Voltage conversion circuit and converter

Abstract

The invention discloses a voltage conversion circuit and a converter, and relates to the field of circuits, bridge circuit modules and first direct current conversion modules are cascaded in a one-to-one correspondence manner and are coupled together through N first windings of a transformer, and impedance modules connected in series are additionally arranged in the circuit; and the impedance module is arranged between the second end of the first side of the ith bridge circuit module and the second side of the first direct current conversion module which is correspondingly cascaded with the (i + 1) th bridge circuit module, wherein circulating current generated by voltage jump of the second end of the first side of the ith bridge circuit module must pass through the second end of the first side of the ith bridge circuit module, so that circulating current suppression is realized. The impedance module is arranged in the circulation loop, so that the impedance of a circulation path can be effectively increased, the circulation is reduced, the influence of the circulation on the soft switching of the switching device in the first direct current conversion module is avoided, the soft switching of the switching device in the first direct current conversion module is ensured, the switching loss is reduced, and the efficiency of the whole voltage conversion circuit is improved.

Description

Technical Field

[0001] The present invention relates to the field of circuits, and in particular to a voltage conversion circuit and a converter. Background Art

[0002] With the continuous development of power electronics technology and the maturity of device technology, the voltage conversion requirements in circuit applications are becoming more and more complex. In order to meet the voltage conversion requirements of different application scenarios, there is currently a circuit topology that cascades the CHB (cascaded h-bridge) topology with a DC converter, which can achieve a more flexible and complex voltage conversion process. On this basis, the topology after the CHB topology and the DC converter are cascaded as a circuit unit, and the first ends of several circuit units are connected in series to achieve a higher voltage output. The second end of each circuit unit is wound on a magnetic core as the primary side of the transformer. However, in this case, the interlayer capacitance of the transformer will provide a circulation path for the common mode voltage that jumps in the CHB topology between the circuit units. The high-frequency circulating current caused by this will affect the realization of soft switching in the subsequent DC converter, resulting in an increase in switching losses. Summary of the invention

[0003] The object of the present invention is to provide a voltage conversion circuit and converter. By setting an impedance module in the circulating current loop, the impedance of the circulating current path can be effectively increased, thereby reducing the size of the circulating current, avoiding the influence of the circulating current on the soft switching of the switching device in the first DC conversion module, ensuring the soft switching of the switching device in the first DC conversion module, reducing switching losses, and improving the efficiency of the entire voltage conversion circuit.

[0004] In order to solve the above technical problems, the present invention provides a voltage conversion circuit, comprising:

[0005] N bridge circuit modules, wherein the first end of the first side of the first bridge circuit module serves as the first end of the first side of the voltage conversion circuit, the second end of the first side of the i-th bridge circuit module is connected to the first end of the first side of the i+1-th bridge circuit module, the second end of the N-th bridge circuit module serves as the second end of the first side of the voltage conversion circuit, and the bridge circuit module is used to perform voltage conversion using a switching device; N is a positive integer greater than 1, i is a positive integer, and i<N;

[0006] N first DC conversion modules cascaded in one-to-one correspondence with the N bridge circuit modules, wherein the first side of the first DC conversion module is connected to the second side of the corresponding bridge circuit module, and is used to convert the DC voltage using a switching device;

[0007] A transformer, wherein N first windings of the transformer are connected to the second sides of the N first DC conversion modules in a one-to-one correspondence, and the second winding serves as the second side of the voltage conversion circuit;

[0008] An i-th impedance module is connected in series in the circuit between the second end of the first side of the i-th bridge circuit module and the second side of the first DC conversion module cascaded corresponding to the i+1-th bridge circuit module, and the impedance module is used to reduce the circulating current generated by the voltage jump at the second end of the first side of the i-th bridge circuit module to a preset range.

[0009] Optionally, also include:

[0010] The second DC conversion module has a first end connected to the first end of the second winding of the transformer, a second end connected to the second end of the second winding of the transformer, and a third end serving as the second side of the voltage conversion circuit.

[0011] Optionally, the second DC conversion module includes:

[0012] a first switching device;

[0013] A first capacitor, a first end of which is connected to the first end of the first switch device and serves as one end of the second side of the voltage conversion circuit;

[0014] A second switching device, a first end of which is respectively connected to the second end of the first switching device and the first end of the second winding of the transformer, and the first switching device and the second switching device are alternately turned on;

[0015] The second capacitor has a first end connected to the second end of the first capacitor and the second end of the second winding of the transformer respectively, and a second end connected to the second end of the second switch device and serves as the other end of the second side of the voltage conversion circuit.

[0016] Optionally, the bridge circuit module includes:

[0017] a third switching device;

[0018] a fourth switching device;

[0019] A first bus capacitor, a first end of which is respectively connected to the first end of the third switching device and the first end of the fourth switching device;

[0020] a fifth switch device, a first end of which is connected to the second end of the third switch device and serves as the first end of the bridge circuit module, the third switch device and the fifth switch device being alternately turned on;

[0021] A sixth switching device, wherein the first end is connected to the second end of the fourth switching device and serves as the second end of the bridge circuit module; the second end is respectively connected to the second end of the fifth switching device and the second end of the first bus capacitor; the fourth switching device and the sixth switching device are alternately turned on.

[0022] Optionally, the i-th impedance module includes:

[0023] A first impedance inductor, wherein a first end is respectively connected to the second end of the fourth switch device in the i-th bridge circuit module and the first end of the sixth switch device in the i-th bridge circuit module, and a second end is respectively connected to the second end of the third switch device in the i+1-th bridge circuit module and the first end of the fifth switch device in the i+1-th bridge circuit module.

[0024] Optionally, the first DC conversion module includes:

[0025] A seventh switching device;

[0026] A third capacitor, a first end of which is respectively connected to the first end of the seventh switch device and the first end of the first bus capacitor of the corresponding bridge circuit module;

[0027] an eighth switching device, a first end of which is respectively connected to the second end of the seventh switching device and the first end of the corresponding first winding, and the seventh switching device and the eighth switching device are alternately turned on;

[0028] The fourth capacitor has a first end connected to the second end of the third capacitor and the second end of the corresponding first winding, and a second end connected to the second end of the eighth switch device and the second end of the first bus capacitor of the corresponding bridge circuit module.

[0029] Optionally, the i-th impedance module includes:

[0030] a second impedance inductor, a first end of which is respectively connected to the first end of the third switch device in the (i+1)th bridge circuit module, the first end of the fourth switch device in the (i+1)th bridge circuit module, and the first end of the first bus capacitor in the (i+1)th bridge circuit module, and a second end of which is respectively connected to the first end of the seventh switch device in the first DC conversion module corresponding to the (i+1)th bridge circuit module and the first end of the third capacitor in the first DC conversion module corresponding to the (i+1)th bridge circuit module;

[0031] The third impedance inductor has a first end respectively connected to the second end of the fifth switch device in the i+1th bridge circuit module, the second end of the sixth switch device in the i+1th bridge circuit module, and the second end of the first bus capacitor in the i+1th bridge circuit module, and a second end respectively connected to the second end of the eighth switch device in the first DC conversion module corresponding to the i+1th bridge circuit module and the second end of the fourth capacitor in the first DC conversion module corresponding to the i+1th bridge circuit module.

