DC voltage converter arrangement, electric vehicle and method for operating a DC voltage converter arrangement

Abstract

The invention discloses a DC voltage converter arrangement for supplying energy to a low-voltage supply system from a high-voltage supply system in an electric vehicle. The DC voltage converter arrangement comprises, in addition to a DC voltage converter, a supplementary auxiliary voltage supply system. This auxiliary voltage supply system can supply control components of the DC voltage converter with electrical energy. The voltage supply system can further feed electrical energy into the low-voltage supply system so that the DC voltage converter can be deactivated when there is a low power requirement in the low-voltage supply system.

Description

[0001] Description

[0002] title and procedures for

[0003] Operating a DC voltage

[0004] Technical area

[0005] The present invention relates to a DC-DC converter arrangement, in particular a DC-DC converter arrangement for transmitting electrical energy from a high-voltage network to a low-voltage network. The present invention further relates to an electric vehicle having such a DC-DC converter arrangement and a method for operating such a DC-DC converter arrangement.

[0006] background

[0007] Vehicles that are fully or at least partially electrically powered usually have two on-board electrical systems. A high-voltage system has an electrical voltage of several hundred volts, for example 400 or 800 volts. This high-voltage system usually contains an electrical energy storage device such as a traction battery. This high-voltage system is primarily used to supply energy to electrical consumers with high power consumption, such as the vehicle's electric drive system and, if applicable, air conditioning units or similar. In addition, electrical consumers with lower power consumption, such as control units, sensors, actuators, comfort functions or multimedia applications, can be supplied with electrical energy via a low-voltage system. This low-voltage system can, for example, have an electrical voltage in the range of 12 volts.

[0008] The publication DE 10 2013 225 097 describes an energy management method for operating an electrical system of a motor vehicle with a high-voltage network and a low-voltage network, wherein in a standby state a consumer in the low-voltage network is supplied with electrical energy from the high-voltage network.

[0009] Disclosure of the invention

[0010] The present invention provides a DC-DC converter assembly, an electric vehicle, and a method for operating a DC-DC converter assembly having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0011] Accordingly, it is provided:

[0012] A DC-DC converter arrangement comprising a DC-DC converter and an auxiliary voltage supply. The DC-DC converter is designed to be coupled to a high-voltage network at a first terminal. Furthermore, the DC-DC converter is designed to be coupled to a low-voltage network at a second terminal. The auxiliary voltage supply is designed to be coupled to the high-voltage network at an input terminal. Furthermore, the auxiliary voltage supply is designed to be coupled to the low-voltage network at an output terminal. Furthermore, the auxiliary voltage is designed to provide a supply voltage for the control circuit at a control circuit of the DC-DC converter.

[0013] Furthermore, it is planned:

[0014] An electric vehicle with a high-voltage network, a low-voltage network and a DC-DC converter arrangement according to the invention.

[0015] Furthermore, it is planned:

[0016] A method for operating a DC-DC converter arrangement, in particular a DC-DC converter arrangement according to the invention. The method comprises a step for monitoring the output of electrical power from the DC-DC converter arrangement into the low-voltage network. The method further comprises a step for deactivating the DC-DC converter if the electrical power from the DC-DC converter arrangement into the low-voltage network falls below a predetermined first threshold. The method further comprises a step for activating the DC-DC converter if the electrical power from the DC-DC converter arrangement into the low-voltage network exceeds a predetermined second threshold. The first threshold and the second threshold can be set to be equal. Alternatively, a hysteresis between the first threshold and the second threshold can also be provided.

[0017] Advantages of the invention

[0018] Electric vehicles usually have a high-voltage network and a low-voltage network, which are linked together via a DC-DC converter arrangement. If such a vehicle is in idle or parked mode, for example, some consumers in the low-voltage network are still active. In conventional systems, these consumers can be supplied with electrical energy via a battery in the low-voltage network, for example. This battery is usually heavy, takes up space and is expensive. However, if this battery is to be omitted, the energy required for the low-voltage network must be provided from the high-voltage network via the DC-DC converter arrangement, even when the vehicle is parked. The DC-DC converter usually used in the DC-DC converter arrangement, however, has a rather low efficiency due to the low power output of a parked vehicle.This means that electrical losses increase when the vehicle is at rest.

