| 摘要 |
PURPOSE:To immediately stop the disconnection of a power line by providing a comparator for comparing the carrier frequency component of a PWM control signal of a current signal with a preset lower limit value. CONSTITUTION:In a system for driving a servo motor 1 by a PWM control amplifier 2, a current flowing through a power line 14 to the motor 1 is produced by a current detector 3. A current signal is passed through a band pass filter 4 for passing only the carrier frequency component of PWM to detect it as an amplitude component by a rectifying and smoothing circuit 5. A comparator 6 always compares the signal with a set lower limit value and outputs a signal to an alarm circuit 7 when it drops to a value lower than the lower limit value. |
