Direct current-direct current bidirectional converter and vehicle-mounted power supply system

Abstract

The invention provides a DC-DC bidirectional converter and a vehicle-mounted power supply system. The DC-DC bidirectional converter comprises a power supply high-voltage side, a power supply low-voltage side, a first inductor, a second inductor, a first low-voltage switch module, a second low-voltage switch module, a high-voltage switch module, a flying capacitor module and a control module. The control module is used for controlling the on-off of each switch, so that the converter works in a first working period or a second working period; the flying capacitor module is used for dividing the voltage during the first working period and the second working period of the converter. The current of the inductor is reduced, the inductor with a smaller size is allowed to be used, the power density is effectively improved, and meanwhile, the problem of current discontinuity is solved.

Description

Technical Field

[0001] This application relates to the field of automotive technology, and more specifically, to a DC-DC bidirectional converter and an on-board power system. Background Technology

[0002] On the road to full electrification in the automotive industry, bidirectional high-voltage / low-voltage converters play a crucial bridging role. They are used to bridge voltage differences and manage power exchange between high-voltage and low-voltage electrical systems, enabling bidirectional energy flow and precise allocation between the two voltage systems.

[0003] Existing bidirectional high-voltage / low-voltage converters suffer from problems such as high voltage stress on each switch, discontinuous current, and excessively large device size due to large inductor current.

[0004] There are limitations in the operating duty cycle range, and the switching transistor must directly withstand the stress of the maximum input voltage. While existing technologies have improved some of the problems in buck mode by using a dual-path approach to reduce inductor current and improve converter performance, they cannot achieve boost mode in bidirectional applications. Although existing technologies can solve the trade-off between voltage conversion ratio and operating duty cycle, the use of coupled inductors results in excessively large device sizes, which cannot meet the high power density requirements of modern automobiles. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of the prior art by providing a DC-DC bidirectional converter that reduces the current in the inductor, thereby allowing the use of a smaller inductor, effectively improving power density, and solving the problem of current discontinuity.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows: In a first aspect, embodiments of this application provide a DC-DC bidirectional converter, including: a high-voltage side of the power supply, a low-voltage side of the power supply, a first inductor, a second inductor, a first low-voltage switching module, a second low-voltage switching module, a high-voltage switching module, a flying capacitor module, and a control module; One end of the first inductor is connected to the high-voltage side of the power supply, and the other end of the first inductor is connected to the first end of the flying capacitor module and the first end of the high-voltage switch module, respectively. The second terminal of the flying capacitor module is connected to the first terminal of the first low-voltage switch module, the third terminal of the flying capacitor module is connected to the second terminal of the high-voltage switch module and the first terminal of the second low-voltage switch module, and the fourth terminal of the flying capacitor module is connected to one terminal of the second inductor and the second terminal of the first low-voltage switch module. The third terminal of the first low-voltage switch module is connected to the other end of the second inductor, the second terminal of the second low-voltage switch module, and the positive terminal of the low-voltage side of the power supply, respectively. The fourth terminal of the first low-voltage switch module and the negative terminal of the high-voltage side of the power supply are connected to the negative terminal of the low-voltage side of the power supply, respectively. The first low-voltage switch module, the second low-voltage switch module, and the high-voltage switch module each include at least one switch, and the third terminal of each switch is connected to the control module. The control module is used to control the on / off state of each switch so that the converter operates during a first working period or a second working period, and performs bidirectional current conversion during both the first working period and the second working period. The flying capacitor module is used to divide the voltage during the first and second operating periods of the converter.

[0007] Optionally, the flying capacitor module includes: a first capacitor and a second capacitor; One end of the first capacitor is connected to the other end of the first inductor and the first end of the high-voltage switch module, and the other end of the first capacitor is connected to the first end of the first low-voltage switch module. One end of the second capacitor is connected to the second terminal of the high-voltage switch module and the first terminal of the second low-voltage switch module, respectively, and the other end of the second capacitor is connected to the second terminal of the first low-voltage switch module and one end of the second inductor, respectively. The first capacitor and the second capacitor together form an additional parallel current path.

[0008] Optionally, the high-voltage switching module includes: a first field-effect transistor; The first end of the first field-effect transistor is connected to the other end of the first inductor, the second end of the first field-effect transistor is connected to the first end of the second low-voltage switching module and the third end of the flying capacitor module, and the third end of the first field-effect transistor is connected to the control module.

[0009] Optionally, the second low-voltage switching module includes: a second field-effect transistor; The first end of the second field-effect transistor is connected to the second end of the high-voltage switch module and the third end of the flying capacitor module, the second end of the second field-effect transistor is connected to the other end of the second inductor and the positive terminal of the low-voltage side of the power supply, and the third end of the second field-effect transistor is connected to the control module.

