Converter system for transmitting electric power

Abstract

This disclosure relates to a converter system for transmitting electricity, a vehicle including such a converter system, and a method for transmitting electricity. The converter system includes a first DC / DC converter module, a second DC / DC converter module, and a control unit. The first DC / DC converter module is connectable to a first high-voltage system and at least connected to a first low-voltage system. The second DC / DC converter module is connectable to a second high-voltage system and at least connected to the first low-voltage system. The first DC / DC converter module includes at least a first main DC / DC converter unit and a first micro DC / DC converter unit. The second DC / DC converter module includes at least a second micro DC / DC converter unit. The first and second micro DC / DC converter units are connectable via a first bidirectional switch unit. The control unit is configured to transmit power from the first high-voltage system to the first low-voltage system via the first micro DC / DC converter unit if the first main DC / DC converter unit is deactivated.

Description

Technical Field

[0001] This disclosure relates to a converter system for transmitting electricity, a vehicle including such a converter system, and a method for transmitting electricity. Background Technology

[0002] In electric vehicles, different power conversion modules exist, each functioning in different scenarios. For example, an onboard charger converts AC to DC to charge the high-voltage battery, while a traction inverter converts DC to AC to drive the vehicle. In both scenarios, either the onboard charger or the traction inverter functions normally. However, to supply power to low-voltage loads and maintain low voltage, the DC-DC converter that transfers power from the high-voltage battery to the low-voltage load must function normally in both scenarios.

[0003] Compared to other power conversion modules, DC-DC converters generally withstand greater stress, making their design more complex. In conventional electric vehicles, the low-voltage control unit relies on the low-voltage battery for power. If the DC-DC converter fails during driving, some vehicle functions powered by the low-voltage system may be at risk, especially when the low-voltage battery's state of charge is low. Furthermore, the DC-DC converter is shut down when the vehicle is keyed off. Therefore, if the vehicle is parked for several months, the low-voltage battery will be deeply discharged, and the vehicle may be completely shut down. Summary of the Invention

[0004] Therefore, it may be necessary to provide an improved converter system that allows for a more reliable low-voltage supply.

[0005] The subject matter of the independent claims of this disclosure at least partially addresses or mitigates this problem, wherein further examples are incorporated in the dependent claims. It should be noted that aspects of this disclosure are described in the context of converter systems for transmitting electricity, vehicles including such converter systems, and methods for transmitting electricity.

[0006] According to this disclosure, a converter system for transmitting power is presented. The converter system includes a first DC / DC converter module, a second DC / DC converter module, and a control unit. The first DC / DC converter module is connectable to a first high-voltage system and at least connected to a first low-voltage system. The second DC / DC converter module is connectable to a second high-voltage system and at least connected to the first low-voltage system. The first DC / DC converter module includes at least a first main DC / DC converter unit and a first micro DC / DC converter unit. The second DC / DC converter module includes at least a second micro DC / DC converter unit. The first and second micro DC / DC converter units are connectable via a first bidirectional switch unit. The control unit is configured to transmit power from the first high-voltage system to the first low-voltage system via the first micro DC / DC converter unit if the first main DC / DC converter unit is deactivated. The control unit is also configured to disconnect the first bidirectional switch unit to transmit power from the second high-voltage system to the first low-voltage system via the second micro DC / DC converter unit if the first main DC / DC converter unit is deactivated and the first micro DC / DC converter unit fails.

[0007] The converter system disclosed herein can reduce the risk of single-point failure within the converter system (i.e., the first DC / DC converter module, the second DC / DC converter module). Specifically, even in the event of a failure in the first converter unit and / or the second converter unit, the converter system can still operate by supplying power to (one or more) low-voltage systems under different vehicle usage scenarios (driving, charging, and / or parking, etc.). Therefore, a high degree of safety integration of the converter system can be achieved.

[0008] Additionally, low-voltage systems can be interconnected within the same housing as the power converter system to ensure maximum power availability and deliver power with the highest efficiency. When the vehicle is not in a driving state, optimal efficiency can be achieved by controlling the output voltage of the DC / DC converter unit.

[0009] The first DC / DC converter module and / or the second DC / DC converter module can transfer power from a high-voltage system to a low-voltage system. The high-voltage system can provide a voltage of 400V or 800V. However, the input voltage of the high-voltage system can vary depending on the configuration of the high-voltage system. For example, depending on the configuration of the high-voltage system, the input voltage of the high-voltage system can vary between 250V and 500V in the case of 400V, and between 500V and 1000V in the case of 800V.

[0010] The first DC / DC converter module and / or the second DC / DC converter module can operate according to load consumption to maximize the efficiency of the converter system. In other words, the first DC / DC converter module and / or the second DC / DC converter module can operate individually or together to provide efficient power.

[0011] The first and second DC / DC converter modules may include isolated DC / DC converter elements. These isolated elements may be electrically isolated and can prevent overvoltages due to isolation failures in the higher-voltage sections of the converter system. The isolated DC / DC converter elements allow for lower costs of at least one auxiliary component and enable compatibility with existing fast-charging DC charging stations.

[0012] Each of the first and second high-voltage systems may include a high-voltage interface that ensures reliable connections between the first DC / DC converter module and the first high-voltage system, and between the second DC / DC converter module and the second high-voltage system, respectively. Each high-voltage system may include one or more battery cells. The first and second high-voltage systems may be identical or separate from each other.

[0013] Similarly, the first low-voltage system may also include a first low-voltage interface to ensure a reliable connection between the first DC-DC module and the first low-voltage system and / or between the second DC / DC converter module and the first low-voltage system. The first low-voltage system may be coupled to low-voltage loads, such as control components for opening doors or windows, starting motors, steering and braking loads.

[0014] The first main DC / DC converter unit can be designed to provide high power, for example, in the range of 3kW to 4kW when activated. The first micro DC / DC converter unit can be designed to provide lower power, for example, in the range of 50W to 200W, when the first main DC / DC converter unit is deactivated and the first micro DC / DC converter unit is activated. If the converter system can be integrated into a vehicle, then the first main DC / DC converter unit can be deactivated during the vehicle's parking state, and only the first micro DC / DC converter unit and / or the second micro DC / DC converter unit can be activated to supply power to low-voltage loads.

