System and procedure for managing electrical loads in a vehicle

Abstract

System (10) for managing electrical loads in a vehicle (12), comprising: a high-voltage energy source (14); an electrical converter (24) capable of receiving high-voltage energy from the high-voltage energy source (14) and providing a low-voltage output to at least one low-voltage load (27); and a control system (20) configured to interrupt energy to at least one of the at least one low-voltage loads (27) when the high-voltage power source (14) cannot supply all of the at least one low-voltage loads (27) with full energy, characterized in that the controller (20) is still configured to allow energy to be supplied to the at least one of the at least one low-voltage loads (27) after its power interruption, if signals received from the converter (24) indicate that the output from the converter (24) can supply the at least one low-voltage load (27) with full energy.

Description

TECHNICAL FIELD

[0001] The present invention relates to a system and method for managing electrical loads in a vehicle. BACKGROUND

[0002] As battery technology changes, for example, from nickel-metal hydride chemistry to lithium-ion chemistry, the operating range of batteries expands. Such batteries can be used for high-voltage applications, such as hybrid electric vehicles or electric vehicles. In vehicle applications, the high-voltage battery can provide energy after voltage reduction not only for high-voltage loads but also for low-voltage loads, for example, via a DC / DC converter.

[0003] Document DE 10 2012 000 442 A1 provides a system for managing electrical loads in a vehicle, including a high-voltage power source, an electrical converter operable to receive high-voltage power from the high-voltage power source and provide a low-voltage output to at least one low-voltage load, and a controller configured to interrupt power to at least one of the at least one low-voltage load if the high-voltage power source cannot fully power all of the at least one low-voltage load. Further relevant prior art relating to the background of the invention is provided by documents US 6 979 977 B2 and EP 0 750 384 A2.

[0004] In addition to the high-voltage battery, a hybrid electric or electric vehicle may also include a low-voltage battery, which can be used to power vehicle lights, engine cooling fans, heated seats, and / or other low-voltage loads. When the electrical loads in the vehicle reach a certain level, the high-voltage battery may not be able to provide all of the power, and the low-voltage battery may need to supplement the power supplied by the high-voltage battery. This could occur, for example, if the high-voltage loads were too large or due to limitations in a DC / DC converter. In such a case, a minimum charge level may need to be maintained in the low-voltage battery to ensure that enough power is available, for example, to turn on the headlights.If the low-voltage battery is too drained, it may require automatic shutdown of certain electrical loads to maintain the minimum charge in the low-voltage battery. When this "reactive" method of managing electrical loads is used, the energy may be so low that it requires such system shutdown that it is very obvious to vehicle occupants. For example, if the low-voltage battery charge reaches a certain level, it may be necessary to turn off an air conditioning system, which is very noticeable and undesirable for occupant comfort.

[0005] Therefore, there is a need for a system and method for managing electrical loads for a vehicle that is largely transparent to the vehicle occupants. SUMMARY

[0006] Embodiments of the present invention include a system for managing electrical loads in a vehicle. A high-voltage power source is operable to supply electrical power to at least one high-voltage load, and an electrical converter is operable to receive a high-voltage power input from the high-voltage power source and provide a low-voltage power output to a plurality of low-voltage loads. In this manner, the high-voltage power source supplies power to at least some of the low-voltage loads. Embodiments of the system further include a control system including at least one controller. The control system is in communication with the converter and is configured to receive signals from the converter related to the converter output.Furthermore, the control system is configured to interrupt power to at least one of the low-voltage loads when the signals received from the converter indicate that the high-voltage power source cannot fully power the low-voltage loads.

[0007] Embodiments of the invention include a system for managing electrical loads in a vehicle, including a high-voltage power source and an electrical converter operable to receive high-voltage power from the high-voltage power source and provide low-voltage power to at least one low-voltage load. The system further includes a controller configured to interrupt power to at least one of the at least one low-voltage load when the high-voltage power source cannot fully power all of the at least one low-voltage load.

