| 摘要 |
PURPOSE:To eliminate the blowing of a fuse at the time of an output short circuit and an overcurrent by reducing the loss of a switch element when a battery voltage drops. CONSTITUTION:When the voltage of a battery 4 drops in the backup operation of the battery 4 to cause the output of a comparator OP2 to fall to a level L and a transistor SW1 is placed in operation in the OFF direction, the voltage of a l4st DC output falls. Then the voltage at the uninverted input terminal of the comparator OP2 never exceeds the l4st DC output voltage through the effect of an added diode D1 (the forward voltage drop across the diode D1 is ignored), so the transistor SW1 is turning OFF and turns OFF completely at last. At the time of the output short circuit on the side of the load RL, on the other hand, the l4st DC output falls to the ground potential immediately, so the transistor SW1 turns OFF simultaneously with the short circuit. |
