A voltage conversion circuit, a charging device and an electric appliance

Abstract

The embodiment of the application provides a voltage conversion circuit, a charging device and a power utilization device, which comprise an N-level conversion unit and N-1 DCDC conversion units. The first input end of the Mth DCDC conversion unit is connected with the Mth output end of the N-level conversion unit, the second input end of the Mth DCDC conversion unit is connected with the M+1th output end of the N-level conversion unit, and the output level of the Mth output end of the N-level conversion unit and the output level of the M+1th output end are adjacent levels. Wherein, N is greater than or equal to 3, and 1 is less than N. The voltage conversion circuit is connected through the N-level conversion unit and the plurality of DCDC conversion units, can realize high-power output, and meets the high-power application scene.

Description

Technical Field

[0001] The present invention relates to the field of power supply technology, and in particular to a voltage conversion circuit, a charging device, and an electrical appliance. Background Technology

[0002] With the development of modern electronic power technology, power converters are widely used in various industrial fields.

[0003] However, the demand for power converters in modern society is increasing, and how to improve the output power of power circuits to meet the needs of high-power applications is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a voltage conversion circuit, a charging device, and an electrical device that can achieve high power output and meet the needs of high-power application scenarios.

[0005] In one aspect, one technical solution adopted in the embodiments of this application is to provide a voltage conversion circuit, including: an N-level conversion unit and N-1 DC-DC conversion units. The N-level conversion unit has N output terminals with different levels. The first input terminal of the Mth DC-DC conversion unit is connected to the Mth output terminal of the N-level conversion unit, and the second input terminal of the Mth DC-DC conversion unit is connected to the (M+1)th output terminal of the N-level conversion unit. The output level of the Mth output terminal and the output level of the (M+1)th output terminal are adjacent levels. Wherein, N≥3, 1≤M<N, 2≤P<N.

[0006] In the technical solution of this application embodiment, by connecting the input terminals of M-1 DC-DC converter units to the N level output terminals of the N-level converter unit, the output power of the voltage conversion circuit can be improved, thereby meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, the output level of the N-level converter unit can be directly adjusted, thereby adjusting the input voltage of the DC-DC converter unit, and ultimately adjusting the output voltage or output current of the DC-DC converter unit. This makes the output voltage or output current of multiple DC-DC converter units equal or nearly equal, achieving voltage or current sharing, and reducing the control difficulty of voltage or current sharing control.

[0007] In some embodiments, the first output terminal of the first DC-DC converter is connected to the first node, the first output terminal of the P-th DC-DC converter is connected to the second output terminal of the (P-1)-th DC-DC converter, and the second output terminal of the (N-1)-th DC-DC converter is connected to the second node; wherein, 2≤P<N.

[0008] In the technical solution of this application embodiment, by connecting the input terminals of M-1 DC-DC converter units to the N level output terminals of the N-level converter unit 10, and connecting the output terminals of the M-1 DC-DC converter units in series between the first node B1 and the second node B2, the output power of the voltage conversion circuit can be increased, thereby meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, the output level of the N-level converter unit can be directly adjusted, thereby adjusting the input voltage of the DC-DC converter unit and ultimately adjusting the output voltage of the DC-DC converter unit, making the output voltages of multiple DC-DC converter units equal or nearly equal, thus achieving voltage equalization and reducing the control difficulty of voltage equalization control.

[0009] In some embodiments, when N=3, the voltage conversion circuit includes a first three-level conversion unit, a first DC-DC conversion unit, and a second DC-DC conversion unit. The first three-level conversion unit has a first output terminal, a second output terminal, and a third output terminal with sequentially decreasing voltage levels. The first input terminal of the first DC-DC conversion unit is connected to the first output terminal of the first three-level conversion unit; the second input terminal of the first DC-DC conversion unit and the first input terminal of the second DC-DC conversion unit are connected to the second output terminal of the first three-level conversion unit; and the second input terminal of the second DC-DC conversion unit is connected to the third output terminal of the first three-level conversion unit. The first output terminal of the first DC-DC conversion unit is connected to a first node; the second output terminal of the first DC-DC conversion unit is connected to the first output terminal of the second DC-DC conversion unit; and the second output terminal of the second DC-DC conversion unit is connected to a second node.

[0010] In the above embodiments of this application, the output power of the voltage conversion circuit can be improved by connecting in the above manner, and the voltage equalization method of the first DC-DC conversion unit and the second DC-DC conversion unit can be simplified under this connection method.

[0011] In some embodiments, the first three-level conversion unit is a single-phase type I three-level conversion unit, a three-phase type I three-level conversion unit, a single-phase type T three-level conversion unit, or a three-phase type T three-level conversion unit. The above embodiments of this application provide various circuit structures for three-level conversion units, improving design flexibility.

[0012] In some embodiments, the first output of each DC-DC converter is connected to the third node, and the second output of each DC-DC converter is connected to the fourth node.

[0013] In the technical solution of this application embodiment, by connecting the input terminals of M-1 DC-DC converter units to the N level output terminals of the N-level converter unit, and connecting the output terminals of the M-1 DC-DC converter units in parallel between the third and fourth nodes, the output power of the voltage conversion circuit can be increased, thereby meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, the output level of the N-level converter unit can be directly adjusted, thereby adjusting the input voltage of the DC-DC converter unit and ultimately adjusting the output current of the DC-DC converter unit. This ensures that the output currents of multiple DC-DC converter units are equal or nearly equal, achieving current sharing and reducing the control difficulty of current sharing control.

[0014] In some embodiments, when N=3, the voltage conversion circuit includes a second three-level conversion unit, a third DC-DC conversion unit, and a fourth DC-DC conversion unit. The second three-level conversion unit has a first output terminal, a second output terminal, and a third output terminal with sequentially decreasing voltage levels. The first input terminal of the third DC-DC conversion unit is connected to the first output terminal of the second three-level conversion unit; the second input terminals of the third and fourth DC-DC conversion units are connected to the second output terminal of the second three-level conversion unit; and the second input terminal of the fourth DC-DC conversion unit is connected to the third output terminal of the second three-level conversion unit. The first output terminals of the third and fourth DC-DC conversion units are connected to a third node, and the second output terminals of the third and fourth DC-DC conversion units are connected to a fourth node.

[0015] In the above embodiments of this application, the output power of the voltage conversion circuit can be improved by connecting in the above manner, and the current sharing method of the third DC-DC conversion unit and the fourth DC-DC conversion unit can be simplified under this connection method.

[0016] In some embodiments, the second three-level conversion unit is a single-phase type I three-level conversion unit, a three-phase type I three-level conversion unit, a single-phase type T three-level conversion unit, or a three-phase type T three-level conversion unit. The above embodiments of this application provide various circuit structures for three-level conversion units, improving design flexibility.

[0017] In some embodiments, the input terminal of the N-level conversion unit is connected to a single-phase AC power supply or a three-phase AC power supply. In the above embodiments of this application, the voltage conversion circuit can be adapted to different AC power supplies, improving the adaptability and compatibility of the voltage conversion circuit.

[0018] In some embodiments, the DC-DC conversion unit is an LLC circuit, a CLLLC circuit, or a PSFB circuit. The above embodiments of this application provide various circuit structures for DC-DC conversion units, improving design flexibility.

