DE102022103289A1 - Heating device and method for heating a component of a motor vehicle - Google Patents

Abstract

The invention relates to a heating device (12) for heating at least one component (15) of a motor vehicle (27), the heating device (12) having a control device (26) and an energy store (15) which comprises at least one battery unit (10), having a battery cell (14). The battery unit (10) comprises two switches (S1, S2) comprising a first switch (S1) and a second switch (S2), the first switch (S1) being connected in series with the battery cell (14) and the second switch (S2) is connected in parallel to the first switch (S1) and to the battery cell (14), at least one of the two switches (S1, S2) being designed as a MOSFET (S1, S2) which has a controllable, heat loss (Q) generating turn-on channel resistance (R), wherein the control device (26) is designed to control the turn-on channel resistance (R) by controlling a control voltage (Ugs) as a function of a predetermined heating parameter (P) in order to control the at least one component (15) to be heated by means of the generated heat loss (Q).

Description

The invention relates to a heating device for heating at least one component of a motor vehicle, the heating device having a control device and an energy store which includes at least one battery unit which has a battery cell. Furthermore, the invention also relates to a method for heating at least one component of a motor vehicle.

Various components can be heated in a motor vehicle. An example of such a component is the energy store of an electric vehicle, which can be designed as a high-voltage battery, for example. The cooling water circuit of the drive is heated for the function of preconditioning the high-voltage battery. For this purpose, a PTC (Positive Temperature Coefficient) heater is used in all electrified vehicles. For the function of this preconditioning, additional high-voltage control devices are usually required as part of these PTC heaters in electric vehicles. This in turn results in numerous disadvantages: Additional high-voltage control units lead to additional costs, weight and installation space. In detail, the additional costs are due to additional manufacturing and material costs, in particular for the PTC heater itself, for coolant hoses of the PTC heater, for the high-voltage wiring and connection of the PTC heater, as well as for installation in the vehicle and for mounting brackets . Further costs are due to high development costs and development efforts, in particular for the hardware and software development of the high-voltage component PTC heater, for validation and testing of the high-voltage component PTC heater, and for the effort involved in integrating the high-voltage component PTC heater into the vehicle. The increase in vehicle weight is in turn due to the additional high-voltage control units, mounting brackets, coolant hoses, packaging in the vehicle and the connection to the high-voltage vehicle electrical system. Further disadvantages result from the lower level of robustness, since additional control devices involve additional sources of error and, above all, the PTC heater provides a critical control device, since this involves providing a heating function in connection with coolant. It would therefore be desirable to provide a heating option that is as inexpensive, simple and weight-saving as possible.

The DE 10 2013 018 411 A1 describes a method for heating a high-voltage battery made up of a large number of battery cells, which are heated in sections by alternating charging and discharging with an intermediate storage device. For this purpose, an alternating current is switched for charging and discharging via semiconductor switching elements. These can be in the form of MOSFETs (metal oxide semiconductor field effect transistors). Due to the individual internal resistances in the battery cells, heat is lost, which leads to the cells heating up accordingly.

Furthermore describes the DE 10 2013 017 342 A1 a cooling device for an energy store in a motor vehicle, which has a cooling circuit with which the energy store and power electronics, which are designed to control an electric drive motor of the motor vehicle, are thermally coupled to one another. The power electronics can be operated in a heating mode in which the electric drive machine can be operated as a motor and which differs from a driving mode in which the electric drive machine consumes an associated reactive electric power in addition to an active electric power in that in the heating mode the reactive power assigned to an active power that is currently being supplied is significantly greater than the reactive power that is assigned to the active power that is currently being supplied in the driving operating mode, in order to heat the cooling circuit and thus the energy store.

Furthermore describes the DE 10 2017 200 088 A1 a method for air-conditioning a component of a power electronic circuit by means of a heating measure, which can include that a power loss within the circuit is increased by changing an operating point or reduced by changing an operating point and for this purpose the power loss of an electrical machine controlled by the circuit is increased. The power loss can be changed by changing a control method or by changing a switching frequency.

The object of the present invention is to provide a heating device and a method that enable at least one component of a motor vehicle to be heated as efficiently as possible.

This object is achieved by a heating device and a method having the features according to the respective independent patent claims. Advantageous configurations of the invention are the subject matter of the dependent patent claims, the description and the figures.

A heating device according to the invention for heating at least one component of a motor vehicle has a control device and an energy store which includes at least one battery unit which has a battery cell. The battery unit has two switches comprising a first and a second switch, the first switch being connected in series with the battery cell and the second switch being connected in parallel with the first switch and the battery cell, with at least one of the two switches acting as a first MOSFET (metal-oxide-semiconductor field-effect transistor) which, when switched on, has a first turn-on channel resistance that can be controlled by means of a first control voltage that can be applied to the first MOSFET and generates heat loss, the control device being designed to control the first turn-on channel resistance as a function of the first control voltage controlled by a predetermined heating parameter in order to heat the at least one component by means of the generated heat loss.

