. For example, when the control signal GH is high, the high-side switch HSD is turned on, while when the complementary control signal GL is high, the low-side switch LSD is turned on. When the high-side switch HSD is turned on and the low-side switch LSD is turned off, the input voltage VIN is applied to the inductor L, causing the inductor current to increase linearly. Energy is stored in the inductor L in the form of a magnetic field. Simultaneously, the output capacitor Cout supplies power to the load, maintaining a stable output voltage. When the high-side switch HSD is turned off and the low-side switch LSD is turned on, a back EMF is generated in the inductor L. The inductor current charges the output capacitor Cout through the low-side switch LSD, causing the inductor current to decrease linearly. The output voltage is determined by the input voltage and the energy stored in the inductor. By periodically repeating the above operation, the output voltage VOUT can be stabilized within a set voltage range.

[0036] Furthermore, the average current sampling circuit 100 provided by the present invention includes a current detection module 101, a current-voltage conversion module 102, a sampling and holding module 103, and a current output module 104. The current detection module 101 is connected to both ends of the low-side switch tube LSD and is configured to detect the drain-source voltage of the low-side switch tube LSD under the control of the low-side control signal GL to generate a sampling current I1 proportional to the switching tube current of the low-side switch tube LSD. The current-voltage conversion module 102 is configured to convert the sampling current I1 into a voltage signal Vr. The sampling and holding module 103 is configured to sample and hold the voltage signal Vr according to the low-side control signal GL to generate a sampling voltage Vsen. The current output module 104 is configured to obtain an average current signal Iavg based on the sampling voltage Vsen.

[0037] In this embodiment, the sampling and holding operation of the sample-and-hold module 103 is synchronized with the switching state of the low-side switch LSD. For example, the sample-and-hold module 103 is configured to sample the voltage signal Vr when the low-side switch LSD is on, and to hold the voltage signal Vr via a capacitor when the low-side switch LSD is off.

[0038] Figure 5 The circuit diagram of the average current sampling circuit for the switching converter provided by the present invention is shown in FIG. Figure 5 As shown, the current detection module 101 of this embodiment includes an operational amplifier OP1, a transistor M1, a resistor R1, and a set of switches S1 and S2. For example, the transistor M1 is, for example, an NMOS transistor, the positive input terminal of the operational amplifier OP1 is connected to the reference ground voltage GND, the output terminal of the operational amplifier OP1 is connected to the gate of the transistor M1, and the negative input terminal of the operational amplifier OP1 is connected to the source of the transistor M1. The first end of the resistor R1 is connected to the negative input terminal of the operational amplifier OP1 and the source of the transistor M1, and the second end is connected to the middle node of the switches S1 and S2. The switches S1 and S2 are used to selectively connect the second end of the resistor R1 to the switch node SW or the reference ground voltage GND according to the low-side control signal GL. Among them, one end of the switch S1 is connected to the switch node SW, and the other end is connected to the second end of the resistor R1. One end of the switch S2 is connected to the ground GND, and the other end is connected to the second end of the resistor R1. The on / off state of the switch S1 is controlled by the low-side control signal GL, and the on / off state of the switch S2 is controlled by the inverted signal GLB of the low-side control signal.

[0039] When the low-side switch LSD is turned on, switch S1 is turned on and switch S2 is turned off. The second end of resistor R1 is connected to the switch node SW, that is, the voltage Vs = Vsw. At the same time, the feedback loop formed by operational amplifier OP1 and transistor M1 makes the voltage at the first end of resistor R1 equal to the reference ground voltage GND. At this time, the voltage drop across resistor R1 is equal to the drain-source voltage of the low-side switch LSD. As a result, a sampling current I1 proportional to the switching current of the low-side switch LSD is obtained in the resistor R1 branch, that is:

[0040] in, is the switching tube current of the low-side switching tube LSD, is the on-resistance of the low-side switch tube LSD, and R1 is the resistance value of the resistor R1.

