As electronic devices become more advanced, the power supply voltage of LSIs used in them is lowered, so their power consumption can be reduced and their speed increased. However, a decrease in the power supply voltage also causes the requirements regarding voltage fluctuations to become more severe, creating a need for high-performance DC-DC converters to fulfill these characteristic requirements, and power inductors are important components that greatly affect their performance. TDK has a widely varied lineup of power inductor products, and this article describes and explains effective methods for using power inductors, and key points for selecting them, according to the required characteristics of DC-DC converters.