The invention is based on several findings at the same time: On the one hand, it is possible, and above all very advantageous, to use so-called smart cells, ie intelligent battery cells, in an energy store. These are constructed as defined for the battery unit mentioned above, ie they comprise a battery cell and two switches, one of which is connected in series with the battery cell and the other is connected in parallel with the series connection of the battery cell and the first switch. This makes it possible to disconnect the battery cell of this battery unit from a cell assembly or to add it to this cell assembly in a particularly flexible manner. For example, if a battery cell is defective, it can be bypassed simply by closing the second switch and opening the first switch, and thus disconnected from the cell assembly. If the energy store therefore has not only one such battery unit but rather a number of interconnected battery units, it is also possible to operate the energy store with only some of the battery units it comprises. This makes it possible, for example, to provide a voltage at the energy store even if one of the battery cells is defective. However, the flexible circuit options provided by these two switches can also be used in a variety of other ways, for example for cell balancing or to compensate for differences in aging between the individual battery cells. The switches are preferably in the form of electronically controllable power switches, in the present case at least one of the two switches being in the form of a MOSFET. This has the great advantage that this MOSFET, more precisely its generated power loss, can now also be used in heat loss for heating the at least one component. The heat loss generated by this MOSFET can even be specifically controlled depending on a heating parameter. This in turn is based on the knowledge that MOSFETs have an ohmic conduction behavior in the "on state", i.e. in the switched-on state, which can be used to regulate the gate-source voltage, which is referred to here as the control voltage , to set or regulate a precise channel resistance and thus a precise power loss. The channel resistance can also be referred to as the drain-source resistance, since it represents the electrical resistance between the drain electrode, also known as the drain connection, and the source electrode, also known as the source connection of the MOSFET. In the switched-off state of such a MOSFET, it does not let any current through, so that the channel resistance is correspondingly very high. Because no current flows, no power loss is generated. Consequently, only the channel resistance of the MOSFET in the switched-on state is of interest within the scope of the present invention, which is why this channel resistance is also referred to here as the on-channel resistance, since it relates to the resistance of the MOSFET in the switched-on state. Depending on the heating requirement, this channel resistance of the MOSFET can be adjusted to a greater or lesser extent. The use of such smart cell battery cells, which are referred to here as battery units, thus enables the at least one component to be heated, for example also the preconditioning of a cooling medium or the entire high-voltage battery. The channel resistance of such a MOSFET can therefore advantageously be used in a targeted manner in order to generate power loss in a defined manner and to heat up the cooling medium. As a result, the number of required PTC heaters and the associated control devices can also be reduced in an advantageous manner, or they can be omitted entirely. This in turn saves manufacturing and material costs, especially for such PTC heaters, for the coolant tubing of the PTC heaters, for the high-voltage wiring and connection of the PTC heaters and for installation in the vehicle and for mounting brackets. In addition, there are no development costs and expenses, in particular for the hardware and software development of the high-voltage component PTC heater, for validation and testing of the high-voltage component PTC heater and for the integration effort of the high-voltage component PTC heater in the vehicle. This also reduces the vehicle weight, in particular due to the elimination of the high-voltage control units, assembly brackets, coolant hoses and packaging in the vehicle, and the connection to the high-voltage vehicle electrical system. At the same time, the robustness of the overall system can also be increased since there are fewer control units, which reduces the overall system's susceptibility to errors, and the PTC heater, as a critical control unit, can also be omitted. For heating via the drive train no electric motor is necessary. This means that heating can also be carried out when stationary without controlling the electric motor. The invention therefore has the enormous advantage that the high-voltage control devices for the PTC heaters can be omitted in future electric cars with Smartcell battery cells. The function is taken over by the power semiconductors of the smart cell battery cells themselves, which represent the discharge resistances, ie the channel resistances, via active regulation of the gate voltage, ie the control voltage. This leads to considerable cost advantages for manufacturing and development costs, a reduction in weight and an increase in robustness.

The first MOSFET, like any other MOSFET mentioned within the scope of the invention, can be constructed as known from the prior art. Such a MOSFET typically has three terminals or electrodes, namely a gate electrode, a source electrode and a drain electrode. In this case, the gate electrode represents a control electrode at which a control voltage can be provided. To be more precise, this control voltage is provided between the gate electrode and the source electrode. The MOSFET can be switched on and off by means of this control voltage, with the drain-source path being conductive when switched on and non-conductive when switched off. The switched-on state of the MOSFET thus corresponds to the closed state of the switch, which is implemented by the MOSFET, and the switched-off state of the MOSFET corresponds to the open state of the switch. At the same time, not only the switching state of the MOSFET can now advantageously be determined by a control voltage, but also the size of the switch-on channel resistance, i.e. the size of the electrical resistance between the Drain connection and the source connection results. Correspondingly, this channel resistance is also referred to as a drain-source resistance, in particular as a drain-source on resistance. The MOSFET is preferably designed as a SiC (silicon carbide) MOSFET.

