DC-DC converter for vehicle

Abstract

The invention relates to a system (1) for supplying a low DC voltage to a vehicle from a high voltage battery (2a, 2b) of the vehicle, the system (1) comprising: a first DC-DC converter (3a) configured to convert a high DC voltage provided by a first battery (2a) of the vehicle into a low DC voltage; and a second DC-DC converter (3b) configured to convert a high DC voltage provided by a second battery (2b) of the vehicle into a low DC voltage, where the first DC-DC converter (3a) is configured to be electrically connected to the first battery (2a), and where the second DC-DC converter (3b) is configured to be electrically connected to the second battery (2b).

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) generally 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 generally has a relatively low voltage, for example 12 V, 24 V, or 48 V.

[0004] Therefore, even vehicles that in principle include an electrical 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, attempts have been made to omit the low-voltage vehicle battery and use the high-voltage traction battery to power the electrical system of an 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 heating, and air conditioning. 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] Accordingly, the DC-DC converter mentioned above must operate efficiently at a wide range of power output levels to supply power to the vehicle's electrical system in both the off state and the key-on state. In addition, 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 a high-voltage battery of the vehicle, the system comprising: a first DC-DC converter configured to convert a high DC voltage provided by a first battery of the vehicle into a low DC voltage; a second DC-DC converter configured to convert a high DC voltage provided by a second battery of the vehicle into a low DC voltage, wherein the first DC-DC converter is configured to be electrically connected to the first battery, and wherein the second DC-DC converter is configured to be electrically connected to the second battery.

[0009] The present invention is not limited to applications involving two different batteries ("first battery" and "second battery"). Instead, the present invention also covers the case of only a single battery. In this case, the "first battery" may be the first part or section of a single battery, and the "second battery" may be the second part or section of a single battery. In addition, in this case, the term "high-voltage battery" should be understood to mean a single battery having multiple parts or sections (at least two). For example, a single battery may include a plurality of stacked battery cells and include multiple power outputs. In addition, it should be noted that the battery itself is 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 to be an electronic circuit or electromechanical device that converts a direct current (DC) source from one voltage level to another voltage level. Accordingly, 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 and the second DC-DC converter may be configured to provide a low DC voltage in both the ignition state and the off state of the vehicle. In this way, a single DC-DC converter can be used for both states. This advantageously reduces the number of components in the system, which not only reduces costs but also increases 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 stationary state. Further, in the key-on state, electrical power is supplied to certain electrical loads, but not in the key-off state. Examples include all systems required for driving, such as actuators, control units, driver assistance systems, etc.

[0013] The first DC-DC converter and the second DC-DC converter can be configured to provide a low DC voltage in the key-off state of the vehicle in a low power mode, in which the active cooling of the DC-DC converter is switched off. This improves the efficiency of the system because active cooling is only effective in the key-on state, which has a much higher power consumption compared to the key-off state. In the key-off state, the power consumption is typically low such that active cooling is not required. The active cooling of the DC-DC converter can be achieved by liquid cooling, air cooling using a fan, a thermal evaporator, etc. The electrical power required for these cooling measures is not needed in the low power mode of the DC-DC converter, such that the DC-DC converter can operate very efficiently in the key-off state and no additional (low power) DC-DC converter is required for the key-off state, which improves the cost-effectiveness, fail-safety, and robustness of the system.

[0014] The first DC-DC converter and the second DC-DC converter can be configured to operate in a low power mode with only passive cooling. Passive cooling typically means that no additional devices are 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 DC-DC converter, which is cost-effective but also increases the fail-safety and robustness of the system because active cooling components introduce additional failure points.

[0015] The first DC-DC converter and the second DC-DC converter can be configured to provide electrical power in a high-power mode with active cooling. As described above, active cooling may be required in the ignition state, in which the DC-DC converter operates in a high-power mode because additional loads are active in the ignition state. However, the DC-DC converter according to the present invention can be configured to cover both the ignition state and the engine-off state by switching between active cooling and passive cooling. In this way, no additional (low-power) DC-DC converter is required for either the engine-off or ignition state. Such an additional DC-DC converter would increase the cost of the system but may also introduce additional failure points, which would be detrimental to the fail-safety and robustness of the system.

