| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply in which noise incident to switching operation is reduced effectively through a simple arrangement. SOLUTION: A DC voltage produced by rectifying an AC voltage from an AC input power supply 2 through a diode bridge 5 is applied, while being divided through resistors 14 and 12, to the resistor connection terminal 11a of a PWM control IC 11 for controlling the switching operation of a switching element 10 and the frequency for controlling the switching operation is varied depending on the amplitude of the AC voltage. Since the frequency for controlling the switching operation of the switching element 10 is increased/decreased depending on the amplitude of the AC voltage from the AC input power supply 2, the control frequency does not fluctuate nor concentrate on a fixed frequency. Consequently, switching noise corresponding to a wave having a frequency n times as high as the switching frequency is distributed. COPYRIGHT: (C)2006,JPO&NCIPI
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