[0032] Optionally, the voltage conversion circuit further includes:

[0033] a first series impedance, wherein a first end is respectively connected to a first end of a third switch device in the first bridge circuit module, a first end of a fourth switch device in the first bridge circuit module, and a first end of a first bus capacitor in the first bridge circuit module, and a second end is respectively connected to a first end of a seventh switch device in a first DC conversion module corresponding to the first bridge circuit module and a first end of a third capacitor in the first DC conversion module corresponding to the first bridge circuit module;

[0034] A second series impedance, wherein the first end is respectively connected to the second end of the fifth switch device in the first bridge circuit module, the second end of the sixth switch device in the first bridge circuit module and the second end of the first bus capacitor in the first bridge circuit module, and the second end is respectively connected to the second end of the eighth switch device in the first DC conversion module corresponding to the first bridge circuit module and the second end of the fourth capacitor in the first DC conversion module corresponding to the first bridge circuit module.

[0035] Optionally, the bridge circuit module includes:

[0036] A ninth switching device;

[0037] A second bus capacitor, a first end of which is connected to the first end of the ninth switch device;

[0038] The tenth switching device has a first end connected to the first end of the tenth switching device and serves as the first end of the bridge circuit module, and a second end connected to the second end of the second bus capacitor and serves as the second end of the bridge circuit module. The ninth switching device and the tenth switching device are alternately turned on.

[0039] To solve the above technical problems, the present invention also provides a converter, comprising a power supply, a load and a voltage conversion circuit as described above, wherein the output end of the power supply is connected to the first side of the voltage conversion circuit, and the second side of the voltage conversion circuit is connected to the load.

[0040] The present invention provides a voltage conversion circuit, including a transformer, N bridge circuit modules and N first DC conversion modules, the bridge circuit modules and the first DC conversion modules are cascaded one by one, coupled together through the N first windings of the transformer, and a series impedance module is added in the circuit, the impedance module is arranged between the second end of the first side of the i-th bridge circuit module and the second side of the first DC conversion module cascaded corresponding to the i+1-th bridge circuit module, through which the circulating current generated by the voltage jump at the second end of the first side of the i-th bridge circuit module must pass, so as to suppress the circulating current. By arranging the impedance module in the circulating current loop, the impedance of the circulating current path can be effectively increased, thereby reducing the size of the circulating current, avoiding the influence of the circulating current on the soft switching of the switching device in the first DC conversion module, ensuring the soft switching of the switching device in the first DC conversion module, reducing the switching loss, and improving the efficiency of the entire voltage conversion circuit.

[0041] The present invention also provides a converter having the same beneficial effects as the above voltage conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A schematic diagram of the structure of a first voltage conversion circuit provided by the present invention;

[0044] Figure 2 A schematic diagram of the structure of a second voltage conversion circuit provided by the present invention;

[0045] Figure 3 A schematic diagram of the structure of a third voltage conversion circuit provided by the present invention;

[0046] Figure 4 A schematic diagram of the structure of a fourth voltage conversion circuit provided by the present invention;

[0047] Figure 5 A schematic diagram of the structure of a fifth voltage conversion circuit provided by the present invention;

[0048] Figure 6 A schematic structural diagram of a voltage conversion circuit provided by the present invention comprising two circuit units;

[0049] Figure 7 A schematic structural diagram of a voltage conversion circuit corresponding to the first impedance module implementation method provided by the present invention;

[0050] Figure 8 A schematic structural diagram of another voltage conversion circuit corresponding to the first impedance module implementation method provided by the present invention;

[0051] Fig. 9 A schematic structural diagram of a voltage conversion circuit corresponding to the second impedance module implementation method provided by the present invention;

[0052] Fig.10 A schematic structural diagram of a voltage conversion circuit corresponding to the third impedance module implementation method provided by the present invention;

[0053] Fig.11 The present invention provides a schematic structural diagram of a voltage conversion circuit when the bridge circuit module is a half-bridge topology. DETAILED DESCRIPTION

[0054] The core of the present invention is to provide a voltage conversion circuit and converter. By setting an impedance module in the circulating current loop, the impedance of the circulating current path can be effectively increased, thereby reducing the size of the circulating current, avoiding the influence of the circulating current on the soft switching of the switching device in the first DC conversion module, ensuring the soft switching of the switching device in the first DC conversion module, reducing switching losses, and improving the efficiency of the entire voltage conversion circuit.

[0055] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of the first voltage conversion circuit provided by the present invention; please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of the second voltage conversion circuit provided by the present invention; please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of the third voltage conversion circuit provided by the present invention; please refer to Figure 4 , Figure 4 This is a schematic diagram of the structure of the fourth voltage conversion circuit provided by the present invention; please refer to Figure 5 , Figure 5 A schematic diagram of the structure of a fifth voltage conversion circuit provided by the present invention; To solve the above technical problem, the present invention provides a voltage conversion circuit, comprising:

[0057] N bridge circuit modules 1, wherein the first end of the first side of the first bridge circuit module 1 serves as the first end of the first side of the voltage conversion circuit, the second end of the first side of the i-th bridge circuit module 1 is connected to the first end of the first side of the i+1-th bridge circuit module 1, the second end of the N-th bridge circuit module 1 serves as the second end of the first side of the voltage conversion circuit, and the bridge circuit module 1 is used to perform voltage conversion using a switching device; N is a positive integer greater than 1, i is a positive integer, and i<N;

[0058] N first DC conversion modules 2 are cascaded in a one-to-one correspondence with the N bridge circuit modules 1, and the first side of the first DC conversion module 2 is connected to the second side of the corresponding bridge circuit module 1, and is used to convert the DC voltage using a switching device;

[0059] Transformer T0, N first windings of the transformer T0 are connected to the second sides of the N first DC conversion modules 2 in a one-to-one correspondence, and the second windings serve as the second side of the voltage conversion circuit;

[0060] An i-th impedance module 3 is connected in series in the circuit between the second end of the first side of the i-th bridge circuit module 1 and the second side of the first DC conversion module 2 cascaded corresponding to the i+1-th bridge circuit module 1. The impedance module 3 is used to reduce the circulating current generated by the voltage jump at the second end of the first side of the i-th bridge circuit module 1 to a preset range.

