Circuit arrangement for diagnosing a service disconnect line of an electrically powered vehicle

Abstract

Circuit arrangement for diagnosing a service disconnect line (4) of an electrically operated vehicle with two on-board electrical systems of different voltages, wherein the service disconnect line (4) is connected between a first terminal (6) and a second terminal (2) and comprises at least one manual disconnecting element (3), wherein during operation of the circuit arrangement in the vehicle, a voltage present at the second terminal (2) is detected by a measuring device (5) and voltage information (s4) representing the voltage is evaluated by a computing unit (30), wherein the computing unit (30) is designed to disconnect the on-board electrical system with the high voltage from consumers connected to it or not depending on the voltage information, wherein the computing unit (30) is further designed to carry out a test routine for determining a fault in the service disconnect line (4) by controlling respective switching elements (13, 21,22) to iteratively impress different voltage or current levels at the first terminal (6) and the second terminal (2), to detect the respective voltage applied to the second terminal (2) with the measuring device (5) and to evaluate the voltage information (s4) representing the voltage by the computing unit (30).

Description

[0001] The invention relates to a circuit arrangement for diagnosing a service disconnect line of an electrically powered vehicle with two on-board electrical systems of different voltages, wherein the service disconnect line comprises at least one manual disconnect element and optionally a fuse and is connected between a first terminal and a second terminal. During operation of the circuit arrangement in the vehicle, a voltage present at the second terminal is detected by a measuring device, and voltage information representing the voltage is evaluated by a computing unit. The computing unit is designed to disconnect or not disconnect the on-board electrical system with the high voltage from consumers connected to it, depending on the voltage information.

[0002] Electric vehicles have two electrical systems with different voltages. A low-voltage electrical system, typically 12 V, 24 V, or 48 V, supplies low-power electrical consumers, such as control units, lights, comfort and ventilation systems, navigation systems, driver assistance systems, and the like. A high-voltage electrical system, also called a high-voltage electrical system, supplies high-power electrical consumers, such as the electric drive of the electric vehicle. The voltage in the high-voltage electrical system can be 400 V or more, depending on its design.

[0003] In this application, an electrically powered vehicle is understood to be a purely battery-powered vehicle (Battery Electric Vehicle, BEV), which uses only an electric motor as its power source, or a hybrid-electric vehicle (Hybrid Electric Vehicle, HEV or Plug-In Hybrid Electric Vehicle, PHEV), which uses a combination of an internal combustion engine and an electric motor as its power sources. An electric vehicle includes not only motor vehicles, but all electrically powered vehicles, such as industrial trucks or forklifts.

[0004] The presence of two on-board electrical systems with different voltages poses safety challenges in the event of an accident and during service work. Any work or manipulation on the high-voltage components of the electric vehicle can be life-threatening under certain circumstances. Neither workshop personnel during maintenance or repair work, nor first responders or firefighters in the event of an accident, may come into contact with the high voltage of the high-voltage on-board electrical system. For quick and safe voltage isolation, a manual disconnect element, also known as a manual service disconnect switch, is provided in a so-called service disconnect line.

[0005] The manual disconnect element is located in the service disconnect line. Opening the manual disconnect element creates a safe state for workshop personnel or emergency services. For this purpose, the voltage applied to a terminal, for example, is recorded with a measuring device during operation of the circuit arrangement. This voltage changes depending on whether the manual disconnect element is open or closed. Voltage information representing the voltage is evaluated by a computing unit. If the manual disconnect element or the service disconnect line is open (e.g., due to intentional disconnection by a rescuer), the computing unit deactivates the high-voltage vehicle electrical system.

[0006] A disadvantage of the solution currently in use is that detection of a fault condition at the terminal at which the voltage is evaluated is incomplete with regard to various fault situations.

[0007] DE 10 2013 009 802 B3 shows a method for checking the absence of voltage of a power electronics module connected to a high-voltage battery and an electric machine in a high-voltage network of a motor vehicle, which has a higher voltage than a low-voltage network of the motor vehicle, wherein the power electronics module has an intermediate circuit capacitor, a passive discharge resistor, a plug connection for at least one high-voltage consumer and a fuse connected upstream of the plug connection.

