Electrical network in a motor vehicle

Abstract

Electrical network (1) in a motor vehicle, wherein the motor vehicle is designed as a partially or fully automated electric or hybrid vehicle, wherein the electrical network (1) comprises at least one high-voltage network (2) with a high-voltage battery (5) and at least two low-voltage networks (3, 4) each with an on-board battery (6, 7), wherein the high-voltage network (2) and the at least two low-voltage networks (3, 4) are connected to each other via a galvanically isolated DC / DC converter (8), wherein the galvanically isolated DC / DC converter (8) has a primary winding (9) assigned to the high-voltage network (2) and a number of secondary windings (10, 11) corresponding to the number of low-voltage networks (3, 4), each of which is assigned to its respective low-voltage network (3, 4), characterized in that each of the windings (9-11) is assigned an active rectifier with at least four switching elements,wherein at least one subnetwork (2-4) is assigned two disconnect switches (TR1, TR2), wherein the disconnecting elements (TR1, TR2) are designed as relays and semiconductor switches.

Description

[0001] The invention relates to an electrical network in a motor vehicle.

[0002] Electric or hybrid vehicles have an electrical network consisting of a high-voltage network (> 60 V) and a low-voltage network (< 60 V). The high-voltage network is also referred to as the traction network, and the low-voltage network as the vehicle electrical system. It is also common to connect the two subnetworks via a galvanically isolated DC / DC converter, allowing the vehicle electrical system to be charged from a high-voltage battery in the high-voltage network.

[0003] Especially in automated vehicles, the on-board electrical system must be redundant to ensure reliability. Accordingly, two galvanically isolated DC / DC converters are required.

[0004] From DE 10 2012 203 612 A1, a battery charger is known, comprising a first and second input terminal, a first and second output terminal, and a first galvanically isolated DC-DC converter. The DC-DC converter has a primary-side inverter coupled to the first and second input terminals. Furthermore, the DC-DC converter has a transformer with a primary-side transformer winding and first and second secondary-side transformer windings. A first secondary-side rectifier is arranged between the first secondary-side transformer winding and the output terminals. A second secondary-side rectifier is coupled to the second secondary-side transformer winding. The battery charger also has a second galvanically isolated DC-DC converter.The second galvanically isolated DC-DC converter comprises a primary-side inverter and a transformer with primary and secondary-side windings. A secondary-side rectifier is also provided, located between the secondary-side transformer winding and the output terminals. The battery charger is designed to provide a first charging voltage for a first battery (high-voltage battery) at the output terminals and a second charging voltage for a second battery (vehicle battery) at the output of the second secondary-side rectifier of the first galvanically isolated DC-DC converter. It is further disclosed that, by using active rectifier circuits, energy transfer from the first to the second secondary-side transformer winding is also possible.

[0005] The invention is based on the technical problem of simplifying the circuitry of an electrical network in a motor vehicle with at least one high-voltage network and at least two low-voltage networks.

[0006] The solution to the technical problem is achieved by an electrical network having the features of claim 1. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0007] For this purpose, the electrical network in a motor vehicle comprises at least one high-voltage network and at least two low-voltage networks. The high-voltage network and the at least two low-voltage networks are interconnected via a galvanically isolated DC / DC converter. This galvanically isolated DC / DC converter has a primary winding assigned to the high-voltage network and a number of secondary windings corresponding to the number of low-voltage networks, each assigned to its respective low-voltage network. This reduces the number of components required compared to two separate DC / DC converters, as only one primary winding needs to be constructed.

[0008] In one embodiment, the DC / DC converter is designed as a bidirectional DC / DC converter. This allows energy to be transferred from the two low-voltage networks to the high-voltage network, for example, to pre-charge an intermediate circuit capacitor in the high-voltage network. This eliminates the need for a pre-charging circuit in the high-voltage network.

[0009] In another embodiment, the DC / DC converter is designed to transfer energy between the secondary windings. This allows the low-voltage networks to continue operating redundantly in the event of a high-voltage network failure.

[0010] In a further embodiment, a separating element is assigned to at least one subnetwork. The separating elements are preferably located between the windings and smoothing or...

[0011] The isolating elements are arranged between the DC link capacitors. Alternatively, they can also be arranged between the smoothing or DC link capacitors and the battery connections. The isolating element(s) can, for example, disconnect a subnetwork during charging or disconnect a defective subnetwork.

[0012] In another embodiment, at least one subnetwork is assigned two separating elements, so that it can be disconnected on all poles.

[0013] In a further embodiment, each subnetwork is assigned at least one separating element; more preferably, each subnetwork is assigned two separating elements.

[0014] In another embodiment, the isolating elements are designed as relays and / or semiconductor switches. The advantage of relays is that they provide galvanic isolation of the subnetworks, whereas semiconductor switches switch faster. This can also be combined in a targeted manner, so that a semiconductor switch quickly disconnects the subnetwork, while the slower relay then provides at least single-pole galvanic isolation of the subnetwork.

