Multi-level dc converter and voltage control method for flying capacitor, control device

Abstract

The embodiment of the application provides a kind of multi-level DC converter and the voltage control method of flying capacitor, control device.Therein, multi-level DC converter includes controller, flying capacitor, two switch tube groups and inductance.The control method of flying capacitor includes: in response to the absolute value of the difference between the sampling voltage of flying capacitor and reference voltage is greater than the first threshold value, according to the size of inductance current, the duty cycle difference between the first switch tube in two switch tube groups or the phase difference between the first switch tube carrier in two switch tube groups is adjusted.Using the embodiment of the application, the voltage of flying capacitor can be controlled, and the stability of multi-level DC converter operation is improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a voltage control method and control device for a multilevel DC-DC converter and a flying capacitor. Background Technology

[0002] Multilevel DC-DC converters can reduce the voltage stress on each switch by adding a flying capacitor. Taking a three-level DC-DC converter with a flying capacitor as an example, half of the input voltage can be stored by the flying capacitor, so that the output level can be 0, 1 / 2 and 1. The variation range is half that of a two-level topology, which allows the use of low-voltage switches to improve the performance of the electronic system.

[0003] Currently, the voltage of the flying capacitor can be controlled by adjusting the difference in duty cycles between the first (or second) switching transistors in the switching group, based on the direction of the inductor current. However, when the inductor current is very small and a high-frequency triangular wave repeatedly switching between positive and negative, controlling the voltage of the flying capacitor based on the instantaneous current direction places extremely high demands on the control chip, making it unsuitable for practical engineering applications. Even if the difference in duty cycles between the first (or second) switching transistors in the switching group is greatly increased, the flying capacitor voltage cannot be effectively raised or lowered, failing to achieve the control objective of stabilizing the voltage of the flying capacitor at the target value. Summary of the Invention

[0004] This application discloses a voltage control method and control device for a multilevel DC-DC converter and a flying capacitor, which can control the voltage of the flying capacitor and improve the stability of the multilevel DC-DC converter operation.

[0005] In a first aspect, embodiments of this application disclose a multilevel DC-DC converter, which includes at least one flying capacitor, two switching transistor groups connected to the flying capacitor, an inductor connected to the positive terminal of the low-voltage power supply of each switching transistor group and the multilevel DC-DC converter, and a controller for controlling the switching transistor groups; wherein, each switching transistor group includes a first switching transistor and a second switching transistor with complementary on and off states, the first switching transistor is connected to one end of the high-voltage power supply of the multilevel DC-DC converter, and the second switching transistor is connected to the other end of the high-voltage power supply of the multilevel DC-DC converter; the controller is used to adjust the duty cycle difference between the first switching transistors in the two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups according to the magnitude of the inductor current when the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor is greater than a first threshold.

[0006] A multilevel DC-DC converter, also known as a multilevel DC-DC converter, is used for direct current (DC) to DC power conversion, such as boost conversion or buck conversion. This application does not limit the specific type of multilevel DC-DC converter; it can be a three-level DC-DC converter, a five-level DC-DC converter, a seven-level DC-DC converter, etc. A multilevel topology corresponding to a multilevel DC-DC converter refers to an output level with at least three states. For example, an output level with three states (1, 1 / 2, and 0) is called a three-level topology, and an output level with five states (1, 3 / 4, 1 / 2, 1 / 4, and 0) is called a five-level topology.

[0007] The first and second switching transistors can be field-effect transistors (FETs), metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), junction field-effect transistors (JFETs), and their parallel diodes, etc., and are not limited here.

[0008] The controller can be a pulse width modulation (PWM) device, a battery management system (BMS) based on PWM technology, a microcontroller unit (MCU), a central processing unit (CPU), other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The controller can be a single chip or multiple chips with communication connections. The controller may include control units corresponding to each switch transistor individually, or it may include control units corresponding to a group of switches, such as the pulse width modulators corresponding to the first and second switches in a switch group, etc., without limitation.

[0009] The sampling voltage of the flying capacitor is the real-time voltage acquired. The reference voltage of the flying capacitor is the target value to be adjusted for the flying capacitor. The current of the inductor, also called the inductor current, can be an instantaneous current value or an average value.

[0010] This application does not limit the first threshold value; it can be 0, etc. It is understood that if the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor is greater than the first threshold value, it indicates that the voltage of the flying capacitor has not yet been adjusted to the target value (for example, the target value for a three-level DC-DC converter can be half the voltage of the high-voltage power supply). In this case, the duty cycle difference between the switches on one side of the flying capacitor, or the phase difference between the carrier waves of the first switch on that side, can be adjusted to control the voltage of the flying capacitor, thereby reducing the voltage stress on the multilevel DC-DC converter. If the difference between the sampled voltage and the reference voltage of the flying capacitor is less than or equal to the first threshold value, it indicates that the voltage of the flying capacitor has been adjusted to the target value, and the current operating state can be maintained. This improves the stability of the multilevel DC-DC converter operation.

[0011] In conjunction with the first aspect, in a first possible implementation, the controller is specifically configured to increase the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups when the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups is determined based on the magnitude of the inductor current, and the sampled voltage of the flying capacitor is less than the reference voltage. This increases the voltage of the flying capacitor.

[0012] In conjunction with the first aspect, in the second possible implementation, the controller is specifically used to reduce the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, provided that the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups is determined based on the magnitude of the inductor current, and the sampled voltage of the flying capacitor is greater than the reference voltage. This reduces the voltage across the flying capacitor.

[0013] In conjunction with the first aspect, or the first possible implementation, or the second possible implementation, in the third possible implementation, the controller is specifically used to adjust the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups when the inductor current is less than the second threshold.

[0014] In conjunction with the first aspect, in the fourth possible implementation, the controller is specifically used to adjust the duty cycle difference between the first switching transistors in the two switching transistor groups when the inductor current is greater than the third threshold.

[0015] In conjunction with the first aspect, or the first possible implementation, or the second possible implementation, in the fifth possible implementation, the controller is specifically used to adjust the duty cycle difference between the first switching transistors in the two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups according to the adjustment method of the previous moment when the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold.

