Power conversion device

Abstract

The invention provides a power conversion device which comprises a first bridge type unit, a transformer, a second bridge type unit and a first capacitor which are in cascade connection, and further comprises an LC filtering unit which is connected between a center tap of the transformer and the second end of a third switch bridge arm and the second end of a fourth switch bridge arm in the second bridge type unit. The two ends of the second capacitor are used for being connected with a low-voltage direct current end, the controller is used for outputting switch control signals for controlling switch tubes in the first bridge type unit and the second bridge type unit, and an external phase shift angle is formed between the switch tubes working correspondingly in the first bridge type unit and the second bridge type unit. And an inner phase shift angle is formed between the pair tubes in the second bridge type unit.

Description

Technical Field

[0001] This application relates to the field of power supplies, and in particular to a power conversion device. Background Technology

[0002] With the development of science and technology and society, new energy vehicles have been widely used and their proportion is increasing.

[0003] The on-board DC-DC converter in electric vehicles is usually a bidirectional converter, which can convert the energy of the high-voltage battery of the electric vehicle into the energy of the low-voltage battery to power the load in the new energy vehicle, and can also convert the low voltage on the low-voltage battery into the high voltage on the high-voltage battery.

[0004] With the development of power supply technology, higher performance requirements have been placed on DC-DC converters, especially the implementation of soft switching over a wide voltage range to achieve high efficiency and high power density.

[0005] In existing technologies, traditional DAB converters struggle to maintain primary-secondary voltage matching across a wide output voltage range, leading to the loss of soft-switching characteristics and decreased efficiency. While combining traditional DAB converters with BUCK converters can address these issues, it results in more complex topologies and control systems, along with lower efficiency and reliability. Summary of the Invention

[0006] According to one embodiment, this application provides a power conversion device, including: a first bridge unit, including a first bridge arm and a second switching bridge arm connected in parallel; a transformer, the two ends of the primary winding are respectively connected to the common node of the first bridge arm and the common node of the second switching bridge arm, and the second end of the first secondary winding is connected to the first end of the second secondary winding to form the center tap of the transformer; a second bridge unit, including a third switching bridge arm and a fourth switching bridge arm connected in parallel, the first end of the first secondary winding is connected to the common node of the third switching bridge arm, and the second end of the second secondary winding is connected to the common node of the fourth switching bridge arm; a first capacitor, connected to... Between the first and second ends of the third and fourth switch bridge arms; an LC filter unit, including a filter inductor and a second capacitor connected in series, is connected between the center tap and the second ends of the third and fourth switch bridge arms, and the two ends of the second capacitor are used to connect to the low-voltage DC terminal; a controller is used to output switching control signals to control the switching transistors in the first and second bridge units, wherein there is an outward phase shift angle between the corresponding switching transistors in the first and second bridge units, and an inward phase shift angle between the transistor pairs in the second bridge unit.

[0007] Furthermore, the voltage between the common node of the third switch bridge arm and the common node of the fourth switch bridge arm has the outward phase shift angle relative to the voltage between the common node of the first bridge arm and the common node of the second switch bridge arm; during a first time period within the outward phase shift angle, the voltage between the common node of the third switch bridge arm and the common node of the fourth switch bridge arm is zero, and the voltage between the center tap and the ground terminal is also zero, the first time period being the inward phase shift angle period.

[0008] Furthermore, the switching transistor in the first bridge unit is ahead of the corresponding operating transistor in the second bridge unit by the outward phase angle.

[0009] Furthermore, the switching transistor in the first bridge unit lags behind the corresponding operating transistor in the second bridge unit by the outward phase shift angle.

[0010] Furthermore, the controller controls the power conversion device to operate in a fixed-frequency mode, and the duty cycle of the switching transistor in the first bridge unit is approximately 50%.

[0011] Furthermore, the controller receives a first current signal flowing to the low-voltage DC terminal and controls the outer phase shift angle based on the first current signal; the controller receives a first voltage sampling signal on the first capacitor and a second voltage sampling signal on the second capacitor and controls the inner phase shift angle based on the first voltage sampling signal and the second voltage sampling signal.

