Multiport converter with unidirectional disconnect switch

Abstract

comprising multiport converter (1) for electric vehicles a first circuit branch (10) with a resonant circuit, a second circuit branch (20) and a third circuit branch (30), wherein the multiport converter (1) is configured to convert voltage in a first operating mode from the first circuit branch (10) as the primary side to the second circuit branch (20) and / or the third circuit branch (30) as the secondary side, and in a second operating mode to convert voltage from the second circuit branch (20) as the primary side to the third circuit branch (30) as the secondary side, and wherein the resonant circuit of the first circuit branch (10) forms a resonant path in the second operating mode and the first circuit branch (10) further comprises a unidirectional disconnect switch (Q3) to interrupt the resonant path at least in the second operating mode.

Description

[0001] The invention relates to a multiport converter with a unidirectional disconnect switch.

[0002] In the state of the art, multiport converters, especially in the form of magnetically integrated DC / DC converters such as LLC topologies, are used in electric vehicles or plug-in hybrids and, for example, as on-board chargers (OBCs) to supply both a connected high-voltage electrical system and a connected low-voltage electrical system from a common energy source.

[0003] These converters typically have multiple ports, each connected to a common transformer via its own windings, allowing energy to be transferred flexibly between different on-board network levels.

[0004] In known solutions, for example US 2022 / 0045619 A1, the particular aim is to enable bidirectional energy flow and simplify system integration through targeted interconnection and control of the ports.

[0005] However, the state of the art reveals the problem that in certain operating modes - especially when energy is transferred from the high-voltage side (secondary branch) to the low-voltage side (tertiary branch) in so-called cross-operation - the resonant circuit of the primary branch oscillates unintentionally.

[0006] This leads to increased power losses, voltage spikes, and avoidable stress on the components on the primary side. Known approaches to interrupting the resonance path, such as mechanical or bidirectional switches, are technically complex, increase the complexity of the control system, and result in additional space and cost requirements.

[0007] Furthermore, integrating such switches into the gate driver supply is often only possible with considerable additional effort and, in particular, only with a separate supply.

[0008] Consequently, the state of the art has significant shortcomings regarding efficiency, component protection and feasibility of a simple and reliable multiport converter and its cross-operation.

[0009] The invention is therefore based on the objective of overcoming the aforementioned disadvantages and providing a simple and efficient multiport converter.

[0010] This problem is solved by the combination of features according to claim 1.

[0011] According to the invention, a multiport converter for electric vehicles, including plug-in hybrids, is proposed. The multiport converter according to the invention, which for clarity can be a DC / DC converter, comprises a first circuit branch, which can also be referred to as the primary branch, with a resonant circuit, as well as a second and third circuit branch, which can be called the secondary and tertiary branches.

[0012] Regarding the circuit branches, it should be noted that the first circuit branch preferably has a first port and a first winding connected to it, which then forms part of the resonant circuit. Furthermore, regarding the second and third circuit branches, it is preferably provided that each of these can also have a port and a winding. Accordingly, the second circuit branch, or secondary branch, can have a second port and a second winding connected to it, and the third circuit branch, or tertiary branch, can have a third port and a third winding connected to it.

[0013] The windings can be arranged on a common magnetic core, thus enabling galvanically isolated energy transfer between the circuit branches.

[0014] Based on the multiport converter proposed according to the invention, it is configured, in a first operating mode, which can be understood, for example, as a charging mode or charging operation for charging the electric vehicle or its batteries, or more generally for the external power supply of the electric vehicle, to convert voltage from the first circuit branch as the primary side to the second circuit branch and / or the third circuit branch as the secondary side, wherein both the second and the third circuit branch can act as the secondary side, or only one of the two circuit branches can act as the secondary side. Furthermore, the multiport converter is configured, in a second operating mode, which can be understood, for example, as a cross-operation independent of the charging operation for supplying a low-voltage electrical system with a high-voltage electrical system, to convert voltage from the second circuit branch as the primary side to the third circuit branch as the secondary side.The aforementioned resonant circuit of the first circuit branch forms a resonance path, particularly in the second operating mode, which is addressed in a loss-generating manner.

[0015] Therefore, according to the invention, the first circuit branch further comprises a unidirectional disconnect switch for interrupting the resonance path at least in the second operating mode and preferably in any operating mode not corresponding to the first operating mode, which is consequently preferably designed to interrupt the resonance path at least in the second operating mode and further, in particular, in any operating mode not corresponding to the first operating mode, so that the resonant circuit of the first circuit path is no longer addressed and no losses occur through it.