[0008] Furthermore, embodiments of the invention include a method for managing electrical loads in a vehicle having a high-voltage power source capable of supplying electrical power to at least one high-voltage load and a plurality of low-voltage loads. The vehicle further includes an electrical converter operable to receive a high-voltage power input from the high-voltage power source and provide a low-voltage power output to the low-voltage loads. The vehicle further includes a control system including at least one controller configured to receive inputs from the converter and control the low-voltage loads.Steps of the method may include monitoring the activity of the converter and interrupting power to at least one of the low voltage loads when the activity of the converter indicates that the high voltage power source cannot fully power the low voltage loads.

[0009] Embodiments of the present invention include a method for managing loads in a vehicle including a high-voltage power source and a converter operable to receive an input from the high-voltage power source and provide a low-voltage output. Steps of the method include monitoring the activity of the converter, monitoring low-voltage load activity, and reducing the low-voltage load activity when the high-voltage power source cannot fully power the low-voltage loads and at least one low-voltage load is present. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic representation of a system according to embodiments of the present invention; Fig. Figure 2 is a diagram illustrating the relationship between voltage input and voltage output for a converter that is part of a system of the present invention; and Fig. 3 shows a flowchart illustrating steps according to an embodiment of the present invention. DETAILED DESCRIPTION

[0010] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in different and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0011] Fig. 1 shows a system 10 for managing electrical loads in a vehicle 12 according to embodiments of the present invention. A high-voltage power source 14, which in this embodiment is a high-voltage battery, includes a high-voltage battery cell assembly 16 and a battery controller 18. The battery controller 18 is connected via a Controller Area Network (CAN) to a control system including a body control module (BCM) 20. In addition to communicating with the battery 14, the BCM 20 communicates with other controllers and systems throughout the vehicle 12, as schematically represented by the other CAN nodes 22. The BCM 20 also communicates with a DC / DC converter 24 configured to receive a high-voltage input from the high-voltage battery 14. The converter 24 outputs low-voltage power that is routed to a low-voltage power distribution box (LV-EVK) or a fuse box 26. As shown in Fig. 1, the low-voltage vehicle loads 27 are connected to the fuse box 26. A low-voltage battery 28 is also connected to the fuse box 26 and can supply power to the fuse box and the low-voltage loads 27 if necessary. In the illustration, a dashed line 30 connects the low-voltage battery 28 to the BCM 20 and represents communication therebetween, which may be part of a method according to embodiments of the invention. In addition to supplying the low-voltage loads 27 with low-voltage power via the converter 24, the high-voltage battery 14 can also supply high-voltage power to high-voltage loads 32, which may be, for example, a traction motor in an electric or hybrid-electric vehicle.

[0012] Fig. Figure 2 shows a diagram 34 illustrating the relationship between the high-voltage power input to the converter 24 and the low-voltage power output. As used herein, the distinction between high-voltage power and low-voltage power is the difference between voltages in the range of 50 volts or below for low-voltage power and 100 volts or above for high-voltage power. Diagram 34 shows three different current levels: 145, 165, and 195 amperes (A). In the example shown, 14.5 volts (V) is considered a full power output for low-voltage loads 27. As in Fig. 2, the 14.5 V is available for all three current levels when the high-voltage power input to the converter 24 is at least 210 V. Below 210 V, the available output voltage drops—initially only for the 195 A current level, but then also for the other two current levels when the high-voltage power input drops below 200 V. As explained below, knowledge of the relationship between the input and output voltages and the full-power requirements for low-voltage loads 27 can be useful for control strategy methods according to the present invention.

[0013] In order to proactively control the low voltage loads 27 in the vehicle 12, the activity of the DC / DC converter 24 is monitored, for example by the BCM 20. This is described in the Fig. 3, particularly in step 38. Step 40 may also be used when monitoring low voltage activity, and this is done by the Fig. 1. As used in this context, "monitoring" the converter 24 or the activity of the low-voltage loads 27 may simply be receiving a signal or signals related to inputs, outputs, or any other parameter that provides the desired information. Based on the information it receives, the BCM 20 determines whether the high-voltage battery 14 can fully power the low-voltage loads 27.

[0014] If it is determined in decision block 42 that the high-voltage battery 14 can fully power the low-voltage loads 27, the method returns to step 38, where converter activity is monitored. However, if the high-voltage battery 14 is unable to fully power the low-voltage loads 27, a method of the present invention reduces the low-voltage load activity—see step 44.