[0012] Furthermore, the controller controls the outward phase angle by controlling the difference between the turn-off time and the turn-on time of the corresponding switch in the second bridge unit and the corresponding switch in the first bridge unit.

[0013] Furthermore, the controller controls the inner phase shift angle by controlling the duty cycle of the switching transistors within the second bridge unit.

[0014] Furthermore, the first bridge unit is a full-bridge unit, and the first bridge arm is a switching bridge arm, including a first and a second switch connected in series. The second switching bridge arm includes a third and a fourth switch connected in series. The first and fourth switches are paired and conduct synchronously. The second and third switches are paired and conduct synchronously. The first and second switches are complementary in conduction. The third and fourth switches are complementary in conduction. The third switching bridge arm includes a fifth and a sixth switch connected in series, and the fourth switching bridge arm includes a seventh and an eighth switch connected in series. The fifth and sixth switches are complementary in conduction. The seventh and eighth switches are complementary in conduction. The first and fourth switches are paired with the fifth and eighth switches. The switching transistors are corresponding to the switching transistors that operate in the same manner. The eighth switching transistor has an outward phase shift angle between its turn-off time and that of the first and fourth switching transistors. The fifth switching transistor has an outward phase shift angle between its turn-on time and that of the first and fourth switching transistors. The fifth switching transistor has an inward phase shift angle between its turn-on time and that of the eighth switching transistor. The second and third switching transistors are corresponding to the sixth and seventh switching transistors that operate in the same manner. The seventh switching transistor has an outward phase shift angle between its turn-on time and that of the second and third switching transistors. The sixth switching transistor has an outward phase shift angle between its turn-off time and that of the seventh switching transistor. The sixth switching transistor has an inward phase shift angle between its turn-on time and that of the seventh switching transistor.

[0015] Furthermore, the first bridge unit is a half-bridge unit. The first bridge arm includes a first bridge arm capacitor and a second bridge arm capacitor connected in series. The second switching bridge arm includes a third switch and a fourth switch connected in series; the third switch and the fourth switch are complementary in conduction. The third switching bridge arm includes a fifth switch and a sixth switch connected in series. The fourth switching bridge arm includes a seventh switch and an eighth switch connected in series; the fifth switch and the sixth switch are complementary in conduction. The seventh switch and the eighth switch are complementary in conduction. The fourth switch is a switch that works corresponding to the fifth switch and the eighth switch. The eighth switch and... The fourth switch has an outward phase angle between its turn-off time and the turn-on time of the fifth switch, and both the turn-on and turn-off times of the fifth switch and the eighth switch have an inward phase angle; the third switch is a switch that works in conjunction with the sixth and seventh switches, and both the turn-on and turn-off times of the seventh switch and the third switch have an outward phase angle between their turn-on times and the turn-off times of the sixth switch and the seventh switch have an inward phase angle.

[0016] The features and technical advantages of this disclosure have been outlined quite extensively above to facilitate a better understanding of the detailed description that follows. Additional features and advantages of this disclosure, which form the subject matter of the claims, will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as the basis for modifying or designing other structures or processes for achieving the same purpose as this disclosure. Those skilled in the art will also recognize that such equivalent structures do not depart from the spirit and scope of this disclosure as set forth in the appended claims. Attached Figure Description