[0010] Optionally, the first low-voltage switching module includes: a third field-effect transistor, a fourth field-effect transistor, and a fifth field-effect transistor; The first terminal of the third field-effect transistor is connected to the second terminal of the flying capacitor module and the first terminal of the fourth field-effect transistor, respectively. The second terminal of the third field-effect transistor is connected to the negative terminal of the high-voltage side of the power supply and the negative terminal of the low-voltage side of the power supply, respectively. The second terminal of the fourth field-effect transistor is connected to the other terminal of the second inductor and the second terminal of the second low-voltage switching module, respectively. The first terminal of the fifth field-effect transistor is connected to one terminal of the second inductor and the fourth terminal of the flying capacitor module, respectively; the second terminal of the fifth field-effect transistor is connected to the negative terminal of the high-voltage side of the power supply and the negative terminal of the low-voltage side of the power supply, respectively. The third terminal of the third field-effect transistor, the third terminal of the fourth field-effect transistor, and the third terminal of the fifth field-effect transistor are respectively connected to the control module.

[0011] Optionally, in buck mode, the sum of the current in the first inductor and the current in the second inductor is (2-D)*IOUT / (2-D 2 ), where D is the operating duty cycle of the converter, and IOUT is the current received by the low-voltage side of the power supply.

[0012] Optionally, the step-down ratio of the converter is (1-D) / (2-D). 2 ).

[0013] Optionally, the boost ratio of the converter is (2-D) 2 ) / (1-D), where D is the duty cycle of the converter.

[0014] Optionally, the voltage stress of the first field-effect transistor is The voltage stress of the second field-effect transistor is The voltage stress of the third field-effect transistor is The voltage stress of the fourth field-effect transistor is Where D is the duty cycle of the converter. This refers to the voltage on the high-voltage side of the power supply.

[0015] Secondly, this application also provides an on-board power system, including the DC-DC bidirectional converter described in the first aspect.

[0016] Thirdly, this application also provides a vehicle including the on-board power system described in the second aspect.

[0017] The beneficial effects of this application are: This application provides a DC-DC bidirectional converter and an on-board power supply system. A first inductor is connected to the high-voltage side of the power supply, and a second inductor is connected to the low-voltage side. Both the first and second inductors are also connected to a flying capacitor module. The flying capacitor module can divide the voltage, reducing the voltage stress on each switching transistor. Furthermore, in buck mode, the flying capacitor module provides an additional current path for the inductor, reducing the inductor current and allowing for the use of a smaller inductor, effectively improving power density. Additionally, the first inductor connected to the high-voltage side solves the problem of discontinuous input current in buck mode, and the second inductor connected to the low-voltage side solves the problem of discontinuous output current in boost mode. The hybrid connection of the flying capacitor module and inductors widens the converter's operating duty cycle range and reduces the voltage stress on each switching transistor. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A circuit diagram of a DC-DC bidirectional converter provided for an embodiment of this application; Figure 2 A circuit diagram of another DC-DC bidirectional converter provided in an embodiment of this application; Figure 3 A circuit diagram of yet another DC-DC bidirectional converter provided in an embodiment of this application; Figure 4 A circuit diagram of another DC-DC bidirectional converter provided in an embodiment of this application; Figure 5 A circuit diagram in buck mode is provided for an embodiment of this application; Figure 6 Another circuit diagram in buck mode provided for an embodiment of this application; Figure 7 A circuit diagram in boost mode is provided for an embodiment of this application; Figure 8 Another circuit diagram in boost mode provided for an embodiment of this application; Figure 9 A working waveform diagram provided for an embodiment of this application; Figure 10A conversion ratio versus D curve in buck mode is provided as an embodiment of this application; Figure 11 This application provides a conversion ratio and D relationship curve in boost mode, which is an embodiment of the present application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0022] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] It should be noted that the term "comprising" will be used in the embodiments of this application to indicate the presence of the features declared thereafter, but does not exclude the addition of other features.

[0024] As the automotive industry moves towards full electrification, 48V power systems are increasingly demonstrating their importance, becoming a key driving force for industry progress. With the increasing number of onboard electronic devices, the power demands of vehicles are constantly rising. Traditional 12V power systems are showing their limitations in the face of ever-increasing electrical loads, struggling to meet the power requirements of devices such as electric power steering and high-power electronic equipment. The emergence of 48V systems offers a new solution to this problem. By providing a higher voltage platform, 48V systems enable vehicles to operate high-power electronic equipment more efficiently while reducing energy loss. This system is not only suitable for internal combustion engine vehicles but is also widely used in mild hybrid electric vehicles and pure electric vehicles, bringing significant performance improvements and efficiency enhancements to various types of vehicles. 48V systems are expected to become the new standard for automotive electrification in the future, further propelling the automotive industry towards a cleaner, more efficient, and smarter future.

