DE102024107357A1 - Counteracting a critical load in an on-board power system - Google Patents

Abstract

The invention relates to a vehicle (EV), in particular an electric vehicle, comprising an on-board power supply system with at least one semiconductor switch (Sw1-Sw4) arranged in a current path of the on-board power supply system (EBN), which semiconductor switch can be placed in a blocking conduction state, a normally conducting conduction state, and at least one abnormally conducting conduction state with a forward resistance that differs from the normally conducting state. The vehicle is configured to place at least one of the semiconductor switches (Sw1-Sw4) into an abnormally conducting conduction state upon detection of a critical load in the on-board power supply system, which counteracts the critical load. The invention also relates to a method for counteracting a critical load in an on-board power supply system of a vehicle, in which at least one semiconductor switch arranged in a current path of the on-board power supply system is placed into an abnormally conducting conduction state upon detection of a critical load in the on-board power supply system, which counteracts the critical load.

Description

The invention relates to a vehicle having an on-board power supply system with at least one semiconductor switch arranged in a current path of the on-board power supply system. The invention also relates to a method for counteracting a critical load in an on-board power supply system of a vehicle. The invention also relates to a method. The invention is particularly advantageously applicable to electric vehicles.

In vehicle power systems, it is known that certain on-board power system components, due to their nature, can feed electrical energy back into the power system in an uncontrolled manner, which can represent an undesirable on-board power system condition. If this amount of fed back energy exceeds the maximum amount of energy that an on-board power system can absorb, the voltage in the on-board power system increases uncontrollably, which in turn can lead to the failure or even destruction of on-board power system components. In known on-board power systems, such feed-back currents are absorbed by low-voltage storage devices (e.g., a lead-acid battery, lithium battery, etc.). Input circuits in on-board power system components (e.g., capacitors) are used as additional energy storage devices to absorb energy in highly dynamic feed-back situations.

However, there is a tendency to continually reduce the energy storage capacity in order to reduce costs and complexity, or even to dispense with energy storage altogether. In this case, the disadvantage is that there is no current sink large enough to absorb the feedback currents and prevent the associated voltage increase.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to provide a simple and cost-effective way of improving the stability of an on-board power supply system of a vehicle.

This object is achieved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

The object is achieved by a vehicle having an on-board power supply system with at least one semiconductor switch arranged in a current path of the on-board power supply system, which semiconductor switch can be brought into a blocking conduction state, a normally conducting conduction state and into at least one abnormally conducting conduction state with a forward resistance that differs from the normally conducting state, wherein the vehicle is configured to put at least one of the semiconductor switches into an abnormally conducting conduction state when a critical load of the on-board power supply system is detected, which counteracts the critical load.

This provides the advantage that critical electrical loads on the power system, such as uncontrolled current feed-in and/or undervoltage and/or elevated temperatures, can be counteracted by specifically changing the on-state resistance, which is not typically varied in an on-board power system. This, in turn, improves the stability and availability of the power system. Furthermore, this concept is simple and cost-effective to implement, especially without the need for additional components.

In one embodiment, the semiconductor switch is a power semiconductor or has at least one power semiconductor. In one embodiment, the semiconductor switch is a transistor or has at least one transistor. In one embodiment, the semiconductor switch is a field-effect transistor, in particular a MOSFET, or an IGBT component, or has at least one (MOS)FET or an IGBT component. In one embodiment, the semiconductor switch is an individual component, i.e., it is not a semiconductor switch from a group of several semiconductor switches integrated in an integrated circuit. The control voltage can, for example, correspond to the gate-source voltage in MOSFETs.

A further development is that the semiconductor switch is capable of autonomously adjusting its conduction state or its on-state resistance. A further development is that the conduction state of the semiconductor switch can be adjusted by another entity, e.g., by another component of the on-board power system, by a vehicle control device, etc.

The blocking conduction state corresponds to an open switch position. Current flow through an associated current path or electrical line containing the semiconductor switch is interrupted accordingly. The blocking conduction state can also be understood or implemented in such a way that no control voltage is applied, or the voltage is too low to conduct current.