[0017] To gain a more complete understanding of this disclosure and its advantages, the following description is given in conjunction with the accompanying drawings, wherein: Figure 1 A schematic diagram of a power conversion device according to an embodiment of this application is shown; Figure 2 A schematic diagram of a power conversion device according to a specific embodiment of this application is shown; Figure 3 A specific embodiment of this application is shown. Figure 2 A schematic diagram of the control waveforms of the power conversion device in the diagram; Figure 4 An embodiment of this application is shown. Figure 2 A schematic diagram of the first operating mode of the power conversion device in the diagram; Figure 5 An embodiment of this application is shown. Figure 2 A schematic diagram of the second operating mode of the power conversion device in the diagram; Figure 6 An embodiment of this application is shown. Figure 2 A schematic diagram of the third operating mode of the power conversion device in the diagram; Figure 7 An embodiment of this application is shown. Figure 2 A schematic diagram of the fourth operating mode of the power conversion device in the diagram; Figure 8 An embodiment of this application is shown. Figure 2 A schematic diagram of the fifth operating mode of the power conversion device in the diagram; Figure 9 An embodiment of this application is shown. Figure 2 A schematic diagram of the sixth operating mode of the power conversion device in the diagram; Figure 10 A schematic diagram of a power conversion device according to another specific embodiment of this application is shown.

[0018] Unless otherwise stated, corresponding numbers and symbols in the various figures generally refer to corresponding parts. These figures are drawn to clearly illustrate relevant aspects of the various embodiments and are not necessarily drawn to scale. Detailed Implementation

[0019] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] One embodiment of this application provides a power conversion device; please refer to [link to relevant documentation]. Figure 1 The schematic diagram shown is of a power conversion device according to an embodiment of this application. The power conversion device proposed in this application includes: The first bridge unit 110 includes a first bridge arm and a second switch bridge arm connected in parallel. The primary winding of transformer T is connected to the common node A of the first bridge arm and the common node B of the second switch bridge arm. The second end d12 of the first secondary winding is connected to the first end d21 of the second secondary winding to form the center tap E of transformer T. The second bridge unit 120 includes a third switch bridge arm and a fourth switch bridge arm connected in parallel. The first end of the first secondary winding is connected to the common node C of the third switch bridge arm, and the second end of the second secondary winding is connected to the common node D of the fourth switch bridge arm. The first capacitor C1 is connected between the first end and the second end N of the third and fourth switch arms; The LC filter unit includes a filter inductor L1 and a second capacitor C2 connected in series, which are connected between the center tap E and the second end N of the third and fourth switch arms. The two ends of the second capacitor C2 are used to connect to the low-voltage DC terminal V_L. The controller 200 is used to output switching control signals to control the switching transistors in the first bridge unit 110 and the second bridge unit 120, wherein there is an outward phase shift angle θ1 between the corresponding switching transistors in the first bridge unit 110 and the second bridge unit 120, and there is an inward phase shift angle θ2 between the transistors in the second bridge unit 120.

[0021] like Figure 1 As shown, the power conversion device also includes a resonant inductor Lr and a magnetizing inductor Lm. The magnetizing inductor Lm is connected in parallel with the primary winding of the transformer T, and the resonant inductor Lr is connected between the primary winding of the transformer T and the first bridge unit 110. In actual implementation, the resonant inductor Lr and the magnetizing inductor Lm can be independent inductors or inductors integrated into the transformer T.

[0022] Please refer to the following: Figure 1 The first bridge unit 110 has two ends used to connect to the high-voltage DC terminal V_H. For electric vehicles, the high-voltage DC terminal V_H can be used to connect to the high-voltage battery inside the electric vehicle, and the low-voltage DC terminal V_L can be used to connect to the low-voltage battery inside the electric vehicle. With the development of new energy vehicles, the voltage ranges of both the high-voltage DC terminal V_H and the low-voltage DC terminal V_L are relatively wide.

[0023] As can be seen from the above, the second bridge unit 120 is a full-bridge switching unit. Please refer to [link / reference]. Figure 1 The third switch bridge arm includes a fifth switch S5 and a sixth switch S6 connected in series, and the fourth switch bridge arm includes a seventh switch S7 and an eighth switch S8 connected in series. The fifth switch S5 and the eighth switch S8 form a pair, and the sixth switch S6 and the seventh switch S7 form a pair.

