Flying capacitor three-level converter and flying capacitor three-level buck-boost converter
By employing parallel capacitors and bridge arm structures in the flying capacitor three-level converter, a complementary and compact switching circuit is formed, and the circuit is arranged on the same-level heat dissipation unit. This solves the voltage stress and thermal stress problems of the switching devices, achieving safe and reliable operation and cost reduction.
Patent Information
- Application Number
- CN202111042825.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-09-07
- Publication Date
- 2026-11-06
- Estimated Expiration
- 2041-09-07
AI Technical Summary
In high-voltage, high-power converter systems, the switching devices of flying capacitor multilevel converters face voltage and thermal stress problems, and the device layout is complex, making it difficult to achieve safe and reliable operation.
The three-level converter structure with flying capacitors is adopted. Each circuit unit includes parallel flying capacitors and bridge arms. The switching devices form a complementary compact loop and are arranged on the same level heat dissipation unit to maximize heat dissipation resources and reduce thermal stress.
It reduces voltage and thermal stress on switching devices, improves device safety and reliability, simplifies internal circuit layout, enhances high-temperature derating capability and fault redundancy load-bearing capability, and reduces costs.
Smart Images
Figure CN115776221B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of converter technology, and more specifically, to a flying capacitor three-level converter, a flying capacitor three-level buck-boost converter, and a flying capacitor multi-level converter. Background Technology
[0002] In high-voltage, high-power converter systems, flying capacitor multilevel converter technology has received increasing attention and application. Multilevel converters utilize a large number of switching devices, especially as the voltage and number of levels increase, leading to a greater number of switching devices per bridge arm. Furthermore, due to the need for increased power capacity, multiple bridge arms are often connected in parallel in an interleaved manner, further increasing the number of switching devices used.
[0003] During the operation of a flying capacitor multilevel converter, on the one hand, the switching devices will generate electrical losses, and heat dissipation channels need to be designed for the switching devices; on the other hand, the switching devices need to withstand voltage stress and current stress during the switching process. In order to reduce the adverse effects of stress on the switching devices, the commutation circuit of the switching devices is often required to be designed very compactly.
[0004] Furthermore, in many applications, the flying capacitor multilevel converter operates in different modes, and the switching devices of multiple bridge arms need to operate in different switching states, with different electrical and structural requirements. These factors further increase the difficulty of switching device layout.
[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention
[0006] This disclosure provides a flying capacitor three-level converter, a flying capacitor three-level buck-boost converter, and a flying capacitor multi-level converter, which can reduce the voltage and thermal stress of switching devices, make the switching operation safer and more reliable, simplify the internal circuit layout of the product, and facilitate electrical and structural design.
[0007] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.
[0008] This disclosure provides a flying capacitor three-level converter, comprising: N circuit units, where N is a positive integer greater than 1; each circuit unit includes a flying capacitor, an input capacitor, and a bridge arm; the input capacitor is connected in parallel with the bridge arm; the bridge arm includes a first switching device, a second switching device, a third switching device, and a fourth switching device, which are connected in series sequentially; the flying capacitor includes a first capacitor and a second capacitor, which are connected in parallel with the second capacitor and also in parallel with a series branch formed by the second and third switching devices; the input capacitor, the first switching device, the first capacitor, and the fourth switching device constitute a first switching circuit; the second capacitor, the second switching device, and the third switching device constitute a second switching circuit.
[0009] In some exemplary embodiments of this disclosure, the flying capacitor three-level converter further includes a first heat dissipation unit and a second heat dissipation unit; the first switching device and the fourth switching device in all the first switching circuits are disposed on the first heat dissipation unit; the second switching device and the third switching device in all the second switching circuits are disposed on the second heat dissipation unit.
[0010] In some exemplary embodiments of this disclosure, the first heat dissipation unit and the second heat dissipation unit have equal or similar heat dissipation conditions.
[0011] In some exemplary embodiments of this disclosure, the input capacitor and the first capacitor are located on a first side of the first heat dissipation unit or a second side corresponding to the first side; the second capacitor is located on a first side of the second heat dissipation unit or a second side corresponding to the first side.
[0012] In some exemplary embodiments of this disclosure, the input capacitor and the first capacitor are disposed close to their corresponding first switching device and the fourth switching device; the second capacitor is disposed close to its corresponding second switching device and the third switching device.
[0013] In some exemplary embodiments of this disclosure, the capacitance value of the first capacitor is not equal to the capacitance value of the second capacitor.
[0014] In some exemplary embodiments of this disclosure, the distance between the first capacitor and the second capacitor is a preset distance.
[0015] In some exemplary embodiments of this disclosure, all of the bridge arms are connected in parallel.
[0016] This disclosure provides a flying capacitor three-level buck-boost converter, comprising N circuit units, where N is a positive integer greater than or equal to 1. Each circuit unit includes a first flying capacitor, a second flying capacitor, an input capacitor, an output capacitor, an inductor, a first bridge arm, and a second bridge arm. The input capacitor is connected in parallel with the first bridge arm; the output capacitor is connected in parallel with the second bridge arm; the first bridge arm includes a first switching device, a second switching device, a third switching device, and a fourth switching device, which are connected in series; the second bridge arm includes a fifth switching device, a sixth switching device, a seventh switching device, and an eighth switching device, which are connected in series; the first flying capacitor includes a first capacitor and a second capacitor, which are connected in parallel. Simultaneously, it is connected in parallel with the series branch formed by the second and third switching devices of the first bridge arm; the input capacitor, the first switching device, the first capacitor, and the fourth switching device constitute a first switching circuit; the second switching device, the third switching device, and the second capacitor constitute a second switching circuit; the second flying capacitor includes a third capacitor and a fourth capacitor, the third capacitor and the fourth capacitor are connected in parallel, and are also connected in parallel with the series branch formed by the sixth and seventh switching devices of the second bridge arm; the output capacitor, the fifth switching device, the third capacitor, and the eighth switching device constitute a third switching circuit; the sixth switching device, the seventh switching device, and the fourth capacitor constitute a fourth switching circuit; the inductor is coupled between the connection point of the second and third switching devices of the first bridge arm and the connection point of the sixth and seventh switching devices of the second bridge arm.
[0017] In some exemplary embodiments of this disclosure, the flying capacitor three-level buck-boost converter further includes a first heat dissipation unit and a second heat dissipation unit; all the first switching devices and the fourth switching devices in the first switching circuit are disposed on the first heat dissipation unit; all the second switching devices and the third switching devices in the second switching circuit are disposed on the second heat dissipation unit; all the fifth switching devices and the eighth switching devices in the third switching circuit are disposed on the first heat dissipation unit; and all the sixth switching devices and the seventh switching devices in the fourth switching circuit are disposed on the second heat dissipation unit.