[0019] In some embodiments, the voltage conversion circuit further includes a control unit. The control unit is connected to the N-level conversion unit and the N-1 DC-DC conversion units respectively. The control unit controls the output level of the N-level conversion unit so that the difference between the output voltages of each DC-DC conversion unit is less than or equal to a first threshold; or, the control unit controls the output level of the N-level conversion unit so that the difference between the output currents of each DC-DC conversion unit is less than or equal to a second threshold.

[0020] In the above embodiments of this application, the output voltage or output current of each DC-DC converter can be made equal or nearly equal by controlling the output level of the N-level conversion unit, thereby achieving the purpose of voltage equalization or current equalization. This voltage equalization control method and current equalization control method do not require adjustment of the frequency, phase shift angle or duty cycle of the DC-DC converter, which can reduce the control difficulty and improve the working stability of the circuit.

[0021] In some embodiments, the control unit is configured to: acquire the output voltage or output current of each DC-DC converter; and control the output level of the N-level converter based on the output voltage or output current of each DC-DC converter.

[0022] In the above embodiments of this application, by controlling the output level of the N-level conversion unit according to the output voltage or output current of each DC-DC conversion unit, the output voltage or output current of each DC-DC conversion unit is equal or basically close, thereby achieving the purpose of voltage or current equalization.

[0023] In some embodiments, the control unit is configured to: control at least one intermediate output level of the N-level conversion unit according to the output voltage or output current of each DC-DC conversion unit, the intermediate output level being located between the maximum output level and the minimum output level of the N-level conversion unit.

[0024] In the above embodiments of this application, the input voltage of two adjacent DC-DC converters can be quickly and flexibly adjusted by controlling at least one intermediate output level of the N-level conversion unit, thereby quickly adjusting the output voltage or output current of multiple DC-DC converters.

[0025] In some embodiments, the control unit is configured to: obtain a reference voltage based on each of the output voltages; subtract each of the output voltages from the reference voltage to obtain a voltage difference corresponding to each of the output voltages; and control at least one intermediate output level of the N-level conversion unit based on each of the voltage differences; or, the control unit is configured to: obtain a reference current based on each of the output currents; subtract each of the output currents from the reference current to obtain a current difference corresponding to each of the output currents; and control at least one intermediate output level of the N-level conversion unit based on each of the current differences.

[0026] In the above embodiments of this application, at least one intermediate output level of the N-level conversion unit can be flexibly controlled according to the relationship between the output voltages of each DC-DC conversion unit, thereby enabling adaptive calculation and voltage or current equalization according to different circuit conditions, thus improving the voltage or current equalization efficiency.

[0027] Secondly, this application provides a charging device that includes a voltage conversion circuit as described in any one of the first aspects.

[0028] Thirdly, this application provides an electrical appliance that includes a charging device as described in the second aspect.

[0029] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0030] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements / modules and steps with the same reference numerals in the drawings are represented as similar elements / modules and steps. Unless otherwise stated, the figures in the drawings do not constitute a limitation on scale.

[0031] Figure 1 This is a schematic diagram of the circuit structure of a voltage conversion circuit provided in an embodiment of this application;

[0032] Figure 2 This is a schematic diagram of the circuit structure of a voltage equalization circuit or current equalization circuit provided in an embodiment of this application;

[0033] Figure 3 This is a schematic diagram of the circuit structure of another voltage conversion circuit provided in the embodiments of this application;

[0034] Figure 4 This is a schematic diagram of the structure of an electric vehicle provided in an embodiment of this application;

[0035] Figure 5 This is a schematic diagram of the circuit structure of another voltage conversion circuit provided in the embodiments of this application;

[0036] Figure 6 This is a schematic diagram of the circuit structure of another voltage conversion circuit provided in the embodiments of this application;

[0037] Figure 7 This is a schematic diagram of the circuit structure of the fifth voltage conversion circuit provided in the embodiments of this application;

[0038] Figure 8 This is a schematic diagram of the circuit structure of a single-phase type I three-level conversion unit provided in an embodiment of this application;

[0039] Figure 9 This is a schematic diagram of the circuit structure of a three-phase type I three-level conversion unit provided in an embodiment of this application;

[0040] Figure 10 This is a schematic diagram of the circuit structure of a single-phase T-type three-level conversion unit provided in an embodiment of this application;

[0041] Figure 11 This is a schematic diagram of the circuit structure of a three-phase T-type three-level conversion unit provided in an embodiment of this application;

[0042] Figure 12 This is a schematic diagram of the circuit structure of the sixth voltage conversion circuit provided in the embodiments of this application;

[0043] Figure 13 This is a schematic diagram of the circuit structure of the seventh voltage conversion circuit provided in the embodiments of this application. Detailed Implementation

[0044] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0046] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0047] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0048] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0049] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0050] With the development of power electronics technology, the demand for charging devices for high-power modules is increasing. Currently, due to the performance limitations of individual switching transistors and the size limitations of magnetic components, multiple low-power voltage conversion circuits are often connected in parallel to form a high-power voltage conversion circuit.

[0051] For example, please see Figure 1 , Figure 1 This is a schematic block diagram of a high-power voltage conversion circuit provided in an embodiment of this application. The circuit consists of a three-level conversion unit 11, a first DC-DC conversion unit 21, and a second DC-DC conversion unit, and the output terminals of the first DC-DC conversion unit 21 and the second DC-DC conversion unit 22 are connected in series.

[0052] exist Figure 1In the circuit shown, when the first DC-DC converter 21 and the second DC-DC converter 22 are operating, it is necessary to ensure that the output voltages of the first DC-DC converter 21 and the second DC-DC converter 22 are consistent. However, due to component inconsistency issues, even if the first DC-DC converter 21 and the second DC-DC converter 22 are designed with the same parameters, the output voltages of the first DC-DC converter 21 and the second DC-DC converter 22 may be inconsistent, resulting in uneven voltage distribution between the two DC-DC converters. If this circuit operates under uneven voltage conditions for a long time, it will lead to problems such as different temperatures, different degrees of component aging, single circuits exceeding their rated design conditions, and shortened lifespan, even with the same parameters.

[0053] To solve the pressure equalization problem, two methods can be used. The first method is... Figure 1 In the circuit shown, firstly, the output voltage between the first and second output terminals of the first DC-DC converter 21, and the output voltage between the first and second output terminals of the second DC-DC converter 22 are obtained respectively. Then, the magnitudes of the output voltages of the first DC-DC converter 21 and the second DC-DC converter 22 are compared. Next, based on the magnitudes of the two output voltages, the switching frequency, phase shift angle, and duty cycle of the switching transistors in the first DC-DC converter 21 and the second DC-DC converter 22 are adjusted to make their output voltages equal. The second method is... (Please refer to...) Figure 2 A virtual controlled voltage source is constructed by inserting the auxiliary windings of transformers from other circuit modules into the resonant cavity of a certain phase LLC resonant converter. Combined with phase shift control, multi-phase voltage equalization is achieved.

[0054] However, if voltage equalization is achieved by adjusting the frequencies of the two DC-DC converters, a frequency difference Δf will appear between them, generating low-frequency harmonic oscillations of Δf, resulting in significant and difficult-to-filter EMI interference. If voltage equalization is achieved by adjusting the phase shift angles of the two DC-DC converters, the circulating current between them will increase when the phase shift angles are different. If voltage equalization is achieved by adjusting the duty cycle of the two DC-DC converters, it can easily cause a DC-DC converter that was originally operating in soft-switching mode to operate under hard-switching mode, leading to excessive temperature rise and potential tube failure.

