Abstract: A vehicle electrical system includes a first system branch with a first nominal voltage U1, a second system branch with a second nominal voltage U2, at least one DC/DC converter configured to transmit energy between the first and second system branches, a first actuating unit to actuate the DC/DC converter(s), a first detection unit to detect an instantaneous voltage Uact,1 of the first system branch, and a comparison unit to compare the detected instantaneous voltage Uact,1 to a first upper voltage threshold value Uo,1 and to a first lower voltage threshold value Uu,1, wherein Uu,1<U1<Uo,1. The first actuating unit actuates the DC/DC converter(s) such that energy is transmitted from the first system branch to the second system branch if Uact,1>Uo,1, and such that energy is transmitted from the second system branch to the first system branch if Uact,1<Uu,1.

Abstract: A method for controlled connection of a plurality of on-board power system branches is disclosed, wherein electrical power is exchanged between first and third on-board power system branches if an uncritical supply state is present and electrical power is exchanged between second and the third on-board power system branches if a critical supply state is present in the first or third on-board power system branch. In a critical supply state, the first on-board power system branch is disconnected from the third on-board power system branch by opening a first switching device, and the second on-board power system branch is then connected to the third on-board power system branch via a second switching device. A second actuation device that actuates the second switching device receives a switch state signal from the first actuation device and closes the second switching device only if the received signal signals an open first switching device.

Abstract: An on-board system for a vehicle and a device for controlling a current flow in an on-board system of a vehicle, as well as a vehicle (e.g., a motor vehicle) including such on-board system or device, are disclosed. The on-board system or device may include a control device and an emergency power source for closing a self-locking switch controlling the current flow in the on-board system in order to prevent a possible parasitic current injection when a faulty voltage drop occurs, and to thus prevent system overheating.

Abstract: An on-board electrical system for a motor vehicle contains a first energy storage unit with a first voltage level and a second energy storage unit with a second voltage level. A control unit controls a flow of current between the first energy storage unit and the second energy storage unit in both directions. A polarity-reversal protection diode connects the first energy storage unit for supplying operating voltage to the control unit. A switching element bridges the polarity-reversal protection diode when the polarity of the first energy storage unit is correct. The first voltage level is compared with the second voltage level by a comparator and the switching element is moved to its open state when the first voltage level drops to a threshold voltage value which is below the second voltage level.

Abstract: A method for controlled connection of a plurality of on-board power system branches is disclosed, wherein electrical power is exchanged between first and third on-board power system branches if an uncritical supply state is present and electrical power is exchanged between second and the third on-board power system branches if a critical supply state is present in the first or third on-board power system branch. In a critical supply state, the first on-board power system branch is disconnected from the third on-board power system branch by opening a first switching device, and the second on-board power system branch is then connected to the third on-board power system branch via a second switching device. A second actuation device that actuates the second switching device receives a switch state signal from the first actuation device and closes the second switching device only if the received signal signals an open first switching device.

Abstract: An electrical system has first and second switches. The switches are used by the electrical system to produce closed circuits from a first energy storage device and/or a second energy storage device to a system load to supply power to the system load. The electrical system has a device for detecting a voltage at the second energy storage device and for comparing the detected voltage with a voltage threshold, and also a control device for producing a third, closed circuit from the second energy storage device to an earth connection by closing the first and second switches, and therefore for discharging the second energy storage device when the detected voltage exceeds the voltage threshold. This prevents the second energy storage device from charging uncontrollably when a system fault occurs in the electrical system or on the current path from the first energy storage device to the second energy storage device.

Abstract: A vehicle electrical system includes a first system branch with a first nominal voltage U1, a second system branch with a second nominal voltage U2, at least one DC/DC converter configured to transmit energy between the first and second system branches, a first actuating unit to actuate the DC/DC converter(s), a first detection unit to detect an instantaneous voltage Uact,1 of the first system branch, and a comparison unit to compare the detected instantaneous voltage Uact,1 to a first upper voltage threshold value Uo,1 and to a first lower voltage threshold value Uu,1, wherein Uu,1<U1<Uo,1. The first actuating unit actuates the DC/DC converter(s) such that energy is transmitted from the first system branch to the second system branch if Uact,1>Uo,1, and such that energy is transmitted from the second system branch to the first system branch if Uact,1<Uu,1.

Abstract: An on-board system for a vehicle and a device for controlling a current flow in an on-board system of a vehicle, as well as a vehicle (e.g., a motor vehicle) including such on-board system or device, are disclosed. The on-board system or device may include a control device and an emergency power source for closing a self-locking switch controlling the current flow in the on-board system in order to prevent a possible parasitic current injection when a faulty voltage drop occurs, and to thus prevent system overheating.

Abstract: An on-board electrical system for a motor vehicle contains a first energy storage unit with a first voltage level and a second energy storage unit with a second voltage level. A control unit controls a flow of current between the first energy storage unit and the second energy storage unit in both directions. A polarity-reversal protection diode connects the first energy storage unit for supplying operating voltage to the control unit. A switching element bridges the polarity-reversal protection diode when the polarity of the first energy storage unit is correct. The first voltage level is compared with the second voltage level by a comparator and the switching element is moved to its open state when the first voltage level drops to a threshold voltage value which is below the second voltage level.

Abstract: An electrical system has first and second switches. The switches are used by the electrical system to produce closed circuits from a first energy storage device and/or a second energy storage device to a system load to supply power to the system load. The electrical system has a device for detecting a voltage at the second energy storage device and for comparing the detected voltage with a voltage threshold, and also a control device for producing a third, closed circuit from the second energy storage device to an earth connection by closing the first and second switches, and therefore for discharging the second energy storage device when the detected voltage exceeds the voltage threshold. This prevents the second energy storage device from charging uncontrollably when a system fault occurs in the electrical system or on the current path from the first energy storage device to the second energy storage device.