Vehicle electrical system

Abstract

Vehicle electrical system (VES) with a DC charging port (DC), an accumulator (AC), a first DC-DC converter (W1), and an electric drive (I, M), wherein the first DC-DC converter (W1) has a first side (1S) which is connected to a connection point (VP) via a first switch (S1), and the first DC-DC converter (W1) has a second side (2S) to which the electric drive (I, M) is connected and which is connected to the accumulator (AC) or directly to the accumulator (AC) via a second switch (S2) and via the connection point (VP), wherein the vehicle electrical system has a second DC-DC converter (W2) which is connected to one side of the first switch (S1).wherein the second DC-DC converter (W2) is connected to the first side of the first DC-DC converter (W1) and wherein a low-voltage branch (NV) of the vehicle electrical system (FB) is connected via the second DC-DC converter (W2) to one side of the first switch (S1).

Description

[0001] Electric vehicles have a battery that can supply the electric drive with energy. The vehicles are known to have a charging port for charging the battery ("plug-in vehicles"). The charging and powering functions of the electric drive are performed by the vehicle's electrical system. Furthermore, there are electrical consumers that require a lower voltage than the electric drive, such as the 12 V on-board electronics.

[0002] US 2018 / 0254658 A1 discloses a dual-voltage power supply having at least one battery with a plurality of battery modules and a first set of switches for connecting the battery modules in series to thereby provide a first voltage for a first circuit when the first switches are closed, and for disconnecting the series connection housing when the first switches are open. At least one connection tap is connected to one of the battery modules to provide its voltage to a second circuit operating at a lower voltage than the first circuit and connected in parallel to other battery modules by a second set of switches. The other battery modules are connected in parallel to one another, and one of the battery modules can be charged with commercially available generators when the second set of switches is closed and not connected in parallel when the second set of switches is open.

[0003] DE 10 2017 001 470 A1 relates to an electrical system for an electrically driven vehicle, comprising a filter unit, a power factor correction filter electrically coupled or coupleable to the filter unit, and a galvanic isolation unit electrically coupled to the power factor correction filter.

[0004] From the document DE 10 2017 213 682 A1 a battery charging device for a motor vehicle is known, which is designed for arrangement in the motor vehicle, with a first stage which has a power correction filter, and a second stage which has an inverter, wherein the first stage is electrically connected to the second stage via an intermediate point, wherein the intermediate point is directly electrically connected to a feed connection for direct voltage, which is designed for direct electrical coupling to a high-voltage on-board network of the motor vehicle.

[0005] From the document US 2018 / 159425 A1 a DC-DC converter is known, comprising: a first transformation unit which includes a first primary winding and a second primary winding and is configured to convert a voltage applied to the first primary winding or the second primary winding and output the converted voltage to a first secondary winding, a second transformation unit which includes a third primary winding and a fourth primary winding and is configured to convert a voltage applied to the third primary winding or the fourth primary winding and output the converted voltage to a second secondary winding, wherein the first primary winding and the third primary winding are connected in series with each other and the second primary winding and the fourth primary winding are connected in series with each other.

[0006] The task is therefore to show a possibility with which the accumulator or the electric drive on the one hand and the consumers on the other hand can be supplied with lower voltage in a simple way.

[0007] This object is achieved by the vehicle electrical system according to claim 1. Further properties, features, embodiments and advantages result from the subclaims, the description and the figure.

[0008] The vehicle electrical system described here comprises a battery, a first DC-DC converter, a second DC-DC converter, and an electric drive. The battery is connected to a first side of the first DC-DC converter via a first switch and to the second side of the DC-DC converter via a second switch. While the electric drive is connected to the second side of the converter, the second DC-DC converter is connected to the first side of the first DC-DC converter (directly or via the first switch).

[0009] This separates the electric drive from the voltage source for the second DC-DC converter, as both the first converter and the second switch can be used to electrically isolate the second DC-DC converter from the electric drive. Furthermore, this approach allows the accumulator to be connected to the second DC-DC converter and supply power to it while the electric drive can be disconnected.

[0010] This means that at least one safety-relevant system of the vehicle can be supplied by the second DC-DC converter, for example a component such as an electric steering system or a control system for an electric brake (or the electric brake itself), if the electric drive is defective or a fault is detected on the second side of the first DC-DC converter. A short circuit on the second side of the first converter, for example caused by the electric drive, can thus be isolated from the second DC-DC converter by means of the second switch and the first DC-DC converter. In addition, a fault on the second side of the first DC-DC converter can be isolated from the accumulator by means of the first DC-DC converter and the second switch, which in this case can, however, supply the second DC-DC converter.The second switch (and the first DC-DC converter) thus serve to isolate a potentially defective network section containing the electric drive, while the section of the vehicle's electrical system that supplies the second DC-DC converter can be powered by the accumulator. Furthermore, the second DC-DC converter allows the voltage level of the power supply to be adjusted to an operating voltage suitable for the aforementioned components.