[0025] During the gradual transition from traditional 12V systems to 48V systems, the 48V system and the existing 12V system will operate in parallel for a period of time. Therefore, in various vehicle types such as mild hybrid electric vehicles and pure electric vehicles, high-performance bidirectional 48V / 12V converters play a crucial bridging role. They are used to bridge voltage differences and manage power exchange between the 12V and 48V electrical systems, responsible for enabling bidirectional energy flow and precise allocation between the two voltage systems.

[0026] Existing technologies suffer from limitations in the range of operating duty cycles, and the switching transistors must directly withstand the stress of the maximum input voltage. While existing technologies have improved some issues in buck mode by employing a dual-path approach to reduce inductor current and improve converter performance, they cannot achieve boost mode in bidirectional applications. Although existing technologies can resolve the trade-off between voltage conversion ratio and operating duty cycle, the use of coupled inductors results in excessively large device sizes, which cannot meet the high power density requirements of modern automobiles.

[0027] Therefore, based on the technical problems existing in the prior art, this application proposes a DC-DC bidirectional converter.

[0028] Figure 1 A circuit diagram of a DC-DC bidirectional converter provided in an embodiment of this application is shown below. Figure 1 As shown, this DC-DC bidirectional converter may include: a high-voltage power supply VH, a low-voltage power supply VL, a first inductor L1, a second inductor L2, a first low-voltage switching module SA1, a second low-voltage switching module SA2, a high-voltage switching module SA3, a flying capacitor module C, and a control module H. The voltage of the high-voltage power supply VH can be, for example, 48V, and the voltage of the low-voltage power supply VL can be, for example, 12V.

[0029] like Figure 1 As shown, one end of the first inductor L1 is connected to the high-voltage side VH of the power supply, and the other end of the first inductor L1 is connected to the first end of the flying capacitor module C and the first end of the high-voltage switch module SA3, respectively.

[0030] Optionally, the second terminal of the flying capacitor module C is connected to the first terminal of the first low-voltage switch module SA1, the third terminal of the flying capacitor module C is connected to the second terminal of the high-voltage switch module SA3 and the first terminal of the second low-voltage switch module SA2 respectively, and the fourth terminal of the flying capacitor module C is connected to one terminal of the second inductor L2 and the second terminal of the first low-voltage switch module SA1 respectively.

[0031] The third terminal of the first low-voltage switch module SA1 is connected to the other terminal of the second inductor L2, the second terminal of the second low-voltage switch module SA2, and the positive terminal of the low-voltage side VL of the power supply. The fourth terminal of the first low-voltage switch module SA1 and the negative terminal of the high-voltage side VH of the power supply are connected to the negative terminal of the low-voltage side VL of the power supply.

[0032] The first low-voltage switch module SA1, the second low-voltage switch module SA2, and the high-voltage switch module SA3 each include at least one switch, and the third terminal of each switch is connected to the control module H.

[0033] The control module H is used to control the on / off state of each switch so that the converter operates in a first working period or a second working period. The first working period is DT, and the second working period is (1-D)T, where D is the duty cycle of the converter and T is the working cycle of the converter. The first working period and the second working period are combined into one working cycle.

[0034] Optionally, during the first operating period, the converter in this embodiment can perform current conversion from the high-voltage side VH to the low-voltage side VL of the power supply, i.e., enter buck mode; or it can perform current conversion from the low-voltage side VL to the high-voltage side VH of the power supply, i.e., enter boost mode. In other words, the converter in this application can enter either buck mode or boost mode during the first operating period.

[0035] Optionally, during the second operating period, the converter in this embodiment can perform current conversion from the high-voltage side VH to the low-voltage side VL of the power supply, i.e., enter buck mode; or it can perform current conversion from the low-voltage side VL to the high-voltage side VH of the power supply, i.e., enter boost mode. In other words, the converter in this application can enter both buck mode and boost mode during the second operating period.

[0036] Optionally, the flying capacitor module C is used to divide the voltage during the first and second operating periods of the converter.