[0019] It is therefore an idea of ​​the present invention to provide an auxiliary voltage tracking device in a DC-DC converter arrangement for coupling the high-voltage network with the low-voltage network. This auxiliary voltage supply can, on the one hand, provide the power supply for control components in a DC-DC converter of the DC-DC converter arrangement. Furthermore, the auxiliary voltage supply can provide the required electrical energy for the low-voltage network even when the power demand in the low-voltage network is low.

[0020] In this way, when power demand in the low-voltage network is low, the DC-DC converter in the DC-DC converter arrangement can be deactivated. Since such an arrangement can always ensure efficient energy transfer from the high-voltage network to the low-voltage network, an additional energy storage device, such as a battery, in the low-voltage network of the electric vehicle can be omitted. This means that even a parked vehicle can have a continuous and efficient energy supply to the consumers in the low-voltage network. The increased efficiency of energy transfer, particularly when energy consumption in the low-voltage network is low, also means that the energy drawn from the traction battery in the high-voltage network can be reduced when the vehicle is parked. This reduces the risk of the traction battery being drained too quickly when the vehicle is parked.

[0021] The high-voltage network and the low-voltage network can each be direct current networks with an electrical voltage at a predetermined voltage level. In principle, it is also possible for the high-voltage network and / or the low-voltage network to comprise several separate subnetworks. These individual subsets can be completely separated from one another. The individual subnetworks of the high-voltage network or the low-voltage network can be electrically coupled to one another, if necessary, using suitable switching or isolating elements.

[0022] According to one embodiment, the auxiliary power supply is designed to use an electrical voltage from the high-voltage network to provide a low-voltage voltage that is galvanically isolated from the high-voltage network to the control circuit of the DC-DC converter and in the low-voltage network. The galvanic isolation of the high-voltage network from the low-voltage side of the auxiliary power supply enables a reliable power supply to the low-voltage consumers. For example, the galvanic isolation can be implemented using a transformer or similar device.

[0023] According to one embodiment, the auxiliary power supply is designed to set a predefined target voltage in the low-voltage network. The target voltage can also be dynamically adjusted if necessary. This allows, for example, the new voltage in the low-voltage network to be reached as quickly as possible in the event of a sudden change in the target voltage. In this way, the auxiliary power supply can stabilize the voltage level in the low-voltage network. In particular, the auxiliary power supply can regulate the target voltage in the low-voltage network within predetermined power limits. In other words, the maximum power or the maximum output current of the auxiliary power supply is limited to a predefined maximum value.

[0024] According to one embodiment, the auxiliary power supply is designed to provide a high-voltage voltage for the high-voltage network that is galvanically isolated from the low-voltage network using an electrical voltage from the low-voltage network. In particular, the auxiliary power supply can provide bidirectional energy transfer between the high-voltage network and the low-voltage network.

[0025] According to one embodiment, the DC-DC converter arrangement comprises a control device. The control device can be designed to activate the DC-DC converter if the electrical power from the auxiliary voltage supply to the low-voltage network exceeds a predetermined threshold. This allows the DC-DC converter to take over the energy supply to the low-voltage network as the power demand in the low-voltage network increases. This ensures a reliable energy supply in the low-voltage network, even if the power demand exceeds a maximum permissible power output of the auxiliary voltage supply. Therefore, the auxiliary voltage supply can be optimized for a low maximum power output, which is typically sufficient for the energy demand of a stationary vehicle as well as the energy demand for starting the DC-DC converter from standby mode.

[0026] According to one embodiment, the DC-DC converter assembly comprises a switching device. The switching device can be designed to open or close an electrical connection between the auxiliary voltage supply and the low-voltage network. In this way, the output of the auxiliary voltage supply can be electrically coupled to the low-voltage network only when needed.

