| 摘要 |
<p>PURPOSE:To make it possible to detect a current to be detected even if the wave-shape of the AC to be detected is distorted by a method wherein a discrimination is performed by a second discrimination level which is lower than a first discrimination level when the charging voltage of a condenser exceeds the predetermined first discrimination level. CONSTITUTION:In a level discrimination circuit 8, the first discrimination level is determined by the sum of the forward direction voltage of a diode 128 and the zener voltage of a zener diode 129. The forward direction voltage of the diode 128 determines a second discrimination level which is lower than the first discrimination level. When the leak is generated and the charging voltage of a condenser 120 exceeds the first discrimination level, the output of an operation amplifier 126 comes to a high level (+Vcc). When the output of the amplifier comes to the high level, a transistor 130 is electrically conducted and level discrimination is performed in the second discrimination level by the amplifier. Therefore, even if the voltage of the condenser 120 is lowered, the discrimination level is lowered and even the leak of a distorted AC such as a phase control signal is sufficiently detected.</p> |
