| 摘要 |
PROBLEM TO BE SOLVED: To provide a drive circuit for DC brushless motor, in which the rotational position of the rotor can be detected accurately, even during lead angle operation and a stabilized operation can be realized. SOLUTION: In a switching circuit 4 comprising series circuits of upstream and downstream transistors for three phases, two-phase conduction is performed by turning on the upstream transistor in one series circuit and the downstream transistor in another series circuit. Two-phase conduction is switched sequentially, by detecting the rotational position of the rotor from the terminal voltage of one remaining nonconducting phase winding. When the induced voltage is varies in the decreasing direction, the upstream switching element among switching elements are turned on for two-phase conduction is turned on/off, and the downstream switching element is turned on. When the induced voltage is varying in the increasing direction, the upstream switching element among the switching elements which are on-timing for two-phase conduction is turned on, and the downstream switching element is turned on/off. |
