Direction of rotation detection device for a brushless 3-phase DC motor

摘要

A range judging circuit (71) judges an electrical angular range of a three-phase brushless DC motor (1) based on an output signal of a resolver (6). A hold time output circuit (73) determines an optimal hold time. A drive direction judging circuit (72) judges a rotating direction of the motor (1) based on a size comparison between a pair of phase currents. A hold circuit (74) holds a judgment result of the drive direction judging circuit (72) at the hold time determined by the hold time output circuit (73), and holds the judgment result until the next hold time comes.