[0061] It can be understood that the bridge circuit module 1 can use the switching devices that are alternately turned on on the same bridge arm to realize the voltage conversion process such as rectification or DC to DC, and the first DC conversion module 2 can also use the switching devices to realize the DC to DC process. By cascading the bridge circuit module 1 and the first DC conversion module 2 to form a cascade module, the bridge circuit module 1 and the first DC conversion module 2 are controlled to cooperate with each other to realize more diverse voltage conversion processes, and on the basis of a single DC to DC conversion, rectification or voltage regulation and other processes are further realized. At the same time, the input side or output side of the N cascade modules are connected in series in sequence, which can realize a voltage conversion process with a wider voltage range. Therefore, N bridge circuit modules 1 and corresponding N first DC conversion modules 2 and N first windings of the transformer T0 can be set in the voltage conversion circuit. For example, the bridge circuit module 1 can be controlled to convert the first DC voltage output by the DC power supply into a second DC voltage, and then converted into a third DC voltage through the first DC conversion module 2. At the same time, the second side of the first DC conversion module 2 is connected to the first winding of the transformer T0, and the transformer T0 can further realize the voltage conversion process. The voltage conversion topology realized by the cascaded bridge circuit module 1, the first DC conversion module 2 and the transformer T0 can effectively meet the voltage conversion requirements in different application scenarios and realize a wider voltage range and a more flexible voltage conversion process.

[0062] It is not difficult to understand that when this voltage conversion topology is applied, in order to reduce switching losses, a soft switching control method is used to control the conduction of the switching devices in the voltage conversion topology. However, due to the interlayer capacitance of the transformer T0, the common-mode voltage jump generated when the switching device in the i-th bridge circuit module 1 is actuated will flow through the i+1-th bridge circuit module 1 and its corresponding first DC conversion module 2, and then return to the first DC conversion module 2 corresponding to the i-th bridge circuit module 1 and the i-th bridge circuit module 1 through the interlayer capacitance of the transformer T0, forming a circulating current; in particular, when the switching device in the first DC conversion module 2 is in a dead zone, a loop will be formed through the junction capacitance of the switching device, and the current will flow through the junction capacitance of the switching device in the first DC conversion module 2 to form a circulating current. In this case, the circulating current will cause the switching device in the first DC conversion module 2 to be unable to achieve soft switching and can only be started directly, which will lead to an increase in switching losses and affect the working efficiency of the entire circuit.

[0063] In order to solve this problem, the present application adds an impedance module 3 in the circulation path. For the i-th bridge circuit module 1, the circulation generated by the voltage jump will definitely flow to the first winding of the transformer T0 through the i+1-th bridge circuit module 1. Therefore, the i-th impedance module 3 is arranged in series on the circuit between the second end of the first side of the i-th bridge circuit module 1 and the second side of the first DC conversion module cascaded corresponding to the i+1-th bridge circuit module 1, which can effectively increase the impedance in the path through which the circulation current flows and reduce the size of the circulation current, thereby helping the switching device in the first DC conversion module 2 to achieve soft switching, reduce switching losses, and improve the efficiency of the entire voltage conversion circuit.

[0064] It is understandable that the specific number and implementation of the bridge circuit module 1, the first DC conversion module 2 and the first winding of the transformer T0 in the voltage conversion circuit are not specifically limited in this application. There are also multiple implementations of the number of impedance modules 3, which are not specifically limited in this application. For any bridge circuit module 1 among the N bridge circuit modules 1, this circulation will be generated between it and the next bridge circuit module 1, so the i-th impedance module 3 corresponding to the i-th bridge circuit module 1 can be set. For N bridge circuit modules 1, at most N-1 impedance modules 3 can be set. The impedance module 3 can be implemented by inductance and other methods. The specific value and implementation method of the preset range are not specifically limited in this application, which can be a target value or a range interval. In actual application, the degree to which the circulation needs to be reduced can be determined according to the specific soft switching requirements of the switching device in the first DC conversion module 2, and then the specific implementation method of the impedance module 3 is determined.

[0065] It is not difficult to understand that the present application can be directly applied to the architecture of CHB cascade cellular DC / DC topology. For the cellular DC / DC topology architecture in which the primary and secondary windings of the CHB rectifier cascade are coupled on a magnetic core, by improving the CHB topology and adding a series impedance module 3 therein, the high-frequency circulating current between the front-stage CHB and the rear-stage cellular DC / DC is reduced, and the problem of soft switch loss in the two-stage AC / DC scheme of the CHB cascade cellular DC / DC is solved. The impedance module 3 only needs to be set in the series loop where the high-frequency circulating current is located. There are many implementation methods, such as Figures 1 to 5 As shown, five implementation methods of setting the position of the impedance module are given. Figure 1 As shown, the i-th impedance module is arranged in series between the second end of the first side of the i-th bridge circuit module and the first end of the first side of the (i+1)-th bridge circuit module. Figure 2 The figure shows that the i-th impedance module is arranged in series in the internal circuit of the i+1-th bridge circuit module. Figure 3 As shown, the i-th impedance module is arranged in series between the second side of the i+1-th bridge circuit module and the first side of the first cascaded DC conversion module corresponding thereto. Figure 4 The figure shows that the i-th impedance module is arranged in series in the internal circuit of the first DC conversion module corresponding to the cascade connection of the i+1-th bridge circuit module. Figure 5 It is shown that the i-th impedance module is arranged in series on the second side of the first DC conversion module corresponding to the cascade of the i+1-th bridge circuit module, that is, between the second side of the i+1-th first DC conversion module and the transformer. The practical application is not limited to these five implementation methods, and this application does not make any special restrictions here.

[0066] It is understandable that for the bridge circuit module 1, especially the bridge circuit module 1 of the CHB topology, it is necessary to add a filter inductor on the first side of the bridge circuit module 1 to improve the stability of the entire topology during design. At the same time, the inductance of the filter inductor can be set according to the inductor ripple requirements to avoid the influence of the inductor current ripple on the efficiency of the entire circuit and the output voltage quality. On this basis, the impedance module 3 is realized by using an inductor, and the filter inductor and the impedance module 3 can be realized at the same time by breaking up the inductance of the filter inductor, so that the voltage conversion circuit can reduce the circulating current without affecting the normal operation and power density of the original design circuit, and avoid the influence on the working state, efficiency and volume of the original design circuit. When designing the voltage conversion circuit, the original inductance of the filter inductor in the bridge circuit module 1 is first determined according to the inductor ripple requirements, and then the inductance is divided into two parts, one part is determined as the adjusted inductance of the filter inductor, and the other part is determined as the inductance of the inductor as the impedance module 3. The filter inductor can be arranged only at the first end of the first side of the first bridge circuit module 1, or can be arranged at the first end of the first side of the first bridge circuit module 1 and the second end of the first side of the Nth bridge circuit module 1 at the same time. There are multiple implementation methods.

