| 摘要 |
PROBLEM TO BE SOLVED: To monitor the feeding condition of AC voltage in real time by outputting an alarm signal, if the voltage value which is detected by a voltage detection means is a prescribed value or lower. SOLUTION: This power supply voltage monitoring circuit is formed such that a voltage detection circuit 40 is connected to the previous stage of a rectification circuit 20, to detect the voltage value of AC voltage before rectification is conducted at the rectifying circuit 20. If the supply of the AC voltage to an AC input terminal 10 is stopped due to the generation of a trouble, power supply output voltage is continuously outputted from an power supply output terminal 30 for a while thereafter, by electric charges which are stored in a smoothing capacitor 23 in the power supply voltage monitoring circuit. If the supply of the AC voltage to the AC input terminal 10 is stopped, the apply of the AC voltage to diodes 41, 42 is stopped immediately after that. Therefore, a voltage value detected at a voltage detection part 44 becomes a prescribed value or lower, and an alarm signal is outputted from an AC interrupt alarm 45. As a result of this, it is possible to monitor the feeding condition of the AC voltage in real time. |
