SENSORLESS VARIABLE CONDUCTION CONTROL FOR BRUSHLESS MOTOR

A power tool is provided including a brushless motor having a stator defining a plurality of phases and a rotor. A power unit is provided including power switches and a control unit outputs a drive signal to the motor switches to drive the phases of the motor using a trapezoidal control scheme over a series of sectors. The control unit sets a conduction band within which each phase is commutated to a baseline value that is greater than 120 degrees, sets at least one commutation transition point as a function of the set conduction band, and within each sector, monitors an open-phase voltage of the motor to detect a back electromotive force (back-EMF) voltage of the motor and control commutation of at least one phase based on the open-phase voltage of the motor in relation to the at least one commutation transition point.