[0018] In some exemplary embodiments of this disclosure, the first heat dissipation unit and the second heat dissipation unit have equal or similar heat dissipation conditions.
[0019] In some exemplary embodiments of this disclosure, the input capacitor and the first capacitor in the first switching circuit are located on a first side of the first heat dissipation unit or on a second side corresponding to the first side; the second capacitor in the second switching circuit is located on a first side of the second heat dissipation unit or on a second side corresponding to the first side; the output capacitor and the third capacitor in the third switching circuit are located on a first side of the first heat dissipation unit or on a second side corresponding to the first side; and the fourth capacitor in the fourth switching circuit is located on a first side of the second heat dissipation unit or on a second side corresponding to the first side.
[0020] In some exemplary embodiments of this disclosure, the input capacitor and the first capacitor are disposed close to their corresponding first switching device and the fourth switching device; the second capacitor is disposed close to its corresponding second switching device and the third switching device; the output capacitor and the third capacitor are disposed close to their corresponding fifth switching device and the eighth switching device; and the fourth capacitor is disposed close to its corresponding sixth switching device and the seventh switching device.
[0021] In some exemplary embodiments of this disclosure, when N is greater than 1, all the first bridge arms are connected in parallel, and all the second bridge arms are connected in parallel.
[0022] This disclosure provides a flying capacitor multilevel converter, comprising N circuit units, where N is a positive integer greater than 1. Each circuit unit includes m flying capacitors, an input capacitor, and a bridge arm, where m is a positive integer greater than or equal to 1. The bridge arm includes 2×(m+1) switching devices, which are connected in series sequentially. Each flying capacitor includes a first capacitor and a second capacitor, which are connected in parallel. The first flying capacitor is connected in parallel across the two ends of a series branch formed by the second to the (2m+1)th switching devices. The input capacitor, the first switching device, the first capacitor of the first flying capacitor, and the (2×(m+1))th switching device constitute the... A switching circuit is provided; the second capacitor of the first flying capacitor, the second switching device, the first capacitor of the second flying capacitor, and the 2m+1 switching device constitute a second switching circuit; the kth flying capacitor is connected in parallel to the two ends of the series branch formed by the (k+1)th switching device to the 2m+2-kth switching devices, where k is a natural number from 2 to m; the second capacitor of the (k-1)th flying capacitor, the kth switching device, the first capacitor of the kth flying capacitor, and the 2m+3-kth switching devices constitute the kth switching circuit; the second capacitor of the mth flying capacitor, the (m+1)th switching device, and the (m+2)th switching device constitute the (m+1)th switching circuit.
[0023] In some exemplary embodiments of this disclosure, the flying capacitor multilevel converter further includes m+1 heat dissipation units; the first and second (m+1)th switching devices in all the first switching circuits are disposed on the first heat dissipation unit; the second and 2m+1th switching devices in all the second switching circuits are disposed on the second heat dissipation unit; the kth switching device and 2m+3-kth switching devices in all the kth switching circuits are disposed on the kth heat dissipation unit; and the (m+1)th and (m+2)th switching devices in all the (m+1)th switching circuits are disposed on the (m+1)th heat dissipation unit.
[0024] In some exemplary embodiments of this disclosure, the m+1 heat dissipation units have equal or similar heat dissipation conditions.
[0025] In some exemplary embodiments of this disclosure, the input capacitor in the first switching circuit and the first capacitor of the first flying capacitor are located on the first side of the first heat dissipation unit or on the second side corresponding to the first side; the second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor in the second switching circuit are located on the first side of the second heat dissipation unit or on the second side corresponding to the first side; the second capacitor of the (k-1)th flying capacitor and the first capacitor of the kth flying capacitor in the kth switching circuit are located on the first side of the kth heat dissipation unit or on the second side corresponding to the first side; the second capacitor of the mth flying capacitor in the (m+1)th switching circuit is located on the first side of the (m+1)th heat dissipation unit or on the second side corresponding to the first side.
[0026] In some exemplary embodiments of this disclosure, the input capacitor and the first capacitor of the first flying capacitor are positioned close to the corresponding first switching device and the second (m+1) switching device; the second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor are positioned close to the corresponding second switching device and the 2m+1 switching device; the second capacitor of the (k-1)th flying capacitor and the first capacitor of the kth flying capacitor are positioned close to the corresponding kth switching device and the 2m+3-kth switching device; and the second capacitor of the mth flying capacitor is positioned close to the corresponding m+1th switching device and the m+2th switching device.
[0027] In some exemplary embodiments of this disclosure, the capacitance value of the first capacitor and the capacitance value of the second capacitor of each of the flying capacitors are not equal.
[0028] In some exemplary embodiments of this disclosure, all of the bridge arms are connected in parallel.
[0029] In the flying capacitor three-level converter provided in this embodiment, each flying capacitor includes a first capacitor and a second capacitor connected in parallel. These two capacitors form switching circuits with the two pairs of complementary driving signal switching devices connected to the flying capacitor, which is beneficial for absorbing switching voltage spikes. Each pair of complementary driving signal switching devices is protected by the switching circuit (including capacitors), resulting in lower voltage stress compared to when all switching devices in the same bridge arm are set together, making the operation of the switching devices safer and more reliable. Each pair of complementary driving signal switching devices has its own compact switching circuit, which simplifies and facilitates the internal circuit layout of the converter, benefiting electrical and structural design. The complementary driving signal switching devices of the same level in different circuit units are placed on the same heat dissipation unit, which is beneficial for uniform heat load distribution, maximizing the utilization of heat dissipation resources. This increases the available heat dissipation capacity of other circuit units when some circuit units are not in operation, thereby reducing thermal stress, improving high-temperature derating capability and fault-tolerant operation capability, and contributing to cost reduction and performance improvement.
[0030] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this disclosure. Attached Figure Description
[0031] The above and other objects, features and advantages of this disclosure will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.
[0032] Figure 1 This is a schematic diagram of a flying capacitor three-level converter according to an exemplary embodiment.
[0033] Figure 2 This is a schematic diagram of another flying capacitor three-level converter according to an exemplary embodiment.
[0034] Figure 3A yes Figure 2 The diagram shows a schematic layout of one type of switching element in a flying capacitor three-level converter.
[0035] Figure 3B yes Figure 2 The diagram shows another switching element layout for a flying capacitor three-level converter.
[0036] Figure 3C yes Figure 2 The diagram shows another switching element layout for a flying capacitor three-level converter.
[0037] Figure 4 This is a schematic diagram of a flying capacitor three-level buck-boost converter according to an exemplary embodiment.
[0038] Figure 5This is a schematic diagram of another flying capacitor three-level buck-boost converter according to an exemplary embodiment.