[0037] In this embodiment, a first inductor is connected to the high-voltage side of the power supply, and a second inductor is connected to the low-voltage side. Both the first and second inductors are also connected to a flying capacitor module. The flying capacitor module can divide the voltage, reducing the voltage stress on each switching transistor. Furthermore, in buck mode, the flying capacitor module provides an additional current path for the inductor, reducing the inductor current and allowing for the use of a smaller inductor, effectively improving power density. Additionally, the first inductor connected to the high-voltage side of the power supply solves the problem of discontinuous input current in buck mode, and the second inductor connected to the low-voltage side solves the problem of discontinuous output current in boost mode. This hybrid connection of the flying capacitor module and inductors widens the converter's operating duty cycle range and reduces the voltage stress on each switching transistor.

[0038] Figure 2 A circuit diagram of another DC-DC bidirectional converter provided in the embodiments of this application is shown below. Figure 2 As shown, the above-mentioned flying capacitor module C may include: a first capacitor C1 and a second capacitor C2.

[0039] One end of the first capacitor C1 is connected to the other end of the first inductor L1 and the first end of the high-voltage switch module SA3, and the other end of the first capacitor C1 is connected to the first end of the first low-voltage switch module SA1.

[0040] One end of the second capacitor C2 is connected to the second end of the high-voltage switch module SA3 and the first end of the second low-voltage switch module SA2, respectively. The other end of the second capacitor C2 is connected to the second end of the first low-voltage switch module SA1 and one end of the second inductor L2, respectively.

[0041] The first capacitor C1 and the second capacitor C2 combine to form an additional parallel current path.

[0042] Figure 3 A circuit diagram of another DC-DC bidirectional converter provided in the embodiments of this application is shown below. Figure 3 As shown, the high-voltage switch module SA3 may include a first field-effect transistor S1.

[0043] Continue to refer to Figure 3 The first terminal of the first field-effect transistor S1 is connected to one end of the first inductor L1 and one end of the first capacitor C1 in the flying capacitor module C. The second terminal of the first field-effect transistor S1 is connected to the first terminal of the second low-voltage switch module SA2 and the third terminal of the flying capacitor module C. Specifically, the second terminal of the first field-effect transistor S1 is connected to one end of the second capacitor C2 in the flying capacitor module C, and the third terminal of the first field-effect transistor S1 is connected to the control module H.

[0044] In this design, the first field-effect transistor S1 can be an NMOS field-effect transistor, with its first terminal being the drain, its second terminal being the source, and its third terminal being the gate.

[0045] Continue to refer to Figure 3 The aforementioned second low-voltage switch module SA2 includes: a second field-effect transistor S2.

[0046] The first terminal of the second field-effect transistor S2 is connected to the second terminal of the high-voltage switch module SA3 and the third terminal of the flying capacitor module C. Specifically, the first terminal of the second field-effect transistor S2 is connected to the second terminal of the first field-effect transistor S1 in the high-voltage switch module SA3 and one terminal of the second capacitor C2 in the flying capacitor module C.

[0047] The second terminal of the second field-effect transistor S2 is connected to the other terminal of the second inductor L2 and the positive terminal of the low-voltage side VL of the power supply, respectively. The third terminal of the second field-effect transistor S2 is connected to the control module H.

[0048] Figure 4 A circuit diagram of another DC-DC bidirectional converter provided in the embodiments of this application is shown below. Figure 4 As shown, the first low-voltage switch module SA1 includes: a third field-effect transistor S3, a fourth field-effect transistor S4, and a fifth field-effect transistor S5.

[0049] In this configuration, the third field-effect transistor (FET) S3, the fourth field-effect transistor (FET) S4, and the fifth field-effect transistor (FET) S5 are all NMOS field-effect transistors. The first terminal of the third FET S3 is the drain, the second terminal is the source, and the third terminal is the gate. Similarly, the first terminal of the fourth FET S4 is the drain, the second terminal is the source, and the third terminal is the gate. Likewise, the first terminal of the fifth FET S5 is the drain, the second terminal is the source, and the third terminal is the gate.

[0050] Reference Figure 4 The first terminal of the third field-effect transistor S3 is connected to the second terminal of the flying capacitor module C and the first terminal of the fourth field-effect transistor S4, respectively. The second terminal of the third field-effect transistor S3 is connected to the negative terminal of the high-voltage side VH and the negative terminal of the low-voltage side VL of the power supply, respectively. Specifically, the first terminal of the third field-effect transistor S3 is connected to the other terminal of the first capacitor in the flying capacitor module C.

[0051] The second terminal of the fourth field-effect transistor S4 is connected to the other terminal of the second inductor L2 and the second terminal of the second low-voltage switch module SA2, respectively. Specifically, the second terminal of the fourth field-effect transistor S4 is connected to the second terminal of the second field-effect transistor S2 in the second low-voltage switch module SA2.

