(Q)Is it ever practical to use an inductor to smooth the output ripple in power supply unit ????
· we typically use large capacitors to smooth out the
output ripple from a rectifying/switching power supply.Until recently, a
capacitor was usually chosen over an inductor because of weight. Also, from a
storage point of view, an inductor stores it's energy in the form of a magnetic
field. When the current stops flowing, the magnetic field collapses. When the
magnetic field is fully dissipated, the stored energy is depleted. This happens
whether or not anything is utilizing the stored energy or not.
A capacitor stores energy in the form of accumulated electrons on the plates of the capacitor. A capacitor charge will deplete in direct proportion to the amount of current drain between it's terminals. This current drain is in the form of both, the internal resistance of the capacitor and the load resistance externally connected to the capacitor terminals. But the capacitor, unlike the inductor, will hold the accumulated charge if not connected to an external load - only to be discharged by the internal resistance of that capacitor.
A capacitor stores energy in the form of accumulated electrons on the plates of the capacitor. A capacitor charge will deplete in direct proportion to the amount of current drain between it's terminals. This current drain is in the form of both, the internal resistance of the capacitor and the load resistance externally connected to the capacitor terminals. But the capacitor, unlike the inductor, will hold the accumulated charge if not connected to an external load - only to be discharged by the internal resistance of that capacitor.
· Also inductors
resist current change and thus smooth current ripple, capacitors smooth voltage
ripple.
A simple power supply has this arrangement:
AC supply ........>> diode or diode bridge.......>>.capacitor ......>>ground. The load goes across the capacitor.
If you wanted to add an Inductor, it should go after the capacitor in line with the load and there should be another capacitor after it to ground. The load goes across the second capacitor.The inductor ideally has no effect on DC current but it will help to limit the AC component on the DC.The input capacitor is important as the inductor can cause voltage spikes which might destroy the diodes if the capacitor wasn't there.
Also, the inductor should be a special one with an air gap in the iron core so that it does not saturate easily with DC passing through it.An inductor is not normally used because voltage regulator ICs are used and these give almost perfect smoothing.
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