Device for electrical power supply with a power source for coupling to an on-board power supply of a motor vehicle.

Abstract

Device for electrical power supply with a power source (Q) for coupling to an on-board power network (B) of a motor vehicle, characterized in that - the device (SV) includes a control unit (CO) which, during operation of the device (SV), generates an output voltage (U) from the current source (Q). BQ ) measures, where the output voltage (U) BQ ) an upper threshold value (T1) is specified, which is greater than the maximum output voltage measured by the control unit (CO) when the current source (Q) is coupled to the power supply network (B) and which is less than or equal to the output voltage (U) measured by the control unit (CO). BQ ) when the on-board power supply (B) is disconnected from the power source (Q); - the control device (CO) is designed in such a way that it causes the power source (Q) coupled to the power supply network (B) to be switched off when the output voltage (U BQ) exceeds the upper threshold (T1).

Description

[0001] The invention relates to a device for electrical power supply with a power source which, during operation of the device, is coupled to an on-board power network of a motor vehicle.

[0002] Modern vehicle electrical systems incorporate a multitude of electrical components, resulting in high energy demands. Consequently, the electrical power sources connected to the electrical system must supply a sufficiently high voltage to power these components. The problem lies in the fact that the voltages to the power sources are not automatically cut off when the electrical system is unexpectedly disconnected from the power source, posing safety risks. In particular, a connecting cable between the power source and the electrical system can become detached in a vehicle accident. This cable then continues to carry the high voltage from the power source, potentially leading to short circuits, sparking, or overheating.

[0003] Publication US 2007 / 0126236A1 discloses a power supply for a vehicle in which electrical generators are controlled depending on the voltage on a power supply bus.

[0004] Document DE 103 35 866 A1 discloses a vehicle inverter with at least one load socket, wherein the vehicle inverter can be switched to operational readiness by inserting an electrical load plug into the load socket. Furthermore, the vehicle inverter can be switched off in the event of an overvoltage or undervoltage in a supply network connected to the vehicle inverter.

[0005] Document US 2008 / 0247105A1 discloses a voltage protection device with switching elements and voltage terminals. Upon detection of an overvoltage, the voltage protection device can protect an electrical load from damage.

[0006] The object of the invention is to create a device for electrical power supply which ensures the safe operation of the on-board power network of a motor vehicle.

[0007] This problem is solved by the device according to claim 1. Further developments of the invention are defined in the dependent claims.

[0008] The device according to the invention comprises a power source for coupling to the vehicle electrical system and a control unit which measures an output voltage generated by the power source during operation. An upper threshold is defined for the output voltage, which is greater than the maximum output voltage measured by the control unit when the power source is coupled to the vehicle electrical system and less than or equal to the output voltage measured by the control unit when the vehicle electrical system is disconnected from the power source. The control unit is further configured such that it switches off the power source, which is normally coupled to the vehicle electrical system, when the output voltage exceeds the upper threshold.This means that the corresponding connections on the device, which are connected to the vehicle's electrical system via wiring, are de-energized, thereby increasing the operational reliability of the vehicle's electrical system, e.g. in the event of a break in the connecting cable or if the connecting cable comes loose in an accident.

[0009] The device according to the invention utilizes the fact that the characteristics of the power source can be used to determine when a deviation from the norm occurs in the vehicle's electrical system. In particular, it is assumed that a malfunction occurs when the power source is not under load, which is always the case when the electrical connection to the vehicle's electrical system is interrupted. This malfunction is detected via the increased output voltage when the power source is unloaded. By appropriately selecting an upper threshold value that is higher than the voltage values ​​during normal operation of the vehicle's electrical system, the power source can be easily switched off when this threshold is exceeded.

[0010] In a particularly preferred embodiment, a lower threshold for the output voltage is further specified, and the control device is designed such that it disconnects the power source originally connected to the vehicle's electrical system when the output voltage falls below this lower threshold. This prevents leakage currents, which can lead to the discharge of the vehicle's electrical system battery. It also ensures that the power source is disconnected in the event of a short circuit.

[0011] The device according to the invention can include any type of power source. In a particularly preferred embodiment, the power source is a thermoelectric generator, which is installed in the exhaust system of the motor vehicle during operation and generates electricity through the temperature gradient that occurs in the exhaust system. The source voltage of such a generator is relatively high, so suitable current cut-off is particularly important. Nevertheless, the device can also include other types of power sources, such as the vehicle's battery or a photovoltaic system, which generates electricity when exposed to sunlight and is fed into the vehicle's electrical system.

[0012] In a further embodiment of the device according to the invention, the control unit comprises a low-pass filter for filtering the output voltage it measures. This smooths out fluctuations in the output voltage, allowing for better evaluation of the output voltage. The smoothed output voltage is then used for comparison with the upper and lower threshold values.

