CN112751487A

CN112751487A - DC-DC power converter and method for DC-DC power converter

Info

Publication number: CN112751487A
Application number: CN201911052847.3A
Authority: CN
Inventors: 吴云; 是亚明
Original assignee: ABB Schweiz AG
Current assignee: ABB AS Norway
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2021-05-04

Abstract

Embodiments of the present disclosure relate to a DC-DC power converter and a method for a DC-DC power converter. The DC-DC power converter includes: a transformer comprising a primary side and a secondary side; an inverter unit coupled to a primary side of the transformer; a plurality of rectifying units respectively coupled to the secondary sides of the transformers, each rectifying unit including a first output terminal and a second output terminal; a switching unit coupled to first and second output terminals of the plurality of rectifying units and capable of switching between a first state in which the switching unit connects the plurality of rectifying units in series and a second state in which the switching unit connects the plurality of rectifying units in parallel; and a control unit coupled to the switching unit and configured to: placing the switching unit in a first state in response to the desired output voltage being higher than the threshold voltage; and placing the switching unit in a second state in response to the desired output voltage being below the threshold voltage.

Description

DC-DC power converter and method for DC-DC power converter

Technical Field

Embodiments of the present disclosure relate generally to the field of power conversion, and more particularly, to a DC-DC power converter and method for a DC-DC power converter.

Background

Direct current-to-direct current (DC-DC) power converters are used to convert a DC voltage of a certain level to a DC voltage of another level. The DC-DC power converter is widely applied to various fields, such as electric vehicles, office automation equipment, industrial instruments, military, aerospace and the like, and relates to various industries of national economy.

Conventional DC-DC power converters typically only provide a single level of output voltage and thus have a narrow output voltage range. For example, the DC-DC power converter in the conventional electric vehicle charging pile can only charge an electric vehicle having a specific charging voltage because it can only output a single level of voltage, and cannot simultaneously satisfy the requirement for charging electric vehicles having different charging voltages.

Disclosure of Invention

It is an object of the present disclosure to provide a DC-DC power converter and a method for a DC-DC power converter to at least partially solve the above-mentioned problems in the prior art.

According to a first aspect of the present disclosure, there is provided a DC-DC power converter comprising: a transformer comprising a primary side and a secondary side; an inverting unit coupled to a primary side of the transformer; a plurality of rectifying units respectively coupled to the secondary sides of the transformers, each of the plurality of rectifying units including a first output terminal and a second output terminal; a switching unit coupled to the first and second output terminals of the plurality of rectifying units and switchable between a first state in which the switching unit connects the plurality of rectifying units in series and a second state in which the switching unit connects the plurality of rectifying units in parallel; and a control unit coupled to the switching unit and configured to: placing the switching unit in the first state in response to the desired output voltage being higher than a threshold voltage; and placing the switching unit in the second state in response to the desired output voltage being below the threshold voltage.

In the embodiments according to the present disclosure, the connection state between the plurality of rectifying units can be changed by adjusting the state of the switching unit according to the magnitude of the desired output voltage. In this way, the DC-DC power converter can output voltages of different levels according to different requirements, has a wider output voltage range, and can meet the requirements of a wider range of applications.

In some embodiments, the plurality of rectifying units includes a first rectifying unit and a second rectifying unit, and wherein the switching unit includes: a first switch coupled between a second output terminal of the first rectifying unit and a first output terminal of the second rectifying unit; a second switch coupled between a second output terminal of the first rectifying unit and a second output terminal of the second rectifying unit; and a third switch coupled between the first output terminal of the first rectifying unit and the first output terminal of the second rectifying unit.

In some embodiments, with the switching unit in the first state, the first switch is closed and the second switch and the third switch are open, and with the switching unit in the second state, the first switch is open and the second switch and the third switch are closed.

In some embodiments, each of the plurality of rectifying units comprises a full bridge rectifying circuit.

In some embodiments, the full bridge rectifier circuit comprises diodes.

In some embodiments, the full bridge rectifier circuit comprises a controllable semiconductor device.