The "normal" conducting state corresponds to a closed switch position, in which the semiconductor switch is in its saturation range. The semiconductor switch is completely switched on and can, in particular, be continuously operated within its specifications. The normally conductive state can also be understood or implemented as applying a control voltage that lies within a component-specific or standard-specified value range or value for the conductive state. This value range or value can be specified, for example, in a technical data sheet for the semiconductor switch.

In its "abnormal" conducting state, the semiconductor switch is conductive but outside its standard-specified saturation range. This can involve two cases: first, a drive voltage lower than the standard-specified drive voltage is applied (resulting in a significantly higher on-resistance than in the normally conducting state), and second, a drive voltage higher than the standard-specified drive voltage is applied (resulting in a further lower on-resistance than in the normally conducting state). The at least one on-resistance that deviates from the normally conducting state can therefore be higher or lower than for the normally conducting state.

In one embodiment, the vehicle is an electric vehicle. The electric vehicle can be, for example, a plug-in hybrid vehicle (PHEV), or a fully electrically powered vehicle, e.g., a battery-powered vehicle (BEV). In one embodiment, the vehicle has an internal combustion engine as the drive motor. The vehicle can be a motor vehicle (e.g., a motor vehicle such as a passenger car, truck, bus, etc., or a motorcycle), a railway, a watercraft (e.g., a boat or ship), or an aircraft (e.g., an airplane or a helicopter). In one embodiment, the vehicle is at least a partially autonomous vehicle, i.e., a partially autonomous and/or fully autonomous vehicle.

It is a further development that the on-board power system is a uniform on-board power system with a single on-board power system voltage. It is a further development that the on-board power system has two or more partial on-board power systems with different partial on-board power system voltages. In this case, at least one such semiconductor switch can be arranged in one, several or all of the partial on-board power systems, wherein upon detection of a critical load in one of the partial on-board power systems, at least one semiconductor switch of this partial on-board power system can be put into an abnormally conductive state, which counteracts the critical load in this partial on-board power system. It is a further development that a partial on-board power system with a lower partial on-board power system voltage is fed from a partial on-board power system with a higher partial on-board power system voltage by means of at least one converter, in particular a DC-DC converter.

It is a further development that the partial on-board power system, in which at least one semiconductor switch can be or is capable of being deliberately placed into an abnormally conductive state, has no battery or a battery with low capacity.

In one embodiment, the on-board power system has a first partial power system with a higher partial power system voltage and a second partial power system with a lower partial power system voltage. In one embodiment, the second partial power system is fed from the first partial power system by means of at least one converter, in particular a DC-DC converter. For example, in a vehicle with an internal combustion engine, the first partial power system can have a partial power system voltage between 24 V and 60 V, e.g., 48 V, while the second partial power system has a partial power system voltage of 12 V. For example, in an electric vehicle, the first partial power system can have a partial power system voltage between 60 V and 1200 V, e.g., 4000 V or 800 V, while the second partial power system has a partial power system voltage between 12 V and 48 V.

The fact that the semiconductor switch is arranged in a current path of the on-board power supply system corresponds in particular to the view that the semiconductor switch is a component of the on-board power supply system, in particular a switching element.

The critical load can be, for example, an uncontrolled current feed-in, a transient overvoltage and/or a transient undervoltage (transient voltage dip).

It is a further development that the critical load is detected or determined by the component of the on-board power system that is causing it. Detection can occur, for example, by means of a measurement taken on the component that is causing it, in particular a voltage and/or current measurement. Alternatively or additionally, a critical load can be determined by monitoring the operating states and/or operating conditions of the component that is causing it, taking into account experimentally derived data and/or historical data. If, for example, it is foreseeable that a critical load is likely or could occur due to a component, this can be considered a detection.

A further development is that the critical load is detected using a measuring device in the on-board power system. The measuring device can be an electronic fuse, for example, in a power distribution board.

A further development is that the critical load on the semiconductor switch is detected, e.g., by measurement, in particular by voltage and/or current measurement and/or temperature measurement. The measurements can include, for example, measurements or evaluations of individual values (amplitudes), average values, gradients, or integrals of measurement curves, etc.

