48 V for  ( delivers four times of 12 V the electrical power without increasing cable thickness, weight, and cost)

    start-stop motor/generator of a mild hybrid vehicle, 

    loads such as electric power steering, 

    electric supercharging, 

    vacuum and water pumps.

Yes to 48 V and also yes to 12 V  in vehicles.  Thus  bidirectional DC-DC converter is needed to transfer power seamlessly between the two battery voltages.  GaN technology is driving changes in automotive systems will be discussed. These applications include 48V power distribution bus for mild hybrid cars, high-frequency DC-DC conversion for infotainment systems, brushless DC (BLDC) motors, and light detection and ranging (lidar) used for autonomous navigation.

(EVs and HEVs)  might use 

operate at higher voltages and temperatures, 

are more rugged, 

have longer lifetimes, 

switch much faster than conventional  semiconductor devices.