[0055] For example, please see Figure 3 , Figure 3 This is a schematic block diagram of another high-power voltage conversion circuit provided in an embodiment of this application, as shown below. Figure 3 As shown, this circuit also consists of a three-level conversion unit 11, a first DC-DC conversion unit 21, and a second DC-DC conversion unit 22, and is similar to... Figure 1The difference in the illustrated embodiment is that the input and output terminals of the first DC-DC conversion unit 21 and the second DC-DC conversion unit 22 are connected in parallel.

[0056] exist Figure 3 In the circuit shown, when the first DC-DC converter 21 and the second DC-DC converter 22 are operating, it is necessary to ensure that the output currents of the first DC-DC converter 21 and the second DC-DC converter 22 are consistent. However, due to component inconsistency issues, even if the first DC-DC converter 21 and the second DC-DC converter 22 are designed with the same parameters, the output currents of the first DC-DC converter 21 and the second DC-DC converter 22 will be inconsistent, resulting in uneven current distribution between the two DC-DC converters. If this circuit operates under uneven current conditions for a long period of time, it will also lead to problems such as different temperatures, different degrees of component aging, single circuits exceeding their rated design conditions, and shortened lifespan, even with circuits having the same parameters.

[0057] To solve the current sharing problem, two methods can be used. The first method is... Figure 3 In the circuit shown, firstly, the output currents of the first DC-DC converter unit 21 and the second DC-DC converter unit 22 are obtained respectively; then, the magnitudes of the output currents of the first DC-DC converter unit 21 and the second DC-DC converter unit 22 are compared; next, based on the magnitudes of their output currents, the switching frequency, phase shift angle, duty cycle, etc., of the switching transistors in the first DC-DC converter unit 21 and the second DC-DC converter unit 22 are adjusted to make their output currents equal. The second method is... (Please refer to...) Figure 2 A virtual controlled voltage source is constructed by inserting the auxiliary windings of transformers from other circuit modules into the resonant cavity of a certain phase LLC resonant converter. Combined with phase shift control, multi-phase current sharing is achieved.

[0058] Similarly, if current sharing is achieved by adjusting the frequencies of the two DC-DC converters, a frequency difference Δf will occur between them, generating low-frequency harmonic oscillations of Δf, resulting in significant and difficult-to-filter EMI interference. If current sharing is achieved by adjusting the phase shift angles of the two DC-DC converters, a difference in phase shift angles will increase the circulating current between them. If current sharing is achieved by adjusting the duty cycle of the two DC-DC converters, a converter that would normally operate in soft-switching mode may be forced to operate in hard-switching mode, leading to excessive temperature rise and potential tube failure.

[0059] To avoid the above problems, this application provides a voltage conversion circuit, a charging device, and an electrical device. By providing a new connection method between a multi-level conversion unit and a DC-DC conversion unit, not only can high power output be achieved to meet high-power application scenarios, but also the output voltage of the multi-level conversion unit can be controlled to control the downstream DC-DC conversion unit to perform voltage or current equalization, instead of controlling the frequency, phase shift angle, and duty cycle of the DC-DC conversion unit, thereby avoiding the above problems.

[0060] The voltage conversion circuit provided in this application can be used, but is not limited to, in electrical devices such as vehicles, ships, or aircraft. These electrical devices include a load that consumes electrical energy, a battery that powers the load, and a charging device for charging the device. The charging device is composed of the voltage conversion circuit provided in this application. This charging device can convert AC power into DC current to power the load or battery. It not only meets the needs of high-power applications but also improves the stability of the circuit by controlling the output voltage of the multi-level converter unit to achieve voltage equalization among multiple DC-DC converter units.

[0061] This application provides an electrical device that uses a battery as a power source. The device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0062] For ease of explanation, the following embodiments use a vehicle 100 as an example of an electrical device according to an embodiment of this application. Please refer to... Figure 4 , Figure 4 This is a structural schematic diagram of a vehicle 100 provided in some embodiments of this application.

[0063] Vehicle 100 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 110 is installed inside vehicle 100, and the battery 110 can be located at the bottom, front, or rear of vehicle 100. The battery 110 can be used to power vehicle 100; for example, the battery 100 can serve as the operating power source for vehicle 100. Vehicle 100 may also include a controller 120 and a motor 130. The controller 120 is used to control the battery 110 to supply power to the motor 130, for example, to meet the power needs of vehicle 100 during starting, navigation, and driving.

[0064] In some embodiments of this application, the battery 110 can not only serve as the operating power source for the vehicle 100, but also as the driving power source for the vehicle 100, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 100.

[0065] Battery 110 refers to any type of energy storage component used to store electrical energy. For example, it can be a single battery cell, a battery module composed of multiple battery cells, or a battery pack containing one or more battery modules. The shape of battery 110 can be appropriate according to actual needs, such as a cylinder, cuboid, etc.

[0066] In some embodiments, the multiple battery cells in a battery module can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple battery cells are connected in both series and parallel configurations. The battery modules that make up a battery pack can also be connected in series, parallel, or a combination thereof. The battery pack or battery module may also include other structures besides battery cells, such as a busbar for realizing electrical connections between multiple battery cells.

[0067] The controller 120 includes at least one battery management system. This battery management system is an electronic system used to manage the battery 110 and ensure its proper functioning. The battery management system may also be connected to a voltage conversion circuit.

[0068] This application provides a voltage conversion circuit. Please refer to [link / reference]. Figure 5 It includes: N level conversion unit 10 and N-1 DC-DC conversion units.

[0069] The N-level conversion unit 10 has N output terminals with different levels. The first input terminal of the Mth DC-DC conversion unit is connected to the Mth output terminal of the N-level conversion unit 10, and the second input terminal of the Mth DC-DC conversion unit is connected to the (M+1)th output terminal of the N-level conversion unit 10. The output level of the Mth output terminal of the N-level conversion unit 10 and the output level of the (M+1)th output terminal of the N-level conversion unit 10 are adjacent levels. Where N≥3, 1≤M<N.

[0070] The N-level conversion unit 10 can convert the AC power input voltage into a multi-level DC output, that is, the N-level conversion unit 10 can output a maximum output level, a minimum output level, and at least one intermediate level between the maximum and minimum output levels. The N-level conversion unit 10 may include multiple switching transistors, and multiple levels can be output by controlling the switching states of the switching transistors, such as multiple high levels, zero levels, and multiple low levels.

[0071] A DC-DC converter unit can convert a DC power supply of one voltage level to a DC power supply of another voltage level. Generally, for the Mth DC-DC converter unit, the first input terminal is the positive input terminal, and the second input terminal is the negative input terminal.

[0072] In this voltage conversion circuit, by connecting the input terminals of M-1 DC-DC converter units to the N level output terminals of the N-level converter unit 10, the output power of the voltage conversion circuit can be increased, thus meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, the output level of the N-level converter unit 10 can be directly adjusted, thereby adjusting the input voltage of the DC-DC converter units and ultimately adjusting the output voltage or output current of the DC-DC converter units. This ensures that the output voltage or output current of multiple DC-DC converter units are equal or nearly equal, achieving voltage or current sharing. It is evident that this connection method simplifies voltage or current sharing control, eliminating the need to control the frequency, phase shift angle, or duty cycle of the DC-DC converter units. This reduces the complexity of software control strategies and improves circuit stability.