[0016] This application does not limit the magnitude of the second and third thresholds, but the second threshold is less than the third threshold. It can be understood that if the inductor current is less than the second threshold, it indicates a small inductor current, possibly indicating a light load. In this case, the phase difference between the carrier waves of the first switching transistors in the two switching groups can be adjusted using phase-shift control without adjusting the duty cycle difference. If the inductor current is greater than the third threshold, it indicates a large inductor current, possibly indicating a heavy load. In this case, the duty cycle difference between the first switching transistors in the two switching groups can be adjusted by adjusting the duty cycle without adjusting the phase difference. If the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold, it may be an intermediate state between light and heavy loads. The adjustment method from the previous moment can be used. For example, if phase-shift control was used in the previous moment, it should continue; if duty cycle adjustment was used in the previous moment, it should continue. In this way, the flying voltage can be controlled through these three scenarios, ensuring a smooth transition of the controlled flying capacitor voltage.

[0017] Secondly, this application discloses a voltage control method for a flying capacitor. The flying capacitor is used in a multilevel DC-DC converter, which also includes two switching transistor groups, an inductor, and a controller. Each switching transistor group includes a first switching transistor and a second switching transistor with complementary on and off states. The voltage control method includes: when the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor is greater than a first threshold, adjusting the duty cycle difference between the first switching transistors in the two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, based on the magnitude of the inductor current. In this way, even if the voltage of the flying capacitor is determined not to have reached the target value, the duty cycle difference between the switching transistors on one side of the flying capacitor, or the phase difference between the carrier waves of the switching transistors on that side, can be further adjusted to control the voltage of the flying capacitor, thereby improving the stability of the multilevel DC-DC converter operation.

[0018] In conjunction with the second aspect, in the first possible implementation, adjusting the duty cycle difference between the first switching transistors in the two switching transistor groups, or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, based on the magnitude of the inductor current, includes: increasing the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups when the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups is determined based on the magnitude of the inductor current and the sampling voltage of the flying capacitor is less than the reference voltage.

[0019] In conjunction with the second aspect, in the second possible implementation, adjusting the duty cycle difference between the first switching transistors in the two switching transistor groups, or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, based on the magnitude of the inductor current, includes: reducing the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups when the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups is determined based on the magnitude of the inductor current and the sampling voltage of the flying capacitor is greater than the reference voltage.

[0020] In conjunction with the second aspect, in the third possible implementation, the duty cycle difference between the first switching transistors in the two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups is adjusted according to the magnitude of the inductor current. This includes: when the inductor current is less than a second threshold, the controller adjusts the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups.

[0021] In conjunction with the second aspect, in the fourth possible implementation, the controller adjusts the duty cycle difference between the first switching transistors in the two switching transistor groups, or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, according to the magnitude of the current, including: in response to the current being greater than a third threshold, the controller adjusts the duty cycle difference between the first switching transistors in the two switching transistor groups.

[0022] In conjunction with the second aspect, in the fifth possible implementation, the controller adjusts the duty cycle difference between the first switching transistors in the two switching transistor groups, or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, according to the magnitude of the current. This includes: in response to the current being greater than or equal to a second threshold and less than or equal to a third threshold, the controller adjusts the duty cycle difference between the first switching transistors in the two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups according to the adjustment method of the previous moment.

[0023] Thirdly, embodiments of this application disclose a control device. The control device includes a controller and a memory; wherein the memory stores instructions, and the controller invokes the instructions stored in the memory to execute the method described in the second aspect.

[0024] It should be understood that the implementations and beneficial effects of the above-mentioned aspects of this application can be referenced from each other. Attached Figure Description

[0025] The accompanying drawings used in the embodiments of this application are described below.

[0026] Figure 1 This is a schematic diagram of the architecture of a photovoltaic power generation system provided in an embodiment of this application;

[0027] Figure 2 A circuit diagram of a three-level DC-DC converter is provided for an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of the structure of a multilevel DC-DC converter provided in an embodiment of this application;

[0029] Figures 4-9 This is a diagram illustrating the operating mode of a three-level DC-DC converter proposed in this application.

[0030] Figures 10-13 The graphs show the relationship between the duty cycle difference and phase difference and the flyover voltage as proposed in this application.

[0031] Figure 14 A schematic diagram illustrating a process for adjusting the voltage of a flying capacitor by a controller, provided in an embodiment of this application;

[0032] Figure 15 This is a flowchart illustrating a voltage control method for a flying capacitor provided in an embodiment of this application. Detailed Implementation

[0033] The term "connection" as described in this application refers to a direct or indirect connection. For example, a connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For instance, A can be directly connected to C, and C can be directly connected to B, thus achieving a connection between A and B through C. A connection can also be referred to as coupling, electrical connection, etc., without limitation. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] This application relates to a multilevel DC-DC converter, or multilevel DC-DC converter, for performing direct current (DC) to DC power conversion. For example, it can be a boost converter or a buck converter, and this application does not specifically limit the specific application scenarios. Furthermore, this application does not limit the application scenarios of the multilevel DC-DC converter; it can be applied to different types of electrical equipment (such as power grids, household appliances, or industrial and commercial electrical equipment). It can be applied to user terminals (e.g., mobile phones, smart devices, televisions, etc.), automobiles, and other electrical equipment fields. It is adaptable to power supply scenarios for large electrical equipment (e.g., power grids, industrial equipment, etc.), small and medium-sized distributed electrical equipment (e.g., vehicle-mounted electrical equipment, household electrical equipment, etc.), and mobile electrical equipment (e.g., mobile phones, smart devices, etc.), among other application scenarios.

[0035] For example, please refer to Figure 1 , Figure 1 This is a schematic diagram of the architecture of a photovoltaic power generation system provided in an embodiment of this application. Figure 1 As shown, the photovoltaic power generation system includes photovoltaic modules, a multilevel DC-DC converter, a battery bank, an inverter circuit, DC loads, AC loads, and a power grid. In this photovoltaic power generation system, solar energy is converted into DC power by the photovoltaic modules. The DC power is boosted by the multilevel DC-DC converter, and the boosted DC power can be supplied to DC loads, stored in the battery bank, or converted into AC power by the inverter to supply AC loads or be connected to the power grid.