[0015] The second DC / DC converter module may also have a similar composition and include at least a second micro DC / DC converter unit. The second micro DC / DC converter unit may also be configured to provide lower power, for example, in the range of 50W to 200W, when the first main DC / DC converter unit is deactivated.

[0016] Preferably, the first micro DC / DC converter unit of the first DC / DC converter module and the second micro DC / DC converter unit of the second DC / DC converter module can be connected to the first low-voltage system. In other words, when the first main DC / DC converter unit is deactivated, the first low-voltage system can receive power from the first high-voltage system and / or the second high-voltage system via the first micro DC / DC converter unit and / or the second micro DC / DC converter unit.

[0017] The control unit may be at least a portion of an electronic control unit (ECU) configured to perform power conversion control. The control unit may include a digital signal processor (DSP) with a dedicated CAN communication interface.

[0018] The first and second miniature DC / DC converter units can be connected via a first bidirectional switching unit. The first bidirectional switching unit may include, for example, two switching elements arranged back-to-back, i.e., in opposite directions. The switching elements may be power semiconductor switching elements such as MOSFETs or IGBTs. The switching elements may include a common source or a common emitter configuration. Therefore, the first bidirectional switching unit can block reverse-flowing current and perform reverse voltage protection.

[0019] Generally, the first bidirectional switching unit can be closed in normal operating mode. In normal operating mode, the converter system is fault-free and / or malfunctioning, and the first main DC / DC converter unit is deactivated to supply power to the first low-voltage system via the first micro DC / DC converter unit and / or the second micro DC / DC converter unit. Preferably, the first micro DC / DC converter unit can be configured to always deliver power when the first main DC / DC converter unit is deactivated. In addition to the first micro DC / DC converter unit, the second micro DC / DC converter unit can also deliver power if the power consumption demand of the first low-voltage system exceeds the capacity of the first micro DC / DC converter unit.

[0020] Specifically, if the power consumption demand of the first low-voltage system exceeds the power limit of the first micro DC / DC converter unit, the first micro DC / DC converter unit can enter a current-limiting mode. Simultaneously, the output low voltage level of the first micro DC / DC converter unit can be reduced to the low-voltage setpoint voltage of the second micro DC / DC converter unit. Therefore, both the first and second micro DC / DC converter units can supply power to the first low-voltage system. In this way, highly efficient power delivery can be achieved when the vehicle is stationary.

[0021] However, in the event of a failure or malfunction of the first miniature DC / DC converter unit, the control unit can disconnect the first bidirectional switch unit to transfer power from the second high-voltage system to the first low-voltage system via the second miniature DC / DC converter unit. In other words, the second miniature DC / DC converter unit can be disconnected from the system in case of a fault; that is, the first miniature DC / DC converter unit and the first low-voltage system can be powered from the second high-voltage system via the second miniature DC / DC converter unit of the second DC / DC converter module. Therefore, even if an internal fault occurs in the converter system, reliable power supply to the first low-voltage system can be ensured.

[0022] In the example, the control unit is also configured to disconnect the first bidirectional switch unit to transfer power from the first high-voltage system to the first low-voltage system via the first micro DC / DC converter unit if the first main DC / DC converter unit is deactivated and the second micro DC / DC converter unit fails. In the case of the deactivated first main DC / DC converter unit, which may refer to a vehicle in a parked state, the first low-voltage system can be configured to receive power from the first high-voltage system via the first micro DC / DC converter unit of the first DC / DC converter module and / or from the second high-voltage system via the second micro DC / DC converter unit of the second DC / DC converter module.

[0023] However, if the second miniature DC / DC converter unit and / or the second DC / DC converter module fails, the control unit can disconnect the first bidirectional switch unit to deliver power from the first high-voltage system to the first low-voltage system solely via the first miniature DC / DC converter unit. In other words, the first miniature DC / DC converter unit can be disconnected from the fault, meaning that the second miniature DC / DC converter unit and the first low-voltage system can be powered from the first high-voltage system solely via the first miniature DC / DC converter unit of the first DC / DC converter module. Simultaneously, the power demand of the first low-voltage system can be adapted to the capacity of the first miniature DC / DC converter unit. Therefore, even if the second miniature DC / DC converter unit of the converter system experiences an internal fault, reliable power supply to the first low-voltage system can be ensured.

[0024] In the example, the second miniature DC / DC converter unit can also be connected to a second low-voltage system. The control unit is configured to deliver power from the first high-voltage system to the second low-voltage system via the first miniature DC / DC converter unit. In other words, in addition to the first low-voltage system, the converter system can also be configured to deliver power to the second low-voltage system. The second low-voltage system can also be coupled to low-voltage loads, such as control components for opening doors or windows, starting motors, steering and braking loads. Some of these loads can be connected to both the first and second low-voltage systems, and some of them can be connected independently of both systems. However, the second low-voltage system can be configured to operate independently of the first low-voltage system.

[0025] The second low-voltage system can be coupled only to the first micro DC / DC converter unit of the first DC-DC module and / or the second micro DC / DC converter unit of the second DC-DC module. Therefore, power can be supplied to the second low-voltage system independently of the state of the first main DC / DC converter unit (which may refer to the vehicle's driving, charging, or parking state) and only via the first micro DC / DC converter unit and / or the second micro DC / DC converter unit.

[0026] The second low-voltage system may also include a second low-voltage interface to ensure reliable connection between the first DC-DC module (particularly the first miniature DC / DC converter unit) and the second low-voltage system, and / or between the second DC-DC converter module (particularly the second miniature DC / DC converter unit) and the second low-voltage system. Generally, the first bidirectional switching unit can be closed in normal operating mode when the converter system is fault-free and / or malfunctioning to supply power from the first high-voltage system to the first and second low-voltage systems via the first miniature DC / DC converter unit.

[0027] In the example, the control unit is also configured to transfer power from both the first high-voltage system and the second high-voltage system to each of the first low-voltage system and the second low-voltage system via the first micro DC / DC converter unit and the second micro DC / DC converter unit if the sum of the power to be transferred to the first low-voltage system and the second low-voltage system exceeds the available power of the first micro DC / DC converter unit.

[0028] Preferably, the first micro DC / DC converter unit can be configured to always deliver power. If the combined power consumption of the first low-voltage system and the second low-voltage system exceeds the capacity of the first micro DC / DC converter unit, then in addition to the first micro DC / DC converter unit, the second micro DC / DC converter unit can also deliver power to the first low-voltage system and the second low-voltage system.

