| 摘要 |
PROBLEM TO BE SOLVED: To avoid the erroneous output of a signal, indicating the abnormality of a brushless motor, even if the motor is driven normally in a transient period from the start to the steady state revolution of the brushless motor. SOLUTION: A counter 22, which counts the number which is equal to the number of FG pulses which are to be outputted during a period from the start to the steady state revolution of a fan motor in a normal state or larger, is provided. While the counter 22 counts the number of the FG pulses, the value of a latch circuit 21 is fixed, regardless of the output of a comparator 20. With this constitution, the level of the output of an alarm terminal LS becomes high, and an erroneous output prior to the steady state revolution of the fan motor can be prevented. |
