EP4302389A1

EP4302389A1 - Common mode filter with y-capacitors and separating switch for decoupling same from the reference potential

Info

Publication number: EP4302389A1
Application number: EP21802250.7A
Authority: EP
Inventors: Guido RASEK; Alexander Bucher; Georgios Lempidis; Maximilian Frank Gerner
Original assignee: Valeo eAutomotive Germany GmbH
Current assignee: Valeo eAutomotive Germany GmbH
Priority date: 2021-03-03
Filing date: 2021-10-28
Publication date: 2024-01-10
Also published as: US20240136912A1; US20240235373A9; DE102021202042A1; WO2022184293A1

Abstract

The invention relates to a power converter (1, 1a, 1b) for an onboard electrical system (101) of a vehicle (100) which can be electrically driven, having a first line (2) for a first potential (P1), - a second line (3) for a second potential (P2) which differs from the first potential (P1), - a third line (4) for a reference potential (P3) which lies between the first potential (P1) and the second potential (P2), and - a filter device (5) which has a first capacitor (6) and a second capacitor (7) and which is designed to establish a first electrically conductive connection between the first line (2) and the third line (4) via the first capacitor (6) and an electrically conductive connection between the second line (3) and the third line (4) via the second capacitor (7) on the basis of control information (13) and sever the electrically conductive connections along at least one current direction.

Description

COMMON MODE FILTER WITH Y CAPACITORS AND DISCONNECTING SWITCH FOR THEIR DECOUPLING FROM THE REFERENCE POTENTIAL The present invention relates to a power converter for an on-board network of an electrically driven vehicle. In addition, the invention relates to a vehicle electrical system for an electrically driven vehicle.

Electrical components that are intended for automotive applications must meet a large number of specifications for electromagnetic compatibility. In particular, limit values for electromagnetic interference are provided. Effective filtering of such interference in a power converter of the vehicle is necessary, particularly in view of the trend towards increasing nominal voltages that are provided by a traction battery of an on-board network. It is generally known to arrange two capacitors between a first line and a second line for different potentials of the power converter and a third line for a reference potential, which capacitors filter common-mode interference as so-called Y-capacitors. Such a power converter is known, for example, from DE 102017 110608 A1, which discloses an inverter with two supply lines. The supply lines are connected in a filter circuit for reducing common-mode interference, which circuit comprises a filter stage. In the filter stage, each supply line is grounded via a Y-capacitor.

During operation of the power converter, the capacitors store electrical energy between the first and second lines on the one hand and the third line, which is typically at a common potential of a chassis of the vehicle as a reference potential, on the other hand. In certain operating situations of the vehicle, however, there is a specification that only a limited amount of energy may be stored in the capacitors, in particular so that this amount of energy does not flow away as current via the third line in the event of a fault can. However, this amount of energy increases quadratically with the voltage across the capacitors, which in turn is proportional to the nominal voltage of the traction battery of the vehicle electrical system. As a result, the capacitance of the capacitors would have to be reduced disproportionately if the nominal voltage were to be increased in order to comply with the specified limit values for the amount of energy. However, reducing the capacitance reduces the filter effect. There is therefore a conflict of objectives between filter effectiveness and the maximum permissible amount of stored energy.

The invention has for its object to provide a way to operate an electrical system of an electrically powered vehicle with a power converter that allows a high filter efficiency even at high nominal voltage of a traction battery.

This object is achieved according to the invention by a power converter for an on-board power supply system of an electrically drivable vehicle, having a first line for a first potential, a second line for a second potential that differs from the first potential, a third line for a reference potential that lies between the first potential and the second potential, and a filter device which has a first capacitor and a second capacitor and is set up to form an electrically conductive connection between the first line and the third line via the first capacitor and an electrically conductive connection between the produce the second line and the third line via the second capacitor as a function of control information and separate it along at least one current direction.

The power converter according to the invention for a vehicle electrical system of an electrically driven vehicle has a first line for a first potential. The power converter also has a second line for a second potential. The second potential differs from the first potential. The power converter also has a third line for a reference potential. The reference potential lies between the first potential and the second potential. The power converter also has a filter facility up. The filter device has a first capacitor. The filter device also has a second capacitor. The filter device is set up to establish an electrically conductive connection between the first line and the third line via the first capacitor and an electrically conductive connection between the second line and the third line via the second capacitor as a function of control information and along at least one current direction separate.

The filter device of the power converter according to the invention enables the electrically conductive connections via the respective capacitor to be interrupted as a function of the control information which can be obtained, for example, from an external control unit. Depending on the operating state of the vehicle represented by the control information, the electrically conductive connections can be established in order to implement a filter effect of the capacitors, or separated in order to avoid a flow of energy from the capacitors to the third line. The capacitors can thus advantageously be designed with regard to their capacity for the desired filter effect to avoid electromagnetic interference, without being restricted because of the amount of electrical energy that can be stored in the capacitors with regard to operating situations in which an energy flow into the third line is to be limited be.

The first line and the second line are formed in particular by busbars, in which the filter device is connected. The third line preferably includes one or more electrical conductors which are connected or can be connected to a housing of the power converter and/or to a chassis of the vehicle.

For the purposes of the present invention, the term “potential” is to be understood as meaning an electrostatic potential. The reference potential is in particular a chassis potential of the vehicle. The reference potential can also be understood or referred to as ground potential or ground potential. Preferably the first Potential higher than the second potential. It is further preferable if a difference between the first potential and the third potential and between the third potential and the second potential is the same. In other words, the vehicle electrical system is symmetrical.

