CHARGING DEVICE FOR AN ELECTRIC VEHICLE
The dual transformer charging device for electric vehicles addresses inefficiencies in existing systems by enabling flexible operation modes and robust power management, ensuring bidirectional power flow and reduced semiconductor usage for high-voltage and low-voltage batteries.
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- MAHLE INT GMBH
- Filing Date
- 2024-11-21
- Publication Date
- 2026-05-21
AI Technical Summary
Existing electric vehicle charging systems lack flexibility and robustness due to independent, unidirectional converters with separate power electronics, leading to inefficiencies and limited design options.
A charging device utilizing a dual transformer configuration with a single primary side, allowing for bidirectional power flow and reducing electronic circuitry, featuring a primary converter, two transformers, and high-voltage and low-voltage converters connected in parallel, with a common control unit for power management.
Enables flexible operation modes, ensures double insulation, minimizes semiconductor usage, and enhances robustness by allowing bidirectional power flow and optimizing power delivery to both high-voltage and low-voltage batteries.
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Abstract
Description
[0001] The present invention relates to a charging device configured for installation in an electric vehicle (EV) for charging a high-voltage battery (HV battery) and / or a low-voltage battery (LV battery) of the electric vehicle. The present invention further relates to an electric vehicle.
[0002] Electric vehicles are typically charged via a charging cable that plugs into a charging port on the vehicle. An on-board charger (OBC) converts the electrical power, which can be direct current (DC) or alternating current (AC), into DC to charge the electric vehicle's traction battery (also known as the high-voltage battery) and, optionally, a low-voltage battery.
[0003] A typical OBC (On-Board Battery) setup includes three converters: an AC-DC converter that rectifies the AC mains voltage, an HV-DC-DC converter responsible for charging the HV battery, and a 12V DC-DC converter (charger) responsible for charging the LV battery. Due to certain synergies, the HV-DC-DC converter and some or all of the other components of the OBC are usually mounted in the same enclosure.
[0004] In most cases, the three converters are independent and do not share any power electronics. The DC-DC converters are typically unidirectional resonant converters, each with its own conversion and isolation stage, meaning its own transformer and switches. Furthermore, their unidirectional operation prevents reverse power flow due to the use of rectifier diodes in the output stage (HV battery side).
[0005] EP 4287482 A1 discloses a power conversion topology for charging an HV battery and / or an LV battery of an electric vehicle. The power conversion topology comprises a three-winding transformer with a primary winding, a secondary winding and a tertiary winding, a grid rectifier, an HV rectifier and an LV rectifier.
[0006] The object of the present invention is to provide a charging device for an electric vehicle that allows for a more flexible design and greater robustness.
[0007] According to a first aspect of the present invention, a charging device is presented comprising: - a primary converter configured to convert supplied direct current into alternating current; - a first transformer whose input is connected to the primary transformer; - an HV converter configured to convert AC to HV DC, with the input of the HV converter connected to the output of the first transformer and the output of the HV converter configured to connect to the HV battery; - an LV converter configured to convert AC to LV DC, with the input of the LV converter connected to the output of the first transformer and the output of the LV converter configured to connect to the LV battery; and - a second transformer connected to the input of the LV converter.
[0008] According to another aspect of the present invention, an electric vehicle is presented which comprises an HV battery, an LV battery and a charging device according to the present disclosure for charging the HV battery and / or the LV battery.
[0009] Preferred embodiments of the invention are defined in the dependent claims.
[0010] The present invention is based on the idea of using two transformers to form a dual transformer with only a single primary side. This ensures double insulation between the high-voltage (HV) and low-voltage (LV) batteries and reduces the electronic circuitry required for the charging device. Furthermore, bidirectional power flow can be implemented.
[0011] In a preferred embodiment, the first output terminal of the first transformer is connected to a first input terminal of the HV converter and a first input terminal of the LV converter, and the second output terminal of the first transformer is connected to a second input terminal of the HV converter and a second input terminal of the LV converter. In this way, both the HV converter and the LV converter are connected in parallel to the output of the first transformer.
