| 摘要 |
PURPOSE:To prevent breakage of a switching element based on magnetic saturation of a core of a transformer, by a method wherein a control section to control the switching element is provided with a setting section which narrows the maximum ON time width as input voltage becomes higher. CONSTITUTION:Input voltage is switched by a switching element 1 and applied to primary winding of a transformer 2. Voltage induced in secondary winding of the transformer 2 is rectified and smoothed by a rectifying and smoothing circuit 3 and supplied to a load, and also compared with reference voltage by a control section 4 and the output controls the ON time of the switching element 1 so that the output voltage shows constant value. The control section 4 is provided with a setting section 5 which narrows the maximum ON time width of the switching element 1 as the input voltage becomes higher.
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