In one embodiment, the vehicle is configured to, upon detection of a critical load in the on-board power system, place at least one of the semiconductor switches into an abnormally conductive state, which counteracts the critical load. This can be implemented, for example, by the detecting entity, such as the causative component, the measuring device of the on-board power system (possibly including the semiconductor switch), outputting a corresponding message upon detection or determination to the at least one semiconductor switch that is intended to respond to the critical load. In one embodiment, the message is output directly to the at least one semiconductor switch that is intended to respond to the critical load.

In one embodiment, when a critical load on the on-board power system is detected, a corresponding message is sent to a control device in the vehicle, and the control device then controls the at least one semiconductor switch that is intended to react to the critical load accordingly. This can include issuing a command to the at least one semiconductor switch to adjust the power state, optionally with information or a command about the magnitude of the forward voltage. In one embodiment, the control device is configured to analyze the critical load (e.g., the source of the critical load, current paths and/or semiconductor switches that can reduce the critical load, etc.) and, based on the result of the analysis, to select at least one specific semiconductor switch and to specify its conduction states, and optionally also the magnitude of the control voltage(s) or forward resistances.

The message can be output, for example, via the vehicle's on-board data network, e.g., a data bus. The message can include, for example, information about the presence of the critical load (e.g., in the form of a flag) and/or a command to adjust the power state, possibly including information or a command about the magnitude of the forward voltage.

Alternatively or additionally, at least one semiconductor switch can react autonomously to the detected critical load, e.g. by independently adjusting the control voltage or the on-state resistance.

It is a further development if at least two semiconductor switches are identical in design. It is a further development if at least two semiconductor switches are not identical in design.

In a further development, the vehicle is configured to return the conduction state of at least one semiconductor switch to its (normally conducting or blocking) conduction state prior to detection of the critical load upon termination of the critical load on the on-board power system. In a further development, the termination of the critical load can occur analogously to the detection of the critical load, e.g., by voltage, current, and/or temperature measurement and/or variables derived therefrom. In a further development, the termination of the critical load is estimated by counting down a timer/counting up a counter to a limit value or by waiting a predetermined period of time.

In one embodiment, the critical load on the on-board power system is a critically high current load on the on-board power system, and the at least one abnormally conductive state is a conduction state with increased forward resistance compared to the normally conductive state. The deliberate or targeted increase in forward resistance advantageously increases the losses or energy loss in the semiconductor switch. This behavior makes it possible to convert the undesired high current load into heat. This, in turn, can prevent, for example, an impermissible voltage increase.

In a further development, the vehicle is configured to switch at least one of the semiconductor switches from a normally conductive state to an abnormally conductive state. Thus, an existing on-state resistance is increased.

It is a further development that the vehicle is designed to switch at least one of the semiconductor switches from a blocking conduction state to an abnormally conducting conduction state. This means that a previously unused through A forward resistance is switched on. In a further development, this allows a load previously switched off by an upstream semiconductor switch or its input circuit to be started up, thereby further reducing the overcurrent. Alternatively, the forward resistance can be set so high that a downstream load or its input circuit is or will not be started up.

In one embodiment, the critical load on the on-board power system, particularly in the form of a critically high current load, occurs due to the feedback of electrical energy (or a "feedback current") from a functional component (also referred to as a "feedback component") into the on-board power system. Such feedback currents typically only occur for a short time. In another embodiment, the on-board resistance in an abnormal power state is matched to typical current values and/or durations of the feedback current, so that a critical thermal load on the semiconductor switch in the abnormal power state is unlikely.

The fact that electrical (“regenerative”) energy can be fed back into the on-board power system by means of a regenerative component means in particular that the regenerative component usually absorbs electrical energy from the on-board power system for its operation, but also feeds electrical energy back into the on-board power system depending on the situation and typically only for a short time (“uncontrolled”). This can also be expressed in such a way that the regenerative component is not a component specifically intended to supply the on-board power system. “Uncontrolled” regenerative action is particularly undesirable. It is a further development that a regenerative component has at least one electrically driven consumer, in particular an electro-hydraulic and/or electromagnetic consumer. It is a further development that the at least one regenerative component comprises or is a braking system, a steering system and/or a motor-driven component such as an engine fan. An energy source intended to supply the on-board power system, such as a battery and/or a converter, does not constitute a feed-in component, in particular because its intended feed-in does not constitute feed-in.

