双电压汽车电源系统的设计

　　双电压汽车电源系统的设计

　　在更高的功率水平需要更高的效率，促使移动到48伏的电源轨，以减少所需的电流时，提供一个给定的功率量。然而，过渡到48伏系统是不简单的安装更大的电池和发电机。

　　本文将讨论为什么汽车需要一个48伏的铁路和全系统的影响，然后引入一个新的DC / DC转换器，可以大大简化电力系统的设计与双电压（12 / 48 V）的能力。然后，它将集中在其他关键48伏组件和系统架构，包括电池管理系统（BMS）的新的48伏锂离子电池。

　　Why automobiles need to move to 48 volts

　　Increasing electrical demands in cars are straining the 12 volt supply. With a 12 volt supply rail， each kW of demand will need about 80 A of current. Also at low temperatures， static-load components can account for the entire power generated by the alternator， up to 3 kW. High currents also translate to higher losses， which run contrary to the need for greater efficiency in order to meet strict year 2020 fuel consumption industry goals， which range from 5.0 to 6.0 L/100 km， depending on location.

　　To boost efficiency at higher power levels， automotive designers are moving to 48 volt power rails， reducing the current needed when delivering a given amount of power. This higher voltage network enables higher loads （up to 10 kW） to be supported with the same or even narrower cable diameters， reducing cable size and weight. That’s significant because today‘s high-end vehicles can have more than 4 km of wiring.

　　In migrating to 48 volts， one configuration a designer should consider is taking the 12 volt electric branch based on a conventional lead-acid battery， and then adding a 48 volt Li-ion battery to power a separate 48 volt branch （Figure 1）。 This approach is already supported by a number of automotive companies.