| 摘要 |
PURPOSE:To eliminate the tap and to increase the reliability, by previously performing the discrimination of 50/60Hz after the control of phase and then controlling the number of revolutions according to the resistance value. CONSTITUTION:The control circuit includes a ventilator motor 5, a full-wave rectifying circuit 10 that gives the full wave rectification to the voltage of an AC power supply, a zero point detecting circuit 11 that detects the zero point of the full-wave rectification obtained through the circuit 10 plus a capacitor which is charged with a prescribed time constant. When the circuit 11 detects the zero point, the charged electric charge is discharge and the sawtooth voltage synchronous with the power supply is produced by a sawtooth voltage generating circuit 12. The discrimination is given to 50/60Hz by the circuit 12 and a clock input circuit 8 which produces a clock synchronous with the power supply. Then prescribed resistances R1-R6 plus 13-18 are selected, and the reference potential is produced by voltage division to a resistance 19. |
