Patent ID: 7573218

Claim:
A sensorless driving method for a brushless DC motor, the method comprising: detecting zero-crossings by a mask-based phase shift digital detection mechanism for detecting zero-crossings; and inhibiting electronic noises caused by transistor switching by an inhibition mechanism; wherein a first counter and a second counter included in the mask-based phase shift digital detection mechanism are used for calculating commutating points of the brushless DC motor, wherein when a first zero-crossing occurs, the first counter starts to count until a next zero-crossing occurs; and then the second counter starts to count, while a value counted by the first counter is divided by 2 and a result is stored in the first counter; foregoing steps are performed repeatedly, wherein a commutating point is obtained when a value counted by the second counter reaches the value stored in the first counter; similarly, another commutating point is obtained when the value counted by the first counter reaches the value stored in the second counter.