[0015] Embodiments of the present invention are configured to interrupt power to one or more of the low-voltage loads 27 when a high-voltage power source, such as battery 14, cannot fully power the low-voltage loads 27. This control strategy may be implemented by a controller, such as BCM 20, alone or in conjunction with other connected controllers, for example, through a CAN. Because embodiments of the present invention make decisions based on the activity of a converter, such as converter 24, power to one or more low-voltage loads 27 may be interrupted before a low-voltage power source, such as battery 28, is used to augment the power received from the high-voltage power source.This allows the interruption of power to the low-voltage loads 27 in a manner that is virtually transparent to a vehicle driver. For example, if the control strategy first determines that the high-voltage power source cannot fully power the low-voltage loads 27, a first "load shedding strategy" may be deployed to terminate specific low-voltage loads 27. These may include, for example, power to one or more heated seats in the vehicle and / or a reduction in the speed of a heater fan. The first load shedding strategy may be implemented to terminate or reduce specific low-voltage loads 27 so that the high-voltage power source can fully power all remaining low-voltage loads 27.When the high-voltage energy source receives an additional charge - for example, through regenerative braking - and is again able to supply all low-voltage loads 27 with full energy, the previously terminated or reduced load(s) can be used again with full energy.

[0016] As mentioned earlier, part of determining when load shedding is desired involves monitoring the activity of an electrical converter, such as the one in Fig. 1. One way to achieve this is to monitor the low-voltage output, knowing that a required minimum level must be met for all low-voltage loads 27 to receive full power. However, embodiments of the present invention employ a different strategy in that the high-voltage input to the converter 24 is analyzed. This is possible because, as shown in diagram 34 in Fig. 2, there is a known relationship between the output voltage and the input voltage. Using the examples of Fig. 1 and Fig. 2, the BCM 20 could implement a first load shedding strategy when the high-voltage input to the converter 24 was 210 V or less. If the current draw from the high-voltage battery was known to be less than 195 A, for example, 145 A or 165 A, then the BCM could wait until the high-voltage input was 200 V or less before implementing the first load shedding strategy. In this way, embodiments of the present invention can be particularly proactive in shedding low-voltage loads 27 prior to requesting assistance from the low-voltage battery and undesirable accessory reductions that may be noticeable to vehicle occupants.

[0017] Embodiments of the present invention may also include several features to further refine the load shedding strategy. For example, a high-voltage power source, such as the one described in Fig. 1, may be subject to transient energy reductions that temporarily render it unable to fully power all of the low-voltage loads 27. If the load shedding strategy is implemented quickly by the BCM 20, then low-voltage loads 27 may be unnecessarily shed if the high-voltage battery returns to a higher energy level very quickly. As previously mentioned, the first load shedding strategy focuses on those loads that are generally unnoticed by the vehicle occupants, and therefore, this transient response is not detrimental to the effectiveness of the strategy.However, if it is desired to reduce the effects of transient energy fluctuations in a high-voltage power source, it is possible to delay the step of delaying the start of the load shedding strategy until the control system has received a signal indicating low energy in the high-voltage battery for a predetermined period of time. In such a case, the predetermined period of time would be relatively short to ensure that the control strategy was still proactive and the low-voltage loads 27 had not become such a burden that energy was being drawn from the low-voltage power source.

[0018] As mentioned above with reference to Fig. 1, a low-voltage energy source, such as the low-voltage battery 28, may communicate with a control system, such as the BCM 20. In such a case, the BCM 20 may monitor low-voltage load activity by measuring one or more parameters of the low-voltage battery 28. Thus, the load shedding strategy may be indicated by signals the BCM 20 receives from the converter 24, but it will not be implemented unless there are low-voltage loads 27 that are subject to the first load shedding strategy. In some cases, there may be no low-voltage loads 27 available to terminate or reduce, and in other situations, low-voltage loads 27 may be available but not included in the first load shedding strategy.For example, if an air conditioning system was active and the high-voltage battery 14 was unable to supply the air conditioning system with full power, and considering that less than full power could be detrimental to one or more components, such as a compressor, a second load shedding strategy may need to be implemented. This is because an air conditioning system may not be part of a first load shedding strategy, and stopping this load would most likely be noticed by the vehicle occupants and considered undesirable. In this case, a second load shedding strategy may be implemented, whereby the BCM 20 first provides an indication to the vehicle operator indicating that it is necessary to stop some vehicle loads.Then, the BCM 20 could terminate power to the air conditioning system, and the vehicle operator would expect this and not consider it a system failure. This second load shedding strategy can be implemented in situations where no loads are subject to the first load shedding strategy, or it can be implemented after all loads have been terminated or reduced according to the first load shedding strategy, but the high-voltage battery is still unable to supply the remaining low-voltage loads 27 with full power.