[0036] This application does not limit the specific type of multilevel DC-DC converter, and it can be a three-level DC-DC converter, a five-level DC-DC converter, a seven-level DC-DC converter, etc. A multilevel topology corresponding to a multilevel DC-DC converter refers to an output level with at least three states. For example, an output level with three states (1, 1 / 2, and 0) is called a three-level topology, and an output level with five states (1, 3 / 4, 1 / 2, 1 / 4, and 0) is called a five-level topology. Furthermore, multilevel topology circuits are further divided into diode-clamped multilevel topology circuits, flying capacitor-clamped multilevel topology circuits, etc. The multilevel DC-DC converter topology circuit involved in this application can be a flying capacitor-clamped multilevel topology circuit, that is, it includes a flying capacitor.

[0037] To enable those skilled in the art to better understand the technical solutions provided in the embodiments of this application, a three-level DC-DC converter is used as an example below. Please refer to... Figure 2 , Figure 2 A circuit diagram of a three-level DC-DC converter is provided for an embodiment of this application. For example... Figure 2 As shown, the three-level DC-DC converter includes a high-voltage power supply V. HCapacitor C1, Switch Q1, Switch Q2, Switch Q3, Switch Q4, Flying capacitor C fly Inductor L1, capacitor C2, and low-voltage power supply V L .

[0038] Among them, the switching transistors Q1, Q2, Q3 and Q4 can be field-effect transistors (FETs), metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), junction field-effect transistors (JFETs) and their parallel diodes, etc., and are not limited here.

[0039] The drain of the switching transistor Q1 is connected to the high-voltage power supply V. H The positive terminal of the parallel capacitor C1 is connected, and the source of the switching transistor Q1 is connected to the drain of the switching transistor Q2 and the flying capacitor C. fly One end is connected. Flying capacitor C fly The other end is connected to the source of switching transistor Q3 and the drain of switching transistor Q4. The source of switching transistor Q2 and the drain of switching transistor Q3 are connected to one end of inductor L1, and the other end of inductor L1 is connected to the low-voltage power supply V. L Connect the negative terminal of (the parallel capacitor C2).

[0040] In this embodiment of the application, the flying capacitor C can be used as a reference. fly The connection relationships between the switching transistors are grouped to obtain the connection with the flying capacitor C. fly Two switching transistor groups are connected. For example, switching transistors Q1 and Q4 form one switching transistor group, and switching transistors Q2 and Q3 form another. Furthermore, the switching transistors can be connected to the high-voltage power supply V of the multilevel DC-DC converter. H The connection relationship between them will connect the switching transistor group to the high-voltage power supply V. H The switching transistor connected to one end is called the first switching transistor, which is connected to the high-voltage power supply V in the switching transistor group. H The other end of the first switch is connected to a switching transistor called the second switching transistor. For example, the first switching transistor is connected to a high-voltage power supply V. H If the positive terminal is connected to the voltage source, then the first switching transistor can be either switching transistor Q1 or switching transistor Q2. The second switching transistor is connected to the high-voltage power supply V. H The negative terminal of the switch can be either switch Q4 or switch Q3.

[0041] In a switching transistor group, the on and off states of the first and second switches are complementary. For example, if the on and off states of switches Q1 and Q4 are complementary, then when switch Q1 is on, switch Q4 is off. Conversely, when switch Q1 is off, switch Q4 is on. Thus, current signals can be transmitted via the carrier wave of the on switch in the first and second switching transistors of the switching transistor group.

[0042] Since the on and off states of the first and second switches within the same switching transistor group are complementary, if the first switch in the switching transistor group is off, the second switch in the same group needs to be turned on. If the first switch in the switching transistor group is closed, the second switch in the same group needs to be turned off. The following description focuses on the method for controlling the first switch in the switching transistor group; the method for controlling the second switch in the same group can be adjusted accordingly by referring to the description of the method for controlling the first switch.

[0043] This application uses a single flying capacitor as an example; in practice, there can be two or more. For example, Figure 2 The flying capacitor C (not shown) fly Another flying capacitor connected in series. Alternatively, a five-level DC-DC converter may have two flying capacitors, one of which is connected in parallel with the first and second switching transistor groups. The second switching transistor group includes a first sub-switching group and a second sub-switching group, and the first and second sub-switching groups are connected in parallel with the other flying capacitor. This application does not limit the size and number of inductors, and the multilevel DC-DC converter may also include capacitors, resistors, etc., connected to the inductors.

[0044] A three-level DC-DC converter may also include Figure 3The controller 101 is used to control the switching transistor group. This controller 101 can be a pulse width modulation (PWM) device, or a battery management system (BMS) based on PWM technology, a microcontroller unit (MCU), a central processing unit (CPU), other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The controller can be understood as a single chip or multiple chips with communication connections. The controller may include control units corresponding to each switching transistor, or it may include control units corresponding to the switching transistor group, for example, pulse width modulators corresponding to switching transistors Q1 and Q4, pulse width modulators corresponding to switching transistors Q2 and Q3, etc., without limitation.

[0045] PWM technology can modulate the carrier waves of switches Q1, Q2, Q3, and Q4, and control their on / off states, enabling real-time bidirectional power flow. When the load is connected to the low-voltage power supply V of the three-level DC-DC converter... L When connected, the input terminal of the three-level DC-DC converter is a high-voltage power supply V. H The output terminal is a low-voltage power supply V. L The current in the three-level DC-DC converter comes from the high-voltage power supply V. H Flow to low voltage power supply V L When the load is connected to the high-voltage power supply V of the three-level DC-DC converter H When connected, the input terminal of the three-level DC-DC converter is the low-voltage power supply V. L The output terminal is a high-voltage power supply V. H The current of the three-level DC-DC converter comes from the low-voltage power supply V. L Flow to high voltage power supply V H .