[0016] Specifically, it may be intended, for example, that the first circuit branch is connected to the vehicle's charging port or that the first port is the vehicle's charging port.

[0017] Furthermore, the second circuit branch can be the high-voltage side, and its second port can be a high-voltage port that can be connected to a high-voltage on-board network, which functions as a high-voltage output (HV output) at least in the first operating mode, but can also act as a high-voltage input, especially in the second operating mode.

[0018] Consequently, the third circuit branch can be the low-voltage side, and its third port can be a low-voltage port connectable to a low-voltage on-board network, which functions as a low-voltage output (LV output) at least in the first operating mode, but preferably also in the second operating mode.

[0019] This design makes it possible to operate the multiport converter flexibly in different operating modes and to selectively interrupt the resonance path of the first circuit branch in order to avoid unwanted losses and sympathetic vibrations at least in the second operating mode, preferably in every operating mode except the first operating mode.

[0020] Furthermore, it has been shown that in the second operating mode not only can the power loss in the first circuit branch be significantly reduced, but that the targeted shutdown of the resonance path in the second operating mode or in cross-operation limits the maximum voltages across the components, especially of the first circuit branch, to a manageable level, whereby the reduction of voltage peaks is crucial for the selection of commercially available components and system reliability.

[0021] By selectively switching off the resonant circuit, the current in the resonant circuit can be significantly reduced. This reduces power loss and, more importantly, limits the maximum voltages across the components in steady state. This enables an economically viable implementation of the DC / DC converter using commercially available components and reduces the complexity of the isolation design.

[0022] In principle, the second and / or third circuit branch could also have a unidirectional disconnect switch to allow for selective disconnection. Furthermore, additional circuit branches analogous to the first, second, or third could be provided to accommodate further voltage levels and to enable alternative operating modes such as charging or cross-connection.

[0023] Advantageously, the unidirectional disconnect switch may be a transistor or unidirectional transistor and further preferably a MOSFET or unidirectional MOSFET.

[0024] By using a transistor as a unidirectional isolating switch, a compact and reliable switching function can be achieved through a switching element that is easy to control and requires no further control elements, and which can be easily integrated into the circuit design of the first circuit branch.

[0025] Another embodiment provides that the unidirectional disconnect switch is arranged in a ground path of the resonant circuit of the first circuit branch.

[0026] The arrangement of the unidirectional disconnect switch in the ground path enables particularly simple control and increases the operational reliability of the multiport converter.

[0027] In the context of the multiport converter according to the invention, the ground path of the resonant circuit is understood to be, in particular, that electrical conductor section of the resonant circuit of the first circuit branch which is connected to the reference potential of the circuit (ground or GND) and through which a resonant current flows back to ground after passing through the resonant circuit. By placing the disconnect switch in this ground path, the entire resonant circuit can be selectively and reliably disconnected from ground, thus interrupting the current flow in the resonant circuit.

[0028] An advantageous further development takes into account that the unidirectional disconnect switch has a control connection for establishing and disconnecting an electrical connection between two terminals of the unidirectional disconnect switch, which is configured to establish the connection when the multiport converter is operating in the first operating mode and to disconnect the connection when the multiport converter is operating in the second operating mode.

[0029] Assuming that the unidirectional disconnect switch is a MOSFET, the control terminal is its gate terminal, and the two terminals between which the electrical connection can be broken or made are its drain and source terminals.

[0030] This design allows the switching state of the disconnect switch to be controlled specifically depending on the operating mode of the multiport converter, enabling the interruption or establishment of the resonance path as required.

[0031] Building on this, a further embodiment provides that the first circuit branch includes at least one switch for generating an alternating voltage. This switch can optionally form a full or half-bridge circuit together with other switches, and may, independently of this, preferably be designed as a MOSFET. The at least one switch for generating an alternating voltage flowing through the resonant circuit has a control terminal that can be connected to a control voltage supply of the first circuit branch. To enable simple and efficient control of the disconnect switch without additional components, the control terminal of the unidirectional disconnect switch is provided in such a way, and in particular directly, i.e.,without the interposition of additional electrical components, electrically connected to the control terminal of the switch and / or the control voltage supply and / or controlled in such a way that the control terminal of the unidirectional disconnect switch establishes the connection between the two terminals of the unidirectional disconnect switch when the multiport converter is operating in the first operating mode and, at least when the multiport converter is operating in the second operating mode, disconnects the connection between the two terminals of the unidirectional disconnect switch.

