DE102018217205A1 - Circuit arrangement for a two-voltage electrical system - Google Patents

Abstract

The invention relates to a circuit arrangement (10) for a dual voltage electrical system. The circuit arrangement (10) comprises a first sub-network (34) which has a first operating voltage, the first sub-network (34) being connected to at least two energy stores (46a, 46b, 46c, 46d) which are connected in series, a first charging arrangement (12) which is connected to the energy stores (46a, 46b, 46c, 46d) connected to the first sub-network (34) and via which these energy stores (46a, 46b, 46c, 46d) can be charged with the first operating voltage , a second sub-network (50) which has a second operating voltage which is lower than the first operating voltage, the second sub-network (50) being connected to at least one energy store (46a), and a second charging arrangement (13) which is connected to the at least one energy store (46a) connected to the second sub-network (50) and via which the at least one energy store (46a) can be charged with the second operating voltage, the E. connected to the first sub-network (34) Energy storage devices (46a, 46b, 46c, 46d) comprise the at least one energy storage device (46a) connected to the second subnetwork (50) and a capacity of the at least one energy storage device (46a) which is additionally connected to the second subnetwork (50) is, as each individual capacity of the remaining energy stores (46b, 46c, 46d) connected exclusively to the first sub-network (34).

Description

The present invention relates to a circuit arrangement for a dual-voltage electrical system and a motor vehicle, which has such a circuit arrangement.

In motor vehicles, electrical systems in the form of multi-voltage electrical systems, in particular dual-voltage electrical systems, are becoming increasingly important. A first sub-network (low-voltage on-board network) can have a first, lower on-board network voltage (in particular 12V, 14V or 28V) and a second sub-network (high-voltage on-board network) can have a second, higher on-board network voltage (in particular 48V). A high-voltage on-board electrical system can have a high-performance energy store (high-voltage battery HVB), for example a 48V Li-ion battery. Such high-voltage batteries are usually assigned its own control unit (BMS battery management system). The interface between the low-voltage electrical system and the high-voltage electrical system is in particular a direct voltage converter (DC / DC converter).

State of the art

From the DE 10 2015 209 227 A1 a two-voltage electrical system is known, in which an operation with a voltage of 48V and a voltage of 12V is realized. Energy storage devices are provided for each sub-network in order to supply the consumers with energy. The voltage of the 48V subnet can be transformed to a voltage of 12V via a DC / DC converter, so that the 12V subnet can be supplied with energy from the 48V subnet.

The background of the invention is that, in addition to the traction on-board electrical system, electric vehicles require a 14V on-board electrical system to supply the auxiliary consumers, such as control units for the brakes, air conditioning, vehicle control, electrical steering, lighting, navigation device or audio system. In the case of a high-voltage electric vehicle, the 14V electrical system is fed via a DC / DC converter. In addition, a 14V backup battery supports the vehicle electrical system voltage.

Such a backup battery is necessary, for example, in the parked state when the high-voltage network is deactivated. Since the DC / DC converter has poor efficiency in extreme part-load operation, this would lead to increased energy consumption and a discharge of the traction battery in the long run. Therefore, the DC / DC converter is not active in this case. The backup battery is also required to compensate for short-term power peaks e.g. from the steering or the braking system, which exceed the power of the DC / DC converter.

It is therefore the object of the present invention to provide a circuit arrangement for a dual-voltage on-board electrical system, in which the aforementioned disadvantages are avoided if the buffer battery is dispensed with.

Disclosure of the invention

The object is achieved by a circuit arrangement for a dual-voltage electrical system according to claim 1. The respective dependent claims refer back to advantageous developments of the invention.

The circuit arrangement according to the invention for a dual-voltage on-board network here comprises a first sub-network which has a first operating voltage, the first sub-network being connected to at least two energy stores which are connected in series, a first charging arrangement which is connected to the energy stores connected to the first sub-network and via which these energy stores can be charged with the first operating voltage, a second sub-network which has a second operating voltage which is lower than the first operating voltage, the second sub-network being connected to at least one energy store, and a second charging arrangement which is connected to the at least one energy store connected to the second subnet and via which the at least one energy store can be charged with the second operating voltage, the energy store connected to the first subnet the at least one energy connected to the second subnet comprise memory and a capacity of the at least one energy storage device, which is additionally connected to the second sub-network, is higher than each individual capacity of the other energy storage devices connected exclusively to the first sub-network.

Any type of energy storage, such as e.g. Batteries or accumulators or capacitors understood. Capacity is understood here to mean the amount of charge that such an energy store can store. A higher capacity is preferably made possible by a higher number of cells connected in parallel or by cells with a higher capacity.

