| 摘要 |
There is provided a brushless motor drive control circuit capable of assuring an S/N ratio of a predetermined counter electromotive voltage and suppressing lowering of efficiency of a brushless motor at a high-speed rotation. More specifically, the brushless motor drive control circuit (6) includes: counter electromotive voltage filter circuits (16u, 16v, 16w) for inputting 3-phase counter electromotive voltage induced at the end of each of the stator coils (Lu, Lv, Lw) and switching between a first and a second time constant according to the rotation speed of the rotor (Ro) so as to pass a low-range frequency component corresponding to the time constant; counter electromotive voltage detection comparators (17u, 17v, 17w) for inputting the counter electromotive voltage which has passed through the counter electromotive voltage filter circuit and comparing it with voltage at a neutral point so as to output counter electromotive voltage polarity signals (Pu, Pv, Pw) as the comparison results; and a motor driver control circuit (15a) for switching/controlling the time constant of the counter electromotive filter circuits (16u, 16v, 16w) and controlling the motor driver (5) according to the counter electromotive voltage polarity signals. |