[0041] When the low-side switch LSD is turned off, the switch S1 is turned off and the switch S2 is turned on. The second end of the resistor R1 is connected to the ground GND, that is, the voltage Vs=GND. At this time, the voltage drop across the resistor R1 is equal to 0, so the sampling current I1=0.

[0042] The current-to-voltage conversion module 102 includes transistors M2 and M3 that form a current mirror, and a resistor R2. Transistors M2 and M3 are, for example, PMOS transistors. The sources of transistors M2 and M3 are connected to a power supply voltage VCC, and the gates of transistors M2 and M3 are short-circuited with the drain of transistor M2. The drain of transistor M2 serves as a current end of the current mirror for receiving a sampled current I1, and the drain of transistor M3 is used to provide a mirrored current I2 of the sampled current I1. A first end of resistor R2 is connected to the drain of transistor M3, and a second end is connected to ground GND. The intermediate node between resistor R2 and transistor M3 is used to output a voltage signal Vr, namely:

[0043] Wherein, K1 is the mirror ratio of the current mirror formed by the transistors M2 and M3, and R2 is the resistance value of the resistor R2.

[0044] The sample-and-hold module 103 includes a switch S3 and an RC filter consisting of a resistor R3 and a capacitor C1. The sample-and-hold module 103 is configured to receive the voltage signal Vr when the switch S3 is on and filter the voltage signal Vr to obtain a sampled voltage Vsen. The sample-and-hold module 103 is also configured to maintain the sampled voltage Vsen via the capacitor C1 when the switch S3 is off.

[0045] In this embodiment, one end of switch S3 is used to receive a voltage signal Vr, the other end of switch S3 is connected to a first end of resistor R3, a second end of resistor R3 is connected to a first end of capacitor C1, a second end of capacitor C1 is connected to ground GND, and a node between resistor R3 and capacitor C1 is used to output a sampled voltage Vsen. The on and off state of switch S3 is controlled by a low-side control signal GL, and its switching state is consistent with the switching state of the low-side switch LSD. Therefore, when the low-side switch LSD is turned on, switch S3 is turned on and the voltage signal Vr is stored on capacitor C1; when the low-side switch LSD is turned off, switch S3 is turned off and the voltage at the node between resistor R3 and capacitor C1 is maintained via capacitor C1.

[0046] As the low-side switch LSD is periodically turned on and off, the final sampling voltage is:

[0047] The current output module 104 includes an operational amplifier OP2 and transistors M4 and M5. Among them, the transistor M4 is, for example, an NMOS transistor, and the transistor M5 is selected from a transistor of the same type as the low-side switch tube LSD. For example, the transistor M5 and the low-side switch tube LSD are both selected from NMOS transistors. The positive input terminal of the operational amplifier OP2 is used to receive the sampling voltage Vsen, the output terminal of the operational amplifier OP2 is connected to the gate of the transistor M4, the negative input terminal of the operational amplifier OP2 is connected to the source of the transistor M4, and the drain of the transistor M4 is used to output the average current signal Iavg. The drain of the transistor M5 is connected to the source of the transistor M4 and the negative input terminal of the operational amplifier OP2, the gate of the transistor M5 is connected to the power supply voltage VCC, and the source of the transistor M5 is connected to the ground GND.

[0048] In this embodiment, the feedback loop formed by the operational amplifier OP2 and the transistor M4 makes the drain voltage of the transistor M5 equal to the sampling voltage Vsen. Since the transistor M5 and the low-side switch LSD are of the same type, the average current signal Iavg obtained in the branch where the transistor M5 is located is:

[0049] Among them, K2 is the ratio between the on-resistance of the low-side switch tube LSD and the on-resistance of the transistor M5, is the load current of the switching converter.