One embodiment of the on-board power system is that it has several semiconductor switches arranged in a feedback current path. This advantageously enables particularly effective reduction of the feedback current via several semiconductor switches.

One embodiment provides that at least two of the semiconductor switches arranged in the feedback current path are electrically parallel to one another. This provides the advantage that the feedback current is divided into different current branches, which in turn advantageously reduces the current load and thus the thermal load on the semiconductor switch in its abnormally conductive state.

In a further development, at least two of the semiconductor switches arranged in the feedback current path are electrically arranged in series with each other. In general, the topography of the semiconductor switches is not limited to series/parallel.

One embodiment provides that semiconductor switches arranged electrically parallel to one another have different forward resistances, at least in their abnormally conductive states. This advantageously allows the distribution of the feedback current path to be adjusted in a particularly variable manner.

In one embodiment, at least three of the semiconductor switches arranged in the regenerative current path are arranged in a cascade. The cascaded arrangement or cascade can be described in particular such that the regenerative current path branches electrically in parallel at least once starting from the regenerative component, at least one of the semiconductor switches is arranged in the still unbranched current branch, and at least one of the semiconductor switches is arranged in a respective one of the branched current branches. The fewer branches the semiconductor switch has to the regenerative component, the shorter its so-called cascade distance. This can also be described such that a semiconductor switch is in a current branch "nth cascade stage", where n represents the number of branches back to the regenerative component. A semiconductor switch in the 0th cascade stage is then arranged unbranched behind the regenerative component, etc. The cascade can in principle have any number n of branches with n > 0.

A semiconductor switch may be present in the 0th cascade stage, but this is not required. If not, two or more semiconductor switches arranged electrically in parallel can be present in the 1st cascade stage, for example. This reflects the fact that there may be regenerative components that are directly connected to the on-board power system via two or more parallel semiconductor fuses.

It is a design that semiconductor switches are arranged in a shorter cascade distance to the return supply source or in a smaller cascade stage are set to a lower on-resistance than semiconductor switches in a longer cascade distance. This can also be expressed as the resistance values of the semiconductor switches can be set or are set in descending order, starting near the interference source with a lowest on-resistance, since this is where a high interference current, especially feedback current, is expected. As a result, the on-resistance should be lower for the same maximum permissible component heating. The further back or away from the interference source a semiconductor switch is arranged in the cascade, the more parallel paths are available for the current to travel and the lower the current load per path. This means that the on-resistance of a more distant - especially identically constructed - semiconductor switch can be set higher for a constant maximum permissible component heating.

One embodiment of the vehicle is designed to deliberately "melt" at least one semiconductor switch, which in particular has a greater cascade distance from the feedback source, i.e., to exceed the thermally permissible range of the semiconductor switch and thus potentially destroy it. This can be advantageous for reducing particularly high current or voltage peaks in the on-board power system.

One embodiment is that the vehicle is configured to measure the temperature of the semiconductor switch and adjust the on-state resistance based on the temperature measurement result. This reliably prevents critical thermal overload of the semiconductor switch, and also generally sets the on-state resistance higher than under general assumptions regarding thermal load.

A further development is that the decision to place a semiconductor switch into its abnormal conduction state depends on whether this would impair a load—particularly one connected downstream of the semiconductor switch. For example, this decision can be made based on whether the load belongs to a specific load class (constant power, constant current, or constant resistance) and/or load function (e.g., required by a user, not required, safety-relevant, etc.). Thus, in a further development, semiconductor switches that protect safety-relevant loads cannot be placed into an abnormal conduction state, or only with a slight deviation from the normal on-state resistance.

In one embodiment, the critical load of the on-board power system is a critical undervoltage in the on-board power system, and the at least one abnormally conductive line state is a line state with a reduced on-state resistance. The undervoltage can, for example, be a transient undervoltage. In one embodiment, the reduction in the on-state resistance comprises a brief, non-critical increase in a drive voltage beyond a continuous specification.

In one embodiment, at least one semiconductor switch is or co-forms a semiconductor fuse. In addition to the at least one semiconductor switch, the semiconductor fuse can also have further components such as a voltage and/or current measuring device and/or a temperature measuring device. The semiconductor fuse can also be referred to as an electronic fuse or "E-fuse."

