| 摘要 |
PURPOSE:To obtain a voltage detecting circuit showing superior response characteristics to the voltage change thereby to prevent the degradation of efficiency due to the decrease of a source voltage and breakage of a part of an air conditioner which applies the voltage detecting circuit, by converting a divided alternating current voltage to be detected to a pulse signal, measuring the time from the rise or fall of the pulse signal to a zero cross point, and calculating the voltage. CONSTITUTION:A voltage of an alternating current source 1 is divided with use of a diode 3 and a voltage dividing circuit 11 comprised of resistances R1, R2. The voltage is converted to a pulse signal by a photocoupler 12. On the other hand, a zero cross point is detected by a zero cross point detecting means 14. The time t1 from the zero cross point to the rise of the pulse signal is measured by a time measuring means 16 and operated at a voltage operating means 17. In this case, a pulse of narrow width is output when an effective voltage is 90V. However, if an effective voltage is 90V or more, a pulse of large width is correspondingly output. Therefore, the voltage is detected by measuring the time from the zero cross point of the voltage waveform to the rise of the pulse signal. In this manner, a detecting circuit with superior response characteristics to the change of voltage is obtained. If the detecting circuit is applied to an air conditioner, the air conditioner is stopped at 80V or lower. |