[0029] Specifically, if the combined power consumption of the first low-voltage system and the second low-voltage system exceeds the power limit of the first micro DC / DC converter unit, then the first micro DC / DC converter unit can enter a current-limiting mode. Simultaneously, the output low voltage level of the first micro DC / DC converter unit can be reduced to the low-voltage setpoint voltage of the second micro DC / DC converter unit. Therefore, both the first and second micro DC / DC converter units can supply power to the first and second low-voltage systems. In this way, highly efficient power delivery can be achieved when the vehicle is stationary.

[0030] In the example, the control unit is also configured to disable the second low-voltage system if the first main DC / DC converter unit is disabled and the second micro DC / DC converter unit fails. If the second micro DC / DC converter unit fails, the control unit can disconnect the first bidirectional switch unit connecting the first and second micro DC / DC converter units to disconnect the first micro DC / DC converter unit from the fault (i.e., the second micro DC / DC converter unit).

[0031] Therefore, the second low-voltage system can be disconnected from the first miniature DC / DC converter unit and coupled only to the faulty second miniature DC / DC converter unit. To prevent further failures or malfunctions, the control unit can disable the second low-voltage system. Thus, the second low-voltage system may not include any necessary low-voltage loads that might be deactivated in the event of a failure in the second miniature DC / DC converter unit. However, power can continue to be supplied to the first low-voltage system from the first high-voltage system via the first miniature DC / DC converter unit.

[0032] In the example, the second DC / DC converter module also includes a second main DC / DC converter unit. The second main DC / DC converter unit is at least connectable to the first low-voltage system. The second main DC / DC converter unit can be configured to transfer power from the second high-voltage system to the first low-voltage system. The second main DC / DC converter unit can be designed to provide high power when activated, for example, in the range of 3kW to 4kW, which may refer to the vehicle's driving and / or charging states. Therefore, if the first main DC / DC converter unit fails during vehicle driving or charging, the first low-voltage system can be powered from the second high-voltage system via the second main DC / DC converter unit.

[0033] In the example, the first low-voltage system can be coupled to each of the first main DC / DC converter unit, the first micro DC / DC converter unit, the second main DC / DC converter unit, and the second micro DC / DC converter unit to continuously deliver power to the first low-voltage system. For example, even if at least one of the first main DC / DC converter unit, the first micro DC / DC converter unit, the second main DC / DC converter unit, and the second micro DC / DC converter unit fails, the first low-voltage system can receive power from the first high-voltage system and / or the second high-voltage system. Moreover, the first low-voltage system can reliably supply power regardless of whether the first main DC / DC converter unit and the second main DC / DC converter unit are activated (e.g., during vehicle driving or charging) or deactivated (e.g., during vehicle parking).

[0034] In the example, the converter system may also include three or more DC / DC converter modules, and the first low-voltage system may be coupled to three or more main DC / DC converter units and / or three or more miniature DC / DC converter units to ensure reliable power supply to the first low-voltage system even in the event of a single point of failure in the converter system.

[0035] In the example, the first low-voltage system includes at least a first low-voltage load and a second low-voltage load. A first single-switch element is disposed between the first low-voltage load and a first miniature DC / DC converter unit. A second single-switch element is disposed between the second low-voltage load and the first miniature DC / DC converter unit. The control unit is configured to disconnect the first single-switch element if the first main DC / DC converter unit is deactivated and the first low-voltage load fails.

[0036] The first low-voltage system may include one or more low-voltage loads. Each low-voltage load may be individually coupled to each of the first main DC / DC converter unit and the first miniature DC / DC converter unit. A single switching element may be arranged between each low-voltage load and the first main DC / DC converter unit and / or between each low-voltage load and the first miniature DC / DC converter unit to switch power transmission from the first high-voltage system to the corresponding low-voltage load. Specifically, the first single switching element may be arranged between the output side of the first miniature DC / DC converter unit and the input side of the first low-voltage load. Similarly, a second single switching element may be arranged between the output side of the first miniature DC / DC converter unit and the input side of the second low-voltage load.

[0037] For example, if the first main DC / DC converter unit is activated, then the first low-voltage load and the second low-voltage load can be powered from the first high-voltage system via the first main DC / DC converter unit. However, if the first main DC / DC converter unit is deactivated, then the first single-switch element and the second switch element can be closed, and the first low-voltage load and the second low-voltage load can be powered from the first high-voltage system via the first miniature DC / DC converter unit.

[0038] If either the first low-voltage load or the second low-voltage load fails, the control unit can disconnect the malfunctioning or faulty low-voltage load by opening the single switching element located at the corresponding low-voltage load. Therefore, even if a fault occurs within the first low-voltage system, reliable power delivery to the operating low-voltage load(s) can be ensured. Furthermore, if the first miniature DC / DC converter unit does not fail, power can also be delivered to the second low-voltage system via the first miniature DC / DC converter unit and the first bidirectional switching unit.

[0039] In the example, the second low-voltage system may include a third low-voltage load and a third single-switch element. The third single-switch element may be positioned between the output sides of the first and second miniature DC / DC converter units and the third low-voltage load of the second low-voltage system. In the event of a failure in the third low-voltage load, the control unit may disconnect the third single-switch element to disconnect the faulty third low-voltage load.

[0040] In the example, the control unit is configured to transfer a high current from the first main DC / DC converter unit to the first micro DC / DC converter unit via a first single-switch element and / or a second single-switch element if the first main DC / DC converter unit is activated and the first micro DC / DC converter unit fails. When the first main DC / DC converter unit is activated, a fault such as a short circuit can occur at the first micro DC / DC converter unit. In this case, the control unit can cause the first main DC / DC converter unit to transfer a high current to the first micro DC / DC converter unit via a first single-switch element disposed at a first low-voltage load and / or a second single-switch element disposed at a second low-voltage load.

[0041] Compared to the first main DC / DC converter unit, the rated current of the first single-switching element and / or the second single-switching element connected to the output side of the first miniature DC / DC converter unit can be smaller. Therefore, if the first main DC / DC converter unit is activated, the first single-switching element and / or the second single-switching element may fail and isolate the first miniature DC / DC converter unit from the first main DC / DC converter unit.

