| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching DC power supply capable of essentially evading influence of switching noises, in equipment for which high stability is required, and its power source synchronizing method. SOLUTION: The switching DC power supply is equipped with a power supply synchronizing circuit 10 actuating a switching circuit 3 in synchronization with a particular phase of a commercial AC power supply 1. The power supply synchronizing circuit 10 includes a high frequency oscillator 12 oscillating a stable clock signal of 1 MHz or more, a phase detection circuit 14 detecting the particular phase (for example, a zero cross point) of the commercial AC voltage, a dividing circuit 16 counting the clock signal and forming a switching clock of 1 to 100 kHz, and an enable circuit 18 outputting an approval signal approving counting of the dividing circuit in synchronization of the particular phase. The dividing circuit 16 counts the clock signal corresponding to the approval signal to output the switching clock to the switching circuit 3. COPYRIGHT: (C)2008,JPO&INPIT
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