Disconnecting device for DC current interruption of a current path and vehicle electrical system of a motor vehicle

Abstract

The invention relates to a disconnecting device (12) for DC current interruption of a current path (8), in particular for a vehicle electrical system (4) of a motor vehicle (2), the disconnecting device having a hybrid switch (14) and a switchable resistor cascade (22), the hybrid switch having a current-conducting mechanical contact system (18) and having a first semiconductor switch (20) connected in parallel with the contact system, the resistor cascade having at least one ohmic resistor (24) and being connected in parallel with the contact system (18) of the hybrid switch (14).

Description

Technical Field

[0001] The present invention relates to a disconnecting device for interrupting a direct current in a current path, in particular to a disconnecting device for an onboard power supply of a motor vehicle. The invention also relates to an onboard power supply for a motor vehicle having such a disconnecting device. Background Art

[0002] The onboard electrical system is used to supply electrical consumers and systems with the operating voltage of the onboard electrical system. This onboard electrical system is usually supplied by means of an energy storage device, for example in the form of an electrochemical battery system. Due to system constraints, this type of battery system permanently supplies an operating current and an operating voltage, which are set within the low voltage range (NV) of 12 V to 48 V (DC) and within the high voltage range (HV) of approximately 1500 V (DC) or even higher. In this case, for example, for the purposes of installation, assembly or maintenance, and especially for general personal protection, it is desirable to reliably disconnect electrical components or devices from the battery system acting as a DC current source. The corresponding disconnecting device must be able to interrupt reliably and safely under load, which means that the DC current source does not need to be disconnected beforehand.

[0003] It is possible to use mechanical switches (switch contacts, contact systems) for load isolation. This has the advantage that, when the contacts are open, electrical isolation is established between the electrical device (consumer) and the DC current source (battery system). In contrast, if high-power semiconductor switches are used for load isolation, power losses in the semiconductor switches are unavoidable even during normal operation. Furthermore, the use of these types of power semiconductors typically makes it impossible to ensure electrical isolation and, therefore, reliable personal protection.

[0004] DE 102 25 259 B3 discloses an electrical plug connector designed as a load splitter. This connector has a semiconductor switch, as well as main and auxiliary contacts, in the manner of a hybrid switch, which are connected to a DC current source. During the disconnection process, the leading main contact is connected in parallel with the trailing auxiliary contact, which is connected in series with the semiconductor switch. The semiconductor switch is controlled for arc avoidance or arc extinguishing, with the semiconductor switch being switched on and off cyclically.

[0005] A hybrid disconnecting device is known from WO 2010 / 108565A1, which has a mechanical contact system and a semiconductor switch connected in parallel with the mechanical contact system. The semiconductor switch is coupled to control electronics without an additional energy source. When the mechanical contact system is closed, the control electronics or the semiconductor switch is current-off, which means that there is virtually no current or no voltage. The control electronics obtains the energy required for operation from the disconnecting device, that is, from the disconnecting switch system itself, and the arc energy generated when the mechanical contact system is opened is used. Here, the control electronics are interconnected with the mechanical contact system on the drive side in such a way that when the contact system is opened, the arc voltage generated due to the arc across the switch contacts of the contact system causes the semiconductor switch to switch to a conducting current.

[0006] Once the control electronics switch to a conducting current, the arc current begins to transfer from the mechanical contact system to the semiconductor switch. Thereby, the arc between the switch contacts of the contact system can be extinguished. SUMMARY OF THE INVENTION

[0007] The object of the present invention is to provide a particularly suitable disconnecting device (hybrid switch or electronic device) for DC current interruption of a current path, in particular for the vehicle electrical system of a motor vehicle. In particular, a disconnecting device is described here, which has improved operating safety even when switching high vehicle electrical system voltages. The object of the present invention is also to describe a particularly suitable vehicle electrical system of a motor vehicle, which has such a disconnecting device.

[0008] In terms of the disconnecting device, according to the present invention, this object is solved by the features of the present invention, and in terms of the vehicle electrical system, it is solved by the features of the present invention.

[0009] The disconnecting device according to the present invention is suitable and configured as a disconnecting switch system for DC current interruption of a current path, in particular for the vehicle electrical system of a motor vehicle. Here, the disconnecting device has a hybrid switch, which has a current-conducting mechanical contact system (switch) and a first semiconductor switch connected in parallel with this contact system. Here, the first semiconductor switch connected in parallel is open, that is, switched to off or non-conducting, when the mechanical contact system is in the closed state, so that the current is guided via the switching path of the mechanical contact system. This ensures particularly low conduction losses in the normal operation of the disconnecting device.

