Understanding the role of inductors in power electronics
Inductors are typically used as energy storage devices in switched-mode power devices to produce DC current. The inductor, which stores energy, supplies energy to the circuit to maintain current flow during “off” switching periods, thus enabling topographies where output voltage exceeds input voltage.
Due to the way they work—by not only altering electric field but the magnetic field around it—many people struggle to understand them.
What is an inductor?
An inductor is arguably the simplest of all electronic components. It’s a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. Typically, an inductor will consist of an insulated wire that’s wound into a coil, much like a resistor. This design was settled on following extensive trial and error methods that considered methods like Hanna curves and area-product.
When the current flowing through the coil changes, the time-varying magnetic field induces voltage in the conductor with a polarity which opposes the change in current that created it. As such, inductors oppose any changes in current that pass through them.
The induced magnetic field also induces an electrical property known as inductance—the ratio of voltage to the rate of change of current. Inductance quantifies how much energy an inductor is capable of storing.
A coil is a generic name for an electrode in the shape of a spiral. Among the different types of coils, there are coils called “inductors” which are used for electrical applications. Inductors can be further categorized into RF inductors used for signal processing, and power inductors for power supply lines. The power inductors discussed in this section form part of the voltage conversion circuit in a DC-DC converter or other device.
Here we will explain the operation of a power inductor in a DC-DC converter. A power inductor is used in a step-up, step-down, or step-up/step-down circuit to convert a certain voltage to the required voltage. Among those different circuits, it is primarily used in a type of circuit called a “switching regulator.”
Figure 1-1 shows an example of a switching regulator step-down circuit.
It uses an IC, power inductor, and capacitor to convert a DC input voltage to the required output voltage. The power inductor works with the capacitor to play the role of rectifying the rectangular wave output from the IC to a direct current.
If either one of these components is missing, the output cannot be properly rectified.