[0052] The first terminal of the fifth field-effect transistor S5 is connected to one end of the second inductor L2 and the fourth terminal of the flying capacitor module C, respectively. The second terminal of the fifth field-effect transistor S5 is connected to the negative terminal of the high-voltage side VH and the negative terminal of the low-voltage side VL of the power supply, respectively. Specifically, the first terminal of the fifth field-effect transistor S5 is connected to one end of the second inductor L2 and the other end of the second capacitor C2 in the flying capacitor module C.

[0053] The third terminal of the third field-effect transistor S3, the third terminal of the fourth field-effect transistor S4, and the third terminal of the fifth field-effect transistor S5 are respectively connected to the control module H.

[0054] Optionally, based on Figure 4 In buck mode, the converter transfers power from the high-voltage side of the power supply to the low-voltage side, and can be divided into two working cycles according to the state of each switch.

[0055] It is worth noting that, Figures 1-4 The connection between the control module and the high-voltage switch module SA3, the first low-voltage switch module SA1, and the second low-voltage switch module SA2 is only illustrative. In a specific embodiment, the control module H can be connected to the third terminal of the first field-effect transistor S1 in the high-voltage switch module SA3, or to the third terminals of the third field-effect transistor S3, the fourth field-effect transistor S4, and the fifth field-effect transistor S5 in the first low-voltage switch module SA1, or to the third terminal of the second field-effect transistor S2 in the second low-voltage switch module SA2.

[0056] Figure 5 A circuit diagram in buck mode is provided as an embodiment of this application, such as... Figure 5 As shown, during the first working period, i.e. Figure 5 During Φ1, the control module H can control the second field-effect transistor S2, the fourth field-effect transistor S4, and the fifth field-effect transistor S5 to be in the on state, and control the first field-effect transistor S1 and the third field-effect transistor S3 to be in the off state.

[0057] Reference Figure 5 During the first operating period, the first capacitor C1 charges and the first inductor L1 discharges. The input current output from the high-voltage side VH of the power supply charges the first capacitor C1 in the flying capacitor module C, and the first inductor L1 discharges at V... H -V C1 -V L The voltage discharge, where V H V is the voltage on the high-voltage side of the power supply. C1 V is the voltage across the first capacitor. L This is the voltage on the low-voltage side of the power supply. Meanwhile, the second inductor L2 uses -V... LThe voltage discharges, and the second capacitor C2 and the second inductor L2 are connected in parallel to discharge to the low-voltage side VL of the power supply.

[0058] Optionally, Figure 5 The circuit forms three current paths: the first current path is VH→C1→S4→VL; the second current path is VH→S5→L2→VL; and the third current path is VH→S5→C2→S2→VL.

[0059] In contrast to the buck mode of traditional bidirectional converters, where the inductor current equals the output current, to ensure converter efficiency, a large-volume inductor with low DC resistance is needed to reduce inductor conduction losses. However, this increases the converter's size and reduces power density. Conversely, a small-volume inductor with high DC resistance increases conduction losses and limits converter efficiency. In this application, during the first operating period of buck mode, three current paths are formed via two inductors and two capacitors. This reduces the inductor current of the first and second inductors, and the capacitors provide additional current paths, further reducing the inductor current and resulting in a smaller inductor size, effectively improving power density.

[0060] Figure 6 Another circuit diagram in buck mode provided for embodiments of this application, as shown below. Figure 6 As shown, during the second working period, i.e. Figure 6 During the Φ2 period, the control module H can control the second field-effect transistor S2, the fourth field-effect transistor S4 and the fifth field-effect transistor S5 to be in the off state, and control the first field-effect transistor S1 and the third field-effect transistor S3 to be in the on state.

[0061] Since the second working period and the first working period constitute one cycle, during the first working period, the first capacitor C1 is charging, the first inductor L1 is discharging, and the second inductor L2 is discharging; therefore, during the second working period, the first inductor L1 is charging, the first capacitor C1 is discharging, and the second inductor L2 is charging.

[0062] Reference Figure 6 During the second operating period, since the third field-effect transistor S3 is in the closed state, the high-voltage side of the power supply VH, the first capacitor C1, and the first inductor L1 form a circuit. Therefore, the first inductor L1 operates at V... H -V C1 The voltage charging is achieved by the input current output from the high-voltage side VH of the power supply and the charge released from the first capacitor C1, forming a parallel current that is transmitted to the second capacitor C2 and the second inductor L2, charging them. The charging voltage of the second inductor L2 is V. C1 -V C2 -V L At the same time, the parallel current flows into the low-voltage side VL of the power supply.

