The AC voltage waveform output of square wave inverter is square wave. The inverter lines used by this kind of inverter are not exactly the same, but the common characteristics are that the lines are relatively simple, the number of power switch tubes used is small, and the design power is generally between hundreds of watts and kilowatts. The advantages of square wave inverter are simple circuit, cheap price and convenient maintenance. The disadvantage is that the square wave voltage contains a large number of high harmonics, in the load electrical equipment with core inductance or transformer will produce additional loss, radio and some communication equipment interference. In addition, this kind of inverter voltage range is not wide enough, the protection function is not perfect, the noise is relatively large and other shortcomings.