| 摘要 |
PURPOSE:To make it possible to accurately detect revolution speed without requiring a pulse generator having high degree of accuracy by detecting a motor current, and detecting current gradient during the specific period in an ON state of a switching element controlling power to a motor to calculate the revolution speed. CONSTITUTION:A difference between target revolution speed set in the outside and revolution speed calculated by an operator 5a is detected by an error detector 8, and an obtained error signal is amplified by an error amplifier 4 and is sent to a pulse width modulator 3. A motor 1 is driven by turning a switching element 2 ON/OFF by a signal modulating the pulse width generated from the pulse width modulator 3. A motor current at that time is detected by a current detector 7, current gradient proportional to revolution speed is detected by a current gradient detector 6 through the current signal, and a revolution speed signal is obtained by multiplying the current gradient by factors through the operator 5a, and the motor 1 is made to feedback and control in the same way based on the revolution speed signal. |
