Daily Archives: April 24, 2024

Is Metal Better than Ferrite for Inductors?

Many power and signal conditioning applications use power inductors as a basic component to store, block, filter, or attenuate energy. Today’s power circuits use increasingly higher switching frequencies and high powers that impose challenges in packaging and material levels for component manufacturers. Consequently, power inductors, while shrinking their form factors, are pushing to provide higher-rated currents.

The above presents a dual challenge to component manufacturers and designers alike. For instance, component designers must use materials other than the traditional ferrite core materials to miniaturize these devices, while maintaining other parameters such as DCR and inductance without change. Taiyo Yuden is meeting the dynamic challenges of these applications by using metal for power inductors.

Engineers typically select power inductors primarily by their inductance value, then by their current rating and DCR or DC resistance value, followed by their operating temperature range. They may also consider whether the inductor will require to have shielding or none. The application circuit that will use the inductor requires optimization of the above parameters.

Applications of power inductors can range from filtering EMI at the AC inputs of a power supply to filtering ripples at the output of a DC power supply. Inductors are indispensable for reducing the ripple in voltage and current in switching power supply outputs. DC-DC converters use inductors for their self-inductance property of storing power—as the switching circuit turns off, the inductor discharges its stored current. Almost all types of voltage regulation circuits, for instance, power supplies, DC-DC converters, switching circuits, and others, take advantage of the characteristics of power inductors.

Semiconductor power supplies are transitioning from the higher 3.3 V rails and lower currents to lower voltages of 1-1.2 V rails and higher currents for catering to advances in chip design technology. This entails the need for a high-current handling power inductor. Furthermore, smaller form factors of enclosures following the development of smaller-sized electronic components are increasing the demand for miniaturization of all associated electronic components, including the power inductor.

However, the size of power inductors and their higher current capability present a tradeoff. Withstanding higher currents typically requires a bigger case size, resulting in a change in land patterns on PCBs. On the other hand, a small size translates into saturation current due to insufficient inductance. Taiyo Yuden uses the patented construction of a wire-wound multilayer power inductor with a unique metal alloy. This construction allows the designer to achieve both the required inductance in a small case size and a high saturation current.

Taiyo Yuden create their multilayer inductor by printing a pattern on a ceramic sheet that contains ferrite. They laminate these sheets before firing them. Then they assemble the final piece, pressure bond them and fire them. At the last stage, they form external electrodes at both ends. The use of material with a high magnetic permeability results in an inductor with a high inductance value.

The construction of wire-wound inductors follows the traditional method. The coil is either on the inside or on the outside surface of a magnetic material, such as ferrite. A high number of turns results in a higher inductance and a higher DC resistance.