[0073] To achieve voltage equalization output, in some embodiments please refer to Figure 6 The first output terminal of the first DC-DC converter 21 is connected to the first node B1, the first output terminal of the Pth DC-DC converter is connected to the second output terminal of the (P-1)th DC-DC converter, and the second output terminal of the (N-1)th DC-DC converter 2(N-1) is connected to the second node B2; where 2≤P<N.

[0074] Generally, for the Mth DC-DC converter unit, the first input terminal is the positive input terminal, the second input terminal is the negative input terminal, the first output terminal is the positive output terminal, and the second output terminal is the negative output terminal. At this time, the first node B1 is used to connect to the positive terminal of the bus, and the second node B2 is used to connect to the negative terminal of the bus.

[0075] In this voltage conversion circuit, by connecting the input terminals of M-1 DC-DC converter units to the N-level output terminals of the N-level converter unit 10, and connecting the output terminals of the M-1 DC-DC converter units in series between the first node B1 and the second node B2, the voltage conversion circuit can be connected to the DC bus through the first node B1 and the second node B2. This increases the output power of the voltage conversion circuit, thus meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, the output level of the N-level converter unit 10 can be directly adjusted, thereby adjusting the input voltage of the DC-DC converter units and ultimately adjusting their output voltages. This ensures that the output voltages of multiple DC-DC converter units are equal or nearly equal, achieving voltage equalization. It is evident that this connection method simplifies the voltage equalization control, eliminating the need to control the frequency, phase shift angle, or duty cycle of the DC-DC converter units for voltage equalization. This reduces the complexity of software control strategies and improves circuit stability.

[0076] In some embodiments, when N=3, please refer to [reference needed]. Figure 7 The voltage conversion circuit includes a first three-level conversion unit 11, a first DC-DC conversion unit 21, and a second DC-DC conversion unit 22. The first three-level conversion unit 11 has a first output terminal A1, a second output terminal A2, and a third output terminal A3 with sequentially decreasing voltage levels. The first input terminal of the first DC-DC conversion unit 21 is connected to the first output terminal A1 of the first three-level conversion unit 11. The second input terminal of the first DC-DC conversion unit 21 and the first input terminal of the second DC-DC conversion unit 22 are connected to the second output terminal A2 of the first three-level conversion unit 11. The second input terminal of the second DC-DC conversion unit 22 is connected to the third output terminal A3 of the first three-level conversion unit 11. The first output terminal of the first DC-DC conversion unit 21 is connected to a first node B1. The second output terminal of the first DC-DC conversion unit 21 is connected to the first output terminal of the second DC-DC conversion unit 22. The second output terminal of the second DC-DC conversion unit 22 is connected to a second node B2.

[0077] Specifically, the first three-level conversion unit 11 includes multiple upper and lower transistors that can output three-level states, namely high level, middle level and low level, through the switching state of the upper and lower transistors. For example, the level of the first output terminal A1 is +U, the level of the second output terminal A2 is 0, and the level of the third output terminal A3 is -U, where U represents the level of the first output terminal. The specific value can be set according to actual needs and is not limited here.

[0078] In this voltage conversion circuit, the above-described connection method can improve the output power of the voltage conversion circuit, thus meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, at least one of the first output terminals A1, A2, and A3 of the first three-level conversion unit 11 can be directly adjusted, thereby adjusting the input voltage of the first DC-DC conversion unit 21 and / or the input voltage of the second DC-DC conversion unit 22. Ultimately, this adjusts the output voltage of the first DC-DC conversion unit 21 and / or the output voltage of the second DC-DC conversion unit 22, making their output voltages equal or nearly equal, achieving voltage equalization. Therefore, this circuit connection method not only improves the output power of the voltage conversion circuit but also simplifies the voltage equalization control method, eliminating the need to control the frequency, phase shift angle, or duty cycle of the DC-DC conversion units for current equalization. This reduces the control complexity of the software strategy and improves circuit stability.

[0079] In some embodiments, the first three-level conversion unit is a single-phase type I three-level conversion unit, a three-phase type I three-level conversion unit, a single-phase type T three-level conversion unit, or a three-phase type T three-level conversion unit.

[0080] For details, please refer to Figure 8 When the first three-level conversion unit is a single-phase type I three-level conversion unit, it consists of four NMOS transistors (Q1-Q4) and two clamping diodes (D1, D2); or, please refer to Figure 9 When the first three-level conversion unit is a three-phase type I three-level conversion unit, it consists of twelve IGBT transistors (Q11-Q34) and six clamping diodes (D11-D32); or, please refer to [link to relevant documentation]. Figure 10 When the first three-level conversion unit is a single-phase T-type three-level conversion unit, it consists of four NMOS transistors (Q5-Q8); furthermore, please refer to... Figure 11 When the first three-level conversion unit is a three-phase T-type three-level conversion unit, it consists of twelve NMOS transistors (Q41-Q64). In practical applications, the above circuit structure or a suitable circuit structure from the prior art can be used as the first three-level conversion unit. In addition, the type of switching transistor can be set according to actual needs, thereby improving the flexibility and freedom of circuit design.

[0081] In some embodiments, the first three-level conversion unit may further include devices such as an input inductor, an input capacitor, an input resistor, or an input capacitor, for example... Figure 8As shown, the single-phase Type I three-level converter unit also includes an input inductor L, an output capacitor C1, an output capacitor C2, and an input capacitor C3. In practical applications, the specific circuit structure of the first three-level converter unit can refer to any suitable circuit structure in the prior art, and is not limited to the above embodiments.

[0082] In some embodiments, the input terminal of the N-level conversion unit 10 is connected to a single-phase AC power supply or a three-phase AC power supply. Specifically, when the first three-level conversion unit is a single-phase type I three-level conversion unit or a single-phase type T three-level conversion unit, its input terminal is connected to a single-phase AC power supply; when the first three-level conversion unit is a three-phase type I three-level conversion unit or a three-phase type T three-level conversion unit, its input terminal is connected to a three-phase AC power supply. By selecting different circuit structures for the N-level conversion unit, different AC power supplies can be adapted, thereby improving the adaptability and compatibility of the voltage conversion circuit.

[0083] In some embodiments, the DC-DC conversion unit is an LLC circuit, a CLLC circuit, a Phase-Shifting Full-Bridge Converter (PSFB) circuit, or any other suitable circuit in the art for voltage level conversion, without limitation. The LLC circuit is a resonant conversion circuit comprising two inductors and one capacitor; the CLLC circuit is a resonant conversion circuit comprising two capacitors and three inductors. The specific structures of the LLC, CLLC, and PFSB circuits can be found in conventional circuits in the prior art, and their specific circuit structures are not described in detail here. Therefore, when designing voltage conversion circuits, different DC-DC conversion unit circuit structures can be selected according to actual needs, improving the flexibility of voltage conversion circuit design.

[0084] In some embodiments, the voltage conversion circuit further includes a control unit. This control unit is connected to the N-level conversion unit and each of the N-1 DC-DC conversion units. The control unit controls the output level of the N-level conversion unit so that the difference between the output voltages of each DC-DC conversion unit is less than or equal to a first threshold.

