Disconnector for power lines

Abstract

The invention relates to a disconnector (100) for a power line, comprising: - at least one first connection part (1); - at least one second connection part (2); - at least one semiconductor switch (3) arranged in the conducting direction between the first connection part and the second connection part; - at least one detection device (4) arranged between the first connection part and the second connection part for measuring the current intensity Iist of a current flowing between the first connection part (1) and the second connection part (2); - at least one monitoring unit (5) which is suitable for comparing the magnitude of the current intensity Iist with a limit value Imax and, if list > Imax, transmitting a disconnection signal to the semiconductor switch (3) and / or which is suitable for comparing the increase in the current intensity ΔIist with a limit gradient ΔImax and, if the limit gradient is exceeded, transmitting a disconnection signal to the semiconductor switch; wherein, - the disconnection signal of the monitoring unit (5) brings about a switching of the semiconductor switch (3) into an open state and an interruption of the current flow between the first connection part (1) and the second connection part (2).

Description

[0001] Disconnect switch for power lines

[0002] The invention relates to a disconnect switch for power lines. Furthermore, the invention relates to a method for switching a disconnect switch.

[0003] The electrical protection of power conductors, especially those in motor vehicles, is a safety-relevant area of ​​automotive technology, with a particular focus on the safety of vehicle occupants. Accordingly, motor vehicle power conductors carrying high currents must be quickly disconnected from the vehicle battery in the event of an accident. If this is not ensured, short circuits with very high currents can occur during accidents.

[0004] Disconnect devices are known in which power lines are severed by pyrotechnic disconnects in the event of an impending short circuit. The disconnection of the power lines using these devices is usually achieved either by mechanically cutting the line. A disadvantage of this method is that arcs can form at the point of separation when a live line is cut, leaving the connecting parts electrically connected. This is particularly common in high-voltage applications, such as in electric or hybrid vehicles, as the high currents and potential differences in these applications greatly increase the likelihood of arcing.

[0005] Applications for suppressing or extinguishing arcs are known from the prior art in which the separation point is opened by forcing a flowable medium towards the separation point via a drive mechanism. The flowable medium is intended to ensure that it spreads into the air gap formed between the two connecting parts at least partially by flowing around the separation point at the moment of separation, thereby suppressing the formation of an arc or extinguishing an existing one. However, even these further improved embodiments with a flowable medium are not sufficiently safe and reliable with regard to extinguishing or suppressing arcs, meaning that a risk to the safety of vehicle occupants cannot be ruled out.

[0006] According to this design, in the event of an accident, the battery should be automatically and promptly disconnected from the other high-voltage components and wiring, thus eliminating any voltage present. Known pyrotechnic disconnect devices can interrupt the current within milliseconds after activation. Even within this timeframe, the current can reach maximum values ​​of, for example, 30 kA in low-inductance systems of, say, 25 pH.

[0007] The challenge, therefore, is to enable the safest possible disconnection of a live conductor while reliably preventing arcing.

[0008] This problem is solved in the present case by a disconnect switch according to claim 1 and a method according to claim 15.

[0009] The disconnect switch according to the invention for a power line comprises at least a first terminal part and a second terminal part, and at least one semiconductor switch arranged in the forward direction between the first terminal part and the second terminal part. The at least one semiconductor switch has a closed state, in which the first terminal part and the second terminal part are electrically connected to each other via the semiconductor switch, and an open state, in which the electrical contact between the first terminal part and the second terminal part is interrupted. Switching the semiconductor switch from the closed to the open state thus interrupts the current flow between the first terminal part and the second terminal part. The disconnect switch further comprises a detection device arranged between the first terminal part and the second terminal part.The term "arranged between the first and second terminals" means that the detection unit is positioned along an electrical conductor connecting the two terminals. Spatially, the detection unit can be located along a line between the terminals or offset from it. The detection unit is capable of measuring the current (li) flowing between the first and second terminals. The disconnect switch includes a monitoring unit capable of comparing the magnitude of the current (li) with a limit value (Imax) and / or the rate of change of the current (Ai) with a limit value (lmax).If the current magnitude is compared to the limit value Imax in the monitoring unit, and the measured current magnitude is greater than the limit value Imax set in the monitoring unit, the monitoring unit can transmit a disconnect signal to the semiconductor switch. As long as the measured current magnitude is less than or equal to the limit value Imax, the current continues to be measured by the detection device and compared to the limit value by the monitoring unit. If the monitoring unit monitors the current increase Ast and compares it to a limit slope Almax, the monitoring unit can output a disconnect signal as soon as the current increase exceeds the limit slope Almax. The limit value and / or the limit slope of the current are stored in the monitoring unit and can be selected depending on the specific application.The limit slope is defined as the maximum permissible increase in current within a unit of time. The monitoring unit outputs a cutoff signal if the increase in measured current within this time unit exceeds the maximum permissible increase. The cutoff signal transmitted by the monitoring unit to the semiconductor switch causes the semiconductor switch to open and interrupts the current flow between the first and second terminals.

[0010] The at least one semiconductor switch is preferably reversibly switchable, thus offering an advantage over irreversible safety systems such as pyrotechnic disconnectors or conventional fuses. This ensures that the disconnector can be used for the entire service life of the device, for example, a motor vehicle.

[0011] The disconnect switch according to the invention can be designed such that the first and second connection parts are current-carrying components of a power line, for example, a vehicle power line. Pyrotechnic disconnect devices for vehicle power lines known in the prior art require several milliseconds after an activation signal to disconnect a power line. Within this time, a short-circuit current has already risen to its maximum value, so that arcing can occur when the line is disconnected. It has been recognized that the extinguishing or suppression of arcing in current-carrying lines with direct current in the high-voltage range is not sufficiently safe and reliable, which still poses a risk to the safety of vehicle occupants in the automotive sector.This is avoided by means of the disconnect switch according to the invention, which effects a disconnection within a fraction of a millisecond and thus before the short-circuit current rises to its maximum value.

