DC-DC converter for vehicle

Abstract

The invention relates to a system (1) for supplying a low DC voltage to a vehicle from at least one high voltage battery (2) of the vehicle, the system (1) comprising: a first DC-DC converter (3a) configured to convert a high DC voltage from the at least one battery of the vehicle into a low DC voltage; a second DC-DC converter (3b) having a lower power than the first DC-DC converter (3a) and configured to convert a high DC voltage from at least one battery of the vehicle to a low DC voltage, where the first DC-DC converter (3a) and the second DC-DC converter (3b) are configured to be connected to at least one high voltage battery (2).

Description

Technical Field

[0001] The present invention relates to a system for supplying a low DC voltage from a high-voltage battery of a vehicle to the vehicle. Background Art

[0002] Modern electric vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fuel cell electric vehicles (FCEVs) typically include a battery with a relatively high output voltage for powering one or more electric motors of the vehicle. In the case of a BEV or FCEV, the electric motor is the sole engine for propelling the vehicle. On the other hand, HEVs and PHEVs include an electric motor in addition to an internal combustion engine. For reasons of efficiency, such electric motors operate at a rather high voltage, for example 400 V, 800 V, or even higher.

[0003] On the other hand, the vehicle includes an electrical system for powering electrical loads such as control units, entertainment systems, navigation systems, driver assistance systems, air conditioners, actuators, seat heating, advanced driver assistance systems (ADAS), and so on. Nowadays, autonomous or semi-autonomous vehicles are becoming increasingly common, which include a plurality of electronic components powered by the electrical system. This electrical system typically has a relatively low voltage, such as 12 V, 24 V, or 48 V.

[0004] Therefore, even vehicles that in principle include an electric power supply (such as BEVs, HEVs, PHEVs, or FCEVs) also include an additional low-voltage battery for powering the electrical and electronic components of the vehicle. This has several disadvantages. First, the additional battery increases the total weight of the vehicle, which increases fuel and / or power consumption and reduces the range of the vehicle. Second, the low-voltage vehicle battery is designed for the typical load cycles of conventional internal combustion engine vehicles. For fully electric or hybrid vehicles, the load cycles are very different, resulting in faster degradation and failure of the low-voltage battery.

[0005] Therefore, an attempt is made to omit the low-voltage vehicle battery and use the high-voltage traction battery to power the electrical system of the electric or semi-electric vehicle. This requires a DC-DC converter in order to convert the high-voltage output of the battery (for example 400 V) to the low voltage (for example 12 V) required by the vehicle's electrical system. However, when the vehicle is stationary, some electrical components of the vehicle must also be powered, which are so-called key-off loads. Examples include alarm systems / anti-theft systems, entertainment / infotainment systems, parking heaters, and air conditioners. In addition, modern cars are usually wirelessly connected, for example via a mobile communication network such as 4G or 5G, even when the engine is turned off. The corresponding connection unit needs to be powered at all times.

[0006] Therefore, the mentioned DC-DC converter must operate efficiently at a wide range of power output levels to power the vehicle's electrical system in the off state and the key-on state. Additionally, some electrical loads may have an Automotive Safety Integrity Level (ASIL) and require certain safety requirements. Depending on the safety level of such loads, some power-consuming devices must be redundantly powered by two low-voltage power rails. SUMMARY OF THE INVENTION

[0007] The present invention addresses these needs through the subject matter of the independent claims. Advantageous embodiments are defined in the dependent claims.

[0008] Accordingly, the present invention relates to a system for supplying a low DC voltage to a vehicle from at least one high-voltage battery of the vehicle, the system comprising: a first DC-DC converter configured to convert a high DC voltage from at least one battery of the vehicle into a low DC voltage; a second DC-DC converter having a lower power compared to the first DC-DC converter and configured to convert a high DC voltage from at least one battery of the vehicle into a low DC voltage, wherein the first DC-DC converter and the second DC-DC converter are configured to be connected to at least one high-voltage battery.

