| 摘要 |
PURPOSE:To prevent a power section from being destroyed, by inserting an electric-discharge-suppressing diode into a space between the smoothing capacitor and detecting section of a driver section. CONSTITUTION:A switching power-supply device is composed of the rectifying bridge D1 of an input power source, a smoothing capacitor C1, the reset circuit (R1, C2, D2) of an output transformer T1 and its primary winding N1, a switching transistor Tr, and a circuit 1 for detecting secondary side output voltage and feeding the voltage back to a driver circuit 2, and the output voltage is kept constant. In this case, between the smoothing capacitor C1 and detecting section 3 of the driver section 2, a diode D4 is set, and when the power source is turned OFF, then the discharge of the smoothing capacitor C4 of the driver section 2 is cut and a time constant circuit is prevented from being inverse-charged. As a result, because of the shortage of driving, a power section can be prevented from being destroyed.
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