[0012] The at least one semiconductor switch of the disconnect switch is preferably implemented as a field-effect transistor (FET). FETs are voltage-controlled switching elements whose control is achieved via the control electrode. The control electrode regulates the semiconductor resistance, thereby controlling the current. FETs have at least three terminals: the control electrode, referred to as the "gate," the source terminal, and the drain terminal. Current flows in through the source terminal, out through the drain terminal, while the gate terminal regulates the current.

[0013] A field-effect transistor with an insulated gate, particularly a metal-oxide-semiconductor field-effect transistor (also known as a MOSFET), is especially preferred for the at least one semiconductor switch. These are particularly advantageous with regard to short switching times and low switching losses. MOSFETs with silicon (Si) and / or silicon carbide (SiC) as semiconductor materials are preferably used, which improves switching performance under high currents or high voltages. SiC MOSFETs are particularly preferred for nominal voltages above 700 V. Alternatively or additionally, gallium arsenide, gallium nitride, and / or organic semiconductors, for example, can be used.

[0014] Preferably, the at least one semiconductor switch is a SiC MOSFET with a resistance of at most Ros.on = 25 mΩ, particularly preferably at most Ros.on = 20 mΩ, and especially at most Ros.on = 15 mΩ at temperatures above 85 °C. If the resistance Ros.on between drain and source is within this range, the power dissipation is reduced.

[0015] According to one embodiment, the disconnect switch comprises at least one MOSFET with a current-carrying capacity of at least 70 A, preferably at least 100 A, and particularly at least 200 A. When several MOSFETs are connected in parallel, the aforementioned values ​​preferably serve as a common limit for this parallel connection. This common limit can be reduced, particularly in parallel connections. MOSFETs can switch such currents without damage and absorb any current spikes that occur.

[0016] In a preferred embodiment, the disconnect switch comprises several semiconductor switches connected in parallel. This advantageously reduces the resistance of the arrangement and increases the current-carrying capacity. In particular, MOSFETs are suitable for use in a parallel circuit due to their positive temperature coefficient.

[0017] Particularly preferred are several semiconductor switches implemented as SiC MOSFETs with a maximum resistance of Ros.on = 25 mQ at a temperature above 85 °C and connected in parallel to each other.

[0018] Preferably, the disconnect switch comprises 2 to 20 semiconductor switches, more preferably 2 to 15 semiconductor switches, and in particular 5 to 10 semiconductor switches, for example 8 semiconductor switches. Within the aforementioned ranges, good current-carrying capacity can be achieved while maintaining acceptable manufacturing costs.

[0019] The detection device of the disconnect switch serves to measure the current flowing between the first and second terminals and is preferably inserted directly into the current-carrying conductor between the first and second terminals. Preferably, the detection device is a current-sensing resistor or magnetoresistive sensor, particularly preferably a Hall sensor. A current-sensing resistor, also known as a shunt, is a low-resistance electrical measuring resistor. A Hall sensor is particularly preferred, which measures the magnetic field induced by the current flow and converts it into a corresponding voltage that is directly proportional to the current to be measured.The use of a Hall sensor is particularly advantageous because it offers fast measurement with high accuracy, making it especially suitable for detecting short circuits, and it also exhibits a high overload capacity. Furthermore, Hall sensors enable non-contact measurement, so the sensor is not exposed to the high voltages present in the disconnect switch. Unlike a shunt, a non-contact Hall sensor also generates no additional power loss.

[0020] In a preferred embodiment, the disconnect switch has a logic section and a power section, wherein the monitoring unit is arranged in the logic section, while the semiconductor switches are located in the power section of the disconnect switch. Particularly preferably, the logic section and the power section are electrically separated from each other. The power section and the logic section are separated, for example, by at least one insulated section arranged between these sections, which has an electrical conductivity of less than 10⁻⁵ Ω. 8 S / m, preferably smaller than 10' 16S / m. The isolated area can be formed, for example, by completely cutting through the conductive layers between two opposing edges of a printed circuit board (PCB). For instance, an electrically isolated area can be incorporated directly during the etching process of the PCB. The cut area without a conductive layer provides the desired electrical isolation between the logic and power sections. This allows the logic and power sections to be mounted on a single PCB, improving the space requirements and ease of use of the disconnect switch. Electrical isolation of the logic and power sections also has a beneficial effect on heat transfer between them. Cutting through the conductive layer significantly hinders heat transfer.Heating caused by high currents in the power section therefore does not directly affect potentially more temperature-sensitive components in the logic section. Additionally, optional cutouts can be provided in the circuit board at the interface between the logic and power sections to improve air and creepage distances.

[0021] In a preferred embodiment, the first connection part and / or the second connection part, particularly preferably both the first and second connection parts, are configured as conductive conductors. This allows the connection parts to be located, for example, outside of a printed circuit board on which the monitoring unit is mounted. The thickness of the connection parts can thus be independent of the thickness of the conductive layer on the circuit board and can be increased if necessary, for example, to improve heat dissipation. Preferably, the first and second connection parts are spaced apart from each other and from the circuit board, which allows for advantageously increased spacing.

