A DC-DC conversion device and a charging pile

Abstract

The embodiment of the application provides a DC-DC conversion device and a charging pile, relates to the technical field of energy, and is used for realizing three-phase interphase current sharing and reducing AC loss, so as to improve the working efficiency of the DC-DC conversion device. The device comprises a first three-phase bridge arm, a resonance circuit, a first inductor circuit, a transformer circuit and a second three-phase bridge arm. The bridge arms of the first three-phase bridge arm are used for connecting a direct-current power supply, the bridge arm midpoints of the first three-phase bridge arm are connected with three first ends of the resonance circuit respectively, three second ends of the resonance circuit are connected with three first ends of a primary winding of the transformer circuit respectively, three ends of the first inductor circuit are connected with the three second ends of the resonance circuit, so that the resonance circuit and the first inductor circuit form a three-phase LLC resonance circuit. Three second ends of a secondary winding of the transformer circuit are connected with bridge arm midpoints of the second three-phase bridge arm respectively. The transformer circuit comprises a first transformer and a second transformer.

Description

Technical Field

[0001] This application relates to the field of energy technology, and in particular to a DC-DC converter and a charging pile. Background Technology

[0002] With the development of electronic technology, high efficiency and high power density have become the main development trend of charging equipment. DC-DC converters are widely used in medium- and high-power charging equipment due to their advantages such as soft switching, low ripple current, electrical isolation, and adjustable output voltage, including electric vehicle charging equipment, blade power supplies, server power supplies, and vehicle power supplies. A DC-DC converter mainly consists of an inverter circuit, a resonant circuit, a transformer circuit, and a rectifier circuit.

[0003] In existing technologies, to achieve phase-to-phase current sharing in three-phase DC-DC converters, the primary winding of the transformer circuit is typically designed with a star (Y) or delta (Δ) connection, resulting in a complex topology. Especially when outputting large currents, the secondary windings of the transformer circuit require cross-connections, leading to additional AC losses, increased thermal stress risk, and reduced efficiency of the DC-DC converter.

[0004] Therefore, how to reduce AC losses caused by cross-connections and improve the working efficiency of DC-DC converters while achieving phase-to-phase current sharing in three phases has become an urgent technical problem to be solved. Summary of the Invention

[0005] This application provides a DC-DC converter and a charging pile, which can reduce AC losses caused by cross-connections while achieving phase-to-phase current sharing in three phases, thereby improving the working efficiency of the DC-DC converter.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, a DC-DC converter is provided, comprising a first three-phase bridge arm, a resonant circuit, a first inductor circuit, a transformer circuit, and a second three-phase bridge arm. The two ends of the first three-phase bridge arm are connected to a DC power supply. The midpoint of the first three-phase bridge arm is connected to the three first terminals of the resonant circuit. The three second terminals of the resonant circuit are connected to the three first terminals of the primary winding of the transformer circuit. The three terminals of the first inductor circuit are connected to the three second terminals of the resonant circuit, thereby forming a three-phase inductor-inductor-capacitor LLC resonant circuit. The three second terminals of the secondary winding of the transformer circuit are connected to the midpoint of the second three-phase bridge arm. The transformer circuit includes a first transformer and a second transformer. The primary winding of the first transformer includes a first winding, the primary winding of the second transformer includes a second winding, the secondary winding of the first transformer includes a third winding, and the secondary winding of the second transformer includes a fourth winding. One end of the first winding is connected to one end of the second winding and serves as a first end of the primary winding. The other ends of the first winding and the second winding serve as the other two first ends of the primary winding. One end of the third winding and one end of the fourth winding are connected and serve as a second end of the secondary winding. The other ends of the third winding and the fourth winding serve as the other two second ends of the secondary winding.

[0008] In the above technical solution, the three second terminals of the resonant circuit are connected to the three terminals of the first inductor circuit, so that the resonant circuit and the first inductor circuit form a three-phase LLC resonant circuit. Compared with the prior art of integrating the magnetizing inductor with the three-phase transformer, the embodiment of this application separates the three inductors in the first inductor circuit from the transformer circuit, which can reduce the air gap size of the transformer core and improve the efficiency and stability of the transformer circuit. In addition, the transformer circuit provided in this embodiment includes two transformers. By changing the connection method of the two transformer windings and the connection relationship between the three inductors in the first inductor circuit and the primary winding of the transformer, the multiplexing of the transformer windings is realized. This allows the DC-DC converter to still achieve the purpose of three-phase current sharing even after reducing the number of transformers. Compared with the prior art which requires three transformers to achieve phase-to-phase current sharing, the transformer circuit provided in this embodiment can reduce the phase-to-phase connections of the transformers, thereby reducing the AC loss of the DC-DC converter wiring and improving the working efficiency of the DC-DC converter.

[0009] In conjunction with the first aspect, in one embodiment, the secondary winding of the first transformer further includes a first switching unit and a second switching unit. The secondary winding of the first transformer also includes a fifth winding, and the secondary winding of the second transformer further includes a sixth winding. One end of the third winding is connected to one end of the fifth winding, and one end of the fourth winding is connected to one end of the sixth winding. The first switching unit is used to: selectively connect one end of the third winding to the second three-phase bridge arm, or selectively connect the other end of the fifth winding to the second three-phase bridge arm. The second switching unit is used to: selectively connect one end of the fourth winding to the second three-phase bridge arm, or selectively connect the other end of the sixth winding to the second three-phase bridge arm.

[0010] Based on the above scheme, when the first switching unit selects to connect the third winding to the second three-phase bridge arm, only the third winding of the first transformer's secondary side participates in the transformation process, while the fifth winding is disconnected. When the first switching unit selects to connect the fifth winding to the second three-phase bridge arm, both the third and fifth windings of the first transformer's secondary side participate in the transformation process. Similarly, when the second switching unit selects to connect the fourth winding to the second three-phase bridge arm, only the fourth winding of the second transformer's secondary side participates in the transformation process, while the sixth winding is disconnected. When the second switching unit selects to connect the sixth winding to the second three-phase bridge arm, both the fourth and sixth windings of the second transformer T2's secondary side participate in the transformation process. The more turns the transformer's secondary winding has, the higher the output voltage of the transformer's secondary winding. In this way, by controlling the conduction state of the first and second switching units, the number of turns of the secondary winding of the transformer circuit can be switched. This allows for the connection of more windings when a higher voltage is required on the secondary side of the transformer circuit, and fewer windings when a lower voltage is required. This enables the transformer circuit to output a wide range of voltages, thereby better meeting the charging needs of different electric vehicles when charging them.

[0011] In conjunction with the first aspect, in one embodiment, the DC-DC converter further includes a third three-phase bridge arm, the secondary winding of the transformer circuit further includes three third terminals, the three third terminals are respectively connected to the midpoint of the bridge arm of the third three-phase bridge arm, the secondary winding of the first transformer further includes a fifth winding, the secondary winding of the second transformer further includes a sixth winding, one end of the fifth winding and one end of the sixth winding are connected and serve as one of the three third terminals, and the other end of the fifth winding and the other end of the sixth winding serve as the other two of the three third terminals.

[0012] Based on the above scheme, this DC-DC converter can perform voltage conversion via either the second or third three-phase bridge arm. Therefore, even if any one of the two three-phase bridge arms malfunctions, the DC-DC converter can still complete the voltage conversion via the other normal three-phase bridge arm, thus improving the reliability of the DC-DC converter. Furthermore, by increasing the number of windings on the secondary sides of the first and second transformers, the DC-DC converter can connect to more three-phase bridge arms without increasing the number of transformers. This reduces AC losses caused by wiring and improves the operating efficiency of the DC-DC converter.

[0013] In conjunction with the first aspect, in one embodiment, the primary winding of the first transformer further includes a third switching unit and a fourth switching unit, and the primary winding of the first transformer further includes a seventh winding. The primary winding of the second transformer further includes an eighth winding. One end of the first winding is connected to one end of the seventh winding, and one end of the second winding is connected to one end of the eighth winding. The third switching unit is used to: select and connect one end of the first winding to a second terminal of the resonant circuit, or select and connect the other end of the seventh winding to a second terminal of the resonant circuit. The fourth switching unit is used to: select and connect one end of the second winding to another second terminal of the resonant circuit, or select and connect the other end of the eighth winding to another second terminal of the resonant circuit.

[0014] Based on the above scheme, when the third switching unit selects to connect the first winding to the second terminal of the resonant circuit, only the first winding of the first transformer's primary side participates in the transformation process, while the seventh winding is disconnected. When the third switching unit selects to connect the eighth winding to the second terminal of the resonant circuit, both the first and seventh windings of the first transformer's primary side participate in the transformation process. Similarly, when the fourth switching unit selects to connect the second winding to the second terminal of the resonant circuit, only the second winding of the second transformer's primary side participates in the transformation process, while the eighth winding is disconnected. When the fourth switching unit selects to connect the eighth winding to the second terminal of the resonant circuit, both the second and eighth windings of the second transformer's primary side participate in the transformation process. In practical applications, the more turns the primary winding of the transformer has, the lower the output voltage of the secondary winding. In this way, by controlling the conduction state of the third and fourth switching units, the number of turns of the primary winding of the transformer circuit can be switched. This allows for the connection of fewer windings when a higher voltage is required on the secondary side of the transformer circuit, and more windings when a lower voltage is required on the secondary side. This enables the transformer circuit to achieve a wide range of voltage output, thus better meeting the charging needs of different electric vehicles when charging them.

[0015] In conjunction with the first aspect, in one embodiment, the DC-DC converter further includes a fifth switching unit. The three terminals of the first inductor circuit are connected to the three first terminals and three second terminals of the resonant circuit via the fifth switching unit. When the first three-phase bridge arm is used to convert the received DC power to AC power, and the second three-phase bridge arm is used to convert the AC power output from the first three-phase bridge arm back to DC power, the fifth switching unit is used to: connect the three terminals of the first inductor circuit to the three second terminals of the resonant circuit, and disconnect the connection between the three terminals of the first inductor circuit and the three first terminals of the resonant circuit. When the second three-phase bridge arm is used to convert the received DC power to AC power, and the first three-phase bridge arm is used to convert the AC power output from the second three-phase bridge arm back to DC power, the fifth switching unit is used to: connect the three terminals of the first inductor circuit to the three first terminals of the resonant circuit, and disconnect the connection between the three terminals of the first inductor circuit and the three second terminals of the resonant circuit.

