阅读说明：本技术 开关设备以及开关设备的运行方法 (Switching device and method for operating a switching device ) 是由 德利特·马库斯 基尔希·克里斯托夫 施豪德·伯哈德 纽伯特·约阿希姆 于 2020-03-12 设计创作，主要内容包括：提出尤其是机动车车载电网的开关设备(2),用于电负载(4)与能量源(6)的电连接,开关设备具有带有开关单元(9)的主电流路径(8),开关单元具有至少一个功率开关(10),电负载凭借功率开关在供应模式中与能量源连接,开关设备还具有与主电流路径并联的旁路电流路径(12),其中布置有第一开关元件(14)。还设有切断模式,其中,所述至少一个功率开关断开且电负载仅与旁路电流路径连接,以减少存储在电负载内的电能。还设有诊断模式,其中,开关单元断开且电负载仅通过旁路电流路径与能量源连接,以对电负载供电。还设有控制单元(22),用于启动诊断模式。此外提出了开关设备的运行方法。(A switching device (2), in particular for an on-board electrical system of a motor vehicle, for electrically connecting an electrical load (4) to an energy source (6), has a main current path (8) with a switching unit (9) having at least one power switch (10) by means of which the electrical load is connected to the energy source in a supply mode, and has a bypass current path (12) which is connected in parallel to the main current path and in which a first switching element (14) is arranged. A disconnect mode is also provided in which the at least one power switch is open and the electrical load is connected only to the bypass current path to reduce the electrical energy stored within the electrical load. A diagnostic mode is also provided in which the switching unit is open and the electrical load is connected to the energy source only through the bypass current path to power the electrical load. A control unit (22) is also provided for initiating the diagnostic mode. A method for operating a switching device is also disclosed.)

1. Switching device (2), in particular for an on-board electrical system of a motor vehicle, for the electrical connection of an electrical load (4) to an energy source (6), having:

a main current path (8) having a switching unit (9) with at least one power switch (10) by means of which the electrical load (4) is connected with an energy source (6) in a supply mode,

a bypass current path (12) in parallel with the main current path (8), in which a first switching element (14) is arranged,

wherein the content of the first and second substances,

-a switch-off mode for switching off the load (4) is provided, in which the switching unit (9) is opened and the electrical load (4) is connected with a bypass current path (12) to reduce the electrical energy stored in the electrical load (4), and

-providing a diagnostic mode in which the at least one power switch (10) is open and the electrical load (4) is connected with an energy source (6) only through a bypass current path (12) for powering the electrical load (4), and,

-wherein the diagnostic mode is activatable by the control unit (22).

2. The switching device (2) according to the preceding claim,

wherein the first switching element (14) is designed in such a way that it automatically switches on when the load (4) is switched off.

3. The switching device (2) according to claim 2,

wherein the first switching element (14) is designed as a semiconductor switch and has a gate connection (16) having a gate potential (U)_G) The gate potential is electrically connected to a ground potential (M).

4. The switching device (2) according to claim 1,

wherein the bypass current path (12) has a diode (18) which is arranged between a gate connection (16) of the first switching element (14) and a ground potential (M) and which is electrically connected to the ground potential (M) in a blocking direction.

5. The switching device (2) according to claim 1,

wherein a power consumer is arranged in the bypass current path (12) for converting electrical energy stored in the electrical load (4).

6. The switching device (2) according to claim 3,

wherein the gate potential (U)_G) In a diagnostic mode having an electrical potential (U) with the energy source_E) The same numerical value.

7. The switching device (2) according to claim 2,

wherein a second switching element (24) is provided for electrically connecting the gate connection (16) of the first switching element (14) with an energy source (6) in a diagnostic mode.

8. The switching device (2) according to claim 1,

wherein the control unit (22) is configured in such a way that an output voltage (U) applied to the electrical load (4) is detected_A)。

9. The switching device (2) according to claim 8,

wherein the control unit (22) is arranged such that it is coupled to the output voltage (U)_A) Diagnosis is initiated accordingly.

10. The switching device (2) according to claim 1,

wherein the control unit (22) is set up in such a way that the at least one power switch (10) is checked in the diagnostic mode.

11. The switching device (2) according to claim 1,

having a load current (I) for detecting the electrical load (4)_L) And the control unit (22) is arranged such that it is coupled to the detected load current (I)_L) Is correlatively switched between a supply mode and a diagnostic mode.

12. The switching device (2) according to claim 1,

wherein the bypass current path (12) is designed for a smaller current than the main current path (8).

