| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply which can reduce power consumption. SOLUTION: A current value, consumed by an image-forming apparatus in its waiting period, is stored in a control unit 20 beforehand. When the image- forming apparatus is in copying operation, switching devices FET11 and FET21 are made to operate at ON-time by PWM signals PWM11 and PWM21, to obtain prescribed control voltage and prescribed drive load voltage, which are supplied to an image-forming apparatus part 10 via output terminals Vout11 and Vout21. In a copying operation state, a current which is not smaller than the current value stored in the control unit 20 is detected by a drive load current detection circuit IS21. When the copying operation of the image-forming apparatus main part 10 is finished and the current value, detected by the drive load current detection circuit IS21, is lowered to a value smaller than the stored current value, after several tens of seconds, the control unit 20 controls the period of the signal PWM21 to be T2 shorter than a period T1 and reduces the ON-time of the switching device of the switching device FET21 to lower the drive load voltage. COPYRIGHT: (C)2003,JPO
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