[0027] According to one embodiment, the switching device of the DC-DC converter arrangement is designed to open the electrical connection between the auxiliary power supply and the low-voltage network if the DC-DC converter is active. Thus, the output of the auxiliary power supply can be decoupled from the low-voltage network if the low-voltage network is supplied with power via the DC-DC converter of the DC-DC converter arrangement. This way, for example, the auxiliary power supply can be protected from interference from the low-voltage network.

[0028] According to one embodiment, the DC-DC converter arrangement comprises a first buffer element. This first buffer element can be electrically coupled to the low-voltage network. In particular, the first buffer element can be designed to compensate for voltage fluctuations in the low-voltage network. The first buffer element can be, for example, a capacitor or a battery with a very low storage capacity.

[0029] According to one embodiment, the DC-DC converter arrangement comprises a second buffer element. The second buffer element can be designed to be electrically coupled to the control circuit and to compensate for voltage fluctuations in the supply voltage of the control circuit. In this way, voltage fluctuations in the control circuit can be compensated, thus ensuring a stable supply voltage. The second buffer element can also be, for example, a capacitor or a battery with a very low storage capacity.

[0030] According to one embodiment of the electric vehicle, the DC-DC converter assembly is designed to deactivate the DC-DC converter when the vehicle is parked. In particular, the DC-DC converter can be deactivated if the energy consumption of loads in the low-voltage network falls below a predetermined limit during idle or parked operation. In such a case, typically only a few loads, such as control components for keyless vehicle access, are active. Therefore, the energy demand in the low-voltage network in this state can be covered solely by the auxiliary power supply.

[0031] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0032] Short description of the drawings

[0033] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0034] Fig.l: a schematic representation of a block diagram of a power supply system for an electric vehicle with a DC-DC converter arrangement according to an embodiment;

[0035] Fig. 2: a schematic representation of a block diagram of a DC-DC converter arrangement according to an embodiment; and Fig. 3: a flowchart underlying a method for operating a DC-DC converter arrangement according to an embodiment.

[0036] Description of embodiments

[0037] Figure 1 shows a schematic representation of an electrical energy supply such as may underlie an electric vehicle. For example, such an electric vehicle may be provided with a high-voltage network 2 and a low-voltage network 3. The high-voltage network 2 may be supplied, for example, by an electrical energy storage device such as a traction battery 20. High-power consumers such as an electric drive system, an air conditioning unit, or possibly other electrical consumers can be supplied via this high-voltage network 2. The low-voltage network 3 may comprise a plurality of electrical consumers 30 with lower power consumption. For example, these consumers 30 may comprise control units, sensors, actuators, auxiliary drives, comfort functions, multimedia components, or the like.Furthermore, this low-voltage network 2 can also contain components for keyless access and communication devices for communication with remote devices, such as a smartphone or similar. This allows certain functions, such as preheating or cooling the vehicle, to be remotely controlled via such wireless connections.

[0038] The high-voltage network 2 can be electrically coupled to the low-voltage network 3 via a DC-DC converter arrangement 1. In this way, the loads 30 in the low-voltage network 3 can be supplied with electrical energy from the high-voltage network 2. In the embodiment shown here, an electrical energy storage device such as a lead battery or similar in the low-voltage network 3 can be expressly dispensed with.

[0039] The DC-DC converter assembly 1 comprises a DC-DC converter 11. This DC-DC converter 11 can convert electrical energy from the high-voltage network 2 into an electrical voltage that corresponds to the electrical voltage in the low-voltage network 3. The DC-DC converter 11 is generally designed for electrical power levels that can also cover the power requirements in the low-voltage network 3 at full load. If necessary, the DC-DC converter 11 can comprise a parallel connection of several DC-DC converter units.

[0040] The DC-DC converter 11 can be controlled via a control circuit 13. The control circuit 13 can take into account setpoint and actual values ​​of the DC-DC converter arrangement 1 for the control process. In particular, semiconductor switching elements in the DC-DC converter 11 can be controlled via corresponding driver circuits in the control circuit 13.