[0085] Specifically, the control unit is connected to the control terminals of the N-level conversion unit and the N-1 DC-DC conversion units respectively. For example, the control unit is connected to the control terminals of the switching transistors in the N-level conversion unit and the control terminals of the switching transistors in the N-1 DC-DC conversion units respectively.

[0086] In this voltage conversion circuit, by controlling the output level of the N-level conversion unit, the input voltage of each DC-DC conversion unit can be adjusted. Thus, since the input voltage of each DC-DC conversion unit changes, the output voltages of each DC-DC conversion unit will also be adjusted. Therefore, by controlling the output level of the N-level conversion unit, the output voltages of each DC-DC conversion unit can be made equal or nearly equal, meaning the difference between the output voltages of each DC-DC conversion unit is less than or equal to a first threshold. The first threshold can be 0A; however, it can be set according to actual needs in practical applications and is not limited here.

[0087] In some embodiments, the control unit is configured to: acquire the output voltage of each DC-DC converter; and control the output level of the N-level converter based on the output voltage of each DC-DC converter.

[0088] Specifically, a voltage sampling unit can be set at the first output terminal of each DC-DC converter unit. Each sampling unit can collect the output voltage data of each DC-DC converter unit. Then, the control unit can obtain the output voltage of each DC-DC converter unit from the output voltage data of each sampling unit. Next, the control unit controls the output level of the N-level converter unit according to the magnitude of each output voltage, so that the output voltages of each DC-DC converter unit are equal or nearly equal, thereby achieving the purpose of voltage equalization control of multiple DC-DC converter units. It can be seen that this voltage equalization control method does not require adjustment of the frequency, phase shift angle, or duty cycle of the DC-DC converter units, which reduces the control difficulty and improves the operating stability of the circuit.

[0089] In practical applications, the voltage sampling unit can be implemented by existing chip modules (such as integrated circuits IC) or conventional circuits in the field. The circuit structure of the voltage sampling unit will not be described in detail here.

[0090] For example, please refer to Figure 7 For a voltage conversion circuit including a first three-level conversion unit 11, the control unit can connect the first three-level conversion unit 11, the first DC-DC conversion unit 21, and the second DC-DC conversion unit 22 respectively; then, the control unit can obtain the first output voltage U1 between the first output terminal and the second output terminal of the first DC-DC conversion unit 21, and obtain the second output voltage U2 between the first output terminal and the second output terminal of the second DC-DC conversion unit 22, and adjust the output level of the first three-level conversion unit 11 according to the magnitude of the first output voltage U1 and the second output voltage U2.

[0091] For example, when the first output voltage U1 is less than the second output voltage U2, the control unit can control the increase of the level of the second output terminal A2 of the first three-level conversion unit 11, thereby increasing the voltage between the first output terminal A1 and the second output terminal A2 of the first three-level conversion unit 11 and decreasing the voltage between the second output terminal A2 and the third output terminal A3 of the first three-level conversion unit 11. This causes the input voltage of the first DC-DC conversion unit 21 to increase and the input voltage of the second DC-DC conversion unit 22 to decrease. Therefore, the output voltage of the first DC-DC conversion unit 21 will increase and the output voltage of the second DC-DC conversion unit 22 will decrease. Similarly, when the first output voltage U1 is greater than the second output voltage U2, the control unit can control the reduction of the voltage level of the second output terminal A2 of the first three-level converter 11, thereby reducing the voltage between the first output terminal A1 and the second output terminal A2 of the first three-level converter 11 and increasing the voltage between the second output terminal A2 and the third output terminal A3 of the first three-level converter 11. This results in a decrease in the input voltage of the first DC-DC converter 21 and an increase in the input voltage of the second DC-DC converter 22. Consequently, the output voltage of the first DC-DC converter 21 will decrease, and the output voltage of the second DC-DC converter 22 will increase. Therefore, through the above control method, the first output voltage U1 of the first DC-DC converter 21 and the second output voltage U2 of the second DC-DC converter 22 can ultimately be made equal or nearly equal, achieving voltage equalization.

[0092] In practical applications, only the voltage level of the first output terminal A1 or the third output terminal A3 of the first three-level conversion unit 11 can be adjusted, thereby changing only the voltage between the first output terminal A1 and the second output terminal A2 of the first three-level conversion unit 11, or changing only the voltage between the second output terminal A2 and the third output terminal A3 of the first three-level conversion unit 11, thereby achieving the purpose of voltage equalization. Such adjustment methods should also fall within the scope of protection claimed in the embodiments of this application.

[0093] In some embodiments, the control unit is configured to: control at least one intermediate output level of the N-level conversion unit based on the output voltage of each DC-DC conversion unit, the intermediate output level being located between the maximum output level and the minimum output level of the N-level conversion unit.

[0094] For details, please refer to Figure 7For a voltage conversion circuit including a first three-level conversion unit 11, the level of the second output terminal A2 of the first three-level conversion unit 11 can be controlled according to the first output voltage of the first DC-DC conversion unit 21 and the second output voltage of the second DC-DC conversion unit 22. The level of the second output terminal A2 is also the intermediate output level of the first three-level conversion unit 11. By adjusting the intermediate output level, the input voltages of the first DC-DC conversion unit 21 and the second DC-DC conversion unit 22 can be quickly adjusted, thereby adjusting the output current of the first DC-DC conversion unit 21 and the second DC-DC conversion unit 22 to make them equal or substantially equal. Therefore, under the connection method provided in this application, the input voltages of two adjacent DC-DC conversion units can be quickly and flexibly adjusted by controlling at least one intermediate output level of the N-level conversion unit, thereby quickly adjusting the output current of the DC-DC conversion unit.

[0095] In some embodiments, the control unit is configured to: obtain a reference voltage based on the output voltage of each DC-DC converter; subtract the output voltage of each DC-DC converter from the reference voltage one by one to obtain the voltage difference corresponding to the output voltage of each DC-DC converter; and control at least one intermediate output level of the N-level converter based on each of the voltage differences.

[0096] Specifically, for a voltage conversion circuit including an N-level conversion unit, the control unit can first obtain the output voltage magnitudes between the first and second output terminals of each DC-DC conversion unit, namely U1, U2, ..., and U(N-1); then, the control unit calculates an average voltage value for these output voltages and uses this average voltage value as a reference voltage; next, it calculates the difference between each output voltage and the reference voltage to obtain the voltage difference corresponding to each output voltage; then, it processes each voltage difference through a PI controller to obtain at least one voltage command; finally, the control unit controls the switching state of the switching transistor of the N-level conversion unit according to the at least one voltage command, thereby controlling at least one intermediate output level of the N-level conversion unit.

[0097] As can be seen, this voltage equalization control method can flexibly control at least one intermediate output level of the N-level conversion unit according to the relationship between the output voltages of each DC-DC conversion unit. This allows for adaptive calculation and voltage equalization based on different circuit conditions, thereby improving voltage equalization efficiency.

[0098] Understandably, in this type of control method, since the control focuses on the intermediate output level of the N-level conversion unit, and the intermediate output terminals of the N-level conversion unit are N-2, the maximum number of voltage commands is N-2. In practical applications, the reference voltage can also be arbitrarily selected from the output currents of each DC-DC conversion unit, such as U1. Typically, to ensure control accuracy, the average value is chosen as the reference voltage.

