PURPOSE: To decrease the conducting loss of an apparatus and to improve its efficiency, by using choppers in the operation for converting DC from a DC power supply into a pulsating current including a part of AC output waveform.

CONSTITUTION: In a non-isolated DC-AC converter, step-up choppers 47, 48 are connected in parallel with a DC input power supply 1 and output terminals u, v of said choppers are combined with each other to form AC output terminals. Said step-up choppers 47∼48 are composed of MOSFET 33 having a parasitic diode 35 and snubber circuit 37, MOSFET 34 having a parasitic diode 36 and a snubber circuit 38, a capacitor 31, and a reactor 32. Thus, said choppers first turn ON the FET 34 to accumulate energy in the reactor 32, and then turn OFF the FET 34 to transfer said accumulated energy to the capacitor 31 to turn ON and OFF the FET 34 so that said voltage changes in a sine wave-like manner. Likewise, the FET 33 is turned OFF, the accumulated energy is fed back to the power supply 1, and an AC voltage output is obtained between terminals u∼v.