[0016] Based on the above scheme, in this embodiment, the process of the first three-phase bridge arm converting the received DC power to AC power, and the second three-phase bridge arm converting the AC power output from the first three-phase bridge arm to DC power and then outputting it, is called the charging process or the forward transmission process. The process of the second three-phase bridge arm converting the received DC power to AC power, and the first three-phase bridge arm converting the AC power output from the second three-phase bridge arm to DC power and then outputting it, is called the discharging process or the reverse transmission process. During forward transmission, the fifth switching unit connects the three terminals of the first inductor circuit to the three second terminals and disconnects the three terminals of the first inductor circuit from the three first terminals of the resonant circuit. This allows the three inductors in the first inductor circuit to form a three-phase LLC resonant circuit with the resonant circuit during the charging process. Since the voltage gain of the LLC resonant circuit can be less than or equal to 1 or greater than 1, the DC-DC converter can achieve both step-down charging and step-up charging. During reverse transmission, the fifth switching unit connects the three terminals of the first inductor circuit to the three first terminals of the resonant circuit, and disconnects the three terminals of the first inductor circuit from the three second terminals of the resonant circuit. This allows the three inductors in the first inductor circuit to form a three-phase LLC resonant circuit with the resonant circuit during discharge. Therefore, the DC-DC converter can achieve both step-down and step-up discharge. This improves the voltage regulation range of the DC-DC converter during both forward and reverse power transmission.

[0017] In conjunction with the first aspect, in one embodiment, the DC-DC converter further includes a sixth switching unit and a second inductor circuit, with three terminals of the second inductor circuit connected to the three first terminals of the resonant circuit. When the first three-phase bridge arm is used to convert received DC power to AC power, and the second three-phase bridge arm is used to convert the AC power output from the first three-phase bridge arm back to DC power and then output it, the sixth switching unit is used to: disconnect at least two of the three terminals of the second inductor circuit from at least two of the three first terminals of the resonant circuit. When the second three-phase bridge arm is used to convert received DC power to AC power, and the first three-phase bridge arm is used to convert the AC power output from the second three-phase bridge arm back to DC power and then output it, the sixth switching unit is used to: connect the three terminals of the second inductor circuit to the three first terminals of the resonant circuit.

[0018] Based on the above scheme, during forward transmission, the sixth switching unit disconnects at least two of the three terminals of the second inductor circuit from at least two of the three first terminals of the resonant circuit, so that the three inductors in the first inductor circuit form a three-phase LLC resonant circuit with the resonant circuit during charging. Since the voltage gain of the LLC resonant circuit can be less than or equal to 1 or greater than 1, the DC-DC converter can achieve both buck charging and boost charging. During reverse transmission, the sixth switching unit connects the three terminals of the second inductor circuit to the three first terminals of the resonant circuit, so that the three inductors in the second inductor circuit form a three-phase LLC resonant circuit with the resonant circuit during discharging. Therefore, the DC-DC converter can achieve both buck discharging and boost discharging. This improves the voltage regulation range of the DC-DC converter during both forward and reverse power transmission.

[0019] In conjunction with the first aspect, in one embodiment, the DC-DC converter further includes a seventh switching unit, a first inductor, a second inductor, and a third inductor. One end of the first inductor, one end of the second inductor, and one end of the third inductor are respectively connected to the three second terminals of the resonant circuit. The other ends of the first inductor, the second inductor, and the third inductor are connected to the three first terminals of the resonant circuit via the seventh switching unit. When the first three-phase bridge arm is used to convert the received DC power to AC power, and the second three-phase bridge arm is used to convert the AC power output from the first three-phase bridge arm into DC power for output, the seventh switching unit is used to disconnect the connection between the other ends of the first inductor, the second inductor, and the third inductor and the three first terminals of the resonant circuit. When the second three-phase bridge arm is used to convert the received DC power to AC power, and the first three-phase bridge arm is used to convert the AC power output from the second three-phase bridge arm into DC power for output, the seventh switching unit is used to connect the other ends of the first inductor, the second inductor, and the third inductor to the three first terminals of the resonant circuit.

[0020] Based on the above scheme, during forward transmission, the seventh switching unit disconnects the connection between the other ends of the first inductor, the second inductor, and the third inductor and the three first terminals of the resonant circuit. This allows the three inductors in the first inductor circuit to form a three-phase LLC resonant circuit with the resonant circuit during charging. Since the voltage gain of the LLC resonant circuit can be less than or equal to 1 or greater than 1, the DC-DC converter can achieve both buck charging and boost charging. During reverse transmission, the seventh switching unit connects the other ends of the first inductor, the second inductor, and the third inductor to the three first terminals of the resonant circuit. This allows the first, second, and third inductors to form a three-phase LLC resonant circuit with the resonant circuit during discharging. Therefore, the DC-DC converter can achieve both buck discharging and boost discharging. This improves the voltage regulation range of the DC-DC converter during both forward and reverse power transmission.

[0021] In conjunction with the first aspect, in one embodiment, the first inductor circuit includes a fourth inductor, a fifth inductor, and a sixth inductor. One end of the fourth inductor, one end of the fifth inductor, and one end of the sixth inductor are connected together, and the other ends of the fourth inductor, the fifth inductor, and the sixth inductor respectively serve as three terminals of the first inductor circuit; alternatively, the fourth inductor, the fifth inductor, and the sixth inductor are connected end-to-end in sequence, and the connection point between the fourth and fifth inductors, the connection point between the fifth and sixth inductors, and the connection point between the sixth inductor and the fourth inductor respectively serve as three terminals of the first inductor circuit.

[0022] Based on the above scheme, two connection methods for the first inductor circuit are provided. The first connection method can be called a star connection, and the second connection method can be called a delta connection, so that different connection methods can be selected according to different application scenarios. For example, a star connection can be selected in application scenarios that require higher voltage and lower current, while a delta connection can be selected in application scenarios that require higher current and lower voltage.

[0023] In conjunction with the first aspect, in one embodiment, the second inductor circuit includes a seventh inductor, an eighth inductor, and a ninth inductor. One end of the seventh inductor, one end of the eighth inductor, and one end of the ninth inductor are connected together, and the other ends of the seventh inductor, the eighth inductor, and the ninth inductor respectively serve as the three terminals of the second inductor circuit; alternatively, the seventh inductor, the eighth inductor, and the ninth inductor are connected end-to-end in sequence, and the connection points between the seventh and eighth inductors, the eighth and ninth inductors, and the ninth and seventh inductors respectively serve as the three terminals of the second inductor circuit.

[0024] Based on the above scheme, two connection methods for the second inductor circuit are provided to allow for selection of different connection methods according to different application scenarios. For example, a star connection can be selected for applications requiring higher voltage and lower current, while a delta connection can be selected for applications requiring higher current and lower voltage. The second inductor circuit and the first inductor circuit can use the same connection method or different connection methods. For example, both inductor circuits can be star connected, or one inductor circuit can be star connected and the other can be delta connected. In practical applications, different connection methods can be selected according to the different voltage and current requirements of the DC-DC converter during the charging and discharging processes.

[0025] In a second aspect, a charging station is provided, comprising: an AC-DC converter, a DC-DC converter as provided in the first aspect or any embodiment thereof, and a charging gun, wherein one end of the AC-DC converter is connected to an AC power source, and the other end of the AC-DC converter is connected to the charging gun via the DC-DC converter.

[0026] The description of the second aspect in this application can be referred to the detailed description of the first aspect; and the beneficial effects of the second aspect can be referred to the analysis of the beneficial effects of the first aspect, which will not be repeated here. Attached Figure Description

[0027] Figure 1 A schematic diagram illustrating a scenario where a charging pile charges an electric vehicle, as provided in an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the structure of a charging pile provided in an embodiment of this application;

[0029] Figure 3 This is a schematic diagram of the circuit topology of a DC-DC converter;

[0030] Figure 4 This is a schematic diagram of the circuit topology of another DC-DC converter.

[0031] Figure 5 This is a schematic diagram of the structure of the first type of DC-DC converter provided in the embodiments of this application;

[0032] Figure 6 Circuit topology diagram of the first DC-DC converter provided in the embodiments of this application Figure 1 ;

[0033] Figure 7 A circuit topology diagram of a resonant circuit provided in an embodiment of this application;

[0034] Figure 8 A circuit topology diagram of a first inductor circuit provided in an embodiment of this application;

[0035] Figure 9 A schematic diagram of the topology of a first type of transformer circuit provided in an embodiment of this application;

[0036] Figure 10 and Figure 11 These are waveform diagrams of a DC-DC converter provided in an embodiment of this application;

[0037] Figure 12 Circuit topology diagram of the first DC-DC converter provided in the embodiments of this application Figure 2 ;

[0038] Figure 13 Circuit topology diagram of the first DC-DC converter provided in the embodiments of this application Figure 3 ;

[0039] Figure 14 Circuit topology diagram of the first DC-DC converter provided in the embodiments of this application Figure 4 ;

[0040] Figure 15 A schematic diagram of the topology of a second transformer circuit provided in an embodiment of this application;

[0041] Figure 16 This is a schematic diagram of the structure of a second type of DC-DC converter provided in an embodiment of this application;

[0042] Figure 17This is a schematic diagram of the structure of a third type of DC-DC converter provided in the embodiments of this application;

[0043] Figure 18 A schematic diagram of the topology of a third transformer circuit provided in the embodiments of this application;

[0044] Figure 19 A schematic diagram of the topology of the fourth transformer circuit provided in the embodiments of this application;

[0045] Figure 20 This is a schematic diagram of the structure of the fourth DC-DC converter provided in the embodiments of this application;

[0046] Figure 21 This is a topology diagram of a fourth type of DC-DC converter provided in the embodiments of this application;

[0047] Figure 22 A schematic diagram of the structure of the fifth DC-DC converter provided in the embodiments of this application.

[0048] Figure 23 A schematic diagram of the topology of a second inductor circuit provided in an embodiment of this application;

[0049] Figure 24 This is a schematic diagram of the structure of the sixth DC-DC converter provided in the embodiments of this application;

[0050] Figure 25 This is a schematic diagram of the structure of the seventh DC-DC converter provided in the embodiments of this application. Detailed Implementation

[0051] The following sections will discuss the fabrication and use of various embodiments in detail. However, it should be understood that many applicable inventive concepts provided in this application can be implemented in a variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways of implementing and using this application and technology, and do not limit the scope of this application.

[0052] Unless otherwise defined, all technical terms used herein have the same meaning as commonly known to one of ordinary skill in the art.

[0053] Each circuit or other component may be described or referred to as "for" performing one or more tasks. In this context, "for" is used to imply a structure by indicating that the circuit / component includes a structure (e.g., a circuit system) that performs one or more tasks during operation. Therefore, even when the specified circuit / component is currently inoperable (e.g., not turned on), it can still be referred to as "for performing that task." Circuits / components used with the term "for" include hardware, such as circuits that perform operations.

[0054] The embodiments of this application use terms such as "first" and "second" to distinguish objects with similar names, functions, or roles. Those skilled in the art will understand that terms such as "first" and "second" do not limit the quantity or execution order.

