Car DC Adapter

Here is a DC adapter to charge mobile phone or play a music system using the power from car battery. The adapter will provide 4.7 volt regulated DC from the 13.5 volt DC power of the car battery

The circuit is basically a DC to DC converter with voltage and current regulation. The 13.5 volt DC from the car battery is given to the collector and base of T1. R1 restricts the base current of T1 to a safer level so that output will be current regulated. Zener diode ZD is an NPN Darlington transistor so that its high gain gives maximum output current. Diode D1 protects the circuit from accidental polarity reversal during connections. By changing the value of ZD, it is possible to get required output voltage. Here the 4.7 volt zener gives regulated 4.7 volts for charging a mobile phone. The adapter can be plugged into the cigarette lighter outlet of the car dash board.