The battery cell can be designed as a lithium-ion cell, for example. In addition, the battery cell can be provided as a prismatic battery cell, round cell or pouch cell or as any other battery cell. The energy store is preferably in the form of a high-voltage energy store and preferably comprises a number of such battery units, which can basically be connected to one another in any desired manner. In general, various parameters can be considered as heating parameters. This can represent, for example, a specified target temperature or a difference between a current temperature and a specified target temperature and/or a binary parameter that indicates whether there is a current heating requirement or not, and/or it can represent a current temperature of the specify the heating component or the tempering medium for tempering the component or the difference between such a current temperature and a predetermined target temperature, or the like. The heating parameter therefore generally specifies whether the heating device should be used for heating or not and/or how much heating is currently required. Accordingly, the control device can advantageously use the control voltage to control or regulate the switch-on channel resistance in order to meet this heating requirement.

In a further advantageous embodiment of the invention, the energy store represents the component. In other words, the heating device is designed to heat the energy store itself, which includes the battery unit. The power loss of the first MOSFET can therefore advantageously be used to heat the energy store itself, for example as part of a preconditioning of the energy store. This is particularly advantageous because the heat loss used for heating can also be generated where it is needed, namely in the energy storage itself get lost. Nevertheless, it is also conceivable that other components of the motor vehicle can be heated by means of the power loss or heat loss provided in this way. For example, the heat loss generated can also be used to heat the interior of the motor vehicle or to heat a cooling medium in a cooling circuit in general.

In a further advantageous embodiment of the invention, the control device is designed to control the first switch-on channel resistance in such a way that the first switch-on channel resistance is greater in a heating mode than in an operating mode that differs from the heating mode. This operating mode, which is different from the heating mode, can therefore represent a normal operating mode in which the heating device should not be used for heating. Due to the fact that the channel resistance is greater in the heating mode than in this normal operating mode, more heat can also be lost due to the greater switch-on channel resistance, and the heating device can therefore produce a greater heating output. To increase the on-channel resistance, the voltage level of the control voltage can be reduced. The lower the control voltage, the greater the corresponding turn-on channel resistance and the greater the heat loss generated. This therefore represents a particularly simple way of generating more heat loss in a targeted manner in the heating mode.

According to a further advantageous embodiment of the invention, the control device can be designed to set an extreme switch-on voltage level of the control voltage to only one predetermined value in the heating mode, which corresponds to a specific value of the first switch-on channel resistance, or to different values depending on the heating parameter. each corresponding to different values of the first turn-on channel resistance. On the one hand, this enables a particularly simple implementation of the heating mode and, on the other hand, a particularly precise and flexible setting of the heating output. In the simplest case, therefore, only a predetermined value of the control voltage can be set for the heating mode, which therefore only corresponds to a specific value of the switch-on channel resistance. In other words, for example, a first voltage level of the control voltage for the heating mode can be provided and a second turn-on voltage level for the normal operating mode, which is then preferably correspondingly greater than the first turn-on voltage level, so that the turn-on channel resistance in the heating mode is greater than in the normal operating mode. This corresponds to simply activating and deactivating the heating function. This is particularly simple and inexpensive to implement and control the MOSFET. Alternatively, however, it is also conceivable that different switch-on voltage levels of the control voltage can be set in the heating mode, which in turn therefore correspond to different switch-on channel resistances. In this way, different heating outputs can be provided in the heating mode, which can be adjusted or set depending on the desired heating requirement, which can be specified by the heating parameter. To be more precise, the control device can be designed to also set the switch-on voltage level of the control voltage in the heating mode only to a predetermined value, but this can be selected from several different, in particular any number of different values for the switch-on voltage level, depending on the heating requirement. This enables a significantly more flexible adaptation to a currently given heating requirement.

As explained in more detail later, the first MOSFET can also be operated in a clocked or pulsed manner in the heating mode. This means that it turns on and off at a predetermined frequency. The control voltage varies accordingly between a switch-on voltage level and a switch-off voltage level and, for example, also runs through all voltage values in between in the meantime. Accordingly, the turn-on voltage level is also referred to above as the extreme turn-on voltage level, to express that the turn-on voltage level should not be understood to mean any of these intermediate values, but rather the extreme value, for example the maximum voltage value in the case of a positive turn-on voltage. In order to operate the MOSFET in a clocked manner, a suitable control voltage can be provided at the control electrode, i.e. at the gate electrode of the MOSFET, more precisely between the gate electrode and the source electrode, i.e. a suitable control voltage which, for example, occurs between the switch-on voltage level and a switch-off voltage level varies. For this purpose, for example, a voltage signal can be provided which is pulse-width modulated, in particular according to a predetermined modulation scheme. This controls the turn-on and turn-off times of the MOSFET accordingly. The switch-on voltage level can advantageously be controlled as a function of the heating parameter in order to generate more or less heat loss depending on the requirement. However, the MOSFET does not necessarily have to be clocked for this. The control device can generally be designed not only to operate the first switch in a clocked manner, but also to switch it on permanently, i.e. closed, for a specific period of time, for example.

