Patent ID: 12208695

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The vehicle electrical system FB illustrated in the FIGURE is connected to external voltage sources via a charging interface LS, namely to the AC voltage source WQ and the DC voltage source GQ. These sources can be implemented as a charging station, for example. The vehicle electrical system FB comprises an AC voltage connection WA and a DC voltage connection GA. It should be noted that the AC voltage connection WA is optional. The connections WA, GA are part of the charging interface LS.

A rechargeable battery AK of the vehicle electrical system is connected to a connecting point VP, it being shown that this connection leads via the optional elements PF (pyrofuse) and FE (disconnecting device). These two optional components are provided at the same potential. A first switching unit comprises a switching element S1for the potential N (negative potential) and a diode D for the positive potential P. The diode has a forward direction that points in the current direction that is set for the charging current of the DC charging connection. However, instead of the diode D, a further switching element is preferably used, which is connected instead of the diode at the point at which the diode is provided. A second switching unit comprises the switching elements S1and S2, with a switch or a switching element being provided here for each potential N, P as well. The switch S2is provided at the negative potential N and the switch S3is provided at the positive potential P. The switching elements are each connected in series (at the relevant potential). As a result, the respective potential-carrying line can be disconnected and connected in a controlled manner.

Parallel paths, each of which comprising one of the two switching units, lead away from the connecting point VP or from the rechargeable battery AK. One of the two switching units is provided in each of the paths (connected in series); different switching units are provided in different paths. A changeover switch US is also connected to the switching units, but on the side opposite the connecting point or rechargeable battery. The changeover switch is the first switching unit and connects a first (two-pole) contact or connection (corresponding to switching position1) of the changeover switch US to the rechargeable battery or the connecting point VP. A second (two-pole) contact or connection of the changeover switch US, which corresponds to switching position2, is connected to the connecting point or to the rechargeable battery AK via the second switching unit.

The center connection of the changeover switch US, that is to say the connection which can be connected selectively to switching positions1or2depending on the switching position, is connected to at least one high-voltage consumer. Here, the high-voltage consumers K and W2are provided. The at least one high-voltage consumer K can stand for a heating element (of the air-conditioning system or an exhaust gas after-treatment system) and/or for an electric air-conditioning compressor (or the drive thereof) and/or for other components.

An electric drive comprises an inverter I and an electric machine M, which is connected via the inverter I to the changeover switch US (in particular to the second contact/connection thereof) and to the second switching unit S2, S3. The changeover switch US is connected between the electric drive (traction drive) on the one hand and the at least one high-voltage consumer or the first switching unit S1, D on the other hand. The at least one high-voltage consumer can thus be connected selectively to the first switching unit S1, D or to the second switching unit S2, S3.

The DC charging connection GA is connected to a connection between the first switching unit S1, D and the changeover switch US (in particular the first contact1thereof). In other words, the DC charging connection GA is connected to a first path that leads from the rechargeable battery or from the connecting point to the changeover switch, while the electric drive is connected to a second path that connects the connecting point VP or the rechargeable battery to the changeover switch US.

A controller ST is connected in a controlling manner to the switches S1to S3(in the case of a switching element in the step of the diode also to this switching element) and to the changeover switch US in a controlling manner. In a charging operation, the DC voltage connection is connected to the connecting point or the rechargeable battery AK via the charging unit S1, D, which is then closed. In the charging state, the second switching unit is open, such that there is no connection to the electric drive I, M from the side of the second switching unit. In the charging state, the changeover switch US is in switching position1and thereby connects the at least one high-voltage consumer to the connecting point VP or to the rechargeable battery AK on the one hand and to the DC charging connection GA on the other hand. As a result, the high-voltage consumers K, W2and NV receive a supply voltage, while the switch position of the changeover switch US in switching position1and the open second switching unit S2, S3disconnect the inverter and thus the entire electric drive I, M. As a result, the Cy capacitors do not affect the DC charging connection GA. A high contact voltage is thus avoided.

As mentioned, heating elements and/or an electric air-conditioning compressor can be provided as high-voltage consumers. These are represented symbolically as component K. An additional DC-DC converter W2, which connects the center connection of the changeover switch US to a low-voltage vehicle electrical system NV in a voltage-converting manner, can be provided as a further high-voltage consumer. A multi-phase additional DC-DC converter W2is illustrated, which is DC-isolating, this output being just one example of many. The low-voltage vehicle electrical system can have a nominal voltage of 12 volts, 13 volts or 14 volts or other values below 60 volts.

As an optional configuration, an AC voltage connection WA can be provided, which is connected in particular to a rectifier GR via an optional switch SW. The rectifier GR thus connects the AC voltage connection to a DC-DC converter W2, in particular to a first side15of the DC-DC converter W1. A second side2S of the DC-DC converter is connected to the at least one high-voltage consumer K, W2, NV.

Now that the switch position in the charging state for the case of DC voltage (=DC voltage charging state) has been described above, an AC voltage charging state is described below. In this case, the changeover switch US is in the second switching state2(that is to say the center connection is connected to the connection in switching position2) and the second switching unit is closed, while the first switching unit is open. As a result of the fact that the changeover switch US does not connect the DC-DC converter W2to the DC charging connection GA here and due to the first switching device S1, which is open, no voltage that results from AC charging (in particular the voltage on the second side2S) is applied to the DC charging connection GA. Since in this case the DC-DC converter W1is also a DC-isolating converter, the Cy capacitors of the inverter I and of the electric machine M do not act on the AC charging connection WA.

An alternative connection point for the DC charging connection is marked with an X, this point being between the second switching unit S2, S3and the changeover switch US. In this case, the DC charging connection is connected directly to the inverter I (and thus also to the electric machine M), it being possible for the Cy capacitors to be switchable and switched off in the charging state.

The connections shown to the left of the second switching unit and above and below the connecting point between the first switching unit, changeover switch and DC charging connection are shown with a single line for simplification. However, these connections are to be understood as two-wire connections and are designed in the same way as those connections which are shown explicitly with two potentials and thus with two lines in the FIGURE. The single line thus stands in particular for a two-wire connection with two potentials (N, P).

In general, starting from the first switching device (equipped with two switching elements or with one switching element and one diode) up to the connecting point of the DC charging connection and the changeover switch, a DC-DC converter (buck or boost) can be provided. The controller can be connected to the DC-DC converter in a controlling manner and be set up to open the (operating) switch or switches of the DC-DC converter in the event of an overcurrent. If the first switching device is designed with a diode D, this forms the working diode of the DC-DC converter. If the DC-DC converter is designed as a step-up converter, then the working diode, which follows the working inductance, is formed by the diode D. Since in one embodiment the diode D is part of both the DC-DC converter and the first switching unit, the DC-DC converter and the first switching unit can be partially integrated into one another and can in particular share one component, namely the diode.

Even in a circuit without a changeover switch as shown in the application DE 10 2019 215 855, incorporated herein by reference, a DC-DC converter (boost, step-up converter) can be provided between the first switching unit and the connecting point of the DC charging connection, the working diode of which DC-DC converter is realized by the diode device. The diode or diode device can therefore be integrated in a DC-DC converter which is integrated with the first switching device.