| 摘要 |
PURPOSE:To perform switching between a normal power source and a backup power source stably by connecting a load resistor to the output of the normal power source when the output voltage of the normal power source is lower than a reference value and separating the load resistor when the output voltage is higher than the reference value. CONSTITUTION:When the output voltage from a power source circuit 1 is higher than a reference level, the output from a power interruption detecting section 21 goes to high level thus turning transistors Tr 23, Tr 22 ON. Consequently, power is fed from the power source circuit 1 to a load circuit 3. Since the inverted output of an inverter 24 goes to a low level, Trs 26, 27, 25 are turned OFF to separate a battery 28 from the load circuit 3 and a resistor R1 from the output of the power source circuit 1. Upon interruption of commercial power source, the power source circuit 1 is separated from the load circuit 3 and the load resistor R1 serves as the load at the output of the power source circuit 1, while furthermore the Tr 25 is turned ON to feed power from the battery 28 to the load circuit 3. |