[0046] Furthermore, by determining the current direction of inductor L1, the charging and discharging time of the flying capacitor can be adjusted to control its voltage. For example, when switching transistors Q1 and Q3 are turned on, the high-voltage power supply V... H The low-voltage power supply V is affected by the switching transistors Q1 and Q3 and the inductor L1. LIf the current in inductor L1 flows from the high-voltage power supply V... H Flow to low voltage power supply V L (With the current direction being positive), then the flying capacitor C fly As the inductor L1 charges, the voltage increases; if the current in inductor L1 flows from the low-voltage power supply V... L Flow to high voltage V H (If the current direction is negative), then the flying capacitor C fly Discharge causes a voltage drop; when switching transistors Q2 and Q4 are turned on, the flying capacitor C... fly The switching transistors Q2 and Q4, along with the inductor L1, act on the low-voltage power supply V. L If the current direction of inductor L1 is positive, then the flying capacitor C... fly Discharge causes a voltage drop; if the current in inductor L1 is negative, then the flying capacitor C... fly When charging, the voltage increases.

[0047] In this embodiment of the application, the flying capacitor C fly The voltage across the inductor can be simply referred to as the flying voltage, and the current in the inductor can be simply referred to as the inductor current. If the inductor current is relatively small and it is a high-frequency triangular wave repeatedly switching between positive and negative, this situation can be called a light load. Conversely, if the inductor current is relatively large and it is always positive or always negative, this situation can be called a heavy load. The difference in duty cycle can be simply referred to as the duty cycle difference, and the difference in phase shift or phase can be simply referred to as the phase difference. The phase shift control method is to adjust the phase while keeping the duty cycle fixed. The duty cycle adjustment method is to adjust the duty cycle while keeping the phase fixed. In this way, the singleness of adjustment can be improved, and the voltage change caused by the effect can be ensured to be smooth.

[0048] In steady-state operation, the duty cycles of switching transistors Q1 (Q3) and Q2 (Q4) are equal, and their phase shift is 180°, meaning the phase difference between the carrier waves of switching transistors Q1 and Q2 is 180°. Therefore, steady-state operation of the three-level DC-DC converter can be achieved by adjusting the difference in duty cycles between switching transistors Q1 and Q2 (referred to as the duty cycle difference). For example, when power is supplied by a high-voltage power supply V... H to low voltage power supply V L Flow (current from high voltage power supply V) H to low voltage power supply V L When the current flows, the flyback voltage can be increased by increasing the duty cycle of switch Q1 and decreasing the duty cycle of switch Q2, that is, increasing the difference in duty cycles between switch Q1 and switch Q2, and vice versa; when the power is supplied by a low-voltage power source V... L to high voltage power supply V H Flow (current from low voltage power supply V) L to high voltage power supply VH When the current is flowing, the flyover voltage can be increased by decreasing the duty cycle of switch Q1 and increasing the duty cycle of switch Q2, that is, by decreasing the difference in duty cycles between switch Q1 and switch Q2, and vice versa.

[0049] However, under light load conditions, controlling the voltage of the flying capacitor based on the instantaneous current direction places extremely high demands on the control chip, making it unsuitable for practical engineering applications. Even if the difference in duty cycle between the first switch (e.g., switches Q1 and Q2) or the second switch (e.g., switches Q3 and Q4) in the parallel switching transistor group connected to the flying capacitor is adjusted to be very large, it is still impossible to effectively raise or lower the voltage of the flying capacitor, failing to achieve the control objective of stabilizing the voltage of the flying capacitor at the target value.

[0050] Based on this, this application proposes a multilevel DC-DC converter, in which the controller is used to adjust the duty cycle difference between the first switching transistors in two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in two switching transistor groups according to the magnitude of the inductor current when the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor is greater than a first threshold.

[0051] The sampling voltage of the flying capacitor is the real-time voltage acquired. The reference voltage of the flying capacitor is the target value to be adjusted for the flying capacitor. For example, the target value for a three-level DC-DC converter can be half the voltage of the high-voltage power supply. The inductor current, also called inductor current, can be an instantaneous current value or an average value. This application does not limit the first threshold and can be 0, etc. It can be understood that if the absolute value of the difference between the sampling voltage and the reference voltage of the flying capacitor is greater than the first threshold, it means that the voltage of the flying capacitor has not yet been adjusted to the target value. The duty cycle difference between the switches connected in parallel on one side of the flying capacitor, or the phase difference between the carrier waves of the first switch on that side, can be adjusted to control the voltage of the flying capacitor and reduce the voltage stress of the multilevel DC-DC converter. If the difference between the sampling voltage and the reference voltage of the flying capacitor is less than or equal to the first threshold, it means that the voltage of the flying capacitor has been adjusted to the target value and can continue to operate in the current state. In this way, the stability of the multilevel DC-DC converter can be improved.

[0052] This application does not limit the method for adjusting the phase difference and duty cycle difference. Taking switching transistors Q1 and Q2 as examples, after determining the duty cycle difference to be adjusted, it can be adjusted based on the aforementioned adjustment method according to the current direction. For example, when the current flows from the high-voltage power supply to the low-voltage power supply, if the flying capacitor C... flyIf the sampled voltage is less than the reference voltage, the duty cycle difference between the first switching transistors in the two switching transistor groups can be increased, i.e., the duty cycle of switching transistor Q1 can be increased and the duty cycle of switching transistor Q2 can be decreased to increase the flyover voltage; or, in the case where current flows from the high-voltage power supply to the low-voltage power supply, if the flyover capacitor C fly If the sampled voltage is greater than the reference voltage, the duty cycle difference between the first switching transistors in the two switching transistor groups can be reduced, i.e., the duty cycle of switching transistor Q1 can be reduced and the duty cycle of switching transistor Q2 can be increased to reduce the flyover voltage; or, in the case where current flows from the low-voltage power supply to the high-voltage power supply, if the flyover capacitor C fly If the sampled voltage is less than the reference voltage, the duty cycle difference between the first switching transistors in the two switching transistor groups can be reduced, i.e., the duty cycle of switching transistor Q1 can be reduced and the duty cycle of switching transistor Q2 can be increased to raise the flyover voltage; or, in the case where current flows from the low-voltage power supply to the high-voltage power supply, if the flyover capacitor C fly If the sampled voltage is greater than the reference voltage, the duty cycle difference between the first switches in the two switching groups can be increased, i.e., the duty cycle of switch Q1 can be increased and the duty cycle of switch Q2 can be decreased to reduce the flyaway voltage. Thus, by adjusting the duty cycle difference, the flyaway capacitor C is reduced based on the direction of the inductor current. fly Adjusting the voltage.