[0055] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0056] Before introducing the embodiments of this application, the application scenarios involved in this application will be introduced first.

[0057] Figure 1 An example is given of a scenario where a charging station 10 charges an electric vehicle 20. For example... Figure 1 As shown in (a) and (b), the charging pile is used to receive the AC power output from the power grid 30, convert the AC power into stable DC power and then deliver it to the electric vehicle 20 to charge the electric vehicle 20.

[0058] In some embodiments, such as Figure 1 As shown in (a) above, the charging pile 10 is a split-type charging pile. Exemplarily, the charging pile 10 includes a charging host 11, one or more charging terminals 12, and one or more charging guns 13. The charging host 11 is connected to each charging terminal 12, and each charging terminal 12 is connected to at least one charging gun 13. Each charging gun 13 is used to connect to an electric vehicle 20. In one embodiment, one charging terminal 12 can connect to at least two charging guns 13, and at least two charging guns 13 can connect to one electric vehicle 20; this embodiment does not specifically limit the scope of the application.

[0059] The aforementioned charging terminal 12 may include a cabinet (also known as a shell), a human-machine interface, a charging control unit, and a metering and billing unit, and is used for information interaction, energy transmission, and metering and billing with the electric vehicle 20.

[0060] The aforementioned electric vehicle 20 is a vehicle powered by electricity. Types of electric vehicles 20 include pure electric vehicles (pure EV / battery EV), hybrid electric vehicles (HEV), range-extended electric vehicles (REEV), or plug-in hybrid electric vehicles (PHEV), etc. This application embodiment does not limit the specific type of electric vehicle.

[0061] In other embodiments, such as Figure 1 As shown in (b), the charging pile 10 is an integrated charging pile. For example, the human-machine interface, charging control unit, and metering and billing unit of the charging pile 10 are directly installed in the charging host 11, in conjunction with the aforementioned... Figure 1 Compared to the scenario shown in (a), the charging pile 10 may include a charging host 11 and one or more charging guns 13 connected to the charging host 11, but does not include a charging terminal 12.

[0062] The above Figure 1 The charging host 11 shown in (a) and (b) includes multiple power conversion devices. Figure 1 (Not shown in the image), multiple power conversion devices are used to convert the AC power output from the grid 30 into stable DC power and then deliver it to the charging terminal 12. The multiple power conversion devices may include multiple alternating current-to-direct current (AC-DC) converters and multiple DC-DC converters.

[0063] The following Figure 1 Taking the charging pile 10 shown as an example, the structure of the multiple power conversion devices installed in the charging host 11 will be described in detail.

[0064] In one embodiment, Figure 2 Example Figure 1 The structure of the split-type charging pile is shown in (a) above. Figure 2As shown, in the charging pile 10, the charging host 11 includes multiple AC-DC converters 111, multiple DC-DC converters 112, a DC bus 113, and a power distribution device 114. The input terminal of the AC-DC converter 111 is connected to the power grid 30. The output terminal of the AC-DC converter 111 is connected to the input terminal of the DC-DC converter 112 via the DC bus 113. The output terminal of the DC-DC converter 112 is connected to the charging terminal 12 in the charging pile 10 via the power distribution device 114. The charging terminal 12 is connected to the charging gun 13, which is used to connect to the electric vehicle 20 to charge the electric vehicle 20.

[0065] In specific implementation, the AC-DC converter 111 converts the alternating current output from the power grid 30 into direct current and outputs it to the DC bus 113. The DC-DC converter 112 further converts the DC power obtained from the DC bus 113 into DC power suitable for the electric vehicle 20 and outputs it to the power distribution device 114. The power distribution device 114 dynamically distributes the DC power output from the DC-DC converter 112 according to the actual charging power required by the electric vehicle 20, and transmits the distributed power to the charging gun 13 through the charging terminal 12, so that the power output by the charging gun 13 to the electric vehicle 20 meets the charging needs of the electric vehicle 20.

[0066] The above Figure 2 The example illustrates the case where multiple AC-DC converters 111 and multiple DC-DC converters 112 are integrated separately, meaning that the AC-DC converters 111 and DC-DC converters 112 in the charging pile 10 can be set up independently and integrated into different housings.

[0067] In another embodiment, the charging pile 10 may include multiple AC-DC conversion modules. Each AC-DC conversion module includes interconnected AC-DC conversion devices 111 and DC-DC conversion devices 112. Specifically, AC-DC conversion devices 111 and 112 can be integrated into a single housing as the AC-DC conversion module. This AC-DC conversion module converts the alternating current output from the power grid 30 into direct current, and further converts this direct current into direct current suitable for the electric vehicle 20 before outputting it to the power distribution device 114. The power distribution device 114 dynamically distributes the received direct current according to the actual charging power required by the electric vehicle 20, and delivers the distributed power to the charging gun 13, so that the power output from the charging gun 13 to the electric vehicle 20 meets the charging requirements of the electric vehicle 20.

[0068] The DC-DC converter provided in this application embodiment can be set separately from the AC-DC converter (e.g., Figure 2As shown in the figure, it can also be integrated with an AC-DC conversion device into a module, but this application does not specifically limit this embodiment.

[0069] The following are Figure 3 and Figure 4 Taking the circuit topology shown as an example, the circuit topology structure of the above-mentioned DC-DC converter will be explained in detail.

[0070] Figure 3 An example circuit topology for a DC-DC converter is shown. For example... Figure 3 As shown, the DC-DC converter 200 includes a capacitor Cin, an inverter circuit 210, a resonant circuit 220, a transformer circuit 230, a rectifier circuit 240, and a filter circuit 250 connected in sequence. The inverter circuit 210 includes three-phase bridge arms, with the two ends of each bridge arm connected in parallel with the two ends of the capacitor Cin to receive DC voltage Vbus. The midpoint of each phase bridge arm is connected to the three input terminals of the resonant circuit 220. The three output terminals of the resonant circuit 220 are connected to the primary windings of the three transformers (T1, T2, and T3) in the transformer circuit 230. The secondary windings of the three transformers (T1, T2, and T3) are connected to the midpoints of the bridge arms of the three-phase bridge arms in the rectifier circuit 240. The two ends of the bridge arms of the three-phase bridge arms in the rectifier circuit 240 are connected to the two ends of the filter circuit 250 and are used to output DC power.

[0071] Reference Figure 3 In the inverter circuit 210, each phase arm includes two series-connected switches with the same freewheeling direction. The arm containing the first switch Q1 and the second switch Q2 can be called the first phase arm (i.e., phase A), the arm containing the third switch Q3 and the fourth switch Q4 can be called the second phase arm (i.e., phase B), and the arm containing the fifth switch Q5 and the sixth switch Q6 can be called the third phase arm (i.e., phase C).

[0072] The first switch Q1 and the second switch Q2 mentioned above, as well as each switch in the embodiments of this application, may include a transistor or a transistor and a diode, and the embodiments of this application do not limit this. Specifically, each switch may include a metal-oxide-semiconductor field-effect transistor (MOSFET), which may also be simply referred to as MOS, and each MOS includes a reverse-biased body diode. Alternatively, refer to... Figure 3 ,by Figure 3Taking the first switching transistor Q1 as an example, each switching transistor may include an insulated-gate bipolar transistor (IGBT) and a diode D. The collector of the IGBT is connected to the negative terminal of the diode D, and the emitter of the IGBT is connected to the positive terminal of the diode D. In this embodiment, each switching transistor includes an IGBT and a diode D as an example for illustrative purposes.

[0073] Continue to refer to Figure 3 The resonant circuit 220 is a three-phase resonant circuit (phase A, phase B, and phase C), and the transformer circuit 230 includes a first transformer T1, a second transformer T2, and a third transformer T3. The phase A resonant circuit includes a capacitor Cr1 and an inductor Lr1 connected in series, the phase B resonant circuit includes a capacitor Cr2 and an inductor Lr2 connected in series, and the phase C resonant circuit includes a capacitor Cr3 and an inductor Lr3 connected in series.

[0074] Each transformer (T1, T2, or T3) includes a built-in magnetizing inductor (Lm1, Lm2, or Lm3), and each magnetizing inductor (Lm1, Lm2, or Lm3) is connected in parallel between the same-name and different-name terminals of the primary winding of each transformer (T1, T2, or T3). The same-name terminals of the primary windings of the three transformers (T1, T2, and T3) serve as the three input terminals of transformer circuit 230, and are connected one-to-one with the three output terminals of the three-phase resonant circuit (phase A, phase B, and phase C). The same-name terminals of the secondary windings of the three transformers (T1, T2, and T3) serve as the three output terminals of transformer circuit 230, and are connected to the midpoint of the three-phase diode bridge arm in rectifier circuit 240. Figure 3 The asterisk (*) in the diagram indicates the same-name terminal of the winding.

[0075] In one embodiment, the three-phase resonant circuit (phase A, phase B, and phase C) can form a three-phase LLC resonant circuit with the magnetizing inductor built into the transformer circuit 230, so as to cover a wide range of power transmission needs when the charging pile 10 charges the electric vehicle 20, thereby adapting to the power requirements of more types of electric vehicles 20.

[0076] Continue to refer to Figure 3Each phase arm of the rectifier circuit 240 includes two diodes connected in series with the same freewheeling direction. The arm containing the first diode D1 and the second diode D2 can be called the first phase arm (phase A), the arm containing the third diode D3 and the fourth diode D4 can be called the second phase arm (phase B), and the arm containing the fifth diode D5 and the sixth diode D6 can be called the third phase arm (phase C). The two ends of each of the three phase arms are also connected to the two ends of the filter circuit 250. For example, the filter circuit 250 includes a resistor Ro and a capacitor Co connected in parallel. The resistor Ro and the capacitor Co form a first-order RC filter structure for filtering the DC output from the rectifier circuit 240.

[0077] To achieve phase-to-phase current sharing in the three phases, the primary and secondary windings of the aforementioned transformer circuit 230 are typically designed with a star (Y) connection or a delta (Δ) connection. For example... Figure 3 As shown, the opposite-named terminals of the primary winding of each transformer (T1, T2, or T3) are connected in a "Y" configuration, i.e., a star connection. The secondary winding of each transformer (T1, T2, or T3) is symmetrical to the primary winding, also forming a "Y" configuration. Figure 4 As shown, the opposite-named terminals of the primary windings in each transformer (T1, T2, or T3) are sequentially connected to the same-named terminals of the primary windings of the adjacent transformers, forming a delta-shaped connection. Because the secondary windings of the transformers need to be cross-connected, this not only increases design complexity but also introduces additional AC losses when the output current is large, leading to increased thermal stress risk and reduced efficiency of the DC-DC converter. Figure 1 In the charging scenario shown, the charging host 11 typically includes multiple three-phase LLC topologies connected in series and parallel to support a wide range of voltage outputs. The thermal stress risk and efficiency loss caused by the above connection method are even more obvious.