[0099] For example, please refer to Figure 7 For the voltage conversion circuit including the first three-level conversion unit 11, the first output voltage U1 of the first DC-DC conversion unit 21 and the second output voltage U2 of the second DC-DC conversion unit 22 can be obtained by the voltage sampling unit. Then, the difference between the first output voltage U1 and the second output voltage U2 is obtained. Next, the voltage difference is processed by a PI controller to obtain a voltage command. The control unit controls the switching state of the switching transistor of the first three-level conversion unit 11 according to the voltage command, thereby controlling the level of the second output terminal A2 of the first three-level conversion unit 11. Finally, the input voltage of the first DC-DC conversion unit 21 and the input voltage of the second DC-DC conversion unit 22 can be adjusted to achieve a voltage equalization effect. At this time, the reference voltage can be selected as the first output voltage, the second output voltage, or the average voltage value of the first output voltage and the second output voltage, which is not limited here.

[0100] In summary, the voltage conversion circuit provided in this application embodiment can not only improve the output power of the voltage conversion circuit to meet high-power application scenarios, but also adjust the output voltage of multiple DC-DC conversion units by adjusting the output level of the N-level conversion unit to achieve the effect of voltage equalization. This voltage equalization control method reduces the difficulty of voltage equalization control.

[0101] To achieve current sharing output, please refer to [link / reference]. Figure 12 The voltage conversion circuit also includes: N level conversion units 10 and N-1 DC-DC conversion units. Figure 6 The embodiment shown differs in that, in this voltage conversion circuit, the first output terminal of each DC-DC conversion unit is connected to the third node C1, and the second output terminal of each DC-DC conversion unit is connected to the fourth node C2.

[0102] Generally, for the Mth DC-DC converter unit, the first input terminal is the positive input terminal, the second input terminal is the negative input terminal, the first output terminal is the positive output terminal, and the second output terminal is the negative output terminal. At this time, the third node C1 is used to connect to the positive terminal of the bus, and the fourth node C2 is used to connect to the negative terminal of the bus.

[0103] In this voltage conversion circuit, by connecting the input terminals of M-1 DC-DC converter units to the N-level output terminals of the N-level converter unit 10, and connecting the output terminals of the M-1 DC-DC converter units in parallel between the third node C1 and the fourth node C2, the output power of the voltage conversion circuit can be increased, thus meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, the output level of the N-level converter unit 10 can be directly adjusted, thereby adjusting the input voltage of the DC-DC converter units and ultimately adjusting the output current of the DC-DC converter units, making the output currents of multiple DC-DC converter units equal or nearly equal, thus achieving current sharing. It is evident that this connection method simplifies current sharing control, eliminating the need to control the frequency, phase shift angle, or duty cycle of the DC-DC converter units, reducing the control complexity of the software strategy, and improving circuit stability.

[0104] In some embodiments, when N=3, please refer to [reference needed]. Figure 13 The voltage conversion circuit includes a second three-level conversion unit 12, a third DC-DC conversion unit 23, and a fourth DC-DC conversion unit 24. The second three-level conversion unit 12 has a first output terminal A1, a second output terminal A2, and a third output terminal A3 with sequentially decreasing voltage levels. The first input terminal of the third DC-DC conversion unit 23 is connected to the first output terminal A1 of the second three-level conversion unit 12; the second input terminal of the third DC-DC conversion unit 23 and the first input terminal of the fourth DC-DC conversion unit 24 are connected to the second output terminal A2 of the second three-level conversion unit 12; the second input terminal of the fourth DC-DC conversion unit 24 is connected to the third output terminal A3 of the second three-level conversion unit 12; the first output terminals of the third DC-DC conversion unit 23 and the fourth DC-DC conversion unit 24 are connected to a third node C1; and the second output terminals of the third DC-DC conversion unit 23 and the fourth DC-DC conversion unit 24 are connected to a fourth node C2.

[0105] Specifically, the second three-level conversion unit 12 includes multiple upper and lower transistors that can output three-level states, namely high level, middle level and low level, through the switching state of the upper and lower transistors. For example, the level of the first output terminal A1 is +U, the level of the second output terminal A2 is 0, and the level of the third output terminal A3 is -U, where U represents the level of the first output terminal. The specific value can be set according to actual needs and is not limited here.

[0106] In this voltage conversion circuit, the above-described connection method can improve the output power of the voltage conversion circuit, thus meeting the needs of high-power applications. Furthermore, in this voltage conversion circuit, at least one of the first output terminals A1, A2, and A3 of the second three-level conversion unit 12 can be directly adjusted, thereby adjusting the input voltage of the third DC-DC conversion unit 23 and / or the input voltage of the fourth DC-DC conversion unit 24. Ultimately, this allows adjustment of the output current of the third DC-DC conversion unit 23 and / or the fourth DC-DC conversion unit 24, making their output currents equal or nearly equal, achieving current sharing. Therefore, this circuit connection method not only improves the output power of the voltage conversion circuit but also simplifies the current sharing control method, eliminating the need to control the frequency, phase shift angle, or duty cycle of the DC-DC conversion units for current sharing. This reduces the control complexity of the software strategy and improves circuit stability.

[0107] In some embodiments, the second three-level conversion unit is a single-phase type I three-level conversion unit, a three-phase type I three-level conversion unit, a single-phase type T three-level conversion unit, or a three-phase type T three-level conversion unit.

[0108] For details, please refer to Figure 8 When the second three-level conversion unit is a single-phase type I three-level conversion unit, it consists of four NMOS transistors (Q1-Q4) and two clamping diodes (D1, D2); or, please refer to Figure 9 When the second three-level conversion unit is a three-phase type I three-level conversion unit, it consists of twelve IGBT transistors (Q11-Q34) and six clamping diodes (D11-D32); or, please refer to [link to relevant documentation]. Figure 10 When the second three-level conversion unit is a single-phase T-type three-level conversion unit, it consists of four NMOS transistors (Q5-Q8); furthermore, please refer to... Figure 11 When the second three-level conversion unit is a three-phase T-type three-level conversion unit, it consists of twelve NMOS transistors (Q41-Q64). In practical applications, the above circuit structure or a suitable circuit structure in the prior art can be used as the second three-level conversion unit. In addition, the type of switching transistor can be set according to actual needs, thereby improving the flexibility and freedom of circuit design.

[0109] In some embodiments, the second three-level conversion unit may further include devices such as an input inductor, an input capacitor, an input resistor, or an input capacitor, for example... Figure 8As shown, the single-phase Type I three-level converter unit also includes an input inductor L, an output capacitor C1, an output capacitor C2, and an input capacitor C3. In practical applications, the specific circuit structure of the second three-level converter unit can refer to any suitable circuit structure in the prior art, and is not limited to the above embodiments.

[0110] In some embodiments, the input terminal of the N-level conversion unit 10 is connected to a single-phase AC power supply or a three-phase AC power supply. Specifically, when the second three-level conversion unit is a single-phase type I three-level conversion unit or a single-phase type T three-level conversion unit, its input terminal is connected to a single-phase AC power supply; when the second three-level conversion unit is a three-phase type I three-level conversion unit or a three-phase type T three-level conversion unit, its input terminal is connected to a three-phase AC power supply. By selecting different circuit structures for the N-level conversion unit, different AC power supplies can be adapted, thereby improving the adaptability and compatibility of the voltage conversion circuit.