[0012] The second transformer is preferably connected between the input of the LV converter and a rectifier of the LV converter; that is, it is connected in parallel to the output of the first transformer and thus can be part of the LV converter. In an alternative embodiment, the second transformer can be connected between the output of the first transformer and the input of the LV converter; that is, it can be an external component that is not part of the LV converter.
[0013] In another embodiment, the charging device further comprises a control unit configured to control the primary converter, the high-voltage converter, and the low-voltage converter. Three separate control units may be provided, but preferably a single common control unit or two control units (one for the primary converter and one common for the high-voltage and low-voltage converters) are provided, thereby saving on the hardware and / or software required for control.
[0014] In another embodiment, the charging device further comprises a control unit configured to control the primary current of the first transformer in order to control the power delivered to the HV battery and / or the LV battery. The control unit can be the same control unit used to control at least the primary converter, and it can be configured to control the switching frequency of the primary converter to control the primary current of the first transformer. A common control unit for controlling the primary current (e.g., via voltage) in the first transformer enables the management of the directional control of the power balancing and avoids imbalances at the transformer ports.
[0015] In one embodiment, the primary converter and / or the HV converter and / or the LV converter are configured to operate as resonant converters. The primary converter may comprise a full-bridge inverter with a variety of switching elements.
[0016] The HV converter and / or the LV converter can each comprise a full-bridge rectifier with a variety of switching elements, such as those commonly known.
[0017] In another embodiment, the control unit is configured to control the switching elements of the primary converter and / or the switching elements of the HV converter and / or the LV converter in order to operate the charging device in various operating modes, including one or more of the following: - a charging mode in which the switching elements of the primary converter are switched to charge the HV battery and / or the LV battery; - a driving mode in which the switching elements of the primary converter are switched off and the switching elements of the HV converter are switched in such a way as to provide a power flow from the HV battery to the LV battery; and - a bidirectional mode in which the switching elements of the primary converter and the HV converter are switched in such a way that they allow a power flow from the primary converter to the HV battery or from the HV battery to the primary converter.
[0018] The charging device may further include a relay connected between an output terminal of the first transformer and an input terminal of the second transformer; and a control unit configured to control the relay. The use of the relay further improves the flexibility of controlling the different charging modes of the charging device.
[0019] The term "electric vehicle" can basically refer to any type of vehicle that has an electric drive, such as a car, a bus, a truck, a robot, a forklift, etc.
[0020] The preceding paragraphs were provided for general introduction only and are not intended to limit the scope of protection of the following claims. A more comprehensive understanding of the disclosure and many of its associated advantages is readily achieved by referring to the following detailed description in conjunction with the accompanying drawings, whereby: Fig. Figure 1 shows a circuit diagram of a first embodiment of a charging device according to the present invention; Fig. Figure 2 shows the circuit diagram of the first embodiment of the in Fig. 1 charging device shown in a charging mode; Fig. Figure 3 shows the circuit diagram of the first embodiment of the in Fig. 1 charging device shown in a driving mode; Fig. Figure 4 shows the circuit diagram of the first embodiment of the in Fig. 1 shown charging device in a bidirectional mode; Fig. 5 shows a circuit diagram of a second embodiment of a charging device according to the present invention; Fig. Figure 6 shows a circuit diagram of a second embodiment of a charging device according to the present invention; and Fig. Figure 7 shows a schematic diagram of an electric vehicle according to the present invention.
[0021] Fig. Figure 1 shows a circuit diagram of an embodiment of a charging device 1 according to the present invention. The charging device 1 is configured for installation in an electric vehicle for charging a high-voltage battery (HV battery) 71, e.g., an HV battery with a voltage in the range of 400-900 V, and / or a low-voltage battery (LV battery) 72, e.g., an LV battery with a voltage of 12 V, of the electric vehicle.
