| 摘要 |
PURPOSE:To stably switch a power source by decreasing the set voltage of an insufficient AC voltage detector of an AC power source during the power source switching time and returning the set voltage to the specified value after the switching of the power source is completed. CONSTITUTION:When the output of an inverter 1 is obtained by a storage battery 15 and when the voltage of an emergency AC power source 3 becomes the normal value, the output is detected, a set altered signal voltage is applied to the base of a transistor 18 to conduct the transistor. Accordingly, the set voltage inputted to a comparator 19 decreases in the amount corresponding to the shortcircuit component of a resistor R3. If an AC power source 3 is interrupted in this state, it decreases lower than the set voltage. Thus, the comparator 19 produces an output, and the inverter 1 is energized by the storage battery 5. However, when the charge of a condenser C1 is finished, the power source 3 becomes the normal voltage, and an emergency AC power source 3 is completely switched. In this manner, the power source can be stably switched. |
