| 摘要 |
A control apparatus for controlling a rotational speed of a brushless direct current motor in accordance with a duty cycle of a pulse signal for controlling by the use of switching transistors exciting current flowing pulsewise through exciting coils of the motor. The apparatus has a detector for detecting the temperature of the transistors and the frequency of the pulse signal is determined in response to the detector so as not to overheat the transistors. Thus, smooth rotation can be obtained in a way that ensures that the transistors will not heat excessively.
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