[0008] DE 10 2006 050 529 A1 discloses a circuit arrangement for insulation and contactor monitoring of the power supply of an electric drive. DE 10 2012 212 123 B4 discloses a device for diagnosing a circuit arrangement for a short circuit and / or a line break, wherein the circuit arrangement comprises at least two load circuits connected in parallel. In the device according to the invention, a current measuring device for providing a current signal representing the current in the common supply line is connected in a common supply line of the at least two load circuits connected in parallel.

[0009] DE 10 2009 036 672 A1 describes a shutdown procedure for an HV system in a motor vehicle. For this purpose, a switching device is provided with a first switch for disconnecting a first terminal from a second terminal and a second switch for disconnecting a third terminal from a fourth terminal.

[0010] The object of the invention is to provide a functionally improved circuit arrangement for diagnosing a service disconnect line of an electrically powered vehicle with two on-board electrical systems of different voltages.

[0011] This object is achieved by a circuit arrangement according to the features of claim 1. Advantageous embodiments emerge from the dependent claims.

[0012] A circuit arrangement for diagnosing a service disconnect line of an electrically powered vehicle with two on-board electrical systems of different voltages is proposed. The service disconnect line is connected between a first terminal and a second terminal and comprises at least one manual disconnect element. Furthermore, a fuse can optionally be provided in the service disconnect line. During operation of the circuit arrangement in the vehicle, a voltage present at the second terminal is detected by a measuring device, and voltage information representing the voltage is evaluated by a computing unit. The computing unit is designed to disconnect or not disconnect the on-board electrical system with the high voltage from consumers connected to it, depending on the voltage information.

[0013] According to the invention, the computing unit is further designed to carry out a test routine for detecting a fault in the service disconnect line, to iteratively impress different voltage or current levels by controlling respective switching elements at the first terminal and the second terminal, to detect the respective voltage applied to the second terminal with the measuring device and to evaluate the voltage information representing the voltage by the computing unit.

[0014] In particular, the computing unit is designed to detect a short circuit in the service disconnect line to the potential of the low-voltage vehicle electrical system or to a reference potential as a fault. Furthermore, the computing unit is designed to detect an interruption in the service disconnect line that is not caused by the manual disconnection element or by a targeted disconnection of the service disconnect line by a rescue worker.

[0015] The circuit arrangement according to the invention therefore provides improved safety for workshop personnel or emergency services, since, in the absence of monitoring, a short circuit between the second terminal and the low-voltage electrical system could prevent the safe state from being established despite the intentional opening of the manual disconnecting element. Furthermore, without the proposed monitoring by the circuit arrangement, a short circuit between the second terminal and the reference potential could prevent the vehicle from being rendered drivable.

[0016] The invention is based on the consideration that detecting a fault condition at the second terminal, which is terminal 30c (abbreviated to: Kl30c) of the vehicle, is not possible solely by evaluating the voltage level present in the lower-voltage electrical system. Rather, detecting a short circuit or an open circuit at the second terminal requires an actively imposed change in the voltage and / or current level at the second terminal.

[0017] The proposed circuit arrangement provides a remedy in that the computing unit is designed to iteratively control respective switching elements at the first and / or second terminal to carry out a test routine, thereby imposing different voltage or current levels. The resulting voltage applied to the second terminal can then be measured by the measuring device. The voltage information(s) representing the voltage is evaluated by the computing unit, which can then conclude that there is a fault or that the service disconnect line has been deliberately disconnected, e.g., by opening the manual disconnect element or by mechanical disconnection by rescue personnel.

[0018] According to an expedient embodiment of a first variant, in which a switchable power supply is provided, a first controllable switching element is connected between a supply voltage and a node of a voltage divider consisting of two resistors. The supply voltage can, for example, be derived from the vehicle's low-voltage electrical system and can be, for example, 12 V, 24 V, or 48 V. The series circuit of the voltage divider consisting of the two resistors is connected between the first terminal and a reference potential.

[0019] According to an expedient embodiment, the computing unit is designed to control the first switching element successively from a conductive state to a non-conductive state and to conclude that there is a short circuit of the service disconnect line with the potential of the vehicle electrical system with the low voltage when the potential of the vehicle electrical system with the low voltage is detected at the second terminal in both switching positions of the first switching element.

[0020] In a further advantageous embodiment, a second controllable switching element is connected to the second terminal via a resistor. The computing unit is expediently designed to control the second switching element sequentially from a conducting state to a non-conducting state, or vice versa, and to conclude that the service disconnect line is short-circuited to reference potential if the reference potential is detected at the second terminal in both switching positions of the second switching element.