[0078] In view of this, in order to solve the above-mentioned technical problems, this application provides a DC-DC conversion device and a charging pile including the DC-DC conversion device, which can reduce the AC loss caused by cross-connection and improve the working efficiency of the DC-DC conversion device while realizing the three-phase phase current sharing.

[0079] The DC-DC conversion device provided in the embodiments of this application will be described below with reference to the accompanying drawings. It is understood that the DC-DC conversion device provided in the embodiments of this application can be applied not only to applications such as... Figure 1 and Figure 2The charging pile 10 shown can also be applied to charging equipment such as power modules in charging stations, on-board chargers for electric vehicles, communication rectifiers, blade power supplies, server power supplies, and on-board power supplies for electric vehicles. As an example and not a limitation, this application describes the application of the DC-DC converter to the charging pile 10 as an example.

[0080] like Figure 5 As shown, the DC-DC converter 300 provided in this application embodiment includes a first three-phase bridge arm 310, a resonant circuit 320, a first inductor circuit 330, a transformer circuit 340, and a second three-phase bridge arm 350. Figure 6 The circuit topology of the DC-DC converter 300 provided in the embodiments of this application is illustrated.

[0081] See Figure 5 and Figure 6 The first three-phase bridge arm 310 has its two ends connected to a DC power supply to receive a DC voltage Vbus. In one example, the DC-DC converter 300 also includes a capacitor Cin, which is connected in parallel across the first three-phase bridge arm 310 to filter the DC power received by the first three-phase bridge arm 310. For example, the DC power supply could be as follows: Figure 2 The DC bus 113 is shown. The specific circuit topology of the first three-phase bridge arm 310 is the same as that of the inverter circuit 210 in the DC-DC device 200 described above. For a description of the circuit topology of the first three-phase bridge arm 310, please refer to the relevant description of the circuit topology of the inverter circuit 210 described above. This embodiment will not repeat the description here. As an example and not a limitation, this embodiment uses the circuit topology of the first three-phase bridge arm 310 as an example. Figure 6 The circuit topology shown is used as an example for explanation.

[0082] Continue reading Figure 6 The resonant circuit 320 is a three-phase resonant circuit (phase A, phase B, and phase C), and each phase of the resonant circuit 320 can adopt the same circuit topology. The resonant circuit 320 includes three first terminals and three second terminals. The three first terminals of the resonant circuit 320 are respectively connected to the midpoint of the first three-phase bridge arm 310, and the three second terminals of the resonant circuit 320 are respectively connected to the three first terminals (a1, b1, and c1) of the primary winding of the transformer circuit 340. The three terminals of the first inductor circuit 330 are connected to the three second terminals of the resonant circuit 320, so that the resonant circuit 320 and the first inductor circuit 330 form a three-phase LLC resonant circuit.

[0083] The following combination Figure 7 Taking the circuit topology of the A-phase resonant circuit as an example, the specific circuit topology of the resonant circuit 320 is illustrated.

[0084] In one example, such as Figure 7 As shown in (a), the phase A resonant circuit includes a capacitor Cr1 and an inductor Lr1 connected in series, which can form an LC resonance.

[0085] In another example, such as Figure 7 As shown in (b) above, with Figure 7 Compared to (a) in the above, the A-phase resonant circuit also includes a capacitor Cr11 connected in parallel across the capacitor Cr1 and the inductor Lr1. The capacitor Cr1, the inductor Lr1 and the capacitor Cr11 can form an LCC resonance.

[0086] In yet another example, such as Figure 7 As shown in (c) in the figure, with Figure 7 Compared to (a) in the above, the A-phase resonant circuit also includes an inductor Lr11 connected in parallel across the capacitor Cr1 and the inductor Lr1. The capacitor Cr1, the inductor Lr1 and the inductor Lr11 can form an LLC resonant circuit.

[0087] As an example and not a limitation, the embodiments of this application are illustrated by taking a case in which each phase resonant circuit includes a capacitor and an inductor connected in series (capacitor Cr1 and inductor Lr1, capacitor Cr2 and inductor Lr2, capacitor Cr3 and inductor Lr3).

[0088] In one embodiment, the first inductor circuit 330 includes three magnetizing inductors (Lm1, Lm2, and Lm3), namely, a fourth inductor Lm1, a fifth inductor Lm2, and a sixth inductor Lm3. These three inductors can be connected in a star configuration or a delta configuration. For example, a star configuration can be chosen for applications requiring higher voltage and lower current, while a delta configuration can be chosen for applications requiring higher current and lower voltage.

[0089] like Figure 8 As shown in (a), one end of the fourth inductor Lm1, one end of the fifth inductor Lm2, and one end of the sixth inductor Lm3 are connected, and the other ends of the fourth inductor Lm1, the fifth inductor Lm2, and the sixth inductor Lm3 respectively serve as the three terminals of the first inductor circuit 330. Furthermore, each phase resonant circuit in the resonant circuit 320 can form LLC resonance with a corresponding magnetizing inductor.

[0090] like Figure 8As shown in (b), the fourth inductor Lm1, the fifth inductor Lm2, and the sixth inductor Lm3 are connected end-to-end in sequence. The connection points of the fourth inductor Lm1 and the fifth inductor Lm2, the fifth inductor Lm2 and the sixth inductor Lm3, and the sixth inductor Lm3 and the fourth inductor Lm1 respectively serve as the three terminals of the first inductor circuit 330. Furthermore, each phase resonant circuit in the resonant circuit 320 can form LLC resonance with a corresponding magnetizing inductor.

[0091] Continue reading Figure 6 In one embodiment, the transformer circuit 340 includes a first transformer T1 and a second transformer T2. The primary winding of the first transformer T1 includes a first winding n1, the primary winding of the second transformer T2 includes a second winding n2, the secondary winding of the first transformer T1 includes a third winding n3, and the secondary winding of the second transformer T2 includes a fourth winding n4. One end of the first winding n1 is connected to one end of the second winding n2 and serves as a first end (e.g., c1) of the primary winding of the transformer circuit 340. The other end of the first winding n1 and the other end of the second winding n2 serve as two other first ends (e.g., a1 and b1) of the primary winding. One end of the third winding n3 and one end of the fourth winding n4 are connected and serve as a second end (e.g., c2) of the secondary winding. The other end of the third winding n3 and the other end of the fourth winding n4 serve as two other second ends (e.g., a2 and b2) of the secondary winding.

[0092] For example, any one of the first winding n1, the second winding n2, the third winding n3, and the fourth winding n4 includes a same-name end and a different-name end. Taking the connection of the first winding n1 and the second winding n2 as an example, the connection between one end of the first winding n1 and one end of the second winding n2 can be either the different-name end of the first winding n1 and the different-name end of the second winding n2, or the different-name end of the first winding n1 and the same-name end of the second winding n2. Figure 9 The circuit topology of transformer circuit 340 is shown in the example.

[0093] In one embodiment, such as Figure 9As shown in (a), the same-name terminal of the first winding n1 is a first terminal (a1) of the primary winding of transformer circuit 340, and the same-name terminal of the second winding n2 is a second first terminal (b1) of the primary winding of transformer circuit 340. The opposite-name terminal of the first winding n1, after being connected to the opposite-name terminal of the second winding n2, serves as the third first terminal (c1) of the primary winding of transformer circuit 340. The same-name terminal of the third winding n3 is a second terminal (a2) of the secondary winding of transformer circuit 340, and the same-name terminal of the fourth winding n4 is a second second terminal (b2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the third winding n3, after being connected to the opposite-name terminal of the fourth winding n4, serves as the third second terminal (c2) of the secondary winding of transformer circuit 340. For ease of description, it can be... Figure 9 The connection method shown in (a) is called a half-star connection.

[0094] In another embodiment, such as Figure 9 As shown in (b), the same-name terminal of the first winding n1 is a first terminal (a1) of the primary winding of transformer circuit 340. The opposite-name terminal of the first winding n1, after being connected to the same-name terminal of the second winding n2, serves as the second first terminal (b1) of the primary winding of transformer circuit 340. The opposite-name terminal of the second winding n2 serves as the third first terminal (c1) of the primary winding of transformer circuit 340. The same-name terminal of the third winding n3 is a second terminal (a2) of the secondary winding of transformer circuit 340. The same-name terminal of the third winding n3, after being connected to the opposite-name terminal of the fourth winding n4, serves as the second second terminal (b2) of the secondary winding of transformer circuit 340. The same-name terminal of the fourth winding n4 serves as the third second terminal (c2) of the secondary winding of transformer circuit 340. For ease of description, it can be... Figure 9 The connection method shown in (b) is called the half-triangle connection.

[0095] Continue reading Figure 6 The three second terminals (a2, b2, and c2) of the secondary winding of transformer circuit 340 are respectively connected to the midpoint of the arm of the second three-phase bridge 350. The two ends of the arm of the second three-phase bridge 350 are used to connect a load. For example, the load could be as follows: Figure 2 The electric vehicle 20 shown. Each phase arm of the second three-phase bridge arm 350 includes two switches connected in series with the same freewheeling direction. Among them, the bridge arm containing the seventh switch Q7 and the eighth switch Q8 can be called the first phase bridge arm (i.e., phase A), the bridge arm containing the ninth switch Q9 and the tenth switch Q10 can be called the second phase bridge arm (i.e., phase B), and the bridge arm containing the eleventh switch Q11 and the twelfth switch Q12 can be called the third phase bridge arm (i.e., phase C).

[0096] In one implementation, when the second three-phase bridge arm 350 adopts as shown in the figure... Figure 6In the circuit topology shown, the DC-DC converter 300 can be a bidirectional DC-DC converter 300. When electrical energy is supplied from the first three-phase bridge arm 310 to the second three-phase bridge arm 350, the first three-phase bridge arm 310 can function as an inverter circuit, and the second three-phase bridge arm 350 can function as a rectifier circuit. That is, the first three-phase bridge arm 310 is used to convert the DC power supplied by the DC power source into AC power, and the second three-phase bridge arm 350 is used to convert the AC power into a suitable DC power and output it to the load. When electrical energy is supplied from the second three-phase bridge arm 350 to the first three-phase bridge arm 310, the second three-phase bridge arm 350 can function as an inverter circuit, and the first three-phase bridge arm 310 can function as a rectifier circuit. That is, the second three-phase bridge arm 350 is used to convert the DC power output from the load into AC power, and the first three-phase bridge arm 310 is used to convert the AC power into a suitable DC power and output it to the DC power source.

