| 摘要 |
PURPOSE:To eliminate an unstable operation by a noise signal by providing a DC bias circuit for shifting the level of an AC signal in a shaper for shaping a rotary position signal of a magnet rotor. CONSTITUTION:The rotary position of a magnet rotor 22 is detected, for example, by a Hall IC as detecting means 25 and the output becomes base control signals of two corresponding transistors of six transistors of a drive circuit 24 by a logic circuit 26. After the output of detecting means 25 is converted by an F/V converter 36, it is supplied as a PWM control signal to a rotating speed controller 37. A rectifier 28 which includes a DC bias circuit 32 is provided at the front stage of the converter 36, and the influence of the noise signal is removed by shifting the level of the AC signal by the bias circuit 32. |