[0041] Furthermore, an auxiliary voltage supply 12 is provided in the DC-DC converter arrangement 1. An input of this auxiliary voltage supply 12 is electrically coupled to the high-voltage network 2, so that the auxiliary voltage supply 12 can continuously draw its electrical energy from this high-voltage network 2. This auxiliary voltage supply 12 can, in particular, supply the control circuit 13 with electrical energy. The output voltages provided by the auxiliary voltage supply 12 are galvanically isolated from the high-voltage network 2. For this purpose, a transformer or similar device can be provided in the auxiliary voltage supply 12 for galvanic isolation.

[0042] In addition, the auxiliary voltage supply 12 can also provide electrical energy for the low-voltage network 3. However, the maximum power output by the auxiliary voltage supply 12 is limited and significantly lower than the maximum power output by the DC-DC converter 11. The maximum possible power output of the auxiliary voltage supply 12 can be dimensioned such that the electrical power provided by the auxiliary voltage supply 12 is sufficient to cover the power requirements of the electrical consumers 30 in the low-voltage network 3 when the vehicle is parked or at rest.Since in such a case, typically only a few components are active in the low-voltage network 3, for example, a receiver for a remote key, components for communication with remote devices, or possibly sensors for an alarm system, the auxiliary power supply 12 can be designed for a relatively low maximum power output while maintaining high efficiency. This allows the standby current requirement of such a vehicle to be reduced.

[0043] As long as the energy demand for the consumers 30 in the low-voltage network 3 can be met by the auxiliary voltage supply 12, especially when the vehicle is stationary, the DC-DC converter 11 can be deactivated. In other words, the energy supply for the low-voltage network 3 is provided entirely via the auxiliary voltage supply 12.

[0044] If the power demand in the low-voltage network 3 exceeds a predetermined threshold, the DC-DC converter 11 can be activated to cover the increased power demand in the low-voltage network 3. Since the auxiliary voltage supply 12 also supplies the control circuit 13 for the DC-DC converter 11 with electrical energy, such activation is possible at any time.

[0045] Furthermore, it is also possible for the auxiliary power supply 12 to transfer electrical energy from the high-voltage network 2 to the low-voltage network 3 (or possibly in the opposite direction) in parallel, i.e., simultaneously with the DC-DC converter 11. In this way, the energy transfer can be controlled, if necessary, such that the DC-DC converter 11 and / or the auxiliary power supply 12 can be operated at the most efficient operating point possible.

[0046] In particular, in this mode of operation, the auxiliary voltage supply 12 can support the energy transfer between the high-voltage network 2 and the low-voltage network 3, even in the ferry operation of an electric vehicle.

[0047] The DC-DC converter 11 and / or the auxiliary voltage supply 12 can, if necessary, also be designed for bidirectional energy transfer between the high-voltage network 2 and the low-voltage network 3. In particular, the power flow through the auxiliary voltage supply 12 can also be limited to a maximum power or a maximum output current. In this way, electrical energy can also be transferred from the low-voltage network 3 towards the high-voltage network 2 if necessary. For example, the energy transfer or the power flow between the high-voltage network 2 and the low-voltage network 3 can be controlled such that an electrical voltage in the low-voltage network 3 is stabilized at a predetermined setpoint. If necessary, the control can also dynamically adjust the electrical voltage in the low-voltage network between a minimum and a maximum setpoint within a predetermined voltage range.

[0048] Figure 2 shows a schematic representation of a block diagram for a DC-DC converter arrangement 1 according to one embodiment. This can, in particular, be the previously described DC-DC converter arrangement 1 according to Figure 1.

[0049] As can be seen in Figure 2, the auxiliary voltage supply 12 can comprise a control device 14. The assembly shown here as a separate control device 14 or its functionality can optionally also be integrated into the control circuit 12 already described. The control device 14 can control the components of the DC-DC converter arrangement 1 and in particular activate or deactivate the DC-DC converter 11. In addition, the control device 14 can also control the further components of the DC-DC converter arrangement 1 described below. For this purpose, the control device 14 can, for example, determine the power requirement for the low-voltage network 3. For this purpose, the control device 14 can, for example, evaluate measured values ​​from current sensors (not shown) in order to determine the electrical current from the DC-DC converter arrangement 1 into the low-voltage network 3 and thus the corresponding power.In addition, the control device 14 can also receive further data or signals. For example, the control device 14 can receive information about an operating state of the vehicle. Accordingly, the control device 14 can, for example, activate the DC-DC converter 11 of the DC-DC converter arrangement 1 only when the vehicle is in a predetermined operating state, for example, in a parking or idle mode. Furthermore, the control device 14 can activate the DC-DC converter 11 when an increased power demand exists in the low-voltage network 3 or is expected based on received data.

