Patent ID: 6559616
Filing Date: 2003-05-06
Classification: H02P,Y10S

Abstract:
A rotational pulse generating circuit for a motor, comprising:a filter adapted and configured to eliminate noise from a signal inputted thereto, which signal is superposed with a ripple whose frequency is dependent on a rotation number of the motor, the filter being adapted and configured to make a cutoff frequency variable on the basis of an external signal; a pulse shaper adapted and configured to convert an output signal of the filter to a pulse signal whose frequency is responsive to the rotation number of the motor; a clock signal generator adapted and configured to generate a clock signal on the basis of the pulse signal and a rotational condition signal of the motor, the clock signal being fed to the filter for making the cutoff frequency thereof variable; and a correction device adapted and configured to preliminarily oscillate the clock signal before turning on the motor, the correction device judging whether or not an initial cutoff frequency is adequate on the basis of the preliminarily oscillated clock signal, the correction device being configured to make the initial cutoff frequency adequate when the result of the judgment is found to be inadequate.