22-09-2020 | | By Sam Brown
Power inductors are a critical component in modern electronics, and making them small can have a significant impact on the final circuit. What are inductors, what are they used for, and why is making them smaller so crucial to engineers?
Inductors are components which are specifically designed to have inductance, and inductance is a property of a component to resist changes in the electrical current flowing through it. Most inductors consist of a coil of wire, and the size of the inductance of an inductor is proportional to the number of turns and the cross-sectional area of the inductor while being inversely proportional to its length.
It is important to understand that inductors resist changes in current, as opposed to DC, whose value does not change. When a current flows through an inductor, a magnetic field is formed, and this field stores magnetic energy. It is this magnetic field that attempts to resist any changes in current through the inductor as changes in current result in the formation of opposing magnetic fields to the magnetic field in the inductor. For example, if the current through an inductor suddenly drops, the magnetic field in the inductor begins to collapse, and as it collapses it induces a current in the coil (changing magnetic fields in a coil induce an EMF), and the direction of the induced current is identical to the one that originally formed the magnetic field.
Inductors come in a wide variety of shapes and sizes with physically larger inductors often having a larger inductance. Transformers are essentially inductors, but utilise magnetic coupling to allow the energy from one coil to be transferred to another coil.
Inductors have a wide range of uses but are mostly found in filtering applications. A typical application where inductors are incredibly useful is switching DC/DC converters. These converters rely on a fast switching transistor to step down a DC voltage which results in exceptionally high efficiencies (greater than 90%). However, the switching transistor can result in injected switching noise into the DC power output, and the noise can upset sensitive electronics as well as generate unwanted EM radiation. An inductor can be added in series to the DC power output to resist the switching noise, and thus create a smooth power supply ideal for sensitive electronics.
Inductors can also be used as a generic filter component to create low-pass, band-pass, and high-pass filters. Their use in filter circuits is opposite to that of capacitors; inductors in the series act as low-pass filters while inductors in parallel act as high-pass filters. If capacitors and inductors are combined, they can produce resonant circuits which can be tuned only to allow a very narrow range of frequencies, and these are highly used in radio circuitry.
The ability to reduce the size of components has a multitude of benefits. The first is the physical reduction in the final size of the circuit, and this results in cheaper PCBs, as well as designs that can be more complex as component density is increased. The second advantage to smaller components is a reduction in the overall mass, and therefore weight, of the final design. This is advantageous for making smaller, more portable designs, and is also beneficial in aerospace and automotive applications where weight reduction is critical. Reducing the size of a component can also help to reduce its price as less material is needed to manufacture the component, and this help to reduce the overall cost of the final product.
Unlike other components, inductors are not the easiest of components to reduce in size, and inductors are often some of the largest components in circuits. Recognising the importance of lowering inductor sizes, Samsung has announced that they have developed the worlds smallest power inductor.
The inductor measures 0.8mm x 0.9mm in size while having a thickness of just 0.65mm. When compared to the industries previous small power inductor or 1.2mm x 1mm, the latest inductor produced by Samsung represents a significant size reduction. According to Samsung, the reduced inductor size was possible using multilayered materials, a process similar to that found in multilayer capacitors.