| 摘要 |
PURPOSE:To prevent an abnormal operation due to noise generated in a power supply, etc., by generating a signal for specifying the timing for masking a zero-cross point accompanying switching and zero-cross point caused by noise and by masking the output of a comparison circuit for detecting a zero-cross point on the basis of this signal. CONSTITUTION:Mask circuits 26, 27 holds an input at the time of the output S31 of a flip-flop 31 being a logical value 1, to mask a zero-cross point accompanying switching of electric current flowing through coils 10a, 10b to eliminate the influence of the zero-cross point on a logical circuit 22 and latch circuits 20, 21. In this case, the output S31 becomes the logical value 1 by the rise of the output S23 of a first differentiating circuit 23 after the output S31 changes into a logical value 0 and the output S23 does not come out thereafter until the output S31 again becomes the logical value 0. Consequently, only the first zero-cross point is detected out of a plurality of zero-cross points caused by noise resulting from a power supply. Therefore, a driver 1 is prevented from malfunctioning. |