[0024] In practical applications, the first bridge unit 110 can be either a full-bridge switching unit or a half-bridge switching unit. The following explanation uses the example of the first bridge unit 110 being a full-bridge switching unit to illustrate its principle. Please refer to [link / reference]. Figure 2The schematic diagram of a power conversion device according to a specific embodiment of this application shows that the first bridge unit 110 is a full-bridge switching unit, and the first bridge arm is also a switching bridge arm, including a first switch S1 and a second switch S2 connected in series. The second switching bridge arm includes a third switch S3 and a fourth switch S4 connected in series. According to the working principle of the bridge circuit, the first switch S1 and the fourth switch S4 are switches that work corresponding to the fifth switch S5 and the eighth switch S8, and the second switch S2 and the third switch S3 are switches that work corresponding to the sixth switch S6 and the seventh switch S7. In a conventional full-bridge converter or DAB converter, the first switch S1 and the fourth switch S4 are synchronously turned on and off with the fifth switch S5 and the eighth switch S8, and the second switch S2 and the third switch S3 are synchronously turned on and off with the sixth switch S6 and the seventh switch S7.

[0025] For the purposes of this application, please refer to the following: Figure 3 The specific embodiment of this application shown Figure 2 The control waveform diagram of the power conversion device is shown below. Specifically, in the first bridge unit 110, the first switch S1 and the fourth switch S4 are a pair of switches, conducting synchronously; the second switch S2 and the third switch S3 are a pair of switches, conducting synchronously; the first switch S1 and the second switch S2 are complementary in conduction (with a dead time); the third switch S3 and the fourth switch S4 are complementary in conduction (with a dead time). In the second bridge unit 120, the fifth switch S5 and the sixth switch S6 are complementary in conduction (with a dead time), and the seventh switch S7 and the eighth switch S8 are complementary in conduction (with a dead time).

[0026] Please refer to the following: Figure 3Furthermore, the switching transistors in the first bridge unit 110 and the second bridge unit 120 that operate correspondingly have an outward phase shift angle θ1, and the transistors in the second bridge unit 120 have an inward phase shift angle θ2. Specifically, the eighth switch S8 has an outward phase shift angle θ1 between its turn-off time and that of the first switch S1 and the fourth switch S4; the fifth switch S5 has an outward phase shift angle θ1 between its turn-on time and that of the first switch S1 and the fourth switch S4; the fifth switch S5 has an inward phase shift angle θ2 between its turn-on time and that of the eighth switch S8; the seventh switch S7 has an outward phase shift angle θ1 between its turn-on time and that of the second switch S2 and the third switch S3; the sixth switch S6 has an outward phase shift angle θ1 between its turn-off time and that of the second switch S2 and the third switch S3; and the sixth switch S6 has an inward phase shift angle between its turn-on time and that of the seventh switch S7. θ2.

[0027] Please refer to the following: Figure 3 This results in the voltage UCD between the common node C of the third switch arm and the common node D of the fourth switch arm having an outward phase shift angle θ1 relative to the voltage UAB between the common node A of the first switch arm and the common node B of the second switch arm. During the first time period within the outward phase shift angle θ1, the voltage UCD between the common node C of the third switch arm and the common node D of the fourth switch arm is zero, and the voltage UEN between the center tap E and the second terminal N of the third and fourth switch arms is also zero. The first time period is the period of the inward phase shift angle θ2.

[0028] from Figure 3 and combined Figure 2 It can be seen that by controlling the outer phase shift angle θ1, the phase shift angle of voltage UCD relative to voltage UAB is controlled. Furthermore, by controlling the inner phase shift angle θ2, the time when the voltage in voltage UCD is zero is controlled, thus realizing the control of the voltage across the first capacitor C1, and controlling voltage UEN, thereby controlling the voltage of the low-voltage DC terminal V_L of the power conversion device. In this way, the voltage of the high-voltage DC terminal V_H and the voltage across the first capacitor C1 are adjusted to match the two, thereby realizing soft switching in the full range and improving the efficiency of the power conversion device.