[0022] Preferably, the first connection element is designed as a conductor and is connected to one of the main surfaces of the printed circuit board (PCB) via electrically conductive spacers, such as metallic bolts, at one of its main surfaces. This ensures a secure mechanical connection that simultaneously establishes the electrical contact between the PCB and the first connection element. The first connection element is preferably configured as a source connection. The second connection element is preferably located next to the first connection element, for example, parallel to it, and forms the drain connection. The first and second connection elements are preferably electrically and mechanically connected via the at least one semiconductor switch.The semiconductor switches are preferably positioned on the second terminal element, with the source terminal of the semiconductor switch projecting onto the first terminal element and electrically contacted there, the gate terminal preferably bent upwards away from the main surface of the second terminal element and contacted with the gate driver, and the drain terminal of the MOSFET guided around the narrow edge of the terminal element to the opposite main surface of the second terminal element and electrically contacted there. The second terminal element thus projects laterally, at least partially, preferably completely, beyond a section of the surrounding edge of the printed circuit board. In this way, the distance between the second terminal element with its drain terminal and the printed circuit board can be maximized.The voltage applied to the circuit board can be reduced, for example, to a maximum of 50 V, preferably a maximum of 25 V, and higher voltages are restricted to the area outside the circuit board.

[0023] The semiconductor switches are preferably soldered to the underlying element, for example the second connection part, or connected using thermal paste to improve heat dissipation to the underlying elements.

[0024] The source terminal of the semiconductor switch is preferably welded or soldered to one of the main surfaces of the first terminal part, particularly preferably welded. In particular, the source terminal is also electrically contacted at the electrically conductive spacers. The drain terminal is preferably also welded or soldered to the second terminal part, particularly preferably welded or soldered to the main surface of the second terminal part that is opposite the main surface on which the semiconductor switch is positioned.

[0025] The detection device is preferably connected directly or indirectly to one of the terminals or directly or indirectly to a supply line of the terminals. The detection device can be located in the power section or the logic section. Preferably, the detection device is arranged in the logic section and contacted via a conductor on one of the terminals, so that the current flowing between the first and second terminals is measured, but the detection device itself can be located in the low-voltage section. A separate power supply for the detection device in the power section is then unnecessary. The detection device is, for example, arranged on a circuit board on a conductor, e.g., a ribbon cable, in the logic section, with the insulated conductor being routed to the power section at the point where a measurement is intended.

[0026] In one possible embodiment, the connecting part or cable on which the detection device is provided has a taper, with the detection device being arranged in the region of this taper. This is advantageous if the detection device is designed as a Hall sensor which has a ferromagnetic U-shaped element that surrounds the cable, and the cable or connecting part is to be wider than the ferromagnetic element.

[0027] Preferably, the disconnect switch is at least partially coated and / or potted with an insulating compound. Particularly preferably, the power section of the disconnect switch is at least partially coated with the insulating compound, and especially potted with the insulating compound. The insulating compound is preferably high-voltage resistant, elastic, and temperature resistant up to at least 180 °C. Silicone compounds have proven particularly advantageous for suppressing arcing, for example, silicone compounds comprising polydimethylsiloxanes with functional groups.

[0028] For example, the first and second connection parts are designed as flat conductors and coated or potted with an insulating compound. Preferably, the monitoring unit comprises at least one comparator and / or one microcontroller.

[0029] A comparator, also known as a comparator stage, is an electronic circuit used to compare two voltages. The comparator outputs a signal indicating which voltage is higher. A window comparator is particularly preferred in monitoring units, comparing an input voltage to upper and lower limits. By comparing the input voltage at the comparator with a second voltage serving as a limit, the magnitude of the current (list) can be determined. The second voltage used as a limit in the comparator is selected according to the desired current limit (Imax). If the input voltage at the comparator exceeds the voltage limit, then (list) > Imax, and a cutoff signal is sent to the semiconductor switch.

[0030] Microcontrollers are well-known to those skilled in the art and are commercially available. Preferably, the microcontroller has at least a processor, a program memory, and a working memory. The microcontroller of the monitoring unit is preferably designed to compare the magnitude of the current *list* measured by the detection unit with the limit value *Imax* and, as soon as *list* is greater than *Imax*, transmit a cutoff signal to the semiconductor switch and / or compare the current rate *Alist* with a limit slope *Almax* and, if the limit slope is exceeded, transmit a cutoff signal to the semiconductor switch. Particularly preferably, a microcontroller is used in the monitoring unit that also monitors the current rate within a time interval in the form of the current rate *Alist*.This is advantageous in order to detect a sudden increase even before reaching the absolute limit Imax, to initiate an early separation and to avoid high currents.

[0031] The monitoring unit preferably comprises at least one comparator and one microcontroller. The output signals of the comparator and the microcontroller are preferably combined in a logic gate, which outputs a disconnect signal if one or both of the output signals are disconnect signals. The logic gate can be implemented as either an AND gate or an OR gate, depending on the application. Preferably, the logic gate is an OR gate. Thus, the monitoring unit preferably comprises an analog system in the form of the comparator and a digital system in the form of the microcontroller, with the two systems being redundant to each other, thereby increasing the reliability of the disconnect switch.

[0032] The logic gate can optionally be integrated into other components, preferably the microcontroller, or provided as a standalone electronic circuit. In addition to the output signals of the comparator and the microcontroller, further boundary conditions can optionally be used to control the output of the logic gate, for example, incorporating additional simultaneous or subsequent measured values ​​in cases where only the comparator outputs a cutoff signal.

[0033] Optionally, the microcontroller has interfaces that can receive peripheral signals and enable communication with other components. When the disconnect switch is used as a vehicle disconnect switch, these are, for example, vehicle components. Depending on the received signals, the microcontroller can trigger a disconnect signal. Preferred interfaces include CAN, USB, LIN, SPI, FC, serial, and Ethernet interfaces. Modern vehicles have a variety of sensors that can also identify accidents, allowing appropriate measures to be taken to secure the vehicle after further processing of the signals.Vehicle interfaces, such as CAN or the outputs of the airbag control unit, typically provide an airbag control signal, signals from impact sensors, and information about the behavior of the seatbelt pretensioner, the seatbelt force limiter, and the rollover bar. Preferably, the microcontroller is capable of receiving such signals from other vehicle components and outputting a disconnect signal in response. This allows the monitoring unit to output a disconnect signal even independently of high currents or sudden increases in current intensity, thus offering further improved safety. The microcontroller particularly preferably has a CAN interface to enable communication with the vehicle's CAN bus or an interface to the airbag control unit.If the power line is disconnected due to exceeding at least one of the limit values ​​Imax and / or Almax, this information is preferably transmitted to other external components via the interface of the disconnect switch, so that information about the switching event can be read out, for example via the on-board computer of a motor vehicle with a disconnect switch.

