| 摘要 |
PURPOSE: A method and an apparatus for controlling speed of a motor drive are provided to exactly measure speed command input voltage which is smaller than resolution of an analog/digital converter. CONSTITUTION: A circuit for controlling speed of a motor drive controls the speed of the motor by measuring a speed command input in a circuit of the motor drive. First OP-amp(20) amplifies differentially a speed command input voltage which is filtered. An analog/digital converter(30) receives the speed command input voltage which is amplified differentially by the first OP-amp(20). A mode switching part(40) is connected between an output terminal of the first OP-amp(20) and an input terminal of the analog/digital converter(40), and outputs a mode switching signal for selecting a mode of the speed command input.
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