13. Method for operating a switching device (2) for electrically connecting an electrical load (4) to an energy source (6), wherein,

-connecting the electrical load (4) with an energy source (6) in a supply mode by switching on the switching unit (9) through a main current path (8) having a switching unit (9) with at least one power switch (10),

-in a switch-off mode, the load (4) is switched off and the switching unit (9) is switched off for this purpose, and the electrical load (4) is connected with a bypass current path (12) by switching on the first switching element (14) to reduce the electrical energy stored in the electrical load (4), and

-in a diagnostic mode, the switching unit (9) is switched off and the first switching element (14) is switched on, so that the electrical load (4) is connected with the energy source (6) only through the bypass current path (12), wherein in the diagnostic mode the at least one power switch (10) is checked and at the same time the supply of electrical energy to the electrical load (4) is ensured through the bypass current path (12).

14. The method of claim 13, wherein the first and second light sources are selected from the group consisting of,

wherein the content of the first and second substances,

-the first switching element (14) is configured as a semiconductor switch which is automatically switched on in the switch-off mode by a voltage pulse caused by the electrical load (4) after switch-off, and

-in the diagnostic mode, the first switching element (14) is actively switched on by the second switching element (24).

Technical Field

The invention relates to a switching device and a method for operating a switching device for electrically connecting an electrical load to an energy source.

Background

In electrical supply networks, in particular in the on-board electrical system of a motor vehicle, existing electrical consumers are usually electrically connected to an energy source by way of a switching device. Here, for example, a battery of a motor vehicle is used as an energy source.

The switching device usually has an electrical power switch, which is arranged as an isolating element between the load and the energy source. The consumers referred to here are in particular high-current consumers, for example electric motors, which have a current consumption of more than 10 amps or more than 50 amps and in particular more than 100 amps during operation.

In order to ensure the functionality of the power switch, the operational capability of the power switch must generally be checked. At the same time, however, the electrical energy supply of the individual consumers which were connected to the energy source via the power switch to be checked should not be interrupted.

The power switch is also protected against negative voltage pulses, which occur in particular when the inductive load is switched off, i.e. is open.

Disclosure of Invention

Starting from this, the object of the invention is to provide a switching device and a method for operating a switching device, by means of which an electrical load is reliably connected to a power supply.

The task for the switching device is accomplished according to the invention by the switching device. The switching device is in particular a switching device for an on-board electrical system of a motor vehicle, for the electrical connection of an electrical load to an energy source, having:

a main current path having a switching unit with at least one power switch by which the electrical load is connected with an energy source in a supply mode,

-a bypass current path in parallel with the main current path, in which bypass current path a first switching element is arranged,

wherein the content of the first and second substances,

-providing a switch-off mode for switching off the load, in which the switching unit is open and the electrical load is connected with a bypass current path to reduce the electrical energy stored in the electrical load, and

-providing a diagnostic mode in which the at least one power switch is open and the electrical load is connected with an energy source only through a bypass current path to power the electrical load, and,

-wherein the diagnostic mode is activatable by the control unit.

The switching device is designed in particular as a switching device for an on-board electrical system of a motor vehicle and for electrically connecting an electrical load to an energy source. In this case, the electrical load is understood to mean, for example, all types of electrical consumers in the motor vehicle, and is preferably an inductive load. The term load here includes one consumer or also a plurality of consumers. In particular, the load relates to a high-current load, as defined at the outset. The energy source is preferably understood here to be a motor vehicle battery or a transformer arranged in the motor vehicle.

The switching device has a main current path with a switching unit having at least one power switch. The main current path and the switching unit are designed to supply a load (one or more consumers) connected thereto with a (maximum) total operating current. In particular in the case of short-term loads, the total operating current is in particular greater than 10 amperes or greater than 50 amperes, and in particular greater than 100 amperes, for example up to 1000 amperes. A circuit breaker is generally understood in this context to be a circuit breaker for switching an electrical load, in particular for switching an electrical current with a current intensity of at least 1 ampere, preferably at least 5 amperes, or also at least 10 amperes. A plurality of power switches are usually arranged in parallel with one another in the switching unit. The one or more power switches are preferably designed as semiconductor switches and in particular as power MOSFETs (metal oxide semiconductor field effect transistors). The electrical load is connected to the energy source in the supply mode by means of the power switch. The supply mode is understood to be an operating mode of the switching device, which corresponds to an operating state in which the at least one power switch is switched on and the electrical load is preferably, without exception, continuously connected to an energy source, so that the electrical load is supplied with electrical energy.