[0039] Figure 6 yes Figure 5 The diagram shows the switch element layout of a flying capacitor three-level buck-boost converter.
[0040] Figure 7 This is a schematic diagram of a flying capacitor multilevel converter according to an exemplary embodiment.
[0041] Figure 8 yes Figure 7 The diagram shows the switch element layout of a flying capacitor multilevel converter. Detailed Implementation
[0042] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.
[0043] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of the specific details omitted, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known structures, methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.
[0044] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
[0045] Figure 1 This is a schematic diagram of a flying capacitor three-level converter according to an exemplary embodiment.
[0046] refer to Figure 1 The flying capacitor three-level converter 10 may include N circuit units, where N is a positive integer greater than 1.
[0047] The following explanation uses one of the circuit units, 101, as an example.
[0048] In this embodiment of the disclosure, circuit unit 101 may include a flying capacitor and an input capacitor C. d and bridge arm.
[0049] Wherein, the input capacitor C d It is connected in parallel with the bridge arm.
[0050] The bridge arm may include a first switching device Q1, a second switching device Q2, a third switching device Q3, and a fourth switching device Q4, which are connected in series.
[0051] In an exemplary embodiment, the bridge arms of all circuit units are connected in parallel, that is, the input capacitance C of all circuit units is connected in parallel. d Parallel connection.
[0052] The flying capacitor may include the first capacitor C 1u Second capacitor C 1d The first capacitor C 1u Second capacitor C 1d It is connected in parallel, and is also connected in parallel with the series branch formed by the second switching device Q2 and the third switching device Q3.
[0053] Among them, the first capacitor C 1u The capacitance value and the second capacitor C 1d The capacitance values can be the same or different.
[0054] In an exemplary embodiment, the first capacitor C 1u The capacitance value is greater than that of the second capacitor C. 1d The capacitance value; or the first capacitor C 1u The capacitance value is less than that of the second capacitor C. 1d The capacitance value.
[0055] In an exemplary embodiment, the first capacitor C 1u With the second capacitor C 1d The distance between them is a preset distance.
[0056] In this embodiment of the disclosure, the first capacitor C 1u With the second capacitor C 1d The distance between them can be set by a preset distance, and the size of the preset distance can be set according to the actual situation. This disclosure does not impose any restrictions on this.
[0057] In this embodiment of the disclosure, the flying capacitor three-level converter 10 can be a bidirectional converter or a unidirectional converter.
[0058] In this embodiment of the disclosure, the input capacitor C dFirst switching device Q1, first capacitor C 1u The first switching circuit is formed by the fourth switching device Q4, and the second capacitor C 1d The second switching device Q2 and the third switching device Q3 constitute the second switching circuit. In this embodiment, the drive signals of switching devices Q2 and Q3 are complementary, while the drive signals of switching devices Q1 and Q4 are complementary.
[0059] In this embodiment of the disclosure, the input capacitor C d First switching device Q1, first capacitor C 1u The fourth switching device Q4 constitutes the first switching circuit, and can form a first compact connection circuit P1u# in terms of layout, and the second capacitor C 1d The second switching device Q2 and the third switching device Q3 constitute the second switching circuit, and can form a second compact connection circuit P1d# in terms of layout.
[0060] In this embodiment of the present disclosure, the first DC voltage at the first terminal of the circuit unit 101 is V. d The second DC voltage at the second terminal of the flying capacitor three-level converter 10 is V. O The circuit unit 101 may also include an inductor L1, and the flying capacitor three-level converter may also include an output capacitor C. O One end of the inductor L1 is electrically connected to the connection point of the second switching device Q2 and the third switching device Q3, and the other end is connected to the output capacitor C. O One end.
[0061] In the flying capacitor three-level converter provided in this embodiment, each flying capacitor includes a first capacitor and a second capacitor connected in parallel. These two capacitors respectively form a switching circuit with two pairs of complementary switching devices connected to the flying capacitor. For example, the first capacitor C 1u The first switching circuit is formed by switching devices Q1 and Q4, and the second capacitor C 1d The second switching circuit, formed by switching devices Q2 and Q3, is beneficial for absorbing switching voltage spikes. Each pair of complementary drive signal switching devices is protected by the switching circuit (including capacitors), resulting in lower voltage stress compared to when all switching devices in the same bridge arm are set together, making the operation of the switching devices safer and more reliable. Each pair of complementary drive signal switching devices has its own compact switching circuit, which simplifies and facilitates the internal circuit layout of the product, and is beneficial for electrical and structural design. The complementary drive signal switching devices of the same level in different circuit units are set on the same heat dissipation unit, which is beneficial for the uniform distribution of heat load and maximizes the utilization of heat dissipation resources. This increases the available heat dissipation capacity of other operating circuit units when some circuit units are not in operation, thereby reducing thermal stress, improving high-temperature derating operation capability and fault-tolerant operation capability, which helps to reduce costs and improve performance.
[0062] Figure 2 This is a schematic diagram of another flying capacitor three-level converter according to an exemplary embodiment.
[0063] Figure 3A , Figure 3B and Figure 3C yes Figure 2 The diagram shows the switch element layout of a flying capacitor three-level converter.
[0064] refer to Figure 2 The following description uses a flying capacitor three-level converter with three circuit units as an example, but this disclosure is not limited to this.
[0065] In this embodiment, the flying capacitor three-level converter has three circuit units: P1#, P2#, and P3#. Each circuit unit includes a flying capacitor and an input capacitor C. d The bridge arms, each including a first switching device Q1, a second switching device Q2, a third switching device Q3, and a fourth switching device Q, and each flying capacitor including a first capacitor C connected in parallel. 1u Second capacitor C 1d .
[0066] In this embodiment, the bridge arms of all circuit units P1#, P2# and P3# are connected in parallel. That is, the input capacitors of the circuit units are connected in parallel to the first terminals BUS+ and BUS- of the flying capacitor three-level converter. The first DC voltage V1 of the first terminal of the flying capacitor three-level converter and the second DC voltage V2 of the second terminal of the flying capacitor three-level converter are also connected.
[0067] Each bridge arm is connected in parallel with the first capacitor C. 1u Second capacitor C 1d Divided into two parts by a boundary, forming a first switching circuit and a second switching circuit respectively. The first and second switching circuits can be two-stage compact connection circuits (a first compact connection circuit and a second compact connection circuit). Each compact connection circuit includes two switching devices with complementary drive signals and a capacitor. For example, the first compact connection circuit includes an input capacitor C. d First switching device Q1, first capacitor C 1u And the fourth switching device Q4, the second compact connection circuit includes the second capacitor C 1d The second switching device Q2 and the third switching device Q3.