The object is also achieved by a method for counteracting a critical load in a vehicle's power supply system, in which at least one semiconductor switch arranged in a current path of the power supply system, which can be switched to a blocking conduction state, a normally conducting conduction state, and at least one abnormally conducting conduction state with a forward resistance that differs from the normally conducting state, is switched to an abnormally conducting conduction state upon detection of a critical load in the power supply system, which counteracts the critical load. The method can be designed analogously to the vehicle, and vice versa, and has the same advantages.

• 1 zeigt eine stark vereinfachte Skizze eines Ausschnitts aus einem Energiebordnetz eines Fahrzeugs.

The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment, which is explained in more detail in connection with the drawings.

• 1 shows a highly simplified sketch of a section of a vehicle's on-board power system.

1 shows a sketch of a section of an on-board power supply system (EBN) of an EV vehicle. The on-board power supply system (EBN) can, for example, be a low-voltage (partial) on-board power supply system with an on-board power supply voltage between 12 V and 48 V. The EV vehicle can be an electric vehicle. The on-board power supply system (EBN) has a component (RSK) that feeds a feedback current I_bs back into the on-board power supply system (EBN) in an uncontrolled manner, e.g., depending on operation. system. Starting from the regenerative component RSK, the current path through which the regenerative current I_bs flows is cascaded. For this purpose, it has, as an example, two cascade stages, namely a zeroth, still unbranched cascade stage KS_0 and a first cascade stage KS_1 branched into three parallel partial current paths. Purely as an example, a semiconductor switch Sw1, Sw2, Sw3, or Sw4 is arranged in both the cascade stage KS_0 and each of the three partial current paths of the cascade stage KS_1. The semiconductor switches Sw1 to Sw4 can be identical in design, but do not need to be.

The semiconductor switches Sw1 to Sw4 are designed here purely as examples as s-channel MOSFETs. Their on-resistance between the source terminal S and the drain terminal D is set by a drive voltage U _GS between the gate terminal G and the source terminal S or by a gate potential. The current I _DS passed between the source terminal S and the drain terminal D depends on a forward voltage U _DS applied between the source terminal S and the drain terminal D: the higher the forward voltage U _DS for the same drive voltage U _GS , the higher the forward current I _DS . A distinction is made between a linear increase in the forward current I _DS with the drive voltage U _GS at lower drive voltages U _GS and a subsequent saturation region at higher forward voltages U _DS , whereby the forward current I _DS changes only slightly in the saturation region and is quasi-asymptotic. A further property is that, for a given forward voltage U _DS , the higher the forward current I _DS , or the lower the forward resistance, the higher the drive voltage U _GS . This behavior of a MOSFET can be illustrated, for example, in corresponding output characteristic curves (above figure). Consequently, by varying the drive voltage U _{GS ,} the forward resistance can be varied, and thus also the forward current I _DS . By varying the drive voltage U _{GS ,} the semiconductor switch Sw1 to Sw4 can be used as a variably adjustable resistor.

For the blocking conduction state, U _GS = 0 or U _GS ≈ 0 applies. The normally conducting conduction state corresponds, in particular, to the maximum U _GS permitted for a continuous specification, but can also be lower. The abnormally conducting conduction state corresponds to a conducting conduction state in between.

If the vehicle EV detects a significant feedback current I_bf in the on-board power supply system EBN, the vehicle EV, e.g. a control device Ctrl thereof, can set at least one of the semiconductor switches Sw1 to Sw4 into an abnormally conductive state with increased on-state resistance compared to a state without feedback current I_bf by reducing the control voltage U _GS , here e.g. all of the semiconductor switches Sw1 to Sw4 shown. In particular, the on-state resistances can be varied such that the semiconductor switch Sw1, which has a shorter cascade distance (cascade stage KS_0) to the feedback source or the feedback component RSK, is set to a lower on-state resistance than the semiconductor switches Sw2 to Sw4, which have a longer cascade distance (cascade stage KS_1).

It is a variant that the vehicle EV is configured to measure a temperature of the respective semiconductor switches Sw1 to Sw4 and to adjust the on-resistance of the semiconductor switches Sw1 to Sw4 depending on a result of the temperature measurement.

Once the feedback current has been sufficiently reduced, the semiconductor switches Sw1 to Sw4 can be returned to their performance state before the feedback current was detected.