The switching device also has a bypass current path in parallel with the main current path, in which bypass current path a first switching element is arranged.

A shut-down mode is provided in which the supply of power to the load via the main current path is interrupted, that is to say the load is shut down. This is achieved by opening the switching unit, i.e. the power switch arranged therein. In this case, the switch-off is to be understood as meaning that the power switch is switched from the on state to the off state, i.e. is switched off. Typically, in the switched-off mode, the load is not supplied with electrical energy originating from an energy source.

In at least one load connected via the switching unit and, if necessary, in the line, high energy, in particular stored inductive energy, must be dissipated. For this purpose, a branch or freewheel path is usually formed parallel to the main current path, to which the load is connected in the switched-off mode and via which the stored electrical energy is reduced and dissipated. For this purpose, the freewheeling path is normally switched on by a switching element. At least one suitable consumer, for example one or more power resistors, is arranged in the freewheeling path in order to reduce the stored energy.

The freewheel path is formed here by a bypass current path. In the off mode, the first switching element arranged in the bypass current path is therefore switched on. In this regard, the electrical load is connected to the energy source only through the bypass current path in the switched-off mode.

In the event of a switch-off command and in particular in the event of a failure of the electrical load, the switching-off and therefore the disconnection of the switching unit is carried out in order to separate the failed electrical load from the vehicle electrical system. The disconnection is also carried out, for example, if a higher-level controller requests it, which issues a disconnection command.

In particular in the case of electrical loads designed as inductive loads, negative voltage pulses (also referred to as negative voltage spikes) occur when the electrical connection between the electrical load and the energy source is broken and thus disconnected. The negative voltage pulse is caused by a drop in the load current flowing through the electrical load in the supply mode and by the inductive energy stored in the electrical load, according to the law of electromagnetic induction. In the case of a defective freewheeling path, the negative voltage pulse causes the switched-off at least one power switch to switch back to the conducting state, i.e., to switch on unintentionally. Then, after the undesired switching-on, inductive energy (also referred to as inductive switch-off energy) stored in the electrical load is discharged in the at least one power switch, which may lead to its overload and thus to a malfunction of the power switch and thus of the switching device.

Since the electrical load is connected to the energy source only via the bypass current path in the switched-off mode, it is achieved that the inductive energy of the electrical load is discharged and dissipated via the bypass current path. In this case, the power consumers mentioned are already arranged in the bypass current path. The power consumer has in particular a plurality of series-connected power resistors. Thus, the at least one power switch is protected in the off mode. The bypass current path is thus also referred to as a branch path.

Furthermore, a diagnostic mode is provided, in which the switching unit is also switched off and the supply of power to the load via the main current path is interrupted. The electrical load is connected to the energy source only through the bypass current path and is supplied with energy from the energy source through the bypass current path. In the diagnostic mode, the electrical connection of the electrical load to the energy source via the bypass current path is used to supply the electrical load, in contrast to the shut-off mode. This is achieved in that the supply of electrical energy to the electrical load is uninterrupted despite the switching unit being open in the diagnostic mode. It is thus achieved that, in addition to the supply of the electrical load via the main current path, the supply of the electrical load is also effected via the bypass current path, and that an uninterrupted supply of the electrical load is also ensured in the event of an opening of the switching unit in the main current path.

In the diagnostic mode, a diagnosis of the switching device and, if necessary, of the connected load is also carried out. In particular, a check of one or more power switches of the switching unit with regard to their functionality is carried out.

Furthermore, a control unit is provided for activating the individual different modes and in particular for activating the diagnostic mode, in particular by actuating the different switching elements, in particular for example by actuating the switching element in the main current path and the first switching element in the bypass current path. The control unit is preferably designed as a microcontroller.

By means of the switching device and the different modes (supply mode, disconnection mode and diagnostic mode), a switching device is created which, on the one hand, is designed such that the inductive energy stored in the electrical load is reduced in the event of disconnection and, on the other hand, ensures uninterrupted power supply to the electrical load, in particular in the event of the at least one circuit breaker being in the disconnected, i.e. blocked, state in the diagnostic mode for checking the functionality of the circuit breaker.

The bypass current path and in particular the first switching element arranged therein for opening and closing the bypass current path is preferably designed here only for a fraction (for example at most 50%, at most 25% and further preferably at least 5% or 10%) of the (maximum) total operating current, while the main current path and the switching unit arranged therein are designed for the (maximum) total operating current.

