Fast charging seems to have become a standard for mobile phones, but there are so many fast charging standards on the market. There are 5V, 9V, and 12V for common voltages. The current covers the range from 1.5A to 4A. It is easy to be dazzled. It also brings a lot of trouble to everyone to buy chargers and mobile power supplies. The following is an analysis of the fast charging standards for everyone one by one.