[0016] The first DC-DC converter and the second DC-DC converter can be configured to be directly electrically connected to the high-voltage battery without any switch therebetween. In this way, the DC-DC converter will provide power in both the ignition state and the engine-off state.

[0017] A system for supplying a low DC voltage from a 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 both the first DC-DC converter and the second DC-DC converter. The power distribution unit allows the low DC voltage to be distributed to the loads within the vehicle. In addition to the 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. Therefore, the power distribution unit can be a zone controller.

[0018] The power distribution unit can be configured to electrically connect each of the plurality of loads to the first DC-DC converter or the second DC-DC converter. Thus, the power distribution unit is connected to the two DC-DC converters such that in the event of a failure of one of the DC-DC converters, a lower power voltage can still be supplied to safety-critical loads. Non-safety-critical loads, i.e., so-called quality management (QM) loads, can be turned off in the event of a failure of one of the DC-DC converters. Therefore, 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 the safety-critical loads.

[0019] Typically, the system may include more than one power distribution unit. Both DC-DC converters may be connected to all power distribution units in the vehicle. At least, both DC-DC converters 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. The power distribution unit that supplies only quality management loads may be connected to one DC-DC converter.

[0020] The power distribution unit may be configured to actively distribute a plurality of loads between the first DC-DC converter and the second DC-DC converter such that the first battery and the second battery are substantially balanced. Battery balancing can increase the available capacity of a plurality of batteries or a single battery having a plurality of parts, sections, or cells, and can increase the battery life. Naturally, the batteries may have slightly different capacities, and thus, may be in different states of charge during the charging and discharging cycles. Therefore, balancing takes into account the different capacities and may, for example, draw the highest current from the most charged battery. According to the present invention, balancing can be achieved by distributing the loads between the DC-DC converters, which is a simple and effective way to balance the batteries.

[0021] 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 may, for example, disconnect the quality management load in the event of a fault such that only the safety-critical loads are powered.

[0022] A system for supplying a low DC voltage from a high-voltage battery of a vehicle to the vehicle may further include: a first electrical master fuse box (eMFB) electrically connected to the first DC-DC converter, the first power distribution unit, and the second power distribution unit; and a second eMFB electrically connected to the second DC-DC converter, the first power distribution unit, and the second power distribution unit. In this way, the two power distribution units are connected to the first DC-DC converter and the second DC-DC converter by means of the respective eMFBs, which increases fail-safety and robustness.

[0023] The low DC voltage mentioned here may be a nominal voltage of 60V or less, 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 the vehicle (except for the main engine) operate at a voltage of 60V or less.

[0024] The high voltage mentioned here can be a nominal voltage greater than 60V, preferably 200V, 400V, 800V or 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 without an additional DC-DC converter. In addition, safety-critical loads can be operated because the two DC-DC converters arranged according to the invention provide fault safety and robustness.

[0025] 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 fault-safe manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Possible embodiments of the present invention are described in more detail below with reference to the following figures:

[0027] Figure 1 Exemplary embodiments of the present invention are illustrated. DETAILED DESCRIPTION

[0028] 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.

[0029] Figure 1 An embodiment of a system 1 for supplying a low DC voltage from a high-voltage battery 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 the high DC voltage provided by the first battery 2a of the vehicle into a low DC voltage, and the second DC-DC converter 3b is configured to convert the high DC voltage provided by the second battery 2b of the vehicle into a low DC voltage. The batteries 2a and 2b are traction batteries for powering the main engine of the 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 vehicle are based on electrochemical cells (such as lithium-ion batteries) with external connections in order to supply power to the vehicle.