[0111] In some embodiments, the DC-DC conversion unit is an LLC circuit, a CLLC circuit, a Phase-Shifting Full-Bridge Converter (PSFB) circuit, or any other suitable circuit in the art for voltage level conversion, without limitation. The LLC circuit is a resonant conversion circuit comprising two inductors and one capacitor; the CLLC circuit is a resonant conversion circuit comprising two capacitors and three inductors. The specific structures of the LLC, CLLC, and PFSB circuits can be found in conventional circuits in the prior art, and their specific circuit structures are not described in detail here. Therefore, when designing voltage conversion circuits, different DC-DC conversion unit circuit structures can be selected according to actual needs, improving the flexibility of voltage conversion circuit design.

[0112] In some embodiments, the voltage conversion circuit further includes a control unit. This control unit is connected to the N-level conversion unit and each of the N-1 DC-DC conversion units. The control unit controls the output level of the N-level conversion unit so that the difference between the output currents of each DC-DC conversion unit is less than or equal to a first threshold.

[0113] Specifically, the control unit is connected to the control terminals of the N-level conversion unit and the N-1 DC-DC conversion units respectively. For example, the control unit is connected to the control terminals of the switching transistors in the N-level conversion unit and the control terminals of the switching transistors in the N-1 DC-DC conversion units respectively.

[0114] In this voltage conversion circuit, by controlling the output level of the N-level conversion unit, the input voltage of each DC-DC conversion unit can be adjusted. Thus, because the input voltage of each DC-DC conversion unit changes, the output current of each DC-DC conversion unit is also adjusted. Therefore, by controlling the output level of the N-level conversion unit, the output current of each DC-DC conversion unit can be made equal or nearly equal, meaning the difference between the output currents of each DC-DC conversion unit is less than or equal to a second threshold. The second threshold can be 0A; in practical applications, it can be set according to actual needs and is not limited here.

[0115] In some embodiments, the control unit is configured to: acquire the output current of each DC-DC converter; and control the output level of the N-level converter based on the output current of each DC-DC converter.

[0116] Specifically, a current sampling unit can be set at the first output terminal of each DC-DC converter unit to collect the output current data of each unit. Then, the control unit can obtain the output current of each DC-DC converter unit from the output current data of each sampling unit. Next, the control unit controls the output level of the N-level converter unit based on the magnitude of each output current, ensuring that the output currents of each DC-DC converter unit are equal or nearly equal, thereby achieving current sharing among multiple DC-DC converter units. It is evident that this current sharing control method does not require adjustment of the frequency, phase shift angle, or duty cycle of the DC-DC converter units, reducing control complexity and improving circuit stability.

[0117] In practical applications, the current sampling unit can be implemented by existing chip modules (such as integrated circuits IC) or conventional circuits in this field. The circuit structure of the current sampling unit will not be described in detail here.

[0118] For example, please refer to Figure 13 For a voltage conversion circuit including a second three-level conversion unit 12, the control unit can connect the second three-level conversion unit 12, the third DC-DC conversion unit 23, and the fourth DC-DC conversion unit 24 respectively; then, the control unit can obtain the first output current I1 of the third DC-DC conversion unit 23 and the second output current I2 of the fourth DC-DC conversion unit 24, and adjust the output level of the second three-level conversion unit 12 according to the magnitude of the first output current I1 and the second output current I2.

[0119] For example, when the first output current I1 is less than the second output current I2, the control unit can control the increase of the level of the second output terminal A2 of the second three-level conversion unit 12, thereby increasing the voltage between the first output terminal A1 and the second output terminal A2 of the second three-level conversion unit 12 and decreasing the voltage between the second output terminal A2 and the third output terminal A3 of the second three-level conversion unit 12. This causes the input voltage of the third DC-DC conversion unit 23 to increase and the input voltage of the fourth DC-DC conversion unit 24 to decrease. Therefore, the output current of the third DC-DC conversion unit 23 will increase and the output current of the fourth DC-DC conversion unit 24 will decrease. Similarly, when the first output current I1 is greater than the second output current I2, the control unit can control the reduction of the voltage level at the second output terminal A2 of the second three-level converter 12, thereby reducing the voltage between the first output terminal A1 and the second output terminal A2 of the second three-level converter 12 and increasing the voltage between the second output terminal A2 and the third output terminal A3 of the second three-level converter 12. This results in a decrease in the input voltage of the third DC-DC converter 23 and an increase in the input voltage of the fourth DC-DC converter 24. Consequently, the output current of the third DC-DC converter 23 will decrease, and the output current of the fourth DC-DC converter 24 will increase. Therefore, through the above control method, the first output current I1 of the third DC-DC converter 23 and the second output current I2 of the fourth DC-DC converter 24 can ultimately be made equal or nearly equal, achieving the purpose of current sharing.

[0120] In practical applications, the voltage levels of either the first output terminal A1 or the third output terminal A3 of the second three-level conversion unit 12 can be adjusted to change the voltage between the first output terminal A1 and the second output terminal A2 of the second three-level conversion unit 12, or to change the voltage between the second output terminal A2 and the third output terminal A3 of the second three-level conversion unit 12, thereby achieving current sharing. Such adjustment methods should also fall within the scope of protection claimed in the embodiments of this application.

[0121] In some embodiments, the control unit is configured to: control at least one intermediate output level of the N-level conversion unit based on the output current of each DC-DC conversion unit, the intermediate output level being located between the maximum output level and the minimum output level of the N-level conversion unit.

[0122] For details, please refer to Figure 13For a voltage conversion circuit including a second three-level conversion unit 12, the level of the second output terminal A2 of the second three-level conversion unit 12 can be controlled according to the first output current of the third DC-DC conversion unit 23 and the second output current of the fourth DC-DC conversion unit 24. The level of the second output terminal A2 is also the intermediate output level of the second three-level conversion unit 12. By adjusting the intermediate output level, the input voltages of the third DC-DC conversion unit 23 and the fourth DC-DC conversion unit 24 can be quickly adjusted, thereby adjusting the magnitude of the output currents of the third DC-DC conversion unit 23 and the fourth DC-DC conversion unit 24 to make them equal or substantially equal. Therefore, under the connection method provided in this application, the input voltages of two adjacent DC-DC conversion units can be quickly and flexibly adjusted by controlling at least one intermediate output level of the N-level conversion unit, thereby quickly adjusting the output current of the DC-DC conversion unit.

[0123] In some embodiments, the control unit is configured to: obtain a reference current based on the output current of each DC-DC converter; subtract the output current of each DC-DC converter from the reference current to obtain the current difference corresponding to the output current of each DC-DC converter; and control at least one intermediate output level of the N-level converter based on the current differences.

[0124] Specifically, for a voltage conversion circuit including an N-level conversion unit, the control unit can first obtain the output current magnitude of the first output terminal of each DC-DC conversion unit, namely I1, I2, ... and I(N-1); then, the control unit calculates an average current value for these output currents and uses this average current value as a reference current; next, the difference between each output current and the reference current is calculated to obtain the current difference corresponding to each output current; then, each current difference is processed by a PI controller to obtain at least one voltage command; finally, the control unit controls the switching state of the switching transistor of the N-level conversion unit according to the at least one voltage command, thereby controlling at least one intermediate output level of the N-level conversion unit.

[0125] As can be seen, this current sharing control method can flexibly control at least one intermediate output level of the N-level conversion unit according to the relationship between the output currents of each DC-DC conversion unit. This allows for adaptive calculation and current sharing based on different circuit conditions, thereby improving current sharing efficiency.

