| 摘要 |
<P>PROBLEM TO BE SOLVED: To highly correctly detect a zero-cross point in driving a motor based on pulse modulation. <P>SOLUTION: A pulse generating section 60 generates a PWM signal Spwm having a duty ratio changing depending on a target torque TRQ of the motor. A counter electromotive detection circuit 20 compares a counter electromotive voltage Vu generated in a coil of the motor 110 with a neutral point voltage Vcom of the coil, and outputs a counter electromotive detection signal BEMF<SB>-</SB>EDGE to be high level at a timing of a zero-cross point. A phase adjusting section 70 compares the phase of the counter electromotive detection signal BEMF<SB>-</SB>EDGE with the phase of a reference signal REF to be a predetermined level at a predetermined timing, and adjusts the duty ratio of the PWM signal Spwm by feedback so that the phase error may be the smallest. A frequency adjusting section 52 adjusts the frequency of the PWM signal Spwm so that the frequency of the PWM signal Spwm may be an integer-multiplied value of the frequency of the counter electromotive detection signal BEMF<SB>-</SB>EDGE. <P>COPYRIGHT: (C)2009,JPO&INPIT |