[0053] Phase difference adjustment flying capacitor C fly The principle is as follows: Increase the phase difference between the carrier waves of the first (or second) switching transistor, so that the flying capacitor C... fly The charging time (area) is greater than the discharging time (area), thus increasing the flying capacitor C. fly The voltage; reduce the phase difference between the carrier waves of the first switch (or the second switch), so that the flying capacitor C fly The charging time (area) is shorter than the discharging time (area), thus reducing the flying capacitor C. fly The voltage. Therefore, in one possible example, the phase difference between the carrier waves of the first switching transistor in the two switching transistor groups is determined based on the magnitude of the inductor current, and the flying capacitor C... fly If the sampling voltage is less than the reference voltage, increase the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups; or adjust the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups based on the magnitude of the inductor current, and the flying capacitor C fly When the sampling voltage is greater than the reference voltage, the phase difference between the carrier waves of the first switching transistor in the two switching transistor groups is reduced.

[0054] This application does not specify whether to adjust the phase difference or the duty cycle difference; the operating conditions of the multilevel DC-DC converter can be analyzed first. Please refer to... Figures 4-9These are the operating modes of a three-level DC-DC converter proposed in this application. Wherein, V0 is the flyover voltage V0 at the beginning of a cycle. fly V1 is the transient voltage V at any time during a cycle. fly V2 is the flyover voltage V at the end of one cycle. fly ;I L The current is the inductor current, which will also be described by i(t) in the formulas below; N / A / B / C / M are the inductor currents I and N, respectively. L The peak value; T0 to T3 are the time points of different stages within a switching cycle. Considering that the dead zone d causes different freewheeling circuits in different modes, the values ​​of T0 to T3 are different; m / k / n are the slopes of the corresponding straight lines in the figure.

[0055] In the following text, P represents the switching period, D1 represents the duty cycle of switch Q1, and D2 represents the duty cycle of switch Q2. The duty cycle D of a three-level DC-DC converter can be understood as the steady-state duty cycle of the converter under ideal conditions. Ideally, the duty cycle D of a three-level DC-DC converter is equal to the duty cycle D1 of switch Q1 and equal to the duty cycle D2 of switch Q2. In reality, due to the flyback voltage deviating from the target value, it is necessary to adjust the difference in duty cycles between switches Q1 and Q2, or the phase difference between the carrier waves of switches Q1 and Q2. If the duty cycle D is less than 0.5, it means that the duty cycles D1 of switch Q1 and D2 of switch Q2 are both less than 0.5. If the duty cycle D is greater than 0.5, it means that the duty cycles D1 of switch Q1 and D2 of switch Q2 are both greater than 0.5. Figures 4-9 These correspond to Mode 1, Mode 2, Mode 3, Mode 4, Mode 5, and Mode 6, respectively, where:

[0056] Mode 1, duty cycle D less than 0.5, inductor current I L A constant positive value indicates a heavy load condition. (See reference...) Figure 4 T0 = ​​D1P T3 = P.

[0057] Mode 2, duty cycle D is less than 0.5, inductor current I L A constant negative value indicates a heavy load. (See reference...) Figure 5 T0 = ​​(D1 + 2d)P T3 = P.

[0058] Mode 3, duty cycle D is less than 0.5, inductor current I L (t) can be negative or positive, representing the light load case. (See reference...) Figure 6 T0 = ​​(D1 + d)P T3 = P.

[0059] Mode 4, duty cycle D greater than 0.5, inductor current I L A constant positive value indicates a heavy load condition. (See reference...) Figure 7 T0 = ​​(1-D1)P T3 = P.

[0060] Mode 5, duty cycle D greater than 0.5, inductor current I L A constant negative value indicates a light load condition. (Refer to...) Figure 8 T0 = ​​[1 - (D1 + 2d)]P T3 = P.

[0061] Mode 6, duty cycle D greater than 0.5, inductor current I L It can be negative or positive, representing a light load. (See reference...) Figure 9 T0 = ​​[1 - (D1 + d)]P T3 = P.

[0062] By establishing a reasonable coordinate system, combined with Figures 4-6 In the freewheeling circuit of the inductor current, in Modes 1, 2, and 3, the dead zone d can be merged into the duty cycle D1 and duty cycle D2 for unified analysis. (Combined with...) Figures 7-9 In the freewheeling circuit of the inductor current, in modes four, five, and six, the dead zone d can be merged into duty cycles D1 and D2 for unified analysis. The following analysis uses modes one and four as examples; the other modes can be analyzed similarly.

[0063] During one switching cycle, the voltage change of the flying capacitor can be obtained by integrating the current flowing through it, as shown in equation (1).

[0064]

[0065] Calculating the common part in equation (1) yields equation (2).

[0066]

[0067] The values ​​of m, n, and k can be determined by referring to the formula below, where L represents the inductance.

[0068]

[0069] If the phase difference between the carrier waves of switch Q1 (or switch Q3) and switch Q2 (or switch Q4) is fixed at 180°, adjusting the duty cycles D1 and D2 can yield the effect of different duty cycle differences on the fly-through voltage. For example, when D < 0.5, substituting the time T0 to time T3 in mode 1 into equation (2) yields equation (3).

[0070]

[0071] When D>0.5, substituting the time T0 to time T3 in mode 4 into equation (2) yields equation (4).