Of course, the present invention is not limited to the embodiment shown.

In general, “a”, “an”, etc. can be understood as a singular or a plural, in particular in the sense of “at least one” or “one or more”, etc., unless this is explicitly excluded, e.g. by the expression “exactly one”, etc.

A numerical value may also include the exact number stated as well as a usual tolerance range, as long as this is not explicitly excluded.

List of reference symbols

Ctrl

Control device

D

Drain connection

EBN

On-board power system

EV

vehicle

G

Gate connection

I_bf

regenerative current

KS_0

Zeroth cascade stage

KS_1

First cascade stage

RSK

Regenerative component

S

Source connection

Sw1 - Sw4

semiconductor switches

Claims (13)

Vehicle (EV), in particular an electric vehicle, comprising an on-board energy supply system (EBN) with at least one semiconductor switch (Sw1 - Sw4) arranged in a current path of the on-board energy supply system (EBN), which semiconductor switch can be brought into a blocking conduction state, a normally conducting conduction state and into at least one abnormally conducting conduction state with a forward resistance that differs from the normally conducting state, wherein the vehicle (EV) is designed to put at least one of the semiconductor switches (Sw1 - Sw4) into an abnormally conducting conduction state, which counteracts the critical load, upon detection of a critical load on the on-board energy supply system (EBN). Vehicle (EV) to Claim 1 , wherein the critical load of the on-board power supply system (EBN) is a critically high current load of the on-board power supply system (EBN) and the at least one abnormally conductive line state is a line state with increased forward resistance. Vehicle (EV) according to one of the preceding claims, wherein the critical load of the on-board energy network (EBN) occurs due to a feedback of electrical energy from a functional component (RSK) into the on-board energy network (EBN). Vehicle (EV) according to one of the preceding claims, wherein the on-board power supply system (EBN) has a plurality of semiconductor switches (Sw1 - Sw4) arranged in a feedback current path. Vehicle to Claim 4 , wherein at least two of the semiconductor switches (Sw2 - Sw4) arranged in the feedback current path are arranged electrically parallel to one another. Vehicle to Claim 5 , wherein at least three of the semiconductor switches (Sw1 - Sw4) arranged in the feedback current path are arranged in cascade and semiconductor switches (Sw1) with a shorter cascade distance (KS_0) to the feedback functional component (RSK) are set to a lower on-resistance than semiconductor switches (Sw2 - Sw4) with a longer cascade distance (KS_1). Vehicle (EV) to Claim 6 , wherein the vehicle (EV) is configured to melt at least one semiconductor switch (Sw1 - Sw4) having a higher cascade distance (KS_1) to the feedback source. Vehicle (EV) according to one of the preceding claims, wherein the vehicle is configured to perform a temperature measurement of a temperature of the semiconductor switch and to adjust the on-resistance depending on a result of the temperature measurement. Vehicle (EV) according to one of the preceding claims, wherein the critical load of the on-board power supply system is a critical undervoltage in the on-board power supply system and the at least one abnormally conductive line state is a line state with reduced on-state resistance. Vehicle (EV) to Claim 9 , wherein the reduction of the on-resistance comprises a short-term, non-critical increase of a drive voltage of the semiconductor switch (Sw1 - Sw4) beyond a continuous specification. Vehicle (EV) according to one of the preceding claims, wherein at least one semiconductor switch (Sw1 - Sw4) is a semiconductor fuse. Vehicle (EV) according to one of the preceding claims, wherein the vehicle (EV) is configured to return the conduction state of the at least one semiconductor switch (Sw1 - Sw4) to its conduction state before detection of the critical load upon termination of the critical load of the on-board power supply system (EBN). Method for counteracting a critical load in an on-board energy supply system (EBN) of a vehicle (EV), in particular a vehicle (EV) designed according to one of the preceding claims, in which at least one semiconductor switch (Sw1 - Sw4) arranged in a current path of the on-board energy supply system (EBN), which can be brought into a blocking conduction state, a normally conducting conduction state and into at least one abnormally conducting conduction state with a forward resistance that differs from the normally conducting state, is placed into an abnormally conducting conduction state when a critical load on the on-board energy supply system (EBN) is detected, which counteracts the critical load.