[0022] The charging device comprises a primary converter 10, a first transformer 20, a high-voltage converter 30, a low-voltage converter 40, and a second transformer 50. The primary converter 10 converts direct current (e.g., an intermediate circuit voltage of, for example, 750 V), supplied by a power supply 70 at the input 11 of the primary converter 10 via a charging cable (not shown), into alternating current. A full-bridge inverter 12 can be used for this conversion. The first transformer 20 is connected at its input 21 to the output 13 of the primary converter 10 and at its output 22 to the input 31 of the high-voltage converter 30. The high-voltage converter 30 converts alternating current at the output 22 of the first transformer 20 into high-voltage direct current. B. by using a full bridge rectifier 32. The output 33 of the HV converter 30 is connected to the HV battery 71 of the electric vehicle.The LV converter 40 converts alternating current at the output 22 of the first transformer 20 into LV direct current, e.g., by using a full-bridge rectifier 42. The input 41 of the LV converter 40 is connected to the output 22 of the first transformer 20, and the output 43 of the LV converter 40 is connected to the LV battery 72 of the electric vehicle. The second transformer 50 is connected to the input 41 of the LV converter 40, in particular between the input 41 of the LV converter 40 and the rectifier 42 of the LV converter 40. The second transformer 50 is preferably connected at its input 51 to the output 22 of the first transformer 20 of the primary converter and at its output 52 to the rectifier 42. In the [reference to be added] Fig. In the embodiment shown in Figure 1, the second transformer 50 is part of the LV converter 40, but it can also be a separate component which is coupled to the input 41 of the LV converter 40 via its output 52.
[0023] In the Fig. In the embodiment shown in Figure 1, the first output terminal 221 of the first transformer 20 is connected to a first input terminal 311 of the HV converter 30 and a first input terminal 411 of the LV converter 40. The second output terminal 222 of the first transformer 20 is connected to a second input terminal 312 of the HV converter 30 and a second input terminal 412 of the LV converter 40.
[0024] The charging device 1 further comprises a control unit 60, which is configured to control the primary converter 10, the HV converter 30, and the LV converter 40. In particular, it controls the switching elements S1 of the respective inverter 12 and the switching elements S3, S4 of the rectifiers 32, 42. The control unit 60 (or a separate control unit (not shown)) can also control the primary current of the first transformer 20 to control the power delivered to the HV battery 71 and / or the LV battery 72. Furthermore, the control unit 60 can be configured to control the switching frequency of the primary converter 10 to control the primary current of the first transformer 20.
[0025] There are different options for implementing the switching elements S1, S3, S4. In the Fig. In the embodiment shown in Figure 1, the switching elements S1, S3, and S4 are implemented using MOSFETs. Other implementations can use diodes, transistors, or other suitable components.
[0026] Preferably the primary converter 10 and / or the HV converter 30 and / or the LV converter 40 are configured to operate as resonant converters.
[0027] Additional capacitors 14, 34, 44 can be provided at the output 13 of the primary converter 10 and the inputs 31, 41 of the HV converter 30 and / or the LV converter 40.
[0028] The present invention therefore proposes the topology of a single resonant converter with a dual transformer to control the HV battery on one side and the LV battery on the other. The converter is divided into a full-bridge stage (the primary converter 10), a transformer (the first transformer 20), and a full-bridge stage in the secondary converter (the HV converter 30) of the DC-DC converter of the OBC, and a transformer (the second transformer 50) plus a full-bridge stage for implementing the DC-DC-LV converter 40. Each secondary side (i.e., the HV converter 30 and the LV converter 40) includes its own resonant circuit to optimize the operating point of the respective battery 71, 72.
[0029] The control is carried out via the primary current, so that the power flow of the HV battery 71 and the LV battery 72 can be controlled by a single converter, i.e. the primary converter 10.
[0030] The control unit 60 can be configured, in particular, to control the switching elements S1 of the primary converter 10 and / or the switching elements S3, S4 of the HV converter 30 and / or the LV converter 40 in order to operate the charging device 10 in different operating modes. In other words, the operating modes of the charging device 1 can be divided into different phases.