[0063] based on Figure 5 and Figure 6 In buck mode, the DC current of the first inductor L1 can be obtained by calculating the charge conservation of the flying capacitor. The DC current of the second inductor L2 is Add the DC current I1 of the first inductor L1 to the DC current I2 of the second inductor L2 to obtain the sum of the DC currents of the first inductor L1 and the second inductor L2. Because of D (0,1), then Less than Where D is the operating duty cycle of the converter, and IOUT is the current received by the low-voltage side VL of the power supply during the first or second operating period.

[0064] The above obtains the DC current of the first inductor L1 DC current of the second inductor The sum of the DC current of the first inductor L1 and the DC current of the second inductor L2 The reasoning process is as follows: Based on Kirchhoff's current law, the current formula (I) for the first operating period can be obtained.

[0065] Formula (1) in, This refers to the current received by the low-voltage side VL of the power supply during the first operating period. For the current of the first inductor L1 during the first operating period, The current of the second capacitor C2 during the first operating period, The current in the second inductor L2 during the first operating period is... This represents the current in the first capacitor C1 during the first operating period.

[0066] Based on Kirchhoff's current law, the current formula (II) for the first operating period can be obtained.

[0067] Formula (II) in, This refers to the current received by the low-voltage side VL of the power supply during the second operating period. For the current of the first inductor L1 during the second operating period, The current of the second capacitor C2 during the second operation period, The current of the second inductor L2 during the second operating period, Let C1 be the current in the first capacitor C1 during the second operating period.

[0068] The following formula (III) can be obtained from the law of conservation of charge of capacitors.

[0069] Formula (3) Where D is the duty cycle of the converter. The current of the first capacitor C1 during the first operating period, The current of the second capacitor C2 during the first operating period, For the current of the first capacitor C1 during the second operation, This represents the current in the second capacitor C2 during the second operating period.

[0070] Based on formulas (I), (II), and (III) above, the current of the first inductor L1 can be obtained. The current in the second inductor The sum of the current in the first inductor L1 and the current in the second inductor L2 .

[0071] Optionally, in buck mode, since the sum of the current in the first inductor L1 and the current in the second inductor L2... Inductor current smaller than that of traditional buck converter topologies The flying capacitor introduces a parallel capacitor current path, which, while ensuring a reduction in DC current loss of the inductor, allows for the use of a smaller inductor, effectively improving power density.

[0072] In the buck mode of a traditional bidirectional converter, discrete input current at the input terminal and parasitic inductance of the PCB wiring can cause voltage ringing and generate severe electromagnetic interference, affecting the normal operation of other electronic devices. This invention solves the problem of discontinuous input current in buck mode by utilizing a first inductor directly connected to the high-voltage side of the power supply.

[0073] Optionally, in boost mode, the power is transferred from the low-voltage side of the power supply to the high-voltage side, and the operation can be divided into two cycles depending on the state of each switch.

[0074] Figure 7 A circuit diagram in boost mode is provided for an embodiment of this application, as shown below. Figure 7 As shown, during the first working period, i.e. Figure 7 During Φ1, the control module H can control the second field-effect transistor S2, the fourth field-effect transistor S4, and the fifth field-effect transistor S5 to be in the on state, and control the first field-effect transistor S1 and the third field-effect transistor S3 to be in the off state.

[0075] exist Figure 7In this circuit, a portion of the input current output from the low-voltage side VL of the power supply charges the second capacitor C2 and the second inductor L2, wherein the charging voltage of the second inductor L2 is V. L The other portion is released through the first capacitor C1 to charge the first inductor L1, and the charging voltage of the first inductor L1 is V. L +V C1 -V H At the same time, these two parts of the current flow into the high-voltage side VH of the power supply.

[0076] Figure 8 Another circuit diagram in boost mode provided for embodiments of this application, as shown below. Figure 8 As shown, during the second working period, i.e. Figure 8 During the Φ2 period, the control module H can control the second field-effect transistor S2, the fourth field-effect transistor S4 and the fifth field-effect transistor S5 to be in the off state, and control the first field-effect transistor S1 and the third field-effect transistor S3 to be in the on state.

[0077] The input current from the low-voltage side VL of the power supply flows through a series path consisting of the second inductor L2 and the second capacitor C2 to the first capacitor C1 and the first inductor L1. Part of the current in the series path charges the first capacitor C1, and the other part discharges through the first inductor L1 to the high-voltage side VH of the power supply. The discharge voltage through the first inductor L1 is V. H -V C1 -V L .