[0021] In another variant, in which current sources and current sinks are used, a current is injected into the first terminal by a first, fixed or variable current source. The computing unit is expediently designed to conclude that the service disconnect line is short-circuited to the potential of the low-voltage vehicle electrical system when the potential of the low-voltage vehicle electrical system is detected at the second terminal.

[0022] According to a further expedient embodiment, the computing unit is designed to conclude that there is a short circuit between the service disconnect line and the reference potential of the vehicle electrical system when the reference potential of the vehicle electrical system is detected at the second terminal.

[0023] According to a further embodiment of this variant, the second terminal is connected via a resistor to a switchable current source arrangement which loads the second terminal or injects a current into it.

[0024] As already described above, the second terminal is terminal 30c (abbreviated to Terminal 30c) of the vehicle. In contrast, the first terminal is a test cycle-specific terminal, which differs significantly from terminal 30 (Terminal 30) of the vehicle.

[0025] According to a further expedient embodiment, the computing unit is designed to perform the test routine once per driving or charging cycle of the vehicle. Alternatively or additionally, the computing unit can be designed to perform the test routine cyclically during vehicle operation.

[0026] The proposed circuit arrangement can prevent incorrect evaluation of the voltage signal applied to the second terminal, which in particular can prevent or exclude dangerous and unwanted vehicle conditions.

[0027] The invention is explained in more detail below using exemplary embodiments in the drawings. They show: Fig. 1 shows a known circuit arrangement in which the conventional wiring of a service disconnect signal loop is shown; Fig. 2 shows a first embodiment of a circuit arrangement according to the invention with a switchable voltage supply; and Fig. 3 a second embodiment of a circuit arrangement according to the invention with current sources and current sinks.

[0028] In the figures, identical elements are provided with identical reference numerals.

[0029] Fig.1 shows a known circuit arrangement of a service disconnect signal loop commonly used in electrically powered vehicles, which is used to bring about a safe condition for workshop personnel or rescue workers.

[0030] The signal loop is formed by a service disconnect line 4 (hereinafter: line 4), in which a manual disconnecting element 3, e.g. in the form of a circuit breaker, is arranged. Line 4 is connected between a terminal 1, terminal 30 (Kl30) of the vehicle, and a terminal 2, terminal 30c (Kl30c) of the vehicle. Terminal 1 is connected to the on-board electrical system with the low voltage, e.g. 12 V. If the on-board electrical system with the low voltage has a voltage other than 12 V, e.g. 24 V, then terminal 1 is connected to 24 V. A measuring device 5 is connected to terminal 2. The voltage currently applied at terminal 2 (Kl30c) is detected by the measuring device 5. Voltage information s4 representing the voltage is fed to a computing unit 30, e.g. a control unit, and evaluated by it.

[0031] If the voltage information s4 corresponds to the voltage of the low-voltage vehicle electrical system (not shown in detail here: 12 V), line 4 connects terminals 1 and 2. A high-voltage battery (not shown in the figures), which is part of a high-voltage vehicle electrical system (also not shown) (hereinafter: high-voltage vehicle electrical system), may then be connected to a wiring harness and / or consumers of the high-voltage vehicle electrical system. If, on the other hand, line 4 is separated using the manual separating element 3, the voltage information s4 determined by the measuring device 5 corresponds to the reference potential GND (where it is assumed here that the high-voltage vehicle electrical system and the low-voltage vehicle electrical system have the same reference potential GND). The computing unit 30 then controls a corresponding switching element to separate the high-voltage battery from the wiring harness and / or the consumers of the high-voltage vehicle electrical system.

[0032] Instead of the manual separating element 3, which is operated by workshop personnel, the separation of the line 4 can also be caused by mechanical (in particular violent) separation of the line 4, for example a cut with rescue shears by rescue workers.

[0033] A short circuit between terminal 2 (Kl30c) and a low-voltage (i.e., 12 V) wire of the vehicle electrical system could prevent the establishment of a safe state after the deliberate opening of the manual isolating element 3 or a mechanical separation of the wire 4. Likewise, a short circuit between terminal 2 (Kl30c) and the reference potential GND could prevent the establishment of a ready-to-drive state.

[0034] The Fig. 2 and Fig.The embodiments shown in Figure 3 enable the detection of a fault condition at terminal 2 (Kl30c) by actively applying a change in the voltage and / or current level at terminal 2 (Kl30c). Terminal 2 (Kl30c) corresponds to a second terminal in the present description.

