The charging pile is a charging station for electric vehicles, automobiles and e-bikes, which looks like a stopwatch. A charging pile can charge two cars at the same time, and the charging time from no charge to full charge is 6 to 8 hours. It can be fully charged in about 4 hours after fast charging. The charging pile can realize the charging of time, power and amount, and can be used as a public power purchase terminal. At the same time, in order to improve the efficiency and practicability of public charging pile, and respond to the national energy conservation and environmental protection strategy, the functions of multi charging and charging for electric bicycle will be added in the future. At present, there are two kinds of charging piles in the market: AC and DC, and DC charging pile is widely used. At present, the following three topologies are widely used