The filter device is preferably set up to establish the electrically conductive connections when the control information is in a first information state, so that the first capacitor and the second capacitor serve as filters for common-mode interference on the first and second line. The first information status represents, in particular, normal operation of the power converter. The filter device can also be set up to disconnect the electrically conductive connections when the control information is in a second information state, so that a flow of energy from the first capacitor and from the second capacitor into the third line is avoided. The second information state represents, in particular, an operating state of the vehicle electrical system, in which it is connected to an electrical system external to the vehicle, in particular for charging a traction battery of the vehicle electrical system. The first capacitor and the second capacitor can also be understood or referred to as Y-capacitors.

The first capacitor and the second capacitor can be part of a filter stage of the filter device. The filter stage may further include a third capacitor connected between the first and second lines. Such a third capacitor can also be regarded as an X-capacitor. The filter stage can also include a choke, which is formed around the first and second lines by a ferrite core or a nanocrystalline core, for example.

The filter device can have a second filter stage which corresponds to the first filter stage and is connected downstream of this. The filter device can be set up to an electrically conductive connection between the first line and the third line via the first capacitor of the second filter stage and establish and disconnect an electrically conductive connection between the second line and the third line via the second capacitor of the second filter stage depending on the control information. Otherwise, the explanations for the first filter stage can be transferred to the second filter stage.

Provision can also be made for the filter device to be set up to produce the electrically conductive connections when the power converter is in an operating state in which a voltage above a predetermined voltage threshold value is present between the first line and the second line and when the control information is received , in particular the second information state to separate. As a result, the filter effect of the filter device can be realized as soon as the voltage between the first and the second line exceeds the voltage threshold value. This allows the filter device to operate normally on. The voltage threshold can be at most sixty volts, preferably at most forty volts, particularly preferably at most twenty volts.

It is preferably provided that the filter device has at least one switching device, which has a first connection, a second connection, a control connection for receiving the control information, and a switching unit, which has at least one control input and is set up, depending on the control information, to initiate a current flow between the first To switch connection and the second connection has. The switching unit can be set up to conduct and/or block the flow of current unidirectionally. Alternatively, the switching unit can be set up to conduct and/or block the flow of current bidirectionally.

The switching element can have an electromechanical switch, for example a relay or a contactor. Alternatively, the at least one switching element can have a semiconductor switch and a diode connected in antiparallel thereto. The or a respective switching element can be a bipolar transistor with iso profiled gate (IGBT) or a field effect transistor, such as a field effect transistor with insulated gate (IGFET), in particular a power mosfet, or a junction field effect transistor (JFET). In this case, the antiparallel diode can be formed by a body diode of the field effect transistor. Alternatively, the or a respective switching element can be a bipolar transistor or a triac, in particular an opto-triac. The switching element can also have a reverse blocking IGBT (RB-IGBT).

The at least one control input of the switching unit can comprise a first control input and a second control input.

In order to implement the bidirectionally conducting and/or blocking switching unit, it can be provided that the switching unit comprises a first switching element and a second switching element, each of which has a first-type connection, a second-type connection, a third-type connection and a connection between the first-type connection and the connection of the second type, the conducting state of which can be predetermined as a function of a voltage present between the connection of the third type and the connection of the second type, the connections of the second type of the first switching element and of the second switching element being connected to one another and the connections of the third type can be controlled depending on the control information. The connection of the first type is in particular a drain connection or a collector connection. The connection of the second type is in particular a source connection or an emitter connection. The connection of the third type is in particular a gate connection or a base connection. As a result, a switching unit in a common source circuit or a common emitter circuit can be formed with two only unidirectionally blocking switching elements. In this case, the connections of the third type of switching elements can receive the same signal representing the control information.

Furthermore, it can be provided that the connection of the first type of the first switching element forms the first connection of the switching device and the connection of the first type of the second switching element forms the second connection of the switching device, with the first control input being connected to the connections of the third type of the first switching element and the second switching element is connected and the second control input is connected to the terminals of the second type of the first switching element and the second switching element. Alternatively, it can be provided that the switching unit comprises a first switching element and a second switching element, each of which has a first-type connection, a second-type connection, a third-type connection and a contact gap formed between the first-type connection and the second-type connection. the conduction state of which can be specified as a function of a voltage present between the connection of the third type and the connection of the second type, the connections of the first type of the first switching element and of the second switching element being connected to one another. As a result, the switching unit can be designed as a common-drain circuit or a common-collector circuit. Alternatively, it can be provided that the switching unit has a bridge rectifier with a switching element connected in parallel. A bidirectionally conducting and/or blocking switching unit can also be realized by this switching device. The switching unit can also have a suppressor diode, which is connected to the first connection and the second connection of the switching device and/or is connected in parallel to the switching elements.

According to a first preferred embodiment, it is provided that the first capacitor is connected between the first line and the first connection of a first switching device of the at least one switching device, with the second connection of the first switching device being connected to the third line. It can be provided that the second capacitor is connected between the second line and the second connection of a second switching device of the at least one switching device, the first connection of the second Switching device is connected to the third line. In this case, both switching devices are connected to the third line. Alternatively, it can be provided that the second capacitor is connected between the third line and the first connection of a second switching device of the at least one switching device, the second connection of the second switching device being connected to the second line. In this case, the switching devices are connected to the respectively lower potential between the lines.

In the first preferred embodiment, a dedicated switching device is assigned to the first capacitor and the second capacitor.

When the electrically conductive connections are made, a common-mode current can flow through the respective capacitor and the semiconductor switch or through the anti-parallel diode, so that there is conductivity in both current directions. If the electrically conductive connections are separated when using a bidirectionally conducting and/or blocking switching unit, the capacitors are neither charged nor discharged via the third line, even if a voltage is present between the first line and the second line. If the electrically conductive connections are separated when using a unidirectionally conducting and/or blocking switching unit, the capacitors are not charged when a voltage is applied between the first line and the second line. If the separation occurs while a voltage is already present between the first line and the second line, the capacitors can be discharged via a discharge resistor - described in more detail below - so that the entire voltage between the first or second line on the one hand and the third conduction, on the other hand, drops across the switching device in a stationary, i.e. discharged, state.