In a further advantageous embodiment of the invention, both switches are embodied as MOSFETs comprising the first MOSFET and a second MOSFET which, when switched on, has a second switch-on channel resistance which can be controlled by means of a second control voltage which can be applied to the second MOSFET and generates heat loss, the control device is designed to control the second turn-on channel resistance by controlling the second control voltage as a function of the predetermined heating parameter in order to heat the at least one component by means of the heat loss generated.

In other words, the second MOSFET can be controlled in the same way as already described for the first MOSFET. Otherwise, all configurations that have been described with reference to the first MOSFET or that are described below can also be implemented in the same way for the second MOSFET. For example, the first switch can be in the form of a first MOSFET and the second switch can be in the form of a second MOSFET, or vice versa. So can So both switches of the battery unit can be designed as MOSFETs and controlled accordingly in order to generate a corresponding heat loss depending on the heating parameter. In this case, however, both switches do not have to be controlled in the same way by the control device at the same time; on the contrary, it can also be the case that at a specific time only one of the two MOSFETs is controlled to generate a specific heat loss. The other of the two MOSFETs can then be in a switched-off state, for example. Basically, it can be provided in normal operation that only one of the two switches of the battery unit is closed and the other is open. Thus, the battery cell is either connected or bridged. In the inactive state of the energy store, it is also possible for both switches to be opened at the same time. For example, that one of the two MOSFETs that is currently in the closed state can always be selectively activated for targeted heat loss generation. It is also conceivable to open and close the two switches acyclically or complementarily and thus to operate them clocked in each case in order to simultaneously generate a desired heating power by regulating the channel resistance. Especially when the energy store has several battery units, there are numerous other and arbitrarily complex control options.

In a further advantageous embodiment of the invention, the first MOSFET or a substrate, in particular a semiconductor substrate, on which the first MOSFET is arranged is or can be coupled to a cooling circuit in order to dissipate the heat loss to the cooling circuit. The same also applies to the optional additional second MOSFET.

The first and/or second MOSFET can be arranged on a circuit board, for example, or can be in the form of a semiconductor chip. In turn, the semiconductor substrate of the chip or the circuit board can be or can be coupled thermally and physically to a cooling circuit. Through direct contact, for example via a heat exchanger, heat can be dissipated from the substrate or the circuit board, in particular the heat loss, to the cooling circuit and this can be heated accordingly. Various other components of the motor vehicle can in turn be correspondingly heated via the cooling circuit. This refinement is particularly advantageous since the heat loss can be used to heat any motor vehicle component via this cooling circuit as a result of the heat loss being released to the cooling circuit.

In a further advantageous embodiment of the invention, at least the first MOSFET or a substrate on which the first MOSFET is arranged is arranged on the battery cell in order to dissipate the heat loss to the battery cell. The substrate can therefore be arranged directly on a cell housing of the battery cell, for example. As a result, the battery cell can be heated directly, even without the intermediate coupling of a cooling circuit. This allows the battery cell to be heated particularly efficiently. In addition, this also makes it possible to heat each battery cell in a targeted and individual manner, in the event that the energy store has a plurality of such battery units, by appropriately actuating the switch or switches of the relevant battery unit.

These configurations can also be combined because, for example, the first MOSFET or the substrate on which it is arranged can be coupled or can be coupled to both the battery cell and the cooling circuit.

There are several ways to operate the first MOSFET in heating mode. For example, if the battery unit is in a state in which the battery cell is electrically conductively coupled to a cell assembly, so that the first switch is closed and the second switch is open, the first switch can now switch to the heating mode more , more precisely the MOSFET, which represents this first switch, can be driven with a corresponding control voltage in order to generate the highest possible or at least higher power loss by setting a higher value for the channel resistance than in the normal operating mode. The first switch can continue to remain closed, in particular permanently. However, this heats up the MOSFET very much, as do the surrounding components. This is due to the fact that the above-mentioned substrate cannot absorb a lot of heat due to its low thermal mass and the heat dissipation via the supply of heat loss to the cooling circuit is relatively slow, at least in comparison to the speed of heating by the heat loss generated.

In order to prevent overheating of the MOSFET and the surrounding components, it is very advantageous, as is provided according to a further advantageous embodiment of the invention, if at least the first MOSFET, which in this example corresponds to the first switch, is clocked or .is operated in a pulsed manner. However, the same also applies analogously to the second MOSFET. Due to the switched-off phases of the MOSFET that are thus interposed, it can cool down temporarily while the heat loss generated is dissipated by the cooling circuit. However, clocked operation of the MOSFET has another great advantage, namely that a desired heating power can also be provided in a targeted manner without having to change the switch-on voltage level itself for this purpose, for example. In contrast to a permanently switched-on operation of the MOSFET, the clocked operation automatically generates less heating power, even with the same extreme turn-on voltage. This also advantageously provides a further possibility for controlling and regulating the power loss generated in a targeted manner with regard to its size.