[0050] Furthermore, a limit for current, voltage, and / or power can be provided for the auxiliary power supply 12. This ensures that the auxiliary power supply 12 is neither overloaded nor that components in the connected high-voltage and low-voltage networks 2, 3 are damaged. Furthermore, the auxiliary power supply 12 can be started automatically if a low-voltage voltage is absent or falls below a certain level in the low-voltage network 3.

[0051] The control of the auxiliary voltage supply 12 can be controlled or regulated either digitally, for example from a central common control unit 13 for the DC-DC converter 11 or a separate control device 14, or also analogously.

[0052] Furthermore, a switching element 15 can be provided in the DC-DC converter arrangement 1, for example, between the auxiliary voltage supply 12 and the low-voltage network 3. This switching element 15 can be closed to establish an electrical connection between the auxiliary voltage supply 12 and the low-voltage network 3. In this state, the auxiliary voltage supply 12 can thus feed electrical energy into the low-voltage network 3. By opening this switching element 15, the electrical connection between the auxiliary voltage supply 12 and the low-voltage network 3 can be interrupted. The switching element 15 can be opened, for example, when the energy supply to the low-voltage network 3 is via the DC-DC converter 11. In this state, any influences from the low-voltage network 3 on the auxiliary voltage supply 12 can thus be avoided.The switching state of the switching element 15 can be controlled, for example, via the control device 14.

[0053] In addition, at the position of reference number 15, i.e. between

[0054] Auxiliary voltage supply 12 and the connection of the DC-DC converter arrangement 11 to the low-voltage network 3, further components, such as filter assemblies, may also be provided, which eliminate or at least partially suppress the frequency of the signals and interference pulses.

[0055] Furthermore, a buffer element 16 can be provided in the DC-DC converter arrangement 1, for example. This buffer element can, in particular, be electrically coupled to the low-voltage network 3. These buffer elements 16 can be, for example, a capacitor or a small battery with a low capacity. Such a buffer element 16 can compensate for voltage fluctuations in the low-voltage network 3. Such voltage fluctuations can occur, for example, during a brief increase in power demand in the low-voltage network 3 or during a change in the power supply between the auxiliary voltage supply 12 and the DC-DC converter 11.

[0056] Additionally or alternatively, a further buffer element 19 may also be provided, which stabilizes the supply voltage for the control circuit 13. This further buffer element 19 may also be, for example, a capacitor or a small battery with a low capacity.

[0057] Figure 3 shows a flowchart that may form the basis of a method for operating a DC-DC converter assembly 1 according to one embodiment. The DC-DC converter assembly 1 may, in particular, be the previously described DC-DC converter assembly 1 according to Figure 1 or 2. Accordingly, the above-mentioned statements also apply to the method described below. Furthermore, the previously described DC-DC converter assembly 1 may also comprise any components that may be required to implement the method described below.

[0058] In a step S1, the electrical power output from the DC-DC converter assembly 1 to the low-voltage network 3 is monitored. In step S2, the DC-DC converter 11 of the DC-DC converter assembly 1 is deactivated if the electrical power from the DC-DC converter assembly 1 to the low-voltage network 3 falls below a predetermined first threshold. In particular, the DC-DC converter 11 can, if necessary, only be activated when an electric vehicle with the DC-DC converter assembly 1 is in a predetermined operating state, for example, in a rest or parking mode or the like.

[0059] In step S3, the DC-DC converter 11 can be activated if the electrical power from the DC-DC converter assembly 1 to the low-voltage network 3 or the power demand in the low-voltage network 3 exceeds a predetermined second threshold. Furthermore, the DC-DC converter 11 can also generally be activated when the operating state of the vehicle changes. For example, the DC-DC converter 11 can be activated when the vehicle's idle state is ended.

