| 摘要 |
<p>PROBLEM TO BE SOLVED: To avoid a service interruption of a load operated by an uninterruptible power supply by detecting the service interruption of an AC power supply voltage without a delay in time. SOLUTION: The absolute value of a voltage compensation value and a compensating voltage limiting value obtained from the difference between a sine wave reference voltage synchronized with the AC power supply voltage generated by a reference voltage oscillator 21 and the AC power supply voltage are compared by a comparator 26 to discriminate the service interruption of the power supply, or a limiting value selecting circuit 32 is provided wherein a first compensating voltage limiting value is selected when the AC power source voltage is higher than a specified voltage, while a secondary compensating voltage limiting value is selected when the power source voltage is short, and the service interruption of the AC power source is discriminated by comparing by the comparator 26 the compensating voltage limiting value selected by the limiting value selecting circuit 32 with the absolute value of the voltage compensation value. Or else, a low pass filter is mounted on the outside of the comparator to carry out an analog process.</p> |