[0068] In an exemplary embodiment, circuit unit P1# may further include inductor L1, circuit unit P2# may further include output inductor L2, circuit unit P3# may further include output inductor L3, and the flying capacitor three-level converter may further include output capacitor C. fOne end of the inductor L1 is electrically connected to the connection point of the second switching device Q2 and the third switching device Q3 in circuit unit P1#, and the other end is connected to the output capacitor C. f One end of the inductor L2 is electrically connected to the connection point of the second switching device Q2 and the third switching device Q3 in circuit unit P2#, and the other end is connected to the output capacitor C. f One end of the inductor L3 is electrically connected to the connection point of the second switching device Q2 and the third switching device Q3 in circuit unit P3#, and the other end is connected to the output capacitor C. f One end.
[0069] In an exemplary embodiment, the flying capacitor three-level converter may further include a first heat dissipation unit 201 and a second heat dissipation unit 202.
[0070] In an exemplary embodiment, the first heat dissipation unit and the second heat dissipation unit have equal or similar heat dissipation conditions.
[0071] The first and fourth switching devices in all first switching circuits (i.e., the first switching circuit in each circuit unit) are disposed on the first heat dissipation unit 201, and the second and third switching devices in all second switching circuits (i.e., the second switching circuit in each circuit unit) are disposed on the second heat dissipation unit 202.
[0072] In terms of the converter's structural layout, all the switching devices of the N first switching loops in the N circuit units can be installed on the first heat sink or in the first heat dissipation area, and all the switching devices of the N second switching loops in the N circuit units can be installed on the second heat sink or in the second heat dissipation area.
[0073] In other words, switching elements in the same compact connection circuit can be installed on the same heat sink or heat dissipation area, while switching elements in different compact connection circuits can be installed on two different heat sinks or heat dissipation areas.
[0074] The first and second heat sinks or heat dissipation areas mentioned above have the same or similar heat dissipation conditions within the converter.
[0075] It should be noted that in the embodiments of this disclosure, the first heat dissipation unit 201 and the second heat dissipation unit 202 can be two parts of the same heat sink, or they can be two separate heat sinks. Having equal or similar heat dissipation conditions in the embodiments of this disclosure does not necessarily require that the heat dissipation conditions of the first heat dissipation unit and the second heat dissipation unit be exactly the same; the difference between the heat dissipation conditions of the first heat dissipation unit and the second heat dissipation unit is acceptable within a certain error range. The aforementioned certain error range can be set according to actual conditions, and this disclosure does not impose any limitations on it.
[0076] Figure 2 In the circuit unit shown, and Figure 1 The same components and connections in the circuit unit shown can be referenced. Figure 1 The relevant textual explanations will not be repeated here.
[0077] refer to Figure 3A In an exemplary embodiment, the input capacitance C of each circuit unit d and the first capacitor C 1u All are located on the first side of the first heat dissipation unit 201, and the second capacitor C 1d It is located on the second side of the second heat dissipation unit 202.
[0078] refer to Figure 3B In an exemplary embodiment, the input capacitance C of each circuit unit d and the first capacitor C 1u Both are located on the second side of the first heat dissipation unit 201, and the second capacitor C 1d Located on the first side of the second heat dissipation unit 202.
[0079] refer to Figure 3C In an exemplary embodiment, the input capacitance C of each circuit unit d and the first capacitor C 1u All are located on the first side of the first heat dissipation unit 201, and the second capacitor C 1d Located on the first side of the second heat dissipation unit 202.
[0080] In an exemplary embodiment, the input capacitor and the first capacitor of each circuit unit are located on the same side of the first heat dissipation unit, and the second capacitor of each circuit unit is located on the same side of the second heat dissipation unit.
[0081] In an exemplary embodiment, the input capacitance C of each circuit unit d and the first capacitor C 1u The second capacitor C is positioned close to its corresponding first switching device Q1 and fourth switching device Q4. 1d It is positioned close to its corresponding second switching device Q2 and third switching device Q3.
[0082] In other words, the input capacitor and the first capacitor of each circuit unit can be set on the side of the first heat dissipation unit 201 close to the first switching device and the fourth switching device corresponding to it, and the second capacitor of each circuit unit can be set on the side of the second heat dissipation unit 202 close to the second switching device and the third switching device corresponding to it.
[0083] In an exemplary embodiment, the distance between the first capacitor and the second capacitor of each flying capacitor is a preset distance, which can be selected according to actual needs.
[0084] In the flying capacitor three-level converter provided in this embodiment, when N circuit units are in parallel operation, interleaved operation or complementary operation, the switching devices of the same level in different circuit units are set on the same heat dissipation unit, which is conducive to the uniform distribution of heat load and maximizes the utilization of heat dissipation resources. This can increase the available heat dissipation capacity of other circuit units when some circuit units are not in operation, thereby reducing thermal stress, improving high temperature derating operation capability and fault redundancy operation load capacity, which is conducive to reducing costs and improving cost performance.
[0085] Figure 4 This is a schematic diagram of a flying capacitor three-level buck-boost converter according to an exemplary embodiment.
[0086] refer to Figure 4 The flying capacitor three-level buck-boost converter may include N circuit units, where N is a positive integer greater than or equal to 1.
[0087] The following explanation uses one of the circuit units, 401, as an example.
[0088] In this embodiment of the present disclosure, circuit unit 401 may include a first flying capacitor, a second flying capacitor, and an input capacitor C. d Output capacitor C o Inductor L1, first bridge arm and second bridge arm.
[0089] Wherein, the input capacitor C d Connected in parallel with the first bridge arm, the output capacitor C o It is connected in parallel with the second bridge arm.
[0090] The first bridge arm may include a first switching device Q1, a second switching device Q2, a third switching device Q3, and a fourth switching device Q4, which are connected in series. The second bridge arm may include a fifth switching device Q5, a sixth switching device Q6, a seventh switching device Q7, and an eighth switching device Q8, which are connected in series.
[0091] The first flying capacitor may include a first capacitor C. 1u Second capacitor C 1d The first capacitor C 1u Second capacitor C 1d It is connected in parallel, and simultaneously connected in parallel with the series branch formed by the second switching device Q2 and the third switching device Q3 of the first bridge arm.
[0092] The second flying capacitor may include a third capacitor C. 2u and the fourth capacitor C 2dThe third capacitor C 2u and the fourth capacitor C 2d It is connected in parallel, and simultaneously connected in parallel with the series branch formed by the sixth switch Q6 and the seventh switch Q7 of the second bridge arm.
[0093] Input capacitor C d First switching device Q1, first capacitor C 1u The first switching circuit is formed by the fourth switching device Q4; the second switching device Q2, the third switching device Q3, and the second capacitor C form the first switching circuit. 1d It forms the second switching circuit.