[0042] Simultaneously, the second main DC / DC converter unit can transfer power from the second high-voltage system to the first low-voltage system (i.e., the first low-voltage load and / or the second low-voltage load) and the second low-voltage system. If the first and second main DC / DC converter units are deactivated, the second miniature DC / DC converter unit can continue to supply power from the second high-voltage system to the first low-voltage system and / or the second low-voltage system.

[0043] In the example, the converter system further includes a second bidirectional switching unit and a third bidirectional switching unit. The second bidirectional switching unit is disposed between the second miniature DC / DC converter unit and the first low-voltage load, and the third bidirectional switching unit is disposed between the second miniature DC / DC converter unit and the second low-voltage load. The control unit is configured to transfer a high current from the second main DC / DC converter unit to the second miniature DC / DC converter unit via the second bidirectional switching unit and / or the third bidirectional switching unit if the first main DC / DC converter unit is activated and the second miniature DC / DC converter unit fails.

[0044] When the first and second main DC / DC converter units are activated, a short circuit may occur at the second miniature DC / DC converter unit. In this case, the control unit can cause the second main DC / DC converter unit to transfer a high current to a second bidirectional switching unit disposed between the output side of the second miniature DC / DC converter unit and the first low-voltage load of the first low-voltage system. Additionally or alternatively, the control unit can cause the second main DC / DC converter unit to transfer a high current to a third bidirectional switching unit disposed between the output side of the second miniature DC / DC converter unit and the second low-voltage load of the first low-voltage system.

[0045] Once the second and / or third bidirectional switching units detect current in both directions—that is, current from the second miniature DC / DC converter unit and current from the second main DC / DC converter unit—the second and / or third bidirectional switching units can disconnect. Specifically, if the current exceeds an overcurrent threshold, the second and / or third bidirectional switching units can turn off. Therefore, a faulty second miniature DC / DC converter unit can be disconnected from the second main DC / DC converter unit.

[0046] Simultaneously, the control unit is configured to supply power from the first main DC / DC converter unit to the first low-voltage load and the second low-voltage load. If the first main DC / DC converter unit is deactivated, the first miniature DC / DC converter unit can supply power to the first low-voltage system via a first single-switch element and to the second low-voltage load via a second single-switch element. Additionally, the first bidirectional switch unit can be disconnected to isolate the first miniature DC / DC converter unit from the faulty second miniature DC / DC converter unit. Additionally or alternatively, the second low-voltage system can be de-energized due to a fault in the second miniature DC / DC converter unit and a high current flowing at the output side of the second miniature DC / DC converter unit.

[0047] In the example, the first and second main DC / DC converter units are configured to provide higher power than the first and second miniature DC / DC converter units. For example, the first and second main DC / DC converter units can be configured to provide high power in the range of 3kW to 4kW. Conversely, the first and second miniature DC / DC converter units can be configured to provide low power in the range of 50W to 200W.

[0048] Therefore, if the converter system is integrated into the vehicle, the first and second main DC / DC converter units can be activated during vehicle driving or charging, and can supply power to the first low-voltage system via the first and / or second main DC / DC converter units. Additionally, the first and second main DC / DC converter units can be turned off when the vehicle is parked, and can supply power to the first low-voltage system via the first and / or second miniature DC / DC converter units.

[0049] In the example, the first miniature DC / DC converter unit is configured to provide lower power than the second miniature DC / DC converter unit. The first and second miniature DC / DC converter units can be configured to provide two different power levels with two different low-voltage setpoints. The setpoints can be adjusted to protect the first and second miniature DC / DC converter units from output overvoltages. For example, the first miniature DC / DC converter unit can be configured to provide lower power (e.g., 50W and 15V low-voltage setpoint) compared to the second miniature DC / DC converter unit (e.g., 200W and 14.5V low-voltage setpoint) to improve power delivery efficiency.

[0050] A first bidirectional switching unit can be positioned between the output side of the first micro DC / DC converter unit and the output side of the second micro DC / DC converter unit. If there is no fault in the converter system, the first bidirectional switching unit can always be closed, allowing both the first low-voltage system and the second low-voltage system to be powered by the first micro DC / DC converter unit if the total power consumption demand is less than the predefined power of the first micro DC / DC converter unit. However, if the sum of the power consumption demands of the first and second low-voltage systems exceeds the predefined power of the first micro DC / DC converter unit, the control unit can enter a current-limiting mode to lower the low-voltage setpoint of the first micro DC / DC converter unit to the low-voltage setpoint of the second micro DC / DC converter unit. Subsequently, both the first and second micro DC / DC converter units can supply power to the first and second low-voltage systems. Therefore, power delivery efficiency can be improved.

[0051] In the example, each of the first, second, and third bidirectional switching units includes a pair of MOSFET elements, and each of the first and second single-switch elements includes a smart FET element. The bidirectional switching unit can be configured to block reverse-flowing current and perform reverse voltage protection. The single-switch element can be configured to allow power delivery and / or current flow by being turned on or off.

[0052] A bidirectional switching unit may comprise a pair of power semiconductor switching elements, such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), arranged back-to-back (B2B) in series. These semiconductor switching elements have no mechanical moving parts. Therefore, compared to relays, they can have very few failures, very low power / switching losses, fast switching open and / or close response times, and long lifespan. Consequently, the first, second, and third bidirectional switching units can allow for highly efficient power switching. Alternatively, the first, second, and / or third bidirectional switching units may comprise bipolar junction transistors (BJTs), insulated-gate bipolar transistors (IGBTs), or thyristors (SCRs, GTOs, MCTs).

[0053] A single switching element may include a smart FET (field-effect transistor) element with diagnostic and / or protection availability. Each single switching element arranged between the main DC / DC converter unit and the low-voltage system and / or between the micro DC / DC converter unit and the low-voltage system may also be replaced by a bidirectional switching unit comprising a pair of power semiconductor switching elements.

[0054] According to this disclosure, a vehicle is presented. The vehicle includes the converter system described above. The vehicle is a hybrid electric vehicle or a hybrid electric vehicle. The converter system allows reliable power transfer between the high-voltage and low-voltage systems in any state of the vehicle, even in the event of a single point of failure in the converter system. In other words, the converter system can meet ASIL D to ensure the availability of power supply to low-voltage loads with high efficiency in the event of any single point of failure. Therefore, the vehicle can provide low-voltage power to one or more of the vehicle's low-voltage systems without requiring any low-voltage energy storage system (such as 12V lead-acid, 12V lithium-ion, or supercapacitors).