[0034] In a monitoring unit comprising several analog or digital systems and optional interfaces, there is preferably an OR connection between these, such that a disconnect signal triggered by one of these systems or received at an interface is sufficient to trigger a disconnect signal from the monitoring unit to the semiconductor switch.

[0035] The disconnect signal output by the monitoring unit is passed directly or indirectly to the semiconductor switch. Preferably, the disconnect signal from the monitoring unit is passed to the semiconductor switch via a gate driver. This advantageously reduces the switching time of the disconnect switch. Preferably, the gate driver is located at the interface between a logic area and a power area of ​​the disconnect switch. A galvanically isolated gate driver is particularly preferred, which is located, for example, at the interface between the logic area and the power area of ​​the printed circuit board.

[0036] The temperature of the semiconductor switch is preferably monitored by a temperature monitoring system of the disconnect switch. This temperature monitoring system is implemented using one or more temperature sensors that detect the temperature of at least one semiconductor switch. This can be done via direct or indirect temperature measurement. Direct measurement is performed directly at one or more semiconductor switches, while indirect measurement takes place in the vicinity of at least one of the semiconductor switches, for example, on the circuit board or a cooling element. Preferably, the signal from the one or more temperature sensors is compared to a maximum target temperature in order to initiate temperature reduction measures if the target temperature is exceeded. Additionally or alternatively, the disconnect switch can be switched off and / or an error message can be output via an interface.

[0037] In a preferred embodiment, the at least one semiconductor switch has an active or passive cooling element. Common passive cooling elements are heat sinks made of materials with high thermal conductivity, which have a large surface area and thus dissipate heat from the components to be cooled to the surroundings. For example, a passive cooling element is a metallic heat sink with cooling fins. Active cooling elements are cooling elements that enable active heat transfer away from the electronic component and are therefore superior to passive heat sinks in their cooling performance. Preferably, the active cooling element includes a fan or a pump that transports a fluid as a coolant, which is guided along the semiconductor switches to dissipate the heat generated at the semiconductor switches. Preferably, an active cooling element with a fan is used, with air serving as the cooling medium.Such a cooling element is both effective in terms of its cooling capacity and cost-efficient. Alternatively, the cooling element can include a pump that circulates a coolant fluid past the semiconductor switches. Another alternative is to include coolant-carrying lines through which the coolant is pumped by a pump located outside the disconnect switch. In this embodiment, for example, integration into the cooling circuit of a system or vehicle is possible, thus eliminating the need for an additional pump as part of the disconnect switch.

[0038] The active cooling element preferably comprises a tubular heat sink, particularly one made of metal, on the outer circumference of which at least one semiconductor switch is arranged. The tubular heat sink preferably has cooling fins along its inner circumference. A fan is arranged adjacent to or inside the tubular heat sink, which, during operation, generates an airflow along the longitudinal direction of the tubular heat sink. In this way, several semiconductor switches can be cooled effectively and cost-efficiently. In a preferred embodiment, the parallel-connected MOSFETs used result in thermal coupling and balancing of the switches.

[0039] In another preferred embodiment, active cooling is omitted and the connection elements are designed as flat conductors spatially spaced from the circuit board. If the thickness of the flat conductors is sufficiently large, additional passive cooling can also be omitted.

[0040] In a preferred embodiment, the disconnect switch comprises at least one temperature sensor that measures the temperature of the at least one semiconductor switch and transmits this information to the monitoring unit, which includes a microcontroller. The microcontroller compares the temperature of the semiconductor switches with a setpoint temperature stored within the microcontroller. If the setpoint temperature is exceeded, the microcontroller sends a signal to the active cooling unit, activating it and deactivating it again when the temperature drops below the setpoint temperature. Alternatively, a temperature window can be used with respect to the setpoint temperature, whereby the cooling unit is only deactivated when the lower limit of the temperature window is reached and is reactivated when the upper limit of the temperature window is reached. This reduces the number of switching operations.

[0041] In a further preferred embodiment, the disconnect switch comprises at least one temperature sensor that measures the temperature of the at least one semiconductor switch and transmits this information to an analog temperature-controlled circuit, which activates the active cooling unit. In a further preferred embodiment, the active cooling unit can be activated both via the microcontroller of the monitoring unit and via an analog temperature-controlled circuit.

[0042] Monitoring the temperature of the semiconductor switches during operation, as described in these implementation examples, makes it possible to immediately initiate suitable measures for cooling the semiconductor switches.

[0043] Furthermore, the disconnect switch preferably includes at least one snubber, which is particularly preferably arranged in parallel with the at least one semiconductor switch. This snubber serves to absorb inductive voltage spikes during disconnection under load, thus protecting the power electronics and the rest of the circuit. A snubber is particularly preferably provided to protect one to three semiconductor switches, for example, one snubber for two semiconductor switches.