[0067] It should be noted that the first side and the second side of the bridge circuit module 1 are opposite sides. When the first side is the voltage input side of the bridge circuit module 1, the second side is the output side, and when the second side is the voltage input side of the bridge circuit module 1, the first side is the output side. The first DC conversion module 2 is similar, and can realize the conversion process of voltage passing through the bridge circuit module 1, the first DC conversion module 2 and the transformer T0 in sequence, and can also realize the conversion process of voltage passing through the transformer T0, the first DC conversion module 2 and the bridge circuit module 1 in sequence. For example, when the first side of the voltage conversion circuit is used as the input side, the first side of the bridge circuit module 1 is the input side, and the second side is the output side, the first side of the first DC conversion module 2 is the input side, and the second side is the output side, the first winding of the transformer T0 is the primary winding, and the second winding is the secondary winding, and the secondary winding serves as the output side of the voltage conversion circuit. When the second side of the voltage conversion circuit serves as the input side, the first winding of the transformer T0 is the secondary winding, the second winding is the primary winding, the primary winding serves as the input side of the voltage conversion circuit, the second side of the first DC conversion module 2 is the input side, the first side is the output side, the second side of the bridge circuit module 1 is the input side, and the first side is the output side.

[0068] In practical applications, there are many application scenarios for voltage conversion circuits. For example, when the first side of the voltage conversion circuit is used as the input side, the first side can be connected to an AC power supply, and the rectification process of AC to DC can be realized through the bridge circuit module 1, and the first DC conversion module 2 and the transformer T0 can be used to adjust the voltage of the converted DC power; the first side can also be directly connected to a DC power supply, and the DC to DC conversion process can be realized through the bridge circuit module 1, the first DC conversion module 2 and the transformer T0. When the second side of the voltage conversion circuit is used as the input side, the second side can be connected to a DC power supply, and after the DC power passes through the transformer T0 and the first DC conversion module 2, the bridge circuit module 1 can be controlled to realize the inversion process of DC to AC. The application scenario of the voltage conversion circuit and the specific connection objects of the first side and the second side are not particularly limited in this application. Various power supply requirements for different levels of AC and DC can be realized by connecting to the power supply; it can also not be connected to the power supply, and only one voltage is converted to another voltage according to application requirements.

[0069] As a specific embodiment, please refer to Figure 6 , Figure 6 A schematic diagram of a voltage conversion circuit provided by the present invention comprising two circuit units; Figure 6 As shown, when there are two circuit units in the voltage conversion circuit, that is, when the number of circuit units N is 2, the topology is improved. At this time, the bridge circuit module 1 is implemented using the CHB topology, and the first end of the first side of the first bridge circuit module and the second end of the first side of the Nth bridge circuit module are respectively connected to the two ends of the AC power supply Vac, and the first side of the voltage conversion circuit is used as the input side. In this topology, the originally designed input inductor is broken up into three parts (L1, L2, L3), and L1=L2=L3=Leq / 3, Leq is the inductance that satisfies the CHB input inductor current ripple size. At this time, L1 and L3 are input inductors, connected to a1 (the first end of the first side of the first bridge circuit module) and b2 (the second end of the first side of the second bridge circuit module) in the CHB topology, and L2 is the impedance inductor between the first bridge circuit module and the second bridge circuit module as the impedance module 3, connected to b1 (the second end of the first side of the first bridge circuit module) and a2 (the first end of the first side of the second bridge circuit module). By adding impedance inductance between circuit units, a larger impedance is added to the path of the circulating current analyzed above, thereby greatly reducing the size of the circulating current, or even making it negligible. For the CHB topology, whether the inductor is connected to the input side or between units, it is connected in series at the midpoint of the bridge arm, so the working state of the bridge circuit module 1 is not affected.

[0070] The present invention provides a voltage conversion circuit, including a transformer T0, N bridge circuit modules 1 and N first DC conversion modules 2, the bridge circuit modules 1 and the first DC conversion modules 2 are cascaded one by one, coupled together through the N first windings of the transformer T0, and a series impedance module 3 is added in the circuit, the impedance module 3 is arranged between the second end of the first side of the i-th bridge circuit module and the second side of the first DC conversion module cascaded corresponding to the i+1-th bridge circuit module, which is generated by the voltage jump of the second end of the first side of the i-th bridge circuit module, so as to suppress the circulating current. By arranging the impedance module 3 in the circulating current loop, the impedance of the circulating current path can be effectively increased, thereby reducing the size of the circulating current, avoiding the influence of the circulating current on the soft switching of the switching device in the first DC conversion module 2, ensuring the soft switching of the switching device in the first DC conversion module 2, reducing the switching loss, and improving the efficiency of the entire voltage conversion circuit.

[0071] As an optional embodiment, the voltage conversion circuit further includes:

[0072] The second DC conversion module has a first end connected to the first end of the second winding of the transformer T0, a second end connected to the second end of the second winding of the transformer T0, and a third end serving as the second side of the voltage conversion circuit.

[0073] It is not difficult to understand that after the second winding of the transformer T0, a second DC conversion module of the subsequent stage can be further set to further convert the voltage. For example, when the first side of the voltage conversion circuit is used as the input side, the DC voltage output by the second winding of the transformer T0 can be further output after voltage regulation through the second DC conversion module. When the second side of the voltage conversion circuit is used as the input side, the voltage input to the voltage conversion circuit can be preliminarily converted by the second DC conversion module before being output to the transformer T0, the first DC conversion module 2 and the bridge circuit module 1 for multi-stage conversion. The subsequent DC / DC converter can be a cellular LLC, CLLC and other topologies; the specific type and implementation method of the second DC conversion module are not specifically limited in this application. The second winding of the transformer T0 can also be connected to other types of voltage conversion modules such as a rectifier circuit, not limited to the second DC conversion module as an implementation method.

[0074] Specifically, by adding a second DC conversion module to the second winding of the transformer T0, the implementation method of the voltage conversion process in the voltage conversion circuit can be further expanded, and it can also avoid that when the second side of the voltage conversion circuit is used as the input end, the external input voltage is directly connected to the second winding of the transformer T0, thereby improving the flexibility and safety of the entire voltage conversion circuit.

[0075] As an optional embodiment, the second DC conversion module includes:

[0076] A first switching device S1;

[0077] A first capacitor C1, a first end of which is connected to a first end of the first switch device S1 and serves as one end of the second side of the voltage conversion circuit;

[0078] A second switch device S2, a first end of which is respectively connected to the second end of the first switch device S1 and the first end of the second winding of the transformer T0, and the first switch device S1 and the second switch device S2 are alternately turned on;

[0079] The second capacitor C2 has a first end connected to the second end of the first capacitor C1 and the second end of the second winding of the transformer T0 respectively, and a second end connected to the second end of the second switch device S2, and serves as the other end of the second side of the voltage conversion circuit.