[0055] In the example, if the first main DC / DC converter unit and / or the second main DC / DC converter unit are deactivated, the vehicle is in a parked state; and if the first main DC / DC converter unit and / or the second main DC / DC converter unit are activated, the vehicle is in a driving and / or charging mode. Since the first main DC / DC converter unit and / or the second main DC / DC converter unit can be configured to provide high power, they can be activated during vehicle driving or charging. However, to improve energy efficiency, the first and second main DC / DC converter units can be deactivated when the vehicle is parked. A first low-voltage system, which should always be on regardless of vehicle status, can be powered via the first micro DC / DC converter unit and / or the second micro DC / DC converter unit.

[0056] According to this disclosure, a method for transmitting electricity is presented. The method includes, but is not necessarily in this order:

[0057] If the first main DC / DC converter unit is deactivated, then power is transferred from the first high-voltage system to the first low-voltage system via the first miniature DC / DC converter unit, and

[0058] If the first main DC / DC converter unit is deactivated and the first micro DC / DC converter unit fails, then the first bidirectional switch unit is disconnected to transfer power from the second high-voltage system to the first low-voltage system via the second micro DC / DC converter unit. The first DC / DC converter module may be connected to the first high-voltage system and at least to the first low-voltage system. The second DC / DC converter module may be connected to the second high-voltage system and at least to the first low-voltage system. The first DC / DC converter module includes at least a first main DC / DC converter unit and a first micro DC / DC converter unit. The second DC / DC converter module includes at least a second micro DC / DC converter unit. The first micro DC / DC converter unit and the second micro DC / DC converter unit may be connected via the first bidirectional switch unit.

[0059] According to this disclosure, a computer program element can be presented. As described above, the computer program element can be configured for a converter system. When the program element is executed by a processing element, the program element is adapted to perform the method steps described above.

[0060] It should be noted that the examples above can be combined with each other, regardless of which aspect is involved. Therefore, this method can be combined with structural features, and similarly, the system can be combined with the features described above regarding the method.

[0061] These and other aspects of this example will become clear from the embodiments described below, and will be illustrated with reference to the examples described below. Attached Figure Description

[0062] Examples according to this disclosure will now be described with reference to the accompanying drawings.

[0063] Figure 1 Examples of converter systems according to this disclosure are illustrated schematically and exemplary.

[0064] Figure 2 Examples of converter systems according to this disclosure are illustrated schematically and exemplary.

[0065] Figure 3 Examples of converter systems according to this disclosure are illustrated schematically and exemplary.

[0066] Figure 4 Examples of converter systems according to this disclosure are illustrated schematically and exemplary.

[0067] Figure 5 Examples of converter systems according to this disclosure are illustrated schematically and exemplary.

[0068] Figure 6 Examples of converter systems according to this disclosure are illustrated schematically and exemplary. Detailed Implementation

[0069] Figure 1 A converter system 1 for transferring electricity from a high-voltage system to a low-voltage system is shown. This converter system 1 can be integrated into vehicles, particularly battery electric vehicles and / or hybrid electric vehicles. The high-voltage system can be a high-voltage energy storage system that provides hundreds of volts as an energy source for operating the vehicle. The high-voltage system can provide a voltage of 400V or 800V. However, the input voltage of the high-voltage system can vary depending on the configuration of the high-voltage system.

[0070] The low-voltage system may include one or more low-voltage loads, such as control components for opening doors or windows, starting motors, steering, and braking loads. The converter system 1 allows reliable power transfer between the high-voltage and low-voltage systems in any state of the vehicle, even in the event of a single point of failure in the converter system 1. In other words, the converter system 1 can meet ASIL D to ensure the availability of power supply to the low-voltage loads with high efficiency in the event of any single point of failure. Therefore, the vehicle may not require any low-voltage energy storage system (such as 12V lead-acid, 12V lithium-ion, or supercapacitors) to provide low-voltage power to the vehicle's (one or more) low-voltage systems.

[0071] The converter system 1 includes a first DC / DC converter module 10, a second DC / DC converter module 20, and a control unit 80. The control unit 80 may be at least a portion of an electronic control unit (ECU) configured to perform power conversion control. The first DC / DC converter module 10 may be connected to a first high-voltage system 13, and the second DC / DC converter module 20 may be connected to a second high-voltage system 23. Each of the first high-voltage system 13 and the second high-voltage system 23 may include a high-voltage interface for connection to each of the first DC / DC converter module 10 and the second DC / DC converter module 20. The first high-voltage system 13 and the second high-voltage system 23 may be the same or different high-voltage systems.

[0072] The first DC / DC converter module 10 can also be connected to the first low-voltage system 41 and the third low-voltage system 71. Therefore, the first DC / DC converter module 10 is configured to deliver power from the first high-voltage system 13 to the first low-voltage system 41 and the third low-voltage system 71. The second DC / DC converter module 20 can also be connected to the first low-voltage system 41, the second low-voltage system 44, and the fourth low-voltage system 74. Therefore, the second DC / DC converter module 20 is configured to deliver power from the second high-voltage system 23 to the first low-voltage system 41, the second low-voltage system 44, and the fourth low-voltage system 74.

[0073] The first DC / DC converter module 10 includes a first main DC / DC converter unit 11 and a first micro DC / DC converter unit 12. The second DC / DC converter module 20 includes a second main DC / DC converter unit 21 and a second micro DC / DC converter unit 22. The first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are configured to provide higher power than the first micro DC / DC converter unit 12 and the second micro DC / DC converter unit 22. Additionally, the first micro DC / DC converter unit 12 is configured to provide lower power than the second micro DC / DC converter unit 22.

[0074] Each low-voltage system may include one or more low-voltage loads. Each of the first main DC / DC converter unit 11, the second main DC / DC converter unit 21, the first miniature DC / DC converter unit 12, and the second miniature DC / DC converter unit 22 may be individually connected to each of the low-voltage loads in each low-voltage system. Each low-voltage load may include a separate low-voltage interface to ensure reliable connection to the first main DC / DC converter unit 11, the second main DC / DC converter unit 21, the first miniature DC / DC converter unit 12, and the second miniature DC / DC converter unit 22.