[0032] This advanced training enables a particularly simple and direct control of the unidirectional disconnect switch by connecting its control terminal directly to the control voltage supply or the control terminal of the switch, so that the disconnect switch is automatically switched depending on the operating mode of the multiport converter.

[0033] Assuming that at least one switch for generating an AC voltage is a MOSFET and the disconnect switch is a unidirectional MOSFET, the control terminal (gate) of the disconnect switch can be directly connected to the low-side driver supply as the control voltage supply for the first circuit branch, which also serves to control the switch for generating the AC voltage. In the first operating mode (charging mode), the driver supply or control voltage supply is active, so that both the switch for generating the AC voltage and the unidirectional disconnect switch are energized. If the multiport converter is switched to the second operating mode (cross-connection) or if the LLC converter is not operating, the driver supply or control voltage supply is switched off, which automatically closes the unidirectional disconnect switch and reliably interrupts the resonant path.In this way, a particularly simple and component-minimized control of the disconnect switch can be achieved.

[0034] In short, if the first circuit branch is not active, i.e., operating in the first operating mode, its driver supply or control voltage supply is switched off, which automatically blocks the MOSFET, which acts as a unidirectional disconnect switch.

[0035] As briefly mentioned earlier, an advantageous further development can provide for the multiport converter to be designed as an LLC converter and, in particular, to include a resonant inductor, a magnetizing inductor, and a resonant capacitor in the resonant circuit of the first circuit branch. By designing it as an LLC converter, the advantages of resonant energy transfer are utilized, which contributes to high efficiency and efficient voltage conversion.

[0036] To protect against voltage spikes that could damage the disconnect switch, an optional but advantageous further embodiment provides that the unidirectional disconnect switch is designed to switch a switching voltage that is higher, and in particular at least 1.5 times higher, than a system voltage of the multiport converter.

[0037] In the context of a multiport converter, the system voltage is understood to be the highest electrical voltage present at one of the ports or within one of the circuit branches during normal operation, and for which the component design is decisive. It represents the rated value on which the dielectric strength of the components used, in particular the unidirectional disconnect switch, is based.

[0038] If the system voltage of the multiport converter is, for example, 400 V, the unidirectional disconnect switch can be designed to switch a voltage that is at least 1.5 times higher, and preferably 2 times higher, i.e., at least 600 V for a system voltage of 400 V. In practice, starting from a system voltage of 400 V, a MOSFET with a voltage rating of 650 V or 750 V can be used, for example, to ensure sufficient safety margins against voltage spikes and transients.

[0039] This ensures that the disconnect switch works reliably even when voltage spikes occur and is not damaged by overvoltage.

[0040] Alternatively or additionally, the first circuit branch may include a protective circuit designed to reduce voltage transients occurring via the disconnect switch and thereby protect it from voltage spikes exceeding a system voltage.

[0041] By integrating a protective circuit into the first circuit branch and for the disconnect switch, such as a snubber or clamp circuit, voltage transients can be effectively limited and the disconnect switch and other components can be protected from overvoltage.

[0042] In an exemplary method for operating a multiport converter in a first operating mode and in a second operating mode, it can be provided that the multiport converter in the first operating mode, which can be understood as charging mode, converts voltage from the first circuit branch as the primary side to the second circuit branch and / or the third circuit branch as the secondary side, and that the unidirectional disconnect switch is controlled in such a way that the resonant circuit can be controlled as intended.Furthermore, the procedure provides that in the second operating mode, which can be understood as cross-operation, the multiport converter converts voltage from the second circuit branch as the primary side to the third circuit branch as the secondary side, and the unidirectional disconnect switch is controlled to disconnect a connection, so that the resonant circuit acting as a resonant path is interrupted and does not resonate with loss.

[0043] This method enables flexible and efficient operation of the multiport converter in different operating modes, whereby the unidirectional disconnect switch is switched as required to minimize losses and increase operational reliability.

[0044] The features disclosed above can be combined in any way, provided that this is technically possible and they do not contradict each other.