[0009] The present invention is not limited to application to one battery. Instead, the present invention also covers cases of more than one battery. Additionally, the term "high-voltage battery" also includes a single battery having multiple parts or sections. For example, a single battery can include a plurality of stacked battery cells and include multiple power outputs. Further, it should be noted that one or more batteries themselves are not part of the system according to the present invention.

[0010] In the context of the present invention, a DC-DC converter (direct current to direct current converter) is understood as an electronic circuit or electromechanical device that converts a direct current (DC) source from one voltage level to another voltage level. Thus, the first DC-DC converter and the second DC-DC converter take the high voltage from the high-voltage battery as input and convert it into a low voltage that is lower compared to the high voltage.

[0011] The first DC-DC converter can be configured to provide a low DC voltage in the ignition state of the vehicle, and the second DC-DC converter can be configured to provide a low DC voltage in the off state of the vehicle. In this way, both the first DC-DC converter and the second DC-DC converter can operate in their optimal domains, which are the high-power mode for the first DC-DC converter and the low-power mode for the second DC-DC converter. Additionally, the first DC-DC converter and the second DC-DC converter can supply power to low-power loads redundantly, which improves fail-safety and reliability.

[0012] In the context of the present invention, the "key-on state" is understood as the state of the vehicle in which electrical power can be immediately supplied to the main engine of the vehicle such that the state of motion of the vehicle is changed (e.g., the vehicle starts moving, accelerates or decelerates). In the "key-off" state, electrical power cannot be supplied to the main engine and the vehicle is typically in a parked state. Further, in the key-on state, electrical power is supplied to certain electrical loads, but in the key-off state, electrical power is not supplied to these loads. Examples include all systems required for driving such as actuators, control units, driver assistance systems, etc.

[0013] The first DC-DC converter can be configured to supply electrical power in a high-power mode with active cooling in the key-on state. This improves the efficiency of the system as active cooling is only effective in the key-on state where the power consumption is much higher compared to the key-off state. In the key-off state, the power consumption is typically low such that active cooling is not required. Active cooling of the DC-DC converter can be achieved through liquid cooling, air cooling using a fan, a thermal evaporator, etc. The electrical power required for these cooling measures is not needed in the key-off state.

[0014] The second DC-DC converter can be configured to supply electrical power in the key-off state with only passive cooling. Passive cooling typically means that no additional equipment is operating for cooling to maintain a low static current. It can include using materials with good heat conduction, vents for heat exchange through (passive) air circulation, cooling fins, etc. These measures do not require additional electrical power for cooling in the low-power mode of the second DC-DC converter, which is cost-effective but also increases the fail-safety and robustness of the system as active cooling components introduce additional points of failure.

[0015] The second DC-DC converter can be configured to be directly electrically connected to at least one high-voltage battery without any switch therebetween. In this way, the second DC-DC converter can supply power in the key-off state. On the other hand, the first DC-DC converter can be connected to the battery downstream of the power switch controlling the motor as their output voltage is only required in the key-on state and not in the key-off state. Thus, the first DC-DC converter can be placed outside the battery.

[0016] A system for supplying a low DC voltage from at least one high-voltage battery of a vehicle to the vehicle may further include at least one power distribution unit configured to provide the low DC voltage to a plurality of loads, wherein the power distribution unit is electrically connected to a first DC-DC converter and a second DC-DC converter. The power distribution unit allows the low DC voltage to be distributed to loads within the vehicle. In the off state, the second DC-DC converter supplies power to the power distribution unit, while in the ignition state, the first DC-DC converter supplies power to the power distribution unit. Thus, any load connected to the power distribution unit can be supplied with electrical power in both the off state and the ignition state. In addition, the first DC-DC converter and the second DC-DC converter can supply power redundantly to at least low-power loads in the ignition state, which improves robustness and fail-safety. In addition to voltage, the power distribution unit can also distribute data via a corresponding data bus, or aggregate data from sensors and peripherals, and distribute the data to actuators. Thus, the power distribution unit can be a zone controller.

