| 摘要 |
PURPOSE:To offer an economical rotating speed control circuit for a DC brushless motor with narrow speed variation width by setting a supply period of phase currents flowing into motor windings for each predetermined rotary cycle of a rotor in accordance with the rotating speed of the rotor. CONSTITUTION:All the output signals V1-V3 in a rotating speed detection circuit 20 become H and the same wave forms (solid lines in A-C) for phase signals phi1-phi3, phi1'-phi3' at the time of low-speed operation after starting a brushless motor. And ON and OFF control (D-I) is applied to transistors 11-13, 14b-16b and phase current are supplied to motor windings 1-3 during the whole cycles T1-T12 of one rotary cycle. With speed increased, V1 becomes L, V2, V3 become H and phi1' remains H, 12 14b remain OFF and energized condition is maintained for a half period of one cycle of T1, T2, T6-T8, T12. Furthermore, with speed increased, V1, V2 become L, V3 becomes H and phi1', phi2' remain H, 11, 16b also remain OFF in addition to the above condition. Then, energized condition is maintained for a 1/6 period of one cycle of T6, T12. And energized condition is interrupted when the speed exceeds setting speed. |