A maximum permissible blocking voltage of a respective switching unit is preferably at least the nominal voltage of the vehicle electrical system or half the voltage to be expected between the first line and the second line. In this way, voltages can also be effectively blocked in the event of a fault in the event of short circuits between one of the first and second lines and the third line. To the If the maximum permissible blocking voltage is to be lower than the nominal voltage, the symmetry of the vehicle electrical system can also be taken into account when designing the switching unit. In a preferred development, the switching device can have a normal operating circuit. This has in particular a voltage limiting element, preferably a zener diode, which is connected between the control input of the switching unit and the second connection of the switching device. Alternatively or additionally, the normal operating circuit has a resistance element, which is connected between the control input of the switching unit and a third connection of the switching device, which is connected to such a pole of the capacitor that is connected neither to the first connection nor to the second connection of the switching device is. The resistance element preferably has a resistance value of at least one megohm, preferably at least ten megohms. The resistance element can be formed by several resistance components connected in series. Preferably, each resistive component has a resistance of at least one megohm. The normal operating circuit enables in particular the previously described normal-on operation in that the control input of the switching unit is supplied with a voltage from the first or second line that is limited by the voltage-limiting element as soon as the predetermined voltage threshold value is reached.

The switching device can also have an input circuit which is connected between the control connection of the switching device and the control input of the switching unit and is set up to actuate the switching unit to interrupt a connection between the first connection and the second connection when the control connection and the second connection are at the same potential. As a result, for example, the control information for separating the electrically conductive connection via the first capacitor by a signal related to the reference potential and to disconnect the electrically conductive connection via the second capacitor by a signal related to the second potential. This is particularly true when using n-channel type switching elements.

It should also be noted that the switching device, even in the case of a voltage resistance test, in which a voltage that is considerably higher than the nominal voltage of the vehicle electrical system, for example two to four kilovolts, is usually between the first line and the third line and/or or between the second line and the third line is not damaged. The voltage across the switching unit of one of the switching devices can be limited in particular via the anti-parallel diode to its forward voltage, which is regularly in the order of 0.7 volts, while the switching unit of the other switching device is protected via the normal operating circuit or other protective measures can be.

As an alternative to the first embodiment, the first capacitor can also be connected between the third line and the second connection of a first switching device of the at least one switching device, with the first connection of the first switching device being connected to the first line. In this case, the second capacitor can be connected between the second line and the second connection of a second switching device of the at least one switching device, the first connection of the second switching device being connected to the third line. Alternatively, the second capacitor can be connected between the third line and the first connection of a second switching device of the at least one switching device, the second connection of the second switching device being connected to the second line. According to a second preferred embodiment it can be provided that the first capacitor is connected to the first line and the second capacitor is connected to the second line, the first capacitor, the second capacitor and the first connection of the switching device is connected to a common circuit node and the second connection of the switching device is connected to the third line. In the second preferred embodiment, a common switching device is therefore provided in a common current path from the first capacitor and from the second capacitor to the third line. This also has the advantage that with the same potential difference between the first line or the second line on the one hand and the third line on the other hand, there is no voltage drop across the switching device. If several filter stages are provided, the first capacitor of the second filter stage can be connected to the first line and the second capacitor of the second filter stage can be connected to the second line, wherein the first capacitor and the second capacitor of the second filter stage can be connected to the common circuit node. Thus, a plurality of parallel filter stages can be connected to or disconnected from the third line by a single switching device.

When the electrically conductive connections are made, a common-mode current can flow through the respective capacitor and through the switching unit. When the electrically conductive connections are separated, the first and second capacitors are connected in series and the switching unit blocks current flow into the third line. The first and the second capacitor are then connected in series and act like a capacitor connected between the first and the second line, ie as an X-capacitor.

A maximum permissible blocking voltage of a respective switching unit is preferably at least the nominal voltage of the vehicle electrical system or half the voltage expected between the first line and the second line. In this way, voltages can also be effectively blocked in the event of a fault in the event of short circuits between one of the first and second lines and the third line. In order to select the maximum permissible blocking voltage lower than the nominal voltage, at When designing the switching unit, the symmetry of the vehicle electrical system must also be taken into account.

It should also be noted that the switching device, even in the case of a voltage resistance test, in which a voltage that is considerably higher than the nominal voltage of the vehicle electrical system, for example two to four kilovolts, is usually between the first line and the third line and/or applied between the second line and the third line is not damaged. In a preferred embodiment, it is provided that the switching device also has a normal operating circuit. The normal operating circuit can have a voltage limiting element, in particular a zener diode, which is connected between the first control input and the second control input of the switching unit. Alternatively or additionally, the normal operating circuit can have a resistance element which is connected between the first control input of the switching unit and the first or second line. The resistance element preferably has a resistance of at least one megohm, preferably at least ten megohms. The resistance element can be formed by several resistance components connected in series. Preferably, each resistive component has a resistance of at least one megohm.

The normal operating circuit enables in particular the previously described normal on operation, in which the control input of the switching unit is supplied with a voltage limited by the voltage limiting element from the first or the second line as soon as the predetermined voltage threshold value is reached between them.

