The current direction of 220V DC does not change with time, while the current direction of 220V AC changes periodically with time. The current size of direct current usually remains constant, while the current size of alternating current changes over time. In terms of use, direct current is often used for power and circuit transmission, as well as circuit breakers, air switches and other equipment; Alternating current is widely used in domestic and industrial power supply, as well as driving motors and other fields. In addition, alternating current can easily change the voltage through a transformer and is suitable for long-distance transmission, while direct current, although there is no eddy current loss during transmission, requires specialized electronic circuits in terms of boost and buck. In the conversion mode, alternating current can be converted to direct current by a rectifier, and direct current to alternating current requires the use of an inverter