[0080] It is understandable that the second DC conversion module can be implemented by using the first switch device S1 and the second switch device S2 that are alternately turned on on the same bridge arm, and the first capacitor C1 and the second capacitor C2 are connected in series to be connected in parallel with the bridge arm of the switch device. The first capacitor C1 and the second capacitor C2 can play a role in current smoothing, reduce the current ripple in the circuit, and also absorb the current impact and voltage spike generated when the switch device is turned on or off. The specific types and implementation methods of the first switch device S1, the second switch device S2, the first capacitor C1 and the second capacitor C2 are not particularly limited in this application. The first switch device S1 and the second switch device S2 can be implemented by using different types of power electronic switch tubes such as MOS tubes (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide Semiconductor Field-Effect Transistor), IGBT (Insulate-Gate Bipolar Transistor, Insulated Gate Bipolar Transistor), and the capacitance of the first capacitor C1 and the second capacitor C2 can be selected and set according to application requirements.

[0081] Specifically, the second DC conversion module can be implemented by a simple first switch device S1 and a second switch device S2 on the same bridge arm, and a first capacitor C1 and a second capacitor C2 are provided to further protect the first switch device S1 and the second switch device S2 and extend the service life; the structure is simple and easy to implement, and the components used are low in cost and small in size, which is conducive to the simple implementation of the entire voltage conversion circuit.

[0082] As an optional embodiment, the bridge circuit module 1 includes:

[0083] A third switching device S3;

[0084] A fourth switching device S4;

[0085] A first bus capacitor C11, a first end of which is respectively connected to a first end of the third switch device S3 and a first end of the fourth switch device S4;

[0086] A fifth switch device S5, a first end of which is connected to the second end of the third switch device S3 and serves as the first end of the bridge circuit module 1, and the third switch device S3 and the fifth switch device S5 are alternately turned on;

[0087] The sixth switch device S6 has a first end connected to the second end of the fourth switch device S4 and serves as the second end of the bridge circuit module 1; a second end is respectively connected to the second end of the fifth switch device S5 and the second end of the first bus capacitor C11; the fourth switch device S4 and the sixth switch device S6 are alternately turned on.

[0088] It is not difficult to understand that the bridge circuit module 1 can be implemented in a full-bridge topology, and specifically a CHB circuit topology can be adopted. The CHB circuit topology specifically includes a third switch device S3, a fourth switch device S4, a fifth switch device S5, a sixth switch device S6 and a first bus capacitor C11. The third switch device S3 and the fifth switch device S5 are on the same bridge arm, and the fourth switch device S4 and the sixth switch device S6 are on the same bridge arm. The voltage conversion process is realized by alternating conduction of the third switch device S3 and the fifth switch device S5 and alternating conduction of the fourth switch device S4 and the sixth switch device S6. At the same time, the first bus capacitor C11 is provided to form an H-bridge structure. The first bus capacitor C11 can have a current smoothing effect, reduce the current ripple in the circuit, and can also absorb the current shock and voltage spike generated when the switch device is turned on or off. The present application does not make any special restrictions on the specific types and implementation methods of the third switch device S3, the fourth switch device S4, the fifth switch device S5, the sixth switch device S6 and the first bus capacitor C11. The third switch device S3, the fourth switch device S4, the fifth switch device S5, and the sixth switch device S6 can be implemented by power electronic switch tubes such as MOS tubes and IGBTs.

[0089] Specifically, the CHB topology can control the voltage to perform rectification, inversion or DC / DC conversion and other voltage conversion processes by using four electronic switches, namely the third switch device S3, the fourth switch device S4, the fifth switch device S5 and the sixth switch device S6. The four switch devices are independently controlled, and different control timings and control methods can be set according to the voltage conversion requirements, which has a wide range of applications.

[0090] Please refer to Figure 7 , Figure 7 A schematic diagram of a voltage conversion circuit corresponding to the first impedance module implementation method provided by the present invention; please refer to Figure 8 , Figure 8A schematic diagram of the structure of another voltage conversion circuit corresponding to the first impedance module implementation mode provided by the present invention; as an optional embodiment, the i-th impedance module 3 includes:

[0091] A first impedance inductor, wherein a first end is respectively connected to the second end of the fourth switch device S4 in the i-th bridge circuit module 1 and the first end of the sixth switch device S6 in the i-th bridge circuit module 1, and a second end is respectively connected to the second end of the third switch device S3 in the i+1-th bridge circuit module 1 and the first end of the fifth switch device S5 in the i+1-th bridge circuit module 1.

[0092] It can be understood that this embodiment provides an implementation method of the impedance module 3. A bridge circuit module 1 will be connected to the first end of the first side of another bridge circuit module 1 through the second end of its first side, so as to realize the series connection between the two bridge circuit modules 1. Therefore, once there is a circulating current caused by a voltage jump in the circuit, the current will definitely flow through the second end of the first side of the bridge circuit module 1 and the first end of the first side of another bridge circuit module 1, and then flow to the transformer T0. Therefore, the i-th impedance module 3 can be arranged between the second end of the first side of the i-th bridge circuit module 1 and the first end of the first side of the i+1-th bridge circuit module 1 to achieve the effect of reducing the circulating current. Specifically, the impedance module 3 can be implemented by inductance, and the specific type and implementation method of the first impedance inductance are not particularly limited in this application.

[0093] As a specific embodiment, Figure 7The figure shows an embodiment of improving the topology when the number of circuit units is N. At this time, the bridge circuit module 1 is implemented using the CHB topology, and the first end of the first side of the first bridge circuit module 1 and the second end of the first side of the Nth bridge circuit module 1 are respectively connected to the two ends of the AC power supply Vac, and the first side of the voltage conversion circuit is used as the input side. In this topology, the inductor is broken up into N+1 parts (L1-L(N+1)), and L1=L2=···L(N+1)=Leq / (N+1), where Leq is the inductance that satisfies the CHB input inductor current ripple size. At this time, L1 and L(N+1) are input inductors, connected to a1 (the first end of the first side of the first bridge circuit module) and bN (the second end of the first side of the Nth bridge circuit module) in the CHB topology, while L2-LN are impedance inductors between circuit units, connected to the corresponding bridge arm midpoints, such as Lk (the i+1th impedance module) connected between the bridge arm midpoint b(k-1) (the second end of the first side of the i-th bridge circuit module) and ak (the first end of the first side of the i+1th bridge circuit module). By adding impedance inductors between circuit units, a larger impedance is added to the path of the circulating current analyzed above, thereby greatly reducing the size of the circulating current and making it negligible. For the CHB topology, whether the inductor is connected to the input side or between units, it is connected in series to the bridge arm midpoint, so the working state of the CHB is not affected. Figure 8 FIG. 1 shows an embodiment of improving the topology when the number of circuit units is N. In this case, the bridge circuit module 1 is implemented using a CHB topology, and the first end of the first side of the first bridge circuit module 1 and the second end of the first side of the Nth bridge circuit module 1 are respectively connected to the two ends of the DC power supply Vdc, and the first side of the voltage conversion circuit is used as the input side. The impedance module 3 is set in the same manner as Figure 7 Be consistent.