[0017] The power distribution unit may be configured to electrically connect each of the plurality of loads to the first DC-DC converter or to the second DC-DC converter. Thus, the power distribution unit is connected to two DC-DC converters such that in the event of a failure of one of the DC-DC converters, power can still be supplied to safety-critical low-power loads. This is especially true in the ignition state, in which the power distribution unit can switch between the first DC-DC converter and the second DC-DC converter. Non-safety-critical loads, so-called quality management (QM) loads, can be turned off in the event of a failure of one of the DC-DC converters. Thus, even in the event of a failure of the other DC-DC converter, the fault-free DC-DC converter can operate safely and supply voltage to low-power safety-critical loads.

[0018] Generally, the system may include more than one power distribution unit. The DC-DC converters may be connected to all power distribution units in the vehicle. The first DC-DC converter and the second DC-DC converter may be connected to all power distribution units in the vehicle that supply safety-critical loads. In this way, fail-safety and robustness are increased. Power distribution units that supply only quality management loads may be connected to one DC-DC converter.

[0019] The power distribution unit may include at least one switch for separating the quality management load from the safety-critical load. The quality management load may be a non-safety-critical load such as heating, air conditioning, and entertainment systems. The power distribution unit can, for example, disconnect the quality management load in the event of a failure so that only the safety-critical load is powered.

[0020] A system for supplying a low DC voltage from at least one high-voltage battery of a vehicle to the vehicle may further include a first electrical main fuse box (eMFB) that is selectively electrically connected to a first DC-DC converter or a second DC-DC converter. In this way, depending on the state of the vehicle (off or ignition), the first eMFB is selectively powered by the first DC-DC converter or the second DC-DC converter. Loads that need to be always on can be powered by the first eMFB.

[0021] The first eMFB may be electrically connected to a first power distribution unit and a second power distribution unit. In this way, the first eMFB selectively connected to the first DC-DC converter and the second DC-DC converter can permanently supply power to the two power distribution units. Accordingly, loads that require a permanent power supply can be connected to the two power distribution units.

[0022] The system may be configured such that in the ignition state of the vehicle, the first DC-DC converter is electrically connected to the first eMFB, and in the off state, the second DC-DC converter is electrically connected to the first eMFB. Thus, at least for low-power loads, power can be supplied to the first eMFB in two vehicle states (off and ignition).

[0023] The system may further include a switch configured to selectively electrically connect the first DC-DC converter or the second DC-DC converter to the first eMFB. In this way, power is selectively supplied by the second DC-DC converter in the off state and by the first DC-DC converter in the ignition state. Further, the switch may be part of an eMFB (such as the first eMFB).

[0024] The system may further include a second eMFB that is electrically connected to the second DC-DC converter, the first power distribution unit, and the second power distribution unit. Thus, loads that do not need to be powered in the off state of the vehicle can be connected to the second power distribution unit, while the first power distribution unit can supply power to loads that need to be always on.

[0025] The low DC voltage mentioned here may be a nominal voltage of 60V or lower, preferably a nominal voltage of 12V, 24V, or 48V. The low DC voltage is the output voltage of the DC-DC converter. As mentioned above, typical loads in a vehicle (except for the main engine) operate at a voltage of 60V or lower.

[0026] The high voltage mentioned herein can be a nominal voltage greater than 60V, preferably 200V, 400V, 800V or a higher nominal voltage. The high voltage is typically supplied to the main engine to propel the vehicle. The DC-DC converter advantageously converts the high voltage supplied by the battery into a low voltage to feed an electrical load within the vehicle. The system according to the invention allows such a load to be operated in both the ignition and off states, while each DC-DC converter is not operating in its optimal power domain. Furthermore, safety-critical loads can be operated because the first DC-DC converter and the second DC-DC converter arranged according to the invention provide fail-safety and robustness.

