| 摘要 |
PROBLEM TO BE SOLVED: To realize a simplified, small-sized and lightweight structure, also to realize high output and moreover to suppress generation of harmonic element of an input current. SOLUTION: A full-wave rectifying circuit 22 is connected to an AC power supply 21, a series circuit of the primary winding 24p of a flyback transformer 24 and a switching element 25 is connected in parallel to an output terminal of this rectifying circuit, a smoothing capacitor 29 is connected in parallel to the secondary winding 24s of the flyback transformer via the forward direction of a diode 28, and a load 30 is then connected in parallel to this smoothing capacitor. When an input voltage from the AC power supply is higher than the threshold voltage, continuous mode operation is executed to always allow a current to flow into the primary winding or secondary winding of the flyback transformer. When the input voltage is lower than the threshold value, discontinuous mode operation is executed to allow a current to flow into the primary winding after a current flowing into the secondary winding of the flyback transformer once stops.
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