According to a preferred embodiment, the first switching element is designed such that it is automatically switched on and, in the event of a switch-off of the load, the load is connected to a power consumer for reducing the stored electrical energy. Thus no active steering is required. The switching on of the branch or freewheel path is therefore effected independently of the control command, solely on the basis of the voltage pulse occurring at the time of switching off.

In particular, the switching element is designed as a semiconductor switch, in particular as a MOSFET and in particular as a power MOSFET. The first switching element therefore has a gate connection which has a gate potential. The first switching element has a source connection portion to which an electric load is connected. The drain connection of the first switching element is preferably connected to an energy source. Preferably, the gate potential is electrically connected to a ground potential through a ground connection.

The preferred embodiment is based on the consideration that, when the at least one power switch is switched off, the electrical load is automatically connected to the energy source via a bypass current path in the presence of a negative voltage pulse by electrical connection of the gate potential to ground potential. In other words, the first switching element of the bypass current path is switched on by a negative voltage pulse by a voltage difference between the gate potential and the source potential, which voltage difference has at least the same value and preferably a larger value than a (predefined and fixed) control voltage, which has to be applied between the gate connection and the source connection, so that the first switching element changes from a (high-impedance) blocking state to a (low-impedance) conducting state. The first switching element therefore switches on automatically in the switch-off mode as a result of the switch-off characteristic of the inductive load. Therefore, in particular no active and/or external switching signals are required. The advantage of this embodiment is, on the one hand, the simplification of the switching effort and, on the other hand, the necessity of an unnecessary active monitoring.

Preferably, the bypass current path has a diode arranged between the gate connection of the first switching element and ground potential. The diode is preferably electrically connected to ground potential in the blocking direction.

Expediently, a resistive element is arranged in the bypass current path as a power consumer. The resistance element preferably relates to an ohmic resistance and in particular to a power resistance. The resistive element is used to convert electrical energy, preferably inductive energy, stored in the electrical load in the off mode. The electrical energy is converted into thermal energy in the switched-off mode by the resistive element. By arranging the resistive element, a simple and reliable switching and thus a dissipation of electrical energy of the electrical load in the switched-off mode is achieved. Furthermore, by designing the resistance element in particular as a power resistance and by designing the first switching element in particular as a power MOSFET, the component has a high heat resistance.

In general, the entire switching device (in particular the resistance element and the first switching element as well as the switching unit), in addition to being suitable for switching high currents and energies, is also used for high temperature requirements, i.e. its functionality is not impaired in the temperature range of preferably 100 ℃ to 150 ℃. The switching device is therefore also suitable for being arranged in thermally demanding areas. For example, it is used in the area of a vehicle that drives an electric motor.

According to a preferred embodiment, in the diagnostic mode, the gate potential of the first switching element has the same value as the potential of the energy source. The same values are to be understood here as meaning that the gate potential has a value which corresponds substantially to the value of the potential of the energy source. Basically, it is to be understood here that the gate potential has a value which, apart from tolerances which may result due to voltage drops occurring during switching, has the same value as the potential of the energy source. The electrical potential of the energy source is understood to be, for example, the operating voltage of a battery arranged in the motor vehicle or the output voltage of the already mentioned transformer.

Preferably, a second switching element is provided to electrically connect the gate connection of the first switching element with the energy source in the diagnostic mode. Thereby, the potential of the energy source is thus applied to the gate connection portion of the first switching element. The electrical connection of the gate connection is preferably made here at the connection, i.e. at the "anode" of the energy source. A reversible and controllable electrical connection of the gate connection to the energy source in the diagnostic mode is achieved by the second switching element.

In the case of the aforementioned initiation of the diagnostic mode by the control unit, the electrical connection of the gate connection to the energy source is therefore carried out by switching on the second switching element.

According to a further advantageous embodiment, the control unit is configured to detect an output voltage applied to the electrical load. For this purpose, the control unit either has a voltage detection unit or is connected to such a voltage detection unit. The output voltage is to be understood here as meaning the voltage with which the electrical load is supplied.

The further development is based on the consideration that, in the case of a supply of power to the load via the bypass current path in the diagnostic mode, the output voltage applied to the electrical load has a value of preferably less than 2V to 4V compared to the output voltage of the electrical load when it is connected to the energy source via the main current path. The voltage difference of the output voltages is caused in such a way that, when the first switching element is turned on by the electrical connection of the gate connection of the first switching element to the energy source and when the gate potential is connected to the potential of the energy source in the diagnostic mode, a part of the supply voltage of the energy source drops and, as a result, the output voltage applied to the electrical load in the diagnostic mode decreases. A part of the supply voltage is understood here to be the 2V to 4V already mentioned.