It can also be provided that the switching device also has an input circuit which is connected between the first control input and the second control input and is set up to switch the switching unit to breaking a connection between the first connection and the second connection by the first control input and the second control input are connected to one another in an electrically conductive manner. In a preferred embodiment, a resistor element can be provided for balancing purposes between the first line and the third line and between the second line and the third line. One of the resistance elements, in particular the resistance element between the first line and the third line, can be formed by the resistance element of the normal operation circuit. As a result, a charge distribution between the first capacitor and the second capacitor can be balanced in a component-saving manner, at least in certain operating states. The respective resistance element preferably has a resistance value of at least one megohm, preferably at least ten megohms. The respective resistance element can be formed by a plurality of resistance components connected in series. Preferably, each resistive component has a resistance of at least one megohm.

In a preferred embodiment of the power converter according to the invention, it is provided that the filter device also has an isolation device, which has an input and an output electrically decoupled from the input and is set up to provide the control information provided at the input to the at least one switching device at the output. The input and the output can be decoupled capacitively, inductively or optically, for example by means of an optocoupler.

As an alternative to the input circuits and/or normal operating circuits described above, it can be provided that the filter device is set up to provide a control voltage dependent on the control information at the at least one control input of the switching unit. The control voltage can be present at the first and second control input or referred to a potential at the first connection or at the second connection of the switching device at the control input. The control voltage can be provided by the isolation device.

In the power converter according to the invention, the filter device can also have a monitoring device which is set up to detect whether the first capacitor and the second capacitor are connected to the third line and to provide a monitoring signal describing a result of the detection. In this case, the isolation device can have a further input and a further output which is electrically decoupled from the further input and can be set up to provide the monitoring signal provided at the further input at the further output.

The monitoring device can be connected to the first connection and to the second connection of the or a respective switching device.

According to a first embodiment of the monitoring device, it has a switching element, for example a bipolar transistor, with a first-type connection, a second-type connection, a third-type connection and a contact gap formed between the first-type connection and the second-type connection for a respective switching device , the conduction state of which can be specified as a function of a voltage present between the connection of the third type and the connection of the second type. The connection of the third type can be connected to the first connection of the switching device via a diode. The connection of the second type is preferably connected to a voltage source. The connection of the first type is preferably connected to the second connection of the switching device via a resistor, it being possible for the monitoring signal to be provided between the connection of the first type and the resistor. Optionally, it can be provided that the terminal of the third type is connected to the voltage source via a resistor and/or to the second terminal of the switching device via a capacitor. According to a second embodiment of the monitoring device, it also has a controlled current source, the current source being connected on the one hand via a diode to the first connection of the switching device and via a diode to the second connection of the switching device and on the other hand to the second control input of the switching unit. wherein the monitoring signal can be provided between the diodes and the power source. Furthermore, a voltage limiting element, for example a zener diode, can be connected in parallel to the current source. The power converter according to the invention can also include an intermediate circuit capacitor which is connected between the first line and the second line. The power converter according to the invention can also include a converter circuit, in particular an inverter circuit or an active rectifier circuit, which is connected between the first line and the second line. The filter device can be arranged on that side of the intermediate circuit capacitor which is remote from the converter circuit.

In this respect, the power converter can be in the form of an AC-DC converter, a DC-AC converter or a DC-DC converter.

The object on which the invention is based is also achieved by an on-board electrical system for an electrically drivable vehicle, having at least one power converter according to the invention, a traction battery, a charging device for charging the traction battery from an electrical network external to the vehicle, and a control device that is set up to Provide disconnection of the electrically conductive connections when the charging device charges the traction battery.

The charging device can also be implemented by a power converter according to the invention. The object on which the invention is based is also achieved by an electric drive for a vehicle, having a power converter according to the invention and an electric machine, in particular a rotating electric machine, which is set up to drive the vehicle, the electric machine being equipped with a power converter, in particular a three-phase , AC voltage can be supplied. The electrical machine can be a synchronous machine, in particular a permanently excited one, or an asynchronous machine.

The object on which the invention is based is also achieved by a vehicle comprising the drive according to the invention and/or the vehicle electrical system according to the invention.

All statements regarding the power converter according to the invention can be transferred analogously to the vehicle electrical system according to the invention, so that the advantages described above can also be achieved with this.

Further details and advantages of the present invention result from the exemplary embodiments described below and from the drawings. These are schematic representations and show:

1 shows a block diagram of a first exemplary embodiment of the power converter according to the invention in an operating state in which the electrically conductive connections are made via the capacitors;

FIG. 2 shows a sectional schematic diagram of the filter device according to the first exemplary embodiment; FIG.

3 shows a sectional circuit diagram of the filter device according to the first exemplary embodiment; 4 shows a sectional circuit diagram of the filter device according to a second exemplary embodiment of the power converter according to the invention;

5 shows a circuit diagram of the monitoring device for the second exemplary embodiment;

6 shows a sectional schematic circuit diagram of the filter device according to a third exemplary embodiment of the power converter according to the invention;

7 shows a sectional circuit diagram of the filter device according to the third exemplary embodiment;

8 shows a sectional circuit diagram of the filter device according to a fourth exemplary embodiment;

9 to 11 each show a circuit diagram of a switching unit according to further exemplary embodiments of the power converter according to the invention; and FIG. 12 shows a schematic diagram of a vehicle with an exemplary embodiment of the on-board electrical system according to the invention.

1 is a block diagram of a first embodiment of a power converter 1 .

The power converter 1 has a first line 2 for a first potential P1, a second line 3 for a second potential P2, which differs from the first potential P1 un, and a third line 4 for a reference potential P3 that between the first potential P1 and the second potential P2 is on. In the present embodiment, the second potential P2 is lower than the first potential P1. The power converter 1 also has a filter device 5 . The filter device 5 includes a first capacitor 6 and a second capacitor 7. FIG. 1 shows an operating state in which an electrically conductive connection between the first line 2 and the third line 4 via the first capacitor 6 and an electrically conductive connection is established between the second line 3 and the third line 4 via the second capacitor 7 . The first capacitor 6 and the second capacitor 7 form Y capacitors.