According to the invention, the at least one energy store is thus connected both to the first subnetwork and to the second subnetwork, while the other energy stores are only connected to the first subnetwork. Consequently, the energy storage, which also with the connected to the second subnet is the highest capacity of all the energy stores connected to the first subnet. “Connected” in the sense of the invention is generally understood to mean an electrical connection between the electrical components.

The invention has the advantage that an additional, separate buffer battery for the low-voltage network can be dispensed with. The buffer battery is thus realized by the additional capacity of the energy store connected to the first and the second sub-network. This can save space and reduce weight. In addition, costs are minimized and losses due to voltage conversion while driving are significantly reduced. In addition, a DC / DC converter can be dimensioned between the high-voltage energy store and the low-voltage energy store with a significantly lower power. This also reduces losses for voltage conversion.

In a preferred embodiment of the invention, the capacity of the at least one energy store, which is also connected to the second subnet, and which goes beyond the capacity of the other energy stores connected exclusively to the first subnetwork, is designed for an average output of secondary consumers. This has the advantage that losses caused, for example, by a downward conversion can be minimized, so that the range is hardly reduced.

In a further preferred embodiment of the invention, the first charging arrangement is a charger, via which the energy stores connected to the first sub-network can be charged with the first operating voltage. With this charger, the energy stores connected to the first sub-network can be charged with the appropriate voltage.

The second charging arrangement is preferably a charger via which the at least one energy store connected to the second sub-network can be charged with the second operating voltage. A charger has the advantage that this one mains voltage can be adapted to the energy store connected to the second sub-network for charging. This would make no additional components necessary.

The charger for the energy store of the first subnet and the charger for the at least one energy store of the second subnet are particularly preferably the same. As a result, no additional chargers are necessary, so that installation space can be saved.

In an advantageous embodiment of the invention, the second charging arrangement comprises the charger, for the energy stores connected to the first sub-network, and a step-down converter, so that the at least one energy store connected to the second sub-network can be charged with the second operating voltage. A step-down converter has the advantage that charge can be shifted from the high-voltage energy store to the low-voltage energy store if necessary. In addition, the losses due to the charge adaptation during the downward conversion during the charging process do not reduce the range of a motor vehicle which has such a circuit arrangement.

A step-down converter also has the advantage that the low-voltage energy store is charged with a higher current than the remaining part of the higher-voltage energy store. As a result, low voltage can be taken into account when charging the higher capacity of the energy store.

In an advantageous development, a contactor is arranged between the first sub-network and the step-down converter, so that the step-down converter can be electrically disconnected from the first sub-network. This has the advantage that the second sub-network, for example in the case of a parked vehicle, can be separated from the first part, so that the charges of the energy stores are not balanced.

In a preferred embodiment, the first operating voltage is 48V . The second operating voltage is advantageous 14V . With such a voltage, the two subnetworks can be connected to the vehicle ground without electrical isolation. Such voltages simplify the electrical structure of the circuit arrangement.

The invention additionally comprises a motor vehicle with the circuit arrangement according to the invention for a dual voltage electrical system. With such a motor vehicle, the advantages mentioned for the circuit arrangement for a dual voltage electrical system can be achieved.

• 1 Schaltungsanordnung für ein Zweispannungsbordnetz nach einem ersten Ausführungsbeispiel, und
• 2 Schaltungsanordnung für ein Zweispannungsbordnetz nach einem zweiten Ausführungsbeispiel.

Embodiments of the invention are shown in the drawing and explained in more detail in the following description. It shows:

• 1 Circuit arrangement for a two-voltage electrical system according to a first embodiment, and
• 2nd Circuit arrangement for a two-voltage electrical system according to a second embodiment.

1 shows a circuit arrangement 10th for a dual voltage electrical system according to a first embodiment. This circuit arrangement 10th points as the first and second loading arrangement 12th , 13 a charger 14 on which to charge with a power grid 18th is connectable. The charger 14 is with a vehicle mass 22 electrically connected and has a first connection 26 for a first operating voltage, which here is for example 48V, and a second connection 30th for a second operating voltage, which is here, for example, 14V.

The circuit arrangement 10th also has a first subnet 34 on which with the first connection 26 the charger 14 is electrically connected. The first subnet 34 includes one with the vehicle mass 22 connected inverter 38 , via which the DC voltage can be converted into a three-phase AC voltage for an electric motor M.

The first subnet 34 is with several in series, with the vehicle mass 22 connected, energy storage 46a , 46b , 46c , 46d , are electrically connected. Electrical energy can thus be stored between these energy stores 46a , 46b , 46c , 46d and the first subnet 34 it will be exchanged.

