In Part-1 We have designed 5 volts smooth DC source for the mobile charger. In this section, we are going to make a short circuit protection circuit so that if any short circuit occurs the whole circuit will not be damaged. This circuit is enough to charge a battery. As shown in the schematic diagram below if the button is pressed the short circuit will occur in this case the D5 LED will glow instead of damaging the whole circuit. The operation of this circuit is shown below
How short circuit protection activated?
The transistor can be used in two application one is to amplify the signal and another is as a switch. In this example, we have used a transistor as a switch. First, if we do not press button is in the case of open circuit first Q2 and then Q1 get activated and the current starts flowing through D6, in that case, D5 get reverse biased so main charging LED glows. And when we short-circuited The path always follows the least resistance in that case both of the transistors go off and D5 get forward biased . and we can obtain output from D6.