As an optional component, the filter device 5 also has a third capacitor 8, which is connected between the first line 2 and the second line 3 as a so-called X-capacitor. Also optionally, the filter device 5 has a choke 9 , for example a ferrite core, which is arranged around the first line 2 and in the second line 3 . The capacitors 6 , 7 , 8 and the inductor 9 form a first filter stage of the filter device 5 .

Optionally, a further filter stage can also be provided, which is constructed like the first filter stage and is connected downstream of this. The second filter stage can have a first capacitor 6a, a second capacitor 7a, a third capacitor 8a and an inductor 9a.

Furthermore, the power converter 1 has, for example, an intermediate circuit capacitor 10 and a converter circuit 11 . In the present exemplary embodiment, the converter circuit 11 is an inverter circuit that is set up to convert a DC voltage provided via the first line 2 and the second line 3 into a three-phase AC voltage. For example, an electrical machine 12 connected to the power converter 1 can be supplied with the three-phase AC voltage. The filter device 5 is arranged on the side of the intermediate circuit capacitor 10 facing away from the converter circuit 11 . FIG. 2 and FIG. 3 are partial circuit diagrams of the filter device 5 according to the first exemplary embodiment. The filter device 5 is set up to the electrically conductive connection between the first line 2 and the third line 4 via the first capacitor 6 and the electrically conductive connection between the second line 3 and the third line 4 via the second capacitor 7 depending on a control - Manufacture and separate formation 13. For this purpose, the filter device has a first switching device 14 and a second switching device 15 . Each switching device 14 , 15 has a first connection 16 , a second connection 17 and a control connection (not shown) for receiving the control information 13 .

The first capacitor 6 is connected between the first line 2 and the first connection 16 to the first switching device 14 . The second connection 17 of the first switching device 14 is connected to the third line 4 . The second capacitor 7 is connected between the second line 3 and the second connection 17 of the second switching device 15 . The first connection 16 of the second switching device 15 is connected to the third line 4 .

Fig. 3 also shows a switching unit 18 of a respective switching device 14, 15. The switching unit 18 has a control input (not shown) and is set up to, depending on the control information 13, a current flow between the first terminal 16 and the second terminal 17, in particular from the first terminal 16 to the second terminal 17 to switch. The switching unit 18 has a switching element 19 with a semiconductor switch 20a and with a diode 20b connected antiparallel thereto. The switching element 19 is formed by, for example, an insulated gate bipolar transistor (IGBT) and a separate diode device. Alternatively, the switching element 19 and the diode 20 can be formed by an insulated gate field effect transistor (IGFET), for example a power MOSFET, with the diode 20b being realized by its body diode. Alternatively, the switching element 19 is formed by an electromechanical switch, for example a relay or a contactor. 3 also shows two discharge resistors 21 which are each connected in parallel with the first capacitor 6 and the second capacitor 7 . The electrical energy stored in the capacitors 6, 7 can be converted into heat by the discharge resistors 21 when the electrically conductive connections via the capacitors 6, 7 are separated by the switching device 14, 15, ie when the respective switching element 19 blocks.

The switching devices 14, 15 shown in FIGS. 2 and 3 can be provided in a corresponding manner in the further first and second capacitors 6a, 7a of the second filter stage shown in FIG.

4 is a partial circuit diagram of the filter device 5 according to a second exemplary embodiment of the power converter 1. The statements relating to the first exemplary embodiment can be transferred to the second exemplary embodiment, unless otherwise described below. Components that are the same or have the same effect are provided with identical reference symbols.

Fig. 4 first shows the control connections 22 of the first switching device 14 and the second switching device 15. The control inputs 23 of a respective switching unit 18 of the first switching device 14 and the second switching device 15 are also shown.

In the second exemplary embodiment according to FIG. 4, the first capacitor 6 is connected between the first line 2 and the first connection 16 of the first switching device 14 . The second connection 17 of the first switching device 14 is connected to the third line 4 . The second capacitor 7 is connected between the third line 4 and the first connection 16 of the second switching device 15 . The second connection 17 of the second switching device 15 is connected to the second line 3 . The switching devices 14, 15 also each have a normal operating circuit 24.

The normal operating circuit 24 includes a voltage limiting element 25 that is connected between the control input 23 of the switching unit 18 and the second terminal 17 . The voltage limiting element is a zener diode, for example, whose cathode is connected to the control input 23 and whose anode is connected to the second terminal 17 . In addition, the normal operation circuit 24 has a resistance element 26 . The resistance element 26 is connected between the control input 23 of the switching unit 18 and a third connection 27 of the switching device 14 , 15 . The third connection 27 is connected to that pole of the capacitor 6, 7 which is connected neither to the first connection 16 nor to the second connection 17 of the switching device 14, 15. In the present exemplary embodiment, the third connection 27 of the first switching device 14 is connected to the first line 2 and the third connection 27 of the second switching device 15 is connected to the third line 4 . The resistance element 26 has, for example, a resistance value of more than ten megohms and is formed from several, for example thirteen, resistance components connected in series, each having a resistance value of one megohm.