In a further advantageous embodiment of the invention, the energy store has a plurality of battery units connected to one another, the switches of which can be controlled by the control device as a function of a power requirement parameter in such a way that all or only some of the several battery cells contribute to the provision of a total voltage that can be tapped at the energy store. Depending on the current power requirement, it can also be provided, at least in the event that several battery units are connected in parallel with one another, that not all of them have to actively contribute to the operation of the energy store, i.e. not all of them have to contribute to the provision of the total voltage that can be tapped at the energy store. If necessary, for example if the driver requests high acceleration of the motor vehicle, all battery units can be switched on so that higher battery currents and correspondingly higher power can be provided. In this case, all battery units contribute to the total voltage that can be tapped from the energy store. This also makes it possible to control the switches, particularly as far as pulsed operation is concerned, in such a way that the output voltage, ie the total voltage that can be tapped off at the energy store, does not change as a result or is not significantly influenced.

Furthermore, a motor vehicle with a heating device according to the invention or one of its configurations should also be regarded as belonging to the invention.

The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

Furthermore, the invention also relates to a method for heating at least one component of a motor vehicle by means of a heating device that has a control device and an energy store that includes at least one battery unit that has a battery cell. The battery unit has two switches, comprising a first switch and a second switch, with the first switch being connected in series with the battery cell and the second switch being connected in parallel with the first switch and in parallel with the battery cell, with at least one of the two switches acting as a first MOSFET is formed, which in a switched-on state has a switch-on channel resistance that generates heat loss and is controlled by means of a first control voltage applied to the first MOSFET, the control device controlling the first switch-on channel resistance by controlling the first control voltage as a function of a predetermined heating parameter controls to heat the at least one component by means of the generated heat loss.

The advantages described for the heating device according to the invention and its embodiments apply in the same way to the method according to the invention.

The invention also includes developments of the method according to the invention, which have features as have already been described in connection with the developments of the heating device according to the invention. For this reason, the corresponding developments of the method according to the invention are not described again here.

The invention also includes the control device for the heating device. The control device can have a data processing device or a processor device that is set up to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and/or at least one microcontroller and/or at least one FPGA (Field Programmable Gate Array) and/or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code which is set up to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

The invention also includes the combinations of features of the described embodiments. The invention also includes implementations that each have a combination of the features of several of the described embodiments, provided that the embodiments are not considered have been described as mutually exclusive.

• 1 eine schematische Darstellung einer Batterieeinheit für eine Heizeinrichtung gemäß einem Ausführungsbeispiel der Erfindung;
• 2 eine schematische Darstellung einer Batterie gemäß dem Stand der Technik;
• 3 eine schematische Darstellung eines mehrere Energieeinheiten umfassenden Energiespeichers für eine Heizeinrichtung gemäß einem Ausführungsbeispiel der Erfindung;
• 4 eine grafische Veranschaulichung der Abhängigkeit des Kanalwiderstands eines MOSFETs von der Steuerspannung im eingeschalteten Zustand für verschiedene Temperaturen, wie diese für eine Heizeinrichtung gemäß einem Ausführungsbeispiel der Erfindung verwendet wird;
• 5 eine schematische Darstellung eines Kraftfahrzeugs und eines vom Kraftfahrzeug umfassten Bordnetzes mit einer Heizeinrichtung gemäß einem Ausführungsbeispiel der Erfindung; und
• 6 eine schematische Darstellung einer Heizeinrichtung gemäß einem weiteren Ausführungsbeispiel der Erfindung.

Exemplary embodiments of the invention are described below. For this shows:

• 1 a schematic representation of a battery unit for a heating device according to an embodiment of the invention;
• 2 a schematic representation of a battery according to the prior art;
• 3 a schematic representation of a plurality of energy units comprehensive energy store for a heating device according to an embodiment of the invention;
• 4 a graphical illustration of the dependence of the channel resistance of a MOSFETs on the control voltage in the on state for different temperatures, as used for a heater according to an embodiment of the invention;
• 5 a schematic representation of a motor vehicle and an on-board network comprised by the motor vehicle with a heating device according to an exemplary embodiment of the invention; and
• 6 a schematic representation of a heating device according to a further embodiment of the invention.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that each also develop the invention independently of one another. Therefore, the disclosure is also intended to encompass combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

In the figures, the same reference symbols designate elements with the same function.