[0031] Fig. Figure 2 shows the circuit diagram of the embodiment of the in Fig. The charging device 1 shown in Figure 1 is in a charging mode. In charging mode, the switching elements S1 of the primary converter 10 are switched such that the HV battery 71 and / or the LV battery 72 is charged. The currents I3 and I4 of both secondary converters 30 and 40 can be referenced to the primary current I1, so that the control unit 60, which can apply a PI (proportional-integral) control strategy, can correct the error by changing the switching frequency of the switching elements S1 of the primary converter 10. In this case, the rectifiers 32 and 42 function as active rectifiers, i.e., their switches S3 and S4 are switched in diode mode, thus minimizing the conduction losses caused by the current flowing through them.
[0032] Fig. Figure 3 shows the circuit diagram of the embodiment of the in Fig. Figure 1 shows the charging device 1 in a driving mode. In driving mode, the switching elements S1 of the primary converter 10 are switched off, and the switching elements S3 of the high-voltage converter 30 are switched to provide a power flow from the high-voltage battery 71 to the low-voltage battery 72. Thus, only the high-voltage converter 30 and the low-voltage converter 40 switch the switching elements S3 and S4 according to the power flow from the high-voltage battery 71 to the low-voltage battery 72. In this configuration, control is performed from the side of the high-voltage converter 30, and the rectifier 42 of the low-voltage converter 40 acts as an active rectifier, thereby minimizing losses in the high-voltage converter 30 and the low-voltage converter 40 and optimizing the resonant circuit (the rectifier 42) at its operating point.
[0033] Fig. Figure 4 shows the circuit diagram of the embodiment of the in Fig. The charging device shown in Figure 1 operates in a bidirectional mode. In bidirectional mode, the switching elements S1 and S3 of the primary converter 10 and the high-voltage converter 30 are switched to allow power flow from the primary converter 10 to the high-voltage battery 71 or from the high-voltage battery 71 to the primary converter 10. This bidirectionality thus enables power output via the AC grid. In this case, switching the switching element S3 of the high-voltage converter 30 as a resonant converter simultaneously allows power flow from the high-voltage battery 71 to the AC grid and power output to the low-voltage battery 72. Control is performed from the side of the high-voltage converter 30.
[0034] Fig. Figure 5 shows a circuit diagram of a second embodiment of a charging device 1a according to the present invention. In this embodiment, the second transformer 50 is located outside the LV converter 40 and is connected between the output 22 of the first transformer 20 and the input 41 of the LV converter 40, i.e., the input of the second transformer 50 is connected to the output 22 of the first transformer 20 and the output 52 of the second transformer 50 is connected to the input 41 of the LV converter 40.
[0035] Fig. Figure 6 shows a circuit diagram of a third embodiment of a charging device 1b according to the present invention. In addition to the components of the first embodiment of a charging device 1b, the following are shown: Fig. The charging device shown in 1 comprises the Fig. The charging device 1b shown in Figure 6 also includes a relay 80, which is connected between the output terminal 22 of the first transformer 20 and the input terminal 51 of the second transformer 50. The control unit 60 (or a separate control unit) controls the relay 80. The relay 80 allows the segmentation of the power transformers 10, 30, 40 and thus enables simple, independent control of the current supply between the three branches.
[0036] Fig. Figure 7 shows a schematic diagram of an electric vehicle 90 according to the present invention. The electric vehicle 90 comprises an HV battery 71, an LV battery 72 and a charging device 1 (which may also be the charging device 1a or 1b) according to the present invention, as disclosed herein, for charging the HV battery 71 and / or the LV battery 72 and for operation in the various modes described above.
[0037] In summary, the present invention presents the integration of primary and secondary converters based on a double transformer with only A primary side is provided. This allows the OBC (the charging device) to operate with bidirectional power flow, from the grid to the vehicle and from the vehicle to the grid. Furthermore, double insulation between the LV battery and the HV battery is ensured. In addition, the number of semiconductors in the charging device is minimized, increasing its robustness.
[0038] Although the invention has been illustrated and described in detail in the drawings and the preceding description, these illustrations and descriptions are to be regarded as illustrative or exemplary and not as limiting; the invention is not limited to the embodiments described. Other variations of the disclosed embodiments can be understood and carried out by persons skilled in the art in practical application of the claimed invention by studying the drawings, the disclosure and the accompanying claims.