In addition, each switching device 14, 15 also has an input circuit 28. The input circuit 28 is connected between the control connection 22 of the switching device 14, 15 and the control input 23 of the switching unit 18 and is set up to activate the switching unit 18 to interrupt the electrically conductive connection between the first connection 16 and the second connection 17 when the Control terminal 22 and the second terminal 17 are at the same potential. In the present exemplary embodiment, the control information 13 (see FIG. 2) can be transmitted for the first switching device 14 by a signal at the reference potential P3 and for the second switching device 15 a signal lying at the second potential P2 can be represented. The input circuit has, for example, a switching element in the form of an npn bipolar transistor. In detail, the switching element 19 of the switching unit 18 of a respective switching device 14, 15 has a first-type connection 29, a second-type connection 30, a third-type connection 31 and a contact gap formed between the first-type connection 29 and the second-type connection 30 The conduction state can be specified as a function of a voltage present between the connection of the third type 31 and the connection of the second type 30 , the connections 29 to 31 being shown only in the second switching device 15 for the sake of clarity. The connection of the first type 29 is connected to the first connection 16 , the connection of the second type 30 is connected to the second connection 17 , the connection of the third type 31 is connected to the control input 23 . In the configuration of the switching unit 18 with an IGBT, the connection of the first type 29 is a collector connection, the connection of the second type 30 is an emitter connection and the connection of the third type 31 is a gate connection. In an embodiment of the switching unit 18 with an IGFET, the connection of the first type 29 is a drain connection, the connection of the second type 30 is a source connection and the connection of the third type 31 is a gate connection.

Fig. 5 is a circuit diagram of a monitoring device 36 for the second embodiment of the power converter 1. The optional monitoring device 36 is set up to detect whether the first capacitor 6 and the second capacitor 7 are connected to the third line 4, and to carry out a result of the Describe detection of the monitoring signal 36a to provide. The monitoring device 36 instructs each switching device 14, 15

Switching element 50, here in the form of a pnp bipolar transistor, with a connection of the first type 50a, a connection of the second type 50b, a connection of the third type 50c and a contact gap formed between the connection of the first type 50a and the connection of the second type 50b, the conduction state of which can be specified as a function of a voltage present between the connection of the third type 50c and the connection of the second type 50b. The connection of the third type 50c is connected to the first connection 16 of the switching device 14, 15 via a diode 51. The connection of the second type 50b is connected to a voltage source 52 . The connection of the first type 50a is connected to the second connection 17 of the switching device 14, 15 via a resistor 53, with the monitoring signal 36a being able to be provided between the connection of the first type 50a and the resistor 53. It can optionally be provided that the terminal of the third type 50c is connected to the voltage source 52 via a resistor 54 and/or to the second terminal 17 of the switching device 14, 15 via a capacitor 55. In the present exemplary embodiment, the monitoring signal 36a also describes which capacitor 6, 7 is connected to the third line 4.

6 and 7 show a filter device 5 according to a third exemplary embodiment of the power converter 1 in the form of a detail. FIG. 6 is a basic sketch and FIG. 7 is a circuit diagram. The explanations for the second exemplary embodiment can be transferred to the third exemplary embodiment, unless otherwise described in the following. Components that are the same or have the same effect are provided with identical reference symbols.

In the third exemplary embodiment, one, in particular precisely one, switching device 14 is provided. The first capacitor 6 is connected to the first line 2 . The second capacitor 7 is connected to the second line 3 . The first capacitor 6, the second capacitor 7 and the first connection 16 of the switching device 14 are connected to a common circuit node 32 being. The second connection 17 of the switching device 14 is connected to the third line 4 .

According to the third exemplary embodiment, the switching unit 18 of the switching device 14 has a first control input 23 and a second control input 23a on. The switching unit 18 comprises a first switching element 19 and a second switching element 19a, each of which has a first-type connection 29, a second-type connection 30, a third-type connection 31 and a contact gap formed between the first-type connection 29 and the second-type connection 30. whose conduction state can be specified as a function of a voltage present between the connection of the third type 31 and the connection of the second type 29 . The connections of the second type 30 of the first switching element 19 and of the second switching element 19a are connected to one another. The connections of the third type 31 can be controlled as a function of the control information 13 (see FIG. 1).

The connection of the first type 29 of the first switching element 19 forms the first connection 16 of the switching device 14 . The connection of the first type 29 of the second switching element 19a forms the second connection 17 of the switching device 14 . The first control input 23 is connected to the connections of the third type 31 of the first switching element 19 and the second switching element 19a. The second

Control input 23a is connected to the terminals of the second type 30 of the first switching element 19 and the second switching element 19a.

In the present exemplary embodiment, the switching elements 19, 19a are each formed by an IGFET, for example by a power MOSFET with a maximum blocking voltage of 1.2 kilovolts. The switching unit 18 forms a bidirectionally conducting and blocking common source circuit from the two switching elements 19, 19a. In addition, the switching unit 18 has a suppressor diode 33 which is connected in parallel to the switching elements 19, 19a to the first connection 16 and to the second connection 17 of the switching device 14.

As in the second exemplary embodiment, the normal operating circuit 24 has the voltage limiting element 25 and the resistance element 26, of which individual resistance components 34 are illustrated in FIG. In this case, the voltage-limiting element 25 is connected between the first control input 23 and the second control input 23a of the switching unit 18 . The cathode of Zener diode is connected to the first control input 23 . The anode of the zener diode is connected to the second control input 23a. The resistance element 26 is connected between the first control input 23 of the switching unit 18 and the third connection 27 of the switching device 14 . The third connection 27 is connected to the first line 2 .

In the third exemplary embodiment, the control connection 22 is connected via the input circuit 28 to the control inputs 23, 23a. The input circuit 28 is formed by an npn bipolar transistor, for example.

The resistance element 26, together with a resistance element 35 of the filter device 5, serves to balance the charge distribution between the first capacitor 6 and the second capacitor 7 in specific operating states. The resistance element 35 is connected between the second line 3 and the third line 4 and like the resistance element 26 of the normal operating circuit 24 is formed.

According to the third exemplary embodiment, the filter device 5 optionally has a monitoring device 36 .

