| 摘要 |
PURPOSE:To exactly detect the capacity escape from an input capacitor, by monitoring the ratio of voltage in proportion to input current, to voltage in proportion to the ripple voltage of the input capacitor. CONSTITUTION:In a power-supply device in switching system, the switching of DC input to primary side input terminals T1, T2 is performed by a switching transistor(Tr)Q, and via secondary side diodes D1-D2, a choke coil L, and the like, the output as DC voltage is generated. Then, an input current detecting means 2 is set, and after the scale of input current is detected by a current transformer 5 and the current is rectified and smoothed 11-12, the current is fed to a level regulating means 6. Of the level regulating means 6, a voltage dividing circuit is composed, and the input to a comparing means 4 made of a comparing circuit 15 is provided. Besides, the input of both end voltage of a capacitor 1 to said comparing means 4 through a ripple voltage detecting means 3 is provided. As a result, regardless of the fluctuation of output current, the capacity escape from the input capacitor 1 can be detected.
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