RIPPLE DETECTING APPARATUS AND ROTATION STATE DETECTING APPARATUS OF DC MOTOR, RIPPLE DETECTING METHOD, AND ROTATION STATE DETECTING METHOD

摘要

PROBLEM TO BE SOLVED: To highly precisely detect a current ripple and a rotation state of a DC motor. SOLUTION: A frequency control part 27 controls feedback of a setting cutoff frequency fc1 and sets a ratio fc2/fc1 of cutoff frequencies so that it corresponds to a ratio of harmonic noise and the current ripple. When low frequency noise is included in a current detection signal IM, low frequency noise and the current ripple are included in signals which main LPF 22 and sub-LPF 23 filter. A microcomputer 30 counts the number of ripple pulses Vo2 output from a ripple detection circuit part 25. When low frequency noise is not included in the current detection signal IM, the current ripple and harmonic noise are included in the signals which main LPF 22 and sub-LPF 23 filter. The microcomputer 30 counts the number of ripple pulses Vo1 outputted from a ripple detection circuit part 24. COPYRIGHT: (C)2008,JPO&INPIT