The filter device 5 optionally has an isolation device 37 which has a first input 38a and an output 39a electrically decoupled from the first input 38a and is set up to provide the control information 13 provided at the first input 38a to the switching device 14 at the first output 39a. In addition, the isolation device 37 can have a second input 38b and a second output 39b electrically decoupled therefrom and be set up to provide the monitoring signal 36a provided at the second input 38b at the second output 39b. The decoupling between a respective input 38a, 38b and a respective output 39a, 39b is done here optically by means of optocouplers. According to alternative exemplary embodiments, the decoupling takes place inductively or capacitively. If the first capacitor 6a and the second capacitor 7a of the second filter stage according to FIG. 1 are provided, the capacitors 6a, 7a can be connected to the common circuit node 32, so that the switching device 14 is provided jointly for both filter stages.

8 is a partial circuit diagram of a filter device 5 according to a fourth exemplary embodiment of the power converter 1, to which the explanations relating to the third exemplary embodiment apply, unless otherwise described below. Components that are the same or have the same effect are provided with identical reference symbols.

In the fourth embodiment, a normal operation circuit and an input circuit are omitted. In this case, the isolation device 37 provides a control voltage 60 that is dependent on the control information at the control inputs 23, 23a of the switching unit 18.

Fig. 8 also shows a further possible configuration of the monitoring device 36. The monitoring device 36 has a current source 70 which is connected via a diode 71 to the first connection 16 of the switching device 14 and via a diode 72 to the second connection 17 of the switching device 14 and on the other hand is connected to the second control input 23a of the switching unit 18, the monitoring signal 36a being able to be provided between the diodes 71, 72 and the current source 70. A voltage limiting element 73, here in the form of a zener diode, is also connected in parallel with the current source 70. The power source 70 of the monitoring device 36 can be operated here by an operating voltage 74 provided by the isolation device 37 .

8 also shows a further resistance element 35a, which is connected between the first line 2 and the third line 4 and, together with the resistance element 35, serves to balance the charge distribution between the first capacitor 6 and the second capacitor 7. The resistance elements 35, 35a are of identical design. 9 to 11 are each a circuit diagram of a switching unit 18 according to further exemplary embodiments of the power converter 1 according to the invention, which otherwise correspond to the third or fourth exemplary embodiment. The same components or those with the same effect are provided with identical reference symbols.

The switching units 18 according to FIG. 9 and FIG. 10 each form a bidirectionally conducting and blocking switching unit on the basis of only unidirectionally conducting and/or blocking switching elements.

In the exemplary embodiment according to FIG. 9, the connections of the first type 29 of the first switching element 19 and of the second switching element 19a are connected to one another. The connections of the second type 30 of the switching elements 19, 19a form the connections 16, 17 of the switching device 14. The switching elements 19, 19a form a common drain circuit or a common collector circuit.

In the exemplary embodiment according to FIG. 10, only one switching element 19 is provided, which is connected in parallel with two half-bridges of a bridge rectifier 40 with diodes 41a, 41b, 41c, 41d. The connections 16, 17 of the switching device 14 are formed by taps between the diodes 41a, 41b and 41c, 41d of a respective half-bridge.

In the exemplary embodiment according to FIG. 11, the switching element 19 is designed as a reverse blocking IGBT (RB-IGBT). The connections 16, 17 of the switching device 14 are formed by connections to a contact gap of the RB-IGBT.

According to further exemplary embodiments, the isolation device 37 is provided in the power converters 1 according to the first or second exemplary embodiment. According to further exemplary embodiments, which correspond to one of the exemplary embodiments described above, the switching unit 18 is formed by an electromechanical switching element, for example a relay or a contactor. According to further exemplary embodiments which correspond to the first or second exemplary embodiment, the switching unit 18 of a respective switching device 14, 15 is designed to be bidirectionally conducting and/or blocking and can correspond to the switching unit 18 according to FIG. 7 or 9 to 11.

Fig. 12 is a schematic diagram of a vehicle 100 with an embodiment of a vehicle electrical system 101.

The vehicle 100 is an electrically powered vehicle, for example a battery electric vehicle (BEV) or a hybrid vehicle.

The vehicle electrical system 101 has a power converter 1 according to one of the exemplary embodiments previously described. The power converter 1 is embodied here as a DC-AC converter for the electrical machine 12, for example. In addition, the vehicle electrical system includes a traction battery 102, for example with a nominal voltage of at least 400 volts. A charging device 103 is also provided for charging the traction battery 102 from an electrical network 104 external to the vehicle. The charging device 103 can be used as a DC-DC converter or AC-DC converter between the electrical network 104 and the vehicle electrical system 101 and in accordance with one of the previously described Embodiments may be designed as a power converter 1a. Optionally, a DC voltage converter 105 can be provided in vehicle electrical system 101, which is set up to couple vehicle electrical system 101 to another vehicle electrical system 106, for example a low-voltage vehicle electrical system with a nominal voltage of 12 or 24 volts, of vehicle 100. The DC-DC converter 105 converter 1b can also be designed in the form of a DC-DC converter in accordance with the exemplary embodiments described above.

Vehicle electrical system 101 also includes a control device 107, which is set up to provide control information 13 for disconnecting the electrically conductive connections in filter devices 5 of power converter 1, and possibly also power converters 1a, 1b, when charging device 103 the traction battery 102 loads. Optionally, the monitoring signal 36a can be transmitted from the power converter 1 or the power converters 1, 1a, 1b to the control device 107.

The power converter 1 and the electric machine 12 form a drive 108 for the vehicle 100 .

Claims

patent claims

1. Power converter (1, 1 a, 1 b) for an on-board network (101) of an electrically drivable vehicle (100), having - a first line (2) for a first potential (P1),

- A second line (3) for a second potential (P2), which differs from the first potential (P1), a third line (4) for a reference potential (P3) between the ers th potential (P1) and the second Potential (P2) is, and - a filter device (5), which has a first capacitor (6) and a second capacitor (7) and is adapted to an electrically lei border connection between the first line (2) and the third line (4) via the first capacitor (6) and an electrically conductive connection between the second line (3) and the third line (4) via the second capacitor (7) depending on control information (13) and along at least one current direction to separate.