[0097] like Figure 5 and Figure 6 As shown, the DC-DC converter 300 also includes a first filter circuit 360. The two ends of the second three-phase bridge arm 350 are also connected to the load through the first filter circuit 360. For example, the first filter circuit 360 and... Figure 3 and Figure 4 The circuit topology of the intermediate filter circuit 250 is the same. For a description of the circuit topology of the first filter circuit 360, please refer to the relevant description of the circuit topology of the filter circuit 250 above; it will not be repeated here. The inductors (Lr1, Lr2, and Lr3), magnetizing inductors (Lm1, Lm2, and Lm3), and the first transformer T1 and the second transformer T2 in the resonant circuit 320 can be discrete devices or magnetically integrated devices; this application does not specifically limit this.

[0098] Figure 10 and Figure 11 They are respectively Figure 6 The diagram shows the waveforms of the DC-DC converter 300. The horizontal axis represents time, and the vertical axis represents current. For example, the simulation conditions for the DC-DC converter 300 can be set as follows: the input DC voltage Vbus is 830V, the inductance values ​​of the inductors (Lr1, Lr2, and Lr3) are all 7uH (microhenries), the capacitance values ​​of the capacitors (Cr1, Cr2, and Cr3) are all 300nF (nanofa), the inductance values ​​of the magnetizing inductors (Lm1, Lm2, and Lm3) are all 60uH, the resistance value of the resistor Ro in the first filter circuit 360 is 12.5 ohms, and the operating frequency of the switching transistor is 109kHz (kilohertz).

[0099] Figure 10 The diagram shows the current waveforms passing through inductors Lr1, Lr2, and Lr3 in the resonant circuit 320. Figure 11 The diagram shows the current waveforms passing through the seventh switch Q7, the ninth switch Q9, and the eleventh switch Q11 in the second three-phase bridge arm 350, respectively. Figure 10 and Figure 11 As can be seen, on the primary side of the transformer circuit 340, the three-phase currents achieve three-phase interleaving and phase-to-phase current sharing; on the secondary side of the transformer circuit 340, the three-phase currents also achieve three-phase interleaving and phase-to-phase current sharing. Therefore, the DC-DC converter 300 provided in this embodiment can achieve the purpose of phase-to-phase current sharing.

[0100] In the DC-DC converter 300 provided in this application embodiment, the three second terminals of the resonant circuit 320 are connected to the three terminals of the first inductor circuit 330, so that the resonant circuit 320 and the first inductor circuit 330 form a three-phase LLC resonant circuit. Compared with the prior art that integrates the magnetizing inductor with the three-phase transformer, in this application embodiment, the three inductors in the first inductor circuit 330 are separated from the transformer circuit 340, which can reduce the air gap size of the magnetic core of the transformer circuit 340 and improve the efficiency and stability of the transformer circuit 340. Furthermore, the transformer circuit 340 provided in this application embodiment includes two transformers. By changing the connection method of the two transformer windings and the connection relationship between the three inductors in the first inductor circuit 330 and the primary winding of the transformer, the multiplexing of the transformer windings is realized. This allows the DC-DC converter 300 to still achieve the purpose of three-phase current sharing even after the number of transformers is reduced. Compared with the prior art which requires three transformers to achieve phase-to-phase current sharing, the transformer circuit 340 provided in this application embodiment can reduce the phase-to-phase connections of the transformers, thereby reducing the AC wiring losses of the DC-DC converter 300 and improving the working efficiency of the DC-DC converter 300.

[0101] Figure 12 , Figure 13 as well as Figure 14 Three circuit topologies for the DC-DC converter 300 are illustrated respectively. Figure 6 compared to, Figure 12 The first inductor circuit 330 is connected in a delta configuration, and the transformer circuit 340 is connected in a semi-star configuration. Figure 13 The first inductor circuit 330 is connected in a delta configuration, and the transformer circuit 340 is connected in a half-delta configuration. Figure 14 The first inductor circuit 330 is connected in a star configuration, and the transformer circuit 340 is connected in a half-delta configuration. The topology of the remaining circuits is similar to... Figure 6 The same applies here, so I will not repeat it again.

[0102] In one embodiment, this application also provides another circuit topology for the transformer circuit 340. For example... Figure 15As shown, the secondary winding of the first transformer T1 also includes a first switching unit K1 and a second switching unit K2. The secondary winding of the first transformer T1 also includes a fifth winding n5, and the secondary winding of the second transformer T2 also includes a sixth winding n6. One end of the third winding n3 is connected to one end of the fifth winding n5, and one end of the fourth winding n4 is connected to one end of the sixth winding n6. The first switching unit K1 is used to: select and connect one end of the third winding n3 to the second three-phase bridge arm 350, or select and connect the other end of the fifth winding n5 to the second three-phase bridge arm 350. The second switching unit K2 is used to: select and connect one end of the fourth winding n4 to the second three-phase bridge arm 350, or select and connect the other end of the sixth winding n6 to the second three-phase bridge arm 350.

[0103] like Figure 15 As shown in (a), the connection method of the primary windings of the first transformer T1 and the second transformer T2 is the same as... Figure 9 The primary windings shown in (a) are connected in the same way, both being semi-star connections, such as... Figure 15 As shown in (b) above, the connection method of the primary windings of the first transformer T1 and the second transformer T2 is the same as... Figure 9 The connection method of the primary winding shown in (b) is the same, which is a half-delta connection. For a detailed description of the primary winding of transformer circuit 340, please refer to the previous text, which will not be repeated here.

[0104] The following combination Figure 15 The connection method of the secondary windings of the first transformer T1 and the second transformer T2 is described. The secondary windings of the first transformer T1 and the second transformer T2 together include four windings. As an example and not a limitation, this embodiment of the application uses the first switching unit K1 and the second switching unit K2 as examples of single-pole double-throw switches. Both the first switching unit K1 and the second switching unit K2 have one fixed terminal and two selection terminals.

[0105] In one example, such as Figure 15As shown in (a), the same-name terminal of the third winding n3 is a second terminal (a2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the third winding n3, the same-name terminal of the fifth winding n5, and a selection terminal of the first switching unit K1 are connected. The opposite-name terminal of the fifth winding n5 is connected to the other selection terminal of the first switching unit K1. The same-name terminal of the fourth winding n4 is a second second terminal (b2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the fourth winding n4, the same-name terminal of the sixth winding n6, and a selection terminal of the second switching unit K2 are connected. The opposite-name terminal of the sixth winding n6 is connected to the other selection terminal of the second switching unit K2. The fixed terminal of the first switching unit K1 is connected to the fixed terminal of the second switching unit K2, serving as the third second terminal (c2) of the secondary winding of transformer circuit 340.

[0106] In another example, such as Figure 15 As shown in (b), the same-name terminal of the third winding n3 is a second terminal (a2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the third winding n3, the same-name terminal of the fifth winding n5, and a selection terminal of the first switching unit K1 are connected. The opposite-name terminal of the fifth winding n5 is connected to another selection terminal of the first switching unit K1. The same-name terminal of the fourth winding n4 is connected to the fixed terminal of the first switching unit K1, serving as the second second terminal (b2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the fourth winding n4, the same-name terminal of the sixth winding n6, and a selection terminal of the second switching unit K2 are connected. The opposite-name terminal of the sixth winding n6 is connected to another selection terminal of the second switching unit K2. The fixed terminal of the second switching unit K2 serves as the third second terminal (c2) of the secondary winding of transformer circuit 340.

[0107] As described above, when the first switching unit K1 selects to connect the third winding n3 to the second three-phase bridge arm 350, only the third winding n3 of the secondary side of the first transformer T1 participates in the transformation process, while the fifth winding n5 is disconnected. When the first switching unit K1 selects to connect the fifth winding n5 to the second three-phase bridge arm 350, both the third winding n3 and the fifth winding n5 of the secondary side of the first transformer T1 participate in the transformation process. Similarly, when the second switching unit K2 selects to connect the fourth winding n4 to the second three-phase bridge arm 350, only the fourth winding n4 of the secondary side of the second transformer T2 participates in the transformation process, while the sixth winding n6 is disconnected. When the second switching unit K2K1 selects to connect the sixth winding n6 to the second three-phase bridge arm 350, both the fourth winding n4 and the sixth winding n6 of the secondary side of the second transformer T2 participate in the transformation process. In practical applications, the more turns the secondary winding of a transformer has, the higher the output voltage of the secondary winding. In this way, by controlling the conduction state of the first switching unit K1 and the second switching unit K2, the number of turns of the secondary winding of the transformer circuit 340 can be switched. This allows more windings to be connected when a higher voltage is required on the secondary side of the transformer circuit 340, and fewer windings to be connected when a lower voltage is required on the secondary side of the transformer circuit 340. This enables the transformer circuit 340 to output a wide range of voltages, thereby better meeting the charging needs of different electric vehicles 20 when charging them.

[0108] It is understood that the first switching unit K1 may also include two single-pole single-throw (SPS) switches. When one of these SPS switches is closed, the other SPS switch is open, thereby switching the number of turns in the secondary winding of the first transformer T1. Similarly, the second switching unit K2 may also include two SPS switches. When one of these SPS switches is closed, the other SPS switch is open, thereby switching the number of turns in the secondary winding of the second transformer T2. Alternatively, the first switching unit K1 and the second switching unit K2 may also be relays, semiconductor switching devices, or other switching devices capable of switching the secondary winding of the transformer circuit 340.

[0109] In one implementation, such as Figure 16 As shown, the DC-DC converter 300 also includes a third three-phase bridge arm 351, and the secondary winding of the transformer circuit 340 also includes three third terminals (a3, b3 and c3), which are respectively connected to the midpoint of the bridge arm of the third three-phase bridge arm 351.

[0110] The structure of the third three-phase bridge arm 351 is the same as that of the second three-phase bridge arm 350, or the same as that of the rectifier circuit 240. That is, the third three-phase bridge arm 351 can be a three-phase switching transistor bridge arm or a three-phase diode bridge arm. This application embodiment does not specifically limit this. For the specific structure of the third three-phase bridge arm 351, please refer to the previous description of the rectifier circuit 240 or the description of the second three-phase bridge arm 350, which will not be repeated here.

[0111] Furthermore, such as Figure 16 As shown, the DC-DC converter 300 also includes a second filter circuit 361, which is connected between the third three-phase bridge arm 351 and the load. The structure of the second filter circuit 361 is the same as that of the first filter circuit 360 described above, and will not be repeated here.

[0112] Based on this, the DC-DC converter 300 can perform voltage conversion not only through the second three-phase bridge arm 350, but also through the third three-phase bridge arm 351. If any three-phase bridge arm 351 in the second or third three-phase bridge arm 350 malfunctions, the DC-DC converter 300 can complete the voltage conversion through the other normal three-phase bridge arm, thereby improving the reliability of the DC-DC converter 300.

