Patent ID: 8487571

Claim:
A zero-crossing detection circuit adapted into a three-phase brushless DC (direct current) motor, the three-phase brushless DC motor comprising a first coil, a second coil and a third coil, a terminal of the first coil, a terminal of the second coil and a terminal of the third coil being electrically coupled together with each other, the zero-crossing detection circuit comprising: a first selection circuit electrically coupled to another terminal of the first coil, another terminal of the second coil and another terminal of the third coil, to obtain a first-terminal voltage, a second-terminal voltage and a third-terminal voltage respectively, and output one of the first-terminal voltage, the second-terminal voltage and the third-terminal voltage according to a selection signal; a second selection circuit electrically coupled to the another terminal of the first coil, the another terminal of the second coil and the another terminal of the third coil, to obtain the first-terminal voltage, the second-terminal voltage and the third-terminal voltage respectively, and output one of the first-terminal voltage, the second-terminal voltage and the third-terminal voltage according to the selection signal; and a comparator configured for comparing an output of the first selection circuit and an output of the second selection circuit, to output a comparing result.