2. Power converter according to claim 1, wherein the filter device (5) is set up to the electrically conductive connections gene in an operating state of the power converter (1, 1a, 1b), in which a voltage lying above a predetermined voltage threshold value between the first line ( 2) and the second line (3), to produce and to separate upon receipt of the control information (13). 3. Power converter according to claim 1 or 2, wherein the filter device (5) has at least one switching device (14, 15) which

- a first connection (16),

- a second connection (17),

- a control connection (22) for receiving the control information (13) and - a switching unit (18) which has at least one control input (23, 23a) and is set up to do so as a function of the control information (13) to switch a current flow between the first terminal (16) and the second terminal (17).

4. Power converter according to claim 3, wherein the switching unit (18) is set up to conduct and/or block the flow of current bidirectionally.

5. Power converter according to claim 3 or 4, wherein the at least one control input (23, 23a) of the switching unit (18) comprises a first control input (23) and a second control input (23a).

6. Converter according to claims 4 and 5, wherein the switching unit (18) comprises a first switching element (19) and a second switching element (19a), each having a connection of the first type (29), a connection of the second type (30), a Connection of the third type (31) and a switching path formed between the connection of the first type (29) and the connection of the second type (30), the conduction state of which depends on a voltage present between the connection of the third type (31) and the connection of the second type (30). can be specified, wherein the connections of the second type (30) of the first switching element (19) and of the second switching element (19a) are connected to one another and the connections of the third type (31) can be controlled depending on the control information (13), the connection first type (29) of the first switching element (19) forms the first connection (16) of the switching device (14) and the connection of the first type (29) of the second switching element (19a) forms the second connection (17) of the switch The device (14) is formed, the first control input (23) being connected to the connections of the third type (31) of the first switching element (19) and the second switching element (19a) and the second control input (23a) being connected to the connections of the second type (30) of the first switching element (19) and the second switching element (19a) is connected.

7. Power converter according to claim 4 or 5, wherein the switching unit (18) a first switching element (19) and a second switching element (19a), each of which has a connection of the first type (29), a connection of the second type

(30), a connection of the third type (31) and a contact gap formed between the connection of the first type (29) and the connection of the second type (30), the conducting state of which depends on a connection between the connection of the third type

(31) and the connection of the second type (30) can be specified, the connections of the first type (29) of the first switching element (19) and of the second switching element (19a) being connected to one another or - a bridge rectifier (40 ) having a switching element (19) connected in parallel or having a reverse blocking switching element (19).

8. Power converter according to one of claims 3 to 7, wherein the first capacitor (6) between the first line (2) and the first connection (16) of a first switching device (14) of the at least one switching device (14, 15) connected is, the second connection (17) of the first switching device (14) being connected to the third line (4), the second capacitor (7) between - the second line (3) and the second connection (17) of a second switching device (15) of the at least one switching device (14, 15), the first connection (16) of the second switching device (15) being connected to the third line (4) or - the third line (4) and the first connection (16) a second switching device (15) is connected to the at least one switching device (14, 15), the second connection (17) of the second switching device (15) being connected to the second line (3).

9. Power converter according to claim 8, wherein the switching device (14, 15) further comprises a normal operation circuit (24) which a voltage limiting element (25) which is connected between the control input (23) of the switching unit (18) and the second connection (17) of the switching device (14, 15), and/or a resistance element (26) which is connected between the control input ( 23) of the switching unit (18) and a third connection (27) of the switching device

(14, 15), which is connected to such a pole of the capacitor (6, 7) that is connected neither to the first connection (16) nor to the second connection (17) of the switching device (14, 15), having.

10. Power converter according to one of claims 3 to 7, wherein the first capacitor (6) to the first line (2) and the second capacitor (7) to the second line (3) are connected, the first capacitor (6), the second capacitor (7) and the first connection (16) of the switching device (14) are connected to a common circuit node (32) and the second connection (17) of the switching device (14) is connected to the third line (4).

11 . Power converter according to 10, when dependent on claim 5, wherein the switching device (14) further comprises a normal operation circuit (24) which includes a voltage limiting element (25) connected between the first control input (23) and the second control input (23a) of the switching unit ( 18) is connected, and/or - a resistance element (26) which is connected between the first control input (23) of the switching unit (17) and the first or second line (2, 3).

12. Power converter according to one of the preceding claims, wherein the filter device (5) further has an isolation device (37) which has an input (38a) and an output (39a) electrically decoupled from the input (38a) and is set up to Input (38a) provided Provide control information (13) of the at least one switching device (14, 15) at the output (39a).

13. Power converter according to one of the preceding claims, wherein the filter device (5) has a monitoring device (36) which is set up to detect whether the first capacitor (6) and the second capacitor (7) with the third line ( 4) are connected, and provide a monitoring signal (36a) describing a result of the detection. 14. Power converter according to one of the preceding claims, further comprising an intermediate circuit capacitor (10) which is connected between the first line (2) and the second line (3), and a converter circuit (11) which is connected between the first line (2) and the second line (3) is connected, the filter device (5) being arranged on the side of the intermediate circuit capacitor (10) remote from the converter circuit (11).

15. Vehicle electrical system (101) for an electrically drivable vehicle (100), having at least one converter (1, 1a, 1b) according to one of the preceding claims, a traction battery (102), a charging device (103) for charging the traction battery (102) from a vehicle-external electrical network (104) and a control device (107) which is set up to provide the control information (13) for separating the electrically conductive connections when the charging device (103) charges the traction battery (102).