[0030] The battery supplies electric power to the vehicle's main engine via outputs 4a and 4b, which will be connected to a traction inverter ( Figure 1 not shown). In addition, corresponding main switches are shown before outputs 4a and 4b, which disconnect all loads when the vehicle is off or in the parking mode. Thus, batteries 2a and 2b will typically be within the battery pack together with DC-DC converters 3a and 3b.

[0031] In Figure 1 , batteries 2a and 2b are shown as distinct components, namely a first battery 2a and a second battery 2b. However, in other embodiments, the first battery 2a can be a first part or section of a single battery, and the second battery 2b can be a second part or section of the single battery. For example, the first battery 2a can include one or more first battery cells, and the second battery 2b can include one or more second battery cells. In such a case, the term "high-voltage battery" should be understood as a single battery having multiple parts or sections (at least two). Furthermore, it should be understood that batteries 2a and 2b are not part of system 1. Instead, the DC-DC converters 3a and 3b of the system of the present invention are configured to be electrically connected to batteries 2a and 2b. Thus, the first DC-DC converter 3a is configured to be electrically connected to the first battery 2a, and the second DC-DC converter 3b is configured to be electrically connected to the second battery 2b. The connection can be a direct electrical connection without any switches in between and can be made, for example, via a plug or a clamp.

[0032] In Figure 1 's example, the first DC-DC converter 3a and the second DC-DC converter 3b are implemented as magnetic DC-DC converters. In these DC-DC converters, energy is periodically stored in and released from the magnetic field within an inductor or a transformer. Alternatively, other types of DC-DC converters, such as capacitive or switched-mode DC-DC converters, can be used. The output voltage of the first DC-DC converter 3a and the second DC-DC converter 3b is a low voltage that is lower than the high voltage at their input. Typically, the low voltage is 60V or less. Generally, the vehicle's electrical system operates at 12V, 24V, or 48V, and the DC-DC converters 3a and 3b can be adapted to supply such voltage levels at their output.

[0033] In Figure 1In the example, the first DC-DC converter 3a and the second DC-DC converter 3b are configured to provide a low DC voltage in both the ignition state and the off state of the vehicle. Typically, the DC-DC converter 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 state, the DC-DC converters 3a and 3b operate in a high-power mode. In this mode, the DC-DC converter can provide, for example, up to 3 kW of power.

[0034] In the off state, the DC-DC converters 3a and 3b will operate using only passive cooling without active cooling. Passive cooling can be achieved by using materials with good heat conduction, vents for heat exchange through (passive) air circulation, cooling fins, etc. In the off state, the DC-DC converters 3a and 3b operate in a low-power mode. In this mode, the DC-DC converter can provide, for example, up to 300 W of power.

[0035] 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. In addition, in the context of the present invention, the number of such power distribution units can be different from two, for example, three or more.

[0036] In Figure 1 the exemplary embodiment of, the power distribution units 5a and 5b are electrically connected to both the first DC-DC converter 3a and the second DC-DC converter 3b. 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, 5b are configured to electrically connect each of the plurality of loads to either the first DC-DC converter 3a or the second DC-DC converter 3b. 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).

[0037] 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, a low voltage from the DC-DC converter 3a or 3b is supplied to the corresponding load connected to the switch. In the off state, no voltage is supplied to the load. Thus, the low voltage can be selectively supplied to the load.

[0038] 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 in 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 in the event of a failure without causing any damage. Thus, in this example, in the event of a failure in 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 power from the remaining fault-free DC-DC converter is supplied to the safety-critical loads.

[0039] The manner of feeding the safety-critical loads as described above allows for functional safety up to the ASIL D level to be achieved through so-called ASIL B(D) decomposition. In this case, the battery, DC-DC converter, eMBF, and zone controller comply with ASIL B, such that ASIL D compliance is achieved by feeding the safety-critical loads redundantly and independently from two branches.

[0040] 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 4a and 4b can be connected to all power distribution units. At a minimum, both DC-DC converters 4a and 4b can be connected to all power distribution units supplying safety-critical loads.