[0113] In another implementation, such as Figure 17 As shown, the DC-DC converter 300 also includes a series switch K5, a parallel switch K6, and a parallel switch K7. The series switch K5, parallel switch K6, and parallel switch K7 are connected between the two DC connection terminals of the second three-phase bridge arm 350 and the two DC connection terminals of the third three-phase bridge arm 351, and are used to adjust the connection relationship between the second three-phase bridge arm 350 and the third three-phase bridge arm 351, thereby adjusting the voltage conversion range of the second three-phase bridge arm 350 and the third three-phase bridge arm 351.

[0114] The two DC connection terminals of the second three-phase bridge arm 350 are the two ends of the bridge arm 350, and the two DC connection terminals of the third three-phase bridge arm 351 are the two ends of the bridge arm 351. Specifically, series switch K5 is connected between the negative DC connection terminal of the second three-phase bridge arm 350 and the positive DC connection terminal of the third three-phase bridge arm 351; parallel switch K6 is connected between the positive DC connection terminal of the second three-phase bridge arm 350 and the positive DC connection terminal of the third three-phase bridge arm 351; and parallel switch K7 is connected between the negative DC connection terminal of the second three-phase bridge arm 350 and the negative DC connection terminal of the third three-phase bridge arm 351.

[0115] Thus, when electrical energy is transferred from the first three-phase bridge arm 310 to the second three-phase bridge arm 350, by closing the series switch K5 and opening the parallel switches K6 and K7, the second three-phase bridge arm 350 and the third three-phase bridge arm 351 can be connected in series; or, by closing the parallel switches K6 and K7 and opening the series switch K5, the second three-phase bridge arm 350 and the third three-phase bridge arm 351 can be connected in parallel. Through the connection relationship between the second three-phase bridge arm 350 and the third three-phase bridge arm 351, the voltage conversion range of the second three-phase bridge arm 350 and the third three-phase bridge arm 351 can be adjusted, enabling the DC-DC converter 300 to achieve a wide range of voltage output, thereby better meeting the charging needs of different electric vehicles 20 when charging them.

[0116] The structure of the DC-DC converter 300, including the third three-phase bridge arm 351, has been described above. The following, in conjunction with... Figure 18 and Figure 19 The circuit topology of transformer circuit 340 under this condition will be described in detail.

[0117] In one implementation, such as Figure 18 As shown, the secondary winding of the first transformer T1 also includes a fifth winding n5, and the secondary winding of the second transformer T2 also includes a sixth winding n6. One end of the fifth winding n5 and one end of the sixth winding n6 are connected and serve as one of the three third terminals of the transformer circuit 340. The other end of the fifth winding n5 and the other end of the sixth winding n6 serve as the other two third terminals among the three third terminals.

[0118] like Figure 18 As shown in (a), the connection method of the primary windings of the first transformer T1 and the second transformer T2 is the same as... Figure 9 The primary windings shown in (a) are connected in the same way, both being semi-star connections, such as... Figure 18 As shown in (b) above, the connection method of the primary windings of the first transformer T1 and the second transformer T2 is the same as... Figure 9 The connection method of the primary winding shown in (b) is the same, which is a half-delta connection. For a detailed description of the primary winding of transformer circuit 340, please refer to the previous text, which will not be repeated here.

[0119] In the first example, such as Figure 18As shown in (a), the same-name terminal of the third winding n3 is a second terminal (a2) of the secondary winding of transformer circuit 340, the same-name terminal of the fourth winding n4 is a second second terminal (b2) of the secondary winding of transformer circuit 340, and the opposite-name terminal of the third winding n3 is connected to the opposite-name terminal of the fourth winding n4 to serve as the third second terminal (c2) of the secondary winding of transformer circuit 340; the same-name terminal of the fifth winding n5 is a third terminal (a3) ​​of the secondary winding of transformer circuit 340, the same-name terminal of the sixth winding n6 is a second third terminal (b3) of the secondary winding of transformer circuit 340, and the opposite-name terminal of the fifth winding n5 is connected to the opposite-name terminal of the sixth winding n6 to serve as the third third terminal (c3) of the secondary winding of transformer circuit 340.

[0120] In the second example, such as Figure 18 As shown in (b), the same-name terminal of the third winding n3 is a second terminal (a2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the third winding n3 is connected to the same-name terminal of the fourth winding n4, serving as the second second terminal (b2) of the secondary winding of transformer circuit 340. The opposite-name terminal of the fourth winding n4 is the third second terminal (c2) of the secondary winding of transformer circuit 340. The same-name terminal of the fifth winding n5 is a third terminal (a3) ​​of the secondary winding of transformer circuit 340. The opposite-name terminal of the fifth winding n5 is connected to the same-name terminal of the sixth winding n6, serving as the second third terminal (b3) of the secondary winding of transformer circuit 340. The opposite-name terminal of the sixth winding n6 is the third third terminal (c3) of the secondary winding of transformer circuit 340.

[0121] Based on the above structure, by increasing the number of windings on the secondary side of the first transformer T1 and the second transformer T2, the DC-DC converter 300 can connect more three-phase bridge arms without increasing the number of transformers. This reduces the AC loss caused by wiring in the DC-DC converter 300 to a certain extent and improves the working efficiency of the DC-DC converter 300.

[0122] In another implementation, such as Figure 19As shown, the primary winding of the first transformer T1 further includes a third switching unit K3 and a fourth switching unit K4, and the primary winding of the first transformer T1 also includes a seventh winding n7. The primary winding of the second transformer T2 further includes an eighth winding n8. One end of the first winding n1 is connected to one end of the seventh winding n7, and one end of the second winding n2 is connected to one end of the eighth winding n8. The third switching unit K3 is used to: select and conduct the connection between one end of the first winding n1 and one second terminal of the resonant circuit 320, or select and conduct the connection between the other end of the seventh winding n7 and one second terminal of the resonant circuit 320. The fourth switching unit K4 is used to: select and conduct the connection between one end of the second winding n2 and the other second terminal of the resonant circuit 320, or select and conduct the connection between the other end of the eighth winding n8 and the other second terminal of the resonant circuit 320.

[0123] like Figure 19 As shown in (a), the connection method of the secondary windings of the first transformer T1 and the second transformer T2 is the same as... Figure 18 The secondary windings shown in (a) are connected in the same way, both being semi-star connections, such as... Figure 19 As shown in (b) above, the connection method of the secondary windings of the first transformer T1 and the second transformer T2 is the same as... Figure 18 The secondary windings shown in (b) are connected in the same way, both being semi-delta connections. For a detailed description of the secondary windings of transformer circuit 340, please refer to the preceding text; it will not be repeated here.

[0124] As an example and not a limitation, this application embodiment uses the third switch unit K3 and the fourth switch unit K4 as examples of single-pole double-throw switches. Both the third switch unit K3 and the fourth switch unit K4 have one fixed terminal and two select terminals.

[0125] In the first example, such as Figure 19 As shown in (a), the same-name terminal of the first winding n1 is a first terminal (a1) of the primary winding of the transformer circuit 340. The opposite-name terminal of the first winding n1, the same-name terminal of the seventh winding n7, and a selection terminal of the third switching unit K3 are connected. The opposite-name terminal of the seventh winding n7 is connected to the other selection terminal of the third switching unit K3. The same-name terminal of the second winding n2 is a second first terminal (b1) of the primary winding of the transformer circuit 340. The opposite-name terminal of the second winding n2, the same-name terminal of the eighth winding n8, and a selection terminal of the fourth switching unit K4 are connected. The opposite-name terminal of the eighth winding n8 is connected to the other selection terminal of the fourth switching unit K4. The fixed terminal of the third switching unit K3 is connected to the fixed terminal of the fourth switching unit K4, serving as the third first terminal (c1) of the primary winding of the transformer circuit 340.

[0126] In the second example, such as Figure 19As shown in (b), the same-name terminal of the first winding n1 is a first terminal (a1) of the primary winding of the transformer circuit 340. The opposite-name terminal of the first winding n1, the same-name terminal of the seventh winding n7, and a selection terminal of the third switching unit K3 are connected. The opposite-name terminal of the seventh winding n7 is connected to another selection terminal of the third switching unit K3. The same-name terminal of the second winding n2 and the fixed terminal of the third switching unit K3 are connected, serving as the second first terminal (b1) of the primary winding of the transformer circuit 340. The opposite-name terminal of the second winding n2, the same-name terminal of the eighth winding n8, and a selection terminal of the fourth switching unit K4 are connected. The opposite-name terminal of the eighth winding n8 is connected to another selection terminal of the fourth switching unit K4. The fixed terminal of the fourth switching unit K4 serves as the third first terminal (c1) of the primary winding of the transformer circuit 340.

[0127] As described above, when the third switching unit K3 selects to connect the first winding n1 to the second terminal of the resonant circuit 320, only the first winding n1 of the primary side of the first transformer T1 participates in the transformation process, while the seventh winding n7 is disconnected. When the third switching unit K3 selects to connect the eighth winding n8 to the second terminal of the resonant circuit 320, both the first winding n1 and the seventh winding n7 of the primary side of the first transformer T1 participate in the transformation process. Similarly, when the fourth switching unit K4 selects to connect the second winding n2 to the second terminal of the resonant circuit 320, only the second winding n2 of the primary side of the second transformer T2 participates in the transformation process, while the eighth winding n8 is disconnected. When the fourth switching unit K4 selects to connect the eighth winding n8 to the second terminal of the resonant circuit 320, both the second winding n2 and the eighth winding n8 of the primary side of the second transformer T2 participate in the transformation process. In practical applications, the more turns the primary winding of a transformer has, the lower the output voltage of the secondary winding. In this way, by controlling the conduction state of the third switch unit K3 and the fourth switch unit K4, the number of turns of the primary winding of the transformer circuit 340 can be switched. This allows for the connection of fewer windings when a higher voltage is required on the secondary side of the transformer circuit 340, and more windings when a lower voltage is required on the secondary side of the transformer circuit 340. This enables the transformer circuit 340 to output a wide range of voltages, thereby better meeting the charging needs of different electric vehicles 20 when charging them.

[0128] It is understood that the aforementioned third switching unit K3 may also include two single-pole single-throw (SPS) switches. When one of these SPS switches is closed, the other SPS switch is open, thereby switching the number of turns in the primary winding of the first transformer T1. Similarly, the fourth switching unit K4 may also include two SPS switches. When one of these SPS switches is closed, the other SPS switch is open, thereby switching the number of turns in the primary winding of the second transformer T2. Alternatively, the third switching unit K3 and the fourth switching unit K4 may also be relays, semiconductor switching devices, or other switching devices capable of switching the primary winding of the transformer circuit 340.