[0011] Thus, there is a connection point to which the accumulator is connected, and from which the first and second switches originate, connecting the connection point to the first or second side of the first DC-DC converter. Since the second DC-DC converter is connected to the first side of the first DC-DC converter, and the connection point itself is connected to the accumulator, a portion of the vehicle electrical system can be shut off using the second switch (which leads to the second side of the first DC-DC converter), in particular a portion containing the electric drive, which can thus be disconnected in the event of a defect. Safety-relevant components such as an electric brake, an electric steering system or controls thereof are connected to the second DC-DC converter, although other components such as driving assistance systems can also be connected to it.

[0012] The DC voltage connection can also be connected to the connection point (e.g., via a switch). This allows the second DC-DC converter and thus the components connected to it to be supplied via the connection point during DC charging, while the first DC-DC converter is not necessarily active. Because both the accumulator and the second DC-DC converter are connected to the same connection point as the DC charging connection, energy can also be transferred from the connection point, DC voltage connection, or accumulator to the second DC-DC converter during the transfer of energy from the DC charging connection to the accumulator.

[0013] A vehicle electrical system is described which has a DC charging connection, a rechargeable battery, a first DC-DC converter, and an electric drive. The first DC-DC converter (hereinafter also: first converter) has a first side which is connected to a connection point via a first switch. The first converter has a second side to which the electric drive is connected. The converter is designed to transfer energy between the first and second sides and, in the process, to change the voltage level. (This also applies to the second converter.) The second side of the first converter is connected to the rechargeable battery, for example directly or via a second switch and via the connection point. The vehicle electrical system has a second DC-DC converter which is connected to one side of the first switch.Thus, the second DC-DC converter is connected to the connection point, either directly or via the first switch. In other words, the second DC-DC converter is connected to the first side of the first converter, either directly or via the first switch. The second DC-DC converter is also referred to as the second converter.

[0014] The vehicle electrical system is preferably a high-voltage electrical system. The DC charging connection is preferably designed according to a standard for line-related charging. The accumulator is preferably a traction accumulator, with the electric drive preferably serving as the vehicle's drive and thus being connected to a vehicle output. This particularly applies to the vehicle in which the vehicle electrical system is provided. The accumulator is, for example, a lithium accumulator. The switches mentioned here are preferably two-pole and are designed to separate a positive or negative voltage potential (thus an all-pole connection) or to provide a corresponding connection at the respective potential.

[0015] The second DC-DC converter is connected (directly, i.e., without a switch or converter) to the first side of the first DC-DC converter. The second DC-DC converter is connected, in particular, to the accumulator, either directly, via the first switch, and / or via a switch used to connect the accumulator to the remaining vehicle electrical system.

[0016] The accumulator is preferably connected to the connection point via a third switch. This third switch serves to switchably connect the accumulator to the remaining vehicle electrical system. The third switch and the accumulator can be provided in a first housing, while the second switch and the converters are provided in another housing. A detachable plug connection can be provided between the third switch and the remaining vehicle electrical system. The third switch can thus be connected to the remaining vehicle electrical system via a detachable connection. The detachable connection comprises, in particular, at least one plug connection and a (at least two-wire) cable.

[0017] The first and second DC-DC converters are preferably each designed as galvanically isolating DC-DC converters. Thus, the converters each comprise at least one transformer that galvanically isolates the first side of the converter from the second side of the converter. The first and second DC-DC converters can thus comprise a chopper, at least one transformer, and a rectifier (connected to each other in this order) to convert a first DC voltage and a second DC voltage.

[0018] The vehicle electrical system comprises a low-voltage electrical system branch, which is connected to one side of the first switch (or to the accumulator) via the second DC-DC converter. The low-voltage electrical system branch can therefore be supplied from the first side of the converter or from the connection point via the second converter. The low-voltage electrical system branch has, in particular, a nominal voltage of 12 volts, 13 volts, or 14 volts, in particular of 12 to 14 volts or of substantially 24 volts. The low-voltage electrical system branch can furthermore have a nominal voltage of 48 volts. The second DC-DC converter is designed to output a voltage of 12 to 14 volts, of substantially 24 volts, or of substantially 48 volts on the side on which it is connected to the low-voltage electrical system branch.The opposite side of the second converter is designed to operate with a voltage of essentially 400 volts, 600 volts or 800 volts and to generate the said nominal voltage of the low-voltage vehicle electrical system branch from this voltage.

