| 摘要 |
PURPOSE:To reduce the ripples of DC voltage and currents by correcting the reference voltage value of the voltage control of an AC-DC conversion section so that the PWM pulse width of an AC output by DC-DC conversion is equalized to pulse width being set. CONSTITUTION:With a power unit containing AC-DC-AC conversion, a three- phase AC power supply 1 is rectified by a rectifier 2, desired DC voltage V is obtained by a chopper circuit consisting of a transistor (hereinafter called Tr) 4, etc., the DC voltage is changed into a square-wave AC output by a single- phase inverter circuit composed of a Tr 8, and load 13 is supplied with DC currents I through a rectifier 10 and a smoothing circuit 11. PWM pulse width is detected from an output from a PWM control circuit 22 at that time, and voltage correction circuits 31-44 correcting the reference voltage VREF of voltage control are added in response to the pulse width. Accordingly, a voltage set value VSET is corrected and transmitted over a voltage control circuit 23, and the waveform of AC output voltage approaches to a duty ratio 1 and the ripple of DC output currents I is reduced.
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