Overall, it can therefore be recognized from the output voltage whether the main current path is open and whether the bypass current path is closed. By detecting the output voltage applied to the electrical load, the switching states of the supply mode and the diagnostic mode can be distinguished from one another on the part of the control unit. In particular, it is thus reliably determined in a simple manner whether the preconditions for the diagnosis to be carried out are present. Accordingly, in a preferred further development, the start of the diagnosis, i.e. in particular the start of the check of the circuit breaker of the switching unit, is defined as a function of the detected output voltage.

Preferably, the control unit is configured to check the at least one power switch in the diagnostic mode. The control unit is provided in such a way that the at least one power switch is checked, in particular with regard to its functionality. In this case, the check is performed without interrupting the power supply to the load. The check is carried out in particular in a low-consumption state, i.e. in the case of a connected load requiring only a part of the total operating load.

Preferably, the control unit is connected to a current measuring element. Alternatively, the control unit has a current measuring element. The current measuring element is arranged here in such a way that it detects the load current flowing through the electrical load. Furthermore, the control unit is configured to switch between the supply mode and the diagnostic mode by actuating the first switching element and preferably by actuating at least one power switch as a function of the detected load current.

The design is based on the consideration that the timing of the diagnosis of the at least one power switch and thus the activation of the diagnostic mode are selected in such a way that the diagnostic mode is activated in the case of a low current consumption of the electrical load and thus a low load current flowing through it. A lower current consumption is to be understood here as a current consumption which occurs, for example, when the electrical load is in a stationary state (also referred to as standby state) or, in a broader sense, in a state with a lower current demand. The rest state is to be understood here as a state of the electrical load in which either all functions of the electrical load are not active or, preferably, only a part of all functions of the electrical load are active. If the electrical load is in such a standstill and this is recognized on the part of the control unit by detecting a lower load current, the control unit switches the supply mode into the diagnostic mode and thus checks the at least one power switch while ensuring that the electrical load is supplied via the bypass current path. Normally, the switching to the diagnostic mode takes place when necessary, i.e. when the load current is lower than the current designed for the bypass current path, i.e. for example 50% or 25% or also 10% lower than the (maximum) total operating current of the switching unit designed for the main current path. The diagnostic mode is preferably only activated when the load is in such a state of low current demand.

Alternatively, the switching unit is actuated from the outside, for example by means of an actuating unit. In this case, the control unit receives a switching command from the control unit to switch off or on the switching unit, so that in this way switching between the supply mode and the diagnostic mode and vice versa.

According to a preferred embodiment, the bypass current path is generally designed for a lower current than the main current path. This applies, for example, to switching elements which are installed in both current paths and/or also to considerations in respect of the (total) conductor cross-section in both paths. The design is based on the consideration that, as already mentioned above, the bypass current path is preferably used during the diagnostic mode for supplying the electrical load, in particular in the stationary state. Thereby, the bypass current path is subjected to a lower current load than the main current path in the diagnostic mode. Material and cost savings are also achieved by designing the bypass current path for lower currents.

The basic advantages of the switching device described herein are represented by the two achievable functions of the switching device, namely on the one hand the reduction of the electrical energy in the electrical load in the case of a switch-off (switch-off mode), and on the other hand the assurance of the supply in the case of a check of at least one power switch (diagnostic mode), wherein both the switch-off mode and the diagnostic mode are essentially realized by a bypass current path. It is also decisive here that the first switching element is connected and can be actuated in such a way that, on the one hand, it is automatically connected for the switch-off mode and, for the diagnostic mode, it is actively switched to the switch-on state. Thus, a dual function is achieved by bypassing the current path and by the first switching element in combination with the second switching element.

The object set forth for the method is achieved according to the invention by a method for operating a switchgear. The method is used, in particular, for electrically connecting an electrical load to an energy source via a switching device, wherein,

-connecting the electrical load with an energy source by switching on the switching unit in a supply mode through a main current path having the switching unit with at least one power switch,

-in a switch-off mode, the load is switched off and the switching unit is switched off for this purpose, and the electrical load is connected with a bypass current path by switching on the first switching element to reduce the electrical energy stored in the electrical load, and

in a diagnostic mode, the switching unit is switched off and the first switching element is switched on, so that the electrical load is connected to an energy source only via a bypass current path, wherein in the diagnostic mode the at least one power switch is checked and at the same time the supply of electrical energy to the electrical load is ensured via the bypass current path.