[0015] A preferred area of ​​application is its use in a partially or fully automated driving vehicle.

[0016] The invention is explained in more detail below with reference to a preferred embodiment. The single figure shows a schematic block diagram of an electrical network in a motor vehicle.

[0017] In the Fig.Figure 1 schematically depicts an electrical network 1 in a motor vehicle. The electrical network 1 comprises a high-voltage network 2, a first low-voltage network 3, and a second low-voltage network 4. For clarity, only a high-voltage battery 5 and two main contactors HS1 and HS2 are shown in the high-voltage network 2. Similarly, only a first on-board battery 6 is shown for the first low-voltage network 3, and only a second on-board battery 7 is shown for the second low-voltage network 4. A galvanically isolated DC / DC converter 8 is arranged between the high-voltage network 2 and the two low-voltage networks 3 and 4. The DC / DC converter 8 has a primary winding 9, a first secondary winding 10, and a second secondary winding 11. Each winding 9-11 is assigned an active rectifier with at least four switching elements S1-S4.Due to the diagonal arrangement of the switching elements S1-S4, depending on the energy transfer direction, either the DC voltage of the associated battery 5-7 can be converted into an AC voltage, or the AC voltage induced in the winding 9-11 can be rectified into a DC voltage. A smoothing capacitor C is also provided in each case. Two isolating elements TR1, TR2 are arranged between the smoothing capacitors C and the switching elements S1-S4 or the windings 9-11. The switching elements S1-S4 and the isolating elements TR1, TR2 are controlled by at least one control unit (not shown).

[0018] If the first auxiliary battery 6 and / or the second auxiliary battery 7 is to be charged from the high-voltage battery 5, an alternating voltage is generated in the primary winding 9, which then induces a voltage in the secondary windings 10, 11. This voltage is then rectified, resulting in a charging current. If one of the two auxiliary batteries 6, 7 is not to be charged, it is disconnected by opening the associated isolating elements TR1, TR2. Even in the event of a defective switching element S1-S4, the corresponding subnetwork can be disconnected by the isolating elements TR1, TR2, so that there are no feedback effects.

[0019] If, on the other hand, an intermediate circuit capacitor of the high-voltage network 2 is to be pre-charged, the DC voltages of the first and / or second on-board battery 6, 7 are converted into an AC voltage, which induces an AC voltage in the primary winding 9. This AC voltage is then rectified and charges the intermediate circuit capacitor. The smoothing capacitor C on the high-voltage side can also be used as an intermediate circuit capacitor.

[0020] Furthermore, energy transfer can also occur via the two secondary windings 10, 11, so that the first on-board battery 6 charges the second on-board battery 7 or vice versa. This is important, for example, if a defective high-voltage network 2 needs to be disconnected. It goes without saying that this principle can also be applied to more than two low-voltage networks 3, 4. Reference symbol list 1 electrical network 2 High-voltage network 3 first low-voltage network 4 second low-voltage network 5 high-voltage batteries 6 first on-board battery 7 second on-board battery 8 DC / DC converters 9 Primary winding 10 first secondary winding 11 second secondary winding S1-S4 switching elements TR1-TR2 separating elements HS1, HS2 Main Gunner C smoothing capacitor 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] DE 102012203612 A1

[0004]

Claims

[1] Electrical network (1) in a motor vehicle, wherein the electrical network (1) has at least one high-voltage network (2) and at least two low-voltage networks (3, 4), wherein the high-voltage network (2) and the at least two low-voltage networks (3, 4) are connected to one another via a galvanically isolated DC / DC converter (8), wherein the galvanically isolated DC / DC converter (8) has a primary winding (9) assigned to the high-voltage network (2) and has a number of secondary windings (10, 11) corresponding to the number of low-voltage networks (3, 4), each of which is assigned to its assigned low-voltage network (3, 4). [2] Electrical network according to claim 1, characterized by that the DC / DC converter (8) is designed as a bidirectional DC / DC converter (8). [3] Electrical network according to one of the preceding claims, characterized bythat the DC / DC converter (8) is designed such that it can transfer energy between the secondary windings (10, 11). [4] Electrical network according to one of the preceding claims, characterized by that at least one circuit breaker (TR1, TR2) is assigned to at least one sub-network (2-4). [5] Electrical network according to claim 4, characterized by that two isolating switches (TR1, TR2) are assigned to at least one sub-network (2-4). [6] Electrical network according to claim 4 or 5, characterized by that at least one disconnector (TR1, TR2) is assigned to each subnetwork (2-4). [7] Electrical network according to one of claims 4 to 6, characterized by that the isolating elements (TR1, TR2) are designed as relays and / or semiconductor switches.

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