[0013] The source voltage of the power source installed in the device, without coupling to the vehicle's electrical system (i.e., the open-circuit voltage of the power source), is, in a preferred embodiment, between 25 and 30 volts, particularly between 28 and 30 volts. A thermoelectric generator typically supplies voltages within this range. Nevertheless, the device according to the invention can also utilize power sources or thermoelectric generators operating in a different voltage range, such as power sources with a source voltage between 56 and 60 volts, which are preferably used in vehicle electrical systems with a nominal voltage of 24 volts.

[0014] To use the device according to the invention in conventional vehicle electrical systems with a system voltage in the range between 12 and 14.5 volts, the upper threshold is preferably set such that it lies between 15.5 volts and 16.5 volts, and particularly between 16 volts and 16.3 volts. This also achieves the advantage of preventing damage to devices installed in the vehicle electrical system, which generally cannot tolerate continuous voltages of more than 16 volts.

[0015] If a lower threshold value is also specified in the control unit of the device according to the invention, this value is preferably set to 10 volts or less, in particular to 9 volts or less and most preferably to 6 volts or less.

[0016] In a further embodiment of the invention, a diode, and in particular a Schottky diode, is connected in the device according to the invention, which prevents a current flow with opposite polarity to the output voltage. This ensures that the thermoelectric generator is not operated in such a way that it generates thermal energy through current flow using the Peltier effect, thereby drawing electrical energy from the vehicle's electrical system. Optionally, the function of the diode can also be performed by the control unit, either additionally or alternatively. In this case, the control unit includes appropriate detection means to detect a current flow with opposite polarity to the output voltage, and upon detection of such a current flow, the control unit disconnects the power source originally connected to the vehicle's electrical system.

[0017] In a further embodiment of the device according to the invention, the control unit can be connected to a data transmission means for communication with one or more components in the motor vehicle, wherein, in the connected state, the control unit can preferably receive information from at least one of the components that causes the control unit to switch off the power source connected to the vehicle's electrical system. The data transmission means can be configured in various ways. In particular, it can be a conventional data bus in a motor vehicle with which information is transmitted digitally. Separate signaling lines can also be provided.

[0018] In a particularly preferred embodiment, the control unit of the device according to the invention can be connected to a motor vehicle safety system via the data transmission medium. The control unit then disconnects the power source originally connected to the vehicle's electrical system when it receives an alarm message from the vehicle's safety system. In particular, such an alarm message can be issued upon detection of an accident, e.g., by the vehicle's airbag system. Disconnecting the power source via an alarm signal increases the operational safety of the vehicle's electrical system.

[0019] In a further embodiment of the device according to the invention, the control unit can be connected to a vehicle's energy management system via the data transmission medium. The control unit transmits a message to the energy management system via the data transmission medium when it causes the power source originally connected to the vehicle's electrical system to be switched off. This message can contain the cause of the switch-off, e.g., whether the switch-off was triggered by an output voltage above or below the upper or lower threshold value, or by a current flow with the opposite polarity to the output voltage. Such information can then be used for diagnostic purposes or for plausibility checks in the energy management system.

[0020] In addition to the device described above, the invention further relates to a motor vehicle comprising an electrical system, wherein the device according to the invention described above is also provided in the motor vehicle. This device is coupled to the electrical system of the motor vehicle.

[0021] An embodiment of the invention is described below with reference to the attached Fig. 1 described in detail. This figure shows a schematic representation of an embodiment of a device according to the invention, which is electrically connected to the power supply network of a motor vehicle.

[0022] The invention is described below using the example of a thermoelectric generator that is installed in the exhaust system of a motor vehicle, and in particular in the muffler of the exhaust system. During operation of the motor vehicle, the generator produces electrical current based on the known Seebeck effect, due to the temperature difference between the exhaust system and the surrounding environment. This electrical current is fed into the vehicle's electrical system and can be used by the corresponding electrical consumers.

[0023] In the schematic representation of the Fig. Figure 1 shows the thermoelectric generator as the power source Q, which is part of the power supply unit SV connected to the vehicle's electrical system. The vehicle's electrical system is labeled B. A corresponding wiring harness K connects the power supply unit SV to the vehicle's electrical system B. Only a small section of the electrical system is shown. In particular, the consumers connected to the electrical system, or the vehicle battery, are not shown. Nevertheless, it is evident that a switch S is present. B The system is designed to allow an energy management unit (not shown) to disconnect the vehicle's electrical system from the wiring when certain criteria are met. A fuse F is also provided, which triggers a disconnection of the vehicle's electrical system from the wiring K in the event of an overcurrent.

