This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term “xEV” is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs) combine an internal combustion engine propulsion system and a battery-powered electric propulsion system, such as 48 volt or 130 volt systems. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Mild hybrids are typically 96V to 130V and recover braking energy through a belt or crank integrated starter generator. Further, a micro-hybrid electric vehicle (mHEV) also uses a “Stop-Start” system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine and operates at a voltage below 60V. For the purposes of the present discussion, it should be noted that mHEVs typically do not use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered as an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives or contributes to drive the wheels. PEVs are a subcategory of electric vehicles that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.
Micro Hybrid technology can use a dual voltage architecture, such as a traditional 12V vehicular electrical system used in conjunction with a lead-acid battery, and a 48 volt vehicular electrical system used in conjunction with a Lithium-ion battery. 12 volt electrical system, as used herein, refers to a traditional vehicular electrical system that operates at a nominal 12 volts. The actual voltage varies dynamically depending in part on the charge state of the battery and the load, and an any point in time can be more or less than 12 volts. 48 volt electrical system, as used herein, refers to a vehicular electrical system that operates at a nominal 48 volts, such as one using an LI-ion battery. The actual voltage varies dynamically depending in part on the charge state of the battery and the load, and an any point in time can be more or less than 48 volts. The 12 volt system can include things such as lights, audio/entertainment, electronic modules and ignition. The 48 volts system can include the A/C compressor, active chassis, and regeneration. These systems support higher power loads and provide redundancy. Typically an 8-10 kW motor/generator captures energy for regeneration, supports re-start and supports higher power loads. A DC/DC converter bridges between the higher 48 volt system and the traditional 12 volt system.
Such a micro hybrid vehicle can change electrical load management due to high power regeneration, and provide for electrification of new loads such as air conditioning, active chassis and safety, electric supercharging, as well as result in increased fuel efficiency.
The DC-DC converter needed for to bridge the systems should be able to provide sufficient power without taking excess space. Moreover, it should be able to withstand the vehicular environment, including high temperatures.