[0010] Furthermore, the disconnecting device includes a switchable resistor cascade, which has at least one ohmic resistor. This resistor cascade is connected in parallel with the contact system of the hybrid switch. The resistor cascade thus serves as a protection circuit for the hybrid switch. Thereby, a particularly suitable and operationally safe disconnecting device is achieved.

[0011] When the contact system is disconnected, the resulting arc is extinguished reliably and safely in operation. By closing the semiconductor switch or switching the semiconductor switch to the conducting state, the switching path of the contact system is short-circuited, whereby the arc current is transferred onto the semiconductor switch and the resistor cascade and thereby extinguished.

[0012] With the separating device according to the invention, a particularly space-saving and compact disconnecting switch system is achieved in particular. This is therefore particularly advantageous for the narrow installation conditions in the vehicle electrical system of a motor vehicle.

[0013] When using the separating device in a vehicle electrical system, it is conceivable, for example, that the resistor cascade or at least one resistor can also be additionally used as a charging and / or discharging resistor for an intermediate circuit capacitor.

[0014] In an advantageous embodiment, the resistor cascade is configured as a cascaded overvoltage limiter (overvoltage arrester). This ensures reliable and safe extinguishing of the arc.

[0015] In a suitable refinement, the resistor cascade has at least one second semiconductor switch, which is connected in series with at least one resistor. Preferably, the resistor cascade has a plurality of such resistor and semiconductor switch pairs, which are connected in series successively in a cascaded manner. It is thereby possible to gradually or continuously force the resulting current to zero. It is preferably provided here that the second semiconductor switch or each second semiconductor switch is switched to the conducting state essentially simultaneously with the first semiconductor switch.

[0016] In a first preferred configuration, the hybrid switch, in particular its mechanical contact system, can be short-circuited by means of a series circuit of the resistor cascade and a third semiconductor switch. Thereby, although there is no electrical separation, dangerous touch voltages on the contact system are reliably avoided. This ensures particularly effective and safe personnel protection (finger safety).

[0017] In a suitable design, the semiconductor switch or each semiconductor switch is guided to a common controller on the drive side. Here, the controller is in particular implemented as a common control unit for the first, second and third semiconductor switches. It is preferably ensured that the semiconductor switches are switched together and reliably. This ensures particularly safe and fast extinguishing of the arc in operation.

[0018] In terms of program and / or circuit technology, the controller is generally adapted and configured to control a semiconductor switch during the closing or opening process of a mechanical contact system. Thus, the controller is specifically configured to control the semiconductor switch during the closing process (during which the contact parts of the contact system are closed) in such a way that the contact system can be switched on without voltage. During the opening process, the controller controls the semiconductor switch in such a way that the arc between the opening contact parts of the contact system is extinguished reliably and quickly, and in particular touch protection is ensured in the sense of sufficient "finger safety".

[0019] In a preferred embodiment, at least the core of the controller is formed by a microcontroller having a processor and a data memory, wherein the function for performing the control is implemented in terms of program technology in the form of a running software (firmware), such that the control (optionally with interaction with the user) is automatically executed in the microcontroller when the running software is implemented.

[0020] Alternatively, within the scope of the present invention, the controller can be formed by non-programmable electronic components, such as an application-specific switching circuit (ASIC), wherein the function for controlling the method is implemented using a medium in terms of circuit technology.

[0021] In a particularly operationally safe configuration, an overcurrent protection device is pre-connected to the hybrid switch. Thereby, the switching task of the disconnecting device is taken over by the semiconductor switch under load, and by the overcurrent protection device in the event of a short circuit. In particular, a safe electrical interruption of the current path is ensured in the event of a fault.

[0022] In an advantageous embodiment, the overcurrent protection device is implemented as a fast fuse, for example in the form of a current-carrying extended wire or a fuse wire. Thereby, an electrical separation of the current path is ensured in the event of a fault.