[0044] If the first and second connection parts are designed as flat conductors, the at least one snubber is preferably attached directly or indirectly to these flat conductors. In a preferred embodiment, the first and second connection parts are arranged essentially parallel to each other, each having first main surfaces lying in one plane and second main surfaces opposite the first main surfaces, also arranged in one plane. The semiconductor switches are preferably mounted on one of the first main surfaces, while the at least one snubber, preferably a snubber for two semiconductor switches, is arranged on the second main surfaces. Electrically conductive spacers are particularly preferably provided on the second main surfaces, between which the snubbers are electrically contacted.The snubbers are arranged outside the printed circuit board (PCB) and have an advantageously large distance to the PCB both in the main plane and orthogonally to it. The electrically conductive spacers can, for example, be designed as metallic bolts. Signal transmission between the components of the logic and power sections is preferably achieved via analog and / or digital isolators, which enable signal transmission between the sections while simultaneously providing galvanic isolation. The isolators are preferably arranged at the interface between the logic and power sections. The signal from the detection device is preferably transmitted to the monitoring unit via an analog isolator. The disconnect switch preferably includes an analog isolator that transmits the signal from the temperature sensors to the microcontroller.A digital isolator is preferably provided for communication between the microcontroller and the active cooling unit.

[0045] An input voltage, for example 12 V, is present on the logic side of the disconnect switch. Depending on the required input voltage of the components on the logic side, this can be further adjusted using a voltage regulator. Preferably, the input voltage is reduced using a voltage regulator to provide lower voltages for the logic components, such as microcontrollers, comparators, gate drivers, interfaces, and / or isolators. In particular, a so-called low-dropout voltage regulator (also known as an LDO) is used for this purpose, which, for example, reduces an input voltage from 12 V to 5 V.

[0046] Preferably, a DC-DC converter, also known as a DC-DC converter, is arranged at the interface between the logic and power sections. This converter is particularly preferably designed as a galvanically isolated DC-DC converter. The DC-DC converter is supplied with the input voltage of the logic side and provides a voltage at its output, located within the power section, to supply the components of the power section. The supplied voltage can, as required, either serve directly as the input voltage for other components or be modified first by additional voltage regulators. In this way, an efficient voltage supply is provided for components of the power section from the input voltage of the logic side, while simultaneously maintaining the galvanic isolation between the logic and power sections.

[0047] For example, a DC-DC converter is arranged at the interface between the logic and power sections, converting the 12 V voltage on the logic side into an output voltage of 24 V on the power section side. This 24 V voltage is then reduced to 18 V by a first voltage regulator, preferably an LDO, which can be used as the input voltage for the gate driver. Furthermore, this 18 V voltage is reduced to 5 V by a second voltage regulator, preferably an LDO, which is suitable for supplying voltage to the temperature sensors.

[0048] Particularly where high currents flow, physical protection of the circuits is advisable. Advantageously, the disconnect switch should have a current-carrying capacity of over 10 amperes, preferably over 20 amperes, and especially over 100 amperes, when closed.

[0049] Similarly, wherever comparatively high voltages are present, physical protection of the circuits is advisable. To ensure safe disconnection, for example of lines in high-voltage vehicle electrical systems, the disconnect switch is advantageously designed such that a potential difference of over 24 V, preferably over 100 V, exists between the terminals when open.

[0050] To achieve the lowest possible energy supply when the disconnect switch is closed, the connection parts are preferably made of an electrically conductive material, such as a copper alloy or an aluminum alloy. The connection parts can also be made of different materials. They can be shaped for connection to electrical wires and cables and may have cable lugs for cable attachment. The connection parts can also be integrated into the vehicle's electrical system. When the disconnect switch is closed, an electric current flows between a load and a power source via the connection parts and the at least one semiconductor switch.

[0051] The disconnect switch according to the invention is applicable wherever live conductors need to be disconnected, for example in buildings, technical installations, or vehicles. The disconnect switch is preferably used in motor vehicles, batteries, or photovoltaic systems, and particularly preferably in electric vehicles. The disconnect switch is thus, for example, a motor vehicle disconnect switch for electric vehicles.

[0052] A further object of the invention is a method for disconnecting a motor vehicle power line comprising the steps: a) measuring the current (list) by means of a detection unit between a first terminal and a second terminal, which are electrically connected in a closed state via at least one semiconductor switch, b) comparing the current (list) with a limit value (Imax) by means of a monitoring unit and / or comparing a current increase (Alist) with a limit slope (Almax) by means of a monitoring unit, c) triggering a disconnect signal by the monitoring unit and transmitting the disconnect signal to a semiconductor switch, provided that (list) > Imax and / or Alist > Almax, or

[0053] Continue with step a), if list <Imax and Ahst < AI max, d) Disconnecting an electrical connection between the first terminal part and the second terminal part by switching the semiconductor switch to an open state. In a first step a) of the method according to the invention, the current strength list of the current flowing between a first terminal part and a second terminal part is measured. The current flow between the first terminal part and the second terminal part occurs via a semiconductor switch in a closed state. The first terminal part and the second terminal part are thus connected to each other via the semiconductor switch in the closed state. The current strength list is measured continuously.

[0054] In a second step b), the current (list) measured by the detection unit is compared with a limit value (Imax) using a monitoring unit. Alternatively or additionally, a slope (Alist) is calculated in the monitoring unit from the continuously obtained measured values ​​(list), which characterizes the increase in current (list) over a unit of time, and this slope (Alist) is compared with a limit slope (Almax). The limit value (Imax) and the limit slope (Almax) can be set variably depending on the application of the method according to the invention.

[0055] According to step c) of the procedure below, the monitoring unit triggers a disconnect signal if at least one of the conditions `list` > `Imax` and `Alist` > `Almax` is met. In this case, the disconnect signal is transmitted to at least one semiconductor switch, and step d) of the procedure follows. If none of the aforementioned conditions are met, or if only one of the values ​​`list` and `Alist` is determined and the aforementioned condition is not met for that value, the procedure restarts, and step a) follows step c). If either the value of `list` or the value of `Alist` is not determined, it is assumed that it is below the limit value or the limit voltage, respectively. As long as `list` < `Imax` and `Alist` < `Almax`, the procedure thus proceeds in the step sequence abc.

