Power Supply Filter Capacitor Design

The filter capacitor must usually be large to provide an acceptable level of filtering.

Power supply filter capacitor design.

Since a single diode will rectify only one half cycle of the ac signal this type of configuration requires a large output filter capacitor for compensating the above limitation. The chart above shows typical power supply filtering frequency ranges. For a typical 5 v power supply a 2 200 μf electrolytic capacitor will do the job. The inductor passes dc.

Simple shunt capacitor filter reduces the ripple voltage but increases the current through the diode. Putting it to work a practical example. This is the most basic form of power supply design which uses a single diode and a capacitor. Regardless of the frequency with which the input voltage is applied a capacitor is used in order to reduce the remaining resistance after rectification.

Why the capacitor in your power supply filter is too big january 21 2016 by david williams the job of the capacitor in the output filter of a dc power supply is to maintain a constant dc value by removing as much power ripple as possible. This is an assumption in cases where the capacitor is oversize it will be perhaps 80 but this is close enough for government work and not very critical. The lc filter shown in fig. Correct design of the decoupling filter ensures that it won t cause more problems than it solves.

This large current may damage the diode and at the same time it causes greater heating of the power transformer resulting in decreased efficiency. Depending on the power supply the smoothing capacitor is combined with other circuits. In addition to the natural output capacitance of the power supply you might add a series inductor and another filter capacitor to further reduce output noise fig. The bigger the capacitor the lower the resulting ripple voltage.

L c filters power supply filters. Probably the most widely used application of smoothing capacitors is the construction of power supplies. For example a 10 ripple in a 5 v power supply means that the actual output voltage varies by 0 5 v. Either lc or rc low pass filters can be used to remove the ripple remaining after the reservoir capacitor.

1 2 3 is more efficient and gives better results than the rc filter shown in fig. Because these capacitors have a dc value they are actually storing a lot of energy that never gets used.