| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-priced permanent magnet motor driving circuit which can determine commutation timing, based on armature current. SOLUTION: When a DC power source 50 is turned on with a switch SW kept at a standby terminal, a rotor preset circuit 5 operates, and the rotor of a single-phase motor 51 is kept in a prescribed position. When the switch SW is switched to an operating terminal from this condition, the rotor preset circuit 5 stops, while a starting compensation circuit 6 operates. As a result, armature current large enough to develop starting torque is passed through respective coils L1, L2 by a current detection circuit 3, a feedback circuit 4, and an inverter circuit 2, and the single-phase motor 51 starts its rotation gradually. When the voltage across a capacitor C2 reaches 0.6 V, a transistor Q4 turns on, the resistance value of the feedback circuit 4 decreases, and the feedback amount of a current detection circuit 3 becomes larger. Therefore, a commutation cycle becomes shorter, and the single-phase motor 51 starts high-speed rotation gradually, so that it reaches roughly constant speed rotation in a short time. |
