| 摘要 |
PURPOSE:To easily remove pulse noise by detecting the pulse noise to remove from a pulse train a pulse having timing that coincides with a pulse due to noise. CONSTITUTION:Pulses of phases A and B mixed with pulse noises are inputted into a D-flip flop F1 and F11. An output of the F1 is inverted to a L level from an H level while an output of the F11 is inverted to the H level from the L level and the pulses via F2 and F12 are supplied to NOR gates H3 and H4 and an NAND gate G15 of a noise detection circuit 7 via NAND gates G1 and G2 and G7 and G8. The gate G15 detects pulses attributed to noises alone to be outputted to NAND gates G13 and G14. On the other hand, NOR gates H1 and H2 output pulses containing the direction of a motor rotation and speed information and the pulses attributed to the noises. When the motor rotates normally, the gate G14 is kept at the L level to generate no pulse. The gate G13 cancels the pulses attributed to the noise coinciding therewith in timing thereby outputting a pulse train alone owing to the pulses of phases A and B. |
