Flux then collapses and is transformed back to electrical energy for maintaining supply to the load during the switch-OFF cycle. Another typical application for inductors is EMI suppression. Inductors present a series of impedance when noise frequency enters through the component. Resistance accounts for the major share of total impedance at high frequency. The reactance is the result of inductance and frequency in which noise is being blocked from going through the inductor.
Reactance contributes to most of the total impedance at low frequency.
There are several types of inductors on the market. These include solenoid, bobbin, shielded and toroid powdered core. Solenoid and bobbin type inductors are typically wound with a ferrite core, whereas an iron powder core is used when extremely high DC current is required. In a case like the discontinuous mode flyback with high frequency ripple current, these inductors can radiate high levels of magnetic flux to their surroundings, causing a potential malfunction in sensitive components nearby. Shielded inductors are typically made with a ferrite sleeve over the bobbin core.