In some embodiments, the controllable semiconductor device comprises a MOSFET or an IGBT.

In some embodiments, each of the plurality of rectifying units further comprises an LLC resonant circuit.

In some embodiments, the inverter unit comprises a full bridge inverter circuit and an LLC resonant circuit, wherein the full bridge inverter circuit comprises controllable semiconductor devices.

According to a second aspect of the present disclosure, there is provided a method for a DC-DC power converter, the DC-DC power converter comprising: a transformer comprising a primary side and a secondary side; an inverting unit coupled to a primary side of the transformer; a plurality of rectifying units respectively coupled to the secondary sides of the transformers, each of the plurality of rectifying units including a first output terminal and a second output terminal; and a switching unit coupled to the first and second output terminals of the plurality of rectifying units, the method comprising: in response to the desired output voltage being above a threshold voltage, placing the switching unit in the first state such that the plurality of rectifying units are connected in series; and in response to the desired output voltage being below the threshold voltage, placing the switching unit in the second state such that the plurality of rectifying units are connected in parallel.

In some embodiments, placing the switching unit in the first state comprises: closing the first switch and opening the second switch and the third switch, and placing the switching unit in the second state comprises: opening the first switch and closing the second switch and the third switch.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the disclosure, nor is it intended to be used to limit the scope of the disclosure.

Drawings

The above and other objects, features and advantages of the embodiments of the present disclosure will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

FIG. 1 shows a block diagram of a DC-DC power converter according to one embodiment of the present disclosure;

FIG. 2 illustrates a circuit schematic of a DC-DC power converter according to one embodiment of the present disclosure;

fig. 3 shows a circuit schematic of a DC-DC power converter in which the switching unit is in a first state;

fig. 4 shows a circuit schematic of a DC-DC power converter in which the switching unit is in a second state; and

fig. 5 shows a block diagram of a DC-DC power converter according to another embodiment of the present disclosure.

Like or corresponding reference characters designate like or corresponding parts throughout the several views.

Detailed Description

Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The term "include" and variations thereof as used herein is meant to be inclusive in an open-ended manner, i.e., "including but not limited to". Unless specifically stated otherwise, the term "or" means "and/or". The term "based on" means "based at least in part on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first," "second," and the like may refer to different or the same object.

As described above, conventional DC-DC power converters can generally provide only a single level of output voltage, and thus have a narrow output voltage range. The DC-DC power converter of the embodiments of the present disclosure can realize a wider output voltage range by outputting voltages of different levels according to different needs. The principles of the present disclosure will be described in detail below in connection with exemplary embodiments with reference to the drawings.

Fig. 1 shows a block diagram of a DC-DC power converter 100 according to one embodiment of the present disclosure. As shown in fig. 1, a DC-DC power converter 100 described herein generally includes an inverter unit 1, a transformer 2, a first rectification unit 3, a second rectification unit 4, a switching unit 5, and a control unit 6.

The inverter unit 1 has an input terminal IN for receiving a dc input voltage. The inverter unit 1 is configured to convert a received dc input voltage into an ac voltage. The output of the inverter unit 1 is coupled to the primary side of the transformer 2. The transformer 2 voltage-converts the received alternating-current voltage and supplies the converted alternating-current voltage to the first rectifying unit 3 and the second rectifying unit 4, respectively.

The first rectifying unit 3 is coupled to the secondary side of the transformer 2 to receive the converted alternating voltage. The first rectifying unit 3 converts the received alternating-current voltage into a first direct-current voltage. The first rectifying unit 3 includes a first output terminal 31 and a second output terminal 32 for outputting a first direct-current voltage. Similarly, the second rectifying unit 4 is coupled to the secondary side of the transformer 2 to receive the converted alternating voltage. The second rectifying unit 4 converts the received alternating-current voltage into a second direct-current voltage. The second rectifying unit 4 includes a first output terminal 41 and a second output terminal 42 for outputting the second direct-current voltage.