The switching device relates in particular to the switching device already mentioned above.

In the method for a main current path with at least one power switch, the electrical load is therefore connected to the energy source in the supply mode by switching on the at least one power switch.

In the switched-off mode, the at least one power switch is switched off and the electrical load is connected to the energy source only via a bypass current path with a first switching element by switching on the first switching element. In this case, the electrical energy stored in the electrical load is reduced via the bypass current path. In this case, a resistive element is preferably arranged in the bypass current path in order to convert the electrical energy into thermal energy.

In a diagnostic mode, the at least one power switch is off and the first switching element is on. In this case, the electrical load is connected to an energy source only via a bypass current path, wherein in the diagnostic mode at least one power switch is checked and at the same time the supply of electrical energy to the electrical load is ensured via the bypass current path.

Preferably, the first switching element is designed as a semiconductor switch which is automatically switched on in the switch-off mode by a negative voltage pulse caused by the load after switching off.

Furthermore, it is preferred that in the diagnostic mode the first switching element is actively switched on by the second switching element.

The advantages and preferred embodiments mentioned in connection with the switchgear are to be applied to the method and vice versa.

Drawings

Embodiments of the invention will be further elucidated below with reference to the drawings. The figures show a very simplified representation of a part.

Figure 1 shows a rough schematic circuit diagram of the switching device,

figure 2 shows exemplarily the distribution of the output voltage of the switching device and the distribution of the load current when switching off and switching on the load again,

fig. 3 shows an exemplary distribution of the output voltage of the switching device in relation to the control signal of the switching element.

Mutually corresponding parts are denoted by the same reference numerals throughout the figures.

Detailed Description

The switching device 2 shown schematically in fig. 1 is designed in particular as a switching device for an electrical system on board a motor vehicle and for electrically connecting an electrical load 4 to an energy source 6. The electrical load relates to one or more consumers, for example an electric motor. The electrical load 4 is in the present exemplary embodiment in the form of an inductive load 4 and is therefore in the circuit diagram according to fig. 1 in the form of a coil. The energy source 6 is only schematically represented in fig. 1. The energy source 6 is, for example, a battery of a not shown motor vehicle, a transformer or a capacitor arranged in the motor vehicle. The switching device 2 has an input E connected to the energy source 6 and an output a connected to the load 4. In operation, an electrical load or output voltage U acts on the output a and thus on the electrical load 4_AAnd provides a load current I at the output terminal a_L。

Furthermore, the switching device 2 has a main current path 8 with a switching unit 9 which comprises at least one power switch 10 and preferably a plurality of power switches 10 connected in parallel to one another. In the present exemplary embodiment, the switching device 2 has two power switches 10. The power switch 10 is constructed as a power MOSFET in the present embodiment. The electrical load 4 is electrically connected to the energy source 6 in the supply mode by means of a power switch 10. The supply mode is to be understood here as meaning the normal operating state of the switching device 2 in which the circuit breaker 10 is preferably permanently switched on, i.e. is conductive. The main current path 8 and the switching unit 9 are designed for a maximum total operating current, typically in the range of more than 50 a to, for example, 500 a or also 1000 a, in particular in the case of short-term loading.

The switching device 2 also has a bypass current path 12, which is connected in parallel to the main current path 8 and in which a first switching element 14, which is embodied in the present exemplary embodiment as a semiconductor switch, is arranged. Thus, an electrically conductive connection between the energy source 6 and the electrical load 4 can likewise be realized by means of the first switching element 14. A power consumer, in particular a resistor 20, is also arranged in series with the first switching element 14 in the bypass current path 12.

The first switching element 14 has a gate connection 16 with a gate potential U_G. Gate connection 16 and thus gate potential U_GElectrically connected to ground potential M. Likewise, the bypass current path 12 has a diode 18 which is arranged between the gate connection 16 and the ground potential M and is electrically connected to the ground potential M in the cut-off direction.

Furthermore, a second switching element 24 is provided as part of the switching device 2, which serves for the controllable electrical connection of the gate connection 16 of the first switching element 14 to the energy source 6, in particular to a connection 26 ("anode") of the energy source 6.

Finally, a control unit 22 is provided, by means of which various functions of the switching device 2 are controlled, as will be explained below. In particular, the control unit 22 is also used to control the power switch 10 and the second switching element 24. In this case, the control unit is connected to the control terminals S of the respective switching elements 10, 24 in a manner not described in detail here.

