This is the first tutorial on power electronics category and In this tutorial, we are going to make a mobile phone charger using easily available components. This is ongoing series and in the first part, we will design a smooth DC voltage source from 230 volts 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 within the very short period of time we need a large amount of currently more than 700 milliamps and to charge within the large period of time lets say 10 Hour we need the small amount of current less than 700 milliamps. And this factor also depends on the capacity of a battery. For the large capacity of battery let’s say 9000 mAh we need large current and need to charge for a long time. So you have to decide what battery you are charging.
Longer it takes to charge the battery the battery life also get longer and less time charged battery it will not work for a long time. In above schematic, I have designed small current source so that my battery will extend for a long time.
Above schematic can be divided into three part, in the first part, we have to convert high voltage (230 volts) 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 by 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 the 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 a 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 a diode to convert them into DC. The in the 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 appears sometimes, 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 the short circuit protection.