[0056] In step d), the electrical connection between the first terminal and the second terminal is broken by switching the semiconductor switch to an open state. Prior to step a) of the method according to the invention, an internal system check (self-test) of the disconnect switch preferably takes place, for example, by a microcontroller contained in the monitoring unit. During system startup, it is first checked whether the expected supply voltages are present and whether the components of the disconnect switch are transmitting signals to the microcontroller. Furthermore, incoming signals, such as measured values ​​from temperature sensors, are checked for plausibility. If errors occur during this system check, the system startup of the disconnect switch is aborted, if necessary, and an error message is communicated via an interface of the disconnect switch.

[0057] The method according to the invention is preferably carried out using the disconnect switch according to the invention. The features described with respect to the disconnect switch according to the invention also apply to the method according to the invention. The features disclosed with respect to the method according to the invention preferably also apply to the disconnect switch.

[0058] The method for separating a motor vehicle power line can preferably be designed in such a way as to avoid the formation of arcs.

[0059] In a preferred embodiment of the method, in step c) when the disconnect signal is triggered, a signal is output via a communication port of the monitoring unit, so that information about the triggering of the disconnect switch is transmitted to other vehicle components and / or a central on-board computer.

[0060] In order to transmit the isolation signal without interference and safely, the isolation signal can preferably be transmitted galvanically isolated from the circuit to be interrupted.

[0061] The subject matter of the invention is explained in more detail below with reference to the drawings. The drawings show:

[0062] Fig. 1a shows a schematic top view of a preferred embodiment of a disconnect switch according to the invention.

[0063] Fig. 1b shows a side view of the disconnect switch of figure 1a,

[0064] Fig. 1c shows another side view of the disconnect switch of figure 1a,

[0065] Fig. 2 shows a block diagram of the preferred embodiment of the disconnect switch according to the invention of figures 1a-c,

[0066] Fig. 3 shows a short-circuit current path between the first connection part and the second connection part until separation by means of a disconnect switch according to the invention.

[0067] Fig. 4 shows an electric vehicle with a traction battery, an electric drive and a disconnect switch according to the invention arranged between them and

[0068] Fig. 5a-c shows another preferred embodiment of a disconnect switch according to the invention.

[0069] Figures 1a, 1b, and 1c show a top view and two side views of a preferred embodiment of the disconnect switch 100 according to the invention. The figures are to be understood as a schematic sketch of the component arrangement, with conductor tracks not shown for clarity. The disconnect switch 100 comprises a first terminal 1 and a second terminal 2, between which current flows when the disconnect switch 100 is closed. This current flow can be interrupted by eight semiconductor switches 3 connected in parallel, which are arranged between the first terminal 1 and the second terminal 2. The semiconductor switches 3 have a common source terminal on the side of the first terminal 1 and a common drain terminal on the side of the second terminal 2.The semiconductor disconnect switches 3 can be switched between a closed state, in which the terminals 1, 2 are electrically connected, and an open state, in which the terminals 1, 2 are electrically disconnected, via a common gate terminal. The semiconductor switches 3 can receive a disconnect signal via their common gate terminal, which initiates a transition to the open state of the switch and is transmitted to the semiconductor switch 3 by other components. According to the invention, disconnection of the power supply should occur when the current flowing between the terminals 1, 2 exceeds a limit value Imax and / or when the change in current Alist exceeds a limit value Almax.For this purpose, the disconnect switch 100 includes a detection unit 4, designed as a Hall sensor, which continuously measures the current between the terminals 1 and 2 and transmits this value to a monitoring unit 5. The monitoring unit 5 comprises a comparator 5.2 and a microcontroller 5.1. The comparator 5.2 performs an analog comparison of the current list with a current Imax stored in the comparator. The microcontroller 5.1 performs a digital comparison of the currents list and Imax. Additionally, the values ​​list can be stored in the microcontroller 5.1 over a time interval, and the slope Al is calculated from this. This slope is then compared with a previously defined maximum tolerable slope Almax stored in the microcontroller 5.1. If at least one of the conditions list > Imax or Alist > Almax is met in the comparator 5.2 or the microcontroller 5.1, the comparator 5.1 outputs a value.2 or the microcontroller 5.1 outputs a disconnect signal. The disconnect signal is transmitted to a gate driver 7, which controls the common gate terminal of the semiconductor switches 3, thereby switching the semiconductor switches 3 to an open state and interrupting the connection between the two terminal parts 1, 2. The semiconductor switches 3 are designed as SiC MOSFETs and are in direct contact with an active cooling element 9, which dissipates the heat generated during operation of the semiconductor switches 3 by means of convection and prevents overheating of the semiconductor switches 3. The active cooling element 9 has a cuboid hollow tube as a heat sink 9.1, on each of whose opposite faces four semiconductor switches 3 are arranged. The faces with semiconductor switches 3 are arranged orthogonally to the circuit board 18. Adjacent to the cuboid hollow tube, the active cooling element 9 includes a fan 9.2, which, when the cooling element is in operation, generates an airflow through the heat sink 9.1, flowing through it in parallel with the semiconductor switches 3 arranged in two rows on the outside. The temperature of the semiconductor switches 3 is monitored by temperature sensors 8, which are arranged on the circuit board 18 adjacent to at least one of the semiconductor switches 3. If the temperature measured by the temperature sensors 8 exceeds a defined maximum temperature, for example 70 °C, the active cooling unit 9 is activated and deactivated again as soon as the temperature sensor 8 detects a temperature below 50 °C. A snubber 12 is arranged in parallel with the semiconductor switches 3, which compensates for voltage spikes when the disconnect switch 100 is switched off. The disconnect switch 100 comprises a circuit board 18 on which all components of the disconnect switch 100 are arranged.The circuit board 18 is divided into a logic area 10 and a power area 11, which are galvanically isolated from each other. The power components of the disconnect switch 100 are arranged in the power area 11, which includes at least the connection parts 1, 2, the semiconductor switches 3 with temperature sensors 8 and active cooling element 9, the detection unit 4, and the snubber 12. The logic area 10 contains the monitoring unit 5, comprising the microcontroller 5.1 and the comparator 5.2. Furthermore, an interface 6, designed as a CAN interface, is provided in the logic area 10, through which the microcontroller 5.1 can communicate with the CAN bus of a motor vehicle. At the interface between the power area 11 and the logic area 12, analog isolators 14.2 and a digital isolator 14.2 are provided as galvanically isolated components.1, a DC / DC converter 13, and the gate driver 7 are arranged, by means of which signal transmission from the logic area 10 to the power area 11 and vice versa, as well as the power supply of the components in the power area 11, takes place. The aforementioned galvanically isolated components are arranged in the area of ​​cutouts 19 of the printed circuit board, with the components projecting beyond the cutouts 19. This advantageously increases air and creepage distances.