[0024] During operation of the on-board power supply system B, an on-board voltage U is present. BThe voltage, which in the embodiment described here lies between 12 volts and 14.5 volts and can fluctuate within this range, is supplied by a device SV. Nevertheless, the maximum vehicle electrical system voltage of 14.5 V is not exceeded during normal operation. In addition to the thermoelectric generator Q, the power supply unit SV comprises a control unit CO, which is implemented as a logic controller and switches the current source Q via the switch S. Q can switch off and thereby disconnect from the vehicle electrical system B. The control unit CO measures the voltage U during operation. BQ The output voltage is provided via the corresponding terminals A1 and A2. This occurs without an electrical load being connected, i.e., with switch S open. B The control unit CO measures an output voltage that is derived from the source voltage U. Q of the thermoelectric generator and the voltage drop U D The voltage is composed via a diode D provided in the current path. That is, the voltage U BQconsists of the source voltage U Q at idle (i.e., without load) minus the voltage drop U D together. The voltage drop U D The voltage across diode D is in comparison to the source voltage U Q The voltage is relatively low and, in the embodiment described here, where a Schottky diode is used, is 0.4 volts. Without a load, this results in an output voltage U. BQ , which, except for a small offset of the source voltage U Q corresponds.

[0025] When the power supply device SV is electrically connected to the vehicle's electrical system (i.e., when switches S are closed) Q and S B ) this results in a reduction of the output voltage U BQ The output voltage then corresponds to the voltage except for the small voltage drop U. K , which is caused by the wiring K, the on-board voltage U BIn a conventional power supply without a control unit CO, the problem now arises that in the event of an unintentional disconnection of the vehicle's electrical system from the power supply, for example by a cable in the wiring K being torn off or coming loose, the source voltage U Q The voltage rises to approximately 30 volts at idle. This elevated voltage is present at wiring K and is a safety hazard. In particular, a short circuit can occur due to a broken wire, potentially leading to sparking and damage to the vehicle or its occupants.

[0026] To avoid this safety risk, the invention makes use of the source properties of the current source Q, i.e., the property that the source voltage U is Q and therefore also the output voltage U BQThe voltage rises significantly when the device SV is disconnected from the vehicle electrical system B. If such a voltage increase is detected, the switch S is opened via the control circuit CO. Q The circuit is opened so that the source voltage is no longer present at terminals A1 and A2 of the power supply SV. An upper threshold value T1 is stored in the control unit CO, which is selected such that, when the power supply SV is properly connected to the vehicle's electrical system B, it lies above the maximum measurable value determined by the vehicle's electrical system voltage U. B is determined. If the voltage U exceeds BQ When the power supply device SV is coupled to the vehicle's electrical system B, this upper threshold is exceeded, and the control unit opens the switch S. Q This ensures that no safety-critical voltage is present on the cables of wiring K. In the embodiment described here, where the on-board voltage UB Since the voltage range is between 12 volts and 14.5 volts, an upper threshold value in the range of 15.5 volts to 16.5 volts proves suitable. Such a threshold value also ensures that the control units installed in the vehicle's electrical system are not damaged, as these devices generally cannot withstand voltages higher than 16 volts for extended periods.

[0027] The diode D installed in the power supply unit SV serves to prevent current flow from the vehicle's electrical system to the thermoelectric generator Q. This prevents heat from being generated by the generator due to the Peltier effect, which can occur, for example, when the thermoelectric generator starts operating. In a specific embodiment, the function of diode D can also be emulated by the control unit CO. In this case, the control unit CO detects a current flow to the source Q, which then triggers the opening of switch S. Q is triggered.

[0028] A lower threshold value T2 may also be stored in the CO control unit. If this lower threshold value is exceeded by the output voltage U BQ If the threshold is undershot, switch S will also open. QBased on a suitable selection of the lower threshold T2, leakage currents, which could lead to the discharge of the on-board battery, are prevented, for example, when the generator is started up. Furthermore, it is ensured that in the event of a short circuit, where the voltage U BQ When the voltage drops to zero, the vehicle's electrical system is disconnected from the power supply device. Preferred values ​​for the lower threshold are 9 volts or less, and particularly 6 volts or less.

[0029] In a further variation of the power supply device SV, the control unit CO can also react to external information which is stored in Fig. 1 are designated with IN. In particular, an alarm signal from a vehicle security system can be supplied to the control unit via a suitable data transmission medium, which also triggers the opening of switch S. Qand thus the switching off of the power source Q is achieved. For example, a corresponding alarm signal can be sent from the airbag control system to the control unit CO in the event of an accident. The information IN can be transmitted to the control unit CO in different ways, depending on the design. In one variant, the control unit is connected to the vehicle's data bus (such as CAN, LIN, Powerline, etc.). Alternatively, a separate signaling line can be provided for transmitting the information IN. This signaling line can then be used to transmit the information, for example, based on pulse width modulation, frequency modulation, or amplitude modulation.