[0023] An additional or alternative aspect of the present invention provides for the use of the above-mentioned disconnecting device in the vehicle electrical system of a motor vehicle. Here, the vehicle electrical system has a DC circuit, which has an energy storage device and at least one current path. The energy storage device is implemented as an electrochemical battery system, for example, which is connected to the current path as a DC current source. The current path is guided, for example, to an intermediate circuit of the vehicle electrical system. Here, the disconnecting device is connected in series in the current path. Thereby, a particularly operationally safe and reliably interruptible vehicle electrical system is achieved. Description of the Drawings

[0024] The embodiments of the present invention will be described in more detail below with reference to the drawings. Among them, the only drawing schematically and simplifiedly shows a vehicle electrical system for a motor vehicle, which has a disconnecting device for interrupting a DC current circuit. Detailed Description

[0025] The drawing schematically and in a simplified manner shows a motor vehicle 2. The motor vehicle 2 has an on-board electrical system 4 shown in sections. The on-board electrical system 4 is implemented with an electrochemical battery system 6 as an energy storage or a direct current source. Current paths 8, 10 are respectively connected to the poles of the battery system 6. The current path 8 leading to the positive pole of the battery system 6 is also referred to as the positive path hereinafter, and the current path 10 leading to the negative pole of the battery system 6 is also referred to as the negative path hereinafter.

[0026] In the illustrated embodiment, in order to interrupt the direct current, a disconnecting device 12 is connected in series in the positive path 8. The disconnecting device 12 has a hybrid switch 14 and an overcurrent protection device 16 disposed in front of the hybrid switch. Here, the overcurrent protection device 16 is implemented as a fuse, for example.

[0027] The hybrid switch 14 has a mechanical contact system 18 for conducting current in the form of a switch, and a semiconductor switch 20 is connected in parallel with the contact system. In addition, a resistor cascade 22 is connected in parallel with the switching paths of the semiconductor switch 20 and the contact system 18 as a cascaded turn-off overvoltage limiter of the disconnecting device 12.

[0028] In the illustrated embodiment, the resistor cascade 22 has an ohmic resistor 24 and a semiconductor switch 26 connected in series with the resistor. Another semiconductor switch 28 is connected in series with the resistor cascade 22, and the other semiconductor switch leads to the negative path 10 on the output side. The semiconductor switches 20, 26, 28 are led to a common controller 30 on the drive control side.

[0029] The semiconductor switches 20, 26, and 28 are implemented as power semiconductors, in particular as transistors, preferably implemented as IGBTs (Insulated-Gate Bipolar Transistors). The input or collector terminals of the semiconductor switches 20 and 26 are connected between the overcurrent protection device 16 and the contact system 18 here. Here, the output or emitter terminal of the semiconductor switch 26 is connected between the resistor 24 and the input or collector terminal of the semiconductor switch 28. The semiconductor switch 28 leads to the negative path 10 on the output or emitter side.

[0030] During the operation in which the disconnecting device 12 is switched on or conducting current, the semiconductor switches 20, 26, and 28 are switched off, that is, switched to the cut-off or non-conductive state, while the mechanical contact system 18 is closed. Thereby, the direct current of the battery system 6 is only led through the mechanical contact portion of the contact system 18. This ensures particularly low conduction losses of the disconnecting device 12.

[0031] During the off process, i.e., during the separation process of the separating device 12, the contact system 18 through which current flows is disconnected. When the contact system 18 is disconnected, an arc is formed due to the operating voltage or vehicle electrical network voltage of the existing vehicle electrical network 4.

[0032] When the contact system 18 is disconnected, the controller 30 switches the semiconductor switch 20 to the conducting state, so that the generated arc current is transferred to the semiconductor switch 20 and thus extinguished. The controller 30 also switches on the semiconductor switch 26 of the resistor cascade 22 basically simultaneously with the semiconductor switch 20.

[0033] Once the switching path of the contact system 18 has sufficient dielectric strength, the semiconductor switch 20 is cut off, whereby the current flowing through the resistor cascade 22 is gradually forced to zero via the resistor 24. Sufficient dielectric strength should be understood here in particular as extinguishing the arc. In order to reliably avoid touch voltages on the contact system 18 that may be dangerous to personnel even in the absence of electrical separation, the controller 30 switches the semiconductor switch 28 to the conducting state. Thereby, due to the series circuit composed of the resistor 24 and the semiconductor switch 28, the contact system 18 is short-circuited. Therefore, this series circuit forms a low-ohmic connection between the positive path 8 and the negative path 10. Therefore, in the event of a fault, the overcurrent protection device 16 is triggered, and thereby the positive path 8 is reliably and operationally safely electrically interrupted.