[0126] Understandably, in this type of control method, since the control focuses on the intermediate output level of the N-level conversion unit, and the intermediate output level of the N-level conversion unit has N-2 output terminals, the maximum number of voltage commands is N-2. In practical applications, the reference current can also be arbitrarily selected from the output currents of each DC-DC conversion unit, such as I1. Typically, to ensure control accuracy, the average value is chosen as the reference current.

[0127] For example, please refer to Figure 13 For the voltage conversion circuit including the second three-level conversion unit 12, the first output current I1 of the third DC-DC conversion unit 23 and the second output current I2 of the fourth DC-DC conversion unit 24 can be obtained through the current sampling unit. Then, the difference between the first output current I1 and the second output current I2 is obtained. Next, the current difference is processed by a PI controller to obtain a voltage command. The control unit controls the switching state of the switching transistor of the second three-level conversion unit 12 according to the voltage command, thereby controlling the level of the second output terminal A2 of the second three-level conversion unit 12. Finally, the input voltage of the third DC-DC conversion unit 23 and the input voltage of the fourth DC-DC conversion unit 24 can be adjusted to achieve the current sharing effect. At this time, the reference current can be selected as the first output current, the second output current, or the average current value of the first output current and the second output current, which is not limited here.

[0128] In summary, the voltage conversion circuit provided in this application embodiment can not only improve the output power of the voltage conversion circuit to meet high-power application scenarios, but also adjust the output current of multiple DC-DC conversion units by adjusting the output level of the N-level conversion unit to achieve the effect of current sharing. This current sharing control method reduces the difficulty of current sharing control.

[0129] As another aspect of the embodiments of this application, the embodiments of this application also provide a charging device, which includes the voltage conversion circuit as described in any of the above embodiments.

[0130] As another aspect of the present application, the present application also provides an electrical device that includes a charging device as described in any of the above embodiments.

[0131] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A voltage conversion circuit, characterized in that, include: An N-level conversion unit has N output terminals with different levels; There are N-1 DC-DC converter units. The first input terminal of the Mth DC-DC converter unit is connected to the Mth output terminal of the N-level converter unit. The second input terminal of the Mth DC-DC converter unit is connected to the (M+1)th output terminal of the N-level converter unit. The output level of the Mth output terminal and the output level of the (M+1)th output terminal are adjacent levels. Where N≥3, 1≤M<N; The change in the output level of the N-level conversion unit causes a change in the output voltage or output current of the N-1 DC-DC conversion units.

2. The voltage conversion circuit according to claim 1, characterized in that, The first output terminal of the first DC-DC converter unit is connected to the first node, the first output terminal of the Pth DC-DC converter unit is connected to the second output terminal of the (P-1)th DC-DC converter unit, and the second output terminal of the (N-1)th DC-DC converter unit is connected to the second node. Where 2 ≤ P < N.

3. The voltage conversion circuit according to claim 2, characterized in that, When N=3, the voltage conversion circuit includes a first three-level conversion unit, a first DC-DC conversion unit, and a second DC-DC conversion unit; The first three-level conversion unit has a first output terminal, a second output terminal, and a third output terminal with successively decreasing levels; The first input terminal of the first DC-DC converter is connected to the first output terminal of the first three-level converter; the second input terminal of the first DC-DC converter and the first input terminal of the second DC-DC converter are connected to the second output terminal of the first three-level converter; and the second input terminal of the second DC-DC converter is connected to the third output terminal of the first three-level converter. The first output terminal of the first DC-DC converter is connected to the first node, the second output terminal of the first DC-DC converter is connected to the first output terminal of the second DC-DC converter, and the second output terminal of the second DC-DC converter is connected to the second node.

4. The voltage conversion circuit according to claim 3, characterized in that, The first three-level conversion unit is a single-phase type I three-level conversion unit, a three-phase type I three-level conversion unit, a single-phase type T three-level conversion unit, or a three-phase type T three-level conversion unit.

5. The voltage conversion circuit according to claim 1, characterized in that, The first output terminal of each DC-DC converter is connected to the third node, and the second output terminal of each DC-DC converter is connected to the fourth node.

6. The voltage conversion circuit according to claim 5, characterized in that, When N=3, the voltage conversion circuit includes a second three-level conversion unit, a third DC-DC conversion unit, and a fourth DC-DC conversion unit; The second three-level conversion unit has a first output terminal, a second output terminal, and a third output terminal with successively decreasing levels; The first input terminal of the third DC-DC converter is connected to the first output terminal of the second three-level converter; the second input terminal of the third DC-DC converter and the first input terminal of the fourth DC-DC converter are connected to the second output terminal of the second three-level converter; and the second input terminal of the fourth DC-DC converter is connected to the third output terminal of the second three-level converter. The first output terminal of the third DC-DC converter and the first output terminal of the fourth DC-DC converter are connected to the third node, and the second output terminal of the third DC-DC converter and the second output terminal of the fourth DC-DC converter are connected to the fourth node.

7. The voltage conversion circuit according to claim 6, characterized in that, The second three-level conversion unit is a single-phase type I three-level conversion unit, a three-phase type I three-level conversion unit, a single-phase type T three-level conversion unit, or a three-phase type T three-level conversion unit.

8. The voltage conversion circuit according to any one of claims 1-7, characterized in that, The input terminal of the N-level conversion unit is connected to a single-phase AC power supply or a three-phase AC power supply.

9. The voltage conversion circuit according to any one of claims 1-7, characterized in that, The DC-DC conversion unit is an LLC circuit, a CLLLC circuit, or a PSFB circuit.

10. The voltage conversion circuit according to any one of claims 1-7, characterized in that, The voltage conversion circuit also includes a control unit; The control unit is connected to the N-level conversion unit and the N-1 DC-DC conversion units respectively; The control unit is used to control the output level of the N-level conversion unit so that the difference between the output voltages of each DC-DC conversion unit is less than or equal to a first threshold. Alternatively, the control unit is used to control the output level of the N-level conversion unit so that the difference between the output currents of each DC-DC conversion unit is less than or equal to a second threshold.

11. The voltage conversion circuit according to claim 10, characterized in that, The control unit is used for: Obtain the output voltage or output current of each DC-DC converter unit; The output level of the N-level conversion unit is controlled according to each of the said output voltages or each of the said output currents.

12. The voltage conversion circuit according to claim 10, characterized in that, The control unit is used for: The intermediate output level of the N-level conversion unit is controlled according to each of the output voltages or the output currents, and the intermediate output level is located between the maximum output level and the minimum output level of the N-level conversion unit.

13. The voltage conversion circuit according to claim 11, characterized in that, The control unit is used for: Based on the output voltages described above, the reference voltage is obtained; The voltage difference corresponding to each output voltage is obtained by subtracting each output voltage from the reference voltage one by one. Based on the voltage differences, control at least one intermediate output level of the N-level conversion unit; Alternatively, the control unit is used for: Based on the output currents described above, the reference current is obtained; The current difference corresponding to each output current is obtained by subtracting the reference current from each of the output currents; Based on the current differences, at least one intermediate output level of the N-level conversion unit is controlled.

14. A charging device, characterized in that, Includes the voltage conversion circuit as described in any one of claims 1-13.

15. An electrical appliance, characterized in that, Includes the charging device as described in claim 14.

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