| 摘要 |
PURPOSE:To prevent an irregular magnetization, saturation of an output transformer due to a DC component by sending an output current of an inverter, i.e., a digital reference sine wave which can cancel a DC component of a current flowing in a smoothing circuit. CONSTITUTION:A digital value input to a microcomputer 19 through a first A/D converter 23 has an operation to off-set a reference sine wave in response to the value to form an output current of an inverter, i.e., a digital reference sine wave which can cancel a DC component of a current flowing in a smoothing circuit 1. Thus obtained digital reference sine wave is analog- converted by a D/A converter 25, the analog reference sine wave is added to an instantaneous value of the output voltage of the inverter from a step-down unit 11 by an adder 13, amplified by an amplifier 14 to obtain an output capable of cancelling the DC component. Thus, an irregular magnetization, saturation of an output transformer 3 due to the DC component can be prevented. |