[0050] Figure 6 This is the working waveform diagram of the average current sampling circuit provided by the present invention. Figure 6, respectively, show waveform diagrams of the switch node voltage Vsw, the low-side control signal GL, the load current ILoad, the low-side switch tube current ILsd, the average current signal Iavg, the voltages of the nodes Vs, Vr and Vp, and the sampling voltage Vsen. Figure 6 As shown, when the low-side switch LSD is on, the voltage signal Vr and the sampled voltage Vsen are consistent with the waveform of the low-side switch current ILsd, indicating that the circuit can accurately sample the current information in the low-side switch LSD. When the low-side switch LSD is off, the sampled current information is stored by capacitor C1 and then converted by current output module 104 into an average current signal Iavg proportional to the load current ILoad of the switching converter.

[0051] Furthermore, taking the output voltage VOUT=1.05V as an example, Figure 7 FIG1 shows a response curve diagram of the average current signal of an embodiment of the present invention under different input voltages when the load current ILoad=4A. Figure 8 FIG shows a response curve diagram of the average current signal of an embodiment of the present invention under different load conditions when the input voltage VIN=12V. Figure 7 and Figure 8 As shown, the average current sampling circuit 100 of the embodiment of the present invention can obtain accurate average current information under different input voltage conditions and different load conditions, and has higher sampling accuracy.

[0052] It should be understood that the average current sampling circuit provided by the present invention is only based on Figure 4 and Figure 5 The buck topology shown is used as an example for illustration and is not limited to the buck topology type. It is also applicable to other topology types. For example, for other topologies such as boost and buck-boost, it is well known to those skilled in the art that adaptive changes to the circuit can be made to achieve this, which will not be repeated here.

[0053] It should be understood that although a single-phase switching power supply is used as an example in the above embodiments, the average current sampling circuit of the embodiment of the present invention is also applicable to a multi-phase switching power supply. By accurately sampling the average current information of each phase circuit, the current sharing function of the multi-phase switching power supply is realized.

[0054] To sum up, the average current sampling circuit provided by the present invention adopts a current detection module to detect the drain-source voltage of the low-side switch tube to generate a sampling current proportional to the switch tube current of the low-side switch tube, and then converts the sampling current into a sampling voltage through the current-voltage conversion module and the sample-and-hold module. Finally, the average current signal is obtained according to the sampling voltage through the current output module, thereby realizing accurate sampling of the average current of the switching converter.

[0055] In addition, the average current sampling circuit of the present invention is different from the traditional MOSFET sampling technology. Since the sampling resistor connected in series at the output end of the switching converter is omitted, the power loss of the circuit can be reduced and the energy utilization rate can be improved. It is particularly suitable for application scenarios with strict efficiency requirements.

[0056] It should be noted that although devices are described herein as certain N-channel or P-channel devices, or certain N-type or P-type doped regions, those skilled in the art will appreciate that complementary devices are also achievable according to the present invention. Those skilled in the art will appreciate that conductivity type refers to the mechanism by which conduction occurs, such as conduction by holes or electrons. Therefore, conductivity type does not refer to doping concentration but rather to doping type, such as P-type or N-type. Those skilled in the art will appreciate that the terms "during," "when," and "when" used herein with respect to circuit operation are not strict terms indicating that an action occurs immediately upon the start of a startup action. Rather, there may be some small but reasonable delay or delays between the start of a startup action and the reaction initiated by the startup action, such as various transmission delays. The terms "approximately" or "substantially" are used herein to indicate that an element has a parameter that is expected to be close to the stated value or position. However, as is well known in the art, slight variations exist that make it difficult to accurately define a value or position as stated. It is well established in the art that a deviation of at least ten percent (10%) (or at least twenty percent (20%) for semiconductor doping concentrations) is a reasonable deviation from the desired goal of accuracy as described. When used in conjunction with a signal state, the actual voltage value or logic state of the signal (e.g., "" or "") depends on whether positive or negative logic is used.