[0075] Therefore, the first low-voltage load 42 of the first low-voltage system 41 can be connected to the first micro DC / DC converter unit 12 via the first single-switch element 51, and the second low-voltage load 43 of the first low-voltage system 41 can be connected to the first micro DC / DC converter unit 12 via the second single-switch element 52. Additionally, the third low-voltage load 45 of the second low-voltage system 44 can be connected to the second micro DC / DC converter unit 22 via the third single-switch element 53.

[0076] The first main DC / DC converter unit 11 can be connected to the fourth low-voltage load 72 of the third low-voltage system 71 via the fourth single-switch element 61, and to the fifth low-voltage load 73 of the third low-voltage system 71 via the fifth single-switch element 62. The second main DC / DC converter unit 21 can be connected to the sixth low-voltage load 75 of the fourth low-voltage system 74 via the sixth single-switch element 67, and to the seventh low-voltage load 76 of the fourth low-voltage system 74 via the seventh single-switch element 68.

[0077] Additionally, the first main DC / DC converter unit 11 can be connected to the first low-voltage load 42 of the first low-voltage system 41 via an eighth single-switch element 63, and to the second low-voltage load 43 of the first low-voltage system 41 via a ninth single-switch element 64. Furthermore, the second main DC / DC converter unit 21 can be connected to the first low-voltage load 42 of the first low-voltage system 41 via a tenth single-switch element 65, and to the second low-voltage load 43 of the first low-voltage system 41 via an eleventh single-switch element 66. The single-switch elements are configured to allow power delivery and / or current flow by opening or closing. Each single-switch element may include a smart FET element.

[0078] The first micro DC / DC converter unit 12 and the second micro DC / DC converter unit 22 can be connected via a first bidirectional switch unit 31. The second micro DC / DC converter unit 22 can be connected to the first low-voltage load 42 via the second bidirectional switch unit 32 and to the second low-voltage load 43 via the third bidirectional switch unit 33. In other words, the first low-voltage load 42 and the second low-voltage load 43 of the first low-voltage system 41 can be connected to both the first DC / DC converter module 10 and the second DC / DC converter module 20. Therefore, the first low-voltage system 41 can be connected to all the first main DC / DC converter units 11, the second main DC / DC converter unit 21, the first micro DC / DC converter unit 12, and the second micro DC / DC converter unit 22 to ensure reliable power supply to the first low-voltage system 41 in any state of the vehicle (i.e., driving, charging, and parking).

[0079] Bidirectional switching units 31, 32, and 33 can be configured to block reverse current flow and perform reverse voltage protection. Each bidirectional switching unit may include a pair of power semiconductor switching elements, such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), arranged back-to-back (B2B) in series.

[0080] Since the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are configured to provide high power, they can be activated during vehicle driving or charging to deliver power from the first high-voltage system 13 and the second high-voltage system 23 to the corresponding low-voltage loads. However, if the vehicle is parked, the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are turned off, and the first micro DC / DC converter unit 12 and / or the second micro DC / DC converter unit 22 deliver power from the first high-voltage system 13 and / or the second high-voltage system 23 to the corresponding low-voltage loads.

[0081] The first miniature DC / DC converter unit 12 and the second miniature DC / DC converter unit 22 can be configured to provide two different power levels with two different low-voltage setpoints. Thus, if there is no fault in the converter system 1, the first bidirectional switch unit 31 is always closed to deliver power to both the first low-voltage system 41 and the second low-voltage system 44 via the first miniature DC / DC converter unit 12, provided that the sum of the two power consumption demands is less than the energy capacity of the first miniature DC / DC converter unit 12. However, if the sum of the power consumption demands of the first low-voltage system 41 and the second low-voltage system 44 exceeds the energy capacity of the first miniature DC / DC converter unit 12, then the second miniature DC / DC converter unit 22 also additionally delivers power to both the first low-voltage system 41 and the second low-voltage system 44.

[0082] The third low-voltage system 71 and the fourth low-voltage system 74 can be configured to be powered only when the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are activated.

[0083] Figure 2 An example is shown where the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are deactivated, i.e., the vehicle is parked, and the first micro DC / DC converter unit 12 has failed. In this case, the control unit 80 is configured to disconnect the first bidirectional switch unit 31 to disconnect the second micro DC / DC converter unit 22 from the fault and transmit power from the second high-voltage system 23 to the first low-voltage system 41 via the second micro DC / DC converter unit 22.

[0084] Specifically, the first low-voltage load 42 of the first low-voltage system 41 is powered via the second bidirectional switching unit 32, and the second low-voltage load 43 of the first low-voltage system 41 is powered via the third bidirectional switching unit 33. In addition, the third low-voltage load 45 of the second low-voltage system 44 is powered from the second high-voltage system 23 via the second miniature DC / DC converter unit 22 and the third single-switching element 53.

[0085] Figure 3 An example is shown where the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are deactivated, i.e., the vehicle is parked, and the second micro DC / DC converter unit 22 fails. In this case, the control unit 80 is configured to disconnect the first bidirectional switch unit 31 to disconnect the first micro DC / DC converter unit 12 from the fault and transmit power from the first high-voltage system 13 to the first low-voltage system 41 via the first micro DC / DC converter unit 12.

[0086] Specifically, the first low-voltage load 42 of the first low-voltage system 41 is powered via the first single-switch element 51, and the second low-voltage load 43 of the first low-voltage system 41 is powered via the second single-switch element 52. However, since the first bidirectional switch unit 31 is open, the second low-voltage system 44, which is otherwise connected only to the second micro DC / DC converter unit 22, cannot be powered. Thus, the second low-voltage system 44 can be selected such that its(one or more) low-voltage loads are not essential components for operating the vehicle and its power consumption is very low during all states of the vehicle (i.e., driving, charging, and parking).

[0087] Figure 4An example is shown where the first low-voltage load 42 of the first low-voltage system 41 fails. This example applies to two scenarios: either the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are deactivated (i.e., the vehicle is parked), or the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are activated (i.e., the vehicle is being driven or charging). In this case, the control unit 80 is configured to disconnect the first single-switch element 51 to disconnect the first miniature DC / DC converter unit 12 from the fault and transfer power from the first high-voltage system 13 to the second low-voltage load 43 via the first miniature DC / DC converter unit 12 and the second single-switch element 52.