[0072]

[0073] If the duty cycle D of duty cycles D1 and D2 is fixed (it can be any fixed value from 0 to 1), and the phase difference between the carrier waves of switching transistors Q1 (or Q4) and Q2 (or Q3) is adjusted to Δθ, the influence of different phase differences on the fly-through voltage can be obtained, that is, the influence of phase-shift control on the fly-through voltage. When D < 0.5, substituting the time T0 to time T3 in mode 1 into equation (2) yields equation (5).

[0074]

[0075] When D>0.5, substituting the time T0 to time T3 in mode 4 into equation (2) yields equation (6).

[0076]

[0077] From equations (5) and (6), it can be seen that the overpass voltage under phase-shift control has a consistent adjustment direction under light and heavy loads and positive and negative power flows, that is: when the phase difference increases, the overpass voltage increases; when the phase difference decreases, the overpass voltage decreases. This relationship is independent of the dead zone.

[0078] Then, please refer to Figures 10-13 The figures shown are the relationship diagrams between the duty cycle difference and phase difference and the flyover voltage proposed in this application. Figure 10 and Figure 11 This describes the effect of different loads on the transient voltage under fixed phase and duty cycle conditions. The horizontal axis represents the inductor current I. L The vertical axis represents the change in cross voltage ΔV. fly The solid line corresponding to the fixed duty cycle difference reflects the adjustment effect of the flying capacitor voltage under different loads when the same duty cycle difference is adjusted for the first switching transistor. The dashed line corresponding to the fixed phase difference reflects the adjustment effect of the flying capacitor voltage under different loads when the same phase difference is adjusted for the first switching transistor. Figure 10 Using equations (3) and (5), we will give an example of an application scenario where D = 0.34 for D < 0.5. Figure 11 Using equations (4) and (6), we will illustrate an application scenario where D = 0.8 versus D > 0.5. Figure 10 and Figure 11It can be seen that under light load (the inductor current can be a high-frequency triangular wave, repeatedly switching between positive and negative, and its value is small, represented by the dotted line in the figure being larger than the solid line and close to 0), the change in flyover voltage is small. Adjusting the duty cycle will cause the flyover voltage to change in the opposite direction. As the load gradually increases, the change in flyover voltage gradually increases, thus allowing for flyover voltage control by adjusting the duty cycle under heavy load. In other words, the control effect of adjusting the duty cycle on the flyover voltage weakens rapidly as the load gradually decreases. In contrast, phase-shift control has a relatively stronger control effect under light load and a relatively weaker control effect under heavy load, thus allowing for phase-shift control under light load, i.e., adjusting the phase difference to control the flyover voltage.

[0079] Figure 12 and Figure 13 This describes the effect of a fixed duty cycle difference and a fixed phase difference on the change in flyover voltage under a fixed load. The horizontal axis represents the duty cycle D, and the vertical axis represents the change in flyover voltage ΔV. fly . Figure 12 The application is under heavy load. Figure 13 Applied to light load conditions. From Figure 12 and Figure 13 It can be seen that the control effect of phase-shift control on the flyover voltage decreases rapidly as the duty cycle increases. However, under light load conditions, phase-shift control maintains a greater regulatory strength compared to adjusting the duty cycle. Therefore, under light load conditions, phase-shift control can be used to control the flyover voltage, while under heavy load conditions, adjusting the duty cycle can be used.

[0080] Based on this, in one possible example, the controller is specifically configured to adjust the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups in response to the inductor current being less than a second threshold. Alternatively, the controller is specifically configured to adjust the duty cycle difference between the first switching transistors in the two switching transistor groups in response to the inductor current being greater than a third threshold. Or, the controller is specifically configured to adjust the duty cycle difference between the first switching transistors in the two switching transistor groups, or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups, according to the adjustment method of the previous time step, in response to the inductor current being greater than or equal to the second threshold and less than or equal to the third threshold.

[0081] This application does not limit the magnitude of the second and third thresholds, but the second threshold is less than the third threshold. It can be understood that if the inductor current is less than the second threshold, it indicates a small inductor current, possibly indicating a light load. In this case, the phase difference between the carrier waves of the first switching transistors in the two switching groups can be adjusted using phase-shift control without adjusting the duty cycle difference. If the inductor current is greater than the third threshold, it indicates a large inductor current, possibly indicating a heavy load. In this case, the duty cycle difference between the first switching transistors in the two switching groups can be adjusted by adjusting the duty cycle without adjusting the phase difference. If the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold, it may be an intermediate state between light and heavy loads. The adjustment method from the previous moment can be used. For example, if phase-shift control was used in the previous moment, it should continue; if duty cycle adjustment was used in the previous moment, it should continue. In this way, the flying voltage can be controlled through these three scenarios, ensuring a smooth transition of the controlled flying capacitor voltage.

[0082] In one possible example, the controller may include a hysteresis module, a first pulse width modulator, and a second pulse width modulator connected to the hysteresis module. The first pulse width modulator adjusts the phase or duty cycle of a first (or second) switch in a switch group connected to a flying capacitor, and the second pulse width modulator adjusts the phase or duty cycle of a first (or second) switch in another switch group connected to the flying capacitor. For example, the first pulse width modulator adjusts the phase or duty cycle of switch Q1 or switch Q4, and the second pulse width modulator adjusts the phase or duty cycle of switch Q2 or switch Q3. The hysteresis module may include a duty cycle controller and a phase controller. The duty cycle controller controls the first and second pulse width modulators to execute a duty cycle control loop to adjust the duty cycle difference between the two switches. The phase controller controls the first and second pulse width modulators to execute a phase control loop to adjust the phase difference between the two switch carriers.

[0083] The hysteresis module is used to respond to the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor being greater than a first threshold. Based on the magnitude of the inductor current, it controls the first pulse width modulator and the second pulse width modulator to adjust the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups or the duty cycle difference between the first switching transistors in the two switching transistor groups.

[0084] Specifically, the hysteresis module is used to adjust the phase difference between the first switching transistor carriers in two switching groups based on the magnitude of the inductor current. If the sampled voltage of the flying capacitor is less than the reference voltage, the phase difference between the first switching transistor carriers in the two switching groups is increased. Alternatively, if the sampled voltage of the flying capacitor is greater than the reference voltage, the phase difference between the first switching transistor carriers in the two switching groups is decreased.

