| 摘要 |
PROBLEM TO BE SOLVED: To obtain a power supply in which the loss of a circuit for rectifying/ smoothing an AC input power supply is reduced, increase in size is suppressed, reliability is enhanced, fluctuation of output incident to the periodic fluctuation of AC input power supply voltage is suppressed and generation of harmonics is reduced. SOLUTION: A power supply comprises first and second switching elements Q1, Q2 being switched at high frequency, in synchronism with positive and negative half cycles of AC input power supply voltage, and third and fourth switching element Q3, Q4 conducting alternately with positive and negative half cycles of AC input power supply voltage to rectify the output of a transformer. The duty ratio of the first and second switching elements Q1, Q2 is increased as the absolute value of the instantaneous AC input power supply voltage decreases, and it is decreased as the absolute value of the instantaneous AC input power supply voltage increases.
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