[0027] The high-voltage battery can be adapted to power the electric motor of the vehicle. As described above, the system according to the invention advantageously allows low-voltage loads to be operated from the high voltage of the traction battery in a cost-effective and fail-safe manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Possible embodiments of the invention are described in more detail below with reference to the following figures:

[0029] Figure 1 Exemplary embodiments of the invention are illustrated. DETAILED DESCRIPTION

[0030] For the sake of brevity, only a few embodiments will be described below. Those skilled in the art will recognize that the features described with reference to these specific embodiments can be modified and combined in different ways, and individual features can also be omitted. The general explanations in the above sections also apply to the following more detailed explanations.

[0031] Figure 1 An embodiment of a system 1 for supplying a low DC voltage from at least one high-voltage battery 2 of a vehicle to a vehicle ( Figure 1 not shown in the figure) is illustrated. The system 1 includes a first DC-DC converter 3a and a second DC-DC converter 3b. The first DC-DC converter 3a is configured to convert a high DC voltage from at least one battery 2 of the vehicle into a low DC voltage. The second DC-DC converter 3b has a lower power than the first DC-DC converter 3a and is configured to convert a high DC voltage from at least one battery 2 of the vehicle into a low DC voltage, wherein the first DC-DC converter 3a and the second DC-DC converter 3b are configured to be connected to at least one high-voltage battery 2.

[0032] The battery 2 is a traction battery for powering the electric main engine of a vehicle. Exemplary vehicles in which the present invention can be implemented include battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fuel cell electric vehicles (FCEVs). The electric motors of such vehicles operate at a relatively high voltage, for example, greater than 60V. Typical voltages include 200V, 400V, 800V, or even higher. Typical batteries for this type of automotive are based on electrochemical cells (such as lithium-ion batteries) with external connections in order to supply power to the vehicle.

[0033] The battery supplies electric power to the main engine of the vehicle via outputs 4a and 4b, which will be connected to a traction inverter ( Figure 1 not shown). In addition, corresponding main switches are shown immediately before outputs 4a and 4b.

[0034] In Figure 1 a single battery 2 is shown. However, in other embodiments, more than one battery may be used. For example, two or more batteries may operate in parallel or in series. In addition, the first battery 2 may include a plurality of battery cells. In such a case, the term "high-voltage battery" should be understood as a single battery having a plurality of parts or sections (at least two). In addition, it should be understood that the battery 2 is not part of the system 1. Instead, the DC-DC converters 3a and 3b of the system 1 of the present invention are configured to be electrically connected to the battery 2. Thus, the first DC-DC converter 3a is configured to be electrically connected to the battery 2, and the second DC-DC converter 3b is configured to be electrically connected to the battery 2. The connection may be a direct electrical connection without any switches in between and may be made, for example, via a plug or a clamp.

[0035] In Figure 1 the example, the first DC-DC converter 3a and the second DC-DC converter 3b are each implemented as magnetic DC-DC converters. In these DC-DC converters, energy is periodically stored in and released from the magnetic field in an inductor or a transformer. Alternatively, other types of DC-DC converters, such as capacitive or switched-mode DC-DC converters, may be used. The output voltages of the first DC-DC converter 3a and the second DC-DC converter 3b are low voltages that are lower than the high voltage at their inputs. Typically, the low voltage is 60V or lower. Generally, the electrical system of a vehicle operates at 12V, 24V, or 48V, and the DC-DC converters 3a and 3b may be adapted to supply such voltage levels at their outputs.

[0036] In Figure 1In the example, the first DC-DC converter 3a is configured to provide a low DC voltage in the ignition state of the vehicle. Typically, the DC-DC converter 3a will be supplied with active cooling during the ignition state because the number and power consumption of the active loads are higher in the ignition state compared to the off state. Active cooling can be achieved, for example, by liquid cooling, air cooling using a fan, a thermal evaporator, etc. In the ignition mode, the DC-DC converter 3a can provide, for example, up to 3 kW of power.

[0037] In the off state, power is provided by the second DC-DC converter 3b, which will typically operate without active cooling and only using passive cooling. Passive cooling can be achieved by using materials with good thermal conductivity, vents for heat exchange through (passive) air circulation, cooling fins, etc. In the off mode, the DC-DC converter 3b can provide, for example, up to 300 W of power.