The switching unit 5 is coupled to the first and

second output terminals

31 and 32 of the first rectifying unit 3 and the first and

second output terminals

41 and 42 of the second rectifying unit 4. The switching unit 5 is capable of switching between a first state and a second state. In the first state, the switching unit 5 connects the first rectifying unit 3 and the second rectifying unit 4 in series, and in the second state, the switching unit 5 connects the first rectifying unit 3 and the second rectifying unit 4 in parallel. The first output terminal 31 of the first rectifying unit 3 serves as a positive output terminal of the output terminal OUT of the DC-DC power converter 100. The second output terminal 42 of the second rectifying unit 4 serves as a negative output terminal of the output terminal OUT of the DC-DC power converter 100.

The control unit 6 is coupled to the switching unit 5 to control the state of the switching unit 5. In case the desired output voltage is higher than the threshold voltage, the control unit 6 places the switching unit 5 in the first state such that the first rectifying unit 3 is connected in series with the second rectifying unit 4, thereby enabling to output a high voltage and a low current via the output terminal OUT. In case the desired output voltage is lower than the threshold voltage, the control unit 6 places the switching unit 5 in the second state such that the first rectifying unit 3 is connected in parallel with the second rectifying unit 4, thereby enabling to output a low voltage and a high current via the output terminal OUT.

By adjusting the state of the switching unit 5 according to the magnitude of the desired output voltage, the connection state between the first rectifying unit 3 and the second rectifying unit 4 can be changed. In this way, the DC-DC power converter 100 can output voltages of different levels according to different needs, has a wider output voltage range, and can meet a wider range of application requirements.

Fig. 2 shows a circuit schematic of the DC-DC power converter 100 according to one embodiment of the present disclosure, fig. 3 shows a circuit schematic of the DC-DC power converter 100 with the switching unit 5 in a first state, and fig. 4 shows a circuit schematic of the DC-DC power converter 100 with the switching unit 5 in a second state. The display of the control unit 6 is omitted in fig. 2 to 4 in order not to unnecessarily obscure the details of these figures.

As shown in fig. 2, the transformer 2 comprises a primary side 21 and a secondary side 22. The primary side 21 and the secondary side 22 shown in fig. 2 each take the form of a parallel arrangement of a plurality of windings. It should be understood, however, that this is by way of example only and is illustrative of the principles of the present disclosure. In other embodiments, the transformer 2 may have various known or future available arrangements, such as a single winding for both the primary side 21 and the secondary side 22, or multiple windings in series or a combination of multiple windings in series and parallel, as the scope of the present disclosure is not limited in this respect.

In one embodiment, as shown in fig. 2, the inverter unit 1 includes a full bridge inverter circuit composed of MOSFETs M1, M2, M3, and M4. The MOSFETs M1 and M2 are connected IN series between two terminals of the input terminal IN. The MOSFETs M3 and M4 are connected IN series between two terminals of the input terminal IN. Furthermore, the inverter unit 1 also comprises an LLC resonant circuit. The LLC resonant circuit comprises a capacitor C0, an inductor L0, and another inductance (not shown). The LLC resonant circuit is a common structure in an inverter unit of a DC-DC power converter, and its specific operating principle will not be described in detail here. The node between the MOSFETs M1 and M2 is connected to the primary side 21. The node between the MOSFETs M3 and M4 is connected to the primary side 21 via a capacitor C0 and an inductor L0.

In some embodiments, the full-bridge inverter circuit may include other controllable semiconductor devices, such as IGBTs, and the scope of the present disclosure is not limited in this respect.

In one embodiment, as shown in fig. 2, the first rectifying unit 3 includes a full-bridge rectifying circuit composed of MOSFETs M5, M6, M7, and M8. The MOSFETs M5 and M6 are connected in series between the first output terminal 31 and the second output terminal 32. The MOSFETs M7 and M8 are connected in series between the first output terminal 31 and the second output terminal 32. Furthermore, the first rectifying unit 3 further includes an LLC resonant circuit. The LLC resonant circuit comprises a capacitor C1, an inductor L1, and another inductance (not shown). The LLC resonant circuit is a common structure in a rectifying unit of a DC-DC power converter, and its specific operating principle will not be described in detail here. The node between the MOSFETs M7 and M8 is connected to the secondary side 22. The node between the MOSFETs M5 and M6 is connected to the secondary side 22 via a capacitor C1 and an inductor L1. The first output terminal 31 of the first rectifying unit 3 serves as a positive output terminal of the output terminal OUT of the DC-DC power converter 100.