[0019] The second DC-DC converter can also comprise a transformer as a galvanically isolating converter, in particular a transformer that provides galvanic isolation. The second DC-DC converter has, in particular, a chopper, a galvanically isolating transformer, and a rectifier, which are connected to one another in this order.

[0020] The second DC-DC converter has a high-voltage side connected to one side of the first switch (and thus connected to the first side of the converter or to the connection point). The high-voltage side can also be considered the first side of the second DC-DC converter, while the second side of the second converter is connected to the low-voltage vehicle electrical system branch.

[0021] The DC charging port is preferably connected to the connection point via a fourth switch. In particular, the DC charging port is connected to the first switch or the third switch via the fourth switch. Furthermore, the DC charging port is connected to the second switch via the fourth switch. The DC charging port is connected, in particular, to the first converter or its first side via the fourth switch and the subsequent first switch.

[0022] The vehicle electrical system may further include an AC charging port. This is preferably connected to the first side of the DC-DC converter via a rectifier device of the vehicle electrical system. The rectifier thus has an AC side connected to the AC charging port and also has a DC side connected to the first converter or its first side. In particular, the AC charging port is connected to the first switch via the rectifier device.

[0023] The AC charging connection is connected to the connection point via the rectifier device and the downstream first switch. The accumulator is also connected to the connection point via the third switch, so that the AC connection can charge the accumulator via the rectifier and the relevant switches. The rectifier device is preferably designed as a power factor correction filter and thus has a rectifying and boosting function. The rectifier device is preferably three-phase, but can also be single-phase. The AC charging connection is also preferably three-phase, but can also be single-phase. The rectifier device can be designed as a full-wave rectifier, preferably as a three-phase full-wave rectifier or as a single-phase full-wave rectifier.The rectifier device can also be designed as a controllable or non-controllable rectifier. Preferably, the rectifier device is designed as a power factor correction filter, in particular as a Vienna filter.

[0024] The right voltage charging port and the DC charging port may be provided in the same charging port module and are preferably designed according to a standard for charging electrically powered vehicles.

[0025] It can be provided that the third switch is connected to the connection point via a detachable connection. As mentioned, this detachable connection can comprise at least one plug-in connection element, preferably at least two plug-in elements, which are connected to one another via a (at least two-wire) cable. Thus, the third switch and the accumulator can be housed in a housing, which is connected to at least parts of the remaining vehicle electrical system via the detachable connection.

[0026] The accumulator and the third switch, on the one hand, and the first switch, the second switch, the first DC-DC converter, and the second DC-DC converter, on the other hand, can be housed in different housings. A first housing can thus enclose the accumulator and the third switch, while a second housing encloses neither the accumulator nor the third switch, but at least the first switch, the second switch, the first DC-DC converter, and the second DC-DC converter.

[0027] The electric drive is preferably designed as a high-voltage component and in particular has a nominal voltage of at least 400 volts, 600 volts, or 800 volts. Alternatively, or in combination, at least one further high-voltage component can be connected to the second side of the first converter. The further high-voltage component can be, for example, an electrically heatable catalyst, another electrical heating device, or an electric motor for driving an electric compressor.

[0028] The second DC-DC converter is preferably designed to be multi-phase. The second DC-DC converter comprises a plurality of individual converters. These are connected to one another, preferably in parallel, on the side of the DC-DC converter that is connected to the low-voltage vehicle electrical system branch. The plurality of individual converters can be connected via a configuration circuit to a first side of the first switch, in particular to the first side of the first converter or to the connection point. The configuration circuit is configured to connect the individual converters to one another in series in a first configuration state and to connect the individual converters to one another in parallel in a second configuration state. This particularly applies to the side of the respective individual converters that is connected to one side of the first switch.In other words, the configuration circuit is connected to the side of the second converter that is facing away from the low-voltage electrical system branch.

