This is a project of a mini USB car charger circuit. The circuit is very simple to build using only three components. Heart of the circuit is a LM78M05 IC which is a 5V positive voltage regulator IC. This IC has many built in featuers like thermal overload protection, short circuit protection, safe operating
area protection etc. The circuit can be easily connected with the cigar socket in car and convert 12 volt DC to 5 volt DC and charge many USB devices. Out put current of the circuit is 500mA which is enough to charge any USB device. The circuit is basically a DC to DC converter and can also be used to run many 5 to 6 volt DC device from car battery. There are also other similar circuits which you can use to run any 5V or 9V devices from car battery like 12V to 5V converter and 12V to 9V converter with 1000mA output current.
Note: It is adviced to check and confirm the connections and 5 volt output voltage of the circuit with multimeter before connecting any USB device for charging to make sure the circuit is working fine without any soldering or wiring error and providing 5 volt DC output.