[0070] Figure 2 shows a block diagram of the preferred embodiment of the disconnect switch 100 according to the invention, as shown in Figures 1a and 1c, where the descriptions in Figures 1a and 1c apply. The block diagram illustrates the signal transmission between the components and the power supply to the components in more detail. In the logic section 10 of the disconnect switch 100, the supply voltage of 12 V is converted via a first voltage regulator 16.1 into an output voltage of 5 V, which serves to supply the gate driver 7, the insulators 14, the interface 6, the microcontroller 5.1, and the comparator 5.2. The supply voltage of 12 V is also present in the logic section 10 at the galvanically isolated DC / DC converter 13, which is arranged between the logic section 10 and the power section 11. The DC / DC converter 13 in turn provides a voltage of 24 V (24VHV) at its output located in the power range 11, which is regulated via a second voltage regulator 16.The voltage is converted into 18 V (18VHV) for the gate driver 18 and, via a third voltage regulator 16.3, into a supply voltage of 5 V (5VHV) for the temperature sensors 8, the temperature monitoring unit 17, the isolators 14, and the detection unit 4. Signal transmission from the logic area 10 to the power area 11 occurs from the microcontroller 5.1 and the comparator 5.2 via an OR gate 15 to the gate driver 7 and from there to the semiconductor switches 3. Communication between the detection unit 4 and the microcontroller 5.1 as well as the comparator 5.2 takes place via an analog isolator 14.2. The signal from a temperature sensor 8 is transmitted to the microcontroller 5.1 via another analog isolator 14.2, while a signal from the microcontroller 5.1 is transmitted to the cooling element 9 via a digital isolator 14.1.The components insulators 14, gate drivers 7, and DC / DC converters 13 are galvanically isolated to maintain complete separation between the logic section 10 and the power section 11. Figure 3 shows a short-circuit current waveform between the first terminal 1 and the second terminal 2 for the embodiment of the disconnect switch 100 according to the invention shown in Figures 1a and 2, up to the point of separation by switching the disconnect switch 100 to the open state, as well as, for comparison, the hypothetical further waveform without separation. To investigate the short-circuit current, the current intensity is plotted against time. The time scale plotted on the x-axis is divided into different ranges AD, which subdivide the measurement states and switching operations of the disconnect switch 100. In range A, the usual operating range applies at current intensities below 200 A, in which no switching operations of the disconnect switch 100 take place.If the current continues to rise (area B), this can provide an initial indication of a short circuit. However, a brief increase in current into this area can occur during operation, so no disconnect signal is yet issued unless the temperature monitoring of the MOSFETs moves into the critical range of, for example, 95 °C. With a further increase in current, the detection and response range of the disconnect switch is reached above 1150 A, in which, in this case, the limit current Imax = 1150 A is exceeded. To account for any interference signals, several measurement cycles can be performed to ensure that the limit is continuously exceeded. While the short-circuit current continues to rise, measurements and calculations are performed in area C, and finally, the disconnect signal is triggered. After the disconnect signal is triggered, the short-circuit current continues to rise in area D, where area D represents the disconnection time of the semiconductor switches 3.In the present embodiment, with a system inductance of 25 pH, the disconnection of the power line by the disconnect switch 100 is achieved after a total of 0.13 ms and a maximum current of 4800 A. This early disconnection, which cannot be achieved with pyrotechnic systems known in the prior art, prevents the occurrence of high currents. The dashed line representing the further current curve in region E shows the hypothetical further increase in current without disconnection. Even slight time delays would lead to significantly higher currents, which can be avoided by means of the disconnect switch 100 according to the invention. Figure 4 shows an electric vehicle 20 with a traction battery 21 and an electric drive 22. The disconnect switch 100 is arranged between the traction battery 21 and the electric drive 22.In the event of an accident involving vehicle 20, the disconnect switch 100 can be activated, thus disconnecting the electrical circuit between battery 21 and drive 22. The disconnect switch 100 can be positioned close to or even inside battery 21. This ensures that the risk to occupants and rescue personnel is minimized.

[0071] Figure 5a-c shows another preferred embodiment of a disconnect switch. The first terminal 1 and the second terminal 2 are designed as flat conductors and are located outside the printed circuit board 18. The semiconductor switches 3 are provided on the main surface of the second terminal 2 facing the plane of the printed circuit board 18. The electrical connection of the terminals 1 and 2 is made via terminals 30, with typically one terminal being used per terminal. The first terminal 1 is connected to the printed circuit board 18 via electrically conductive spacers 31, while the second terminal 2 is contacted on the first terminal 1 via the semiconductor switches 3. Further electrically conductive spacers 31, having a distal surface 32, are provided on the main surfaces of the first terminal 1 and the second terminal 2 facing away from the printed circuit board 18.Snubbers (not shown here) are provided between each spacer element 31 of the first terminal part 1 and an opposing spacer element 31 of the second terminal part 2, so that the eight semiconductor switches 3 are protected by a total of four snubbers. The spacers 31 are implemented as brass bolts. The features not described with reference to Figure 5a-c preferably correspond to the embodiment described in Figure 1ac.

