| 摘要 |
PROBLEM TO BE SOLVED: To seek the reduction of the number of pins of an IC, the reduction of chip area, and the reduction of external parts, and the downsizing of equipment, by using a terminal in common to a charge circuit for soft start and a discharge circuit for protective operation, and to enable the further expansion of its function. SOLUTION: A switching power source includes a soft operation executing circuit and a protective operation executing circuit at the same time. The soft operation executing circuit charges a capacitor with a first set current by a charge circuit, by connecting the capacitor to a single control terminal, and raises it to a set voltage value in a set time and executes soft start operation by the terminal voltage of the capacitor. The protective operation executing circuit detects the abnormal state of the operation of the switching power source, while keeping the voltage of the set voltage value, after finish of the soft start operation, and discharges the capacitor and stops the operation of the switching power source, when it detects the abnormal state successively for a prescribed time after start of charge of the capacitor from the set voltage value. Furthermore, it is possible to execute the soft start operation by discharging the capacitor since the voltage of a single control terminal after finish of the soft start operation is at a set voltage value. COPYRIGHT: (C)2010,JPO&INPIT
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