To convert voltages to useful levels without suffering massive losses in efficiency.
> What applications cannot be made to work at 48?
Basically every logic-level transistor will not work at 48V. It's nice that these last-century analog devices could be made to operate at different voltages: present-day semiconductors are not so conveniently flexible.
Simple physics dictates that required inductors to step between voltages increase in physical size (and weight, and material cost) as that voltage disparity increases. Capacitance required, etc. all increases with it. Efficiency plays into both of these as a triangle. Heat increases as this disparity increases. These properties are unacceptable for a myriad of use cases.
You didn't have to convert voltages all the time for things you did in a car until relatively recently. All the typical 12V stuff could've run at 48V no problem. By the time we wanted to put computers in cars and charge our cell phones, switching supplies were readily available. The only part of the system now that really benefits from lower voltages are semiconductors.
To convert voltages to useful levels without suffering massive losses in efficiency.
> What applications cannot be made to work at 48?
Basically every logic-level transistor will not work at 48V. It's nice that these last-century analog devices could be made to operate at different voltages: present-day semiconductors are not so conveniently flexible.
Simple physics dictates that required inductors to step between voltages increase in physical size (and weight, and material cost) as that voltage disparity increases. Capacitance required, etc. all increases with it. Efficiency plays into both of these as a triangle. Heat increases as this disparity increases. These properties are unacceptable for a myriad of use cases.