[0078] In the boost mode of a traditional bidirectional converter, the output current is discontinuous because there is no inductor directly connected to the high-voltage side output terminal. To stabilize the output current, an additional large-capacity capacitor needs to be added to the high-voltage side, which not only increases the size and cost of the capacitor but also increases the size and cost of the entire system. Therefore, in this application, the problem of discontinuous output current in boost mode is solved by using a first inductor L1 directly connected to the high-voltage side of the power supply.

[0079] Optionally, the converter's step-down ratio is (1-D) / (2-D). 2 The boost ratio of the converter is (2-D). 2 ) / (1-D), where D is the duty cycle of the converter.

[0080] The following is the reasoning process for the pressure drop ratio and pressure boost ratio: Based on the principle of inductor volt-second balance, the following formula (IV) can be obtained.

[0081] Formula (IV) in, This is the voltage on the high-voltage side of the power supply. Where is the voltage on the low-voltage side of the power supply, and D is the duty cycle of the converter. Let V be the node on the circuit. SW2 The voltage of Φ2 during the second operating period, where, .

[0082] Then, we can obtain the result using formula (iv). ; .

[0083] The buck ratio described in this application can achieve a buck ratio of 0 to 0.5, allowing the converter to stably control the output voltage at half or even lower than the input voltage when the input voltage is high. The boost ratio, greater than 2, allows the converter to boost the output voltage to a level far exceeding the input voltage even when the input voltage is low. Therefore, based on the buck and boost ratios described in this application, the converter's operating duty cycle range can be widened, giving the converter an ultra-wide voltage gain adjustment capability. This enables it to efficiently and stably complete voltage matching tasks with a single-stage structure in scenarios with drastic input voltage fluctuations or variable output demands, thereby improving system integration, reliability, and energy efficiency. This also solves the problem that the limited voltage gain of traditional bidirectional converters results in an operating duty cycle of 0.25 / 0.75 during bidirectional conversion, restricting their operating range.

[0084] This application takes into account the mainstream lead-acid and lithium batteries, and can perform bidirectional conversion within a high-voltage side conversion range of 34.5~60V and a low-voltage side conversion range of 11.1~14.4V. While ensuring coverage of the entire conversion range, it can guarantee high efficiency and power density.

[0085] Optionally, the voltage stress of the first field-effect transistor S1 is The voltage stress of the second field-effect transistor S2 is The voltage stress of the third field-effect transistor S3 is The voltage stress of the fourth field-effect transistor S4 is Where D is the duty cycle of the converter. This is the voltage on the high-voltage side of the power supply.

[0086] During the first operating period of the converter, the voltage stress on the first field-effect transistor S1 is V. SW1 - V L = V C1 =(2-D)*V H / (2-D 2 The voltage stress on the third field-effect transistor S3 is V. L =(1-D)*V H / (2-D 2 ).

[0087] During the second operating period of the converter, the voltage stress on the second field-effect transistor S2 is V. C1 - V L = V H / (2-D 2 The voltage stress on the fourth field-effect transistor S4 is V. L =[(1-D)* VH / (2-D 2 The voltage stress on the fifth field-effect transistor S5 is V. X =V H / (2-D 2 ).

[0088] The voltage stress of each traditional switch is V H Therefore, through the effect of capacitive voltage division in this application, the voltage stress of each switch is effectively reduced compared to the voltage stress of conventional switches.

[0089] Table 1 below shows the voltage stress and current conditions of the switch and capacitor in buck mode provided in the embodiments of this application.

[0090] Table 1

[0091] Figure 9 This is a working waveform diagram provided for an embodiment of this application. Figure 10 This application provides a curve showing the relationship between the conversion ratio and D in buck mode. Figure 11 This application provides a conversion ratio and D relationship curve in boost mode, which is an embodiment of the present application.

[0092] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and devices described above can be referred to the corresponding processes in the method embodiments, and will not be repeated here. In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed mutual coupling or direct coupling or communication connection can be through some communication interfaces; the indirect coupling or communication connection of devices or modules can be electrical, mechanical, or other forms.