[0029] It can be provided that each individual converter has an intermediate circuit capacitor. This is preferably provided at the point where the individual converters are connected to the configuration circuit. Each individual converter thus comprises an intermediate circuit capacitor that is connected to one side of the first switch via the configuration circuit. The intermediate circuit capacitors are connected to one another in series or in parallel, depending on the configuration state. In other words, the configuration circuit is designed to connect the intermediate circuit capacitors to one another in parallel or in series in different configuration states. In particular, the intermediate circuit capacitors are connected to one another in series when the configuration circuit is in the first configuration state. The intermediate circuit capacitors are connected to one another in parallel when the configuration circuit is in the second configuration state.The intermediate circuit capacitors are located primarily at the inputs of the individual converters. These are located on the side of the second converter facing away from the low-voltage electrical system.

[0030] A low-voltage accumulator can be located in the low-voltage vehicle electrical system branch, while the accumulator connected to the connection point can be a high-voltage accumulator. The accumulator, which is (switchably) connected to the connection point, preferably has a nominal voltage of at least 400, 600, or 800 volts. The accumulator within the low-voltage vehicle electrical system preferably has a nominal voltage of essentially 12 to 14 volts, essentially 24 volts, or essentially 48 volts.

[0031] A controller may be provided that is connected to the first and second switches for controlling purposes, and may also be connected to the third, fourth, and / or fifth switches for controlling purposes. Furthermore, the controller may be connected to the first and second converters for controlling purposes.

[0032] The Fig. 1 serves to explain in more detail the vehicle electrical system described here and how it works.

[0033] The vehicle electrical system FB shown is connected to an AC voltage source WQ and a DC voltage source GQ via a charging interface LS. These can be considered part of a charging station (outside the vehicle electrical system FB). The respective sources WQ and GQ are connected to the corresponding charging ports WA and GA of the vehicle electrical system FB via isolating switches T1 and T2. In particular, these sources WA and GA are connected to the AC charging port WA of the vehicle electrical system and to the DC charging port GA of the vehicle electrical system FB.

[0034] The vehicle electrical system FB comprises a rechargeable battery AK, which is connected to a first DC-DC converter W1 via a first switch S1. This converter has two sides (a first side 1S and a second side 2S) that are electrically isolated from each other. The vehicle electrical system FB further comprises a second switch S2. Like the first switch S1, this second switch is connected to the connection point VP. Furthermore, the rechargeable battery AK is connected to this connection point VP via a third switch S3. A fourth switch S4 connects the DC charging connection GA to the connection point VP.

[0035] A detachable connection LV connects the third switch S3 (via which the accumulator AK is connected to the connection point VP) to the connection point VP. The connection point VP is connected via the first switch S1 to the first side 1S of the first converter W1 and via the second switch S2 to the second side 2S of the first converter W1.

[0036] A second DC-DC converter W2 is connected to the first switch S1. In particular, the converter W2 is connected to one side of the first switch S1, in particular to the side of the first switch connected to the first side 1S of the first converter W1, or to the connection point VP, i.e., to the first side of the first switch S1 connected to the connection point VP. The latter connection is shown in dashed lines. Both possible connections are alternative to each other. Via the second converter W2, a low-voltage vehicle electrical system branch NV is connected to the first side 1S of the first converter W1, or to the connection point VP (to which the accumulator is connected via the third switch S3).The low-voltage electrical system branch NV can (in addition to a second accumulator) comprise at least one safety-relevant component, for example, an electric steering drive or its control, or an electric brake or its control. The accumulator and both sides of the first converter W1 are preferably designed for high-voltage applications, in particular for nominal voltages of at least 400 volts. The circuit shown allows the low-voltage electrical system branch to be supplied via the second converter W2, even if the second switch S2 is open, for example, to discharge defective loads.

[0037] The second switch S2 can connect the connection point VP to the first converter W1 or to its second side 2S. Alternatively (shown in dotted lines), the second switch S2 can connect the accumulator AK to the first converter W1 or to its second side 2S. In this case, as shown in dotted lines, the second switch is not connected to the connection point VP.

[0038] The DC charging terminal GA is connected to the connection point VP via a fourth switch S4. The DC charging terminal GA is thus connected to the first side 1S of the first converter W1 via the fourth switch S4 and the first switch S1. The AC voltage terminal WA is connected to the first side 1S of the first converter W1 (and thus also to the first switch S1) via the fifth switch S5 and a rectifier device GR.