[0094] It should be noted that voltage conversion circuits have many application scenarios, such as Figure 7As shown, the first side of the voltage conversion circuit is used as the input side and connected to the AC power source Vac. At this time, it is necessary to set the input inductor for the bridge circuit module 1 and the impedance inductor as the impedance module 3. For the cellular DC / DC architecture in which the primary and secondary windings of the CHB rectifier cascade are coupled on a magnetic core, the originally designed input inductor can be broken up into (N+1) parts, which are respectively placed at the two input ends of the input side of the CHB circuit and between the two adjacent CHB circuits, forming a new AC / DC two-stage architecture. For the cellular DC / DC cascade CHB inverter architecture in which the primary and secondary windings are coupled on a magnetic core, that is, when the first side of the voltage conversion circuit is used as the output side and the second side is used as the input side and connected to the DC power source Vdc, it is necessary to set the output inductor for the bridge circuit module 1 and the impedance inductor as the impedance module 3. The originally designed output inductor can be broken up into (N+1) parts, which are respectively placed between the two adjacent CHB units and the two output ends of the output side of the CHB circuit, forming a new DC / AC two-stage architecture. This embodiment only takes these two cases as examples for explanation, and the impedance module 3 can be similarly configured in other application scenarios.

[0095] Specifically, the impedance module 3 can be implemented by using a first impedance inductor, and its setting position can be specifically between the second end of the first side of the i-th bridge circuit module 1 and the first end of the first side of the i+1-th bridge circuit module 1, and is set between two adjacent bridge circuit modules 1. It can directly and effectively suppress the loop current formed between the two adjacent bridge circuit modules 1, effectively reduce the switching loss of the switching device in the corresponding first DC conversion module 2, and improve the efficiency of the entire circuit.

[0096] As an optional embodiment, the first DC conversion module 2 includes:

[0097] A seventh switching device S7;

[0098] A third capacitor C3, a first end of which is respectively connected to a first end of the seventh switch device S7 and a first end of a first bus capacitor C11 of the corresponding bridge circuit module 1;

[0099] An eighth switch device S8, a first end of which is respectively connected to the second end of the seventh switch device S7 and the first end of the corresponding first winding, and the seventh switch device S7 and the eighth switch device S8 are alternately turned on;

[0100] The fourth capacitor C4 has a first end connected to the second end of the third capacitor C3 and the second end of the corresponding first winding, and a second end connected to the second end of the eighth switch device S8 and the second end of the first bus capacitor C11 of the corresponding bridge circuit module 1.

[0101] It is not difficult to understand that the first DC conversion module 2 can be implemented by using the seventh switch device S7 and the eighth switch device S8 that are alternately turned on on the same bridge arm, and the third capacitor C3 and the fourth capacitor C4 are connected in series to be connected in parallel with the bridge arm of the switch device. The third capacitor C3 and the fourth capacitor C4 can play a role in current smoothing, reduce the current ripple in the circuit, and also absorb the current impact and voltage spike generated when the switch device is turned on or off. The specific types and implementation methods of the seventh switch device S7, the eighth switch device S8, the third capacitor C3 and the fourth capacitor C4 are not particularly limited in this application. The seventh switch device S7 and the eighth switch device S8 can be implemented by using different types of power electronic switch tubes such as MOS tubes and IGBTs. The capacitance values ​​of the third capacitor C3 and the fourth capacitor C4 can be selected and set according to application requirements.

[0102] Specifically, the first DC conversion module 2 can be implemented by simply using the seventh switch device S7 and the eighth switch device S8 on the same bridge arm, and at the same time, a third capacitor C3 and a fourth capacitor C4 are set to further protect the seventh switch device S7 and the eighth switch device S8 to extend their service life; the structure is simple and easy to implement, and the components used are low in cost and small in size, which is conducive to the simple implementation of the entire voltage conversion circuit.

[0103] Please refer to Fig. 9 , Fig. 9 A schematic diagram of a voltage conversion circuit corresponding to the second impedance module implementation method provided by the present invention; please refer to Fig.10 , Fig.10 A schematic diagram of a voltage conversion circuit corresponding to the third impedance module implementation provided by the present invention; as an optional embodiment, the i-th impedance module includes:

[0104] a second impedance inductor, wherein a first end is respectively connected to a first end of a third switch device S3 in an i+1th bridge circuit module, a first end of a fourth switch device S4 in an i+1th bridge circuit module, and a first end of a first bus capacitor C11 in an i+1th bridge circuit module, and a second end is respectively connected to a first end of a seventh switch device S7 in a first DC conversion module 2 corresponding to an i+1th bridge circuit module and a first end of a third capacitor C3 in a first DC conversion module 2 corresponding to an i+1th bridge circuit module;

[0105] The third impedance inductor has a first end respectively connected to the second end of the fifth switch device S5 in the i+1th bridge circuit module, the second end of the sixth switch device S6 in the i+1th bridge circuit module and the second end of the first bus capacitor C11 in the i+1th bridge circuit module, and a second end respectively connected to the second end of the eighth switch device S8 in the first DC conversion module 2 corresponding to the i+1th bridge circuit module and the second end of the fourth capacitor C4 in the first DC conversion module 2 corresponding to the i+1th bridge circuit module.

[0106] It can be understood that when the first DC conversion module 2 is implemented by a bridge topology similar to the bridge circuit module 1, the i-th impedance module 3 can also be implemented by being arranged on the second side of the i+1-th bridge circuit module 1. At this time, there are two connection ends on the second side of the i+1-th bridge circuit module 1, namely, the two ends of the first bus capacitor C11, and the first bus capacitor C11 is connected in parallel with the bridge arm in the i+1-th bridge circuit module 1 and the corresponding bridge arm in the first DC conversion module 2. Therefore, the i-th impedance module 3 can be specifically implemented as follows: Fig. 9 In the manner shown, it is arranged between the first bus capacitor C11 of the i+1th bridge circuit module 1 and the bridge arm in the i+1th bridge circuit module 1. Fig. 9 For example, in the second bridge circuit module, inductors L21 and L31 are set as impedance modules, and in the Nth bridge circuit module, inductors L2N and L3N are set as impedance modules. Fig.10 In the manner shown, it is arranged between the first bus capacitor C11 of the i+1th bridge circuit module 1 and the bridge arm of the first DC conversion module 2 correspondingly connected to the i+1th bridge circuit module 1. Fig.10 For example, in the second bridge circuit module, inductors L21 and L31 are set as impedance modules, and in the Nth bridge circuit module, inductors L2N and L3N are set as impedance modules. This embodiment is described by taking the i-th impedance module 3 being set between the first bus capacitor C11 and the bridge arm in the first DC conversion module corresponding to the i+1-th bridge circuit module as an example, which does not constitute a limitation on the setting method of the impedance module 3.