1 shows a schematic representation of a battery unit 10 for a heating device 12 (compare, for example, 3 ) according to an embodiment of the invention. This battery unit 10 is sometimes also referred to below as a smart cell. This battery unit 10 includes a battery cell 14, for example a lithium-ion cell, and two switches S1 and S2. Both switches S1, S2 are designed as MOSFETs, in particular as silicon carbide MOSFETs. The first switch S1 is connected in series with the battery cell 14, and the second switch S2 in parallel with the series connection of the first switch S1 and the battery cell 14. As a result, individual cells 14 can be connected or disconnected and bridged as desired in the subsequent storage system. If a cell 14 is to be switched on, the first switch S1 is closed and the second switch S2 is opened accordingly, and if the battery cell 14 is to be bypassed or switched off, the first switch S1 is opened and the second switch S2 is closed. The use of such smart cell battery cells 10 advantageously enables the preconditioning of a cooling medium or an entire high-voltage battery 15 (cf 3 ). Due to their ohmic conduction behavior in the on state, i.e. in the switched-on state of a respective MOSFET, which provides the corresponding switch S1, S2, a precise channel resistance and thus a precise power loss can be set.

2 shows an example of a traction memory 16 according to the prior art. This also has a number of battery cells 18 . In this example, three of the battery cells 18 are connected in parallel with one another, while these parallel circuits are in turn connected in series with one another. The battery voltage U0 is thus provided at the output 20 . In this example, individual cells 18 cannot be bridged or switched on and off.

3 shows in comparison to this a schematic representation of an energy store 15 for a heating device 12 according to an exemplary embodiment of the invention, which has a plurality of battery units 10, such as these 1 have been described includes. In other words, the energy store 15 is made up of smart cells 10 in the present case. In this example, in turn, three of these smart cells 10 are connected in parallel with one another, these parallel circuits in turn being connected in series with one another. Correspondingly, a total battery voltage UG can again be tapped off at the output 22 of the energy store 15 . The individual smart cells 10 within the energy store 15 can be connected to one another in any way. In particular, numerous other such units can be provided from battery units 10 connected in parallel, which are connected in series with one another. A respective parallel connection unit 24 can also include more or fewer than three smart cells 10, for example only one battery unit 10 or two. The

Heating device 12 now advantageously also includes a control device 26, which is designed to control the individual switches S1, S2 of a respective battery unit 10, this being shown in FIG 3 is illustrated as an example for only one of the battery units 10 . To drive the switches S1, S2, the control device 26 applies a corresponding control voltage Ugs to them. This can also differ for the respective switches S1, S2, if they are to be driven differently, with regard to their current control value or voltage level. In a heating mode, power loss can now advantageously be generated in a targeted manner by appropriate activation of the individual switches S1, S2. In this case, the control can take place as a function of a heating parameter P, which signals and/or quantizes a current heating requirement. The generation of the power loss that can be used for heating is taken over by the power semiconductors that provide the corresponding switches S1, S2, in particular the SiC (silicon carbide) MOSFETs S1, S2, since these are in the conducting state (English: On State/Output Characteristics) have an ohmic characteristic. Here, the dependence of the resistance R (compare 4 and 6 ) in the conducting state of the relevant MOSFET from the gate voltage Ugs, i.e. the control voltage Ugs. This connection is exemplified in 4 illustrated.

4 shows graphically the dependency of the channel resistance R in the conducting state of the MOSFET S1, S2 on the gate-source voltage Ugs for different temperatures based on several corresponding curves K1, K2, K3, K4, K5, K6, in particular for a SiC MOSFET with a collector current of Id of 10 amperes. Each of these curves K1 to K6 relates to a different temperature. Curve K1 represents the curve for a temperature of 150 degrees Celsius, curve K2 the curve for a temperature of 125 degrees Celsius, curve K3 the curve for a temperature of 100 degrees Celsius, curve K4 the curve for a temperature of 75 degrees Celsius, the curve K5 for a temperature of 50 degrees Celsius and the curve K6 for a temperature of 25 degrees Celsius.

As can be seen, the channel resistance R decreases as the control voltage Ugs increases. For example, in order to increase the amount of heat loss generated, the control voltage Ugs can be reduced in a targeted manner so that the channel resistance R increases accordingly. With a smaller gate voltage Ugs, the channel resistance R increases steadily and has a maximum just above its threshold voltage, which is also referred to as the threshold voltage. If the gate voltage Ugs is deliberately set to lower voltage values in the range greater than the threshold voltage and less than 18 volts, for example, defined channel resistances R can be set. These resistors R can now be used to generate power loss in a targeted manner and to heat up the cooling medium.

4 shows the physical dependency of the resistance R in the conductive state of the MOSFET S1, S2 on the respective gate voltage Ugs. With increasing gate voltage Ugs, the resistance decreases significantly, which leads to minimization of the conduction losses in vehicle operation. However, if the gate voltage Ugs is actively regulated to a low level via the gate driver, a defined resistance R can be set and used for targeted power loss generation. As a result, the high-voltage control devices known in the prior art for the PTC heaters can be omitted, which leads to considerable cost advantages in terms of manufacturing and development costs, weight reduction and increased robustness.