[0038] Figure 1 The system 1 of the exemplary embodiment of also includes two power distribution units 5a and 5b, which are configured to supply a low DC voltage to a plurality of loads ( Figure 1 not shown in). It should be noted that the power distribution unit is optional in the context of the present invention. Additionally, in the context of the present invention, the number of such power distribution units can be different from two, for example, three or more.

[0039] In Figure 1 the exemplary embodiment of, the power distribution units 5a and 5b are electrically connected to the second DC-DC converter 3b and selectively connected to the first DC-DC converter 3a. The power distribution units 5a and 5b distribute the low DC voltage to the loads within the vehicle. As Figure 1 shown in, the power distribution units 5a and 5b are configured to electrically connect each of the plurality of loads to the second DC-DC converter 3b and selectively electrically connect to the first DC-DC converter 3a. To this end, the first power distribution unit 5a includes corresponding switches 6a, 6b, 6c, and 6d. The second power distribution unit 5b includes corresponding switches 6e, 6f, 6g, and 6h. In other embodiments, the number of switches can be different. Figure 1 The switches in the embodiment of are implemented based on field effect transistors (FETs), for example, as power metal oxide semiconductor field effect transistors (MOSFETs).

[0040] The switches 6a, 6b, 6c, 6d, 6e, 6f, 6g and 6h can be controlled by a microcontroller, which is part of the power distribution units 5a and 5b or a separate component in, for example, a control unit. The switches 6a, 6b, 6c, 6d, 6e, 6f, 6g and 6h in the power distribution units 5a and 5b allow switching between an on state and an off state. In the on state, the low voltage from the DC-DC converters 3a and 3b is supplied to the respective loads connected to the switches. In the off state, no voltage is supplied to the loads. Thus, the low voltage can be selectively supplied to the loads.

[0041] In the example, the outputs of the power distribution units 5a and 5b associated with the switches 6a, 6b, 6e and 6f can be connected to safety-critical loads, while the outputs associated with the switches 6c, 6d, 6g and 6h can be connected to quality management loads. More specifically, the outputs associated with the switches 6a and 6e can feed a first safety-critical load, and the outputs associated with the switches 6b and 6f can feed a second safety-critical load. The safety-critical loads will be connected to two rails such that even in the event of a failure of one of the battery, DC-DC converter or eMFB, the safety-critical loads will still be powered. In contrast, the quality management (QM) loads are not critical and can be powered off without causing any damage. Thus, in this example, in the event of a failure of one of the DC-DC converters, the switches 6c, 6d, 6g and 6h can turn off their corresponding QM loads, while the switches 6a, 6b, 6e and 6f are turned on so that the power from the remaining fault-free DC-DC converter is supplied to the safety-critical loads. If the high-power DC-DC converter 3a is about to fail, power can be provided up to the maximum power capacity of the low-power DC-DC converter 3b. Conversely, if the low-power DC-DC converter 3b is about to fail, power can be provided up to the maximum power capacity of the high-power DC-DC converter 3a.

[0042] In Figure 1 the example, two power distribution units 5a and 5b are shown. In other embodiments, the system 1 can include more than two power distribution units. In those embodiments, both DC-DC converters 3a and 3b can be connected to all power distribution units.

[0043] In Figure 1In an exemplary embodiment, system 1 further includes a first electrical main fuse box (eMFB) 7a electrically connected to the first DC-DC converter 3a and electrically connected to the second DC-DC converter 3b. At the other end, eMFB 7a is electrically connected to the first power distribution unit 5a and the second power distribution unit 5b. A switch 8 is arranged between the first DC-DC converter 3a and the second DC-DC converter 3b and the eMFB 7a to selectively connect the first DC-DC converter 3a or the second DC-DC converter 3b to the eMFB 7a according to the state of the vehicle. Thus, in the off state, power is supplied by the second DC-DC converter 3b, which is particularly adapted to operate in a low power mode preferably without active cooling. In the ignition state, on the contrary, power is provided by the first DC-DC converter 3a, which is particularly adapted to operate in a high power mode preferably with active cooling.

