| 摘要 |
PROBLEM TO BE SOLVED: To provide a position detection method of a brushless DC motor for accurately detecting the crossing time between back electromotive force and reference potential, by utilizing a phase voltage outputted from the brushless DC motor regardless of the on/off of a pulse width modulation signal that is inputted to the brushless DC motor. SOLUTION: The position of a brushless DC motor 50 is detected by successively performing a process for setting a phase voltage being outputted from the motor 50 to a previous phase voltage and storing it along with detection time for detecting the voltage when the phase voltage is equal to or less than preset reference potential, and a process for storing a phase voltage as a current phase voltage when the phase voltage being outputted from the motor 50 is equal to or more than preset reference potential and then determining the position detection time by utilizing the current phase voltage and a phase voltage before the stored one and the detection time.
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