The output of the square wave inverter is poor quality square wave alternating current, and its maximum value in the positive direction to the maximum value in the negative direction are generated almost at the same time, which will cause severe and unstable effects on the load and the inverter itself. At the same time, its load capacity is poor, only 40-60% of the rated load, and it cannot carry inductive load. If the load is too large, the third harmonic component contained in the square wave current will increase the capacitive current flowing into the load, which will damage the power filter capacitor of the load in severe cases. In response to the above shortcomings, modified sine wave (or improved sine wave, quasi-sine wave, analog sine wave, etc.) inverters have appeared in recent years. There is a time between the output waveform from the positive maximum value to the negative maximum value. Interval, the use effect has been improved, but the waveform of the corrected sine wave is still composed of broken lines, which still belongs to the category of square wave, and the continuity is not good, and there is a dead zone. Modified Sine Wave Inverter generally adopts non-isolated coupling circuit, while pure sine wave inverter adopts isolated coupling circuit design. The price is also very different. Modifying the sine wave switching inverter power supply not only saves the bulky power frequency transformer, but also greatly improves the inverter efficiency by 90%.