[0107] It is not difficult to understand that this embodiment provides another implementation of the impedance module 3, and this implementation can also be used simultaneously with an implementation of the impedance module 3 provided in the above embodiment to implement the impedance module 3, or one of the two implementations can be selected to set the impedance module 3. The specific type and implementation of the second impedance inductor and the third impedance inductor are not particularly limited in this application.

[0108] Specifically, the impedance module 3 can be implemented by combining the second impedance inductor and the third impedance inductor, and is set on the necessary loop between the bridge circuit module 1 and the corresponding first DC conversion module 2. It can also directly and effectively suppress the loop current formed between two adjacent bridge circuit modules 1, effectively reduce the switching loss of the switching device in the corresponding first DC conversion module 2, and improve the efficiency of the entire circuit.

[0109] As an optional embodiment, the voltage conversion circuit further includes:

[0110] A first series impedance L11, a first end of which is respectively connected to a first end of a third switch device S3 in the first bridge circuit module 1, a first end of a fourth switch device S4 in the first bridge circuit module 1, and a first end of a first bus capacitor C11 in the first bridge circuit module 1, and a second end of which is respectively connected to a first end of a seventh switch device S7 in a first DC conversion module 2 corresponding to the first bridge circuit module 1 and a first end of a third capacitor C3 in a first DC conversion module 2 corresponding to the first bridge circuit module 1;

[0111] The second series impedance L12 has a first end respectively connected to the second end of the fifth switch device S5 in the first bridge circuit module 1, the second end of the sixth switch device S6 in the first bridge circuit module 1 and the second end of the first bus capacitor C11 in the first bridge circuit module 1, and a second end respectively connected to the second end of the eighth switch device S8 in the first DC conversion module 2 corresponding to the first bridge circuit module 1 and the second end of the fourth capacitor C4 in the first DC conversion module 2 corresponding to the first bridge circuit module 1.

[0112] It is not difficult to understand that, on the basis that the impedance module 3 includes the second impedance inductor and the third impedance inductor, in order to achieve consistency between the cascade modules, a first series impedance L11 similar to the second impedance inductor and a second series impedance L12 similar to the third impedance inductor can also be added to the first bridge circuit module 1. The specific types and implementation methods of the first series impedance L11 and the second series impedance L12 are not particularly limited in this application, and they can also be implemented by inductance. At the same time, the first series impedance L11 and the second series impedance L12 can also further suppress the circulating current between the first bridge circuit module 1 and other bridge circuit modules 1, further reduce switching losses, and improve circuit efficiency. The setting positions of the first series impedance L11 and the second series impedance L12 are similar to those of the second impedance inductor and the third impedance inductor, and are not limited to being set between the first bus capacitor C11 of the first bridge circuit module 1 and the bridge arm in the first bridge circuit module 1 or between the first bus capacitor C11 of the first bridge circuit module 1 and the bridge arm in the first DC conversion module 2 corresponding to the first bridge circuit module 1.

[0113] Specifically, by adding a first series impedance L11 and a second series impedance L12 in the first bridge circuit module 1, the circuit consistency between each cascade module can be maintained, which facilitates the design and application of the entire voltage conversion circuit and is conducive to achieving unified design and unified control.

[0114] Please refer to Fig.11 , Fig.11 The bridge circuit module provided by the present invention is a schematic diagram of a voltage conversion circuit when the bridge circuit module is a half-bridge topology. As an optional embodiment, the bridge circuit module 1 includes:

[0115] A ninth switching device S9;

[0116] A second bus capacitor C12, a first end of which is connected to a first end of a ninth switch device S9;

[0117] The tenth switch device S10 has a first end connected to the first end of the tenth switch device S10 and serves as the first end of the bridge circuit module 1, and a second end connected to the second end of the second bus capacitor C12 and serves as the second end of the bridge circuit module 1. The ninth switch device S9 and the tenth switch device S10 are alternately turned on.

[0118] It is understandable that, in the application process of the voltage conversion circuit, the bridge circuit module 1 can not only be used as an AC / DC converter, but also can work as a DC / DC converter. In this application case, the bridge circuit module 1 can be implemented using a simpler half-bridge topology. Therefore, the bridge circuit module 1 can also specifically include a ninth switch device S9, a tenth switch device S10 and a second bus capacitor C12, and the voltage conversion process is realized by alternately conducting the ninth switch device S9 and the tenth switch device S10. Correspondingly, the setting of the impedance module 3 can also be directly applied when the bridge circuit module 1 is a half-bridge topology, and the same setting method is adopted when the bridge circuit module 1 is implemented with a full-bridge topology, that is, the i-th impedance module can be specifically arranged between the second end of the first side of the i-th bridge circuit module and the first end of the first side of the i+1-th bridge circuit module and / or between the first bus capacitor C11 of the i+1-th bridge circuit module and the bridge arm in the i+1-th bridge circuit module and / or between the first bus capacitor C11 of the i+1-th bridge circuit module and the bridge arm in the first DC conversion module 2 corresponding to the i+1-th bridge circuit module.

[0119] As a specific embodiment, Fig.11As shown, for a DC / DC architecture in which the primary and secondary windings of a cascaded half-bridge are coupled on a magnetic core, when the first side of the voltage conversion circuit is used as the input side, the input inductor can be broken up into (N+1) parts and placed respectively between the two input terminals of the input side of the bridge circuit module 1 and multiple half-bridge topologies.

[0120] Specifically, the bridge circuit module 1 can also be implemented using a half-bridge topology, and the impedance module 3 can be set in the same manner as when the full-bridge topology is implemented to suppress possible circulating currents in the circuit. At the same time, the circuit structure of the half-bridge topology is simple and easy to implement, and the number of components used is smaller, the cost is low, and the size is small, which is conducive to the simple implementation of the entire voltage conversion circuit.

[0121] To solve the above technical problems, the present invention also provides a converter, including a power supply, a load RL and a voltage conversion circuit as described above, wherein the output end of the power supply is connected to the first side of the voltage conversion circuit, and the second side of the voltage conversion circuit is connected to the load RL.

[0122] It is not difficult to understand that the voltage conversion circuit can be specifically applied as a converter, and the different levels of AC and DC power supply requirements of the load RL can be realized by connecting the power supply and the load RL. The specific type of the power supply and the implementation method are not particularly limited in this application. It can be implemented with an AC power supply or a DC power supply. The load RL can be connected according to the actual application requirements, and this application does not make any special restrictions here.

