A control system operates with a PWM speed regulation of a sensorless BLDC motor with a plurality of windings. A hybrid method is present in the invention utilizing BEMF induced in stator windings to indicate the commutation instant and a falling edge detection method to override PWM chopping and commutation noises. The present invention achieves reliable sensorless rotor position detection with relative concise and low cost circuit as well as little software expense. The control device of the present invention includes a comparator for generating the BEMF zero crossing points (ZCP), and means for deriving rotor position information by detecting the falling edge (or rising edge for low-side chopping case) of the generated ZCPs.