[0019] Although exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms of the invention. Instead, the terms used in the description are for the purpose of illustration rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Furthermore, the features of the various implementation embodiments may be combined to form further embodiments of the invention. Key to symbols Fig. 2 Vin[V] Vein[V] Vout[V] Vab[V] Io=195A lab=195A Io=165A lab=165A Io=145A lab=145A Fig. 3 38 Monitor converter activity 40 Monitor LV load activity Yes Yes 42 Can HV source supply LV loads with full energy? No No 44 Reduce LV load activity

Claims

[1] A system (10) for managing electrical loads in a vehicle (12), comprising: a high-voltage energy source (14); an electrical converter (24) operable to receive high voltage power from the high voltage power source (14) and to provide a low voltage output to at least one low voltage load (27); and a controller (20) configured to interrupt power to at least one of the at least one low-voltage load (27) when the high-voltage power source (14) cannot supply all of the at least one low-voltage load (27) with full power, characterized in that the controller (20) is further configured to allow power to the at least one of the at least one low-voltage load (27) after its power interruption when signals received from the converter (24) indicate that the output from the converter (24) can fully power the at least one low-voltage load (27). [2] The system (10) of claim 1, wherein the controller (20) is configured to interrupt power to at least one of the at least one low voltage load (27) so that the high voltage power source (14) can supply full power to the remaining at least one low voltage load (27). [3] The system (10) of claim 1, further comprising a low voltage power source (28) capable of powering the at least one low voltage load (27), and wherein the controller (20) interrupts power to at least one of the at least one low voltage load (27) before the low voltage power source (28) delivers power to the at least one low voltage load (27). [4] The system (10) of claim 1, wherein the controller (20) is further configured to delay the step of interrupting power to at least one of the at least one low voltage load (27) until the signals received from the converter (24) have been received for a predetermined period of time. [5] The system (10) of claim 1, wherein there is a known relationship between transducer input and transducer output, and the signals received by the controller (20) from the transducer (24) related to the transducer output are signals indicative of the transducer input from the high voltage power source (14). [6] The system (10) of claim 1, wherein the controller is further configured to provide an indication to an operator of the vehicle (12) after power to at least one of the at least one low voltage load (27) has been interrupted and the high voltage power source (14) cannot fully power the remaining at least one low voltage load (27). [7] A method for managing electrical loads in a vehicle (12) having a high-voltage power source (14) capable of supplying electrical power to at least one high-voltage load (32) and a plurality of low-voltage loads (27), an electrical converter (24) operable to receive a high-voltage power input from the high-voltage power source (14) and to provide a low-voltage power output to the low-voltage loads (27), and a control system including at least one controller (20) configured to receive inputs from the converter (24) and to control the low-voltage loads (27), the method comprising the steps of: monitoring the activity of the transducer (24); and Interrupting the power to at least one of the low-voltage loads (27) if the activity of the converter (24) indicates that the high-voltage power source (14) cannot supply the low-voltage loads (27) with full power, characterized by the fact that the method comprises providing power to at least one of the low-voltage loads (27) after interrupting its power when the input of high-voltage power to the converter (24) increases, and signals received from the converter (24) indicate that the output from the converter (24) is large enough to supply the low-voltage loads (27) with full power. [8] The method of claim 7, wherein the converter output is related to the converter input and the step of monitoring the activity of the converter (27) comprises monitoring the input to the converter (24) to determine when the output from the converter (24) is so low that the high voltage power source (14) cannot supply the low voltage loads (27) with full power output.

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