[0029] Specifically, in combination Figure 4 An embodiment of this application is shown. Figure 2 The diagram shows the first operating mode of the power conversion device in the diagram. Please refer to the diagram for reference. Figure 3During the time interval t0 to t1, the controller 200 controls the first switch S1 and the fourth switch S4 to turn on, and controls the corresponding fifth switch S5 and eighth switch S8 to turn on, while the other switches are turned off. At this time, both voltage UAB and voltage UCD are at a high level, and therefore voltage UEN is also at a high level.

[0030] See also Figure 3 At time t1, the controller 200 controls the first switch S1 and the fourth switch S4 in the first bridge unit 110 to turn off, and switches the second switch S2 and the third switch S3 to turn on (with a certain dead time). However, it still controls the fifth switch S5 and the eighth switch S8, which work corresponding to the first switch S1 and the fourth switch S4, to remain on until time t3, when it controls the eighth switch S8 to turn off (the seventh switch S7 turns on). The time between time t1 and time t3 is called the period of the outer phase shift angle θ1. At time t2, between time t1 and time t3, it controls the fifth switch S5 to turn off (the sixth switch S6 turns on). That is, the turn-off time of the fifth switch S5 and the turn-off time of the eighth switch S8 have a phase shift, which is the inner phase shift angle θ2.

[0031] Specifically, in combination Figure 5 An embodiment of this application is shown. Figure 2 The diagram illustrates the second operating mode of the power conversion device. During the time interval t1 to t2, the controller 200 controls the second switch S2 and the third switch S3 to conduct, and controls the fifth switch S5 and the eighth switch S8 to remain conducting, while the other switches are turned off. At this time, voltage UAB has switched to a negative voltage, voltage UCD remains at a high level, and therefore voltage UEN is also at a high level.

[0032] Specifically, in combination Figure 6 An embodiment of this application is shown. Figure 2 The diagram illustrates the third operating mode of the power conversion device. During the time interval t2 to t3, the controller 200 controls the second switch S2 and the third switch S3 to conduct, and controls the sixth switch S6 and the eighth switch S8 to remain conducting, while the other switches are turned off. At this time, the voltage UAB remains negative. Because the common node C of the third switch bridge arm and the common node D of the fourth switch bridge arm are switched to zero level by the short-circuit voltage UCD, the voltage UEN is also zero.

[0033] Specifically, in combination Figure 7 An embodiment of this application is shown. Figure 2 The diagram shows the fourth operating mode of the power conversion device in the diagram. Please refer to the diagram for reference. Figure 3During the time interval t3 to t4, the controller 200 keeps the second switch S2 and the third switch S3 on, and keeps the corresponding sixth switch S6 and seventh switch S7 on, while turning off the other switches. At this time, both voltage UAB and voltage UCD are negative, so voltage UEN is rectified to a positive level.

[0034] Please combine Figure 3 At time t4, the controller 200 controls the second switch S2 and the third switch S3 in the first bridge unit 110 to turn off, switching the first switch S1 and the fourth switch S4 to turn on. However, it still controls the sixth switch S6 and the seventh switch S7, which work in accordance with the second switch S2 and the third switch S3, to remain on until time t6, when the sixth switch S6 is controlled to turn off (the fifth switch S5 turns on). The time between time t4 and time t6 is called the period of the outer phase shift angle θ1. At time t5, between time t4 and time t6, the seventh switch S7 is controlled to turn off (the eighth switch S8 turns on). This means that the turn-off time of the sixth switch S6 and the turn-off time of the seventh switch S7 have a phase shift, which is the inner phase shift angle θ2.

[0035] Specifically, in combination Figure 8 An embodiment of this application is shown. Figure 2 The diagram illustrates the fifth operating mode of the power conversion device. During the time interval t4 to t5, the controller 200 controls the first switch S1 and the fourth switch S4 to conduct, and controls the sixth switch S6 and the seventh switch S7 to remain conducting, while the other switches are turned off. At this time, voltage UAB has switched to a positive voltage, while voltage UCD remains at a low level, and voltage UEN is rectified to a high level.

