C = Value of the capacitance to be used.R = Required output voltage divided by maximum required output current.Now to design the capacitor we use the simple equation, Y=1/(4√3fRC) Now the output after the capacitor will be Since the bridge rectifier has already been discussed in a previous page,I will not be going deeper into that section, so lets gets straight to the regulator circuit, Simple Circuit Diagramįirstly let us discuss about the need for the smoothing capacitance.As you know the out put of the bridge rectifier will be as followsĪs you can see, although the waveform can be considered to be a DC voltage since the output polarity does not invert itself, the large ripples that exist inthe output makes sit almost impossible to be used in any powering applications.So it is to remove these ripples that the smoothing capacitor is used. Now this voltage can be fed into our load. This unregulated DC voltage is fed into a voltage regulator which will keep a constant output voltage and suppresses unregulated voltage ripples. But this voltage will change according to varying load and input stability. The following bridge rectifierand a smoothing capacitor to convert his AC voltage into unregulated DC voltage. Here, we have got an input high voltage AC going into a transformer which usually steps down the high voltage AC from mains to low voltage AC required for our application.

This circuit, like all voltage regulators must follow the same general block diagram

Until now we had discussed about different voltage regulator IC’s including 7805,723 etc but what’s to be noted was that these were all fixed voltage regulators.So now we shall see how design a simple variable voltage regulator using an LM317 IC.

317 voltage regulator