[0129] In one implementation, such as Figure 20 As shown, the DC-DC converter 300 also includes a fifth switching unit 370, and the three terminals of the first inductor circuit 330 are connected to the three first terminals and three second terminals of the resonant circuit 320 through the fifth switching unit 370.

[0130] When the first three-phase bridge arm 310 is used to convert the received DC power to AC power, and the second three-phase bridge arm 350 is used to convert the AC power output from the first three-phase bridge arm 310 back to DC power, the fifth switching unit 370 is used to: connect the three terminals of the first inductor circuit 330 to the three second terminals of the resonant circuit 320, and disconnect the three terminals of the first inductor circuit 330 from the three first terminals of the resonant circuit 320. When the second three-phase bridge arm 350 is used to convert the received DC power to AC power, and the first three-phase bridge arm 310 is used to convert the AC power output from the second three-phase bridge arm 350 back to DC power, the fifth switching unit 370 is used to: connect the three terminals of the first inductor circuit 330 to the three first terminals of the resonant circuit 320, and disconnect the three terminals of the first inductor circuit 330 from the three second terminals of the resonant circuit 320.

[0131] By way of example and not limitation, this embodiment of the application uses the fifth switching unit 370, which includes three single-pole double-throw switches (S1, S2, and S3), as an example for illustration. It is understood that the fifth switching unit 370 may include multiple relays, semiconductor switching devices, or any other switching devices capable of switching the connection between the first inductor circuit 330 and the resonant circuit 320.

[0132] For ease of description, in this application embodiment, the process of the first three-phase bridge arm 310 converting the received DC power to AC power, and the second three-phase bridge arm 350 converting the AC power output from the first three-phase bridge arm 310 back to DC power and then outputting it, is referred to as the charging process or the forward transmission process. The process of the second three-phase bridge arm 350 converting the received DC power to AC power, and the first three-phase bridge arm 310 converting the AC power output from the second three-phase bridge arm 350 back to DC power and then outputting it, is referred to as the discharging process or the reverse transmission process.

[0133] During forward transmission, the fifth switching unit 370 connects the three terminals of the first inductor circuit 330 to the three second terminals, and disconnects the three terminals of the first inductor circuit 330 from the three first terminals of the resonant circuit 320. This allows the three inductors in the first inductor circuit 330 to form a three-phase LLC resonant circuit with the resonant circuit 320 during charging. Since the voltage gain of the LLC resonant circuit can be less than or equal to 1 or greater than 1, the DC-DC converter 300 can achieve both buck charging and boost charging. During reverse transmission, the fifth switching unit 370 connects the three terminals of the first inductor circuit 330 to the three first terminals of the resonant circuit 320, and disconnects the three terminals of the first inductor circuit 330 from the three second terminals of the resonant circuit 320. This allows the three inductors in the first inductor circuit 330 to also form a three-phase LLC resonant circuit with the resonant circuit 320 during discharging. Therefore, the DC-DC converter 300 can achieve both buck discharging and boost discharging. This improves the voltage regulation range of the DC-DC converter 300 during both forward and reverse power transmission.

[0134] Furthermore, the aforementioned DC-DC converter 300 also includes a third filter circuit 380 and a first capacitor circuit 390. The third filter circuit is connected between the first three-phase bridge arm 310 and the DC power supply, and is used to filter the DC power output from or received by the first three-phase bridge arm 310. The first capacitor circuit 390 is connected between the transformer circuit 340 and the second three-phase bridge arm 350, and is used to isolate the DC component of the electrical energy transmitted between the transformer circuit 340 and the second three-phase bridge arm 350, while retaining the AC ripple component, thereby ensuring that the transformer circuit 340 can operate normally and improving the stability of the second three-phase bridge arm 350 during the process of DC to AC or AC to DC conversion.

[0135] Figure 21 for Figure 20 The circuit topology diagram of the DC-DC converter 300 is shown. Figure 21As shown, the third filter circuit 380 includes a capacitor Cin, and the first capacitor circuit 390 includes three capacitors (Cs1, Cs2, and Cs3). Specifically, the two ends of capacitor Cs1 are connected to terminal a2 of transformer circuit 340 and the midpoint of the A-phase bridge arm of the second three-phase bridge arm 350, respectively. The two ends of capacitor Cs2 are connected to terminal b2 of transformer circuit 340 and the midpoint of the B-phase bridge arm of the second three-phase bridge arm 350, respectively. The two ends of capacitor Cs3 are connected to terminal c2 of transformer circuit 340 and the midpoint of the C-phase bridge arm of the second three-phase bridge arm 350, respectively. The three capacitors in the first capacitor circuit 390 are used to isolate the DC component in each phase of the AC power transmitted between transformer circuit 340 and the second three-phase bridge arm 350, and to retain the corresponding AC ripple component.

[0136] In one implementation, such as Figure 22 As shown, the DC-DC converter 300 also includes a sixth switching unit 371 and a second inductor circuit 331. The three terminals of the second inductor circuit 331 are connected to the three first terminals of the resonant circuit 320. When the first three-phase bridge arm 310 is used to convert the received DC power to AC power, and the second three-phase bridge arm 350 is used to convert the AC power output from the first three-phase bridge arm 310 back to DC power, the sixth switching unit 371 is used to disconnect at least two of the three terminals of the second inductor circuit 331 from at least two of the three first terminals of the resonant circuit 320. When the second three-phase bridge arm 350 is used to convert the received DC power to AC power, and the first three-phase bridge arm 310 is used to convert the AC power output from the second three-phase bridge arm 350 back to DC power, the sixth switching unit 371 is used to connect the three terminals of the second inductor circuit 331 to the three first terminals of the resonant circuit 320.

[0137] As an example and not a limitation, this embodiment of the application uses the sixth switching unit 371, which includes two switches (S4 and S5), as an example for illustration. When switches S4 and S5 are in the off state, at least two of the three terminals of the second inductor circuit 331 are disconnected from at least two of the three first terminals of the resonant circuit 320. When switches S4 and S5 are in the closed state, the three terminals of the second inductor circuit 331 are connected to the three first terminals of the resonant circuit 320, which can form a three-phase LLC resonant circuit with the resonant circuit 320 when electrical energy is transmitted in reverse.

[0138] It is understood that the aforementioned switches S4 and S5 can also be relays, semiconductor switching devices, or any other switching devices capable of switching the connection between the second inductor circuit 331 and the resonant circuit 320. For example, the sixth switching unit 371 may also include a double-pole double-throw switch. When the double-pole double-throw switch is closed, the three terminals of the second inductor circuit 331 are connected to the three first terminals of the resonant circuit 320. When the double-pole double-throw switch is closed, at least two of the three terminals of the second inductor circuit 331 are disconnected from at least two of the three first terminals of the resonant circuit 320.

[0139] During forward transmission, the sixth switching unit 371 disconnects at least two of the three terminals of the second inductor circuit 331 from at least two of the three first terminals of the resonant circuit 320, so that the three inductors in the first inductor circuit 330 form a three-phase LLC resonant circuit with the resonant circuit 320 during charging. Since the voltage gain of the LLC resonant circuit can be less than or equal to 1 or greater than 1, the DC-DC converter 300 can achieve both buck charging and boost charging. During reverse transmission, the sixth switching unit 371 connects the three terminals of the second inductor circuit 331 to the three first terminals of the resonant circuit 320, so that the three inductors in the second inductor circuit 331 form a three-phase LLC resonant circuit with the resonant circuit 320 during discharging. Therefore, the DC-DC converter 300 can achieve both buck discharging and boost discharging. This improves the voltage regulation range of the DC-DC converter 300 during both forward and reverse power transmission.

[0140] In one embodiment, the second inductor circuit 331 includes three magnetizing inductors: a seventh inductor Lm7, an eighth inductor Lm8, and a ninth inductor Lm9. These three inductors can be connected in a star configuration or a delta configuration. For example, a star configuration can be chosen for applications requiring higher voltage and lower current, while a delta configuration can be chosen for applications requiring higher current and lower voltage.

[0141] like Figure 23 As shown in (a), one end of the seventh inductor Lm7, one end of the eighth inductor Lm8, and one end of the ninth inductor Lm9 are connected. The other ends of the seventh inductor Lm7, the eighth inductor Lm8, and the ninth inductor Lm9 serve as the three terminals of the second inductor circuit 331, respectively. Furthermore, during the discharge process, when the sixth switching unit 371 is turned on, each phase resonant circuit in the resonant circuit 320 can form LLC resonance with one of the magnetizing inductors in the second inductor circuit 331.

[0142] like Figure 23As shown in (b), the seventh inductor Lm7, the eighth inductor Lm8, and the ninth inductor Lm9 are connected end-to-end in sequence. The connection points of the seventh inductor Lm7 and the eighth inductor Lm8, the eighth inductor Lm8 and the ninth inductor Lm9, and the ninth inductor Lm9 and the seventh inductor Lm7 respectively serve as the three terminals of the second inductor circuit 331. Furthermore, during the discharge process, when the sixth switching unit 371 is turned on, each phase resonant circuit in the resonant circuit 320 can form LLC resonance with one of the magnetizing inductors in the second inductor circuit 331.

[0143] The second inductor circuit 331 and the first inductor circuit 330 can use the same connection method or different connection methods. For example, both inductor circuits can be star-connected, or one inductor circuit can be star-connected and the other can be delta-connected. In practical applications, different connection methods can be selected according to the different voltage and current requirements of the DC-DC converter 300 during the charging and discharging processes. This application embodiment does not specifically limit this.

[0144] In one implementation, such as Figure 24 As shown, the DC-DC converter 300 also includes a seventh switching unit 372, a first inductor Lm4, a second inductor Lm5, and a third inductor Lm6. One end of the first inductor Lm4, one end of the second inductor Lm5, and one end of the third inductor Lm6 are respectively connected to the three second terminals of the resonant circuit 320. The other ends of the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 are connected to the three first terminals of the resonant circuit 320 through the seventh switching unit 372. When the first three-phase bridge arm 310 is used to convert the received DC power into AC power, and the second three-phase bridge arm 350 is used to convert the AC power output from the first three-phase bridge arm 310 into DC power and output it, the seventh switching unit 372 is used to disconnect the connection between the other ends of the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 and the three first terminals of the resonant circuit 320. When the second three-phase bridge arm 350 is used to convert the received DC power into AC power, and the first three-phase bridge arm 310 is used to convert the AC power output from the second three-phase bridge arm 350 into DC power and then output it, the seventh switch unit 372 is used to: connect the other end of the first inductor Lm4, the other end of the second inductor Lm5, and the other end of the third inductor Lm6 to the three first terminals of the resonant circuit 320.