[0036] Specifically, in combination Figure 9 An embodiment of this application is shown. Figure 2 The diagram illustrates the sixth operating mode of the power conversion device. During the time interval t5 to t6, the controller 200 controls the first switch S1 and the fourth switch S4 to conduct, and controls the sixth switch S6 and the eighth switch S8 to conduct, while the other switches are turned off. At this time, the voltage UAB remains positive. Because the common node C of the third switch arm and the common node D of the fourth switch arm are switched to zero level by the short-circuit voltage UCD, the voltage UEN is also zero.

[0037] It enters the same working mode as at time t0 at time t6, which will not be elaborated here.

[0038] It can be seen that by controlling the time from t1 to t3 and the time from t4 to t6, that is, by controlling the external phase shift angle θ1, the time when the voltage UCD switches to negative or positive following the voltage UAB can be controlled, thereby controlling the magnitude of the voltage UCD.

[0039] It can be seen that by controlling the time from t2 to t3 and the time from t5 to t6, that is, by controlling the inner phase shift angle θ2, the common node C of the third switch bridge arm and the common node D of the fourth switch bridge arm can be short-circuited, that is, the voltage UCD and voltage UEN are at zero level for the time, thereby controlling the voltage across the first capacitor C1 and the voltage of the low-voltage DC terminal V_L of the power conversion device.

[0040] In practical applications, the first bridge unit 110 is also a half-bridge switching unit, as can be found in [reference needed]. Figure 10 The schematic diagram of a power conversion device according to another specific embodiment of this application shows that the first bridge unit 110 is a half-bridge unit. The first bridge arm includes a first bridge arm capacitor C11 and a second bridge arm capacitor C12 connected in series. The second switching bridge arm includes a third switch S3 and a fourth switch S4 connected in series; the third switch S3 and the fourth switch S4 are complementary in conduction. The third switching bridge arm includes a fifth switch S5 and a sixth switch S6 connected in series. The fourth switching bridge arm includes a seventh switch S7 and an eighth switch S8 connected in series; the fifth switch S5 and the sixth switch S6 are complementary in conduction; the seventh switch S7 and the eighth switch S8 are complementary in conduction. The fourth switch S4 is a switch that works corresponding to the fifth switch S5 and the eighth switch S8. The eighth switch S8 and the fourth switch S4 have an outward phase shift angle θ1 between their turn-off times; the fifth switch S5 and the fourth switch S4 have an outward phase shift angle θ1 between their turn-on times; and the fifth switch S5 and the eighth switch S8 both have an inward phase shift angle θ2 between their turn-on and turn-off times. The third switch S3 corresponds to the sixth switch S6 and the seventh switch S7. The seventh switch S7 and the third switch S3 have an outward phase shift angle θ1 between their turn-on times; the sixth switch S6 and the third switch S3 both have an outward phase shift angle θ1 between their turn-off times; and the sixth switch S6 and the seventh switch S7 both have an inward phase shift angle θ2 between their turn-on and turn-off times. Its principle is the same as that of the first bridge unit 110, which is a full-bridge switching unit, and will not be repeated here.

[0041] In practical applications, controlling the switching transistor in the first bridge unit 110 to lead the corresponding operating transistor in the second bridge unit 120 by the external phase shift angle θ1 (also referred to as the external phase shift angle θ1 being a positive value) allows energy to be transferred from the high-voltage DC terminal V_H to the low-voltage DC terminal V_L. Conversely, controlling the switching transistor in the first bridge unit 110 to lag the corresponding operating transistor in the second bridge unit 120 by the external phase shift angle θ1 (also referred to as the external phase shift angle θ1 being a negative value) allows energy to be transferred from the low-voltage DC terminal V_L to the high-voltage DC terminal V_H. Therefore, controlling the external phase shift angle θ1 can control the power flow direction of the power conversion device and can also control the voltage UCD between the common node C of the third switching bridge arm and the common node D of the fourth switching bridge arm.

