ithin the next 10 years, the electrical systems in some luxury automobiles will be so changed as to be almost unrecognizable. Although they will doubtless employ the old reliable 12-V lead-acid battery, their loads will be driven by a variety of voltages, both ac and dc, perhaps derived from a single ac distribution network. Designers will be able to match voltages to individual loads for best efficiency and performance--lights perhaps at 6 V ac, electronics at 5 V dc, active suspension at 350 V dc, and motors and actuators at 42 V dc. The digital signals controlling those loads will be carried by a separate communications network [Fig. 1].
That, at least, is how a working group of engineers from makers of autos and automotive components envision the electrical systems of luxury vehicles in the 20052015 time frame. The group, which gathered under the auspices of the Massachusetts Institute of Technology at the request of Mercedes-Benz AG, expects the technology to spread to less opulent models as costs drop [see "Planning for 2005"].
Semiconductors, of course, are the enabling technology that will make it all possible (as well as making it all necessary). The costs of solid-state power converters, switches, and logic devices have been dropping steadily. The cost per watt today is less than half what it was in 1990 and is fast arriving at a level that is practical for certain automotive applications.
Two main forces are driving cars to multivoltage systems--the quest for ever-greater fuel economy and the emergence of new power-hungry automotive functions. Novel electrical equipment, like electromechanical valve actuators and active suspensions, will triple the aggregate electrical power demand in some cars--from 800 W today to an average of 2500 W and a peak value above 12 kW by perhaps as early as 2005. That power can be more effectively distributed and utilized at voltages much higher than today's 12 V dc.
All the same, a large, complex infrastructure now supports the 12-V system with components and services. Surmounting this obstacle will require agreement within the industry on many new system parameters, and reaching that agreement will take time.