[0041] In Figure 1In an exemplary embodiment, the power distribution units 5a and 5b actively distribute a plurality of loads between the first DC-DC converter and the second DC-DC converter such that the first battery and the second battery are substantially balanced. To this end, the switches 6a, 6b, 6c, 6d, 6e, 6f, 6g and 6h electrically connect specific loads to specific DC-DC converters to achieve a desired power consumption from a specific battery relative to the power consumption from the other battery.

[0042] In Figure 1 In an exemplary embodiment of, the system 1 further includes a first electrical master fuse box (eMFB) 7a electrically connected to the first DC-DC converter 3a. At the other end, the eMFB 7a is electrically connected to the first power distribution unit 5a and the second power distribution unit 5b. The system 1 further includes a second eMFB 7b electrically connected to the second DC-DC converter 3b. At the other end, the eMFB 7b is electrically connected to the first power distribution unit 5a and the second power distribution unit 5b. The eMFB contains fuses that interrupt the current in the event of overcurrent to protect the loads, the DC-DC converters, and the batteries.

Claims

1. A system (1) for supplying a low DC voltage from a high-voltage battery (2a, 2b) of a vehicle to the vehicle, the system (1) comprising: A first DC-DC converter (3a) configured to convert a high DC voltage provided by a first battery (2a) of the vehicle into a low DC voltage; A second DC-DC converter (3b) configured to convert a high DC voltage provided by a second battery (2b) of the vehicle into a low DC voltage, wherein the first DC-DC converter (3a) is configured to be electrically connected to the first battery (2a), and wherein the second DC-DC converter (3b) is configured to be electrically connected to the second battery (2b).

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

3. The system (1) according to claim 2, characterized in that The first DC-DC converter (3a) and the second DC-DC converter (3b) are configured to provide the low DC voltage in the off state of the vehicle in a low-power mode, in which active cooling of the DC-DC converters is turned off.

4. The system (1) according to claim 3, characterized in that The first DC-DC converter (3a) and the second DC-DC converter (3b) are configured to operate in a low-power mode with only passive cooling.

5. The system (1) according to any one of claims 1-4, characterized in that, The first DC-DC converter (3a) and the second DC-DC converter (3b) are configured to provide electrical power in a high-power mode with active cooling.

6. The system (1) according to any one of claims 1-5, characterized in that, The first DC-DC converter (3a) and the second DC-DC converter (3b) are configured to be directly electrically connected to the high-voltage battery without any switch therebetween.

7. The system (1) according to any one of claims 1-6, 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 both the first DC-DC converter (5a) and the second DC-DC converter (5b).

8. The system (1) according to claim 7, 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 the second DC-DC converter (3b).

9. The system (1) according to claim 8, characterized in that, The power distribution unit (5a, 5b) is configured to actively distribute the plurality of loads between the first DC-DC converter (3a) and the second DC-DC converter (3b) such that the first high-voltage battery (2a) and the second high-voltage battery (2b) are substantially balanced.

10. The system (1) according to any one of claims 7-9, characterized in that, The power distribution unit includes (5a, 5b) at least one switch for separating a quality management load from a safety-critical load.

11. The system (1) according to any one of claims 7-10, further comprising: A first electrical main fuse box eMFB (7a) electrically connected to the first DC-DC converter (3a), the first power distribution unit (5a) and the second power distribution unit (5b); and 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).

12. The system (1) according to any one of claims 1-11, characterized in that, The low DC voltage is a nominal voltage of 60V or less, preferably a nominal voltage of 12V, 24V, or 48V.

13. The system (1) according to any one of claims 1 to 12, characterized in that, The high voltage is a nominal voltage greater than 60V, preferably a nominal voltage of 200V, 400V, 800V, or higher.

14. The system (1) according to any one of claims 1 to 13, characterized in that The high-voltage batteries (5a, 5b) are adapted to supply power to the electric motors of the vehicle.

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