[0093] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. If the functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0094] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A DC-DC bidirectional converter, characterized in that, include: The power supply includes a high-voltage side, a low-voltage side, a first inductor, a second inductor, a first low-voltage switch module, a second low-voltage switch module, a high-voltage switch module, a flying capacitor module, and a control module. One end of the first inductor is connected to the high-voltage side of the power supply, and the other end of the first inductor is connected to the first end of the flying capacitor module and the first end of the high-voltage switch module, respectively. The second terminal of the flying capacitor module is connected to the first terminal of the first low-voltage switch module, the third terminal of the flying capacitor module is connected to the second terminal of the high-voltage switch module and the first terminal of the second low-voltage switch module, and the fourth terminal of the flying capacitor module is connected to one terminal of the second inductor and the second terminal of the first low-voltage switch module. The third terminal of the first low-voltage switch module is connected to the other end of the second inductor, the second terminal of the second low-voltage switch module, and the positive terminal of the low-voltage side of the power supply, respectively. The fourth terminal of the first low-voltage switch module and the negative terminal of the high-voltage side of the power supply are connected to the negative terminal of the low-voltage side of the power supply, respectively. The first low-voltage switch module, the second low-voltage switch module, and the high-voltage switch module each include at least one switch, and the third terminal of each switch is connected to the control module. The control module is used to control the on / off state of each switch so that the converter operates during a first working period or a second working period, and performs bidirectional current conversion during both the first working period and the second working period. The flying capacitor module is used to divide the voltage during the first and second operating periods of the converter.

2. The DC-DC bidirectional converter according to claim 1, characterized in that, The flying capacitor module includes: a first capacitor and a second capacitor; One end of the first capacitor is connected to the other end of the first inductor and the first end of the high-voltage switch module, and the other end of the first capacitor is connected to the first end of the first low-voltage switch module. One end of the second capacitor is connected to the second terminal of the high-voltage switch module and the first terminal of the second low-voltage switch module, respectively, and the other end of the second capacitor is connected to the second terminal of the first low-voltage switch module and one end of the second inductor, respectively. The first capacitor and the second capacitor together form an additional parallel current path.

3. The DC-DC bidirectional converter according to claim 1, characterized in that, The high-voltage switch module includes: a first field-effect transistor; The first end of the first field-effect transistor is connected to the other end of the first inductor, the second end of the first field-effect transistor is connected to the first end of the second low-voltage switching module and the third end of the flying capacitor module, and the third end of the first field-effect transistor is connected to the control module.

4. The DC-DC bidirectional converter according to claim 1, characterized in that, The second low-voltage switching module includes: a second field-effect transistor; The first end of the second field-effect transistor is connected to the second end of the high-voltage switch module and the third end of the flying capacitor module, the second end of the second field-effect transistor is connected to the other end of the second inductor and the positive terminal of the low-voltage side of the power supply, and the third end of the second field-effect transistor is connected to the control module.

5. The DC-DC bidirectional converter according to claim 1, characterized in that, The first low-voltage switching module includes: a third field-effect transistor, a fourth field-effect transistor, and a fifth field-effect transistor; The first terminal of the third field-effect transistor is connected to the second terminal of the flying capacitor module and the first terminal of the fourth field-effect transistor, respectively. The second terminal of the third field-effect transistor is connected to the negative terminal of the high-voltage side of the power supply and the negative terminal of the low-voltage side of the power supply, respectively. The second terminal of the fourth field-effect transistor is connected to the other terminal of the second inductor and the second terminal of the second low-voltage switching module, respectively. The first terminal of the fifth field-effect transistor is connected to one terminal of the second inductor and the fourth terminal of the flying capacitor module, respectively; the second terminal of the fifth field-effect transistor is connected to the negative terminal of the high-voltage side of the power supply and the negative terminal of the low-voltage side of the power supply, respectively. The third terminal of the third field-effect transistor, the third terminal of the fourth field-effect transistor, and the third terminal of the fifth field-effect transistor are respectively connected to the control module.

6. The DC-DC bidirectional converter according to any one of claims 1-5, characterized in that, In buck mode, the sum of the current in the first inductor and the current in the second inductor is (2-D)*IOUT / (2-D 2 ), where D is the operating duty cycle of the converter, and IOUT is the current received by the low-voltage side of the power supply.

7. The DC-DC bidirectional converter according to any one of claims 1-5, characterized in that, The step-down ratio of the converter is (1-D) / (2-D) 2 ).

8. The DC-DC bidirectional converter according to any one of claims 1-5, characterized in that, The boost ratio of the converter is (2-D) 2 ) / (1-D), where D is the duty cycle of the converter.

9. The DC-DC bidirectional converter according to any one of claims 1-5, characterized in that, The voltage stress of the first field-effect transistor is The voltage stress of the second field-effect transistor is The voltage stress of the third field-effect transistor is The voltage stress of the fourth field-effect transistor is Where D is the duty cycle of the converter. This is the voltage on the high-voltage side of the power supply.

10. A vehicle-mounted power supply system, characterized in that, Includes the DC-DC bidirectional converter according to any one of claims 1-9.

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