Patent ID: 7966157
Filing Date: 2011-06-21
Classification: G01D,G01P

Abstract:
1. A signal processing circuit for a rotation detector for detecting rotation of an object, comprising: first and second sensor elements for outputting first and second rotation signals, respectively, wherein the first and second rotation signals have individual phases for representing rotation of a rotor that rotates together with the object; first and second waveform reshaping elements for reshaping the first and second rotation signals into first and second pulse signals having first and second pulse signal levels, respectively; and first and second filters for outputting first and second filter signals having first and second filter signal levels, respectively, wherein, when a period in which one of the first and second pulse signal levels is constant is equal to or longer than a predetermined period, a corresponding filter outputs a corresponding filter signal with a corresponding filter signal level after the predetermined period elapses, the corresponding filter signal level being equal to the filter signal level in the period, and wherein, when one of the first and second pulse signal levels is changed within the predetermined period, a corresponding filter sets a corresponding one of first and second logic retaining periods in a corresponding filter signal, wherein a corresponding filter signal level is maintained to a previous value during the corresponding one of the first and second logic retaining periods, wherein the previous value is the filter signal level before the change, and wherein the corresponding one of the first and second logic retaining periods is set after the change until the predetermined period elapses; a phase difference compensation deciding element for deciding whether one of the first and second logic retaining periods set in a leading one of the first and second filter signals is longer than the other one of the first and second logic retaining periods set in a following one of the first and second filter signals, wherein a noise occurs within the predetermined period so that the leading one precedes the following one; a phase difference compensation executing element for outputting first and second phase difference compensation output signals corresponding to the first and second filter signals, respectively, wherein, when the phase difference compensation deciding element determines that the one set in the leading one is longer than the other one set in the following one, the phase difference compensation executing element prolongs the other one set in the following one to be equal to or longer than the one set in the leading one so that a phase relationship between the first and second filter signals after decision of the phase difference compensation deciding element is equal to a phase relationship between the first and second filter signals just before the decision of the phase difference compensation deciding element, and the phase difference compensation executing element outputs the first and second filter signals as the first and second phase difference compensation output signals, respectively, and wherein, when the phase difference compensation deciding element determines that the one set in the leading one is not longer than the other one set in the following one, the phase difference compensation executing element directly outputs the first and second filter signals as the first and second phase difference compensation output signals, respectively; a rotation direction deciding element for repeatedly deciding based on the phase relationship between the first and second phase difference compensation output signals whether a rotation direction of the rotor is a first direction or a second direction, which is opposite to the first direction; and an output element for outputting an output signal, which relates to rotation information that includes decision of the rotation direction of the rotor.