In one embodiment, as shown in fig. 2, the second rectifying unit 4 includes a full-bridge rectifying circuit composed of MOSFETs M9, M10, M11, and M12. The MOSFETs M9 and M10 are connected in series between the first output terminal 41 and the second output terminal 42. The MOSFETs M11 and M12 are connected in series between the first output terminal 41 and the second output terminal 42. The second rectifying unit 4 further includes an LLC resonant circuit. The LLC resonant circuit comprises a capacitor C2, an inductor L2, and another inductance (not shown). The node between the MOSFETs M11 and M12 is connected to the secondary side 22. The node between the MOSFETs M9 and M10 is connected to the secondary side 22 via a capacitor C2 and an inductor L2. The second output terminal 42 of the second rectifying unit 4 serves as a negative output terminal of the output terminal OUT of the DC-DC power converter 100.

In some embodiments, the full bridge rectifier circuits in the first and

second rectifier units

3, 4 may include other controllable semiconductor devices, such as IGBTs, and the scope of the present disclosure is not limited in this respect.

In one embodiment, as shown in fig. 2, the switching unit 5 includes a first switch S1, a second switch S2, and a third switch S3. The first switch S1 is coupled between the second output terminal 32 of the first rectifying unit 3 and the first output terminal 41 of the second rectifying unit 4. The second switch S2 is coupled between the second output terminal 32 of the first rectifying unit 3 and the second output terminal 42 of the second rectifying unit 4. The third switch S3 is coupled between the first output terminal 31 of the first rectifying unit 3 and the first output terminal 41 of the second rectifying unit 4. With the switching unit 5 in the first state, the first switch S1 is closed and the second switch S2 and the third switch S3 are opened, so that the first rectifying unit 3 and the second rectifying unit 4 are connected in series. A first state of the switching unit 5 is shown in fig. 3. In the case where the switching unit 5 is in the second state, the first switch S1 is opened and the second switch S2 and the third switch S3 are closed, so that the first rectifying unit 3 and the second rectifying unit 4 are connected in parallel. A second state of the switching unit 5 is shown in fig. 4.

The DC-DC power converter 100 shown in fig. 2 may operate bi-directionally. Specifically, IN some cases, the input terminal IN and the output terminal OUT may be interchanged, i.e., the output terminal OUT is used as the input of the DC-DC power converter 100 and the input terminal IN is used as the output of the DC-DC power converter 100. Accordingly, the secondary side 22 of the transformer 2 operates as the primary side at this time, the primary side 21 of the transformer 2 operates as the secondary side at this time, the first rectifying unit 3 and the second rectifying unit 4 operate as the inverter circuit at this time, and the inverter unit 1 operates as the rectifier circuit at this time.

In some embodiments, capacitors C1 and C2 and inductors L1 and L2 may be omitted. In such an embodiment, the first and

second rectifying units

3 and 4 convert the received alternating-current voltage into corresponding direct-current voltages only through the full-bridge rectifying circuit.

In some embodiments, the full-bridge rectifier circuits employed in the first and

second rectifier units

3 and 4 may also employ other architectures. For example, the first rectifying unit 3 and the second rectifying unit 4 may be respectively formed using diodes. In such embodiments, the capacitors C1 and C2 and the inductors L1 and L2 may also be omitted.

Fig. 5 shows a block diagram of a DC-DC power converter 100 according to another embodiment of the present disclosure. The DC-DC power converter 100 shown in fig. 5 has a similar structure to the DC-DC power converter 100 shown in fig. 1, except that the DC-DC power converter 100 shown in fig. 5 further includes an additional rectifying unit 7. Only the difference between the two will be described herein, and the same parts will not be described again.