A cut-off mode:

gate connection 16 and gate potential U_GThe electrical connection to ground potential M is used for automatic switching-on of the first switching element 14 in the off mode. The switch-off mode is to be understood as an operating mode of the switching device 2 in which the load 4 is switched off by switching off the switching unit 9, i.e. the switching unit 9 is open-circuited.

The (surplus) energy is stored in the load 4 and possibly in the supply line for the load 4. In the case of an inductive load 4, a negative reverse voltage in the form of a negative voltage pulse results from the law of electromagnetic induction and a drop in the load current and the inductive energy stored in the load 4.

Due to the negative voltage pulse, the control voltage at the gate connection 16 of the first switching element 14 is exceeded and thus the first switching element 14 is automatically switched on when switched off, on account of the electrical connection of the gate connection 16 to the ground potential M.

Thus, when the load 4 is disconnected, the electrical load 4 is automatically electrically connected to the energy source 6 through the bypass current path 12. The current which is still flowing after the switch-off due to the stored energy is therefore led out via the bypass current path 12. The stored (surplus) electrical energy is converted and converted into thermal energy in the resistor 20. This protects the power switch 10 of the switching unit 9 in the main current path 8.

If the reverse voltage is again below a certain value, the first switching element 14 is automatically opened again, so that the load 4 is completely disconnected from the energy source 6.

The switch-off mode is therefore used to reduce the electrical energy stored in the electrical load 4 in the event of switching-off of the switching unit 9.

The voltage and current profiles in the switched-off situation, i.e. during the switched-off mode, are shown by way of example in accordance with fig. 2:

the upper curve shows the output voltage U at the output A_AAnd thus shows the distribution of the load voltage applied to the load 4. The lower curve shows the load current I_LDistribution of (2). In this case the dashed line "HS" shows the load current I through the main current path 8_LWhile the thick solid line "NS" shows the bypass currentLoad current I of current path 12_LDistribution of (2). The values of voltages and currents indicated are exemplary only and not actual values.

At a time of approximately 0.5 milliseconds, the load 4 is switched off by the switching unit 9, i.e. the power switch 10 is opened. This results in a negative voltage pulse (e.g., from +15V to about-20V). After said cut-off, the load current I_LFrom a nominal current of, for example, several hundred amperes (e.g., about 300 amperes) to 0 amperes continuously in a few nanoseconds or milliseconds. As a result of the negative voltage pulse, the first switching element 14 is switched on and the load current I_LFlows through the bypass current path 12. If the load voltage or output voltage U_AUp again to a certain value, in this example about-3V, the first switching element 14 is opened again and the load 4 is disconnected from the energy source 6.

After the switching unit 9 has been switched on, in the present example approximately at 5 milliseconds, the load current I_LAnd an output voltage U_AAnd then up to the output value.

And (3) diagnosis mode:

furthermore, a diagnostic mode is provided in which the switching unit 9 is also open and the load 4 is connected to the energy source 6 only via the bypass current path 12. During this diagnostic mode, one or more power switches 10 are specifically checked.

For this purpose, a control unit 22 is provided, which in the present exemplary embodiment is part of the switching device 2, as per fig. 1. The control unit 22 is preferably designed as a microcontroller or has a microcontroller. The control unit 22 is not necessarily an integral part of the switching device. For example, the control unit is designed as a separate structural unit or is arranged in a separate structural unit. This control unit is arranged, for example, separately from the switching device or from the remaining components of the switching device 2. It relates to a higher-level control device, for example. The individual components of the switching device 2, whether or not provided with a control unit 22, are preferably arranged on the same circuit board.

Furthermore, the control unit 22 is designed to initiate the diagnostic mode. In this case, the second switching element 24 is appropriately actuated by the control unit 22, so that the gate connection 16 of the first switching element 14 is connected to the energy source 6.

By the electrical connection of the gate connection 16 of the first switching element 14 to the phase connection 26 of the energy source 6, the gate potential U_GIn a diagnostic mode having a potential U with the energy source_EThe same numerical value. Potential U of energy source 6_EIn this case, this corresponds to the operating voltage of the motor vehicle battery, for example.

By this measure, the first switching element 14 is switched on, so that the load 4 is connected with the energy source 6 via the bypass current path 12. The unpowered closed circuit breaker 10 is then checked within a defined diagnostic range.

In principle, it should be noted that the load (i.e. the one or more consumers) operates in a plurality of different load states. This is controlled by a control device not further shown here. The load/consumer is, for example, an electric motor, so that its load capacity and the current contained are controlled as required by the control device.