[0034] During the on process of the separating device 12, first the controller 30 turns off the semiconductor switch 28, that is, drives it to the cut-off state. Immediately afterwards, the semiconductor switch 26 is switched on, and thus the load circuit or intermediate circuit connected to the vehicle electrical network 4 is pre-charged via the resistor 24. If the charging current flowing during this process gradually weakens to a certain value, the controller 30 switches on the semiconductor switch 20. In order to monitor the charging current, the controller 30 has, for example, a current meter (not shown in detail) in the positive path 8.

[0035] By switching the semiconductor switch 20 to the conducting state, the mechanical contact system 18 is bridged, whereby the contact system can be switched on without voltage. Thereby, the locking of the mechanical contact part of the contact system 18 is reliably and simply avoided. Since the voltage of the mechanical switching path is lower, the current will completely transfer from the semiconductor switch 20 to the contact system 18. Finally, the controller 30 switches off the semiconductor switches 20 and 26 without current.

[0036] Therefore, the semiconductor switches 20, 26, and 28 only bear short-term and low loads during the operation of the separating device 12. Thereby, the heat losses of the semiconductor switches 20, 26, and 28 are reduced, and thereby the heat sink of the separating device 12 can be basically eliminated.

[0037] The switching task of the disconnecting device 12 is assumed by the semiconductor switches 22, 26, and 28 under load, and by the overcurrent protection device 16 in the event of a short circuit or fault. It is thereby possible to dimension the switching points of the contact system 18 solely with respect to the current to be conducted in the vehicle electrical system.

[0038] The invention is not limited to the above-described embodiments. Rather, those skilled in the art can also derive other variants of the invention therefrom without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiments can also be combined with one another in other ways without departing from the subject matter of the invention.

[0039] In particular, it is conceivable, for example, that the resistor cascade 22 has a plurality of cascaded pairs of resistors 24 and semiconductor switches 26, such that the resistors 24 can be switched in or out stepwise or continuously by means of the semiconductor switches 26. Heat losses can thereby be dissipated particularly effectively and operationally safely during the current conversion process.

[0040] List of reference numerals

[0041] 2 Motor vehicle

[0042] 4 Vehicle electrical system

[0043] 6 Battery system / energy storage

[0044] 8 Current path / positive path

[0045] 10 Current path / negative path

[0046] 12 Disconnecting device

[0047] 14 Hybrid switch

[0048] 16 Overcurrent protection device

[0049] 18 Contact system

[0050] 20 Semiconductor switch

[0051] 22 Resistor cascade

[0052] 24 Resistor

[0053] 26 Semiconductor switch

[0054] 28 Semiconductor switch

[0055] 30 Controller.

Claims

1. A separating device (12) for interrupting a direct current in a current path (8), the separating device having: - a hybrid switch (14) having a mechanical contact system (18) for conducting current and having a first semiconductor switch (20) connected in parallel with the contact system, and - a switchable resistor cascade (22) having at least one ohmic resistor (24) and connected in parallel with the contact system (18) of the hybrid switch (14), the resistor cascade (22) having at least one second semiconductor switch (26) connected in series with the at least one ohmic resistor (24), the hybrid switch (14) being short-circuitable by means of a series circuit of the resistor cascade (22) and a third semiconductor switch (28), all three semiconductor switches being guided on the drive side to a common controller (30).

2. The separating device (12) according to claim 1, characterized in that the resistor cascade (22) is configured as a cascaded turn-off overvoltage limiter.

3. The separating device (12) according to any one of claims 1 to 2, characterized in that an overcurrent protection device (16) is provided in front of the hybrid switch (14).

4. The separating device (12) according to claim 3, characterized in that the overcurrent protection device (16) is embodied as a fuse.

5. The separating device (12) according to any one of claims 1 to 2, It is characterized in that wherein the separating device is a separating device for an on-board electrical system (4) of a motor vehicle (2).

6. The separating device (12) according to any one of claims 1 to 2, It is characterized in that wherein the contact system (18) of the hybrid switch can be short-circuited by means of a series circuit of the resistor cascade (22) and a third semiconductor switch (28).

7. Vehicle electrical system (4) for a motor vehicle (2), said vehicle electrical system having a DC circuit which has an energy storage device (6) and a current path (8), wherein, The current path (8) has a separating device (12) according to any one of claims 1 to 6.

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