As shown in fig. 5, an additional rectifying unit 7 is coupled to the secondary side of the transformer 2 to receive the converted alternating voltage. The additional rectifying unit 7 converts the received alternating voltage into a third direct voltage. The additional rectifying unit 7 includes a first output terminal 71 and a second output terminal 72 for outputting the third direct-current voltage. The first output terminal 31 of the first rectifying unit 3 serves as a positive output terminal of the output terminal OUT of the DC-DC power converter 100. The second output terminal 72 of the additional rectifying unit 7 serves as a negative output terminal of the output terminal OUT.

The switching unit 5 is coupled to the first output terminal 71 and the second output terminal 72 of the additional rectifying unit 7. In the case where the switching unit 5 is in the first state, the switching unit 5 can connect the first rectifying unit 3, the second rectifying unit 4, and the additional rectifying unit 7 in series, so that a high voltage and a low current can be output via the output terminal OUT. In the case where the switching unit 5 is in the second state, the switching unit 5 can connect the first rectifying unit 3, the second rectifying unit 4, and the additional rectifying unit 7 in parallel, so that a low voltage and a high current can be output via the output terminal OUT.

The state transition of the switching unit 5 may be controlled via the control unit 6. In case the desired output voltage is higher than the threshold voltage, the control unit 6 may place the switching unit 5 in the first state such that the first rectifying unit 3, the second rectifying unit 4 and the additional rectifying unit 7 are connected in series. In case the desired output voltage is lower than the threshold voltage, the control unit 6 may put the switching unit 5 in the second state such that the first rectifying unit 3, the second rectifying unit 4 and the additional rectifying unit 7 are connected in parallel.

Similar to the DC-DC power converter 100 described in connection with fig. 2 to 4, the switching unit 5 may include a plurality of switches connected between output terminals of the respective rectifying units. For example, the first rectifying unit 3, the second rectifying unit 4, and the switches S1, S2, and S3 shown in fig. 2 may be regarded as one overall circuit, and the overall circuit may be connected with the additional rectifying unit 7 using three more switches, which may be arranged similarly to the switches S1, S2, and S3.

It should be understood that the DC-DC power converter 100 can also be extended to include more rectification units. These rectifying units may be coupled by a switching unit 5 connected between the output terminals of the respective rectifying units. By controlling the state of the switching unit 5 by the control unit 6, the respective rectifying units can be connected in series or in parallel, thereby achieving a wide voltage range.

The DC-DC power converter 100 according to the embodiments of the present disclosure may be used in various fields, such as electric vehicles, office automation equipment, industrial instrumentation, military, aerospace, and the like. For example, when the DC-DC power converter 100 is applied to an electric vehicle charging pile, voltages of different levels can be output according to different requirements, so that the requirement for charging electric vehicles with different charging voltages can be met.

A method of power conversion by the DC-DC power converter 100 described hereinabove is also provided in embodiments according to the present disclosure. The method comprises the following steps: in response to the desired output voltage being higher than the threshold voltage, placing the switching unit 5 in a first state such that the plurality of rectifying

units

3, 4, 7 are connected in series, thereby providing a high voltage and a low current; and in response to the desired output voltage being below the threshold voltage, placing the switching unit 5 in a second state such that the plurality of rectifying

units

3, 4, 7 are connected in parallel, thereby providing a low voltage and a high current.

In case the DC-DC power converter 100 employs the architecture shown in fig. 2 to 4, placing the switching unit 5 in the first state comprises closing the first switch S1 and opening the second switch S2 and the third switch S3, and placing the switching unit 5 in the second state comprises opening the first switch S1 and closing the second switch S2 and the third switch S3.

Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A DC-DC power converter (100), comprising:

a transformer (2) comprising a primary side (21) and a secondary side (22);

-an inverter unit (1) coupled to a primary side (21) of the transformer (2);

a plurality of rectifying units (3, 4, 7) respectively coupled to a secondary side (22) of the transformer (2), each of the plurality of rectifying units (3, 4, 7) comprising a first output terminal and a second output terminal;

a switching unit (5) coupled to the first and second output terminals of the plurality of rectifying units (3, 4, 7) and switchable between a first state in which the switching unit (5) connects the plurality of rectifying units (3, 4, 7) in series and a second state in which the switching unit (5) connects the plurality of rectifying units (3, 4, 7) in parallel; and

a control unit (6) coupled to the switching unit (5) and configured to:

in response to the desired output voltage being higher than a threshold voltage, placing the switching unit (5) in the first state; and

in response to the desired output voltage being lower than the threshold voltage, the switching unit (5) is placed in the second state.

2. The DC-DC power converter (100) of claim 1, wherein the plurality of rectifying units (3, 4, 7) comprises a first rectifying unit (3) and a second rectifying unit (4), and wherein the switching unit (5) comprises:

a first switch (S1) coupled between the second output terminal (32) of the first rectifying unit (3) and the first output terminal (41) of the second rectifying unit (4);

a second switch (S2) coupled between the second output terminal (32) of the first rectifying unit (3) and the second output terminal (42) of the second rectifying unit (4); and

a third switch (S3) coupled between the first output terminal (31) of the first rectifying unit (3) and the first output terminal (41) of the second rectifying unit (4).

3. The DC-DC power converter (100) of claim 2, wherein with the switching unit (5) in the first state, the first switch (S1) is closed and the second switch (S2) and the third switch (S3) are open, and

wherein with the switching unit (5) in the second state, the first switch (S1) is open and the second switch (S2) and the third switch (S3) are closed.

4. The DC-DC power converter (100) of claim 1, wherein each of the plurality of rectifying units (3, 4, 7) comprises a full-bridge rectifying circuit.

5. The DC-DC power converter (100) of claim 4, wherein the full-bridge rectification circuit comprises diodes.

6. The DC-DC power converter (100) of claim 4, wherein the full-bridge rectification circuit comprises controllable semiconductor devices.

7. The DC-DC power converter (100) of claim 6, wherein the controllable semiconductor devices comprise MOSFETs or IGBTs.

8. The DC-DC power converter (100) of claim 6, wherein each of the plurality of rectifying units (3, 4, 7) further comprises an LLC resonant circuit.

9. The DC-DC power converter (100) of claim 8, wherein the inverting unit (1) comprises a full bridge inverting circuit and an LLC resonant circuit, wherein the full bridge inverting circuit comprises controllable semiconductor devices.

10. The DC-DC power converter (100) of claim 9, wherein the controllable semiconductor devices comprise MOSFETs or IGBTs.

11. A method for a DC-DC power converter, the DC-DC power converter comprising: a transformer (2) comprising a primary side (21) and a secondary side (22); an inverter unit (1) coupled to a primary side (21) of the transformer (2); a plurality of rectifying units (3, 4, 7) respectively coupled to a secondary side (22) of the transformer (2), each of the plurality of rectifying units (3, 4, 7) comprising a first output terminal and a second output terminal; and a switching unit (5) coupled to the first and second output terminals of the plurality of rectifying units (3, 4, 7), the method comprising:

in response to the desired output voltage being higher than a threshold voltage, placing the switching unit (5) in the first state such that the plurality of rectifying units (3, 4, 7) are connected in series; and

in response to the desired output voltage being lower than the threshold voltage, the switching unit (5) is placed in the second state such that the plurality of rectifying units (3, 4, 7) are connected in parallel.

12. The method of claim 11, wherein the plurality of rectifying units (3, 4, 7) comprises a first rectifying unit (3) and a second rectifying unit (4), and wherein the switching unit (5) comprises:

13. The method according to claim 12, wherein placing the switching unit (5) in the first state comprises: closing the first switch (S1) and opening the second switch (S2) and the third switch (S3), and

wherein placing the switching unit (5) in the second state comprises: opening the first switch (S1) and closing the second switch (S2) and the third switch (S3).