Patent ID: 8102135
Filing Date: 2012-01-24
Classification: H02P

Abstract:
1. A drive circuit for an AC motor, the AC motor having a stator with a combination of a coil body, a movable body with a permanent magnet and a sensor, the coil body having a plurality of coils, the permanent magnet having a plurality of magnet pole elements, the plurality of magnet pole elements being arranged to become alternating opposite poles, and the sensor being disposed at the stator, detecting a periodic magnetic field change caused by movement of the permanent magnet and outputting an analog signal, the drive circuit comprising: a frequency to voltage converter that converts a frequency of the analog signal to a voltage signal; a hysteresis level setting part that sets a hysteresis level based on the voltage signal; a window comparator that compares the analog signal and the hysteresis level, and creates the Pulse Wide Modulation signal; and a coil drive circuit that excites the plurality of coils of the AC motor with the Pulse Wide Modulation signal.