| 摘要 |
PURPOSE:To reduce a waveform distortion over a wide frequency range by dividing the entire frequency band of the output voltage of an inverter into a plurality of regions, and distributing the bit resolution per one period to the intrinsic value of the minimum necessary value in each frequency range. CONSTITUTION:Many sinusoidal wave approximate logic patterns pulse-width- modulated corresponding to many inverter output voltages of different amplitudes at every frequency are stored in a ROM 15. A bit resolution switching circuit 14 receives a frequency region discrimination signal from a bit resolution instructing circuit 12 and an output from a voltage pattern instructing circuit 11 to designate the read-out input terminal of the ROM 15 in response to the frequency range set by a frequency setter 16. The voltage pattern read out from the ROM 15 is input to a waveform composite circuit 20, and a signal for controlling to turn ON and OFF a switching element of an inverter main circuit is output. |
