Patent ID: 9287807
Filing Date: 2016-03-15
CPC Classification: H02P

Claim Text:
1. An apparatus of decreasing a speed of a sensorless brush less direct current (BLDC) motor, comprising: a switching unit configured to switch a direct current (DC) power depending on a plurality of pulse width modulation (PWM) signals to generate a three-phase alternating current (AC) power and apply the generated three-phase AC power to the BLDC motor to drive the BDLC motor; a plurality of voltage dividers configured to divide voltages of reverse electromotive forces generated in the BLDC motor; and a controlling unit configured to calculate a current rotation speed of the BLDC motor using output signals of the plurality of voltage dividers, generate the plurality of PWM signals depending on the calculated current rotation speed and a command rotation speed and output the plurality of PWM signals to the switching unit, divide a rotation phase angle of the BLDC motor into a speed decreasing region and a zero crossing point (ZCP) detecting region in the case of decreasing a rotation speed of the BLDC motor, decrease the rotation speed of the BLDC motor in the case in which the rotation phase angle of the BLDC motor is in the speed decreasing region, and detect ZCPs of the reverse electromotive forces in the case in which the rotation phase angle of the BLDC motor is in the ZCP detecting region.