This is first tutorial on power electronics catagory and In this tutorial we are going to make a mobile phone charger using easily available components . This is on going series and in the first part we will design a smooth DC voltage source from 230 volt 60 Hz power supply which is generally used in our home .
To charge a mobile phone we need 5 volt DC source and current needed for charging is 700 milliamp . But the current depends upon how much time you need to charge a mobile phone . To charge a mobile battery with in very short period of time we need large amount of current more than 700 milli amp and to charge within large period of time lets say 10 Hour we need small amount of current less than 700 milli amp . And this factor also depends on capacity of battery . For large capacity of battery let's say 9000 mAh we need large current and need to charge for longer time . So you have to decide what battery you are charging .
Longer it take to charge battery the battery life also get longer and less time charged battery it will not work for long time .In above schematic I have designed small current source so that my battery will extend for long time .
Above schematic can be divided into three part , in first part we have to convert high voltage (230 volt ) AC source into low voltage (9-12) volt using a transformer . The conversion of high voltage AC source to low voltage AC source depends upon coupling factor of the transformer . Generally we can calculate the coupling factor dividing output voltage by input voltage but this is not accurate Generally you have to find flux of each coil and calculate blah blah blah ( do not worry you do not need to calculate coupling factor ) just use a transformer that can produce output of 9-12 volt AC output .And if you are using Proteus to simulate the circuit then you can download the complete file from this link smooth DC generation electronify
In second part of the schematic we need to convert AC to DC . Since the generated output voltage from the transformer is not DC we have to use diode to convert them into DC . The in first cycle of AC source two opposite diode conduct electricity and in second cycle remaining only two diode conduct electricity and using a capacitor we can make DC power supply .
Third part : The converted DC source is not smooth DC there will be some ripple and high voltage signal appear some time , it can damage the whole circuit , so we have to make smooth DC source . In the circuit above i have used 7805 IC to regulate the DC source but you can use any other IC like LM317 or something like that .
Now finally we have generated smooth 5 volt DC source which can be used to charge your battery . But this circuit is not enough to make a charger . We have to use short circuit protection so that in case of any short circuit occur the whole circuit would not be damaged . In next part we will discuss about the short circuit protection .