[0094] Output capacitor C o Fifth switching device Q5, third capacitor C 2u The third switching circuit is formed by the sixth switching device Q6, the seventh switching device Q7, and the fourth capacitor C. 2d This forms the fourth switching circuit.
[0095] In this embodiment of the disclosure, the input capacitor C d First switching device Q1, first capacitor C 1u The fourth switching device Q4 constitutes the first switching circuit, and can form a first compact connection circuit P1u#a in terms of layout, and the second capacitor C 1d The second switching device Q2 and the third switching device Q3 constitute the second switching circuit, and can form a second compact connection circuit P1d#a in terms of layout; the output capacitor C o Fifth switching device Q5, third capacitor C 2u The sixth switch, Q6, the seventh switch, Q7, and the fourth capacitor C form the third switching circuit, and can be arranged in a third compact connection circuit P1u#b; the seventh switch, Q7, and the fourth capacitor C form the third switching circuit. 2d It forms a fourth switching circuit and can be arranged to form a fourth compact connection circuit P1d#b.
[0096] The inductor L is electrically coupled between the connection point of the second switching device Q2 and the third switching device Q3 in the first bridge arm and the connection point of the sixth switching device Q6 and the seventh switching device Q7 in the second bridge arm.
[0097] In an exemplary embodiment, when N is greater than 1, all the first bridge arms are connected in parallel, and all the second bridge arms are connected in parallel.
[0098] In the flying capacitor three-level buck-boost converter provided in this embodiment, each flying capacitor includes two capacitors connected in parallel. These two capacitors form a switching circuit with the two pairs of complementary driving signals of the flying capacitor, which is beneficial for absorbing switching voltage spikes. Each pair of complementary driving signals of the switching devices is protected by the switching circuit (including capacitors), and the voltage stress is smaller than that of all the switching devices in the same bridge arm when set together, making the operation of the switching devices safer and more reliable. Each pair of complementary driving signals of the switching devices has a dedicated switching circuit, which makes the internal circuit layout of the product simple and convenient, and is beneficial to electrical and structural design.
[0099] Figure 5 This is a schematic diagram of another flying capacitor three-level buck-boost converter according to an exemplary embodiment.
[0100] Figure 6 yes Figure 5 The diagram shows the switch element layout of a flying capacitor three-level buck-boost converter.
[0101] refer to Figure 5 The following description uses a three-level buck-boost converter with two circuit units as an example, but this disclosure is not limited to this.
[0102] In this embodiment of the disclosure, the flying capacitor three-level buck-boost converter has two parallel circuit units, P1# and P2#. Each circuit unit can be a two-bridge-arm three-level buck-boost converter. Each circuit unit includes a first flying capacitor, a second flying capacitor, an input capacitor, a first bridge arm, and a second bridge arm.
[0103] Each bridge arm is divided into two parts by the flying capacitor, forming a first switching circuit (or a third switching circuit) and a second switching circuit (or a fourth switching circuit). The first and third switching circuits can both be first compact connection circuits, and the second and fourth switching circuits can both be second compact connection circuits. Each compact connection circuit includes two switching devices with complementary drive signals and a capacitor. The first terminals of circuit units P1# and P2# are connected in parallel to the first terminals A+ and A- of the flying capacitor three-level buck-boost converter; the second terminals of circuit units P1# and P2# are connected in parallel to the second terminals B+ and B- of the flying capacitor three-level buck-boost converter.
[0104] In an exemplary embodiment, the flying capacitor three-level buck-boost converter may further include a first heat dissipation unit 501 and a second heat dissipation unit 502.
[0105] In an exemplary embodiment, the first heat dissipation unit and the second heat dissipation unit have equal or similar heat dissipation conditions.
[0106] Specifically, the first and fourth switching devices in all first switching circuits (i.e., the first switching circuit in each circuit unit) are mounted on the first heat dissipation unit; the second and third switching devices in all second switching circuits (i.e., the second switching circuit in each circuit unit) are mounted on the second heat dissipation unit; the fifth and eighth switching devices in all third switching circuits (i.e., the third switching circuit in each circuit unit) are mounted on the first heat dissipation unit; and the sixth and seventh switching devices in all fourth switching circuits (i.e., the fourth switching circuit in each circuit unit) are mounted on the second heat dissipation unit.
[0107] In terms of the converter's structural layout, all the switching devices of the N first switching circuits and the third switching circuits in the N circuit units can be placed on the first heat sink or in the first heat dissipation area, and all the switching devices of the N second switching circuits and the fourth switching circuits in the N circuit units can be placed on the second heat sink or in the second heat dissipation area.
[0108] In other words, switching elements in the same compact connection circuit can be installed on the same heat sink or heat dissipation area, while switching elements in different compact connection circuits can be installed on two different heat sinks or heat dissipation areas. This is beneficial for even heat load distribution, maximizing the utilization of heat dissipation resources, reducing thermal stress, improving high-temperature derating capability and fault-tolerant operation capacity, and ultimately reducing costs and improving cost-effectiveness.
[0109] Figure 5 In the circuit unit shown, and Figure 4 The same components and connections in the circuit unit shown can be referenced. Figure 5 The relevant textual explanations will not be repeated here.
[0110] refer to Figure 6 In an exemplary embodiment, the input capacitor C in the first switching loop of each circuit unit d and the first capacitor C 1u Located on the first side of the first heat dissipation unit 501 or on the second side corresponding to the first side; the second capacitor C in the second switching circuit 1d Located on the first side of the second heat dissipation unit 502 or on the second side corresponding to the first side; the output capacitor C in the third switching circuit o and the third capacitor C 2u Located on the first side of the first heat dissipation unit 501 or on the second side corresponding to the first side; the fourth capacitor C in the fourth switching circuit 2d Located on the first side of the second heat dissipation unit 502 or on the second side corresponding to the first side.
[0111] In other words, the input capacitor, first capacitor, output capacitor, and third capacitor of each circuit unit are located on the same side of the first heat dissipation unit, and the second capacitor and fourth capacitor of each circuit unit are located on the same side of the second heat dissipation unit.
[0112] In an exemplary embodiment, the input capacitance C of each circuit unit d and the first capacitor C 1u The second capacitor C is positioned close to its corresponding first switching device Q1 and fourth switching device Q4. 1d The output capacitor C is positioned close to its corresponding second switching device Q2 and third switching device Q3. o and the third capacitor C 2u The fourth capacitor C is positioned close to its corresponding fifth and eighth switching devices Q5 and Q8. 2d It is positioned close to its corresponding sixth switch Q6 and seventh switch Q7.
