| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply device improved in responsiveness to a change in frequency, and smooth in the rise of a voltage. SOLUTION: The switching power supply device 1 comprises: a rectifying circuit B1 which rectifies an alternate current from an AC power supply to a direct current; a switching circuit which switches a current rectified at the rectifying circuit B1 by utilizing a switching element Q1; a pulse oscillating circuit IC71 which outputs a switching signal to the switching element Q1; and a transforming circuit T1 which boosts or steps down a voltage by using a current switched by the switching circuit IC71. An pulse output of the switching circuit Q1 is detected by a frequency switching means 15, a resistance value is changed by utilizing resistors R74, R76 on the basis of the state of the pulse output, and a frequency of the switching signal in the pulse oscillating circuit IC71 is switched. COPYRIGHT: (C)2008,JPO&INPIT
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