| 摘要 |
PURPOSE:To drive a three-phase brushless DC motor, provided with no position sensor, accurately by providing means for applying an impulse voltage corresponding to the excitation pattern of a spindle winding, an A/D converter, and a driving means. CONSTITUTION:A magnetic disc unit comprises means 3 for applying impulse voltages in plural types of exciting pattern onto respective phases of spindle windings 4a-4c, means 5a-5c for sustaining response voltages induced in the spindle windings 4a-4c, an A/D converter 7 for converting respective response voltages into digital signals, and means 2 for selecting the maximum response voltage and determining the exciting phase at the time of start based on the corresponding excitation pattern thus driving a magnetic disc. When a DC brushless spindle motor employing no position sensor is started, pulse driving is carried out and the exciting pattern at the starting time is detected based on the difference of impulse response. By such arrangement, reverse rotation is prevented at starting time and the head or the medium material in the unit can be protected against breakdown. |