[0113] In other words, the input capacitor and the first capacitor of each circuit unit can be located on the side close to the first heat dissipation unit of the corresponding first and fourth switching devices, the output capacitor and the third capacitor of each circuit unit can be located on the side close to the first heat dissipation unit of the corresponding fifth and eighth switching devices, the second capacitor of each circuit unit can be located on the side close to the second heat dissipation unit of the corresponding second and third switching devices, and the fourth capacitor of each circuit unit can be located on the side close to the second heat dissipation unit of the corresponding sixth and seventh switching devices.
[0114] In an exemplary embodiment, the distance between the first capacitor and the second capacitor of each flying capacitor is a preset distance, which can be selected according to actual needs.
[0115] In the flying capacitor three-level buck-boost converter provided in this embodiment, when different circuit units are operating in parallel, interleaved, or complementary modes, their complementary drive signals and switching devices are installed in the same heat dissipation area or on the same heat sink. This is beneficial for uniform heat load distribution and maximizing the utilization of heat dissipation resources. It can increase the available heat dissipation capacity of other operating circuit units when some circuit units are not in operation, thereby reducing thermal stress, improving high-temperature derating operation capability and fault redundancy operation load-bearing capability, and helping to reduce costs and improve cost performance.
[0116] Figure 7 This is a schematic diagram of a flying capacitor multilevel converter according to an exemplary embodiment.
[0117] Figure 8 yes Figure 7 The diagram shows the switch element layout of a flying capacitor multilevel converter.
[0118] In this embodiment, the flying capacitor multilevel converter may include N circuit units, where N is a positive integer greater than 1. Each circuit unit may include m flying capacitors, an input capacitor, and a bridge arm, where m is a positive integer greater than or equal to 1. Each bridge arm includes 2×(m+1) switching devices, which are connected in series sequentially. Each flying capacitor includes a first capacitor and a second capacitor, which are connected in parallel. The first flying capacitor is connected in parallel across the two ends of the series branch formed by the second to the 2m+1th switching devices. The input capacitor, the first switching device, the first capacitor of the first flying capacitor, and the 2×(m+1)th switching device constitute a first switching loop. The second capacitor of the first flying capacitor, the first capacitor of the second flying capacitor, the second switching device, and the 2m+1th switching device constitute a first switching loop. The switching devices constitute the second switching circuit; the kth flying capacitor is connected in parallel across the two ends of the series branch formed by the (k+1)th switching device to the (2m+2-k)th switching device, where k is a natural number from 2 to m; the second capacitor of the (k-1)th flying capacitor, the kth switching device, the first capacitor of the kth flying capacitor, and the (2m+3-k)th switching device constitute the kth switching circuit; the second capacitor of the mth flying capacitor, the (m+1)th switching device, and the (m+2)th switching device constitute the (m+1)th switching circuit.
[0119] refer to Figure 7 The following description uses an example where each circuit unit includes 3 (i.e., m=3) flying capacitors, but this disclosure is not limited to this.
[0120] For example, each circuit unit may include three flying capacitors, an input capacitor, and a bridge arm. Each bridge arm includes eight switching devices (Q1 to Q8), which are connected in series. Each flying capacitor includes a first capacitor and a second capacitor, which are connected in parallel.
[0121] The first flying capacitor is connected in parallel across the two ends of the series branch formed by the second switching device Q2 to the seventh switching device Q7, and the input capacitor C d The first switching device Q1, and the first capacitor Q of the first flying capacitor. 1u The first switching circuit is formed by the first and eighth switching devices Q3 and Q8; the second flying capacitor is connected in parallel across the two ends of the series branch formed by the third to sixth switching devices Q6; and the second capacitor Q of the first flying capacitor is... 1d The second switching device Q2, and the first capacitor Q of the second flying capacitor. 2uThe second switching circuit is formed by the 7th switching device Q7; the 3rd flying capacitor is connected in parallel across the two ends of the series branch formed by the 4th switching device Q4 to the 5th switching device Q5; the second capacitor Q of the 2nd flying capacitor... 2d The third switching device Q3, and the first capacitor Q of the third flying capacitor. 3u The third switching circuit is formed by the third and sixth switching devices Q6; the second capacitor Q of the third flying capacitor... 3d The fourth switching device Q4 and the fifth switching device Q5 constitute the fourth switching circuit.
[0122] In an exemplary embodiment, the flying capacitor multilevel converter may further include m+1 heat dissipation units; wherein, the first switching device and the 2×(m+1)th switching device in the first switching circuit are installed in the first heat dissipation unit; the second switching device and the 2m+1th switching device in the second switching circuit are installed in the second heat dissipation unit; the kth switching device and the 2m+3-kth switching device in the kth switching circuit are installed in the kth heat dissipation unit; and the m+1th switching device and the m+2th switching device in the m+1th switching circuit are installed in the m+1th heat dissipation unit.
[0123] Let's take the example of each circuit unit having 3 (i.e., m=3) flying capacitors for illustration.
[0124] refer to Figure 8 For example, the flying capacitor multilevel converter also includes four heat dissipation units (801-804); wherein, the first switching device Q1 and the eighth switching device Q8 in the first switching circuit are disposed on the first heat dissipation unit 801; the second switching device Q2 and the seventh switching device Q7 in the second switching circuit are disposed on the second heat dissipation unit 802; the third switching device Q3 and the sixth switching device Q6 in the third switching circuit are disposed on the third heat dissipation unit 803; and the fourth switching device Q4 and the fifth switching device Q5 in the fourth switching circuit are disposed on the fourth heat dissipation unit 804.
[0125] In an exemplary embodiment, all of the above-mentioned heat dissipation units may have the same or similar heat dissipation conditions.
[0126] In terms of the structural layout of the converter, all the switching devices of the N first switching loops in the N circuit units can be set on the first heat sink or in the first heat dissipation area. All the switching devices of the N second switching loops in the N circuit units can be set on the second heat sink or in the second heat dissipation area. All the switching devices of the N (m+1)th switching loops in the N circuit units can be set on the (m+1)th heat sink or in the (m+1)th heat dissipation area.
[0127] In other words, switching elements in the same compact connection circuit can be placed on the same heat sink or in the same heat dissipation area, while switching elements in different compact connection circuits can be placed on two different heat sinks or in different heat dissipation areas.
[0128] In an exemplary embodiment, the input capacitor in the first switching circuit and the first capacitor of the first flying capacitor are located on the first side of the first heat dissipation unit or on the second side corresponding to the first side; the second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor in the second switching circuit are located on the first side of the second heat dissipation unit or on the second side corresponding to the first side; the second capacitor of the (k-1)th flying capacitor and the first capacitor of the kth flying capacitor in the kth switching circuit are located on the first side of the kth heat dissipation unit or on the second side corresponding to the first side; the second capacitor of the mth flying capacitor in the m+1th switching circuit is located on the first side of the m+1th heat dissipation unit or on the second side corresponding to the first side.