[0039] In the illustrated embodiment, the second DC-DC converter W2 is multi-phase, in particular two-phase. In the specific example illustrated, the second converter W2 comprises two individual converters connected to the low-voltage vehicle electrical system branch NV. A configuration circuit KO connects the second converter W2 (or its individual converter) to one side of the first switch S1. The configuration circuit KO is configured to switchably connect the side of the individual converters connected to the first switch S1 in parallel or series (and also to connect these sides to the first switch). On the side of the low-voltage vehicle electrical system branch NV2, the individual converters of the second converter W2 are preferably connected to one another in parallel. The side of the second converter W2 connected to one side of the first switch S1 comprises one or more intermediate circuit capacitors; in the case of multiple individual converters, multiple intermediate circuit capacitors.These are also connected to each other in series or in parallel using the configuration circuit KO, especially since these are connected in parallel to the respective inputs of the individual converters.

[0040] In addition to the inverter I and the motor M, which together form part of the electric drive, a high-voltage component K is connected to the second side 2S of the first converter W1. It can be seen that the second converter W2 is not connected as a load or component, but rather to the first side 1S of the first converter. Thus, the electric drive and the second converter are connected to two different, opposite sides 1S, 2S of the first converter W1.

[0041] There may be a controller ST that is connected to the first and second switches, preferably also to the third switch, the fourth switch, and the fifth switch, if present. Furthermore, the controller ST can be connected to the first converter W1 and the second converter W2 in order to at least adjust their activity state (inactive / active).

Claims

[1] Vehicle electrical system (FB) with a DC charging connection (GA), a rechargeable battery (AK), a first DC-DC converter (W1), and an electric drive (I, M), wherein the first DC-DC converter (W1) has a first side (1S) which is connected to a connection point (VP) via a first switch (S1), and the first DC-DC converter (W1) has a second side (2S) to which the electric drive (I, M) is connected and which is connected to the rechargeable battery (AK) or directly to the rechargeable battery (AK) via a second switch (S2) and via the connection point (VP), wherein the vehicle electrical system has a second DC-DC converter (W2) which is connected to one side of the first switch (S1),wherein the second DC-DC converter (W2) is connected to the first side of the first DC-DC converter (W1) and wherein a low-voltage electrical system branch (NV) of the vehicle electrical system (FB) is connected to one side of the first switch (S1) via the second DC-DC converter (W2). [2] Vehicle electrical system (FB) according to claim 1, wherein the accumulator is connected to the connection point (VP) via a third switch (S3). [3] Vehicle electrical system (FB) according to claim 1 or 2, wherein the first and the second DC-DC converter (W1, W2) are each galvanically isolating DC-DC converters. [4] Vehicle electrical system (FB) according to one of the preceding claims, wherein the second DC-DC converter (W2) has a high-voltage side which is connected to one side of the first switch (S1) and has a low-voltage side which is connected to the low-voltage vehicle electrical system branch (NV). [5] Vehicle electrical system (FB) according to one of the preceding claims, wherein the DC charging connection (GA) is connected to the connection point (VP) via a fourth switch (S4). [6] Vehicle electrical system (FB) according to one of the preceding claims, further comprising an AC charging terminal (WA) which is connected to the first side (1S) of the first DC-DC converter (W1) via a rectifier device (GR) of the vehicle electrical system (FB). [7] Vehicle electrical system (FB) according to claim 6, wherein the AC charging terminal (WA) is connected to the rectifier device (GR) via a fifth switch (S5) and the rectifier device (GR) is connected to the first side (1S) of the first DC-DC converter (W1). [8] Vehicle electrical system (FB) according to one of the preceding claims, wherein the rectifier device is designed as a power factor correction filter. [9] Vehicle electrical system (FB) according to one of the preceding claims, wherein the third switch (S3) is connected to the connection point (VP) via a detachable connection (LV). [10] Vehicle electrical system (FB) according to one of the preceding claims, wherein the accumulator (AK) and the third switch (S3) on the one hand and the first switch (S1), the second switch (S2), the first DC-DC converter (W1) and the second DC-DC converter (W2) on the other hand are accommodated in different housings. [11] Vehicle electrical system (FB) according to one of the preceding claims, wherein the electric drive (I, M) is designed as a high-voltage component and at least one further high-voltage component (K) is connected to the second side (2S) of the first DC-DC converter (W1). [12] Vehicle electrical system (FB) according to one of the preceding claims, wherein the second DC-DC converter (W2) has a plurality of individual converters which are connected to one side of the first switch (S1) via a configuration circuit (KO), wherein the configuration circuit (KO) connects the individual converters in series with one another in a first configuration state and connects the individual converters in parallel with one another in a second configuration state. [13] Vehicle electrical system (FB) according to claim 12, wherein each individual converter has an intermediate circuit capacitor which is connected to one side of the first switch (S1) via the configuration circuit (KO), the intermediate circuit capacitors being connected to one another in series or in parallel depending on the configuration state.

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