The circuit arrangement 10th also has a second subnet 50 on which with the second connector 30th the charger 14 is electrically connected. The second subnet 50 is with a secondary consumer 54 electrically connected. The secondary consumer 54 includes consumers such as control units for the brakes, air conditioning, vehicle control, electrical steering, lighting, navigation device or audio system. This secondary consumer 54 is also with the vehicle mass 22 electrically connected.

The second subnet 50 is with the energy storage 46a , is electrically connected. Compared to those with only the first subnet 34 connected energy storage 46b , 46c , 46d , which have a capacity of X Ah, has the energy storage 46a , which additionally with the second subnet 50 a capacity of X + Y Ah is electrically connected. The capacity of this energy storage 46a is thus larger by the amount of Y Ah than the capacity of those with only the first subnet 34 connected energy storage 46b , 46c , 46d .

In 2nd is a circuit arrangement 10th shown for a dual voltage electrical system according to a second embodiment. This embodiment differs from the first embodiment in particular in that the charger 14 only the first connection 26 for the first operating voltage, which is 48V here. In the second exemplary embodiment, the second charging arrangement comprises 13 therefore in addition to the charger 14 a buck converter 58 .

The down converter 58 is a common step-down converter, which has a diode D, a coil L and a capacitor 62 includes. The down converter 58 is with the vehicle mass 22 and with the energy storage 46a electrically connected. Via a contactor S, which is between the buck converter 58 and the first subnet 34 is arranged is the step-down converter 58 from the first subnet 34 electrically separable.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102015209227 A1 [0003]

Claims (9)

Circuit arrangement (10) for a dual-voltage on-board network, the circuit arrangement (10) comprising: - a first sub-network (34) which has a first operating voltage, the first sub-network (34) having at least two energy stores (46a, 46b, 46c, 46d) , which are connected in series, - a first charging arrangement (12) which is connected to the energy stores (46a, 46b, 46c, 46d) connected to the first sub-network (34) and via which these energy stores (46a, 46b , 46c, 46d) can be charged with the first operating voltage, - a second sub-network (50) which has a second operating voltage which is lower than the first operating voltage, the second sub-network (50) being connected to at least one energy store (46a) , and - a second charging arrangement (13) which is connected to the at least one energy store (46a) connected to the second sub-network (50) and via which the at least one energy store (46a) is connected to the second operating voltage g is chargeable, characterized in that the energy stores (46a, 46b, 46c, 46d) connected to the first sub-network (34) comprise the at least one energy store (46a) connected to the second sub-network (50) and a capacity of the at least one energy store (46a), which is additionally connected to the second sub-network (50), is higher than each individual capacity of the remaining energy stores (46b, 46c, 46d) exclusively connected to the first sub-network (34). Circuit arrangement (10) for a two-voltage electrical system according to Claim 1 , characterized in that the capacity of the at least one energy store (46a) which goes beyond the capacity of the other energy stores (46b, 46c, 46d) connected exclusively to the first subnetwork (34) and which is additionally connected to the second subnetwork (50) is designed for an average output of secondary consumers (54). Circuit arrangement (10) for a two-voltage electrical system according to Claim 1 or 2nd , characterized in that the first charging arrangement (12) is a charger (14), via which the energy stores (46a, 46b, 46c, 46d) connected to the first sub-network (34) can be charged with the first operating voltage. Circuit arrangement (10) for a dual-voltage electrical system according to one of the preceding claims, characterized in that the second charging arrangement (13) is a charger (14), via which the at least one energy store (46a) connected to the second sub-network (50) is connected to the second Operating voltage is loadable. Circuit arrangement (10) for a two-voltage electrical system according to Claim 3 , characterized in that the second charging arrangement (50) comprises the charger (14) for the energy stores (46a, 46b, 46c, 46d) connected to the first sub-network (14), and a step-down converter (58), so that the at least one an energy store (46a) connected to the second sub-network (50) can be charged with the second operating voltage. Circuit arrangement (10) for a two-voltage electrical system according to Claim 5 , characterized in that a contactor (S) is arranged between the first sub-network (34) and the step-down converter (58), so that the step-down converter (58) can be electrically separated from the first sub-network (34). Circuit arrangement (10) for a two-voltage electrical system according to one of the preceding claims, characterized in that the first operating voltage is 48V. Circuit arrangement (10) for a two-voltage electrical system according to one of the preceding claims, characterized in that the second operating voltage is 14V. Motor vehicle with a circuit arrangement (10) for a dual voltage electrical system according to one of the preceding claims.

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