雙電壓汽車電源系統的設計

　　在更高的功率水平需要更高的效率，促使移動到48伏的電源軌，以減少所需的電流時，提供一個給定的功率量。然而，過渡到48伏系統是不簡單的安裝更大的電池和發電機。

　　本文將討論為什么汽車需要一個48伏的鐵路和全系統的影響，然后引入一個新的DC / DC轉換器，可以大大簡化電力系統的設計與雙電壓（12 / 48 V）的能力。然后，它將集中在其他關鍵48伏組件和系統架構，包括電池管理系統（BMS）的新的48伏鋰離子電池。

　　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.