In order to set the specific resistances R of the MOSFETs S1, S2, it can be provided that, in addition to conventional PWM (pulse width modulation) regulation, the magnitude of the gate-source voltage Ugs is also regulated via a driver. For this shows 5 a schematic representation of a motor vehicle 27 with a vehicle electrical system 28 and a heating device 12 according to an exemplary embodiment of the invention. The vehicle electrical system 28 is divided into a low-voltage vehicle electrical system 30, for example a 12-volt vehicle electrical system, and a high-voltage vehicle electrical system 32. On the high-voltage side 32 is the high-voltage battery 15, of which only a single battery unit 10 is illustrated as an example. The control device, which can be designed as a microcontroller, controls the switches S1, S2 designed as MOSFETs via a gate driver 34. In the present example, the gate connection of a respective switch S1, S2 is denoted by G, the source connection by S and the drain connection by D.

The communication as well as the voltage supply for the control device 26, in particular the microcontroller, takes place via the low-voltage vehicle electrical system 30. A supply voltage, for example 20 volts, can be generated on the high-voltage side 32 via a galvanically isolated DC/DC converter 36, which the circuit parts of the Smart cell 10 supplied on the high-voltage side 32. Communication takes place via bus communication, for example CAN bus, with the vehicle. The corresponding communication unit is in 5 denoted by 38 and can be designed as a CAN transceiver. Communication is via a galvanically isolated digital isolator 40 brought up to the control device 26. In addition, the control device 26 can ascertain further information, for example cell voltage, cell currents, cell temperatures and so on. A unit 42 for measuring the voltage and a unit 44 for measuring the current via a current measuring shunt 46 can also be provided for this purpose. The unit for the temperature measurement is denoted by 48. These measured variables can be transmitted back to the low-voltage side 30 via the digital isolator 40 and communicated to the vehicle via the bus transceiver, that is to say the communication unit 38 . Furthermore, 50 designates the voltage supply for the low-voltage vehicle electrical system 30, and 52 the voltage supply for the control device 26, with the voltage supply 52 being able to provide a 5-volt voltage, for example, and also being designed as a DC/DC converter. Furthermore, a voltage supply for the gate driver 34 is denoted by 54 . This voltage supply 54 can provide two different voltage values, for example 15 volts, which can be used accordingly as the switch-on voltage, and -8 volts, which can be used accordingly as the switch-off voltage. These voltage values therefore correspond to the different switching states of the switches S1, S2. In order to keep one of the switches S1, S2 in the closed state, the positive voltage of 15 volts can be applied to the gate terminal G, while the voltage of -8 volts corresponds to the open state of the power switches S1, S2 in question. As already described above, the switch-on voltage level of 15 volts can be regulated, ie this value can also be regulated to lower voltage level values by the gate driver in order to correspondingly increase the channel resistance R and correspondingly generate more power loss.

According to the prior art, the illustrated control voltages, that is, for example, the switch-on voltage of +15 volts, are constant voltages and cannot be regulated. Thus, from the prior art, MOSFETs are turned on with a typical voltage of +15 volts and turned off with a voltage of -8 volts.

A regulation of the gate-source voltage level is now provided within the scope of the invention. It is thus possible to set the channel resistance R of the MOSFETs S1, S2 precisely and, for example, to generate losses in a targeted manner.

6 shows, according to a schematic representation, the resulting resistance network in the switched-on state of the MOSFETs, ie the respective first and second switches S1, S2. In particular shows 6 again in a schematic representation, an example of a heating device 12 with a high-voltage battery 15, which in turn is made up of several individual battery units 10. The heating device 12 can be designed as described above, in particular as to 3 described. In this example, only two such battery units 10 are connected in parallel to one another and result in a parallel connection unit 24 instead of three battery units 10 as in FIG 3 . A plurality of these parallel connection units 24 are also connected in series with one another here as well. A further number of such parallel circuit units 24 can be provided. In principle, the energy store 15 can include any number of battery cells 14 and corresponding battery units 10 . To activate the switches S1, S2, the control device 26 applies a corresponding control voltage Ugs to them as a function of the heating parameter P, this only being illustrated here for one of the battery units 10 for reasons of clarity. The individual switches S1, S2 are illustrated as their channel resistances R in the resistance equivalent circuit diagram. Due to the existing, very good connection of the MOSFETs S1, S2 to active cooling, there is the best possible option for dissipating power loss and thus heat Q into the cooling medium. A cooling device is denoted by 56 in the present case. This cooling device 56 can be connected to a cooling circuit. The cells 14 can also be coupled to a further cooling device connected to this cooling circuit.

