During the past, several decades we have seen the power density of power supplies increase by orders of magnitude. Operating at higher frequencies has brought the greatest reduction but seems to be running out of steam. Apart from topology, the specific devices that have limited reduction have been either magnetic components, capacitive components, or semiconductors. Today, with bandgap (GaN & SiC) switching devices, the focus is on controllers, topologies and low parasitic in passive components. When magnetics is small, the area used by the capacitors usually increases. Some designs show small magnetics on one side of the board but not the sea of capacitors on the other. High frequency has made inductance values at the same level as previous parasitic inductances. Inductors appear to be merely a loop of wire with a core. Small ceramic capacitors have large swings in value with applied voltage negating their size advantage. One promising area of development is transient load voltage regulation (TLVR), where magnetics is employed to reduce the number of capacitors required for fast transient response. This reflects an ongoing "tug of war" between magnetics and capacitors in power supply design.
.jpg "Jim Marinos photo")