[0045] Other advantageous embodiments of the invention are characterized in the dependent claims or are described in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. The figures show: Fig. 1 multiport converter; Fig. 2. First circuit branch of the multiport converter.

[0046] The figures are schematic examples. Identical reference symbols in the figures indicate identical functional and / or structural features, whereby the Fig. 2. A detailed view of the first circuit branch of the multiport converter is shown below. Fig. 1 shows that the statements concerning the figures apply to both figures.

[0047] Fig. Figure 1 shows a schematic overview of the multiport converter 1 for electric vehicles. The multiport converter 1 comprises a first circuit branch 10 (primary branch), a second circuit branch 20 (secondary branch), and a third circuit branch 30 (tertiary branch). The first circuit branch 10 has a first port 11 and a connected first winding 12, which is part of a resonant circuit. The second circuit branch 20 has a second port 21 and a second winding 22, and the third circuit branch 30 has a third port 31 and a third winding 32. The windings 12, 22, and 32 are arranged on a common magnetic core and enable galvanically isolated power transfer between the circuit branches.

[0048] In the first circuit branch 10 there is an input capacitor C lnThe circuit is designed as a half-bridge together with switches Q1 and Q2, which are implemented as MOSFETs. Switches Q1 and Q2, and thus the half-bridge itself, serve to generate an alternating voltage that is fed to the resonant circuit. The resonant circuit of the first branch 10 consists of the first winding 12, the resonant inductance Lr, the magnetizing inductance Lm, and the resonant capacitor Cr. The specific arrangement of these components shown in the figures is purely exemplary, as, for example, the resonant capacitor Cr and the resonant inductance Lr could be interchanged depending on the chosen representation. The unidirectional disconnect switch Q3, implemented as a unidirectional MOSFET, is arranged in the ground path of the resonant circuit; its control terminal G, as well as terminals D and S, are shown.The control voltage supply 13 is assigned to the first circuit branch 10 and serves to control the switches Q1, Q2 and the disconnect switch Q3, which consequently establishes a connection when a control voltage is applied, i.e., the driver supply for the switches Q1 and Q2 designed as MOSFETs is active.

[0049] At least when operating the multiport converter 1 in the first operating mode, an input voltage U can be applied to the first port 11. ln The second port 21 serves as an HV output in the first operating mode, so that a high voltage U is present here. HV is generated to supply the high-voltage network. In the second operating mode, in which the second circuit branch acts as the primary side, the second port 21 serves as the HV input, so that a high voltage U is present here. HVwhich is applied via the multiport converter to supply the low-voltage network at the third port 31 of the third circuit branch 30, which accordingly serves as an LV output, so that a low voltage U LV of the low-voltage network.

[0050] In the first operating mode (charging mode), electrical energy is transferred from the first circuit branch 10 (primary side) to the second circuit branch 20 and / or the third circuit branch 30 (secondary side). In the second operating mode (transverse operation), energy is transferred from the second circuit branch 20 (primary side) to the third circuit branch 30 (secondary side).

[0051] According to the invention, the unidirectional disconnect switch Q3 is open in the second operating mode, so that the resonance path formed by the resonant circuit of the first circuit branch 10 is interrupted and unwanted sympathetic vibrations and losses in the resonant circuit are avoided. This increases efficiency and protects the components from voltage spikes.

[0052] Fig. Figure 2 shows the first circuit branch 10 in detail. The first port 11 is connected to the first winding 12, which, together with the resonant inductance Lr, the magnetizing inductance Lm, and the resonant capacitor Cr, forms the resonant circuit. The input capacitor C ln It is connected to switches Q1 and Q2, forming a half-bridge that generates the alternating voltage. Switches Q1 and Q2 are each connected to the control voltage supply 13, which controls the switches.

[0053] The unidirectional disconnect switch Q3, provided by a unidirectional MOSFET, is located in the ground path of the resonant circuit. The disconnect switch Q3 has a control terminal G as well as terminals D and S. The control terminal G is directly connected to the control voltage supply 13, so that the control of the disconnect switch Q3 depends on the operating mode of the multiport converter 1. In the first operating mode, the control voltage supply 13 is active, which switches Q3 on and closes the resonant path. In the second operating mode, and especially in any operating mode other than the first, as well as generally when the control voltage supply 13 is switched off, Q3 automatically switches off, thus interrupting the resonant path and preventing unwanted losses or voltage spikes.