Furthermore, by controlling the gate-source voltage level, it is possible to control or set a wide variety of heating powers by means of different channel resistances R to be set. A power loss and thus heat loss Q can now be generated in a targeted manner via the resistances R set in the switched-on state of the respective switches S1, S2, and the high-voltage storage device 15 can thus be preconditioned. The precise setting of the power loss and thus the heat loss Q takes place via pulsed operation of the respective MOSFETs, i.e. via clocked operation. The switch-on voltage Ugs is regulated in such a way that the desired resistance value R and thus the desired power loss or heat loss Q result.

Overall, the examples show how the invention can be used to precondition the high-voltage battery through the targeted introduction of power loss in the smart cell semiconductors through active regulation of the gate-emitter voltage, i.e. the gate-source voltage, and the setting of the drain Source on-resistance can be provided.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102013018411 A1 [0003]
• DE 102013017342 A1 [0004]
• DE 102017200088 A1 [0005]

Claims (10)

Heating device (12) for heating at least one component (15) of a motor vehicle (27), the heating device (12) having a control device (26) and an energy store (15) which comprises at least one battery unit (10) which has a battery cell ( 14), characterized in that the battery unit (10) has two switches (S1, S2) comprising a first switch (S1) and a second switch (S2), the first switch (S1) being connected to the battery cell (14) in is connected in series and the second switch (S2) is connected in parallel to the first switch (S1) and to the battery cell (14), at least one of the two switches (S1, S2) being designed as a first MOSFET (S1, S2) which in a switched-on state, has a first switch-on channel resistance (R) that can be controlled by means of a first control voltage (Ugs) that can be applied to the first MOSFET (S1, S2) and generates heat loss (Q), wherein the control device (26) is designed to transmit the first Switch-on channel resistance (R) by controlling the first control voltage (Ugs) as a function of a predetermined heating parameter (P) in order to heat the at least one component (15) by means of the generated heat loss (Q). Heating device (12) after claim 1 , characterized in that the energy store (15) represents the component (15). Heating device (12) according to one of the preceding claims, characterized in that the control device (26) is designed to control the first switch-on channel resistance (R) in such a way that the first switch-on channel resistance (R) is greater in a heating mode, than in an operation mode different from the heating mode. Heating device (12) according to one of the preceding claims, characterized in that the control device (26) is designed to, in the heating mode, an extreme switch-on voltage level of the control voltage (Ugs) - to only a predetermined value which is at a specific value of the first switch-on channel resistance (R) corresponds; or - set to different values depending on the heating parameter (P), each corresponding to different values of the first turn-on channel resistance (R). Heating device (12) according to one of the preceding claims, characterized in that both switches (S1, S2) are designed as MOSFETs (S1, S2) comprising the first MOSFET (S1, S2) and a second MOSFET (S1, S2) which in a switched-on state, has a second switch-on channel resistance (R) that can be controlled by means of a second control voltage (Ugs) that can be applied to the second MOSFET (S1, S2) and generates heat loss (Q), wherein the control device (26) is designed to transmit the second To control the switch-on channel resistance (R) by controlling the second control voltage (Ugs) depending on the predetermined heating parameter (P) in order to heat the at least one component (15) by means of the generated heat loss (Q). Heating device (12) according to one of the preceding claims, characterized in that at least the first MOSFET (S1, S2) or a substrate on which the first MOSFET (S1, S2) is arranged is coupled or can be coupled to a cooling circuit (56). is to deliver the lost heat (Q) to the cooling circuit (56). Heating device (12) according to one of the preceding claims, characterized in that at least the first MOSFET (S1, S2) or a substrate on which the first MOSFET (S1, S2) is arranged is arranged on the battery cell (14) in order to to deliver the lost heat (Q) to the battery cell (14). Heating device (12) according to one of the preceding claims, characterized in that at least the first MOSFET (S1, S2) is operated in clocked mode in the heating mode. Heating device (12) according to one of the preceding claims, characterized in that the energy store (15) has a plurality of battery units (10) connected to one another, the switches (S1, S2) of which can be controlled by the control device (26) as a function of a power requirement parameter in such a way that that all or only some of the several battery units (10) contribute to the provision of a total voltage (UG) that can be tapped off at the energy store (15). Method for heating at least one component (15) of a motor vehicle (27) by means of a heating device (12) which has a control device (26) and an energy store (15) which comprises at least one battery unit (10) which has a battery cell (14) characterized in that the battery unit (10) has two switches (S1, S2) comprising a first switch (S1) and a second switch (S2), the first switch (S1) being connected in series with the battery cell (14). and the second switch (S2) is connected in parallel to the first switch (S1) and to the battery cell (14), at least one of the two switches (S1, S2) being designed as a first MOSFET (S1, S2) which is in a switched-on state has a waste heat (Q) generating switch-on channel resistance (R) which is controlled by means of a first control voltage (Ugs) applied to the first MOSFET (S1, S2), the control device (26) changing the first turn-on channel resistance (R) by controlling the first control voltage (Ugs) as a function of a predetermined heating parameter (P) controls in order to heat the at least one component (15) by means of the generated heat loss (Q).

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