[0042] Furthermore, the controller 200 controls the power conversion device to operate in a fixed-frequency mode, and the duty cycle of the switching transistor in the first bridge unit 110 is about 50%, so that the voltage UAB between the common node A of the first bridge arm and the common node B of the second switching bridge arm only has a high level and a low level, that is, the primary side is fully duty cycle controlled.

[0043] In one embodiment of this application, please refer to... Figure 2 The controller 200 receives a first current signal Io flowing to the low-voltage DC terminal V_L, and controls the outward phase angle θ1 based on the first current signal Io.

[0044] In one embodiment of this application, please refer to... Figure 2 The controller 200 receives a first voltage sampling signal U1 on the first capacitor C1 and a second voltage sampling signal UV_L on the second capacitor C2, and controls the inner phase shift angle θ2 based on the first voltage sampling signal U1 and the second voltage sampling signal UV_L.

[0045] More specifically, in one embodiment of this application, the controller 200 controls the external phase angle θ1 by controlling the difference between the turn-off time and the turn-on time of the corresponding working switch in the second bridge unit 120 and the corresponding working switch in the first bridge unit 110, so as to control the power flow direction and voltage UCD of the power conversion device.

[0046] More specifically, in one embodiment of this application, the controller 200 controls the inner phase shift angle θ2 by controlling the duty cycle of the switching transistors in the second bridge unit 120. Based on controlling the outer phase shift angle θ1 to control the power flow direction and voltage UCD of the power conversion device, the controller further controls the inner phase shift angle θ2 by controlling the duty cycle of the switching transistors in the second bridge unit 120 to control the voltage UCD and voltage UEN, achieving voltage matching between the high-voltage DC terminal V_H and the first capacitor C1, thus enabling soft switching across the entire range and improving the efficiency of the power conversion device.

[0047] Although embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the present disclosure as defined by the appended claims.

[0048] Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, apparatuses, methods, and steps described in the specification. As will be readily understood by those skilled in the art from the disclosure of this publication, processes, machines, manufactures, compositions of matter, means, methods, or steps that perform substantially the same function, currently exist or will be developed or implemented thereafter, will yield substantially the same results as the corresponding embodiments described herein that are available according to this disclosure. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, apparatuses, methods, or steps within their scope.

Claims

1. A bidirectional DC / DC converter, characterized in that, include: The first bridge unit includes a first bridge arm and a second switch bridge arm connected in parallel. The transformer has its primary winding connected to the common node of the first bridge arm and the common node of the second switch bridge arm, respectively. The second end of the first secondary winding is connected to the first end of the second secondary winding, forming the center tap of the transformer. The second bridge unit includes a third switch bridge arm and a fourth switch bridge arm connected in parallel. The first end of the first secondary winding is connected to the common node of the third switch bridge arm, and the second end of the second secondary winding is connected to the common node of the fourth switch bridge arm. The first capacitor is connected between the first and second ends of the third and fourth switch arms. The LC filter unit includes a filter inductor and a second capacitor connected in series, which are connected between the center tap and the second ends of the third and fourth switch arms. The two ends of the second capacitor are used to connect to the low-voltage DC terminal. The controller is used to output switching control signals to control the switching transistors in the first bridge unit and the second bridge unit, wherein there is an outward phase shift angle between the corresponding switching transistors in the first bridge unit and the second bridge unit, and there is an inward phase shift angle between the transistors in the second bridge unit.

2. The power conversion device according to claim 1, characterized in that, The voltage between the common node of the third switch bridge arm and the common node of the fourth switch bridge arm has the outward phase angle relative to the voltage between the common node of the first bridge arm and the common node of the second switch bridge arm; During the first time period within the outer phase shift period, the voltage between the common node of the third switch bridge arm and the common node of the fourth switch bridge arm is zero, and the voltage between the center tap and the ground terminal is also zero. The first time period is the inner phase shift period.