[0057] In addition, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0058] The embodiments of the present invention are described above, but these embodiments do not describe all details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and modify and use it based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. An average current sampling circuit for a switching converter, the switching converter comprising a high-side switch, a low-side switch, and an inductor, the high-side switch and the low-side switch being used to control the charging and discharging of the inductor to control the switching converter to achieve power transmission, the average current sampling circuit comprising: A current detection module, configured to detect the drain-source voltage of the low-side switch tube under the control of a low-side control signal, so as to generate a sampling current proportional to the switch tube current of the low-side switch tube; A current-voltage conversion module, configured to convert the sampled current into a voltage signal; A sampling and holding module, configured to sample and hold the voltage signal according to the low-side control signal to generate a sampled voltage; as well as The current output module is used to generate an average current signal according to the sampled voltage.

2. The average current sampling circuit according to claim 1, wherein: The sampling and holding module is used to sample the voltage signal when the low-side switch tube is turned on, and to hold the voltage signal when the low-side switch tube is turned off.

3. The average current sampling circuit according to claim 1, wherein: The current detection module includes: a first operational amplifier, a positive input terminal of which is connected to a reference ground voltage; a first transistor, having a first end for outputting the sampling current, a control end connected to the output end of the first operational amplifier, and a second end connected to the negative input end of the first operational amplifier; a first resistor, a first end of which is connected to the negative input terminal of the first operational amplifier and the second end of the first transistor; and A set of switches is configured to selectively connect the second end of the first resistor to the switch node or the reference ground voltage according to the low-side control signal.

4. The average current sampling circuit according to claim 3, wherein: The set of switches is used to connect the second end of the first resistor to the switch node when the low-side switch tube is turned on, and to connect the second end of the first resistor to the reference ground voltage when the low-side switch tube is turned off.

5. The average current sampling circuit according to claim 1, wherein: The current-voltage conversion module includes: A second transistor and a third transistor constitute a current mirror, wherein the first terminals of the second transistor and the third transistor are connected to a power supply voltage, and the control terminals of the second transistor and the third transistor are short-circuited with the second terminal of the second transistor. The second end of the second transistor is used to receive the sampling current, and the second end of the third transistor is used to provide a mirror current of the sampling current; and a second resistor, a first end of which is connected to the second end of the third transistor, and a second end of which is connected to a reference ground voltage; The common node between the second resistor and the third transistor is used to output the voltage signal.

6. The average current sampling circuit according to claim 1, wherein: The sample and hold module comprises: a switch, wherein a first end of the switch is connected to the voltage signal, and a control end of the switch is used to receive the low-side control signal; and a filter composed of a third resistor and a first capacitor, wherein a first end of the third resistor is connected to the second end of the switch, a second end of the third resistor is connected to the first end of the first capacitor, and a second end of the first capacitor is connected to a reference ground voltage; The switching state of the switch is consistent with the switching state of the low-side switch tube, so that the sampling voltage is obtained at the middle node between the third resistor and the first capacitor.

7. The average current sampling circuit according to claim 1, wherein: The current output module includes: a second operational amplifier, a positive input terminal of which is used to receive the sampled voltage; a fourth transistor, having a first terminal for outputting the average current signal, a control terminal connected to the output terminal of the second operational amplifier, and a second terminal connected to the negative input terminal of the second operational amplifier; and A fifth transistor has a first terminal connected to the second terminal of the fourth transistor, a control terminal connected to a power supply voltage, and a second terminal connected to a reference ground voltage.

8. The average current sampling circuit according to claim 7, wherein: The fifth transistor and the low-side switch are selected from the same transistor type.

9. A switching converter comprising: A high-side switch tube, a low-side switch tube and an inductor, wherein the high-side switch tube and the low-side switch tube are used to control the charging and discharging of the inductor to control the switching converter to realize power transmission; as well as The average current sampling circuit according to any one of claims 1 to 8.

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