[0039] In the claims, the word "comprising" does not exclude any other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit can perform the functions of several elements mentioned in the claims. The mere fact that certain measures are listed in different dependent claims does not mean that a combination of these measures cannot be used advantageously.
[0040] Any reference numerals in the claims should not be interpreted as limiting the scope of protection. QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0000] EP 4287482 A1
[0005]
Claims
[1] Charging device (1, 1a, 1b) configured for installation in an electric vehicle (90) for charging a high-voltage battery (HV battery) (71) and / or a low-voltage battery (LV battery) (72) of the electric vehicle, the charging device comprising: - a primary converter (10) configured to convert supplied direct current into alternating current; - a first transformer (20) which is connected to the primary transformer via its input (21); - an HV converter (30) configured to convert alternating current to HV direct current, wherein the input (31) of the HV converter is connected to the output (22) of the first transformer and the output (33) of the HV converter is configured to connect to the HV battery; - an LV converter (40) configured to convert alternating current to LV direct current, wherein the input (41) of the LV converter is connected to the output (22) of the first transformer and the output (43) of the LV converter is configured to connect to the LV battery; and - a second transformer (50) which is connected to the input (41) of the LV converter. [2] Charging device according to claim 1, wherein the first output terminal (221) of the first transformer (20) is connected to a first input terminal (311) of the HV converter (30) and a first input terminal (411) of the LV converter (40), and wherein the second output terminal (222) of the first transformer (20) is connected to a second input terminal (312) of the HV converter (30) and a second input terminal (412) of the LV converter (40). [3] Charging device according to claim 1 or 2, wherein the second transformer (50) is connected between the input (41) of the LV converter (40) and a rectifier (42) of the LV converter (40). [4] Charging device according to claim 1 or 2, wherein the second transformer (50) is connected between the output (22) of the first transformer (20) and the input (41) of the LV converter (40). [5] Charging device according to any of the preceding claims, further comprising a control unit (60) configured to control the primary converter, the HV converter and the LV converter. [6] Charging device according to any of the preceding claims, further comprising a control unit (60) configured to control the primary current of the first transformer in order to control the power delivered to the HV battery and / or the LV battery. [7] Charging device according to claim 6, wherein the control unit (60) is configured to control the switching frequency of the primary converter in order to control the primary current of the first transformer. [8] Charging device according to any of the preceding claims, wherein the primary converter (10) and / or the HV converter (30) and / or the LV converter (40) are configured to operate as a resonant converter. [9] Charging device according to any one of the preceding claims, wherein the primary converter (10) comprises a full-bridge inverter (12) with a plurality of switching elements (S) and / or wherein the HV converter (30) and / or the LV converter (40) each comprise a full-bridge rectifier (32, 42) with a plurality of switching elements (S). [10] Charging device according to claims 5 and 9, wherein the control unit (60) is configured to control the switching elements (S1) of the primary converter (10) and / or the switching elements (S3, S4) of the HV converter (30) and / or the LV converter (40) to operate the charging device in various operating modes, including one or more of the following: - a charging mode in which the switching elements (S1) of the primary converter (10) are switched to charge the HV battery and / or the LV battery; - a driving mode in which the switching elements (S1) of the primary converter (10) are switched off and the switching elements (S3) of the HV converter (30) are switched so that they provide a power flow from the HV battery to the LV battery; and - a bidirectional mode in which the switching elements (S1, S3) of the primary converter (10) and the HV converter (30) are switched in such a way that they allow a power flow from the primary converter to the HV battery or from the HV battery to the primary converter. [11] Charging device according to any one of the preceding claims, further comprising: - a relay (80) connected between an output terminal of the first transformer and an input terminal of the second transformer; and - a control unit (60) configured to control the relay. [12] Electric vehicle (90) comprising a high-voltage battery (HV battery) (71), a low-voltage battery (LV battery) (72) and a charging device (1, 1a, 1b) according to any of the preceding claims for charging the HV battery and / or the LV battery.