[0060] If necessary, the predetermined first threshold and the predetermined second threshold can be set to be equal. Alternatively, a hysteresis between the predetermined first threshold and the predetermined second threshold is also possible.

[0061] In summary, the present invention relates to a DC-DC converter arrangement for supplying power to a low-voltage network from a high-voltage network in an electric vehicle. In addition to a DC-DC converter, the DC-DC converter arrangement comprises an additional auxiliary power supply. This auxiliary power supply can, on the one hand, supply control components of the DC-DC converter with electrical power. On the other hand, the power supply can also feed electrical power into the low-voltage network, so that the DC-DC converter can be deactivated when the power demand in the low-voltage network is low.

Claims

Claims 1. DC voltage converter arrangement (1), comprising: a DC voltage converter (11) which is designed to be coupled to a high-voltage network (2) at a first terminal and to be coupled to a low-voltage network (3) at a second terminal, and an auxiliary voltage supply (12) which is designed to be coupled to the high-voltage network (2) at an input terminal, to be coupled to the low-voltage network (3) at an output terminal, and to provide a supply voltage for the control circuit (13) at a control circuit (13) of the DC voltage converter (11).

2. DC voltage converter arrangement (1) according to claim 1, wherein the auxiliary voltage supply (12) is designed to provide a low voltage, which is galvanically separated from the high-voltage network (2), to the control circuit (13) of the DC voltage converter (11) and in the low-voltage network (3) using an electrical voltage from the high-voltage network (2).

3. DC voltage converter arrangement (1) according to claim 2, wherein the auxiliary voltage supply (12) is designed to set a predetermined target voltage in the low-voltage network (3) within predetermined power limits.

4. DC voltage converter arrangement (1) according to one of claims 1 to 3, wherein the auxiliary voltage supply (12) is designed to provide a high voltage for the high voltage network (2) that is galvanically separated from the low voltage network (3) using an electrical voltage from the low voltage network (3). DC voltage converter arrangement (1) according to one of claims 1 to 4, with a control device (14) designed to activate the DC-DC converter (11) if an electrical power delivered from the auxiliary voltage supply (12) into the low-voltage network (3) exceeds a predetermined threshold value. DC-DC converter arrangement (1) according to one of claims 1 to 5, with a switching device (15) designed to open or close an electrical connection between the auxiliary voltage supply (12) and the low-voltage network (3). DC voltage converter arrangement (1) according to claim 6, the switching device (15) is designed to open the electrical connection between the auxiliary voltage supply (12) and the low-voltage network (3) if the DC voltage converter (11) is active. DC voltage converter arrangement (1) according to one of claims 1 to 7, with a first buffer element (16) designed to be electrically coupled to the low-voltage network (3) and to compensate for voltage fluctuations in the low-voltage network. DC voltage converter arrangement (1) according to one of claims 1 to 5, with a second buffer element (19) designed to be electrically coupled to the control circuit (13) and to compensate for voltage fluctuations at the supply voltage of the control circuit (13).Electric vehicle, comprising: a high-voltage network (2), a low-voltage network (3); and a DC voltage converter arrangement (1) according to one of claims 1 to 9. Electric vehicle according to claim 10, wherein the The DC voltage converter assembly (1) is designed to deactivate the DC voltage converter (11) in a standby mode of the electric vehicle if the energy consumption of consumers (30) in the low-voltage network (3) falls below a predetermined limit. A method for operating a DC voltage converter assembly (1) according to claim 1, comprising the steps: Monitoring (Sl) a delivery of electrical power from the DC voltage converter arrangement (1) into the low-voltage network (3); Deactivating (S2) the DC-DC converter (11) if the electrical power from the DC-DC converter arrangement (1) into the low-voltage network (3) falls below a predetermined first threshold value; Activating (S3) the DC-DC converter if the electrical power from the DC-DC converter assembly (1) to the low-voltage network (3) exceeds a predetermined second threshold. The method according to claim 12, wherein the DC-DC converter (11) is only deactivated if the electric vehicle with the DC-DC converter assembly (1) is in a predetermined operating mode.

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