[0035] Fig. Figure 2 shows an embodiment in which a change in the voltage level at the second terminal 2 (Kl30c) is actively carried out. In contrast to the arrangement known from the prior art according to Fig. 1, line 4 is now connected between the second terminal 2 (Kl30c) and a first terminal 6, which is a terminal specific to the test cycle and, in particular, is different from terminal 1 (Kl30) of the vehicle. The manual disconnect element 3 is again connected in line 4. Terminal 1 (Kl30) is not relevant for the present circuit arrangement and is Fig.2 is shown for information purposes only, to illustrate that the first terminal 6 is a different terminal from terminal 1 (Kl30).

[0036] A first controllable switching element is connected between a node 15 of a voltage divider consisting of two resistors and a diode 14, which is connected to a supply voltage, e.g., 12 V. The supply voltage can, for example, be the vehicle electrical system's low-voltage voltage. In principle, the supply voltage can also be a different voltage. The controllable switching element 13 is switched on or off by means of a control signal s1 from the previously described computing unit 30. The series circuit of the voltage divider 11, 12, consisting of two resistors, is connected between the first terminal 6 and the reference potential GND.

[0037] An optional second controllable switching element 21 is connected to the second terminal 2 (terminal 30c) via a resistor 23. The other end of the second controllable switching element 21 is connected to the supply voltage (here: 12 V). Also shown is another optional third controllable switching element 22, which is connected between a node 24 formed between the second controllable switching element 21 and the resistor 23, and the reference potential GND. The second controllable switching element 21 is switched on or off by the computing unit 30 via a second control signal s2. The third controllable switching element 22 is switched on or off by the computing unit 30 via a third control signal s3.

[0038] The switching arrangement connected to the second terminal 2 (Kl30c) can be omitted in whole or in part to simplify the functionality of the circuit arrangement.

[0039] The computing unit 30 is designed to control the first switching element 13 sequentially from a conductive state to a non-conductive state. If the potential of the vehicle electrical system with the low voltage is detected at the second terminal 2 (Kl30c) in each of the two consecutive switching positions of the first switching element 13, the computing unit 30 concludes that there is a short circuit in line 4. The presence of the second and third controllable switching elements 21, 22 is not required to perform this test. However, if these two controllable switching elements are present, they are each switched to the blocking position.

[0040] The different variants of switch positions of the first switching element and voltage information s4 received at the second terminal 2 (Kl30c) are shown again in the following table: Table 1: Error state matrix Switching element 13 terminal 2 (Kl30c) Conductive blocking Approx. 12 V Connection ok or short circuit to 12 V Short circuit to 12 V 0 V Line break or separating element closed Connection ok or line break or separator open or short circuit to reference potential GND

[0041] To determine whether line 4 is short-circuited to reference potential GND, the processing unit 30 is configured to successively control the second switching element 21 from a conducting state to a non-conducting state. The switching sequence can also be reversed. While the second controllable switching element 21 is controlled, the first and third controllable switching elements 13, 22 are each switched to the off state. If the reference potential is detected at the second terminal 2 (Kl30c) in both switching positions of the second switching element 21, a short-circuit of line 4 to the reference potential can be determined.

[0042] Fig.3 shows a second exemplary embodiment in which current sources and current sinks are used instead of a switchable voltage supply. The first terminal 6 is connected to a first current source 16, which is supplied with the 12 V supply potential (either the supply voltage of the vehicle electrical system or a different supply voltage). A switch arrangement comprising the first and second controllable switching elements 21, 22 is connected to the second terminal 2 (Kl30c). The first controllable switching element 21 is connected between the node 24 and a current source 25. The current source 25 is connected to the 12 V supply potential. The second controllable switching element 22 is connected between the node 24 and a current source 26, which is connected to reference potential.

[0043] The computing unit 30 is designed to determine whether there is a short circuit between line 4 and the low-voltage vehicle electrical system potential when the low-voltage vehicle electrical system potential is detected at the second terminal 2 (terminal 30c). This check is performed by switching the second and third controllable switching elements 21, 22 to the off-state.

[0044] A short circuit between line 4 and the low-voltage reference potential GND of the vehicle electrical system can be determined if the reference potential GND of the vehicle electrical system is activated at the second terminal 2. The test is performed by switching the second controllable switching element 21 to conducting and the third controllable switching element 22 to blocking.