[0088] Additionally, if the sum of the power consumption requirements of the second low-voltage load 43 and the third low-voltage load 45 is less than the power availability of the first micro DC / DC converter unit 12, then the first bidirectional switch unit 31 remains closed to transfer power from the first high-voltage system 13 to the second low-voltage system 44 (i.e., the third low-voltage load 45) via the first micro DC / DC converter unit 12 and the third single switch element 53. If the sum exceeds the power availability of the first micro DC / DC converter unit 12, then the control unit 80 may cause the second micro DC / DC converter unit 22 to additionally transfer power from the second high-voltage system 23 to the second low-voltage load 43 of the first low-voltage system 41 via the second bidirectional switch unit 32 and to the third low-voltage load 45 of the second low-voltage system 44 via the third single switch element 53.

[0089] Figure 5 An example is shown where the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are activated, i.e., the vehicle is in a driving or charging state, and the first micro DC / DC converter unit 12 malfunctions. For example, the malfunction could be a short circuit. In this case, the control unit 80 is configured to transfer a high current from the first main DC / DC converter unit 11 to the first micro DC / DC converter unit 12 via a first single-switch element 51 and a second single-switch element 52, thereby disconnecting the first micro DC / DC converter unit 12.

[0090] Compared to the first main DC / DC converter unit 11, the rated current of the first single-switch element 51 and / or the second single-switch element 52 connected to the output side of the first miniature DC / DC converter unit 12 can be smaller. Therefore, the first single-switch element 51 and / or the second single-switch element 52 may fail due to the high current sent from the first main DC / DC converter unit 11 and isolate the first miniature DC / DC converter unit 12 from the first main DC / DC converter unit 11.

[0091] Meanwhile, during vehicle driving or charging, the second main DC / DC converter unit 21 is configured to transfer power from the second high-voltage system 23 to the first low-voltage load 42 via the tenth single-switch element 65, and to transfer power to the second low-voltage load 43 via the tenth single-switch element 66. Furthermore, the third low-voltage load 45 is powered via the second miniature DC / DC converter unit 22 and the third single-switch element 53.

[0092] If the first main DC / DC converter unit 11 and the main DC / DC converter unit 21 are deactivated, the second miniature DC / DC converter unit 22 is configured to transfer power from the second high-voltage system 23 to the first low-voltage load 42 via the second bidirectional switching unit 32, to the second low-voltage load 43 via the third bidirectional switching unit 33, and to the third low-voltage load 45 via the third single switching element 53. Therefore, even if the first miniature DC / DC converter unit 12 fails, the second miniature DC / DC converter unit 22 can continue to supply power from the second high-voltage system 23 to the first low-voltage system and / or the second low-voltage system 44.

[0093] Figure 6 An example is shown where the first main DC / DC converter unit 11 and the second main DC / DC converter unit 21 are activated, i.e., the vehicle is in a driving or charging state, and the second micro DC / DC converter unit 22 malfunctions. For example, the malfunction could be a short circuit. In this case, the control unit 80 is configured to transfer a high current from the second main DC / DC converter unit 21 to the second micro DC / DC converter unit 22 via a second bidirectional switch unit 32 and a third bidirectional switch unit 33, thereby disconnecting the second micro DC / DC converter unit 22.

[0094] Specifically, the control unit 80 can cause the second main DC / DC converter unit 21 to deliver high current to a second bidirectional switching unit 32 disposed between the output side of the second miniature DC / DC converter unit 22 and the first low-voltage load 42 of the first low-voltage system 41. Additionally or alternatively, the control unit 80 can cause the second main DC / DC converter unit 21 to deliver high current to a third bidirectional switching unit 33 disposed between the output side of the second miniature DC / DC converter unit 22 and the second low-voltage load 43 of the first low-voltage system 41.

[0095] Once the second bidirectional switching unit 32 and / or the third bidirectional switching unit 33 detects current in both directions, i.e., current from the second miniature DC / DC converter unit 22 and from the second main DC / DC converter unit 21, the second bidirectional switching unit 32 and / or the third bidirectional switching unit 33 can be disconnected. Therefore, the faulty second miniature DC / DC converter unit 22 can be disconnected from the first low-voltage system 41 and the second low-voltage system 42.

[0096] Simultaneously, the first main DC / DC converter unit 11 is configured to transfer power from the first high-voltage system 13 to the first low-voltage load 42 via the eighth single-switch element 63 and to the second low-voltage load 43 via the ninth single-switch element 64 during vehicle driving or charging. However, due to a failure of the second miniature DC / DC converter unit 22 and the high current transmitted on the output side of the second miniature DC / DC converter unit 22, the second low-voltage system 44 is de-energized.

[0097] If the first main DC / DC converter unit 11 and the main DC / DC converter unit 21 are deactivated, the control unit 80 is configured to supply power to the first micro DC / DC converter unit 12 via the first single-switch element 51 to the first low-voltage load 42 and via the second single-switch element 52 to the second low-voltage load 43. Therefore, even though the first main DC / DC converter unit 11 is deactivated and the second micro DC / DC converter unit 22 fails, the first micro DC / DC converter unit 12 can continue to supply power from the first high-voltage system 13 to the first low-voltage system 41.

[0098] It should be noted that the examples in this disclosure are described with reference to different subject matter. In particular, some examples are described with reference to method type declarations, while others are described with reference to device type declarations. However, those skilled in the art will conclude from the foregoing and following description that, unless otherwise mentioned, any combination of features related to different subject matter, in addition to any combination of features belonging to one type of subject matter, is also considered to be disclosed with this application. However, all features can be combined to provide synergies, rather than simply being a sum of features.

[0099] While this disclosure has been described and illustrated in detail in the accompanying drawings and description, such description and illustration should be considered illustrative or exemplary rather than restrictive. This disclosure is not limited to the disclosed examples. Other variations of the disclosed examples will be understood and implemented by those skilled in the art upon study of the drawings, this disclosure, and the dependent claims in the practice of the claimed disclosure.

