| 摘要 |
PURPOSE:To improve the stability of rotating speed by controlling the trigger point of a voltage phase to be applied to a fan motor on the basis of a zero- cross detection pulse produced by comparing a power source voltage with a stable reference voltage. CONSTITUTION:A comparator 3 compares a voltage similar to a power source voltage output from a full-wave detector 1 with a stable reference voltage, and outputs a zero-cross detection pulse when the reference voltage is larger. A microcomputer 6 outputs a trigger pulse to a triac 8 through a photocoupler 7 with the zero-cross detection pulse generation point as a reference after a trigger control time. Thus, even if a power source voltage is varied, the rotating speed of a fan motor 9 can be stabilized. |
