| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a humidity detection circuit which uses a humidity sensor for outputting a humidity detection signal upon the application of AC voltage and prevents the deterioration of a humidity sensor even if a PWM signal for controlling the DC voltage applied to the humidity detection circuit to AC voltage is stopped. <P>SOLUTION: The humidity detection circuit 107 includes transistors TR1, TR2 and TR3 and a humidity sensor HS1. When the AC voltage, wherein the DC voltage supplied from the emitter side of the transistor TR3 by the function of the transistors TR1 and TR2 is controlled on the basis of the PWM signal supplied from the base side of the transistor TR1, is applied to the humidity sensor HS1, the humidity sensor HS1 outputs the humidity detection signal and the PWM signal supplied from the base side of the transistor TR1 is stopped while a reset signal [H] is supplied from the base side of the transistor TR3. Whereupon, the transistor TR3 is turned OFF and the application of DC voltage to the humidity sensor HS1 is cut off. <P>COPYRIGHT: (C)2008,JPO&INPIT |
