Co-fired ceramic inductors with variable inductance, and voltage regulator having same

Abstract

Ceramic inductors are made from stacked sheets of co-fired ceramic. At least one of the ceramic sheets has a slot with a conductor disposed in the slot. The conductor has a thickness equal to a thickness of the ceramic sheet containing the slot. The conductor has a large thickness (compared to prior art co-fired ceramic inductors) and therefore can carry large currents. The present ceramic inductor can be used in power electronics applications due to the ability to carry large currents. The present ceramic inductor preferably has an inductance that decreases with increasing current. A decreasing inductance characteristic tends to increase energy efficiency in a voltage regulator when the inductor is used as an output inductor. Specifically, the variable inductance tends to substantially increase energy efficiency at low current loads without adversely affecting efficiency at high loads.