| 摘要 |
A motor speed control system detects a rotation speed of a motor, compares a detected output signal with a reference voltage or a reference frequency to produce an error signal, produces a saw-tooth wave signal of an appropriate repetition frequency, compares the error signal with the saw-tooth wave signal to produce a switching signal, and drives a motor by the switching signal to control the speed of the motor. The system includes a first driver circuit for driving the motor by the output signal of a first comparator circuit which produces the error signal, and a second driver circuit for driving the motor by the output signal of a second comparator circuit which produces the switching signal. The motor is normally driven by the second driver circuit for speed control and is driven by the first driver circuit when the motor is started or overloaded or when the second driver circuit is defective.
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