The AC voltage waveform of square wave inverter is square wave. The circuits used in such inverters are not exactly the same, but the common characteristic of them is that the circuits is relatively simple, and use a small number of power switches. The power is generally designed between 100w to 1kw. Square wave inverter has the advantage of simple, cheap, easy to maintenance. The disadvantage is that due to the square wave voltage contains a large number of high harmonics, with iron core inductance or transformer load with electrical equipment will produce additional loss, and can interfere some communication equipment. In addition, this type of inverter has some other disadvantages such as the voltage regulation range is not wide enough, the protection function is not perfect, the noise is relatively large and so on.