| 摘要 |
PURPOSE:To reduce the number of parts of a revolution detecting means by knowing the number of revolutions through detecting the period of a counter- electromotive force generated in a coil. CONSTITUTION:Respective terminals of a brushless motor 1 are connected with comparators 3a, 3b, 3c via a resistor 2 so that a voltage between two terminals is referred to. Said comparators 3a, 3b, 3c output a high level signal to CPU 5, when the input is positive, and a low level signal thereto, when said input is negative. The output of one of the comparators (output of the comparator 3a) is inputted to a frequency-dividing circuit 4, divided into 1/4 period, and inputted to the CPU 5 as an index signal 7. The CPU 5 refers to said signals to control a driver 6 and to maintain the appropriate number of revolutions. |
