| 摘要 |
<P>PROBLEM TO BE SOLVED: To restrain the loss of synchronism in a brushless motor from occurring. <P>SOLUTION: In a brushless motor drive device, an energization mode in which two phases of a three-phase brushless motor are energized is switched from one to another on the basis of an induction voltage induced in a non-energized phase. When a target duty ratio Dt which is the duty ratio of a PWM signal corresponding to a target rotation speed becomes less than a detection limit value Dlim which is the lower limit of an induced voltage detectable duty ratio, detection timing (1/N) for detecting the induced voltage according to the cycle of the PWM signal is set (S349), and a detection time duty ratio D1 which is the duty ratio of the PWM signal at detection timing is limited to Dlim (S350). Also, non-detection time duty ratios D2 to DN which are duty ratios at a time when the induced voltage is not detected are set so that an average duty ratio derived by adding up and averaging the detection time duty ratio D1 limited to Dlim and the duty ratios D2 to DN between points of time in successive detection timing will get closer to Dt (S351). <P>COPYRIGHT: (C)2013,JPO&INPIT |