[0054] The arrangement shown enables efficient and simple operation of the multiport converter 1 in operating modes that differ from the first operating mode, and in particular in a second operating mode, which represents a cross-operation in which the voltage conversion takes place from the second circuit branch 20 to the third circuit branch 30. Reference symbol list 1 Multiport converter 10 First circuit branch (primary branch) 11 first port 12 first winding 13 Control voltage supply of the first circuit branch 20 Second circuit branch (secondary branch) 21 second port 22 second winding 30 third circuit branch (tertiary branch) 31 third port 32 third winding Q1 is a first switch for generating an alternating voltage Q2 a second switch for generating an alternating voltage Q3 unidirectional disconnect switch (e.g. MOSFET) G Control terminal (gate) of the unidirectional disconnect switch Q3 D First terminal / Drain terminal of the disconnect switch Q3 S second terminal / Source terminal of the disconnect switch Q3 Lr Resonant Inductance Lm Magnetizing inductance Cr resonant capacitor C ln Input capacitor U ln Input voltage applied to the first port U HV High voltage of the high-voltage network applied to the second port U LV Low voltage of the low-voltage network applied to the third port 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] US 2022 / 0045619 A1

[0004]

Claims

[1] Having a multiport converter (1) for electric vehicles a first circuit branch (10) with a resonant circuit, a second circuit branch (20) and a third circuit branch (30), wherein the multiport converter (1) is configured to convert voltage in a first operating mode from the first circuit branch (10) as the primary side to the second circuit branch (20) and / or the third circuit branch (30) as the secondary side, and in a second operating mode to convert voltage from the second circuit branch (20) as the primary side to the third circuit branch (30) as the secondary side, and wherein the resonant circuit of the first circuit branch (10) forms a resonant path in the second operating mode and the first circuit branch (10) further comprises a unidirectional disconnect switch (Q3) to interrupt the resonant path at least in the second operating mode. [2] Multiport converter according to claim 1, wherein the unidirectional disconnect switch (Q3) is a transistor and in particular a MOSFET. [3] Multiport converter according to claim 1 or 2, wherein the unidirectional disconnect switch (Q3) is arranged in a ground path of the resonant circuit of the first circuit branch (10). [4] Multiport converter according to one of the preceding claims, wherein the unidirectional disconnect switch (Q3) has a control terminal (G) for establishing and disconnecting an electrical connection between two terminals (D, S) of the unidirectional disconnect switch (Q3), which is configured to establish the connection when the multiport converter (1) is operating in the first operating mode and to disconnect the connection when the multiport converter (1) is operating in the second operating mode. [5] Multiport converter according to the preceding claim, wherein the first circuit branch (10) has at least one switch (Q1, Q2) for generating an alternating voltage, which has a control terminal that can be connected to a control voltage supply (13) of the first circuit branch (10), wherein the control terminal (G) of the unidirectional disconnect switch (Q3) is electrically connected and / or controlled to the control terminal (13) of the switch (Q1, Q2) and / or the control voltage supply in such a way that the control terminal (G) of the unidirectional disconnect switch (Q3) establishes the connection between the two terminals (D, S) of the unidirectional disconnect switch (Q3) when the multiport converter (1) is operating in the first operating mode and, at least when the multiport converter (1) is operating in the second operating mode, the connection between the two terminals (D, S) of the unidirectional disconnect switch (Q3) is controlled in a disconnecting manner. [6] Multiport converter according to one of the preceding claims, wherein the multiport converter (1) is configured as an LLC converter and comprises a resonant inductor (Lr), a magnetizing inductor (Lm) and a resonant capacitor (Cr) in the resonant circuit. [7] Multiport converter according to one of the preceding claims, wherein the unidirectional disconnect switch (Q3) is designed to switch a switching voltage which is higher and in particular at least 1.5 times higher than a system voltage of the multiport converter. [8] Multiport converter according to one of the preceding claims, wherein the first circuit branch (10) has a protection circuit which is configured to reduce voltage transients occurring via the disconnect switch (Q3) and thereby protect it from voltage spikes exceeding a system voltage. [9] Multiport converter according to any one of the preceding claims, wherein the first circuit branch (10) has a first port (11) and a first winding (12) connected thereto, which is part of the resonant circuit, and / or wherein the second circuit branch (20) has a second port (21) and a second winding (22) connected to it and / or wherein the third circuit branch (30) has a third port (31) and a third winding (32) connected to it.

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