[0044] System 1 further includes a second eMFB 7b electrically connected to the second DC-DC converter 3b. At the other end, eMFB 7b is electrically connected to the first power distribution unit 5a and the second power distribution unit 5b. The eMFB contains a fuse that interrupts the current in the case of overcurrent to protect the load, the DC-DC converter, and the battery.

Claims

1. A system (1) for supplying a low DC voltage to a vehicle from at least one high-voltage battery (2) of the vehicle, the system (1) comprising: A first DC-DC converter (3a) configured to convert a high DC voltage from the at least one battery of the vehicle into a low DC voltage; A second DC-DC converter (3b) having a lower power compared to the first DC-DC converter (3a) and configured to convert the high DC voltage from the at least one battery of the vehicle into the low DC voltage, Wherein the first DC-DC converter (3a) and the second DC-DC converter (3b) are configured to be connected to the at least one high-voltage battery (2).

2. The system (1) according to claim 1, characterized in that, The first DC-DC converter (3a) is configured to provide the low DC voltage in an ignition state of the vehicle, and the second DC-DC converter (3b) is configured to provide the low DC voltage in a non-ignition state of the vehicle.

3. The system (1) according to claim 2, wherein, The first DC-DC converter (3a) is configured to provide electric power in the ignition mode in a high-power mode with active cooling.

4. The system (1) according to any one of claims 1 to 3, characterized in that, The second DC-DC converter (3b) is configured to provide electric power in the non-ignition state with only passive cooling.

5. The system (1) according to any one of claims 1-4, characterized in that, The second DC-DC converter (3b) is configured to be directly electrically connected to the at least one high-voltage battery (2) without any switch therebetween.

6. The system (1) according to any one of claims 1-5, further comprising at least one power distribution unit (5a, 5b), the at least one power distribution unit (5a, 5b) being configured to supply the low DC voltage to a plurality of loads, wherein, The power distribution unit (5a, 5b) is electrically connected to the first DC-DC converter (3a) and the second DC-DC converter (3b).

7. The system (1) according to claim 6, characterized in that, The power distribution unit (5a, 5b) is configured to electrically connect each of the plurality of loads to the first DC-DC converter (3a) or to the second DC-DC converter (3b).

8. The system (1) according to any one of claims 6-7, characterized in that, The power distribution unit (5a, 5b) includes at least one switch for separating a quality management load from a safety-critical load.

9. The system (1) according to any one of claims 1-8, further comprising: A first electrical master fuse box eMFB (7a) selectively electrically connected to the first DC-DC converter (3a) or the second DC-DC converter (3b).

10. The system (1) according to claim 9, characterized in that, The first eMFB (7a) is electrically connected to a first power distribution unit (5a) and a second power distribution unit (5b).

11. The system (1) according to any one of claims 9-10, characterized in that, The system (1) is configured such that in an ignition state of the vehicle, the first DC-DC converter (3a) is electrically connected to the first eMFB (7a), and in a non-ignition state, the second DC-DC converter (3b) is electrically connected to the first eMFB (7a).

12. The system (1) according to claim 11, further comprising a switch (8), the switch (8) being configured to selectively electrically connect the first DC-DC converter (3a) or the second DC-DC converter (3b) to the first eMFB (7a).

13. The system (1) according to any one of claims 12, further comprising a second eMFB (7b), the second eMFB (7b) being electrically connected to the second DC-DC converter (3b), the first power distribution unit (5a), and the second power distribution unit (5b).

14. The system (1) according to any one of claims 1 to 13, wherein, The low DC voltage is a nominal voltage of 60V or less, preferably a nominal voltage of 12V, 24V, or 48V.

15. The system (1) according to any one of claims 1 - 14, characterized in that, The high voltage is a nominal voltage greater than 60V, preferably a nominal voltage of 200V, 400V, 800V, or higher.

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