[0085] Specifically, the hysteresis module is used to adjust the duty cycle difference between the first switching transistors in two switching groups based on the magnitude of the inductor current. If the current flows from the high-voltage power supply to the low-voltage power supply and the sampling voltage of the flying capacitor is less than the reference voltage, the duty cycle difference between the first switching transistors in the two switching groups is increased; or if the current flows from the high-voltage power supply to the low-voltage power supply and the sampling voltage of the flying capacitor is greater than the reference voltage, the duty cycle difference between the first switching transistors in the two switching groups is decreased; or if the current flows from the low-voltage power supply to the high-voltage power supply and the sampling voltage of the flying capacitor is less than the reference voltage, the duty cycle difference between the first switching transistors in the two switching groups is decreased; or if the current flows from the low-voltage power supply to the high-voltage power supply and the sampling voltage of the flying capacitor is greater than the reference voltage, the duty cycle difference between the first switching transistors in the two switching groups is increased.

[0086] Specifically, the hysteresis module is used to control the first pulse width modulator and the second pulse width modulator to adjust the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups in response to the current being less than the second threshold; or to control the first pulse width modulator and the second pulse width modulator to adjust the duty cycle difference between the first switching transistors in the two switching transistor groups in response to the current being greater than the third threshold; or to control the first pulse width modulator and the second pulse width modulator to adjust the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups or the duty cycle difference between the first switching transistors in the two switching transistor groups in response to the current being greater than or equal to the second threshold and less than or equal to the third threshold, according to the adjustment method of the previous moment.

[0087] Taking the first switching transistors as Q1 and Q2 as examples, please refer to... Figure 14 , Figure 14 This application provides a schematic diagram of a controller adjusting the voltage of a flying capacitor. For example... Figure 14 As shown, the hysteresis module can first determine the sampling voltage V of the flying capacitor. fly_ad and the reference voltage V of the flying capacitor fly_ref Does the absolute value of the difference between them exceed the first threshold? If so, and the average value of the inductor current i LAVGIf the value is less than the second threshold, the phase-shifting control loop corresponding to the phase controller can operate while keeping the duty cycle constant (the output limiting of the duty cycle control loop changes linearly to zero). This allows the first pulse width modulator to apply the output of the current duty cycle control loop to the steady-state duty cycle based on the direction of the inductor current. Then, the second pulse width modulator adds the output of the phase-shifting control loop to the carrier wave of the corresponding switch, causing the phase difference between the carrier waves of the first and second pulse width modulator switches Q1 and Q2 to be dynamically adjusted around 180°. When i LAVG If the value is greater than the third threshold, the duty cycle control loop corresponding to the duty cycle controller can be controlled to operate while keeping the phase difference constant. This allows the first and second pulse width modulators to apply the output of the current phase shift control loop to the carrier wave corresponding to the second pulse width modulator based on the direction of the inductor current, thus dynamically adjusting the duty cycle difference between switches Q1 and Q2 to near 0. When i LAVG When the voltage is between the second and third thresholds, the phase-shift control loop corresponding to the control phase controller is kept in operation in the previous moment, so that the first and second pulse width modulators adjust the phase ratio difference between the carriers of switch Q1 and switch Q2, or the duty cycle control loop corresponding to the duty cycle controller is controlled to operate, so that the first and second pulse width modulators adjust the duty cycle difference between switch Q1 and switch Q2.

[0088] Please refer to Figure 15 , Figure 15 A flowchart illustrating a voltage control method for a flying capacitor provided in this application. This flying capacitor can be applied to, for example... Figure 3 The multilevel DC-DC converter shown includes at least one flying capacitor, two switching transistor groups connected to the flying capacitor, an inductor connected to the positive terminal of the low-voltage circuit of each switching transistor group and the multilevel DC-DC converter, and a controller for controlling the switching transistor groups. Each switching transistor group includes a first and a second switching transistor with complementary on and off states. Figure 15 As shown, the voltage control method may include step S101, wherein:

[0089] S101: When the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor is greater than the first threshold, the controller adjusts the duty cycle difference between the first switching transistors in the two switching transistor groups or the phase difference between the carrier waves of the first switching transistors in the two switching transistor groups according to the magnitude of the inductor current.

[0090] It is understandable that if the absolute value of the difference between the sampled voltage and the reference voltage of the flying capacitor is greater than the first threshold, it means that the voltage of the flying capacitor has not yet been adjusted to the target value. The phase difference between the switches connected in parallel on one side of the flying capacitor, or the duty cycle difference between the switches on that side, can be adjusted to control the voltage of the flying capacitor and improve the stability of the multilevel DC-DC converter.

[0091] In one possible example, a method for adjusting the duty cycle difference between the first switching transistors in two switching groups, or the phase difference between the carrier waves of the first switching transistors in two switching groups, based on the magnitude of the inductor current, may include the following steps: increasing the phase difference between the carrier waves of the first switching transistors in two switching groups when the phase difference is determined to be adjusted based on the magnitude of the inductor current, and the sampled voltage of the flying capacitor is less than a reference voltage; or decreasing the phase difference between the carrier waves of the first switching transistors in two switching groups when the phase difference is determined to be adjusted based on the magnitude of the inductor current, and the sampled voltage of the flying capacitor is greater than a reference voltage. Thus, increasing the phase difference between the carrier waves of the first switching transistors in two switching groups raises the voltage of the flying capacitor. Decreasing the phase difference between the carrier waves of the first switching transistors in two switching groups decreases the voltage of the flying capacitor.

