Patent ID: 7176677
Filing Date: 2007-02-13
Classification: G01D

Abstract:
1. A stationary position detection circuit for a motor including a rotor and at least one-phase load, for detecting the position of said rotor in stationary mode, the stationary position detection circuit comprising: a current amount detector; a time counter; a time difference amplifier; and a position determinator, wherein said current amount detector operates in such a manner that an alternating current flowing alternately in a first direction and a second direction opposite to said first direction is rendered to flow through said load by a control circuit for controlling an inverter circuit for driving said motor, the fact that said alternating current flowing in said first direction has reached a value α is detected, after which said alternating current is rendered to flow in said second direction by gradually decreasing amount of said alternating current through said control circuit, and the fact that said alternating current flowing in said second direction has reached a value β equal to and opposite in sign to said value α is detected, after which said alternating current is rendered to flow in said first direction again by gradually decreasing amount of said alternating current through said control circuit, the detection of said values α and β and the control of said alternating current by said control circuit being subsequently repeated a predetermined number of times, said time counter counts the first time for which said alternating current changes from α to β and the second time for which said alternating current changes from β to α, said time difference amplifier converts said counted first time and second time into electrical signals and amplifies said electrical signals in accordance with the accumulation of said first time and second time by said predetermined number of times, and said position determinator determines the position of said rotor in stationary mode in accordance with the value of said electrical signals.