[0123] For an introduction to a converter provided by the present invention, please refer to the above-mentioned embodiment of the voltage conversion circuit, and the present invention will not be described in detail here.

[0124] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. It should also be noted that in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0125] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A voltage conversion circuit, characterized in that: include: N bridge circuit modules, wherein the first end of the first side of the first bridge circuit module serves as the first end of the first side of the voltage conversion circuit, the second end of the first side of the i-th bridge circuit module is connected to the first end of the first side of the i+1-th bridge circuit module, the second end of the N-th bridge circuit module serves as the second end of the first side of the voltage conversion circuit, and the bridge circuit module is used to perform voltage conversion using a switching device; N is a positive integer greater than 1, i is a positive integer, and i<N; N first DC conversion modules cascaded in one-to-one correspondence with the N bridge circuit modules, wherein the first side of the first DC conversion module is connected to the second side of the corresponding bridge circuit module, and is used to convert the DC voltage using a switching device; A transformer, wherein N first windings of the transformer are connected to the second sides of the N first DC conversion modules in a one-to-one correspondence, and the second winding serves as the second side of the voltage conversion circuit; An i-th impedance module is connected in series in the circuit between the second end of the first side of the i-th bridge circuit module and the second side of the first DC conversion module cascaded corresponding to the i+1-th bridge circuit module, and the impedance module is used to reduce the circulating current generated by the voltage jump at the second end of the first side of the i-th bridge circuit module to a preset range.

2. The voltage conversion circuit according to claim 1, characterized in that: Also includes: The second DC conversion module has a first end connected to the first end of the second winding of the transformer, a second end connected to the second end of the second winding of the transformer, and a third end serving as the second side of the voltage conversion circuit.

3. The voltage conversion circuit according to claim 2, characterized in that: The second DC conversion module comprises: a first switching device; A first capacitor, a first end of which is connected to the first end of the first switch device and serves as one end of the second side of the voltage conversion circuit; A second switching device, a first end of which is respectively connected to the second end of the first switching device and the first end of the second winding of the transformer, and the first switching device and the second switching device are alternately turned on; The second capacitor has a first end connected to the second end of the first capacitor and the second end of the second winding of the transformer respectively, and a second end connected to the second end of the second switch device and serves as the other end of the second side of the voltage conversion circuit.

4. The voltage conversion circuit according to any one of claims 1 to 3, characterized in that: The bridge circuit module comprises: a third switching device; a fourth switching device; A first bus capacitor, a first end of which is respectively connected to the first end of the third switching device and the first end of the fourth switching device; a fifth switch device, a first end of which is connected to the second end of the third switch device and serves as the first end of the bridge circuit module, the third switch device and the fifth switch device being alternately turned on; A sixth switching device, wherein the first end is connected to the second end of the fourth switching device and serves as the second end of the bridge circuit module; the second end is respectively connected to the second end of the fifth switching device and the second end of the first bus capacitor; the fourth switching device and the sixth switching device are alternately turned on.

5. The voltage conversion circuit according to claim 4, characterized in that: The i-th impedance module includes: A first impedance inductor, wherein a first end is respectively connected to the second end of the fourth switch device in the i-th bridge circuit module and the first end of the sixth switch device in the i-th bridge circuit module, and a second end is respectively connected to the second end of the third switch device in the i+1-th bridge circuit module and the first end of the fifth switch device in the i+1-th bridge circuit module.

6. The voltage conversion circuit according to claim 4, characterized in that: The first DC conversion module comprises: A seventh switching device; A third capacitor, a first end of which is respectively connected to the first end of the seventh switch device and the first end of the first bus capacitor of the corresponding bridge circuit module; an eighth switching device, a first end of which is respectively connected to the second end of the seventh switching device and the first end of the corresponding first winding, and the seventh switching device and the eighth switching device are alternately turned on; The fourth capacitor has a first end connected to the second end of the third capacitor and the second end of the corresponding first winding, and a second end connected to the second end of the eighth switch device and the second end of the first bus capacitor of the corresponding bridge circuit module.

7. The voltage conversion circuit according to claim 6, characterized in that: The i-th impedance module includes: a second impedance inductor, a first end of which is respectively connected to the first end of the third switch device in the (i+1)th bridge circuit module, the first end of the fourth switch device in the (i+1)th bridge circuit module, and the first end of the first bus capacitor in the (i+1)th bridge circuit module, and a second end of which is respectively connected to the first end of the seventh switch device in the first DC conversion module corresponding to the (i+1)th bridge circuit module and the first end of the third capacitor in the first DC conversion module corresponding to the (i+1)th bridge circuit module; The third impedance inductor has a first end respectively connected to the second end of the fifth switch device in the i+1th bridge circuit module, the second end of the sixth switch device in the i+1th bridge circuit module, and the second end of the first bus capacitor in the i+1th bridge circuit module, and a second end respectively connected to the second end of the eighth switch device in the first DC conversion module corresponding to the i+1th bridge circuit module and the second end of the fourth capacitor in the first DC conversion module corresponding to the i+1th bridge circuit module.

8. The voltage conversion circuit according to claim 7, characterized in that: The voltage conversion circuit further includes: a first series impedance, wherein a first end is respectively connected to a first end of a third switch device in the first bridge circuit module, a first end of a fourth switch device in the first bridge circuit module, and a first end of a first bus capacitor in the first bridge circuit module, and a second end is respectively connected to a first end of a seventh switch device in a first DC conversion module corresponding to the first bridge circuit module and a first end of a third capacitor in the first DC conversion module corresponding to the first bridge circuit module; A second series impedance, wherein the first end is respectively connected to the second end of the fifth switch device in the first bridge circuit module, the second end of the sixth switch device in the first bridge circuit module and the second end of the first bus capacitor in the first bridge circuit module, and the second end is respectively connected to the second end of the eighth switch device in the first DC conversion module corresponding to the first bridge circuit module and the second end of the fourth capacitor in the first DC conversion module corresponding to the first bridge circuit module.

9. The voltage conversion circuit according to any one of claims 1 to 3, characterized in that: The bridge circuit module comprises: A ninth switching device; A second bus capacitor, a first end of which is connected to the first end of the ninth switch device; The tenth switching device has a first end connected to the first end of the tenth switching device and serves as the first end of the bridge circuit module, and a second end connected to the second end of the second bus capacitor and serves as the second end of the bridge circuit module. The ninth switching device and the tenth switching device are alternately turned on.

10. A converter, characterized in that: It comprises a power supply, a load and a voltage conversion circuit as claimed in any one of claims 1 to 9, wherein the output end of the power supply is connected to a first side of the voltage conversion circuit, and the second side of the voltage conversion circuit is connected to the load.

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