[0072] Reference symbol list

[0073] 1 first connection part

[0074] 2 second connection part

[0075] 3 semiconductor switches

[0076] 4 detection units

[0077] 5 monitoring unit

[0078] 5.1 Microcontrollers

[0079] 5.2 Comparator

[0080] 6 interfaces

[0081] 7 Gate Drivers

[0082] 8 Temperature sensor

[0083] 9 Cooling element

[0084] 9.1 Heat sink

[0085] 9.2 Fan

[0086] 10 Logic area

[0087] 11 Performance area

[0088] 12 Snubber

[0089] 13 DC / DC converters

[0090] 14 insulators

[0091] 14.1 Digital Isolator

[0092] 14.2 Analog Isolator

[0093] 15 OR gates

[0094] 16 voltage regulators

[0095] 16.1 First voltage regulator

[0096] 16.2 Second voltage regulator

[0097] 16.3 Third voltage regulator

[0098] 17 Temperature monitoring

[0099] 18 circuit boards

[0100] 19 cutouts

[0101] 20 Electric vehicle 21 Traction battery

[0102] 22 electric drive

[0103] 30 connections, 31 electrically conductive spacers

[0104] 32 surface for mounting snubber

[0105] 100 disconnect switches

Claims

P a t e n t a n s p r ü c h e 1. Disconnect switch (100), in particular for motor vehicles, for a power line comprising at least a first terminal part (1), at least a second terminal part (2), at least a semiconductor switch (3) arranged in the forward direction between the first terminal part (1) and the second terminal part, at least a detection device (4) arranged between the first terminal part (1) and the second terminal part (2) for measuring the current ...wherein the disconnect signal of the monitoring unit (5) causes the semiconductor switch (3) to switch to an open state and interrupts the current flow between the first terminal part (1) and the second terminal part (2).

2. Disconnect switch according to claim 1, wherein the at least one semiconductor switch (3) is designed as a field-effect transistor, preferably as a MOSFET.

3. Disconnect switch (100) according to one of the preceding claims comprising several semiconductor switches (3) connected in parallel to each other.

4. Disconnect switch (100) according to one of the preceding claims, wherein the detection device (4) is a current measuring resistor or magnetoresistive sensor, preferably a Hall sensor.

5. Disconnect switch (100) according to one of the preceding claims, wherein the monitoring unit (5) is arranged in a logic area (10) of the disconnect switch (100) and the semiconductor switches (3) are arranged in a power area (11) of the disconnect switch (100) and preferably the logic area (10) and the power area (11) are electrically separated from each other.

6. Disconnect switch (100) according to one of the preceding claims, wherein the first connection part (1 ) is configured as the first flat conductor and the second connection part (2) is configured as the second flat conductor.

7. Disconnect switch (100) according to claim 6, wherein the first connection part (1 ) is mechanically and electrically connected to a circuit board (18) comprising the monitoring unit (5) and is spaced apart from the circuit board (18) and the second connection part (2) is connected to the first connection part (1 ) via the at least one semiconductor switch (3).

8. Disconnect switch (100) according to claim 6 or 7, wherein the first terminal part (1 ) is connected to the source terminal of the at least one semiconductor switch (3) and the second terminal part (2) is connected to the drain terminal of the at least one semiconductor switch (3) and the at least one semiconductor switch (3) is preferably mounted on a main surface of the second terminal part (2).

9. Disconnect switch (100) according to one of claims 6 to 8, wherein the detection device (4) is connected indirectly or directly to one of the connection parts (1 , 2) or indirectly or directly to a supply line of the connection parts (1 , 2), preferably the detection device (4) is located in the logic area (10) and is contacted via a conductor at one of the connection parts (1 , 2).

10. Disconnect switch (100) according to one of the preceding claims, wherein the power area (11 ) of the disconnect switch (100) is at least partially coated with an insulating compound, preferably potted with an insulating compound.

11. Disconnect switch (100) according to one of the preceding claims, wherein the monitoring unit (5) comprises at least one microcontroller (5.1 ) and / or one comparator (5.2).

12. Disconnect switch (100) according to one of the preceding claims, wherein the disconnect signal of the monitoring unit (5) is passed to a gate driver (7) which controls a control terminal of the semiconductor switch (3).

13. Disconnect switch (100) according to one of the preceding claims, wherein at least one snubber (12) is arranged in parallel with at least one semiconductor switch (3).

14. Disconnect switch (100) according to one of claims 6 to 13, wherein at least two semiconductor switches (3) are provided on a main surface of a terminal part (1 , 2) and at least one snubber (12) is attached to the opposite main surface of the terminal part (1 , 2) and connects the two terminal parts (1 , 2) to each other.

15. Method for disconnecting a motor vehicle power line comprising the steps: a) Measuring the current strength by means of a detection unit (4) between a first terminal part (1 ) and a second terminal part (2) which are electrically connected in a closed state via at least one semiconductor switch (3), b) Comparison of the current list with a limit value Imax by means of a monitoring unit (5) and / or comparison of a rise in the current Alist with a limit slope lmax by means of a monitoring unit (5), c) Triggering a disconnect signal by the monitoring unit (5) and transmitting the disconnect signal to a semiconductor switch (3) if list > Imax, and / or Alist > Almax or proceeding with step a) if list < Imax and Alist < Almax, d) Disconnecting an electrical connection between the first terminal part (1 ) and the second terminal part (2) by switching the semiconductor switch (3) to an open state.

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