[0092] In one possible example, a method for adjusting the duty cycle difference between the first switching transistors in two switching transistor groups, or the phase difference between the carrier waves of the first switching transistors in two switching transistor groups, based on the magnitude of the inductor current, may include the following steps: When determining the duty cycle difference between the first switching transistors in two switching transistor groups based on the magnitude of the inductor current, if the current flows from a high-voltage power supply to a low-voltage power supply and the sampling voltage of the flying capacitor is less than a reference voltage, then increase the duty cycle difference between the first switching transistors in the two switching transistor groups; or if the current flows from a high-voltage power supply to a low-voltage power supply and the sampling voltage of the flying capacitor is greater than a reference voltage, then decrease the duty cycle difference between the first switching transistors in the two switching transistor groups; or if the current flows from a low-voltage power supply to a high-voltage power supply and the sampling voltage of the flying capacitor is less than a reference voltage, then decrease the duty cycle difference between the first switching transistors in the two switching transistor groups; or if the current flows from a low-voltage power supply to a high-voltage power supply and the sampling voltage of the flying capacitor is greater than a reference voltage, then increase the duty cycle difference between the first switching transistors in the two switching transistor groups. Thus, by adjusting the duty cycle difference, the voltage across the flying capacitor is adjusted according to the direction of the inductor current.

[0093] In one possible example, the method of adjusting the duty cycle difference between the first switching transistors in two switching groups or the phase difference between the carrier waves of the first switching transistors in two switching groups, based on the magnitude of the inductor current, may include the following steps: adjusting the phase difference between the carrier waves of the first switching transistors in two switching groups when the inductor current is less than a second threshold; or adjusting the duty cycle difference between the first switching transistors in two switching groups when the inductor current is greater than a third threshold; or adjusting the duty cycle difference between the first switching transistors in two switching groups or the phase difference between the carrier waves of the first switching transistors in two switching groups according to the adjustment method at the previous moment when the inductor current is greater than or equal to the second threshold and less than or equal to the third threshold. In this way, the flying voltage can be controlled through these three cases, ensuring a smooth transition of the voltage across the controlled flying capacitor.

[0094] This application also discloses a control device. The control device includes a controller and a memory; wherein the memory is used to store instructions, and the controller is used to call the instructions stored in the memory to execute the method described in any of the above aspects.

[0095] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-level DC converter, characterized by The multi-level DC converter comprises at least one flying capacitor, two switch tube groups connected with the flying capacitor, an inductor connected with each of the switch tube groups and a positive terminal of a low-voltage power supply of the multi-level DC converter, and a controller for controlling the switch tube groups; wherein each of the switch tube groups comprises a first switch tube and a second switch tube which are complementary in on and off states, the first switch tube is connected with one end of a high-voltage power supply of the multi-level DC converter, and the second switch tube is connected with the other end of the high-voltage power supply of the multi-level DC converter; The controller is configured to, in a case where an absolute value of a difference between a sampling voltage of the flying capacitor and a reference voltage is greater than a first threshold value, adjust a duty cycle difference between the first switch tubes in the two switch tube groups or a phase difference between first switch tube carriers in the two switch tube groups according to a size of the inductor current; The controller is specifically configured to, in a case where the inductor current is less than a second threshold value, adjust the phase difference between the first switch tube carriers in the two switch tube groups; The controller is specifically configured to, in a case where the inductor current is greater than a third threshold value, adjust the duty cycle difference between the first switch tubes in the two switch tube groups; The controller is specifically configured to, in a case where the inductor current is greater than or equal to the second threshold value and less than or equal to the third threshold value, adjust the duty cycle difference between the first switch tubes in the two switch tube groups or the phase difference between the first switch tube carriers in the two switch tube groups according to an adjustment method at a previous moment.

2. The multi-level DC converter according to claim 1, characterized in that The controller is specifically configured to, in a case where it is determined to adjust the phase difference between the first switch tube carriers in the two switch tube groups according to the size of the inductor current and the sampling voltage of the flying capacitor is less than the reference voltage, increase the phase difference between the first switch tube carriers in the two switch tube groups.

3. The multi-level DC converter according to claim 1, characterized in that, The controller is specifically configured to, in a case where it is determined to adjust the phase difference between the first switch tube carriers in the two switch tube groups according to the size of the inductor current and the sampling voltage of the flying capacitor is greater than the reference voltage, decrease the phase difference between the first switch tube carriers in the two switch tube groups.

4. A voltage control method of a flying capacitor, characterized by, The flying capacitor is applied to a multi-level DC converter, the multi-level DC converter further comprises two switch tube groups, an inductor and a controller, each of the switch tube groups comprises a first switch tube and a second switch tube which are complementary in on and off states; the voltage control method comprises: In a case where an absolute value of a difference between a sampling voltage of the flying capacitor and a reference voltage is greater than a first threshold value, the controller adjusts a duty cycle difference between the first switch tubes in the two switch tube groups or a phase difference between first switch tube carriers in the two switch tube groups according to a size of the inductor current; The controller adjusts the duty cycle difference between the first switch tubes in the two switch tube groups or the phase difference between the first switch tube carriers in the two switch tube groups according to the size of the inductor current, comprising: In a case that the inductor current is less than a second threshold value, the controller adjusts a phase difference between first switch carrier waves in the two switch groups; or In a case that the inductor current is greater than a third threshold value, the controller adjusts a duty cycle difference between the first switches in the two switch groups; or In a case that the inductor current is greater than or equal to the second threshold value and less than or equal to the third threshold value, the controller adjusts the duty cycle difference between the first switches in the two switch groups or the phase difference between the first switch carrier waves in the two switch groups according to an adjustment method at a previous time.

5. The voltage control method according to claim 4, characterized by, The controller adjusts the duty cycle difference between the first switches in the two switch groups or the phase difference between the first switch carrier waves in the two switch groups according to the magnitude of the inductor current, comprising: In a case that it is determined to adjust the phase difference between the first switch carrier waves in the two switch groups according to the magnitude of the inductor current, and the sampling voltage of the flying capacitor is less than the reference voltage, the controller increases the phase difference between the first switch carrier waves in the two switch groups; or In a case that it is determined to adjust the phase difference between the first switch carrier waves in the two switch groups according to the magnitude of the inductor current, and the sampling voltage of the flying capacitor is greater than the reference voltage, the controller decreases the phase difference between the first switch carrier waves in the two switch groups.

6. A control device characterized by comprising: The control device comprises a controller and a memory; wherein the memory is used to store instructions, and the controller is used to call the instructions stored in the memory to execute the voltage control method in claim 4 or 5.

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