[0100] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plural. A single processor or other unit can perform the functions of several items stated in the claims. The fact that certain measures are stated only in mutually different dependent claims does not mean that a combination of these measures cannot be advantageous. Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A converter system (1) for transmitting electricity, comprising: a first DC / DC converter module (10), The second DC / DC converter module (20), and Control unit (80) The first DC / DC converter module (10) is capable of being connected to the first high-voltage system (13) and at least to the first low-voltage system (41). The second DC / DC converter module (20) can be connected to the second high-voltage system (23) and at least to the first low-voltage system (41). The first DC / DC converter module (10) includes at least a first main DC / DC converter unit (11) and a first micro DC / DC converter unit (12). The second DC / DC converter module (20) includes at least a second micro DC / DC converter unit (22). The first miniature DC / DC converter unit (12) and the second miniature DC / DC converter unit (22) can be connected via a first bidirectional switch unit (31). The control unit (80) is configured to transfer power from the first high-voltage system (13) to the first low-voltage system (41) via the first micro DC / DC converter unit (12) if the first main DC / DC converter unit (11) is deactivated. The control unit (80) is also configured to disconnect the first bidirectional switch unit (31) to transfer power from the second high-voltage system (23) to the first low-voltage system (41) via the second micro DC / DC converter unit (22) if the first main DC / DC converter unit (11) is deactivated and the first micro DC / DC converter unit (12) fails.

2. The converter system (1) according to claim 1, wherein the control unit (80) is further configured to disconnect the first bidirectional switch unit (31) to transfer power from the first high-voltage system (13) to the first low-voltage system (41) via the first micro DC / DC converter unit (12) if the first main DC / DC converter unit (11) is deactivated and the second micro DC / DC converter unit (22) fails.

3. In the converter system (1) according to claim 1 or 2, the second micro DC / DC converter unit (22) is also capable of being connected to a second low-voltage system (44), and the control unit (80) is configured to transmit power from the first high-voltage system (13) to the second low-voltage system (44) via the first micro DC / DC converter unit (12).

4. The converter system (1) according to claim 3, wherein the control unit (80) is further configured to transmit power from both the first high-voltage system and the second high-voltage system (44) to each of the first low-voltage system and the second low-voltage system (44) via the first micro DC / DC converter unit (12) and the second micro DC / DC converter unit (22) if the sum of the power to be transmitted to the first low-voltage system (41) and the second low-voltage system (44) exceeds the available power of the first micro DC / DC converter unit (12).

5. The converter system (1) according to claim 3, wherein the control unit (80) is further configured to disable the second low-voltage system (44) if the first main DC / DC converter unit (11) is disabled and the second micro DC / DC converter unit (22) fails.

6. The converter system (1) according to claim 1 or 2, wherein the second DC / DC converter module (20) further comprises a second main DC / DC converter unit (21), the second main DC / DC converter unit (21) being at least capable of being connected to the first low-voltage system (41).

7. The converter system (1) according to claim 1 or 2, wherein the first low-voltage system (41) includes at least a first low-voltage load (42) and a second low-voltage load (43). A first single-switch element (51) is arranged between the first low-voltage load (42) and the first miniature DC / DC converter unit (12). A second single-switch element (52) is arranged between the second low-voltage load (43) and the first miniature DC / DC converter unit (12), and The control unit (80) is configured to disconnect the first single-switch element (51) if the first main DC / DC converter unit (11) is deactivated and the first low-voltage load (42) fails.

8. The converter system (1) according to claim 7, wherein the control unit (80) is configured to transfer a high current from the first main DC / DC converter unit (11) to the first micro DC / DC converter unit (12) via the first single-switch element (51) and / or the second single-switch element (52) if the first main DC / DC converter unit (11) is activated and the first micro DC / DC converter unit (12) fails.

9. The converter system (1) according to claim 7, the converter system (1) further comprising a second bidirectional switching unit (32) and a third bidirectional switching unit (33), the second bidirectional switching unit (32) being disposed between the second miniature DC / DC converter unit (22) and the first low-voltage load (42) and the third bidirectional switching unit (33) being disposed between the second miniature DC / DC converter unit (22) and the second low-voltage load (43), the second DC / DC converter module (20) further comprising a second main DC / DC converter unit (21), the second main DC / DC converter unit (21) being at least connectable to the first low-voltage system (41), and The control unit (80) is configured to transfer a high current from the second main DC / DC converter unit (21) to the second micro DC / DC converter unit (22) via the second bidirectional switch unit (32) and / or the third bidirectional switch unit (33) if the first main DC / DC converter unit (11) is activated and the second micro DC / DC converter unit (22) fails.

10. The converter system (1) according to claim 1 or 2, wherein the second DC / DC converter module (20) further comprises a second main DC / DC converter unit (21) which is at least connected to the first low-voltage system (41), and the first main DC / DC converter unit (11) and the second main DC / DC converter unit (21) are configured to provide higher power than the first micro DC / DC converter unit (12) and the second micro DC / DC converter unit (22).

11. The converter system (1) according to claim 1 or 2, wherein the first micro DC / DC converter unit (12) is configured to provide lower power than the second micro DC / DC converter unit (22).

12. The converter system (1) according to claim 9, wherein each of the first bidirectional switching unit (31), the second bidirectional switching unit (32) and the third bidirectional switching unit (33) comprises a pair of MOSFET elements and each of the first single switching element (51) and the second single switching element (52) comprises a smart FET element.

13. A vehicle comprising a converter system (1) according to any one of claims 1 to 12, wherein the vehicle is a battery electric vehicle or a hybrid electric vehicle.

14. The vehicle according to claim 13, wherein if the first main DC / DC converter unit (11) and / or the second main DC / DC converter unit (21) are deactivated, the vehicle is in a parked state, and if the first main DC / DC converter unit (11) and / or the second main DC / DC converter unit (21) are activated, the vehicle is in a driving and / or charging mode.

15. A method for transmitting electricity, comprising: If the first main DC / DC converter unit (11) is deactivated, then power is transferred from the first high-voltage system (13) to the first low-voltage system (41) via the first miniature DC / DC converter unit (12), and If the first main DC / DC converter unit (11) is deactivated and the first miniature DC / DC converter unit (12) fails, then the first bidirectional switch unit (31) is disconnected to transfer power from the second high-voltage system (23) to the first low-voltage system (41) via the second miniature DC / DC converter unit (22). The first DC / DC converter module (10) is capable of being connected to the first high-voltage system (13) and at least to the first low-voltage system (41). The second DC / DC converter module (20) is capable of being connected to the second high-voltage system (23) and at least to the first low-voltage system (41). The first DC / DC converter module (10) includes at least the first main DC / DC converter unit (11) and the first micro DC / DC converter unit (12). The second DC / DC converter module (20) includes at least the second miniature DC / DC converter unit (22), and The first micro DC / DC converter unit (12) and the second micro DC / DC converter unit (22) can be connected via the first bidirectional switch unit (31).

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