[0129] In other words, the input capacitor of each circuit unit and the first capacitor of the first flying capacitor are located on the same side of the first heat dissipation unit; the second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor of each circuit unit are located on the same side of the second heat dissipation unit; the second capacitor of the (m-1)th flying capacitor and the first capacitor of the mth flying capacitor of each circuit unit are located on the same side of the mth heat dissipation unit; and the second capacitor of the mth flying capacitor of each circuit unit is located on the same side of the (m+1)th heat dissipation unit.
[0130] In an exemplary embodiment, the input capacitor and the first capacitor of the first flying capacitor are positioned close to their corresponding first switching device and second (m+1) switching device; the second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor are positioned close to their corresponding second switching device and 2m+1 switching device; the second capacitor of the (k-1)th flying capacitor and the first capacitor of the kth flying capacitor are positioned close to their corresponding kth switching device and 2m+3-k switching device; and the second capacitor of the mth flying capacitor is positioned close to its corresponding m+1th switching device and m+2th switching device.
[0131] In other words, the input capacitor of each circuit unit and the first capacitor of the first flying capacitor can be located on the side close to the first heat dissipation unit of the corresponding switching device. The second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor of each circuit unit can be located on the side close to the second heat dissipation unit of the corresponding switching device. The second capacitor of the (m-1)th flying capacitor and the first capacitor of the mth flying capacitor of each circuit unit can be located on the side close to the mth heat dissipation unit of the corresponding switching device. The second capacitor of the mth flying capacitor of each circuit unit can be located on the side close to the (m+1)th heat dissipation unit of the corresponding switching device.
[0132] refer to Figure 8 For example, the input capacitance C of each circuit unit d And the first capacitor Q of the first flying capacitor 1u The second capacitor Q of the first flying capacitor in each circuit unit is located on one side of the heat dissipation unit 801 near the first switching device Q1 and the eighth switching device Q8. 1d And the first capacitor Q of the second flying capacitor 2u The second capacitor Q of the second flying capacitor in each circuit unit is located on one side of the heat dissipation unit 802 near the second switching device Q2 and the seventh switching device Q7. 2d And the first capacitor Q of the third flying capacitor 3u The second capacitor Q of the third flying capacitor in each circuit unit is located on one side of the heat dissipation unit 803 near the third switching device Q3 and the sixth switching device Q6. 3d It is located on one side of the heat dissipation unit 804, which is close to the fourth switching device Q4 and the fifth switching device Q5.
[0133] In this embodiment of the disclosure, the capacitance values of the first capacitor and the second capacitor of the flying capacitor may be equal or unequal.
[0134] In an exemplary embodiment, the capacitance values of the first capacitor and the second capacitor of each flying capacitor are not equal.
[0135] In an exemplary embodiment, the distance between the first capacitor and the second capacitor of each flying capacitor is a preset distance, which can be selected according to actual needs.
[0136] In an exemplary embodiment, all bridge arms are connected in parallel, that is, the first ends and the second ends of all circuit units are connected in parallel.
[0137] In the flying capacitor multilevel converter provided in this disclosure, each flying capacitor includes two capacitors connected in parallel. These two capacitors form switching circuits with the two pairs of complementary driving signals connected to the flying capacitor, which is beneficial for absorbing switching voltage spikes. Each pair of complementary driving signals is protected by the switching circuit (including capacitors), resulting in lower voltage stress compared to when all switches in the same bridge arm are set together, making switching operation safer and more reliable. Each pair of complementary driving signals has its own dedicated switching circuit, which simplifies and facilitates the internal circuit layout of the product, and is beneficial for electrical and structural design. In addition, when each circuit unit is operating in parallel, interleaved, or complementary mode, the complementary driving signals of its peers are set in the same heat dissipation area or on the same heat sink, which is beneficial for uniform heat load distribution and maximizing the utilization of heat dissipation resources. This allows for an increase in the available heat dissipation capacity of other operating circuit units when some circuit units are not in operation, thereby reducing thermal stress, improving high-temperature derating capability and fault-redundant operation load capacity, and helping to reduce costs and improve cost-effectiveness.
[0138] Exemplary embodiments of this disclosure have been specifically illustrated and described above. It should be understood that this disclosure is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this disclosure is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.
Claims
1. A flying capacitor three-level converter, characterized in that, The flying capacitor three-level converter includes N circuit units, where N is a positive integer greater than 1. Each circuit unit includes a flying capacitor, an input capacitor, and a bridge arm. The input capacitor is connected in parallel with the bridge arm; The bridge arm includes a first switching device, a second switching device, a third switching device, and a fourth switching device, which are connected in series in sequence. The flying capacitor includes a first capacitor and a second capacitor. The first capacitor is connected in parallel with the second capacitor and is also connected in parallel with the series branch composed of the second switching device and the third switching device. The input capacitor, the first switching device, the first capacitor, and the fourth switching device constitute a first switching circuit; The second capacitor, the second switching device, and the third switching device constitute a second switching circuit; The flying capacitor three-level converter also includes a first heat dissipation unit and a second heat dissipation unit, and all the first switching devices and the fourth switching devices in the first switching circuit are disposed on the first heat dissipation unit. The second and third switching devices in all the second switching circuits are mounted on the second heat dissipation unit.
2. The flying capacitor three-level converter according to claim 1, characterized in that, The first heat dissipation unit and the second heat dissipation unit have the same or similar heat dissipation conditions.
3. The flying capacitor three-level converter according to claim 1, characterized in that, The input capacitor and the first capacitor are located on the first side of the first heat dissipation unit or on the second side corresponding to the first side. The second capacitor is located on the first side of the second heat dissipation unit or on the second side corresponding to the first side.
4. The flying capacitor three-level converter according to claim 1, characterized in that, The input capacitor and the first capacitor are positioned close to their corresponding first and fourth switching devices. The second capacitor is positioned close to the corresponding second and third switching devices.
5. The flying capacitor three-level converter according to claim 1, characterized in that, The capacitance of the first capacitor is not equal to the capacitance of the second capacitor.
6. The flying capacitor three-level converter according to claim 1, characterized in that, The distance between the first capacitor and the second capacitor is a preset distance.
7. The flying capacitor three-level converter according to claim 1, characterized in that, All of the bridge arms are connected in parallel.
