Sensorless brushless motor and control circuit and method thereof

Abstract

A method for electronically commutating a motor having a plurality of phase windings associated therewith is disclosed. In an exemplary embodiment, the method includes sensing a back electromotive force (BEMF) generated by each of the phase windings, and scaling the magnitude of the sensed BEMF values for each of the phase windings to a normalized value to produce gain corrected BEMF signals. The gain corrected BEMF signals are then used to determine a rotor position of the motor.

Description

technical field [0001] The invention relates to a control circuit for a sensorless brushless motor. Background technique [0002] Brushless direct current (DC) motors (electronically commutated motors) are well known in the art. The windings of each phase are sequentially energized at appropriate times to generate a rotating magnetic field associated with the permanent magnet rotor. The timing of the sequential energization is a function of the position of the permanent magnet rotor relative to the particular phase winding being energized. To date, various approaches have been used to sense the position of the permanent magnet rotor relative to each phase winding. These methods include the use of optical sensors and Hall effect devices to feed a position signal to the switching logic circuit, causing the latter to selectively turn on or off the excitation of the corresponding phase windings. However, such sensing devices add cost and complexity to the system and sometimes...

AI Technical Summary

Problems solved by technology

Not surprisingly then, there is considerable problem with calculating the exact commutation instant by the controller 20 when receiving relatively low amplitude back EMF signals

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