[0045] If the second and third controllable switching elements s2 and s3 are conductive, the switchable current source arrangement acts like a voltage divider, resulting in a medium voltage at the second terminal 6 (terminal 30c), i.e., a voltage between the reference potential and the supply voltage (here: 12 V). If a voltage differing from this is present at terminal 6 (terminal 30c), a short circuit with the low-voltage vehicle electrical system can be concluded.

Claims

[1] Circuit arrangement for diagnosing a service disconnect line (4) of an electrically operated vehicle with two on-board electrical systems of different voltages, wherein the service disconnect line (4) is connected between a first terminal (6) and a second terminal (2) and comprises at least one manual disconnecting element (3), wherein during operation of the circuit arrangement in the vehicle, a voltage applied to the second terminal (2) is detected by a measuring device (5) and voltage information (s4) representing the voltage is evaluated by a computing unit (30), wherein the computing unit (30) is designed to disconnect the on-board electrical system with the high voltage from consumers connected to it or not depending on the voltage information, wherein the computing unit (30) is further designed to carry out a test routine for determining a fault in the service disconnect line (4) by controlling respective switching elements (13, 21,22) to iteratively impress different voltage or current levels at the first terminal (6) and the second terminal (2), to detect the respective voltage applied to the second terminal (2) with the measuring device (5) and to evaluate the voltage information (s4) representing the voltage by the computing unit (30). [2] Circuit arrangement according to claim 1, in which the computing unit (30) is designed to detect as an error a short circuit of the service disconnect line (4) with the potential of the on-board network with the low voltage or with a reference potential (GND). [3] Circuit arrangement according to claim 1 or 2, in which the computing unit (30) is designed to detect an interruption in the service disconnect line (4) as an error. [4] Circuit arrangement according to one of claims 1 to 3, in which a first controllable switching element (13) is connected between a supply voltage (12V) and a node (15) of a voltage divider (11, 12) consisting of two resistors, wherein the series circuit of the voltage divider consisting of the two resistors (11, 12) is connected between the first terminal (6) and a reference potential (GND). [5] Circuit arrangement according to claim 4, in which the computing unit (30) is designed to control the first switching element (13) successively from a conductive state to a non-conductive state, and to conclude that there is a short circuit of the service disconnect line (4) with the potential of the vehicle electrical system with the low voltage when the potential of the vehicle electrical system with the low voltage is detected at the second terminal (2) in both switching positions of the first switching element (13). [6] Circuit arrangement according to claim 4 or 5, in which a second controllable switching element (21) is connected to the second terminal (2) via a resistor (23). [7] Circuit arrangement according to claim 6, in which the computing unit (30) is designed to control the second switching element (21) successively from a conductive state to a non-conductive state, or vice versa, and to conclude that there is a short circuit of the service disconnect line (4) with the reference potential (GND) when the reference potential (GND) is detected at the second terminal (2) in both switching positions of the second switching element (13). [8] Circuit arrangement according to one of claims 1 to 3, in which a current is impressed into the first terminal (6) by a first, fixed or variable current source (16). [9] Circuit arrangement according to claim 8, in which the computing unit (30) is designed to conclude that there is a short circuit between the service disconnect line (4) and the potential of the vehicle electrical system with the low voltage when the potential of the vehicle electrical system with the low voltage is detected at the second terminal (2). [10] Circuit arrangement according to claim 8 or 9, in which the computing unit (30) is designed to conclude that there is a short circuit between the service disconnect line (4) and the reference potential of the vehicle electrical system when the reference potential (GND) of the vehicle electrical system is detected at the second terminal (2). [11] Circuit arrangement according to one of claims 8 to 10, in which the second terminal (2) is connected via a resistor (23) to a switchable current source arrangement (21, 22, 25, 26) which loads the second terminal (2) or injects a current into it. [12] Circuit arrangement according to one of the preceding claims, in which the second terminal (2) is the terminal 30c of the vehicle. [13] Circuit arrangement according to one of the preceding claims, in which the first terminal (6) is a terminal specific to the test cycle which is different from terminal 30 of the vehicle. [14] Circuit arrangement according to one of the preceding claims, in which the computing unit (30) is designed to carry out the test routine once per driving or charging cycle of the vehicle. [15] Circuit arrangement according to one of the preceding claims, in which the computing unit (30) is designed to carry out the test routine cyclically during operation of the vehicle.

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