What is the working principle of car charger

Car charger is to convert 12V voltage of cigarette lighter socket into 5V USB voltage, and then connect the power cable to charge the mobile phone. Usually, the car charger converts 12V (car 12V, truck 24V) DC into 5-20v DC for charging the car mobile device, which is characterized by low power consumption, simple and convenient, and low price.This configuration is simple and easy to use, but if it is not operated properly, it will lead to damage to electronic equipment, or even danger.