[0145] As an example and not a limitation, this embodiment of the application uses the seventh switch unit 372, which includes three switches (S6, S7, and S8), as an example for illustration. When switches S6, S7, and S8 are in the off state, the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 are disconnected from the three first terminals of the resonant circuit 320. When switches S6, S7, and S8 are in the closed state, the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 are connected to the three first terminals of the resonant circuit 320, which can form a three-phase LLC resonant circuit with the resonant circuit 320 when electrical energy is transmitted in reverse.

[0146] It is understood that the aforementioned switches S6, S7, and S8 can also be relays, semiconductor switching devices, or any other switching device capable of switching the connection relationship between the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 and the resonant circuit 320. This application does not specifically limit this.

[0147] During forward transmission, the seventh switch unit 372 disconnects the connection between the other ends of the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 and the three first terminals of the resonant circuit 320. This allows the three inductors in the first inductor circuit 330 to form a three-phase LLC resonant circuit with the resonant circuit 320 during charging. Since the voltage gain of the LLC resonant circuit can be less than or equal to 1 or greater than 1, the DC-DC converter 300 can achieve both buck charging and boost charging. During reverse transmission, the seventh switch unit 372 connects the other ends of the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 to the three first terminals of the resonant circuit 320. This allows the first inductor Lm4, the second inductor Lm5, and the third inductor Lm6 to form a three-phase LLC resonant circuit with the resonant circuit 320 during discharging. Therefore, the DC-DC converter 300 can achieve both buck discharging and boost discharging. This improves the voltage regulation range of the DC-DC converter 300 during both forward and reverse power transmission.

[0148] In one embodiment, such as Figure 25 As shown, when the DC-DC converter 300 includes a third three-phase bridge arm 351, the transformer circuit 340 can adopt the above-described... Figure 18 or Figure 19The circuit topology is shown. The DC-DC converter 300 may further include a second capacitor circuit 391, a second filter circuit 361, and series switches K5, parallel switches K6, and parallel switches K7. The second capacitor circuit 391 is connected between the three third terminals of the transformer circuit 340 and the third three-phase bridge arm 351. It isolates the DC component of the electrical energy transmitted between the transformer circuit 340 and the third three-phase bridge arm 351, while retaining the AC ripple component. This ensures the normal operation of the transformer circuit 340 and improves the stability of the third three-phase bridge arm 351 during DC-to-AC or AC-to-DC conversion.

[0149] The structure of the second capacitor circuit 391 is the same as that of the first capacitor circuit 390, and will not be described again here.

[0150] This application embodiment also provides a charging pile 10, which includes: an AC-DC converter, a DC-DC converter provided in the above embodiment, and a charging gun 13. One end of the AC-DC converter is used to connect to an AC power source, and the other end of the AC-DC converter is connected to the charging gun 13 through the DC-DC converter.

[0151] The detailed description of the charging pile 10 above can be found in [reference]. Figure 1 and Figure 2 The relevant statements and analyses of the beneficial effects of the charging pile 10 can be applied to the DC-DC converter 300, and will not be repeated here in the embodiments of this application.

[0152] Finally, it should be noted that the above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A DC-DC to DC-DC converter, characterized in that, The DC-DC converter includes a first three-phase bridge arm, a resonant circuit, a first inductor circuit, a transformer circuit, and a second three-phase bridge arm. The two ends of the first three-phase bridge arm are used to connect to a DC power supply; the midpoint of the first three-phase bridge arm is connected to the three first terminals of the resonant circuit; the three second terminals of the resonant circuit are connected to the three first terminals of the primary winding of the transformer circuit; the three terminals of the first inductor circuit are connected to the three second terminals of the resonant circuit, so that the resonant circuit and the first inductor circuit form a three-phase inductor-inductor-capacitor LLC resonant circuit; the three second terminals of the secondary winding of the transformer circuit are connected to the midpoint of the second three-phase bridge arm. The transformer circuit includes a first transformer and a second transformer. The primary winding of the first transformer includes a first winding, the primary winding of the second transformer includes a second winding, the secondary winding of the first transformer includes a third winding, and the secondary winding of the second transformer includes a fourth winding. One end of the first winding is connected to one end of the second winding and serves as a first end of the primary winding. The other end of the first winding and the other end of the second winding serve as the other two first ends of the primary winding. One end of the third winding and one end of the fourth winding are connected and serve as a second end of the secondary winding. The other end of the third winding and the other end of the fourth winding serve as the other two second ends of the secondary winding.

2. The DC-DC converter according to claim 1, characterized in that, The secondary winding of the first transformer further includes a first switching unit and a second switching unit. The secondary winding of the first transformer further includes a fifth winding. The secondary winding of the second transformer further includes a sixth winding. One end of the third winding is connected to one end of the fifth winding. One end of the fourth winding is connected to one end of the sixth winding. The first switching unit is used to select and connect the connection between one end of the third winding and the second three-phase bridge arm, or to select and connect the connection between the other end of the fifth winding and the second three-phase bridge arm. The second switching unit is used to select and connect one end of the fourth winding to the connection between the second three-phase bridge arm, or to select and connect the other end of the sixth winding to the connection between the second three-phase bridge arm.

3. The DC-DC converter according to claim 1, characterized in that, The DC-DC converter further includes a third three-phase bridge arm, and the secondary winding of the transformer circuit further includes three third terminals, which are respectively connected to the midpoint of the bridge arm of the third three-phase bridge arm. The secondary winding of the first transformer further includes a fifth winding, and the secondary winding of the second transformer further includes a sixth winding. One end of the fifth winding and one end of the sixth winding are connected and serve as one of the three third terminals. The other end of the fifth winding and the other end of the sixth winding serve as the other two third terminals.

4. The DC-DC converter according to any one of claims 1-3, characterized in that, The primary winding of the first transformer further includes a third switching unit and a fourth switching unit. The primary winding of the first transformer further includes a seventh winding. The primary winding of the second transformer further includes an eighth winding. One end of the first winding is connected to one end of the seventh winding, and one end of the second winding is connected to one end of the eighth winding. The third switching unit is used to select and connect the connection between one end of the first winding and a second end of the resonant circuit, or to select and connect the connection between the other end of the seventh winding and a second end of the resonant circuit. The fourth switching unit is used to select and connect the connection between one end of the second winding and the other second end of the resonant circuit, or to select and connect the connection between the other end of the eighth winding and the other second end of the resonant circuit.

5. The DC-DC converter according to any one of claims 1-4, characterized in that, The DC-DC converter further includes a fifth switching unit, through which the three terminals of the first inductor circuit are connected to the three first terminals and the three second terminals of the resonant circuit; When the first three-phase bridge arm is used to convert the received DC power into AC power, and the second three-phase bridge arm is used to convert the AC power output by the first three-phase bridge arm into DC power and output it, the fifth switching unit is used to connect the connection between the three terminals of the first inductor circuit and the three second terminals of the resonant circuit, and disconnect the connection between the three terminals of the first inductor circuit and the three first terminals of the resonant circuit. When the second three-phase bridge arm is used to convert the received DC power into AC power, and the first three-phase bridge arm is used to convert the AC power output by the second three-phase bridge arm into DC power and then output it, the fifth switching unit is used to connect the connection between the three terminals of the first inductor circuit and the three first terminals of the resonant circuit, and disconnect the connection between the three terminals of the first inductor circuit and the three second terminals of the resonant circuit.

6. The DC-DC converter according to any one of claims 1-4, characterized in that, The DC-DC converter further includes a sixth switching unit and a second inductor circuit, wherein the three terminals of the second inductor circuit are connected to the three first terminals of the resonant circuit; When the first three-phase bridge arm is used to convert the received DC power into AC power and the second three-phase bridge arm is used to convert the AC power output by the first three-phase bridge arm into DC power and then output it, the sixth switching unit is used to disconnect the connection between at least two of the three terminals of the second inductor circuit and at least two of the three first terminals of the resonant circuit. When the second three-phase bridge arm is used to convert the received DC power into AC power, and the first three-phase bridge arm is used to convert the AC power output by the second three-phase bridge arm into DC power and then output it, the sixth switching unit is used to connect the three terminals of the second inductor circuit with the three first terminals of the resonant circuit.

7. The DC-DC converter according to any one of claims 1-4, characterized in that, The DC-DC converter further includes a seventh switching unit, a first inductor, a second inductor, and a third inductor. One end of the first inductor, one end of the second inductor, and one end of the third inductor are respectively connected to the three second terminals of the resonant circuit. The other ends of the first inductor, the second inductor, and the third inductor are connected to the three first terminals of the resonant circuit through the seventh switching unit. When the first three-phase bridge arm is used to convert the received DC power into AC power, and the second three-phase bridge arm is used to convert the AC power output by the first three-phase bridge arm into DC power and then output it, the seventh switch unit is used to disconnect the connection between the other end of the first inductor, the other end of the second inductor, and the other end of the third inductor and the three first ends of the resonant circuit. When the second three-phase bridge arm is used to convert the received DC power into AC power, and the first three-phase bridge arm is used to convert the AC power output by the second three-phase bridge arm into DC power and then output it, the seventh switching unit is used to connect the other end of the first inductor, the other end of the second inductor, and the other end of the third inductor to the three first terminals of the resonant circuit.

8. The DC-DC converter according to any one of claims 1-7, characterized in that, The first inductor circuit includes a fourth inductor, a fifth inductor, and a sixth inductor, wherein: One end of the fourth inductor, one end of the fifth inductor, and one end of the sixth inductor are connected, and the other ends of the fourth inductor, the fifth inductor, and the sixth inductor respectively serve as the three terminals of the first inductor circuit; or, The fourth inductor, the fifth inductor, and the sixth inductor are connected end to end in sequence. The connection point between the fourth inductor and the fifth inductor, the connection point between the fifth inductor and the sixth inductor, and the connection point between the sixth inductor and the fourth inductor respectively serve as the three terminals of the first inductor circuit.

9. The DC-DC converter according to claim 6 or 8, characterized in that, The second inductor circuit includes a seventh inductor, an eighth inductor, and a ninth inductor, wherein: One end of the seventh inductor, one end of the eighth inductor, and one end of the ninth inductor are connected, and the other ends of the seventh inductor, the eighth inductor, and the ninth inductor respectively serve as the three terminals of the second inductor circuit; or, The seventh inductor, the eighth inductor, and the ninth inductor are connected end to end in sequence. The connection point between the seventh inductor and the eighth inductor, the connection point between the eighth inductor and the ninth inductor, and the connection point between the ninth inductor and the seventh inductor respectively serve as the three terminals of the second inductor circuit.

10. A charging pile, characterized in that, The charging pile includes: an AC-DC converter, a DC-DC converter as described in any one of claims 1 to 9, and a charging gun. One end of the AC-DC converter is used to connect to an AC power source, and the other end of the AC-DC converter is connected to the charging gun through the DC-DC converter.

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