8. A flying capacitor three-level buck-boost converter, characterized in that, The flying capacitor three-level buck-boost converter includes N circuit units, where N is a positive integer greater than or equal to 1. Each circuit unit includes a first flying capacitor, a second flying capacitor, an input capacitor, an output capacitor, an inductor, a first bridge arm, and a second bridge arm. The input capacitor is connected in parallel with the first bridge arm; the output capacitor is connected in parallel with the second bridge arm. The first bridge arm includes a first switching device, a second switching device, a third switching device, and a fourth switching device, which are connected in series in sequence. The second bridge arm includes a fifth switch device, a sixth switch device, a seventh switch device, and an eighth switch device, which are connected in series in sequence. The first flying capacitor includes a first capacitor and a second capacitor. The first capacitor is connected in parallel with the second capacitor and is also connected in parallel with the series branch formed by the second switching device and the third switching device of the first bridge arm. The input capacitor, the first switching device, the first capacitor, and the fourth switching device constitute a first switching circuit; The second switching device, the third switching device, and the second capacitor constitute a second switching circuit; The second flying capacitor includes a third capacitor and a fourth capacitor. The third capacitor is connected in parallel with the fourth capacitor and is also connected in parallel with the series branch formed by the sixth and seventh switching devices of the second bridge arm. The output capacitor, the fifth switching device, the third capacitor, and the eighth switching device constitute the third switching circuit; The sixth switching device, the seventh switching device, and the fourth capacitor constitute the fourth switching circuit; The inductor is coupled between the connection point of the second and third switching devices of the first bridge arm and the connection point of the sixth and seventh switching devices of the second bridge arm; The flying capacitor three-level buck-boost converter also includes a first heat dissipation unit and a second heat dissipation unit, and all the first switching devices and the fourth switching devices in the first switching circuit are disposed on the first heat dissipation unit. The second and third switching devices in all the second switching circuits are mounted on the second heat dissipation unit.
9. The flying capacitor three-level buck-boost converter according to claim 8, characterized in that, All the fifth and eighth switching devices in the third switching circuit are mounted on the first heat dissipation unit; The sixth and seventh switching devices in all of the fourth switching circuits are mounted on the second heat dissipation unit.
10. The flying capacitor three-level buck-boost converter according to claim 9, characterized in that, The first heat dissipation unit and the second heat dissipation unit have the same or similar heat dissipation conditions.
11. The flying capacitor three-level buck-boost converter according to claim 9, characterized in that, The input capacitor and the first capacitor in the first switching circuit are located on the first side of the first heat dissipation unit or on the second side corresponding to the first side. The second capacitor in the second switching circuit is located on the first side of the second heat dissipation unit or on the second side corresponding to the first side; The output capacitor and the third capacitor in the third switching circuit are located on the first side of the first heat dissipation unit or on the second side corresponding to the first side; The fourth capacitor in the fourth switching circuit is located on the first side of the second heat dissipation unit or on the second side corresponding to the first side.
12. The flying capacitor three-level buck-boost converter according to claim 9, characterized in that, The input capacitor and the first capacitor are positioned close to their corresponding first and fourth switching devices. The second capacitor is positioned close to its corresponding second and third switching devices; The output capacitor and the third capacitor are positioned close to the corresponding fifth and eighth switching devices; The fourth capacitor is positioned close to the corresponding sixth and seventh switching devices.
13. The flying capacitor three-level buck-boost converter according to claim 8, characterized in that, When N is greater than 1, all the first bridge arms are connected in parallel, and all the second bridge arms are connected in parallel.
14. A flying capacitor multilevel converter, characterized in that, The flying capacitor multilevel converter includes N circuit units, where N is a positive integer greater than 1. Each circuit unit contains m flying capacitors, an input capacitor, and a bridge arm, where m is a positive integer greater than or equal to 1. The bridge arm includes 2×(m+1) switching devices, and the 2×(m+1) switching devices are connected in series in sequence; Each of the flying capacitors includes a first capacitor and a second capacitor, wherein the first capacitor and the second capacitor are connected in parallel. The first flying capacitor is connected in parallel to both ends of the series branch formed by the second to the 2m+1th switching devices. The input capacitor, the first switching device, the first capacitor of the first flying capacitor, and the 2×(m+1)th switching device constitute the first switching circuit. The second capacitor of the first flying capacitor, the second switching device, the first capacitor of the second flying capacitor, and the 2m+1th switching device constitute a second switching circuit; The kth flying capacitor is connected in parallel to both ends of the series branch formed by the (k+1)th switching device to the (2m+2-k)th switching device, where k is a natural number from 2 to m; The second capacitor of the (k-1)th flying capacitor, the kth switching device, the first capacitor of the kth flying capacitor, and the 2m+3-kth switching device constitute the kth switching circuit; The second capacitor of the m-th flying capacitor, the (m+1)-th switching device, and the (m+2)-th switching device constitute the (m+1)-th switching circuit; The flying capacitor multilevel converter further includes m+1 heat dissipation units, wherein the first switching device and the second × (m+1) switching devices in all the first switching circuits are disposed on the first heat dissipation unit; The second and the 2m+1th switching devices in all the second switching circuits are disposed on the second heat dissipation unit.
15. The flying capacitor multilevel converter according to claim 14, characterized in that, The kth switching device and the 2m+3-kth switching device in all the kth switching circuits are disposed on the kth heat dissipation unit; The (m+1)th and (m+2)th switching devices in all the (m+1)th switching circuits are disposed on the (m+1)th heat dissipation unit.
16. The flying capacitor multilevel converter according to claim 15, characterized in that, The m+1 heat dissipation units have the same or similar heat dissipation conditions.
17. The flying capacitor multilevel converter according to claim 15, characterized in that, The input capacitor in the first switching circuit and the first capacitor of the first flying capacitor are located on the first side of the first heat dissipation unit or on the second side corresponding to the first side; The second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor in the second switching circuit are located on the first side of the second heat dissipation unit or on the second side corresponding to the first side; The second capacitor of the (k-1)th flying capacitor in the kth switching circuit and the first capacitor of the kth flying capacitor are located on the first side of the kth heat dissipation unit or on the second side opposite to the first side; The second capacitor of the m-th flying capacitor in the (m+1)-th switching circuit is located on the first side of the (m+1)-th heat dissipation unit or on the second side corresponding to the first side.
18. The flying capacitor multilevel converter according to claim 15, characterized in that, The input capacitor and the first capacitor of the first flying capacitor are positioned close to the corresponding first switching device and the second (m+1) switching device; The second capacitor of the first flying capacitor and the first capacitor of the second flying capacitor are arranged close to the corresponding second switching device and the 2m+1 switching device. The second capacitor of the (k-1)th flying capacitor and the first capacitor of the kth flying capacitor are positioned close to the corresponding kth switching device and the 2m+3-kth switching device. The second capacitor of the m-th flying capacitor is positioned close to the (m+1)-th and (m+2)-th switching devices corresponding to it.
19. The flying capacitor multilevel converter according to claim 14, characterized in that, The capacitance values of the first capacitor and the second capacitor of each of the flying capacitors are not equal.
20. The flying capacitor multilevel converter according to claim 14, characterized in that, All of the bridge arms are connected in parallel.
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