| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a brushless motor drive control circuit, capable of securing the desired S/N ratio of a counter electromotive voltage and suppressing the deterioration of the efficiency of the brushless motor at high-speed revolutions. <P>SOLUTION: This brushless motor drive control circuit 6 is provided with counter electromotive voltage filtering circuit 16<SB>U</SB>, 16<SB>V</SB>, 16<SB>W</SB>that input three-phase counter electromotive voltages that are induced at the end of each phase of stator coils L<SB>U</SB>, L<SB>V</SB>, L<SB>W</SB>; for switching first and second time constants, according to the rotational speed of a rotor R<SB>O</SB>, and making low-frequency components corresponding to the time constant pass through counter electromotive voltage detecting comparators 17<SB>U</SB>, 17<SB>V</SB>, 17<SB>W</SB>, that input the counter electromotive voltages that pass the counter electromotive voltage filtering circuits and output counter electromotive voltage polarity signals P<SB>U</SB>, P<SB>V</SB>, P<SB>W</SB>, the results of the comparisons in magnitude with a voltage at the neutral point; and a motor driver control circuit 15a that controls the switching of the time constant of the counter electromotive voltage filtering circuit 16<SB>U</SB>, 16<SB>V</SB>, 16<SB>W</SB>and a motor driver 5, according to the counter electromotive voltage polarity signals. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