[0030] In a further embodiment, the CO control unit can also transmit information to the vehicle using the data transmission medium. For example, the control unit can transmit information to the vehicle's energy management system about why switch S was closed. Q The system was opened, i.e., whether a voltage above or below the threshold T1, or an incorrect current direction, triggered the shutdown. This information can then be further processed appropriately for diagnostic purposes in the energy management system.

[0031] The invention has been described using an exemplary embodiment of a power source in the form of a thermoelectric generator. However, instead of a thermoelectric generator, any other power source connected to an electrical system can also be used. For example, the invention can also be used for photovoltaic systems that generate electricity from solar radiation and feed it into the vehicle's electrical system. The open-circuit voltage of such systems is typically in the range of 19 to 20 volts.

[0032] The device according to the invention has a number of advantages. In particular, a power source in a motor vehicle does not supply any voltage if it is disconnected from the vehicle's electrical system. Thus, the wiring between the vehicle's electrical system and the power source is de-energized in this case, thereby increasing safety in the event of an unintentional disconnection or unintentional loosening of the wiring. By using an upper and a lower threshold, above or below which the power source is switched off, the power source is deactivated both in the event of an interruption of the supply line or ground line and in the event of a short circuit. In a special embodiment, the power source can also be switched off by additional information, such as an alarm signal. Furthermore, the control unit can, if necessary,A current direction towards the power source can also be detected, whereupon the power source is also switched off.

Claims

[1] Device for electrical power supply with a power source (Q) for coupling to an on-board power network (B) of a motor vehicle, characterized by , that - the device (SV) includes a control unit (CO) which, during operation of the device (SV), generates an output voltage (U) from the current source (Q). BQ ) measures, where the output voltage (U) BQ ) an upper threshold value (T1) is specified, which is greater than the maximum output voltage measured by the control unit (CO) when the current source (Q) is coupled to the power supply network (B) and which is less than or equal to the output voltage (U) measured by the control unit (CO). BQ ) when the on-board power supply (B) is disconnected from the power source (Q); - the control device (CO) is designed in such a way that it causes the power source (Q) coupled to the power supply network (B) to be switched off when the output voltage (U BQ) exceeds the upper threshold (T1). [2] Device according to claim 1, characterized by , that furthermore a lower threshold (T2) for the output voltage (U BQ ) is specified and the control device (CO) is designed such that it causes the power source (Q) coupled to the power supply network (B) to be switched off when the output voltage (U BQ ) falls below the lower threshold (T2). [3] Device according to claim 1 or 2, characterized by , that the power source (Q) is a thermoelectric generator which is installed in the exhaust system of the motor vehicle during operation and generates electricity through the temperature gradient that occurs in the exhaust system. [4] Device according to any one of the preceding claims, characterized by , that the control unit (CO) has a low-pass filter to filter the measured output voltage (U) BQ ) includes. [5] Device according to any one of the preceding claims, characterized by , that the source voltage (U Q ) the voltage of the power source without coupling to the vehicle's electrical system (B) is between 25 and 30 volts. [6] Device according to any one of the preceding claims, characterized by , that the upper threshold (T1) lies between 15.5 volts and 16.5 volts. [7] Device according to one of the preceding claims in combination with claim 2, characterized by that the lower threshold (T2) is less than or equal to 10 volts. [8] Device according to any one of the preceding claims, characterized by , that a diode (D) is connected in the device (SV), which allows a current flow in the opposite polarity to the output voltage (U). BQ ) prevented. [9] Device according to any one of the preceding claims, characterized by , that the control device (CO) allows a current flow in the opposite polarity to the output voltage (U) BQ) can detect, whereby the control unit (CO) causes the power source (Q) coupled to the power supply network (B) to be switched off upon detection of such a current flow. [10] Device according to any one of the preceding claims, characterized by that the control unit (CO) is connectable to a data transmission device for communication with one or more components in the motor vehicle. [11] Device according to claim 10, characterized by , that the control unit (CO) can be connected to a motor vehicle security system via the data transmission means, wherein the control unit (CO) causes the power source (Q) coupled to the vehicle's electrical system (B) to be switched off when it receives an alarm message from the motor vehicle security system. [12] Device according to claim 10 or 11, characterized by, that the control unit (CO) can be connected to a motor vehicle energy management system via the data transmission medium and that the control unit (CO) transmits a message to the energy management system via the data transmission medium when it causes the power source (Q) coupled to the vehicle's electrical system (B) to be switched off. [13] Motor vehicle comprising an on-board power supply (B), characterized by , that a device according to one of the preceding claims is provided in the motor vehicle, which is coupled to the vehicle's electrical system (B).

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