Typically the diagnosis is performed without the load 4 being separate from the energy source 6. In this case, the diagnosis is performed during a low-load operating state of the load 4. In order to ensure that the diagnosis is reliably performed in the low load state and that the load 4 is supplied with power at the same time, the following special measures are specified.

First, the control unit 22 is arranged so as to detect the output voltage U_A. For this purpose, the control unit 22 is connected in the present exemplary embodiment to a voltage detection unit 30. The control unit 22 sets this in such a way that the output voltage U detected_AThe supply mode and the diagnostic mode are coherently discriminated. This embodiment is based on the consideration that the output voltage U in the diagnostic mode_ACompared to the output voltage U in the supply mode_APreferably 2V to 4V. In general, the supply mode is characterized in that the switching unit 9 is switched on, and in addition, the first switching element 14 is preferably switched off.

Thus, the output voltage U, whether for supply mode or diagnostic mode_ASet with a representative voltageA value according to which the control unit 22 distinguishes the two modes (supply mode and diagnostic mode) from each other, i.e. in particular the switching states of the switching unit 9 and the first switching element 14.

The control unit 22 is further arranged to determine the real-time load current I_LAnd for this purpose is connected, for example, to a current measuring element 28 of the switching device 2. Alternatively, the control unit 22 also obtains the load current I in real time by other means_LFor example, from a control device, for example from a motor control mechanism of a motor serving as a load. However, this is not provided for in the preferred embodiment variants.

The current measuring element 28 is used in the present embodiment for directly measuring the load current I flowing through the electrical load 4_L. Furthermore, the control unit 22 is arranged such that it is synchronized with the detected load current I_LBy actuating the first switching element 14 and the at least one power switch 10, the switching between the supply mode and the diagnostic mode takes place. Therefore, if dependent on the load current I_LRecognizing a low load condition, the bypass current path 12 is activated by a controlled switching-on of the first switching element 14 (by means of the second switching element 24).

Preferably, the control unit 22 is also used to operate the power switch 10 to open it. Thereby, the overall transition is made from the supply mode, in which the switching unit 9 is switched on and the first switching element 14 is switched off, to the diagnostic mode. For this switching, the control unit 22 delivers the mentioned control or switching signals to the respective control terminals, which cause the power switch to be switched off and the first switching element 14 to be switched on. In this case, the first switching element 14 is preferably switched on in time (shortly, less than 1 millisecond) before the at least one power switch 10 is switched off, so that, in a short time interval, the electrical load 4 is electrically connected to the energy source 6 both via the main current path 8 and via the bypass current path 12. Since the electrical load 4 is supplied via the bypass current path 12, an uninterrupted supply of power to the electrical load, in particular in the diagnostic mode, is achieved.

The transition between the supply mode and the diagnostic mode is illustrated with reference to fig. 3.

The upper curve shows the output voltage U_AAccording to which the two modes are distinguishable. The lower part-view shows two curves, wherein the upper curve shows the distribution of the first switching signal S1 for the switching of the switching unit 9, and the lower curve shows the distribution of the second switching signal S2 for the switching of the second switching element 24.

As can be clearly seen, first of all in the supply mode, the switching signal S1 is at a high level, so that the power switch is actuated in such a way that the power switch and thus the main path 8 are switched on. Then, in addition, the switching signal S2 is applied to the second switching element 24, so that the bypass current path 12 is also switched on and the supply takes place for a short period of time via the two paths 8, 12. Then, the control voltage of the first switching signal is reduced at least to the extent that the power switch 10 is turned off. This becomes evident in the output voltage due to a typical voltage drop of about 3V. However, sufficient output voltage U continues to be applied_AThereby continuing to power the load 4.

In the diagnosis mode, the diagnosis is performed before the next switching to the supply mode again (raising the control voltage of S1 and cutting off the control voltage of S2).

The invention should not be limited to the embodiments described herein. Rather, other variations of the invention will suggest themselves to those skilled in the art from this disclosure without departing from the subject matter of the invention. Furthermore, in particular, all individual features described in connection with the embodiments can also be combined with one another in other ways without departing from the subject matter of the invention.

List of reference numerals:

2 switching device

4 electric load

6 energy source

8 main current path

9 switch unit

10 power switch

12 bypass current path

14 first switching element

16 grid connection part

18 diode

20 resistance element

22 control unit

24 second switching element

26 phase connection part

28 Current measuring element

30 voltage detection unit

U_AOutput voltage

U_ESupply voltage of an energy source

U_GGrid potential

I_LLoad current

M ground potential

E input end

A output end

S control terminal

S1 switching signal

S2 switching signal