3. The power conversion device according to claim 2, characterized in that, In the first bridge unit, the corresponding switching transistor in the second bridge unit is ahead of the outward phase shift angle.

4. The power conversion device according to claim 2, characterized in that, The switching transistor in the first bridge unit lags behind the corresponding operating transistor in the second bridge unit by the outward phase shift angle.

5. The power conversion device according to claim 3 or 4, characterized in that, The controller controls the power conversion device to operate in a fixed-frequency mode, and the duty cycle of the switching transistor in the first bridge unit is about 50%.

6. The power conversion device according to claim 5, characterized in that, The controller receives a first current signal flowing to the low-voltage DC terminal and controls the outward phase shift angle based on the first current signal. The controller receives a first voltage sampling signal on the first capacitor and a second voltage sampling signal on the second capacitor, and controls the inner phase shift angle based on the first voltage sampling signal and the second voltage sampling signal.

7. The power conversion device according to claim 6, characterized in that, The controller controls the outward phase angle by controlling the difference between the turn-off time and the turn-on time of the corresponding switch in the second bridge unit and the corresponding switch in the first bridge unit.

8. The power conversion device according to claim 7, characterized in that, The controller controls the inner phase shift angle by controlling the duty cycle of the switching transistors in the second bridge unit.

9. The power conversion device according to claim 1 or 8, characterized in that, The first bridge unit is a full bridge unit, the first bridge arm is a switch bridge arm, including a first switch and a second switch connected in series, and the second switch bridge arm includes a third switch and a fourth switch connected in series. The first switch and the fourth switch are a pair and conduct synchronously. The second and third switching transistors are a pair and conduct synchronously. The first switch and the second switch are complementary in conduction; The third switch and the fourth switch are complementary in conduction; The third switch bridge arm includes a fifth switch and a sixth switch connected in series, and the fourth switch bridge arm includes a seventh switch and an eighth switch connected in series. The fifth switch and the sixth switch are complementary in conduction; The seventh switch and the eighth switch are complementary in conduction; The first switch and the fourth switch are switches that operate corresponding to the fifth switch and the eighth switch. The eighth switch has an outward phase shift angle between its turn-off time and that of the first and fourth switches. The fifth switch has an outward phase shift angle between its turn-on time and that of the first and fourth switches. The fifth switch has an inward phase shift angle between its turn-on time and that of the eighth switch. The second and third switches are switches that operate corresponding to the sixth and seventh switches. The seventh switch has an outward phase shift angle between its on-time and the turn-off times of the second and third switches. The sixth switch has an outward phase shift angle between its on-time and the turn-off times of the second and third switches. The sixth switch has an inward phase shift angle between its on-time and the turn-off times of the seventh switch.

10. The power conversion device according to claim 1 or 8, characterized in that, The first bridge unit is a half-bridge unit, the first bridge arm includes a first bridge arm capacitor and a second bridge arm capacitor connected in series, and the second switching bridge arm includes a third switching transistor and a fourth switching transistor connected in series. The third switch and the fourth switch are complementary in conduction; The third switch bridge arm includes a fifth switch and a sixth switch connected in series, and the fourth switch bridge arm includes a seventh switch and an eighth switch connected in series. The fifth switch and the sixth switch are complementary in conduction; The seventh switch and the eighth switch are complementary in conduction; The fourth switch is a switch that works in correspondence with the fifth and eighth switches. The turn-off time of the eighth switch and the fourth switch has the outer phase shift angle, the turn-on time of the fifth switch and the fourth switch has the outer phase shift angle, and the turn-on time of the fifth switch and the eighth switch both have the inner phase shift angle. The third switch is a switch that works in conjunction with the sixth and seventh switches. The seventh switch and the third switch have an outward phase shift angle between their on-time and off-time, and the sixth switch and the third switch have an outward phase shift angle between their off-time and off-time. The sixth switch and the seventh switch both have an inward phase shift angle between their on-time and off-time.

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