| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply unit for maintaining input power factor by attaining high accuracy of zero-cross detection of an AC power supply. SOLUTION: The power supply unit maintaining a high power factor is constituted of an input section 8 waiting for an edge of only one direction of either a leading edge or a trailing edge of a binary signal in short-circuiting an AC power supply via a reactor 2, on the basis of the binary signal corresponding to a magnitude relation between an AC voltage of the AC power supply 1 and a predetermined reference signal; a determining section 9 for determining whether the time detected from a pulse width of the binary signal and the edge direction should be stored and whether the edge direction a waited for by the input section 8 should be switched; a storage section 10 for storing the time and the edge direction of the loading edge or the trailing edge of the binary signal, on the basis of the determining section 9; and a calculating section 11 for calculating a subsequent zero-cross point by using an intermediate point between the times corresponding to the leading edge and the trailing edge stored most recently in the storage section 10 and the cycle of the AC power supply. COPYRIGHT: (C)2011,JPO&INPIT
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